Design Of Control System Of Straight-line Drawing Machine Based On Frequency Control Technique

With the popularization of electrical energy and the rapid development of society, the using amount of cable wires is greatly increased. Drawing machine is used to make lager-diameter mental cable wires into small-diameter mental wires through drawing die.As the demand of cable wires is greatly increased, many medium-small private enterprises take part in the wire drawing industry. Among these medium-small private enterprises, many of them are still using backward wire drawing equipments because the prices of high and new technology equipments are too expensive. These backward machines often have the problems of wire broken, equipment fault and so on, which would decrease the production efficiency, make the quality of products defective and increase the cost of operation and maintenance of equipment. Besides, it would increase the operator’s workload and hidden danger. So. the most important is to reform equipment and improve their competitiveness for these enterprises.To solve the above problems, the current equipments of the enterprises are analyzed firstly. And then, a tilt sensor used for constant-tension control of drawing process is proposed, which can simplify the mechanism of tension control device and reduce the cost of production, installation and maintenance. To change the present situation that many analog I/O modules must be used in the drawing machines, the tilt sensor signal is directly fed back to frequency converter with PID function and RS-485 communication technology is used to control frequency converter. This scheme can reduce the quantity of analog I/O module and the occupied PLC point number. And the middle-large size PLC used in drawing machine can be replaced with small size PLC. The cost of hardware can be reduced and the dynamic property and precision will be improved.The tilt sensor is used to measure the swing angle of the swing link in the tension tuning roller. By analyzing the geometric relationship between swing angle and the wire length among pre and post passes, the mathematical model of the speed change between pre and post passes and the change of swing angle of the swing link is established. Combined with the mathematical model of frequency converter and induction motor, the control system model is established and simulated with Matlab/Simulink. The simulated result shows that the proposed control system can converge to stable operation state quickly, and it has good dynamic performance and stronger anti-interference ability.To verify the feasibility of the control system and simulate the operation of wire drawing machine, a simplified speed control system experimental platform was established with WEINVIEW HMI, Mitsubishi FX-3U PLC, Omron 3G3RV-ZV1 frequency converter, induction motor,485BD communication module and so on.With the experimental platform, the communication control and monitoring functions of the control system of straight-line drawing machine was designed firstly. The control program and some interfaces were designed to control the motor speed and monitor some parameters of frequency converters. And then, combined with the mathematical model, the model verification experiment was designed and accomplished. The actual motor speed was measured by encoder and the speed curves were showed on the HMI. Compared the actual speed curves with the simulated speed curves, the curves had high similarity. So, it can be said that the control model is accurate and feasible, and the proposed scheme is valuable for engineering application.