| This thesis describes the design, construction, and control of a class of computer controlled human-assisted robotic systems. This robotic system is a robot worn by a human to increase human mechanical ability. The system is referred to as an extender since it extends the human's mechanical ability to maneuvering objects. Commands are transferred to the extender via the contact forces between the human and the extender, eliminating the need for joystick, push-button or keyboard to transfer such commands. Instead, the operator becomes an integral part of the extender while executing the task. When the worker uses the extender to touch and manipulate a load, the extender transfers to her/his arm, as natural feedback, a scaled-down value of the actual load weight which the extender is manipulating: the human "feels" the load weight in the manipulations.; An experimental electric two-degree-of-freedom direct-drive extender has been designed and constructed for this Ph.D. study. With high-torque/wide-bandwidth actuators, and the direct-drive architecture, this experimental extender can track the human arm maneuvers to the extent that the human feels minimum restriction in his motions. The extender is interfaced with an 486/25 IBM AT compatible computer for control. The human and environment dynamics play significant roles in the performance and stability of an extender. Modelling the human and environment dynamics inside a control loop were performed first. Then expressions for the performance and stability were derived based on the human and environment dynamic models. The stability analysis, and the performance specifications lead to the controller design methods. The dynamic models, the control technique, and the trade-off between the stability and performance specification were verified experimentally by using the prototype 2 degree of freedom extender. |
