Research On Active Disturbance Rejection Control For Wafer Level Flip Chip Equipment Motion Platform

As a kind of advanced packaging equipment for wafer level flip chip welding,wafer level flip chip equipment needs to meet the packaging requirements of high precision and high output,and the high performance motion control system is the key to achieve high quality packaging.Active disturbance rejection control(ADRC)is a new control technology which can actively observe and compensate the disturbance.Its core idea is to classify the unknown dynamic and external disturbance of the controlled object into the total disturbance,estimate and compensate the total disturbance,so as to transform the controlled object into an ideal integral series structure for control.In order to improve the tracking performance and disturbance rejection ability of the motion platform control system of wafer level flip chip equipment,this paper studies the application of active disturbance rejection control for the core motion platform of wafer level flip chip equipment.The main research contents are as follows:(1)According to the precise positioning control requirements of the motion platform,the servo system of the motion platform adopts three closed-loop control structure,and introduces the feedforward controller to improve the tracking performance of the system.(2)The open-loop modeling is carried out for the motion platform servo system,and the controlled objects include the driver and the linear motor.The mechanism of the linear motor is analyzed,and its mathematical model is established.The transfer function between the voltage of the driver and the displacement of the linear motor is deduced based on the driver link,and the pole zero information is used as the basis of system identification.The open-loop input and output data of the system were obtained through sine sweep experiment,and the transfer function model of the controlled object was identified by using the MATLAB system identification toolbox.(3)The speed loop ADRC of the servo system is studied.The concept of relative order is used to design the first-order ADRC instead of the high-order ADRC,which simplifies the design of the controller and reduces the burden of parameter tuning.Based on the S-type point trajectory planning adopted in the control system of the motion platform,the forward channel tracking differentiator(TD)of the ADRC is omitted.In order to solve the problem that the speed feedback signal of linear motor is noisy,the TD with filtering function is added into the speed feedback channel,and the differential prediction algorithm is used to compensate the phase loss caused by the filtering of TD.The simulation results show that the servo system can obtain better speed control performance and anti-disturbance ability by using the ADRC.(4)The ADRC of the position loop is studied based on the speed loop ADRC,and the second-order linear active disturbance rejection control(LADRC)which is applicable to most engineering objects is adopted for the position loop.The traditional LADRC is designed,and the key parameter(7₀ is determined by the initial acceleration of the step response.The simulation results show that the dynamic response of the position loop is not fast enough with the traditional LADRC.Therefore,the control law introducing velocity signal is further studied,and the control law introducing acceleration error is proposed by using the acceleration signal provided by the TD in the velocity loop feedback channel.The simulation results show that the control law introducing velocity signal and acceleration error can effectively improve the tracking performance of the LADRC and meet the control requirements of the motion platform,and the LADRC with acceleration error has the best tracking performance.The system using LADRC has stronger disturbance suppression ability than the system using traditional PID.