[LQG control]

Is it possible to obtain better accuracy in turbo pmac by the usage of alternative control strategies such as LQG control or H∞ control ? I understand that turbo pmac is flexible enough to implement these by the way of bypassing the existing firmware pmac PID filter and replacing it by user written servo algorithms.

 

Can I get some practical guidelines for implementing advanced servo algorithms on turbo pmac ? I am not much initiated in advanced control strategies. I only know the mechanism of open servo.

[UMAC and host computer connection over Ethernet]

I have tried killing PCommServer, but it does not help. Even if I re-cycle power to the host computer, UMAC keeps holding the TCP connections.

[UMAC and host computer connection over Ethernet]

I have an existing application where UMAC communicates with host computer over Ethernet over 100 meters distance through a couple of Ethernet switches. The host application uses PCommServer drivers.

 

After several months of observation, it is observed that there are data breaks in the Ethernet link on rare occasions. In host software, I am checking for interruption by sensing an unlikely set of field input values. In case of interruption, I am closing the communication by the call PmacDoc.Close(0) and then trying to re-open the communication by the call PmacDoc.Open(0, pbSuccess). When the opening call is a success, the host application resumes its work. Sometimes it so happens that host application has to close without issuing a PmacDoc.Close(0) call.

 

In this process, it is observed that after a few days involving a few data breaks, UMAC is "holding" a TCP/IP connection even if the host application is not running. Observation is, UMAC communication works ok upto 4 TCP connections. When UMAC holds up all 4 connections, PmacDoc.Open(0, pbSuccess) fails even if ping is a success.

 

Then the only alternative is to switch off the power to UMAC and then to switch it on again.

 

To avoid this scenario, I would like to know if there is a command in PCommServer command set for releasing all the TCP/IP holdups. Maybe there is a command for graceful closing the communication which includes releasing all the holdups.

 

I know some devices having TCP/IP communications having "reset" port. A connection to this port results into release of all the connections including the connection to reset port itself.

[ACC-53E / ACC-84S and Multiturn Absolute Encoders]

Thank you for the information.

 

Does this apply to brick controller, geo brick drive and geo pmac having appropriate options selections for absolute SSI encoder feedback ?

[ACC-53E / ACC-84S and Multiturn Absolute Encoders]

I want to interface SSI multiturn encoder to ACC-53E/ACC-84S. Multiturn resolution will be 12 bits and single turn resolution will be 17 bits. The encoder output will be in extended SSI format as specified in attachment. Is this possible ? As per my knowledge, currently encoder conversion table does not have a format to allow this.

Technical_Manual_SSI_BiSS_ACURO_en.pdf

[Auto track in antenna application]

What is the resolution of the analog (I suppose) feedback? How do you have the cascaded loop set up? if you have a virtual motor then you can make full use of the PID of that motor to tighten up the tracking. E.g. Quick step move using the PewinPro2 Tuning. It will be as responsive as your input signal is.

 

By the way, inherently, tracking will always have some error during motion. There is no such thing as zero error. You cannot predict where the target is going, otherwise you would just pre-program it.

 

Resolution of the analog feedback is +/-10 volts maps into 0 to 65535 counts. After applying secant correction (using open servo), I am feeding this signal to a virtual axis through encoder conversion table. I am closing the virtual loop by giving command #1j=32767 which means that I want the error to become zero. I have integrated the output of the virtual loop and then applied to real axis through electronic gearing as described in the Turbo PMAC user manual.

 

I have observed that step response is acceptable when I set the Ix30 of virtual loop correctly. This is a good setting on which the system is running currently. The performance is acceptable even at moderate speeds, meaning that lag is within acceptable limits.

 

It is only at the high speeds of the target that there is a large lag (during zenith pass).

 

I have noted your point about lag being inherently present in the tracking applications.

[Auto track in antenna application]

You want the tracking error to be zero but you don't want it to be zero?

Sorry, I don't understand what the problem is or what are you trying to achieve. Can you try to explain better?

