It’s all about drive-by-wire…

With all of the hoopla and news coverage about the Toyota recalls what has been lost in the noise is that all cars are somewhere in the process of shifting over to drive-by-wire systems in major areas like the speed/acceleration control (the thing that we quaintly still call the gas pedal), the braking systems and the steering systems. Older readers will smile knowingly when I mention that I remember when cars had carburetors (you can still see those relics on some street rods) and those carburetors were actually attached to the gas pedal with a physical linkage. When you stepped on the gas the carburetors air flap would move and gas would either be drawn into the intake air stream or in some cases squirted into it. How quaint is that?

Now days when you “step on the gas” you are likely just moving the arm of a rheostat somewhere, which is them signaling a computer chip somewhere else and causing one or more solenoids to move to open the air flap and commanding the fuel injectors to spray more fuel into the intake manifold. You are driving by wire ands there is no physical linkage between the pedal that you still push and the engine components that control acceleration and speed. Some nice little computer interprets what you are doing with your foot and sends commends to other components, based upon a computer program that it has stored inside.

The same thing is starting to be true of both braking and steering in many cars. The issue that was just recently uncovered with the Toyota Prius is one that is caused more by the little program in the braking computer than anything else. Cars will also soon have electronically assisted steering, rather than the old hydraulically powered power steering. Then, some little computer somewhere in the car will evaluate what you just did with the steering wheel and factor in things like the vehicle speed and maybe input from other sensors, like anti-skid sensors, plus input from the brake computer and maybe the engine control computer and it will decide how much electronic assistance to render with what you are trying to do (make a turn, in case you forgot).

So, driving our cars has slowly become more like playing a video game than a real mechanical interaction with the car. There’s not anything wrong with that, I guess; however, I’ve been around computers long enough to know that you can never be 100% sure that they are going to operate as planned and as required. Earlier versions of drive-by-wire had some problems with those little rheostats going bad, since they are basically mechanical devices themselves. Volvo had some rheostat issues with their early drive-by-wire implementation for the gas pedal, as I recall.

Now we hear that Toyota is going to reprogram the brake computer on their Prius and we see pictures of dealership personnel sitting in recalled Toyotas cars with laptop computers hooked up, apparently reprogramming some part of the computer code that controls the engine (the gas pedal). In both cases the Toyota folks have discussed putting failsafe code into those little computers so that they can’t unintentionally make the car accelerate or maybe refuse to apply the brakes. I suppose they will reprogram recalcitrant steering computers, too. One has to wonder; however, why fail safes weren’t built into the computer code to begin with? Did someone make a “this is good enough” decision somewhere in Toyota and who is making similar decisions in the rest of the world’s car companies?

There is now more computer power built into most modern cars than was on-board the lunar spacecraft that made it to the moon and back. That means hundreds of thousands of lines of computer code (maybe millions of lines) and the probability of at least a few errors in the code, even if they are mainly errors of omission (no fail safe code). I shudder to think that my car may have a glitch and need to reboot someday while I’m cruising down the road at 70 miles per hours and need to brake or turn or accelerate. It’s one thing to watch Super Mario slam into a wall in the video game and quite a different thing to see myself heading towards the wall with a car that won’t respond to my computer inputs.