Overview of the development of steering system of

Overview of the development of automobile steering system

the steering system is the most basic component system in the whole vehicle system. The driver manipulates and controls the direction of the car through the steering wheel, so as to realize his driving intention

for more than 100 years, the automotive industry has been advancing with the development of mechanical and electronic technology. Today, the automobile is no longer the automobile in the pure mechanical sense. It is the comprehensive product of machinery, electronics, materials and other disciplines. With the development of the automotive industry, the automotive steering system has undergone a long evolution

the traditional automobile steering system is a mechanical steering system. The steering of the automobile is controlled by the driver, and the wheel deflection is realized through a series of mechanical steering components such as steering gear, so as to realize steering

since the 1950s, the application of hydraulic power steering system in automobiles marks the beginning of the steering system revolution. The source of automobile steering power has changed from human power to human power plus hydraulic power

hydraulic power steering (HPS) is a hydraulic system added to the mechanical steering system. The hydraulic system is generally connected with the engine. When the engine starts, part of the engine energy provides kinetic energy for the car to move forward, and the other part provides power for the hydraulic system. Because of its reliable work and mature technology, it is still widely used. The main feature of this power steering system is that the hydraulic pressure supports the steering movement, reduces the driver's force on the steering wheel, and improves the portability of vehicle steering and the stability of vehicle operation

but at the same time, the hydraulic power system also has some shortcomings:

◆ after the completion of vehicle design and manufacturing, the power assisted characteristics of vehicle steering cannot be changed. The direct consequence is that when the assistance characteristics are biased towards low-speed assistance, the car can get good assistance in the low-speed segment, but when a better road feel is required in the high-speed segment, the driver does not have a better road feel because the assistance characteristics cannot be adjusted; When the assistance characteristic is biased towards high-speed assistance, it can not get a good assistance effect in the low-speed segment

◆ even if the vehicle does not turn, the hydraulic system must work under the drive of the engine. As a result, engine energy is consumed and fuel consumption is increased

◆ there is a problem of hydraulic oil leakage, which not only pollutes the environment, but also easily damages other parts

◆ under low temperature, the working performance of the hydraulic system is relatively poor

in recent years, with the wide application of electronic technology in automobiles, electronic devices are increasingly used in steering systems. Therefore, the steering system has entered the era of electronic control, and the corresponding electro-hydraulic power steering system has appeared. Electrohydraulic power steering can be divided into two categories: electro-hydraulic power steering system EHPS (electro-hydraulic P also led to changes in the packaging industry) and electronically controlled hydraulic power steering ECHPS (electronically controlled hydraulic power steering). The electro-hydraulic power steering system is developed on the basis of the hydraulic power system. Different from the hydraulic power system, the power source of the hydraulic system in the electro-hydraulic power system is not the engine but the motor. The hydraulic system is driven by the motor, which saves the engine energy and reduces the fuel consumption. Electronic hydraulic power steering is also developed from the traditional hydraulic power steering system. The difference between them is that the electronic control device is added to the electronic hydraulic power steering system. The electronic control device can change the power assisted oil pressure of the hydraulic system according to the steering speed of the steering wheel, vehicle speed and other vehicle operating parameters, so as to realize the change of power assisted characteristics at different vehicle speeds. Moreover, the hydraulic system driven by the motor can stop rotating when there is no steering operation, so as to reduce energy consumption

although the electro-hydraulic power steering system overcomes some shortcomings of hydraulic power steering when the experimental conditions cannot meet the requirements. However, due to the existence of the hydraulic system, it also has the problem of hydraulic oil leakage, and the electro-hydraulic power steering system introduces the drive motor, which makes the system more complex, the cost increases, and the reliability decreases

in order to avoid the shortcomings of electro-hydraulic power steering system, electric power steering system EPS (electric power steering) was born at that time. The biggest difference between it and the aforementioned power steering systems is that there is no hydraulic system in the electric power steering system. Originally, the steering power generated by the hydraulic system is completed by the motor. Electric power steering system is generally composed of torque sensor, microprocessor, motor, etc. The basic working principle is: when the driver turns the steering wheel to drive the steering shaft to rotate, the torque sensor installed on the rotating shaft converts the torque signal into an electrical signal and transmits it to the microprocessor. The microprocessor obtains the direction and magnitude of the power assisted by the power assisted motor according to the torque signal and other vehicle operating parameters such as vehicle speed according to the processing method set in the program in advance. Since 1988, Suzuki company of Japan first equipped the power steering system on its Cervo car, the electric power steering system has been widely recognized by people

the advantages of power steering system are mainly reflected in the following aspects:

