基于LuGre摩擦模型前馈补偿的模糊PID控制系统设计

Design of fuzzy PID control system based on feedforward compensation of the LuGre friction model

牙科CT在拍摄X光片时,牙科CT转台需要低速运转。在低速运转时摩擦带来的非线性最严重,为解决非线性摩擦,提出将摩擦模型前馈补偿与模糊PID结合实现对转台的控制。摩擦模型选用LuGre,并对摩擦模型参数离线辨识,确定出牙科CT转台的摩擦模型,在Simulink软件中分别对摩擦模型和模糊PID控制器进行封装建模,搭建了基于LuGre摩擦模型前馈补偿的模糊PID控制系统。通过仿真验证了采用该控制系统避免了位置跟踪平顶、速度跟踪过零时出现‘死区’等缺陷,并且跟踪误差很小、响应快,稳态稳定。通过实验验证了采用摩擦模型前馈补偿的模糊PID控制系统定位精度高,证明该控制系统的设计能很好地解决低速运转时摩擦带来的非线性问题。

When the X-film is taken by dental CT,the turntable of dental CT needs to run at a low speed.The nonlinearity caused by friction at the low speed is the most serious.In order to solve the nonlinear friction,it was proposed to combine the friction feedforward compensation with the fuzzy PID to realize the control of the turntable.The friction model was selected with LuGre,and the friction model parameters were identified offline to determine the friction model of the dental CT turntable.The friction model and fuzzy PID controller were packaged and modeled in Simulink software respectively.A fuzzy PID control system based on LuGre friction model feedforward compensation was built.It is verified by simulation that the control system avoids the defects such as flat top at position tracking,and the‘dead zone’appearing when the speed tracking at crosses zero,etc,and the tracking error is small,the response is fast,and the steady state is stable.The experimental results show that the fuzzy PID control system with friction feedforward compensation has high positioning accuracy.It is proved that the design of the control system can well solve the nonlinear problem caused by friction during low speed operation.