7 ms·
Lag in Cybertruck's drive-by-wire system
- meltyness 3y agoThe car with autopilot? There's standards for control like MIL-STD-1472 which I'll bet this meets. I'm sure none of them are "the highly redundant sensor fusion system with absurd levels of automation and sensing, the operator should not be able to notice any lag"
- hef19898 3y agoProps for throwing out some MIL-STD reference, sounds always tough and tacticool, and proclaiming a system meets those without any proof.
- meltyness 3y agouhhh, 100ms isn't particularly stringent for a local system... nor should be the tolerance for the impact of control in a system that's literally at rest. unless we're playing soccer / free-kicks, in which case, yeah, overengineer the hell out of it, sport. ps, chapter 5 precisely specifies tolerances and minimums for things like latency of specific controls, for a control system for heavy machinery intended to be controlled by a human... and thanks for your input.
- yrral 3y agoIs this even an issue? Presumably without a steer by wire system a human would not be able to turn the wheel this fast. Also the delay looks longer than it actually is because of the slow-mo. Say this is playing at 25% speed and it is delayed by 1/2 a second, that means at regular speed the delay is only 125ms.
- solardev 3y ago125ms is pretty bad though. In an online game that'd be borderline unacceptable lag... no local system should be THAT slow? Try it yourself here to see how bad that feels: https://www.skytopia.com/stuff/lag.html https://www.skytopia.com/stuff/lag.html That page also links to a great video on what it's like on a touchscreen: https://www.youtube.com/watch?v=vOvQCPLkPt4 https://www.youtube.com/watch?v=vOvQCPLkPt4
- tgv 3y ago1/8 of a second is terribly slow. Delays like that fuck up your perception/feedback loop. If you put on headphones, and listen to your own speech delayed by that amount of time, you can hardly speak (delayed auditory feedback). If you have to control a device that delays that much, you're prone to overreacting, and then entering a run-away correction cycle, which isn't nice in a heavy, fast moving machine.
- solardev 3y agoYeah, it's really not great. To be fair, though, in the dialup days, many of us learned to cope with that ping while still playing Quake 2 or whatever. You can adapt, it just takes a while, and you learn to lead your target. You can make similar adaptations to vehicle control (like playing a racing game on a really laggy old-school plasma TV), but it's not pleasant. I really wouldn't want highway drivers in that monster truck to have any barriers to their reactions, especially with its nontraditional crumple zone :(
- lttlrck 3y agoPower assist lets you turn a wheel with one finger at any ratio the manufacturer chooses... at most you'll get a lag in the assist but not in the mechanical movement (and I'd be amazed if that is perceptible with electric assist let alone hydraulic) There isn't really any excuse for this. It's hardly a performance car so perhaps it's not a big issue, but it really should not the there and should be fixed.
- dominicdoty 3y agoBecause the steering ratio is variable, the movement shown in the video is about the equivalent of two full turns of a normal steering wheel. I tend to agree with the parent, it'd be hard for a human to equal this performance.
- solardev 3y agoYou know, I rewatched the video, and you convinced me. There's not actually THAT much latency (delay between input and response). There IS some acceleration curve being applied (X degrees of input = X^Y degrees of steering, buffered over time), but that's totally different. It's probably safer this way vs suddenly jerking the actual wheels back and forth.
- jeffbee 3y agoSteering backlash is always non-zero but for a new vehicle should be imperceptible. But that isn't a direct analogy for lag. With backlash, once you've taken it up it's gone. Any continued turn in the same direction translates to wheel movement without delay.
- deleted 3y ago[deleted]
- aaronscott 3y agoI agree with your observation, although it seems unpopular at the moment. It’s clear the video is slowed down and seeing how his hands respond at the end of his action, it looks like he’s throwing the wheel very quickly. The tires start moving immediately, so it looks more like a limit in how quickly they change direction. It appears laggy because they don’t finish the movement when he does. They do respond right away when he shifts his arms a little in the middle of the video.
- eschneider 3y ago125ms is...horrendous. Electronic steering controls are part of my day job and usually you're going for about 5ms delay. If you're more than 10ms, it's a problem.
- 0x38B 3y agoIron for an account called 'facts chaser' to not link to the source they took the video from.
- karmicthreat 3y agoSeems like the same sort of whinging people do about traction control. “Trust me bro I need total control and traction control makes me unsafe” etc. Same sort of thing with people that complain about iterm being too laggy.
- rpmisms 3y agoTraction control absolutely leads to a false sense of security, especially in hazardous conditions. However, steering lag is a bug, not a feature, and having your car go in the direction you point it is very important.
- greggsy 3y agoI think the tone of the tweet is off putting, and while the lag doesn’t seem totally unsafe, it does look a bit poor. That said, how much play is in a normal steering system, powered or otherwise?
- rpmisms 3y agoI hope this can get optimized down to imperceptible levels.
- uconnectlol 3y agoinput lag is usually just a bug / because the devs were lazy. this has to be a joke.
