Predictive Regenerative Braking

Discussion in 'Prime Technical Discussion' started by Silent Propulsion, Aug 12, 2017.

  1. Silent Propulsion

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    Regarding predictive regenerative braking, is there a trick or tallent to getting the green dots/leaves on the map? I try at certain locations with no success varying my braking. Then out of nowhere i get one or two to pop up. This has been very intermitttent too. Anybody have success with this feature?

    Posted via the PriusChat mobile app.
     
  2. Mark57

    Mark57 Senior Member

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    There's a section in the manual that goes into it but you have to pass the same location several times for it to get enough data on it to make a recommendation. If you drove the same route every day, It'd take about a week. More varied routes only get remembered as you re-drive them.
     
  3. Alan Winston

    Alan Winston Junior Member

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    That feature is something I had missed, and good news: obviously it is tracking GPS, so suggests that more useful topography- and traffic-based predictive regen/charging could conceivably be a software + map data upgrade away - ala forthcoming (overdue?) Kia Nico plug-in: "For the mileage obsessed, Kia offers an Eco Driving Assistant system with coasting and predictive energy-guide features. Using information from the GPS-linked navigation system, it coaches drivers on when to brake, coast, and use road topography to best consume or preserve energy." I might actually start routinely using routing (entering destination, not getting audio turn-by-turn), since obviously that should benefit a system like that.

    I think about stuff like that a lot, with this daytrip ...
    Screenshot 2017-08-13 at 07.55.21.png
    ... being part of my thought exercise. And yes, the two higher passes are both over 4000 ft, the lowest elevations are just above sea level. And just to add interest, that more-or-less level stretch around 60-70 milepoints is a construction zone, where my next door neighbors lost two and a half hours, creeping along at ~5 mph, last week (right to left). I've done the loop (with various starting points), several times over the decades, and the first or third passes, over and back, many many times. Haven't been able to much by myself for a quite a while, but intend to again once i have adaptive cruise control, etc.

    I'd like to at least have the option to see a profile like this, with current position shown, whenever I have a route shown on the nav. Take advantage of some of that large vertical screen.
     
  4. Raelx

    Raelx Junior Member

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    I drive very predictable routes but after a few months i have the leaves at every stop sign, most lights and a few longer downhill sections. There are a few spots i can see it increasing the regen braking without me touching either pedal, this is when approaching a leaf. SO it does work. Wish i had some actual long down hill sections, but CT does not offer a lot of elevation.
     
  5. Silent Propulsion

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    So i recently gained a few leaves and actually lost one. I still don't understand what is required to gain a leaf as there is one particular stop i come to on my way to work that i can't seem to aquire. Yet there were a few last week that suddenly popped up. One wasn't even a stop but a decelerate to make a right turn. I think i lost that one as i would also travel straight through it. I experiment with different ways of stopping, early, soft, somewhat hard and it doesnt seem to make a difference. The topography of my city is mostly sloped from lake level to a mountain range. I live maybe 2/3 to 3/4 up this slope so going to work and downtown, predictave regenerative braking is a big plus to me. I will continue to study this feature and try to figure it out.
     
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  6. DavidA

    DavidA Prius owner since July 2009

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    I find that this feature is unpredictable. Every now and then the route I take every day those granny smith apples don't appear and no regen happens, despite that they have been mostly working for weeks. All I have on those days is the green dots. I have not been messing with any of the settings.

    Also, I wonder why on the same daily routes some stop sign intersections have never had a green dot. Yet, some corners where I don't even use the brakes DO have the dot and granny smith apples appear. I wish there was a way to edit that data and create spots where it will auto regen, and delete other spots where it has somehow set them where they're useless.
     
  7. Tideland Prius

    Tideland Prius Moderator of the North
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    Good feedback. Hopefully @Prius Team sees this.
     
