Research On Vibration Suppression Method Of Hybrid Stepping Motor In Digital Slice Scanner

With the advantages of simply driving control and no accumulative errors,a two-phase hybrid stepping motor has been widely used in economic CNC positioning system with high resolution.However,there are two obvious disadvantages.First,the vibration and noise is relatively large at low speed rotation.Second,the locked-rotor,lost step or overshoot will lead to larger vibration when the frequency mutation is too large.These two disadvantages will have a greater impact on the accuracy of the positioning system.The purpose of this research is to find methods to suppress the vibration of the stepper motor in the digital slicing scanner with micron level.The vibration of the stepping motor during running will result in inaccuracy of the scanned image,and it will sometimes even be out of focus;additionally,it will lead to a longer scan time.Therefore,the research on the vibration suppression method of the stepping motor in the digital slice scanner is meaningful and has great practical value.The paper is composed of four parts: understanding of the motor,measurement of vibration quantity,method of reducing vibration and the system experiment.First of all,a systematic overview of the digital slice scanner was presented,the working principles and running performance of the stepping motor was studied and five kinds of driving methods for stepping motors were compared.Next,the reason for the vibration of the stepping motor was studied,and the main reasons for vibration of the stepping motor in a digital slice scanner were pointed out.Three schemes to suppress the vibration of the stepping motor were also researched,and the subdivision of step angle and the design of frequency raising-lowering curve are presented as the main ways to suppress the vibration of the stepping motor.Without changing the original mechanical structure,this paper presented a scheme for the vibration measurement of the stepping motor in a scanner,in which the regular scan camera with a high-speed camera was replaced to shoot the position of the focal plane of the slice combined with an auto-focusing gradient algorithm this reflected the vibration of the stepping motor by the fluctuation of the focal line position.The collected vibration data was processed and analyzed by MATLAB software programming and the frequency raising-lowering control of the stepping motor was studied in detail.The compound curve velocity control function of the stepping motor was established on the basis of exponential regular velocity function of the stepping motor.Four different kinds of vibration time tests of the stepping motor were also compared and analyzed.At last,the vibration test experiments were carried out on the subdivision of the step angle and compound curve frequency raising-lowering control modes in the experiment and performance analysis parts.The actual scanning verification experiments were carried out respectively under the four conditions: non-subdivision of trapezoidal velocity curve step angle,16-subdivision of trapezoidal velocity curve step angle,non-subdivision of compound velocity curve step angle and 16-subdivision of compound velocity curve step angle.Meanwhile,the effect of vibration suppression and the experimental results were analyzed.Through this paper,the vibration of the stepping motor can be accurately measured,the vibration of the stepping motor can be effectively suppressed and the scan time of the scanner can be shortened.The result of the research improved the performance of the digital slice scanner,and became a strong experimental foundation for the subsequent product improvement.