Experimental Study On New Methods For Optimizing Traveling Wave Signal Of Parasitic Time-grating Displacement Sensor

Displacement measurement is the key technology of CNC machine tools,precision processing equipment and national defense weapon equipment.It is an important symbol to measure the development level of precision processing and manufacturing in a country.Owing to its significant characters with low cost and high accuracy,Time grating sensor has been regarded as a promising sensor by scientific researchers and businessmen.In order to measure the rotating angle of the shafting under extreme conditions(large,hollow,strong impact vibration),a parasitic time grating technology is developed.Through theoretical and technological innovation,this dissertation reveals the mathematical mechanism of parasitic time grating measurement.The systematic error is divided into space error and time error for the first time,and the induced signal items of each error items are reconstructed.The theory of traveling wave optimization including three-parameter compensation algorithm,differential calibration algorithm and rotating coordinate system separation algorithm,is studied.Experiments are carried out to verify the correctness,validity and practicability of the proposed method.The experimental results show that those methods can effectively eliminate the first order error caused by flux leakage and uneven winding,the installation error caused by unbalanced installation and the second order error caused by non-orthogonal phase and unbalanced amplitude.This greatly improves the error distribution of parasitic timegrating and brings great convenience for later self-calibration work.The research contents of this dissertation are as follows:(1)The errors of the parasitic time grating displacement sensor are analyzed based on the induced signal.The errors include the first order error term in the pole,the second order error term in the pole,the odd error terms in the pole and the uneven error terms of the whole cycle teeth.The mathematical model of traveling wave signal is revealed,and the corresponding relationship between traveling wave signal and error term is established.The theoretical study provides a theoretical basis for the following traveling wave waveform optimization.(2)An algorithm that eliminating the first order error during the pole is proposed,which effectively reduces the first order error in the pole caused by magnetic flux leakage,uneven winding and parasitic capacitance.Firstly,the cause of the error term is studied carefully,and the mathematical model of the first order term error in the induced signal of the Time-grating sensor is established.The traveling wave signal expression is fitted by the least square method which is based on the equation of state in different positions is established to solve the amplitude,phase and bias of the traveling wave signal.Experiments show that the algorithm is accurate,effective and practical.(3)An algorithm that eliminating the second order error during the pole is proposed,which can effectively reduce the quadratic error term.Because of the existence of asymmetry,the system will inevitably appear uneven amplitude and phase,which will lead to the second order error of the output angle.This algorithm re-examines the principle of sensor measurement under the change of time and space coordinates,maps the measurement process in space,and establishes a set of coordinate systems of space axis and time axis.The experimental data show that the algorithm can effectively suppress the secondary error caused by uneven amplitude.It has good practical value for time grating displacement sensor(4)A calibration algorithm to solve the installation error is proposed.The condition of signal difference is constructed by the analysis of signal characteristics.The measured part moves slowly at low speed,accurately sampled the signals of each cycle.The output is used as the measurement standard to find special points,and the characteristic equation is established to correct the installation error.The theoretical and experimental results show that the algorithm effectively eliminates the first order error caused by the installation error,and partly eliminates the second order error caused by the installation error.The overall effect is very obvious.(5)A new digital solution system is redesigned,which has the characteristics of miniaturization,high integration and low cost.After tracing the error term of parasitic time grating displacement sensor and finding the mapping relationship with the induction signal,and putting forward the compensation algorithm which can suppress the error,a complete digital solution system is developed.The system provides a set of general sensor solutions,including the generation of the excitation signal,the acquisition and pre-processing of induction signal,and the real-time output of the sensor angle.The software integrates all the theories and methods proposed in this paper and have been applied to parasitic time grating angular displacement sensors.