ROCR is an Oscillating Climbing Robot
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| X’s indicate wall attachment |
Introduction to ROCR
We present a novel climbing robot, with a recursive name: ROCR is an Oscillating Climbing Robot. ROCR is a pendular two-link, serial chain robot that utilizes alternating hand-holds and an actuated tail to propel itself upward in a climbing style based on observation of human climbers and brachiating gibbons. ROCR’s bio-inspired oscillating climbing strategy is efficient, requiring a minimum of input energy in order to climb vertical walls. This robot is intended for autonomous surveillance and inspection on sheer vertical surfaces. ROCR’s physical design is presented, hardware choices are justified and it’s climbing strategy is explained. Several locomotion gait strategies (already investigated in simulation) are presented, defined and implemented in hardware.
Fig 1. Solid model screen capture of ROCR, as designed, is shown with components labelled
Fig 2. ROCR will initially use magnetic gripping mechanisms, these are shown in section view above. Note magnetic piston, topped by encoder, slides within bushing which rotates within bearings. The bushing is capped with a urethane friction ring which works to prevent the piston from sliding as body pivots about grip.
Fig 3. ROCR, in a preliminary assembly, is shown with components labelled
Bio-Inspired Climbing Strategy
Proficient human climbers take advantage of both subtle and dramatic mass shifting to gain elevation with minimal physical effort. A simple lateral body movement prior to changing handholds often enables a human climber to reach higher with less pull-up effort. Human climbers often engage in dramatic mass shifting in preparation for highly dynamic climbing motions, essentially winding-up and then releasing their potential energy (PE) into a large vertical gain.
Brachiation is most notably employed by gibbons when they swing from one handhold to the next in a very dynamic pattern of gripping and swinging. Brachiative motion strings together a sequence of pendular paths with coordinated grip changes to achieve lateral motion. In this method of lateral swinging motion, very little input energy is required to maintain physical progress. ROCR turns standard gibbon brachiation vertical, combining it with human style mass shifting into a tail-swinging body-oscillating scansorial climbing strategy.
By mimicking climbing strategies employed by human climbers and animals, a simple, energy efficient climbing strategy has been developed. ROCR uses precise mass shifts, affected by a carefully controlled tail motion, to raise one hand at a time. Combining and integrating these behaviors enables ROCR to climb efficiently with a minimum of mass and moving parts.
Initial Climbing Gaits
The pendular two-link design of ROCR dictates the method by which the robot will climb; however, many climbing gaits are possible. Different gaits engage and disengage the wall (or holds) with their gripping mechanisms (or hands) at different times during the oscillatory swinging of the tail (or shifting of their mass). Two preliminary climbing gaits were identified for ROCR. These gaits, shown in Fig 4, are called Static and Simple Oscillator gaits.
Fig 4. vertical motion of ROCR for 3 preliminary climbing gait strategies
Related Publications
- S. Jensen-Segal, S. Virost, W.R. Provancher, “ROCR: Energy Efficient Vertical Wall Climbing with a Pendular Two-Link Mass-Shifting Robot”, Presented at the International Conference on Robotics and Automation (ICRA) 2008, Pasadena, CA, USA, May 19–23, 2008.
