The Research On Automatic Trimming Algorithm Of Circle Type Precise Carbon Film Potentiometer And System Establishment

Circle type precise carbon film potentiometers (CTPCFP) are widely used as angular displacement transducers in the hydraulic servo systems in the area of aeronautics and astronautics. With the expansion of aeronautics and space technique, more and more potentiometers are needed and the traditional trimming method could not meet the requirements. In this paper, a general trimming algorithm is proposed based on this type of potentiometer in order to improve the nonlinearity error and increase the trimming efficiency through developing an automatic measuring and trimming system.Analyzed the working principle and evaluation indexes of circle type precise carbon film potentiometers, a new automatic total voltage feedback trimming algorithm based on constant current supply is proposed aiming at improving the nonlinearity error. This algorithm requires voltage as the only input data and could trim the carbon film free from the help of electric brush, which will greatly simplify the measuring and trimming process. Several automatic homing zero methods could make the electric brush and milling cutter locate on the initial position automatically.An automatic trimming system which consists of hardware and software is developed based on the algorithm proposed. The hardware part is made up with purchased parts, newly designed jig and fixtures, measuring mechanics and special purpose circuits, while the easy operating software is written with VC++2010 combining axis driving, measuring, trimming, data saving and printing together and calling them with multithread technique.Several experiments are conducted to determine key technological parameters during processing such as feed rate and stabilization time of voltage measurement. Analyzed several factors that could influence the nonlinearity, error compensation algorithms are proposed, for example, milling cutter compensation, mechanical hysteresis effect, zero position compensation and calibration of eccentric quantity. The experiments show that this algorithm is feasible and high efficiency and the system is reliable and stable. The results could meet the requirements of client. Finally, for a more efficient and more accurate system close-loop control technology and high speed data collection need to be discussed in the future study.