The Hydraulic Power Generation and Transmission on Agricultural Tractors: Feasible architectures to reduce dissipation and fuel consumption-Part i

This paper is aimed at investigating the benefits in terms of energy efficiency of new electro-hydraulic architectures for power distribution systems of a medium-size agricultural tractor, with a focus on the hydraulic high-pressure circuit. The work is part of a wider industrial research project called TASC (Smart and Clean Agricultural Tractors [1]). Traditional and alternative architectures have been modelled and energetically compared through simulation, using a lumped parameter approach. Experimental data previously acquired have been used to validate the models and to replicate real working conditions of the machine in the simulation environment. A typical on-field manoeuvre has been used as duty cycle, to perform an effective energetic analysis. The standard hydraulic circuit is a multi-users load sensing system that uses a single variable displacement pump to feed steering, trailer brake and auxiliary utilities in that order. The key idea of the proposed solutions is the separation of steering from the other implements, to optimize the entire energy management. In particular, the paper investigates new and flexible solutions for the auxiliary utilities, including an electro-hydraulic load sensing architecture with variable pump margin, an electronic flow matching and flow sharing architecture, and an electronic strategy for automatic pressure compensation. The simulation results show that good energy saving can be achieved with the alternative architectures, so that physical prototyping of the most promising solutions will be realized as next step of the project

전자유압밸브를 이용한 자율 주행 트랙터 조향성능 향상 연구

학위논문 (석사)-- 서울대학교 대학원 농업생명과학대학 바이오시스템·소재학부, 2017. 8. 김학진.The most common solution to achieving automated steering in an agricultural tractor is the use of an electric motor in parallel with a conventional hydrostatic valve-based hydraulic steering system owing to its simplicity and low cost. However, the existing overlap, or dead band, of a hydrostatic valve has limited its potential benefit to automated tractor steering in terms of providing various agricultural operations, including planting and spraying, at higher speeds. The main objective of this study was to develop an electro hydraulic steering system applicable to an auto-guidance system, and to compare the performance of the developed system with a conventional automatic steering system. A proportional-feedforward control algorithm was implemented to effectively compensate the non-linear behaviors of the hydraulic cylinders used for changing the steered wheel angle of the tractor. A computer-controlled hardware-in-the-loop electro-hydraulic steering simulator consisting of two different types of valve sub-systems s, i.e., hydrostatic valve and EHPV sub-system, was designed and built for the development of the steering control algorithms and to verify the feasibility of the developed steering controller for accurate steering of the system with acceptable response times. A field test was conducted using a Real Time Kinematic GPS based autonomous tractor equipped with the developed EHPV-based steering system and an EPS-based steering system used as a control to compare and investigate their potential in enhancing the path tracking functionality of an auto-guided system. The use of the EHPV-based steering controller was shown to improve the tracking error by about 29% and 50% for straight and curved paths, respectively, as compared to the EPS-based steering system.Chapter 1. Introduction 1 1.1. Study Background 1 1.2. Description of Tractor Steering System 6 1.3. Automatic Steering System 10 1.3.1. Electric Power Steering System 10 1.3.2. Electro Hydraulic Steering System 12 1.4. Review of Literature 13 1.5. Research Purpose 16 Chapter 2. Materials and Methods 17 2.1. Preliminary Performance Test of Conventional Steering System 17 2.1.1. Purpose of Preliminary Test 17 2.1.2. Zero-Load Test 21 2.1.3. Tractor Traveling Test 22 2.2. Hardware-in-the Loop Simulator 24 2.2.1. Hydraulic Circuit 25 2.2.2. Hardware Description 27 2.3. ISO 11783 Network 37 2.3.1. ISO 11783 (ISOBUS) 37 2.4. Steering Control Algorithm 45 2.4.1. Dead Time 48 2.4.2. Dead Band 51 2.4.3. Static Friction 57 2.5. Virtual Terminal 61 2.6. Vehicle Traveling Test 66 2.6.1. Hardware Configurations 66 2.6.2. Trajectory Tracking Control 72 2.6.3. Zero-Load Test 74 2.6.4. Sinusoidal Tracking Test 75 2.6.5. Path-Tracking and Test Methods 76 2.6.6. Evaluation Method of Path Tracking Deviation 79 Chapter 3. Results and Discussion 81 3.1. Preliminary Test Results of EPS-based Hydrostatic Steering System 81 3.2. Experiment Results of Steering Behavior of Hydrostatic Steering System using HIL simulator 85 3.3. Experiment Results of Electrohydraulic Steering System using HIL simulator 81 3.3.1. Dead-Time Approximation 88 3.3.2. Dead-Band Compensation 90 3.3.3. Static Friction Compensation 92 3.3.4. Steering Controller Test under Load Conditions 94 3.4. Performance Evaluation of Tractor Steering System 96 3.4.1. Zero Load Test 96 3.4.2. Sinusoidal Steering Test 96 3.4.3. Path-Tracking Test 99 Chapter 4. Conclusions 107Maste

