Design and Control of a Novel Grip Amplifier to Support Pinch Grip with a Minimal Soft Hand Exoskeleton

Design and Preliminary Evaluation of a Soft Finger Exoskeleton Controlled by Isometric Grip Force

“…The exoskeleton is controlled using an isometric grip force control strategy (IFC) [24], which measures grip force from the remaining digits to control actuation of the index finger. Force is measured using a uni-axial load cell (LSB 200, Futek, Irvine, CA, USA) capable of measuring tensile and compressive forces in one direction (specifically the z axis).…”

“…The amplification gain is applied to decrease the force required from the user to control the actuator. In this control paradigm, the thumb is held in opposition while the index finger is assisted by the exoskeleton [24]. Furthermore, the force measured from digits 3-5 are used to control movement of the exoskeleton.…”

“…Robotic assistive devices such as hand exoskeletons offer a potential solution to increase usage of the impaired limb, and over the past two decades there have been many research groups that have developed hand exoskeletons with this goal in mind [16][17][18][19][20][21][22][23][24]. But, despite the fact that the functionality of these devices has continuously increased over the years, robust and reliable detection of the user's intent remains a major challenge and is often one of the barriers of acceptance for hand exoskeletons.…”

“…In addition to the challenge that is presented by control, another common challenge lies in the selection of an appropriate actuation strategy for the exoskeleton device. There are several different actuation strategies that have been explored in the design and development of hand exoskeletons [12,24,30,32,33,35,36], but at present exoskeleton designs have been dominated by the use of either electromagnetic actuators or soft fluidic actuators. Soft fluidic actuators using either water or air have excellent power to weight ratios.…”

“…For individuals with stroke, this allows the affected hand to drive exoskeleton movement, potentially offering therapeutic benefits and possibly being more intuitive compared to current switch-based or EMG-based control strategies. We recently demonstrated with a rigid tabletop hand exoskeleton that abled-bodied individuals are able to take advantage of the force control strategy and use it to improve performance on a given task [24], warranting further investigation of the strategy in a more portable form factor. Below, we discuss the results of a preliminary study evaluating the control strategy in the IGripX with able-bodied users, as well as the details of the design of the exoskeleton.…”