Monitoring the Performance of Grain Drill on-the-go for Robot Tractor

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1 Monitoring the Performance of Grain Drill on-the-go for Robot Tractor Ahmad A. Al-Mallahi 1 *, Kataoka Takashi 1 1 Hokkaido University, , Sapporo, Kita 9 Nishi 9, Research School of Agriculture, Sapporo, Japan *Corresponding author: Ahmad A. Al-Mallahi. ahmad@bpe.agr.hokudai.ac.jp Abstract The performance of a grain drill was evaluated and perspective to developing it for the use by robot tractor was discussed. The grain drill discharges seeds and fertilizers from 20 and 10 feeding systems respectively. The uniformity of the discharge of seeds was examined by continuous running of the machine and sample collection. Results indicated that although variation in the discharge does occur, the variation did not exceed 10% after sowing 2,025 m2 of the field. This indicates the possibility of estimating the overall flow rate of all the feeding systems by monitoring two of them only which would reduce the costs in developing an entire grain drill monitoring system. Key words: Flow rate, Light sensor, Robot tractor, Variable Application 1. Introduction A grain drill opens a small furrow in which it drops seeds and fertilizers in a flow rated by feeding systems. It is usually propelled by a tractor while the metering valves are controlled by a gear system connected to one of its tires. The grain drill has two hoppers; one for the seeds and another for the fertilizers. The bottom of each hopper contains a number of the feeding systems which are intended to discharge seeds and fertilizers through tubes uniformly. Theoretically, the amount of seeds and fertilizers per unit area can be estimated using calibration curves provided by grain drill manufacturer. Most of the calibration methods relate the amount of seeds or fertilizers discharged with the number of rotations of the tires of the grain drill, so that the amount will be uniform per unit area even if the speed of the propelling tractor changes. However, in practice many factors such as slips of the tires and blockages of the discharge tubes due to clods or stones may affect the uniform flow of the seeds and fertilizers. This means that regular checks by the operator to the amount remaining in the hoppers should be performed to assert continuity of the seed distribution. Recently, autonomous tractor operations have been researched (Scarlett, 2001). This means the need to perform the regular checks on the flow rates and the amount remaining in the hoppers autonomously. In other words, it is demanded to develop a monitoring system on the grain drill using suitable sensors, which would be followed by a communication system between the grain drill and the tractor so that the tractor can be instructed when the amount of seeds or fertilizers drop in the hoppers or if any blockages in the discharge units by clods or stone occurs, etc. Since the grain drill has wide hoppers with multi feeding systems and discharge tubes, monitoring each system using independent set of sensors might be very costly and affect the future perspective of using such monitoring system in the future for economical reasons. Therefore, finding the suitable sensors and optimizing their numbers is a challenge which is going to be tackled in this research. The objectives are; to determine the kind of sensors required to monitor the amount of seeds in the hopper, the flow rate and the existence of any obstacles in the discharge tubes and to carry out a performance test for the grain drill to optimize the number of sensors required.

2 2. Materials and Methods 1. Grain drill The grain drill used in this research is TUME (KL, 2500). Figure 1 shows a back view of the grain drill which is 2.5 m wide with 10 and 20 discharge units for fertilizers and seeds respectively. It is designed to sow all kinds of seeds including cereals, oil plants and grass mixtures. For fertilizers, it is designed so that it will work well with granulated fertilizers but not with pulverized ones. The feeding system consists of a feeding chamber separated from the hopper by a locking plate, a flute roller, driven by the tire of the grain drill, and a spring loaded bottom valve. The bottom valve holds a certain amount of seeds while the flue roller pushes the seeds off the bottom valve toward the discharge tube by its fins. The rate of seeds discharged is determined by the size of the fins and the rotational speed of the roller. Theoretically, the amount of seeds can be estimated by the rotation of the flute roller. However, deficiencies of the operation caused by slips of the tires and wears of the springs may reduce the accuracy of the estimation. The bottom valve regulating lever is adjusted according to the variety of the seeds. The feeding roller rotates proportionally with the tire so that a constant amount of seeds will fall in the unit area as long as the feeding rate is the same. The feeding rate itself can be adjusted by a hand wheel in a scale of 100 increments. In the bottom part of the grain drill, there are discs which open furrows for the placement of the fertilizers and seeds. Also, the seed coulter spring loading can be adjusted to cover different kinds of soils and plants. In addition, press wheels are used to assert the emergence of the seeds inside the furrow. The placement depth for fertilizer is adjustable for applications on the surface directly until 120 mm depth in the soil. 2. Perspective of developing monitoring system In applications using robot tractor, the main parameters which should be informed to the tractor are the continuity of the flow, the uniformity of the flow, and the amount of seeds and fertilizers remaining in the hopper. This will inform the tractor about the time and the location at which the grain drill hoppers should be refilled. As a first step, a method to estimate the flow rate of the seeds leaving the feeding system was considered. In fact, estimating the flow of seeds was tackled in different researches in the past. More recent researches have discussed the use of optical sensing such as Swisher et al (2002) who designed and tested a laser sensor which could measure granular fertilizer flow in an air stream in high accuracy rates, and Grift and Crespi (2008) who tackled this issue using laser sensors to count granules. Figure 1. Back view of the grain drill when attached to tractor

