px4_autopilot/test/test_EKF_imuSampling.cpp

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#include <gtest/gtest.h>
#include <math.h>
#include "EKF/ekf.h"
#include "EKF/imu_down_sampler.hpp"

class EkfImuSamplingTest : public ::testing::TestWithParam<std::tuple<float,float,Vector3f, Vector3f>>
{
 public:

	Ekf _ekf{};

	uint32_t _t_us{0};

	// Setup the Ekf with synthetic measurements
	void SetUp() override
	{
		_ekf.init(0);

	}

	void TearDown() override
	{

	}
};

TEST_P(EkfImuSamplingTest, imuSamplingAtMultipleRates)
{
	// WHEN: adding imu samples at a higher rate than the update loop
	// THEN: imu sample should be down sampled
	// WHEN: adding imu samples at a same or lower rate than the update loop
	// THEN: imu sample should reach buffer unchanged

	uint32_t dt_us = std::get<0>(GetParam()) * (_ekf.FILTER_UPDATE_PERIOD_MS * 1000);
	uint32_t expected_dt_us = std::get<1>(GetParam()) * (_ekf.FILTER_UPDATE_PERIOD_MS * 1000);

	Vector3f ang_vel= std::get<2>(GetParam());
	Vector3f accel = std::get<3>(GetParam());
	imuSample imu_sample;
	imu_sample.delta_ang_dt = dt_us * 1.0e-6f;
	imu_sample.delta_ang = ang_vel * imu_sample.delta_ang_dt;
	imu_sample.delta_vel_dt = dt_us * 1.0e-6f;
	imu_sample.delta_vel = accel * imu_sample.delta_vel_dt;

	// The higher the imu rate is the more measurements we have to set before reaching the FILTER_UPDATE_PERIOD
	int n_samples = 0;
	for(int i = 0; i<(int)20/std::get<0>(GetParam()); ++i)
	{
		n_samples++;
		imu_sample.time_us = _t_us;
		_ekf.setIMUData(imu_sample);
		_t_us += dt_us;
	}

	// Get the imu sample that was put into the buffer
	imuSample imu_sample_buffered = _ekf.get_imu_sample_delayed();
	EXPECT_NEAR(expected_dt_us / 1e6f, imu_sample_buffered.delta_ang_dt, 1e-5f);
	EXPECT_NEAR(expected_dt_us / 1e6f, imu_sample_buffered.delta_vel_dt, 1e-5f);

	// WHEN: downsampling the imu measurement
	// THEN: the delta vel should be accumulated correctly
	// Allow for accumulation of rounding error with each sample
	EXPECT_TRUE(matrix::isEqual(ang_vel, imu_sample_buffered.delta_ang/imu_sample_buffered.delta_ang_dt, float(n_samples) * 1e-7f));
	EXPECT_TRUE(matrix::isEqual(accel, imu_sample_buffered.delta_vel/imu_sample_buffered.delta_vel_dt, float(n_samples) * 1e-7f));
}

INSTANTIATE_TEST_SUITE_P(imuSamplingAtMultipleRates,
			EkfImuSamplingTest,
			::testing::Values(
				std::make_tuple<float,float,Vector3f,Vector3f>(1.0f,  1.0f,Vector3f{0.0f,0.0f,0.0f},Vector3f{-0.46f,0.87f,0.20f}),
				std::make_tuple<float,float,Vector3f,Vector3f>(0.5f,  1.0f,Vector3f{0.0f,0.0f,0.0f},Vector3f{-0.46f,0.87f,0.20f}),
				std::make_tuple<float,float,Vector3f,Vector3f>(1.6f,  1.6f,Vector3f{0.0f,0.0f,0.0f},Vector3f{-0.46f,0.87f,0.20f}),
				std::make_tuple<float,float,Vector3f,Vector3f>(0.333f,1.0f,Vector3f{0.0f,0.0f,0.0f},Vector3f{-0.46f,0.87f,0.20f}),
				std::make_tuple<float,float,Vector3f,Vector3f>(1.0f,  1.0f,Vector3f{1.0f,0.0f,0.0f},Vector3f{0.0f,0.0f,0.0f}),
				std::make_tuple<float,float,Vector3f,Vector3f>(0.5f,  1.0f,Vector3f{1.0f,0.0f,0.0f},Vector3f{0.0f,0.0f,0.0f}),
				std::make_tuple<float,float,Vector3f,Vector3f>(1.6f,  1.6f,Vector3f{1.0f,0.0f,0.0f},Vector3f{0.0f,0.0f,0.0f}),
				std::make_tuple<float,float,Vector3f,Vector3f>(0.333f,1.0f,Vector3f{1.0f,0.0f,0.0f},Vector3f{0.0f,0.0f,0.0f}),
				std::make_tuple<float,float,Vector3f,Vector3f>(1.0f,  1.0f,Vector3f{0.0f,1.0f,0.0f},Vector3f{0.0f,0.0f,0.0f}),
				std::make_tuple<float,float,Vector3f,Vector3f>(0.5f,  1.0f,Vector3f{0.0f,1.0f,0.0f},Vector3f{0.0f,0.0f,0.0f}),
				std::make_tuple<float,float,Vector3f,Vector3f>(1.6f,  1.6f,Vector3f{0.0f,1.0f,0.0f},Vector3f{0.0f,0.0f,0.0f}),
				std::make_tuple<float,float,Vector3f,Vector3f>(0.333f,1.0f,Vector3f{0.0f,1.0f,0.0f},Vector3f{0.0f,0.0f,0.0f}),
				std::make_tuple<float,float,Vector3f,Vector3f>(1.0f,  1.0f,Vector3f{0.0f,0.0f,1.0f},Vector3f{0.0f,0.0f,0.0f}),
				std::make_tuple<float,float,Vector3f,Vector3f>(0.5f,  1.0f,Vector3f{0.0f,0.0f,1.0f},Vector3f{0.0f,0.0f,0.0f}),
				std::make_tuple<float,float,Vector3f,Vector3f>(1.6f,  1.6f,Vector3f{0.0f,0.0f,1.0f},Vector3f{0.0f,0.0f,0.0f}),
				std::make_tuple<float,float,Vector3f,Vector3f>(0.333f,1.0f,Vector3f{0.0f,0.0f,1.0f},Vector3f{0.0f,0.0f,0.0f})
			));

