Fuzzy Logic Thermal Error Compensation for Computer Numerical Control Noncircular Turnning System

With the new emerging technologies of high performance machining and the increasing demand for improved machining accuracy in recent years, the problem of thermal deformation of machine tool structures is becoming more critical than ever. The computer numerical control (CNC) turning system for noncircular section pistons is designed with giant magnetostrictive actuator (GMA) as the turning module. When the temperature of the cooler system of the GMA varies for about 6degC, the dimension error of the surface contour varies for about 20 micron, and cannot meet the precision requirement of the piston´s contour dimension. In this paper, a method using fuzzy logic control for the compensation of the thermally induced error is developed. The fuzzy rule is used to compensate directly for the nonlinearity and uncertainty of the cooler system. The rule development strategy for the compensation system is to change the feed quantity of GMA to control the tool the pistons dimension. The fuzzy logic control developed here is a two-input single-output controller. The two inputs are the temperature deviation from setpoint error, and error rate. The output is the compensated value of the feed system. The triangular membership functions are used to define the input linguistic variables and the output linguistic variables. The fuzzy logic approach incorporates many advantages of using fuzzy logic such as the incorporation of heuristic knowledge, ease of implementation and the lack of a need for an accurate mathematical model. The experimental results are presented and the effectiveness of the fuzzy thermal error compensation control technique is discussed. Accuracy is greatly improved using the developed error compensation system