Characterisation of Self-locking High-contraction Electro-ribbon Actuators

Taghavi, Majid; Helps, Tim; Rossiter, Jonathan

doi:10.1109/icra40945.2020.9196849

Cited by 11 publications

(8 citation statements)

References 28 publications

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“…The time of actuation is in line with the experimental characterization [25]. However, qualitatively, the initial expansion of the actuator and the consistently increasing closing velocity are not in line with the experimental data [22].…”

Section: Time-dependent Analysissupporting

confidence: 48%

Modular simulation framework for Electro-ribbon Actuators

Castro

Diteesawat

Taghavi

et al. 2021

2021 IEEE 4th International Conference on Soft Robotics (RoboSoft)

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The Electro-ribbon Actuator (ERA) is a new class of soft robotic actuator that is light weight, low cost and has high contraction strain. The combination of compliance and dielectrophoretic liquid zipping introduces significant nonlinearity to the ERA and makes modelling challenging. This article introduces a lumped-parameter model (LPM) to simulate the actuation behavior and performance of ERAs. The ERA is made of two flexible opposite insulated electrodes attached together at both ends. The application of a bead of liquid dielectric to the attaching points of the electrodes provides a large force amplification and enables high contraction over 99% and high force-to-weight ratio. The proposed method can simulate a flexible and deformable beam, the main structure of the ERA, predicting the ERA's deformation under external loads with < 5% errors. It computes the electrostatic force generated between two electrodes and simulates the zipping behaviour. A multiphysics finite element analysis has been performed to validate the model and, a comparison is show with the experimental data in a series of stationary and time-dependent tests. This work provides a rapid route to design and modelling of future soft robots and soft machines.

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Section: Time-dependent Analysissupporting

confidence: 48%

Modular simulation framework for Electro-ribbon Actuators

Castro

Diteesawat

Taghavi

et al. 2021

2021 IEEE 4th International Conference on Soft Robotics (RoboSoft)

Self Cite

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“…In addition, electro-ribbon actuators exhibit voltage-displacement hysteresis due to the inverse square relationship between actuation force and displacement at a given voltage (Taghavi et al, 2018 ). This hysteresis has been studied in detail in Taghavi et al ( 2020 ).…”

Section: Resultsmentioning

confidence: 87%

Closed-Loop Control of Electro-Ribbon Actuators

et al. 2020

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Electro-ribbon actuators are lightweight, flexible, high-performance actuators for next generation soft robotics. When electrically charged, electrostatic forces cause the electrode ribbons to progressively zip together through a process called dielectrophoretic liquid zipping (DLZ), delivering contractions of more than 99% of their length. Electro-ribbon actuators exhibit pull-in instability, and this phenomenon makes them challenging to control: below the pull-in voltage threshold, actuator contraction is small, while above this threshold, increasing electrostatic forces cause the actuator to completely contract, providing a narrow contraction range for feedforward control. We show that application of a time-varying voltage profile that starts above pull-in threshold, but subsequently reduces, allows access to intermediate steady-states not accessible using traditional feed-forward control. A modified proportional-integral closed-loop controller is proposed (Boost-PI), which incorporates a variable boost voltage to temporarily elevate actuation close to, but not exceeding, the pull-in voltage threshold. This primes the actuator for zipping and drastically reduces rise time compared with a traditional PI controller. A multi-objective parameter-space approach was implemented to choose appropriate controller gains by assessing the metrics of rise time, overshoot, steady-state error, and settle time. This proposed control method addresses a key limitation of the electro-ribbon actuators, allowing the actuator to perform staircase and oscillatory control tasks. This significantly increases the range of applications which can exploit this new DLZ actuation technology.

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“…The improvement of electrostatic force in dielectric zipping actuators using different materials has been investigated in (43), suggesting that materials with high permittivity are preferred and that the insulator permittivity should be higher than the medium permittivity. Consequently, silicone oil and PVC tape were selected to be used as dielectric liquid and insulator due to their high permittivity and electrical breakdown strength, resulting in high electrostatic force amplification.…”

Section: Manufacture Of Electro-pneumatic Pumpmentioning

confidence: 99%

Electro-pneumatic pumps for soft robotics

et al. 2021

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Soft robotics has applications in myriad fields from assistive wearables to autonomous exploration. Now, the portability and the performance of many devices are limited by their associated pneumatic energy source, requiring either large, heavy pressure vessels or noisy, inefficient air pumps. Here, we present a lightweight, flexible, electro-pneumatic pump (EPP), which can silently control volume and pressure, enabling portable, local energy provision for soft robots, overcoming the limitations of existing pneumatic power sources. The EPP is actuated using dielectric fluid–amplified electrostatic zipping, and the device presented here can exert pressures up to 2.34 kilopascals and deliver volumetric flow rates up to 161 milliliters per second and under 0.5 watts of power, despite only having a thickness of 1.1 millimeters and weight of 5.3 grams. An EPP was able to drive a typical soft robotic actuator to achieve a maximum contraction change of 32.40% and actuation velocity of 54.43% per second. We highlight the versatility of this technology by presenting three EPP-driven embodiments: an antagonistic mechanism, an arm-flexing wearable robotic device, and a continuous-pumping system. This work shows the wide applicability of the EPP to enable advanced wearable assistive devices and lightweight, mobile, multifunctional robots.

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Characterisation of Self-locking High-contraction Electro-ribbon Actuators

Cited by 11 publications

References 28 publications

Modular simulation framework for Electro-ribbon Actuators

Modular simulation framework for Electro-ribbon Actuators

Closed-Loop Control of Electro-Ribbon Actuators

Electro-pneumatic pumps for soft robotics

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