in New Energy Heavy-Duty Trucks
The power steering of new-energy heavy-duty trucks is achieved by a motor-driven oil pump that pressurizes hydraulic oil, which in turn rotates the steering gear, assisting the driver in steering. We will use the dual-source integrated electric hydraulic pump, which is widely used in the market at present, as an example to introduce the control principle of the electric hydraulic power steering pump.
The dual-source integrated electric hydraulic pump consists of three parts:
① Oil pump, which pressurizes the hydraulic oil through rotation.
② Motor, which rotates via a high-voltage three-phase AC power supply or a 24V DC power supply. This is why it is called "dual-source".
③ Motor controller, which receives IG power, receives and provides feedback from CAN signals, and converts 24V low-voltage DC power. Because the motor and oil pump are integrated, it is called "integrated".
Starting: After the IG power supply passes through the fuse, it wakes up the motor controller. After high-voltage power is applied, the VCU sends a "run start signal" to the multi-function controller PEU-OAC in the form of a message. After the multi-function controller performs a self-test and finds no faults, it outputs high-voltage three-phase AC power to the motor, and the motor begins to work. Simultaneously, the system monitors the motor speed, controller voltage/current/temperature/pre-charge status/controlled status, and oil pump status (including fault information).
Shutdown: There are three shutdown scenarios.
① High-voltage power-off shutdown.
② Temporary shutdown: Under high-voltage power-on conditions, in neutral (N) gear, with vehicle speed at zero and parking brake signal lasting for more than 5 seconds, if all three conditions are met simultaneously, the VCU stops sending "start signal" messages, and the electric hydraulic power steering pump shuts down. This scenario primarily aims to reduce power consumption; operation resumes immediately if any condition is not met.
③ High-voltage fault shutdown: If a serious vehicle malfunction causes a high-voltage power-off, the EHPS controls the 24V battery to provide power for 30 seconds to drive the electric hydraulic power steering pump, achieving a safe stop.
Electric hydraulic power steering pump shutdown. This scenario primarily aims to reduce power consumption; operation resumes immediately if any condition is not met.
③ High-voltage failure shutdown: When a serious vehicle malfunction causes the high voltage to drop, the EHPS controls the 24V battery to provide power for 30 seconds to drive the electric hydraulic power steering pump to work and achieve a safe stop.