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Research On Control Algorithm For Laser Scanner Driven By Voice Coil Motor

Posted on:2011-01-20Degree:MasterType:Thesis
Country:ChinaCandidate:X G XiongFull Text:PDF
GTID:2218330362456658Subject:Optical Engineering
Abstract/Summary:PDF Full Text Request
Fast steering mirror is one type of optical scanners, and it is divided as two categories. One is driven by VCM(voice coil motor), another PZT(piezoelectric transducer).Because of the easily scanning in x and y axis directions synchronously, the scanner driven by VCM is popular among the various applications, such as laser scanner, optoelectric tracking, self-adaption optical system. Constrained by the nonlinearity, and hysteresis, VCM cannot be more popular in application until there is a algorithms to improve its disadvantages if it is used in high precise application, for example, laser scanner. So our design of laser scanner is constructed with feedback optical loop to improve its performance. But the traditional methods for optical tracking, such as improved PID algorithm, converse design based on optimum loop characteristics can't be used and the scanner can't be stable, easily oscillating. What is the problem? How to properly resolve the problem with feedback loop is the key problem when the VCM is selected to drive laser scanner.After analyzing the reason of oscillation of laser scanner, we find that for the limit space of laser scanner driven by VCM, there is lots of high frequency noise when the optical beam reflected in the compact feedback space. The traditional methods include integrator, and the integration of high frequency causes the integration saturation, then cause the oscillation. The construction of laser scanner driven by VCM is fixed, so how to improve algorithm is the only method to resolve the oscillation.If the forward compensation compound method is used, the contradiction between the static error and oscillation is resolved with avoiding oscillation factor and reducing the static error at the same time. Considering the lots of high frequency noise in the feedback loop, a low pass filter is used and the coefficient of feedback loop is decreased to reduce the effect of feedback control. The result after improving is that the scanner not only can work stably, without oscillation, but also has good performance at the linearity, repeatability, bandwidth.We found that if a low pass filter is added into the feedback loop, the bandwidth of the filter should be changed as the frequency of the input signal changes. So it is very trouble. At the same time, the triangle wave signal is put down because of the effect of lowpass filter. Carefully analyzing the character of the noise, we creatively use compensation compound method to reduce the noise although the noise can't be measured. The forward compensation compound method is used at the same time to increase the stability of the scanner. So this method can also be used to improve the performance at the linearity, repeatability, and bandwidth.Because all the control algorithms are implemented in the DSP, using AD and DA to sample the data to control scanner, the detailed study on the transfer function of the D/A, A/D is important for the digital control algorithm. We try to apply dead-beat ripple-free method on the scanner driven by voice coil motor. Finally, in the x direction of the implementation of peace-keeping y dimension a dimension control, but the experiment on a voice coil actuator two-dimensional scanning is not very well, so the reason is found and a two-dimensional scan control algorithm is proposed.
Keywords/Search Tags:Laser scanning system, Close loop performance, Voice Coil Motor (VCM), Fast Steering Mirror (FSM)
PDF Full Text Request
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