3 ms·

Think of normal mode more like adaptive cruise control with lane keeping. When everything works, it’s much easier to control the car, but if the data necessary

Think of normal mode more like adaptive cruise control with lane keeping. When everything works, it’s much easier to control the car, but if the data necessary to feed the control laws go bad, the car has to drop back to the regular old gas/brake + steering wheel (i.e., direct mode) or it may crash. Getting the handover right is obviously tricky though. In this case, if your IMU or airspeed data looks bad, your attitude estimate can’t be relied on and you can’t be certain that any derived values you’re controlling to are valid or stable. Current designs assume the best course of action in those cases is to hand control over to the pilot.

andrewaylett 1y ago
Cruise control was one of the things I was thinking of, actually -- but the brake and accelerator on every car I've used cruise control with, still act as a brake and an accelerator. If I engage with the controls, they act in the way they'd act if the assistance was missing. Sometimes with warnings or stops (lane departure, speed limiters), often with smarter behaviour than might be apparent (regenerative braking, hybrid power trains, adaptive steering, radar/lidar support). Airbus's Normal Law sounds more akin to a car that maintains its current speed and rate of turn if no inputs are given, so if you lift your foot off the accelerator then the car doesn't slow down and if you let go of the steering wheel then it doesn't wobble or re-centre. It might be easier to drive when the assistance is working, but it's not going to be easy to transition to regular brake, accelerator, and steering functions if the assistance needs to switch off.
- fisherjeff 1y ago
  Well at a high level, ADAS and normal law both basically function as a way to remove the steady state effort of steering, allowing the driver/pilot to focus solely on fine corrections. You can still avoid potholes, overtake cars, etc., when ADAS is on but that’s the majority of your inputs. I think really the biggest difference between the two systems is that ADAS does not abstract away nearly so many actions. Once direct mode is activated, obviously you suddenly have to start doing all the low-frequency yoke movement, but then you also need to work rudders to coordinate your turns, trim control surfaces, etc., etc., and if you are unaware that the mode has changed then it is not going to go well.

andrewaylett 1y ago

Cruise control was one of the things I was thinking of, actually -- but the brake and accelerator on every car I've used cruise control with, still act as a brake and an accelerator. If I engage with the controls, they act in the way they'd act if the assistance was missing. Sometimes with warnings or stops (lane departure, speed limiters), often with smarter behaviour than might be apparent (regenerative braking, hybrid power trains, adaptive steering, radar/lidar support). Airbus's Normal Law sounds more akin to a car that maintains its current speed and rate of turn if no inputs are given, so if you lift your foot off the accelerator then the car doesn't slow down and if you let go of the steering wheel then it doesn't wobble or re-centre. It might be easier to drive when the assistance is working, but it's not going to be easy to transition to regular brake, accelerator, and steering functions if the assistance needs to switch off.

fisherjeff 1y ago
Well at a high level, ADAS and normal law both basically function as a way to remove the steady state effort of steering, allowing the driver/pilot to focus solely on fine corrections. You can still avoid potholes, overtake cars, etc., when ADAS is on but that’s the majority of your inputs. I think really the biggest difference between the two systems is that ADAS does not abstract away nearly so many actions. Once direct mode is activated, obviously you suddenly have to start doing all the low-frequency yoke movement, but then you also need to work rudders to coordinate your turns, trim control surfaces, etc., etc., and if you are unaware that the mode has changed then it is not going to go well.