Design and experimental testing of a force-augmenting exoskeleton for the human hand

Abstract

Background Many older Americans suffer from long-term upper limb dysfunction, decreased grip strength, and/or a reduced ability to hold objects due to injuries and a variety of age-related illnesses. The objective of this study was to design and build a five-fingered powered assistive exoskeleton for the human hand, and to validate its ability to augment the gripping and pinching efforts of the wearer and assist in performing ADLs. Methods The exoskeleton device was designed using CAD software and 3-D printed in ABS. Each finger’s movement efforts were individually monitored by a force sensing resistor at each fingertip, and proportionally augmented via the microcontroller-based control scheme, linear actuators, and rigid exoskeleton structure. The force production of the device and the force augmenting capability were assessed on ten healthy individuals with one 5-digit grasping test, three pinching tests, and two functional tests. Results Use of the device significantly decreased the forearm muscle activity necessary to maintain a grasping effort (67%, p < 0.001), the larger of two pinching efforts (30%, p < 0.05), and the palmer pinching effort (67%, p < 0.001); however, no benefit by wearing the device was identified while maintaining a minimal pinching effort or attempting one of the functional tests. Conclusion The exoskeleton device allowed subjects to maintain independent control of each digit, and while wearing the exoskeleton, in both the unpowered and powered states, subjects were able to grasp, hold, and move objects such as a water bottle, bag, smartphone, or dry-erase marker.

Exoskeletons for Elderly Activity of Daily Living Assistance: A Review of Upper Limb Exoskeletons and Assessments

“…There are six hand exoskeletons: Force Augmenting Exoskeleton [69], Cable-driven Hand Exoskeleton (known as mano) [65], Hand Extension Robot Orthosis Grip Glove (HERO) [66], Kist Upper-Limb Exoskeleton (KULEX) [44], [67], EXOMUSCLE [68], and Soft Power-Assist Glove [70].…”

“…Among the 18 upper limb exoskeletons, 16 are in the prototyping stage [44], [48], [49], [51], [55]- [70], while two are in the embodiment design stage [53], [54]. Based on structural design, there are six soft exoskeletons [61], [62], [65], [66], [68], [70], eleven rigid exoskeletons [44], [48], [49], [51]- [56], [58]- [60], [64], [67], [69] and one hybrid exoskeleton [63]. Three of the soft exoskeletons are cable-driven [65], [66], [68] and two are pneumatic-driven exoskeletons [61], [62].…”

“…Categorised by mode of operation, i.e. active or passive, there are fifteen active [44], [48], [49], [51], [53]- [56], [58]- [63], [65]- [67], [69], [70], two passive [64], [68] and one hybrid exoskeleton which operates based on user's capability [52]. Table 2 lists the reviewed exoskeletons regarding the exoskeleton category, name, development stage, structural design (rigid, soft or hybrid), mode of operation (active, passive or hybrid) and supported upper limb joint movement.…”

“…Motorised WREX [59], [60], and Soft Power-Assist Glove [70] were assessed on the control strategies. Force Augmenting Exoskeleton underwent structural design optimisation and performance evaluation to counterbalance gravitational torque during shoulder flexion extension [69]. As a result, these five exoskeletons, namely SPEXO, CABexo, Motorised WREX, Soft Power-Assist Glove and Force Augmenting Exoskeleton, are excluded from Table 3.…”

Grip Strength and Body Balance in Static and Dynamic Push Walkers Measurement Using Force Sensing Resistors and Kinect System

“…The connection series of sensor FSR is described in Figure 4. The FSR sensor is attached to the glove according to the middle of the thumb (thumb proximal phalanx), the middle of the middle finger (middle proximal phalanx), and the palm of the little finger (fifth metacarpal) position because of the natural anatomy of the hand as the most pressure during gripping [19], [23]. The gloves make it easier to install when testing the device on a toddler-the grip strength measuring is shown in Figure 5.…”