Vibration at 3-4 mph at the end of regenerative braking

[Ingineer]

[On a different note]

I have a 2013 plain ol' S 85, and just concluded a long trip through Utah and back, and noticed rear wheel vibration on the Utah interstates where speeds are 80mph and trucks fly by at 85-90.

Never felt it before. Only happens above 75mph, and occasionally at that. But when it happens it's like, oh hey that's like old cars with badly balanced wheels that wiggle at certain speeds. Exactly what it feels like -- a sudden wiggle/vibration coming from rear area. Nothing felt in steering wheel.

Anyone else noticed something like that, and is there a separate thread for discussing it?

[And now back to your regularly scheduled thread]

Sounds like one of your rear wheels is out of balance. (maybe lost a balance weight?) Seems to center right around 81mph with 19" wheels.

 

[vvanders]

Same here after .36, 85D.

Called Portland service and they hadn't heard of it yet but pulled logs and will call back with an update.

I mentioned the thread and they def seemed concerned, mentioned doing a software update(maybe rollback?) if that is the root cause.

A little concerned something made this through QA but hopefully they can issue a quick fix.

 

[boonedocks]

+1 It is a subtle shudder. Not violent or scraping or grinding just a perceptible slight shudder at the 3-5 mph range slowing without braking

 

[hadfiiw]

Glad I found this thread (thanks Paul!). Very slight rumble when it gets down to 3 MPH and only if I am not using the brake to slow down.

Doesn't seems like a huge deal. Very curious on what in the SW could be causing it.

 

[GlmnAlyAirCar]

Yep. Happens right at 3 mph in my 70 D with .36.

 

[vvanders]

If I had to guess it's oscillating between regen and coast, seems to happen less on uphill and more on downhill(where you'd get positive feedback in that type of situation).

 

[alin3]

It doesn't seem to happen when accelerating from a standstill. I doesn't happen when I brake to a stop. It only seems to happen during regen coasting to a stop. I'm on "standard" regen.

 

[Wayneb]

I experienced something similar but more intense a month or so ago but was never able to isolate or duplicate. It happened several times, always at low speed. I noticed this new effect just today, did update yesterday. S85D, delivered May 15, 2015.

 

[pmoa]

My service center called me to confirm that it is a software bug. Pretty awesome that he said that the California office saw my post here.

 

[mobe]

My 85d does it at 3-4 mph.

 

[MarcG]

So I tried to replicate the problem you guys are experiencing with my P85D a dozen times today and just couldn't feel it...

Can someone please explain in minute details how you're able to replicate this 100% of the time?

 

[prasad]

I noticed the same more than a month back. My car got towed to service center and came back with no concerns and nothing specific about software bug. The grinding noise was stopped for few weeks and it is back again.

 

[beeeerock]

So I tried to replicate the problem you guys are experiencing with my P85D a dozen times today and just couldn't feel it...

Can someone please explain in minute details how you're able to replicate this 100% of the time?

I haven't worked out how to replicate 100% of the time, but I can make it happen perhaps 50% of the time. Note that this seems to be tied to the .36 firmware that downloaded the night before last...

For me, it happens when I coast to a stop with normal regen and NO BRAKES. Just before I stop, I feel a bit of a rumble from the rear end of the car... a bit like going over a rumble strip. It lasts for a very short time, so short you almost wonder if you imagined it. It's very subtle. I think I'm going slower than the 4 mph suggested here, but that number could be because the speedo is still dropping and reads higher than actual - I haven't watched the speedo because it doesn't seem accurate in this decel situation and have just judged my speed myself instead...

 

[neroden]

+1. Their software is behind machinery that is directly responsible for the safety of people. I once contracted for a company that developed software for the military. I'm not going to say exactly what I worked on but if there were bugs, people may be seriously injured. It had the most stringent change control process I've ever experienced. Developers did not have direct access to the software repository. Before we were even allowed to change one line of code, we had to attend change control meetings to justify what files we needed to modify, why we needed to change it and provide stacks of documentation for support. Only after it was approved were we allowed access to files. Before code commits were done, we had attend another change control/code review meeting with a team of guys with decades of software development experience. Code was scrutinized line by line, tons of questions from the team and another stack of paper documenting and supporting every change with proof of dev testing every change. The rejection rate was high and if one single person was uncomfortably with the code or if you were unable to answer one question, you changes were not going in. That was the only place I worked at where there were no bugs released in production, ever. Tesla releasing something with a bug that didn't exist before shows me their software development and software release control is broken. People's lives are on the line. While there's probably no need for Tesla to follow the stringent process with my prior employment, they should not be releasing their software like its a website or system where the worst consequence is losing revenue.

Absolutely.

The code should actually be modularized into different modules, and I certainly hope that it is.

The modules which are more safety-critical should have more stringent change requirements than the less safety-critical modules.

So, the media player should be a "quick to change" module, with minimal review.

Anything related to throttle response should have extremely difficult code review, as serious as your military software review.

Something related to the dashboard should have an intermediate level of review, more difficult than the media player but easier than the throttle response.

 

[Chasedrgc1223]

Just tried it with and without range mode... Prior to this, my understanding was that range mode didn't change anything drivetrane related, however after being able to replicate it 100% of the time without range mode, I tried it with range mode on and was unable to replicate the issue.

 

[pmoa]

I also work for a company that reviews code to military safety standards and while code reviews are tough and nit picky. There are VERY good COTS packages that allow engineers to verify code via branch level testing. It will go through your code and perform its testing and it allows you to see where lines of code and cases that never get hit

I'm sure tesla engineers have employed this type of testing, but then again I've seen instances where thorough testing was not performed. DO178 is the standard the FAA and other agencies use to perform safety testing.

 

[alin3]

Just another data point: In "range mode" No shuddering @ 3-4 mph

Not in "range mode" Definite shudder at 3-4 mph only while coasting on regen and not during active braking. Also none noted during acceleration.

 

[MarcG]

I haven't been able to reproduce the issue in my P85D, but I always leave RANGE MODE in the ON position.

So I have a theory: since range mode torque sleeps the rear motor, and the shudder is being felt coming from the rear end of the car but only when range mode is off (per above reports), this points to the issue being with torque being sent to the rear motor during slow-down. It won't be felt when range mode is on since the rear motor is put to sleep, at least in these sorts of conditions.

 

[mspohr]

I tried to see if I could feel this today in my 85D but could not feel or hear any "shuddering". Just the same smooth deceleration I've always felt.
Range mode off. I tried both going uphill and downhill and on the level.

 

[Summitman7]

Just another data point: In "range mode" No shuddering @ 3-4 mph

Not in "range mode" Definite shudder at 3-4 mph only while coasting on regen and not during active braking. Also none noted during acceleration.

Tried this today with my 70d. Exact same results.