Research On Train Precision Stop Control Algorithm Based On LQR

In order to satisfy the high efficiency and high density request of urban railway traffic system, automatic train operation (ATO) can replace the experienced driver to complete the driving task. It can realize the train's traction and brake control based on ground information, and always make the train stay at optimal movement state. The stop precision is an important performance index of ATO system, and usually requested to be +/-30 centimeters. Stopping at the inaccurate position will affect passenger's up and down, especially in the platform which has shield gate. It also has the possibility to affect the communication between the train and ground. In order to realize precise stop, the core of this problem is precise speed control. But the train movement system is a complex non-linear dynamics system, the instability of movement characteristic cause the speed control difficulty.Therefore, based on the system analysis and the summary of research results, this thesis have combined the vehicle dynamics model, system identification theory and linear quadratic optimal control theory, and designed the precise stop control algorithm based on the linear quadratic optimal regulator (LQR). It can improve the ATO system's speed control ability, and meet the +/-30 centimeters performance index of stop precision. The paper's research emphasized on several aspects as follows:1. Train's traction and brake characteristic has been studied. Then we have analyzed the influencing factor of train's basic resistance and additional resistance. The single-particle train model is used. Considered the influence of power servo on the movement characteristic of train, the vehicle dynamics model is established.2. The experiment data of Dalian railway line three are analyzed. And we use the least square parameter identification method and carry on the identification to its vehicle's basic resistance parameter, traction brake parameter and power servo parameter. Dalian light rail vehicle model is established, and its accuracy is confirmed through the simulation.3. Based on the Dalian light rail vehicle model, the structure and influencing factor of ATO system are analyzed. Then we have designed the precise stop PID controller according to the system performance index, and convert the optimal control track problem into the optimal regulator problem. The precise stop LQR control algorithm has been proposed.4. The precise stop LQR control algorithm is confirmed through the simulation. In the same condition, the performance of LQR controller is compared with optimized PID controller. The simulation results show that the LQR controller's track performance is better than PID controller's, and the brake level change quantity is less than the PID controller. The precise stop performance index meets +/-30 centimeters. Finally the influencing factor of LQR controller's performance is analyzed, such as line condition, speed measure error, system time lag and weighting matrix. Then speed control precision, brake level change characteristic and stop precision in different situation have been obtained.Through the laboratory simulation, the results show that the performance index of precise stop LQR control algorithm meets +/-30 centimeters, when speed measure error does not exceed 0.5 km/h, system time lag is 0.6s, line slope value is -1, and weighting matrix R=1,Q>1000. It provides the theory foundation to develop practical ATO system.