Central issue:
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Theoretical basis of electronic control of automobile chassis
Application of sensors in electronic control systems for driving and braking
solution:
Sensor application in traction control system TCS
Sensor application in ESP
Sensor application in automotive anti-lock braking system ABS
With the development of electronic technology, the degree of electronicization of automobiles is also increasing. The connection between the device and the actuator of the chassis control system also enters the electrical signal connection phase by a simple mechanical connection phase. A good chassis electronic control system improves the adhesion between the wheel and the ground, thereby improving the safety, power and comfort of the car. The application of electronic control systems in automotive chassis technology has improved the active safety of automobiles.
Common chassis control systems are available in the following categories: traction control, brake control, suspension control, and steering control. The sensor is the core device in the electronic technology. It is a device for signal transformation. Its function is to transform the measured non-electricity signal into a power signal, which is a key device to promote the comprehensive development of automotive technology. In the electronic control system of the car chassis, it is inseparable from the sensor. Sensors for chassis control refer to sensors distributed in the transmission control system, power steering system, suspension control system, braking system, etc. They function differently in different systems, but the working principle is the same.
Theoretical basis of electronic control of automobile chassis
The main function of the car chassis is to allow the car to move according to the driver's wishes, such as acceleration, deceleration and steering. The driver expresses his or her wishes by manipulating the steering wheel, throttle and brake pedal in the car. The amount of execution corresponding to these controls is the steering angle of the front wheels and the driving or braking torque on the wheels. What works is the longitudinal and lateral forces of the tire.
The main factors affecting the tire force of the car are the adhesion coefficient of the road surface, the normal force of the wheel, the wheel slip rate and the wheel side yaw angle. The basic principle of the car chassis control design is to properly adjust and control the wheel slip rate and the wheel side declination under the premise of the road surface adhesion coefficient and the wheel normal force, thereby indirectly controlling the longitudinal force and side of the tire. For the purpose of force, to maximize the use of adhesion between the tire and the road surface, to achieve the purpose of improving the car's active safety, mobility and comfort. The electronic control of the car chassis is a complex system engineering that interacts and interacts with multiple systems. The specific performance is as follows:
(1) The same control system may have multiple actuators and control multiple variables simultaneously.
(2) The same control target can be controlled by different control systems individually or by multiple systems.
(3) The same control target is simultaneously controlled by different control systems.
(4) Different control systems may share the same sensor or control unit.
Application Status of Sensors in Electronic Control of Automobile Chassis
1 sensor application in power steering system
In the power steering system, the control object of the sensor is the steering angle of the wheel, and the electronic steering control of the steering angle of the wheel achieves the purpose of controlling the power steering system. Common power steering systems are: active front wheel superimposed steering system AFS, active front wheel power steering system ESP and active rear wheel steering system RWS. The sensors used mainly include an engine speed sensor, a vehicle speed sensor, a torque sensor, etc., and the power steering electronic control system increases the output power and reduces the engine loss while achieving a light steering function and improved response characteristics. It also saves fuel.
The working principle of all power steering systems ESP, AFS and RWS is commanded by the driver. The sensor senses the condition of the road surface and transmits the road surface condition to the electronic controller and actuator through the network in the form of electrical signals. For example, in the EPS system, the microcomputer-controlled steering assist system has the characteristics of small components, small mass, and small size. When the system works, if we choose the best transmission ratio, we can get the fastest response: when the car is driving at high speed, the steering speed ratio will become smaller, and the steering force will gradually increase, which will make the car direction more. Stable and safer to drive.
When driving at a very low driving speed, the steering speed ratio will become larger. At this time, the steering wheel is only slightly lightly angled, and the body displacement will change greatly, which makes a lot of work easier, such as Parking is in place; the system is characterized by improved steering and steering response, as well as increased stability at high speeds and maneuverability at low speeds. In addition, since the EPS can apply an extra torque to the steering wheel as needed, the driver can turn the steering according to the prompt signal of this torque, which is the function suggested by the steering of the system. The system mainly consists of an electronic controller, an electric motor and a motion transmission mechanism, a motor speed sensor, a steering torque sensor and a steering wheel angle sensor. Other systems, like the EPS system, each play an irreplaceable and important function.
