Catherine Holloway

Statically vs dynamically balanced gait: Analysis of a robotic exoskeleton compared with a human

In recent years exoskeletons able to replicate human gait have begun to attract growing popularity for both assistive and rehabilitative purposes. Although wearable robots often need the use of external support in order to maintain stability, the REX exoskeleton by REX Bionics is able to self-balance through the whole cycle. However this statically balanced gait presents important differences with the dynamically balanced gait of human subjects. This paper will examine kinematic and kinetic differences between the gait analysis performed on a subject wearing the REX exoskeleton and human gait analysis data as presented in literature. We will also provide an insight on the impact that these differences can have for both rehabilitative and assistive applications.

Linking wheelchair kinetics to glenohumeral joint demand during everyday accessibility activities

The aim of the study was to investigate if push-rim kinetics could be used as markers of glenohumeral joint demand during manual wheelchair accessibility activities; demonstrating a method of biomechanical analysis that could be used away from the laboratory. Propulsion forces, trunk and upper limb kinematics and surface electromyography were recorded during four propulsion tasks (level, 2.5% cross slope, 6.5% incline and 12% incline). Kinetic and kinematic data were applied to an OpenSim musculoskeletal model of the trunk and upper limb, to enable calculation of glenohumeral joint contact force. Results demonstrated a positive correlation between propulsion forces and glenohumeral joint contact forces. Both propulsion forces and joint contact forces increased as the task became more challenging. Participants demonstrated increases in trunk flexion angle as the requirement for force application increased, significantly so in the 12% incline. There were significant increases in both resultant glenohumeral joint contact forces and peak and mean normalized muscle activity levels during the incline tasks. This study demonstrated the high demand placed on the glenohumeral joint during accessibility tasks, especially as the gradient of incline increases. A lightweight instrumented wheelchair wheel has potential to guide the user to minimize upper limb demand during daily activity.

A micro-level approach to measuring the accessibility of footways for wheelchair users using the Capability Model

There are a growing number of people with mobility impairments who use wheelchairs to get around the built environment. This number is likely to increase in the future due to an increasingly ageing population combined with advances in medical technology which help to overcome some of the barriers to access that have hitherto prevented people from leading as full a life as they would have liked. Footways form an integral part of the transport network and therefore it is essential they can be accessed by all people. Currently, however, there is no well-defined method to measure the accessibility of footways for wheelchair users. One aspect of a footway is the crossfall – the transverse gradient designed to facilitate surface water drainage – which adds to a wheelchair users difficulty when progressing along the footway. This paper first reviews previous research on measuring the effect of crossfalls on wheelchair accessibility, highlighting the need for a new approach. It then proposes the Capability Model as a starting point for this new approach. The model is updated and populated with an initial capability set chosen to measure footway accessibility across footways with three different crossfall gradients (0%, 2.5% and 4%). The focus is on the physical work provided by the user to the wheelchair in order to keep it travelling in a straight line. It is shown that in order to travel in a straight line when a footway is flat only a single principal capability is required: the ability to produce sufficient force over the required distance to overcome the inertia and rolling resistance and keep the wheelchair moving at the chosen velocity. When a positive crossfall gradient is introduced a second capability is required: the ability to apply different levels of force to the left and right sides of the wheelchair. It is concluded that it is possible to measure these two capabilities and these provide a good insight into the effect of crossfalls on footway accessibility for wheelchair users.

A comparison between smartphone sensors and bespoke sensor devices for wheelchair accessibility studies

With the emergence of cheap sensors, there has been a proliferation of novel applications aimed at providing personalized services - from location and routing to daily energy consumption. Most existing applications are aimed at the able-bodied; however, Internet of Things technologies bring the potential to revolutionize the lives of the whole of our population. In this paper, our application area lies in supporting wheelchair users to navigate around the built environment in a way that best suits their disability. This is founded on the availability of good sensor data, and there are essentially two approaches to gathering this: (i) use bespoke sensors, with tight control over exactly what data is gathered and when; (ii) repurpose smartphone sensors to gather the necessary data. This represents a potential tradeoff between accuracy and easy availability. In this paper, we examine the differences in the data quality obtained from different kinds of devices and demonstrate that the smartphones can give a comparable data quality to bespoke devices. We also investigate how, and to what extent, the holding or mounting of the smartphone affects the measurements.

Street rehab: Linking accessibility and rehabilitation

As part of the Accessible Routes from Crowdsourced Cloud Services project (ARCCS) we conducted a series of experiments using the ARCCS sensor to identify push style of wheelchair users. The aim of ARCCS is to make use of a set of well-calibrated sensors to establish a processing chain that then provides ground truth of known accuracy about location, the nature of the environment, and physiological effort. In this paper we focus on two classification problems 1) The push style employed by people as they push themselves and 2) Whether the person is being pushed by an attendant or pushing themselves (independent of push style). Solving the first enables us to develop a level of granularity to pushing classification which transcends rehabilitation and accessibility. The first problem was solved using a wrist-mounted ARCCS sensor, and the second using a wheel-mounted ARCCS sensor. Push styles were classified between semi-circular and arc styles in both indoor and outdoor environments with a high-decrees of precision and recall (>95%). The ARCCS sensor also proved capable of discerning attendant from self-propulsion with near perfect accuracy and recall, without the need for a body-worn sensor.

