Friction and damping of a compliant foot based on granular jamming for legged robots

Peter Eckert, Simon Lukas Hauser, Auke Ijspeert, Alexandre Tuleu
Ieee, 2016
Article de conférence

Moving away from simple foot designs of current quadruped robots towards a more bio-inspired approach, a novel foot design was implemented on the quadruped robot Oncilla. These feet mimic soft paw-pads of dogs and cats with high traction and soft underlying tissue. Consisting of a granular medium enclosed in a flexible membrane, they can be set to different pressure/vacuum conditions. Tests of general properties such as friction force, damping and deformation were completed by proof of concept tests on the robot. These included flat ground locomotion as well as ascending a slope with different inclination. Comparison tests with the previous feet were performed as well, showing that the new feet have a high friction and strong damping properties. Additionally, the speed of flat ground locomotion is comparable to the maximum speed of the robot with the previous feet while retaining the desired trotting gait. These are promising aspects for legged locomotion. The jamming of granular media previously has been used to create a universal gripper which in the future also opens up opportunities to use the feet both in locomotion and simple object manipulation (although the manipulation is not tested here).

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Peter Eckert, Simon Lukas Hauser, Auke Ijspeert, Alexandre Tuleu
Ieee, 2016
Article de conférence

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https://infoscience.epfl.ch/record/225686?ln=fr

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This work investigates the usage of compliant universal grippers as a novel foot design for legged locomotion. The method of jamming of granular media in the universal grippers is characterized by having two distinct states: a soft, fluid-like state which in locomotion can be used to damp impact forces and enable passive shape adaptation especially on rough terrain, and a hard, solid-like state that is more suited to transmit propulsion forces. We propose a system that actively uses and switches between both states of a foot design based on granular jamming and detail the implementation on a quadruped robotic platform. The mechanism is inspired by the stiffness varying function of the tarsal bones in a human foot, and our aim is to understand how the change of foot stiffness can be used to improve the locomotion performance of legged robots. Using the same open loop trot gait in all experiments, it is shown that a fast state transition enables the robot to profit from both states, leading to more uniform foot placement patterns also on rough terrain compared to other tested feet. This results in overall faster gaits and even enables the robot to climb steeper inclined surfaces.

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