Differential-Drive Multi-Axis Actuator for Compact Continuous Rotation
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Solution Overview
Problem
Existing multi-axis actuators are too large for miniature applications, face challenges in miniaturization due to torque motor and angle encoder hysteresis, and require complex components like slip rings and flexible couplings, which increase cost, complexity, and mass, limiting their use in small form factor designs.
Innovation Solution
A rotary actuator with a differential drive mechanism that provides two degrees of freedom, featuring a payload support, a rotatable disk, and an elevation wheel, allowing continuous rotation with integral angle feedback, and eliminating the need for rotating joints and slip rings through a design with open bore torque motors and flexure springs for precise control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional multi-axis actuators are used with separate actuators for each degree of freedom, then positioning control is achieved, but the device size and mass increase significantly
Solution Approach 1:
The patent combines multiple actuation functions into a single integrated mechanism. The differential drive system merges two rotational inputs into a unified mechanism that simultaneously controls both degrees of freedom, eliminating the need for separate actuators and reducing overall device mass while maintaining positioning precision
Solution Approach 2:
The single actuator mechanism performs multiple functions by providing both azimuth and elevation control through differential drive. This multi-functional approach allows one device to replace what would traditionally require multiple separate actuators, reducing device complexity and mass
2Ease of operation
If slip rings are used to complete electrical connections in rotating mechanisms, then electrical connectivity is maintained, but rotational friction increases
Solution Approach 1:
The patent eliminates slip rings entirely from the design by using a different electrical connection approach. The system uses flexible printed circuit boards or other non-contact electrical connection methods that do not require physical sliding contacts, thereby removing the source of rotational friction while maintaining electrical connectivity
Solution Approach 2:
The mechanical slip ring system is replaced with an alternative electrical connection method that does not rely on mechanical sliding contacts. This substitution eliminates the friction associated with slip rings while maintaining the necessary electrical connectivity for the actuator
3Ease of operation
If flexible couplings are used to complete electrical connections, then electrical connectivity is maintained, but the angular range of rotation is limited
Solution Approach 1:
The patent removes flexible couplings from the system by implementing electrical connections that do not require flexible components. The design uses rigid or flexible printed circuit boards that can accommodate the full range of motion without imposing angular limitations, thereby eliminating the rotation range constraint while maintaining electrical connectivity
Solution Approach 2:
The electrical connection system is designed to be dynamic and adaptable to the full range of motion. The connection method accommodates varying angles and positions without requiring flexible couplings, allowing the mechanism to achieve its complete angular range of rotation unrestricted by coupling limitations
4Measurement precision
If conventional actuator designs are used, then positioning control is achieved, but the device complexity and cost increase
Solution Approach 1:
The patent merges multiple control functions into a single integrated actuator mechanism. By combining azimuth and elevation control into one differential drive system, the design reduces the number of separate components, simplifies the overall structure, and lowers cost while maintaining precise positioning control capabilities
Solution Approach 2:
The actuator is designed as a multi-functional device that performs both azimuth and elevation control through a single mechanism. This universal approach eliminates the need for multiple specialized actuators, reducing device complexity and cost while preserving full positioning control functionality
Data Source
AI summary
A multi-axis rotary actuator includes a payload support configured to be rotatable about a first axis, a disk surrounding at least a portion of the payload support, and an elevation wheel rotatably coupled to the payload support. The disk is configured to be rotatable about the first axis. The elevation wheel is configured to be in contact with the disk and to be rotatable about a second axis perpendicular to the first axis. The actuator can include a mirror or other device coupled to the elevation wheel. The mirror or other device is configured to be rotatable about the first axis and the second axis as the payload support and the elevation wheel rotate about the first axis and the second axis, respectively.