tailieunhanh - Land Vehicle Navigation Systems - Phần 2

The previous chapter supplied the theoretical foundation for the analysis in this thesis. As the previous chapter demonstrated, a complete sensitivity analysis requires two systems of stochastic equations | Chapter 3 Sensor Error Models Introduction The previous chapter supplied the theoretical foundation for the analysis in this thesis. As the previous chapter demonstrated a complete sensitivity analysis requires two systems of stochastic equations one that models the time history of the reference system s state and one that models the time history of the Kalman filter s state. For the problem addressed in this thesis a detailed description of both systems of equations will be deferred until Chapter 5. Before the detailed equations can be presented however it is first necessary to discuss the performance characteristics of various sensors commonly found in land-vehicle navigation systems. In this chapter each sensor s performance is discussed and a mathematical model for the error in each sensor s output is given. Some models are derived in this chapter while others are borrowed from the literature. The error models presented in this chapter will reappear in Chapter 5 as part of the reference system s and Kalman filter s stochastic equations. It is important to point out that for some sensors the error models that appear in the Kalman filter s equations differ from those that appear in the reference system s equations. The reason for this has to do with the fact that some error models depend on parameters that cannot be reliably estimated by a Kalman filter. The error model for the fluxgate compass bias is an example. Therefore certain error models cannot 35 CHAPTER 3. SENSOR ERROR MODELS 36 be mechanized in a Kalman filter and must be supplanted with simpler ones that can. However such error models can generally be used in a sensitivity analysis. Differences between the error models in the Kalman filter and those in the sensitivity analysis will be noted. Rate Gyro Error Modeling Example Rate Gyros Rate gyros are found in many existing land-vehicle navigation systems 38 . Two popular low-cost rate gyros are the Murata Gyrostar and the Systron Donner .