资源描述
附 录附录 A.Car ABS Technology and Development TrendIn the car before the emergence of abs, used car is the open loop brake system. Its characteristic is the brake torque only and drivers of the size of the manipulation of the force, braking force distribution regulation and the size of the brakes on and type. With no wheel the motion of feedback signal measurement, cant know during wheel brake speed and holding in death, car you may adjust accordingly wheel cylinder or the gas chamber of the size of the brake pressure. So in an emergency brake, inevitably appear wheel on the ground, holding in death dragged the phenomenon of sliding. When the wheel lock, the ground of the performance was poor, the lateral attached can provide the lateral adhesion is small, car by external force in any minute under the action of will appear direction, easily happened instability problems of traffic accidents. In the wet pavement or snow and ice on the road, the direction of brake the instability of the phenomenon can more serious. towing It is through the basic function of sensors wheel each transient state of motion, and according to the motion correspondingly adjust the size of the brake torque in to avoid the wheels holding in death, it is a phenomenon of closed-loop brake system.It is the electronic control technology in cars of the most successful application project, one of auto brake antilock brake systems can make the car in the braking maintain stability and shorten the direction braking distance, effectively improve the driving safety. Car ABS can say is the most important car safety history of the three great inventions (the other two are airbag with seat belt), ABS is also other safety device (such as ESP driving dynamic stability system and EBD braking forces based distribution system) Because money spent too big, ABS the practical use of the early railway vehicle or aircraft. 70 s, digital electronic technology and large scale integrated circuit, for the rapid development of ABS system lays a foundation to practical application. Bosch company in 1978 first launched the digital electronic control unit of the brake system, and ABS2 Bosch holding device in the Mercedes Benz, which opened on the modern ABS system development sequence Although the Bosch ABS2 of electronic control device is a separation of the components, but due to the digital electronic control device and analog electronic control device, the reaction speed, compared to the control accuracy and reliability are significantly improved, therefore, Bosch ABS2 control effect already is quite good. From then on, Europe, America and Japan, many professional company and brake car companies have developed a variety of ABS system. According to statistics, the whole world has more than 60% of new cars equipped with ABS device. When the car brake wheel speed and the differences between body speed, can lead to the wheel and the road, when the wheel slippage between produce pure rolling way and the pavement at contact, the slip rate is zero, and wheel lock the slip rate is 100%. When the slip rate between 10% 30%, the largest transfer of power. The basic principle of braking antilock brake system (2, 3 is based on the above research, through the control regulation system in power, braking process, to the wheel in the slip rate control, within the scope of the right to obtain the best braking effect. ABS system hardware mainly by the wheel sensor, electronic control devices, brake pressure regulator three major components, constitute a to the slip rate is the control of the target of the closed-loop control system. The wheel speed sensor and the data transfer to the electronic control device. Control device is a microprocessor, according to the wheel speed sensor signal to calculate the speed of the car. In the braking process, reducing speed and control device of programmed ideal reducing the speed of characteristic curve in comparison. If control device judge the wheel reducing speed too large and the wheel will embrace died, signal to hydraulic regulator, hydraulic regulator is according to the control device of the signal to the brake wheel cylinder of hydraulic control (the boost, the pressure or blood pressure). Brake pressure to adjust the frequency of the cycle up to 6 20 H z. ABS technology at the core of theproblem is the control algorithm of research. The control car ABS is a complex, essential nonlinear control problem. In recent years, domestic and foreign scholars in the control of ABS calculate Method on the many theoretical research, mainly in the following several control methods. Now automotive ABS system most of the products are the addition, subtraction speed control, and additional threshold some auxiliary threshold, not involve specific mathematical model. Threshold control for nonlinear systems is an effective control method. In the braking process, can be a primary angular velocity threshold, when actual angular velocity over the threshold, the controller order to release, the wheel brake pressure to rotate faster; A Angle acceleration, when the threshold of angular velocity to reach this threshold, controller and issue commands to control moment, increased, and the wheel as slow movement. Can use a wheel angular velocity sensor as a single wheel signal, and electronic controller in set reasonable add, subtract speed threshold method, can come true to the embrace of the brake cycle. Logic threshold control the fault is that control system of the various threshold and the holding time is from repeated test that experience, and no sufficient data the theoretical basis of the stability of the system and the quality is difficult to evaluation. The optimal control method is based on state space method of modern control theory method. The optimal control method and threshold control method is different, it is a kind of based on the analysis of the model control method. The idea is based on the abs all the control requirements, according to the principle of optimization for brake antilock brake system optimal control goals. This control method is considered the control process of state changes course and make the control process smoothly; Defect is the control effect of quality mainly depends on the mathematical model of the system, quality control is difficult to accurately. The classic of PID control parameters setting is set up on the basis of gather together in try, as long as the scene setting PID parameters, you can get right better control effect. In the ABS in a definition of the expected sliding rate S and actual sliding rate for the input of the difference of the PID, the PID control algorithm is calculate control air pressure value feedback to brake system, a typical feedback control. Its defect is control effect quality depends on the accuracy of the parameter setting. Fuzzy control is based