Somasoid MEP Homepage

A prosthesis is any device that is intended to replace a body part, internal or external, that has been lost due to injury or disease. The term myoelectric, in this context, implies that the electrical signals that the body uses to actuate muscles are leveraged to control the overall movement of the prosthesis.

The Somasoid MEP (MyoElectric Prosthesis) is an open-source (Creative Commons ShareAlike v3) project aimed at the development of a low-cost, safe, and robust prosthesis platform that can be used as a standalone solution or further customized by advanced users.

Table of Contents

• Overview
  • Project Description
  • Need
• Specifications
• Components
• Schematic and Board Layout
• Mechanical Design
• Software
• Project Details

Overview

Project Description

The goal of this project is to design a 3 digit prosthesis whose actuation is enabled through motors controlled by muscle impulses recorded via surface electromyography (sEMG).

Need

Low-cost, easy to maintain prostheses are always in high demand. There are many options that fit this category, but many myoelectric prostheses fall short in terms of their ease of calibration for the patient. A low-cost prosthesis with either a self- or assisted-calibration feature would improve the usability and quality of life of the users, as minute changes in electrode placement from day to day use produce significant changes in motor control performance.

Specifications

It is necessary that the prosthesis design fit several criteria to ensure the efficacy of the final product, its ease-of-use and comfort in daily life, and the safety of the user.

For a full list of current specifications for this project, see [Specifications].

Components

The components for this project include electrode leads (myoelectric control), a PCB (signal preamplification, motor control, battery charging), prosthesis casing (electrical enclosure, grip mechanism), two batteries (RC for motors, 9V for board), and several others.

For a full list of current components for this project, see [Components].

Schematic and Board Layout

The Somasoid MEP board schematic and layout describe the electrical system behind the project. The schematic is roughly divided into sections of functionally similar components, which are connected to the microcontroller or external inputs as necessary. The physical board layout is similarly partitioned.

The physical board measures 69.85mm x 86.06 mm (2.75in x 3.39in). Copies can be ordered here, through OSHPark (in multiples of 3).

For the schematic and PCB layouts for the project, see [Schematics and Layout].

Mechanical Design

For the current mechanical design for the project, see [Mechanical Design].

Software

The prosthesis' software, currently under development, is driven by a task-based real-time operating system (RTOS), FreeRTOS.

Documentation for the current software is viewable here.

For further information about this project's software, including an overview of planned functionality - described with a task diagram and finite state machine representations for each task - see [Software].

Project Details

Project Members:

• Aaron Jen (admin)
• Robert Zimmerman (admin)