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Engine speed governor

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sensiblefuel

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Hi, new to this forum so if this has been discussed before I am sorry,all I could find in the archives was one other fellow with a similar problem but no reply.

I have built a small diesel generator but the mechanical governor does not seem to respond quick enough.I would like to build an electronic governor that will also have overspeed shutdown protection.

I have built a couple of simple electronic controllers for my biogas projects from schematics but I am certainly not an electronics tech.

The engine is from a refridgeration unit that was electroniclly controlled so their is a sensor over the flywheel for speed siginal to the controller.

If anyone out their can help with this project it would be very much appreciated.

Thanks,
Danny
 
diesel gensets run best at 1800rpm. I think if you are going to alter the motors rpms to that of the electrical load, you'd be circumventing one of the benefits of going diesel over gasoline. The idea would be to have a generator/alternator large enough to handle surge loads while the motor still purrs near 1800.
 
sensiblefuel said:
Hi, new to this forum so if this has been discussed before I am sorry,all I could find in the archives was one other fellow with a similar problem but no reply.

I have built a small diesel generator but the mechanical
governor does not seem to respond quick enough.I would like to build an electronic governor that will also have overspeed shutdown protection.
Would you be interested in fixing the existing governor ?
Have you cleaned and lubed it ?
That would be easier.... What you are suggesting may be more then you want to do. Do you know how to program ?

On the other hand it would be a fun project.

The first step is to figure out how to use the flyweel sensor. In short build a digital tach. I am sure you can find examples of them on the web. Adapt one of the designs to use your flywheel sensor.

After the tach works do the throttle positioning Just the ability to move it and keep track of where it is.

When both the tack and the throttle positioning work you can start working on the control code. Even if you had the code to do it you would still have to find the right settings to get it to work with your engine/load. Search the web for info on the subject first. Then write the code. May even be an app for fuzzy logic. :)

3v0
 
Some thoughts to possibly help you along.

1. Is the output DC (generator) or AC (alternator)?
2. If DC, is your intent to run at a relatively constant voltage?
3. If AC, is your intent to run at a relatively constant RPM/Hz?
4. How much error can you tolerate? The more error you can tolerate the simpler the control can be.

A controller of this type might actually need to be quite complex depending on what you expect from it. It might help to read up a bit on proportional control - and see if you can google for some uncomplicated discussion on what is called PID control. I'll jump ahead and say that you might find proportional control to be sufficient for your needs with some occasional tweaking.
 
Thanks for the replies stevez,3v0 and HiTech,
I will try to address all of your questions and thoughts in a single post.

I have matched the KW of the generator head to the HP.of the diesel engine for opptimum fuel efficiency.It works fine up to approx. half the output but then starts to lag.I can manually increase the RPM's with the throttle lever and the engine responds quickly leading me to believe it has enough power for the job.

I have tried fixing the existing governer by replacing the internal tension spring with one that was designed for use with generators.The next step would be to take the pump to a specialist to have it rebuilt and bench tested.This would take 1-2 weeks and $800-1200.It is not so much the money but the down time.This generator set up is part of a stand alone co-generation project that is powering and heating my biodiesel manufacturing facility and can be not shut it down for that length of time this time of year.

I too feel that this would be a fun project as well as useful for other power generation projects.Because the system is working as is until I need more power, I have time to iron out the problems that will certainly arise building a governor.

I do not have the expertise to write code,the extent of my experiance is building a small,simple controller and setting its operating parameters.

The power I am producing is AC and need to keep my RPM as close to 1800/60 Hz as possible.I have a 10% RPM tolerance although I would Like to keep it closer to 5% if possible.

I will take the advice and do some research on the subjects suggested.

sensiblefuels
 
"It works fine up to approx. half the output but then starts to lag.I can manually increase the RPM's with the throttle lever and the engine responds quickly leading me to believe it has enough power for the job."
I think the spring position is the problem. Find the adjusting procedure. If the spring is farther out on the arm that it controls, it has more leverage. Closer, it works faster. Then readjust the RPM.
 
I am in the process of finishing up a home built diesel generator which suffers from the same problem. The stock governor would drop from 1800 rpm to 1700 rpm when a full load was applied. I was able to change to a longer spring and improve the performance somewhat, but still not to the level I was hoping for.

I built a controller based upon an ATMega8 which uses a stepper motor to "apply a bias" to the governor to correct for the rpm sag. I implemented a fixed point PID controller to do the job. I'm still tweaking the gain variables, but at this point, the controller keeps the RPM at 1800 +- 5 rpm regardless of load. (not counting excursions when load changes)

Here is a graph showing the system response from no load to full load. The purple line shows the stock configuration. The green line shows the response with the PID controller helping out.
**broken link removed**
I'm still working the kinks out of the PID controller. Because of my fixed point implementation, I'm having troubles getting the Integral portion to work without causing oscillation.

You can read about my project at http://martin.nile.googlepages.com/automaticgeneratorcontroller

The beta level software is available at http://code.google.com/p/ngencontrol/

The system is implemented in C and does a lot more than just controlling the RPM.
 
excellent work regarding your project

Dear Mr.Martin,
I analyzed your post and found it to be very knowledgeable. I have a request with you. could you please mail me your project to my mail id shanbhag@sequentindia.com. in pdf format. this is for my academic understanding only and is not intended for any commercial purposes.
Thanks and regards
Shrimant Shanbhag

I am in the process of finishing up a home built diesel generator which suffers from the same problem. The stock governor would drop from 1800 rpm to 1700 rpm when a full load was applied. I was able to change to a longer spring and improve the performance somewhat, but still not to the level I was hoping for.

I built a controller based upon an ATMega8 which uses a stepper motor to "apply a bias" to the governor to correct for the rpm sag. I implemented a fixed point PID controller to do the job. I'm still tweaking the gain variables, but at this point, the controller keeps the RPM at 1800 +- 5 rpm regardless of load. (not counting excursions when load changes)

Here is a graph showing the system response from no load to full load. The purple line shows the stock configuration. The green line shows the response with the PID controller helping out.
**broken link removed**
I'm still working the kinks out of the PID controller. Because of my fixed point implementation, I'm having troubles getting the Integral portion to work without causing oscillation.

You can read about my project at automaticgeneratorcontroller (martinnile)

The beta level software is available at ngencontrol - Project Hosting on Google Code

The system is implemented in C and does a lot more than just controlling the RPM.
 
electronic governor for gas engine

We are manufacturing elelctronic governor system for gas engine .contact me in email ;electrodynamics1@rediffmail.com or call me on 00-91-9892982324 on mobile

Regards
AS babu
 
You might try a weaker spring. The strength of the spring determines the feedback gain of the governor. A weaker spring requires less speed change to move the throttle a given amount to correct the speed. But too weak a spring can lead to hunting and oscillation of the speed. You just have to experiment to see how weak you can go. Obviously it has to be strong enough to overcome friction and open the throttle when the speed drops, so that's the lower limit.
 
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