More error checks to avoid div by zero. (3e87d8da) · Commits · e / os / android_frameworks_native

services/sensorservice/Fusion.cpp

+55 −4

Original line number	Diff line number	Diff line
		@@ -47,9 +47,41 @@ static const float biasVAR = 1e-8; // (rad/s)^2 / s (guessed)
		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 FREE_FALL_THRESHOLD = 0.981f;
		static const float SYMMETRY_TOLERANCE = 1e-10f;

		/*
		* Accelerometer updates will not be performed near free fall to avoid ill-conditioning and
		* div by zeros.
		* Threshhold: 10% of g, in m/s^2
		*/
		static const float FREE_FALL_THRESHOLD = 0.981f;
		static const float FREE_FALL_THRESHOLD_SQ = FREE_FALL_THRESHOLD*FREE_FALL_THRESHOLD;

		/*
		* The geomagnetic-field should be between 30uT and 60uT.
		* Fields strengths greater than this likely indicate a local magnetic disturbance which
		* we do not want to update into the fused frame.
		*/
		static const float MAX_VALID_MAGNETIC_FIELD = 100; // uT
		static const float MAX_VALID_MAGNETIC_FIELD_SQ = MAX_VALID_MAGNETIC_FIELD*MAX_VALID_MAGNETIC_FIELD;

		/*
		* Values of the field smaller than this should be ignored in fusion to avoid ill-conditioning.
		* This state can happen with anomalous local magnetic disturbances canceling the Earth field.
		*/
		static const float MIN_VALID_MAGNETIC_FIELD = 10; // uT
		static const float MIN_VALID_MAGNETIC_FIELD_SQ = MIN_VALID_MAGNETIC_FIELD*MIN_VALID_MAGNETIC_FIELD;

		/*
		* If the cross product of two vectors has magnitude squared less than this, we reject it as
		* invalid due to alignment of the vectors.
		* This threshold is used to check for the case where the magnetic field sample is parallel to
		* the gravity field, which can happen in certain places due to magnetic field disturbances.
		*/
		static const float MIN_VALID_CROSS_PRODUCT_MAG = 1.0e-3;
		static const float MIN_VALID_CROSS_PRODUCT_MAG_SQ =
		MIN_VALID_CROSS_PRODUCT_MAG*MIN_VALID_CROSS_PRODUCT_MAG;

		// -----------------------------------------------------------------------

		template <typename TYPE, size_t C, size_t R>
		@@ -240,8 +272,10 @@ void Fusion::handleGyro(const vec3_t& w, float dT) {

		status_t Fusion::handleAcc(const vec3_t& a) {
		// ignore acceleration data if we're close to free-fall
		if (length(a) < FREE_FALL_THRESHOLD)
		if (length_squared(a) < FREE_FALL_THRESHOLD_SQ) {
		LOGW("handleAcc: near free fall, not updating!");
		return BAD_VALUE;
		}

		if (!checkInitComplete(ACC, a))
		return BAD_VALUE;
		@@ -253,15 +287,32 @@ status_t Fusion::handleAcc(const vec3_t& a) {

		status_t Fusion::handleMag(const vec3_t& m) {
		// the geomagnetic-field should be between 30uT and 60uT
		// reject obviously wrong magnetic-fields
		if (length(m) > 100)
		// reject if too large to avoid spurious magnetic sources
		const float magFieldSq = length_squared(m);
		if (magFieldSq > MAX_VALID_MAGNETIC_FIELD_SQ) {
		LOGW("handleMag: magnetic field too large, not updating!");
		return BAD_VALUE;
		} else if (magFieldSq < MIN_VALID_MAGNETIC_FIELD_SQ) {
		// Also reject if too small since we will get ill-defined (zero mag) cross-products below
		LOGW("handleMag: magnetic field too small, not updating!");
		return BAD_VALUE;
		}

		if (!checkInitComplete(MAG, m))
		return BAD_VALUE;

		// Orthogonalize the magnetic field to the gravity field, mapping it into tangent to Earth.
		const vec3_t up( getRotationMatrix() * Ba );
		const vec3_t east( cross_product(m, up) );

		// If the m and up vectors align, the cross product magnitude will approach 0.
		// Reject this case as well to avoid div by zero problems and ill-conditioning below.
		if (length_squared(east) < MIN_VALID_CROSS_PRODUCT_MAG_SQ) {
		LOGW("handleMag: magnetic field too aligned with up vector, not updating!");
		return BAD_VALUE;
		}

		// If we have created an orthogonal magnetic field successfully, then pass it in as the update.
		vec3_t north( cross_product(up, east) );

		const float l = 1 / length(north);

services/sensorservice/vec.h

+9 −0

Original line number	Diff line number	Diff line
		@@ -207,6 +207,15 @@ TYPE PURE length(const V<TYPE, SIZE>& v) {
		return sqrt(dot_product(v, v));
		}

		template <
		template<typename T, size_t S> class V,
		typename TYPE,
		size_t SIZE
		>
		TYPE PURE length_squared(const V<TYPE, SIZE>& v) {
		return dot_product(v, v);
		}

		template <
		template<typename T, size_t S> class V,
		typename TYPE,