Dae-Hyun Lee

Evaluation of Tractor PTO Severeness during Rotary Tillage Operation

Analysis of load on major parts of the tractor power drive line is critical for efficient and optimum design of a tractor. The purpose of this study was to evaluate severeness of the tractor PTO driving axle during rotary tillage operation. First, S-N (stress vs. number of cycle) curve of a PTO driving gear was obtained through the fatigue life test using a PTO dynamometer. Second, PTO severeness was evaluated during rotary tillage operation. Torque measurement system was constructed with strain-gauge sensors to measure torque of a PTO axle, an I/O interface to acquire the sensor signals, and an embedded system to calculate severeness. The severeness of PTO was analyzed using measured torque data during rotary tillage. In the PTO gear life fatigue test, breakage time and bending stress of the gear were measured by tooth widths and torque change during the fatigue life test. The S-N curve showed a good linear relationship between bending stress and number of cycle (life) with a coefficient of determination of 0.97. For PTO severenss evaluation, rotary tillage operations were conducted at two PTO rotational speeds (level-1, level-2) under different paddy and upland field sites with different soil conditions. Results of averaged relative severeness for PTO level-1 and PTO level-2 were 1.96 and 3.34, respectively, at paddy field sites, and they were 1.36 and 2.51, respectively, at upland field sites. The results showed that the PTO driving axle experienced more severe load during rotary tillage at paddy fields than at upland sites, and relative severeness was greater at the higher PTO rotational speed under all of the soil conditions.

Analysis of Power Requirement of Agricultural Tractor during Baler Operation

Purpose of this study was to analyze power requirement of an agricultural tractor for baler operation. First, a power measurement system was developed and installed in a 75 kW agricultural tractor. Strain-gages with a telemetry system were used to measure torques of transmission and PTO input shafts. An engine tachometer was used to measure rotational speed of transmission and PTO input shafts. The measurement system also included pressure sensors to measure pressure of hydraulic pumps, an I/O interface to acquire the sensor signals, and an embedded system to determine power requirements. Second, field experiments were conducted at two PTO speed levels, and proportion of utilization ratio of rated engine power and power consumption of major parts (transmission input shaft, PTO input shaft, main hydraulic pump, and auxiliary hydraulic pump) were analyzed. Results of usage proportion of engine power for PTO speed level 1 and 2 were 4.1 and 2.2%, 31.5 and 16.3%, 49.6 and 59.7%, 14.4 and 20.8%, and 0.4 and 1.0%, respectively, for ratio of measured engine power to rated engine power of less than 25%, 25 ~ 50%, 50 ~ 75%, 75 ~ 100%, and greater than 100%. The results showed that the usage proportion increased in the range with the ratio of power requirement to rated engine power of over than 50% when the PTO gear was shifted from P1 to P2. Averaged engine power requirement for baling operation, tying and discharging operation, and total operation were 43.3, 37.3, and 42.0 kW and 49.0, 37.0, and 47.4 kW, respectively, for PTO speed level 1 and 2. Paired t-test showed significant difference in power consumption of engine, transmission input shaft, and PTO input shaft for different PTO speed levels. Therefore, the power consumption of engine for baler operation increased when the PTO gear was shifted from P1 to P2. It was indicated that the power requirement of tractor was affected by the PTO rotational speed for baler operation.

Development of Electric Actuator Position Control System for Automatic Shuttle Shifting of Tractor

The purpose of this study was to develop position control system of an electric actuator for automatic shuttle shifting of a tractor. The electric actuator was installed at the link of the forward-reverse gearshift of the tractor transmission, and controlled in the ranges of forward, neutral, and reverse positions. The position control system of the electric actuator was developed based on PID (Proportional Integral Derivative) controller and transfer function of the electric actuator. The coefficients of the PID controller were determined by Ziegler-Nichols (Z-N) method and optimized using simulation program. The prototype AMT (Automated Manual Transmission) test unit of the tractor was installed and used to evaluate the performance of the position control. The evaluation system for the control performance consisted of forward-reverse actuator, motor driver, and controller. The tests were conducted as the controlled positions of the actuator were changed from neutral position to forward, neutral, and reverse positions in sequence. The sequential tests were repeated 20 times. The operations of changing the gearshift were considered as the step response of the control system. Maximum overshoot, settling time, and steady-state error were analyzed. The results showed that performance of the position control system was reasonable and qualified. The maximum overshoots, the steady-state errors, and the settling times of the position control system were 10~20%, 1~5%, and 0.92~1.49 sec, respectively. The modifications of the electric actuator will be required to enhance the performance of position control during field operation.

