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Closed-Loop Control Through Self-Sensing of a Joule-Heated Twisted and Coiled Polymer Muscle
Joost van der Weijde1, Heike Vallery1, Robert Babuška1
1Robotics Institute, Delft University of Technology, Delft, The Netherlands.
Soft Robotics
|May 31, 2019
Summary
Self-sensing technology enables closed-loop control for low-cost, lightweight twisted and coiled polymer muscles (TCPMs). This method estimates both deflection and force without extra sensors, making TCPMs more suitable for cost-sensitive robotic applications.
Area of Science:
- Robotics
- Materials Science
- Control Systems Engineering
Background:
- Twisted and coiled polymer muscles (TCPMs) offer low weight and cost advantages for robotic actuators.
- Traditional closed-loop control of TCPMs necessitates additional sensors, increasing weight and cost, thereby diminishing their inherent benefits.
- Self-sensing presents a viable alternative, enabling feedback control without supplementary sensors.
Purpose of the Study:
- To investigate the feasibility of self-sensing for closed-loop control of Joule-heated TCPMs.
- To develop and validate a system for simultaneous muscle driving and inductance-based sensor measurements.
- To establish a mathematical framework for estimating deflection and force using self-sensing data.
Main Methods:
- Utilized a hardware module for driving the TCPM and acquiring inductance-based measurements.
- Developed a mathematical model correlating inductance measurements with muscle deflection.
- Integrated a force model with the deflection model to estimate both parameters concurrently.
Main Results:
- The self-sensing method achieved high accuracy in estimating deflection and force within specified operational ranges.
- For deflection estimation, a 95% confidence interval of 2.14 mm around a mean error of -0.27 mm was observed.
- For force estimation, a 95% confidence interval of 29.0 mN around a mean error of 7.5 mN was achieved.
Conclusions:
- Self-sensing is a feasible approach for closed-loop control of Joule-heated TCPMs.
- This technique preserves the low-cost and lightweight advantages of TCPMs.
- The findings support wider adoption of TCPMs in applications where cost and weight are critical factors.
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