On the Mechanism Design of Tendon-Driven Manipulators with Fail-Safe Characteristics
Date Issued
2012
Date
2012
Author(s)
Sheu, Jinn-Biau
Abstract
Tendon-driven manipulators have been widely used in many applications. Recently, tendon-driven manipulators have successfully been used for some robot-assisted medical surgery. Fail-safe design features should be incorporated into such manipulators to increase safety. There are many safety features to be concerned, e.g., fail-safe design of hazard detectors, protection against software/hardware failures, intrusion monitoring, or use of panic buttons. In this paper, a tendon-driven manipulator with redundant tendons is used to increase fail-safe feature in the event of hardware failure. A tendon-driven manipulator having redundant tendons may also possess additional flexibility in operation such as capable of optimizing the performance of tendons, reducing the burden of each tendon, and allowing fault tolerance for actuation. The purpose of this paper is to develop a methodology for synthesizing tendon-driven manipulators with redundant tendons and fail-safe features, and to optimize the distribution of tendons force of the system. Characteristics of tendon-driven manipulators and fail-safe features are briefly discussed. Criteria for the tendon-driven manipulator with fail-safe features are derived from the null space of the structure matrix. With these constraints, manipulators can remain controllable when any of the tendons fails to function. Finally, procedures for determining the structure of the tendon-driven manipulator are developed via geometric method and optimization-based numerical method. Solutions found by geometric method can be used for the initial estimate of optimization method. The objective of optimization method is to even the burden of each tendon and to reduce cost.
Subjects
tendon-driven
structure matrix
fail-safe
null space
condition number
Type
thesis
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