Research On Active Semi-active Suspension Model And Its Fractional Order Pid Control Algorithm

In the background of fractional order calculus theory is widely used in the study of vehicle suspension system,in order to better study the suspension system and improve its vibration damping performance,this paper combined with the fractional calculus theory of semi-active suspension system and active suspension system were studied.The semiactive suspension is semi-actively controlled by an electric oil-pneumatic actuator,and the active suspension is actively controlled by a ball screw type energy recovery actuator.In the study of semi-active suspension,the fractional order nonlinear suspension system model with nonlinear stiffness and fractional order damping is derived in consideration of the Viscoelastic characteristic of oil and gas suspension,and is used as the research object of this type of suspension by combining fractional order calculus theory.In the process of studying active suspension,in order to analysis the performance indicators of the suspension system more comprehensively,this paper establishes a model of the seven degrees of freedom suspension system of the whole vehicle and uses it as the research object of active suspension control.For the semi-active suspension,an electric oil-pneumatic actuator based on fractional order PID position feedback control is designed,through which the damping coefficient of the suspension system is adjusted,thus realizing semi-active control of the suspension.Using the road surface unevenness as the basis for the damping adjustment,a particle swarm algorithm(PSO)is used to find the optimal objective function for different road surface classes to obtain the optimal angle value for the actuator motor.A fractional order PID position feedback control circuit is used to control the motor angle,thus realizing the damping adjustment of the suspension system.Simulation of this type of suspension is carried out via MATLAB/Simulink,and an isometric experimental rig is built for this type of suspension system.For the active suspension,a ball screw type energy-feeding active suspension under fractional order PID control is proposed and studied.A mathematical model of the energyfeeding actuator is established,an energy-feeding test rig is built,the energy recovery power at different frequencies is measured experimentally,and the electromagnetic torque constant,which represents the proportional relationship between the output torque and current of the energy-feeding motor,is calculated based on the experimental results.The parameters of the fractional order PID controller of the complete vehicle suspension system are adjusted using the beetle antennae search algorithm(BAS)to calculate the desired control force to be provided by the motor in the actuator.The fractional order PID control circuit is used to control the current of the energy-feeding motor to achieve the actual control force output.An energy management strategy is proposed for the actuator operating mode switching,and the designed suspension system is modeled using MATLAB/Simulink,and the energy management results and active control results are simulated and analyzed.For both types of suspension control circuits,a mathematical model of the control circuit is developed and the numerical implementation of the fractional order PID control circuit for corner control and current control is derived by means of equations.The STM32-F407 development board is used as the carrier for the PID and fractional order PID control algorithms to control the motor angle and current,thus ensuring that the actual control effect of the suspension system is close to the ideal control effect,and the comparison of the control results of the two algorithms is used to verify the superiority of the fractional order PID control algorithm compared to the integer order PID control algorithm.The simulation and test results prove that the designed semi-active suspension effectively achieves the optimization of suspension system damping performance,the designed active suspension effectively achieves the active damping and energy recovery of the suspension system,and the designed fractional order PID controller has better control effect than the PID controller in each research direction.