Electric Power Steering (EPS)
发布时间：1/19/2025 4:41:46 PM
Electric Power Steering (EPS) is the future direction of steering system development. The system directly provides steering assistance by electric power steering machine, eliminating the power steering oil pump, hose, hydraulic oil, conveyor belt and pulley installed on the engine required by hydraulic power steering system, which saves energy and protects the environment. In addition, it has the characteristics of simple adjustment, flexible assembly and steering assistance under various conditions. It is precisely because of these advantages that the electric power steering system, as a new steering technology, will challenge the hydraulic steering system that everyone is very familiar with and has a history of more than 50 years.
◎Electric Power Steering System
The electric power steering system was proposed in the mid-1980s. The fastest-growing and most mature technology is TRW Steering System and Delphi Sagiaw Steering System, and Delphi Sagiaw Steering System represents the forefront of steering system development. She was the first to market the hydraulic power steering system in the 1950s. Since then, Delphi Steering has developed a more mature hydraulic power steering system, which has been equipped with most commercial vehicles and about 50% of cars. Now, Delphi Steering has led a new revolution in the automotive steering system - the electric power steering system. The electric power steering system conforms to the design concept of modern automotive mechatronics. The system consists of a steering sensor, a vehicle speed sensor, a power-assisting mechanical device, a steering power-assisting motor and a microcomputer control unit.
When the system is working, the steering sensor detects two signals, the torque on the steering shaft and the steering wheel position, and continuously inputs them into the microcomputer control unit together with the vehicle speed signal measured by the vehicle speed sensor. The control unit determines the steering direction and the required optimal power value through data analysis, and then issues corresponding instructions to the controller to drive the motor and realize the steering of the car through the power-assisting device. Through precise control algorithms, the torque of the motor can be arbitrarily changed, so that the transmission mechanism can obtain any required power value.
◎ Characteristics of the electric power steering system
The hydraulic power steering system has been developed for more than half a century, and its technology is quite mature. However, with the development of automotive microelectronics technology, the requirements for automobile energy saving and environmental protection are constantly increasing. The inherent deficiencies of this system, such as energy consumption and possible pollution to the environment, have become increasingly obvious and cannot fully meet the requirements of the development of the times.
The electric power steering system applies the latest power electronics technology and high-performance motor control technology to the automotive steering system, which can significantly improve the dynamic and static performance of the vehicle, improve the comfort and safety of the driver during driving, and reduce environmental pollution. Therefore, once the system was proposed, it was valued by many large automobile companies and developed and researched. In the future steering system, electric power steering will become the mainstream steering system. Compared with other steering systems, the outstanding advantages of this system are reflected in:
a. Reduced fuel consumption. The hydraulic power steering system requires the engine to drive the hydraulic oil pump so that the hydraulic oil flows continuously, wasting some energy. On the contrary, the electric power steering system (EPS) only needs the energy provided by the motor when steering operation is required. The energy can come from the battery or the engine. Moreover, the energy consumption is related to the steering of the steering wheel and the current vehicle speed. When the steering wheel is not turning, the motor does not work. When the steering wheel needs to turn, the motor starts to work under the action of the control module, outputting torque of corresponding size and direction to generate power steering torque. Moreover, the system outputs the maximum steering torque when the car is turning in place. As the speed of the car changes, the output torque also changes. This system truly realizes "energy on demand" and is a true "on-demand" system. When the car starts in the cold winter, the traditional hydraulic system reacts slowly and can only work normally after the hydraulic oil is preheated. Since the electric power steering system is designed not to rely on the engine and has no hydraulic oil pipes, it is not sensitive to cold weather. The system can work even at -40℃, so it provides a fast cold start. Since the system does not have preheating at start-up, energy is saved. Without the use of hydraulic pumps, the parasitic energy loss of the engine is avoided, and fuel economy is improved. The comparison experiment between vehicles equipped with electric power steering system and vehicles equipped with hydraulic power steering system shows that when not steering, the fuel consumption of vehicles equipped with electric power steering system is reduced by 2.5%, and when steering is used, the fuel consumption is reduced by 5.5%.
