The design of digital magnetic compass with tilt compensation
|School||Nanjing University of Technology and Engineering|
|Course||Precision instruments and machinery|
|Keywords||magnetic electronic compass error compensation TMS320F2812 magnetic sensor accelerometer|
Magnetic electronic compass is an important device for navigation positioning, which is using the earth’s magnetic field and gravitational acceleration to realize it. High precise electronic compass is widely used in navigation and position, and it also plays a major role in aviation, navigation and national defense. In this paper, on the basis of analysis of the angle compensation algorithm, a digital electronic magnetic compass with compensation of angle and interference fields is designed.Firstly, this paper minutely expounds the principle and the causes of the magnetic electronic compass, in order to improve the accuracy of angle compensation, the compensation methods of BP neural net algorithm and modified least square are put forward with analyzing the principle and error model of inclination measuring, through experiments the latter is selected. And after analyzing the compass deviation, a12-position calibrating method without north reference and elliptical fitting method are used to compensate the compass deviation. Then the design plan of the digital magnetic electronic compass with compensation of angle is determined, which consists of magnetic sensor HMC1021/1022, accelerometer ADXL335and DSP TMS320F2812. According to electrical characteristics of the sensor, the power circuit, signal processing circuit, set/reset circuit of the magnetic sensor and DSP minimum system are designed, the code is written in the CCS, and then debugging the prototype to realize the magnetic heading angle real-time measurement and digital display. Fourthly, in order to verify the feasibility of the prototype and the effectiveness of the error compensation, calibration test, angle test, peripheral test and hardware and software debugging test are required.The tests results show that the angle measurement error is within±0.3°between-30°～+30°.At last, a comparison experiment is implemented between the prototype and HMR3000to verify the precision of prototype. The result shows that the magnetic heading angle difference between the above two is no more than±0.6°between0°～360°.