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BYD's cheapest electric cars to have Lidar self-driving tech

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Re: BYD's cheapest electric cars to have Lidar self-driving tech

#141

Post by CamperBob2 »

addaon wrote: post #135
CamperBob2 wrote: post #133

Earlier quoted context omitted.

I think we may have had this discussion before, but from an engineering perspective, I don't buy it. For coding, the number of pulses per second is what matters, not power. Large numbers of bits per unit of time are what it takes to make two sequences correlate (or not), and large numbers of bits per unit of time are not a problem in this business. Signal power limits imposed by eye safety requirements will kick in l…

> For coding, the number of pulses per second is what matters, not power. I haven't seen a system that does anti-interference across multiple pulses, as opposed to by shaping individual pulses. (I've seen systems that introduce random jitter across multiple pulses to de-correlate interference, but that's a bit different.) The issue is you really do get a hell of a lot of data out of a single pulse, and for interestin…

I haven't seen a system that does anti-interference across multiple pulses...

My naive assumption would be that they would do exactly that. In fact, offhand, I don't know how else I'd go about it. When emitting pulses every X ns, I might envision using a long LFSR whose low-order bit specifies whether to skip the next X-ns time slot or not. Every car gets its own lidar seed, just like it gets its own key fob seed now.

Then, when listening for returned pulses, the receiver would correlate against the same sequence. Echoes from fixed objects would be represented by a constant lag, while those from moving ones would be "Doppler-shifted" in time and show up at varying lags.

So yes, you'd lose some energy due to dead time that you'd otherwise fill with a constant pulse train, but the processing gain from the correlator would presumably make up for that and then some. Why wouldn't existing systems do something like this?

I've never designed a lidar, but I can't believe there's anything to the multiple-access problem that wasn't already well-known in the 1970s. What else needs to be invented, other than implementation and integration details?

Edit re: the 20 Hz constraint, that's one area where our assumptions probably diverge. The output might be 20 Hz but internally, why wouldn't you be working with millions of individual pulses per frame? Lasers are freaking fast and so are photodiodes, given synchronous detection.

Re: BYD's cheapest electric cars to have Lidar self-driving tech

#142

Post by VerifiedReports »

JumpCrisscross wrote: post #136
VerifiedReports wrote: post #127

Earlier quoted context omitted.

But who gets the ticket when a self-driving car is at fault?

> who gets the ticket when a self-driving car is at fault? Whoever was in control. This isn’t some weird legal quagmire anymore, these cars are on the road.

Apparently it IS still a legal conundrum: https://www.motortrend.com/news/who-gets-a-ticket-when-a-way...

And will continue to be until every municipality implements laws about it.

Re: BYD's cheapest electric cars to have Lidar self-driving tech

#143

Post by AnotherGoodName »

cameronh90 wrote: post #131
AnotherGoodName wrote: post #5

Lidars come down in price ~40x. https://cleantechnica.com/2025/03/20/lidars-wicked-cost-drop... Meanwhile visible light based tech is going up in price due to competing with ai on the extra gpu need while lidar gets the range/depth side of things for free. Ideally cars use both but if you had to choose one or the other for cost you’d be insane to choose vision over lidar. Musk made an ill timed decision to go vision…

If you have to choose one over the other, it has to be vision surely? Even ignoring various current issues with Lidar systems that aren’t fundamental limitations, large amounts of road infrastructure is just designed around vision and will continue to be for at least another few decades. Lidar just fundamentally can’t read signs, traffic lights or road markings in a reliable way. Personally I don’t buy the argument t…

For full self driving sure but the more regular assisted driving with basic ‘knows where other cars are in relation to you and can break/turn/alarm to avoid collisions’ as well as adaptive cruise control lidar can manage well enough.

I think fsd should be both at minimum though. No reason to skimp on a niw inexpensive sensor that sees things vision alone doesn’t.

Re: BYD's cheapest electric cars to have Lidar self-driving tech

#144

Post by polishdude20 »

g947o wrote: post #36
cyberax wrote: post #16

Keep in mind, that $25k AUD is just $16600. And for that price, you're getting a real car with driver-assist features and a reasonable crash safety rating. The US car manufacturers are cooked.

US manufacturers are going to be ok as long as there are policies banning foreign cars and there are tariffs, which is going to be true for a long time. And somehow US consumers feel comfortable paying more for worse cars.

Man, living in Canada, I wish we were allowed to import Chinese cars. If America is putting tariffs on us and threatening our sovereignty, that's all the more reason to divest from American made cars.

Re: BYD's cheapest electric cars to have Lidar self-driving tech

#145

Post by cpgxiii »

cameronh90 wrote: post #131
AnotherGoodName wrote: post #5

Lidars come down in price ~40x. https://cleantechnica.com/2025/03/20/lidars-wicked-cost-drop... Meanwhile visible light based tech is going up in price due to competing with ai on the extra gpu need while lidar gets the range/depth side of things for free. Ideally cars use both but if you had to choose one or the other for cost you’d be insane to choose vision over lidar. Musk made an ill timed decision to go vision…

If you have to choose one over the other, it has to be vision surely? Even ignoring various current issues with Lidar systems that aren’t fundamental limitations, large amounts of road infrastructure is just designed around vision and will continue to be for at least another few decades. Lidar just fundamentally can’t read signs, traffic lights or road markings in a reliable way. Personally I don’t buy the argument t…

For one, no one is seriously contemplating a LIDAR-only system, the question is between camera+LIDAR or camera-only.

> Lidar just fundamentally can’t read signs, traffic lights or road markings in a reliable way.

