Vibration control of flexible structures using fusion of inertial sensors and hyper-stable actuator-sensor pairs

This paper discusses sensor fusion techniques that can be used to increase the control bandwidth and stability of active vibration isolation systems. For this, a low noise inertial instrument dominates the fusion at low frequency to provide vibration isolation. Other types of sensors (relative motion, smaller but noisier inertial, or force sensors) are used at higher frequencies to increase stability. Several sensor fusion configurations are studied. The paper shows the improvement that can be expected for several case studies

Carotid-femoral pulse wave velocity estimated by an ultrasound system

To date, regional aortic stiffness can be evaluated by the reference tonometric technique via the pulse wave velocity (PWV) measured in two points: the carotid and the femoral arteries. Based on a similar intersecting tangent algorithm, we have developed a new method for the determination of carotid-femoral PWV using a high-resolution echo tracking ultrasound system. Herein, PWV can be computed from the measurement of the transit time between the foot of the carotid diameter waveform and the foot of the femoral diameter waveform. The study was carried out on 50 consecutive patients at rest (29 men, mean age 30 ± 18 yrs) recruited on the occasion of a vascular screening for atherosclerosis. Carotid-femoral PWV was determined by a trained operator using a tonometric technique, (PWVpp, PulsePen, Italy), and an echotracking ultrasound system, (PWVus, e-tracking Alpha 10, Aloka, Japan). Relationship between PWVpp and PWVus was evaluated by linear regression. A Pearson’s correlation coefficient of r=0.95 was found between both variables (95% confidence interval 0.90-0.99; P<0.0001; PWVus= 0,91*PWVpp+0.44). The Bland–Altman plot comparing PWVpp and PWVus showed a systematic offset of -0.07 m.s-1 with a limit of agreement from -1,33 to 1,19 m.s-1. Our results show an excellent and significant correlation between both techniques which confirms that ultrasound system can provide a reliable estimate of the regional aortic stiffness like the tonometric technique does. Additional studies are now needed to show the simplicity of the measurement using ultrasound system while maintaining reliability even in overweight patients

Control-based continuation of nonlinear structures using adaptive filtering

Control-Based Continuation uses feedback control to follow stable and unstable branches of periodic orbits of a nonlinear system without the need for advanced post-processing of experimental data. CBC relies on an iterative scheme to modify the harmonic content of the control reference and obtain a non-invasive control signal. This scheme currently requires to wait for the experiment to settle down to steady-state and hence runs offline (i.e. at a much lower frequency than the feedback controller). This paper proposes to replace this conventional iterative scheme by adaptive filters. Adaptive filters can directly synthesize either the excitation or the control reference adequately and can operate online (i.e. at the same frequency as the feedback controller). This novel approach is found to significantly accelerate convergence to non-invasive steady-state responses to the extend that the structure response can be characterized in a nearly-continuous amplitude sweep. Furthermore, the stability of the controller does not appear to be affected