Dear all,
thank you for your comments on the energy model in SUMO. I am just

`internally answering my colleague Jan to his questions but think that
``you
`could be interested in some of my observations.
Despite bugs mentioned by Burford, their correction (that is certainly

`important in SUMO) will only slightly impacts our energy results for
``these
`reasons:
1. Change of Rotational Energy << Change of Kinetic Energy

`since the internal moment of inertial << mass of the vehicle (for
``example
`for our simulated trolleybus J_int = 0.03*mass)

`2. The calculation of the Curvature Energy Loss is applicated only 3
``times
``per trolleybus No. 13 line circulation in simulation without
``surrounding
``traffic. The reason for such behavior is that the diff of route angle
``is
`not zero only at three time-steps of the simulation from total ca 5k.
3. Fortunately we use the default SUMO length 1 s of the time-step and

`therefore, the confusion of power [W] vs energy [Ws] vanishes. (It
``counts
``both for the bug in the constat power of aux system calculation and for
``the
``order logic of energy/power calculations in SUMO's emission/energy
``model).
`
Finally, the paper [ I. Sagaama, A. Kchiche, W. Trojet and F. Kamoun,

`"Proposal of More Accurate Energy Model of Electric Vehicle For SUMO]
``you
`mentioned proposes three changes for SUMO model
b. calculation of efficiency as \eta_bat*\eta_inv*\eta_mot

`I don't understand the difference between such calculation in
``comparison
``with using only one constant eta, that can be precalculated of course
``using
`the above-mentioned formula.

`Maybe in our case would be interesting to consider different values for
``the
`efficiency of propulsion using energy from battery

`(battery->inverter->motor) and from overhead wire (owhd wire ->
``inverter ->
``motor) but again fortunately these values are almost the same in
``practice.
`

`a. using the proposed modified equation for calculation of the energy
``of
``auxiliary drives corresponds to the common approach in SUMO if the
``ambient
`temperature is 20°C
c. the modification of efficiency of regenerative breaking is already
integrated into the SUMO
https://github.com/eclipse/sumo/blob/4358260686c4a331c75bce1b5d7702e3eda5cdde/src/utils/emissions/HelpersEnergy.cpp#L132
.
Best,
Jakub

`On Thu, Oct 15, 2020 at 11:55 PM Jan Přikryl <prikryl@xxxxxxxxxx>
``wrote:
`

Dear Joerg,
I am just curious: Do you have (or will you have) any comparison with
measurements of real vehicles in real traffic? We are namely using the

`original HelpersEnergy subsystem to compute energy flows in the
``ElecHybrid
`device and, to be sure, we have tried to validate the outputs of SUMO

`against telemetry that we have from trolleybuses -- and, given the
``natural
`variance of the data that you get from such a vehicle in real traffic

`(different saloon occupation and hence different mass, different
``traffic
``conditions, different daily temperatures resulting in heavy variations
``in
`auxiliary power consumption and so on) and given that for the modelled
vehicle you get at least three different sets of drag and resistance

`parameters (one set provided by the manufacturer of the vehicle, a
``second
``set from the provider of the chassis, and the third one from the
``vehicle
`operator), we were quite happy with the results even with the current

`implementation (the only change is that we try to limit the
``acceleration of
`a vehicle based on its power limits).
On the other hand, there is a paper from 2018 (
https://ieeexplore.ieee.org/document/8450371) that reports a 23-29%
difference

`in energy consumption compared to a test with a real electric vehicle.
``I
`did not read it yet, I just came across it recently.

`That leaves me wondering whether our comparison is correct and whether
``we
`should not crosscheck it one more time...
Jan
On Thu, 15 Oct 2020, at 10:23 PM, joerg.schweizer@xxxxxxxx wrote:
> Thanks Michael for putting your hands on this, and sorry it took time to
> find the file.
>
> It has been quite crucial for the project as the determination of the
> energy consumption has been the main goal.
>
> Hope it gets fixed soon.
>
> Thanks again,
>
> Joerg
>
>
> On 15/10/20 21:53, Michael Behrisch wrote:
> > Hi,
> > thanks for the report and sorry for the delay. Unfortunately we have
> > several places in the code which calculate energies. I suppose you are
> > referring to HelpersEnergy::compute
> >
https://github.com/eclipse/sumo/blob/master/src/utils/emissions/HelpersEnergy.cpp#L57
> > ?
> > This function seems to have some problems indeed not only the ones you
> > mention but in total it should return power and not energy because the
> > time scaling is done outside the function when used as an emission
> > model. For the battery device however energy is expected. Sorry for the
> > hassle, it is now tracked here:
https://github.com/eclipse/sumo/issues/7695
> >
> > Thanks again for finding out!
> >
> > Best regards,
> > Michael
> >
> > Am 11.10.20 um 06:40 schrieb Burford Furman:
> >> Hello,
> >>
> >> We are running SUMO ver 1.6.0 under Windows 10, and we just discovered
> >> that the SUMO source code is calculating the Rotational Kinetic
Energy,
> >> the Curvature Energy Loss, and the Constant Auxiliary Energy Demand
> >> incorrectly. The SUMO documentation lists the correct equations, but
for
> >> some reason the source code is not correct in ver 1.6.0. Our findings
> >> are summarized below:
> >>
> >> image.png
> >>
> >> image.png
> >>
> >> Thank you.
> >>
> >> Burford Furman
> >>
> >> --
> >>
************************************************************************************
> >> Burford J. Furman
> >> Professor
> >> Department of Mechanical Engineering
> >> San Jose State University
> >> One Washington Square
> >> San Jose, CA 95192-0087
> >> Phone: (408) 924-3817 Email: Burford.Furman@xxxxxxxx
> >> <mailto:Burford.Furman@xxxxxxxx>
> >> Web page: http://www.sjsu.edu/people/burford.furman/
> >> <http://www.engr.sjsu.edu/bjfurman/>
> >>
************************************************************************************
> >> "We must remember that intelligence is not enough. Intelligence plus
> >> character--that is the goal of true education." - Dr. Martin Luther
King
> >> Jr., 1947
> >>
> >> "/Instrumental or mechanical science
> >> is the noblest and above all others, the most useful.../" - Leonardo
da
> >> Vinci
> >>
> >> _______________________________________________
> >> sumo-dev mailing list
> >> sumo-dev@xxxxxxxxxxx
> >> To unsubscribe from this list, visit
https://www.eclipse.org/mailman/listinfo/sumo-dev
> >>
> >
> _______________________________________________
> sumo-dev mailing list
> sumo-dev@xxxxxxxxxxx
> To unsubscribe from this list, visit
> https://www.eclipse.org/mailman/listinfo/sumo-dev
>
--
Jan Přikryl
prikryl@xxxxxxxxxx