Problems like a stiff steering wheel or loose steering while driving are directly related to the steering system. As the core of vehicle control, its structure determines driving experience and safety. Below is a step-by-step breakdown of steering systems from basic to advanced types.
1. Mechanical Steering System (Traditional Structure)
The mechanical steering system is the most basic configuration, consisting of a steering wheel, steering shaft, rack and pinion, tie rods, and wheels. It is driven entirely by the driver's arm strength with no additional power assistance, and is commonly found in older model trucks. Its advantages are a simple structure and low maintenance costs, while its disadvantages include strenuous steering at low speeds-usually requiring 3 to 4 turns of the steering wheel to complete a U-turn.
2. Hydraulic Power Steering (HPS)
Based on the mechanical structure, the hydraulic power steering system adds a hydraulic pump, control valve, and power piston. The engine drives the hydraulic pump to generate high-pressure oil, and the valve controls oil pressure to push the piston for steering assistance. The assistance can be amplified 2 to 3 times at low speeds for easier operation, but it increases fuel consumption by about 5% and requires regular hydraulic oil replacement, typically every 3 years or 60,000 kilometers.
3. Electric Power Steering (EPS)
Electric power steering is the current mainstream, with a core structure including a steering wheel, torque sensor, ECU, power-assist motor, rack and pinion, and wheels. The torque sensor detects steering force, and the ECU adjusts motor assistance in combination with vehicle speed-amplifying assistance 3 to 5 times at low speeds and reducing it at high speeds to prevent loose steering. It consumes 3% to 5% less energy than hydraulic systems, requires no maintenance, and is compatible with autonomous driving functions such as lane keeping.
4. Steer-By-Wire (SBW)
Steer-by-wire is the future trend of steering systems. It eliminates the mechanical connection between the steering wheel and wheels, converts steering commands into electrical signals via angle sensors, and directly controls the steering motor to drive the wheels. The steering ratio can be customized; for some models such as the NIO ET5T, a U-turn only requires half a turn of the steering wheel. It also frees up cockpit space and supports more precise automatic lane changes.
5. Rear-Wheel Steering Coordination
Rear-wheel steering coordination is a high-end configuration. At low speeds, the rear wheels rotate in the opposite direction by 3° to 5°, which can reduce the turning radius-for example, the Audi A8L's turning radius can be shortened by 1.2 meters. At high speeds, the rear wheels rotate in the same direction by 2° to 3°, keeping the body more stable during lane changes. Currently, it is mainly equipped on high-end sedans and SUVs such as the Porsche 911 and BMW 7 Series.