SINAMICS V90 PN Travel to Fixed Stop Application (S Mode)
This application example explains how to implement a “travel to fixed stop” function using SINAMICS V90 PN operating in speed control mode (S-mode), allowing the motor to move toward a mechanical stop while safely limiting torque without triggering a fault.
The method is commonly used when a machine must detect a physical end position using controlled force rather than sensors.
Application Overview
The “travel to fixed stop” function moves the axis until a defined torque limit is reached; once the stop is detected, the drive maintains the specified torque level instead of generating an error condition.
This behavior allows controlled clamping, referencing, or positioning against mechanical limits.
Function Activation Principle
The function is activated via:
- Control word STW2.8 → enables the travel-to-stop command
- Status word ZSW2.8 → confirms the stop has been reached How to realize (travel to fixed…
This signal exchange allows the PLC to supervise the process through PROFIdrive communication.
Torque Limiting Concept
When the torque setpoint reaches the configured limit, the drive restricts torque to the defined value (TLIM), preventing overload while maintaining controlled force.
Two selectable torque-limit sources can be used via digital input selection, enabling flexible configuration for different machine requirements.
Torque Reduction (MOMRED) Function
The MOMRED control word dynamically scales the torque limit as a percentage of rated torque, allowing smooth adjustment of the applied force during operation.
Actual torque is calculated as:
Actual Torque Limit = Configured Torque × (1 − Reduction Percentage)
This makes the solution suitable for delicate mechanical contact processes.
Implementation in TIA Portal
The application uses the MC_TorqueLimiting function block to activate torque/force limiting or detect a fixed stop during motion control tasks.
Two operating modes are available:
- Mode 0 → Force/torque limiting
- Mode 1 → Fixed stop detection How to realize (travel to fixed…
This block works together with positioning or synchronous axes within the technology object configuration.
Technology Object Configuration
Within the axis Technology Object, engineers configure:
- Torque or force limits (motor-side or load-side)
- Position tolerance used to detect when the axis has reached the stop
- Following error threshold acting as the detection criterion
These parameters define how the system recognizes mechanical contact safely.
Communication Requirements
The application requires Siemens telegram 102 or 105, since torque-reduction data is exchanged through these telegram structures.
Standard telegram 1 cannot be used because it does not include the required control/status words for this function.