◆ electric power steering system can provide different power characteristics at different speeds. When driving at low speed, increase steering power to make steering more portable; Reduce steering power when driving at high speed, and even increase steering damping to improve road feel

◆ the electric power steering system only works when steering, providing power for steering, thus reducing energy consumption

◆ the motor is powered by the battery, so the electric power steering system can work when the engine is not working

◆ electric power steering system has no hydraulic system, and its assembly automation is higher than that of hydraulic power steering system. Moreover, the electric power steering system can easily change the power assisted characteristics by changing the power assisted program algorithm in the microprocessor

the development of science and technology is always changing with each passing day. The traditional steering system is composed of steering control mechanism (steering wheel), steering gear and steering transmission mechanism. But the spark of thought can always surprise people! The birth of the electronic steering system SBW (steering by wire) overturned the old concept of the three parts of the steering system. It replaced the steering transmission mechanism with a microcontroller and changed from three parts to two parts. Electronic steering system is one of the most advanced and cutting-edge technologies of automotive steering system. It is mainly composed of three modules: steering wheel control module, steering execution module and microcontroller

the main function of the steering wheel control module is to detect the driver's steering intention through the steering torque sensor, and transmit the detected signals (including rotation direction and rotation speed) to the microcontroller through the bus, and then the microcontroller will feed back a correction torque to the steering wheel control module according to this signal and combined with the vehicle speed signal, so that the driver can feel the road feeling. But this kind of road feeling is virtual, which is the "experience road feeling" formed by developers based on thousands of test data, and is solidified in the microcontroller in the form of program. Therefore, it has a certain corresponding relationship with the speed, steering speed and steering torque

the steering actuator consists of angle sensor, steering motor, steering motor controller, etc. Its function is to drive the steering executive motor to rotate a certain angle and complete the steering action according to the control command of the microcontroller. At the same time, the angle sensor monitors the size of the angle and feeds it back to the microcontroller to form a closed-loop control system to complete the precise steering action

microcontroller is the core of electronic steering system. It receives the detection signal and sends the corresponding control signal after processing

because the microcontroller replaces the steering transmission mechanism, the mechanical connection between various components is reduced, and the response speed and accuracy of the steering system are improved. Moreover, the steering strategy can be controlled by software programming to realize the arbitrary setting of transmission ratio; It can be integrated with other equipment, such as ABS and automatic navigation equipment. The reduction of transmission mechanism also brings more interior space of the car, which brings more fun to driving and riding. Moreover, the steering behavior can be recorded by software and saved in EEPROM, which will help to further improve the steering control strategy in the future, and even provide evidence for traffic accidents

automobile safety has always been the focus of public attention. The combination of steering system and light system after 3 years can bring better safety to vehicles driving at night. As shown in the left figure on the previous page, the traditional vehicle lighting system shines straight ahead of the vehicle. If the pedestrian is at the corner, it will be difficult for the driver to find the pedestrian in the corner, which is very likely to cause traffic accidents and then heat and pressurize. If the lighting system is combined with the steering system, as shown in the above figure, when the driver turns the steering wheel to the right, the light shines to the right with the change of the steering wheel angle, and the illumination inside the curve is wider and the illumination range is larger, then pedestrians in the road corner will be easy to be found. At present, this lighting technology has been applied in mid-range Citroen triumph and Toyota Camry

at present, the reliability and cost of electronic steering system are the main factors that hinder its development. The main performance is that if there is a problem with the microcontroller, the steering system will completely fail. Unlike the electric power steering system and the electric hydraulic power steering system, it can also control the car manually when there is a problem with the motor or hydraulic system. If the microcontroller of the electronic steering system fails, it is impossible to control the steering of the car because there is no mechanical system that can connect the steering wheel and steering gear. However, electronic steering system is still one of the development directions of steering system in the future.) (end)