| With the development of high speed,high precision machinery industry,processing of high precision balls has become a research focus in the field of ultra-precision machining.The pressure of the process had a great effect on the machining accuracy of the ball,it directly determines the final quality of the work piece in the process of polishing and the polishing efficiency.The loading method of traditional polishing machine is mostly based on pneumatic or hydromantic systems,but the loading process cannot be achieved quickly and accurately.In this paper,a new type of stepper motor pressure loading system is proposed,it is implemented with a torque control method,and is combined with the fuzzy PID algorithm to achieve the pressure control system of loading of polishing machine faster and more precise.First of all,this paper based on ball polishing machine as the research object,describes the equipment composition and working principle of the ball polishing machine,analyzes the characteristics of pressure loading system in this machine;To improve the accuracy of the pressure control,a vector torque control method is proposed to realize the pressure loading,and established the mathematical model of pressure loading system,including a two-phase hybrid stepping motor mathematical model and a mechanical model of a soft loading device loading device’s mechanical model,and derived the formula for calculating the current amplitude and pressure;Used the MATLAB/Simulink to build the pressure loading system simulation platform,the simulation results show that under the condition of a given maximum torque,it can an realize accurate loading pressure.Secondly,aim at this pressure control scheme of vector torque control mode,current-pressure double closed-loop control strategy is designed in this paper,the current loop as the inner loop,the pressure loop as the outer loop.An incremental PID algorithm is adopted in the current loop,a fuzzy PID algorithm is adopted in the pressure loop.And expounds the design process of the fuzzy PID controller by taking current as the control variable;and the fuzzy PID control simulation of the loading system is calculated in the MATLAB/Simulink,the simulation results show that it will has high response rate and strong anti-interference ability,and the response rate of pressure is high.Then,in order to realize the intelligent control of the pressure loading system,pressure loading control system was designed according to the functional requirements of the key techniques of the hardware and software design of control system of pressure loading based on STM32;described the content of man-machine interface,monitoring system that was designed by force control configuration software.Finally,pressure performance test and the ceramic ball polishing experiment was designed.The results show that: static error of load force is limit to 1%,and dynamic error of load force is limit to 4.2%,the pressure system possess the high precision and the fast response characteristics;in the processing of G5 ceramic balls the roundness rate reach 93%,and the quality of the finished balls are better than domestic products which were processed using traditional pressure system. |
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