Spherical Planar Motor for 3-Axis Electro-Optic Gimbal Control
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Solution Overview
Problem
Existing ball joint gimbal systems for electro-optic systems are limited in achieving full three-axis steering control over an extended range of motion, as they are kinematically constrained, leading to drift and limited motion in the third rotational axis.
Innovation Solution
The implementation of a spherical planar motor that applies two-dimensional non-contacting electro-magnetic forces in planes tangential to the inner ball at multiple control points, allowing independent rotation around any axis or combinations thereof, with the motor being inertially isolated from the ball and using active magnetic levitation to eliminate contact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If nested gimbals are used to control two-axis pointing, then each axis of the nested gimbal controls one axis of rotation, but the third rotational axis is kinematically constrained and cannot be independently controlled
Solution Approach 1:
The patent replaces the mechanical nested gimbal system with a spherical motor that uses electromagnetic forces to rotate the inner ball about any axis. This substitution eliminates the kinematic constraints of mechanical gimbals and enables independent control of all three rotational axes through non-contact electromagnetic actuation.
Solution Approach 2:
The patent transitions from two-axis control to three-axis control by adding rotational freedom in the third dimension. The spherical motor enables the inner ball to rotate about any axis passing through its center, providing full 3D orientation capability that was not achievable with the constrained nested gimbal mechanism.
2Adaptability or versatility
If ball joint gimbal with ultrasonic drive motors is used, then rotational forces are applied about contact points along orthogonal axes, but the third axis is not rigidly constrained and can drift over repeated positioning
Solution Approach 1:
The patent replaces contact-based ultrasonic drive motors with a non-contact spherical motor that uses electromagnetic fields to apply torques. This eliminates mechanical contact and associated wear, friction, and drift, providing stable and repeatable positioning while maintaining full three-axis rotational capability.
Solution Approach 2:
The patent introduces electromagnetic fields as an intermediary to transmit rotational forces without mechanical contact. The spherical motor uses magnetic fields to couple the stator and rotor, enabling force transmission without physical contact points that would cause drift or wear.
3Ease of operation
If linear electro-magnetic permanent magnet motor technology is used, then three dimensions simultaneous control is achieved, but the motor pole pitch must be large enough to maintain alignment over the range of motion, limiting motion to about plus or minus 3 degrees
Solution Approach 1:
The patent uses a spherical motor design where the inner ball can rotate about any axis passing through its center. This spherical geometry naturally accommodates large ranges of motion without requiring the pole pitch constraints of linear motor designs, enabling motion ranges exceeding plus or minus 3 degrees while maintaining three-axis control capability.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution provides inertially stabilized full 3-axis steering control over an extended range of motion, enabling the ball joint gimbal to independently rotate around any axis, addressing the limitations of kinematic constraints and drift in existing systems.
Implementation Method 1
A spherical planar motor applies non-contacting electro-magnetic forces in planes tangential to the inner ball at at least two control points on different diameters of the inner ball
Implementation Method 2
The motor is inertially isolated from the ball and uses active magnetic levitation to eliminate contact
Data Source
AI summary
A ball gimbal electro-optic system comprises a ball gimbal mounted on a platform. The gimbal includes a socket mounted on the platform and an inner ball captured within the socket and free to rotate about combinations of three orthogonal axes to point a pointing axis. A directional electro-optic element is mounted within the inner ball to transmit or receive an optical beam along the pointing axis. A spherical planar motor comprises a plurality of two-dimensional drive elements configured to apply non-contacting electro-magnetic forces in planes tangential to the inner ball at at least two control points on different diameters of the inner ball in commanded two-dimensional directions within the tangential planes to rotate the inner ball within the socket to point the pointing axis. In different embodiments, the spherical planar motor may be configured as a spherical planar DC motor or a spherical planar induction motor. Other systems such as power, ball position readout and data I/O may also be configured as “non-contacting” systems to maintain the inertial stabilization of the inner ball.