Relationship among hand forces imparted on a viscoelastic hand-handle interface

Abstract

Design of a flexible thin-film hand sensor is presented for reliable measurements of the contact pressure/force distribution at a viscoelastic hand-handle interface, including the contact force developed by a gloved-hand grasping a tool handle. The static properties of the developed hand sensor were evaluated in terms of its drift, linearity, repeatability and hysteresis under global as well as local loads. The measured results revealed low hysteresis (<6%) and drift (≈2.9% over 30s), good linearity (r 2 =0.99) and repeatability (CoV=1.5%). Subsequently, an experiment was designed to establish a relationship among the grip, push and contact forces imparted on a flexible hand-handle interface. The hand-handle contact force was measured considering three interface conditions: (i) bare hand grasping an instrumented rigid handle (BH); (ii) hand grasping the instrumented handle covered by an anti-vibration material (MT); and (iii) gloved hand grasping the handle (GV). The measurements with each interface were conducting with five male subjects and nine combinations of grip (10, 30 and 50 N) and push (25, 50 and 75 N) forces. The measured data were analyzed via multiple linear regression method to explore relationships among the grip (F g ), push (F p ) and contact (F c ) forces for each hand-handle interface. The data were further analyzed to investigate the effect of anti-vibration (AV) gloves on the hand grip strength. The relationship obtained for the hand grasping a rigid handle showed good agreement with those in the reported studies, which verified the hand sensor feasibility for application to curved surfaces. The relationship obtained for the bare hand grasping the handle with flexible anti-vibration material, however, showed higher coefficients of grip (α g ) and push (α p ) forces compared to those observed with the rigid handle of the same diameter. A similar trend was also obtained for the gloved hand grasping the handle, which suggested higher grip strength demand II for a gloved hand (GV) and hand coupling a viscoelastic handle (MT) compared to the BH condition for realizing the same level of grip/push force combination.

The Progress of Research into Flexible Sensors in the Field of Smart Wearables

“…This sEMG sensor and its optimal arrangement was useful for achieving highly accurate individual finger control for the bionic arm and did so relatively cheaply. In a separate development work, Yao et al [ 118 ] proposed a flexible thin-film hand sensor, designed to reliably measure the contact pressure distribution at the viscoelastic handle interface and detect the contact force generated by the limb grasping the tool at that location. Innovatively, Wang et al [ 52 ] constructed a high-performance, energy-efficient, and fully flexible piezoelectric haptic sensor by integrating piezoelectric materials with the electromechanical conversion function and signal of PVDF.…”

Isolating In-Situ Grip and Push Force Distribution from Hand-Handle Contact Pressure with an Industrial Electric Nutrunner

“…Uniaxial grip and push forces have been separately measured directly using an instrumented split handle and a force plate [15]. Those measurements are independently relevant to quantify the health effects and have been extensively used for many years for studying hand-transmitted vibration [16][17][18][19]; however, they have been difficult to implement in real work environments [15]. Similar custom instrumented cylindrical handles have also been used to report force distributions when gripping, pushing and pulling a cylinder [20], but the results are only applicable to those independent actions.…”

Assessing Increased Activities of the Forearm Muscles Due to Anti-Vibration Gloves: Construct Validity of a Refined Methodology

“…However, relatively thick vibration-reducing materials used in AV gloves generally impede hand performance in view of manual dexterity and grip strength. Wearing gloves usually requires a relatively higher grip exertion by the operators compared with bare hand (BH; Hamouda et al, 2018; Welcome et al, 2012; Willms et al, 2009; Wimer et al, 2009; Yao et al, 2019; Young et al, 2012; Yu et al, 2015). Higher grip strength demand can increase the risk of hand-arm musculoskeletal disorders (MSDs) among operators, such as hand tendonitis, strained muscles, and carpal tunnel syndrome (Chang & Shih, 2007; Silverstein et al, 1987; Wimer et al, 2010).…”

“…Such measurement systems are not suited for assessing grip strength reduction by AV gloves, which may alter the distribution of contact pressure and thus force. Alternatively, few studies have developed flexible thin-film sensors and sensing grids for direct measurements of contact force developed at the palmar side surface of a gloved hand grasping a handle (Lemerle et al, 2008; Yao et al, 2019). The application of the glove sensor, however, was reported to be either high-cost and cumbersome, or low-cost but with notable drift (Lemerle et al, 2008; Yao et al, 2019).…”

“…Alternatively, few studies have developed flexible thin-film sensors and sensing grids for direct measurements of contact force developed at the palmar side surface of a gloved hand grasping a handle (Lemerle et al, 2008; Yao et al, 2019). The application of the glove sensor, however, was reported to be either high-cost and cumbersome, or low-cost but with notable drift (Lemerle et al, 2008; Yao et al, 2019). Moreover, glove sensors pose calibration challenges when wrapped around the handle.…”