A Directional Vibrotactile Feedback Interface for Ergonomic Postural Adjustment

Abstract

The objective of this paper is to develop and evaluate a directional vibrotactile feedback interface as a guidance tool for postural adjustments during work. In contrast to the existing active and wearable systems such as exoskeletons, we aim to create a lightweight and intuitive interface, capable of guiding its wearers towards more ergonomic and healthy working conditions. To achieve this, a vibrotactile device called ErgoTac is employed to develop three different feedback modalities that are able to provide a directional guidance at the body segments towards a desired pose. In addition, an evaluation is made to find the most suitable, comfortable, and intuitive feedback modality for the user. Therefore, these modalities are first compared experimentally on fifteen subjects wearing eight ErgoTac devices to achieve targeted arm and torso configurations. The most effective directional feedback modality is then evaluated on five subjects in a set of experiments in which an ergonomic optimisation module provides the optimised body posture while performing heavy lifting or forceful exertion tasks. The results yield strong evidence on the usefulness and the intuitiveness of one of the developed modalities in providing guidance towards ergonomic working conditions, by minimising the effect of an external load on body joints. We believe that the integration of such lowcost devices in workplaces can help address the well-known and complex problem of work-related musculoskeletal disorders.

Performance Analysis of Vibrotactile and Slide-and-Squeeze Haptic Feedback Devices for Limbs Postural Adjustment

“…The main goal of this work is to compare two haptic devices previously presented in the literature, the ErgoTac [19] and the Clenching Upper-limb Force Feedback device (CUFF) [20], in a postural correction setting. These two devices have been already previously used for postural and ergonomic correction [17], [18]. This section presents the mechanical structure and the main working principles of the two devices, followed by the description of the modular environment in which they are integrated.…”

“…The SPOT modality, as represented in Fig. 2b, uses two ErgoTac units per joint: information on the desired direction is provided through repulsive vibration feedback on the opposite side of the limb (see [17] for more detail).…”

“…Each experimental session was composed of two blocks, one using the CUFF and the other using the ErgoTac, respectively, as haptic guidance feedback. The order of the two blocks was randomized REFER TO [17] per participant. Each block was composed of three subblocks randomized within each block: i) upper limb guidance (focusing on the shoulder joint), ii) lower limb guidance (focusing on the knee joint), and iii) multi-joint guidance (focusing on both the shoulder and the knee joints at once).…”

“…Each block was composed of three subblocks randomized within each block: i) upper limb guidance (focusing on the shoulder joint), ii) lower limb guidance (focusing on the knee joint), and iii) multi-joint guidance (focusing on both the shoulder and the knee joints at once). Three reference angles on the sagittal plane were chosen for the shoulder and the knee, and three couples of angles were chosen for the combination of shoulder and knee; the selection was based on previous literature [17]. The chosen angles were ´10 ˝, 45 ˝, and 90 ˝for the shoulder and 30 ˝, 80 ˝, and 115 ˝for the knee.…”

“…As in the "directional vibrotactile feedback modalities" experiment in [17], each trial concluded when the participant stated to be in the position goal. Additionally, in this work, we added a 90 s limit per trial; once the limit is reached, the trial was considered failed.…”