From the current development of chassis technology, more and more new electronic control devices are used in automobiles, and many of the new chassis control technology devices play an important role in the safety, dynamics and operational stability of automobiles. . It includes full-circuit braking system (BBW, Brake-by-Wire), automotive steering control systems (RWS, ESPII, etc.), automotive suspension control systems (ADC, ARC, etc.) and the current development of automotive chassis wire control technology ( Wire-controlled shifting system, brake system, suspension system, booster system, throttle system and steering system, etc., coupled with the application of automotive CAN bus, 42V voltage technology research, now the chassis control technology is becoming electronic Informatization, networking, and integration.
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Full Circuit Brake System (BBW)
BBW is a new braking mode that uses embedded bus technology and can be used with anti-lock braking system (ABS), traction control system (TCS), electronic stability control program (ESP), active collision avoidance system. The active safety system of the vehicle (ACC) is more convenient to work together. By optimizing the control algorithm in the microprocessor, the working process of the brake system can be accurately adjusted, the braking effect of the vehicle can be improved, and the braking safety performance of the vehicle can be enhanced. BBW uses electrical energy as a source of energy to drive the brakes through a motor or electromagnet. Therefore, the structure of the BBW is simple, more modular, and easier to install and maintain.
The control unit is the control core of the BBW, which is responsible for the collection and processing of the BBW signal, and the inference of the signal and the braking signal to the brake accordingly. In addition, according to the development trend of automobile intelligentization, various electronic control systems on the chassis of the automobile will be highly integrated with the brake control system, and at the same time, they will complement each other in function. BBW adopts double closed-loop control mode. Firstly, there are brake torque sensors in each electric energy brake, which can monitor the braking torque in real time and realize closed-loop control of braking torque. Secondly, during the braking process, each wheel speed sensor constantly monitors the running process of the wheel, and the ABS determines the running state of the wheel based on the signal of the wheel speed sensor.
According to the current research results of BBW, a series of problems need to be solved after putting into use, mainly the improvement of the structure and performance of the electric energy brake. The electric energy brake must ensure that the vehicle can be effectively braked independently, and must generate a large enough braking torque to raise the internal drive motor (or drive electromagnet body), the drive torque transmission system, and the external power supply system. Requirements. The more mature idea is to increase the power supply voltage of the car from the original 12V to 42V. The voltage increase can effectively solve the energy problem of BBW.
Car steering control system
1. Rear wheel steering system (RWS)
The RWS can actively move the tie rods of the two rear wheels of the car laterally relative to the vehicle body, so that the two rear wheels generate a steering angle. The RWS is composed of an electronic control unit, a sensor, an actuator, and the like, and its actuators are of an integral type and a separate type. Integral means that the tie rods of the two rear wheels of the car are adjusted by the same actuator, while the split type means that the tie rods of the two rear wheels of the car are adjusted by two different actuators. For integral RWS actuators, the steering angle of the two rear wheels can be determined with a tie rod displacement sensor, but the split RWS actuator requires at least two displacement sensors. Due to the large number of components of the separate RWS actuators, the control and coordination of the two rear wheels is more complicated, and now more and more developed RTS actuators. The integral RWS actuator is divided into hydraulic and electromechanical. It consists of motor, nut screw drive mechanism and safety lock mechanism. In order to improve the reliability of the system, a motor angle sensor and a screw are installed in the actuator. Displacement sensor, when the RWS fails, the motor is automatically locked, and the steering angles of the two rear wheels no longer change until the fault is eliminated.
In normal operation, the steering angle of the rear wheel is a function of the steering angle of the steering wheel and the speed of the car. When the car is running at low speed, when the steering wheel actuator gives the rear wheel a corresponding steering angle in the opposite direction, the car turns at a low speed or When parking, the turning radius becomes smaller, making the car steering and parking easier, faster and more comfortable. When the car is driving at a high speed, the rear wheel has a steering angle that is consistent with the steering angle of the front wheel, and the front and rear wheels of the car are simultaneously turned in the same direction, which can improve the directional stability of the car, especially when the car is changing lanes at a high speed. Unnecessary yaw motion is greatly reduced, which enhances the directional stability of the car. When the car is braking on the road surface, it can cooperate with the system to balance the yaw moment generated by the braking force through the active rear wheel steering angle, which can maintain the directional stability of the car and maximize the use of the front wheel. Braking power to improve the braking performance of the car.
2. ESPII (or ESPplus)
Since the ESP system interferes with the running state of the car, the driving stability of the car is adjusted only by applying a brake to a single wheel, and the vibration of the car caused by the pulse braking force can be felt by the occupant. ESPII can identify the adhesion coefficient between the steering wheel and the ground. If the car brakes on the opposite road surface with different adhesion coefficients on both sides of the road surface, it tends to rotate toward the side with a larger adhesion coefficient of the road surface, that is, the so-called The "brake pull" phenomenon, in this case, ESPII can make appropriate steering rotation through the steering wheel to the side with less adhesion coefficient to balance the "brake pull" trend.
