A pneumatic loudspeaker for intensive sounds is presented. It operates by modulation of air from over- and underpressure reservoirs, as opposed to siren-like loudspeakers that use compressed air only. The symmetric construction makes the behavior more linear both with respect to aperture amplitudes and frequency bandwidth. Therefore, it may be used as secondary source in industrial active noise control problems where generation of large volume velocities are necessary. It is also shown that a Hammerstein model can model the loudspeaker over a wide frequency band. © 2001 EUCA.

When walking on inclined ground the biological foot adjusts the ankle angle accordingly. Prosthetic foot users have often a limited range of motion in their ankle which makes walking on hills uncomfortable. This paper describes a system which can autonomously correct the ankle angle to the inclination. The ground angle is estimated using an accelerometer. The angle foot blade to heel is then adjusted with a DC-motor. Since the controller only activates the motor when the foot is lifted and thus not loaded, a small powered system can be used.

A control procedure is proposed for an ankle-footorthosis (AFO) for different gait situations, such as inclinations and stairs. This paper presents a novel AFO control of the ankle angle. A magneto-rheological damper was used to achieve ankle damping during foot down and locking at swing, thereby avoiding foot slap as well as foot drop.

The controller used feedback from the ankle angle only. Still it was capable of not only adjusting damping within a gait step but also changing control behavior depending on level walking, ascending and descending stairs. As a consequence, toe strike was possible in stair gait as opposed to heel strike in level walking.

Tests verified the expected behavior in stair gait and in level walking where gait speed and ground inclinations varied. The self-adjusted AFO is believed to improve gait comfort in slopes and stairs.

An embedded measurement system for foot orthosis during gait is proposed. Strain gauge sensors were mounted on a foot orthosis to give information about strain in the sagittal plane. The ankle angle of the orthosis was fixed and strain characteristics were therefore changed when walking on slopes. With a Fourier series representation of the strain during a gait cycle, ground angle at different walking speeds and inclinations could be estimated with similar accuracy as previous studies using kinematically based estimators. Furthermore, if the angle of the mechanical foot ankle was changed, the sensing technique still could estimate ground angle without need for recalibration as opposed to kinematical sensors. This indicates that embedded strain sensors can be used for online control of future orthoses with inclination adaptation. Also, there would be no need to recalibrate the sensing system when changing shoes with different heel heights.

A portable gait measurement system for foot dynamic analysis is proposed. Portable cheap sensors are suitable in active control rehabilitation equipments such as prostheses and orthoses. A system of one gyroscope and two accelerometers was used to measure the foot movement in the sagital plane. Both ground inclination during stance and foot angle relative to ground during swing are estimated. This enables fast detection of changing environments such as hills and stairs.

A ground angle estimation technique for use on ankle-foot-orthosis AFO, during gait is proposed. Strain gauge sensors were mounted on a foot orthosis in order to give information about strain in the sagittal plane. The ankle angle of the orthosis was fixed. Strain characteristics were therefore changed when walking on slopes. It was investigated if strain information could be used for detection of inclination and estimation of inclination angle. With a Fourier series representation of the strain during a gait cycle, ground angle at different walking speeds and inclinations could be estimated with similar accuracy as previous studies using kinematically based estimators. This indicates that embedded strain sensors can be used for online control of future orthoses with inclination adaptation.

Gait measurement is of interest for both orthopedists and biomechanical engineers. It is useful for analysis of gait disorders and in design of orthotic and prosthetic devices.

In this chapter an algorithm is presented to suit estimation of one foot angle in the sagital plane, independent on gait conditions. Only one gyro is used during swing and two accelerometers are needed for calibration during stance. Also, the sensor placement at the front foot avoids the need for heel strike for stance transition. Stair walking can therefore be studied. From the estimated swing trajectory three different gait conditions: up stair, horizontal and down stair are classified.

An embedded measurement system for foot orthosis during gait is proposed. In this paper strain gauge sensors are mounted on a foot orthosis in order to give information about strain in the sagital plane. The ankle angle of the orthosis is fixed. Strain characteristics are therefore changed when walking on slopes. It is investigated if strain information can be used for detection of inclination and estimation of inclination angle. Also walking speed influence is studied. It is shown that strain sensing only gives significant information about up hill walking. At a known walking speed ground angle can be estimated for up hill walking.

In an aircraft the weight of the active noise control (ANC) system is a critical property. Therefore one aims at minimizing the number of microphones and loudspeakers. In doing so, only a reduced number of sensors and actuators may be used. Only recently has the relevance of placing sensors and actuators, in achieving a good global active noise control system, been considered. In this paper we will present two stochastic search methods for optimally placing the ANC-system -loudspeakers and -control microphones in a turboprop SAAB2000 aeroplane. The problem of optimal placement has not yet been showed to be analytically solvable. The number of possible configurations is large, indicating that stochastic search methods are strong candidates. In this work we show that genetic algorithms outperform simulated annealing in the case of the studied aeroplane. The method using genetic search also outperforms other known non stochastic methods.