 

I want the tracking error to be zero. But I have observed appreciable lag (non zero tracking error) at higher speeds of the load. I am attributing this to the topology of usage of the cascade loop itself. Is there any control method better than cascading ?

[Auto track in antenna application]

Does lowering the gearing ratio or loop gains provide any improvement?

 

Electronic gear ratio at the output of cascade is 1. Cascade loop gains lowering is not helping as it results into deteriorating step response.

[Auto track in antenna application]

What is your current implementation of the cascade loop?

 

Currently I am comparing auto error with zero reference and the resultant (negative of auto error) is being fed to cascade loop. Output of the cascade loop is being integrated and fed to the real axis with electronic gearing as described in the Turbo PMAC User Manual. Secant correction is being applied too. This introduces lag during high elevation trajectories which demand high rates in elevation over azimuth mounts.

[Auto track in antenna application]

For monopulse auto tracking in antenna application, I am using cascade loop for auto error to make it zero. However, for sustaining high speeds, finite auto error is necessary. This defeats the requirement of making auto error zero.

 

How to overcome this ?

[Turbo PMAC Command buffer overflow]

Do you use "LINEAR" for this ? What values do you use for F, TA & TS ? Could you please provide a sample code ?

[Real motors following the phantom axes command position]

I have a requirement where a motion program is running on phantom coordinate system and real motors in another coordinate system have to closely follow the phantom command positions.

 

There will be routine occurrences in the application when real motors will have to move away by a large distance from the phantom positions. Then after some time, real motors have to follow phantom motors again. During all this time, motion program in phantom coordinate system keeps running.

 

When the real motors have to move back to phantom positions, it is necessary to have good response and high (controlled) speed without causing large overshoot and oscillations.

 

Can anybody tell me how to achieve this ?

[Turbo PMAC Command buffer overflow]

Through PLC program, I want to use following construction:

 

If (I5111 !> 0)

CMD"#1j=* #3j=*"

I5111=100*8388607/I10

EndIf

 

Above program will issue jog command every 100 milli seconds.

 

My query is: How fast can I issue jog command like above ensuring that Turbo PMAC command buffer will not overflow ?

[Brick Controller Mounting]

Can I mount Brick Controller horizontally ? Please see the attached picture. It shows "width" which is horizontal dimension.

[UMAC Host Application on Standard user login for Windows Server 2008]

I have been running my UMAC host application (over ethernet) on Admin login on Windows Server 2008. Now I have to run it on standard user login.

 

However, PEWin32Pro2 does not detect / communicate with UMAC on standard user login.

 

Can anybody tell me why this is so ?

[Power PMAC, PMAC-NC-Pro2 and Advantage 900]

Can I create a 5 axis CNC solution with Power PMAC ? Is there any CNC software available for this which I can deploy on Advantage 900 ?

[Power PMAC, PMAC-NC-Pro2 and Advantage 900]

Has anybody used Advantage 900, Pmac-NC Pro2 and Power PMAC combined together to create a CNC control solution ? If yes, are there any application software modules (set of programs) readily available for Power PMAC in order to make it work with PMAC-NC-Pro2 ? Or any application notes available ?

[How do I control speed with Turbo PMAC ?]

Thank You.

 

-Abhijit Dandekar

[How do I control speed with Turbo PMAC ?]

With this approach, what can we say about the bandwidth of the velocity loop ? Will I get bandwidth similar to the one obtained by usage of classical velocity control ?

[How do I control speed with Turbo PMAC ?]

I want to have functions like counter torque to be achieved from Turbo PMAC, which let me use two servo drives in current mode and two servo motors connected to same axis via large backlash prone gear boxes.

[How do I control speed with Turbo PMAC ?]

How to configure PMAC PID filter in order to control the speed of a servo motor? External servo drive is configured in torque mode and PMAC will receive speed command on an analog input. Feedback is the simulated quadrature encoder pulses from servo drive.