Research On Error Analysis And Modeling For New Precision Direct Driving Turntable

Gear measuring center using direct drive motor as axis of rotation，can directcoupling between Motor and Loading，this completely removes mechanical transmission，and its characteristics are as follows: accurate location, high-speed dynamic response.Using time grating sensor onto turntable system can improve positioning accuracy andreduce cost. The main research contents as follows:1. Through the analysis of the overall scheme of turntable, confirming industrial PCand PMAC card as the main controlling system platform. and using "the position loop+speed feedforward" named two loop control strategy. Drive motor directly drive turntable.Debugging direct driving servo system by using PMAC. Through the step response andsine-wave response, ensure servo system has good steady characteristics and dynamiccharacteristics.2. According to direct driving system,analyze its system error,find out error source,the causes of error. and the influence of direct driving turntable accuracy. Analyzing mainkinds of errors such as: error of time grating sensor, eccentricity error by axis between timegrating sensor and turntable are not perpendicular, spindle rotation induced error, error bynot perpendicular between turntable and axis and so on. Through the establishment ofdynamic mathematical model, we can get the system dynamic error transfer function anderror transfer function when existing disturbance torque. Research dynamic feedback errorbased on working principle of time grating sensor.3. Through the combination model for dynamic measurement data, study dynamicmeasurement data features. The random error modeling theory is studied, based on timeseries prediction. Predictive modeling of random error by the method of time seriesanalysis is proposed. Research data pretreatment and error separation method. Analyzerecasting errors compared with Real-time Error., and a data processing circuit is designedfor studying the method of parameter real-time solution of forecasting model.4. Precision experiment of direct drive turntable is carried out, and the followingconclusion is got.1. It exists correlation between prediction error and the change of the turntableacceleration. direct drive turntable based on time grating sensor’s dynamic prediction erroris4,when acceleration value is not more than0.03282/ms2. 2. Detecting direct drive turntable based on time grating sensor’s indexing error anddraw the turntable indexing precision is5″by laser interference angle measurementsystem.To sum up，the research of analyzing system error sources and error modeling methodof direct drive rotary table based on time grating sensor ascertain the main factors whichaffect the precision of direct driving system and the characteristics of the error, and thesystem dynamic measurement random error model is established, these would be of greatimportance in error correction and improving the accuracy of direct driving system.