2 sensor application in suspension system control
The operation of the sensor in the suspension system control is to intervene and adjust the characteristics of the vehicle suspension components, so as to achieve the purpose of vehicle dynamics control. When working, the system integrates the motion state of the car and the information detected by these sensors, and calculates the optimal damping coefficient of each wheel suspension damper, and then makes work orders such as automatically adjusting the vehicle height and suppressing the change of the vehicle posture. Thereby control of steering stability, driving stability and vehicle comfort is achieved. The continuous damping control system ADC consists of four control units, CAN, four wheel vertical acceleration sensors, four body vertical acceleration sensors and four damper proportional valves.
Application of sensors in electronic control systems for driving and braking
1 sensor applied in the traction control system TCS
Since the driving torque of the driving wheel of the automobile is too large, the driving wheel will slide relative to the ground. According to the calculation, the safe slip rate of the drive wheel should not exceed 20%. Therefore, we need to control the drive wheel slip rate. The system that controls the drive wheel slip rate is the traction control system TCS. It is developed on the basis of ABS. In most cars, TCS and ABS share an ECU. The job of the sensor is to sense the slip of the car, and then input the obtained information into the system as an electrical signal. The system analyzes the signal input by the sensor to identify and judge the driving condition of the car, and accordingly takes corresponding measures.
2 sensor application in automotive dynamics electronic stability system ESP
The ESP system is an active safety system that enables the car to have more comfortable maneuverability and better direction stability. The basic working principle is to identify the driver's desired motion state by analyzing the sensor input signal and performing logical operations. The actual movement state of the car is known by adjusting the longitudinal force of the wheel and the driver's expectation of the car. Therefore it requires more sensors than the ABS and TCS to control the yaw motion of the car. This type of sensor identifies the driver's expectations for the car, including the steering wheel sensor, the lateral acceleration sensor, the vehicle yaw rate sensor, and the hydraulic sensor of the brake master cylinder.
Application of 3 sensors in automobile anti-lock braking system ABS
Anti-lock braking system ABS is an important safety component in automotive electronic devices with the longest development time and the fastest application. Its working principle is: control to prevent the wheel from locking when the car brakes, and to ensure the best sliding rate between the wheel and the ground (5%-20%). In this way, no matter what kind of road is braked on the road, the vertical peak adhesion coefficient and the large lateral adhesion coefficient can be achieved between the wheel and the ground, so that the vehicle can be braked without braking. Loss of steering conditions and other unsafe conditions, reducing the braking distance, improving the handling stability and safety of the car.
The functioning sensor is an anti-lock brake sensor. It mainly detects the wheel speed by using the wheel angular velocity sensor, and controls the brake oil pressure when the slip ratio of each wheel is 20%, thereby improving the braking performance. Ensure the purpose of vehicle handling and stability. Among them, the wheel speed sensor is a very important device of ABS. Its main job is to provide reliable and accurate wheel speed to the ECU in time. If there is no wheel speed sensor, the work of the system can not be completed, and the accuracy of the wheel speed sensor will directly affect the work of the system. The wheel speed sensor is mainly There are several types of electromagnetic, Hall, and magnetoresistive.
4 trends in the application of sensors in electronic control of automotive chassis
With the development of electronic technology and the automotive industry, the development of automotive sensors will become one of the key factors affecting the development of high-end, electronic and automation of automobiles. The higher the degree of automation of the car, the greater the dependence on the sensor. Therefore, many automotive electronics industries regard the vehicle sensor technology as a key research and development technology project. Since the electronic control system of the car chassis is composed of many systems, the types and quantities of sensors required are also various. Therefore, it is necessary and necessary to develop new sensors with high precision, high reliability and low cost. In order to meet this need, the development trend of the sensor of the electronic control system of the automobile chassis in the future will definitely be toward the direction of integration, intelligence and miniaturization; on the basis of basic research, discover new phenomena, adopt new principles, and develop new ones. Materials and new processes. The sensor is becoming more and more accurate, and the technology content is getting higher and higher, so as to better promote the development of electronic technology and even the automotive industry.
