Name: Gain-compensation Methodology for a Sinusoidal Scan of a Galvanometer Mirror in Proportional-Integral-Differential Control Using Pre-emphasis Techniques (Video) | JoVE Journal
Uploaded: 2017-04-04T12:00:00.000+00:00
Duration: 9 min 1 s
Description: Learn a gain-compensation method for galvanometer mirrors using proportional-integral-differential control with pre-emphasis techniques. This approach minimizes motion blur in optical engineering applications without requiring additional hardware.

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The authors have no acknowledgements.

1. Acquisition of Gain Data for a Galvanometer Mirror
<ol>
	<li>Fix the galvanometer mirror such that it is stabilized to protect it from damage while oscillating. Not only the galvanometer mirror, but also the body of the galvanometer mirror, moves if not fixed in place using a custom-made metal jig with a circular hole for the galvanometer mirror. Fix the jig onto an optical carrier and an optical bench.</li>
	<li>Connect BNC cables from the AD/DA board through a terminal block to the input and position sockets in the servo driver of the galvanometer mirror.</li>
	<li>Program the sine-wave function generator as a graphical user interface (GUI) using the SDK of the AD/DA board with C++, which is able to set an arbitrary frequency, amplitude, and duration, as shown in Figure 3. 
	NOTE: This customized function generator contributes to cutting the temporal cost for continuous trials in step 1.5, since the trial is conducted many times.</li>
	<li>Set the frequency to vary from 100 Hz to 500 Hz in 100-Hz intervals, and set the amplitude to vary from 10 mV to 500 mV in 10-mV intervals in the GUI. Overall, 250 combinations exist. To test 250 combinations, a double loop is efficient to implement. The first loop is for frequencies from 100 Hz to 500 Hz, which is implemented 50 times. The second loop is for amplitudes from 10 mV to 500 mV, which is implemented for 50 times.</li>
	<li>Add the sine-wave path signal into the AD/DA board for 2,000 samplings as duration in the GUI. Simultaneously record the position signal of the galvanometer mirror to read the analogue value of the AD/DA board. In C++ coding using a library of AD/DA board, use the same thread for writing and reading in programming. Calculate the current angle of galvanometer mirror θ (writing information) by this equation 
	<img alt="Trigonometric equation for oscillatory motion, θ=A_in sin(2πft), mathematical representation." src="/files/ftp_upload/55431/55431eq2.jpg" data-altupdatedat="1788250015000" data-alt="Equation 2"> 
	where t is time, <img alt="Static equilibrium concept, ΣFx=0, equation, mechanics study, physics formula." src="/files/ftp_upload/55431/55431eq3.jpg" data-altupdatedat="1788250015000" data-alt="Equation 3"> is amplitude, ƒ is frequency.</li>
	<li>Save the position signal data as a .csv file and include the value of the frequency and amplitude in its filename.</li>
	<li>Repeat steps 1.4 - 1.6 for 250 iterations.</li>
</ol>
2. Calculation to Get Pre-emphasis Coefficients
<ol>
	<li>Apply a median filter for the csv files (recorded signals) to avoid noise effects. The spatial size of the median filter is 5.</li>
	<li>Run the script to calculate the peak-to-peak value (corresponding with the amplitude multiplied by 2), using MATLAB for each of the csv files, as shown in Figure 4 (the graph represents the data of the sine-wave path).</li>
