Position signal interface for the robotic arm control system

There is often a significant gap between the results of theoretical studies based on simulations and the results obtained from an actual implementation. The robotic arm control system (RACS), developed at Tennessee Technological University, provides a testbed to implement user-defined control schemes on a VAL II Mk III controller. The position signal interface (PSI), which provides the primary position feedback path in the RACS, is described in the paper. It keeps track of all the joint positions and allows real-time access to the position and error data. The PSI is built on a single DIP plugboard and fits into the Unimation controller rack. Feedback signals from the six optical encoders are used by the PSI to determine absolute joint positions and for error detection. Two important errors, lost encoder synchronization and no zero index pulse, are reported to the RACS controller if detected. The PSI also provides joint position data to the VAL communication interface of the RACS for operation in a `VAL-dependent´ mode. Features of the PSI and its initial integration into the RACS are described. The results of the integration efforts demonstrate fast, efficient operation