Five degree of freedom intertial measurement device

A method of measuring linear acceleration of a body along a first axis, a second axis, and a third axis, angular acceleration of the body about the second axis, and angular acceleration of the body about the third axis, wherein the first axis, the second axis, and third axis are substantially mutually orthogonal and intersect at an origin point, the method comprising:

• positioning a first accelerometer in a fixed position relative to the body, the first accelerometer measuring linear acceleration in directions along both the second axis and the third axis;
• positioning a second accelerometer in a fixed position relative to the body, the second accelerometer measuring linear acceleration in directions along both the second axis and third axis, the first and second accelerometers positioned on a plane defined by the first axis and the second axis, and
• determining an angular acceleration of the body about the second axis, and an angular acceleration of the body about the third axis, using no other acceleration signals other than the linear acceleration signals from the first and second accelerometers.

The method according to 11, wherein at least one of the first accelerometer and the second accelerometer is a tri-axial accelerometer, the tri-axial accelerometer measuring linear acceleration along the first, second and third axis, and wherein no other acceleration signals other than the linear acceleration signals from the first and second accelerometers are used in determining linear acceleration of the body along the first axis, the second axis, and the third axis, angular acceleration of the body about the second axis, and angular acceleration of the body about the third axis.

A five degree of freedom inertial measurement unit capable of measuring linear acceleration of a body along a first axis, a second axis, and a third axis, angular acceleration of the body about the second axis, and angular acceleration of the body about the third axis, wherein the first axis, the second axis, and third axis are substantially mutually orthogonal and intersect at an origin point, the unit comprising:

• a first accelerometer in a fixed position relative to the body, the first accelerometer measuring linear acceleration in directions along both the second axis and the third axis;
• a second accelerometer in a fixed position relative to the body, the second accelerometer measuring linear acceleration in directions along both the second axis and third axis, the first and second accelerometers positioned on a plane defined by the first axis and the second axis, and
• means for determining an angular acceleration of the body about the second axis, and an angular acceleration of the body about the third axis, using no other acceleration signals other than the linear acceleration signals from the first and second accelerometers.

The inertial measurement unit according to claim 18, wherein at least one of the first accelerometer and the second accelerometer is a tri-axial accelerometer, the tri-axial accelerometer measuring linear acceleration along the first, second and third axis, and wherein the means for determining uses no other acceleration signals other than the linear acceleration signals from the first and second accelerometers to determine linear acceleration of the body along the first axis, the second axis, and the third axis, angular acceleration of the body about the second axis, and angular acceleration of the body about the third axis.