Two-Axis Payload Pointing With a Virtual Pivot Focal Point
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Solution Overview
Problem
Conventional antenna pointing mechanisms suffer from signal degradation due to defocussing and depointing when the reflector is steered relative to a fixed signal source, as the focal point moves away from the source.
Innovation Solution
A two-axis pointing system with three struts connected to the payload by spherical bearings, allowing the payload to rotate around a virtual pivot point close to its focal point, using two orthogonal actuators to maintain proximity to the signal source.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the reflector is steered relative to a fixed signal source using conventional pointing mechanisms, then the reflector can be positioned to point at the source, but the focal point moves away from the source causing signal degradation
Solution Approach 1:
The patent changes the geometric parameters of the positioning system by introducing a virtual pivot point located at the focal point of the reflector. The struts are positioned and dimensioned such that their axes intersect at this virtual pivot point, ensuring that during payload movement, the focal point remains stationary relative to the signal source. This parameter optimization resolves the contradiction by maintaining both pointing accuracy and signal quality simultaneously.
2Reliability
If the focal point is kept close to the signal source during reflector movement, then signal degradation is minimized, but the mechanism complexity increases
Solution Approach 1:
The patent segments the positioning function into two independent parts: (1) the virtual pivot point mechanism that ensures the focal point remains stationary, and (2) the payload orientation mechanism that allows the reflector to point accurately at the source. This segmentation is achieved through the strut arrangement that creates the virtual pivot point, decoupling the focal point position control from the pointing direction control, thereby reducing overall system complexity while maintaining signal quality.
Solution Approach 2:
The virtual pivot point acts as an intermediary element that mediates between the signal source and the moving payload. By positioning the virtual pivot point at the focal point and arranging the struts to intersect at this point, the system creates a reference point that remains stationary during payload movement. This intermediary ensures that the focal point-stationary requirement is met without requiring direct mechanical connection to the signal source, thus reducing mechanism complexity.
Data Source
AI summary
Provided herein is a two-axis pointing system and methods for pointing a payload, including a first actuator connected to the payload by at least a first connecting rod, wherein the first actuator controls movement of the payload along a first actuator axis by moving the first connecting rod, a second actuator connected to the payload by a second connecting rod, wherein the second actuator controls movement of the payload along a second actuator axis by moving the second connecting rod, and a first strut, a second strut, and a third strut, wherein each strut is movably connected to the payload at a first end and movably connected to a base at a second end, wherein the first strut, second strut, and third strut restrict movement of the payload, caused by the first actuator and the second actuator, to rotation around a virtual pivot point.