Controlling Robotic Arms Using Series Elastic Actuators

Fall 2012

Student
Kenneth Payson
Advisor
Ralph Hollis
Project description

The goal of this project is to improve the performance of the two degree of freedom series elastic robotic arms on Ballbot, a dynamically stable mobile robot. Due to several current hardware and software issues, the arms are not capable of high fidelity motion. In order to achieve high fidelity motion, I intend to correct the backlash in the arms by remounting the springs on the series elastic actuators and improving the arms' gearing. Additionally, I intend to create a new arm controller that takes full advantage of the series elastic actuators. Currently, position control is done using only feedback from the arm position encoders. More graceful and accurate motion can be achieved if position control is done using both position and force feedback. In order to measure the results of the improved hardware and software, I will measure the phase shifts for commanded arm positions against the resulting arm position. I expect that within a reasonable range of commanded frequencies for arm trajectories, position control can be achieved with minimal phase lag. Additionally, I intend to test the arms' ability to exert commanded forces as well as accurately detect forces exerted on the arms.

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