Abstract

Due to their energy density and softness that are comparable to human muscles dielectric elastomer (DE) transducers are well-suited for soft-robotic applications. This kind of transducer combines actuator and sensor functionality within one transducer so that no external senors to measure the deformation or to detect collisions are required. Within this contribution we present a novel self-sensing control for a DE stack-transducer that allows to control several different quantities of the DE transducer with the same controller. This flexibility is advantageous e.g., for the development of human machine interfaces with soft-bodied robots. After introducing the DE stack-transducer that is driven by a bidirectional flyback converter, the development of the self-sensing state and disturbance estimator based on an extended Kalman-filter is explained. Compared to known estimators designed for DE transducers supplied by bulky high-voltage amplifiers this one does not require any superimposed excitation to enable the sensor capability so that it also can be used with economic and competitive power electronics like the flyback converter. Due to the behavior of this converter a sliding mode energy controller is designed afterwards. By introducing different feed-forward controls the voltage, force or deformation can be controlled. The validation proofs that both the developed self-sensing estimator as well as the self-sensing control yield comparable results as previously published sensor-based approaches.

Highlights

  • Soft-bodied robots exploit the full potential of robotic systems in terms of safe humanmachine-interactions and, are in the scope of research

  • As a dielectric elastomer (DE) transducer consists of a very thin, elastomeric dielectric film covered with compliant electrodes, its behavior can be described by a shape varying capacitor

  • Within this publication we extend them to a self-sensing controller that is able to universally control the voltage, force or deformation of the DE transducer by just measuring the terminal voltage vDE and current iDE

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Summary

INTRODUCTION

Soft-bodied robots exploit the full potential of robotic systems in terms of safe humanmachine-interactions and, are in the scope of research. Within this publication we extend them to a self-sensing controller that is able to universally control the voltage, force or deformation of the DE transducer by just measuring the terminal voltage vDE and current iDE. For this purpose, 2 the considered control plant comprising a DE stack-transducer (Maas et al, 2015) fed by a bidirectional flyback converter (Eitzen et al, 2011b; Hoffstadt and Maas, 2016) is introduced and modeled.

MODEL OF THE DE TRANSDUCER SYSTEM
EKF-BASED SELF-SENSING ALGORITHM
SELF-SENSING SLIDING MODE CONTROL
Design of the Sliding Mode
Reachability
Test Setup for the Experimental Validation
Validation of the EKF-Based
Validation of the Self-Sensing Control
Energy Control With Voltage Feed-Forward Control
Energy Control With Position Feed-Forward Control
Energy Control With Force Feed-Forward Control
Findings
CONCLUSION

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