On 10/18/2011 9:57 PM, Dave wrote: > On 10/18/2011 9:34 PM, Tom Easterday wrote: > >> On Oct 18, 2011, at 9:06 PM, sam sokolik wrote: >> >> >>> Could you explain your system a little. When you where explaining it on >>> irc - It seemed to me that you had a bit too small of servos for the >>> application you had. iirc - you have about 1.5 turns of the servo per >>> inch? or was it 2.5 turns per inch? Again - It was just a feeling. >>> >>> >>> >> We think the motors are a good size for what we designed. They might be a >> little too big if anything This might be part of the problem we are having >> tuning it, that the truck is fairly light and motor fairly beefy. One turn >> of the motor is pi/2 (1.57) inches of movement linearly. Another thing we >> think might be of issue is that we are using rack and pinion and that it >> isn't 100% linear either. Servos tend to like a consistent load and we >> think some areas of movement along the rack are easier, some are harder, >> just due to the inaccuracies of the rack and pinion and the design of the >> bearings/rails/assembly we are using. All of this is speculation at this >> point, just things we have discussed. We thought we had made progress on >> tuning the Granite drives but when we went to run EMC, the axis will fault >> fairly often even at very low accel and speeds and nearly always faults at >> one specific location (within a couple inches of a specific point). We have >> scrutinized that place and can see nothing different from another other >> place, but it just faults there quite often and when moving in one specific >> direction. It is baffling. We have been over the mechanicals and wiring >> separately and together (two of us having been working on this), and we are >> quite sure everything is mechanically sound and nothing is wired incorrectly >> or improperly. >> >> These are the motors: http://www.kelinginc.net/KL34-180-90.pdf >> >> We are really about to give up and put steppers on it. >> -Tom >> >> >> >> > Tom, > > 1 turn of the motor to 1.57 inches of movement sounds like you are very > short on gear reduction. You likely have too much reflected inertia > from the load at the motor shaft. > > If you have an inertial mismatch that is too great, the servo system > will be impossible to tune. > > http://www.copperhillmedia.com/VisualSizer/ > I've used this software with great success. It has a little bit of a > learning curve, but it is used as the basis of many other commercial > servo sizing software packages. > > The software is free. Get the specs from Keling on your motors rotor > inertia, make a model of your loads in the software and it will likely > become clear that you have a mismatch and need more gear reduction. > > Dave > > > > Tom,
If you try that software and get stuck, drop me a private email. I go through Ann Arbor once in a while. I'm northeast of Fort Wayne, IN. I'm very familiar with Ann Arbor. I grew up in Plymouth, MI and still have family in the area. I'm guessing that you will need either a 5:1 or 10:1 reduction to make that work. Keling had some inexpensive (relatively) Nema 34 in and out gear boxes for sale the last time I looked that might solve your problems. Dave ------------------------------------------------------------------------------ All the data continuously generated in your IT infrastructure contains a definitive record of customers, application performance, security threats, fraudulent activity and more. Splunk takes this data and makes sense of it. Business sense. IT sense. Common sense. http://p.sf.net/sfu/splunk-d2d-oct _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
