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How to Monitor Part Presence with the Robotiq Gripper

Detect drops using grip_check at key moments or continuously with a background thread

Context

In applications where part retention is critical, ensuring that a part remains gripped during movement is essential. Robotiq’s  gripper provides a grip_check function to help detect whether a part has been dropped. This article explains two recommended methods to use grip_check either before and after motion or continuously during robot movement.

 

 

Method 1: Check at the Start and End of Motion

This is the simplest way to verify grip integrity without requiring extra programming complexity.

  1. Before the motion begins, call the grip_check() function.

  2. If the function returns False, it indicates the part is not present—halt the process or trigger an alert.

  3. After the motion ends, call grip_check() again to ensure the part is still present.

This method works well for most stable operations and reduces computational load on the robot.

 

 

Method 2: Continuous Grip Check Using a Thread

For dynamic applications, especially those involving fast movements or possible part loss—you can monitor the grip in real time by running grip_check() in a parallel thread.

  1. Create a separate thread in your robot program.

  2. Inside the thread, use a loop to repeatedly call grip_check() during the robot’s movement.

  3. Add a short delay (e.g., sleep(0.1)) inside the loop to avoid overloading the processor.

  4. Start the thread just before the motion begins.

  5. Stop the thread once the motion ends or the grip needs to be released.

This method ensures real-time monitoring and can help trigger immediate safety actions or error handling.

 

 

Best Practices

  • Use the simplest method when possible to reduce code complexity.

  • Always debounce your loop with a sleep() delay to prevent performance issues.

  • Test thoroughly to ensure thread-based checks don’t interfere with motion execution.

  • Refer to official documentation: grip_check details are on page 98 of the Gripper Manual

 

Conclusion

Using grip_check, you can ensure reliable part presence monitoring during robot operations. Whether you need a quick check before and after motion, or continuous real-time verification, Robotiq offers flexible options that adapt to your cell’s reliability needs.