Browsing by Author "Stavdahl, Oyvind"

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    A BUS PROTOCOL FOR INTERCOMPONENT COMMUNICATION IN ADVANCED UPPER-LIMB PROSTHESES
    (2005) Stavdahl, Oyvind; Mathisen, Geir
    Microcontrollers are ubiquitous in modern electronic products, powered prosthetic components being no exception. Likewise, digital communication buses are the key technology for interconnecting such smart devices for reasons such as reduced wiring requirements, high information throughput, robustness in the presence of noise and flexibility. This flexibility contains the potential of interoperability, which means that similar components from different manufacturers may communicate in the same way so that one can easily be replaced by another or components from different manufacturers can be combined in one and the same system. However desirable this situation is, it requires an open, sandardised communication protocol that is adhered to by the majority of the manufacturers and research organisations. Presently no such standard exists in the prosthetics industry, while it has existed in related fields such as wheelchairs and environmental controllers for a number of years. In this paper we propose such a bus standard, and outline the potential benefits for end users, prosthetists and technicians, healthcare providers, manufacturers and researchers. We then list several important aspects of a prosthesis bus that must be carefully considered, and invite interested parties to engage in the completion of a draft specification.
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    THE NTNU REVOLUTE WRIST DEVICE (NRWD): A KINEMATICALLY OPITMIZED EXTERNALLY POWERED WRIST PROSTHESIS
    (2005) Stavdahl, Oyvind; Skjelten, Haakon
    Transradial amputation implies the loss of the wrist. It therefore also implies the loss of the ability to do flexion/extension and radioulnar deviation as well as the forearm’s ability to rotate the wrist (prosupination). Prosupination is offered by some prostheses, but many users choose not to use a powered wrist because the benefits are literally outweighed by its weight, poor cosmesis and the complexity of controlling multiple degrees of freedom. This is also why a wrist with more than one motorized function is considered by many not to be a viable concept. This paper reports a study that aims at producing a lightweight, single-degree-of-freedom, externally powered wrist whose kinematic properties are optimized to match the movements of a healthy wrist in conjunction with certain Activities of Daily Living (ADL). The rationale for this is the assumption that reducing the need for compensatory movements whilst keeping the weight and control complexity unchanged will improve user acceptance and utilization of the device. The prosthesis provides for digital communication and coordinated motion.
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    Ultrasound Based Estimation Of Muscle Contraction
    (1997) Stavdahl, Oyvind; Gronningsaeter, Aage; Malvig, Kjell E.
    In the absence of a single satisfactory control path horn the amputee to the prosthesis, the search for new alternatives is of great interest. This paper introduces the idea of using ultrasound measurements of human tissue as a basis for generation of control inputs to a piosthesis. One of the methods employed, an optical flow estimation algotithm, is based on the work of others, but a simpler, onedimensional implementation is developed. The second method presented is based on cross correlation and is demonstrated to yield smooth muscle force estimates under ideal conditions The results are compared to those obtained with an EMG based technique. Weaknesses are discussed and suggestions for further research are given.