Anti-delay closed-loop input shaper to improve manual control of flexible system

One example of the manual control of flexible system is the crane operator trying to move a swinging payload from point to point as fast and as accurate as possible. The payload swing definitely slows the task. Recent work has proposed placing an input shaper inside the feedback loop, so-called closed-loop signal shaping, to suppress the residual vibration of the flexible system. The residual vibration was successfully suppressed. However, there was a delay between the time the operator stops giving the command and the time the system actually stops. This is due to the modification of the command by placing the input shaper inside the feedback loop. The delay results in lower accuracy in placing the payload because the operator must guess where the system will stop. This paper presents an improvement on the present closed-loop signal shaping by placing the Smith predictor inside the feedback loop. The predictor significantly reduces the delay. Experiments have shown that operators can maneuver the flexible system using less time and with less subjective difficulty.