Servo Feedback Control of an Audio Subwoofer by Dalimar Vélez Advisor: Shawn Hunt.
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Transcript of Servo Feedback Control of an Audio Subwoofer by Dalimar Vélez Advisor: Shawn Hunt.
![Page 1: Servo Feedback Control of an Audio Subwoofer by Dalimar Vélez Advisor: Shawn Hunt.](https://reader035.fdocuments.in/reader035/viewer/2022062421/56649d005503460f949d177c/html5/thumbnails/1.jpg)
Servo Feedback Control of an Audio Subwoofer
by
Dalimar Vélez
Advisor: Shawn Hunt
![Page 2: Servo Feedback Control of an Audio Subwoofer by Dalimar Vélez Advisor: Shawn Hunt.](https://reader035.fdocuments.in/reader035/viewer/2022062421/56649d005503460f949d177c/html5/thumbnails/2.jpg)
Overview
• Objectives• Background and Concepts• Problem• Implementation Design• Procedure• Results• Conclusion
![Page 3: Servo Feedback Control of an Audio Subwoofer by Dalimar Vélez Advisor: Shawn Hunt.](https://reader035.fdocuments.in/reader035/viewer/2022062421/56649d005503460f949d177c/html5/thumbnails/3.jpg)
Objectives
• Designing and building a Digital Servo-Feedback Control of an Audio Subwoofer.
![Page 4: Servo Feedback Control of an Audio Subwoofer by Dalimar Vélez Advisor: Shawn Hunt.](https://reader035.fdocuments.in/reader035/viewer/2022062421/56649d005503460f949d177c/html5/thumbnails/4.jpg)
Background and Concepts
• A subwoofer is a speaker who reproduces low frequencies (20 to 500 Hz).
• An accelerometer measures the acceleration of a system. (ex. ADXL150)
• Harmonics are integral multiple of the fundamental frequency.
nffh
![Page 5: Servo Feedback Control of an Audio Subwoofer by Dalimar Vélez Advisor: Shawn Hunt.](https://reader035.fdocuments.in/reader035/viewer/2022062421/56649d005503460f949d177c/html5/thumbnails/5.jpg)
Background and Concepts
• Filters:– Low pass
– Adaptive filter structure for system identification
– Adaptive filter structure for noise cancellation
Pass Band
Wc
Stop Band
W
H|(jw)|
Unknown System
X(n)
d(n)
y(n)+
- e(n)Adaptive Filter
n‘(n)
d(n)
y(n)+
- e(n)Adaptive Filter
s(n) + n(n)
![Page 6: Servo Feedback Control of an Audio Subwoofer by Dalimar Vélez Advisor: Shawn Hunt.](https://reader035.fdocuments.in/reader035/viewer/2022062421/56649d005503460f949d177c/html5/thumbnails/6.jpg)
Problem
• The subwoofer creates most of the harmonic distortion in a speaker.
• To improve this:– Measure subwoofer motion cone– Compare the output with the input– Correct the difference
This is called a Servo Feedback Control
![Page 7: Servo Feedback Control of an Audio Subwoofer by Dalimar Vélez Advisor: Shawn Hunt.](https://reader035.fdocuments.in/reader035/viewer/2022062421/56649d005503460f949d177c/html5/thumbnails/7.jpg)
Implementation Design
• In order to reduce the noise in the subwoofer output is essential to know the distortion added by the system to the input signal.
• A system identification adaptive filter was developed to obtain the response of the subwoofer.
• This response is going to be used to modify the input of the subwoofer.
• These modifications will cancel the distortions, making the output of the subwoofer clearer.
![Page 8: Servo Feedback Control of an Audio Subwoofer by Dalimar Vélez Advisor: Shawn Hunt.](https://reader035.fdocuments.in/reader035/viewer/2022062421/56649d005503460f949d177c/html5/thumbnails/8.jpg)
Procedure
• Music is filtered by a low pass.
DSP Board
ADC LPF AdaptiveFilter DAC
Weights
Music
Acc
AdaptiveFilter
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Procedure• The accelerometer is connected directly to the
cone, without signal amplification, to an Analog to Digital Converter (ADC) in the DSP board.
