Scary highway brake

[windscar911]

I just experienced it. In a faster freeway lane, rounding a corner and visually being blocked by a semi in the other lane. Couldn’t see that traffic had slowed in front of me because of the blocking semi. I began to brake. The collision warning came on and it felt as if the brakes got ‘soft’ making me brake harder. Not sure if the ABS came on. This all happened in a split second. Definitely didn’t hit the wrong pedal because I was already breaking. I avoided collision but am very concerned about this issue. To me, it seems like a problem with the collision warning and braking system.

sucks that it happened to you. Please let customer care know and DM @mcr16 here with a timestamp or any other information you can think of.

 

[ac.bill]

The brake and accelerator are at the same height and close together. It ias very easy to press both at the same time.

 

[windscar911]

The brake and accelerator are at the same height and close together. It ias very easy to press both at the same time.

And yet I can say with 100% certainty that it was not the case when I experienced this.

 

[Shuasha]

The brake and accelerator are at the same height and close together. It ias very easy to press both at the same time.

Doesn't matter, the accelerator shouldn't do anything if the brake is depressed past a point.

 

[SilverAlert]

The brake and accelerator are at the same height and close together. It ias very easy to press both at the same time.

Uh, no. My foot was ON THE BRAKE AND BRAKING when the collision avoidance came on and the pedal went 'soft' making me push harder to avoid a rear ender. I can see why some say it accelerated because losing your brakes for that brief second feels like acceleration when in actuality you're only losing your deceleration momemtum. The split second when you're trying to avoid a collision and you can't feel the brakes is a very scary split second and probably costs few feet in stopping distance which may be the difference between a safe stop and a collision.

 

[wux]

I think the car didn’t actually accelerate. It just lost the regen torque, and brake pad is barely touching. It feels like acceleration. But it just lost braking power. So push brake harder will stop it. You know as a human, the first reaction is “am I pushed the wrong paddle?” so 1 more seconds hesitation made this situation worse.

Little bit deeper if anyone is interested. My guess is when the brake paddle touch the rotor, the sudden change of phase made motor control lost the detection of motor rotor position. If you have a high brake torque at this time. It my lost completely. Or maybe push the power to wrong direction. I think it is a common issue with EV. All the control engineer are facing it and solving it one way or another. It is tricky and may have coner cases. I cannot reproduce it later today. Hopefully the data Lucid got from my car help then fix something.

I am not lucid engineer so could be completely wrong. No responsible for it.

This can easily be tested. In an open road, let the regen on then press the brake pad to see if you feel any kind of "acceration". Press brake pad should not take over or reduce regen brake, only add brake force.

 

[chinesejpl]

this has happened to me on 2 separate occasions and both times at high speed (i.e. freeway/highway). Both times, I recall slowing down by releasing the accelerator but then when the car in front slows down or stops more abruptly, I need to press the brakes as I'm approaching too fast and I realize the regen isn't going to be enough then it happens just as previously described. It is almost like there is a split second when the collision warning system tries to process the situation and determines there is a risk of a collision but doesn't recognize that my foot is already on the brake slowing down so it disengages the brake (ie. brake goes soft) before re-engaging the brake as an emergency brake maneuver. It's for a split second, like a quick pause, which is why I feel like the computer is trying to assess and determine how/if it needs to intervene. It's is very un-nerving and has almost led to 2 rear enders had I not mashed on the brakes even harder.

 

[Negan1000]

this has happened to me on 2 separate occasions and both times at high speed (i.e. freeway/highway). Both times, I recall slowing down by releasing the accelerator but then when the car in front slows down or stops more abruptly, I need to press the brakes as I'm approaching too fast and I realize the regen isn't going to be enough then it happens just as previously described. It is almost like there is a split second when the collision warning system tries to process the situation and determines there is a risk of a collision but doesn't recognize that my foot is already on the brake slowing down so it disengages the brake (ie. brake goes soft) before re-engaging the brake as an emergency brake maneuver. It's for a split second, like a quick pause, which is why I feel like the computer is trying to assess and determine how/if it needs to intervene. It's is very un-nerving and has almost led to 2 rear enders had I not mashed on the brakes even harder.

Have you reported to CC?

 

[Trekforever]

I experienced something similar today. I was on the freeway traveling around 60-65mph when the car in front of me abruptly slowed down and stopped. I immediately hit the brakes, but the brakes felt super light / soft and it felt the car lunged forward a bit as I hit it. Luckily. the collision avoidance system took over and applied the emergency brakes - and I was able to stop.

Just reported the issue to CC via email.

 

[GopsandLuci]

Glad I read this thread here on brakes. Mine did lunge forward once and I had to hit the ME breaks hard - this was about 3 months ago when I received my Lucid. Lately, the car is rolling forward frequently quite some distance and regen breaks are taking their time to activate. Noticed this with speeds of 20-30mph. This is an off and on situation with my Lucid b/c there are times when it will stop fine. Is this an issue?

