Research On Measurement And Control System Of Articulation Module Of Self-driven AACMM

The measuring range of articulated arm coordinate measuring machine(AACMM)is not limited by the size of guide rail,scale and table.It is easier to go deep into the workpiece part where the orthogonal coordinate measuring machine is difficult to penetrate,and has the advantages of flexibility,portability and economy.However,due to the manual measurement method of manual dragging,it is possible to introduce unpredictable artificial measurement errors.It is difficult to meet the requirements of online and automatic measurement.For this reason,a self-driving AACMM is proposed.In this paper,the self-driving AACMM is taken as the research object,and the measurement and control system of the joint module based on FPGA is studied,including angle measurement,motor control,drive and communication,etc,which lays a foundation for the AACMM:Firstly,the structure of the self-driven joint module and the measurement model of the self-driven AACMM are introduced.Based on this,the measurement and control system scheme is designed.The working principle of brushless DC motor is introduced,and its mathematical model is established.The position-speed-current three closed-loop system control model of brushless DC motor is built with MATLAB/Simulink software.The PI algorithm is used as the control algorithm.The simulation analysis is carried out.The designed measurement and control system is based on FPGA,and mainly includes two parts: measurement circuit and control circuit.The measuring circuit comprises a current collecting circuit,an angle collecting circuit,a Hall signal collecting circuit and the like;the control circuit is mainly a motor driving control circuit.At the same time,the hardware program design is carried out on the FPGA.For the grating sensor,the signal shaping,four fine resolution and reversible counter programs are designed.For the current sensor,the program for sampling the AD converter is designed.Motor commutation and speed measurement program is designed according to hall signal.PWM pulse width modulation,commutation logic program and PID control algorithm program are designed to achieve the control of brushless DC motor,and the serial communication program with host computer is designed.Through simulation analysis,the above circuit program design is correct.Finally,the joint module circuit was developed and an experimental platform was established.The grating calibration system based on multi-faceted prism and selfcollimator is used to debug and verify the position acquisition module of this design,which verifies the reliability of angle measurement.The brushless DC motor control experiment was carried out to verify the control program and motor drive circuit on the FPGA.