On Thu, 2011-02-03 at 22:41 -0600, Igor Chudov wrote: > My opinion only: it is very hard to govern a small engine like Onan CCK with > mechanical fuel supply, to achieve perfect speed regulation in the face of > varying loads that are close to its rated power. > > There is a fundamental delay between any control system change and the > change in the amount of fuel burning in the cylinders. This alone makes any > tight regulation hard to achieve. > > If you have an electric servo motor, you can instantly vary supply of > electricity to it. With a fuel burning motor, there is always a delay > between change in control and amount of fuel available. > > A very large (and dangerous) flywheel may help.
The way I see it, the lag between the input throttle change and the rate of RPM correction should not be too much of a problem. The frequency regulation won't need to be more than +/- a few percent, the correction can take up to a second, and overshoots are allowed. A problem I have seen on a similar setup was a self energizing oscillation due to very poor PID tuning. Another problem that comes to mind, if the load suddenly increases the throttle can open quickly and drop the vacuum too far and cause a stall. It might be wise to also have a vacuum sensor to guard against the throttle opening too far. It might also be good to have the throttle set to idle or a start position until a valid vacuum is sensed. Low vacuum coupled to a low RPM could signal an engine overload. For sudden reductions in load, it might be handy to allow the throttle to close faster than the opening rate. > If you want encoder type feedback, just add a little rubber idler wheel to > an encoder and get a reading off of the alternator belt. > > i Sensing the AC output should be the same as a low count encoder, but if the output fails or the field gets turned off, this might be seen as the engine slowing down and cause the throttle to open all the way. Here is another place for a safeguard or a magnetic pickup might be more reliable. -- Kirk Wallace http://www.wallacecompany.com/machine_shop/ http://www.wallacecompany.com/E45/index.html California, USA ------------------------------------------------------------------------------ The modern datacenter depends on network connectivity to access resources and provide services. The best practices for maximizing a physical server's connectivity to a physical network are well understood - see how these rules translate into the virtual world? http://p.sf.net/sfu/oracle-sfdevnlfb _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
