H2-CTRIO(2) IBOX Load Profile Limit input

[Dan R]

I'm using the IBOX load profile instruction to run a parallel synchronous pick and place system using pulse (step/direction). My homing search profile works well but the limit 1 options are limited to channels on the CTRIO card itself.  In this case - Ch1C.  Since I intend to use encoders for both motors (fed through the one CTRIO card) I will be using the Ch1C input with one of my encoders.  I'd like to use this simple IBOX Load Profile instruction with my Limit 1 input as a simple DC input from anothed card in my PLC rack. Is this possible using the IBOX instruction with say input X1 from a D2-16ND3-2 card?

[BobO]

Sorry, no. In order to deliver the tighter timing that is expected from a high speed module, it is necessary for the I/O to be directly on the module itself.

You could certainly use a velocity profile and control it from PLC logic. For homing that might be fast enough.

[Dan R]

I'm back at the H2-CTRIO(2) phase of the project after installing the two drives onto the machine (press). As a test I have an S-Curve profile and Trapezoid Plus profile loaded plus a Home and Jog circuit.  My HMI allows me to test all these profiles in a Test mode (press is idle).  Also, in the Run mode (press is cycling) I can test the Trap & S-Curve profiles alone.  In the Test mode I can move the drives without an issue by means of the HMI's screen push-buttons (Up & Down). But when the press is in the Run mode, the pulse signal that initiates the S-Curve or Trap profile will either allow the drives to run as they should (down then up with each press cycle) or they move the short distance in the opposite direction, reach their max travel proximity sensors and stop due to logic. And to further complicate things, when I enter the Run mode and select the Trapezoid profile, only the S-Curve now operates - and occasionally it faults out due to opposite travel (max travel proximity sensor).  My Trap profile seems to be ignored even though the logic shows that's the profile selected.

My ladder logic shows all profiles have successfully loaded per the IBOX control bits.  Likewise, none of the IBOX fault bits show faults.  So all my profiles are loaded and I select which one is to be used through the ladder logic.  Only one profile is programmed to run at a time, e.g. in RUN Mode with TRAP profile selected - both drives run up, momentary delay after full travel per the pulse train value, then both drives are to move down full travel. That's one press cycle. I enter the pulse train length through a numeric data entry.

Sometimes this works in the RUN Mode, sometimes not (by moving in direction opposite to the intended direction and reaching max travel).

Not sure what's going on here.  Any idea what might be causing this erratic action?

[ATU]

 Can you post your project file or send it to me, I'll take a look at it.

[Dan R]

Will do Monday. Using the IBOX instruction to control the CTRIO outputs is the Reset instruction required? I'm not using it in my program.

[Dan R]

I now realize where my problem was. That being the CTRIO's pulse train only runs once per load command.  I read that before but I thought that since my success and error bits remained true (after the pulse train completed) I didn't need to repeat the IB-1001 CTRIO Load Profile ibox instruction each time I wanted the stepper motors to actuate.  I was relying on logic of the success and error bits (within the ibox instruction) along with other logic (found in my ENABLE OUTPUT output bits for the CTRIO)when attempting to put the motors in motion.  When I added a store positive differential contact to each of my IB-1001 Load Profile rungs at the beginning of my program, the motors actuated as intended when the machine went into its run mode.

I should have read that chapter more closely.  But I still don't know for certain if a RESET bit (output) rung is necessary for ibox instructions.  Maybe I should read on.

[Greg]

Dan R: "I now realize where my problem was. That being the CTRIO's pulse train only runs once per load command."

Actually, more accurately, you can repeat the pulse train by simply toggling the Enable Output bit (ON --> OFF --> ON).

Dan R: "But I still don't know for certain if a RESET bit (output) rung is necessary for ibox instructions."

Not entirely clear what you mean by this. The CTRLDPR IBox executes once and runs to completion each time it is enabled. That instructions copies the configured table from CTRIO RAM into its operating RAM for the particular CTRIO output you designate. After it is completed you need to enable that output with the Enable Output bit. That's when the pulse profile will execute. To execute that profile again you do not have to reload it (re-execute the CTRLDPR IBox), instead, as I mentioned above, you can reset the Enable Output bit OFF and then set it back ON.

[Dan R]

Strange thing now seen - both drives are inching from their stop points but in one direction only. The program is rather straight forward. The steppers are driving linear belt drives. Both drives start in the up position (top dwell position),then downward travel (100,000 pulses), then bottom dwell for half second, then upward travel (same 100,000 pulses), then top dwell again for same half second, constantly repeats cycle of down, wait, up, wait, down...  One drive motor must turn clockwise while the other turns ccw in order for them to travel parallel & synchronous.

What I see is motor "A" slowly inches upward each cycle from its stop point in the top dwell position and motor "B" slowly inches downward each cycle from its stop point in the bottom dwell position.  The "inching" distance is equal for each motor. I tied in an encoder to monitor the position for motor "A" and programmed in an up/down counter. The down stroke always gave me the exact 100,000 pulse reading as what I have programmed in the Trap+ profile.  But the upstroke always ends with 4 pulses displayed. Every stroke the accumulated value at the end of the upstroke has another 4 pulses added.  4, 8, 12, etc. This happens for motor B in the bottom dwell position.

Any idea what might be resulting in the 4 pulse incremental offset?
Also, I'm using a brake on each stepper motor as a safety device to prevent travel when employees are setting up the machine. Is it not advisable to make use of the brake to assist in accuracy? Would I be overtaxing the brake by cycling it on every time the stepper motor Enable Output is energized? 

 

[ATU]

What is the resolution of the stepper motor?

[Dan R]

2000 step/rev
The drive is Automation Direct's STP-DRV-4850 configured for pulse & direction.

[ATU]

Is the move repeatable or is the error accumulative?

[Dan R]

Accumulative. 4 pulses each cycle.

[ATU]

Are you 4 pulses short when you come back to top stop or over shoot by 4?  How is your inertia match with the load? Is it possible to try it with no load, only the motors running?

  

[Dan R]

Yes - 4 pulses short. I had just altered my inertia to a default of (1.0 x rotor inertia). Under the motor config I have set up for my NEMA 23 motor: holding torque 2.0Nm, max A 5A, rotor inertia 0.48Nm, waveform smooth 25,phase 0,max volt 100%, max lead angle 120 at 25 rev/sec

idle current delay 0.40 sec, idle current % 50%, load inertia 0.497 kgcm2, wave smooth off

[BobO]

You are using a trap+ profile? Are you using encoder feedback?