Cable-Driven Actuation for Highly Dynamic Robotic Systems

Abstract

This paper presents design and experimental evaluations of an articulated robotic limb called Capler-Leg.The key element of Capler-Leg is its single-stage cable-pulley transmission combined with a high-gap radius motor. Our cable-pulley system is designed to be as light-weight as possible and to additionally serve as the primary cooling element, thus significantly increasing the power density and efficiency of the overall system. The total weight of active elements on the leg, i.e. the stators and the rotors, contribute more than 60% of the total leg weight, which is an order of magnitude higher than most existing robots. The resulting robotic leg has low inertia, high torque transparency, low manufacturing cost, no backlash, and a low number of parts. Capler-Leg system itself, serves as an experimental setup for evaluating the proposed cablepulley design in terms of robustness and efficiency. A continuous jump experiment shows a remarkable 96.5 % recuperation rate, measured at the battery output. This means that almost all the mechanical energy output used during push-off returned back to the battery during touch-down.

An Open Torque-Controlled Modular Robot Architecture for Legged Locomotion Research

“…Planetary gears share loading among multiple teeth [35]. Cable [14], [20], belt [25], and chain-driven [13], [16] actuators exhibit high robustness against external peak torque and can transmit power over a larger distance at low reflected inertia. Here, we use a low weight, dual-stage timing belt transmission with 9:1 gear reduction.…”

“…High resolution encoders provide motor shaft position feedback. (b) We compacted an off-the-shelf TI Evaluation Board 13 , into our MPI Micro-Driver electronics board14 . It controls two brushless motors, with feedback from two optical encoders.…”

A Time-Freezing Approach for Numerical Optimal Control of Nonsmooth Differential Equations With State Jumps

“…We consider a hopping robot that has to jump over three holes to reach a desired target. Thereby an OCP formulation for synthesizing dynamics motions of the single-legged 2D robot Capler [11,16] is derived. The robot is described by four degrees of freedom q = (x B , z B , φ knee , φ hip ).…”

Improved Performance on Moving-Mass Hopping Robots with Parallel Elasticity

“…of locomotion [4], [10], [8] to allow for long-term hopping using on-board power. These improvements were achieved through a variety of means such as lessening the mass of components, using more direct actuation input, or using more efficient elastic elements.…”

“…These improvements were achieved through a variety of means such as lessening the mass of components, using more direct actuation input, or using more efficient elastic elements. With improved efficiency of actuation, researchers have been able to push the capabilities of the robots further towards higher hops [10], [8] and over complex terrain [9]. When using high-power actuation in critical environments such as when humans are present, the task of safety becomes a critical concern.…”