BrakeReleaseController

Use this controller to deactivate the brakes at startup on any Duatic DuaDrive equipped with brakes.

Why is this controller needed?
The DuaDrives use pin brakes. If the full weight of an arm is loaded onto a pin brake it is possible that the pin cannot be pulled. For this case the pin needs to be unloaded.

Usage

Add entry in controllers.yaml and in your launch infrastructure. Do not directly activate it during startup
Make sure to deactivate the FreezeController
Activate the BrakeReleaseController
If it was for some reason not successful -> Retry (deactivate -> activate)
Deactivate the controller to release the position/velocity interfaces

NOTE: The “manual” mode assumes the GravityCompensationController is up and running

How does it work ?

Mode: “auto”

The controller calculates the currently needed joint torques to hold the arm in its current configuration. Therefore a properly configured URDF is needed.

It then commands a small position “kick” into the same direction of the corresponding torque. This unloads the brakes and helps releasing them.

Mode: “manual”

In this mode the controller simply performs the unlock lifecycle by:

“excite brakes” -> give user “timeout” seconds to move joints -> “put drives into hold”

Interaction

Mode: “auto”

None, only activate, deactivate

Mode: “manual”

Activate, manually move all joint around to unlock all the brakes, deactivate

Parameters

Name	Description	Default	Bounds
`joints`	List of joint names as described in the URDF the controller shall handle	-	may not be empty
`position_kick	Distance each actuator shall move against gravity in [rad].	0.005	[0.0, 0.2]
`mode`	Select as an alternative manual mode	“auto”	“auto” or “manual”
`timeout`	Time in manual mode until brakes are put into hold mode	50.0	>= 0.0

Notes

This controller needs a correctly configured URDF including masses