A Control Method to Maintain Operation by Overcoming Abnormalities of Environment in FA Systems

Abstract

In recent years, with increased globalization of manufacturing sites in the industrial field, the demand of minimization of TCO (Total Cost of Ownership) from system design phase to maintenance phase has risen rapidly in FA (Factory Automation) systems. The machine of the manufacturing devices which utilizes servo systems has conventionally intended to the high speed and high torque control of the servo motors, and raised the operation speed of the machine to realize higher productivity. However, reduction of the machine stop time and machine stop frequency, which occurs from the abnormalities in the environment, comes to be also considered as a very important factor for total productivity.When a power failure occurs or an excessive load is applied to the servo system, the machine has been stopped for safety in the conventional way of control. This paper proposes the position droop compensation control method to maintain the operation in such abnorrmalities of environment and to keep the productivity level by ensuring the stable speed control. The proposed method is like that, first to accumulate the position droop of the torque which cannot be transitionally generated by the motor in an abnormal environment and then return it into the position control after having enough torque margin. The effectiveness of this method is verified by implementing to control software of servo amplifiers and spindle amplifiers of machine tools.