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Multiportal Crane - difference between teoretical and simulation times using hook speed

Experimenter
Experimenter

Hello,

I am working with Multiportal Cranes and after some time I found out that there is a difference between reality and simulation in time which take to lower or raise MU with hook. This difference is not influenced by speed or distance of the portal neither by speed of the trolley, neither by height which hook needs to travel. My question is if this is a problem with my approach to the MPC or with some wrong settings of the MPC or if this is a problem with the MPC itself. I found out that difference between reality and simulation is aproximatly constant and it is time_difference = 0,2*hook_speed^-1. In simulation hook travels distance earlier than it should have in reality. I attach simplified model which can be used to get time from simulation of the hook. Real times was counted by formula distance = speed * time. Thank you in advance for any answers or help.

 

 

P.S.: Note that first row of the realtimestat table has information about how many columns are filled in that comlumn for easier indexation.

7 REPLIES

Re: Multiportal Crane - difference between teoretical and simulation times using hook speed

Siemens Phenom Siemens Phenom
Siemens Phenom

Hello Argo,

 

please update your model using the latest version of the cranes library (Cranes 11.0.17)

 

Regards

 

GG

Regards
GG

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Re: Multiportal Crane - difference between teoretical and simulation times using hook speed

Solution Partner Legend Solution Partner Legend
Solution Partner Legend

I am having the same problem as the OP - it seems as though the hook descending/ascending speed is not taken into account. A good example is from the examples collection: Continuous material flow -> Portal Crane -> Feeding Two Machines.

 

Only for the "MoveTo"-command with supplied coordinates does the hook move up/down at its defined speed. For the rest of the simulation, it seems as though the crane skips the "move hook up"/"move hook down" commands, as no time is consumed to do these steps (even by setting the hook speed to 0.01m/s).

 

I am running the crane library 12.0.4 on Plant Simulation 12.2

Re: Multiportal Crane - difference between teoretical and simulation times using hook speed

Siemens Phenom Siemens Phenom
Siemens Phenom

Please update to version 12.0.7 of the Cranes library

Regards
GG

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Re: Multiportal Crane - difference between teoretical and simulation times using hook speed

Solution Partner Legend Solution Partner Legend
Solution Partner Legend

Edit: I managed to solve it by changing the Portal Height in the example model. The portal height was lower than the lift height of the trolley, which caused some error. Changing the portal height to a larger value (10 meters) and changing the trolley height to be the same (10 meters) makes the example model work properly.

 

===========

 

Thank you, but the example model is still showing signs of not regarding the hook time. I had to lower the hook speed to 0.00001 to achieve a "movingHook" statistic of 1.2 seconds over about 9 days of simulation. Any reasonable value on the hook speed returns 0 movingHook statistic.

 

It seems as though it is still not running the "<portal>.moveHook( Z );" commands properly.

 

Are you able to reproduce the problem? Perhaps I am doing something incorrectly.

 

I am running the updated library version 12.0.7 with the same example model on Plant Simulation 12.2

 

Re: Multiportal Crane - difference between teoretical and simulation times using hook speed

Siemens Phenom Siemens Phenom
Siemens Phenom

Hello 7SEG,

 

i checked your model and again, I also checked the Cranes library.

Both are working well.

In your model, the Hook moves 0.5m with a speed of 0.5m/s so the movement takes exactly 1 sec which you are showing in your table RealtimeStat.

 

Regards

 

GG

Regards
GG

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Re: Multiportal Crane - difference between teoretical and simulation times using hook speed

Siemens Phenom Siemens Phenom
Siemens Phenom

Hello 7Seg,

 

attached you will find a test model of the cranes library sghowing, that the moveHook command works as designed.

 

Regards

 

GG

Regards
GG

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Re: Multiportal Crane - difference between teoretical and simulation times using hook speed

Solution Partner Legend Solution Partner Legend
Solution Partner Legend

Yes thank you, it worked fine all along. It was I who overlooked that the trolley lift height in my model was larger than the portal height, and I was referencing points on the Z-axis that exceeded the portal height but not the trolley height, so it would skip the lowering/raising sequence of the hook until I set the trolley lift height within the limits of the portal height.