Embedded control system for cybernetic wrist prosthesis
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This master thesis treats the NTNU Rotary Wrist Device(NRWD). The wrist has been developed through several projects and assignments, all derived from Øyvind Stavdahls PhD thesis from 2002, which led to a document of functional specifications. This thesis follows from a specialization project by the writer during autumn 2009. The project looked into the error-prone circuit board that was made to control the NRWD, and came to the conclusion that it could not be used, and that a different approach was necessary. Based on the experience achieved by previous assignments a suggestion for the complete hardware circuitry has been designed. In September 09 the first revision of a protocol for communication in electrical prosthesis were released. The protocol was developed at University of New Brunswick (from here referred to as the UNB-protocol), and is presented as a proposal for a standard communication protocol in the world of electrical prosthesis. This thesis suggests an expansion to this protocol. The expansion is about device profiles, meaning that a device (e.g., a wrist prosthesis, elbow prosthesis, sensory or the like) connecting to an electrical prosthesis system will let the system know what functions it can provide, without the need of updating of the system. A complete functional specification for the NRWD has been written. The specifications are based on those from the originals made by Stavdahl, with revisions in the requirements involving communication. This to make them comply with the UNB-protocol. The protocol is build on a CAN-bus, so in practice this means that all digital communication interfaces except CAN has been removed. In addition there have been added a requirement to prevent the motor from overheating. During the assignment a complete circuit diagram for a new control system has been developed. The circuitry is ready for testing and construction. It has been emphasized to use small components and making the NRWD hardware compatible with the UNB-protocol. There are also suggested some guidelines for the software development.