Construction and Parameterization

The sketch is the following one:

Figure 21: Hydraulic Wheatstone bridge sketch

This type of valve is typically used on power steering units. When the driver inputs a steering angle command, this steering valve opens. This allows the oil to flow into the hydraulic jack, with a pressure proportional to the valve opening. The oil pressure acts on the jack piston to create an actuating force proportional to the pressure. This actuating force then assists the driver in moving the jack piston and the mechanism connected to it (rack, tires ...).

The rotary valve can be represented as a Wheatstone bridge, where each branch is one direction of the valve. The flow area of each path depends on the strain of the torsion bar. The simplest model of this part is a rotary spring attached on one side on the pinion and on the other to the steering column. The flow area on the valve is controlled by the strain of the torsion bar.