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

GRIDCC: Real-time workflow system

The Grid is a concept which allows the sharing of resources between distributed communities, allowing each to progress towards potentially different goals. As adoption of the Grid increases so are the activities that people wish to conduct through it. The GRIDCC project is a European Union funded project addressing the issues of integrating instruments into the Grid. This increases the requirement of workflows and Quality of Service upon these workflows as many of these instruments have real-time requirements. In this paper we present the workflow management service within the GRIDCC project which is tasked with optimising the workflows and ensuring that they meet the pre-defined QoS requirements specified upon them

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

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

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

The use of underactuation in prosthetic grasping

Underactuation as a method of driving prosthetic hands has a long history. The pragmatic requirements of such a device to be light enough to be worn and used regularly have meant that any multi degree of freedom prosthetic hand must have fewer actuators than the usable degrees of freedom. Aesthetics ensures that while the hand needs five fingers, five actuators have considerable mass, and only in recent years has it even been possible to construct a practical anthropomorphic hand with five motors. Thus there is an important trade off as to which fingers are driven, and which joints on which fingers are actuated, and how the forces are distributed to create a functional device. This paper outlines some of the historical solutions created for this problem and includes those designs of recent years that are now beginning to be used in the commercial environment. &lt;br&gt;&lt;br&gt; &lt;i&gt;This paper was presented at the IFToMM/ASME International Workshop on Underactuated Grasping (UG2010), 19 August 2010, Montréal, Canada.&lt;/i&gt

Upper- and lower-limb amputees show reduced levels of eeriness for images of prosthetic hands

The uncanny phenomenon describes the feeling of unease associated with seeing an image which is close to appearing human. Prosthetic hands in particular are well-known to induce this effect. Little is known, however, about this phenomenon from the viewpoint of prosthesis users. We studied perceptions of eeriness and human-likeness for images of different types of mechanical, cosmetic, and anatomical hands in upper-limb prosthesis users (n=9), lower-limb prosthesis users (n=10), prosthetists (n=16), control participants with no prosthetic training (n=20), and control participants who were trained to use a myoelectric prosthetic hand simulator (n=23). Both the upper- and lowerlimb prosthesis user groups showed a reduced uncanny phenomenon (i.e., significantly lower levels of eeriness) for cosmetic prosthetic hands compared to the other groups, with no concomitant reduction in how these stimuli were rated in terms of human-likeness. However, a similar effect was found neither for prosthetists with prolonged visual experience of prosthetic hands, nor for the group with short-term training with the simulator. These findings in the prosthesis users therefore seem likely to be related to limb absence or prolonged experience with prostheses

Report of the working group on the measurement of triple gauge boson couplings

The working group discussed several aspects of triple gauge coupling analysis viewed in the light of experiences with the first high energy data recorded at energies above the W pair threshold. Some analysis methods were reviewed briefly, and consideration given to better ways of characterising the data. The measurement of CP violating parameters was discussed. Results were prepared to further quantify the precision attainable on anaomalous couplings in the four-quark channel using jet-charge methods, and finally the trade off between maximum LEP energy-vs-luminosity was quantified.The working group discussed several aspects of triple gauge coupling analysis viewed in the light of experiences with the first high energy data recorded at energies above the W pair threshold. Some analysis methods were reviewed briefly, and consideration given to better ways of characterising the data. The measurement of CP violating parameters was discussed. Results were prepared to further quantify the precision attainable on anaomalous couplings in the four-quark channel using jet-charge methods, and finally the trade off between maximum LEP energy-vs-luminosity was quantified