	<li>Plot the peak-to-peak data on a graph to determine the linearity at each frequency, and limit the usage region of the input amplitude when the plots are nonlinear, as shown in Figure 5. 
	NOTE: The nonlinear part of the graph represents saturation of the PID control; hence, it is advisable to avoid using them to secure the limitation of specification of control.</li>
	<li>Execute linear regression for peak-to-peak data in a spreadsheet to obtain the linear interpolation coefficients of each frequency. In this process, five sets of slopes and intercepts are obtained. They correspond with the frequencies from 100 Hz to 500 Hz at each 100 Hz. An approximation of the straight line of 300 Hz is displayed in Figure 5(A), and the linear interpolation coefficients of each frequency are shown in Table 1.</li>
	<li>Using quadratic multiple linear regression, execute quartic interpolation to obtain the quartic interpolation coefficients (pre-emphasis coefficients) in the spreadsheet for the linear interpolation coefficients of each frequency. The pre-emphasis coefficients are shown in Table 2. 
	NOTE: In this research, the linear interpolation coefficients vary in the form of a quadratic curve; however, other types of functions, such as quadratic and cubic equations, are applied if the error is minimal.</li>
</ol>
3. Online Signal Amplification Based on the Pre-emphasis Technique
<ol>
	<li>Execute the software that calculates the updated input amplitude value <img alt="Static equilibrium equation; ΣFx=0; ΣFy=0; Στ=0; diagram; vector forces, torque analysis." src="/files/ftp_upload/55431/55431eq5.jpg" data-altupdatedat="1788250015000" data-alt="Equation 5"> from the ideal input amplitude value <img alt="Static equilibrium concept, ΣFx=0, equation, mechanics study, physics formula." src="/files/ftp_upload/55431/55431eq3.jpg" data-altupdatedat="1788250015000" data-alt="Equation 3"> and the frequency ƒ using the pre-emphasis coefficients.
	<ol>
		<li>Save the pre-emphasis coefficients as constant values in the C++ software. When the device is updated, these constant values are also updated.</li>
		<li>Program a function 
		<img alt="Equation for polynomial fitting; algebraic expression; scientific data modeling; math analysis." src="/files/ftp_upload/55431/55431eq7.jpg" data-altupdatedat="1788250015000" data-alt="Equation 7"> 
		in the C++ software and obtain the linear interpolation coefficients. Substitute them for ai, bi, ci, di, and ei from the equation and Table 2.</li>
		<li>Program a function 
		<img alt="Chemical formula equation, A'in = k(o,f) Ain + k(1,f), kinetics analysis method." src="/files/ftp_upload/55431/55431eq13.jpg" data-altupdatedat="1788250015000" data-alt="Equation 13"> 
		in the C++ software and obtain an updated input amplitude value <img alt="Static equilibrium equation; ΣFx=0; ΣFy=0; Στ=0; diagram; vector forces, torque analysis." src="/files/ftp_upload/55431/55431eq5.jpg" data-altupdatedat="1788250015000" data-alt="Equation 5"> to substitute for <img alt="Static equilibrium concept, ΣFx=0, equation, mechanics study, physics formula." src="/files/ftp_upload/55431/55431eq3.jpg" data-altupdatedat="1788250015000" data-alt="Equation 3"> and the linear interpolation coefficients that were obtained in step 3.1.2.</li>
	</ol>
	</li>
	<li>Repeat steps 1.4 - 1.6 for arbitrary times with <img alt="Static equilibrium equation; ΣFx=0; ΣFy=0; Στ=0; diagram; vector forces, torque analysis." src="/files/ftp_upload/55431/55431eq5.jpg" data-altupdatedat="1788250015000" data-alt="Equation 5"> using the pre-emphasis technique in the GUI.NOTE: To avoid saturation of the region of PID control, set 400 mV for up to 200 Hz, 200 mV for up to 300 Hz, 100 mV for up to 400 Hz, and 50 mV for up to 500 Hz.</li>
