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 ------------------------------------------------------------------------------ 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
