A sharp increase in resistance when turning the steering wheel at low speed or a complete disappearance of effort often indicates a malfunction of the torque sensor or overheating of the electric motor. Unlike classical hydraulic systems, where the pressure is constantly generated by the pump, electric power steering (EUR) is activated only at the moment of turning, consuming energy from the on-board network. Understanding the physics of the process helps to quickly localize the problem: if the motor hums, but the shaft does not turn, a mechanical failure of the gearbox is likely, while a lack of response to commands indicates an electrical circuit.
Modern car control systems require precise tuning Electronic Power Steering, as the electronics analyze hundreds of parameters per second to ensure comfort and safety. Any discrepancy in sensor readings leads to the system going into emergency mode or completely disabling the assist function. That is why diagnostics begin not with disassembling the unit, but with reading error codes and checking the integrity of the wiring connecting the control unit with the actuators.
Basic architecture of the EUR system
The fundamental difference between the electric booster is the absence of hydraulic fluid, high-pressure hoses and a drive belt. The whole system is built around electric motor, which through a mechanical transmission adds force to the steering rack or steering column shaft. Structurally, the units are divided into two main groups: systems with the motor located on the steering shaft (column type) and systems integrated directly into the steering rack (rack type). The first option is cheaper and easier to maintain, the second provides more precise control and less play.
The central element of the architecture is control unit (ECU), which receives signals from various sensors and calculates the necessary force compensation. The operating algorithms are programmed by the manufacturer and can change the steering stiffness depending on the vehicle speed. At high speeds, the electronics artificially “weight” the steering wheel to increase stability, and in parking lots it makes it as light as possible for maneuverability.
Types of EUR layout
Depending on the car model, the electric motor can be built into the steering column, mounted on the rack housing, or be part of a mechanism with two gears (dual-pinion).
To transmit rotation, a special mechanical unit is used, most often worm gear or timing belt. This element is critically important, since it is the one that converts the rotation of the engine rotor into linear or rotational motion of the steering mechanism. The quality of lubrication and the precision of teeth manufacturing directly affect the absence of squeaks and jams in the operation of the system.
The role of sensors and sensory group
Correct operating principle of electric power steering is impossible without accurate data on the driver’s actions and the condition of the car. The key element here is torque sensor (Torque Sensor) mounted on the steering column shaft. It detects the slightest force applied by the driver and transmits this information to the control unit. If this sensor fails, the system “does not understand” where and with what force the wheels need to be turned.
The second most important source of data is speed sensor car. The signal comes either directly from the gearbox or via the CAN bus from the ABS/ESP unit. Based on this data, a gain map is constructed: the lower the speed, the higher the assistance coefficient. Also, the control loop often involves an engine speed sensor to prevent the battery from being discharged when the amplifier is idling.
⚠️ Attention: When replacing a steering rack or column, steering position sensor (SAS) calibration is often required. Without this procedure, the stabilization system and the amplifier itself may not work correctly.
Additionally, the system reads the temperature of the electric motor and control unit. During intensive work, for example during frequent parking maneuvers, temperature sensor initiates power reduction (assist) to prevent overheating of the windings and melting of the insulation. This phenomenon is known as thermal protection and is a normal situation, although it causes discomfort to the driver.
Electric motor operation algorithm
The heart of the system is brushless electric motor (BLDC) or, in older models, a brushed motor. The principle of its operation is to create a magnetic field that rotates the rotor, transmitting torque to the output shaft. Control occurs via pulse width modulation (PWM), which allows you to smoothly adjust the power and direction of rotation without mechanical switches.
The process of processing the command is as follows: the driver begins to turn the steering wheel -> the torque sensor records the force -> the control unit reads the speed -> the required current for the engine is calculated -> the motor creates force in the desired direction. This entire cycle takes milliseconds, which makes the operation of the amplifier almost imperceptible to humans, creating the feeling of “one finger”.
- 🚗 Start: Fixation of steering shaft rotation even at a minimum angle.
- ⚡ Calculation: The ECU determines the vector and strength of the required assistance.
- 🔄 Execution: Supplying current to the motor windings of the appropriate polarity.
- 🛑 Stop: When the steering wheel is leveled, the motor goes into hold mode or turns off.
It is important to note that the direction of rotation of the motor changes instantly when the direction of rotation of the steering wheel changes. For this purpose, the control unit uses a powerful inverter, which changes the polarity of the supplied voltage. The reliability of power switches (transistors) plays a decisive role here, since they experience significant current loads.