Impact of Platform Edge Doors on Passengers’ Boarding and Alighting Time and Platform Behavior

Platform edge doors (PEDs) are becoming an international benchmark for metro systems because of their potential to facilitate the transition to fully automated train operation and to reduce the social and operating costs of accidents and obstacles on the platform–train interface. However, there are concerns that the presence of PEDs may lengthen the dwell time; this result could severely hinder service reliability in high-frequency services such as those operated by the London Underground. This paper explores the impact of PEDs on boarding and alighting time and on passenger behavior from two perspectives: through laboratory experiments under controlled conditions and through the analysis of video footage recorded on the London Underground network. Both approaches led to similar conclusions, showing that the presence of PEDs does not have a detrimental impact on the boarding and alighting time and does affect passenger behavior at the platform, inducing a more organized boarding and alighting process in which boarders wait beside the doors rather than in front of them and give way to alighters more often than without PEDs.

MoRe-T2 (Mobility Research Trajectory Tracker): Validation and Application

It is important to assess the suitability of mobility aids before prescribing them to patients. This assessment is often subjectively completed by a therapist and it often includes a variety of basic practical tests. An objective assessment of a patients capability, which captures not only speed of task completion and success, but also accuracy and risk of manoeuvres, would be both a fairer and safer approach. Yet until now such an assessment would have been cost-prohibitive, especially in low resource settings. We pave the way towards this end goal, by describing, validating and demonstrating a low-cost computer vision based system called MoRe-T2 (mobility research trajectory tracker). The open-source MoRe-T2 system uses low-cost off-the-shelf webcams to track the pose of fiducial markers, which are simply printed onto regular office paper. In this article, we build upon previous work and benchmark the accuracy of MoRe-T2 against an industry standard motion capture system. In particular, we show that MoRe-T2 achieves accuracy comparable to CODA motion tracking system. We go on to demonstrate a use case of MoRe-T2 in assessing wheelchair manoeuvrability over a relatively large area. The results show that MoRe-T2 is scalable at a much lower cost than typical industry-standard motion trackers. Therefore, MoRe-T2 can be used to develop more objective and reliable assessments of mobility aids, especially in low-resource settings.

Innovative strategies for urban car-sharing systems and a simulator to assess their performance

In this paper, three innovative car-sharing systems for urban areas are proposed, based on fleets of individual intelligent vehicles with three service characteristics: instant access, open-ended reservations and one-way trips. These features provide high flexibility but create an uneven distribution of vehicles among stations. Therefore, relocation of vehicles must be performed. Three different system procedures are proposed: in the first system, relocations are performed by users; in the other two, vehicles relocate automatically, thanks to their automation. In the first two systems, vehicles are accessible only at stations, whereas in the third they are also accessible along roads. In order to provide transport managers with a tool to test systems in different realities, an object-oriented simulator is developed. The simulation provides outputs of system performance, in terms of user waiting times and system efficiency. The proposed systems are simulated for the city of Genoa, in Italy, and a comparative analysis is presented.

Assisting control for attendant propelled wheelchair based on force velocity relationship

There is a need to develop an assisting device which can be adapted to the individual capabilities of elderly attendants, which would allow them to maintain a level of fitness when pushing a wheelchair, while minimising the risk of injury to them. Furthermore there is a need to reduce the overall energy consumption of the device in keeping with the current trends of reducing carbon emissions. The control system for attendants pushing wheelchairs that reduces the energy needed by the assisting device is an increasing trend of optimisation of assistive technology devices to individual capabilities to ensure less energy expenditure of the attendant. The control parameters for existing assisting systems for attendant wheelchair propulsion are difficult to optimise for individual capabilities. We focus on the individual propelling performance, and propose an assisting control method based on the force velocity relationship of the individual. Our proposed assisting controller generates an assisting force when the attendants propelling force exceeds an assisting boundary defined by the force velocity relationship. In this paper, we tested the performance of the assisting controller based on force velocity (FV) relationship using simulation. The simulation used an attendant wheelchair model with parameters determined from experiments. From the simulated results of the assisting force trajectories, the FV assisting system worked as we defined. The FV assisting system used less energy consumption than the existing proportional assisting systems. Also the FV assisting system would have a limit of maximum attendant propelling power, so the distribution between the attendant force and the assisting force can be easily adjusted to the individuals force velocity relationship. Our proposed FV assisting system would be useful as it would allow an optimised system based on individual capabilities to be created for rehabilitation/training systems, which would allow optimum energy consumption when propelling a wheelchair.

The effect of liner design and materials selection on prosthesis interface heat dissipation

Background and aim: Thermal discomfort often affects prosthesis wearers and could be addressed by increasing liner thermal conductivity. This note explores a liner made from thermally conductive silicone and two additional alternative liner designs. Technique: Thermally conductive silicone was used to create a conductive liner and a hybrid liner. Additionally, one with open elements was made. These were compared with a plain silicone liner and a no liner scenario. Scaled down liner prototypes were used due to the high-cost of the thermally conductive silicone. Temperature decay profiles were collected by attaching thermistors to a heated liner phantom and used to evaluate scenarios. Discussion: No scenario performed much better than the plain silicone liner. Implementation of passive solutions may be easier, but alternative liner materials are unlikely to affect dissipation enough to address thermal discomfort. Based on this work, future research efforts may be better spent developing active thermal discomfort solutions. Clinical relevance Thermal discomfort can increase the probability of skin damage, reduce prosthesis satisfaction and, ultimately, the quality of life. The prosthesis-wearing experience could be improved if thermal discomfort can be addressed by technological improvements.