Angular Positioning Device Using Imbricated Dead Centre Assemblies
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Solution Overview
Problem
Conventional mechanical devices for angular positioning, such as step motors and piezoelectric actuators, face challenges in achieving precise, stable, and reliable positioning, especially when requiring low transmission ratios and multiple distinct angular positions, which is critical in optical instrumentation like calibrating mirrors.
Innovation Solution
A mechanical angular positioning device comprising two interconnected mechanical assemblies with connecting rods that generate dead centers, allowing for precise positioning around multiple axes, utilizing rotary motors and pivot connections to achieve low transmission ratios and increased speed between positions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a step motor with speed reducer is used to achieve precise angular positioning, then angular precision is improved, but device complexity and size increase due to requiring a large number of toothed wheels for low transmission ratios
Solution Approach 1:
The positioning system is divided into two independent mechanical assemblies, each responsible for one angular position. Each assembly uses a simplified mechanism with only two dead centres, avoiding the need for complex multi-gear reducers while achieving the required low transmission ratio for precise positioning.
Solution Approach 2:
The patent introduces a mechanical assembly with connecting rods as an intermediary mechanism between the motor and the mirror. This intermediary uses dead centre positions to achieve low transmission ratio without requiring multiple toothed wheels, thus reducing device complexity while maintaining angular precision.
2Measurement precision
If a speed reducer with many toothed wheels is used to achieve low transmission ratio, then angular precision is improved, but play and resistant torque are introduced
Solution Approach 1:
The patent converts the typically harmful play in mechanical transmissions into a beneficial feature by using dead centre positions. At these dead centres, the connecting rods create natural positioning points where play is eliminated, providing stable and reliable angular positions without requiring complex play-elimination devices that would add resistant torque.
3Measurement precision
If a mechanical assembly with two dead centres is used for angular positioning, then transmission ratio is reduced, but only two positions are available which is insufficient for three-position calibration
Solution Approach 1:
The patent merges two independent mechanical assemblies, each providing two dead centre positions, to create a combined system with three distinct angular positions. The first assembly provides positions for calibration, and the second assembly provides the scene position, achieving the required three-position calibration capability while maintaining low transmission ratios through the dead centre mechanisms.
Data Source
AI summary
In the transmission of mechanical movements, a mechanical angular positioning device is provided, and applies to optical instruments to position an element like a mirror according to three predefined positions. The angular positioning device comprises a frame and two imbricated mechanical movement transmission assemblies. The first assembly comprises a first support in pivot connection with the frame according to a first axis, which is rotatable by a first motor via two connecting rods which generate two dead centers for the first support. The second mechanical assembly comprises a second support in pivot connection with the first support, according to a second axis, not parallel with first axis. This second support is rotatable by a second motor via two connecting rods which generate two dead centers for the second support. One of the dead centers of the first support can coincide with one of the dead centers of the second support.