An accelerometer comprising first, second, and third two degree of freedom gyros coupled to a platform and a computing means,
- wherein each of said gyros comprises:
- A. a stator including two sets of series connected coils wound in quadrature, each set of coils being disposed in a substantially annular configuration about a spin reference axis and substantially parallel to a plane defined by first and second input axes, said first and second input axes and said spin reference axis being mutually orthogonal and having a common point of intersection, wherein the axis of each coil is substantially parallel to said spin reference axis,
- B. a rotor adapted for rotation about a spin axis, and adapted for rotational displacements about said first and second input axes, said rotor including a set of permanent magnets disposed in a substantially annular configuration about said spin axis, said annular configuration of magnets having substantially the same mean radius as said annular configuration of coils, and wherein the magnetic moment of each of said magnets is substantially parallel to said spin axis, and wherein the magnetic moments of adjacent magnets in said set are oppositely directed,
- C. means for positioning said rotor with respect to said stator whereby said annular configuration of magnets is adjacent to said annular configuration of coils so that magnetic flux from said magnets is coupled to said coils,
- D. return means connected to said rotor for establishing a magnetic flux return path therein, said return path completing a circuitous path for magnetic flux passing through said coils,
- E. means for exciting said sets of coils including servo means for detecting back emf in said sets of coils and for generating control signals related thereto for driving alternating currents in the respective sets of coils, said currents having a 90.degree. relative phase shift and being in-phase with the detected back emf for the respective sets of coils,
- F. first and second means for detecting rotational displacements of said rotor about said first and second input axis, respectively, relative to said stator, and for generating first and second balance control signals representative thereof, and
- G. first and second torquer means connected to said housing member and responsive to said first and second balance control signals for applying torque to said rotor about said first and second input axes, respectively, whereby said spin reference and spin axes are maintained substantially coaxial,
- wherein the spin reference axis of said first gyro is aligned with a first reference axis and the rotor of said first gyro is non-pendulous, and said first gyro includes means for generating a first gyro signal representative of the angular velocity of said platform about second and third reference axes, said first, second and third reference axes being mutually orthogonal,
- wherein the spin reference axis of said second gyro is aligned with said second reference axis and the rotor of said second gyro is pendulous, and said second gyro includes means for generating a second gyro signal representative of the angular velocity of said platform about said first and third reference axes and the linear acceleration of said platform along said first and third reference axes,
- wherein the spin reference axes of said third gyro is aligned with said third reference axis and the rotor of said third gyro is pendulous, and said third gyro includes means for generating a third gyro signal representative of the angular velocity of said platform about said first and second reference axes and the linear acceleration of said platform along said first and second reference axes, said acceleration portion of said third gyro signal being opposite in polarity from the corresponding portion of said second gyro signal, and
- wherein said computing means is responsive to said first, second and third gyro signals to generate separate output signals representative of the acceleration and angular velocity of said platform with respect to each of said first, second, and third reference axes.