Modeling and Design of a Mechanical Tendon Actuation System

Basic dynamics of single tendons are modeled, isolated, and measured. Fundamental transmission line models are presented with assumptions applicable to using the models for tendons. The models are verified by careful experimental design. It is then shown how to use this fundamental data to design and determine bandwidth limitations of tendon actuation systems. Short, stiff, light tendons transmit force and velocity best. Pulley friction in the tests reported was primarily Coulombic, causing signal delay. This delay was significant for tendons routed across bushings or bare metal pegs, but it was not a factor when the tendons were routed over pulleys mounted on bearings. Increasing the number of pulleys increased the delay in the case of the pegs or bushings enough to cause instability in some systems. Assuming a second order load, curves were generated relating bandwidth to tendon system and load parameters.