Frustrated Total Internal Reflection Measurement System for Pilot Inceptor Grip Pressure

Sensing the interaction between the pilot and the control inceptors can provide important information about the pilot’s activity during flight, potentially enabling the objective measurement of the pilot workload, the application of preventive actions against loss of situational awareness, and the identification of the insurgence of adverse couplings with the vehicle dynamics. This work presents an innovative pressure-sensing device developed to be seamlessly integrated into the grips of conventional aircraft control inceptors. The sensor, based on frustrated total internal reflection of light, is composed of low-cost elements and can be easily manufactured to be applicable to different hand pressure ranges. The characteristics of the sensor are first demonstrated in laboratory calibration tests. Subsequently, applications in flight simulator testing are presented, focusing on the objective representation of the pilot’s instantaneous workload

A data-driven method to reduce excessive contact pressure of hand orthosis using a soft sensor skin

Discomfort under customised hand orthosis has been commonly reported in clinics due to excessive contact pressures, leading to low patient adherence and decreased effectiveness of orthosis. However, the current orthosis adjustment by clinicians to reduce pressures based upon subjective feedback from patients is inefficient and prone to variability. Therefore, a quantitative method to guide orthosis adjustment was proposed here by developing a data-driven method. Firstly, Verbal Protocol Analysis was employed to convert the implicit process of orthosis customisation into working models of clinicians. Relevant data to inform a new solution development to reduce excessive contact pressure were extracted from the working models in terms of time consumption and iterations of tasks. Secondly, a new soft sensor skin with strategically placed sensing units to measure static contact pressures under hand orthoses was developed. Finite element simulations were conducted to reveal the required contact pressure range (0.02 – 0.078 MPa) and the distribution of relatively high pressures in 12 key areas. A new fabrication method was proposed to produce the sensor skin, which was then characterised and tested on the subject. The results show that the sensor unit has a pressure range from 0.01 MPa to 0.1 MPa with the maximum repeatability error of 6.4% at 0.014 MPa, and the maximum measurement error of 8.26% at 0.023 MPa. Thirdly, a new method was proposed to predict contact pressures associated with the moderate level of discomfort at critical spots under hand orthoses. 40 patients were recruited to collect contact pressures under two types of orthoses using the sensor skin, and their discomfort perceptions were measured with a categorical scale. Based on these data, artificial neural networks for five identified critical spots on the hand were built to predict pressure thresholds that clinicians can use to adjust orthoses, thus reducing excessive contact pressures. The neural networks show satisfactory prediction accuracy with R2 values over 0.89 of regression between network outputs and measurements. Collectively, this thesis proposed a novel method for clinicians to adjust orthoses quantitatively and reduce the need for subjective assessment for patients. It provided a platform to further investigate the pressure for patients with other conditions.Open Acces

A preliminary study to identify data needs for improving fit of hand and wrist orthosis using verbal protocol analysis

This is the author accepted manuscript. The final version is available from Taylor & Francis via the DOI in this recordThe delayed delivery, poor fitting and discomfort of customised orthoses are reported in rehabilitation clinics as resulting in more invasive interventions. The current practice of orthosis customisation relies heavily upon the experience and fabrication processes of therapists. In order to better understand the current practice, and thus identify data that is required for better comfort moving towards a data-driven customisation, this article describes a study generating working models of therapists. Customisations of hand and wrist orthoses for 18 patients were observed. Verbal protocol analysis was employed to extend the current understanding of fabrication processes. Working models of four therapists were established with quantitative evaluation on major phases, interactive activities and iterations of performing tasks during fabrication, revealing different working models between in- and out-patient departments (e.g. fabrication for in-patients was more complex and focussed on ergonomic fitting whereas fabrication for out-patients paid attention to durability) which were qualitatively explained. Practitioner summary: Fit and comfort are imperative for orthosis design and fabrication, however the current practice of customisation of an orthosis relies upon the experience of individual hand therapist. The article presents working models of hand therapists, and relevant data that would enable customisation of orthosis for better fit. Abbreviations: VPA: verbal protocol analysis; h&w: hand and wrist; LTT: low temperature thermoplastic; ANOVA: analysis of variance.Affiliated Xuzhou Rehabilitation Hospital of Xuzhou Medical UniversityXuzhou Central HospitalChina Scholarship CouncilImperial College Londo

A soft pressure sensor skin for hand and wrist orthoses

Side effects caused by excessive contact pressure such as discomfort and pressure sores are commonly complained by patients wearing orthoses. These problems leading to low patient compliance decrease the effectiveness of the device. To mitigate side effects, this study describes the design and fabrication of a soft sensor skin with strategically placed 12 sensor units for static contact pressure measurement beneath a hand and wrist orthosis. A Finite Element Model was built to simulate the pressure on the hand of a subject and sensor specifications were obtained from the result to guide the design. By testing the fabricated soft sensor skin on the subject, contact pressure between 0.012 MPa and 0.046 MPa was detected, revealing the maximum pressure at the thumb metacarpophalangeal joint which was the same location of the highest pressure of simulation. In this letter, a new fabrication method combining etching and multi-material additive manufacture was introduced to produce multiple sensor units as a whole. Furthermore, a novel fish-scale structure as the connection among sensors was introduced to stabilize sensor units and reinforce the soft skin. Experimental analysis reported that the sensor signal is repeatable, and the fish-scale structure facilitates baseline resuming of sensor signal during relaxation