3 ms·
What would a hardware limit even look like in an electric car? A centrifugal governor on the axle that physically interrupts a kiloamp-scale conductor? A clock
by addaon 4y ago
What would a hardware limit even look like in an electric car? A centrifugal governor on the axle that physically interrupts a kiloamp-scale conductor? A clock comparator between a Hall sensor on the wheel and a calibrated oscillator that keeps a contactor closed when the former is slower than the latter? These seem like heavy, error-prone systems that add more failure modes than they remove, compared to just having a software limit...
- lm28469 4y ago> What would a hardware limit even look like in an electric car? A properly sized motor ? My electric scooter can't reach 200kph, even without the 25kph software throttle
- addaon 4y agoA motor sized to be have a maximum speed of, say, 100 mph means by definition that the power the motor can send to the wheels at 100 mph exactly equals the power lost to drag etc. by the vehicle at 100 mph (under the design conditions, presumedly dry flat road). Which means that the time to accelerate to 100 mph is infinite; and, more importantly, the time to accelerate from 70 mph to 80 mph is going to be ridiculously long. In other words, a vehicle that is power-limited to a "reasonable" speed is unsafe for normal highway driving because of insufficient acceleration to pass and avoid hazards. There's a reason that even a modern econobox can easily exceed reasonable speed. If you want to limit speed, you have to do it based on (wheel) rpm, not based on power.
- lm28469 4y agoStill, do you need to do 0-60 on 2.9s in your 3 tonnes tesla ? There is a whole spectrum between 0-100 in an "infinite time" and 0-100 faster than a supersport car of the 90s