Soft Robotics: Actuation, Control, and Application

A special issue of Actuators (ISSN 2076-0825). This special issue belongs to the section "Actuators for Robotics".

Deadline for manuscript submissions: 30 September 2025 | Viewed by 9942

Special Issue Editor

School of Mechanical Engineering and Automation, Harbin Institute of Technology Shenzhen Graduate School, Shenzhen 518055, China
Interests: super dexterous flexible soft robots; cable-driven parallel robots

Special Issue Information

Dear Colleagues,

Robotics research is rapidly advancing and has attracted the attention of a large number of researchers. Based on the material characteristics of their bodies, robots can generally be classified as rigid robots and soft robots. Rigid robots have reliable structures and high motion precision, and can withstand large loads. Soft robots, taking advantage of their compliance, can adapt to complex and irregular environments and have a relatively strong resistance to impacts. Compared to traditional rigid robots, they offer better safety and adaptability. With their unique advantages, soft robots hold tremendous potential in fields like medical endoscopy and surgery, search and rescue in ruins, food processing, and dexterous manipulation. Compared to traditional rigid robots, soft robots exhibit strong specificity in actuation, sensing, and control. Currently, new types of soft actuators, sensors, and circuits are emerging in large numbers. This Special Issue will focus on the actuation, sensing, control, and application of soft robots, publishing a series of high-level papers to showcase the latest research findings in the field of soft robots and promote the transition of soft robotics from theory to application.

This Special Issue’s main goal is to present a cutting-edge collection of articles presenting novel developments in soft robot actuation, control, and application, as well as experimental studies relating to their use in real-world applications. This Special Issue covers a variety of contributions from different fields.

Dr. Han Yuan
Guest Editor

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Keywords

  • soft actuators
  • soft robots
  • flexible electronics
  • strain sensors
  • artificial muscle
  • electroactive polymers
  • compliant mechanism
  • sensors
  • tactile sensors

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Published Papers (5 papers)

