This paper proposes a scheme to control the low-frequency vibration of pipelines by using magneto-rheological (MR) vibration reduction technology. The state equation and the transfer function of the pipeline system are established, and its stability and the sinusoidal excitation response are analyzed. The prototype of MR damper is developed. The dynamic characteristics of MR damper are tested and the double-sigmoid model of MR damper is established. The two-state control, Proportion Integration Differentiation (PID) control and sliding-mode-variable-structure (SMVS) control methods of pipeline vibration using MR damper are analyzed comparatively, and the vibration control laws are deduced. The simulation analyses are carried out to predict the control effect of different pipeline vibration control algorithms. The verification tests through a semi-active measurement and control platform are carried out, and the feasibility and applicability of different pipeline vibration control strategies are analyzed. The test results show that the three kinds of pipeline vibration control methods based on MR damper can effectively control the pipeline vibration. Especially, SMVS control has the best vibration control effect, the pipeline amplitude drop and the acceleration drop can reach 22.31 dB and 16.34 dB respectively, while the amplitude attenuation rate and the acceleration attenuation rate can reach 92.34% and 84.77%, respectively.

Aiming at the problem of low-frequency vibration of the hydraulic pipeline, a new type of semi-active damping magnetorheological (MR) damping clamp structure is designed. The structure size and material of the MR damping clamp were determined. The control model of the vibration damping system was established, and the control method combining fuzzy control and Proportional-Integral-Derivative (PID) control was used to carry out the numerical simulation, which proved that the fuzzy–PID control algorithm is effective and stable. The results show that the MR damping clamp proposed in this paper can effectively suppress the axial displacement and acceleration of the hydraulic pipeline in the excitation frequency range of 1 Hz~10 Hz. This research provides a new technical approach for low-frequency vibration control of hydraulic pipelines.

To improve the abrasion resistance performance of the critical tribopairs within water hydraulic piston pumps, tribological characteristics of the stainless steel 17-4PH and 17-4PH coated with Cr₃C₂-NiCr, WC-10Co-4Cr, Cr₂O₃ and Al₂O₃-13%TiO₂ sliding against carbon fiber reinforced polyetheretherketone (CF-PEEK) composite under water-lubricated condition were experimentally studied using a pin-on-ring test bench with different working conditions. It has been demonstrated by the experimental results that the tribological behaviors of CF-PEEK/cermet coatings tribipairs were better than that of CF-PEEK/17-4PH tribopair under water lubrication. However, the Cr₃C₂-NiCr coating could be damaged under high rotational speed. Due to the reaction film produced by the Al₂O₃-13%TiO₂ and water, the CF-PEEK/Al₂O₃-13%TiO₂ material combination exhibits more excellent tribological behaviors than other tribopairs lubricated with water, and could preferentially be used in water hydraulic piston pumps.

The high-speed pneumatic on/off valve is one of the critical components in pneumatic systems, which has been widely investigated in the last decades. In this research, a new voice coil motor direct drive high-speed pneumatic on/off valve (VCM-DHPV) is proposed, and the mathematical model of VCM-DHPV, which consists of the fluid subsystem and electro-mechanical subsystem, is established. In addition, the key structural parameters of VCM-DHPV are optimized through the simulation analysis to improve its dynamic performance. The experiment results show that the developed VCM-DHPV has a good sealing performance by adopting the face-seal type in the valve port, and a large flow rate up to 5500 L/min, and its opening response time is 8.2 ms under the gas supply pressure of 8 MPa and exiting voltage of 240 V. With the supply pressure and the exciting voltage rising, the opening response time of VCM-DHPV is gradually increasing, and the variation tendency of the spool displacement curves is in accordance with the simulation results. This research will have significantly effects on raising the performance of the high-speed pneumatic on/off valve and the development of pneumatic precision motion control.