Comparison with hydraulic booster
To better understand the advantages and disadvantages of electrics, it is necessary to make a comparison with classical hydraulics (power steering). In hydraulic systems, the pump operates constantly, creating pressure even when the steering wheel is stationary, which leads to loss of engine power and increased fuel consumption. Electric booster is devoid of this drawback, consuming energy only during operation.
| Comparison parameter | Hydraulic booster (power steering) | Electric power steering (EUR) |
|---|---|---|
| Energy source | Engine belt, pump | On-board network, generator |
| Fuel consumption | Constant (pump always spins) | Only when turning the steering wheel |
| Service | Replacing fluid, belts, seals | Lack of scheduled maintenance |
| Temperature dependence | Thickens in the cold | Works stably in any climate |
| Integration | It is difficult to implement car parking | The basis for autonomous driving |
In addition, hydraulic fluid prone to aging, seal leaks and viscosity changes at extreme temperatures. The electrical system is free of these problems, making it more environmentally friendly and easier to use. However, the cost of repairing electronics in case of serious breakdowns can be higher than restoring hydraulics.
The main advantage of the ESD is fuel economy of up to 0.5 liters per 100 km and the possibility of implementing autonomous parking systems.
Typical faults and diagnostics
Despite the high reliability, electric power steering may fail. One of the most common problems is wear of brushes in brushed motors or failure of the Hall sensor in brushless motors. Symptoms include jerking of the steering wheel, an extraneous hum, or a complete loss of effort. Overheating of the control unit located in close proximity to hot engine components is also common.
Diagnostics should begin by checking the voltage in the on-board network. When the battery is low or the alternator is faulty, the system can be forced to shut down to save energy. A visual inspection of the wires for chafing and oxidation of contacts is also mandatory, especially in the area of the steering column, where constant movement of elements occurs.
☑️ Primary check of EUR
If the mechanical part is intact and the electrical parts are working properly, but the steering wheel is jerky, the problem may lie in the software or the need to adapt the system. In some cases, resetting errors and re-learning the extreme positions of the steering wheel through a diagnostic scanner helps.
⚠️ Attention: Operating a car with a faulty EUR is prohibited if the steering has become heavy and unsafe for maneuvering in traffic.
Development prospects and integration
Modern operating principle of electric power steering is evolving towards a complete abandonment of the mechanical connection between the steering wheel and wheels. Technology Steer-by-Wire (steer-by-wire) is already used on some models where the steering column shaft is not physically connected to the wheels. This opens up the possibility of changing gear ratios on the fly and customizing the shape of the steering wheel.
Integration of the ESD with ADAS (driver assistant) systems allows you to implement the functions of lane keeping, automatic obstacle avoidance and parking without human intervention. The electronics turn the wheels themselves using the same booster motor. The reliability and speed of modern controllers make such scenarios safe and effective.
- 🤖 Autonomy: Full computer control of the vehicle's trajectory.
- ⚙️ Customizability: Ability to change force and gear ratio programmatically.
- 📡 Communication: Deep integration with vehicle radar and cameras.
In the future, the role of mechanical components will be reduced to a minimum, and the main work will be done by software code and electric motors. This will require auto mechanics to have greater knowledge of electronics and programming, shifting the focus of service from wrenches to diagnostic laptops.
Why does the electric power steering hum when turning?
The hum often occurs due to wear on the motor bearings, lack of lubrication in the worm pair, or problems with the electrical part (for example, current runout). Also, the motor itself can produce sound when operating at maximum currents.
Is it possible to drive if the EUR is disabled?
You can drive, since the mechanical connection between the steering wheel and the wheels is maintained. However, the steering will become very heavy, especially at low speeds and when parking. You should move with extreme caution, avoiding sudden maneuvers.
How often do you need to change the fluid in the EUR?
There is no working fluid in the electric power steering. The system operates solely on electricity and mechanical transmission. If your car has a reservoir with steering fluid, you have power steering (power steering) or electric power steering (EGUR).
When parked for a long time with the wheels turned all the way, the load on the power steering is minimal, unlike the power steering, where the pressure in the system remains high.
⚠️ Attention: Do not hold the steering wheel in the extreme position for more than 5 seconds while the engine is running, this may lead to an overload of the electrical circuit and tripping of the protection.
Modern electric power steering systems are able to compensate for the car pulling to the side during gusts of side winds or different tire pressures, increasing traffic safety.