4 research outputs found
Fast response Antiwindup PI speed controller of Brushless DC motor drive: Modeling, simulation and implementation on DSP
Most of the Brushless DC (BLDC) motors drive adopts proportional, integral and derivative (PID) controller and pulse width modulation (PWM) scheme for speed control. Hence, BLDC motor drive has strong saturation characteristics. The saturation results in a typical windup phenomenon. The paper presents an Antiwindup drive for BLDC motor. An Antiwindup controller (AWC) has been used in the paper. AWC has been modeled in MATLAB/Simulink and comparison has been done between conventional PI controller and AWC at different starting loads. Dynamic characteristics of the BLDC motor drive have been examined and results are presented and discussed in detail in this paper. Details of DSP based experimental validation of the simulated results are also presented here
A study on the effect of pulsed power ultrasound waves on marine biofouling
2169-2174<span style="font-size:9.0pt;line-height:
115%;font-family:" times="" new="" roman";mso-fareast-font-family:calibri;mso-bidi-font-family:="" "times="" roman";background:white;mso-ansi-language:en-us;mso-fareast-language:="" en-us;mso-bidi-language:ar-sa"="" lang="EN-US">Ultrasonic technique is one of the promising
non-invasive technologies to control biofilm formation on the marine
substratum. A prototype ultrasonic
system was designed and developed to control biofouling in the marine
environment. The Ultrasonic technique was utilized to control the biofilm
formation on copper test coupons suspended in a continuous seawater flow
through system. The colonization of microorganisms promotes settlement of higher
order organisms; therefore, deactivation of microorganisms is likely to affect
the fouling density. <span style="font-size:9.0pt;line-height:
115%;font-family:" times="" new="" roman";mso-fareast-font-family:"times="" roman";="" mso-bidi-font-family:"times="" roman";mso-ansi-language:en-us;mso-fareast-language:="" en-us;mso-bidi-language:ar-sa"="" lang="EN-US">Ultrasonic sound waves at 25 kHz with an
electric drive power of 500 watts were used to control aquatic biofouling and
growth in an open seawater circulation experimental setup. The ultrasonic waves
create microscopic cavitations which damages the outer cell structure of
microorganisms destroying them and preventing them from growing around the
ultrasound exposure areas.<span style="font-size:9.0pt;
line-height:115%;font-family:" times="" new="" roman";mso-fareast-font-family:calibri;="" mso-bidi-font-family:"times="" roman";background:white;mso-ansi-language:en-us;="" mso-fareast-language:en-us;mso-bidi-language:ar-sa"="" lang="EN-US"> The experiments were
conducted continuously over a period of 21 days and were repeated several times
to ensure reliability. A reduction in the microorganism activation was observed
on the ultrasound exposed area besides preventing damages to the structure of
the test coupon. Based on the encouraging results, a low cost prototype
ultrasonic digital system controlled by pre-programmed microchips was custom
built and the same is being planned for further studies in the frequency range
20 – 40 kHz. </span
Techniques adopted in the post processing of active sonar data from Royapuram site-off Chennai
164-171<span style="font-size:9.0pt;font-family:
" times="" new="" roman","serif";mso-fareast-font-family:"times="" roman";mso-ansi-language:="" en-gb;mso-fareast-language:en-us;mso-bidi-language:hi"="" lang="EN-GB">A buried object
detection SONAR has been developed by the marine sensors and systems group of
National Institute of Ocean Technology and the analysis of the data from a
specific site is reported in the paper.
Handling the unpredictable noise is a major concern in sonar signal
processing, especially in buried object detection sonar systems. To improve the
signal to noise ratio and also to preserve the boundaries of targets, special
post processing techniques are to be applied. Signal averaging is found to be a
useful technique in this regard and this paper compares and analyzes various
averaging techniques including moving averaging, exponential averaging, and
median filter. The exponential averaging with median filter is found to be one
of the best suitable methods for noise reduction in detecting buried objects in
shallow waters, since it significantly improves the signal to noise ratio by
preserving the boundaries of targets. It is
observed that the original sonar image with 6% noise level is improved
to 0.03 to 0.04 noise variance using the combination
of exponential moving average and median filter and the same trend is
observed up to 35% noise level when corrupted by
Gaussian noise. Performance evaluation of the techniques has been
carried out and is quantitatively verified with the data collected during the
sea trials.</span