Research On Adaptive Servo Drive System For Six Degrees Of Freedom Parallel Stewart Platform

As an important tool for astronomical observation,large optical telescopes have an important position in the field of astronomy.With the gradual improvement of my country’s national strength,building a large optical telescope in the country is bound to be the goal of future development.The high-performance small Stewart platform as a secondary mirror adjustment mechanism is a key prerequisite for the construction of optical telescopes.The Stewart platform is a typical six-degree-of-freedom parallel mechanism,which has the common advantages of high load and high precision in general parallel mechanisms.Due to this special application occasion,the size of the Stewart platform is required to be as small as possible and the control system to be integrated.However,the specifications,dimensions and control characteristics of the general-purpose servo drives commonly used in the market do not meet the application requirements of secondary mirror adjustment.Therefore,the design of a small high-performance servo drive dedicated to the Stewart platform has important application value.This thesis will study the application scenarios and characteristics of each equipment based on the Stewart mechanism,and then select a permanent magnet brushless coreless motor with excellent performance as the original moving part of the platform branch chain according to the requirements of the project subject.Then it is a special servo driver for the motor.By studying the basic structure of the motor,and pushing the mathematical model and coordinate transformation of the electric motor according to the classic motor theory,the motor control principle is more concise and efficient.Analyze the algorithm principle of vector control for brushless motor drive and the formula derivation and modulation details of SVPWM.Secondly,considering the problem that the electrical parameters of the motor will change in different application scenarios,the principle of motor multi-parameter identification based on the model reference adaptive method is discussed,and simulation verification is carried out.For the three-closed-loop control commonly used in motor control,this thesis will derive the mathematical model of the current loop and the speed loop to simplify the corresponding equivalent.According to the classic control theory,the closed-loop regulator based on PI controller is designed,and the analytical formulas of some parameters are deduced for the characteristics of engineering application.For the control of the position loop of the servo drive,a feedforward-based proportional controller is used to verify the steady-state performance of the position loop based on the simulation results.This thesis will analyze the commonly used control structure of the servo system,select the driver hardware with the TMS320F28379 S microcontroller as the core,and select the combination design of the pre-drive chip and six MOSFETs for the structure of the inverter.And design part of the protection module of the drive control system.Discuss the main program code frame flow that the microcontroller runs,and the realization logic of the vector control code.At the end of the article,through experiments on the actual mechanical structure driving the Stewart platform,it is verified whether the repeat positioning accuracy of the servo system in the axial direction meets the platform design requirements.