Body stability control
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ESP: Electronic Stablity Program
The ESP system is usually a function that supports ABS and ASR (drive anti-skid system, also known as traction control system). It helps the vehicle maintain dynamic balance by analyzing the vehicle's driving status information from each sensor and then issuing correction commands to ABS and ASR. ESP allows the vehicle to maintain optimum stability under all conditions and is more effective in situations of oversteer or understeer.
ESP generally requires the installation of steering sensors, wheel sensors, side-slip sensors, lateral acceleration sensors, and so on. The ESP monitors the car's driving status and automatically applies braking force to one or more wheels to keep the car running in the normal lane, and in some cases can brake 150 times per second. At present, there are three types of ESP: a four-channel or four-wheel system capable of independently applying braking force to four wheels; a two-channel system capable of independently applying braking force to two front wheels; capable of independently applying braking force to two front wheels and A three-channel system that applies braking force to the rear wheels at the same time.
Dynamic Stability Control (DSC)
The third-generation DSC system developed by BMW uses anti-lock brakes (ABS), four-wheel traction control and a “turn brake control†(CBC) mechanism to ensure even the toughest driving conditions. The stability of the car.
If it is detected that the car may be taxiing, the DSC system reduces the engine power and, if necessary, applies additional braking force to the particular wheel to take the necessary corrective action on the car.
Therefore, the DSC can stabilize the car on the selected road in one second.
However, even such an advanced system cannot violate the laws of nature, so the driver should always maintain the best condition, understand the road conditions, and drive with heart.
DSC implies a complex computer control technique, the “stability algorithmâ€, which recognizes the weight of the trailer and automatically compensates for the increased load on the car.
VSC
For different models of ESP, they are often given different names. For example, BMW calls it DSC, Toyota and Lexus call it VSC, and Volvo car calls it DSTC, but its principle and function are basically the same. It's just a different name for the manufacturer.
Anti-lock brake
ABS anti-lock Braking System anti-lock brake system, the signal that the wheel will be locked by the sensor mounted on the wheel, the controller commands the regulator to reduce the oil pressure of the wheel brake cylinder, Reduce the braking torque, after a certain period of time, then restore the original oil pressure, such a cycle (up to 5 to 10 times per second), always keep the wheel in rotation and have the maximum braking torque.
If the car is not equipped with ABS, if the brake pedal is pressed hard during driving, the wheel speed will decrease rapidly. When the braking force exceeds the friction between the wheel and the ground, the wheel will be locked. The fully locked wheel will make the tire The friction with the ground is reduced. If the front wheels are locked, the driver cannot control the direction of travel of the vehicle. If the rear wheels are locked, the side slip phenomenon is very likely to occur.
ABS, which was originally applied to aircraft, is now very popular. It can be seen on cars of more than 100,000 yuan. Some buses also have ABS. Vehicles equipped with ABS can safely operate the steering wheel for braking when it encounters slippery roads such as snow, ice or rain. It not only effectively prevents accidents, but also reduces the damage to the tires, but it does not shorten the braking distance of the car, but in some cases it will increase.
Tip: In the event of an emergency, the brake pedal must be stepped on to activate the ABS system. At this time, the brake pedal will have some jitter, and sometimes there will be some sound, but it will not be released. This indicates that the ABS system starts. It works.
Traction control
Traction Control System, referred to as TCS. The role is to enable the car to get the best traction under all driving conditions. When the car is driving, the acceleration needs the driving force, and the turning requires the lateral force. Both of these forces are derived from the friction of the tire against the ground, but the friction of the tire to the ground has a maximum. On a smooth road with a small friction coefficient, the driving force and lateral force of the car are small.
The control device of the traction control system is a computer. Using the computer to detect the speed of the four wheels and the steering angle of the steering wheel, when the car accelerates, if it is detected that the difference between the driving wheel and the non-driving wheel is too large, the computer immediately judges that the driving force is too large, and issues a command signal to reduce the fuel supply of the engine. , reducing the driving force, thereby reducing the slip rate of the driving wheel tire. The computer grasps the driver's steering intention through the steering wheel angle sensor, and then uses the left and right wheel speed sensors to detect the left and right wheel speed difference; thereby determining whether the vehicle steering degree is the same as the driver's steering intention. If it is detected that the car is understeering (or oversteering), the computer immediately judges that the driving force of the driving wheel is too large, and issues an instruction to lower the driving force in order to achieve the driver's steering intention.
When the tire's slip rate is moderate, the car can get the maximum driving force. If the tire is caused to make a large slip during cornering, the acceleration capability of the car will be improved. The system can detect the running state of the car by using the steering wheel angle sensor, determine whether the car is traveling straight or turning, and appropriately change the slip rate of each tire.
ASR is the abbreviation of Acceleration Slip Regulation. Its function is to prevent the driving wheel from slipping during the start and acceleration of the car, especially to prevent the car from spinning on the asymmetric road or turning, and to control the slip rate to 10 %—20% range. Since ASR is mostly controlled by adjusting the driving force of the driving wheels, it is also called a driving force control system, or TCS for short, and is also called TRC or TRAC in Japan and the like.
