Slip ring transmitters in robot controllers

Slip ring transmitters in robot controllers

Slip ring transmitters in robot controllers

Slip ring transmitters are frequently used in continuously rotating systems where e.g. motors and control units also turn. Both the drive power and the control and feedback signals (mostly via bus connections) are transmitted via a continuously rotating slip ring.

Detailed application description

Description of problem:

A freely moving service robot developed by Fraunhofer IPA (Institute for Manufacturing Engineering and Automation) acts as a universal helper in everyday environments. The robot’s potential applications range from simple assistance services (e.g. helping customers locate desired products in an electronics store) to complex medical problems (e.g. care for the elderly).

The robot required three freely rotating drive wheels to give it a 360° range of motion and also allow rotation “on the spot”. In order to avoid complex and heavy belt or chain drives, the motor and controller are installed below the wheel suspension. For this design, both the motor and the control unit have to be supplied with electrical power and bus signals at all times – even with a full motion range exceeding 360°.

Description of solution:

To allow the service robot to move through the maximum 360° range and rotate “on the spot”, the freely rotating drive wheels had to be integrated as “feet” and reliably supplied with power and control signals. The solution is based on LTN’s compact SC045 slip ring, which fits perfectly into the space available. Low-voltage power is supplied to the motor (rated for 10 A continuous current/channel) via four separate channels. Four signal paths are reserved for conventional control signals and two for the industrial bus. In particular, the circlip arrangement on the LTN brush block enabled a small installation space with high current density and highly reliable transmission of the bus signals. Gold-gold contact technology was selected.

Since the slip rings are only a few centimetres above the ground, robust, enclosed ball bearings protect the mechanics against unpredictable environmental influences – just in case the robot gets wet feet.

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