I should probably have responded in more detail on this matter:
"For a given gear, the stored kinetic energy of the vehicle at 2800 RPM will be 1.4 times what it would be at 2400 RPM. Then remember that an EDR value of 2800 RPM might indicate an RPM of up to 3199 RPM. so in this case the ratio of stored kinetic energy between 2,400 and 3199 RPM is 1.8 to 1."
The most direct response I should have made was, since the gear selected at any given time is apparently NOT a stored value in the black box, RPM is irrelevant to computing kinetic energy of the car. That computation must be made with the speed sensor value. *If* the selected gear was a stored value, then indeed an accurate respresentation of RPM could be used to confirm the validity of the speed sensor's data. But that's not the case.
So, RPM, combined with the speed reported, is probably good enough to make a reasonable conclusion on the gear selected. It would show whether the car was accelerating or going at a steady speed/coasting, for instance.
"I think we should distinguish between the deficiencies in the Toyota software that Dr Barr has identified, for which Toyota should be held responsible, and the limited data capturing capability of the EDR for which Toyota are not responsible, since the EDR conforms to a standard agreed to by all the automobile manufacturers and NHTSA."
On this, we agree. I was just pointing out how not being clear can lead the non-fanatic to the wrong conclusions.
"Hold on now. The SENSORS measuring each one of these four parameters are definitely different sensors. If indeed task X is reading all of them and recording them, then that's a different matter. Of course, that would be a bad idea. It doesn't make a lot of sense to have the same app that operates on parameters be the one that stores them in the black box."
All the sensors feed either directly into the ECU or via the CAN bus. As I understand it the EDR reads stored variables from the CAN bus. So you are right: task X reads all the variables and records the values. These are sampled by the EDR and recorded on a continuous loop basis on a 1 second basis.
I agree with you that to combine control monitoring and data recording tasks all within Task X is a bad idea. The sensor outputs should have been fed direct to the EDR then the values would not have gone haywire if Task X died. It is normal industrial practice to keep control, switching/isolation and monitoring functions separate from one another. In this case it seems that Toyota has brought control and monitoring functions together into Task X and more or less ignored the switching/isolation function, or rather it has brought part into Task X and ignored the rest - hence no kill switch or other means of reducing engine power independent of the ECU.
You have the independently measured speed, right? So why pretend that the RPM figure is all you have to go by, to compute kinetic energy? All the RPM figure is meant to indicate, I suppose, is what gear the car is in (presumably, that info is not stored separately).
I was trying to point out that the scale of, for example RPM, is so coarse that it is very difficult to deduce anything. But that does not stop people claiming that the EDR results mean much more than they possibly could. It would be much easier to get an accurate picture of what occurred before the accident with finer graduations of the variables recorded and very much faster sampling. Memory these days is very cheap.
My point is, when you're dealing with an attorney who is not well versed in car things, and never mind the jury, these omissions of information seem designed to obfuscate rather than educate.
The problems are threefold (1) the EDR results, or rather the interpretation put upon them, may well not be justified and (2) the EDR results may be corrupted by the death of task X and (3) you have no way of knowing if the results reflect the actual pre fault situation or not. In the light of what Dr Barr has revealed about the EDR results, I would have thought that both parties would want to exclude EDR evidence from the trial and rely on circumstantial evidence. So we will just have to wait and see with the Vance v Toyota case which will be the next to come up I believe in February.
If I were the lawyer, I would have asked up front, "Did the brakes work throughout this event? Yes or no?" Then I would have asked, "Was power cut when the brakes were applied, when task X died? Under what circumstances was power cut or not cut?" Then I would have asked, "Are these four parameters being stored correctly during task X death?"
There are, as they say, many ways of skinning a cat especially when the cat has experienced eight task deaths already and is now come into the orbit of task X for the ninth.
If it took us three or four articles to get to the "whole truth" on these matters, how likely is it that the jury or the judge got a good idea in real time?
It seems to me that both the judge and the jury made a good job of getting to the heart of the matter in real double-quick-time. Placed in the double-quick time lane we might do better or worse than the jury or the judge, but I would not want to hazard a guess as to which might be the more likely.
NASA's Orion Flight Software Production Systems Manager Darrel G. Raines joins Planet Analog Editor Steve Taranovich and Embedded.com Editor Max Maxfield to talk about embedded flight software used in Orion Spacecraft, part of NASA's Mars mission. Live radio show and live chat. Get your questions ready.
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