Application of CS-ARAS and CS-A2LAS gyro in vehicle stability system

As cars enter thousands of households, safety becomes more and more important. The safety of drivers and passengers is closely related to whether the electronic system of the vehicle is advanced. The airbag ABS (Anti-lock Break system) system is a common safety protection system that everyone is very familiar with. The vehicle stability system is a more advanced vehicle safety protection system. According to a German survey, the installation of a vehicle stability system can reduce 50% of vehicle accidents. Many people may only know the term, but do not understand its meaning. And due to different car series, the term is also different.

In fact, the core of the vehicle stability system is to add an inertial sensor, and measure the angular rate and acceleration or inclination of the vehicle's rotation through the inertial sensor. Then the ECU sends a control command to a certain wheel to ensure normal and safe driving.
There are many different names for the vehicle stability system, but the essence is similar. There are mainly the following different terms:

ESP: Electronic Stability Program.
ESC: Electronic Stability Control.
VDC: Vehicle Dynamic Control.
VSC: Vehicle Stability Control.
RSC: Roll Stability Control
DSC: Dynamic Stability Control.

ESP is based on the ABS anti-lock braking system. It collects information such as the steering wheel rotation angle and lateral acceleration through peripheral sensors. This information is processed by a microprocessor and then the hydraulic regulator issues a braking command to the wheel brake to correct the side slip. Especially when turning, that is, when the lateral force is acting, ESP stabilizes the vehicle and keeps it driving safely. ABS and TCS only work in the longitudinal direction. ESP not only uses all the components of ABS and TCS, but also includes a yaw rate sensor and direction sensor integrated with a lateral acceleration sensor. ESC is functionally equivalent to a combination of multiple functions such as ABS (anti-lock braking system), EBD (electronic brake force distribution), TCS (traction control system), AYC (active yaw control), etc. It can automatically correct oversteering and understeering, and can keep the car on the correct route by comparing the driver's intention to drive in the direction with the actual direction of the car. When deviation is detected, ESC brakes each wheel independently and reduces engine torque to help the driver maintain control of the car. ESC is actually a braking system that can brake four wheels separately or simultaneously, which is impossible for even the most skilled drivers. VDC is based on ABS and TCS, adding an angular velocity sensor for lateral swing when the car is turning. The ECU controls the driving force and braking force of the inner and outer wheels, front and rear wheels, to ensure the lateral dynamic stability of the car. The successful development of VDC provides active and effective driving safety guarantees for drivers under all working conditions. The system mainly uses wheel speed sensors, steering wheel angle sensors, yaw rate sensors, lateral acceleration sensors, and wheel displacement sensors. VSC will detect the driving status of the vehicle at any time. When the vehicle is in a critical state of over-turning during a turn, the system will automatically reduce the power output of the engine , and the front outer wheels will brake to generate an outward force to pull the vehicle back to a normal driving state; if the vehicle is about to understeer, the engine power output is also reduced, and the rear wheels are braked according to the degree of understeer to restore the vehicle to a normal driving path. The RSC roll stability control system uses a gyro sensor. When the driver makes a sharp turn or quick turns, the following operations are completed in an instant: the system records the speed of change of the vehicle's tilt angle; based on this speed, it calculates the final angle of tilt to determine the degree of risk of rollover; if there is a risk of rollover, the braking system is activated to stabilize the vehicle, thereby buying time for the driver to respond calmly and deal with the dangerous situation. DSC is a further extension of the acceleration anti-skid control or traction control system. It can ensure that the car still has the best traction when turning to ensure driving stability. In order to ensure that the car still has good traction when turning, the system is equipped with more advanced detection and control equipment. For example, it can detect the wheel speed, the steering wheel rotation amplitude, the vehicle speed, and the lateral acceleration of the vehicle. According to the above detected information, it is judged whether the wheel is in danger of slipping during the turning process. If there is a risk of slipping or it has already slipped, the computer will immediately command the brake oil pressure control system to apply appropriate braking to the slipping wheel, or reduce the output of the engine power by reducing the injection amount and delaying the ignition, so as to achieve the phenomenon of preventing the tire from slipping under various driving conditions, so that the vehicle can obtain good traction during the process of starting acceleration, re-acceleration, turning, etc. From the above, we can see that in addition to the existing speed sensor and steering wheel angle sensor, these systems all need a sensor that can measure the rotation of the vehicle body to measure the angular velocity or angular rate of rotation, and some also need to measure the lateral and longitudinal acceleration of the vehicle. This leads to the issue of inertial sensors.

