S7-1200PLC motion control case introduction

In this case, we mainly learn the motion control function of 1200PLC. We use this three-axis device (as shown in Figure 1) to draw a square with a length and width of 50mm.

On the HMI (as shown in Figure 2), you can manually enable the axis, manually run the X-axis in the positive and negative directions, manually run the Y-axis in the positive and negative directions, manually run the Z-axis in the positive and negative directions, teach the reference position point, etc. In automatic mode, press the "Start" button to automatically draw a square with a length and width of 50 mm.

Programming ideas

1) You can set a reference point (as shown in Figure 3), and then calculate other position points in sequence.

2) Use absolute positioning instructions to reach the relevant position point.

Figure 3

2

Programming

1) Create a process object: Create the process object of the X axis (as shown in Figure 4 to Figure 10). The process objects of the Y axis and Z axis are similar and will not be described here.

Figure 4

Figure 5

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Figure 7

Figure 8

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Fig.10

2) Because our device has three axes, X, Y, and Z, and each axis has a position value, we can create a "UDT data type" to store the position values ​​of the three axes. The data type name of UDT is "Pos", as shown in Figure 11 and Figure 12.

Figure 12 Figure 11

3) Manual control program (FC1), as shown in Figures 13 to 16, mainly implements the functions of axis enabling, jog control of three axes, homing of three axes, fault reset of three axes, etc.

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Fig.16

4) Position calculation (FC2), to calculate the 4 position points of a square, you can use SCL language to write. When the value of "inst_Pos".HMI_SetBase" (derived from the button on the HMI) is 1, calculate the 4 position points. As shown in Figures 17 and 18,

Fig.17

Fig.18

The calculated position values ​​are stored in array variables, as shown in Figure 19. The coordinate values ​​of the four points correspond to the four position values ​​of Figure 3.

Fig.19

3) Main program

①Segment 1 mainly calls the manual control program. And after pressing the "inst_Pos".HMI_Start" button on the HMI, the status step MW36 is set to 1.

② "inst_Pos".HMI_SetBase" is the button for setting the reference point on the touch screen. When this button is pressed, a reference point can be set, and a square is drawn according to the reference points. Since the calculated position values ​​of the third and fourth positions are opposite, the values ​​in the address are swapped. "inst_Pos".Pos[1] is given to "inst_Pos".FinalPos[1], "inst_Pos".Pos[2] is given to "inst_Pos".FinalPos[2], "inst_Pos".Pos[3] is given to "inst_Pos".FinalPos[4], and "inst_Pos".Pos[4] is given to "inst_Pos".FinalPos[3]. The starting point and the end point are the same point, so "inst_Pos".Pos[1] is given to "inst_Pos".FinalPos[5]. The "inst_Pos".FinalPos variable is shown in Figure 20.

Fig. 20

③Call the position calculation program

④Current position of the axis

⑤ Status step judgment, and then reach different positions