What is the working principle of power steering?
3 Answers
The working principle of power steering is: when the steering shaft rotates, the torque sensor converts the relative angular displacement between the input shaft and output shaft caused by the torsion bar into an electrical signal and transmits it to the ECU. The ECU determines the rotation direction of the motor and the magnitude of the assist current based on signals from the vehicle speed sensor and torque sensor, thereby achieving real-time control of power steering. Electric power steering is a system that directly relies on an electric motor to provide auxiliary torque. The reasons for its variable weight are: 1. Tire pressure too low; 2. Vehicle speed too low; 3. Battery undercharged; 4. Lack of power steering fluid; 5. Gap with rolling bearing too small; 6. Power booster system malfunction or poor contact; 7. Dirty power steering fluid; 8. Fuse damaged; 9. Plane bearing failure.
I've been running a repair shop for twenty years, and the lightness of the steering wheel all comes down to the power steering system. Older cars mostly use hydraulic power steering: the engine drives a hydraulic pump, which sends oil pressure into the steering gear. When you turn the steering wheel, the control valve inside adjusts the flow of hydraulic fluid, pushing the steering linkage. This system provides strong force but consumes more fuel, and if there's an oil leak, the steering can suddenly become heavy. Nowadays, new cars use electric power steering, with a torque sensor hidden beneath the steering wheel. When you turn the wheel, it sends a signal to the motor to provide assistance. This design is precise and fuel-efficient, but you have to be careful with water puddles to avoid damaging the motor. Last time, a car owner installed a steering wheel cover that jammed the sensor, causing the power assistance to fluctuate—showing that modifications also require understanding the principles.
My daughter always complains about the heavy steering wheel when taking her driving test. In fact, most cars nowadays come with Electric Power Steering (EPS). The core component is the torque sensor on the steering column, which works like human nerves sensing wrist force. Once it detects your steering input, the vehicle's computer instantly calculates how much assistance is needed and commands the motor to provide additional force to the steering gear through a worm gear mechanism. Our tests show this system responds three times faster than hydraulic systems, and it has built-in safety redundancy—even if the motor fails, the mechanical steering structure can still control the vehicle, though it becomes much harder to steer. Driving this car in rain or snow is noticeably more stable.
