Modelling the interaction between wearable assistive devices and digital human models-A systematic review

Abstract

Exoskeletons, orthoses, exosuits, assisting robots and such devices referred to as wearable assistive devices are devices designed to augment or protect the human body by applying and transmitting force. Due to the problems concerning cost- and time-consuming user tests, in addition to the possibility to test different configurations of a device, the avoidance of a prototype and many more advantages, digital human models become more and more popular for evaluating the effects of wearable assistive devices on humans. The key indicator for the efficiency of assistance is the interface between device and human, consisting mainly of the soft biological tissue. However, the soft biological tissue is mostly missing in digital human models due to their rigid body dynamics. Therefore, this systematic review aims to identify interaction modelling approaches between wearable assistive devices and digital human models and especially to study how the soft biological tissue is considered in the simulation. The review revealed four interaction modelling approaches, which differ in their accuracy to recreate the occurring interactions in reality. Furthermore, within these approaches there are some incorporating the appearing relative motion between device and human body due to the soft biological tissue in the simulation. The influence of the soft biological tissue on the force transmission due to energy absorption on the other side is not considered in any publication yet. Therefore, the development of an approach to integrate the viscoelastic behaviour of soft biological tissue in the digital human models could improve the design of the wearable assistive devices and thus increase its efficiency and efficacy.

Keywords: digital human model; interaction modelling; multi-body dynamic; musculoskeletal modelling; soft tissue; systematic review; wearable assistive device.

FIGURE 1

Misalignment shown on a simple degree of freedom joint attached with a WAD based on (Schiele and van der Helm, 2006); (A) initial aligment of human limb and WAD limb, (B) Occurring relative motion between human limb and WAD limb due to movement of the single degree of freedom joint of the human limb.

FIGURE 2

PRISMA flow diagram of study selection and screening process.

FIGURE 3

Identified approaches for modelling the interaction between WADs and DHMs arranged according to their reproducibility of the real interface behaviour, represented on the example of an ankle-foot-orthosis (AFO). To symbolise the possible motions at the interface of WAD and AFO figures of mechanical support structures are used.

FIGURE 4

Identified approaches for simulating the occurring interaction force at the interface between DHM und WAD based on the contact models (A) based on the deviation of the two contact nodes and the calculation of the force via a spring-damper system (B) based on the integration of the device node in the cylindrical area around the model node and generation of the force; blue indicates the node of the DHM, grey indicates the node of the WAD.

FIGURE 5

Number of publications arranged according to the year of publication of the included papers to the literature review, the dotted line is the trend of publications; 2022* indicates that literature is only considered that has been published to the date of literature search.