A simple and novel control strategy for semi-active vibration suppression by a magnetorheological damper

Conventional skyhook-based ON–OFF control switches the damping force on a vibration suppression target according to the sign of the product of the target and relative velocities (which is called the condition function). Here, we propose a control strategy that uses a novel condition function for improved performance. The proposed strategy is formulated based on the theory of forced vibration with base excitation. Its effect upon semi-active vibration performance is investigated via numerical simulations and experimental tests of the vibration suppression of a small structure equipped with a magnetorheological (MR) damper. In the simulations, the proposed control strategy can offer high-performance semi-active vibration suppression, even in the presence of force delays in the damper. The experiments show that the displacement response with the proposed control is lower than that with the conventional skyhook-based control over the entire frequency range; furthermore, the desired performance can be achieved when the proposed condition function is used with velocity-proportional control. The simplicity and high performance demonstrated by the proposed control strategy make it applicable to semi-active vibration suppression of practical systems, even in the presence of unavoidable force delays in controllable dampers.

Comprehensive predictive control for vibration suppression based on piecewise constant input formulation

We propose a novel semi-active vibration suppression method based on model predictive control (MPC). Semi-active vibration suppression provides excellent damping performance, energy consumption, and stability during control. As the semi-active control input is often discontinuous, it may be difficult to predict. Hence, we combine semi-active vibration suppression and MPC to determine the control input trajectory arbitrarily. The proposed method, called predictive switching based on piecewise constant input (PSPCI), assumes that the piezoelectric charge remains constant when the control circuit is in the open state. Under this assumption, the future system state can be predicted for semi-active vibration suppression while reducing the computational load. The PSPCI method predicts the future work done by the transducer and effectively suppresses vibrations. Its effectiveness and robustness are demonstrated through simulations and experiments. The proposed PSPCI method enables the prediction of the semi-active control input and diversifies the control input determination for effective semi-active vibration suppression.

High dynamic range and high dispersion stability of a magnetorheological grease damper for semi-active vibration suppression

In this study, the dynamic range and dispersion stability of a shear-type magnetorheological (MR) grease damper were experimentally investigated as important characteristics affecting the performance of semi-active vibration suppression. Furthermore, the damper was applied to the semi-active vibration suppression of a small single-degree-of-freedom model structure subjected to seismic excitation. The performance test results of the damper indicated that it has a dynamic range of 157 times, which is much higher than that of conventional MR dampers. Also, because of the high dispersion stability of MR grease, the results showed that its performance can be kept for 9 days longer in comparison with a similar damper using MR fluid. Moreover, the structural vibration suppression test results demonstrated that the damper can suppress vibration response over a wide frequency range by applying skyhook-based control, which can take full advantage of the damper’s high dynamic range.

Agile Attitude Maneuvers with Active Vibration-suppression for Flexible-spacecraft

This paper addresses the agile attitude stabilization maneuver control of flexible-spacecraft using control moment gyros (CMGs) in the absence of modal information. Here, piezoelectric actuators are employed to actively suppress the vibration of flexible appendages. Both the attitude dynamics and the proposed robust controller are globally developed on the Special Orthogonal Group SO(3), avoiding ambiguities and singularities associated with other attitude representations. More specifically, an observer is first designed to estimate the modal information of vibration. A robust control law is developed by synthesizing a proportional derivative (PD) controller, an adaptive sliding mode controller, and an active vibration-suppression controller, which use the information of the estimated structural modes. The stability of the closed-loop system is proved using Lyapunov stability theory. Finally, numerical examples are performed to show the effectiveness of the proposed method.

Active Fractional-Order Sliding Mode Control of Flexible Spacecraft Under Actuators Saturation

In this article, a novel multi-purpose modified fractional-order nonsingular terminal sliding mode (MFONTSM) controller is designed for the flexible spacecraft attitude control and appendages passive vibration suppression, assuming the control torque saturation in the system dynamics. Furthermore, an active FONTSM controller is proposed separately to perform active vibration suppression of the flexible appendages using piezoelectric actuators. The fixed-time stability of the closed-loop system for both the passive and active controllers is analyzed and proved using the Lyapunov theorem. Finally, the performance of the proposed controllers has been tested in the presence of uncertainties, external disturbances, and the absence of the damping matrix in order to study the effectiveness of the proposed method.