Dynamic gravity vector estimation for memory constrained devices

A method, comprising:

• generating, using a gyroscope, rotational data;
• estimating an angular rate of change based on the rotational data;
• determining a rotational versor based on the rotational data;
• estimating a gravity vector based on the angular rate of change and the rotational versor;
• generating, using an accelerometer, an acceleration measurements vector indicating acceleration along a three axes of movement;
• estimating a linear acceleration based on acceleration measurements vector;
• determining an acceleration versor based on the acceleration measurements vector;
• determining a correction factor based on the linear acceleration;
• estimating an error in the estimated gravity vector based on the acceleration versor;
• and
• generating a dynamic gravity vector based on the estimated gravity vector, the correction factor and the estimated error in the estimated gravity vector, wherein the acceleration versor is determined according to:
• a
• ^
• =
• a
• ❘
• "\[LeftBracketingBar]"
• a
• ❘
• "\[RightBracketingBar]"
• where â is the acceleration versor, a is the acceleration measurements vector and |a| is a magnitude of the acceleration measurements vector.

A system, comprising:

• one or more sensors, which, in operation, generate rotational data and acceleration data;
• and
• processing circuitry coupled to the one or more sensors, wherein the processing circuitry, in operation:
• estimates an angular rate of change based on rotational data generated by the one or more sensors;
• determines a rotational versor based on the rotational data;
• estimates a gravity vector based on the angular rate of change and the rotational versor;
• estimates a linear acceleration based on acceleration data generated by the one or more sensors, the acceleration data including an acceleration measurements vector indicating acceleration along three axes of movement;
• determines an acceleration versor based on the acceleration data;
• determines a correction factor based on the linear acceleration;
• estimates an error in the estimated gravity vector based on the acceleration versor;
• and
• generates a dynamic gravity vector based on the estimated gravity vector, the correction factor and the estimated error in the estimated gravity vector, wherein the processing circuitry, in operation, determines the acceleration versor according to:
• a
• ^
• =
• a
• ❘
• "\[LeftBracketingBar]"
• a
• ❘
• "\[RightBracketingBar]"
• where â is the acceleration versor, a is the accelerometer measurements vector and |a| is a magnitude of the acceleration measurements vector.