Abstract:

A control scheme was put forward for vertical CNC plane lapping machine based on torque limit and dimensioned mechanism, aiming at some technology characteristics and practical requirements of plane lapping. Through the theoretical analysis and experiments, the pressure was equivalent to torque, and the functional relationship between output torque of Z axis motor and lapping pressure was set up. A method of controlling the lapping pressure was achieved by controlling the motor output torque in speed mode. In addition, the torque limit was an effective way to avoid phenomenon known as surface burns. A dimensioned mechanism was designed by which a position detection of terminal load in outer loop was achieved. The mechanism makes the size control of workpiece directly, the errors of intermediate links can be ignored. The results show that, using the force/position control scheme, lapping effect is satisfactory, stabilization of pressure control and positioning accuracy meet the technological requirements. Compared with traditional methods, the lapping vertical machine tool using the proposed control scheme can get rid of complicated hydraulic or pneumatic actuator, which simplifies machine structure and reduce production costs. Simultaneously, manual measurement in the case of shutdown is avoided, which both reduces the cycle time and reject rate.

Key words: lapping pressure, force/position control, servo motor, torque limit, dimensioned mechanism

摘要：

针对平面研磨的加工特点及现实要求,提出了一种扭矩限制与定尺寸控制相结合的立式数控平面研磨机力/位控制方法。将压力控制等效为扭矩控制,通过理论分析和试验找出了Z轴电机输出扭矩与研磨压力之间的函数关系,在速度模式下通过限制电机输出扭矩实现了研磨压力的调节。同时,利用伺服电机速度模式下的扭矩限制有效避免了加工中出现压力过大灼伤加工面的情况。设计了定尺寸机构实现最终负载端外环位置检测,直接控制工件加工尺寸,避免了中间环节的误差。试验结果表明该力/位控制方法研磨效果良好,压力控制稳定性和定位精度均能够满足研磨加工的工艺要求。与传统立式研磨机的控制方法相比,该方法不仅提高了研磨质量,且省去了液压或气压机构,避免了停机人工测量,提高了加工效率。
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关键词: 研磨压力, 力/位控制, 伺服电机, 扭矩限制, 定尺寸机构