At present, the safety of automobile prevention is getting more and more attention. MEMS sensors are used in many fields of automotive safety technology. The following are the top ten application knowledge points of MEMS sensors in the automotive field:
1 Electronic Stability Control System (ESC)The ESC (Electric Stability Control) is a device for preventing the vehicle from slipping on a road or a curved road section that is slippery after rain. The device uses an acceleration sensor of Murata Electronics Oy (hereinafter referred to as MFI).
Usually, ABS and traction control systems alone cannot meet the driving safety requirements of vehicles on curved sections. In this case, the Electronic Stability Control (ESC) can control the vehicle so that it does not deviate from the road by correcting understeer or oversteer in the driver's operation.
The system measures the yaw angle of the vehicle by using a gyroscope while measuring the lateral acceleration with a low gravity acceleration sensor. The obtained measurement data is compared with the results calculated from the two data of the traveling speed and the wheel tilt angle, thereby adjusting the steering of the vehicle to prevent side slip.
The acceleration sensor is typically mounted independently of the center of gravity of the vehicle or mounted as a mounting assembly on the printed circuit board as part of the sensor assembly. The standard measurement range is ±1.5 to 2.0 g; the offset is stable to 100 mg or less regardless of temperature or time of use; the frequency band is in the range of 0 to 50 Hz.
Electronic Stability Control (ESC) systems typically require the vehicle's lateral direction as the detection axis to ensure that the effects are minimized when subjected to longitudinal acceleration or vehicle deceleration. When the MFI accelerometer is mounted on a printed circuit board, two mounting directions can be selected, ie whether the detection axis is parallel or perpendicular to the mounting surface. If you are using a stand-alone accelerometer, you need to select the appropriate bracket according to the installation position.
Globally, standards and regulations on ESC are being actively promoted. Under the framework of the United Nations “World Vehicle Regulatory Coordination Forum†“1998 Agreementâ€, the Global Technical Regulations (GTR) for “Light Vehicle Electronic Stability Control System†was completed in 2008 and approved by WP29 (ie GTR8).
Countries and regions such as the United States, Europe, the United States, Japan, Australia, and South Korea have or are using ESC as a mandatory installation. As a signatory to the "1998 Agreement", China has fully participated in the coordination process of ESC's global technical regulations since 2007, and has put forward several proposals in combination with domestic ESC product development, application and testing capabilities, and is developing relevant national standards.
2 electronic parking brake system (EPB)The EPB (Electronic Parking Brake) replaces the traditional parking brakes based on mechanical levers and chains, providing the driver with more efficient parking assistance.
And because the parking brake lever between the main and the driver's seat is cancelled, the space around the driver's seat can be more effectively utilized.
The EPB system continuously adjusts the braking force according to the inclination of the longitudinal direction of the vehicle body. The brakes are locked simply by pressing the corresponding button on the dashboard; the brakes are automatically unlocked when the vehicle is started and accelerated.
The system is also capable of assisting the vehicle in low-speed traction to prevent the vehicle from slipping naturally on the slope. After the system is docked with the distance sensor system signal, parallel parking can even be done in a narrow area.
If integrated with the engine anti-theft system, a set of the most reliable anti-theft mechanism can be formed. The actual measurement starting point of the sensor in the system is usually within ±3°; the corresponding gravitational acceleration value is approximately 50 mg. This coincides with the vehicle's offset stability requirements over the entire service life and temperature range. The frequency range of the internal sensors of the system should be kept as low as possible, and the upper limit should not exceed 10-50 Hz.
3 anti-lock brake system (ABS)In a four-wheel drive vehicle, the body speed and wheel speed parameters required for the ABS system cannot be measured by the sensor because each wheel may slip. Therefore, the acceleration/deceleration information of the vehicle can only be obtained by measuring the acceleration in the front-rear direction. The acceleration sensor of the ABS system can be installed in other sensors in addition to the ABS controller in the form of separate components or integrated on the printed circuit board.
The measurement range of the acceleration sensor used in the ABS system is usually 1 to 2G (G is the gravitational acceleration). The error offset can always be below 100 mg during the detection temperature range and vehicle life. The direction of the detection axis of the sensor must be the front and rear direction of the vehicle. Murata Electronics Oy's accelerometers are ideal for a wide range of sensor units and printed circuit board placement applications.
4 electronically controlled suspension system (ECS)The main purpose of the Electronically Controlled Suspension System (ECS) is to adjust the suspension system based on information such as driving speed, road conditions, steering conditions, shifting conditions, and different driving conditions to provide the driver with good operational stability and ride comfort. The ECS system presents users with a variety of driving experiences from smooth soothing to high speed. The driver can switch between the sporty, normal and comfortable driving modes simply by pressing the selector button.
The acceleration sensor inside the ECS system can be used to detect the motion state of the vehicle body, and sometimes to detect the motion state of the front wheel in the vertical direction. Two acceleration sensors for detecting the motion state of the vehicle body are installed near the front shock absorber and the spring top fixed point.
The acceleration sensor near the hub is mounted in the vicinity of the shock absorber and the wheel spring. In this way, the vertical distance difference between the vehicle body and the wheel can be calculated from the measurement data of the two sets of sensors. In more advanced hub sensor systems, the acceleration sensor is replaced by a distance sensor for direct measurement of the distance between the wheel and the vehicle body.
In addition, in many ECS systems, an acceleration sensor for detecting vehicle bumps is additionally installed in the middle or rear of the vehicle. It is possible to slightly eliminate the tilt of the vehicle body during acceleration or deceleration.
Air suspension systems are now used in most mid- to high-end, luxury vehicles, including sport utility vehicles (SUVs). The suspension setting can be corrected by adjusting the volume of air in the tank at the corners of the body. The system usually consists of a special gas compressor, 1 to 2 gas storage tanks, 4 damping units consisting of air springs and conventional shock absorbers, 2 to 5 independent acceleration sensors, and an electronic control unit ( ECU).
Since air suspension systems are more expensive for small and medium-sized vehicles, suspension systems that replace air with oil are often used. Although the system for adjusting the amount of oil is relatively inexpensive, the efficiency and comfort of the air suspension system cannot be achieved. The adjustment of the oil quantity is achieved by a special electronic valve, which uses 3 to 5 independent acceleration sensors.
5 anti-rolling stability control system (ARC)As part of vehicle stability control, vehicle rollover stability control systems (ARC) are often integrated into electronic stability control systems (ESC) or suspension systems. The anti-rolling control prevents the vehicle body from being shaken a lot when the brake device or the balance bar is activated. When integrating the ARC system into the ESC system, an additional acceleration sensor (measurement range of 1 to 2 g) for detecting the acceleration in the longitudinal direction of the vehicle is required.
When the system is used in vehicles such as SUVs or off-road vehicles with a high overall body or a high suspension position, it is sometimes designed as a stand-alone system. In this case, a separate sensor is required to be mounted on the top of the car, and the other is placed in the corresponding position on the lower floor.
Lead-acid-lithium Hybrid Power System
High Rate Performance Power System,Backup Power System,Lead-Acid-Lithium System Integration,Lead-Acid-Lithium Hybrid Power System
Wolong Electric Group Zhejiang Dengta Power Source Co.,Ltd , https://www.wldtbattery.com