Use of accelerometers in the control of practical prosthetic arms

Accelerometers can be used to augment the control of powered prosthetic arms. They can detect the orientation of the joint and limb and the controller can correct for the amount of torque required to move the limb. They can also be used to create a platform, with a fixed orientation relative to gravity for the object held in the hand. This paper describes three applications for this technology, in a powered wrist and powered arm. By adding sensors to the arm making these data available to the controller, the input from the user can be made simpler. The operator will not need to correct for changes in orientation of their body as they move. Two examples of the correction for orientation against gravity are described and an example of the system designed for use by a patient. The controller for all examples is a distributed set of microcontrollers, one node for each joint, linked with the Control Area Network (CAN) bus. The clinical arm uses a version of the Southampton Adaptive Manipulation Scheme to control the arm and hand. In this control form the user gives simpler input commands and leaves the detailed control of the arm to the controller

Ideas and networks: The rise and fall of research bodies for powered artificial arms in America and Canada, 1945-1977

This paper examines the rise and fall of research and development funding programs for upper-limb myoelectric prosthetics in America and Canada from 1945 to 1977. Despite similarities in overall technological goals—to produce electronic arms and hands for veterans in the US and children with phocomelic limbs in Canada—we argue that the reasons for starting and ending the programs reflected different national preoccupations. In the US the reasons for the creation in 1945 and termination in 1977 of funding programs focused on the lack of fundamental research in the field, and role that science could have in the development and design in prosthetics. In Canada, by contrast, there was little discussion about science and its relationship to technology in knowledge creation when the prosthetics research and training unit (PRTU) funding program was founded in 1963 and wound up in 1975. Instead, the policy discussion focused on the importance of regional representation and relationships among different professional groups and sectors of society

Characterisation of the Clothespin relocation task as a functional assessment tool

Method: The Clothespin Relocation Task has been adapted from an arm training tool to create an instrument to measure hand function. It is based in the time to move three clothespins from a horizontal to a vertical bar, and back. To be generally useful, the measures need to have their psychometric properties investigated. This paper measures the characteristics of an able bodied population to gain an understanding of the underlying statistical properties of the test, in order that it can then be used to compare with different subject groups. Fifty adults (29 males, 21 females, mean age 31) were tested with five runs of three clothespins moved up and then down. Ten subjects returned twice more to observe repeatability. Results: There was a non-Gaussian range of times, from 2.5s to 7.37s. Mean time for Up was 4.1s, and was 4.0s for Down, with a skew towards the faster times of 0.57 for Up and 0.97 for Down. Over the three sessions there was a small (not significant) increase in speed 4.1+/-0.5s first run Down to 3.5 +/-0.4s for third. Conclusion: These initial tests confirm that it has potential to be used as a measurement of the performance of arm movement

System training and assessment in simultaneous proportional myoelectric prosthesis control

Background Pattern recognition control of prosthetic hands take inputs from one or more myoelectric sensors and controls one or more degrees of freedom. However, most systems created allow only sequential control of one motion class at a time. Additionally, only recently have researchers demonstrated proportional myoelectric control in such systems, an option that is believed to make fine control easier for the user. Recent developments suggest improved reliability if the user follows a so-called prosthesis guided training (PGT) scheme. Methods In this study, a system for simultaneous proportional myoelectric control has been developed for a hand prosthesis with two motor functions (hand open/close, and wrist pro-/supination). The prosthesis has been used with a prosthesis socket equivalent designed for normally-limbed subjects. An extended version of PGT was developed for use with proportional control. The control system’s performance was tested for two subjects in the Clothespin Relocation Task and the Southampton Hand Assessment Procedure (SHAP). Simultaneous proportional control was compared with three other control strategies implemented on the same prosthesis: mutex proportional control (the same system but with simultaneous control disabled), mutex on-off control, and a more traditional, sequential proportional control system with co-contractions for state switching. Results The practical tests indicate that the simultaneous proportional control strategy and the two mutex-based pattern recognition strategies performed equally well, and superiorly to the more traditional sequential strategy according to the chosen outcome measures. Conclusions This is the first simultaneous proportional myoelectric control system demonstrated on a prosthesis affixed to the forearm of a subject. The study illustrates that PGT is a promising system training method for proportional control. Due to the limited number of subjects in this study, no definite conclusions can be drawn

Design of an occupancy monitoring unit: a thermal imaging based people counting solution for socio-technical energy saving systems in hospitals

Aside from their physical exterior/interior design, the energy demands of industrial buildings are strongly related to how they are used. It follows that the behaviour of the occupants contributes and is related to the energy consumption of a building. In a hospital, this could mean equipment usage, heating, water and so on. This implies that energy consumption in a specific area may be measured as a function of occupancy, making occupancy monitoring an important part of an organisation’s energy management plan. This paper presents the design, implementation and testing of an Occupancy Monitoring Unit (OMU), based on thermal imaging technology, to provide occupancy data on individual selected wards/areas of Medway NHS Foundation Trust (MWNFT). The paper also presents successful tests performed to assess the functionality of the OMU in counting people and identifying the direction of motion. The results show the potential for the OMU to count individual people as well as groups

From design to research: Upper limb prosthetic research and development in Canada, 1960-2000

This paper examines the history of the research and development (R&D) of myoelectric upper limb prosthesis in Canada from 1960 to 2000. It focuses on two of the prosthetic research and training units (PRTUs) that were created and funded by the federal government as a result of the Thalidomide tragedy: the Rehabilitation Centre at the Ontario Crippled Children’s Centre (OCCC) and successor organizations, and the University of New Brunswick’s (UNB) Institute of Biomedical Engineering (the Institute or IBME). Both developed commercial systems for myoelectrically controlled arms and hands. We argue that, in contrast to the common view that research in universities and public research institutions has increasingly moved away from basic problems and to product development and commercialization over the period, research in this field has moved in the opposite direction. We explore these cases in detail and examine the forces at work in this change from a design-oriented approach to one that became research intensive

Skill assessment in upper limb myoelectric prosthesis users: Validation of a clinically feasible method for characterising upper limb temporal and amplitude variability during the performance of functional tasks

Upper limb myoelectric prostheses remain challenging to use and are often abandoned. A proficient user must be able to plan/execute arm movements while activating the residual muscle(s), accounting for delays and unpredictability in prosthesis response. There is no validated, low cost measure of skill in performing such actions. Trial-trial variability of joint angle trajectories measured during functional task performance, linearly normalised by time, shows promise. However, linear normalisation of time introduces errors, and expensive camera systems are required for joint angle measurements. This study investigated whether trial-trial variability, assessed using dynamic time warping (DTW)of limb segment acceleration measured during functional task performance, is a valid measure of user skill. Temporal and amplitude variability of forearm accelerations were determined in 1) seven myoelectric prosthesis users and six anatomically-intact controls and 2) seven anatomically-intact subjects learning to use a prosthesis simulator over repeated sessions. 1: temporal variability showed clear group differences (p<0.05). 2: temporal variability considerably increased on first use of a prosthesis simulator, then declined with training (both p<0.05). Amplitude variability showed less obvious differences. Analysing forearm accelerations using DTW appears to be a valid low-cost method for quantifying movement quality of upper limb prosthesis use during goal-oriented task performance