Multi-motor automatic synchronous control system of suspension conveying line

Abstract

The utility model discloses a multi-motor automatic synchronous control system of a suspension conveying line, and relates to the field of coating automation. The system comprises a human-computer interaction interface, a PLC control module, a communication unit, a frequency converter unit, a motor unit and an encoder unit, wherein the encoder unit comprises an incremental encoder; the frequency converters are connected with the motors in a one-to-one correspondence mode and used for reading frequency and current of the motors, each motor is connected with a chain wheel through a speed reducer, and the chain wheels are used for driving a conveying chain in a line body. One chain wheel is selected as a main chain wheel to be connected with the incremental encoder, the output end of the incremental encoder is connected with the PLC control module, and the incremental encoder is used for measuring the accumulated displacement of the driven conveying chain. According to the utility model, the multi-motor automatic synchronous control can be realized only by one encoder, the mechanical structure design of the line body is simplified, and the response speed of line body problem monitoring is accelerated at the same time.

Description

Technical Field

[0001] The utility model relates to the field of coating automation, in particular to a multi-motor automatic synchronous control system for a suspension conveyor line. Background Art

[0002] With the improvement of economic level and the advancement of science and technology, the scale of the coating industry has continued to expand, and its production process has experienced the development from manual spraying to automated spraying. In the field of coating production automation, it usually includes multiple hanging conveyor lines, through which materials are transported between different processing processes. These conveyor lines generally require synchronous speed and position control to avoid frequent movement of staff, reduce labor intensity, and improve work efficiency and processing quality.

[0003] The main structure of the suspension conveyor line is a very long circulating chain used to transport materials. The circulating chain achieves cyclic movement through the cooperation of multiple motors placed at a certain distance from each other in the direction of chain movement, and the materials can be suspended on the chain through various devices and move with the chain.

[0004] The existing synchronization schemes mainly include encoder synchronization and tensioning angle displacement synchronization.

[0005] The principle of encoder synchronization is to detect the speed of each drive motor. Under the condition that the mechanical structure error and tolerance are reasonable, if the motor output speed is consistent, each section of the chain can be considered to move synchronously. This method is simple to control, but its disadvantage is that it requires frequent speed adjustment, and the line body cannot quickly reach a stable state of synchronization. In addition, during the production process, due to different changes in the load conditions of the line body, some encoder pulse counts may be the same, but the actual speed of the drive motor is different, and the accumulated error cannot be corrected. Manual recalibration is required over time.

[0006] The principle of tension angular displacement synchronization is to add a retractable large elbow after each drive motor, and monitor the extension and contraction of the large elbow through angular displacement, while retaining an encoder to monitor the speed of the line body, and all other encoders are cancelled. During the operation of the line body, the drive motor with an encoder is responsible for controlling the speed of the line body, and the other motors assist in following the rotation of the motor. During the operation, if the large elbow has a telescopic movement, it proves that the corresponding motor speed is slow or fast, and the motor speed can be adjusted through the control system to make the line body return to a balanced state. Although this control method has increased stability compared to the encoder synchronization method, the mechanical structure of the line body is more complicated and requires a higher level of designers. At the same time, since the essence of angular displacement monitoring is to monitor the positional relationship of the line body, the response is slow. Once the line body has unexpected situations such as jamming, the angular displacement must be monitored after the consequences of the unexpected situation have completely occurred, which is not as sensitive as encoder synchronization. Utility Model Content

[0007] The utility model aims to overcome the deficiencies of the prior art and provide a multi-motor automatic synchronous control system for a suspension conveyor line.

[0008] The purpose of this utility model is achieved through the following technical solutions:

[0009] A multi-motor automatic synchronous control system for a suspension conveyor line, comprising a human-machine interaction interface, a PLC control module, a communication unit, a frequency converter unit, a motor unit and an encoder unit, wherein the human-machine interaction interface is bidirectionally connected to the PLC control module, the frequency converter unit comprises a plurality of frequency converters, the motor unit comprises a plurality of motors, and the encoder unit comprises an incremental encoder;

[0010] The frequency converter unit is connected to the PLC control module through the communication unit, and the frequency converter is connected to the motor in a one-to-one correspondence. The frequency converter is used to read the frequency and current of the motor. Each motor is connected to a sprocket through a reducer, and the sprocket is used to drive the transport chain in the line body;

[0011] A sprocket is selected as the main sprocket to connect the incremental encoder, and the output end of the incremental encoder is connected to the PLC control module. The incremental encoder is used to measure the cumulative displacement of the driven transport chain.

[0012] Preferably, the communication unit is specifically a MODBUS bus communication mode.

[0013] The beneficial effects of the utility model are:

[0014] The utility model uses only one incremental encoder to monitor the line speed, which simplifies the mechanical structure design of the line. The control method of the multi-motor automatic synchronous control system in conjunction with the suspension conveyor line detects the stress condition of the motor by monitoring the running current of the motor, adjusts the motor speed according to the stress condition of the motor, and realizes multi-motor synchronization; this method simplifies the mechanical structure design of the line while retaining the advantages of the tensioning angular displacement synchronization method, and at the same time speeds up the response speed of line problem monitoring. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 A block diagram of a multi-motor automatic synchronous control system for a suspension conveyor line provided by an embodiment;

[0016] Figure 2 A flow chart of a control method for a multi-motor automatic synchronous control system for a suspended conveyor line provided in accordance with an embodiment. DETAILED DESCRIPTION

[0017] The following will be combined with the embodiments to clearly and completely describe the technical solution of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments of the utility model, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the utility model.

