# How to execute the same code for a specific time?

2 views (last 30 days)
saleh shlimet on 21 Jan 2023
Commented: Image Analyst on 22 Jan 2023
I want to estimate the shaft speed of a motor and to do that I obtain the speed error between the reference speed and the estimated speed. Then, if the error is greater than 10 the estimated speed multiplied by 1/3. if error is less than 10 then the estimated speed multiplied by a different gain. What I am looking for is when the error is > 10 I want the estimated speed multiplied by 1/3 for a specific time for example 1 second and not to be interrupted by anything even if the error becomes less than 10.

Image Analyst on 21 Jan 2023
Try a while loop. In the loop get the estimated speed and compute the error. Here is a start:
% Demonstration of how to avoid an infinite loop by setting up a failsafe.
% Set up a failsafe
maxIterations = 500; % Way more than you think it would ever need.
loopCounter = 0;
% Now loop until we obtain the required condition: a random number equals exactly 0.5.
% If that never happens, the failsafe will kick us out of the loop so we do not get an infinite loop.
refSpeed = 1000; % Initialize so we can enter the loop the first time.
estimatedSpeed = 1; % Initialize so we can enter the loop the first time.
speedDifference = abs(refSpeed - estimatedSpeed);
while speedDifference > 10 && loopCounter < maxIterations
loopCounter = loopCounter + 1;
fprintf('Iteration #%d.\n', loopCounter)
estimatedSpeed = however you get it;
speedDifference = abs(refSpeed - estimatedSpeed);
if speedDifference > 10
% Somehow change the motor speed.
end
end
% Loop is done
% Alert user if we exited normally, or if the failsafe kicked us out to avoid an infinite loop.
if loopCounter < maxIterations
% Then the loop found the condition and exited early, which means normally.
fprintf('Loop exited normally after %d iterations.\n', loopCounter);
else
% Then the loop never found the condition and exited when the number of iterations
% hit the maximum number of iterations allowed, which means abnormally.
fprintf('Loop exited abnormally after iterating the maximimum number of iterations (%d) without obtaining the exit criteria.\n', maxIterations);
end
fprintf('All done after %d iterations.\n', loopCounter)
I'd recommend you do a bilinear search to home in on the best speed rather than doing the 3* or 1/3* multiplication.
saleh shlimet on 22 Jan 2023
Thank you for your answer. I do not know if you understood my question. to make it clearer see attached. I have two input variables, estimated speed and reference speed. If the error is less than 10 then the output is estimated speed *1/3. If the error >10 then the output is estimated speed*1/4, but in this case(error>10) I want the output to stick to this value(estimated speed*1/4) for a period of time for example 0.5 second even if the condition changed to error<10. I thought the while loop could sort it out but it failed.
Image Analyst on 22 Jan 2023
Use pause
pause(0.5); % Wait 0.5 seconds.

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