Actually, given that basically every meaningful LIDAR on the market gives an "intensity" value for each return, in surprisingly many cases you could get this kind of imaging behavior from LIDAR so long as the point density is sufficient for the features you wish to capture (and point density, particularly in terms of points/sec/$, continues to improve at a pretty good rate). A lot of the features that go into making road signage visible to drivers (e.g. reflective lettering on signs, cats eye reflectors, etc) also result in good contrast in LIDAR intensity values.

Re: BYD's cheapest electric cars to have Lidar self-driving tech

#146

Post by pests »

ares623 wrote: post #140
gbnwl wrote: post #137

Earlier quoted context omitted.

Sorry if this is obvious, but are there actually any systems that "choose one over the other"? My impression's always been it was either vision + LIDAR, or vision alone. Are there any examples of LIDAR alone?

Roombas

I don't think they would be as well accepted into peoples homes if they had a mobile camera on it. Didn't they already leak peoples home mappings?

Re: BYD's cheapest electric cars to have Lidar self-driving tech

#147

Post by addaon »

CamperBob2 wrote: post #141
addaon wrote: post #135

Earlier quoted context omitted.

> For coding, the number of pulses per second is what matters, not power. I haven't seen a system that does anti-interference across multiple pulses, as opposed to by shaping individual pulses. (I've seen systems that introduce random jitter across multiple pulses to de-correlate interference, but that's a bit different.) The issue is you really do get a hell of a lot of data out of a single pulse, and for interestin…

I haven't seen a system that does anti-interference across multiple pulses... My naive assumption would be that they would do exactly that. In fact, offhand, I don't know how else I'd go about it. When emitting pulses every X ns, I might envision using a long LFSR whose low-order bit specifies whether to skip the next X-ns time slot or not. Every car gets its own lidar seed, just like it gets its own key fob seed now…

I suggest looking at a rotating lidar with an infrared scope... it's super, super informative and a lot of fun. Worth just camping out in SF or Mountain View and looking at all the different patterns on the wall as different lidar-equipped cars drive by.

A typical long range rotating pulsed lidar rotates at ~20 Hz, has 32 - 64 vertical channels (with spacing not necessarily uniform), and fires each channel's laser at around 20 kHz. This gives vertical channel spacing on the order of 1°, and horizontal channel spacing on the order of 0.3°. The perception folks assure me that having horizontal data orders of magnitude denser than vertical data doesn't really add value to them; and going to a higher pulse rate runs into the issue of self-interference between channels, which is much more annoying to deal with then interference from other lidars.

If you want to take that 20 kHz to 200 kHz, you first run into the fact that there can now be 10 pulses in flight at the same time... and that you're trying to detect low-photon-count events with an APD or SPAD outputting nanoamps within a few inches of a laser driver putting generating nanosecond pulses at tens of amps. That's a lot of additional noise! And even then, you have an 0.03° spacing between pulses, which means that successive pulses don't even overlap at max range with a typical spot diameter of 1" - 2" -- so depending on the surfaces you're hitting, on their continuity as seen by you, you still can't really say anything about the expected time alignment of adjacent pulses. Taking this to 2 MHz would let you guarantee some overlap for a handful of pulses, but only some... and that's still not a lot of samples to correlate. And of course your laser power usage and thermal challenges just went up two orders of magnitude...

Re: BYD's cheapest electric cars to have Lidar self-driving tech

#148

Post by spiderfarmer »

mft_ wrote: post #87
AnotherGoodName wrote: post #5

Lidars come down in price ~40x. https://cleantechnica.com/2025/03/20/lidars-wicked-cost-drop... Meanwhile visible light based tech is going up in price due to competing with ai on the extra gpu need while lidar gets the range/depth side of things for free. Ideally cars use both but if you had to choose one or the other for cost you’d be insane to choose vision over lidar. Musk made an ill timed decision to go vision…

Given a good proportion of his success has rested on somehow simplifying or commodifying existing expensive technology (e.g. rockets, and lots of the technology needed to make them; EV batteries) it's surprising that Musk's response to lidar being (at the time) very expensive was to avoid it despite the additional challenges that this brought, rather than attempt to carve a moat by innovating and creating cheaper and…

The ways in which Musk dug himself in when experts predicted this exact scenario confirmed to me he was not as smart as some people think he was. He seemed to have drank his own koolaid back then.

And if he still doesn’t realize and admit he is wrong then he is just plain dumb.

Pride is standing in the way of first principles.

Re: BYD's cheapest electric cars to have Lidar self-driving tech

#149

Post by analog31 »

rafabulsing wrote: post #126
mrtksn wrote: post #53

Earlier quoted context omitted.

I wonder if ubiquity doesn’t effect the lidar performance? Wouldn’t the systems see each other’s laser projections if there are multiple cars close to each other? Also is LIDAR immune to other issues like bright 3rd party sources? At least on iPhone I’m having faceid performance degradation. Also, I suspect other issues like thin or transparent objects net being detected. With vision you rely on external source or fl…

I'm not a self-driving believer (never had the opportunity to try it, actually), but I'd say bad traffic would be the number one case where I'd want it. I don't mind highway driving, or city driving if traffic is good, but stop and go traffic is torture to me. I'd much rather just be on my phone, or read a book or something. Agreed that public transportation is usually the best option in either case, though.

Unfortunately in my region highway traffic is quite congested, and so called "adaptive cruise control" is a game changer. I find it reduces fatigue by a lot. Usually the trucks are all cruising at the speed limit and I just hang with them. I only change lanes if they slow down or there's an obstruction etc.
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