**Contents**


## **About the Editors**

**TaeWon Seo** received his B.S. and Ph.D. degrees from the School of Mechanical and Aerospace Engineering, Seoul Nat'l Univ., Korea in 2003 and 2008, respectively. He is an Associate Professor at the School of Mechanical Engineering, Hanyang Univ., Korea. Before Hanyang Univ., he was a postdoctoral researcher at Nanorobotics Lab., Carnegie Mellon Univ., a visiting professor at Biomimetic Millisystems Lab., UC Berkeley, visiting scholar at University of Michigan, and an Associate Professor at the School of Mechanical Engineering, Yeungnam Univ., Korea. His research interests include robot design, analysis, control, optimization, and planning. Dr. Seo received the Best Paper Award of the IEEE/ASME Transaction on Mechatronics in 2014. He was a Technical/Associate Editor of IEEE/ASME Transaction on Mechatronics and Intelligent Service Robots, and was Associate Editor of IEEE Robotics and Automation Letters.

**Dongwon Yun** received his B.S. degree in mechanical engineering from Pusan National University, Korea, in 2002, an M.S. degree in mechatronics engineering in 2004 from GIST, Korea, and a Ph.D. degree in mechanical engineering from KAIST, Korea, in 2013, respectively. He was a Senior Researcher for Korea Institute of Machinery and Materials from 2005 to 2016. He joined the Department of Robotics Engineering, DGIST in 2016 and he is an Associate Professor in DGIST. His research interests include bio-mimetic robot systems, industrial robot systems and mechatronics, soft robotics, and sensors and actuators. He was a board member of Korean Society of Mechanical Engineering(KSME) and Military Robotics Society(MRS), and a Senior member of IEEE. He was also on an organizing committee for the International Conference on Multisensor Fusion and Integration for Intelligent Systems (MFI 2019) and International Conference of Mechatronics Technology (ICMT).

**Gwang-Pil Jung** received his B.S. degree in mechanical engineering from the KAIST, Daejeon, Korea, in 2010 and the Ph.D. degree in mechanical engineering from Seoul National University, Seoul, Korea. He is an Assistant Professor at the Department of Mechanical and Automotive Engineering, SeoulTech, Korea. His current research interests include the design and fabrication of biologically inspired robots and novel mechanisms using smart materials, structures, and actuators. Dr. Jung received the Best Video Award in IROS 2013. He was an Associate Editor of Journal of Mechanical Science and Technology.

## **Preface to "Advances in Bio-Inspired Robots"**

Bio-inspiration is a good starting point for designing innovative mechanical systems, including robots. Additionally, it is a good way to solve engineering design and control problems. Recently, creative design has become very important in the robotics field, not just following previous design solutions but also suggesting novel system designs for various tasks. Bio-inspiration is becoming more and more popular in order to obtain innovative solutions inspired by animals and insects.

In this Special Issue, nine excellent papers are published on advances in bio-inspired robots. The papers are categorized into three groups as follows:


**TaeWon Seo, Dongwon Yun, Gwang-Pil Jung** *Editors*

## *Editorial* **Special Issue on Advances in Bio-Inspired Robots**

**TaeWon Seo 1,\*, Dongwon Yun 2 and Gwang-Pil Jung 3**


Bio-inspiration is a good starting point of designing innovative mechanical systems, including robots. Additionally, it is a good way to solve engineering design and control problems. Recently, creative design has become very important in the robotics field, not just following previous design solutions but also suggesting novel system designs for various tasks. Bio-inspiration is becoming more and more popular in order to obtain innovative solutions inspired by animals and insects.

In this Special Issue, nine excellent papers are published on advances in bio-inspired robots. The papers are categorized into three groups as follows:


The detail contents can be summarized as follows.

#### **1. Biomimetic Robot Design**

#### *1.1. Soft Jumping Robot Using Soft Morphing and the Yield Point of Magnetic Force*

Soft-morphing, deformation control by fabric structures and soft-jumping mechanisms using magnetic yield points are studied. The soft jumping mechanism can transfer energy more efficiently and stably using an energy storage and release mechanism and the rounded ankle structure designed using soft morphing [1].

