Importance

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Abstract

A safety circuit is described that monitors a number of sensors for intrusion of objects or people into the workspace of a robot and controls the drive power to the motion control system via an emergency-stop circuit. The system monitors the motion control system and models it as just another sensor to ensure that it is working properly. In the event that there is intrusion, the safety circuit assigns a degree of intrusion (e.g., precautionary or serious). For serious intrusions, the safety circuit kills drive power thereby preventing additional motion of the robot. Killing drive power (de-energizing the emergency-stop circuit) requires a qualified operator to restart for further operation. For precautionary intrusions, the safety circuit takes control of the motion control system by disabling the power stages of motion control amplifiers but retaining drive power there. This inhibits further motion. The safety circuit keeps the amplifiers inhibited for a period to permit the intrusion time to clear. In the event that the intrusion clears quickly, the safety circuit releases control of the power stage to permit continued operation (automatic recovery). This can reduce the occurrences of nuisance trips of the emergency-stop circuit. Various means in the architecture are described here to ensure and verify that the system is safe. This is advantageous because scrutiny of the approach can be focused on the limited functionality (software, hardware) of the safety circuit. Highly complex functionality (software, hardware) of the motion control system can be safely modeled as potentially unsafe, thereby requiring far less scrutiny.

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First Claim