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A SEED TRANSPORT AND DELIVERY MECHANISM FOR THE REVOLVING SPADE PLANTER By JEMAN YEON A DISSERTATION PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE REQUIREMENT FOR THE DEGREE OF DOCTOR OF PHILOSOPHY UNIVERSITY OF FLORIDA 2000 ACKNOWLEDGMENTS I would like to express sincere appreciation to Dr. Lawrance N. Shaw for his guidance, insight, and patience throughout my course work and research. Special thanks go to Dr. Allen R. Overman, Dr. Richard C. Fluck, Dr. William M. Stall, and Dr. John K. Schueller for their advice on my research as members of the supervisory committee. In addition to their academic advice, they provided me great academic experiences in study and research in this institution. I would also like to acknowledge that all of this academic experience will be a great asset in my life as an engineer. Gratitude is expressed to Mr. Ralph Hoffman and Mr. Terry Slean for their support in fabrication and installation of the research equipment. I am also grateful to all professors and friends in the Department of Agricultural and Biological Engineering at the University of Florida who have helped and inspired me during my study and research. I sincerely thank my mother and my brother and sisters for their patience and faith in me. TABLE OF CONTENTS page ACKNOWLEDGMENTS............................................................................................ ii ABSTRACT......................................................................................................................... v CHAPTERS 1. IN TR O D U CTION .................................................................................................. 1 2. REVIEW OF LITERATURE................................................................................. 5 2.1 SpadePunch Planter..................................................................................... 5 2.2 Seed Metering and Transporting Mechanisms............................... ............ 6 2.3 Revolving Spade Planter and its Applications.............................. ........... .. 12 3. THEORETICAL ANALYSIS FOR SEED TRANSPORT AND DELIVERY M ECHANISM DESIGN ....................................................................................... 17 3.1 Feature of a Revolving Spade Planter with Seed Transport and Delivery M mechanism ................................................................................................... 17 3.2 Coordinate Frames of the Design.................................................................... 19 3.3 Theoretical Analysis for Feasible Design Cases of Seed Transport and Delivery M echanism ................................................... .............................. 23 3.3.1 D esign Case I.............................................................................. 24 3.3.2 Design Case II................................................ ........................ 27 3.3.3 Consideration on the Theoretical Analysis for Design................ 33 4. DESIGN OF A SEED TRANSPORT AND DELIVERY MECHANISM M O D EL ............................................................................................................... 37 4.1 Principle Methodology in Design............................................................ 37 4.2 Model Design and Preparation for Experimental Evaluation....................... 44 5. RESULTS AND DISCUSSION......................................................................... 60 6. CONCLUSIONS................................................................................................... 86 7. RECOMMENDATIONS FOR FUTURE STUDIES............................. ............ 88 APPENDIX A. COORDINATE TRANSFORMATION ............................................ 90 APPENDIX B. SOLUTION OF THE DESIGN CASE II ......................................... 92 APPENDIX C. SOLUTION FOR THE COORDINATE (x2, Y2)............................... 94 APPENDIX D. SEED MOTION IN GROOVE AND DELIVERY INTO SPADE....... 97 REFEREN CES ........................................................................................................ 117 BIOGRAPHICAL SKETCH.......................................................................................... 119 Abstract of Dissertation Presented to the Graduate School of the University of Florida in Partial Fulfillment of the Requirement for the Degree of Doctor of Philosophy A SEED TRANSPORT AND DELIVERY MECHANISM FOR THE REVOLVING SPADE PLANTER By JeMan Yeon December, 2000 Chairman: Lawrance N. Shaw Major Department: Department of Agricultural and Biological Engineering A major objective of this study is to develop a seed transport and delivery mechanism for the revolving spade planter for higher speed planting operations. Based on the theoretical analysis of possible design cases for the planter concept, a suitable transport and delivery mechanism was developed for the current design of the revolving spade planter. The design planting speed for the planter was 5 MPH which was higher than any other current revolving spade planter can successfully plant. The experimental model was built and evaluated for the design planting speed. The evaluation results showed that the design concept was suitable for the speed range up to the design planting speed. The design method could be applicable to the revolving spade planter at a higher planting speed. CHAPTER 1 INTRODUCTION Seeding methods have been developed to achieve a high yield in food production. Applications of planting techniques have been concerned with the appropriate selection of farming operations such as tilled or untilled planting and random or precision planting. Drilling has been a widely used technique to deposit seeds into furrows opened by tools such as shoes, discs, or packer rings. Broadcastseeding has been used to place seeds randomly over relatively wide areas. In most applications of broadcastseeding, a secondary tillage is necessary to cover the seeds with soil. The improved performance of seed providing better germination and emergence, the increased cost of seed, and the desire to eliminate overplanting and thinning have resulted in the need for precision planting. Thus, precision planting could be one of the most important operations for maximum yield and minimum costs. Precision planting is referred to as accuracy in seed metering, planting depth control and spacing. Precision drilling is an example of precision planting applied to crops planted in rows. Vegetable and small grain production have been the object of studies and experiments in the technology of precision planting (Giannini et al, 1967). An advancement in precision planting has come with the development of punch planters equipped with plungers, dibbles or spades. An early type of punch planter was a plunger type which has been 1 studied experimentally on spacing and depth control (Sawant, 1972). A development in precision planting which could be applied to various types of crops is the spadepunch or revolving spade planter (Shaw and Kromer, 1987). The revolving spade planter has several design characteristics needed for precision planting. The revolving spade planter has the ability to open or dibble holes to the appropriate depth and spacing and to deposit seeds, which is significant to achieve the uniformity of crop growing, the elimination of overplanting, and the reduction of thinning operations. With the improvement of seed quality, the preparation of seed beds or soil holes by planters might be as important as to achieve the desired germination and emergence after planting. Desired conditions for seeds placed in the beds or soil holes are proper contact between seed and soil which is necessary for water movement and sufficient oxygen supply to seeds. The development of a well prepared soil hole by the spade planter design (Shaw and Kromer, 1987) is explained in figure 1.1. The bottom area of the soil hole where the seed is placed features a zone of a notcompacted but simply cut smooth surface (Zone 1) and a zone of a slightly compacted soil surface (Zone 2). Zone 1 is useful to provide a good soilseed contact with enough water movement to seeds under normal soilmoisture conditions. Zone 2 is extremely important to provide enough water movement to seeds under dry weather conditions. These two important zones are obtained by the revolving spade planter constructed with the yaw angle (Shaw and Kromer, 1987). Most of the research on this type of planter has been focused on the design of spade punches and applications of commercially available seed metering devices. To extend the o o "o No Ct Q C) so 00 N +'I 3 C) C) 0 C) C) U) C44 4 performance of the spadepunch planter to the level of high speed precision planting, it is necessary to study seed transport and delivery mechanisms to get the desired number of seeds singulated from a seed hopper and transported to the soil opening spade. And also, it is desired to minimize the number of moving parts on the planter; especially moving parts like doors or valves that contact the soil. The objective of this research is to combine a seed transport and delivery mechanism with a revolving spade planter for high speed precision planting operations. The mechanism will be conceptualized and studied theoretically to find the most appropriate design. The design model will be tested to evaluate the design concept. The major objectives include the following; 1. Theoretical analysis of the design concept of a seed transport and delivery mechanism. 