[0018] See also Figure 1-Figure 2 , the utility model provides a technical solution:

[0019] A multi-motor automatic synchronous control system for a suspension conveyor line, comprising a human-machine interaction interface, a PLC control module, a communication unit, a frequency converter unit, a motor unit and an encoder unit, wherein the human-machine interaction interface is bidirectionally connected to the PLC control module, the frequency converter unit comprises a plurality of frequency converters, the motor unit comprises a plurality of motors, and the encoder unit comprises an incremental encoder;

[0020] The frequency converter unit is connected to the PLC control module through the communication unit, and the frequency converter is connected to the motor in a one-to-one correspondence. The frequency converter is used to read the frequency and current of the motor. Each motor is connected to a sprocket through a reducer, and the sprocket is used to drive the transport chain in the line body;

[0021] A sprocket is selected as the main sprocket to connect the incremental encoder, and the output end of the incremental encoder is connected to the PLC control module. The incremental encoder is used to measure the cumulative displacement of the driven transport chain.

[0022] Preferably, the communication unit is specifically a MODBUS bus communication mode.

[0023] In this embodiment, the number of the frequency converters and the number of the motors are both four.

[0024] The motors used to drive the conveyor line are all controlled by a frequency converter, which can read the frequency and current of the motor; an incremental encoder is added to a main drive motor, which is used to calculate the actual running speed of the line.

[0025] Reference Figure 2 This embodiment provides a control method for a multi-motor automatic synchronous control system for a suspension conveyor line, and the main process includes the following steps:

[0026] Step 1, start the line synchronization system, and the PLC control module obtains the rated relationship table of the motor frequency and current from the touch screen of the human-machine interface; before the line synchronous operation, it is necessary to first obtain the rated relationship between the frequency and current of the motor in the line through experiments, and import it into the control system before the line operation.

[0027] Step 2: After the line is running, obtain the operating frequency F1, F2, F3, F4 of each motor, the operating current a1, a2, a3, a4 of each motor and the pulse count value n1 of the encoder every 0.1 second.

[0028] Step 3, calculate the line running speed through the sprocket circumference and n1: V=z / N*n1 / t, V is the actual running speed of the line, N is the total count of one revolution of the encoder; during the actual operation of the line, there is a fixed requirement for V, and the PID algorithm provided by the PLC can be used to ensure that V is as stable as possible during the actual operation of the line.

[0029] Step 4, through the current frequency and the rated relationship between the frequency and the current of the motor, the rated current Ae1, Ae2, Ae3, Ae4 of the motor under the frequency can be obtained.

[0030] Step 5, calculate A1=|Ae1-a1|, A2=|Ae2-a2|, A3=|Ae3-a3|, A4=|Ae4-a4|, and determine whether any value of A1 to A4 is greater than Ag, where Ag is the maximum error between the actual current and the rated current, input by the touch screen of the human-computer interaction interface; if any value is greater than Ag, the line body stops running immediately.

[0031] Step 6: If no value is greater than Ag, calculate Fp1=K(Ae1-a1), Fp2=K(Ae2-a2), Fp3=K(Ae3-a3), Fp4=K(Ae4-a4), where K is a constant input by the touch screen.

[0032] Step 7, let F1=F1+Fp1, F2=F2+Fp2, F3=F3+Fp3, F4=F4+Fp4, and assign F1 to F4 to the corresponding inverter through the modbus protocol to change the frequency of the inverter.

[0033] Step 8: Delay 0.1 seconds and repeat steps 2-7.

[0034] This method detects the stress condition of the motor by monitoring the motor's operating current, adjusts the motor speed according to the motor's stress condition, and achieves multi-motor synchronization; this method retains the advantages of the tensioning angular displacement synchronization method while simplifying the mechanical structure design of the line body and speeding up the response speed of line problem monitoring.

[0035] The above is only a preferred embodiment of the utility model. It should be understood that the utility model is not limited to the form disclosed herein, and should not be regarded as excluding other embodiments, but can be used in various other combinations, modifications and environments, and can be modified within the scope of the concept described herein through the above teachings or the technology or knowledge of the relevant field. The changes and modifications made by those skilled in the art do not deviate from the spirit and scope of the utility model, and should be within the scope of protection of the claims attached to the utility model.

Claims

1. A multi-motor automatic synchronous control system for a suspension conveyor line, comprising a human-machine interface, a PLC control module, a communication unit, a frequency converter unit, a motor unit and an encoder unit, wherein the human-machine interface is bidirectionally connected to the PLC control module, and is characterized in that: The frequency converter unit includes a plurality of frequency converters, the motor unit includes a plurality of motors, and the encoder unit includes an incremental encoder; The frequency converter unit is connected to the PLC control module through the communication unit, and the frequency converter is connected to the motor in a one-to-one correspondence. The frequency converter is used to read the frequency and current of the motor. Each motor is connected to a sprocket through a reducer, and the sprocket is used to drive the transport chain in the line body; A sprocket is selected as the main sprocket to connect the incremental encoder, and the output end of the incremental encoder is connected to the PLC control module. The incremental encoder is used to measure the cumulative displacement of the driven transport chain.

2. According to claim 1, a multi-motor automatic synchronous control system for a suspension conveyor line is characterized in that: The communication unit is specifically a MODBUS bus communication mode.

Images