Design and Implementation of Actuator for the Swing Mechanism of Bio-mimosa Robot

Abstract

Shape memory alloy (SMA) has been widely used in industrial and medical fields in recent years. Through specific alloying processes, metals are shaped with memory capacity. For the present study, we used SMA to create a swing mechanism in a bionic mimosa robot. The mechanism design and a pulse width modulation (PWM) control method were adopted to drive the SMA. Meanwhile, the optical sensor can detect the status of the environment, which allows the leaves of the robot to contract when necessary. The heat shrinkage characteristics of nickel-titanium (Ni-Ti) alloy were used in the swing mechanism of the bionic mimosa. The Ni-Ti alloy is intended for the design of a linear control actuator capable of changing the shape of the metal type. First, the processed SMA was placed into the polydimethylsiloxane (PDMS) material of the leaf. Then, the actuator that controls the swing mechanism was designed. A PWM technique was utilized to drive and control the SMA. Finally, the tip shift was calculated through experimental results. Meanwhile, a thermal imager was adopted to analyze the temperature generated by SMA under different voltages. The values of tip shift obtained through analysis serve as reference for bionic mimosa mechanisms and output electric current of microcontroller in order to obtain the best swing quality. The proposed method can be applied to future biomimetic micro-robot systems, as well as to greenhouse systems.