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A lunar lander autopilot for lunar.unnecessarymodification.com
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| // A lunar lander autopilot for https://lunar.unnecessarymodification.com/ | |
| function clamp(x, a, b) { | |
| return Math.min(Math.max(x, a), b); | |
| } | |
| function threshold(x, th) { | |
| return Math.abs(x) >= th ? x : 0; | |
| } | |
| function spow(x, p) { | |
| return Math.sign(x) * Math.pow(Math.abs(x), p); | |
| } | |
| function nangle(a) { | |
| if (a > 180) { | |
| return 360 - a; | |
| } else if (a <= -180) { | |
| return 360 + a; | |
| } | |
| return a; | |
| } | |
| class Vec { | |
| constructor(x, y) { | |
| this.x = x; | |
| this.y = y; | |
| } | |
| static fromAngle(a) { | |
| let arad = a / 180 * Math.PI; | |
| return new Vec( | |
| -Math.sin(arad), | |
| -Math.cos(arad), | |
| ); | |
| } | |
| norm() { | |
| let len = this.abs(); | |
| return new Vec( | |
| this.x / len, | |
| this.y / len, | |
| ); | |
| } | |
| dot(v) { | |
| return this.x * v.x + this.y * v.y; | |
| } | |
| angle() { | |
| // The reference direction is towards the ground, same as the lander orientation. | |
| return nangle(-Math.atan2(this.y, this.x) * 180 / Math.PI - 90); | |
| } | |
| abs() { | |
| return Math.sqrt(this.x * this.x + this.y * this.y) | |
| } | |
| neg() { | |
| return new Vec( | |
| -this.x, | |
| -this.y, | |
| ); | |
| } | |
| add(v) { | |
| return new Vec( | |
| this.x + v.x, | |
| this.y + v.y, | |
| ); | |
| } | |
| sub(v) { | |
| return new Vec( | |
| this.x - v.x, | |
| this.y - v.y, | |
| ); | |
| } | |
| mul(k) { | |
| return new Vec( | |
| this.x * k, | |
| this.y * k, | |
| ); | |
| } | |
| } | |
| let { | |
| x_position, | |
| altitude, | |
| angle, | |
| userStore, | |
| log, | |
| plot | |
| } = arguments[0]; | |
| let pos = new Vec(x_position, altitude); | |
| let a = angle; | |
| if (!("pos" in userStore)) { | |
| userStore.pos = pos; | |
| userStore.a = a; | |
| return { | |
| rotThrust: 0, | |
| aftThrust: 0, | |
| userStore: userStore, | |
| }; | |
| } | |
| let v = pos.sub(userStore.pos); | |
| let w = a - userStore.a; | |
| let vset = new Vec( | |
| threshold(v.x * 0.8, 0.5), | |
| Math.max(v.y, spow(-pos.y / 70, 1.2)), | |
| ); | |
| let verr = vset.sub(v); | |
| let aset = clamp(v.add(verr.mul(0.8)).angle(), -90, 90); | |
| let aerr = aset - a - spow(w, 1) * 4; | |
| let wset = clamp(spow(threshold(aerr / 20, 0.1), 0.5), -4, 4); | |
| let werr = wset - w; | |
| let thrust = clamp(Vec.fromAngle(a).dot(verr.neg().norm()) * verr.abs() * 2.5, 0, 1); | |
| thrust_rot = clamp(werr, -1, 1); | |
| plot({ | |
| vset: vset.abs(), | |
| v: v.abs(), | |
| thrust: thrust * 10, | |
| }); | |
| userStore.pos = pos; | |
| userStore.a = a; | |
| return { | |
| rotThrust: thrust_rot, | |
| aftThrust: thrust, | |
| userStore: userStore, | |
| }; |
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