	<li>Repeat step 2.2 and plot peak-to-peak data as a graph to view the improvement in the gain.</li>
</ol>
4. Experiment on Motion-blur Compensation
<ol>
	<li>Prepare a conveyor belt that can move at 30 km/h using a belt that can adhere to sticky textures. The custom-made conveyor belt is composed with a speed-control motor, an iron rubber belt, and so on. It can be replaced with ready-made conveyor belt which can control speed.</li>
	<li>Print a fine-texture pattern onto printable tape and paste it onto the conveyor belt. 
	NOTE: The pasted texture is shown in Figure 6. The stripes are programmed using a library "ofxPDF" in openFrameworks, and the photographic image is from a stock photo company.</li>
	<li>Set up optical devices such as a camera, a lens, and an illumination, as shown in Figure 2. Place the galvanometer mirror in front of the lens which is connected to the camera, and place the illumination to illuminate the conveyor belt.
	<ol>
		<li>Set the camera frequency to 333 Hz, the exposure time to 1 ms, and the number of pixels to 848 * 960 (width * height).</li>
	</ol>
	</li>
	<li>Synchronize the rotational timing of the galvanometer mirror and the exposure time of the camera. In the software, when the angle of the galvanometer mirror arrives the position where to start exposure, the program sends a software trigger into the camera. The timing of software trigger is illustrated in Figure 7.</li>
	<li>Input the speed of the conveyor belt vt (30 km/h) and the distance from the camera to the conveyor belt L(3.0 m) to calculate required angular velocity ωr of the galvanometer mirror in the GUI as in Figure 8. ωr is calculated as follows: 
	<img alt="Static equilibrium equation: ωr = 2tan⁻¹(vt/L); mathematical expression for analysis." src="/files/ftp_upload/55431/55431eq18.jpg" data-altupdatedat="1788250015000" data-alt="Equation 18"></li>
	<li>Input the frequency ƒ(330.0 Hz) in the GUI as in Figure 8 to calculate original input amplitude <img alt="Static equilibrium concept, ΣFx=0, equation, mechanics study, physics formula." src="/files/ftp_upload/55431/55431eq3.jpg" data-altupdatedat="1788250015000" data-alt="Equation 3">. Calculate <img alt="Static equilibrium concept, ΣFx=0, equation, mechanics study, physics formula." src="/files/ftp_upload/55431/55431eq3.jpg" data-altupdatedat="1788250015000" data-alt="Equation 3"> as follows: 
	<img alt="Static equilibrium equation, Ain=ωr/4f, formula used in physics calculations." src="/files/ftp_upload/55431/55431eq19.jpg" data-altupdatedat="1788250015000" data-alt="Equation 19"></li>
	<li>Copy and paste <img alt="Static equilibrium concept, ΣFx=0, equation, mechanics study, physics formula." src="/files/ftp_upload/55431/55431eq3.jpg" data-altupdatedat="1788250015000" data-alt="Equation 3"> into the source code, and rotate the galvanometer with the pre-emphasized control value θ for the galvanometer servo driver as follows: 
	<img alt="Angular motion formula θ=A'in sin(2πft), mathematical equation for oscillatory motion analysis." src="/files/ftp_upload/55431/55431eq20.jpg" data-altupdatedat="1788250015000" data-alt="Equation 20"> 
	where t is time. Figure 7 illustrates how θ is calculated from A.</li>
	<li>Record images when the conveyor belt is moving at vt (30 km/h). 
	NOTE: Figure 9 illustrates the motion of the conveyor belt.</li>
</ol>

