Bioinspired SMA based Actuator

Prof. Bishakh Bhattacharya, Kanhaiya Lal Chaurasiya, Abhishek Kumar Singh

Dec 12, 2022 Ongoing

Project Status: Ongoing

Challenge #1: DC motor based actuators are being widely used in various fields; however, they mostly depend upon the embedded gear train mechanism to provide required torque output. The use of gear trains, in turn, increases the cost, size, and weight of the actuators.
Challenge #2: Yuan et al. (2017) reviewed shape memory alloy (SMA) based rotary actuators available and reported that their output torque capacity is limited to 1.1 N-m with a design envelope size of approximately (140 x 90 x 60 mm). The survey also reported that the overall dimension of the SMA based actuator keeps on increasing drastically with an increase in output torque requirement for a particular mechanical design.

All the n unipennate structure (n=6 in this figure) have been connected in series with Vin as the input voltage. Stage I: schematic of SMA wires in a bipennate configuration under zero voltage condition; Stage II: depicts the structure under actuation where the SMA wires have contracted because of the reverses transformation as represented by red lines.

The plot depicts the experimental results for the temperature of the SMA wires as well as the force generated by the SMA-based bipennate actuator over two cycles. The input voltage was provided in two 10 s cycles (as shown by the red dots) with a 15 s cooling period between each cycle. The SMA wire used for the experimentation is the 0.51 mm diameter Flexinol wire from Dynalloy, Inc. (a) The graph depicts the experimental force obtained over the course of two cycles, (c, d) show two independent instances of the movable arm of actuator striking the PACEline CFT/5kN piezoelectric force transducer, (b) the graph depicts the maximum temperature across the entire length of the SMA wire during the two cycles, and (e) shows the snapshot of the temperature across the SMA wires obtained from the LWIR camera using the FLIR ResearchIR software.

(a) Displays the simulation output of the temperature distribution as well as the stress-induced transition temperature of the SMA-based bipennate actuator. When the temperature of the wire crosses the austenite transition temperature in the heating phase, the modified austenite transition temperature starts to rise, and likewise the martensite transition temperatures drops when the temperature of the wire crosses the martensite transition temperature in the cooling phase, (b) a Simulink block diagram of the mathematical model for a bipennate-based SMA linear actuator that was utilised for analytical modelling of the actuation process.

Therefore, the current project proposes to provide a solution to tackle both of the abovementioned challenges. The idea behind the project is based on the biomimetic approach, which provides an abundance of designs and solutions which are optimized and efficient in nature to solve complex human problems. The solution to this problem can be obtained from the biomimicry of muscles located in the human body. These types of muscles generally allow higher force production but a smaller range of motion. The design of muscle provides the flexibility of controlling the length of fiber (in our case, SMA wire) to obtain the torque requirement without having any significant effect on the overall dimensions, weight, and cost of the actuator.

The proposed shape memory alloy-based actuator has wide applications ranging from building automation controls to precise drug delivery methods Being in compact nature, it can also be used to control microvalves for precise drug delivery systems for cancer patients. SMA controlled actuators can be optimized towards aspects like reliability, low-cost production, safety, and minimal dimensions.