Electro Hydraulic Power Steering
- Hydraulic fluid, pressure side
- Hydraulic fluid, return side.
When the electrical power steering module (EPS) receives a 15 supply via the ignition switch which "wakes up" the control module. This is to diagnose certain functions and to prepare to start the pump motor. When the engine is started, the control module will activate the pump motor in the system so that the power steering function is activated.
The following is measured when the driver turns the wheel:
- steering angle speed
- the vehicle speed
- maximum permitted power consumption
- engine status (engine running).
These input signals, together with the internal signals (pump motor speed, temperature in the control module, power consumption of the pump motor etc) are used by the control module to control and diagnose the electro hydraulic power steering. This gives optimal power steering adaptation.
The control module controls the power consumption of the pump motor using the internal power stage. For efficient control of the pump motor, a pulse width modulated supply is used. By controlling the pulse ratio, the control module is able to regulate the output of the pump motor and therefore the speed which indirectly controls the hydraulic pressure in the power steering system. Principally the control module continuously monitors the following:
- the power consumption of the pump motor
- the speed (RPM) of the pump motor
- the temperature in the control module.
This means that the system is regulated constantly so that the hydraulic pressure is correct. The functionality of the system can also be diagnosed efficiently.