Diverse Redundant Drive Architecture with External Diagnostics Enables Safety-Related Motor Control based on Proven Standard Components at Low Cost

A concept for safety-related motor control for autonomous mobile robots (AMR), automated guided vehicles (AGV), etc. is presented. The drive-internal safety functions are reduced to safe torque off (STO) and safe brake control (SBC) via a safety-related fieldbus for a reliable stopping of the motor. The safe protocol data units (SPDUs) for safe motion are evaluated in a higher-level safety programmable logic controller (PLC). The current and position SPDUs from the drives are transmitted to the safety PLC via a safety-related fieldbus using the gray-channel-principle. Similar to safety-related encoders, the concept is based on the fact that a major part of the diagnostics from the drive is performed externally in the higher-level safety PLC. In combination with a diverse redundant drive architecture, low-cost standard components can be used instead of more expensive safety-certified components. As a result, a fully certified safe logic is not required in the drive.