The Electronic Stability Program (ESP) is a patent of Bosch [1]. Ten years ago, Bosch was the first company to put Electronic Stability Program (ESP) into mass production. Because ESP is a patented product of Bosch, only Bosch's body electronic stability system can be called ESP. After Bosch, many companies have developed similar systems, such as the Vehicle Dynamic Control (VDC) developed by Nissan [2], and the Vehicle Stability Control (VSC) developed by Toyota. [3], the Vehicle Stability Assist Control (VSA) developed by Honda [4], the Dynamic Stability Control (DSC) developed by BMW [5] and so on.
ESP Overview
The ESP system is actually a traction control system. Compared with other traction control systems, ESP not only controls the driving wheels, but also the driven wheels. For example, when there is too much steering in rear-wheel drive cars, when the rear wheels lose control and drift, ESP will brake the outer front wheels to stabilize the car; when there is too little steering, in order to correct the tracking direction, ESP will brake Slow the inner rear wheels to correct the direction of travel.
The ESP system includes ABS (anti-lock braking system) and ASR (anti-skid system), which is a functional extension of these two systems. Therefore, ESP can be regarded as the most advanced form of current automobile anti-skid device. The ESP system consists of a control unit and a steering sensor (monitoring the steering angle of the steering wheel), a wheel sensor (monitoring the speed of each wheel), a sideslip sensor (monitoring the rotation of the car body around the vertical axis), and a lateral acceleration sensor (monitoring when the car is turning). centrifugal force) and other components. The control unit uses the signals from these sensors to judge the operating status of the vehicle and then issues control instructions. The difference between cars with ESP and cars with only ABS and ASR is that ABS and ASR can only react passively, while ESP can detect and analyze vehicle conditions and correct driving errors before they happen. ESP is particularly sensitive to oversteer or understeer. For example, when a car oversteers to the left (turns too sharply) on a slippery road, it will drift to the right. When the sensor senses the slip, it will quickly brake the right front wheel to restore steering. Apply force to produce an opposite torque to keep the car in its original lane. Of course, everything has a range of degrees. If the driver blindly drives fast, it will be difficult to protect any current safety device;
Components of ESP
1. Sensor: Steering Sensors, wheel sensors, sideslip sensors, lateral acceleration sensors, steering wheel accelerator brake pedal sensors, etc. These sensors are responsible for collecting data on the status of the vehicle body.
2. ESP computer: Calculate the data collected by the sensor, calculate the body status and compare it with the preset data in the memory. When the computer calculation data exceeds the pre-stored value in the memory, that is, when the vehicle body is about to lose control or is already out of control, it commands the actuator to work to ensure that the vehicle body's driving status can satisfy the driver's intention as much as possible.
3. Actuator: To put it bluntly, the ESP actuator is the braking system of the four wheels. In fact, ESP helps the driver apply the brakes. Unlike cars without ESP, the brake system of a car equipped with ESP has a pressure accumulation function. To put it simply, pressure accumulation means that the computer can pressurize the brake oil pipe of a certain wheel for the driver when the driver does not apply the brake according to needs, so that the wheel can generate braking force. In addition, ESP can also control the power output of the engine and so on. Anyway, he can get involved in related equipment!
4. Communication with the driver: ESP light on the instrument panel.
Key technologies of ESP
The structure of a typical automobile control system now includes traditional brake system vacuum booster, pipelines and brakes, sensors, wheel speed sensors, and steering wheels. Angle sensor, lateral acceleration sensor, yaw rate sensor, brake master cylinder pressure sensor, hydraulic regulator, vehicle stability control electronic control unit and auxiliary system engine management system.
Therefore, the development of the system depends on the breakthrough of the following key technologies
①Improvement of sensing technology." The sensors used in the system include vehicle yaw angular velocity sensor, side sensor Axial acceleration sensors, steering wheel angle sensors, brake pressure sensors and throttle opening sensors are all indispensable and important components in the system. Improving their reliability and reducing costs have always been the goals pursued by developers in this area.
②Structure design of small size, light weight, low-cost hydraulic braking system.
③Software and hardware design due to the need to estimate the state variables and calculations of vehicle operation. The corresponding motion control volume, so the computing processing power and program capacity are several times larger than the system. Software research is the top priority. Modern control theory based on models has been difficult to adapt to such a system. For the control of complex systems, we must seek robust nonlinear control algorithms.
④ By improving the interconnection between the control function and the engine and transmission system, it can better perform the control function. For example, the automatic transmission transmits the current mechanical transmission ratio, torque converter torque ratio and gear position to estimate the driving force on the driving wheels. When it recognizes that it is on a road with a low adhesion coefficient, it will The driver is prohibited from shifting into low gear. When starting on such a road, the transmission system will be informed to shift into second gear in advance, which will significantly improve the starting comfort of high-power cars.