There are many things in common in the working principle of ASR and ABS, so they are often combined to form a brake anti-lock and drive wheel anti-skid control (ABS/ASR) system. The system is mainly composed of wheel speed sensor, ABS/ASR ECU, ABS actuator, ASR actuator, sub-throttle control stepper motor and main and auxiliary throttle position sensors. During the start, acceleration and operation of the car, the ECU determines that the slip ratio of the drive wheel exceeds the threshold according to the signal input by the wheel speed sensor, and then enters the anti-skid rotation process: first, the ECU passes the sub-throttle stepping motor to make the sub-section The valve opening is reduced to reduce the amount of intake air and to reduce the engine output torque. When the ECU determines that it is necessary to brake the drive wheel, it will transmit a signal to the ASR actuator to independently control the drive wheel (usually the rear wheel) to prevent the drive wheel from slipping and keep the slip ratio of the drive wheel Within the specified range.
The mechanical structure of the TRC active traction control system can prevent the driving wheel from idling while traveling on a wet road such as snow in the vehicle, so that the vehicle can start and accelerate smoothly, and support the basic functions of the vehicle. On snow or muddy roads, the TRC Active Traction System guarantees smooth acceleration. In addition, TRC can also properly control the side slip of the wheel in the off-road conditions of the four-wheel drive vehicle, such as up and down steep slopes, sinister rocky roads, etc., compared to vehicles equipped with traditional central differential locks. In other words, the TRC-equipped vehicle has a sense of driving and maneuverability that the former cannot match.
Active steering system
With the help of EPS (Electronic Power Steering System), the vehicle can obtain a large boost at low speeds to make the steering lighter. At high speeds, the steering assist is reduced, thereby increasing the steering stability of the vehicle. However, due to the influence of the speed of the road and the condition of the road, the problem of understeering or oversteering in the turning of the vehicle is often caused, which poses a great danger. For experienced drivers, it is possible to avoid danger by correcting the steering angle, but for the average driver, there is something that is not enough.
BMW's innovative active steering system revolutionizes the traditional steering process, allowing the steering angle of the front wheels to be exactly as the driver wishes. In this system, an electronically controlled mechanical governor is mounted between the steering wheel and the steering wheel. The planetary gear has two input shafts and one output shaft, one input shaft is connected to the steering wheel and the other input shaft is The motor is controlled by a self-locking worm gear drive and the output shaft is connected to the steering column. The overall steering angle that is ultimately transmitted from the output shaft is formed by the angle of the steering wheel input by the driver superimposed on the angle of the electric motor. In addition, other components of the active steering system include an independent control unit and a plurality of sensors that determine current driving conditions and driver commands. In addition, the active steering system is always networked with the DSC (Dynamic Stability Control) unit via the in-vehicle network.
The biggest feature of the active steering system is that it automatically adjusts the steering ratio of the vehicle according to driving conditions, thereby increasing or decreasing the steering angle of the front wheels. At low speeds, the action of the motor is the same as the direction in which the driver turns the steering wheel, and the steering ratio is increased, which reduces the driver's need for steering force. At high speeds, the direction of operation of the motor is opposite to the direction in which the driver turns the steering wheel, which reduces the steering angle of the front wheels, reduces the steering ratio, and improves steering stability.
Because the active steering system continuously adjusts the steering ratio, it improves steering comfort. For example, when driving a BMW 530i equipped with an active steering system for a driving school routine training subject, the pile-pushing test, the action of playing the wheel during the original transfer is made simple. A typical vehicle needs to turn the steering wheel three times to drive the wheel from one locked position to the other, while the BMW 30i equipped with an active steering system reduces this operation to two turns. This will save the driver a lot of time when parking in a narrow parking space or making a sharp turn in the city.
In the snake-shaped pile test, the BMW 530i equipped with the active steering system can change the direction continuously, the driver only needs to turn the steering wheel gently, instead of turning to the two-handed cross, the steering wheel can be obtained. A large steering angle that bypasses obstacles and makes steering very flexible. This feature allows the driver to operate the vehicle with a fixed position on the steering wheel while driving on a winding mountain road, while the driver can easily operate the multi-function button on the steering wheel.
In addition to being more comfortable and flexible, an important point of the active steering system is that it is safer, which is mainly reflected in the sudden turn of the vehicle during high-speed driving. For example, when suddenly changing lanes on a highway to overtake another vehicle and then returning to the lane, or suddenly finding obstacles in front of a high-speed driving that require a sharp turn, it is easy to understeer or oversteer, and the vehicle will deviate from itself. The intended direction may be out of control. In this case, the BMW system's DSC system usually controls the stability of the vehicle by intervening in the braking process, and the driving speed will be greatly reduced, increasing the energy loss. The active steering system judges the situation after the steering from the beginning of the steering, and automatically corrects the steering angle through the electronically controlled mechanical governor to intervene to reduce the occurrence of yaw. The DSC system does not have to interfere with driving as in other vehicles, ensuring the smoothness of the vehicle. However, when the active steering system is unable to complete the control of the vehicle, the DSC system will participate in the work. Therefore, the active steering system needs to be used in conjunction with the DSC system.
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