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Re: [sumo-user] [SUMO][CF-MODEL][STEP LENGTH]
Hello,
1) predicting the speed of a vehicle in advance is generally not feasible since you need to replicate all the computation done by SUMO (stops, anticipation of speed limits, lane changing, randomness, ....). If you want to assume constant speed or constant acceleration then its trivial.
As a side note:
- classes prefixed with 'ME' are exclusive to the mesoscopic model (http://sumo.dlr.de/wiki/Simulation/Meso). You will want to look at the MS (microsim) classes.
- arrivalPos only defines the arrival position on the destination edge and is generally not updated during the simulation

2) Models are known to behave differently with different step-lengths
- this is partly due to the effects of extreme accelerations caused by euler integration so you can reduce the effect by using ballistic integration. This should also be noticeable at intersections
- another source for differing behavior is the effective reaction time which is currently tied to the step-length (vehicles can choose  to change their speed during every step). We are working on an extension to decouple the decision making interval from the step length but it's not quite ready yet.
- there are some known issues with ballistic update where vehicles take longer to find a gap for lane-changing. The vehicles are somewhat conservative with their safety constraints which is less noticeable with the higher accelerations afforded by the euler integration. The effect should be less pronounced with lower step-length.
- generally, we intend to make ballistic update the default behavior because it generates more realistic trajectories. If you notice something odd your are likely to get support fairly quickly so I would already recommend to use ballistic integration.

regards,
Jakob


2017-12-06 10:31 GMT+01:00 Luca Di Costanzo <dicostanzo.luca@xxxxxxxxx>:

Hi all,


Me and my fellows are trying to implement a more sophisticated dynamic for the vehicle in SUMO using specific mechanical software (VI-grade or IPS-CarMaker) interacting during the simulation through traci4matlab.


We’d like to know if it is possible to obtain, at step “X” the speed and the position that the vehicle will have at the step “X+dT”.

We would compare the desired vehicle speed and arrival position at step “X+dT” with the one coming out from the dynamic vehicle’ software named above.


I saw, probably, some interesting functions as MEVehicle::getSpeed() or   MEVehicle::getArrivalPos() but I’m not sure if those are the proper ones. Do you have any suggestion?


Secondly, based on you experience, how works CF-models with step-length < 1 second? Presumably we need to use step-length of, at least, 0.1s since the dynamic vehicle’s model have a really high update frequency so it is important that SUMO simulation works good.

In my tests the vehicle works differently near an intersection if I’m using a time step of 1 second or 0.1 second. Moreover would you suggest to use Euler or Ballistic Integrate model?


Regards



Ing. Luca Di Costanzo

-----------------------------
MsC in Hydraulic and Transportation Engineering 
Bsc in Civil Engineering 
skype: lucadicostanzo82
tel: +39 333 43 92 544

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