“Touch Probe” function

Operating principle

The “Touch Probe” function detects the position of the drive based on defined input signals. The digital inputs on the ASI8100 can be used for this purpose.

In the tab Process data the necessary inputs and outputs can be added. The abbreviation TP1 stands for Touch Probe 1, and is linked to input 1. The abbreviation TP2 stands for Touch Probe 2, and is linked to input 2.

Each Touch Probe input can only detect edges of one direction at any time (rising or falling). It is not possible to respond to both edges at the same time. There is no dependency between the inputs: A rising edge can be detected at TP1, while a falling edge is detected at TP2.

Use the “Tc2_MC2” PLC library The TwinCAT library “Tc2_MC2” contains the “MC_TouchProbe” function block, which simplifies the mapping and handling of the “Touch Probe” function.

MC_TouchProbe | from the “Tc2_MC2” PLC library

The TwinCAT Motion Control PLC library Tc2_MC2 contains function blocks for programming machine applications. It is based on the PLCopen specification for Motion Control function blocks V2.0.

Wiring

The Touch Probe inputs must be wired using single-wire technology (24 V DC).

Configuration

The digital inputs are configured in Drive Manager 2 to use the “Touch probe” function. To describe the function, input 1 (TP1/Probe unit 1) is used as an example here.

Process image

Checking the checkbox under “digital I/O” automatically adds the necessary process data to the process image of the ASI8100.

Fig.8: Process image (to follow)

Fig.8: Mapping touch probe status (Inputs)

Fig.8: Mapping touch probe control (Outputs)

TP1 is used here as an example to illustrate the mapping's functionality.

Process data

Memory area for the latched position value

The stored position can be read from the PDOs underTP1 pos position(positive edge) andTP1 neg position(negative edge), depending on the edge.

Latch parameter

TP1 Trigger mode is not relevant to the ASI8100 and has no function.

Handling

Examples

Latching on every rising edge

Latching on first falling edge

Cyclic/repeated latching on the first falling edge

To latch onto the first falling edge again, you must disable TP1 Enable and then re-enable it. The position is saved again on the first negative edge.