b. Enhanced steering followability. In the electric power steering system, the electric power motor is directly connected to the power mechanism, so that its energy can be directly used for wheel steering. The system uses the function of inertial shock absorber to greatly reduce the wheel reversal and steering front wheel shimmy. Therefore, the anti-disturbance ability of the steering system is greatly enhanced. Compared with the hydraulic power steering system, the rotational torque is generated by the motor, and there is no steering hysteresis effect of the hydraulic power steering system, which enhances the steering wheel's following performance to the steering wheel.
c. Improved steering return characteristics. Until today, the development of power steering system performance has reached its limit, and the return characteristics of the electric power steering system have changed all this. When the driver turns the steering wheel an angle and then releases it, the system can automatically adjust the wheel back to the center. The system also allows engineers to use software to adjust design parameters to the maximum extent to obtain the best self-centering characteristics. From the lowest speed to the highest speed, a cluster of self-centering characteristic curves can be obtained. Through flexible software programming, it is easy to obtain the torque characteristics of the motor at different speeds and different vehicle conditions. This torque characteristic enables the system to significantly improve the steering ability and provide a steering self-centering characteristic that matches the vehicle dynamic performance camera. In traditional hydraulic control systems, to improve this characteristic, the mechanical structure of the chassis must be modified, which is difficult to achieve.
d. Improved handling stability. The stability characteristics of the car are tested by the method of oversteering the car at high speed. Using this method, an excessive turning angle is given to a car traveling at high speed (100km/h) to force it to tilt. During the short self-centering process, due to the use of microcomputer control, the car has higher stability and the driver feels more comfortable.
e. Provide variable steering assistance. The steering force of the electric power steering system comes from the motor. Through software programming and hardware control, a variable steering force covering the entire vehicle speed can be obtained. The magnitude of the variable steering force depends on the steering torque and vehicle speed. Whether parking, driving at low speed or high speed, it can provide a reliable and controllable feeling, and it is easier to operate in the parking lot. For traditional hydraulic systems, variable steering torque is very difficult and expensive to obtain. To obtain variable steering torque, additional controllers and other hardware must be added. However, in electric power steering systems, variable steering torque is usually written into the control module and can be obtained by rewriting the software, and the cost is very small.
f. Adopt "green energy" to meet the requirements of modern cars. The electric power steering system uses the "cleanest" electricity as energy, completely abolishes hydraulic devices, and there is no problem of liquid oil leakage in the hydraulic power steering system. It can be said that the system conforms to the trend of the times of "greening". The system avoids pollution because it has no hydraulic oil, no hoses, oil pumps and seals. The polymer used in the oil pipe of the hydraulic steering system cannot be recycled and is easy to pollute the environment.
g. The system has a simple structure, small space, convenient layout and excellent performance. Since the system has a good modular design, it is not necessary to redesign, test, and process different systems, which not only saves costs, but also provides great flexibility for designing different systems and is easier to assemble on the production line. Since there is no oil pump, oil pipe, or pulley on the engine, engineers have more room to design the system, and the control module of the system can be designed together with the gear rack or separately, and the space utilization rate of the engine components is extremely high. The system eliminates the pulley and oil pump installed on the engine, and the space left can be used to install other components. Many consumers are very concerned about the maintenance and care of the vehicle when buying a car. Cars equipped with electric power steering systems have no oil pumps and no hose connections, which can reduce many worries. In fact, in traditional hydraulic steering systems, the accident rate of hydraulic oil pumps and hoses accounts for 53% of the entire system failure, such as hose leakage and oil pump leakage.
h. Good assembly of the production line. The electric power steering system does not have the oil pump, oil pipe, flow control valve, oil storage tank and other components required by the hydraulic system, and the number of parts is greatly reduced, which reduces the workload of assembly, saves assembly time, and improves assembly efficiency.
Since the electric power steering system was proposed in the mid-1980s, it will replace the existing mechanical steering system, hydraulic power steering system and electronically controlled hydraulic power steering system as the development direction of future automobile steering systems.
Electric power steering system (EPS) is the development direction of future steering systems. The system directly provides steering assistance by an electric power steering machine, eliminating the power steering oil pump, hose, hydraulic oil, conveyor belt and pulley installed on the engine required by the hydraulic power steering system, which saves energy and protects the environment. In addition, it has the characteristics of simple adjustment, flexible assembly and steering assistance in various conditions. It is precisely because of these advantages that the electric power steering system, as a new steering technology, will challenge the hydraulic steering system that everyone is very familiar with and has a history of more than 50 years.