Research On Pointing Precision And Drive Control Of Precision Turntable Based On Ultrasonic Motor

In the process of missile flight guidance,the coordinator at the front of the missile plays an important role.Therefore,the tracking accuracy of the front position marker is very important for the missile which needs precision strike.The key test instrument used in the test phase of the positioner is the test tracking turntable.In order to ensure the tracking accuracy of the positioner,the accuracy of the test turntable must be guaranteed first.So it is very meaningful for the research of turntable precision and drive control.Firstly,this paper introduces the history and development of turntable research field,compares different turntable types and turntable accuracy analysis methods to get its characteristics,introduces the research status of ultrasonic motor drive technology,and describes the main work of this paper.Combined with the specific technical indicators,the overall scheme of the non-magnetic turntable is given,including the selection of driving method,guide rail and position feedback system.Combined with the technical index,the load and bearing stiffness of the two axes of the turntable are calculated.The electric control system scheme of the non-magnetic turntable is given,and the flow chart of the control program is introduced.The angle measurement error and uncertainty of non-magnetic turntable are analyzed,and the rotation angle when the angle measurement error is the largest is obtained.According to the angle measurement error and static installation error,the pointing error and the pointing uncertainty of the turntable are analyzed,and the error and the type of uncertainty that have the greatest impact on the pointing accuracy of the turntable are obtained,thus the assembly error that needs to be reduced most is determined when assembling the turntable.The driving ability of the ultrasonic motor is analyzed.Firstly,the locus and range of the friction between the driving foot and the ceramic ring are given.The specific friction type is not the traditional sliding friction,but a relatively unstable stick sliding friction,and the calculation method of the stick sliding friction is given.The relationship between preload and contact angle is analyzed,and the specific calculation formula is obtained.At the same time,the relationship between the pretightening force,contact angle and the output torque and the maximum speed of the ultrasonic motor is analyzed under the conditions of intermittent contact and continuous contact.It is found that the output torque of the ultrasonic motor can be divided into driving torque and resistance torque with the different rotation speed of the ceramic ring,and the optimal installation pretightening force of the ultrasonic motor is obtained,which provides a reference for the installation of the ultrasonic motor.Finally,the angle measurement uncertainty of the turntable is tested,and the angle measurement uncertainty data of the turntable is obtained,which provides experimental verification for the theoretical analysis of the dynamic uncertainty of the turntable in Chapter3.The PID control parameters of the turntable in two modes are adjusted,and the optimal PID parameters are obtained.It is found that although there is velocity fluctuation,there is no large overshoot,which is acceptable for the position control turntable.And the positioning accuracy of the turntable is tested,and the positioning error of the motion curve and the control software is observed.The positioning accuracy of the turntable can meet the technical requirements.The output torque of the turntable motor is tested,and the torque fitting curve is obtained,which is consistent with the theoretical analysis.