Waving Tentacles 8×8

When we see the wriggling movement and the shape of a tentacle like the sea anemone under the sea, we feel an existence of a primitive life. The goal of this research is to realize the expression of a kinetic artwork or interactive artwork like waving tentacles of sea anemones by robotics. At present, soft actuators bending in multi directions is developed in several areas. However, these have a complex structure or are expensive. To realize the expression of waving tentacles needs a large number of actuators. Therefore, we developed a budget actuator with a simple structure. Previously, we have introduced three motion patterns for controlling a SMA actuator that can bend in three directions and an experimental system with 9 actuators. In this paper, we introduce an experimental system with 64 actuators that react to a hand’s movement by an optical flow algorithm.

Fig. 1(a) is a drawing the SMA actuator structure. The actuator has a simple structure: a silicone tube, three BioMetal Fibers (BMF150, developed by TOKI Corporation), a LED chip, and a diffuser cap. A BioMetal Fiber is a thin shape-memory alloy wire that contracts by heat and extends to its original length by cooling. The heat of each BioMetal Fiber is controlled through a pulse-width modulation voltage. The actuator can bend in three directions by extension and contraction of three BioMetal Fibers. Furthermore, The actuator can bend in six directions by controlling two of the voltages V1, V2, V3 simultaneously (Fig.1(b)).



Figure 1.  Working principle of a SMA actuator


Images from the infrared camera above 64 actuators are analyzed  by an optical flow algorithm. Bending directions and strength of the actuator are calculated by the orientation and magnitude of the optical flow field (Fig. 2).


Figure 2.  Optical flow field and behavior of actuators (e.g. 3×3)



Figure 3.  A control application based on openFrameworks



Figure 4.  An experimental system with 64 actuators (size: 25x25cm)



Figure 5.  An actuator and electric circuit with PIC24FJ64GA004


All each actuator is independently controlled and reacts to a hand’s movement and bends slowly. 64 actuators behaves like waving tentacles of sea anemones under the sea (Fig. 6).



Figure 6.  64 actuators in the darkness


We believe a larger number of actuators will allow the presentation of expressions that are easier to understand. In the future, we will build an interactive art with over one thousand actuators and an interactive system based on fluid dynamics. Applications include interactive walls, digital signage using visual expressions, moving dolls in theme parks and a music visualizer.


This work was supported by JSPS KAKENHI Grant-in-Aid for Scientific Research(C) 26330418.


International Conference :
Nakayasu, A. 2015. Waving Tentacles 8×8: Controlling a SMA Actuator by Optical Flow. In SIGGRAPH ASIA 2015 Posters, ACM.