| Electric power steering system is a system with high efficiency,energy-saving, environmental protection and comfort which demonstrates the future of vehicle steering system.And it will have a good market.Because of the disturbance factors such as the random road excitation,the measurement noises of the torque sensor in the electric power steering system,the mathematical models of electric power steering system were established and the state-space formula with random disturbance signal was performed.Then the LQG state feedback controller and the Kalman filter were designed,that is LQG optimal controller. The target function used in simulation was based on the minimum use of both the energy consumption and the assist current error.The results showed that LQG optimal controller’ robustness is stronger than PID controller’,and it can attenuate the external disturbance effectively,reduce the energy consumption,and minimize the error between the actual assist current and the target current.At the same time,the software and hardware of EPS control system were designed.In the aspect of hardware,the single chip system was mainly introduced,and the signal processing circuit,the motor driving circuit and the failure alarm circuit were designed;In the aspect of software,the main program of control system,A/D transform program,speed signal collection program,failure diagnosis program and LQG optimal control algorithm program were designed.At last,the steering portability experiment and the LQG close-loop optimal control experiment were carried out on the test-bed of electric power steering system.The results validated the exactness of the system model and feasibility of the system control strategy. |
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