Design and Test of Measurement and Control System for Rapid Prototype Platform Used in Electric Tractors

Electric tractors get more and more attention due to increasingly stringent exhaust emission policies around the world, which makes more and more test benches for electric tractors have been developed. However, in these studies the focus is primarily on the two problems of matching parameters and energy management of the powertrain architectures performing transportation or ploughing operations, and little attention is paid to the design of measurement and control system for electric tractors. The objective was to develope the design method for a reconfigurable measurement and control system. More specifically, a rapid prototype test platform for a series hybrid electric tractor with a dual-motor independent drive structure was selected to implement the rotary tillage operation. A diesel engine and two permanent magnet synchronous motors were taken as the power source, which can meet the development test of electric tractors with power below 80.8 kW. A rapid prototyping real-time control system was designed by the combination of dSPACE and Matlab/Simulink. Design methods of communication modularization and control strategy modularization were proposed to improve the utilization efficiency of the test bench and reduce the costs. The experiments of rotary tillage operation in the terms of pure electric mode and hybrid electric mode were carried out by the Rule-based control strategy. The results showed that when the load torque of rotary tillage varied from 31 N•m to 64 N•m, the speed fluctuation of power take-off (PTO) motor was 529~550 r/min, the maximum relative error compared with the set value was about 2.037%. In addition, the maximum relative errors of the speed of the drive motor 2, the left and right load motor, and the engine generator set were 0.396%, 0.889%, 1.333%, and 0.625%, respectively, which were all within the control allowable range. It was demonstrated that the response speed and control effect of the measurement and control systems of the test platform was good. In the hybrid mode, the battery voltage and SOC were gradually increased over time by starting the engine generator set, because the charging current of the engine generator set subsystem was greater than the discharging current of whole system, indicating that the series hybrid electric mode operated normally, which verified that the design method of the communication modularity and control strategy modularization for the test bench was reasonable and feasible. The design method proposed for developing the measurement and control system of the platform was general and can be extended to other engineering applications, which had a certain reference value and guiding significance for engineers and researchers to develop similar platforms. © 2022, Chinese Society of Agricultural Machinery. All right reserved.