This article is an instrument panel design for an integrated TPMS function of an electric vehicle. This design reduces the TPMS receiver in the form of a sub-board in the instrument panel, which reduces the cost and inconvenience of independent installation, and convenient to install and disassemble, To meet the requirements of different electric vehicles. The system structure, TPMS antenna design and instrument panel software design are analyzed according to TPMS, the working principle of the instrument panel and its integration. The SP37 design TPMS transmitter is used to solve the problem of emission efficiency and service life by designing the adaptive control algorithm by designing the adaptive control algorithm. Problem.
The instrument panel is a multi-faceted car information display platform. It is a window for information exchange with the car. The electric vehicle dashboard is a high-tech product that adapts to electronics, digitization, and information development. Information display platform, display speed, gear position, motor speed, motor state, battery pack status, etc., and realize motor failure alarm, battery pack low pressure, uneven alarm and other functions. TPMS (Tirepressure Monitoring System) is a car tire pressure monitoring system for automatic monitoring of tire pressure and temperature in the car to ensure driving safety, belonging to the automotive active parts.
It is currently widely used in direct TPMS, which uses a lithium battery installed in each tire to directly measure the air pressure of the tire, and transmitted through radio frequency modulation to the receiver and monitor mounted on the ground. . Due to the limitations of automotive structures and interiors, TPMS receiver and monitor installation positions become a more difficult problem, there are currently two solutions, one is a stand-alone receiver and monitoring of battery powered or automotive cigarettes. One is to integrate the receiver and monitor in the navigator or multi-function inner rearview mirror or dashboard. In the first way, due to the installation position is not fixed, there is a safety hazard during driving, and there will be a certain cost problem, but due to strong independence, it can be applied to various models; the second mode is fixed, and the installation position is fixed, and can be lowered Cost, but need to be customized to meet integration requirements, do not have applicability.
The TPMS receiver is integrated in the form of a sub-board in the form of a sub-board, and the tire temperature pressure is received on the dashboard, and the tire pressure data display and alarm is performed by the instrument panel LCD, LED, and buzzer to avoid TPMS receivers. And the independent design and installation of the monitor. At the same time, the TPMS receiver can be easily loaded or unloaded according to the requirements of different models.
1 system structure
The system includes two parts of the TPMS transmitter and the dashboard. The MEMS chip of the transmitter is the core of the TPMS system. This program uses the SP37 design of Infertiling, which is responsible for completing the detection of air pressure, temperature, electricity, and acceleration. And send data to the receiver through wireless modulation. The acquisition of information is the core function of the instrument panel. Its display interface includes a stepper motor and its pointer, LED, LCD, and buzzer, and the dashboard integrates the TPMS receiver in the form of a sub-board, and takes a tire temperature on the instrument panel. Confusible reception, tire thermostat data display and alarms by LCD, LED, and buzzers, avoiding independent design and installation of TPMS receivers and monitors. When a temperature or pressure of a tire is lower than a certain threshold, you can pass the LED and the buzzer sound alarm, and the temperature and pressure value of 4 tires can be viewed through the mode buttons on the dashboard, and can be convenient for different requirements according to different models. Load or unload the TPMS receiver. The system structure is shown in Figure 1.
Figure 1 System structure diagram
2 TPMS transmitter design
This scenario uses the SP37 designed TPMS transmitter of Yingfine. It is used as the MEMS chip of integrated tire pressure sensors, MCU and RF emitter. SP37 completes air pressure, temperature, electricity and acceleration detection, and transmits data to receive data through wireless modulation. The specific function design sections are not described here again, and the paper focuses on the design points of the antenna design of the transmitter.
The antenna design of the transmitter is the key to the design of the transmitter, which determines the accuracy and real time of the entire TPMS system, and also determines the service life of the transmitter. If the launch antenna is not designed, the built-in tire pressure monitoring transmitter will improve the system accuracy and real time by increasing the frequency of emission, which will greatly consume battery power, thereby reducing service life.
In this paper, the transmission of wireless data is achieved by using the radiant metal sheet shaped antenna, and the length is close to the radio transmission frequency of the transmitter, and the wireless emission efficiency is improved by changing the thickness, shape and length of the transmitter metal sheet antenna, reducing the transmit power. Extend the life of the transmitter battery, the metal sheet antenna directly into the emitter housing, placed in which only the transmitter of the antenna is connected to the board, thereby reducing the thickness of the transmitter with the circuit board when making a transmitter housing. And reduce the production cost, the antenna is covered by the outer casing, which can be resistant to the high temperature high pressure inside the tire and does not deform because of the high speed of the tire, and has a high degree of reliability and stability.
3 instrument panel design
The workload of the automotive electronic electronic control unit software is 80% of its entire product design. Therefore, it is important to introduce the software design points of the dashboard. Stepping motor control is the core function of the meter display, below the motor The control algorithm describes the software design of the dashboard.
The design instrument panel in the article uses a stepper motor drive pointer to display the speed, operating current, and battery pack voltage. Since the stepper motor has a minimum step-off angle, there is no position feedback, it is easy to jitter, overshoot, and out. Information indication is not accurate, this paper uses subdivision techniques and acceleration control technology on the underlying control technology, the single-step and single-segment control of stepper motor is realized on the microscopic level, and the foundation of the underlying control technology The adaptive control algorithm is further design, and the continuous control of the stepping motor on a long-term span is achieved, ensuring that the stepper motor type automotive dashboard has a steady operation of various working conditions throughout the working time period. The specific algorithm is designed as follows:
First, according to the minimum subdivision requirements of the automotive instrument application, the segmentation control table changes the change of the motor coil current sine regulation, and the segmentation control of the underlying stepper motor is achieved by adjusting the control table index step; on the pointer scheduling control, Divided the scheduling cycle in the form of a variable long time slot, the pointer is controlled to the pointer, the rotation mode in a single scheduling period is accelerated start, uniformly, decelerated, and the inertial deactivates 4 phases. By designing the steady start and stop of the various pointers of the automotive dashboard by the design of the car instrument dial, the start-up time is designed by the rotating angular velocity control, the coil position update, the coil current adjustment step, the operation scheduling period is time, the start of the speed, the stop speed, the inertial deactivation time is designed. The rapid response to the rapid change information and the smooth reflection of the slow change information can be quickly started and stopped smoothly and there is no jitter when running at low speed. The algorithm process is shown in Figure 2.
Figure 2 Stepper motor adaptive control flow chart
4 Conclusion
The system structure of the electric vehicle dashboard integrated with TPMS function is analyzed, and the antenna design of the TPMS transmitter is introduced, and the design of the instrument panel into the motor adaptive control algorithm is analyzed. The instrument panel is loaded, and the operation is stable and function. Reliable, it has now entered a small batch pretty production stage, which has high practical value.
Source: Wiku Electronic Market Network
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