Electrically-driven phase transition actuators to power soft robot designs

Diogo Fonseca, Pedro Neto

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High Performance Liquid-Gas Phase Transition Actuators: System Overview



  • Capabilities: We introduce an electric soft actuator capable of contractile strain rates of over 16%/s and pressurization rates over 100 kPa/s. Blocked forces exceeding 50 N were achieved while operating at voltages up to 24 V.
  • Advantages: Low voltage operation, controllability, scalability, and ease of integration into soft robots.


    • Exploring the limits of liquid-gas phase transition



  • Identifying the Source of Instabilities: Different boiling regimes have different effects on actuator performance. These were analized through an experimental approach. The main thermodynamic instability responsible for actuator vibration was observed to be the collapse of vapour bubbles during operation in subcooled boiling conditions.
  • Control Strategies: We demonstrate that actuator vibrations can be significantly reduced by developing control strategies that promote thermodynamic saturated conditions within the actuators throughout the entire duration of the actuation cycle.



    • Soft Actuators to Power Innovative Robot Designs

    Phase transition soft actuators enable soft robots to tackle difficult locomotion tasks. We designed and implemented Bixo, the first electric soft quadruped robot powered by liquid-gas phase transition. Bixo is a development platform that can perform complex locomotion tasks such as climbing tubes and crawling along trees. We designed Bixo to enable rapid replacement of the mechatronic components, specifically the sliding structure and the five actuators.





    The combination of high actuation forces with a compact form factor makes phase transition soft actuators an attractive option to power various other systems. In this work we demonstrate how this technology can be used to power tendon-driven biomimetic hands, as well as soft robotic grippers.






    Strategies For Actuator Optimization

    We establish a comprehensive method for selecting working fluids. This allows actuators to be further optimized to operate within a desired range of temperatures and pressures.



    Paper

    Paper thumbnail

    BibTex

    @misc{fonseca2024untappedpotentialelectricallydrivenphase,
  title={The untapped potential of electrically-driven phase transition actuators to power innovative soft robot designs}, 
  author={Diogo Fonseca and Pedro Neto},
  year={2024},
  eprint={2411.06963},
  archivePrefix={arXiv},
  primaryClass={cs.RO},
  url={https://arxiv.org/abs/2411.06963}, 
}