- rpmisms 3y agoIt's obviously well-done, but it should be lower. Tesla's engineering philosophy is "our only limitations are the laws of physics"
- uconnectlol 3y agoyou appeal to authority and yet every "good" company has made this same mistake and only gets worse since the digital era.
- rpmisms 3y agoI'm not appealing to authority. I'm saying that if you're trying to replace a physical system, it should be very very good.
- deleted 3y ago[deleted]
- dom96 3y agoThe most ridiculous thing about the Cybertruck is that it is completely illegal in the EU. For good reason IMO and it's sad that the US allows this risk for pedestrians on the roads.
- SmellTheGlove 3y agoIt would be even worse in the EU. Here in America, both our pedestrians and our cars are larger, so we’ll at least leave a mark when that monstrosity hits us on autopilot. I’m only half joking. I’d be worried in the EU because they don’t drive around mostly in SUVs like we do. A cybertruck versus a panda would not go well.
- Geee 3y agoI don't think this is true. Source?
- nabilhat 3y agoMany jurisdictions in the US have safety regulations specifically around steering. In some jurisdictions it's illegal to drive a car on public roads with steering that has no mechanical connection to the steering wheel. Some areas have a minimum steering wheel diameter that's larger than the cybertruck steering wheel's minor diameter. Some areas have laws requiring a minimum (multiple...) number of turns lock-to-lock. Many areas require your steering to be operable in the event of power loss (I'd bet that everyone on or near a road would like that too). DMV's and police agencies sometimes regulate what they independently perceive as safety problems regardless of law, if someone with the means to declare internal policy gets the urge. And that's for all cars operating on public roads, not just registered, in an area. It might be legal to drive a cybertruck where one lives, but not in a neighboring city or state. Moving fast and ignoring regulations on Tesla's part only works for their customers until regulatory agencies encounter a reason to pay attention.
- ajross 3y agoIs this actually control lag or just an authority limit? If the car takes that long to respond to every control input, it's a serious problem. If it's just that the hydraulics can't move the wheel through full travel as fast as the control can be moved, it's a non-issue. My guess, based on the shitposty tone of the linked tweet, is the latter. Needless to say, if you put someone at the wheel of a vehicle with regular power assist steering, the wheels aren't going to move any faster.
- hef19898 3y agoThe problem is the disconnect between control input and reaction, and that is far from being a non-issue.
- ajross 3y agoNo, "the problem" as described is control lag, and decoupled input simply is not the same thing. What you describe as "far from a non-issue" is a characteristic shared by literally every fly/drive-by-wire system. If you trust your Airbus to get you to your destination, you can trust a Cybertruck[1] to get you home. Or if you don't, you need to come to the debate with evidence and not misleading garbage tweets like this one. [1] Or others. Tesla is not the first company to offer steer-by-wire, just the first to engender this kind of nonsense debate about every decision they make.
- Animats 3y agoYes, it's control lag. Our 2005 DARPA Grand Challenge vehicle, a Polaris Ranger ATV, looked like that in manual mode. The steering wheel was drive by wire, and used a simple PI controller. Stationary, with the steering system fighting static friction, the normal P value useful for driving is too low, so there's lag. The I term cranks up the force until the error goes to 0, but that takes time. Our remote dashboard had two pointers on the steering meter - commanded steering angle and actual steering angle. We could watch the lag. Half a second of lag was OK, because we didn't do any aggressive maneuvers. Manual mode was just for positioning the vehicle before going autonomous. That slowdown at the end of the Tesla video looks like normal operation of a PI controller. Does Tesla have steering force feedback? If the steering wheel is leading the wheels, the steering wheel should be pushing back on the driver if there's significant error.
- kingforaday 3y agoLots of cars throughout the last two decades have suffered from latent issues as a result of new drive by wire implementations. It was very frustrating in some models from early 2000s where the electronic throttle modules where severely delayed. You'd push the pedal to the floor and get no immediate feedback. Terrifying when you're trying to get out of the way.
- deleted 3y ago[deleted]
- Zancarius 3y agoI've had issues with throttle-by-wire but not so much latency as much as the traction control nannies telling me how to drive. First time I had this happen in a '14 Tundra it scared the crap out of me, because it works by cutting throttle to the drive tires if it detects loss of traction. Then it seems like the vehicle is not responding to throttle inputs until the computer decides traction has been regained. I get that it's "safer" for your typical driving conditions, but I'd imagine trying to get out of the way in a hurry it could be a problem... Knowing that's the case now, I kind of expect it, so it's changed my driving habits slightly and has made me plan ahead more than normal. But I can't imagine how actual input latency would feel after that experience.
- Svip 3y agoThey were able to do it in the 1970s without the latency: https://en.wikipedia.org/wiki/DIRAVI https://en.wikipedia.org/wiki/DIRAVI Just no road feedback...
