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Improving the safety of vehicle occupants has gained increasing attention among automotive manufacturers and researchers over the past three decades. Generally, more recent vehicle safety improvement and injury prevention techniques could benefit from accurate knowledge of the occupant presence, characteristics, and/or position within the interior space of the vehicle. There is increased potential for injury mitigation systems to be applied more effectively if the proximity of the occupant to restraint devices is obtained in real-time during vehicle operation. A particular application is the position of the head relative to the head restraint for mitigating neck injuries from rear end impacts, which has led to the development of “active” head restraint systems.

Flow rate monitoring plays a crucial role for precise motion control in many hydraulic systems and for detection of faults and fluid loss in hydraulic system components and circuits. In some situations, however, direct measurement of fluid flow is not possible. Besides, flowmeters are generally non-robust, expensive, and slow in response. In this paper, we have proposed an alternative approach to direct flow measurement for circuits that contain a combination of proportional valves and actuators. A nonlinear state-space representation is used to model the valve orifice area variation with respect to the valve spool position. Kalman Filtering is then utilized to estimate the valve's orifice area in real-time by fusing data from robust low-cost pressure transducers and position sensors. A close agreement is achieved between the estimated and the measured orifice areas for a valve with a complex wedge-shape orifice profile.