Development trend introduction
The intelligent sensor is a sensor with a microcomputer and various functions such as detection, judgment, and information processing. Compared with traditional sensors, it can correct the measurement data by determining the working state of the sensor, thus reducing environmental factors such as temperature. Its greatest advantage lies in its ability to fully understand the driver's and passenger's condition, traffic facilities and surrounding environment information; to determine whether the driver and passengers are in the best condition, whether the vehicle and people will be in danger, and take appropriate measures in a timely manner. The difference is that it uses software to solve problems, which are difficult to solve in ordinary sensors. For example, the calculation and processing of data are completed, and the intelligent sensor not only has large range coverage, large output signal, high precision, high signal-to-noise ratio, good anti-interference performance, and many self-test functions. In the future, if this sensor can be applied to the electronic control system of the car chassis, it will bring a lot of convenience to the driver.
The versatile integrated sensor is a sensor that integrates multiple functionally sensitive components and multiple sensitive components of the same function. This sensor can detect two or more characteristic parameters or chemical parameters, which reduces the number of chassis sensors and improves the accuracy of its electronic control system.
Micro-sensors use micromachining technology to package micron-sized sensitive components, signal processors, data processing devices, etc. on a single chip. This sensor is easy to integrate, small in size, and inexpensive, and small and sophisticated components can be clearly Improve system test accuracy. At present, this technology has gradually matured, and it is possible to produce various miniature sensors such as mechanical quantity, magnetic quantity, and thermal quantity. This sensor is used in the electronic control system of the car chassis and will greatly optimize many of the car's performance.
Research methods, direction introduction
The research and development of sensors is the inevitable development of electronic technology. The basic principles of various sensors are the same, that is, the use of physical phenomena, chemical reactions and biological effects. Therefore, discovering new phenomena and new effects is an important basis for the development of modern sensors.
Another important basis for the development of sensor technology is functional materials. Due to the rapid development of materials science, material manufacturing has reached a very high level, that is, we can arbitrarily control the composition of materials when manufacturing various materials. In view of this, we can also design and manufacture a variety of functional materials for sensors. For example, by adding different semiconductor oxides, gas sensors of various properties can be manufactured; optical fibers can be used as materials for sensors, which is a major discovery of sensor functional materials; in addition, many experts in automotive electronics at home and abroad also There has been a strong interest in organic materials, and they are speculating whether organic materials can be used as functional materials in sensors, which remains to be further studied by experts.
For a sensor, the performance of its sensitive components is highly dependent on the functional materials used. However, the processing also has a certain impact on the performance of the component. Therefore, improving the processing technology will also be a direction for future research. As various new materials such as semiconductors, ceramics, etc. are applied to sensor sensitive components, many modern advanced processing technologies are gradually introduced into automotive sensor manufacturing processes, such as ion implantation technology, integration technology, and micro-machining technology. By using these new technologies, it is possible to manufacture new sensitive components with high reliability, small size, light weight and stable performance. For example, due to the rapid development of technology, microelectromechanical systems (MEMS) technology has matured, and this technology has evolved from semiconductor integrated circuit technology. Micro-electromechanical systems can be used to create a variety of miniature sensors that sensitively detect mechanical, magnetic, thermal, chemical, and biomass quantities.
The wide application of electronic technology in automotive technology makes the control system of automobile chassis develop rapidly in the direction of electronic and intelligent, which leads to the emergence of many electronic control systems for automobile chassis, and the sensor is the core device of electronic technology. More and more sensors are used in the chassis of the car, and the brake handling performance, steering performance and safety performance of the vehicle are greatly improved due to the use of the sensor.
At the same time, it also improves the economy and safety of the car. The effects of various electronic steering control systems such as AFS, EPS and RWS are even more pronounced. They can make reasonable recommendations to the driver when necessary or make necessary corrections to the driver's instructions. With the further development and improvement of electronic sensor technology, by integrating these new information with the electronic control system of the car chassis, more new functions and new systems will emerge, thus providing sufficient conditions for the development of the automotive industry. basis.
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