<ol><li>Bass, M. <a target="_blank" href="http://scholar.google.com/scholar?hl=en&safe=off&q=author%3aBass%2C+M+%22Handbook+Of+Optics%22">Handbook Of Optics</a>. 3, 2nd ed, (1995).</li>
<li>Marshall, G. F., Stutz, G. E. <a target="_blank" href="http://scholar.google.com/scholar?hl=en&safe=off&q=author%3aMarshall%2C+GF+%22Handbook+of+optical+and+laser+scanning%22">Handbook of optical and laser scanning</a>. , CRC Press. (2011).</li>
<li>Aylward, R. P. <a target="_blank" href="http://www.emeraldinsight.com/doi/abs/10.1108/02602280310481968">Advanced galvanometer-based optical scanner design.</a> Sensor Rev. 23 (3), 216-222 (2003).</li>
<li>Duma, V., Rolland, J. P., Group, O., Vlaicu, A., Ave, R. <a target="_blank" href="http://proceedings.spiedigitallibrary.org/proceeding.aspx?articleid=1840700">Advancements on galvanometer scanners for high-end applications.</a> Proc SPIE. 8936, Cm 1-12 (2014).</li>
<li>Duma, V. -F., Lee, K., Meemon, P., Rolland, J. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Experimental+investigations+of+the+scanning+functions+of+galvanometer-based+scanners+with+applications+in+OCT%5BTitle%5D)+AND+%22Appl+Opt%22%5BJournal%5D)">Experimental investigations of the scanning functions of galvanometer-based scanners with applications in OCT.</a> Appl Opt. 50 (29), 5735-5749 (2011).</li>
<li>Wang, C., Shumyatsky, P., Zeng, F., Zevallos, M., Alfano, R. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Computer-controlled+optical+scanning+tile+microscope%5BTitle%5D)+AND+%22Appl+opt%22%5BJournal%5D)">Computer-controlled optical scanning tile microscope.</a> Appl opt. 45 (6), 1148-1152 (2006).</li>
<li>Jofre, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Fast+beam+steering+with+full+polarization+control+using+a+galvanometric+optical+scanner+and+polarization+controller%5BTitle%5D)+AND+%22Opt+Exp%22%5BJournal%5D)">Fast beam steering with full polarization control using a galvanometric optical scanner and polarization controller.</a> Opt Exp. 20 (11), 12247-12260 (2012).</li>
<li>Liu, X., Cobb, M. J., Li, X. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Rapid+scanning+all-reflective+optical+delay+line+for+real-time+optical+coherence+tomography%5BTitle%5D)+AND+%22Opt+lett%22%5BJournal%5D)">Rapid scanning all-reflective optical delay line for real-time optical coherence tomography.</a> Opt lett. 29 (1), 80-82 (2004).</li>
<li>Li, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Laser+beam+scanning+by+rotary+mirrors.+II.+Conic-section+scan+patterns%5BTitle%5D)+AND+%22Appl+opt%22%5BJournal%5D)">Laser beam scanning by rotary mirrors. II. Conic-section scan patterns.</a> Appl opt. 34 (28), 6417-6430 (1995).</li>
<li>Duma, V. I. L., Tankam, P. A., Huang, J. I., Won, J. U., Rolland, J. A. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Optimization+of+galvanometer+scanning+for+optical+coherence+tomography%5BTitle%5D)+AND+%22Appl+opt%22%5BJournal%5D)">Optimization of galvanometer scanning for optical coherence tomography.</a> Appl opt. 54 (17), 5495-5507 (2015).</li>
<li>Hayakawa, T., Watanabe, T., Ishikawa, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Real-time+high-speed+motion+blur+compensation+system+based+on+back-and-forth+motion+control+of+galvanometer+mirror%5BTitle%5D)+AND+%22Opt+Exp%22%5BJournal%5D)">Real-time high-speed motion blur compensation system based on back-and-forth motion control of galvanometer mirror.</a> Opt Exp. 23 (25), 31648-31661 (2015).</li>
<li>Hayakawa, T., Watanabe, T., Senoo, T., Masatoshi, I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Gain-compensated+sinusoidal+scanning+of+a+galvanometer+mirror+in+proportional-integral-+differential+control+using+the+pre-emphasis+technique+for+motion-blur+compensation%5BTitle%5D)+AND+%22Appl+opt%22%5BJournal%5D)">Gain-compensated sinusoidal scanning of a galvanometer mirror in proportional-integral- differential control using the pre-emphasis technique for motion-blur compensation.</a> Appl opt. 55 (21), 5640-5646 (2016).</li>
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<li>Ortega, R., Kelly, R. <a target="_blank" href="http://ieeexplore.ieee.org/document/4158562/">PID Self-Tuners: Some Theoretical and Practical Aspects.</a> IEEE Transa Ind Electron. 31 (4), 332-338 (1984).</li>
<li>Mnerie, C., Preitl, S., Duma, V. -F. <a target="_blank" href="http://proceedings.spiedigitallibrary.org/proceeding.aspx?articleid=1687383">Mathematical model of a galvanometer-based scanner: simulations and experiments.</a> Proc SPIE. 8789, 878915(2013).</li>
<li>Mnerie, C. A., Preitl, S., Duma, V. <a target="_blank" href="http://ieeexplore.ieee.org/document/6608952/">Performance Enhancement of Galvanometer Scanners Using Extended Control Structures.</a> 8th IEEE International Symposium on Applied Computational Intelligence and Informatics. , 127-130 (2014).</li>
<li>Mnerie, C., Preitl, S., Duma, V. -F. <a target="_blank" href="http://spie.org/Publications/Proceedings/Paper/10.1117/12.2043034">Control architectures of galvanometer-based scanners for an increased precision and a faster response.</a> Proc of SPIE. 8925, 892500(2014).</li>
<li>Farjad-rad, R., Member, S., Yang, C. K., Horowitz, M. A., Lee, T. H. <a target="_blank" href="http://www-smirc.stanford.edu/papers/VLSI98p-ramin.pdf">A 0.4- m CMOS 10-Gb/s 4-PAM Pre-Emphasis Serial Link Transmitter.</a> IEEE J Solid-State Circuits. 34 (5), 580-585 (1999).</li>
<li>Buckwalter, J. F., Meghelli, M., Friedman, D. J., Hajimiri, A. <a target="_blank" href="http://ieeexplore.ieee.org/document/1637603/">Phase and amplitude pre-emphasis techniques for low-power serial links.</a> IEEE Journal of Solid-State Circuits. 41 (6), 1391-1398 (2006).</li>
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The authors have nothing to disclose.