2. Experimental model design of the seed transport and delivery mechanism for a revolving spade planter. 3. Experimental evaluation of a design model. CHAPTER 2 REVIEW OF LITERATURE Planters have three major functions: soil opening, seed metering and placement and seed covering. Precision planting has adopted two different concepts of soil opening: furrows and holes (Kromer et al., 1987). Kromer et al. (1987) reported a hole seeding method originated from the principle of hand seeding where seeds were pushed into the soil. The hole seeding method was also considered to have advantage over the furrow seeding method from the points of view of uniform seed spacing for planting into plastic mulch (Shaw and Kromer, 1987). Seeding tools such as the plunger, dibber, punch or spade have been used for hole seeding (Debicki and Shaw, 1996). Several dibble and punch planters have been developed (Heinemann et al., 1973) including the spade planter, and the latter concept will be addressed in the research. 2.1 SpadePunch Planter The design concept was called the revolving spade planter which was the application of a new hole forming system (Shaw and Kromer, 1987). They reported that spades were mounted perpendicular to the axis of the planter wheel to open the soil and form the seed cavities. And also they suggested that the axis of the planter wheel be designed to be inclined on an angle of 30from the vertical in order to mount a seed metering device as 5 closely as possible to the spades and to facilitate the penetration of the spades into the soil. The most significant feature of the design was the yaw angle 7 of the planter disk wheel. This yaw angle caused cavities for seeds to be formed in the soil and prevented the dragging of seeds out of the dibbled holes when the spades withdrew from the soil. Based on their theoretical analysis and model test on the concept about the yaw angle, a cavity is formed into the crosssectional shape of the end of a very thin ellipse as described and referenced in figure 2.1. The cavity created by the spade was reported to provide a good soilmoisture environment for seeds as described and referred to in chapter 1 using figure 1.1 .To simplify the design and construction of the planter, the inclination angle of the planter disk wheel from the vertical might not be necessary if a seed metering and transport mechanism was made as a part of the body of the planter disk wheel. The CENTRAFLO planter (anonymous, 1978) is an example of a planter whose seed metering mechanism could satisfy the necessity of zero angle of the inclination. The mechanism is called gravity ejection where seeds are metered by a stationary pickup ring on a rotating disk and transported while falling freely by gravity inside the rotating disk grooves to be eventually released into a furrow. The seed spacing on this device can not be easily adjusted and the machine is expensive, so it was not available for evaluation as a delivery system for the revolving spade planter. 2.2 Seed Metering and Transporting Mechanisms Seed metering (Srivastava et al., 1993) is accomplished by two functional processes, which are metering rate, referring to the number of seeds released per unit time from a \ Spade \ hel \ Seed 0 I Displaced Soil 0 Elliptical Path of Spade Open Gate Area Figure 2.1 Rear view of revolving spade planter soil opener(Shaw and Kromer, 1987). \ seed container, and singulation, referring to individual seed placement into soil at proper spacing. Early mechanisms for metering seeds adopted the principle of regulating the volumetric flow rate by changing an orifice size (Srivastava et al., 1993). Usually metered seeds are discharged and flow by gravity into a tube leading to the furrow. The fluted wheel has been used as a seed metering mechanism for the drill seeder (Srivastava et al., 1993). The flow rate of seed in the mechanism is controlled by an adjustable gate and the effective width of the fluted wheel or by the rotating speed of the fluted wheel which is positioned at the bottom of a seed container. The doublerun or internal force feed mechanism (Srivastava et al., 1993) has also been used for grain drills. The rotating rim disk with corrugated inner surface carries seeds from a hopper into a delivery tube in which seeds flow by gravity. An application of the principle regulating the volume flow rate to planter design had to be changed with the introduction of precision planting which was critical in the production of vegetable crops. This led to the development of new seed devices (Giannini et al., 1967) for metering individual seeds. As a first generation of individual seed metering mechanisms, seed plate hoppers had been used to meter individual seeds for precision planting (Richey et al., 1967). Various types of seed plates inside the hopper could be installed to meter seeds. The metering device was classified by the type of plates which were vertical, inclined or horizontal. The metering rate in this mechanism might be considered to be controlled by volume even with improved control methods. As technology progressed, the finger pickup planter (Anonymous, 1968) might be recognized as plateless seed planter which was found to be suitable for planting corn and other large seeds. Each springloaded finger mounted in a rotating disk inside a seed hopper picks up seeds in the bottom of the hopper and only one seed among all the seeds is then passed on as the finger is pushed and held in an indentation of a stationary disk onto a seed belt to be dropped into a seed tube. The rest of the seeds on the finger are dropped and remain in the hopper. This design concept using rotating seed fingers is found as a different form in a recently developed seeder (Chang et al., 1998) in which seed holes or seed loading cells were adopted to pick up seeds. The air planter (Anonymous, 1971) was also introduced and this featured a pressurizedperforated seed drum running at approximately 35 rpm that singulated seeds. Seeds flowing from a hopper into the drum are held at a shallow depth at the bottom of the drum. Each seed orifice on the inner surface of the drum holds a seed by differential pressure until it is released into a seed tube with the help of an external wheel which blocks the orifice on the drum, removing the differential pressure. Other plateless planters were developed about this time including the pressuredisk planters which were equipped with separate seed reservoirs for each planting row. Giannini et al.(1967) reported this design concept and the development of a vacuum seed metering mechanism where the pressure differential was provided by vacuum. The major objective in the planter development has been to improve the pickup effectiveness of the vacuum metering device for small, irregularly shaped seeds. Vegetable crops such as lettuce were difficult to meter because small orifices were easily clogged by particles of dust or materials on seed and caused the seed held on the small orifice to be easily dislodged. On one design the orifices were like hypodermic needles which could be easily matched to the size of the crop seeds. The vacuum pressure mechanism was designed so that each orifice was independently connected to its own vacuum pressure pump cylinder (Giannini et al., 1967). And also they demonstrated a unique feature of the design of a seed positioning wheel which lifted seeds from the hopper to locate the seeds on each orifice to minimize the seed dislodgement from the orifice. The minimization of seed dislodging tendency was achieved by minimizing the relative velocity between the orifice and the seed. Moysey et al. (1988) suggested that volume flow rate provides a better comparison than mass flow rate because of the difference of bulk density in different kinds of seeds. They reported empirical volume flow rate equations according to the design characteristics of hopper and orifice. They obtained the empirical volume flow rate equations for circular, square and rectangular orifices centered at the flat bottom of hopper as Q= 2.05+ 46.21A, gDv (21) and for circular, square and rectangular orifices adjacent to the wall of a flatbottom hopper as Q = 2.20 + 53.04 A. gsD (22) where Q = volume flow rate from orifice of hopper (liter/min.) A, = net effective area of orifice (mm2) De = hydraulic diameter of orifice (mm) g = gravitational acceleration (=9801 mm/sec.2) The application rate in planting operation by volume metering is obtained by the following equation (Srivastava et al., 1993): 10000ooooQp R, WV (23) where R, = seeding rate (kg/ha) Q = flow rate of seeds from the metering unit (liter/sec.) ps = seed density (kg/liter) W = width of coverage of the planter (m) V = travel speed of planter (m/sec.) The volume flow rate for the fluted wheel (Srivastava et al., 1993) is suggested as Q = (24) 60* 106 where Q = volume flow rate (liter/sec.) Vc = volume of each cell (mm3) = number of cells on periphery of fluted wheel n = rotational speed of fluted wheel (rpm) For an individual seed metering mechanism, the theoretical seeding rate is given by the following equation (Srivastava et al., 1993): 10000 Rs = (25) WXS where Rt = theoretical seeding rate (seeds/ha) W = row width (m) Xs = seed spacing along the row (m) For the equation (25), X, is obtained as 60V X = (26) ACn where V = travel speed of planter (m/sec.) kc = number of seeds delivered per revolution of the metering device n = rotational speed of metering device (rpm) Many seed transport mechanisms utilize vertical delivery tubes to carry seeds from the seed meter to the soil opener. On broadcaster seeders, the seeds must be delivered in the horizontal direction and it is necessary to consider the effect of friction between seeds and the surface on which seeds contact (Srivastava et al., 1993). The theory of seed transport for the broadcaster seeders was reported by Cunningham (1963) and Pitt et al. (1982). If seeds are transported from the hub of a revolving spade planter, friction must be taken into consideration. 