Design of a High-Speed Prosthetic Finger Driven by Peano-HASEL Actuators

Abstract

Current designs of powered prosthetic limbs are limited by the nearly exclusive use of DC motor technology. Soft actuators promise new design freedom to create prosthetic limbs which more closely mimic intact neuromuscular systems and improve the capabilities of prosthetic users. This work evaluates the performance of a hydraulically amplified self-healing electrostatic (HASEL) soft actuator for use in a prosthetic hand. We compare a linearly-contracting HASEL actuator, termed a Peano-HASEL, to an existing actuator (DC motor) when driving a prosthetic finger like those utilized in multi-functional prosthetic hands. A kinematic model of the prosthetic finger is developed and validated, and is used to customize a prosthetic finger that is tuned to complement the force-strain characteristics of the Peano-HASEL actuators. An analytical model is used to inform the design of an improved Peano-HASEL actuator with the goal of increasing the fingertip pinch force of the prosthetic finger. When compared to a weight-matched DC motor actuator, the Peano-HASEL and custom finger is 10.6 times faster, has 11.1 times higher bandwidth, and consumes 8.7 times less electrical energy to grasp. It reaches 91% of the maximum range of motion of the original finger. However, the DC motor actuator produces 10 times the fingertip force at a relevant grip position. In this body of work, we present ways to further increase the force output of the Peano-HASEL driven prosthetic finger system, and discuss the significance of the unique properties of Peano-HASELs when applied to the field of upper-limb prosthetic design. This approach toward clinically-relevant actuator performance paired with a substantially different form-factor compared to DC motors presents new opportunities to advance the field of prosthetic limb design.

A Pocket‐Sized Ten‐Channel High Voltage Power Supply for Soft Electrostatic Actuators

“…Although this work focuses primarily on using the 10-channel HVPS to drive HASEL actuators, this architecture is applicable to other electrostatic devices requiring voltages up to 10 kV, such as DEAs and electroadhesives. [5,18] To power complex machines with high DOF, such as muscular hydrostats or prosthetic hands, [60,61] the described methods can be extended to an arbitrary number of channels (by adding more than 10 optocoupler half bridges), though adjustments to the main power source (i.e., battery) are required to sustain the power draw from the additional switching elements. Future work will look to integrate tens to hundreds of various electrostatic devices to create smart, multi-functional soft robots.…”

Flying Hydraulically Amplified Electrostatic Gripper System for Aerial Object Manipulation

“…The actual strength of an eagle's grip stems from his upper leg. As shown in [2], a bio-inspired, tendon-driven design would not be feasible for drone integration due to its large size. Consequently, a design inspired by [3] was sought after.…”

“…Certain variations even exceed muscle-like performance in specific areas, showing up to 24% of strain [12]. Furthermore, HASELs offer fast actuation speeds and low power consumption that surpasses a DC motor [2], making them well-suited for use in soft robotic systems.…”

“…Another gripper concept where the force is induced outside of the joints is found in the field of prosthetics. There, Peano-HASELs behave like artificial muscles in combination with tendons acting as ligaments [2]. Despite the higher force output of Peano-HASELs [17], outweighing DC motors in terms of speed and energy consumption, the pinching force is considerably smaller.…”

Review of soft fluidic actuators: classification and materials modeling analysis

“…This linear actuator can lift more than 200 times its weight with a strain rate of 900% per second at 10 kV. The fast response speed, self-sensing and self-healing advantages of HASEL actuators make them a promising candidate for applications in different soft robotic mechanisms such as untethered soft robots for manipulation and continuum applications [111], tubular pump [136], and prosthetic finger driven by Peano-HASEL [137]. Rothemund et al [67] reviewed the latest advances and future opportunities of HASEL in the soft actuators field.…”