Views: 86 Author: Site Editor Publish Time: 2020-05-13 Origin: Site
In this scheme, Infineon SP37 is adopted to design TPMS transmitter, which is a MEMS chip integrated with tire pressure sensor, MCU and RF transmitter. SP37 detects the air pressure, temperature, electric quantity and acceleration, and sends the data to the receiver through wireless modulation. This paper focuses on the key points of antenna design of the transmitter.
The antenna design of transmitter is the key of transmitter design, which determines the accuracy and real-time of the whole TPMS system, as well as the service life of transmitter. If the design of the transmitting antenna is improper, the built-in TPMS transmitter will improve the accuracy and real-time of the system by increasing the transmitting frequency, which will greatly consume the battery power and reduce the service life.
In this paper, the wireless data transmission is realized by adopting the radiation metal sheet heteromorphic antenna, whose length is close to 1 / 4 wavelength of the wireless transmission frequency of the transmitter. By changing the thickness, shape and length of the metal sheet antenna of the transmitter, the wireless transmission efficiency is improved, the transmission power is reduced, and the service life of the transmitter battery is extended. The metal sheet antenna is directly injected into the transmitter housing, and is put into the transmitter housing when it is made. Only the transmitter end and the grounding end of the antenna are connected with the circuit board, so as to reduce the thickness of the transmitter and cut down the production cost. The antenna itself is covered by the plastic shell, which can withstand the high temperature and pressure inside the tire, and will not be deformed due to the high-speed rotation of the tire, with high reliability and stability.
The workload of software design for electronic control unit of automobile accounts for 80% of the total product design, so this paper focuses on the key points of the software design of the dashboard. Stepping motor control is the core function of the meter display in the instrument. So take the following stepping motor control algorithm as an example to introduce the software design of the dashboard.
The design of the dashboard in this paper adopts the stepping motor to drive the pointer to display the speed, working current and battery voltage. Because the stepping motor has the limitation of the minimum step angle, and there is no position feedback. It is easy to have a series of problems such as jitter, overshoot, out of step and inaccurate information indication. Through the application of subdivision technology and acceleration and deceleration control technology in the bottom control, the single-step and single-stage control of stepping motor is realized in the micro level, and on the basis of the bottom control technology, the adaptive control algorithm is further designed to realize the continuous control of stepping motor in a long time span, so as to ensure that each pointer of stepping motor type automobile dashboard is in smooth operation in the whole working time period under various working conditions.
On January 1, 2020, China began to implement mandatory tire pressure monitoring regulations. Not long ago, a document entitled ‘performance requirements and test methods for passenger car tire pressure monitoring system’passed the mandatory national standard technical review and was officially released and implemented after being approved by the National Standards Committee. This means that TPMS has become a mandatory‘standard’for new cars in China in the future. China is a big country of automobile consumption, and tire pressure monitoring system (TPMS) has become the research and development hotspot of automobile electronics industry in China. The demand of TPMS makes a new industry rising.
In the next five years, it is estimated that 701 million tires worldwide will need to be equipped with tire pressure monitoring sensors. The U.S. law requires that all passenger cars and light trucks sold in the U.S. from August 2007 must be equipped with tire pressure monitoring system, and the corresponding regulations also have been issued in Europe.
For example, BMW, Volvo, Nissan, Audi, Cadillac, Volkswagen, Isuzu, Mazda, Ford, Porsche, Hyundai, Buick, Toyota, Landrover, Lexus and so on, cars of these companies all adopt TPMS. That is, tire pressure sensors are installed on four wheels to directly sense tire pressure and monitor the temperature of the tire as well. This way is much more advanced and sensitive.
The tire pressure monitoring system is still in need of improvement. For the indirect system, the condition of lack of air in coaxial or more than two tires cannot be displayed, or the monitoring fails when the vehicle speed is more than 100 km / h. For the direct system, the stability and reliability of wireless signal transmission, the service life of the sensor, the accuracy of the alarm prompt (Whether there is a false alarm or not) and the pressure resistance of the sensor all need to be improved.
It is believed that with the further development of science and technology, TPMS will be more and more perfect, and will bring more powerful guarantee to the driving safety.
