Based on the portability and practicality, a new design of the pedestrian dead reckoning device is proposed. The 3D accelerometer and the electronic compass integrated chip LSM303DLHC and the gyro integrated chip MPU3050 are used to collect the real-time motion information of the pedestrian. The STM32F103RBT6 single-chip microcomputer with ARMCortex-M3 core collects sensor data and performs dead reckoning processing on the data. The track information is displayed on the TFTLCD. Experiments show that the device has high estimation accuracy and can meet the needs of practical applications.

The pedestrian heading estimation device is mainly composed of a three-dimensional sensor module, a data conversion module and a processing module, and a specific composition block diagram is shown in FIG. 1 . The three-dimensional sensor module is divided into a three-axis accelerometer and an electronic compass integrated chip LSM303DLHC, a gyroscope integrated chip MPU3050, and a single-chip microcomputer STM32F103RBT6 for data processing. In actual operation, the three-axis sensor module is placed in the waist of the pedestrian, and the three-dimensional accelerometer is used to collect the acceleration in the front left and upper directions, used to calculate the pitch and tilt angles of the module, and the step count and step of the walker. Estimation; electronic compass collects the pedestrian's real-time heading angle data; the gyroscope measures the three-axis angular velocity per unit time to correct the calculated pitch angle and tilt angle; the MCU is responsible for converting the raw data of the sensor, using serial port and data processing The module communicates. The core of the data processing module also uses the single-chip STM32F103RBT6. While communicating with the serial port of the 3D sensor module, the data required for the dead reckoning is stored in the SD card through the FAT32 file system. The display module uses TFTLCDILI9320. When the pedestrian needs to view the current position information, the MCU can retrieve the original data from the SD card through the FAT32 file system, perform the dead reckoning process, and finally display the pedestrian's track on the TFTLCD. on.

Figure 1 system composition block diagram

Both the master and slave MCUs use the industrial-grade control chip STM32F103RBT6 with ARMCortex-M3 core produced by ST. It has a clock frequency of 72MHz, the internal ROM storage capacity is 128KB, and the RAM storage capacity is 20KB. It has 8 timing counters, 3 SPI, 2 I2C bus, 3 UART, 1 USB, 1 CAN bus and other communication ports. These communication ports can fully meet the needs of the system in the design process.

The STM32F103RBT6 chip is powered by 3.3V, while the external power supply is a 5V battery. Therefore, the buck chip AMS1117-3.3 is used, which can reduce the output voltage and stabilize it at 3.3V with an accuracy of 1%.

The LSM303DLHC chip can operate normally from a low voltage of 2.16 to 3.6V. It has a built-in three-axis accelerometer with a range of ±2g to ±16g. The electronic compass range can be ±1.3～±8.1gauss. The MCU communicates with the I2C bus through the SCL and SDA pins. The programming register CTRL_REG4 can set the three-axis acceleration measurement range. The programming register CRB_REG_M can set the electronic compass range. The peripheral circuit is shown in Figure 2.

Figure 2 LSM303DLHC peripheral interface schematic

MPU3050 can work normally under the low voltage of 2.1~3.6V. Its built-in gyroscope can measure the angular displacement of ±250～±2000°/s in the three-axis direction. The gyroscope can be selected by programming its register DLPF_FS. The range of the microcontroller, through the I2C bus, can read the three-axis raw data from the six data registers X_OFFS_USRH / L, Y_OFFS_USRH / L, Z_OFFS_USRH / L, the peripheral circuit shown in Figure 3.

Figure 3 MPU3050 peripheral interface schematic

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