Tips

Free-axis stop on collision

Check the setting labeled “free-axis collision” (軸フリー衝突).

COBOTTA supports two collision-response modes:

  • Stop immediately upon collision.

  • Free axis upon collision.

In free-axis mode, the controller can exit the free-axis state and enter a recoverable continue-stop state when the applicable recovery conditions are met, such as:

  • COBOTTA motion comes to a stop, even if contact persists in the free-axis state.

  • The robot remains stopped for at least one second after collision detection.

  • An axis moves by at least 10 degrees after the collision is detected (after the axis has been released).

This makes software-only recovery possible even after a collision leads to a stop. In limited testing, this feature operated as expected.

However, the ease and reliability of recovery depend on the circumstances. It is still difficult to determine whether free-axis collision handling can safely be incorporated as an expected step in an automated sequence.

Nevertheless, this collision-response option significantly broadens the possible operating and motion strategies for COBOTTA.

Configuring free-axis collision handling

  1. Arm

  2. Auxiliary functions

  3. Collision / interference

  4. Collision detection

  5. Collision detection settings

The parameter can be set up to 1000%. A higher value makes collision detection less sensitive.

Maximum-speed parameters

COBOTTA’s dedicated hardware parameter configuration utility provides the settings shown below. After installing DENSO’s WINCAP3, create a project, configure the controller, and load its settings from the controller to access the parameter screen.

Parameter tool:

The screen suggests that speed limits can be adjusted over a fairly wide range. However, when the hardware speed limit was actually changed and measured:

Actual J1 speed with the maximum setting:

Actual J1 speed with the normal setting:

The measured J1 speed changed by only about 6%, with no noticeable difference in operation.

For J6, by contrast:

J6 normal speed setting:

J6 maximum speed setting:

The measured speed increased by nearly a factor of 1.5.

This suggests that changing the speed limit is more effective for motions involving higher-numbered axes. For load-bearing axes such as J1, the benefit appears smaller.

Configuring the parameters

Use WINCAP3 and the Parameter Setting Tool installed alongside it. A WINCAP3 license is provided with the purchase of a COBOTTA unit.

  1. Install WINCAP3.

  2. Create a new project in WINCAP3; the Parameter Setting Tool requires a project even if WINCAP3 itself is not used to move the robot.

    • The project is required to access the robot and retrieve controller parameters.

    • The Parameter Setting Tool uses the WINCAP3 project for this operation.

  3. Launch the Parameter Setting Tool (installed with WINCAP3).

  4. Open the project.

    • Choose Add scene. Different scenes can hold different parameter sets.

    • Parameters can be configured in newly added scenes.

    • The actual-machine and factory-default scenes cannot be edited.

  5. Transfer the parameters using the Parameter Setting Tool’s communication function.