Control and Evaluation Methods for Multi-Mode Steering

A self-propelled agricultural sprayer was modified to enable both front and rear wheel steering through electrohydraulic control valves. These modifications, in conjunction with a digital controller, enabled the vehicle to be four-wheel steered in multiple modes. The research focused on modeling and evaluating the effect of multi-mode four-wheel steering on vehicle handling characteristics and vehicle performance of the sprayer. The multi-mode steering system was evaluated by driving the sprayer through specified paths in the different steering modes. The position and heading of the vehicle were measured for each mode using two dual frequency DGPS receivers. From the measure of vehicle posture, sprayer performance measures such as over/underspray and crop damage were assessed for each steering mode. Preliminary results show that drivers were able to take advantage of added maneuverability in headland turning procedures. Crab steering reduced the amount of area sprayed in error during lateral course adjustments. The steering and vehicle models yielded similar responses to steering inputs as experimental responses

Design and Development of an Automatic Steering System for Agricultural Towed Implements

While an auto steered tractor can improve the overall accuracy and efficiency of an operation, for operations that involve towing an implement, a significant portion of the efficiency reduction comes from uncontrolled motions of the towed implement. Therefore, there is a crucial need to study auto steering system for towed implement as well. In this study different requirements of an auto steering system for a towed implement were developed and studied. In this study the guiding performance of two local positioning sensors (Tactile and Ultrasonic sensors) under similar conditions were studied for reading different trajectories at different traveling speed. Furthermore, a fuzzy logic control algorithm was developed to continually generate correction steering signals and keep the tractor and towed implement within a certain boundary of the reference trajectory. Finally, the designed controller was implemented in a hardware-in-loop (HIL) system to analyze the performance of the controller in real world conditions. The result of this study showed that although the local guidance sensors could locate the tractor or towed implement positions with respect to plant rows accurately, limitations to the performance of sensors were also observed in certain conditions. Sensors were prone to various noises and digital filters were required to apply to collected data. Data analysis showed that at lower speeds (less than 1.79 m/s) the accuracy of sensors was ?2 cm or better. The fuzzy logic controller improved the trajectory tracking accuracy at slow speeds (1-5 m/s) for following non-complex trajectories while no major improvements were achieved for complex trajectories at these speeds. Therefore, the controller had an acceptable accuracy following straight trajectory with negligible deviations at slow speeds. Moreover, experimental results showed that the hydraulic cylinder followed the controller signals with sufficient accuracy. During the experiment the angular displacements remained in the range of ?10? and never hit the constraint of maximum achievable angle, which was ?30?. The satisfactory results showed that the designed automatic steering control system has a good tracking performance with a fast response, thus meeting the navigation control requirement of agricultural equipment to a certain extent

Development and Evaluation of Automated Slip and Draft Control System for Tractor

254-261A microcontroller-based Automatic Slip Control System (ASCS) and Automatic Draft Control System (ADCS) for 2WD tractors was devised to automatically alter the depth of operation to keep the wheel slip and implement draft within a prespecified range. An electro hydraulic lift link system was devised to control the depth of the implement's operation. The technology continuously checks wheel slip and draft in the field and notifies the hydraulic system, which changes the implement's depth if the wheel slip and draft exceeds the specified range. Experiments were conducted with defined slip ranges of 10–15, 15–20, and 20–25% for ploughing and cultivating activities. Field capacity and drawbar specific fuel consumption were measured as performance criteria. With the ASCS, the slip was found to range from 15–24%, versus the desired range of 15–20%, while with the current draft control system, it was found to range from 12–48% Tractor Draft Control System (TDCS). Fuel consumption was determined to be 20.13, 21.11, and 22.98 l/ha for ploughing operations with TDCS at initial depth settings of 150, 180, and 220 mm, respectively. However, ASCS resulted in a significant increase in fuel efficiency, with an 11.2% reduction in consumption. When compared to the TDCS, it consumed 4 to 14% less fuel during ploughing operations. Field capacity was increased by 3.4–14.5% due to ASCS and ADCS. The measuring efficiency of the devised system was determined to be greater than 99%

The Design and Development of an Automatic Guiding System for a Tractor

Mechanization and Automation are very fashionable words in present day Agriculture. Both imply a reduction in the amount of human effort necessary to achieve certain ends, and to accept the need for either of them is to assume that it will lead to some financial gain. Automation as applied to Agriculture is to improve many limited factors which affect the final yield of any agricultural crop. One of these factors, the mechanical operation, requires considerable care and attention to more nearly insure maximum yield and high quality. Numerous methods have been adopted through research and development to minimize field losses of a crop and to improve the quality of product with the use of more adaptable and accurate machines. As such, the objective of this study was: 1. To design, develop, and construct an automatic steering device which would enable a tractor to guide itself down the crop row accurately. The system was to be designed in a manner that would make it possible for the tractor to be used for a variety of crops with little or no change in the automatic steering components. 2. To design a system which could be justified economically where labor is scarce and expensive or unskilled, or where the tractors are operated in hazardous conditions

Volume 1 – Symposium: Tuesday, March 8

Group A: Digital Hydraulics Group B: Intelligent Control Group C: Valves Group D | G | K: Fundamentals Group E | H | L: Mobile Hydraulics Group F | I: Pumps Group M: Hydraulic Components:Group A: Digital Hydraulics Group B: Intelligent Control Group C: Valves Group D | G | K: Fundamentals Group E | H | L: Mobile Hydraulics Group F | I: Pumps Group M: Hydraulic Component