- virtue3 3y agoSo if you operate a bicycle you might understand what's actually going on here a bit more. The first parts of the movement are actually quite responsive but don't result in a huge change. If the wheels moved as the drive dictated the car would flip over. You can't just magically make all the forward momentum go lateral without relying on road and tire friction to get the job done. This can hit limits / you just end up skidding the tires and going ass over end instead of turning because you yanked the wheels too dramatically. It would be like riding a bicycle and then turning the handlebars completely to one side while going at a good pace forward. You could argue why isn't the car just doing it because they're at a standstill and it should be safe to do so? It's probably a sane default in case there are no sensors / no velocity reading / etc.
- hef19898 3y agoA cybertruck can put the front wheels in a 90° angle? What is this, a professional drift car? By the way, if this is true, it is beyond stupid...
- sonofhans 3y ago> If the wheels moved as the drive dictated the car would flip over. Do you mean “… at high speed?” To me, it looks like the person just wants this car to steer the way literally every other car does. Your bicycle analogy — yes, that’s how they work, so pretty quickly you learn how to do that.
- mutatio 3y agoSatirical post I assume? The demo shows the person stearing couldn't apply urgency in directing the wheel, sounds dangerous. Onus should be on the driver being capable of making the steering angle appropriate for the conditions, defending eventually consistent steering is comical, now drivers must account for where and by what speed the wheel angle reaches the desired position?
- itishappy 3y ago> defending eventually consistent steering is comical That's how things work though. Momentum and material strain mean that nothing reacts instantly, and that changes with your speed, steering angle, and rate of change in speed and steering angle. So yes, all drivers must account for the where and by what speed the wheel angle reaches the desired position.
- rainbowzootsuit 3y agoI recognized this as being an outtake from the Engineering Explained YouTube channel. Driving Tesla Cybertruck - Overhyped or the Pickup Reinvented? https://www.youtube.com/watch?v=TeqE1kOO3dE https://www.youtube.com/watch?v=TeqE1kOO3dE From about 10m into the video.
- itishappy 3y agoTimestamp: https://www.youtube.com/watch?v=TeqE1kOO3dE&t=709 https://www.youtube.com/watch?v=TeqE1kOO3dE&t=709
- thimp 3y agoAnyone who has driven a radio controlled car will know how quickly this will turn into a big problem.
- deleted 3y ago[deleted]
- peter422 3y agoI’ve watched many reviews of the cybertruck, including people that have driven thousands of miles with it, and I’ve not heard a single one of them complain about the steering or lag. So my guess is this tweet with one short video and no additional evidence or reasoning behind their claim is wrong.
- uconnectlol 3y agoi would definitely not engineer my system on what truckers' opinion is this topic has been beaten to death throughout all aspects of computing, it always goes like this: 1. someone complains about input lag, because he feels it and it's annoying and prohibitive 2. other people who are slow and / or have misconfigured systems with such worse problems that they don't notice this disagree 3. 7 years later its proven to a wider audience that the lag is there and all the people who said it was there were right 4. the company sells an all new "low input lag" model (which doesn't actually require any money to implement, aside from a few hours dev time)
- jauntywundrkind 3y agoIf you turn audio on, the audio is very slowed down. Watching sound off it seemed absurd, horrifying, but perhaps the lag is only mild.
- uconnectlol 3y agohere it is, folks. we finally have cars with the shit design where you just shove random components that add lag in because you're too lazy / uneducated to understand your 'stack' or well-established science (such as the fact that input lag matters and the more of it you have, the more mistakes the human makes, even when the total lag is below the human 'reaction time'). the market is driven by who has the most clout, regardless of whether your product is sound. this is also why i don't use drive-by-wire, it was just obvious that they'll eventually mess this up (even if this tweet is not accurate).
- tommi 3y agoIf I would like to do quick lane change as an evasive manoeuvre, then how much would this lag affect at 80 km/h?
- 39 3y agoImagine trying to course correct while hydroplaning or skidding on snow.
- Zandikar 3y agoThe vehicle isn't moving. It's a several ton vehicle. No matter the rate of turn, it has no forward momentum to assist the turn. This is the same reason that non-power-assisted steering vehicles are easy to turn at high speed, and difficult at low/no speed. It takes more energy. This means the quicker (in terms of acceleration and velocity) you turn the drive wheels the more energy it takes and the more wear and tear it places on the steering components and tires. Even if this wasn't by design and is a limit of the "power" of the power steering system unable to "keep up", so what? Try going 0.5mph and see how it feels. Also notice its not LAG. It starts turning THE MOMENT you turn the steering wheel, it's rate of change just isn't the same. That's not latency. The vehicle still turns the wheels when you ask it to, even when stopped. In what scenario do you need a stopped vehicles tires to steer from lock to lock in under 3 seconds? There is plenty to complain about the cybertruck. This aint it, chief.
- oldcigarette 3y ago>muh lag Every car for the last 150 years has had mechanical connection from the steering wheel to the tires and nobody is talking about the reliablity and safety concerns. The absolute state of hacker news.