The paper presents an experimental analysis of the selected feedback vibration control schemes dedicated to magnetorheological dampers, related to ride comfort and road holding. They were applied in a complex vibration control system installed in a commercially available off-road vehicle. Original shock-absorbers of the vehicle were replaced with magnetorheological dampers. The control system takes advantage of numerous sensors installed in the vehicle tracking its motion, i.e. accelerometers, suspension deflection sensors (linear variable differential transformer) and IMU module. Vibration control algorithms: Skyhook, PI, and Groundhook were tested experimentally using mechanical exciters adapted for diagnosis of a vehicle suspension system. Since the presented semi-active vibration control requires the magnetorheological damper inverse model to be applied, accurate operation of this model significantly influences the quality of vibration control. Therefore, additional analysis was related to application of measurements from accelerometers or suspension deflection sensors in the inverse model. Presented variants of control algorithms were compared by means of transmissibility characteristics evaluated in the frequency domain as well as using ride-comfort-and drivingsafety-related quality indices. It was confirmed that the Skyhook control as well as PI improved ride comfort, whereas Groundhook control improved road holding and decreases vibration of the wheels. Furthermore, it was shown that both approaches to the relative velocity estimation, based on accelerometers and linear variable differential transformers, can be used in this application. However, the first solution gives better results in the case of the Skyhook and PI control, whereas application of LVDT sensors is better for the Groundhook algorithm.

The paper presents an analysis of vehicle vibration, ride comfort and handling which have a decisive influence on health and safety of a driver. Experiments were carried out for a commercially available experimental all-terrain vehicle in the field in hard conditions with retaining the sufficient repeatability. The vehicle is equipped with a complex vibration control system, taking advantage of four automotive magnetorheological dampers. Numerous sensors, which measure acceleration in four points of the vehicle body, near the driver's seat, feet and hands, body orientation in space and speed of vehicle wheels, are available in the vehicle. They were used for evaluation of magnetorheological dampers' control signals and analysis of vibration affecting the driver. Constant values of magnetorheological damper control current were used for emulation of different settings of passive suspension. The analysis performed in frequency domain showed how vibration propagates in a medium-sized all-terrain vehicle and indicated that driver's hands are mostly affected by the road-induced vibration. It was also confirmed that the greatest improvement of ride comfort can be obtained for the soft suspension, i.e. uncontrolled magnetorheological dampers. Furthermore, the Skyhook algorithm was implemented, including the proportional control of the magnetorheological damper force and the inverse Tanh model of the magnetorheological damper. It was validated for the wideband road-induced excitation contrary to the experiments commonly presented in the literature, which are performed only for harmonic excitation. It was shown that the properly tuned Skyhook algorithm enables improving vehicle handling compared to the passive suspension and simultaneously it can maintain the similar or even better results of ride comfort.

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