Off-Centre Scanning Device with Eccentric Lever Arm
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Solution Overview
Problem
Existing scanning devices in the space industry are bulky and require large sizes to maintain high position accuracy, which limits their angular movement and precision, especially when using high-precision optical instruments for planetary or satellite observations.
Innovation Solution
A scanning device with a lever arm, a gear motor, and an eccentric system that imparts angular oscillating motion to the object, utilizing a position reference sensor and a preload spring for backlash compensation, allowing for reduced size and high positioning accuracy without the need for an optical encoder, operating in an open loop system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a brushless motor actuator connected to a mirror with an optical encoder is used, then high positioning accuracy is achieved, but the device size becomes large
Solution Approach 1:
The patent extracts and removes the optical encoder from the system, transitioning from a closed-loop control system to an open-loop system. This elimination of the encoder and its associated infrastructure significantly reduces device size while maintaining positioning accuracy through alternative means (eccentric mechanism with lever arm and position reference sensor)
Solution Approach 2:
The patent replaces the electrical/optical closed-loop control system (brushless motor + optical encoder) with a mechanical open-loop system (geared motor + eccentric mechanism + lever arm + position reference sensor). This substitution achieves positioning accuracy through mechanical means rather than continuous electronic feedback, reducing overall device complexity and size
2Volume of moving object
If the device size is reduced using an eccentric rotary actuator, then the footprint is smaller, but the complexity of controlling angular positioning increases
Solution Approach 1:
The patent introduces a lever arm as an intermediary mechanical element between the eccentric actuator and the mirror. This lever arm transforms the circular motion of the eccentric into angular oscillation of the mirror, simplifying the control mechanism while maintaining compact size. The position reference sensor acts as another intermediary to provide feedback for backlash compensation.
Solution Approach 2:
The patent employs backlash compensation by dynamically adjusting control parameters (overshoot control) to compensate for mechanical play in the geared motor. This parameter adjustment approach manages control complexity without requiring additional mechanical components, maintaining both compact size and positioning accuracy.
3Measurement precision
If backlash compensation is implemented, then positioning accuracy is improved, but the device complexity increases
Solution Approach 1:
The patent implements feedback through a position reference sensor that monitors the mirror's angular position. This feedback is used in a backlash compensation control system that adjusts the actuator's motion to compensate for mechanical play in the gearbox, improving positioning accuracy without requiring complex additional hardware.
Solution Approach 2:
The backlash compensation system performs preliminary adjustment by intentionally overshooting the target position and then correcting back to the exact position. This preliminary action accounts for and compensates for the mechanical backlash in the geared motor, achieving high positioning accuracy through control strategy rather than mechanical 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
The solution significantly reduces the bulk of scanning devices while maintaining high positioning accuracy and improving service life by eliminating play through backlash compensation, enabling precise angular movements for space industry applications.
Implementation Method 1
A geared motor is an actuator comprising a stepper motor and a gearbox
Implementation Method 2
An eccentric system configured to impart an angular oscillating motion to the object to be oriented via the pivoting distal end of the lever arm, the eccentric system comprising a geared motor and an eccentric
Implementation Method 3
utilizing a position reference sensor and a preload spring for backlash compensation
Data Source
Figure 1A~1B
Figure 2~3
Figure 4
AI summary
The invention relates to a scanning device (10), comprising: - An object (12) to be oriented, such as a mirror, - A lever arm (18) comprising a proximal end (18A) fixed to the object to be oriented, and a pivoting distal end (18B), - A reference sensor (22) for the position of the object to be oriented, - An eccentric system (16) configured to impart an angular oscillation movement to the object to be oriented via the pivoting distal end of the lever arm, the eccentric system comprising a geared motor (20) and an eccentric (21).