Combined feedback and command shaping controller for multistate control with application to improving positioning and reducing cable sway in cranes

Abstract

Disclosed are algorithms for controlling multiple states of a dynamic system, such as controlling positioning and cable sway in cranes. Exemplary apparatus and methods may be implemented using first and second serially coupled feedback loops coupled to a plant and payload that are to be controlled. The first feedback loop comprises a first control module. It generates a filtered actuator command from an error signal derived from a signal representing a desired system state and a feedback signal indicative of the actual system state. The generated signal is operative to position the payload. The second feedback loop comprises a second control module that generates a second actuator command that is operative to cause the plant to have an output of zero, to eliminate disturbance-induced oscillations. Input shaping may be employed in the first loop for eliminating motion-induced oscillations. The first control module is used for precise payload positioning, and the second control module is used to reject disturbance-induced oscillations. A model reference loop may be employed that outputs a modeled response that is an estimate of the response of the plant in the absence of external disturbances, and which may be used to generate a second actuator command for causing the plant to follow the modeled response.