Hybrid Steering Systems for Automotive Applications

The paper presents the results of the researches performed in order to find out the static and dynamic performances of some recent types of hybrid electrohydraulic servomechanisms. The new concept was generated by the needs of the modern aerospace technology called “flight by wire”, directed to the use of compact actuators composed mainly by a brushless motor driving a hydrostatic pump connected in a close loop with a hydraulic cylinder. The numerical simulations performed with Simcenter Amesim language pointed out the possibility of saving a lot of energy with this new concept, already used on civil airplanes and fighters. The new wave of autonomous driving generated a lot of combinations of electric and hydraulic components, according the peculiarities of applications. The authors studied the accuracy of the hybrid steering system of an articulated tractor based on a digital industrial servo valve combined with an ORBITROL standard unit. The structure of the last generation of the trucks hybrid steering systems was also studied, taking into account the real performances of each component. Finally, the effect of the strong penetration of the hybrid servo systems in the automotive manufacturing systems is assessed

Digital control for automating feed distribution in feedlots

An investigation was conducted to determine the feasibility of automatic controls to automate feed distribution in feedlots. The control approach was restricted to compatibility with conventional feeding equipment. Input control signals were taken to originate from commonly available mechanical and electronic sensors. The control system was implemented with standard digital logic components;The proposed digital control system is based on a railguided, self-propelled automatic vehicle capable of delivering feed sequentially to 255 pens located on both sides of a single feeding path. A manual, closed-loop control system consisting of the following functions was developed: (1) pen identification, (2) initialization control, (3) feeding mode, (4) exit from feeding mode, (5) re-entry into feeding mode, (6) end of feeding cycle, (7) ground drive and conveyor control, (8) interface and auto/manual mode, (9) monitoring of automated system and (10) data and failure display and alarm. The control system allows either automatic or manual operation of the feeding vehicle. Digital electronic circuits capable of implementing the desired control functions were designed;The feeding cycle is manually initiated and automatically terminated when feed has been delivered to all pens requiring feed. It can be partially programmed to enable feed delivery to sections of the feedlot. Two feed rations can be delivered. The feeding status of each pen is recorded. The pen feed rations are stored in reprogrammable memories;The operation of the automated feeding system is based on the automatic identification of the feedlot pens. The number assigned to a pen is coded, using binary pulse-code modulation. Frequency-shift keying is used to transmit the coded number. The received coded number is recovered by specialized communication circuits and then validated;The control system monitors the vehicle components and the major electronic circuits to detect failures, prevent damage and produce a safe operation. Furthermore, it incorporates safety sensors and logic circuitry to meet the basic safety requirements pertaining to automated vehicles;The proposed automated feed distribution system for feedlots is expected to: (1) reduce management requirements through automatic distribution of feed to cattle raised in pens, (2) increase efficiency of feeding operation by eliminating time losses associated with secondary feed transfer, (3) eliminate damage to feedbunks through positive guidance of the vehicle by rails, and (4) save energy by eliminating secondary feed transfer

Development and evaluation of multi-mode four-wheel electrohydraulic steering system on a sprayer vehicle

The trend in North American agricultural equipment is to produce larger, faster machinery in order to increase productivity. Agricultural sprayer vehicles are being designed with boom lengths exceeding 100 ft and field speeds up to 20 mph. These two parameters, along with the movement towards automatic guidance of sprayers, make steering control of the utmost importance. The availability of four-wheel multi-mode electrohydraulic steering provides steering options to potentially increase the spray accuracy and efficiency, while reducing crop damage and increasing vehicle maneuverability. In this research, a self-propelled agricultural sprayer was modified to allow the rear wheels to be steered using electrohydraulic control valves. This enabled the vehicle to be steered in multiple modes. The research focused on evaluating the effect of multi-mode four-wheel steering on the vehicle handling characteristics and vehicle performance of the sprayer. This thesis presents the research conducted in modeling the vehicle, developing the control and evaluation methods, and interpreting the results of the testing. Four-wheel multi-mode steering enables the vehicle to have the option of steering with two wheels (conventional), all four wheels in the same direction (crab), or steering the front two wheels in one direction and the rear two wheels in the opposite direction (coordinated). The multi-mode steering system was evaluated by driving the sprayer through specified paths in the different steering modes. The position and heading of the vehicle was measured for each mode using two dual frequency DGPS receivers. From the GPS data, sprayer performance measures such as over/underspray, skip and overlap, and crop damage were assessed for each steering mode. This research showed that multi-mode four-wheel electrohydraulic steering is a practical option for sprayer vehicles. The results of the research show that there are performance advantages and disadvantages for each mode of steering. Coordinated steering increased the maneuverability of the vehicle, while crab steering reduced the misapplication during a lateral path adjustment. The research also showed that there are different levels of driver variability between modes of steering. This indicates that for multi-mode steering to be an efficient option, the driver needs to be trained to operate the vehicle in each modes of steering