Delta Motion with AD SureServo

Brian123

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Join Date
Sep 2007
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Nebraska
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307
Hello all,
I will be working on a motion project for the first time shortly and am looking for a few tips to get it going.

The machine is a single axis vertical position application. It uses a ballscrew with a directly connected servo to position the load, which rides on linear bearings. The ballscrew has proximity sensors mounted to the case to provide physical up/down limits and a home position.

I am going to use an AD SureServo (with brake) to move the carriage. Unfortunately, the integrated indexing isn't quite advanced enough to provide the proper motion control that we will require, so I will be using a Delta RMC75E to perform this task.

I am assuming that the preferred configuration for this type of system is to put the servo into velocity control mode (it supports position, velocity and torque modes) and have the RMC provide a velocity signal. It seems obvious to me that the home prox switch should be wired to the RMC, but I'm a little fuzzy on the preferred connection of the limit switches. I'm thinking that the RMC would be better able to use the information, but somehow the system would seem safer if the limits were wired directly to the servo drive.

I'm guessing a middle ground is actually the preferred arrangement. The limit switches wired to the RMC as inputs and an output wired from the RMC to the servo as a Drive Enable signal.

Any thoughts? Hopefully someone that has used this combination (or similar) can point me in the right direction.

Brian
 
I am assuming you have a RMC75E-QA1.
I wish you said what the application is. Most vertical systems require position control. You can specify a speed and acceleration you want to use to get to the desired position using the Move Absolute command. The controller will output +/- 10 volts to your drive. The drive should be put in 'dumb' mode and only act as a velocity loop where the drive controls to a speed proportional to the voltage we send it.

Wire the home, negative and positive proxes to the RMC directly. Also, there is an enable output that should be run from the RMC to the drive or break. There should also be a fault signal generated by the Sure Servo that can used as an input to the RMC.

This should work well. However a lot depends on the velocity loop inside the drive ( AD Sure Servo ) and how it is tuned. If the Sure Servo has a good auto tuning algorithm this shouldn't be a problem.

For best performance you can run in torque/current mode but this can be dangerous. WARNING, YOU MUST USE THE BRAKE. In torque/current mode the RMC's output will go to 0 when there is a fault depending on how the auto stop bits are configured. If the RMC's output goes to 0 there will be NO braking torque to stop the load so the load will coast to a stop or crash which ever comes first. It is best not to let the load coast after an error so use the brake.

Since this is your first time I recommend using the velocity mode so when the RMC gets a fault it will output a 0 volt signal to the drive and the drive and brake will stop the load.

We do have a forum at forum.deltamotion.com. There isn't as much activity there but we get notifications when people post questions.
 
I am assuming you have a RMC75E-QA1.
Yep, that's the one. I don't actually have it yet, but my understanding is that you guys are working diligently to fulfill the order I placed through a distributor. :)

I wish you said what the application is. Most vertical systems require position control. You can specify a speed and acceleration you want to use to get to the desired position using the Move Absolute command. The controller will output +/- 10 volts to your drive. The drive should be put in 'dumb' mode and only act as a velocity loop where the drive controls to a speed proportional to the voltage we send it.
The application is simply a vertical carriage positioning application. The machine is a induction heat-treating machine. The part to be heat-treated (say, a machined shaft, for instance) is placed in the carriage between suitable centers. When the cycle is started, the carriage will move the part into the heating coil and quench rings, then scan across a portion of the part at some specified rate, then move to a cooling position, then return to a load/unload position. All of these positions, scan rates, and dwell times are editable by the operator, including the number of steps for a particular part. Some of these steps will just be a change in the rate of scanning speed when a particular position is reached. These are the motion profiles that are just a bit too complicated for the AD stuff to do.

Edit: Simply put, this application will be based on absolute position control.

In addition, the machine will need to be put into a manual mode where the axis can be jogged and homed, but I'm guessing that will be simple stuff.

Wire the home, negative and positive proxes to the RMC directly. Also, there is an enable output that should be run from the RMC to the drive or break. There should also be a fault signal generated by the Sure Servo that can used as an input to the RMC.
Ok, that's what I was thinking would be the logical thing to do. The SureServo can operate the brake based on the enable servo input that will get from the RMC. Also, there is a fault signal that can be wired back to the RMC.

This should work well. However a lot depends on the velocity loop inside the drive ( AD Sure Servo ) and how it is tuned. If the Sure Servo has a good auto tuning algorithm this shouldn't be a problem.
No idea on the tuning algorithm quality in the SureServo, but I'm guessing it's at least decent. I was hoping that others might have chimed in on this front.

