Hybrid Optical Mount With Encoder-Corrected Harmonic Drive
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Solution Overview
Problem
Conventional optical instrument mounts using worm gears require counterweights in equatorial mode, leading to portability issues and increased size, while harmonic gears are costly and prone to periodic errors.
Innovation Solution
A hybrid mount employing a worm gear for declination axis positioning and a harmonic gear for right-ascension axis positioning, with an optical encoder for correcting harmonic errors, allowing operation without counterweights and reducing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If worm gears are used for equatorial mount positioning, then the mount can provide stable angular positioning, but counterweights are required which increase weight and size
Solution Approach 1:
The patent divides the positioning system into two independent segments: worm gears for declination axis positioning and harmonic gears for right-ascension axis positioning. This segmentation allows each gear type to be optimized for its specific function, eliminating the need for counterweights on the right-ascension axis while maintaining stable positioning on the declination axis.
2Reliability
If counterweights are added to worm gear mounts, then slipping and wear are prevented, but portability is impaired and size increases
Solution Approach 1:
By separating the positioning functions into two independent axes with different gear types, the patent eliminates the need for counterweights on the right-ascension axis. The harmonic gear's inherent ability to resist turning moments without counterweights improves portability while the worm gear on the declination axis maintains reliable engagement.
3Ease of operation
If harmonic gears are used for right-ascension positioning, then counterweights are not needed and backlash is reduced, but periodic errors increase
Solution Approach 1:
The patent incorporates an optical encoder that provides feedback on the actual position of the right-ascension axis. This feedback enables the control system to detect and correct periodic errors caused by the harmonic gear, maintaining high positioning precision while enjoying the benefits of counterweight-free operation and low backlash.
4Ease of manufacture
If harmonic gears are used instead of worm gears, then cost is reduced and backlash is minimized, but periodic errors are introduced
Solution Approach 1:
The optical encoder provides real-time position feedback that enables the control system to identify and compensate for periodic errors inherent in harmonic gear operation. This feedback mechanism allows the system to achieve high positioning accuracy despite the periodic errors, making the harmonic gear a cost-effective choice.
Data Source
AI summary
A hybrid mount for an optical instrument and an associated method employs a worm gear for angular positioning about a declination axis and a harmonic gear for angular positioning about a right-ascension axis. An optical encoder measures right-ascension angles and provides a basis for correcting periodic errors introduced by the harmonic gear.