Theory and applications of robotics in teleoperation and medical systems

This dissertation addresses several important issues of robotics in teleoperation and medical systems: stability, safety, positive realness, tracking, transparency and adaptive control. Communication time delay appears commonly in teleoperation systems. A time delay in a bilateral teleoperation reduces system stability and performance. Therefore to design a stable teleoperation system in the presence of time delay is an important issue. However, to analyze and design such a system is difficult because the time delay turns a finite-dimensional system into an infinite-dimensional system. Some special teleoperation requirements, such as telepresence or transparency, and safety requirements from medical applications further complicate the design and analysis. Despite recent progresses in this area, there are many challenging open issues.; In this dissertation, we developed several robot control schemes which will ensure stable and tracking or transparent performance in the presence of manipulator uncertainties, unconstruct and varying environment dynamics as well as communication time delays. Some control schemes are applied in robot-aided neurosurgery, breast biopsy and clinical laboratory automation. In summary, (1) We proposed a non-linear two-port transformer to represent the transmission of the master's acceleration to the slave site. With this representation, the stability of acceleration transmission was analyzed in both non-time delay and time delay cases. The acceleration transmission in a teleoperation system will cause the lose of passivity. However we proved that this passivity lose is small and can be compensated. (2) We developed a force reflecting control scheme, in which the master's acceleration is transmitted to and used by the slave control. This scheme ensures the slave position tracking to the master's arbitrary continuous trajectory for non-contact tasks. A force compensation design is further proposed for the slave control to achieve slave position tracking performance in the presence of communication time delays. Stability of the resulting teleoperation system is obtained in the sense of passivity. (3) We proposed the concepts of weak transparency, asymptotic weak transparency and approximate weak transparency for the teleoperation system with uncertain and time varying dynamics. (4) We developed adaptive transparency control schemes for teleoperation systems with unknown jumping, with known or unknown time-varying environment dynamics. Stability of the resulting teleoperation systems is guaranteed, and related weak transparent performance is achieved. (5) We presented a strictly passive communication law and a passive four-channel communication law. Combining with those communication laws, our transparency control schemes can be extended to the time delay case, and system stability will be ensured in the presence of time delay. (6) We developed a robot control scheme for the robotic breast needle biopsy system, which ensures stable and asymptotic position tracking in the presence of tissue friction, tissue flexibility and needle flexibility. Adaptive version of this control scheme is also presented for uncertain tissue friction and flexibility parameters. (7) We built 3D simulations to illustrate the concepts of robot-aided clinical laboratory automation, and coded the control software for a robot-aided lab cell.