Research And Analysis On Automatic Calibration System For Time Grating Turntable

The time grating sensor is new type of precision displacement sensor which isdeveloped based on the innovative ideas that “to the time measureable space”, avoiding thestringent requirements for precision engraved lines during the manufacturing process of thetraditional grid displacement sensors. It can achieve high precision displacementmeasurement relying solely on general machining, and has significant advantages such ashigh accuracy, strong anti-jamming capability and low manufacturing costs,so it has verybroad application prospects in national defense, industry, scientific research etc. The timegrating turntable,as the early mature product of time grating sensor in practical application,is applied to high precision machine tools indexing. Like other precision instruments, thetime grating turntable also need to be calibrated to ensure its accuracy in the productionprocess and after used for a period of time. Aiming at the problem that the low automation,low efficiency and difficult to ensure the accuracy during the calibration process of theturntable,which impact the industrialization process of the turntable, an automaticcalibration system used for high-precision calibration of time grating turntable is designed.The main research contents as follows:1) Researched the structure and working principle of the time grating sensor and thetime grating turntable deeply, determined the whole scheme which takes the laserinterferometer as the reference after analyzed and compared the method of the existingturntable calibration.2) Completed the design of control system of the time grating turntable in lowermachine, using LPC2148as the main chip in hardware circuits, for the realization of thesystem functional designed of serial communication module, motor drive modules, LCDmodules, function modules etc. In order to achieve precise positioning control of the timegrating turntable, took the signal of the laser interferometer as control feedback and usedone-way approach strategies for the controlling of step motor.3) Researched and analysised the form of data input and output of the Renishaw laserinterferometer software, achieved real-time data acquisition of laser interferometer by thehook function, and took it as the benchmark of calibration and feedback of location in thesystems.4) Designed the interface by MFC under the environment of Visual C++in the IPC, the laser interferometer and the time-grating turntable communicated with the IPC throughserial port, so the test data of the two independent devices was integrated together, thengot the error value of the time-grating turntable on the circumference, and then pruducedthe fitting curve of the least squares polynomial through programming with the Matlab,finally download the curve of error into the electric appliance box of the for errorcorrection, thus the accuracy of the time-grating turntable was improved.Experimental results shows that the calibration system designed in this paper canautomatically complete calibration work of the time grating turntable efficiently, which hasvery important realistic significance for mass production and industrialization process ofthe time grating turntable.