Basics of shape memory alloys as actuators
Shape memory alloys, or SMA for short, are materials that exhibit unique behavior. The best-known material in this regard is a binary nickel-titanium alloy. FGLs can remember their previously imprinted original shape after deformation. The original shape is firmly imprinted in advance by an annealing process.
The thermal effect is characterized by the fact that, for example, an SMA wire is deformed in the cold state. This deformation remains until the wire is heated above a certain switching temperature and resumes its initial shape, approximately linear to the temperature. In the process, the wire generates mechanical work.
In this context, shape memory alloys have the highest energy density of all known actuator principles.
For example, a shape memory wire of 2 mm diameter and one (1) meter length is capable of lifting a weight of 120 kg by 8 cm. The wire weighs only 30 g. A comparable lifting magnet would weigh about 5 kg to achieve this performance.
Functional principle of a shape memory actuator:
The basic principle of an actuator is quickly explained. The FG wire shortening due to the flow of current takes the actuator along, performing a linear motion.
The principle can be well illustrated in the following animation:
Our standard shape memory actuators:
- FG-ONE / FG-ONEeasy: our standardized FG actuator for unlocking and adjusting tasks
- FG-FLEX: a miniature actuator as flexibly mountable as a cable
- FG-Valve: proportional valve for industrial applications
Individual shape memory actuators:
Thanks to many years of experience, we are able to accompany your product from the planning stage to beyond the market launch and provide you with competent and professional support in achieving your goals.
In this context, we offer the following services:
- Matching your target parameters with the application possibility of shape memory actuators
- Series-compliant development of your individual SMA actuator with reference to applicable guidelines and standards (e.g. VDI-2248)
- System integration of SMA into already existing products
- Supply of SMA actuators in small, medium and high annual batches
Advantages of shape memory actuators
The use of shape memory alloys (SMA) as actuators will also have a positive impact on your company / product.
- Saving weight and installation space.
Due to the compact design of the shape memory wires, it is possible to adjust almost 100 N with 10 mm³ SMA.
However, for proper, durable and reliable operation, the actuator structure is required. These components make up our standardized actuators, which show a 50% reduction in installation space compared to an E-magnet of the same performance class. The weight savings to the E-magnet can be, depending on the application, up to 80%.
- Insensitivity to weathering.
The NiTi shape memory alloys (nickel-titanium alloy) we use are insensitive to typical weathering conditions such as those found in automotive, building services and agriculture. The material shows no signs of corrosion and no changes in reliability in these areas.
- No noise emission.
Shape memory alloys do not generate any noise during their transformation, which is why they can usefully take over cyclic positioning tasks where noise is equivalent to quality reductions or even functional limitations.
- Linear working movements.
Due to the physical properties, FGL can be used well as linear drives, which do without gear reductions. This results in no abrasion and no gear noise.
- Simple design.
The number of actuator components, and therefore the weight of the components, is further reduced compared to a gearmotor. Fewer components means less effort in design and assembly, less susceptibility to faults, idR simpler control of the end position – so less cost.
- Smooth / Soft working movements possible.
The movement of an FG actuator is not jerky like a solenoid, but smooth and continuous. The speed can be controlled, of course, as well as the path, but can not be executed “abruptly”. It works vibration-free.
- Compatibility with existing actuator infrastructure.
Typically, our shape memory actuators operate in voltage range between 0-5V or 0-12 V (AC or DC).
If the shape memory actuator is connected to an existing control unit, the following standards can be used to put the actuator into operation with a control output stage if necessary:
– TTL signal level as control signal / if necessary also PWM signal
– LIN- / CAN- / Profibus- connectivity by our own control units
– I2C- / SP- interface connectivity through our own control units
- Electromagnetic insensibility.
An actuator based on a shape memory alloy has no electric magnetic field and no permanent magnetic field, making any shielding completely unnecessary.
- Built-in overload protection.
Our SMA actuators inherently feature protection against overload as well as overheating protection.