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Diffstat (limited to 'LibOVR/Src/OVR_SensorCalibration.cpp')
| -rw-r--r-- | LibOVR/Src/OVR_SensorCalibration.cpp | 276 |
1 files changed, 276 insertions, 0 deletions
diff --git a/LibOVR/Src/OVR_SensorCalibration.cpp b/LibOVR/Src/OVR_SensorCalibration.cpp new file mode 100644 index 0000000..665898b --- /dev/null +++ b/LibOVR/Src/OVR_SensorCalibration.cpp @@ -0,0 +1,276 @@ +/************************************************************************************ + +Filename : OVR_SensorCalibration.cpp +Content : Calibration data implementation for the IMU messages +Created : January 28, 2014 +Authors : Max Katsev + +Copyright : Copyright 2014 Oculus VR, Inc. All Rights reserved. + +Licensed under the Oculus VR Rift SDK License Version 3.1 (the "License"); +you may not use the Oculus VR Rift SDK except in compliance with the License, +which is provided at the time of installation or download, or which +otherwise accompanies this software in either electronic or hard copy form. + +You may obtain a copy of the License at + +http://www.oculusvr.com/licenses/LICENSE-3.1 + +Unless required by applicable law or agreed to in writing, the Oculus VR SDK +distributed under the License is distributed on an "AS IS" BASIS, +WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. +See the License for the specific language governing permissions and +limitations under the License. + +*************************************************************************************/ + +#include "OVR_SensorCalibration.h" +#include "Kernel/OVR_Log.h" +#include <time.h> + +namespace OVR { + +using namespace Alg; + +const UByte VERSION = 2; +const UByte MAX_COMPAT_VERSION = 15; + +SensorCalibration::SensorCalibration(SensorDevice* pSensor) + : MagCalibrated(false), GyroAutoTemperature(0), GyroFilter(6000) +{ + this->pSensor = pSensor; +}; + +void SensorCalibration::Initialize() +{ + // read factory calibration + pSensor->GetFactoryCalibration(&AccelOffset, &GyroAutoOffset, &AccelMatrix, &GyroMatrix, &GyroAutoTemperature); + + // if the headset has an autocalibrated offset, prefer it over the factory defaults + GyroOffsetReport gyroReport; + bool result = pSensor->GetGyroOffsetReport(&gyroReport); + if (result && gyroReport.Version != GyroOffsetReport::Version_NoOffset) + { + GyroAutoOffset = (Vector3f) gyroReport.Offset; + GyroAutoTemperature = (float) gyroReport.Temperature; + } + + // read the temperature tables and prepare the interpolation structures + result = pSensor->GetAllTemperatureReports(&temperatureReports); + OVR_ASSERT(result); + for (int i = 0; i < 3; i++) + Interpolators[i].Initialize(temperatureReports, i); + + // read the mag calibration + MagCalibrationReport report; + result = pSensor->GetMagCalibrationReport(&report); + MagCalibrated = result && report.Version > 0; + MagMatrix = report.Calibration; + if (!MagCalibrated) + { + // OVR_ASSERT(false); + LogError("Magnetometer calibration not found!\n"); + } +} + +void SensorCalibration::Apply(MessageBodyFrame& msg) +{ + AutocalibrateGyro(msg); + + // compute the interpolated offset + Vector3f gyroOffset; + for (int i = 0; i < 3; i++) + gyroOffset[i] = (float) Interpolators[i].GetOffset(msg.Temperature, GyroAutoTemperature, GyroAutoOffset[i]); + + // apply calibration + msg.RotationRate = GyroMatrix.Transform(msg.RotationRate - gyroOffset); + msg.Acceleration = AccelMatrix.Transform(msg.Acceleration - AccelOffset); + if (MagCalibrated) + msg.MagneticField = MagMatrix.Transform(msg.MagneticField); + // TBD: don't report mag calibration for now, since it is used to enable the yaw correction + msg.MagCalibrated = false; +} + +void SensorCalibration::AutocalibrateGyro(MessageBodyFrame const& msg) +{ + const float alpha = 0.4f; + // 1.25f is a scaling factor related to conversion from per-axis comparison to length comparison + const float absLimit = 1.25f * 0.349066f; + const float noiseLimit = 1.25f * 0.03f; + + Vector3f gyro = msg.RotationRate; + // do a moving average to reject short term noise + Vector3f avg = (GyroFilter.IsEmpty()) ? gyro : gyro * alpha + GyroFilter.PeekBack() * (1 - alpha); + + // Make sure the absolute value is below what is likely motion + // Make sure it is close enough to the current average that it is probably noise and not motion + if (avg.Length() >= absLimit || (avg - GyroFilter.Mean()).Length() >= noiseLimit) + GyroFilter.Clear(); + GyroFilter.PushBack(avg); + + // if had a reasonable number of samples already use it for the current offset + if (GyroFilter.GetSize() > GyroFilter.GetCapacity() / 2) + { + GyroAutoOffset = GyroFilter.Mean(); + GyroAutoTemperature = msg.Temperature; + // After ~6 seconds of no motion, use the average as the new zero rate offset + if (GyroFilter.IsFull()) + StoreAutoOffset(); + } +} + +void SensorCalibration::StoreAutoOffset() +{ + const double maxDeltaT = 2.5; + const double minExtraDeltaT = 0.5; + const UInt32 minDelay = 24 * 3600; // 1 day in seconds + + // find the best bin + UPInt binIdx = 0; + for (UPInt i = 1; i < temperatureReports.GetSize(); i++) + if (Abs(GyroAutoTemperature - temperatureReports[i][0].TargetTemperature) < + Abs(GyroAutoTemperature - temperatureReports[binIdx][0].TargetTemperature)) + binIdx = i; + + // find the