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Closed Loop with HiCON Integra
« on: November 25, 2014, 04:58:55 PM »
Hi Guys,

I am using the HiCON Integra Motion Controller with Panasonic Servo Systems MINAS A5 and Mach3 for a milling machine. Today all works fine  :)
As a next step I want to activate and use the closed loop feature of the HiCON Controller, but I have no idea what is useful and possible.
In the attached PDF file you can see the actual configuration and two potential options.
Currently I do not understand what the advantage when I use the pulse output of the Servo Controller for the HiCON feedback. (Similar the Drive Interface Board EPx-DIB from Vitalsystems)
I think the use of an additional linear encoder is much better because of direct measure of the axis and backlash compensation...
Is it possible to configure this? Rotary- and Linear Encoder has different resolutions!
Has anyone experience with closed loop?

Many thanks in advance for your help
Florian
« Last Edit: September 28, 2015, 05:15:07 PM by Vital System Support »
Re: Closed Loop with HiCON Integra
« Reply #1 on: November 25, 2014, 07:47:18 PM »
On HiCON Integra, you get these features when Closed loop option is enabled:

1.  Closed loop will account for any missing steps during transmission, and will compensate them at the start of the next move.  It will prevent any error from accumulating.

2.  You only home (reference) the machine once.  even if mach resets or estops, the axis position is not lost.

3.  You see the actual position of the axis from the Motor Encoders on Mach DROs. The step counters are not shown on mach DROs.

4. Manual mode operation.

5. 6 Additional Encoder Channels on the base units are enabled.  The pins are single ended type and available on J7 and J8.  You can use the 7737 breakout board to convert them to 5Volt Differential and RJ45 plugs.

6.  You can use the linear encoder instead of the encoder output on the servo drive.  Using the feedback gain you can match the step resolution.

hope this helps
Regards,
VitalSystem Support
Re: Closed Loop with HiCON Integra
« Reply #2 on: November 27, 2014, 01:26:33 PM »
Hello,

thank you for your quick reply! I think I understand it :-)
First i will try to use the encoder output on the servo drive.
In a second step I will use a linear encoder together with the servo driver in
full-closed mode. In full-closed control the servo drive works with an external scale for position feedback.
The encoder output source is mapped to the external scale.
Let's see if this works....

Is the closed loop fuction of the HiCON across all used axes?
In other words: Will a second or third axis wait until the first axis finished the previous move?

Yours sincerely
Florian
Re: Closed Loop with HiCON Integra
« Reply #3 on: November 27, 2014, 04:20:11 PM »
yes, the closed loop feature is applied to all axis independently.  one axis don't have to wait on other axis.

regards,
Rufi
Re: Closed Loop with HiCON Integra
« Reply #4 on: November 27, 2014, 04:47:05 PM »
Is this good? I think about driving curves.

regards
Florian
Re: Closed Loop with HiCON Integra
« Reply #5 on: December 01, 2014, 11:29:12 AM »
Hello Florian,

I can't see how it can be a bad thing.

You shouldn't have any problems with curve type motion as long as your Servo Drives are tuned properly. And Step/Dir signals have less of a following delay compared to +/-10 Analog Voltage.

Re: Closed Loop with HiCON Integra
« Reply #6 on: December 04, 2014, 04:09:55 PM »
Let me explain it with an example. Maybe it helps you for understanding me.

G-Code in Mach3:
N10 G01 X0Y0Z0
N20 G01 X20Y20Z0

Configuration in Mach3:
1000 Steps / mm

In case of linear motion the controller have to move more than one axis at the same time so the axis follows a straight line to the destination.

In this example how many times the HiCON controller checks the position befor the next step was executed? 
Two times on row N10 and N20 or every single Step (ca. 20.000 times)?

regards,
Florian
Re: Closed Loop with HiCON Integra
« Reply #7 on: December 05, 2014, 11:00:03 AM »
I believe you're asking about the motion resolution then? As in how fine the motion is, which does play a big part with the result of curved motion.

Motion vectors are plotted with a resolution of milliseconds. Given that an arc is just a set of straight-line moves that keep changing directions to make the actual arc, when you do a curve, the straight lines are as small as a millisecond (axis directions are changing every millisecond) making the arc very fine as long as you're moving at a reasonable velocity. By reasonable velocity, I mean setting the velocity accordingly to the material being cut, or if you're just freely moving.

In your example, Mach will not necessarily generate 20,000 vectors for the trajectory because the number of vectors generated will be dependent on your configured motor speeds and accel (slower speeds generate more vectors because it takes more time to get to the final position). To give you an accurate example, if your machine takes exactly 5 seconds to move from the initial to target position, then you'll get 5000 vectors plotted for the trajectory. That being said, you'll get your 20,000 vectors IF the motion takes 20 seconds to finish.

As a general rule, the more vectors are plotted for your trajectory, the finer the trajectory, meaning a slower move with an arc will generate a finer curve. But even if you were to command the motors to go full speed on an arc move, the resolution is still very fine.

Counts per unit is a somewhat irrelevant factor in the trajectory ONLY IF they are accurately configured for the motor.