An integrated relative velocity sensor for real time damping applications

Semi-active suspension systems using real time damping (RTD) provide significant improvement in vehicle ride and handling without the high cost of fully active suspensions. RTD systems require a variable rate damper (shock absorber), a relative velocity sensor (RVS), and a controller. To reduce the cost of such systems, a method for integrating a moving magnet relative velocity sensor directly into the shock absorber is presented. This integrated relative velocity sensor (IRVS) uses existing hydraulic and mechanical components as part of its magnetic circuit to reduce part count and cost. Sensitivity to key design parameters is analyzed using a finite element model. The IRVS is self energizing, requires no signal processing electronics, and can be integrated into standard shock absorber configurations. Prototype sensors were tested on a vehicle and provided excellent performance under all testing conditions.