Project Description

Motion Capture System

System based on great number of small accelerometers

Motion Capture System

System is based on usage of three axis accelerometers. Accelerometry has found its application in walk analysis of patients with disorder or injuries of primary locomotor system and nerves. This method generates data used for determining the state of body balance and kinematic of locomotor system enabling the discovery of quality methods to prevent falls within risk groups (older people, patients with neuromuscular disorder etc.). Data can be used for monitoring mobility of particular body parts, their acceleration and position, as well as for getting other useful information. Besides already stated, accelerometry has found its application in planning the trainings and monitoring athlete performance, controlling the performance of orthopedic aids and walk analysis of small laboratory animals.

Device is composed of three major units, unit for conversion and acquisition, accelerometers, and communication-control unit. Conversion unit is capable of sampling analog signal from 128 channels with speed of 300ksps (kilo samples per second), that is 2300 samples per second per each channel. Resolution of the each channel is 12 bit (4096 discrete levels) in analogue range from 0 to 3.3 Volts, which gives maximal resolution of 800 μV.

On existing prototype 96 channels are used for sensors, while the rest of channels are used for calibration and self diagnostic of device. Sensor is based on three-axis accelerometer, which has ability to measure acceleration of all three axis in range of ±1.5g, ±2g, ±4g and ±6g (g=9.81ms-2), depending on the needs of certain application. Sensors can also be put in standby mode which enables greater autonomy with battery powered devices. Accelerometer outputs three analog values in range of 0 to 3.3V depending on acceleration and gravity. The base of communication-control unit is 8 bit microcontroller which performs 10 MIPS (million instructions per second), followed by integrated circle which communicates with computer, and reference voltage source. Microcontroller is in charge of controlling LCD (liquid crystal display), sampler system, communication with computer and self diagnostic of device. This prototype uses RS-232C protocol for communication with computer.

Motion Capture System graf

Device was primary designed for comparative analysis of walk prior to and after the usage of orthopedic aids. With its application we want to supplement current methods for controlling the effects of orthopedic aids like digital pedobarography.