Solved: Transporter moving backwards

oscar_c13 · ‎12-29-2021

[ FlexSim 21.2.1 ]

Hi,
I have seen that it has been a frequent question, and I understand that the solution to a transporter moving backwards is in the "Flip Treshold" field, but I only want it to go backwardas in a specific part of the line
How can I do it?
I have looked at these questions
https://answers.flexsim.com/questions/101744/run-backwards.html

https://answers.flexsim.com/questions/96581/transporter-reverse-travel.html

https://answers.flexsim.com/questions/96292/forklift-backing-up-on-a-specific-area.html

It is said that a trigger can be made in some node to modify the treshold but I did not find the way.

In the attached model, I want the transport to only go backwards when it has to go towards NN1, and not when it goes towards queue3.
Backwards.fsm

jason_lightfootVL7B4 · ‎12-29-2021

I would just add a curved path from NN1 to Queue3 or create an intersection that forces the correct directions.

The flip threshold checks against the angle between two vectors, so forward to reverse travel is 180 degrees. I usally use curved paths to ensure the arrival paths at a destination are all close to being aligned and then set the flip threshold to 170 or higher.

backwards_jl.fsm

mitregatomasz90 · ‎12-29-2021

Hi

You Can use if function like this:

if(toedge==1){ 
setvarnum(traveler,"flipthreshold",0); 
}else{ 
setvarnum(traveler,"flipthreshold",180);

The to edge and from edge number is dependent on the order of connection to the network node

I attach the model

backwards_1.fsm

jason_lightfootVL7B4 · ‎12-29-2021

Also - to get the transporter to arrive at the Queue1 on the network you should give it a Travel task first and not just rely on the Load task to get it there via offset travel.

oscar_c13 · ‎12-29-2021

I have not understood very well why it works for you, if I put a curve, it continue to works erroneously. I don´t know if something escapes me

Backwards.fsm

jason_lightfootVL7B4 · ‎12-30-2021

It's not working in your model because the transporter has already turned beyond the 10 degrees (so flip calculation is <170) because of offset travel. If you want to control better the orientation I would consider turning off offset travel - or position your pickup items so that the angle is straighter.

In my opinion, you shouldn't need to switch the flip threshold back and forth - this gets messy since at some point you'll need to know the direction of travel and base the flip on how it arrived. The flip threshold is better just set and forgotten and rely on the network layout to perform the flip - otherwise you need tests like yours all over the model, which historically have been hard to manage.

Transporter moving backwards

Transporter moving backwards

Photos