2.3 Revolving Spade Planter and its Applications The first spadepunch planter, the revolving spade planter developed by Shaw and Kromer (1987), has been a model to study precision planters by researchers and manufacturers for vegetable production and notill field grain seed planting. Debicki and Shaw (1996) developed a spadepunch planter which was equipped with a commercial vacuum seed meter. The unique feature of this spadepunch planter was found in the shape of the spadepunch, which was prismatic in shape with a rectangular base. The prismatic shape was developed by analyzing the motion of the seed from the seed meter to the spade. The partial opening in the base of the punch was used to deposit seed into the soil opened by the side motion of the punch, which was caused by the yaw referred to by Shaw and Kromer (1987). In the research, the mounting position of the vacuum seed meter was experimentally optimized relative to the punch (Debicki and Shaw, 1996). Molin (1996) reported on research of a spadepunch planter for notill operations with a study to optimize the shape of the spadepunches. He particularly studied the width of the 13 punch to minimize the penetration force. He suggested empirical equations of penetration force for the spadepunch 30 mm wide as = 12627+0.919*In(PFI) PF =e (27) and for a 60 mm wide spadepunch wide as P2.0317+0.8791n(PFI) (2 PF = e (28) where PF = penetration force of the spadepunch (N) PF1 = penetration force of cone penetrometer (N) He confirmed that the design concept of the 7 yaw angle (Shaw and Kromer, 1987) was a key design factor to avoid soil adhering to the internal wall of the punch in notill sandy loam soil. He also reported that the planter wheel's inclination angle of 22 was optimum in forming a good shape of hole in notill sandy loam soil, as compared to the 300 inclination angle reported for wet and tilled rough clay soil (Shaw and Kromer, 1987). Studies on the spadepunch planter have been focused on improving and applying the design model of Shaw and Kromer (1987) in the areas such as soil opening and deposition of seeds in various field conditions. Other aspects such as seed metering and transport method, hole shape design, soil deformation in the soil zone created by the spade punch, and seeding depth control mechanism have been pursued in the studies of the spadepunch planter for high speed precision planting operation by the following researchers. Pearce et al. (1996) reported research results about the dibble shape and depth on the germination and spiral root development of burley tobacco seedlings. They evaluated both pyramid and dome shapes of dibbles. The treatment using the dome shaped dibble at a depth of 0.5 to 0.75 inch gave good germination with the least spiral root incidence. Sawant (1972) suggested that the draft required to operate a planter equipped with plungers shaped as long solid rods attached on a wheel be obtained by the equation as T+_ A rh H= i + + dz (29) where H = draft (N) T, = torque due to friction on cam ring holding plungers (Nm) T2 = torque due to metering device (Nm) r, = radius of the planter wheel including plungers (m) A = area of plunger face (cm2) L = plunger spacing (cm) h = depth of penetration (cm) J0h pdz = area under the curve of soil resistance versus depth (N/cm) He also observed that the moisture transfer was improved in the compacted soil zone compared to the undisturbed soil zone and the evaporation above the seed was not reduced, particularly when the hole was only partially filled with soil. The effects of seeding depth and the depth of soil cover in using a drill seeder were reported by Rainbow et al. (1992) and McGahan et al. (1992) in grain farming. Rainbow et al. (1992) studied the relationship of grain yields with seeding depth, soil cover depth and firming, and correct seed placement using different types of soil openers and press wheels with planters. They reported that optimum seeding depths were similar in all types of soil openers but soil firming pressure was significant for the improvement in emergence and plant growth with increased seeding depth, particularly when the seed bed was left very loose by soil opening. McGahan and Robotham (1996) reported an empirical equation as a function of planting depth to estimate potential yield of wheat as the following: y = 59.16+ 20.67x 0.16x2 (210) where y = wheat yield (kg/ha) x = planting depth (mm) From the potential yield estimation function (210), the maximum yield could be evaluated. They used nine drill seeders in the experiment to measure the seeding depth, which was found to be highly variable, ranging from 30 to 100 mm from a planter, on a number of different machines in different soil types. Kromer et al. (1987) reported that the planting spacing in a planter utilizing the principle of the hole seeding system could be calculated by the following equation: 2;r (R, S) PDth = (1 ra) (211) N where PDt, = theoretical plant distance in the row (mm) R = peripheral radius of the imbedding element (mm) SD = seeding depth (mm) N = number of seeding tools in effect on the periphery a =slip They also suggested a modified equation for plant distance considering the factors such as germination rate, machine function and field factor affecting the plant distance as PDSe = GR* F PD,, (212) where PDeff = average of the actual plant distance distribution (mm) GR = germination rate Ff = field factor PDt, = theoretical plant distance in the row (mm) The method to measure the accuracy in planting spacing for planters using a single seed metering device was suggested by Kachman and Smith (1995). They reported the statistical measures such as the mean, standard deviation, quality of feed index, multiple index, miss index and precision. Among those measures, they reported that the mean and standard deviation were inappropriate as tools to indicate accuracy. They referred the quality of feed index to the percentage of spacing more than half but no more than 1.5 times the theoretical spacing, the multiple index to the percentage of spacings less than or equal to half of the theoretical spacing, the miss index to the percentage of spacings greater than 1.5 times the theoretical spacing, and the precision to a measure of the variability in spacing between plants after accounting for variability due to both multiples and skips. CHAPTER 3 THEORETICAL ANALYSIS FOR SEED TRANSPORT AND DELIVERY MECHANISM DESIGN 3.1 Features of a Revolving Spade Planter with Seed Transport and Delivery Mechanism The general design of the spadepunch planter for this study was developed from the version of the revolving spade planter of Shaw and Kromer (1987). Figure 3.1 shows the concept of a revolving spade planter for this study with the hub, seed path groove and seed pocket as a seed transport and delivery system and with the spadepunch as a seed placement system. The seed transport and delivery mechanism could be embedded in the body of the planter wheel disk. This could make it possible to eliminate the inclination angle from the vertical of the first version for structural design simplification. Another advantage of delivering the seed to the wheel at the hub would be the elimination of the problem of synchronizing the seed drop with the movement of the spade as was the situation with the design used by Debicki et al. (1996) and Molin (1996). With these earlier designs, desired seed delivery was only achieved within a certain range of planter speed without adjustment of the seed drop timing. Since there is only relative rotational motion between the planter frame and the wheel at the hub, it was decided to explore the possibility of delivering the seed to the wheel at the hub and then transporting it out radially on the wheel to each spade. The planter wheel disk is ground driven with the angular velocity o following the towing velocity V, of a tractor. The 18 E0 aa Cd) U d, U b c 001 bto al I QEE iU 19 towing velocity VT is assumed to be constant, which results in a constant angular velocity co. The individual seeds metered inside the hub as shown in figure 3.1 enter into the path groove with a small velocity to slide down to the spade. It was initially desired to drop the seed directly from a seed groove into a spade when the latter was at maximum soil penetration. It was desired to transport the seed from the hub to the spade in possibly a quarter revolution of the wheel. After some preliminary analysis, it was found that this was not possible over a wide range of planter speeds, so it was decided to explore the use of some type of "seed pocket" that could receive and hold a seed near a spade and have it positioned to drop into the spade at the time of maximum soil penetration. The initial velocity of the seeds at the moment when the seeds move into the path groove is assumed to be nearly zero in the following design analysis. Since the hub and path groove are embedded in the whole planter disk wheel rotating with the angular velocity o, the hub and path groove are also rotating with the same angular velocity as the planter wheel disk. The sectional width of the path groove is wide enough to accommodate the largest seed. The seeds are assumed to keep contact with the surface of the groove without bouncing in order to prevent being damaged while they are moving through the groove to the seed pocket. 