Shape Memory Alloy Actuator Control Unit for Stroke and Thermal Management
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Solution Overview
Problem
Existing shape memory alloy actuators face challenges in efficiently controlling the driving stroke and preventing excessive heating, which can lead to performance deterioration due to residual stress and external environment changes, especially when increasing the driving stroke and controlling the expansion and contraction of the shape memory alloy.
Innovation Solution
A control method and unit for a shape memory element actuator that includes a hollow tube member with a shape memory element inserted through it, where one end is fixed, and the other end is mechanically linked to a driven body. This setup uses a force imparting member and a stopper to limit movement, with a feedback resistance circuit optimizing electric power input by adjusting voltage patterns to maintain a predetermined resistance value, thereby controlling the shape memory element's temperature and position changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the length of the shape memory alloy wire is increased to increase the driving stroke, then the driving stroke is increased, but the time required to scan the limit condition and reset the resistance value increases
Solution Approach 1:
The patent applies periodic action by implementing a limit condition scanning process that is executed periodically at predetermined intervals during actuator operation. This periodic scanning allows the system to maintain awareness of the resistance value limits without requiring continuous monitoring, thus reducing the time penalty associated with longer shape memory alloy wires while ensuring reliable detection of limit conditions.
Solution Approach 2:
The patent applies preliminary action by performing an initial scanning of the limit condition at the start of actuator operation and at predetermined intervals thereafter. This preliminary scanning establishes the resistance value limits before normal operation proceeds, allowing the system to quickly reference pre-determined limits during operation rather than continuously measuring, thereby reducing the time impact of increased wire length.
2Speed
If a high voltage is applied to quickly reset the resistance value at the start of use, then the scanning of limit condition is completed in short time, but the shape memory element may be damaged due to excessive electric power supply
Solution Approach 1:
The patent applies feedback by continuously monitoring the resistance value of the shape memory alloy wire and comparing it against predetermined limit values that were established during the scanning process. This feedback mechanism allows the control system to detect when the resistance value approaches dangerous levels and immediately adjust or terminate power supply, thereby protecting the element from damage while maintaining fast scanning capability through controlled high-voltage pulses.
Solution Approach 2:
The patent applies parameter changes by dynamically adjusting the voltage applied to the shape memory alloy wire based on the measured resistance value. During limit condition scanning, high voltage is applied temporarily to quickly establish baseline values, but during normal operation, the voltage is modulated in real-time based on resistance feedback, preventing excessive power supply that could damage the element while maintaining scanning speed.
3Stability of the object's composition
If the resistance value is not accurately reset at the start of use, then the control stability deteriorates, but increasing the voltage to reset quickly may cause excessive heating
Solution Approach 1:
The patent applies feedback by implementing a closed-loop control system that continuously measures the resistance value of the shape memory alloy wire and adjusts the applied voltage accordingly. This feedback mechanism ensures accurate resetting of the resistance value at the start of use by monitoring when the resistance reaches predetermined threshold values, thereby achieving control stability without requiring excessively high voltages that would cause overheating.
Solution Approach 2:
The patent applies periodic action by performing resistance value scanning and resetting at predetermined intervals rather than continuously. This periodic approach allows the system to maintain control stability by regularly updating resistance values while avoiding continuous high-voltage application that would generate excessive heat, thus balancing stability requirements with thermal management.
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 method allows for a short-time scanning of the limit condition at the start of usage, reduces the amplitude of the movable body, and prevents deterioration from excessive electric power supply, enhancing the stability and controllability of the shape memory element actuator.
Implementation Method 1
A shape memory element undergoes a phase transition due to a change in a temperature, and has a change of shape.
Implementation Method 2
A shape memory element undergoes a phase transition due to a change in a temperature, and has a change of shape.
Implementation Method 3
the shape of a shape memory element is changed by supplying an electric power to the shape memory element
Implementation Method 4
a resistance value which changes with the shape change is detected
Data Source
AI summary
At the time of start of usage, a voltage to be applied to a shape memory alloy wire 102 by a feedback control circuit 120 is set to a first voltage value (step S1), and at a limit resistance value detection step, (the feedback control circuit) measures a limit resistance value when the shape memory alloy wire 102 can be contracted (step S2), and upon storing the limit resistance value, a value of the maximum voltage to be input by the feedback control circuit 120 is set to a second voltage value (step S3). At an input electric power optimization step, a target resistance value is indicated, and the feedback control is carried out such that the resistance value indicated is not lower than the limit resistance value (step S4). Thereafter, voltage is stopped at the time of stopping the use of the actuator.