Poisson-Effect Actuator Structure for Picometer Positioning Under Load
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Solution Overview
Problem
Existing actuators fail to provide picometer-level resolution and sufficient load-bearing capacity for applications like space telescopes, with flexure-based systems being vulnerable to buckling and fatigue.
Innovation Solution
Actuators utilizing piezoelectric transducers apply forces orthogonal to the desired direction, leveraging the Poisson effect and mechanical motion reduction to achieve picometer-class motions while supporting large loads, with tunable motion reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If piezoelectric actuators are used to achieve nanometer level positioning, then positioning precision is improved, but movement resolution remains insufficient for picometer-level requirements
Solution Approach 1:
The patent introduces an intermediary mechanical system consisting of a bulk material and bendable arms between the piezoelectric actuator and the load. The piezoelectric actuator applies force to the bulk material, which then deforms through Poisson's effect to drive the bendable arms, ultimately moving the load. This intermediary mechanism amplifies the picometer-level displacements from the PZT to achieve nanometer-level positioning precision.
Solution Approach 2:
The patent utilizes Poisson's ratio as a key parameter to transform the displacement. When the piezoelectric actuator applies a force in one direction to the bulk material, the material expands or contracts in perpendicular directions due to Poisson's effect. This parameter change enables the conversion of small axial displacements into larger lateral movements, achieving the required positioning precision.
2Measurement precision
If flexures are used to reduce motion for nanometer level positioning, then positioning precision is improved, but load bearing capacity deteriorates due to thin element vulnerability
Solution Approach 1:
The patent employs bendable arms that function as flexible structural elements. These arms are designed to be sufficiently thick and robust to bear large loads while still being flexible enough to respond to the Poisson effect-driven forces from the bulk material. This resolves the contradiction by providing both load-bearing capacity and motion reduction capability.
Solution Approach 2:
The actuator is segmented into distinct functional components: the piezoelectric actuator, the bulk material, the bendable arms, and the load. This segmentation allows each component to be optimized for its specific function - the PZT for precision actuation, the bulk material for Poisson effect utilization, the bendable arms for load bearing and motion reduction, and the load for the applied force. This modular approach enables simultaneous achievement of high positioning precision and load bearing capacity.
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
Enables picometer-level actuation with high mechanical stiffness and load-carrying capabilities, suitable for space-based environments.
Implementation Method 1
A piezoelectric transducer (PZT) or other similarly high precision actuator is used to apply a force to a bulk material in the plane orthogonal to the desired direction of actuation
Implementation Method 2
In response to a compressive force, the material expands in directions perpendicular to the direction of the applied force due to Poisson's ratio. Conversely, in response to a tensile force, the material contracts in directions perpendicular to the direction of the applied force
Implementation Method 3
The action of the bulk material in the actuation direction is reduced from the displacement caused by the actuators by the inclusion of bendable arms
Data Source
AI summary
Actuator systems and methods are provided. The actuator enables small positional changes to be made between a base and a moveable element. The actuator includes prime movers that apply a force to change a dimension of a body or stem of the actuator in a first direction, which changes a dimension of the stem in a second direction that is perpendicular to the first direction due to the Poisson effect. The prime movers can be coupled to opposite sides of the actuator stem by a pair of arms that form a hoop about the actuator stem. Alternatively, the prime movers can couple a hoop formed by a pair of arms to the actuator stem. A base of the stem can be mounted to the platform, while the moveable element can be mounted to an actuation platform of the stem on a side of the stem opposite the base.