This article presents a procedure capable of expanding the sine-wave frequency range to achieve high-accuracy trajectory tracking with PID control. Because the responsiveness of a galvanometer mirror is limited by its inertia, it is critical to use a galvanometer mirror when the control path is steep. However, in this research, we propose a method to improve the specification of control and then prove the method by obtaining experimental results.
In our procedure, step 2.5 is the most critical...

Various optical actuators and control methods suitable for various optical applications have been proposed and developed1,2. These optical actuators are able to control the optical path; galvanometer mirrors especially offer a good balance in terms of accuracy, speed, mobility, and cost3,4,5. Actually, the advantage offered by the speed and accuracy of galvanometer mirrors has led to the realization of a variety of optical applications, such as target tracking and drawing, scanning control, and motion-blur compensation6,7,8,9,10,11,12. However, in our previous motion-blur compensation system, a galvanometer mirror using a proportional-integral-differential (PID) controller provided a small gain; hence, it was difficult to achieve a higher frequency and a faster speed11.
On the other hand, PID control is a widely-used method, as it satisfies a certain level of tracking accuracy13. A variety of methods have been proposed to correct the gain in PID control. As a typical solution, PID control parameter tuning is conducted manually. However, it takes time and special skill to maintain. A more sophisticated method, an auto-tuning function to automatically determine the parameters, has been proposed and is widely used14. The tracking accuracy for high-speed operations is improved using the auto-tuning function when the proportional gain value P increases. However, this also increases the convergence time and noise in the low-speed range. Hence, the tracking accuracy is not necessarily improved. Although a self-tuning controller can be tuned to set suitable parameters for PID control, the tuning introduces a delay because of the need to obtain suitable parameters; therefore, it is difficult to adopt this method in real-time applications15. An extended PID controller16,17 and an extended predictive controller18 have been proposed to extend general PID control and to enhance the tracking performance of galvanometer mirrors for a variety of tracking paths, such as triangular waves, sawtooth waves, and sine waves. However, in those systems, the galvanometer system was regarded as a black box, whereas a model of the control system was required, and the control system was not regarded as a black box. Hence, those methods require that their model for each galvanometer mirror be updated. Moreover, although Mnerie et al. validated their method of focusing on a detailed output wave and phase, their research did not include the attenuation of the entire wave. In fact, in our previous research11, the gain was significantly decreased when the sinusoidal frequency was high, thereby indicating the necessity to compensate for the gain of the entire wave.
In this research, our procedure for gain compensation with PID control12 is based on the pre-emphasis technique19,20,21&#8212;a method to enhance the quality or speed of communication in communications engineering&#8212;which enables the construction of an experimental system using existing equipment. Figure 1 shows the flow structure. The pre-emphasis technique is able to obtain in advance the desired output value from an input value, where PID control is not effective, even if the galvanometer mirror and its controller are regarded as black boxes. This enables them to expand the frequency and amplitude range in which a gain of 0 dB can be obtained without tuning the PID control parameters.
When the gain is amplified, the response characteristics of the galvanometer mirror generally differ at different frequencies, and therefore, we need to amplify each frequency with amplification coefficients. Thus, a sine wave is suitable for the pre-emphasis technique, as there is only one frequency in each sine wave. In this research, because we apply gain compensation to accomplish motion-blur compensation, the control signal is limited to sine-wave scanning, and the sine-wave signal constitutes a single frequency, unlike other waves, such as triangular and sawtooth waves. Further, the input signal into the galvanometer mirror is updated immediately within the next cycle because of the open loop after the pre-emphasis coefficients are set. In other words, we need to know only the input-to-output ratio to regard the controller as a black box, and detailed modeling is not required. This simplicity allows our system to be easily embedded in applications.
The overall goal of this method is to establish an experimental procedure of motion-blur compensation as an application by gain compensation using the pre-emphasis technique. Multiple hardware devices are used in these procedures, such as a galvanometer mirror, a camera, a conveyor belt, illumination, and a lens. Central software user-developed programs written in C++ also constitute part of the system. Figure 2 shows a schematic of the experimental setup. The galvanometer mirror rotates with gain-compensated angular velocity, thereby making it possible to evaluate the amount of blur from the images.

