Eight-Wire SMA Actuator Layout for Camera Motion Control
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Solution Overview
Problem
Existing SMA actuators using eight wires for autofocus and optical image stabilization in cameras face limitations in achieving precise positional control and efficient movement with multiple degrees of freedom, particularly in miniaturized camera modules.
Innovation Solution
An actuator design featuring eight SMA wires connected between a first and second part, with specific configurations and offsets of connection points, allowing the second part to move with at least two degrees of freedom, enhancing movement control and resonant frequency, and incorporating features like bearings and flexures for additional support.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If eight SMA wires are arranged and inclined with respect to a notional primary axis to provide movement along the primary axis and lateral movement, then the actuator can achieve autofocus and optical image stabilization, but the device complexity increases due to the need for precise wire arrangement and connection point offsets
Solution Approach 1:
The actuator divides the wire arrangement into four sides with two SMA wires on each side, creating distinct functional groups. Each side can be independently configured with specific connection point offsets to achieve different movement patterns, allowing complex motion control through modular wire segment arrangement.
Solution Approach 2:
The patent introduces asymmetric connection point offsets where corresponding connection points on opposite sides are offset from each other in a direction parallel to the primary axis. This asymmetric configuration enables the actuator to achieve specific movement patterns and resonant frequency characteristics that would not be possible with symmetric wire arrangements.
2Measurement precision
If the SMA wires are configured with specific inclination angles to increase resonant frequency, then movement precision is improved, but the manufacturing precision requirements increase
Solution Approach 1:
The patent optimizes the inclination angle parameter of the SMA wires relative to the primary axis to increase the resonant frequency. By carefully selecting and controlling this angular parameter, the actuator achieves improved movement precision and stability while managing manufacturing complexity through a well-defined geometric relationship.
3Adaptability or versatility
If connection points are offset in a direction parallel to the primary axis to enable additional degrees of freedom, then movement control is enhanced, but the device complexity increases
Solution Approach 1:
The patent introduces offsetting of connection points in a direction parallel to the primary axis, adding a dimensional degree of freedom to the wire arrangement. This additional spatial dimension allows the actuator to achieve multiple degrees of freedom movement while maintaining a systematic and manageable connection point configuration pattern.
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 actuator provides improved positional control and stability, enabling efficient autofocus and optical image stabilization functions in compact camera modules, with enhanced movement capabilities and reduced complexity.
Implementation Method 1
eight shape memory alloy, SMA, wires connected between the first part and the second part
Implementation Method 2
On contraction, a first group of four of the SMA wires each provide a force on the second part
Data Source
Figure 1A~1E
Figure 2
Figure 3A~3E
AI summary
An actuator (18) includes a first part (3), a second part (2) and eight shape memory alloy, SMA, wires (41, …, 48) connected between the first part (3) and the second part (2) so as to enable the second part (2) to be moved relative to the first part (3) with at least two degrees of freedom. Two of the SMA wires (41, …, 48) are located on each of four sides (s 1 , …, s 4 ). The four sides (s 1 , …, s 4 ) extend in a loop around a primary axis (z). On contraction, a first group (41, 43, 45, 47) of four of the SMA wires each provide a force on the second part (2) with a component in a first direction along the primary axis (z), and a second group (42, 44, 46, 48) of the other four of the SMA wires each provide a force on the second part (2) with a component in a second, opposite direction along the primary axis (z). Each of the eight SMA wires (41, …, 48) is configured such that a length perpendicular to the primary axis (z) is foreshortened relative to a length (l 1 , …, l 4 ) of a corresponding one of the four sides (s 1 , …, s 4 ).