Self-Powered Active Suspension For Railway Vehicles

With the development of high-speed rail technology, the increased speed of railway transportation can lead to significantly increased car body vibrations which will affect the running stability and ride comfort of railway vehicles and there is an increased requirement for the use of advanced suspension. Due to the selected stiffness and damping parameters, conventional passive suspensions can not be adapt to different railway situations. Hence to overcome the shortcomings of passive suspensions, active suspensions based on the actuation technology are proposed by researchers. According to the vehicle’s running states and railway situations, active suspensions can tune the damping force on line to follow the demand for smooth running with high speed and the improvement of ride quality. However, active suspensions are dependent on the input of external power to support the actuators which is the main drawback to limit the practical engineering application with active suspensions. Therefore, this paper studies a class of energy regenerative active suspensions for lateral secondary suspensions of railway vehicles. The presented suspension can harvest the car body’s vibration energy in response to the track irregularities and provide the feedback energy to realize the vibration suppressing by the actuator without using any external power.The main contributions of this paper are given as follows.(1)A design methodology based on LQR optimal control for the development of self-powered active lateral secondary suspensions for rail vehicles is presented. By introducing two parameters which are represent the power loss in actuators and the power source respectively, it firstly investigates the energy flow in the active lateral secondary suspensions and analyzes the conditions for self-powered control in detail. Also by tuning the weightings of the quadratic performance index, the impact of the controller design on both the ride quality and the energy consumption is then analyzed to guide the design/specification of actuators and to define key actuator parameters in order to achieve both expected performance improvement and zero-energy consumption for the actuators. Furthermore, a control strategy for dealing with larger than expected energy consumptions by the active suspensions is proposed to eliminate excessive power requirements, but also to ensure the ride quality improvement in comparison to that of passive suspensions.(2)An analytical design approach in frequency domain for the development of self-powered active suspensions is investigated and is applied to optimise the control system design for an active lateral secondary suspension for railway vehicles. The conditions for energy balance are analyzed and the relationship between the ride quality improvement and energy consumption is discussed in detail. The modal skyhook control is applied to analyze the energy consumption of this suspension by separating its dynamics into the lateral and yaw modes, and based on a simplified model, the average power consumption of actuators is computed in frequency domain by using the Power Spectrum Density (PSD) of lateral alignment of track irregularities. Then the impact of control gains and actuators’key parameters on the performance for both vibration suppressing and energy recovery is analyzed. Computer simulation based on the complete model is used to verify the obtained energy balance condition and to demonstrate that the improved ride comfort is achieved by this self-powered active suspension without any external power supply.(3) In case of the quadratic performance index including the cross-term, a robust optimal guaranteed cost controller and a guaranteed cost/H∞controller are studied for a class of linear system with the state delay, the control input delay, and norm bounded uncertain parameters, respectively. To satisfy the requirements of both the system stability and performance indicators, the control design of the closed-loop system is transformed into solving a group of linear metrix inequalities to obtain the active control gain by applying the Lyapunov function method. The numerical simulation shows that the given controllers optimize the performance and the given algorithms are efficient to stabilize the uncertain system with both the state delay and the input delay.(4) A robust controller is designed for a quarter car model of active suspension with norm bounded parameters by optimizing the quadratic performance index. The energy balance conditions are then analyzed on the system parameter perturbation. Furthermore, a full car model with uncertain parameters is used to verify the obtained analysis and self-powered conditions, and the assessments for the suspension performance are given by comparing the designed robust control, the convensional LQR control and passive control.(5) To follow a hybrid performance index by using a quadratic and H∞ performance indicator, a guaranteed cost/H∞ controller is studied for a quarter car model of active suspension with the actuator delay. The impact of the time delay on energy consumption is then analyzed and the relationship between the time delay and the actuator parameter on energy balance is also presented. Moreover the obtained guaranteed cost/H∞controller and self-powered conditions are applied to a full car model with the actuator delay. The performance of the guaranteed cost/H∞control for the lateral secondary suspension is assessed then.