on experience of the rules of the control, and have not rely on the mathematical model of the object, easy to use the experience, knowledge is robust and simple practical. Control rules to the law of thinking. Defect is no effective general calculation method, can only rely on industrial automation instrument and a plan of the device experience and repeated test. By automobile braking antilock brake the basic principle of the braking process, it is known that the nature of the problem is to the wheel the slip rate control adhesion coefficient in the peaks of the Sk, the sliding mode variable structure according to the system of the state, and deviation and at that time, in different derivative value area, in order to control the ideal switch mode switch control the amount of and symbols, in order to ensure that the system in sliding area is small, within the scope of the state trajectory S sliding in the pitch curve sliding into a control target tsinghua university song jian and other car braking process according to the physical nature of international proposed first to brake dissipation power as the target of the control method. Considering the car of the deceleration process, in fact, is the average kinetic energy of the car into other forms of energy dissipation process. Accordingly, if you take the reasoning brake friction power (or says dissipation power) maximum control targets of ABS, have the potential to give consideration to the braking stability and brake performance. This method than the threshold method has good stability, high efficiency of braking, strong adaptability and control of road surface features obvious etc. Characteristics. Research shows that the control method can have a good application prospect. Drive torque system (hereinafter referred to the ASR) is perfect and added. ABS ASR system can improve the car is in the most slippery road stability and acceleration of the electronic device. Its role is mainly through the control engine torque and a car braking system means to control the driving force, to prevent the wheels idling sliding, maintain the best driving force. ABS guarantee The car braking process, the stability of the direction is guaranteed the car ASR process (beginning, the direction of the acceleration) stability and handling. Many of the cars, the modern electronic control device equipped with ABS ASR electronic control signal devices to exchange interface. And ASR and a major part of the ABS (such as electronic controller, wheel sensor, brake pressure regulators) can be used with or Shared with the car with the ABS ASR system, just the premise, differential control valves and engine control cylinder engine can. This shows, ABS and ASR combination, can make full use of the relevant parts of the car, and active safety will be more assured. Vehicle stability control device (hereinafter referred to as VSC) use two sensors were sensor car yaw-rate and lateral acceleration, and car will shift to Angle and the actual direction are compared. When it found the car is not according to the intention of motorists road, immediately sent to the ASR and ABS correction signal, indicating they take measures to make the car to the correct direction. These system although functions and the structure is different, but the work is similar to the process is sensor signal, she is calculated, the execution processing ECU institutions take corresponding actions. In the system composition, pick the accuracy of the sensor signal directly influence the results of ECU, additional, wheel sensor most is installed in the bad environment, especially near to heat resistant, vibrationresistant sex, the magnetic, corrosion resistance has high request, to the improvement of the performance of the sensor is very important. ABS and electronic throttle control system, electronic all control type (or half controlled) suspension, electronic control four-wheel steering, electronic control hydraulic turn To the electronic control, automatic transmission, cruise control system, global positioning system, etc. Various kinds of electronic control system, can make the combined use of car movement remains in the best state. Along with the electronic control units in car has more and more application, vehicle electronic equipment of the data communication between becomes more and more important, the distributed control system for infrastructure automobile vehicle electronic network system is very necessary. Large amounts of data exchange, high reliability and rapid sex is cheap to automobile electronic network system requirements. The network system, the processor independent operation, the control to improve the performance of the car on something, and in the other processors need to provide according to service. When The structure of the network inside the car relies mainly on the bus transmission technology. Car through a kind of communication is bus transfers of agreement will car electronic control units (engine, ABS, automatic transmission, etc.), intelligent sensor, intelligent instrument, and link up a car interior network. Its advantages are: reduced the number of cable and wire harness in volume, improve the electronic system reliability and maintainability; The general sensors, achieve the purpose of sharing data; Improve the flexibility of the system, that is, through the system software can realize the change of system function. Car ABS technology has been acknowledged as the world, ABS change Good the car brake performance, and the shorter the braking distance. Avoid the wheel lock so as to avoid the loss of car to ability, lose the direction stability of the phenomenon. It would be expected that the recent all kinds of vehicles will be equipped with the technology. Of course, ABS technology is still have defects, such as the stability of system still need to improve, control algorithm of further research and improvement. Through the simulation shows, in the design of fuzzy controller, through the adjustment of the fuzzy controller membership functions, the error in the basic fuzzy subsets of domain non-uniform distribution and ZO interval of the retreat to small enough, without any increase in the control strategy of the case, make the steady-state error of the fuzzy controller is greatly reduced, has the good control effect, short setting time, no overshoot, the improved fuzzy controller in steady precision at the same time, continued to parameter time-variance and fuzzy controller of interference has strong adaptability. All in all, this method improves the fuzzy control the system steady control precision, to improve the system dynamic and static quality. Due to the adjustment of the fuzzy controller membership function is very convenient, and therefore, this method is simple and useful for the fuzzy controller is widely used, provide an easy method.
展开阅读全文