Constrained low-cost GPS/INS filter with encoder bias estimation for ground vehicles׳ applications

In this paper, a constrained, fault-tolerant, low-cost navigation system is proposed for ground vehicle׳s applications. The system is designed to provide a vehicle navigation solution at 50 Hz by fusing the measurements of the inertial measurement unit (IMU), the global positioning system (GPS) receiver, and the velocity measurement from wheel encoders. A high-integrity estimation filter is proposed to obtain a high accuracy state estimate. The filter utilizes vehicle velocity constraints measurement to enhance the estimation accuracy. However, if the velocity measurement of the encoder is biased, the accuracy of the estimate is degraded. Therefore, a noise estimation algorithm is proposed to estimate a possible bias in the velocity measurement of the encoder. Experimental tests, with simulated biases on the encoder׳s readings, are conducted and the obtained results are presented. The experimental results show the enhancement in the estimation accuracy when the simulated bias is estimated using the proposed method.