ESPII designs its steering wheel steering column in two parts, some of which contain a gearing mechanism through which the electric motor in the system exerts an influence on the angle of the steering wheel. ESPII's interference with car braking and steering is controlled by an ESP control based on an extended software.
Car suspension control system
1. Active suspension damper control system (ADC)
The ADC (sometimes referred to as the Continuous Damping Control System CDC) consists of an electronic control unit, CAN, four wheel vertical acceleration sensors, four body vertical acceleration sensors, and four damper proportional valves. According to the motion condition of the car and the sensor signal, the electronic control unit calculates the optimal damping coefficient of each wheel suspension damper, and then adjusts the damper proportional valve accordingly, automatically adjusts the vehicle height, and suppresses the change of the vehicle. The car's suspension system provides better car comfort, safety and stability.
2. Active Lateral Stabilizer (ARC)
When the car is traveling in a curve, the centrifugal force generates a roll moment on the car body. This roll moment causes the body to roll on the one hand, and the load quality of the wheel is transferred from the inner wheel to the outer wheel on the other hand. The active stabilizer bar can apply a continuously variable initial roll angle or initial roll moment to each stabilizer bar according to the specific situation. The active roll stabilizer bar has two different structural forms: one is the passive side. The tilting stabilizer bar is separated from the middle, and the left and right parts of the stabilizer bar are connected by a rotating motor. The rotating motor can rotate the left and right parts, the torque of the rotating motor can be adjusted; the other is at one end of the passive stabilizer bar. A differential hydraulic cylinder mechanism is installed. One end of the differential hydraulic cylinder mechanism is connected with the stabilizer bar, and the other end is connected with the lateral swing arm of the same wheel, and the distance between the two ends of the differential hydraulic cylinder mechanism can be adjusted.
The working principle of ARC is to actively make the relative displacement of the left and right ends of the stabilizer bar in the vertical direction, balance the roll moment of the car body, and make the roll angle of the car body close to zero, which improves the comfort. Since the two active stabilizer bars in the front and rear of the car can adjust the distribution ratio of the roll moment of the vehicle body, the dynamic characteristics of the car can be adjusted, and the safety and maneuverability of the car are improved.
Wire control technology for car chassis
The so-called wire control replaces the parts that were connected by mechanical, hydraulic or pneumatic systems in the past, such as shifting links, throttle wires, steering gears, brake oil circuits, etc., which not only replaces the connection, but also includes Changes in steering mechanisms and handling methods, as well as electrification of the actuators, will change the traditional structure of the car. The realization of full-line control will mean the transformation of the car from mechanical to electronic systems. The wire-controlled technology requires good real-time and high reliability of the network, and some wire control parts require redundancy of functions to ensure that certain faults will occur. The basic functionality of this device can still be achieved. Just like the current ABS and power steering, it still has the basic functions of braking and steering in the event of line failure, which requires high speed, good time characteristics and high reliability of the network data transmission with wire control.
At present, the wire control technology of the automobile chassis includes a wire shifting system, a brake system (such as an electrohydraulic brake system EHB, an electromechanical brake system EMB), a suspension system, a booster system, a throttle system, and a steering system. Wire-controlled technology has the advantage of eliminating the need for hydraulic brakes or any other hydraulic device to make the car more environmentally friendly; reducing potential hazards in frontal collisions and providing more space for car design; The cost in automotive design, engineering, and manufacturing processes is greatly reduced, and maintenance requirements and body weight are reduced.
Automotive chassis integration technology
The modern car chassis electronic control system is developing from the initial single control to today's multi-variable multi-objective integrated coordinated control, which can share sensors, control devices, and circuits in hardware, reducing the number of parts, thereby reducing connection points and improving reliability. Information fusion and centralized control are implemented on the software to enhance and expand their respective individual control functions, including integration of ABS/ASR/ESP and integration of ABS/ASR/ACC.
At present, there are several new technological developments in chassis technology, and the future will have a significant impact on enhancing the safety of automobiles. For example, in 2010, Continental developed the ESA emergency steering assist system, which is associated with ESC, EPS and other functions. It uses sensors to help the chassis monitor the road conditions. When the driver has no time to step on the brakes, the traffic can be reduced by helping the steering to avoid maneuvering. The probability of an accident. Nissan's MR16DDT and torque vector system should also attract attention, because Nissan's latest JUKE four-wheel drive model 16GTFOUR uses the torque vector system TVS (TorqueVectoringSystem), which can distribute power to the front and rear wheels in a 50/50 ratio. For extra traction, the torque of the rear wheels can be equally divided equally between the wheels on both sides. The torque vectoring system gives the vehicle a more flexible and attractive driving maneuverability, counteracting the negative impact of the JUKE model's chassis ground clearance on stability and steering.
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