Detecting absolute human knee angle and angular velocity using accelerometers and rate gyroscopes

Abstract

Knee joint angle and angular velocity were calculated in real time during standing up and sitting down. Two small modules comprising rate gyroscopes and accelerometers were attached to the thigh and shank of two able-bodied volunteers and one T5 ASIA(A) paraplegic assisted by functional electrical stimulation (FES). The offset and drift of the rate gyroscopes was compensated for by auto-resetting and auto-nulling algorithms. The tilt of the limb segments was calculated by combining the signals of the accelerometer and the rate gyroscope. The joint angle was calculated as the difference in tilt of the segments. The modules were also tested on a two-dimensional model. The mean differences between the rate gyroscope-accelerometer system and the reference goniometer for the model, able-bodied and paraplegic standing trials were 2.1 degrees, 2.4 degrees and 2.3 degrees respectively for knee angle and 2.3 degrees s(-1), 5.0 degrees s(-1) and 11.8 degrees s(-1) respectively for knee velocity. The rate gyroscope-accelerometer system was more accurate than using the accelerometer as a tilt meter, possibly due to the greater bandwidth of the rate gyroscope-accelerometer system.

Compensation of magnetic disturbances improves inertial and magnetic sensing of human body segment orientation

“…The total flux is calculated by taking the absolute value of the three magnetic sensor components (8) Under nondisturbed conditions, this value is normalized to . In order to calculate the magnetic dip angle, first, the measured magnetic sensor signals should be expressed in the global frame using (9) Then, the dip angle in the global frame is (10) If and there is a homogeneous magnetic field without ferromagnetic materials and the disturbance equals zero (11) When and change, should change by updating (12) where and are vectors consisting of three equal components, which determine the contributions of the changes in total flux and dip angle, respectively.…”

“…disorders [8]- [11], and mixed and augmented reality [12]- [14]. It should be noted that there are important limitations in the current systems.…”

Sensor Module for Detecting Postural Change and Falls

“…Williamson et al studied that the gyroscope signal was integrated to an angle estimate [5]. Rueterbories et al analyzed the existing methods for monitoring gait and detecting gait events [6].…”

Development of a ubiquitous healthcare monitoring system combined with non-conscious and ambulatory physiological measurements and its application to medical care

“…Moreover, some wearable instruments monitoring activities have been developed to keep the activities in high condition and avoid becoming bedridden [9]- [11].…”