Controlling brushless servo motor using Maxon DEC 70/10 and PCI 7358

[Wenbinlim]

Hi,

I am currently using NI 7358 to control some Maxon motors. The amplifier I am using is Maxon DEC70/10. However, I am unable to control the motor using MAX. At the one axis interactive tag (in MAX), I am totally unable to control the motor. It refuses to accept any comments and rotate at a constant speed. It cannot be controlled even with different PID values. I set the DEC in current mode.

The encoder is totally fine as the reading reflected seem correct. I borrowed an amplifier (Advanced Motion Control AMC B15A8) to test the motor and the card. This B15A8 is able to control the motor so it means that the PCI card and the motor are working well. I controlled the motor with a simple PID value (P=1, I=0, D=0) and it is able to complete the motion. I controlled the motor with an external power supply (without PCI 7358) and it is able to produce the required result (increasing torque with higher voltage). Hence my initial conclusion for this problem is the the compatibility between PCI7358 and DEC70/10 or some special setting that is required when DEC70/10 is used.

Attached is a document that Maxon sent to me before the purchase. Page 3 (PDF pages) clearly indicates that the NI motion controller is able to control Maxon motor with DEC 70/10. I was told that DEC 70/10 uses square signal to control the brushless motors, unlike other amplifiers (or Maxon DES series) which uses sinusoidal signal. Hence is there any difference in the setting in MAX that I need to look out for? Hope to get some advice from you. Thanks.  

Regards

Wenbin

[Jochen]

Wenbin,

the combination between an NI 7358 motion controller and a Maxon DEC 70/10 is a very common thing and I have worked with a lot of customers who didn't experience any trouble when using these devices.

As you have done most of the tests already, that I would recommend in such a situation, here are some other ideas that might help:

• Double check the cabling. Are you 100% sure, that the axis' analog output is connected to the drive's command input? What about the ground connetion?
• Have you measured the output voltage of the 7358 when it is connected to the DEC?
• What about the status indicators in MAX (1-D Interactive)? Are there any red lights? Which?
• Is it possible to kill (disable) the axis from MAX? Is the inhibit output connected correctly to the drive?
• Which connector block (UMI) are you using?
• Please double check all the basic settings (Is the axis enabled? Is the board initialized?...)

I'm pretty sure, that there is a minor root cause of the issue, but sometimes especially these minor issues are hard to detect.

If these hints don't help, it might a bit hard to help you via the forums. In this case please contact your local NI branch for help.

Kind regards,

Jochen Klier

National Instruments

[Wenbinlim]

Hi Jochen,

Thanks for your prompt reply. The matter is solved.

The polarity of the drive's command input for DEC70/10 is different from AMC amplifiers. I changed the polarity of the drive's command input and it works well now. So it is AOGND to '+Set value' and AOUT to '-Set value'

Thanks for the help.

Regards

Wenbin