3 On the other hand, a new fiber sensor is introduced and tested in this research work. Besides being cheaper than the laser sensors, fiber sensor has the advantage of having constant emission width regardless the location of the reflection point. This means the error in estimating the size of the falling seed when it intersects with the emitted light anywhere within the tube will be avoided. Figure 2 shows the fiber sensor (KEYENCE, FU-E40) which was placed so that the falling seeds will interrupt the light transmitted. The width and the thickness of the beam of light emitted by the sensor are 40 mm and 3 mm respectively. Once seeds interrupt the beam of light, a change in the output voltage of the meter is detected in a frequency of 10 Hz. Figure 2. Fiber sensor which consists of light emitter and receiver placed around the feeding system to detect falling seeds Inside the hopper, another sensor is suggested to estimate the level of seeds inside. Since the hopper is very wide, estimating the level should be obtained by placing the sensors in selected places and predicting the level via a calibration method. 3. Performing grain drill basic test In order to optimize the application of the sensors, the performance of the grain drill had to be evaluated. This included estimating the amount of discharge at different distances and the distribution of the seeds from the different feeding systems. The discharge tubes were replaced with Plastic containers placed underneath 9 feeding systems to collect discharged seeds. In one of the feeding systems, the fiber sensor was placed to find the relationship between the weight of seeds and the output of the fiber sensor. The grain drill was set to run at a constant speed of 1 m/s throughout the test. However, the distances which were covered varied between 10, 30 and 50 m. The amount of seeds collected in each container was measured using a scale after each run. Also, 3 different readings of the hand wheel were chosen to investigate the variation in the distribution at lower and higher flow rates. 3. Results and Discussion Figure 3 shows the amount of seeds discharged from one feeding system (No. 5) in 11 trials when the hand wheel was set at 7.0. Although the variation between the maximum and minimum discharges reached 44%., the existence of human error are believed that it contributed in this big variation. For instance, the speed of the tractor needed some time to accelerate until the specified speed in the beginning of the run, and to decelerate in the end of the run which was short especially at 10 m. Besides, the measurement of the distance was performed manually which increased the margin of error. The manual calculation of speed showed that the speed ranged between 0.9 and 1.05 m/s which means that the inaccuracy due to the instability of the speed of the tractor was approximately 16.6%.

4 Figure 3. The amount of seeds discharged from one feeding system per meter when the hand wheel is set to 7.0 However, Figure 4 shows the discharge from all feeding systems simultaneously at 3 different hand wheel settings. Although the average discharge increased proportionally with increasing the dials, there was still fluctuation among the feeding systems. This fluctuation reached 33% when the hand wheel was at 8.0, while it dropped to approximately 18% when the wheel was at 9.0. Figure 5 on the other hand shows the amount of seeds discharged throughout the test from each feeding system; that is, after running the machine for 810 m. This is equal to 2025 m2 (approximately 0.2 ha) as the width of the implement is 2.5 m. The figure indicates that the fluctuation reduced to 10% approximately among all the feeding systems, which suggests the hypothesis that the fluctuation is rather random and will reduce proportionally with the length of the agricultural operation. Previous indoor tests of the fiber sensor indicated that a linear relationship between the output voltage and the weight of seeds can be obtained. Assuming uniform discharge of the feeding systems, one fiber sensor should be suitable for estimating the flow rate. However, considering fluctuations which occur among the systems, additional sensor can be thought of as a correction sensor for the estimation performed by the first sensor in practice. Alternatively, the average of the two sensors can be used to increase the accuracy in estimating the flow rate. However, proving the hypothesis that the fluctuation in discharging seeds follows normal distribution will enhance the robustness in using 2 sensors only to estimate the flow rate of 20 feeding systems. Since the amount of seeds and fertilizers remaining in the tank are unknown, a method to monitor the inner of the hopper is required. The plan is to place vertically ultrasonic sensors which will estimate the distance until the surface of the seeds in the hopper. However, challenges which will be encountered are the non-uniformity of the surface of the grainsunlike fluids-, and the pattern in which the level of seeds drop in the hopper while they are being discharged. Therefore, basic tests so as to analyse the shape changing pattern of the seeds should be first conducted. Next, the number of sensors required to perform the estimation and their layout inside the hopper will be investigated. Figure 4. Amount of seeds discharged from for 3 different hand wheel settings

5 Figure 5. Accumulative amount of seeds discharged from 9 outlets after seeding an area of 2025 m 2 4. Conclusion In this paper, the performance of the grain drill was evaluated and the requirements to monitor its performance toward applications on robot tractor were discussed. The challenges are that the implement is mere mechanical and that the discharge units are so many that monitoring them all would be very expensive. The performance tests, carried out by running the machine several times at different distances showed that although fluctuation in the discharge is observed in short distances, the fluctuations reduced by increasing the distance of running. The results showed that after covering approximately 0.2 ha, the maximum fluctuation was approximately 10%. Reduced fluctuation will allow optimizing the number of sensors to as minimum as possible. The fiber sensor suggested in this research can estimate the flow rate of seeds and fertilizers by relating the weight of seeds in a unit time with the output voltage in the same period of time. Two sensors are expected to accomplish the task of estimating the flow rate. In the next step, performance test for the hopper of the grain drill will be conducted to grasp the reducing patterns of the seeds in the hopper so that the sensor suitable for the estimation and the number of sensors needed will be optimized. This will be conducted by placing vertically ultrasonic sensor which will estimate the distance until the surface of the seeds in the hopper. Knowing these information will enable estimating the time and location at where the hopper will be empty so that automatic hopper refilling could be conducted. References Grift T. and C. Crespi (2008) Estimation of the flow rate of free falling granular particles using a poisson model in time. Biosystems Enginnering. 101 : Scarlett A. (2001) Integrated control of agricultural tractors and implements. Computers and electronics in agriculture. 30, Swicher D., S.Brogelt and K.Sudduth (2002) Optical Sensor for Granular Fertilizer Flow Rate Measuerment, American Society of Agriculutral Engineers.,45(4): Tume Agri Oy (2006). Manual Tume combine drill Finland

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