First some criticisms: (1) About three weeks ago I posted a question "How does regenerative braking work" No one had an answer. Now numerous people appear to know something about regenerative braking. (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.
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)." 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. 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 <ev-boun...@lists.evdl.org> on behalf of Lee Hart via EV <ev@lists.evdl.org> 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 The Sunrise EV2 Project Homepage. Welcome! 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