Lecture Review: Soft Actuators and Soft Robots
On June 12, Professor Jian Zhu who would join AIRS Research Center on Intelligent Robots, gave a wonderful lecture on "Soft Actuators and Soft Robots". The lecture was hosted by Prof. Zhenglong Sun from the School of Science and Engineering in the Chinese University of Hong Kong, Shenzhen.
Prof. Zhu first introduced the currently widely-used soft actuators and soft robots (Figure 1), including shape memory alloys, shape memory polymers, and pneumatic/fluid actuators. Designers can choose soft actuators based on the application because these soft actuators have their own characteristics.
Figure 1: Soft actuators and soft robots（Ref：Rus and Tolley, Design, fabrication and control of soft robots, Nature 521, 467-475, 2015. ）
Prof. Zhu then briefly introduced the dielectric elastomer actuators (Figure 2) and some underwater soft robots based on this actuator. The dielectric elastic actuator has the characteristics of large deformation (> 100%), light weight, fast response, and noiseless. More importantly, it can exhibit muscle-like behaviors which are very challenging and difficult to achieve for traditional actuators.
Figure 2: Dielectric elastomer actuator（Ref：Pelrine, et al., High-speed electrically actuated elastomers with strain greater than 100%. Science 287, 836，2000。)
Underwater soft robots based on dielectric elastomer actuator include jellyfish robots and frog robots. The jellyfish robot is actuated by an air chamber covering a dielectric elastomer. Through the deformation of the soft actuator, water can be ejected, and the force are induced by water injection. At the same time, the volume of the air chamber can also cause changes in buoyancy force.
Figure 3: The bionic jellyfish robot design and prototype（Ref：Godaba, Li, Wang, Zhu, A soft jellyfish robot driven by a dielectric elastomer actuator, IEEE Robotics and Automation Letters 1, 624-631, 2016，this paper was also presented in the 2016 ICRA).
Prof. Zhu then introduced the work of some untethered soft robots (Figure 4). The robot's body is composed of a dielectric elastomer actuator, and its two feet are composed of electro adhesion actuators. By controlling the voltage applied to the three actuators, the robot can move fast and stable. In addition, unlike most pneumatic robots, this robot can place battery, microcontroller and other components on the robot body, so the robot can be less affected by energy and wires, thus becoming a more independent system.
Figure 4: untethered soft robots（Ref：Cao, J.W., Qin, L., Liu, J., Ren, Q.Y., Foo, C.C., Wang, H.,Q., Lee, H.P., and Zhu, J. (*), Untethered soft robot capable of stable locomotion using soft electrostatic actuators, Extreme Mechanics Letters 21, 9-16, 2018）
Prof. Zhu also used soft actuators to create artificial muscle to achieve facial expressions of humanoid robots, including artificial muscles for jaw movements (Figure 5) and artificial muscles for 3D motion of eye-ball (Figure 6).
Figure 5: Artificial muscles for jaw movements（Ref：Gupta, U., Wang, Y.Z., Ren, H.L., and Zhu, J., Electromechanical modeling and feedforward control of jaw movements driven by viscoelastic artificial muscles, IEEE/ASME Transactions on Mechatronics 24, 25-35, 2019）
Figure 6: Artificial muscles for 3D motion of eye-ball （Ref：Li, L., Godaba, H., Ren, H.L., and Zhu, J. (*), Bioinspired soft actuators for eyeball motions in humanoid robots, IEEE/ASME Transactions on Mechatronics, IEEE/ASME Transactions on Mechatronics 24, 100-108, 2019）
Finally, Professor Zhu conducted a friendly interaction with the audience who participated in the lecture online, and answered related questions in his research field.