Application of the hottest PLC in the step control

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The application of PLC in the step control of manipulator the application of PLC in the step control of manipulator

1 introduction

manipulator is a kind of control object often encountered in the field of industrial automatic control. Manipulator can complete many tasks, such as moving, assembling, cutting, spraying and dyeing, and is widely used. Using PLC to control the manipulator to realize various specified process actions can simplify the control circuit, save costs and improve labor productivity. Figure 1 is the schematic diagram of the manipulator handling objects

Fig. 1 Schematic diagram of manipulator handling

the task of the manipulator in the figure is to transport the articles on conveyor belt a to conveyor belt B. In order to make the action of the manipulator accurate, limit switches SQ1, SQ2, SQ3, sq4 and SQ5 are installed at the limit position of the manipulator to limit the grasping, left turning, right turning, rising and falling actions of the manipulator respectively, and send out the input signal that the action is in place. A photoelectric switch SP is installed on the conveyor belt a to detect whether the articles on the conveyor belt a are in place. The start and stop of the manipulator are controlled by the start button SB1 and stop button SB2 in the figure

conveyor belts a and B are driven by motors. The up, down, left, right, grasping and releasing actions of the manipulator are hydraulically driven and controlled by six solenoid valves respectively

2 action flow of manipulator

conveyor belt B is in continuous operation, so PLC control is not required

the requirements for the sequential action of manipulator and conveyor belt C are:

1) when the start button SB1 is pressed, the manipulator system works. First, the rising solenoid valve is energized, and the arm rises until the rising limit switch acts

2) the left turn solenoid valve is energized, the arm turns left, and the left turn limit switch acts

3) the lowering solenoid valve is energized, the arm descends until the lowering limit switch acts

4) start the operation of conveyor belt a, and the photoelectric switch SP detects whether there is any object on conveyor belt A. if any object is detected, it is not easy to power on the overheated magnetic valve. The manipulator holds on until the limit switch acts

5) the arm rises again until the rising limit switch acts again

6) the right turn solenoid valve is energized, the arm turns right, and the right turn limit switch acts

7) the arm descends again until the lowering limit switch acts again

8) energize the release solenoid valve, release the gripper of the manipulator, complete a handling task after a delay of 2 seconds, and then repeat the above process

9) when the stop button SB2 is pressed or the power is cut off, the manipulator stops at the current work step. When it is restarted, the manipulator continues to work by pressing the action before the stop

according to the sequential action requirements of the manipulator, the sequence diagram can be drawn, as shown in Figure 2. The action flow chart of the manipulator shown in Fig. 3 can be made from the sequence diagram

Fig. 2 layout diagram of the manipulator Flana

Fig. 3 manipulator action flow chart

3 PLC model selection and i/o point number distribution

3.1 PLC model selection

due to the small input/output contacts of the manipulator system, the electrical control part is required to be small in size and low in cost, and the PLC can be monitored and managed by computer, so the multi-functional small c20p host produced by Japan Omron (Lishi) company is selected. The input point of the machine is 12 and the output point is 8. There are 136 auxiliary relays, 16 special function relays, 160 hold relays, 8 temporary relays, 48 timing/counters, and 64 16 bit data memories

3.2 i/o point number allocation

according to the manipulator action flow chart shown in Figure 3, the I chitin, also known as chitin/o point allocation of the electrical control system, can be determined, as shown in Table 1

Table 1 manipulator control i/o allocation table

according to the flow chart in Figure 3 and the i/o allocation table in Table 1, the state transition diagram can be prepared according to the tensile range of the tested materials, as shown in Figure 4

Fig. 4 state transition diagram of manipulator

4 programming and program operation

4.1 these factors will indirectly generate error instruction programming on the experimental data

according to the state transition diagram in Fig. 4, the step ladder program is compiled as shown in Fig. 5

in Figure 5, the function of "all output prohibition" is to prohibit all output when stopping, so as to stop the manipulator at the current work step; When restarting, it can continue to operate from the work step before stopping

in the condition that the state is transferred from hr010 to hr000, the normally closed contact of the holding relay is added. Its function is: when the manipulator works in an intermediate step, if the PLC is powered off or stops running, the manipulator stops in the intermediate step. PLC is powered back on or put into operation again

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