3.2 Coordinate Frames of the Design Figure 3.2 shows coordinate systems related to the planter wheel traveling on the ground. The XiYZ, coordinate system is a fixed reference frame on the ground. The non rotating XYZ coordinate system yawed with angle y about Y, is translating from the A 3 / ~ E I!f *1 2 4C4 K I Hi * * g I. a ~ / i / v V 0 V if C. 21 X,YZ, coordinate frame with the traveling speed, VT, of the planter. The xyz coordinate system is rotating with angular speed co about z or Z axis on the XYZ coordinate system and translating with the traveling speed, V,. The xyz coordinate system is embedded on the planter wheel disk. Since the seed path groove on the planter wheel disk is designed in terms of the xyz coordinate system, it is necessary to define the coordinate systems related to the seed and planter wheel motion. As shown in figure 3.2, the planter wheel disk is positioned with a fixed yaw angle y about the towing direction X, in the moving, translating only, reference frame XiYZ, where the axis X, is parallel to the ground surface and assumed to be horizontal. The origins of the coordinate systems of XY,Z,, XYZ and xyz are made to coincide as denoted by O in figure 3.2. The rotating angle 0 of the xyz coordinate system about the XYZ coordinate system is measured between the x and X axes and between the y and Y axes. When the rotating angle 0 is equal to zero, it is assumed that the inlet of the path groove is positioned on the Y or y axis and the seed should start moving into the inlet with zero initial velocity. Thus, the coordinate conversion between the coordinate systems XYZ and xyz is obtained as the following (refer to appendix A): X cos0 sin90 0 x Y sin cosO 0 (31) or x cos0 sin f 0 X y = sin0 cos 0 (32) z 0 0 1 Z Assuming that the planter wheel disk is rolling without slip, the angular velocity o of the planter wheel disk is expressed as d) (33) Reff cosy where o = angular velocity of the planter wheel disk (rad/sec.) VT = towing velocity of the tractor (m/sec.) Rff = R Dp, effective radius of the planter wheel disk (m) R = radius of the planter wheel disk (m) y = yaw angle (rad) D, = seeding depth (m) The towing velocity for planting operation is assumed to be constant, which results in the constant angular velocity of the planter wheel disk. Since the slip was assumed to be zero, the planting spacing regarding with equation (211) is obtained as, referring to figure 3.1, 2l(R D,) Sp = N p (34) N, where Sp = planting spacing (m) R = radius of the planter wheel disk (m) Dp = seeding depth (m) N, = number of spade punches of the spade punch planter A theoretical analysis for the seed metering and transport mechanism is particularly focused on obtaining the most appropriate shape of the seed path groove since a high speed planting operation with the design concept as shown in figure 3.1 depends on whether the seed could be transported as quickly as possible from the inlet of the groove to the spade. Thus, the path of the seed should be designed to transfer the seed from the inlet to the spade in the shortest time under gravity. The seed is assumed to enter downward into the inlet of the groove with zero or very low initial velocity when the inlet is positioned on the Y axis in the positive direction of the axis. The seed sliding on the surface of the groove is assumed as a particle. The air resistance on the seed will be ignored in the following analysis (refer to table 18.1 on page 188 ofRichey et al., 1961). One of the most important features in the revolving spade planter is the concept of the yaw angle y mentioned with figure 1.1 for the formation of soil hole. To describe the motion of seed and revolving spade, it is necessary to convert the coordinate of the relationships expressing the motion. With the existence of the yaw angle, the coordinate systems of XYZ and XY,Z, are converted in a similar manner referring to appendix A as X cosy 0 sin7 X Y$ = 0 1 0 (35) Z, siny 0 cosy Z Thus, the coordinates between xyz and XYZ, are transformed using the relationships of (31) and (35) as Xl cosy cos cosysin9 siny ]x S= sinO cosO 0 y (36) Zl siny cos0 siny sinI cosy z 3.3 Theoretical Analysis for Feasible Design Cases of Seed Transport and Delivery Mechanism The design of a seed transport and delivery mechanism was intended to achieve a higher planting speed than was possible when seeds are dropped directly into the spades. It is desirable to transport metered seeds in the shortest time from an initial position at the hub to a final position at the spade for a higher planting speed. This path from an initial position to a final position was mentioned as the path groove on the planter wheel disk in figure 3.1. The path can be described as using design data in the xyz coordinate system. When the seed path is observed moving with the same traveling speed, it can also be described using the XYZ coordinate system. The observation of seed motion in the XYZ coordinate system can be transformed by the relationship (3.2) to determine the actual design data for the seed path groove. While the initial position in seed motion is fixed to the inlet of the seed path groove, the final positions could be considered in various ways from engineer's point of view. The first possible final position could be considered a point on Y axis as shown in figure 3.3 to obtain a path of the shortest time, which is noted as design case I. But the second final position could be considered a point on the fourth quadrant as shown in figure 3.5 to determine a path of shortest time, which is noted as design case II. These two feasible cases of design will be considered to determine the best way of design in terms of accuracy in delivering seed into a soil hole and advantage in design and fabrication. 3.3.1 Design Case I Since the final position was selected as a point on Y axis in case I, the solution for a path of a shortest time between the initial and final position is a straight line which is a straight line on Y axis. Thus, the particle motion should be a free fall under gravity without any resistance such as friction between the particle and the path. The straight line is observed on XYZ coordinate system and it should be transformed into the xyz 25 IN etc C) wl, rnU 8A 44cca 0 o Aa coordinate system using the relationship (32) for designing the seed path groove. The first case in design is described in figure 3.3 as the concept that seed entering into the inlet of the path groove falls freely to the final position which could be an inlet position of the spade. The seed enters the groove with zero initial velocity when the inlet reaches the positive side of Y axis. In this case of design, the seed would reach the final position when the corresponding spade is fully penetrated into soil. Thus, the seed would be deposited into the soil hole during the time the spade is withdrawing out of the soil. Since the seed falls freely under gravity, the acceleration of the particle is equal to the gravitational acceleration, g. The velocity of the particle, Vp, observed in XY coordinate frame is obtained by integrating the acceleration as V,p= fgdt=gt+c, (37) where Vp = particle velocity at time t g = gravitational acceleration (9.801 m/sec.2) c, = constant of the integration which is equal to zero by the condition of zero initial velocity of the particle Since the motion of the particle was assumed as a free fall with referring to figure 3.3, X coordinate of the particle position, (X,Y), is equal to zero. And Y coordinate of the particle position at time t is given as Y= Vdt 1 (38) 2gt2 +c2 where the integration constant c2 is determined using the initial value of Y. Since the initial position of the particle is equal to Rh of the hub radius, the constant c2 is also equal to Rh. Therefore, the position coordinate, (X, Y), of the particle at time t is obtained as X=0 1 (39) Y= gt2 + Rh The seed path in figure 3.3 is obtained by the coordinate transformation using the relationship (32) using the coordinate, (X, Y), of equation (39) as x(t) = (Igt2 + Rh)sinO 2 (310) y(t) = (Igt2 + Rh)cos where 0 is equal to cot for constant angular velocity of the planter disk wheel. The solution for case I is shown in figure 3.4 at various traveling speeds. The time required for seed to move from the inlet of the path groove to the spade is obtained from equation (39) as t, = 2(R, R)/g (311) where t, = traveling time of seed from the inlet to the spade in design case I (sec.) R = radius to the position of the seed pocket (m) Rh = radius of the hub, as shown (m) g = gravitational acceleration (9.801 m/sec.2) 3.3.2 Design Case II Figure 3.5 describes the concept of the design of the seed path groove where the seed, particle, slides into the inlet of the path groove with zero initial velocity to reach the spade. The effects of sliding friction and air resistance on the seed are ignored. And also the seed is assumed to reach the spade when the corresponding spade is about to contact C .a .C a .E a E ES 00 0 r o E~ 000.2'. cc I I: b0 I . ... .. . ... . ... ..:. . .. C . . .. . C r > v 0 Nr Cs C~l M C "I 29 the ground surface to penetrate into the soil. The path of the seed motion is designed for the seed to move from the inlet to the spade in the