Study Of Evaluating The Tracking Performace Of Photoelectric Theodolite Using The Dynamic Target Equipment

The tracking performance is one of the key technical indexes of influencing the properties of the optoelectronic theodolite. Therefore, an efficacious evaluation of the tracking performance is necessary during the process of development, debugging and testing of the optoelectronic theodolite tracking servo system. The testing of tracking performance indoor is an important part during the testing process. However, the present testing equipments and methods can't cope with the development of the optoelectronic theodolite. Therefore, the new evaluation means of the tracking performance by using optic dynamic target are putted forward in this paper. The primary researches of this paper are the testing methods of making use of the equivalent sine testing method to evaluate the tracking performance of photoelectric theodolite by using the dynamic target equipment, and the rationality of the testing methods.The model structure of dynamic target and the space relationship between dynamic target and theodolite are introduced. A simulative model between the optoelectronic theodolite tracking system and the dynamic target is built under MATLAB/SIMULINK. On this basis, we analyses the influence factors of evaluating the tracking performance using dynamic target.Two approaches are proposed to evaluate the tracking performance. We introduce the way of the establishing the equivalent mathematic model of tracking error of theodolite firstly. First, an equivalent mathematic model of tracking error is established by system identification. Then, the equivalent sine signal is inputted to the equivalent model, and the outputs are sampled. The results of evaluating the tracking performance are obtained based on the statistical calculation of output produced by equivalent model. From now on, another method is given. The dynamic target can be represented by a finite number of weighted sums for the base frequency harmonic and high harmonics which the frequencies are the integral times of base frequency. The angular frequency and amplitude of equivalent sine signal are designed according to the testing desire. The amplitude-frequency characteristic function value of tracking error system is tested by using the harmonic signal that has the same angular frequency with the equivalent sine signal. And the harmonic signal is generated by dynamic target affirmatively. The amplitude of equivalent sine and function value are multiplied to get the maximum equivalent tracking error. The tracking performance is evaluated by using equivalent sine testing method. So the tracking performance of the photoelectric theodolite is evaluated by this method.Two kinds of methods of system identification which are least squares identification and neural network identification are adopted here. The paper gives the principle of building and identifying the equivalent model of tracking error, and the design approach of equivalent sine signal which is designed according to the theodolite checking and testing desire. Because of the dynamic characteristic of theodolite needing to be inspirited fully by input signal for getting the accuracy parameters of equivalent model of tracking error, the frequency of dynamic target is modulated continuously.The time-frequency characteristics of signals including LFM signal, target frequency-modulated signal, and their corresponding outputs of tracking error system are studied. According to requirement of time-frequency analysis, we give the way of constructing analytic signal. At last, the means, route and the difficulties of testing the curve of amplitude-frequency of tracking error system are discussed briefly.The experiments are performed using simulation model and photoelectric theodolite of the different model for validating the methods of evaluating the tracking performance. The study proves that it can realize the accurate evaluation of tracking performance using the equivalent sine testing method by dynamic target equipment.