By analyzing the shortcomings of the traditional fuzzy PID(Abbreviation for Proportional, Integral and Differential) control system (FPID), a multiple fuzzy PID suspension control system based on road recognition (MFRR) is proposed. Compared with the traditional fuzzy PID control system, the multiple fuzzy control system can identify the road grade and take changes in road conditions into account. Based on changes in road conditions and the variable universe and secondary adjustment of the control parameters of the PID controller were carried out, which makes up for the disadvantage of having too many single input parameters in the traditional fuzzy PID control system. A two degree of freedom 1/4 vehicle model was established. Based on the suspension dynamic parameters, a road elevation algorithm was designed. Road grade recognition was carried out based on a BP neural network algorithm. The experimental results showed that the sprung mass acceleration (SMA) of the MFRR was much smaller than that of the passive suspension system (PS) and the FPID on single-bump and sinusoidal roads. The SMA, suspension dynamic deflection (SDD) and tire dynamic load (TDL) of the MFRR were significantly less than those of the other two systems on roads of each grade. Taking grade B road as an example, compared with the PS, the reductions in the SMA, SDD and TDL of the MFRR were 40.01%, 34.28% and 32.64%, respectively. The control system showed a good control performance.

The hydraulic force has a great negative effect on the cartridge poppet valve system. Based on the law of momentum, the calculation formula of flow force of outflow poppet valve is modified, and a new valve core structure is designed. The compensation effect of the improved main valve core structure on the hydraulic force is discussed; secondly, CFD simulation is carried out to obtain the influence rules of these parameters on hydrodynamic forces. According to the analysis, the influence of main valve core arc structure on hydrodynamic force compensation under different opening degrees is also studied; then the optimal parameters of the arc structure are obtained through analysis. AMEsim system simulation model and test-bed are built to verify the hydrodynamic formula and simulation results. The experimental results verify that the new valve core structure has a good hydrodynamic compensation effect.

In view of the working principle of a swashplate axial piston pump, a simulation model of the piston pump was built in AMESim and its output flow pulsation characteristics were simulated and analyzed. We mainly analyzed the influence of the speed of the prime mover, the swashplate angle, the diameter of the piston, and port plate structure on the flow pulsation of the piston pump. The result of this research shows that the port plate structure, the swashplate angle, and the speed of the prime mover have an important influence on the flow pulsation of the piston pump. In order to effectively reduce the flow pulsation generated by the piston pump and reduce the noise generated in the process of flow distribution, the opening of the pre-compression angle and misalignment angle of the port plate of the piston pump must be reduced appropriately and the swashplate angle and the rotation speed of the prime mover should be controlled within a certain range. The flow pulsation of the axial piston pump decreases with the increase of the piston number and the decrease in the misalignment angle. The research results provide a reference for reducing the flow pulsation of the axial piston pump.

In this study, a structurally improved spool was designed. The diameter of one side of the spool stem was reduced, making the spool stem into a rounded table shape. A triangular groove was circumscribed on the step and on the same side. After liquid flow was guided through the triangular groove, the flow direction changed. A flow component in the negative direction was generated, which reversely impacted the liquid flow in the positive direction. The liquid flow angle at the outlet increased; that is, jet angle increased and flow force decreased. The simulation results show that, increasing the depth, H, of the triangular groove has a positive effect on flow-force compensation and was conducive to the stability of the valve core. Properly increasing the groove’s bottom diameter, D₁, of the triangular groove was conducive to the stability of the spool, but when D₁ was too large, the flow force increased. The experimental results are consistent with the simulation results, which proves that the improved structure can effectively reduce the flow force of the spool.

The steady-state fluid dynamic force of the cone valve core reduces the stability of the cone valve, thereby affecting its vibration characteristics. This study first derived the formula for calculating the steady-state fluid dynamic force of the valve core using the momentum theorem. Then, the study used the Computational Fluid Dynamics (CFD) method to explore the variation of steady-state fluid dynamic force with the opening degree of the cone valve and the pressure difference at the inlet and outlet. The study also analyzed the steady-state fluid dynamic force of the improved structure cone valve. Combining the CFD calculation results with the established axial vibration and dynamic models of the valve core spring system, a system dynamics simulation model was developed. Innovatively, the study combined experimental and simulation methods to investigate the vibration characteristics of the cone valve and the impact of steady-state fluid dynamic force on these characteristics. The experimental results aligned well with the simulation results, showing that the influence of steady-state fluid dynamic force on vibration characteristics is similar to that of spring force. At a small opening degree, the compensation structure of steady-state fluid dynamic force can reduce axial vibration amplitude. Increasing the inlet pressure from 2.0 MPa to 2.5 MPa results in a decrease in axial amplitude and an increase in the numerical value of the vibration balance position. Increasing the outlet pressure from 0.5 MPa to 0.9 MPa initially decreases axial amplitude and axial waveform factor, followed by an increase. Increasing the spring preload from 9.4 mm to 13.4 mm leads to a decrease in the numerical value of the balance position, a reduction in amplitude, and a decrease in the waveform factor of the axial vibration of the valve core. The study reveals systematic effects of inlet pressure, outlet pressure, and spring preload on the vibration characteristics of the cone valve. The research results in this paper can provide theoretical support for the structural design of hydraulic valves, reduce the impact of fluid dynamics on vibration, and thereby improve the stability of hydraulic system operation.

In this study, the piezomagnetic force sensor used in the electro-hydraulic lifting equipment of agricultural machinery is analyzed, and a vertical cross force sensor is proposed. The sensor has two excitation cores, which can detect the force at multiple shear planes at the same time. Compared with the cylindrical force sensor, the sensor has two excitation cores, and the magnetic field bias increases when the sensor is stressed. The two excitation poles are arranged vertically and crosswise, which can detect the force along the two excitation poles at the same time, which is more in line with the actual working conditions. The magnetic circuit of the sensor is analyzed and deduced. The static and dynamic performances of the sensor are analyzed by experiments. The results show that the sensitivity of the vertical cross force sensor is 2.732mV/kN, which is 277.35% higher than that of the cylindrical force sensor. The linearity of the vertical cross force sensor is 6.55%, which is 38.44% lower than that of the cylindrical force sensor. The accuracy and resolution of the vertical cross force sensor are 6.63% and 0.87kN. Compared with cylindrical force sensor, they have obvious improvement. Vertical cross force sensor has better static and dynamic performance.