Research On Reflector Antenna Pointing Compensation And Digital Filtering Based On Inclinometer

Large-aperture and high-frequency bands are the development trend of today's radio telescopes.High-frequency bands have higher requirements for antenna pointing accuracy.However,with the continuous increase of the antenna's aperture,the weight of the structure itself increases,the natural frequency becomes lower,and it is easily affected by the environment.Load interference causes structural deformation to increase,making highprecision orientation a key problem for engineering realization.This paper takes the 25-meter radio telescope of Nanshan Observatory as the research object,and carries out the research of antenna pointing error compensation.Aiming at the shortcomings of the small adaptation range of the 8-parameter pointing compensation model used in radio astronomy,this paper establishes an 8-parameter model online correction method based on the measurement data of the dual-axis inclinometer.First,the relationship between the deformation of the antenna mount and the coefficients in the 8-parameter model is analyzed.Second,the relationship model between the coefficients and the inclinometer in the 8-parameter model is derived by combining the geometric relationship of the antenna mount structure with the inclinometer,and the results are obtained at different positions.And the conversion value of the coefficient at different elevation angles,which improves the application range of the 8-parameter model and ensures the pointing accuracy of the antenna.Aiming at the problem that the noise of the data collected by the dual-axis inclinometer affects the compensation value,the Kalman filter method is used to deal with the noise.In order to ensure the practicability of the research method,this paper uses the autoregressive model method to establish the state space expression of the inclinometer based on the measured data on the 25-meter radio telescope in Nanshan,and uses the empirical mode decomposition method to extract the measurements in the time series of the inclinometer Noise value.Aiming at the problem that the traditional interpolation method requires multiple iterations,an improved method based on cubic B-spline interpolation and extreme point continuation is proposed.The improved EMD decomposition method is used to decompose the time series of the inclinometer into intrinsic mode functions and margins.In order to obtain the noise information in the intrinsic mode function,this paper designs an intrinsic mode function classification method based on the energy attenuation law and similarity measure.This method divides the intrinsic mode function into pure noise,signalto-noise aliasing and The three parts of pure signal overcome the shortcoming that the traditional method can only classify the intrinsic mode function as noise and signal.And extract the noise information in the signal-noise aliasing part and combine the pure noise part to calculate the measured noise value.Aiming at the problem of outliers in the measurement process of the inclinometer,this paper constructs a sliding window outlier detection method.This method uses the data on both sides of the detection point to calculate the reasonable range of the point and judge whether it is an abnormal value.Finally,the above-mentioned method is verified by the measured data of more than 60 groups of inclinometers in July and August.The experimental results show the feasibility of the method proposed in this paper.