The debate over unintended acceleration, having lingered around the periphery of the auto industry for more than two decades, may be about to receive a fatal blow.
The National Highway Traffic Safety Administration (NHTSA) has proposed inclusion of a system that would shut down the throttle in the event that the brake and accelerator pedal were depressed simultaneously, and most automakers appear to be squarely behind it. Known as a brake-throttle override (BTO), the system would minimize the risk that drivers would lose control of their vehicles due to a stuck accelerator or entrapped floormat.
"We support the idea of making it standard," Wade Newton, a spokesman for the Alliance of Automobile Manufacturers, told Design News. "We've been behind it since it was first discussed in 2010." He said that the Alliance is now reviewing the proposal and will offer specific comments at a later date.
The Toyota Matrix was one of the vehicles that was recalled due to problems with unintended acceleration in 2010. (Source: Toyota)
The "unintended acceleration" debate goes back to the mid-1980s, when a class-action lawsuit was filed by a large group of Audi owners, stating that their vehicles experienced unexplained power surges. Audi argued that the surges were caused by drivers' misapplication of the pedals.
The debate was resurrected in 2009 and 2010, when some Toyota owners complained their vehicles accelerated unintentionally. In the Toyota case, however, a subsequent study by NHTSA revealed that there was no electronic cause for the phenomenon. The agency's conclusion was reached after hiring NASA engineers to examine the circuitry and comb through 280,000 lines of software code.
"We enlisted the best and the brightest engineers to study Toyota's electronics systems, and the verdict is in," US Transportation Secretary Raymond LaHood said in a 2011 news conference. "There is no electronic-based cause for unintended high-speed acceleration in Toyotas. Period."
Although the new proposal is still out for comment, auto industry experts said they expect the mandate to build atop the widespread availability of electronic throttle control (ETC) systems. ETC operates the throttle with a sensor and small electric motor, essentially eliminating the mechanical cable that would otherwise run from the accelerator to the throttle valve. Because such systems are essentially electronic, automakers could add the override capability with little or no additional hardware, simply by employing software that initiates a throttle cut-off if the accelerator is stuck and the brake is depressed.
The mentioned dual-pedal-application fix, and the many posters problem with it preventing intentional dual pedal use when needed could be remidied by having a timer delay in the software coding, say requiring 3-5 seconds of continuous dual pedal application to trigger the shutoff. That would allow the occasional valid use of dual pedals that is occasionally useful, and yet maintain the shutdown feature when it is really needed.
Not really. While a manual transmission obviously requires hill holding skill for even the mildest incline, steep roads will even cause an automatic to roll backwards as the idle speed does not produce sufficient torque through the converter. First hand knowledge, don't ya know. :-) But either way a gas/brake interlock has to be smart and tolerant or it'll be an annoyance at best and dangerous at worst.
I find it telling that Toyota was still using carbon pots for the critical throttle position sensor, while at that time the whole automotive industry had long abandoned carbon pots for digital encoders for the volume control of their car radios, because pots were too noisy.
Not that other sensors aren't susceptible to analogous disturbances.
A couple of months back I took a new Toyota Sienna for a test drive. After all, it's the only van "recommended" by Consumers Reports. I found it very difficult to control its speed. Even on a flat smooth and level road, with my foot braced against the center console, the car would slow down and speed up by itself making driving tiring. When I engaged the cruise control, everything settled right down. As you may expect the saleslady with me denied there was anything wrong. Apparently she gets these paranoid test drivers all the time. My hunch was a throttle control problem - still.
How does one go about checking 280,000 lines of code? One immediately thinks of Microsoft Windows, which gets updated ("corrected") weekly. A car manufacturer doesn't have this luxury.
Today's development cycle is highly cost and time constrained. How often have you heard the announcement, "Well, it seems to work. Let's get it out into the field." Further tests are costly and would rob our lead in the marketplace. Then when problems develop in the field, it's always the "stupid users" fault. Wouldn't it make sense to design with the "stupid user" in mind? We can blame it all on human nature's tendency to pass the buck and blame the victim.
Let's just give a thought to how many of our electronic devices have failed in some way in the last 10 years. Couldn't most of those failures been avoided by better design? Same old - same old lousy engineering. We're all human after all.
I would think manual transmissions would be exempt from this measure. Other reasons (besides starting uphill) could exist that the operator might want or need to press brake and accelerator at the same time.
The manual transmission is about the operator having control of power delivery rather than the machine having control over it. Drivers who prefer manual transmissions are generally going to be of a higher skill level and less likely to forget that there are numerous ways to stop unintentional acceleration - and the clutch pedal is right next to the brake. (Yes, I've been using manual transmissions on a wide range of vehicle types for over 30 years. I started very young.:))
Here's another solution looking for a problem. I do not like idea of putting this on every car in the universe simply because a few people fail to hit the correct pedal. I am tired of seeing this panic everytime a problem like this hits the news. Yes, its unfortunate that someone gets hurt or killed, but life is full of risk.
Besides - If we are still in the land of the free and home of the brave, (not sure about that anymore).. I would really like to retain the option to hold the brake and roast the tires. OR - at least know that it is still possible even if I'm too much of an old fuddy-duddy to actually do it.
The gas pedal sensor has been called a potentiometer, and now a dual-pot encoder in these posts. A 'pot' or potentiometer is not an encoder. Does someone know the exact nomenclature of this device ? The encoders that I am familiar with are optical = led's and a rotary grating.
I think that trying to get to feature to work in software and co-exist with times when you might want to depress the throttle and brake is an exercise in futulity.
The 'safety' feature needs to exist apart from the normal throttle, brake and gear shift controls. We already have plenty of experience providing this type of safety system.
I am amazed that auto manufacturers haven't had to do what industrial equipment makes have had to do--- install a big red e-stop (panic) button. When we still had mechanical keys we effectively had this.
Now that electronic 'keyless' systems have been in wide use, we have lost the method for shutting down a misbehaving system and this current condition was bound to happen.
You mentioned "tin whiskers" and I have some recent experience supporting this hypothesis. For several years, I've been 'rebuilding' 2001-03 Prius accelerator assemblies. A dual-pot encoder, when they become "noisy" the control computers detect this and trigger a safe-home mode. This caused the vehicle to behave as if a big-hand was holding the vehicle back.
The replacement accelerator assembly cost ~$500 not counting labor to install. So Doug Schaffer figured out how to rebuild the encoder and I carried this on when he went to China. A simple process, we used a Dremel tool to remove the cover and clean the contacts and surfaces. Reassembled using JB Weld epoxy, it was a cost effective solution. But eventually with the low volumes, I stopped doing this. Then I read the 'tin whisker' papers from GSFC.
I still had a number of 'broken' encoders so following the procedure described in the papers, verified the broken ones had similar characteristics. Then using a 9 V battery to 'burn out' the tin whiskers, I retested them and their failure symptoms were gone.
Modern encoders are Hall effect devices, not dual-pots, so the tin whisker threat is significantly reduced. Furthermore, the older 2001-03 Prius are going out of service and the data suggests these problems were limited to the first year or two of production. The 2003 model year encoders haven't shown similar failure rates. Regardless, 'burning out' the tin whiskers turned out to be a simple and effective solution.
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