Hey Robert, > Il giorno 23 feb 2017, alle ore 5:56 PM, ROBERT <[email protected]> ha > scritto: > > First some criticisms: (1) About three weeks ago I posted a question "How > does regenerative braking work" No one had an answer.
Not everyone reads every message; if you have questions to the list, post detailed information. > Now numerous people appear to know something about regenerative braking. People like to help. > (2) My original question was "has anyone installed a wheel speed sensor on an > EV conversion that was not originally equipped with a wheel speed sensor" I > did not state my reason for the question because of what would follow. I > answered one of the e-mails and stated my reason and got a lot of replies but > no answer to my question. That’s because the answer is simple: no one has done this. And in practice, I seriously doubt that adding a wheel speed sensor to each wheel will actually help with stability given the fact that available AC controllers are pretty weak (I’ll assume it is a Curtis controller). I’ll ignore the fact that you could buy a crashed tesla controller/motor, since I doubt you are doing this — but again, you haven’t really provided all the info on what you are doing. > > I posted this same question to the 914 Club website. Dr914 stated that > Porsche installed wheel speed sensors in the CV joints in early models for > cruise control. > > Response to the replies: > > Congratulations to Lee Hart. He understands why all car manufacturers use > wheel speed sensors data for regenerative braking. > > "If you're going to use regenerative braking to provide this same feature, > your > controller needs to know the speed of each wheel. Otherwise, one wheel can be > slipping, and you'd lose braking in *both* wheels (probably rather suddenly).” This is obvious for production cars. For a conversion…uh, good luck. You’d have to translate sensor information into the regen input on the Curtis controller, and splice that in with whatever other mechanism you are using to do normal regen. > > Peri Hartman > > "First, I wonder what Tesla does. If they do it, it's probably well > thought out.” > > Quote from a Tesla test engineering report: > > "Safety: Negative torque applied to the rear wheels can cause a car to become > unstable. Since regen braking is a source of negative torque, the Tesla > Roadster uses the traction control system to limit regen if the rear wheels > start to slip. I was part of the team that developed and verified this safety > feature on a frozen lake in Arvidsjaur, Sweden." > > Corbin Dunn > > "For some reason, this doesn't make sense to me. You are saying that you need > a speed sensor on each wheel, or else regen would create instability. You > could say the same thing for forward power applied by the motor. I think > this would only matter if you had a controller on each wheel -- which, maybe > you do...I'm not exactly sure what you are trying to do without way more > information." > > You are incorrect. Uh, seriously — you are going to have more problems with forward torque control rather than regen causing any sort of issue. corbin > > Cor van de Water > > "He is trying to create a traction control device AKA ABS controller by > verifying that each wheel is spinning for application of regen (and, I > presume also acceleration as that typically puts more torque on each > wheel from the controller than the regen braking part)" > > I will not install an ABS system because of the liability. I will use the > original mechanical brakes with upgrades. In addition, I will install a > brake pedal positioner sensor (analog) and digital signal for brake > activation. The regen will occur between 0 - 6 degrees of pedal movement. > After 6 degrees the mechanical brake will take over. I will be able to > select between accelerator pedal regen (like the Tesla and Leaf) or brake > pedal regen (I think this system is used by BMW) > > "More than likely the OEM ABS (tone ring) wheel sensors and/or suspension > compression measurement will do the job." > > Great, now tell me the tone wheel, hub assembly, or bearing assembly with > built in tone wheel that I can use on a Porsche 914. > > > > > > From: EV <[email protected]> on behalf of Lee Hart via EV > <[email protected]> > Sent: Thursday, February 23, 2017 5:26 PM > To: corbin dunn; Electric Vehicle Discussion List > Subject: Re: [EVDL] Wheel Speed Sensor > > corbin dunn via EV wrote: > > For some reason, this doesn't make sense to me. You are saying that you > > need a speed sensor on each wheel, or else regen would create instability. > > You could say the same thing for forward power applied by the motor. I > > think this would only matter if you had a controller on each wheel -- > > which, maybe you do...I'm not exactly sure what you are trying to do > > without way more information. > > I think he's basically correct. Think about anti-lock brakes. Each wheel has > its > own speed sensor, and controls the braking to that particular wheel to keep > it > from skidding. If you're on ice or other poor-traction conditions, there can > be > a considerable difference in how much braking force each wheel can handle. > > If you're going to use regenerative braking to provide this same feature, > your > controller needs to know the speed of each wheel. Otherwise, one wheel can be > slipping, and you'd lose braking in *both* wheels (probably rather suddenly). > > -- > Anyone can make the simple complicated. Creativity is making the > complicated simple. -- Charles Mingus > -- > Lee Hart, 814 8th Ave N, Sartell MN 56377, www.sunrise-ev.com > <http://www.sunrise-ev.com/> > The Sunrise EV2 Project <http://www.sunrise-ev.com/> > www.sunrise-ev.com <http://www.sunrise-ev.com/> > The Sunrise EV2 Project Homepage. Welcome! 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