 

[hydbob]

Glad I read this thread here on brakes. Mine did lunge forward once and I had to hit the ME breaks hard - this was about 3 months ago when I received my Lucid. Lately, the car is rolling forward frequently quite some distance and regen breaks are taking their time to activate. Noticed this with speeds of 20-30mph. This is an off and on situation with my Lucid b/c there are times when it will stop fine. Is this an issue?

Is it set to high regen?

 

[Pete44]

I experienced something similar today. I was on the freeway traveling around 60-65mph when the car in front of me abruptly slowed down and stopped. I immediately hit the brakes, but the brakes felt super light / soft and it felt the car lunged forward a bit as I hit it. Luckily. the collision avoidance system took over and applied the emergency brakes - and I was able to stop.

Just reported the issue to CC via email.

Same happened to me yesterday. Cruise control was on, I touched the brake and it deactivated cruise control but lurched forward and then I really jumped on the brake to stop the car.

 

[GopsandLuci]

Is it set to high regen?

It is - never changed my drive mode.

 

[MoniputerLM]

Same happened to me yesterday. Cruise control was on, I touched the brake and it deactivated cruise control but lurched forward and then I really jumped on the brake to stop the car.

This happened to me a couple of times. I am not sure if the car moved forward or just the regen not kicking in. Could have been either.

 

[changinator]

This happened to me in my Pure the other day.

Tried allowing my regenerative braking to slow me down, but wasn't slowing fast enough. Collision detection kicked in and alerted to brake. Pressed on brakes, and it slowed down to a set speed but wouldn't slow down any further. Lucid Stability Control light turned on solid and stayed on for a couple minutes and went away. I had to let go of my brakes and allow regenerative braking to kick in again in order to slow down to a stop. From that perspective, it felt like pressing on the brakes was making me move faster than letting go of brakes and allowing regen braking.

 

[Lucken]

Normally I‘d think the friction brakes would kick in once the regen has maxed out. I can’t imagine why a firm pressing of the brakes wouldn’t engage the friction braking. That sounds like a significant issue that service needs to address.

 

[TakeDuo]

Glad I read this thread here on brakes. Mine did lunge forward once and I had to hit the ME breaks hard - this was about 3 months ago when I received my Lucid. Lately, the car is rolling forward frequently quite some distance and regen breaks are taking their time to activate. Noticed this with speeds of 20-30mph. This is an off and on situation with my Lucid b/c there are times when it will stop fine. Is this an issue?

Do you happen to have a high state of charge (above 90%) when you notice this happen? You link it to speed so this is why I ask. If you have a high SoC, regen is automatically reduced/non-existent by the car because there is nowhere to regen the power to. The higher the speed, the more noticeable no regen because it is generating more power. You will feel the regen slowly come back at lower speeds because it is generating much less power. Again, this is only at high SoC and specific to this post.

However, the reason I bring it up is that for those that have experienced the “acceleration” after the BRAKE! indication could “repeat” it in a controlled environment to see if the feel was similar. If you charge to near 100% you will lose regen. On a clear road, you could get to speed and let go of the go pedal and feel the lack of regen to compare to the “acceleration” you feel under the unique conditions you highlight. The regen on high is incredibly powerful and the lack of it is startling the first time you experience. I think @windscar911 description is spot on

 

[wux]

This has nothing to do with reduced regen. The problem reported is that the friction brakes failed to engage in such scary case. Seems that there might an issue how the regen brakes and friction brakes are "linked". There are too many reports on this

 

[georgedao]

Scary highway brake! Just experience this today. This is a traffic, car in front of me start slow down . I travel about 70mph. Lift the throttle slowly, car regen brake, not enough, start apply ME brake. So far is totally normal and under control. If it is a regular car, it would been fine, and no drama. As soon as I touch the Me brake, lucid start accelerate, I have to push hard on brake get to ABS enable. Almost hit the front car. From outside of my car it must be stupid that the guy accelerate when approaching traffic ! Hope there a bug the they can fix!

I have had the same experience for a while. When I released the accelerator pedal to allow regenerative braking and shortly after, stepped on the brake, the car transitioned from Regenerative Braking to Manual Braking and caused a small acceleration. If I left Regenerative Braking to do its work for a few more seconds, Manual Braking would not show any noticeable acceleration.

 

[georgedao]

Do you happen to have a high state of charge (above 90%) when you notice this happen? You link it to speed so this is why I ask. If you have a high SoC, regen is automatically reduced/non-existent by the car because there is nowhere to regen the power to. The higher the speed, the more noticeable no regen because it is generating more power. You will feel the regen slowly come back at lower speeds because it is generating much less power. Again, this is only at high SoC and specific to this post.

However, the reason I bring it up is that for those that have experienced the “acceleration” after the BRAKE! indication could “repeat” it in a controlled environment to see if the feel was similar. If you charge to near 100% you will lose regen. On a clear road, you could get to speed and let go of the go pedal and feel the lack of regen to compare to the “acceleration” you feel under the unique conditions you highlight. The regen on high is incredibly powerful and the lack of it is startling the first time you experience. I think @windscar911 description is spot on

Yes, my SoC was high when the acceleration was noticeable.