The (spring loaded) inverted pendulum was one of the earliest analyzed models of legged locomotion.
Thats what all those self-balancing scooters are.
Both are useful.
Is the sample solution just hardcoded or is there some maths behind it to make it work from any location/initial speed?
function controlFunction(block)
{
let L = Math.floor;
let x = block.x;
// Use Collatz. L(x+½) is the closest integer.
return
-(L(x+0.5) % 2 === 0
? x/2 // Even, we chop it
: 3*x + 1 // Odd, we triple-plus-one it.
);
}
Pretty neat website overall. Seems like I'll be wasting some time on it.
On the "Cruise Control Intro" challenge it's not made clear what the output of the controlFunction is. Am I returning a throttle position? A delta to the throttle position? Something else?
I didn't have any trouble until I got to "Ball on Platform: Balance" which seems to be multiple steps more difficult than the previous ones.
Don't get me wrong, I think this is really awesome! We are only talking about a few UI improvements to what is already an excellent resource.
This would probably not be a concern in this digital simulator, but such an error can pop up when trying the same thing out in real life.
See slide 17 here for a plot: https://www.slideserve.com/sibyl/finite-settling-time-design
https://backreaction.blogspot.com/2022/12/how-chaos-control-...
I actually made a similar thing based on writing your own autopilot for a Lunar Lander [1]. It's hard to make the difficulty increase linearly though. I like the use of different scenarios in this one.
function controlFunction(block)
{
const max_force=1000000000;
const margin=0.01;
const friction_comp=0.2;
if(block.x<-1-(margin/2))
return max_force*(1+friction_comp);
else if(block.x<-1.15*margin)
return -max_force;
else
return -block.x;
}The rest of the puzzles get pretty interesting, I shouldn't have just stopped on the first and spent all the time optimizing it.
If the author sees this thread it would be fun if you could disturb the dynamics with the mouse after completing one. I wanna watch the ball catching piston right the ball if I poke it.
@ajtulloch might be the world’s leading expert in making 100 billion bucks in 2 months with a device that can be built out of mechanical parts.
So in many, if not most, contemporary Information Retrieval (IR) problems, there is a total document set larger than could be explored on an interactive basis and so the data structures get laid out in such a way that with some probability north of a coin, you’ll find “better” documents in the “front” half. This is hand-waving a lot of detail away, so if you’d like me to go into some detail about multi-stage ranking, and compact posting lists and stuff I’m happy to do that in subsequent comment.
But it’s a useful fiction as a model and the key part is that there’s still “good” stuff in the “back” half: you’d like to consider everything if you had time.
A PID controller (again oversimplifying a bit) is charged with one primary task: given some observed quantity (temperature in a room) and some controlled quantity (how hard to run the AC), maintain the observed quantity as close to a target as possible via manipulating the controlled quantity.
If you hook one of these things up to an IR/search system (web search, friend search, eligible ads, you name it) where the observer quantity is e.g. the p95 or p99.9 latency of the retrieval, and the controlled quantity is how “deep” to go into the candidate set something magical happens: you always do something close to your best even as the macro load on the system varies.
That’s again a pretty oversimplified (to the point of minor technical inaccuracies) TLDR, but I think it makes the important point.
If you’d like more depth feel free to indicate that in a comment and I’ll do my best.
function controlFunction(block) { let x = 5; if (block.dx > 0) { x = block.dx; } if (block.T > 1.75) { return 0; } return 2 * x; }
function controlFunction(block)
{
const t = Math.round(block.T / 0.02);
return (t <= 10) ? +50
: (t <= 18) ? -50
: (t == 19) ? -22.4538198550841
: (t == 20) ? -27.5461801449159
: 0;
}
Beware: time flies past
function controlFunction(block) { return -500 * block.x -60 * block.dx; }