  8. DavidA

    DavidA Prius owner since July 2009

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    Yes, and I hope they still read PC. Haven't seen a post from them in ages. I actually thought I had the problem figured out that it didn't work when I was listening to FM radio, but did work when on Satellite radio. That premise evaporated a few days ago as the behavior changed independent of the audio source. Haven't tried it with audio off entirely yet.
     
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  9. DavidA

    DavidA Prius owner since July 2009

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    I was right, and wrong, in the above comment. I retested PRB again today with FM and Satellite radio. I began my trips in FM, and the first couple green points didn't develop into the apples, and no auto-regen braking happened. Following those non-working intersections, I immediately switched to Satellite radio, and all successive points began to auto-regen. Following the switch, either FM or Satellite allowed for the auto-regens to happen. Retested on my return trip, and same thing happened.

    For me, at least, the PRB seems to be dependent on having the Satellite radio working. This is bad news, as I only have a few weeks left of Satellite service left, and I really don't wish to sign up with SiriusXM just for the PB to work.

    I would like someone else to test this with their car, if they have had successful PRB fully working for a while.
     
  10. DavidA

    DavidA Prius owner since July 2009

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    Update. I have no idea what this feature is doing anymore. I did a test one day of no audio turned on at all, and the first couple green points never worked (and they have before), and others in the middle of my route did. So the behavior is intermittent no matter what I do. Still wish there was some user control. As it is, this feature seems like an unfinished trial and is completely unpredictable.
     
  11. Buzzhead

    Buzzhead Non-Interference w/ devel of pre-Warp civs

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    Concur with the "no idea what this feature is doing." I hadn't seen the dots at all before I put the XM on, as suggested. Have left it on, but sometimes they're there, and sometimes not. The XM reception is much better than on my wife's 2010, so that doesn't seem to figure in. And I drive like the veritable crippled snail, so I'd think I'd have more green dots and leaves, anyway.
     
  12. Krzysiek_KTA

    Krzysiek_KTA Active Member

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    Count me in.
    I have this feature enbled since March'17 and 95% of the time I use NAV guidance whereever I go.
    The green dots appear, sometimes the Leafs also. Whenever I see Leaf I give it a try and switch to D mode - it slows the car down by increasing re-gen. I also notticed that the acceleration guide behaviour changes when the NAV guiance is on according to accumulated green dots and Leafs. Nevertheless I have not notticed any logic at all where and when the Leafs appear and what is the governance model of this feature.

    Anyway my habit is to use B mode to slow down before known stops and slow downs, so the feature is useless for me.

    Just my five cents.

    Cheers
     
  13. DavidA

    DavidA Prius owner since July 2009

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    UPRB is my new acronym for this feature. I am completely convinced they rushed this out at the very last minute before the firmware was being finalized.

    U = Unpredictable.
     
  14. john1701a

    john1701a Prius Guru

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    There's no way predict without lots of real-world data. Software can be updated at any time. My PHV had over-the-air updates. It's becoming more of a norm to expect upgrade after purchase anyway. Look at how successful Tesla has been with that. So, more to come...

    We know an Entune update is on the way.
     
  15. HypersonicPrime

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    I highly doubt that the audio has anything to do with the Predictive Efficient Drive (Predictive Deceleration Support or PDS). This is probably illusory correlation. For what it's worth, mine works when I have FM playing. An excerpt from the navigation manual about PDS follows:

    "The system automatically stores and registers support points where the driver always decelerates or stops based on pedal operation and the vehicle speed of the driver. The registered points are shown on the map as icons for use as predictive deceleration support points. When registered support points are approached, the optimal timing for releasing the accelerator pedal is notified to the user using the eco acceleration guide of the hybrid system indicator along with emphasizing the display of the icon. (Refer to the separate Prius Prime owner’s manual for details on the eco acceleration guide) After releasing the accelerator pedal, the engine brake (regeneration brake) amount increases. (regeneration boost control). As a result, the battery charge amount can be increased when decelerating or stopping the vehicle contributing to improved power and fuel economy. This function only operates in the contiguous United States."

