Design, tech, engineering and science. Head of Design and User Research.
function onTick() {
// Keep total time elapsed up to date
mutable totalMsElapsed = mutable totalMsElapsed + msPerTick;
const oldGasPedal = mutable gasPedal;
const oldX = mutable x;
const oldV = mutable v;
// 1. Update pos as defined by current v
mutable x = oldX + actualV * sPerTick;
// 2. Update v as defined by a
mutable v = Math.max(0, oldV + a * sPerTick);
// 3. Update gas pedal values
mutable gasPedal = desiredGasPedal;
console.log(mutable gasPedal, oldGasPedal);
// 4. Cruise control
// 4.1 Track how long velocity has been retained
if (roundV(oldV) === roundV(v)) {
mutable vRetainedFor = mutable vRetainedFor + msPerTick;
} else {
mutable vRetainedFor = 0;
}
// 4.2
// Evaluate if cruise control should be turned on
if (
!mutable cruiseControlIsActive &&
!brakePedal && // Never activate when break is used
actualV >= minCruiseControlV &&
vRetainedFor > minCruiseControlActivationT
) {
mutable cruiseControlV = actualV;
mutable cruiseControlIsActive = true;
}
// 4.3
// Turn cruise control off when breaking
if (mutable cruiseControlIsActive && brakePedal) {
mutable cruiseControlIsActive = false;
}
// 4.4
// Turn cruise control off when user accelerates
// We could compare V, but we're specifically interested in user interaction (V could increase when going downhill)
if (mutable cruiseControlIsActive && mutable gasPedal > oldGasPedal) {
// We must reset this counter, or CC will just be turned on in the next cycle
mutable vRetainedFor = 0;
// Turn CC off
mutable cruiseControlIsActive = false;
}
}
minCruiseControlV = cruiseControlDisabled
? 10000 // hack to implement disabling
: (minCruiseControlVKmh / 3.6) // km/h -> m/s
minCruiseControlActivationT = minCruiseControlActivationTSec * 1000 // ms
mutable cruiseControlV = 0
// Cruise control is turned on, but user might still have foot on gas pedal
mutable cruiseControlIsActive = false
// FIXME: This should measure/calculate the actual force to keep constant speed
// Now it naively accelerates or breaks intermittently without this constant base force
cruiseControlF = {
// Maximum force for CC to use
const maxF = 7500;
// deltaV = actualV - cruiseControlV // Difference in target vs current speed
// F = ma
// v = s/t
// currentA = a
// calculate time it would take to reach a
// First iteration: increase force linearly based on V
// 180 / 3.6 / 50 = 1 -> full throttle at 180 km/h
const multiplier = actualV / 50;
const F = multiplier * maxF;
// Only break when exceeding speed limit significantly
if (actualV > cruiseControlV && toKmh(actualV - cruiseControlV) < 5) {
return 0;
}
// Accelerate or decelerate
return actualV < cruiseControlV ? F : -F;
}
mutable gasPedal = 0
maxGasForce = 1000 * 7.5 // N
maxBreakForce = -(15 * 1000) // N
// Force produced by engine
// FIXME: it would be more accurate to model a separate force for brakes
engineF = {
// Breaking (takes precedence over everything else)
if (brakePedal) {
return maxBreakForce * brakePedal;
}
// Cruise control looks at target speed and
if (cruiseControlIsActive) {
return cruiseControlF;
}
return maxGasForce * gasPedal;
}
g = 9.81
m = 800 // kg
mutable x = 0.0 // m
mutable v = 0.0 // m/s
mutable vRetainedFor = 0 // ms, how long current speed has been retained
a = totalF / m // m/s²
actualV = Math.max(0, v) // Braking, friction and air cannot push the car backwards
breakF = 0.0
frictionF = {
const f = 0.075 * g * m;
return v > 0 ? -1 * f : 0; // N
}
airF = -1 * 1 * Math.pow(actualV, 2.3) // N
totalF = engineF + breakF + frictionF + airF // N
E = 0.5 * m * Math.pow(actualV, 2) // J
msPerTick = 1000 / 40 // frames per second
function onUpdate(msSinceLastFrame) {
const isRunning = loop.isRunning();
if (mutable simulationIsRunning != isRunning) {
mutable simulationIsRunning = isRunning;
}
// Simulate n number of ticks (the actual simulation happens here)
const ms = leftoverMs + msSinceLastFrame;
const tickCount = Math.floor(ms / msPerTick);
for (let i = 0; i < tickCount; ++i) {
onTick(msPerTick);
}
// Store number of leftover ms that was not enough to get its own tick
mutable leftoverMs = ms - tickCount * msPerTick;
// Finally, update plots and analysis
const maxAnalysisCount = 20 / sPerTick;
mutable analysis = mutable analysis.concat([getAnalysis()]);
}
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