Design And Implementation Of Dynamic Measuring System For Ball Screws

The ball screw has the advantages of small friction,high transmission performance,and at the same time,it also has the characteristics of changing the circular motion into linear motion and changing the linear motion into circular motion,so the ball screw has been widely used in machine tool industry,automobile industry,national defense Military and other fields.In addition,the ball screw is an important machine drive and positioning device,its manufacturing accuracy determines the accuracy of machine tool processing,so it's necessary to design a ball screw measuring system,it will provide reliable data to support the indicators of ball screw in producing of the machine.For the company,the company also needs a set of measurement system to make their products more competitive by testing of screw quality.In this paper,the function of the measurement system is determined by the requirement analysis,the structure of the measurement system is determined according to the dynamic measurement principle of the ball screw and the manual of the grating.The architecture of the measurement system is divided into two parts,computer and measurement controller,which communicate data through USB to serial port.The computer interacts with the user by graphical interface.After the measurement and motion controller receives the command of start measurement that sent by the computer,it will drive the servo motor running,measure and count the pulse signal with the precision grating measuring instruments,and then calculate the stroke error of the ball screw,and finally send the measured data to the computer.The computer will draw the stroke error curve dynamically,and finally calculate the screw inspection results.The measurement and motion controller of the system uses the STM32F407 as CPU to replace the traditional raster pulse counting card and servo motor drive card,which can reduce the complexity in the architecture of system and the cost of the hardware circuit,it will improve the product stability,at the same time,it is beneficial to the maintenance of the system.The serial communication protocol between the computer and the controller satisfies the function of error automatic retransmission and the overtime automatic retransmission,which greatly improves the stability of the transmission.In addition,the system has fault self-test function which can helptechnicians locate the point failure of the equipment quickly.The system also uses the following points to improve the measurement accuracy of the ball screw:(1)using XL-80 laser interferometer to calibrate the long grating;(2)using the sliding window filtering algorithm to deal with the gross error of measurement data;(3)using the measurement and motion controller to control the pulse signal of the circular grating and the long grating directly,which can reduce the error caused by the asynchronous sampling of the grating signal.The screw measuring system has been tested for more than two months and now delivered to the screw manufacturing companies to use,the test results show that the system is stable.By changing the parameters of the grating measuring instrument,the system can also be applied to another 2m screw measuring platform,which shows that the system has a certain degree of versatility.In addition,the elimination of the gross errors in the measurement and the use of laser measuring instrument for the calibration of long grating,which are better to improve the system's measurement accuracy.Therefore,the measurement system can meet the needs of practical applications and have a certain value.