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BlurDavinci

Syncronization

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Guys: I would like to know how to make two Servo Motor syncronize making use only Analogue Output and External Encorder and a Fast Counter Module with Controllogix. ( Pls don't ask me why Axis Driver is not used, there is no way to change the module at the moment, NO BUDGET! HA HA). Two Encoder with 1000 pulses/rev Scenario: Rotary Movement 0 to 5000 ( which translate to 5000 -->1 revolution, well) with speed control by means of Analogue Output. Horizontal Movement in milimeter . Case---> If Horizontal movement target is 20mm, but will have to tie with Rotary Action. i.e rotary action is master, say the target is 1000 at the speed 0f 30%, if it achieve target, the horizontal movement must be hitting the Target as well (20mm for example). How do I write the formulae?

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HI: Can the Motion Group and Motion Instruction be used with normal Analog Ouput and External Encoder? I read some sample but those are link to power flex. I have a difficult task as current hardware limitation. The Controllogix equiped only with 1 Analog Output Card (4 Channel of +/- 10v) and 1 HSC Card (2 Channel). I could not figure out how to syncronize the 2 axis (well accuracy may not seems to be a problem). Both Axis (1 rotary and 1 linear (horizontal)) will have to be syncronize in order to complete individual task in sync. As the Target for Both can be vary depending on setting . Can Some one provide me some guidance? Thanks Library_VR_2Axis_PF700_L6x_V01_01.ACD

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I'm not sure how to help you, but you only need 1 topic per subject. It's impolite to spam up the board with the same problem. I'd say stick with the other topic because you offer up more info, but attach your .acd file there as well.

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Fixed Thanks TW

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I don't have my Logix PC home this weekend to open your code, but let me see if I get your question correctly. You have two Axes - Axis One is Circular is driven by an analog output {assume 4-20 ma} and provides feedback from an encoder thru a HSC input {assume 5000 counts per revolution}. Axis Two is Linear is driven by an analog output {assume 4-20 ma} and provides feedback from an encoder thru a HSC input {assume 5000 counts per 20 mm}. You need the axes to move in sync count for count and stop at relatively the same time. Now the stuff you didn't give us that will make or brake us is: You don't mention if the driving motors are servo or VFD but I suspect VFD driven. You don't mention minimum or top speeds and ACC/DEC curves could kill everything. You don't mention inetial loads and this will affect sync as well. Now what I can answer. IF for example the axes are geared such that 30 hz produces 100 rpm on the final axis circular and 30 hz produces 2000 mm/min on the linear axis then with identical acc and dec you only need feed the same signal to both. IF they gear differently this become a calculation nightmare.

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Also you don't mention how far out of sync they can get and how big of a mess you are going to have when, not if, they get out of sync.

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No it is really quite simple, at a basic level. There is no reason why Blur can't maintain a ratio between mm and angle. The problem is that one needs to calculate feed forwards to keep the lag from causing following errors. There is also this little problem with the 'chain rule'. Look it up. It is first year calculus stuff. The point is that if Blur really understood what he was asking he would make a case to have his budget expanded. As for the rest of you, you have done a good job of dodging the real problem.

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The answer to Blur's budget restraints could be explained in a simple ROI ( Return On Investment). I go thru this on a daily basis. So much so I spend almost as much time doing accounting as I do engineering. That being said, what your asking is a gear ratio with acel/decel figured in. If A needs to move at X speed to get to a point then how fast does B need to move to get to its same point at the correct time. So at the end if A is master then B better be able to react faster. The first thing I would do is make sure my accel and decel on A was slower than B. Where I work we do this little job every day. We use robots to remove parts from injection mold machines. We watch how fast the mold is moving then we know how fast we can move the robot arms in. If we know the velocity the mold is moving and where it is going to slow down then we can calculate where the robot arms need to be at the same time. Basically if the mold is moving at X mm/per second the we know it will be at a certain position at a certain time. The tricky part is when the mold is decelerating. This is when the distance moved in time is constantly changing, hince my earlier statement, B needs to be able to react faster than A. FYI... I headge my bets. If my robot has moved futher than it should have I have sensors to detect this and shut the robot down.

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Clay B, the point is that you have a motion controller and you didn't roll your own. It is easy to set up the motion in your case because you can jog the mold and then jog the robot to where it should be and then hit a button and the master and slave positions go into your cam tables ( one for each robot axis ). You then repeat this process for the range of motion. This makes programming easy but again, the software that allows you to do that is in the motion controller. Blur is trying to reinvent the wheel and do it on a PLC too. 1. A PLC is not the right platform to do this. 2. The math would require more than just a few post on a forum 3. Would you even understand the math? There is some calculus involved. The math skills on these PLC forums is not good. Buy a good motion controller.

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