Sliding-Joint Rotation Mechanism for Decoupled Two-Axis Optics
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Solution Overview
Problem
Existing rotation mechanisms for optical elements in small digital cameras, such as those used in surveillance and automotive applications, face challenges in achieving two degrees of freedom (DOF) rotation with a Gimbal design, often requiring multiple fixed or rotating motors and bearings, which can be complex and inefficient.
Innovation Solution
A rotation mechanism with two rotation axes around distinct points, utilizing a static base, a first and second rotation arm, and a magnetic follower to maintain a constant distance, allowing independent rotation around each axis with stationary motors and reduced mechanical connections, and incorporating sensing mechanisms like magnets and Hall sensors for precise position determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a Gimbal design is used for two-DOF rotation, then the mechanism can achieve the desired optical function, but the rotation axis of the internally rotating DOF is rotated by the external DOF causing complexity
Solution Approach 1:
The mechanism is divided into independent rotation arms (first and second rotation arms) that rotate around fixed points on the static base. Each arm handles one DOF independently, preventing the coupling effect that causes complexity in traditional Gimbal designs.
Solution Approach 2:
A follower member is introduced as an intermediary element that maintains a constant distance from the second rotation arm while being coupled to the payload. This follower member decouples the motion transmission, allowing independent rotation without axis rotation.
2Reliability
If two fixed motors with more than three bearings are used, then the Gimbal problem is solved, but the device complexity and number of components increases
Solution Approach 1:
The follower member is extracted from direct mechanical contact with the second rotation arm, using magnetic coupling instead. This eliminates the need for additional bearings at the follower interface, reducing the total bearing count while maintaining reliability.
Solution Approach 2:
Magnetic coupling is used to replace mechanical contact between the follower member and the second rotation arm. This substitution eliminates the need for physical bearings at this interface, reducing component count while maintaining precise motion control.
3Reliability
If two rotating motors with two bearings are used, then the Gimbal problem is solved, but the device complexity increases
Solution Approach 1:
The first rotation arm serves dual purposes: it provides the first DOF rotation and simultaneously supports the follower member that guides the second DOF motion. This self-service approach reduces the need for separate motor-bearing assemblies for each DOF.
Solution Approach 2:
The static base serves multiple functions: it provides the mounting surface for motors, defines the fixed rotation points, and supports the overall structure. This multi-functionality reduces the need for additional components that would increase complexity.
4Device complexity
If magnetic coupling is used between follower member and second rotation arm, then mechanical contact is reduced, but precision maintenance requires constant air-gap
Solution Approach 1:
The air-gap distance is optimized to a specific range that provides sufficient magnetic coupling strength while allowing for manufacturing tolerances. This parameter optimization balances the reduction of mechanical contact with the practical constraints of manufacturing precision.
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 design enables efficient two-DOF rotation with reduced mechanical complexity, using only three bearings and decoupled position determination, enhancing the precision and simplicity of optical element positioning in small digital cameras.
Implementation Method 1
the follower member is a magnetic member separated from the second rotation arm by a constant air-gap
Implementation Method 2
a sensing mechanism comprises at least one pair of a magnet and a Hall sensor
Data Source
AI summary
Rotation mechanisms for rotating a payload in two, first and second degrees of freedom (DOF), comprising a static base, a first rotation arm coupled mechanically to the static base through a first rotation joint and used for rotating the payload relative to the static base around a first rotation axis that passes through the first rotation joint, a second rotation arm coupled mechanically to the static base through a second rotation joint and used for rotating the payload relative to the static base around a second rotation axis that passes through the second rotation joint, and a follower member rigidly coupled to the payload and arranged to keep a constant distance from the second rotation arm, wherein the rotation of the first arm rotates the payload around the first DOF and the rotation of the second arm rotate the payload around the second DOF.