Keywords: drive chain, synchronous control, frequency control

I. Preface At present, in the coating industry, due to the large number of coating processing processes and the large scale, mechanized production lines have replaced artificial production lines. Most of the workpieces being processed are conveyed by overhead lines or site lines, and are circulated throughout the process flow. Transmission chains are generally long, ranging from a few hundred meters to several kilometers. In this way, if a single motor drive cannot be realized at all and several motors are required to drive a single drive chain at the same time, the motor must be synchronously controlled. Otherwise, the chain can easily accumulate or break.

Second, control methods and control requirements to solve multiple motors for synchronous control Most manufacturers mostly use two control methods.
1, using slip speed motor drag (commonly known as VS motor controller or speed ratio control). Use the limit switch to adjust the slip. The VS motor controller is a fairly simple, single-phase thyristor rectifier controller with voltage negative feedback. Its controller outputs a DC supply to the excitation coil of the VS motor. The load characteristics of this control system are rather poor, and the speed is extremely unstable at low speed, which can easily cause the system chain to accumulate or break, and the failure rate is high.
2, using the inverter plus asynchronous motor drag, use the limit switch to adjust the speed difference. The control principle is: In each transmission section of the chain, a drive seat and an adjustment seat are installed. The adjustment base can be moved and can be used to store too many chains. When the speed of the chain sections is not uniform, the chain will stretch and tighten. In this way, the adjustment of the movement of the seat will cause a change in the state of the travel switch so as to adjust the speed of the motor so as to achieve the purpose of balanced transportation. When this system works, the adjustment is based on the travel switch to detect the elongation and tightening of the chain in each section. We know that the adjustment seat cannot be made too long and the travel switch cannot be installed too much. Therefore, the speed adjustment of the motor is graded and jumped. The adjustment rate is relatively large, and the adjustment base is continuously adjusted, resulting in frequent system movements. Fast mechanical wear and running speed of the chain

Next, I will introduce a drive chain automation drive scheme with better performance and lower cost.
First of all, we use the G11 series multi-function vector control inverter produced by Shenzhen Anbangxin Electronics Co., Ltd., because this inverter has the following advantages in terms of automated drive chain drive.
a. Vector control technology, steady speed accuracy is open-loop speed sensorless vector control: ±0.5%, closed-loop speed sensor vector control: ±0.02%
b, low-frequency torque, 0.5HZ full torque output.
c. Powerful and unique frequency source selection mode and given mode, X, Y mode

d, process PID control system.
Just introduce the feedback signal from the analog input port (0-+10V/0-20MA) to realize the automatic control of the process PID system.
Therefore, in the entire system, automation products such as PLCs are not required for the process PID system and other functions. As long as a simple line connection is made, the entire drive chain can be automatically controlled.
(1) The drive motors are basically synchronized and the drive chain is not stacked and does not break.
(2) The maximum line speed can reach 10m/min
(3) The smaller the adjustment adjustment, the better.
(4) The adjustment seat needs to be installed with extreme protection.

Third, the control principle:
1. An angular displacement sensor is installed on the fixed pulley of the adjusting seat, and the elongation or tightening change rate of the chain is detected by the sensor and converted into an analog signal of 0-10V/0-20mA as the feedback signal of the PID. Return to frequency converter.
2. Through the keyboard setting of the inverter, adjust the balance point of the seat. The system compares the feedback signal with the balance point given by the PID to determine the adjustment direction and speed of the motor.
3. As the PID system reacts, the system adjusts immediately when the adjustment base and the balance point slightly deviate, thus ensuring effective adjustment at high speed.
4. Because the inverter adopts vector control, the speed does not change with the load. At the same time, it overcomes the disadvantage of unstable speed at low speeds.
5, the use of master-slave structure, all inverter control mode is open-loop vector control mode, the speed can be set by the panel or external potentiometer given. One E11 vector inverter is used as the main drive output, and the slave drives are all G11 series products. Multiple slave drives can share one master drive.
6. The main drive operating frequency is output through the AO analog port as the initial synchronous speed of the drive inverter. The deviation can be corrected through the definition of the zero offset and gain of the analog output port AO.
7. The auxiliary frequency source of the slave is derived from PID. In this way, from the speed of the drive motor, the speed of the main drive motor is tracked by the signal of the adjustment base, and the purpose of synchronization is achieved.
8. Install limit switches at each adjustment seat to prevent accidents.
Simple circuit diagram:

IV. Concluding remarks After optimizing the parameter values ​​in this system, the operation of the drive chain is very stable. Moreover, the electrical configuration of the system is concise and the logic is clear. Compared with the original old system, the expensive synchronous control board and the PLC are omitted, and the cost is greatly reduced. In the industry application is a cost-effective program. This solution has been successfully applied in many customers in Guangdong, Zhejiang, and Jiangsu.