In view of the complicated hydraulic system, the many driving parts and the great load variation in the combine harvester, and on-line monitoring methods of hydraulic actuating parts such as cutting tables, conveyors and threshing drums were studied. By analyzing the working principle of the hydraulic system of the combine harvester, a mathematical model of the hydraulic system of the combine harvester was established; a simulation model for the fault diagnosis of the hydraulic system of the combine harvester was established based on AMESim. The load signal was introduced to simulate the feeding amount, and the simulation test was carried out. According to the simulation analysis results, the best position of each monitoring point was determined. The on-line monitoring system of the hydraulic actuators of the combine harvester was designed by using LabView, which can collect and display the working parameters of the main working parts of a combine harvester in real time, and alarm the user to faulty working conditions. The field experiment results show that the function and precision of the monitoring system completely meet the requirements of field operation condition monitoring of combine harvesters. The accuracy rate of the fault alarm is 96.5%, and the automatic diagnosis time of the fault alarm is less than 1 min and 18 s, which greatly improves the operation efficiency of the combine harvester.

To improve the quality and control accuracy of the farming tractor electro-hydraulic hitch system, a variable-universe fuzzy control algorithm is introduced herein based on force–position mixed adjustment. (1) Background: This research sought to improve the operation quality and control precision of the tractor electro-hydraulic suspension operation system by solving the slow response and low precision problems in the target value control of the system. (2) Methods: According to the characteristics of the operating system, the working principle is discussed. The variable-universe fuzzy controller and the control module were designed based on MC9S12XS128. At the same time, we used Matlab/Simulink to study the step response, and field tests were carried out based on the existing test conditions. (3) Results: In the response stage, the variable-universe fuzzy control only needs 5.85 s, and there is no overshoot problem; in the normal tillage stage, the maximum tillage depth difference is only 1.6 cm, and the traction force is 428 N, which is closer to the expected value. (4) Conclusions: The farming quality and efficiency of the operating system were improved. Additionally, the operating system can also provide technical support for intelligent agricultural machinery and the field management mode in the future.

Pilot-operated electro-hydraulic proportional directional valve is a key hydraulic component to control the motion of large power equipment such as construction machinery and agricultural equipment. The control accuracy and response speed of the valve control element are very important to the performance of the hydraulic system. In this paper, control strategies for dead-zone control and valve control systems are reviewed. In order to eliminate the dead-zone of pilot-operated proportional valve control, the current control schemes for dead-zone detection and dead-zone compensation are summarized, and the control schemes are evaluated. The proportional–integral–derivative-related control, nonlinear control, and robust control of the pilot-operated electro-hydraulic proportional directional valve control system are reviewed, the relationship between the control strategies is analyzed, and the different control algorithms are evaluated. The shortcomings of the research program are analyzed, and the corresponding solutions are proposed. Based on the current research, future research progresses for eliminating the control dead-zone and optimizing control strategies are presented.

Double-coil inductive displacement transducer is a non-contact type high-precision displacement measurement element, which is widely used in industrial manufacturing and large power equipment systems. Since the inductive displacement transducer has a parasitic capacitance, the frequency of the excitation signal has a great influence on the performance that has been little studied so far. In this paper, the method of determining the optimal excitation frequency of double-coil inductive displacement transducer is studied. The working principle and characteristics were analyzed, a signal conditioning circuit was proposed and a circuit simulation model was established. According to the simulation results, the influence law of the frequency of excitation signal on the double-coil inductive displacement transducer is obtained. The effect of frequency on the displacement transducer was analyzed in five aspects: frequency characteristics, output signal, sensitivity, the residual voltage at zero and linearity. Finally, the effectiveness of the simulation results was verified through experiments. The simulation and experiment show that the proposed signal conditioning circuit can realize the demodulation of the double-coil inductive displacement transducer signal. Taking DIPT14 displacement transducer as the research object, the frequency of excitation signal has influence on the sensitivity, residual voltage at zero and linearity. When the frequency is low, the parasitic parameters have little effect on the performance of the transducer and can be ignored. However, when the frequency is high, the parasitic parameter has a great influence on the performance of the transducer. The method presented in this paper is of great significance for the study of the characteristics, signal conditioning circuit and the determination of the optimal frequency of the excitation source of double-coil inductive displacement transducers.

The high-speed switching electromagnet (HSE) is a crucial component in high-speed switching valves (HSVs), and it directly impacts the performance of the valves. This article reviews the current status of research on HSEs and discusses methods for enhancing their performance. An HSE with two magnetic isolation gaskets (MIGs) is proposed. The structure and working principle of HSE are described, and the characteristics of HSE are analyzed. A drive and control method of HSE is proposed based on an MCU chip, and the drive control circuit is designed. To investigate the influence of MIG on HSE performance, an experimental platform was established. By changing the frequency and duty cycle of driving signals, the effects of MIG on coil current, armature displacement, armature motion lag, and current response time were studied. Experimental results indicate that when frequency changes, MIG reduces the average coil current variation and energy loss by 9.7% , and increases the average armature displacement variation by 21.6% . However, the average armature motion lag and current response time remain essentially consistent. When the duty cycle changes, MIG reduces the average coil current variation and energy loss by 8.2% , decreases the average armature displacement variation by 16.9% , reduces the average armature motion lag phase angle by 16.8% , and shortens the current response time by 6.7% . It can be seen that MIG can improve the performance of HSE. This article proposes a novel optimization method that is significant for enhancing HSE performance.