Research On Sliding Mode Control Of Human Seat Suspension Dynamics Mode

With the development of the automotive industry,more and more people are paying attention to the safety and ride quality of automobiles.Significant research has been devoted to isolating the perturbations caused by the road with an uneven surface profile using various methods and approaches to reduce the health risks induced by vehicular vibration and shocks and provide passengers with a better travel experience.A variety of new technologies and methods have emerged to meet the constantly increasing demand for improved ride comfort from consumers.Sliding mode control,a control method based on sliding mode variables,has been widely used to improve vehicle comfort,as it can effectively handle system nonlinearities and uncertainties.However,it is hard to compare the control implications because of the variables of different control strategies.In this work,robust control designs are proposed to achieve the output tracking of the desired trajectories of the sprung mass based on the conventional sliding mode control with different reaching laws,i.e.,the constant rate reaching law,exponential reaching law,and power rate reaching law.The main achievements of this work are organized as follows:(1)The 7-DOF quarter car model coupled with a biodynamic model is used in simulation because of accuracy and efficiency.The equations of motion of the human body by using the Newton’s second law and Simulink models are obtained.(2)The sliding mode controller has been designed using the constant rate,exponential,and power rate reaching law for the quarter car model coupled with human body model under the same road surface vibration and external disturbance in this study.Note that the displacement power spectral density of random road profile is consistent with the road class A-B of ISO 8608.In order to check the performance of proposed controller,the acceleration and displacement results of head and neck,upper torso,viscera,and lower torso are obtained.The results of transfer function between all parts of human body model and road input,and the root mean square(RMS)accelerations are also acquired in this study.The results demonstrate that these sliding mode controllers using three different reaching law with different parameters can generate an important improvement in ride comfort for the ideal position selection in the initial position of the sprung mass.However,the effects of control parameters on different parts of the human body are different.When the ideal position of the sprung mass is not in the initial position of the sprung mass,the displacement and acceleration results with a larger controller parameter present higher overshoot,whereas the system in this case reaches the sliding mode quickly,especially in the case of exponential reaching law.(3)To better evaluate the performance of the proposed controller,controller force and power consumption with respect to time are investigated in this study.The values of results are reasonable,although there are some differences of controller force and power consumption between their different parameter combinations using sliding mode controller.The controller force and power consumption of actuator with larger parameter combinations are impractical for the ideal position of the sprung mass is inconsistent with the initial position.Therefore,when parameter is greater than zero,the sliding mode controller can achieve asymptotic stability.However,the reasonable parameters need to be further investigated because of the actuator.Moreover,a controller may not improve the ride comfort of occupants because the human body is not the main objective for the sliding mode system.These results can help suspension designers to study the whole-body vibration response under active control in the early design of an active suspension system to virtually assess the ride comfort.