<table><tbody><tr><td>Galvanometer mirror</td><td>Cambridge Technology</td><td>M3s X axis</td><td></td></tr><tr><td>Custom-made metal jig</td><td>ASKK</td><td>-</td><td>With circular hole for galvanometer mirror</td></tr><tr><td>Optical carrier</td><td>SIGMAKOKI</td><td>CAA-60L</td><td></td></tr><tr><td>Optical bench</td><td>SIGMAKOKI</td><td>OBT-1500LH</td><td></td></tr><tr><td>Oscilloscope</td><td>Tektronix</td><td>MSO 4054</td><td></td></tr><tr><td>AD/DA board</td><td>Interface</td><td>PCI-361216</td><td></td></tr><tr><td>PC</td><td>DELL</td><td>Precision T3600</td><td></td></tr><tr><td>Galvanometer mirror servo controller</td><td>Cambridge Technology</td><td>Minisax</td><td></td></tr><tr><td>Lens</td><td>Nikon</td><td>AF-S NIKKOR 200mm f/2G ED VR II&amp;nbsp;</td><td></td></tr><tr><td>High-speed camera</td><td>Mikrotron</td><td>Eosens MC4083</td><td>Discontinued, but sold as MC4087. The cable connection is different from MC4083</td></tr><tr><td>Conveyor belt</td><td>ASUKA</td><td>-</td><td>With a speed-control motor(BX5120A-A made by Oriental Motor), iron rubber belt(100-F20-800A-J made by NOK), and so on</td></tr><tr><td>Printable tape</td><td>A-one</td><td>F20A4-6</td><td></td></tr><tr><td>Photographic texture</td><td>Shutterstock, Inc.</td><td>231357754</td><td>Printed computer motherboard with microcircuit, close up</td></tr><tr><td>Terminal block</td><td>Interface</td><td>TNS-6851B</td><td></td></tr><tr><td>CoaXPress board</td><td>AVALDATA</td><td>APX-3664</td><td></td></tr><tr><td>MATLAB</td><td>mathworks</td><td>MATLAB R2015a</td><td></td></tr></tbody></table>

