Power-Assisted Steering Mechanism

This example shows a simplified version of a power-assisted steering mechanism displaying all its major parts: double-acting hydraulic cylinder; rotational valve; fixed-displacement pump; pressure-relief valve; mechanical load consisting of a reduced to a driving shaft inertia, damping, and stiffness; and torsion bar installed between the steering wheel and the pinion of a rack-and-pinion mechanism. The rotation of the steering wheel causes the torsion bar to twist with respect to the pinion position. The deformation of the bar is transformed into opening of the rotational valve, which connects ports of the cylinder to pressure or exhaust lines depending on the direction of rotation. If deformation exceeds 9 deg the wheel is connected directly to the pinion through the hard stops installed in parallel with the torsion bar. The cylinder moves the steering rods and, at the same time, twists the torsion rod in the opposite direction until the valve is in neutral position.