shortest time for the high speed planting operation. In this design, the seed could be deposited in the opened soil hole before the spade starts to withdraw out of the soil, which is an advantage in terms of simple construction design of the planter. The path observed on xy coordinate frame is the seed path groove, and the path observed on XY coordinate frame might be a curved path shown as the dotted curve in figure 3.5. Since the surface of the groove is assumed to be frictionless, the normal force N acting on the particle does not constrain the analysis of the motion. Figure 3.5 shows the particle motion observed in XY coordinate frame. The curved path shown as the dotted curve in figure 3.5 is shown in figure 3.6 with normal and tangential coordinates to the path curve. Since the path, the seed path groove, was intended to have the feature that the traveling time of the particle motion on the path should be minimized, the particle motion observed on XY coordinate frame should be completed in the minimum time. From the particle motion in figure 3.6, Newton's law of motion gives an equation as dV d gsina (312) Substitution of the relationships as dY sina dS (313) dS dt into equation (312) and multiplying V on both sides of the equation (312) gives the P)L o ,~ Ch cry CU Cu 0* C. 0: 0 32 relation as d dY (V)= 2g (314) dt dt Integration of equation (314) with the initial conditions of V(t = 0) = 0 (315) Y(t = 0) = Rh gives the relationship for the velocity as V= /2g(Y Rh) (316) which could be also obtained from conservation of energy. The traveling time from the inlet to the spade is given as = 2dt (317) where J = traveling time from the inlet to the spade t, = time measured when the particle enters into the inlet, considered to be zero t = time measured when the particle reaches the spade Using the following relationship as dS + dXX dt = ( R (318) V 2g(YRh) since the differential arc length, dS, of the path is given as dS = dX2 + dY2 the functional (317) can be written as J = dX (319) Jo 2g(Y Rh) where the coordinate (X2, Y2) as in figure 3.4 for the final position of the particle is used. Therefore, this design problem is formulated as the following optimization problem: Sx, Vl+ y2 minimize J= J dX (320) where the prime denotes differentiation with respect to X. Referring to appendix B, the solution for the path of a shortest time in the problem (320) was obtained as Y= Rh + c3(1 cos) .X=c3(sin) (321) X=C, (f sincf) The solution (321) for the case II is shown in figure 3.7 compared with the solution for the case I in an example of a planter disk with radius 305.31 mm (12.02 inch), which shows the final position close to the Y axis. Both solutions have a common ground that the particle moves under only gravitational force from the initial to final position. But they are different only in the assigned final position. 3.3.3 Consideration on the Theoretical Analysis for Design The final position of the design case II is very close to Y axis as shown in figure 3.7. In the design case I, the final position is given on Y axis. When the final position is assumed to be the spade, it could be very difficult to drop the seed into the spade at time of maximum soil penetration. Probably the seed will not arrive at the exact final position u) U) N C\j No CD N ' b cli . . .) 4 ) .. . cu r 00 W)0 . .. Ci 0* 1 I U) 4 a M, ........ a) LC) ... ...... *... ...... .. ...... .. ...U) cts  LO LO U LO O U LO O L 0 L Lo C CQ C r.: C 35 at theoretically expected time as desired. The seed could arrive at the final position either earlier or later. Thus, it could be considered to use some type of "seed pocket" to hold the seed at the position 1 as shown in figure 3.8. The seed which is held inside the seed pocket will be contained inside the pocket until the position 2 as shown in figure 3.8. If the seed pocket has an open side, the seed could slide down on the inclined surface under gravitational force through the open side. Since it is necessary to control the release position into the spade, the seed sliding out of the seed pocket should be held on the inclined surface with the help of a stationary ring as illustrated by position 3 in figure 3.8. The seed held by the stationary ring will be released at the open end into the spade. This description of the open and closed side of the seed pocket, the inclined surface and the stationary ring will be adopted to design a model for this research. Since the final position of the design case II is very close to Y axis as shown in figure 3.7, it is very hard to expect that there is enough time to drop the seed into the spade at time of maximum penetration. There is no great advantage in the design case II over the design case I. Therefore, design case I will be used to design the seed transport and delivery mechanism. 4. g ( . I *lid is (B S i c a A, W 0 t 0/1 a ~ 1178 Uo g uI Ig g4 u CHAPTER 4 DESIGN OF A SEED TRANSPORT AND DELIVERY MECHANISM MODEL 4.1 Principal Methodology in Design The first design parameters to be considered are planting spacing (S,) and planting speed (VT) for a revolving spade planter. As discussed in section 3.3, the planting speed could be the maximum speed which would be recommended for any seed planting operation with the revolving spade planter. Considering the number of spades (Ns,) and the planting depth (Dp), the radius (R) and the angular velocity (o) of the planter disk wheel are determined from equations (33) and (34) as S, N, R= + DP (41) 2xV, 0 = o(42) S, N, cosy where R = radius of the planter wheel disk (m) co = angular velocity of the planter wheel disk (rad/sec.) VT = planting speed (m/sec.) Sp = planting spacing (m) Nsp = number of spades y = yaw angle (rad) Dp = planting depth SpNp = effective wheel circumference From equations (41) and (42), the design value of the planting depth is fixed for each crop. Then, the number of spades would be determined. Figure 4.1 shows the conceptual feature of a hub in a revolving spade planter. The hub of a radius, Rh, is used to contain a 37 38 seed singulation device from which single or multiple seeds would be released and guided to move into the inlet of the groove under the assumed zero initial velocity. The hub radius should be determined considering the dimension of the seed singulation device and the width (w,) of the groove. And the width and depth (ds) of the groove must be given depending on the size and the number of seeds to be delivered. As shown in figure 4.1, design of the groove needs first to establish the coordinates (x(t), y(t)) the surfaces on which the seeds slide. The coordinates (x2(t), y2(t)) of the surface on the other side are obtained from equations as (refer to appendix C) SIGN(tan a2 (t)) x2(t)= x(t)+ w ,s1+ V1+ tan2 a2 () (43) tana2 () Y2(t)= y(t) W, 1+ tan a2 2( where x(t) and y(t) from equation (310) w, = width of the groove SIGN(A) = +1 when A is positive, or 1 when A is negative a(t) = the angle in radian at time t between X axis and the normal direction at the position of x(t) and y(t) Since a seed pocket is adopted to hold seeds before delivering seeds into the corresponding spade, the motion of the seeds needs no longer to follow the path defined by equation (310). On the path defined by equation (310), the normal force between the seed and the groove path is zero since the seed is falling nearly free through space. However, upon entering the new path of the seed pocket, the normal force between the seed and the contact surface inside the seed pocket could be greater than zero. This normal force greater than zero could prevent the seeds from sliding forward, which means 4 I 12 0 o 0 o, SI Y I) I  I c I "\ \ ".. S o 0.  4" 0 0 0 0i I 0   Soo I +0 4 a 'i 40 that in a critical situation the seeds might stick to the surface inside the seed pocket when a centrifugal force is greater than the gravitational force. Therefore, the position of the seed pocket must be determined to avoid the situation that the normal force between seed and contact surface inside the seed pocket is greater than zero particularly when seed might be positioned at the critical position as shown at the top of figure 4.2. The normal force (FN) acting on the seed at the critical position is obtained as: FN = mRco 2 mg (44) where FN = normal force acting on the seed at the critical position (N) R, = radius to the critical position of the seed (m) co = angular velocity of the planter wheel disk (rad/sec.) m = mass of the seed (Kg) g = gravitational acceleration (9.81 m/sec.2) The seed entering into the seed pocket is observed as a motion following the Yaxis as discussed in chapter 3. Thus it might be reasonable to make the seeds inside the seed pocket hold the lower or bottom position inside the seed pocket in any rotating position, which might be better way to get the seeds ready to slide out of the outlet to be delivered into the spade. This design constraint could be achieved by determining the position of the seed pocket to prevent the normal force in a possible critical position of seed from being greater than zero. Thus, the position of the seed pocket could be determined using the value of R. from equation (44) when the normal force, FN, of equation (44) is less than or equal to zero. As discussed in the design concept in chapter 3, the seed held in a seed pocket should be released into a spade at the proper time or position for uniform planting depth. It might 0 3 0. zo > 4 p E 3 )~x a8 S o 0 / 0o /0 F U U; be necessary to release seed at a proper position of the rotating planter wheel disk, for