This paper presents a positioning error model and a control compensation scheme for a six-degree-of-freedom (6-DOF) micro-positioner based on a compliant mechanism and piezoelectric actuators (PZT). The positioning error model is established by means of the kinematic model of the compliant mechanism and complete differential coefficient theory, which includes the relationships between three typical errors (hysteresis, machining and measuring errors) and the total positioning error. The quantitative analysis of three errors is demonstrated through several experimental studies. Afterwards, an inverse Presiach model-based feedforward compensation of the hysteresis nonlinearity is employed by the control scheme, combined with a proportional-integral-derivative (PID) feedback controller for the compensation of machining and measuring errors. Moreover, a back propagation neural network PID (BP-PID) controller and a cerebellar model articulation controller neural network PID (CMAC-PID) controller are also adopted and compared to obtain optimal control. Taking the translational motion along the X axis as an example, the positioning errors are sharply reduced by the inverse hysteresis model with the maximum error of 12.76% and a root-mean-square error of 4.09%. In combination with the CMAC-PID controller, the errors are decreased to 0.63% and 0.23%, respectively. Hence, simulated and experimental results reveal that the proposed approach can improve the positioning accuracy of 6-DOF for the micro-positioner.

Commercial vehicles are usually equipped with suspension seats to improve ride comfort. As a semi-active intelligent device, magnetorheological damper can effectively improve seat comfort when applied to seat suspension. Firstly, a novel damper with built-in magnetorheological valve (MRVD) based on the squeeze mode of magnetorheological fluid (MRF) is designed, which integrates the magnetorheological valve (MRV) into the piston. This structure adopts a bidirectional controllable flow channel, double coil, and double squeeze chamber. Secondly, the mathematical model of the MRVD is derived based on the Bingham plastic model of the MRF. Then, the distribution of magnetic flux density in the effective damping gaps is simulated using finite element method. Finally, it is shown from a comparative work between the simulation results from the derived mathematical model and experimental test results of the MRVD that the established mathematical model can predict the field-dependent damping force well. The idea of integrating the MRV into the piston provides a new approach for the application of magnetorheological technology.

Semi-active seat suspension with a magnetorheological (MR) damper has been a popular study issue in recent years. Since the response time delay of the MR damper can reduce the control effect and even make the vibration more severe, there is an urgent need to compensate for the response time delay. In this paper, gray prediction is introduced into the vibration control study of commercial vehicle seat suspension. A gray skyhook prediction controller is designed to compensate for the response time delay. This proposed controller does not rely heavily on controller parameter optimization and requires fewer state variables than other typical time delay compensation controllers. The mechanical property of the MR damper has been tested, modeled, and analyzed. A seat suspension dynamic model considering geometric nonlinearity is established based on the motion relationship between the components of the suspension. Subsequently, the effect of the response time delay on seat suspension vibration control has been verified by simulation. The results show that the control effect deteriorates significantly after considering the response time delay. Finally, prediction accuracy and vibration reduction performance of the designed gray skyhook predictive controller are verified by simulation and bench testing. The results illustrate that the gray skyhook predictive controller provides excellent time delay compensation and can significantly improve the ride comfort and handling stability of the driver. This study provides a reference for vibration control research of the MR seat suspension.

Due to fluid excitation and the vibration of connected equipment, industrial pipelines are prone to long-term medium-high frequency and small amplitude vibration. Magnetorheological (MR) dampers with a multi-stage squeeze plate structure were proposed to solve the problem of medium-high frequency vibration in the industrial pipeline. The dynamic characteristics of the industrial pipeline were analyzed to determine the installation position of the MR dampers. The mechanical properties of the proposed squeeze-mode MR dampers were tested, and the hyperbolic tangent mechanical model of the MR damper was established. The vibration control model of the industrial pipeline was built for simulation analysis. In addition, the Acceleration-Driven-Damper (ADD) control and the Proportional-Integral-Derivative (PID) control were used for simulation to predict the vibration reduction effect. Constant current experiments and control algorithm experiments were carried out on the vibration control platform of the industrial pipeline. The experimental results show that the maximum vibration attenuation rate of the MR dampers with constant current reaches 61.95%, while those with ADD control and PID control are 65.43% and 67.46%, respectively. Therefore, the squeeze-mode MR dampers can effectively reduce the medium-high frequency vibration of the industrial pipeline, and the control algorithms can further improve the vibration reduction performance.

Magnetorheological (MR) grease has advantages of the anti-settlement behavior and excellent sealing property compared with conventional MR materials. However, the rheological behaviors of MR effect and shear yield stress are too small to limit the further applications with MR grease. This paper proposes a composite lithium-based MR grease with boric acid-hydroxyl stearic acid to improve the rheological behaviors. Eight different samples of composite lithium-based MR grease with different ratios of mass between lithium stearate and lithium borate are prepared by the saponification method. The rheological behaviors are tested and discussed with qualitative and quantitative analysis. The experimental results show that the off-state viscosity reduces with the decrement of the ratio of mass under low shear rate which changes from 68.7 Pa·s to 16.5 Pa·s. Lithium stearate content has more effects with off-state viscosity. Based on the Herschel-Bingham model, the shear stress of composite lithium-based MR grease can be improved dramatically by adjusting the ratio of mass which is increased by 170% under the magnetic flux density of 0.2 T. Compared with single lithium-based MR grease, the maximum yield shear stress is increased by 166.7% at off-state and the maximum MR effect is also increased by 19.1%. The MR effect can reach 23,600% with a specific mass ratio of the composite MR grease. The experimental results validate that the feasibility of the performance improvement by the composite lithium-based MR grease.