Patent Trend of Unmanned and Automated Agricultural Production - Open Field Operation -

This study was conducted to determine the major patent and analyze the patent trend of unmanned and automated agricultural production for the open field operation. As a result of conducting a search for patent applications related to these technologies, 1,080 valid patents were selected by evaluating the relevance of the patents and removing noise patents. As a result of the country-based analysis using the selected valid patents, it was found out that the largest number of patent applications were filed in the United States with 541 cases, followed by Japan with 326 cases, the European Union with 128 cases, and Korea with 85 cases. Upon classifying the valid patents into core technology, the path generation and tracking technology accounts for 33% with 353 cases; the implementing control with environmental condition technology accounts for 22% with 236 cases; the robot design technology accounts for 21% with 228 cases; the plant and environment sensing technology accounts for 19% with 206 cases; the yield and quality monitoring technology accounts for 5% with 58 cases. Finally, 10 core patents were selected by performing a patent index evaluation. The United States registered all of the 10 core patents. The results showed that Korea falls behind in the open fieldrelated unmanned and automated agricultural production, compared to other developed agricultural countries.

FFT Analysis of Load Data during Field Operations Using a 75-kW Agricultural Tractor

Analysis of load data during field operations is highly important for optimum design of power drivelines for agricultural tractor. Objective of the paper was to analyze field load data using FFT to determine magnitude of meaningful cyclic patterns. Rotary tillage, plowing, baling, and loader operations were selected as major field operations of agricultural tractor. An agricultural tractor with power measurement system was used. The tractor was equipped with strain-gauge sensors to measure torque of four driving axles and a PTO axle, speed sensors to measure rotational speed of the driving axles and an engine shaft, pressure sensors to measure pressure of hydraulic pumps, an I/O interface to acquire the sensor signals, and an embedded system to calculate power requirement. Load data of tractor major components such as driving axle part, PTO part, main hydraulic part, and auxiliary hydraulic part were measured and FFT analysis was conducted with the data. Results of the study would provide information on power utilization patterns and on better design of power drive lines.

Development of a Plow Tillage Cycle for an Agricultural Tractor

Abstract. Various field tests are needed to improve agricultural tractor performance; however, field tests require expenditures for constructing an experiment system and time for conducting the tests repeatedly. In addition, it is difficult to acquire reliable data because field tests depend on environmental conditions. For this reason, indoor tests using dynamometers have been used in the automotive industry instead of field tests. To ensure the reliability of indoor tests, standardized driving cycles are needed as input data for the dynamometer. Therefore, this study aimed to develop a standardized plow tillage cycle for agricultural tractors using real field data. A load measurement system was installed on a tractor to collect real field data from loads acting on the four driving axles and the hydraulic pumps. Plow tillage was conducted on ten farmlands of similar size (3000 m 2 ; 100 m x 30 m) at three sites (A, B, and C). The plow tillage cycles for each site were developed using the driving cycle construction method for conventional vehicles with the measured load data. At one site, the entire dataset from the ten farmlands was first classified into micro-trips, which were the minimum patterns of plow tillage including plowing, three-point hitch ascending, and tractor turning. The arbitrary working cycles were generated by combining micro-trips, and less than 5% absolute percentage error was achieved between the entire dataset and the generated arbitrary working cycle. Second, the plow tillage cycle was determined considering the sum square difference (SSD) with a torque and torque variation probability distribution. The selected working cycle with the lowest SSD was determined as the plow tillage cycle. Third, the performance values (PVs) of the plow tillage cycles of agricultural tractors and the driving cycles of conventional vehicles were compared to evaluate the performance of the plow tillage cycle. The results showed that the ranges of absolute percentage error relative to the entire dataset were 1.0% to 4.9% for all sites. The SSDs of the plow tillage cycles were 1195.96, 958.77, and 1202.50, and the PVs of the plow tillage cycles were 99.60, 77.90, and 84.15 for sites A, B, and C, respectively. The PVs of the commonly used driving cycles were low, at 60% to 125% of the plow tillage cycles. The plow tillage cycles had especially higher performance than some of the international standard driving cycles by 104% to 125% for site B. The results showed that the developed plow tillage cycles can be applied to indoor tests for performance evaluation of agricultural tractors.