    https://www.toyota.com/t3Portal/document/omnav-s/OM47B68U/pdf/OM47B68U.pdf

    I think comparing PDS to acceleration advise (via the Eco bar) is a useful analogy. The Eco bar is a good help for people to understand efficient acceleration rates. It can do this because when you step on the accelerator, it assumes you're accelerating to some unknown (higher) speed and advises to limit it based on the (darker) blue bar. This is easy to do because it starts advising immediately and you generally accelerate for a while. For braking, it can't give advice because it generally doesn't know when you need to stop and people decelerate pretty quickly. I bet the programmers added this feature to give some advice for stops that you do consistently and then you can apply proper braking techniques to other situations. The main thing that is important for braking is letting off the accelerator at the right time and I bet this is the main goal.

    It seems the Prius Prime decides where to place the leaves based on many factors. I bet if sometimes you stop and other times you "glide" though the same intersection, it won't place a leaf (or it'll take it away) because it can't give a good recommendation on what to do. It also probably won't work at intersections with a lot of traffic because you're coming to a stop at different times/locations. It's probably only intersections where you consistently do the same thing (while meeting other criteria--high enough starting speed, low enough slow speed, etc). That's what my criteria would be if I had to program it. Try being consistent every time for a dozen times (for a situation where you slow down at least, maybe, 25 mph) and I bet you'll get a leaf and it'll stay. Anyways, the fact that it can do this is just icing on the cake for an already great vehicle. I realize that once I have learned effective accelerator/brake control, this feature actually adds little benefit. I think it's more of an initial tutorial to help people understand when to start decelerating.

    To summarize: all it does when you get near a leaf is alert you the proper time to let off the accelerator pedal (by having the Eco bar gradually disappear) and then give a higher regen braking than normal since it knows when you generally come to a stop. You can easily do these steps without PED enabled. I wouldn't use "B" mode: it is designed to turn the engine on to apply engine-braking for long downhills to avoid overheating your friction brakes. I haven't seen anything saying it increases regen (correct me if I'm wrong) and I'd worry about it starting the engine unnecessarily.
     
  16. DavidA

    DavidA Prius owner since July 2009

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    I wish it really did work as described in the manual. There are several intersections near my house, with stop signs, that have never received the coveted green dots let alone the granny smith apples. And every single day I fully stop at those intersections with brake pedal depressed (beyond regen). Yet there also remain oddly placed green dots along some roads that turn into the apples at curved parts of those roads where I've never once stopped and only hardly slow down, that apples appear and predictive regen begins to happen unnecessarily. The bizarre behavior of UPRB working one day and not another still happens mystifies me. I will say that about 85% of the predictive green dot spots do seem to work properly.
     
  17. HypersonicPrime

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    That is interesting. All of mine make logical sense so far. As for any algorithm, I'm sure there are situations that don't fit it well that might have not been caught during testing. At least you can turn it off I suppose. For the stops that don't have a dot that you think should, try letting off the accelerator at exactly the same location and coming to a stop at exactly the same location and keeping the charge bar above the horizontal dashed line. As for the curves, I wonder if you maintained a more constant speed around them (no braking), the green dots would go away. It's worth trying if you're really interested. If you do want/need to decelerate noticeably on the curves, it might actually be doing the right thing to predictively regen on them (I hadn't considered that it might do that as well, but it makes sense).
     
  18. DavidA

    DavidA Prius owner since July 2009

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    Yup, tried all that, except the turning the feature off part. Maybe it is telling me I need to slow down around those curves? Still wish there was an edit function.
     
  19. HypersonicPrime

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    Recently it put a leaf on a road where I curve 60 degrees to the right (no stop sign). Normally I tap on the brakes slightly. Today I let off the accelerator when it advised and it regeneratively braked harder than normal--just the right amount for me to go around without using the brake pedal. That was pretty neat.
     
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