TEST_F(EkfImuSamplingTest, accelDownSampling)
{
	ImuDownSampler sampler(0.008f);

	Vector3f ang_vel{0.0f,0.0f,0.0f};
	Vector3f accel{-0.46f,0.87f,0.0f};
	imuSample input_sample;
	input_sample.delta_ang_dt = 0.004f;
	input_sample.delta_ang = ang_vel * input_sample.delta_ang_dt;
	input_sample.delta_vel_dt = 0.004f;
	input_sample.delta_vel = accel * input_sample.delta_vel_dt;
	input_sample.time_us = 0;

	// WHEN: adding samples at the double rate as the target rate
	EXPECT_FALSE(sampler.update(input_sample));
	input_sample.time_us = 4000;

	// THEN: after two samples a first downsampled sample is ready
	EXPECT_TRUE(sampler.update(input_sample));

	// THEN: downsampled sample should fit to input data
	imuSample output_sample = sampler.getDownSampledImuAndTriggerReset();
	EXPECT_FLOAT_EQ(output_sample.delta_ang_dt, 0.008f);
	EXPECT_FLOAT_EQ(output_sample.delta_vel_dt, 0.008f);
	EXPECT_TRUE(matrix::isEqual(ang_vel * 0.008f, output_sample.delta_ang, 1e-10f));
	EXPECT_TRUE(matrix::isEqual(accel * 0.008f, output_sample.delta_vel, 1e-10f));
}

TEST_F(EkfImuSamplingTest, gyroDownSampling)
{
	ImuDownSampler sampler(0.008f);

	Vector3f ang_vel{0.0f,0.0f,1.0f};
	Vector3f accel{0.0f,0.0f,0.0f};
	imuSample input_sample;

	input_sample.delta_ang_dt = 0.004f;
	input_sample.delta_ang = ang_vel * input_sample.delta_ang_dt;
	input_sample.delta_vel_dt = 0.004f;
	input_sample.delta_vel = accel * input_sample.delta_vel_dt;
	input_sample.time_us = 0;

	// WHEN: adding samples at the double rate as the target rate
	EXPECT_FALSE(sampler.update(input_sample));
	input_sample.time_us += 4000;

	// THEN: after two samples a first downsampled sample is ready
	EXPECT_TRUE(sampler.update(input_sample));
	input_sample.time_us += 4000;

	// THEN: downsampled sample should fit to input data
	imuSample output_sample = sampler.getDownSampledImuAndTriggerReset();
	EXPECT_FLOAT_EQ(output_sample.delta_ang_dt, 0.008f);
	EXPECT_FLOAT_EQ(output_sample.delta_vel_dt, 0.008f);
	EXPECT_TRUE(matrix::isEqual(ang_vel * 0.008f, output_sample.delta_ang, 1e-10f));
	EXPECT_TRUE(matrix::isEqual(accel * 0.008f, output_sample.delta_vel, 1e-10f));

	ang_vel = Vector3f{0.0f,1.0f,0.0f};
	input_sample.delta_ang = ang_vel * input_sample.delta_ang_dt;
	input_sample.delta_vel = accel * input_sample.delta_vel_dt;

	// WHEN: adding samples at the double rate as the target rate
	EXPECT_FALSE(sampler.update(input_sample));
	input_sample.time_us += 4000;

	// THEN: after two more samples a second downsampled sample is ready
	EXPECT_TRUE(sampler.update(input_sample));
	input_sample.time_us += 4000;

	// THEN: downsampled sample should fit the adapted input data
	output_sample = sampler.getDownSampledImuAndTriggerReset();
	EXPECT_FLOAT_EQ(output_sample.delta_ang_dt, 0.008f);
	EXPECT_FLOAT_EQ(output_sample.delta_vel_dt, 0.008f);
	EXPECT_TRUE(matrix::isEqual(ang_vel * 0.008f, output_sample.delta_ang, 1e-10f));
	EXPECT_TRUE(matrix::isEqual(accel * 0.008f, output_sample.delta_vel, 1e-10f));

	ang_vel = Vector3f{1.0f,0.0f,0.0f};
	input_sample.delta_ang = ang_vel * input_sample.delta_ang_dt;
	input_sample.delta_vel = accel * input_sample.delta_vel_dt;

	// WHEN: adding samples at the double rate as the target rate
	EXPECT_FALSE(sampler.update(input_sample));
	input_sample.time_us += 4000;

	// THEN: after two more samples a second downsampled sample is ready
	EXPECT_TRUE(sampler.update(input_sample));
	input_sample.time_us += 4000;

	// THEN: downsampled sample should fit the adapted input data
	output_sample = sampler.getDownSampledImuAndTriggerReset();
	EXPECT_FLOAT_EQ(output_sample.delta_ang_dt, 0.008f);
	EXPECT_FLOAT_EQ(output_sample.delta_vel_dt, 0.008f);
	EXPECT_TRUE(matrix::isEqual(ang_vel * 0.008f, output_sample.delta_ang, 1e-10f));
	EXPECT_TRUE(matrix::isEqual(accel * 0.008f, output_sample.delta_vel, 1e-10f));
}