A Study On The Precision Control Method For Rotary Precision Synthetic Carbon Film Potentiometer Trimming

Rotary precision carbon film potentiometers are uasully used as position feedback element in aerospace and aviation field because of high resolution and continuous decrease of voltage.The main index to evaluate potentiometers is its linearity.With the rapid development of China's national defense,in some applications,the potentiometers whose linerity are within 0.1% are in urgent demand.In order to improve the linearity of potentiometers,the industries generally take the methods of trimming carbon film to change the local resistance,up to now,the rotary synthetic carbon film potentiometers after trimming cannot satisfy the linerity demands of such precise element,the reason is that the multiple trimming technology details are not perfect enough.Therefore,on the basis of studying the trimming technology at home and abroad,the key technology of carbon film potentiometer trimming system is completed by analyzing the characteristics of rotary precision synthesis carbon film potentiometer and the functional requirements of the system.First of all,through analyse the funtion needs of the trimming system,each function module is designed.The program control function of constant current resource and voltage acquisition function are mainly realized;the unidirection zero-searching algorithm and target slope appoching method are proposed;the method of comparing the regression-slope is proposed to determine the trimming direction;the potentiometer automatic trimming algorithm and linear precision testing algorithm are designed;with the knowledge of ergonomics,according to customer demands,man-machine interface is designed;Secondly,the potentiometer process parameters of the timming technology through experients.Through analising the influence of voltage acquisition error to the improvement of potentiometer linearity,the extremum mean method is taken to filter voltage datas,the sample number of data filtering was determined according to accuracy requirements;the best parameters of zero-searching and trimming were chosed;Then,the trimming experiments and linerity testing experients of the rotary carbon film potentiometer were carried out to verify the feasibility of the trimming system;Finally,the sources of the potentiometer nonlinear error was analyzed,the error compensation measures of trimming precision compensation,voltage acquisition delaying process,adjusting the cutter posture were put forward.The experimental results show that the potentiometer after trimming can meet the0.1% linearity requirements according to the trimming methods described in this paper.