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AKD Profinet RealTime Jog | 13 Dec 2017 | |

AKD Profinet RealTime Jog

Hello,

I am using an AKD Profinet with firmware 01-16-00-000 in position mode with telegram 352 and PLC S7-300, and I have some problem with real time jog.

I have not found any information about real time jog in the manual. (How to use bits STW1_12 and STW1_13). Only after some tests, I discovered that without the STW1_8 bit the motor does not run.

Now I'am in this condition:

- If the requested speed is <> 0 then I drive the bits STW1_8 and STW1_12 at the same time.

- If the speed is < 0 then I drive the bit STW1_13.

 

image

I found this information in a S7-1500 project on your website. This configuration works but sometimes the motor does not seem to move, in reality the motor moves at the jog speed set in the driver at the position SM. and not at the MDI_Velocity.

How I can solve this problem? In my application, I need to change direction and speed often (speed is the result of a PID)

Thanks for the support.

Fabio Daini

Comments & Answers

jcoleman02 | Wed, 12/13/2017 - 14:39
The problem may be due to the fact that you are setting bit 8 and bit 12 at the same time.  If bit 8 is turned on before bit 12 (or possibly in the same PLC scan as bit 12), then the AKD will perform the jog move with the speed based on SM.V1 (PNU 1004).

There are two ways to do a jog move in the AKD through Profinet:
1. STW1 bit 12 = 0 -- Use STW1 bits 8 or 9 to start a jog move, where the speed is defined by SM.V1 (for bit 8) and SM.V2 (for bit 9).  The direction is based on the sign of the value of SM.V1 or SM.V2 (whichever is used).  SM.V1 can be set in Workbench or with PNU 1004.  SM.V2 can be set in Workbench or with PNU 1005.
2. STW1 bit 12 = 1 -- Use STW1 bit 8 to start a jog move, where the speed is defined by MDI_VELOCITY of Telegrams 9, 352, 353, or 400.  The direction is specified by STW1 bit 13.  First set bit 12.  Then set bit 13.  Then start the jog move with bit 8.

Keep in mind that the Profinet communication update rate is fixed at 16ms, which is very slow for closing a PID position loop.  As a comparison, the position loop in the AKD drive is updating at 250 microseconds.  In your case, the AKD is closing position loop and you are closing another position loop to command a jog speed into the position loop of the AKD.  It will work, but your control loop in the PLC will be slow.

jcoleman02 | Wed, 12/13/2017 - 15:27
Also for STW1 bit 12 = 1, the acceleration is specified by MDI_ACC and the deceleration is specified by MDI_DEC.  If these are set to zero, then the axis will not move.  The drive does not need to be homed prior to running a jog move, even in position mode.

Fabio Daini | Wed, 12/13/2017 - 15:55
Thank you for your answer, I try to do what you you suggested. But now, when I start the machine I give to the driver bit 8 and bit 12 at the some time. These bits remain set all the time until the machine is stopped or the speed is =0.

According to what you suggested, I have to reset only the bit 8 every time that I want to change direction after that, set bit 13 wait a little time and set again bit 8.
When you write:
" First set bit 12.  Then set bit 13.  Then start the jog move with bit 8."
How much time is needed between the commands?

I chose to control the driver in profinet because I need the position. 
There is a better way to control the driver in speed direction and know the position?
Thank you

jcoleman02 | Wed, 12/13/2017 - 16:59
First, turn on bit 12 to enable the "real-time jog" feature.  Then use bit 8 to start/stop the jog move and use bit 13 to control the direction.  You don't have to stop the move to change direction.  But if you turn of bits 8 and 12 at the same time, then the drive doesn't have time to process the command to enable the real-time jog feature, so the jog may use the SM.V1 parameter for the speed.  If you want to use real-time jog, make sure bit 12 is turned on prior to turning on bit 8.

Fabio Daini | Fri, 12/15/2017 - 12:38
I'am sorry but I have the same problem.
Now I turn on the bit 12 and still at 1 forewer then after 100ms I turn on the bit 8, instead the bit 13 goes up and down based on the sign of speed.
The machine works for 20-30 minuts well and suddenly the motor go to SM.V1. The bit 12 still at 1.

I can't believe it, but why?

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Fabio Daini
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