One of my main concerns is the variety of parts that we run on these kind of machines. I need to weigh the carriage itself, or get an approximation. The parts we place on the carriage can be anywhere from fractions of a pound to 150 pounds. I'm not sure what fraction of the carriage (and therefore the percent variation of the total load) that is.

For best performance you can run in torque/current mode but this can be dangerous. WARNING, YOU MUST USE THE BRAKE. In torque/current mode the RMC's output will go to 0 when there is a fault depending on how the auto stop bits are configured. If the RMC's output goes to 0 there will be NO braking torque to stop the load so the load will coast to a stop or crash which ever comes first. It is best not to let the load coast after an error so use the brake.
I wondered if this mode was possible. And yes, there are additional complications to using this mode. Would the servo enable output from the RMC go to off when the axis faults? If so, the SureServo should disable its output and apply the brake automatically.

Since this is your first time I recommend using the velocity mode so when the RMC gets a fault it will output a 0 volt signal to the drive and the drive and brake will stop the load.
I think I might proceed with configuring the machine in velocity mode. The only thing that worries me about this approach is that I have two places to adjust tuning for the axis as a whole, and the interactions might be a little confusing. If the drive were in torque mode, there is no tuning to adjust in it (I think...), so all of the tuning would be done in the RMC. It seems that this might be simpler, in a sense.

We do have a forum at forum.deltamotion.com. There isn't as much activity there but we get notifications when people post questions.
I did see the forum that you have, and have read through many of the threads there. I decided to post here as there is better traffic, and I already have an account :) I knew that you were a regular here and would probably stop by.

Thanks for taking the time to discuss my application!
 
I jogging is easy. I prefer doing it in closed loop mode. I usually give a command to the positive or negative limit or just short of the limit when the jog button is pushed. When the job button is released issue a stop command. Use the event triggers for this.

Homing requires a slow move velocity command towards the home limit switch. Some times the negative limit switch will do. Then the arm home command is issued and then the motor is told to move in the other direction until the z pulse resets the position then the motor is told to stop.
 
I jogging is easy. I prefer doing it in closed loop mode. I usually give a command to the positive or negative limit or just short of the limit when the jog button is pushed. When the job button is released issue a stop command. Use the event triggers for this.

I noticed this method in the example videos. Seems like a good way to handle jogging. I'm guessing that for jogging before the axis is homed, an open loop velocity command will need to be used to move the carriage around.

Homing requires a slow move velocity command towards the home limit switch. Some times the negative limit switch will do. Then the arm home command is issued and then the motor is told to move in the other direction until the z pulse resets the position then the motor is told to stop.
I'm planning to have the operator position the carriage in a suitable position (say within 1 inch of the home limit, but below it) using velocity commands. When they have the carriage positioned properly and it is stopped, they would press a button on the HMI to start a home routine. It sounds like the routine would be to Arm Home, then send a slow Move Velocity command toward the home switch. Once Home is found, I can stop the axis. I suppose I could additionally watch how much relative distance has passed and limit the home routine to something like 3" total travel, in case the home switch is broken or something. Not sure that that would really be necessary..
 
You can use the move velocity command while homing. Yes you can use open loop but the move velocity command will be more consistent.
Hmm, Ok. I think I was confusing some terms. For some reason, I was associating open loop with 'not homed yet', but now that I think about it a bit more, I can see how that wouldn't be the case.

I'm guessing that more of the terminology will become clear once I have a better chance to dive into the programming.
 
With the RMC, I believe that when Peter says "open-loop" he is referring to a pure voltage output. For example, just telling the RMC to output 5VDC (on a +/- 10VDC scale) to the drive. No feedback is involved, and what actually happens with the motor is purely up to the drive.
 
With the RMC, I believe that when Peter says "open-loop" he is referring to a pure voltage output. For example, just telling the RMC to output 5VDC (on a +/- 10VDC scale) to the drive. No feedback is involved, and what actually happens with the motor is purely up to the drive.
Yeah, after reading a bit more in the manuals, your description seems to be the proper one for open-loop operations.
Thanks!
 
Open loop is a pure voltage output.
The reason I said homing can be done using a move velocity is that the positions do not need to be calibrated, homed, to use a Move Velocity command. However changes in encoder counts are still used to make sure the motor is moving at the correct speed.
 
Open loop is a pure voltage output.
The reason I said homing can be done using a move velocity is that the positions do not need to be calibrated, homed, to use a Move Velocity command. However changes in encoder counts are still used to make sure the motor is moving at the correct speed.
That makes sense. Thanks for the clarification!
 

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