example a proper angular position (0,) as shown in figure 4.3, to place the seed into a soil hole opened by the revolving spade. The proper angular position is also related to the design and construction of a device called the stationary ring shown in figure 4.3 which would retain the seed on the rotating disk until being released into the spade after sliding out of the seed pocket. The release angular position (0,) is obtained from the following relationships (45); X(t) = R, sin 0 Rot cos0, 1 (45) Y(t) = R, cos s + Rct sin 0, + gt2 2 where X(t) and Y(t) = position coordinates of the seed after leaving the stationary ring observed on XY coordinate frame R, = inside radius of the stationary ring 08 = angle between Y axis and the edge of the stationary ring, which is equal to Otf where tf is a time measured at the moment of the spade center line passes the Y axis and time, t, is zero at the moment of the seed leaves the edge of the stationary ring o = angular velocity of the planter wheel disk t = time measured from the instant when the seed is to leave the edge of the stationary ring g = gravitational acceleration Using the relationships (45) to obtain a proper value of 0,, some conditions should be considered for the best planting operation which is satisfied by proper delivery of seeds into the soil hole opened by a spade. As shown in figure 4.3, the shape of a spade adopted in this research has a open gate in the opposite side of the spade side face which pushes the soil to open the soil hole by the function of the yaw angle discussed in section 3.1 and shown in figure 2.1. The seed moving inside a spade after being released from the stationary ring must reach the gate area after the gate area is fully engaged in the soil as shown in figure 4.3. This condition in obtaining the proper value of the angle, 0s, can be described as a constraint in simulating the relationships of equation (4.5), as illustrated in figure 4.3, as X(t)2 + (t2 < (RW d when O(t) > 0 (46) X(t)2 + Y(t)2 (R d ) when O(t) < O (47) X(t) > 0 (48) where R, = radius of the planter wheel disk dg = open gate height of a spade 0(t) = cot where t is measured from the instant of the seed leaving the edge of the stationary ring co = angular velocity of the planter wheel disk 9, = angle measured between Yaxis and the spade center line passing to the center of the planter wheel disk at the time when the open gate of the spade starts to be fully engaged into the soil as shown in figure 4.3 4.2 Model Design and Preparation for Experimental Evaluation As discussed in the design methodology, initial design requirements for a specific crop should be given for the design of the seed transport and delivery mechanism for the revolving spade planter. The initial design requirements for a specific crop include a maximum planting speed (VT), a required spacing (Sp), and a planting depth (Dp). Given these data shown in figure 4.4, the design could proceed to determine first the radius of the planter wheel disk which determines the basic shape and size of the planter. The number of the spade (Nsp) is arbitrary initially in the design process and is determined in the relation with the width of the spade since there should be enough space between INITIAL DESIGN DATA : Planting Speed(VT) Planting Spacing(Sp) Panting Depth(Dp) Number of Spade(N ,) Hub Radius(Rh) min. and max. Spade Width(wsP Compute the Effective Radius (Rx ) Ns, = Np 1 Nsp = Np/2 of the Planter Wheel Disk RP = min. ofRP no , e ma Compute the Design Data of the Groove: mayesx. (x, y) and (X21 Y2 when R2Z = x2Z + y2Z, (x0, 20) = (x2 y2) R= Rh= +AR ,bsp tan'(x20/y2o)> s O Compute: (x, y), (x,, yz), and (x,, YO)S Figure 4.4 Design procedure for the seed transport and delivery mechanism. neighboring spades, which is explained as the relationship; ebsp > esp (49) As shown in figure 4.5, the angle, Obsp, between the center lines of the neighboring spades is obtained as 2)r Obsp = N (410) sP and the angle, Osp, for each spade is obtained as, considering ground clearance C,, S= 2smi (411) 2(R, Cg,) where ground clearance Cg = Rf R, (refer to figure 4.5) Wsp = the width of the spade Rff = the effective radius of the planter wheel disk After the effective radius with the proper number of spades is determined, the angular velocity of the planter wheel disk is obtained by the relationship (42). The radius, Rh, of the central hub is initially made large enough to accommodate a device supplying seeds into the inlet of the seed groove. However, as shown in figure 4.1, since it is necessary to have an appropriate circumferential space where seeds are staying just before sliding into the groove, the radius of the hub should be determined under the consideration of the groove width and the circumferential space. The appropriate circumferential space is described by the angle, 08,, in figure 4.1 which should be determined and given according to the size and number of seeds supplied into the groove at one time. If the initial radius of the hub is not large enough to create the required circumferential arc space as shown in figure 4.1, the radius of the hub should be increased o U, U .. .. . until it could create the space. To determine the appropriate hub radius, the coordinate (x2, Y2) for each coordinate (x, y) should be computed using equation (43) until the coordinate has the relationship as Rh = X2 + Y22 (412) And then, the angle (0,,) is checked as 2r x = tan 2 (413) to see whether the angle is enough for a specific seed. For this experimental model design to use bean and corn seeds, minimum value of the angle (0s,) was 6 considering the size of those seeds. The seeds' size can be compared with the corresponding circumferential arc (Sa,) to the angle using the following relationship: Sarc = OtRh (414) After the hub radius is determined, the seed groove is to be determined by obtaining the coordinates of (x, y) and (x2, Y2). Next it is necessary to check the critical radius (Re) in equation (44). The possible center position (xos, yo) of the seed pocket must be determined so the relationship RC = Rpk + VXo2 + yos2 (415) is satisfied where Rpk is a given radius of the seed pocket. When the relationship (415) is satisfied, the process of determining the shape of the seed groove and the seed pocket position is finished. For the model design, the following data were used; 1. width of seed path groove: 12.7 mm (0.5 inch) 2. diameter of cylinder hole for seed pocket: 50.8 mm (2.0 inch) As shown in figure 3.8 to describe an idea of a seed pocket, the seed motion following the positions which were noted as position 1, 2 and 3 in figure 3.8 could be a motion following the position p2, p3 and p4 as shown in figure 4.6. The motion following the position p2, p3 and p4 could be a motion following a spiral. When a seed sliding in the groove reaches the seed pocket (position p2 in figure 4.6), it should be kept sliding in the spiral groove under its own gravitational force so it progresses in the positive z direction as shown in figure 4.6 while the planter wheel is rotating. As it progresses through the spiral of the seed pocket (from p2 to p3 and from p3 to p4), it reaches an appropriate position to be released into the exit groove which transports it to the spade. If the seed arrives prematurely at the radius of the wheel disk, it may be held by the retainer ring until the appropriate time for it to be released into a spade. After it was concluded that a seed pocket would be desirable to carry a seed or seeds for nearly three quarters of a planter wheel revolution until they could be discharged into a spade, the question was what design would be appropriate. Several features were required for a satisfactory design and these included simplicity and some means of preventing the seed from falling back toward the hub when the spade wheel had turned about half a revolution after the seed initially entered the seed groove. The idea of incorporating a spiral path into the seed pocket as shown in figure 4.6 was developed. With this design, seed could travel radially away from the planter wheel hub through a seed groove and enter the seed pocket spiral while the wheel was turning. In space the spiral would actually rotate and carry the seed 9< / . o I:z a "\ ^" I:, O U \0 *. \ou ': 4)*T (a : 5 4 t.. ** ** y IO .. * / \ " y~ ...................... in the positive z direction and trap the seed so it couldn't fall back toward the hub. The spiral could be designed so that the seed could be discharged into an exit groove that would carry it radially out to an individual spade. To provide for timely delivery of the seed into the individual spades, an adjustable, stationary retainer ring could be used. The retainer ring provides adjustment of the final drop into each spade. In model design, a left hand spiral which is shown schematically by a wire frame model as shown in figure 4.7 and the photo of the solid model is shown in figure 4.8. For the design model, the following data were fixed to develop the helix: 1. major diameter (Do) = 50.8 mm (2.0 inch) 2. minor diameter (D,) = 19.05 mm (0.75 inch) 3. lead in axial direction for 2700 rotation angle (0), L, = 19.05 mm (0.75 inch) The shape of helix as shown in figure 4.7 is obtained using the following relationship: Do x= cos0 2 Do sin0 y= sm0 2 (416) 2 = tan( ) 0.75;rDo z= 125 Do tan2 where x, y, z = coordinates in figure 4.7 X = helix angle The left hand screw has 25.4 mm (1 inch) pitch, 9.04306 helix angle and 50.8 mm (2.0 inch) outside diameter with 19.05 mm (0.75 