Quote:
Originally Posted by e*clipse
The unintended accelleration/decelleration problem is a big concern for me.
My CNC machines had a huge red E-stop button that everyone operating them had to instinctively know about. Expensive problems can happen awfully fast. With an automobile, it goes WAY beyond merely expensive.
Regarding decelleration, I would suggest going into some "coast" mode. Let the driver decide whether to hit the brakes or not. Depending on traffic, etc hitting the brakes randomly (and it would seem random to the driver) could cause a huge problem.
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Bare in mind this is not Paul's inverter we're talking about, I'm just sharing my own testing, on my setup, and ideas to implement this stuff.
I have brake override feature activated and that triggers an hardware buffer to cut down power. Same with an over current. In fact I am working on the replacement of the mechanical contactor with an IGBT, which should cut power much faster in case of a problem. Effectively I am leaving the fuses as a last resource. They are expensive and testing shows they don't blow instantaneously.
The issue I found with my REV3 inverter was when the car was starting to move, while the encoder is going very slowly but the motor is magnetically saturated, for example while parking. The car at times jumps forward. This happened about half a dozen of times over the course of the last two years, when the weather is very wet, for example after or during a significant rain. Luckily the motor is not operating in closed loop anymore, so hitting the brakes hard is enough to stop it. REV4 should not have such issues, due to a number of changes (different design altogether) but it I may still suffer erratic operation due to data corruption and I haven't found a variable I could use for redundancy. I trust no design is completely free from this issue.
Quote:
Originally Posted by e*clipse
For my part, I'm making the resolver output center on 2.5V and range from 0.5V to 4.5V. Anything above/below the range will be an error. The Honeywell throttle position sensors used this method, which I think is very smart. With it, you can easily detect open or short circuits.
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Beyond that, I think the brake pedal or the e-brake lever could act as an intuitive override (E-stop button), just in case all the safety logic Paul built into this fails for some reason.[/QUOTE]
I'm not sure what is that you are using? Throttle? I use that method for the throttle, as manufacturers use. The throttle sits between 0.5 and 4.5V and anything below or above will trow an error. In addition, as mentioned, pressing both the brake and the throttle will shutdown the whole thing. This is done by external logic.