9-axis sensor fusion with Kalman filter
Add support for 9-axis gravity and linear-acceleration sensors
virtual orientation sensor using 9-axis fusion
Change-Id: I6717539373fce781c10e97b6fa59f68a831a592f
diff --git a/services/sensorservice/Fusion.h b/services/sensorservice/Fusion.h
new file mode 100644
index 0000000..571a415
--- /dev/null
+++ b/services/sensorservice/Fusion.h
@@ -0,0 +1,86 @@
+/*
+ * Copyright (C) 2011 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * 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.
+ */
+
+#ifndef ANDROID_FUSION_H
+#define ANDROID_FUSION_H
+
+#include <utils/Errors.h>
+
+#include "vec.h"
+#include "mat.h"
+
+namespace android {
+
+class Fusion {
+ /*
+ * the state vector is made of two sub-vector containing respectively:
+ * - modified Rodrigues parameters
+ * - the estimated gyro bias
+ */
+ vec<vec3_t, 2> x;
+
+ /*
+ * the predicated covariance matrix is made of 4 3x3 sub-matrices and it
+ * semi-definite positive.
+ *
+ * P = | P00 P10 | = | P00 P10 |
+ * | P01 P11 | | P10t Q1 |
+ *
+ * Since P01 = transpose(P10), the code below never calculates or
+ * stores P01. P11 is always equal to Q1, so we don't store it either.
+ */
+ mat<mat33_t, 2, 2> P;
+
+ /*
+ * the process noise covariance matrix is made of 2 3x3 sub-matrices
+ * Q0 encodes the attitude's noise
+ * Q1 encodes the bias' noise
+ */
+ vec<mat33_t, 2> Q;
+
+ static const float gyroSTDEV = 1.0e-5; // rad/s (measured 1.2e-5)
+ static const float accSTDEV = 0.05f; // m/s^2 (measured 0.08 / CDD 0.05)
+ static const float magSTDEV = 0.5f; // uT (measured 0.7 / CDD 0.5)
+ static const float biasSTDEV = 2e-9; // rad/s^2 (guessed)
+
+public:
+ Fusion();
+ void init();
+ void handleGyro(const vec3_t& w, float dT);
+ status_t handleAcc(const vec3_t& a);
+ status_t handleMag(const vec3_t& m);
+ vec3_t getAttitude() const;
+ vec3_t getBias() const;
+ mat33_t getRotationMatrix() const;
+ bool hasEstimate() const;
+
+private:
+ vec3_t Ba, Bm;
+ uint32_t mInitState;
+ vec<vec3_t, 3> mData;
+ size_t mCount[3];
+ enum { ACC=0x1, MAG=0x2, GYRO=0x4 };
+ bool checkInitComplete(int, const vec3_t&);
+ bool checkState(const vec3_t& v);
+ void predict(const vec3_t& w);
+ void update(const vec3_t& z, const vec3_t& Bi, float sigma);
+ static mat33_t getF(const vec3_t& p);
+ static mat33_t getdFdp(const vec3_t& p, const vec3_t& we);
+};
+
+}; // namespace android
+
+#endif // ANDROID_FUSION_H