Investigation of Capstan Friction and its Potential Use as a Mechanical Amplifier

Abstract

Actuation is one of the fundamental aspects of robots.Optimization of a robotic system poses a complex problem for engineers.For developing robots that mimic biological systems, the robot actuation problem becomes more complicated because of stringent limitations on space and power output.It is hypothesized that a system can be designed which would allow a rotating capstan to act as a mechanical amplifier when a flexible member such as a cord or rope is wrapped around it.When a tension is applied to the end of the cord pointing in the direction of the capstan's rotation, friction will be transferred to the cord and the tension will effectively be amplified.Experimentation was performed to validate a traditional assumption for how the dynamics of the system should work.The capstan equation was found to be only a rough estimation of the behavior of the system.A new equation was formed by combining known curves and fitting them to the data.Simulation of the new equation provides an initial insight into the behavior of a combined capstan amplifier system.