gain-compensation methodology for a sinusoidal scan of a galvanometer mirror in proportional-integral-differential control using pre-emphasis techniques

Gain-compensation Methodology for a Sinusoidal Scan of a Galvanometer Mirror in Proportional-Integral-Differential Control Using Pre-emphasis Techniques

Galvanometer mirrors are used for optical applications such as target tracking, drawing, and scanning control because of their high speed and accuracy. However, the responsiveness of a galvanometer mirror is limited by its inertia; hence, the gain of a galvanometer mirror is reduced when the control path is steep. In this research, we propose a method to extend the corresponding frequency using a pre-emphasis technique to compensate for the gain reduction of galvanometer mirrors in sine-wave path tracking using proportional-integral-differential (PID) control. The pre-emphasis technique obtains an input value for a desired output value in advance. Applying this method to control the galvanometer mirror, the raw gain of a galvanometer mirror in each frequency and amplitude for sine-wave path tracking using a PID controller was calculated. Where PID control is not effective, maintaining a gain of 0 dB to improve the trajectory tracking accuracy, it is possible to expand the speed range in which a gain of 0 dB can be obtained without tuning the PID control parameters. However, if there is only one frequency, amplification is possible with a single pre-emphasis coefficient. Therefore, a sine wave is suitable for this technique, unlike triangular and sawtooth waves. Hence, we can adopt a pre-emphasis technique to configure the parameters in advance, and we need not prepare additional active control models and hardware. The parameters are updated immediately within the next cycle because of the open loop after the pre-emphasis coefficients are set. In other words, to regard the controller as a black box, we need to know only the input-to-output ratio, and detailed modeling is not required. This simplicity allows our system to be easily embedded in applications. Our method using the pre-emphasis technique for a motion-blur compensation system and the experiment conducted to evaluate the method are explained.

The results presented here were obtained using an AD/DA board and a camera. Figure 1 shows the procedure of the pre-emphasis technique; therefore, it is the core of this article. It is unnecessary to set the parameters of the PID control after the initialization state; hence, the online process is significantly simple.
Figure 10 shows the results obtained by applying the pre-emphasis technique t...

We propose a method to extend the corresponding frequency by using a pre-emphasis technique. This method compensates for the gain reduction of a galvanometer mirror in sine-wave path tracking using proportional-integral-differential control.

Galvanometer mirrors are used for optical applications such as target tracking, drawing, and scanning control because of their high speed and accuracy. ...

