Dynomotion

Group: DynoMotion Message: 8501 From: daveymahomh600e Date: 10/22/2013
Subject: Using KFlop/SnapAmp for Force Control
Hello Tom,

My machine uses a KFlop/SnapAmp combo to drive a 2 axis closed-loop servo/ballscrew slide.

I was hoping to be able to use a Gamepad to move the slide around and limit the force that will be applied by the slide by capping the output voltage from the SnapAmp.

What are your thoughts on this?

Thanks,
David.
Group: DynoMotion Message: 8504 From: Tom Kerekes Date: 10/22/2013
Subject: Re: Using KFlop/SnapAmp for Force Control
Hi David,

The MaxOutput parameter can be used to cap the max voltage that SnapAmp will apply.  But I think that will limit your max speed also.

Another problem will be what to do when the voltage gets capped?  If the Gamepad keeps moving the position then the result will be a big following error between the commanded and actual positions and result in a following error fault.  Of course you can turn off following errors but you probably don't want to do this.

A KFLOP User Program could be written to monitor the 3 phase motor current and report that back to the PC.  The PC/Gamepad program could then monitor that and limit the motion.  But this would be somewhat involved and the PC is not 100% real-time deterministic.

Regards
TK

Group: DynoMotion Message: 8505 From: az@aimele.com Date: 10/22/2013
Subject: Re: Using KFlop/SnapAmp for Force Control
Hello TK et al.

Does the MaxOutput parameter limit the current out of the SnapAmp or the voltage?

It sounded like David wants to limit force, not speed. Limiting the motor current would limit the
torque (force) but the speed would only be limited by the bus voltage available unless I'm confused
about what MaxOutput does.

AZ



Group: DynoMotion Message: 8512 From: daveymahomh600e Date: 10/22/2013
Subject: Re: Using KFlop/SnapAmp for Force Control

Thanks Fellas,


I am okay with a speed reduction, but I didn't think about the following error.


I do want to record the motion, so would it possible to record the encoder position instead of the Gamepad position? Maybe with a modified Teachmotion?


David



---In DynoMotion@yahoogroups.com, <dynomotion@yahoogroups.com> wrote:

Hello TK et al.

Does the MaxOutput parameter limit the current out of the SnapAmp or the voltage?

It sounded like David wants to limit force, not speed. Limiting the motor current would limit the
torque (force) but the speed would only be limited by the bus voltage available unless I'm confused
about what MaxOutput does.

AZ



Group: DynoMotion Message: 8513 From: Tom Kerekes Date: 10/22/2013
Subject: Re: Using KFlop/SnapAmp for Force Control
Regarding MaxOutput: it limits the Servo Output which for a SnapAmp in DC Servo Mode or 4PH Servo mode is a current command,  for 3PH Servo mode is a voltage.

David,

I know you don't like the look, size, cost of the Force Feedback Joystick compared to the wireless GamePad but I still can't stop thinking that it would be so cool to apply the measured motor current to the Force Feedback Joystick.

Anyway to record the actual encoder position in stead of the commanded destination in TeachMotion Form1.cs change:

                    if (CaptureOn.Checked)
                        CapList.Add(new CPoint(MainStatus.Destination[1] / YResolution,
                                               MainStatus.Destination[0] / XResolution,
                                               MainStatus.TimeStamp));

to

                    if (CaptureOn.Checked)
                        CapList.Add(new CPoint(MainStatus.Position[1] / YResolution,
                                               MainStatus.Position[0] / XResolution,
                                               MainStatus.TimeStamp));

Regards
TK
Group: DynoMotion Message: 8514 From: daveymahomh600e Date: 10/22/2013
Subject: Re: Using KFlop/SnapAmp for Force Control

Thanks Tom.


The force feedback joystick most probably is the best way to properly use the technology. The biggest problem is with this machine the teacher has to be in 3 different places at once to properly move the slide and it is a lot easier to move around with the wireless unit. The FF joystick kind of needs a proper parking space and it is really hard to find just the right spot in this application.


I will modify the code and run it around the block a time or two and let you know what shakes loose.


Thanks again,

David.



---In DynoMotion@yahoogroups.com, <dynomotion@yahoogroups.com> wrote:

Regarding MaxOutput: it limits the Servo Output which for a SnapAmp in DC Servo Mode or 4PH Servo mode is a current command,  for 3PH Servo mode is a voltage.

David,

I know you don't like the look, size, cost of the Force Feedback Joystick compared to the wireless GamePad but I still can't stop thinking that it would be so cool to apply the measured motor current to the Force Feedback Joystick.

Anyway to record the actual encoder position in stead of the commanded destination in TeachMotion Form1.cs change:

                    if (CaptureOn.Checked)
                        CapList.Add(new CPoint(MainStatus.Destination[1] / YResolution,
                                               MainStatus.Destination[0] / XResolution,
                                               MainStatus.TimeStamp));

to

                    if (CaptureOn.Checked)
                        CapList.Add(new CPoint(MainStatus.Position[1] / YResolution,
                                               MainStatus.Position[0] / XResolution,
                                               MainStatus.TimeStamp));

Regards
TK