DSP Board
ADC LPF AdaptiveFilter DAC
Weights
Music
Acc
AdaptiveFilter
![Page 10: Servo Feedback Control of an Audio Subwoofer by Dalimar Vélez Advisor: Shawn Hunt.](https://reader035.fdocuments.in/reader035/viewer/2022062421/56649d005503460f949d177c/html5/thumbnails/10.jpg)
Procedure
• Develop algorithm for feedback loop.
DSP Board
ADC LPF AdaptiveFilter DAC
Weights
Music
Acc
AdaptiveFilter
![Page 11: Servo Feedback Control of an Audio Subwoofer by Dalimar Vélez Advisor: Shawn Hunt.](https://reader035.fdocuments.in/reader035/viewer/2022062421/56649d005503460f949d177c/html5/thumbnails/11.jpg)
Procedure
• Develop algorithm for frequency response and motion deviations correction.
DSP Board
ADC LPF AdaptiveFilter DAC
Weights
Music
Acc
AdaptiveFilter
![Page 12: Servo Feedback Control of an Audio Subwoofer by Dalimar Vélez Advisor: Shawn Hunt.](https://reader035.fdocuments.in/reader035/viewer/2022062421/56649d005503460f949d177c/html5/thumbnails/12.jpg)
Photos
![Page 13: Servo Feedback Control of an Audio Subwoofer by Dalimar Vélez Advisor: Shawn Hunt.](https://reader035.fdocuments.in/reader035/viewer/2022062421/56649d005503460f949d177c/html5/thumbnails/13.jpg)
Photos
![Page 14: Servo Feedback Control of an Audio Subwoofer by Dalimar Vélez Advisor: Shawn Hunt.](https://reader035.fdocuments.in/reader035/viewer/2022062421/56649d005503460f949d177c/html5/thumbnails/14.jpg)
Photos
![Page 15: Servo Feedback Control of an Audio Subwoofer by Dalimar Vélez Advisor: Shawn Hunt.](https://reader035.fdocuments.in/reader035/viewer/2022062421/56649d005503460f949d177c/html5/thumbnails/15.jpg)
• Distortion produced by the cone:
Results
![Page 16: Servo Feedback Control of an Audio Subwoofer by Dalimar Vélez Advisor: Shawn Hunt.](https://reader035.fdocuments.in/reader035/viewer/2022062421/56649d005503460f949d177c/html5/thumbnails/16.jpg)
• The green graph represents the input of the system and the violet graph shows the output distortion created by the subwoofer
Results
![Page 17: Servo Feedback Control of an Audio Subwoofer by Dalimar Vélez Advisor: Shawn Hunt.](https://reader035.fdocuments.in/reader035/viewer/2022062421/56649d005503460f949d177c/html5/thumbnails/17.jpg)
Results
• The adaptive filter identified the response of the subwoofer system.
• The algorithm reduced the harmonic distortion.
• The 180 Hz harmonic for this case was attenuated from -46.5dB to -65 dB.
![Page 18: Servo Feedback Control of an Audio Subwoofer by Dalimar Vélez Advisor: Shawn Hunt.](https://reader035.fdocuments.in/reader035/viewer/2022062421/56649d005503460f949d177c/html5/thumbnails/18.jpg)
Conclusion
• The distortion was caused by the physical properties of the subwoofer driver.
• The reduction of harmonics at the output of the subwoofer was accomplished thanks to the usage of the coefficients found by the adaptive filter.
• The hardware can be implemented in any other application independently of the driver used.
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References
• [1] ±50g Single Axis Accelerometer with Analog Output - http://www.analog.com/
• [2] Harmonic – http://whatis.techtarget.com
• [3]Chassaing, Rulph. DSP Applications Using C and the TMS320C6x DSK. John Wiley & Sons, nc, NY 2002
• [4]Antoniou, Andreas. Digital filters, analysis, design and applications, 2th ed. Mc Graw Hill, Inc ,1993.
• [5]Doucet, Dougla., Fasani Rob. Hasenkamp, Pete r. and Senesky Matthew. Using an Accelerometer to Make an Active Subwoofer.
www.webee.com/Schematics/Active%20Subwoofer/SubWoof.htm#con
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Questions?
For more info:http://ece.uprm.edu/~s998705/investigacion.htm