The overall goal of this procedure is to demonstrate a technique to compensate for the gain reduction of galvanometer mirrors in sine-wave path tracking. Using proportional-integral-differential control for motion blur compensation. This method can be applied in the field of optical engineering to such problems as target tracking, scanning control and motion blur compensation.The main advantage of this technique is that it relies on pre-configured parameters and the input-to-output ratio, and does not require additional active contour models and hardware. Perform the experiment at an optical bench. And prepare a galvanometer mirror to mount on the bench.The mirror should be in a custom-made jig, to prevent the mirror and its body from moving during oscillations. Place the jig and mirror in an optical mount. Then, fix the mount to the optical bench to continue.Control the mirror with a computer equipped with an A/D D/A Board. Extend properly connected cables from the board to the mirror. There, connect the cables to the input and position sockets of the galvanometer mirror.At the computer, employ a graphical user interface for a sine-wave function generator. Program the interface to perform multiple trials while varying Frequency and Amplitude. For this experiment, use an outer loop over a frequency range.Set the Minimum frequency to 100 Hertz. Set the Maximum frequency to 500 Hertz. Increment the frequency by 100 Hertz.The inner loop is over the voltage amplitude. Use a minimum voltage of 10 millivolts. For a maximum voltage, use 500 millivolts.Increment the voltage by 10 millivolts. Enter the duration of the sine-wave path signal as 2000 samplings. Drive the mirror with the computer and simultaneously record its position signal and determine its angle.Use a separate file to save the data for each frequency, and each voltage amplitude. Once all of the data is collected, plot the output amplitude as a function of the input amplitude for each of the frequencies. Note that the data for the low frequencies show greater output amplitude as a function of input amplitude than the high frequencies.This demonstrates the reduction in gain as a function of frequency, for which this technique compensates. Exclude the non-linear behavior and focus on the approximately linear portion of the plots to obtain the pre-emphasis coefficients. This experiment requires a moving image in view of the mirror.To achieve this, employ a conveyor belt that can move at 30 kilometers per hour. The image for this experiment, a fine texture pattern, has been printed onto tape and applied to the belt. Now, move on to set up the optical elements.Arrange a camera with a telephoto lens, so that it can use the galvanometer mirror to track the motion of the conveyor belt. Ensure that the galvanometer mirror is connected to the control computer with pre-emphasis software. In order to capture decent images, illuminate the conveyor belt with an appropriate light source.At the bench, set the appropriate lens focus for the computer display. Next, work to synchronize the mirror and exposure time of the camera. Then, input the camera settings for the expected images.This image illustrates the timing used by the trigger software. As a function of time, the mirror angle is given by the blue sinusoidal curve. The Red triangle function represents the ideal mirror angle for a scan as a function of time.Center the exposure time when the angle is at zero degrees and moving with a positive angular velocity. This is where the two curves intersect. Set the software to trigger the camera half of the exposure time earlier and end half of the exposure time later.Using the pre-emphasis software, input the conveyor belt speed in kilometers per hour. Then, enter the distance from the camera to the belt in meters. The software will calculate the required angular velocity.Next, enter the frequency at which the mirror is driven. The software calculates the input amplitude. Use the amplitude in the pre-emphasis software.Once all the parameters have been entered, return to the conveyor belt. Start the belt moving at the speed used in the software to create a moving image. Start the control software and begin recording images from the camera.the controller compensates for the inertia of galvanometer mirror to improve image blur. Before the pre-emphasis technique, this was the plot of the output signal as a function of the input signal. After applying the technique, this is the plot.Almost all of the output plots are on the line y equals x. Similarly, before the pre-emphasis technique, this was the plot of gain as a function of the input signal. After applying the technique, almost all of the amplitude plots are on the line y equals zero dB.This is an image that was placed on the conveyor belt, shown when the belt is at rest. The blue line indicates where the profile at the right was taken. This is the same image when the conveyor belt moves at 30 kilometers per hour and no motion blur compensation is active.Here, there is motion blur compensation, but pre-emphasis is inactive. In this final version, both motion blur compensation and the pre-emphasis technique are active. It represents a great improvement over the two other options.Once mastered, this technique can be done in one hour if it is performed properly. After its development, this technique paved the way for researchers in the field of optical engineering to explore motion blur compensation in high-speed scanning.

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Learn a gain-compensation method for galvanometer mirrors using proportional-integral-differential control with pre-emphasis techniques. This approach minimizes motion blur in optical engineering applications without requiring additional hardware.

Gain-compensation Methodology for a Sinusoidal Scan of a Galvanometer Mirror in Proportional-Integral-Differential Control Using Pre-emphasis Techniques (Video) | JoVE Journal

Gain-compensation Methodology for a Sinusoidal Scan of a Galvanometer Mirror in Proportional-Integral-Differential Control Using Pre-emphasis Techniques

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