Double Position Loop And Follow-up Control Technology Of Gear Measuring Center

CNC gear measuring center is a high-precision mechatronics instrument for measuring gears,and the performance of its measurement and control system directly determines the measurement level.At present,our gear measuring center uses semi-closed-loop control,whose mechanical transmission error affects the measurement results.In addition,the gear measuring center can only measure the gear whose tooth surface equation is known,while the gear which has unknown tooth surface equation and large error in tooth surface cannot be accurately measured.Based on the original semi-closed-loop control,a dual-position loop control is designed to compensate for the mechanical transmission errors which exist in the original semi-closed-loop control,so that the tracking errors of the four axes are as consistent as possible.And the following control of the probe value is designed to achieve the measurement of gears with unknown tooth equation and large errors on tooth surface.In this paper the mathematical modeling of the servo system of the gear measuring center is carried out.The command data and actual data of each axis of the measuring machine are obtained through the discriminative data acquisition experiment on the measuring machine.The parameters of the mathematical model of each axis of the measuring machine are discriminated through the system discriminative toolbox,thus the transfer functions of the four axes is obtained.The dual-position loop control is implemented in FPGA by hardware means.When we designs the dual-position loop control,the grating signal on each axis table is fed back to the dual-position loop compensator.Thus a dual-position loop on the basis of the original semi-closed-loop control system is built,and incremental PID algorithm is used for position compensation in the dual-position loop controller.Through adjusting the parameters of the PID controller through simulation experiments and on-board experiments,the control effect can be optimized.Finally,the following-up control of probe display value is realized,which is used as the feedback signal and adjusts the following axis motion through the following controller in the FPGA to keep the probe value within the tracking range during measurement and achieve the purpose of tracking measurement.After experimental debugging,the parameters in the controller is optimized to achieve the best probe tracking effect.The machine experiment proves that the tracking error of the four axes of the measuring machine is more stable and consistent under the dual-position loop control,which improves the stability of measurement in multi-axis linkage.The tracking measurement of the probe in the following control mode can be realized by the designed probe indication value following control,which solves the problem of measuring gears with unknown tooth equation and large error on tooth surface,improves the measurement performance,and extends the measurement function of the gear measuring center.