Digitally controlled servo-hydraulic crash simulator

The automotive industry is moving to newer technologies for crash simulation to minimize time-to-market for new models, reduce costs, and meet consumer demand for safer cars and trucks.

For years, crash simulation was dominated by an all-pneumatic, open-loop system. This technology was greatly improved with the introduction of servo-hydraulic simulation systems in the mid-1980s. Drawing on this body of knowledge, engineers have developed new programmable crash simulators that meet automaker demands for greater accuracy, higher response, and better timing.

Figure 1 shows a typical configuration of a four-way spool valve that is used in servo-hydraulic control applications. The term “four-way” refers to the fact that there are four metering edges controlling flow out of two separate control ports. The spool is positioned by applying hydraulic pressure to its ends. Measurement of the position of the spool permits precise servo control of its position. When each control port is connected to opposite sides of a hydraulic cylinder, the valve is capable of controlling the speed of both the extension and the retraction of the cylinder's piston rod.