FFT analysis of load data during field operations using a 75-kW agricultural tractor

Analysis of load data during field operations is highly important for optimum design of power drive lines for agricultural tractor. Objective of the paper was to analyze field load data using FFT to determine frequency and the energy levels of meaningful cyclic patterns. Rotary tillage, plowing, baling, and wrapping operations were selected as major field operations of agricultural tractor. An agricultural tractor with power measurement system was used. The tractor was equipped with strain-gauge sensors to measure torque of four driving axles and a PTO axle, speed sensors to measure rotational speed of the driving axles and an engine shaft, pressure sensors to measure pressure of hydraulic pumps, an I/O interface to acquire the sensor signals, and an embedded system to calculate power requirement. In rotary tillage, calculated frequency was decreased as travel speed increased. In baler operation, calculated frequency was increased as PTO speed was increased. The calculated peak frequency levels and expected levels were similar. Results of the study would provide information on power utilization patterns and on better design of power drive lines.

Development of Path Planning Algorithm for an Autonomous Mower Tractor

Abstract Path planning is an essential part for autonomous mower tractor to travel and mow. Objectives of the paper were to analyze operation patterns by a farmer, to extract and optimize waypoints, and to demonstrate generation of formatted planned path for autonomous mower tractors. An 18-kW mid-mower tractor was operated by a skilled farmer on grass fields. To measure tractor travel and operation characteristics, an RTK-GPS antenna with a 2-cm RMS error, an inertia motion sensing unit, a gyro compass, a wheel angle sensor, and a mower on/off sensor were mounted on the mower tractor, and all the data were collected at a 10-Hz rate. And all of sensor data were transferred through a program to show the status immediately on the notebook. From 3 grass field tests, total 53,412 data points (every 0.1s) were obtained, and amount the data 73% was straight steering, 22% was turning steering, and 5% was for others (e.g. artificial error, needless work). Field test data showed some overlap, especially in the turning areas. Based on the human operation patterns, path planning algorithm was suggested for autonomous mower tractor. Finally path generation was demonstrated in a formatted file and graphic display. Results of the study would be useful to implement and test autonomous mower tractor, but further research needs to be done to improve the performance.

Development of Automated Manual Transmission of Agricultural Tractor Using Electric Actuators

The purpose of this study was to develop an automated manual transmission (AMT) of agricultural tractors using an electric actuator. A shuttle shifting actuator and a clutch actuator were developed to control a manual type shuttle gearbox and transmission. To evaluate performance of the AMT, the experimental test-bed was used. The test-bed was consisted of a powertrain of the agricultural tractor, an electric motor instead of a tractor engine, a three-phase inverter to control the motor speed, the actuators, and I/O interface modules. The actuators were installed at the link of the shuttle gearbox and transmission of the powertrain, respectively. The potentiometer signals of the actuators and the rotational speed of the input shaft of the motor and the transmission axle were measured and used to control the actuators. A PID simulation program was developed to optimize position control of the actuators. The AMT control algorithm was developed and experimental tests were conducted to evaluate the performance of the AMT at speed levels. The results showed that the actuators were controlled properly to achieve the maximum overshoot of less than 5%, the settling time of less than 1.5 s, and the steady-state error of less than 1% at all speed levels. The averaged total duration of all speed levels was less than 2.5 s and the speed of driving shaft reached the target speed within 3 s. The results showed that the developed shuttle shifting transmission control algorithm could be useful for the automated manual transmission (AMT) of agricultural tractors.