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51 lines
1.3 KiB
C++
51 lines
1.3 KiB
C++
// Copyright (c) 2023 Oleg Kalachev <okalachev@gmail.com>
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// Repository: https://github.com/okalachev/flix
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// Attitude estimation from gyro and accelerometer
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#include "quaternion.h"
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#include "vector.h"
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#include "lpf.h"
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#define ONE_G 9.807f
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#define WEIGHT_ACC 0.5f
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#define RATES_LFP_ALPHA 0.2 // cutoff frequency ~ 40 Hz
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LowPassFilter<Vector> ratesFilter(RATES_LFP_ALPHA);
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void estimate() {
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applyGyro();
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applyAcc();
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signalizeHorizontality();
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}
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void applyGyro() {
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// filter gyro to get angular rates
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rates = ratesFilter.update(gyro);
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// apply rates to attitude
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attitude *= Quaternion::fromAngularRates(rates * dt);
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attitude.normalize();
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}
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void applyAcc() {
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// test should we apply accelerometer gravity correction
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float accNorm = acc.norm();
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bool landed = !motorsActive() && abs(accNorm - ONE_G) < ONE_G * 0.1f;
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if (!landed) return;
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// calculate accelerometer correction
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Vector up = attitude.rotate(Vector(0, 0, -1));
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Vector correction = Vector::angularRatesBetweenVectors(acc, up) * dt * WEIGHT_ACC;
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// apply correction
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attitude *= Quaternion::fromAngularRates(correction);
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attitude.normalize();
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}
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void signalizeHorizontality() {
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float angle = Vector::angleBetweenVectors(attitude.rotate(Vector(0, 0, -1)), Vector(0, 0, -1));
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setLED(angle < radians(15));
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}
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