#### *1.2. Snake Robot with Driving Assistant Mechanism*

A driving assistant mechanism is proposed for a snake robot, which assists locomotion without additional driving algorithms and sensors. The driving assistant mechanism can prevent roll down on a slope and can increase the locomotion speed [2].

#### *1.3. A Miniature Flapping Mechanism Using an Origami-Based Spherical Six-Bar Pattern*

A novel transmission is proposed for DC motor-based flapping-wing micro aerial vehicles. The proposed origami-based fabrication method reduces the number of relative moving components by replacing rigid links and pin joints with facets and folding joints, which shortens the assembly process and reduces friction between components [3].

#### **2. Mechanical System Design from Bio-Inspiration**

#### *2.1. Bioinspired Divide-and-Conquer Design Methodology for a Multifunctional Contour of a Curved Lever*

Bioinspired design methodology for a multifunctional lever is proposed based on the morphological principle of the lever mechanism in the Salvia pratensis flower. Four partial contours are designed to satisfy three types of functional requirements. The final design for the lever contour is manufactured and verified with visual measurement experiments [4].

**Citation:** Seo, T.; Yun, D.; Jung, G.-P. Special Issue on Advances in Bio-Inspired Robots. *Appl. Sci.* **2021**, *11*, 8492. https://doi.org/10.3390/app11188492

Received: 19 August 2021 Accepted: 9 September 2021 Published: 13 September 2021

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**Copyright:** © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

#### *2.2. Cable Tension Analysis Oriented the Enhanced Stiffness of a 3-DOF Joint Module of a Modular Cable-Driven Human-Like Robotic Arm*

Inspired by the structure of human arms, a modular cable-driven human-like robotic arm is developed for safe human–robot interaction. Due to the unilateral driving properties of the cables, the robotic arm is redundantly actuated and its stiffness can be adjusted by regulating the cable tensions [5].

#### *2.3. A Novel Type of Wall-Climbing Robot with a Gear Transmission System Arm and Adhere Mechanism Inspired by Cicada and Gecko*

A novel type of wall-climbing robot is proposed with a new gear transmission system arm and an adherence mechanism inspired by cicadas and geckos. The adherence force experiments demonstrate that the bionic spines and bionic materials achieved good climbing on cloth, stone, and glass surfaces [6].

#### **3. Bio-Inspired Analysis on A Mechanical System**

*3.1. Control Strategy for Direct Teaching of Non-Mechanical Remote Center Motion of Surgical Assistant Robot with Force/Torque Sensor*

A control strategy is proposed from bio-inspiration that secures both the precision and manipulation sensitivity of remote center motion with direct teaching for a surgical assistant robot. Instead of the bulky mechanically constrained remote center motion mechanism, a conventional collaborative robot is used to mimic the wrist movement of a scrub nurse [7].

#### *3.2. Empirical Modeling of Two-Degree-of-Freedom Azimuth Underwater Thruster Using a Signal Compression Method*

Empirical modeling of a two-degree-of-freedom (DoF) azimuth thruster is presented based on bio-inspiration using the signal compression method. Empirical models of force and moment for rotational motion were derived for practical use through frequency analysis [8].

#### *3.3. Energy-Efficient Hip Joint Offsets in Humanoid Robot via Taguchi Method and Bio-Inspired Analysis*

The offsets of hip joints in humanoid robots are optimized via the Taguchi method to maximize energy efficiency. Through two optimization stages, near-optimal results are obtained for small power consumption [9].

**Acknowledgments:** This Special Issue would not have been possible without the help of a variety of talented authors, professional reviewers, and the dedicated editorial team of *Applied Sciences*. Thank you to all the authors and reviewers for this opportunity. Finally, thanks to the *Applied Sciences* editorial team.

**Conflicts of Interest:** The author declares no conflict of interest.