The development of MEMS technology (micro-electromechanical machining system), especially its high cost performance, has brought possibilities and realization to vehicle stability systems. Xi'an Zhongxing Measurement and Control Co., Ltd. uses advanced MEMS technology to develop two types of vehicle gyroscopes and stabilizers for vehicle stability control according to the requirements of domestic and foreign manufacturers to meet the needs of different customers. CS-ARAS contains an angular rate gyro and a linear acceleration, which can simultaneously measure the angular rate of vehicle body rotation and the lateral or longitudinal linear acceleration (depending on the installation direction). The CS-A2LAS stabilizer contains an angular rate sensor and a two-axis acceleration sensor, which can simultaneously measure the lateral or longitudinal acceleration and the angular velocity of vehicle body rotation, and has obtained three national patents. The products are exported to Finland, Italy and Israel.

The CS-ARAS series of inertial sensors for trains is independently developed by Xi'an Zhongxing Measurement and Control Co., Ltd. and is used to measure angular rate and acceleration. The CS-ARAS series of vehicle gyroscopes are a type of low-precision gyroscopes and accelerometers. It is mainly used in high-reliability automotive electronics , and can also be used in antenna stabilization, camera, robot and other systems. The angular rate gyroscopes of the CS-ARAS series automotive sensors work on the resonator gyro principle. Two polysilicon sensing structures, each containing a high-frequency vibrating frame, are electrostatically driven to resonate, forming the necessary velocity element. The two outer ends of the frame form a capacitive sensing structure to sense the Coriolis motion generated when there is angular velocity and generate an electrical signal, which is transmitted to the amplifier and demodulation stages to output an electrical signal proportional to the angular velocity. The accelerometer of the CS-ARAS series automotive sensor is a surface MEMS polysilicon structure built on top of a silicon wafer. The polysilicon reed is suspended from the structure on the surface of the wafer and provides a resistance to overcome the acceleration sensing force. The deflection of the polysilicon structure proportional to the acceleration is measured by a differential capacitor mechanism consisting of two independent fixed plates and a central plate connected to the moving mass, thereby generating a voltage output signal. CS-ARAS and CS-A2LAS are both designed to resist electromagnetic interference considering the electromagnetic interference of the vehicle. At the same time, the individual needs of customers are met according to different system requirements. In addition to analog signal output, CAN bus output has been developed recently, and the appearance can also be made according to customer requirements. CS-ARAS automotive gyro has similar functions to similar products of foreign companies. It has been tried in a small number of heavy trucks of a certain model in Europe. At the same time, it has been applied to a certain special vehicle in China and has received good reviews. CS-A2LAS stabilizer meets the requirements of ESP or ESC. It is being tested in several domestic universities and research institutes. It is believed that it can meet the requirements. Different system names are proposed, named and used by different automobile manufacturers or automotive electronics manufacturers. In terms of function, ESP, ESC, VSC and DSC are almost the same. Bosch and Mercedes-Benz of Germany use ESP system; Continental, TRW and Delphi of the United States use ESC system; Toyota of Japan uses VSC system, among which Guangzhou Toyota 09 Camry G series is one; DSC system is adopted by BMW brand of Germany, while Volvo calls it DSTC system. These systems can use one CS-A2LAS stabilizer or two CS-ARAS automotive gyro launched by Xi'an Zhongxing Measurement and Control Co., Ltd. The VDC system is adopted by Nissan of Japan. In the early days, Bosch of Germany also called this system VDC. Volvo, such as XCPO off-road vehicles and JAGVAR brands, adopt the RSC system. This system is suitable for high adhesion coefficient roads and is mainly used to prevent rollover. Both VDC and RSC systems can use the CS-ARAS vehicle gyro launched by Xi'an Zhongxing Measurement and Control Company.