Research On Servo Control System For Industrial Lockstitch Sewing Machine

Ac servo drives employing permanent magnet synchronous motors are being used for various purposes in consumer products and industry applications. Although their technical advantages are generally acknowledged, researchers are becoming aware of their cost and are exploring the possibility of cost reduction. Especially for industrial sewing machines, a servo control system with low cost but high performance is needed.A current sensorless space voltage vector control algorithm is presented to the control of permanent magnet synchronous motors using simple low-resolution photoelectric encoder. This method directly control voltage vector and compensate the difference between voltage vector and current vector. The hardware and software are simplified without current sensors and cost is reduced.A cascaded control structure is presented for the sevo control system. PID controller is used to control the motor speed to improve interference immunity. Predictive functional control (PFC) is use to control the position to obtain good tracking performance and high robustness. Stability analysis of univariable and multivariable constrained PFC is fulfilled.A simple real-time operation system - MotionOS is designed to improve adaptablity of the servo control system. Speed and postion servo functions are integrated into it and preemptive static task schedule is used. MotionOS can be applied to many applications such as sewing and textile machinery to improve development effiency.Servo control system for industrial lockstitch sewing machine is developed based on MotionOS. It provides fast response and sufficient precision control of speed and position. Automatic functions such as needle positioning, automatic trimmer and wiper, backtacking, constant-stitch sewing are fulfilled. Dozens of tunable parameters are provided to improve flexibility. Pedal sensor is designed for speed adjustment and synchronizer using magnetic sensors is designed for needle positioning. An operatation panel is also designed to set sewing pattern and these sewing parameters are downloaded to master control board. And CAN interface is preserved for remote network control.TMS320F2407A digital signal processor (DSP) is selected as the CPU of the whole system and PM20CS060 intelligent power module (IPM) is selected for power drive. Hardware design is precise and flexible. Circuits have strong ability of noise resistance. Some isolation and shield methods are used to improve performance of electro magnetic compatibility (EMC). Results of system test and plant probation show that the whole control system has good performance with lower cost and hasbright market prospect.