inch) inside diameter. After the seed moves to the end of the spiral described by the outdirection in figure 4.7, it is necessary that the seed be released to the exit groove. The seed moving into the  o 0 i0 * 2 .. L 1 T LA 0 LO c1i 0 r z ; : . /.. ... . ; ; ;. ;I /.. .. .. : ' ~"~""........... I 1 i 54 exit groove is sliding and reaching to the inside wall of the stationary ring. At the end of the stationary ring, the seed is no longer retained and is dropped into the open top of the spade. When the seed is released at the end of the stationary ring, the corresponding spade is beginning to engage the soil to open the soil hole. The seed released at the end of the stationary ring is falling free inside the open space of the spade to be delivered into the bottom of the soil hole. The seed should contact the bottom of the soil hole before the spade starts to leave the ground after full penetration into the soil, as was discussed with equation (45). The final position of the seed on the bottom of the soil hole after release from the end of the stationary ring was plotted to obtained a best release angle 0, shown in figure 4.3. From figure 4.9, the release angle of 31.5 was selected to design the model for evaluation as shown figure 4.11. This model for the revolving spade planter was designed using a maximum planting speed of 8.0 km/hr (5 mile/hr), after considering speeds that many planters operate at of about 4.8 km/hr (3.0 mile/hr). A design for corn planting was modeled with the plant spacing of 16.5 cm (6.496 in) and the planting depth of 5.08 cm (2.0 in). The planter wheel disk based on the design featured in figure 4.10 is shown in figure 4.12 to show all seed path grooves, seed pocket holes and exit grooves. The planter wheel disk and spade of the working model as shown in figure 4.11 was fabricated with plexiglas to observe the seed motion. The spiral pocket is made of "Delrin". The rotating speeds of the planter wheel were adjusted by an electrical motor driven ZeroMax variable speed drive. The rotating speeds were measured by ZIVY speed indicator reading by rpm. The evaluation was focused on whether the motion of seed followed the design concept by examining the video image of the motion. First, an 55 eu!l pl!os tG1eu!pJooo A to to to LO LO) t LO to Co C) c,c co c t , Lo t Lo co c6 N C to to LO to CV) .. .. .. ... ... .. .. .. .. .. .. . Cr) 03 : .. .. .. . .. C 0 .. .~ . .. .t o.. . C 0 1 14 .............. .. ... ... ... ... ...... 0) S .. . .. . .. . .0. L.) ............ .... .... .. . to . 1 C14 00 ouNl to: to p e 0 U!j P8IO vUpOO ^" o N 0 *S r~ oi a; *" m a rwovo v >r> * I, II * ^sgS^" ^ II I1 11 I r ^^i^ ~....................................... co I .,. 00 N ^OtM 0 00' %` 9  .1 II II.I II 0 a. A 40)v 00 o C., It to ci a.) 3 au i o a) 0 r: o ,3, 57 aa) ~. a) cFs Q) ) I' 0 a a C.) Ii 4h P ~I~~CC~ C IL% C . a)P ,~9s~s~8~~a) a) zi4~ E ~BC~ PU, a)J 58 00 (0 o I t ? I 7 I I ,  I.......~! ~ ..........., , cr ....... Go cli C~ oC/ I D 0 0 j C 59 artificial seed was used for the evaluation. Later seeds including corn and bean were used to take images of their motion during operation of the apparatus. Since the design speed was 8.0 km/hr (5 mile/hr), the evaluation tests were conducted with the planting speeds of 8.0km/hr (5 mile/hr), 7.2 km/hr (4.5 mile/hr), 6.4 km/hr (4.0 mile/hr), 5.6 km/hr (3.5 mile/hr), 4.8 km/hr (3.0 mile/hr), 4.0 km/hr (2.5 mile/hr) and 3.2 km/hr (2.0 mile/hr). CHAPTER 5 RESULTS AND DISCUSSION Since the seed transport and delivery mechanism was designed based on the maximum operation speed of 8.0 km/hr (5 mile/hr) for the revolving spade planter, it was also evaluated at speed ranges lower than the maximum operation speed. The operation test to evaluate the design concept was conducted with several operation speeds as 8.0 km/hr (5 mile/hr), 7.2 km/hr (4.5 mile/hr), 6.4 km/hr (4.0 mile/hr), 5.6 km/hr (3.5 mile/hr), 4.8 km/hr (3.0 mile/hr), 4.0 km/hr (2.5 mile/hr) and 3.2 km/hr (2.0 mile/hr). The seed path groove in the mechanism model was first evaluated visually with video images captured every 1/30 second of the seed movement. The artificial seed was made of a plastic "Delrin". The sliding motion of the artificial seed following a path in the grooves was compared to theoretical motion along the Y axis at the design speed of 8.0 km/hr. The positions of an artificial seed were determined by examining sequential video images as the seed progressed from the hub to the spiral pocket at a planting speed of 8.0 km/hr. The path of the seed was compared to the theoretically expected drop and is shown in figure 5.1. Measurements were made of the Y coordinate position of the artificial seed for ten passages of the seed and these are given in table 5.1. Figure 5.2 shows the video images of the motion of the artificial seed at the design speed of 8.0 km/hr. They show very stable motion following the path groove by moving very close to the Yaxis. 61 d A . So I TO E 0o   o o I G2 0 "0 I IA I i 4 ^ . ^ '\  _ 2 I = 00 0 'i N S 0 vi *q 0 0 0 e ? 000 SIf 0 00 I 0 rf  Soo fm N 00 If o o o '* ^ 00 I t 00 S 00 0 N 00; in ad g0\ s 412 00 0` 0 0 0 H o ?m b0 0 0006 oEo 00 N o0 as EE 0 E 0 00 e E EE 0 000 0 0 0 00 00 Si li a s  5 o4 0 0S2 ^ *" e s c "" ^' O M r f CB OrCC r $g  .^ e c ^ swos Css o'^^^^uSa h ? ~~~S3oS0!~N S6 3o 3 i E~^ o = N Y (1) at time t = 0/30 sec. (1) at time t = 0/30 sec. (2) at time t = 1/30 sec. Figure 5.2 Artificial seed motion at the planting speed of 8.0 km/hr. (3) at time t = 2/30 sec. Seed . (4) at time t = 3/30 sec. Figure 5.2 Artificial seed motion at the planting speed of 8.0 km/hr (continued). See (5 (5) at time t = 4/30 sec. (6) at time t = 24/30 sec. Figure 5.2 Artificial seed motion at the planting speed of 8.0 km/hr (continued). Mwww ) L ~PL~L~'~ / ~"' f (7) at time t = 25/30 sec. (7) at time t = 25/30 sec. (8) at time t = 26/30 sec. Figure 5.2 Artificial seed motion at the planting speed of 8.0 km/hr (continued). (9) at time t = 27/30 sec. (10) at time t = 28/30 sec. Figure 5.2 Artificial seed motion at the planting speed of 8.0 km/hr (continued). Seed (11) at time t= 29/30 sec. (12) at time t = 30/30 sec. Figure 5.2 Artificial seed motion at the planting speed of 8.0 km/hr (continued). (13) at time t = 31/30 sec. (14) at time t = 32/30 sec. Figure 5.2 Artificial seed motion at the planting speed of 8.0 km/hr (continued). 70 The positions of the artificial seed were measured from the center of the hub at each time as in figure 5.1. The differences between the theoretical distances and the mean distances in table 5.1 suggest some contact between the artificial seed and the groove surface, particularly at the time frame of 3/30 second. As discussed in chapter 3, the seed motion on the groove surface was expected to have a nearly zero normal contact force. The difference between the theoretical value and measured value of the travel distance could be understood as some existence of contact between the seed and the sliding surface of the seed path groove. From table 5.1, the maximum mean difference from the theoretical position is 3.5 mm (0.138 inch) for the position at time t = 3/30 sec. This difference of distance is equivalent to seed moving time difference of 0.004 sec, which could be considered acceptable. Based on the observation that the final motion of the seed entering into the seed pocket was timely, the difference might be acceptable. Entering motion into the seed pocket with the error of 1.954 % might be understood that seed could avoid some damage caused by bumping or bouncing off possibly caused by untimely entering into the seed pocket. The seed motions during the remainder of the tests at lower operation speeds are referred to appendix D, which show an existence of sliding motion under the positive normal force between the seed and the groove surface as expected in the design analysis from figure 3.4. In order for the seed to be placed into the soil hole without being damaged, the seed should be released into the spade from the end of the stationary ring before the center line of the spade leaves the Yaxis as shown in figure 5.2. As in the photographs of figure 5.3, the seed is observed to reach the bottom line of the spade before the spade reaches 71 x C* C (u __ __M_ __ (0d '' . .. C ) . ....... ........ o ~ . . I . .. . vv .. . HIC\ l . . CO cli C0D 0 w to 04N 0 N l CD co 0 N Q C.0 i  A~ 0 P N4* C4. *4 t *1 OX + vvo D I . .... .. ....... .. .. .. .... .... ..... \ \ x . ... \ .: . .\ .*X \ .X\ \. : ,'. ...* ..* *" ~... ;...' x \ \ . f.