The control of the robot is realized by using PLC technology, and its task is to carry the workpiece from the conveyor belt A to the conveyor belt B. Use the shift instruction to design the sequence program.

The schematic diagram of the action of the robot is shown in Figure 1. It is a mechanical device capable of producing horizontal/vertical displacement for transporting the workpiece from the left table to the right table.

figure 1

1. Process and control requirements

The entire action of the robot is driven by the cylinder, which in turn is controlled by the corresponding solenoid valve. Among them, the rise/fall and the left turn/right turn are respectively controlled by the double coil two-position solenoid valve. For example, when the lowering solenoid valve is energized, the robot is lowered; when the lowering solenoid valve is powered off, the robot is stopped to stop. The manipulator only rises when the rising solenoid valve is energized; when the rising solenoid valve is de-energized, the manipulator rises and stops. Similarly, the left turn/right turn are controlled by a left turn solenoid valve and a right turn solenoid valve, respectively. The robot's relaxation/clamping is controlled by a single-coil two-position solenoid valve (called a clamping solenoid valve) to control the movement of the cylinder. When the coil is energized, the robot clamps; when the coil is de-energized, the robot relaxes.

When the robot is moved to the right and ready to descend, in order to ensure safety, the robot must be allowed to descend when there is no workpiece on the right table. That is to say, if the workpiece that was transported to the right table has not been removed, the robot should automatically stop descending and use the photoelectric switch I0.5 to detect no workpiece.

The action process of the robot is shown in Figure 2. Starting from the origin, press the start button, the solenoid valve is energized, and the robot is lowered. When the bottom is lowered, the lower limit switch is touched, the lowering solenoid valve is de-energized, and the lowering stops; at the same time, the clamping solenoid valve is turned on and the robot is clamped. After clamping, the rising solenoid valve is energized and the robot is raised. When it rises to the top, it hits the upper limit switch, the rising solenoid valve is de-energized, and the rise and stop; at the same time, the right-hand solenoid valve is turned on, and the manipulator moves to the right. When the right shift is in place, the right limit switch is touched, the right shift solenoid valve is powered off, and the right shift stops. If there is no workpiece on the right table at this time, the photoelectric switch is turned on, the lowering solenoid valve is energized, and the manipulator is lowered. When it is lowered to the bottom, it hits the lower limit switch, and the lowering solenoid valve is de-energized and stops. At the same time, the clamping solenoid valve is de-energized and the manipulator is relaxed. After relaxation, the rising solenoid valve is energized and the robot is raised. When it rises to the top, it hits the upper limit switch, the rising solenoid valve is powered off, and the rise and stop; at the same time, the left shift solenoid valve is turned on, and the manipulator moves to the left. When moving to the origin left, the left limit switch is touched, the left shift solenoid valve is powered off, and the left shift stops. At this point, the robot completed a cycle of actions after eight steps.

figure 2

The operation mode of the robot is divided into manual operation mode and automatic operation mode. The automatic operation mode is divided into three modes: stepping, single cycle and continuous operation.

(1) Manual operation: It is the button operation to control the movement of each step of the robot separately. For example, when the up/down motion is selected, the start button is pressed and the robot is lowered; when the stop button is pressed, the robot is raised. When the left/right motion is selected, the start button is pressed and the robot moves to the right; when the stop button is pressed, the robot moves to the left. When the clamping/relaxing motion is selected, the start button is pressed and the robot is clamped; when the stop button is pressed, the robot is relaxed.

(2) Stepping operation: Each time the start button is pressed, the robot automatically stops after completing one step.

(3) Single-cycle operation: The robot starts from the origin, presses the start button, and the robot automatically stops after one cycle of action.

(4) Continuous operation: The robot starts from the origin and presses the start button. The action of the robot will automatically and continuously cycle continuously. If the stop button is pressed during work, the robot will continue to complete the cycle and then automatically return to the origin.

2, the operation panel layout

Figure 3 is a diagram of the operation panel layout.

Turning on I0.7 is a single mode of operation. Press the position of the load selector switch and use the start/stop button to select the load operation. When the load selector switch is pressed to the “left and right” position, press the start button and the robot will go to the right; if the stop button is pressed, the robot will go to the left. Use the above operation to stop the robot at the origin.

Turning on I1.0 is the stepping mode. When the robot is at the origin, press the start button to move forward one step; each time the start button is pressed, one step is performed. Turning on I1.1 is a one-cycle operation. When the robot is at the origin, press the start button to automatically operate for one cycle. Turning on I1.2 is a continuous operation. When the robot is at the origin, press the start button to continuously perform the automatic cycle operation. When the stop button is pressed, the robot automatically returns to the origin after the cycle is completed and no longer operates.

image 3

3. Input/output terminal address distribution The PLC used in the robot control system is the S7-200CPU214 produced by Siemens AG of Germany. Figure 4 is the address assignment diagram of the input/output terminal of the S7-200 CPU214. The robot control system uses a total of 14 inputs and 6 outputs.

Figure 4

4, the overall program structure

The overall program structure of the robot is shown in Figure 5. If the single operation mode is selected, I0.7 is disconnected, and then a single operation procedure is executed. (Single operator can be independent of the automatic operation program and can be designed separately).

The automatic operation program can be executed in the single cycle mode and the continuous mode. In the stepping mode, execute the stepping operation program, press the start button to perform an action, and proceed in the specified order.

When the automatic operation mode is required, the intermediate relay M1.0 is turned on. The same output relay is used for stepping mode, single operation mode and automatic operation mode.