Vehicle self-velocimeter for navigation system based on a linear image sensor

摘要

The idea of using the method of spatial filtering velocimetry based on a linear CMOS image sensor is proposed to provide accurate velocity information for vehicle self-contained navigation system. A new method is proposed to determine the error source of the system. The image sensor is employed both as a detector and as a pair of differential spatial filters so that the system is simplified. The spatial filtering operation is fully performed in a field programmable gate array (FPGA). The approach of fast Fourier transform (FFT) is employed to obtain the power spectra of the filtered signals. Because of limited frequency resolution of FFT, a frequency spectrum correction algorithm, called energy centrobaric correction, is used to improve the frequency resolution. The velocities of the side surface of a high precision rotary table and the radiating frequencies of an LED are measured. The experimental results show that the measuring error of velocity of a rotary table is about 0.73% and the measurement uncertainty of 1000 times tests is 0.55%; the radiating frequency of an LED is measured under the condition of no imaging system, and the measurement uncertainty turns out to be within 10~(-5). Error sources of the system are analyzed and it is concluded that the main error source of the device is the imaging system. In a word, the velocimeter can satisfy the requirements of non-contact, real-time, high precision and high stability velocity measurement of moving surfaces and has the potential of application to vehicle self-contained navigation system.