A controller design framework for telerobotic systems

This research work focuses on development of a framework for designing a telerobotic system controller. We define telefunctioning as a robotic manipulation method in which the dynamic behaviors of the slave robot and the master robot are functions of each other; these functions are the designer's choice and depend on the application. In a subclass of telefunctioning called telepresence, all of the relationships between the master and the slave are specified as "unity" so that all of the master and slave variables (e.g., position, velocity) are dynamically equal. To create telefunctioning, we arrive at a minimum number of functions relating the robots' variables. We then develop a control architecture which guarantees that the defined functions govern the dynamic behavior of the system. The stability of the closed-loop s) stem (master robot, slave robot, human, and the load being manipulated) is analyzed and sufficient conditions for stability are derived. 1. A CCO MPLISHMENTS 1) We have introduced a new control architecture for telerobotic systems. This control architecture is different from the two most common telerobotic control architectures in present use: "position error architecture" and "forward flow architecture". The architecture proposed here is the most general extension of the two present architectures and allows a variety of performance specifications. One important property of this new control architecture is ,hat it can be formulated as an Hoo problem after applying the ex~ ~t linearization method to ~he robot dynamics. Our proposed control architecture has led to {;, ffitrollers which exhibit robustness in the presence of changes in the human and load dynamics. 2) 3) The physical interface between 1 telerobotic system and a human has introduced a new concept: the exchange of I2ower and inflrmation signals between the master robot and the human arm which is in physical contact with the master. The human wears the master robot, so power transfer is unavoidable and infol mation signals from the human help to control the machine. We have studied such human-machine interaction when this new proposed control architecture governs the system behavior. Our study has led to an understanding of the role of human dynamics in the control of telerobotic systems. We have experimentally verif;ed the system performance when the system is subjected to changes in the human dynamic) and the environment dynamics. We have evaluated both the system performance and the sy~tem stability experimentally. Figure 1 shows the experimental setup: a two-degree-of-freedon'. XY table was used as the. master robot. A three-degree-offreedom composite robot was u~'ed as the slave robot. Sinc~ the master robot operates only on a horizontal plane, one of the slave's robot actuators is phys1.cally locked so that the slave robot operates on the horizontal plane also. As shown in Figure 7, the operator's hand grasps a handle mounted on a force sensor. A .)iezoelectric force sensor between the handle and the XY table measures the human's force, fill. along the X and Y directions. 4)