Design And Realization Of TPMS With Relay Used For The Large-scale Automobile

With the development of society, automobile has been a significant part of people’s life. Automobile brings convenience to people’s life, but also brings a lot of security risks. According to the survey, more than 70% accidents on the highway are caused by tire pressure problems. Therefore, tire pressure monitoring system(TPMS) attracts more attentions gradually, and becomes a new area of automotive safety technology. With this technology, the driver can get the real-time tire pressure information and be warned timely when the tire pressure is abnormal. Currently,on the market, most of the TPMS products are designed for small cars, and few for large-scale automobiles. The long body and complex environment of chassis affect the stability of the wireless signal transmission greatly. Therefore, the design of TPMS with a stable RF performance used for large-scale automobiles has important practical significance.Based on Freescale’s latest FXTH87 tire pressure sensor, we design the TPMS with relay used for large-scale automobiles. The FXTH87 sensor has the smallest size on the market, and this provides a guarantee for the miniaturization of product design in the future. The designed system uses relay to enhance RF performance. We also design a omni-directional array antenna used in relay module. On this basis, we propose a novel three-dimensional beam scanning antenna. The main work of the paper is organized as follows:First of all, through research, we choose Freescale’s FXTH87 sensor as tire pressure sensor module’s chip element, and complete the selection of other devices. The hardware circuit is designed,and method for the design of RF circuit is given. We also program the software,which focuses on the RF-driven design. The module realizes the data collection and RF transmission function. What’s more, the timing wake, RF transmission interval monitoring and anomaly detection are used to achieve the low-power design.Then, relay module and the receiving host based on freescale’s wireless transceiver chip KW01 are designed. The software based on MQX-Lite is designed. In the software, the RF driver matching the FXTH87 is designed to ensure the normal communication. We also design the application components of OLED display screen to ensure normal display. Several application files and schedule for the software are also designed. Finally, the system realizes the function of relay and display.After completing the system design, we design a Omni-directional antenna at the frequency of 433 MHZ, which is applied to the relay module. The antenna is composed of directional antenna radiating elements and the feed network made up of a four-way, equal-split power divider. Measured return loss of the antenna meets the design requirements. Based on this, we propose a novel three-dimensional beam scanning antenna and explain its significance for automatic positioning of tires. At the same time, we make preliminary simulation for the feed network of the beam scanning antenna.Finally, the integration and test of the system are made. Tests show that each module of the system can work normally and stably. The designed TPMS with relay can well realize the function of tire pressure monitoring.