What is the principle of power steering?

[VanHazel]

Electronic Hydraulic Power Steering (EHPS) operates on the same principle as traditional mechanical hydraulic power steering systems but incorporates an electric steering pump, whose activation and deactivation are controlled by the ECU. Below is an introduction to the principle of power steering: 1. When no steering action is performed, the electric steering pump is turned off, unlike mechanical hydraulic power steering pumps that are constantly connected to the engine via a belt. Normally, the speed of the electric steering pump is inversely proportional to the vehicle speed. At low speeds, the pump operates at 3000r/min, while at high speeds, it reduces to 800r/min. This results in light steering during parking and a firm, stable feel at high speeds. 2. During steering, the torque sensor detects the steering wheel's torque and direction of rotation, sending these signals to the ECU. The ECU comprehensively analyzes data such as steering wheel torque, rotation direction, and vehicle speed, then issues command signals to the motor controller. The motor then outputs corresponding torque in size and direction to provide assistance. When the vehicle is not steering, the ECU does not send command signals to the motor controller, and the motor remains inactive, helping to reduce fuel consumption. Additionally, the ECU determines the force applied to the steering wheel via an electro-hydraulic converter based on the vehicle speed signal, reducing the "floating" sensation of the steering wheel during high-speed driving.

[IsaacAnn]

I've been driving for thirty years, and power steering is actually quite simple. It mainly relies on hydraulics or electricity to save you effort. Older cars commonly use hydraulic power steering—the engine drives the power steering pump, which pressurizes fluid to push pistons in the steering gear. When you turn the steering wheel, a valve opens, allowing the pressurized fluid to assist the gears in turning the front wheels, making it easier on your hands. When the wheel returns to center, the valve closes, and the fluid circulates. Just remember not to hold the steering wheel at full lock for more than 5 seconds to avoid burning out the pump. If the steering feels heavy, squeaks, or leaks, it's likely due to a cracked hose or a failing power steering pump. The mechanical principle is straightforward but reliable, though steering can feel heavier when the car is cold in winter.

[StNadia]

As a female car owner who frequently drives new cars, the most noticeable change is the steering wheel's weight variation. Electric power steering is now much more mainstream, with a torque sensor hidden beneath the steering wheel. When you turn, the sensor informs the computer how much force is applied, and the computer immediately directs the motor to assist on the steering column or rack. This type of assistance is far smarter than hydraulic systems—light as a feather at low speeds for easy maneuvering with just a finger, yet heavier at high speeds for better stability. Two years ago, my dashboard suddenly lit up with a power steering fault light, but the dealership diagnosed it as a sensor misjudgment due to unstable battery voltage—replacing the battery fixed it. Electronic systems eliminate the hassle of changing power steering fluid, but they also place higher demands on the electrical circuits.

[Emmy]

The most annoying thing when repairing a car is encountering a steering wheel with abnormal noise. The inspection sequence is quite particular: first check if the tire pressure is low (low tire pressure naturally makes steering heavier); then inspect the fluid level of the hydraulic power steering reservoir (if it's below the MIN line, top it up immediately) and the color of the fluid (if it's black, it needs to be replaced); next, turn the steering wheel while stationary to listen for any humming noise (a sign that the power steering pump is about to fail); after turning off the engine, turn the steering wheel left and right—if there's a noticeable gap, the steering gear is loose. For cars with electronic power steering, read the fault codes first; water ingress causing a short circuit in the steering column motor connector is a common issue. Don't underestimate a suddenly heavy steering wheel—last year, a client insisted on driving with it, and the steering gear locked up, nearly causing a collision with a guardrail.

[LaGideon]

Hyundai's Electric Power Steering is a systematic engineering: sensors capture the steering angle when the wheel is turned, and the onboard computer adjusts the assist force in real-time based on vehicle speed signals (less assist at higher speeds). The actuator motor is mounted on the steering column or gear, working with a reduction mechanism to amplify torque. For example, when making minor adjustments on the highway, the computer provides only 10% assist; whereas when navigating tight turns in a mall parking garage, the motor delivers up to 90% power assistance. This EPS system also integrates with driving aids—features like lane-keeping subtly apply steering force to correct deviations. However, electronics have vulnerabilities: cases of EPS failure after water exposure are three times more frequent than with hydraulic systems.

[AaronFitz]

Power steering is essentially a torque amplification device, directly related to handling safety. If the steering wheel suddenly becomes heavy, don't force it: for hydraulic power steering, it could be belt slippage or oil passage blockage; for electric power steering, common issues include motor overheating protection or fuse blowout. In extreme cases, such as power steering failure at 100 km/h, remember to grip the steering wheel tightly instead of making sudden turns (the required steering force increases several times). During routine maintenance, remind the technician to check the water content in the power steering fluid (for hydraulic systems) and the sealing of wiring harness connectors (for electronic systems), especially for vehicles over five years old. Rusted steering linkage is also dangerous; last year, some accident vehicles were found to have chassis components rusted to the point of excessive play.