Research on the Laser Doppler Torque Sensor

Transcription

1 Journal of Physics: Conference Series Research on the Laser Doppler Torque Sensor To cite this article: Z Meng and B Liu 006 J. Phys.: Conf. Ser Recent citations - Optical control of the radius of a wheel rolling on a rail Yu. N. Dubnishche et al - Self-Powered Telemetric Torque Meter Abel Caalcante Lima Filho et al View the article online for updates and enhancements. This content was downloaded from IP address on 19/10/018 at 04:5

2 Institute of Physics Publishing Journal of Physics: Conference Series 48 (006) 0 06 doi: / /48/1/037 International Symposium on Instrumentation Science and Technology Research on the Laser Doppler Torque Sensor Z Meng and B Liu Institute of Electrical Engineering Yanshan Uniersity, Qinhuangdao, , China mzysu@ysu.edu.cn Abstract. Based on laser Doppler effect, single section rotational speed of a rotating shaft was measured. By measuring the two sections rotational speed, the difference of the rotational speed between the two could be made. Integrating the rotational speed difference, the relatie torsional angle of the two sections under the action of torsional irbration was receied, so the rotating shaft torque was gotten. Non-contact torque measurement of rotary machine was achieed. The system was designed and the experiment was done on the torque experiment equipment. The result of experimentation indicate that the relatie error between Laser Doppler and conentional torque measuring method that was less than 0.%, and the measurement accuracy of Laser Doppler was high. 1. Introduction Torque measurement decides the work capability, efficiency, life and safety performance of machine equipment, and is one of the most important characters in all kinds of machine parameters and has became the necessary content in the deelopment research, test analysis, quality examine, safety design and priority control of the ariety of machine production [1]. Because the torque measurement task is special, the deelopment of torque sensor does not still satisfy the social need at present [-4]. Thus the design of torque sensor, which has high-definition, low-depletion ang easy-installation, has became the technology problem to be soled quickly in social produce.. Measuring principle Based on laser Doppler effect, single section rotational speed of rotating shaft is measured. The measuring principle is shown in Figure1. The elocity of point A and Point B in optical beam-direction is gien by formula (1) and formula (). Ax = V A cos α A Vx = ωr A cosα A Vx (1) Ax = VB cos α B Vx = ωrb cosα B Vx () According to Doppler principle the scatter light frequency of backtrack ray is gien by formula (3) and formula (4). f DA = Ax (3) f DB = Bx (4) The Doppler shift is f D = f DB f DA = ( ν Bx ν Ax ) = ωd = V iˆ (5) Where V is the kinematic elocity of the object, î is the direction ector of the irradiation light. 006 IOP Publishing Ltd 0

3 03 Figure 1. Single section rotational speed measuring principle of rotating shaft. Based on laser Doppler effect of the rotating shaft s single section rotational, the rotational speed difference of two sections could be measured by measuring the two sections rotational speed. The measurement schematic diagram is shown in Figure. Figure. Optical path of torque measurement. The distance between section A and section B is a, the distance between two parallel beams of the same section is d. when the reoling shaft is irradiated by laser, the Doppler shift of the scatter light is r f D = V iˆ (6) Suppose the reoling shaft has transersal ibration and the ibration elocity is V L, the Doppler shift that receied by detector is r r f DA = ( VA + VL ) iˆ (7) r r f DB = ( VB + VL ) iˆ (8) The Doppler frequency difference is r f D = f DB f DA = ωll Z iˆ 0 (9) If incoming ray is incidence from random angle, i ˆ = (cosα, cos β, cosγ ), L r = (cosε,, cos ) 0 γ

4 04 f D = ωl( cosα cosε cos β ) (10) Formular (10) shows that f D is direct ratio with the reoling shaft angular elocity ω. The rotational speed difference of two sections can be measured by measuring the two sections rotational speed. f D1 f D ω Δ = ω1 ω = ( ) ( ) l1 cosα1 cos δ1 cos ε1 cos β1 l cosα cos δ cos ε cos β (11) f = D1 f D r r r r r r l1l01 Z1 K i1 l L0 Z K i The relatie torsion angle of the two sections is gotten by integrating the rotational speed difference. t f D f D 1 θ = dt l L Z Ki l L Z K i (1) t f D f D = 1 l ( ) l ( ) dt 0 1 cosα1 1 cosε1 cos β1 cosα cosε cos β When the light path structure and the incidence direction of the section A equal to the Section B, the two denominators of formular (1) are same. t f D1 f D t θ = r r ( ) dt = r f D f D dt 0 ll Z i ll Z i 0 1 ˆ 0 ˆ 0 t f D1 f D = ( ) dt (13) 0 l cosα cosε cos β t = ( ) ( ) f D f D dt l 0 1 cosα cosε cos β Then the torque of rotating shaft is gotten. M = GI pθ a (14) From formular (11) and (14), the rotational speed difference and the torque of rotating shaft are gotten, and the torque is measured. 3. System structure and experiment The measurement system is shown in Figure3. Figure 3. Chart of torque measurement system. The whole process is made up of three parts: the laser torque measuring, electric circuit adjustment part and the computer processing part. The laser torque measuring part use laser Doppler effect to transform without contact the twisted angle of the rotation shaft produced by the torque into Doppler shift signal, then use the photo electric detector to transform the beat into oltage signal and send them to the succeeding circuits for processing. This part transforms the signal, and it is a key part of the system. The circuit processing part is responsible for the amplification, zero setting, filtering and normalizing of the signals. Because the signals collected in the torque measuring part are often weak,

5 05 they need to be amplified to a large extent. This bring a series of problems such as the disturbance of scattered laser spots, the offset oltage of the operational amplifier, null shift and the system zero setting. This part is the important part of the system. The computer processing part use A/D collection panel to feed the signals into the computer, and analyze them and get the final alue of the torque measured. The measurement test is carried on the torque experiment platform YDJX-19. The structure of all parts is shown in Figure4. 1- electromotor, - reducer casing, 3-JN338-A torque sensor, 4,6- bracket, 5-ring flange, 7-accelerator, 8-power load, 9-foundation, 10- sizing block, 11- crash pad, 1-base flatform Figure 4. Measurement experiment flatform. The alternating-transduce tunable generator dries the axis of rotation turning. The direct current generator is used as the load. Thus the axis of rotation endures the effect of torque, and causes deformity. Two plate 5 are used to install the receier of high frequency wireless induce source and emitter of wireless signal transmission. In order to compare with this tester, the torque sensor JN338-A is used to measure the standard alue of torque. The test data is shown in Table1. The result indicates that the measure alues of laser Doppler and that of torque sensor JN338-A are the same. Table1. Experiment data comparison. rotational speed/rpm JN338-A/N.m Method of laser Doppler/N.m Error/N.m The test system is designed and the experiment is done. The experiment result indicates that this kind of sensor has good appliance prospect, realizes the drie monitor of rolling equipment driing.

6 06 Torque non-contact measurement of rotary machine is achieed. Torque of the rotating shaft is monitored. It proides a foundation for rotary machine dynamics monitoring intelligence and automatization. References [1] Shang W L, Miao D Y and Qian S Z 1999 Modern Torque Measurement Technolog (Shanghai: Jiaotong Uniersity) [] Chen C Y 1997 Opto-Electronic Engineering [3] Luo D Y, Ren Y P and Chen W Y 1997 Chinese Journal of Lasers [4] Zheng Z M, Sun J Z and Yang X Y 1995 Chinese Journal of Lasers 17-