Introduction to Advanced Soft Robotics

Soft robots are an important part of the development of robotics. The research and development of flexible structures are important bases for the development of soft robots. In this chapter, we first introduce the design concepts of soft robots from different perspectives. The soft robot is systematically introduced from the perspectives of drive, material, and structure. In addition, the origin of soft robots is reviewed, and the early development of soft robots is systematically discussed. Finally, the further development of soft robots is researched and discussed, and the prospect of further development of soft robots is explored.

The objective of this chapter is to examine and explore the relevant aspects of soft actuation technology. Unlike traditional rigid robots, soft robots are predominantly composed of flexible materials. Soft robots exhibit exceptional adaptability and flexibility, enabling them to execute various tasks in complex environments. Nevertheless, the classification of soft robot driving modes presents a challenging problem due to the wide range of driving forms and materials utilized in their design.

Firstly, we present a comprehensive definition of soft actuation technology and classify robots into three groups based on their driving methods and motion forms: traditional rigid robots, soft-mimicking robots, and soft robots. Subsequently, our attention turns to the classification of soft robot driving modes. Based on the principles of different driving modes, we categorize the driving modes of soft robots into two groups: structure-function-driven and materialfunction-driven. Furthermore, we provide comprehensive explanations and analyses of several prevalent driving modes for soft robots, such as fluid-driven, magnetic-driven, cable-driven, shape memory material-driven, and electro-active polymer-driven, in addition to highlighting recent advancements in these domains.

Finally, we summarize the issues and challenges encountered in the advancement of soft robot actuation technology after examining various soft robot driving modes in recent years. 

This section introduces the sensing and perception of the soft robots. First, the sensor of the soft robots are classified. Then, the state of the soft robot’s sensing and perception model is introduced, i.e., passive mode, semi-active mode, active mode and interactive perceptive mode. Moreover, according to the sensing and perception mode, several sensing and perception technologies are presented. In the end, several challenges regarding the sensing and perception of the soft robots are summarized. 

Elastomer, hydrogel, shape memory polymers, electro-active polymers, and liquid metal possess some advantages and special performance, especially in soft robots. The flexibility of soft robots, for example, also derives from biologically inspired structural designs and numerous additive manufacturing methods.

This chapter provides a detailed overview of the above five types of materials. The concepts, composition, classification, synthesis principles and properties of these materials are discussed in details. We also summarize and classify the design of release structures for soft robots, including crawling soft robots on land and underwater soft-bodied robots. We analysis and summarize the design and manufacturing methods of soft robots through the existing relevant research results, and finally elaborate on the problems facing future development, in the hope that it can help and guide the direction of research related to soft robots. 

This section introduces the classification of soft robots modeling and control methods. In this section, we present the following modeling methods of soft robots, i.e., mechanics models, geometrical models, discrete material models and surrogate models. In addition, based on above models, three kinds of control framework are described, which consist of model-based control, model-free control and hybrid control approach. In the end, the summaries and challenges are also presented to conclude the modeling and control framework of the soft robots. 

Soft robots have become increasingly prevalent in today's AI era due to their ability to meet the specialized needs and technological advancements that rigid robots cannot. Soft robots are characterized by their flexibility, deformability, and variable stiffness, which greatly compensate for the limitations of rigid robots in specialized environments. This chapter aims to provide extensive examples of how soft robots are being applied in various areas including underwater exploration, agriculture, medicine, industry and space. The chapter will discuss the types of soft robots, their movement characteristics, driving methods, and the advantages they bring to different applications. By showcasing the vast potential and research value of soft robots, this chapter underscores their significant role in promoting technological innovation and societal progress.

In recent years, soft robotics has developed very rapidly and has been widely used in industrial, agricultural, marine and military fields. However, the field of soft robotics still faces many problems. This chapter introduces the current challenges in the field of soft robotics, including actuation, sensing, materials, design, fabrication, modeling and control. Finally, we propose some suggestions and outlooks to overcome these challenges.