Dual loop control of cable-conduit actuated devices

Nonlinearities in cable-conduit actuation has been a major drawback in operating flexible endoscopes, catheters and other robotic devices. Generally, these nonlinearities are manually compensated by the human in the loop in the absence of any automated control of cable-conduit transmission. Furthermore, size and safety constraints limit the type of sensors that can be used for feedback control. In this paper, a dual loop adaptive robust control is implemented while utilizing the limited output feedback available in conjunction with the intermediate actuator position feedback. Experiments are performed on a gastroscope operated using a DC motor, with output feedback provided through a medical grade magnetic tracker at a very low sampling rate. Experimental results show substantial performance improvement over traditional manual operation. Limitations in the controller design and possible changes have been discussed.