\ .:.. "N S i:.... ., : i it 0(0 o 0 C, "0 El o c c 0 ' S >T r . . : .. : .. . maximum penetration in the soil. This observation could be interpreted as a satisfactory delivery and placement of the seed into the soil hole. In figure 5.3 the seed motion after release from the end of the stationary ring are in good comparison at each corresponding position with the theoretically expected positions. Figures 5.3 and 5.4 show data plot from the evaluation of seed delivery into the soil hole after seed release from the end of the stationary ring at the design speed. The data plot on figure 5.4 shows that data of the evaluation test spreads within the range of 5% (dashed line plot) from theoretical expectation (dotted line plot). The design of the seed metering mechanism was based on assuming a seed as a particle as discussed in design analysis of chapter 3. However, crop seeds are all different and irregular in shape. Thus, tests at a design speed of 8.0 km/hr (5 mile/hr) were also conducted to see the versatility of the performance with crop seeds as shown in figure 5.5. The bean seed is similar in shape to the artificial seed in dimensions and weight. But the corn seed is very irregular and flat in shape. The lettuce seed was considered but was not tested because of its size. The lettuce seed which is tiny, needlelike and light weight might be applicable to this mechanism if coating on the seed changes the shape. Figure 5.6 shows a bean seed moving on the groove, which shows very close positions to Y axis. Test of corn seed shows a different feature form what was observed in the tests of the artificial seed and the corn seed. Figure 5.7 for test of corn seed shows seed positions on the left side of Y axis, which could be interpreted as a retarded motion. The retarded motion might be caused by the flat shape of the corn which could result in more contact area and more friction force. The artificial seed and the bean seed are similar in round 74 shape as shown in figure 5.5, which means that there are more rolling motion than sliding motion in the corn seed. However, in delivery motion into soil hole, both bean and corn seeds show satisfactory results as shown in figure 5.8 and 5.9. As understood in equation (45), the delivery motion into soil hole is not related with the shape of a seed. eL) ~II II lED~ ~ a 4L T A nI a oo i '^ f7P Figure 5.6 Bean seed motion on the seed path groove at the planting speed of 8.0 km/hr. Figure 5.6 Bean seed motion on the seed path groove at the planting speed of 8.0 km/hr (continued). Figure 5.6 Bean seed motion on the seed path groove at the planting speed of 8.0 km/hr (continued). Figure 5.7 Corn seed motion on the seed path groove at the planting speed of 8.0 km/hr. Figure 5.7 Corn seed motion on the seed path groove at the planting speed of 8.0 km/hr (continued). Figure 5.7 Corn seed motion on the seed path groove at the planting speed of 8.0 km/hr (continued). [fRELEASE # 1 'RELEASE #1 SRELEASE # 2 I1 RELEASE # 2 Figure 5.8 Bean seed delivery motion inside the spade after being released from the end of the stationary ring at the planting speed of 8.0 km/hr. 83 RELEASE # 3 RELEASE # 4 Figure 5.8 Bean seed delivery motion inside the spade after being released from the end of the stationary ring at the planting speed of 8.0 km/hr (continued). 84 I RELEASE # 1 r   I RELEASE # 2 Figure 5.9 Corn seed delivery motion inside the spade after being released from the end of the stationary ring at the planting speed of 8.0 km/hr. 85 !RELEASE # 3 I i RELEASE # 4 Figure 5.9 Corn seed delivery motion inside the spade after being released from the end of the stationary ring at the planting speed of 8.0 km/hr (continued). CHAPTER 6 CONCLUSIONS A seed transport and delivery mechanism was designed with the concept of free fall in gravity and evaluated to show the feasibility of the design concept with the model test. The most important feature of the design concept was whether it worked at high planting speed of 8.0 km/hr (5 mph). Seed damage was not evaluated but it appears that this design should handle seed gently. The design concept was theoretically evaluated on a few feasible theoretical cases and a typical case was chosen and evaluated. This design and model was compared to the current design of the revolving spade planter which has been equipped with a relatively complicated seed transport and delivery mechanism. As predicted theoretically, the mechanism was compatible with the original revolving spade planter design and can operate at higher speed. Thus the mechanism could work under any variation of traveling speeds. Based on the results and discussions, the following conclusions were drawn: 1) The seed transport and delivery mechanism can be adopted to the current revolving spade planter to achieve a high speed precision planting machine. 2) The seed path in the mechanism could be designed to the maximum speed limit which might be desired in a planting operation. 3) The maximum mean difference from the theoretical position in seed motion in terms of 87 the displacement was 3.5 mm, which is equivalent to time difference of 0.004 sec. This difference can be acceptable, considering the overall accuracy of machining the groove and operating speed because the actual planting will always be operated a little lower that the design speed, the highest speed. 4) Small seeds in physical dimension might be used in the form of pellet to be planted with this mechanism. CHAPTER 7 RECOMMENDATIONS FOR FUTURE STUDIES This research project to develop a seed transport and delivery mechanism for a revolving spade planter might be continued to bring the machine to an operational field version. To accomplish this, the following might be recommended for future studies on the revolving spade planter with the seed transport and delivery mechanism: 1) A variable traveling speed control system might be valuable to study the functionality of the mechanism to study the simulation of the virtual situation of the field operation. 2) To perform all of the development process in laboratory, a soil bin for planting might be prepared to evaluated the field adaptability of the whole system of the revolving spade planter. 3) Physical properties such as friction coefficient of seeds might be evaluated with the materials which would be used for the seed groove. 4) For the case of planting a pellet seed, the study of the pellet material must be followed with selection of the design material for the seed path groove. 5) The formation of the soil hole must be analyzed in terms of compaction, related with the shape of the spade. 6) The shape of the spade must be optimized in terms of the resistance in traveling motion and the seed delivery motion inside the spade. 89 7) Finally, the soil covering tool might be studied to provide the best condition for germination and emergence of seeds. The firming pressure might be varied according to the soil condition which might be measured mechanically or electrically. APPENDIX A COORDINATE TRANSFORMATION S unit base vector: / I, J : for XY coordinate system " / i, j : for xy coordinate system o/ ~I x X / I X i .... 5 Y (XMY) y, ,y )( Figure A.1 Rotation about coordinate axis The coordinate system xyz results from the rotation ofZ axis about the coordinate system XYZ with the directional angle 0 as shown in figure A. 1. The position vector r in figure A. 1 can be represented using unit base vectors of both coordinate systems as r = XI + YJ = xi + yj (Al) Using the relationships of the unit base vectors as I = cos0i sinOj (A2) J = sin0i + cos0j , the position vector is expressed as r = XI + YJ = (Xcos0 + Ysin0)i + (Xsin0 + Ycos0)j (A3) Comparing the relationships (Al) and (A3), coordinate transformation between XYZ 91 and xyz is obtained as x cos sin 0 X y sin cos 0 z 0 0 1 Z or (A4) X cos0 sin9 0 x Y = sin cos 0 jy Z 0 0 1 z APPENDIX B SOLUTION FOR THE DESIGN CASE II The design problem is formulated as the following optimization problem: x2 V1+Y2 minimize J= R )dX (B1) where the prime denotes differentiation with respect to X. Since the necessary condition for the existence for a minimum value of the functional (B1) is the vanishing of the first variation(Weinstock, 1974), i.e. 6J = 0, the variation process for Y gives the Euler Lagrange equation as 9F d( dF Y d (B2) dY dX \Y) where the function F(X;Y,Y') is the integrand in the function (B2) as F = (B3) V2g(Y Rh) The EulerLagrange equation (B2) becomes 2(Y Rh)Y" + ,2 + 1 = 0 (B4) Multiplying Y' on the both side of equation (B4), equation (B4) becomes equivalent to the following: [(Y Rh Y')]0 (B5) Integration of equation (B5) with using integration constant 2c results into the following: S 2c (Y Rh) Y R, F Y Rh(B6) dX Y R, dY 2c (Y Rh) From equation (B6), the coordinate X of the path is obtained using X(t=0) = 0 as X = 2c (YRh dY (B7) To evaluate the integration (B7), a new parameter P (Weinstock, 1974) is applied to change Y as Y= Rh+ 2csin (B8) where c3 is a constant to be determined using the known coordinate of both end points. Substitution of equation (B8) into the integration (B8) gives a solution as X = c(f sin/l) (B9) Thus, the path observed on XY coordinate frame is expressed with the relationships (B8) and (B9). Therefore, the seed path groove is obtained by the coordinate transformation as x(t) = c(f sinfl)cos0 + [Rh + c3(1 cosf)] sin0 (B10) y(t) = c(l sin/)sin0 + [Rh + c3(1 cos/)] cos0 where 0 = cot APPENDIX C SOLUTION FOR THE COORDINATE (x2, Y2) e,: tangential unit vector S e,: normal unit vector ," w, : distance between (x,, y,) and (x2, y2) e. I ', e, ~ Ss / i\ I S(/ Y2) // ", (x,yz y, e, , S(X2, Y/ dy ;. a2 i' dy dx When tana, < 0 I e, SWhen tana, 0 +y Figure C. 1 Coordinate relationship between (x, y) and (x2, Y2) The position coordinate (x2, Y2) of the surface on the other side is apart from the seed path coordinate (x, y) with a distance w, which is a width of the seed path groove. When tan a2 is greater or equal to zero, the following relationship is obtained; dx tan a2 (Cl) dy The coordinate (x2, Y2) is obtained as (C2) y2 = w sina2 And also using the following relationships as 1 COSO2 /1 + tan2 a2 n a2 (C3) sin a2 V1+ tan2 2 Substitution the relationship (C3) into (C2) gives the coordinate (x2, Y2) as 1 X2 = x+ W, T a )' W +tan2a2 Y2 =yws l 2 1+tan2 2 where tan a2 20. When tan a2 is less than zero, the following relationship is obtained as dx tan=  dy (C5) tan/f = tan(r a2) where tan 13 20. From figure C.1, the coordinate (x2, Y2) is obtained as x2 = x w, cos/ (C6) y2 = ws sin/ The relationship (C6) can be given as 