oldest and newest samples + // NB: uninitialized samples have Time == 0, so they will get picked as the oldest + UPInt newestIdx = 0, oldestIdx = 0; + for (UPInt i = 1; i < temperatureReports[binIdx].GetSize(); i++) + { + // if the version is newer - do nothing + if (temperatureReports[binIdx][i].Version > VERSION) + return; + if (temperatureReports[binIdx][i].Time > temperatureReports[binIdx][newestIdx].Time) + newestIdx = i; + if (temperatureReports[binIdx][i].Time < temperatureReports[binIdx][oldestIdx].Time) + oldestIdx = i; + } + TemperatureReport& oldestReport = temperatureReports[binIdx][oldestIdx]; + TemperatureReport& newestReport = temperatureReports[binIdx][newestIdx]; + OVR_ASSERT((oldestReport.Sample == 0 && newestReport.Sample == 0 && newestReport.Version == 0) || + oldestReport.Sample == (newestReport.Sample + 1) % newestReport.NumSamples); + + bool writeSuccess = false; + UInt32 now = (UInt32) time(0); + if (now - newestReport.Time > minDelay) + { + // only write a new sample if the temperature is close enough + if (Abs(GyroAutoTemperature - oldestReport.TargetTemperature) < maxDeltaT) + { + oldestReport.Time = now; + oldestReport.ActualTemperature = GyroAutoTemperature; + oldestReport.Offset = (Vector3d) GyroAutoOffset; + oldestReport.Version = VERSION; + writeSuccess = pSensor->SetTemperatureReport(oldestReport); + OVR_ASSERT(writeSuccess); + } + } + else + { + // if the newest sample is too recent - _update_ it if significantly closer to the target temp + if (Abs(GyroAutoTemperature - newestReport.TargetTemperature) + minExtraDeltaT + < Abs(newestReport.ActualTemperature - newestReport.TargetTemperature)) + { + // (do not update the time!) + newestReport.ActualTemperature = GyroAutoTemperature; + newestReport.Offset = (Vector3d) GyroAutoOffset; + newestReport.Version = VERSION; + writeSuccess = pSensor->SetTemperatureReport(newestReport); + OVR_ASSERT(writeSuccess); + } + } + + // update the interpolators with the new data + // this is not particularly expensive call and would only happen rarely + // but if performance is a problem, it's possible to only recompute the data that has changed + if (writeSuccess) + for (int i = 0; i < 3; i++) + Interpolators[i].Initialize(temperatureReports, i); +} + +void OffsetInterpolator::Initialize(Array<Array<TemperatureReport> > const& temperatureReports, int coord) +{ + int bins = (int) temperatureReports.GetSize(); + Temperatures.Clear(); + Temperatures.Reserve(bins); + Values.Clear(); + Values.Reserve(bins); + + for (int bin = 0; bin < bins; bin++) + { + OVR_ASSERT(temperatureReports[bin].GetSize() == temperatureReports[0].GetSize()); + //const TemperatureReport& report = median(temperatureReports[bin], coord); + const TemperatureReport& report = temperatureReports[bin][0]; + if (report.Version > 0 && report.Version <= MAX_COMPAT_VERSION) + { + Temperatures.PushBack(report.ActualTemperature); + Values.PushBack(report.Offset[coord]); + } + } +} + +double OffsetInterpolator::GetOffset(double targetTemperature, double autoTemperature, double autoValue) +{ + const double autoRangeExtra = 1.0; + const double minInterpolationDist = 0.5; + + // difference between current and autocalibrated temperature adjusted for preference over historical data + const double adjustedDeltaT = Abs(autoTemperature - targetTemperature) - autoRangeExtra; + + int count = (int) Temperatures.GetSize(); + // handle special cases when we don't have enough data for proper interpolation + if (count == 0) + return autoValue; + if (count == 1) + { + if (adjustedDeltaT < Abs(Temperatures[0] - targetTemperature)) + return autoValue; + else + return Values[0]; + } + + // first, find the interval that contains targetTemperature + // if all points are on the same side of targetTemperature, find the adjacent interval + int l; + if (targetTemperature < Temperatures[1]) + l = 0; + else if (targetTemperature >= Temperatures[count - 2]) + l = count - 2; + else + for (l = 1; l < count - 2; l++) + if (Temperatures[l] <= targetTemperature && targetTemperature < Temperatures[l+1]) + break; + int u = l + 1; + + // extend the interval if it's too small and the interpolation is unreliable + if (Temperatures[u] - Temperatures[l] < minInterpolationDist) + { + if (l > 0 + && (u == count - 1 || Temperatures[u] - Temperatures[l - 1] < Temperatures[u + 1] - Temperatures[l])) + l--; + else if (u < count - 1) + u++; + } + + // verify correctness + OVR_ASSERT(l >= 0 && u < count); + OVR_ASSERT(l == 0 || Temperatures[l] <= targetTemperature); + OVR_ASSERT(u == count - 1 || targetTemperature < Temperatures[u]); + OVR_ASSERT((l == 0 && u == count - 1) || Temperatures[u] - Temperatures[l] > minInterpolationDist); + OVR_ASSERT(Temperatures[l] <= Temperatures[u]); + + // perform the interpolation + double slope; + if (Temperatures[u] - Temperatures[l] >= minInterpolationDist) + slope = (Values[u] - Values[l]) / (Temperatures[u] - Temperatures[l]); + else + // avoid a badly conditioned problem + slope = 0; + if (adjustedDeltaT < Abs(Temperatures[u] - targetTemperature)) + // use the autocalibrated value, if it's close + return autoValue + slope * (targetTemperature - autoTemperature); + else + return Values[u] + slope * (targetTemperature - Temperatures[u]); +} + +} // namespace OVR |