The kinematics of the swing phase obtained from accelerometer and gyroscope measurements

The kinematics needed to calculate the knee moment during the initial swing phase were obtained from a set of eight leg-mounted uni-axial accelerometers and two gyroscopes. The angular and linear accelerations of shank and thigh were calculated from the signals of two accelerometers mounted on each of the leg segments directed tangentially and radially to the movement. The angular velocities of shank and thigh were measured by the gyroscopes. The absolute angles of shank and thigh were obtained by integration of the gyroscope signal plus an added offset angle, estimated from radial and tangential accelerometer signals registered while standing. Movement was assumed to be in the saggital plane. The accuracy of the quantities found from the leg mounted sensors was calculated in terms of correlation and the RMS error by comparing against measurements obtained by a VICONTM system. The results were indistinguishable. The system was later applied in research measurement

Quantifiying the stability of walking using accelerometers

A dynamic analysis method is sought to measure the relative stability of walking, using a triaxial accelerometer. A performance parameter that can be calculated from the data from the accelerometer is defined; it should give a measure of the stability of the subject. It is based on the balancing forces as reflected in the power spectrum. Preliminary experiments have been done. The results suggest that the performance parameter can order different gait patterns in terms of relative stability. Further experiments are being set up to test the usefulness of the performance parameter in clinical applications and other parameters may be define

Accelerometer and rate gyroscope measurement of kinematics: an inexpensive alternative to optical motion analysis systems

A general-purpose system to obtain the kinematics of gait in the sagittal plane based on body-mounted sensors was developed. It consisted of four uniaxial seismic accelerometers and one rate gyroscope per body segment. Tests were done with 10 young healthy volunteers, walking at five different speeds on a treadmill. In order to study the system's accuracy, measurements were made with an optic, passive-marker system and the body-mounted system, simultaneously. In all the comparison cases, the curves obtained from the two systems were very close, showing root mean square errors representing <7% full range in 75% of the cases (overall mean 6.64%, standard deviation 4.13%) and high coefficients of multiple correlation in 100% of cases (overall mean 0.9812, standard deviation 0.02). Calibration of the body-mounted system is done against gravity. The body-mounted sensors do not hinder natural movement. The calculation algorithms are computationally demanding and only are applicable off-line. The body-mounted sensors are accurate, inexpensive and portable and allow long-term recordings in clinical, sport and ergonomics setting

Standing stability evaluation using a triaxial accelerometer

A triaxial accelerometer is placed at the back of the subject at the height of the center of mass. Force plate data are collected simultaneously. Subjects stand in a comfortable position with eyes open, eyes closed and doing cognitive tasks; and with feet together with eyes open and closed. The cognitive tasks are: mathematical, auditory Stroop and memory. The force plate data are processed to obtain the center of pressure and from it the parameters of: mean radius, speed and frequency, and base of support. The same parameters are obtained from the combined accelerations vector projection on the floor, found from the triaxial accelerometer data. The mean angular velocity, angular acceleration and accelerations in the horizontal plane at the level of the accelerometer are calculated T-tests indicate that for most parameters the accelerometer measurements are able to distinguish between the different test conditions as well as the force plate (p&les;0.05