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Research

17 pages, 8500 KiB  
Article
Stiffness Analysis of Cable-Driven Parallel Robot for UAV Aerial Recovery System
by Jun Wu, Honghao Yue, Xueting Pan, Yanbing Wang, Yong Zhao and Fei Yang
Actuators 2024, 13(9), 343; https://doi.org/10.3390/act13090343 - 6 Sep 2024
Viewed by 1082
Abstract
Unmanned Aerial Vehicle (UAV) aerial recovery is a challenging task due to the limited maneuverability of both the transport aircraft and the UAV, making it difficult to establish an effective capture connection in the airflow field. In previous studies, we proposed using a [...] Read more.
Unmanned Aerial Vehicle (UAV) aerial recovery is a challenging task due to the limited maneuverability of both the transport aircraft and the UAV, making it difficult to establish an effective capture connection in the airflow field. In previous studies, we proposed using a Cable-Driven Parallel Robot (CDPR) for active interception and recovery of UAVs. However, during the aerial recovery process, the CDPR is continuously subjected to aerodynamic loads, which significantly affect the stiffness characteristics of the CDPR. This paper conducts a stiffness analysis of a single cable and a CDPR in a flow field environment. Firstly, we derive the stiffness matrix of a single cable based on a model that considers aerodynamic loads. The CDPR is then divided into elements using the finite element method (FEM), and the stiffness matrix for each element is obtained. These element stiffness matrices are assembled to form the stiffness matrix of the CDPR system. Secondly, we analyze the stiffness distribution of a single cable at various equilibrium positions within a flow field environment. Aerodynamic loads were observed to alter the equilibrium position of the cable, thereby impacting its stiffness. The more the cable bends, the greater the reduction in its stiffness. We examine the stiffness distribution characteristics of the CDPR’s end-effector within its workspace and analyze the impact of varying flow velocities and different cable materials on the system’s stiffness. This research offers a methodology for analyzing the stiffness of CDPR systems operating in a flow field environment. Full article
(This article belongs to the Special Issue Soft Robotics: Actuation, Control, and Application)
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20 pages, 1385 KiB  
Article
Hybrid Control of Soft Robotic Manipulator
by Arnau Garriga-Casanovas, Fahim Shakib, Varell Ferrandy and Enrico Franco
Actuators 2024, 13(7), 242; https://doi.org/10.3390/act13070242 - 27 Jun 2024
Cited by 4 | Viewed by 1635
Abstract
Soft robotic manipulators consisting of serially stacked segments combine actuation and structure in an integrated design. This design can be miniaturised while providing suitable actuation for potential applications that may include endoluminal surgery and inspections in confined environments. The control of these robots, [...] Read more.
Soft robotic manipulators consisting of serially stacked segments combine actuation and structure in an integrated design. This design can be miniaturised while providing suitable actuation for potential applications that may include endoluminal surgery and inspections in confined environments. The control of these robots, however, remains challenging, due to the difficulty in accurately modelling the robots, in coping with their redundancies, and in solving their full inverse kinematics. In this work, we explore a hybrid approach to control serial soft robotic manipulators that combines machine learning (ML) to estimate the inverse kinematics with closed-loop control to compensate for the remaining errors. For the ML part, we compare various approaches, including both kernel-based learning and more general neural networks. We validate the selected ML model experimentally. For the closed-loop control part, we first explore Jacobian formulations using both synthetic models and numerical approximations from experimental data. We then implement integral control actions using both these Jacobians, and evaluate them experimentally. In an experimental validation, we demonstrate that the hybrid control approach achieves setpoint regulation in a robot with six inputs and four outputs. Full article
(This article belongs to the Special Issue Soft Robotics: Actuation, Control, and Application)
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21 pages, 9698 KiB  
Article
Soft Electrohydraulic Bending Actuators for Untethered Underwater Robots
by Hao Lin, Yihui Chen and Wei Tang
Actuators 2024, 13(6), 214; https://doi.org/10.3390/act13060214 - 8 Jun 2024
Cited by 1 | Viewed by 1593
Abstract
Traditional underwater rigid robots have some shortcomings that limit their applications in the ocean. In contrast, because of their inherent flexibility, soft robots, which have gained popularity recently, offer greater adaptability, efficiency, and safety than rigid robots. Among them, the soft actuator is [...] Read more.
Traditional underwater rigid robots have some shortcomings that limit their applications in the ocean. In contrast, because of their inherent flexibility, soft robots, which have gained popularity recently, offer greater adaptability, efficiency, and safety than rigid robots. Among them, the soft actuator is the core component to power the soft robot. Here, we propose a class of soft electrohydraulic bending actuators suitable for underwater robots, which realize the bending motion of the actuator by squeezing the working liquid with an electric field. The actuator consists of a silicone rubber film, polydimethylsiloxane (PDMS) films, soft electrodes, silicone oils, an acrylic frame, and a soft flipper. When a square wave voltage is applied, the actuator can generate continuous flapping motions. By mimicking Haliclystus auricula, we designed an underwater robot based on six soft electrohydraulic bending actuators and constructed a mechanical model of the robot. Additionally, a high-voltage square wave circuit board was created to achieve the robot’s untethered motions and remote control using a smart phone via WiFi. The test results show that 1 Hz was the robot’s ideal driving frequency, and the maximum horizontal swimming speed of the robot was 7.3 mm/s. Full article
(This article belongs to the Special Issue Soft Robotics: Actuation, Control, and Application)
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14 pages, 2586 KiB  
Article
High-Performance Nanocellulose-Based Ionic Electroactive Soft Actuators
by Yujiao Wu, Qiyuan Cui and Fan Wang
Actuators 2024, 13(6), 200; https://doi.org/10.3390/act13060200 - 24 May 2024
Cited by 2 | Viewed by 1413
Abstract
High-performance electroactive polymer actuators with large bending, fast response, and high durability have gained attention in the development of micromanipulators and multifunctional bionic soft robots. Herein, we developed high-performance electroactive soft actuators fabricated with ultrathin free-standing microfibrillated cellulose (MFC)-reinforced poly(3,4-ethylenedioxythiophene)/poly(4-styrenesulfonate) (PEDOT/PSS) with multi-walled [...] Read more.
High-performance electroactive polymer actuators with large bending, fast response, and high durability have gained attention in the development of micromanipulators and multifunctional bionic soft robots. Herein, we developed high-performance electroactive soft actuators fabricated with ultrathin free-standing microfibrillated cellulose (MFC)-reinforced poly(3,4-ethylenedioxythiophene)/poly(4-styrenesulfonate) (PEDOT/PSS) with multi-walled carbon nanotube (MWCNT)-doped composite electrode films and ion-exchange Nafion membranes by a hot-pressing method. The prepared PEDOT/PSS-MFC-MWCNT electrodes have good film-forming properties with a Young’s modulus of 448 MPa and an electrical conductivity of 75 S/cm. The proposed PEDOT/PSS-MFC-MWCNT/Nafion soft actuators have a sustained peak displacement of 2.1 mm and a long-term cyclic stability of 94% with no degradation over 1 h at 1.0 V, 0.1 Hz. Furthermore, we fabricated soft micro-grippers based on the actuators for mimicking actual finger actions for grasping, pointing, and counting, which introduces new possibilities for the next-generation development of micromanipulators and bionic soft robotics. Full article
(This article belongs to the Special Issue Soft Robotics: Actuation, Control, and Application)
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17 pages, 38360 KiB  
Article
Design and Characterization of Soft Fabric Omnidirectional Bending Actuators
by Kyungjoon Lee, Khulan Bayarsaikhan, Gabriel Aguilar, Jonathan Realmuto and Jun Sheng
Actuators 2024, 13(3), 112; https://doi.org/10.3390/act13030112 - 14 Mar 2024
Cited by 4 | Viewed by 2809
Abstract
Soft robots, inspired by biological adaptability, can excel where rigid robots may falter and offer flexibility and safety for complex, unpredictable environments. In this paper, we present the Omnidirectional Bending Actuator (OBA), a soft robotic actuation module which is fabricated from off-the-shelf materials [...] Read more.
Soft robots, inspired by biological adaptability, can excel where rigid robots may falter and offer flexibility and safety for complex, unpredictable environments. In this paper, we present the Omnidirectional Bending Actuator (OBA), a soft robotic actuation module which is fabricated from off-the-shelf materials with easy scalability and consists of three pneumatic chambers. Distinguished by its streamlined manufacturing process, the OBA is capable of bending in all directions with a high force-to-weight ratio, potentially addressing a notable research gap in knit fabric actuators with multi-degree-of-freedom capabilities. We will present the design and fabrication of the OBA, examine its motion and force capabilities, and demonstrate its capability for stiffness modulation and its ability to maintain set configurations under loads. The mass of the entire actuation module is 278 g, with a range of omnidirectional bending up to 90.80°, a maximum tolerable pressure of 862 kPa, and a bending payload (block force) of 10.99 N, resulting in a force-to-weight ratio of 39.53 N/kg. The OBA’s cost-effective and simple fabrication, compact and lightweight structure, and capability to withstand high pressures present it as an attractive actuation primitive for applications demanding efficient and versatile soft robotic solutions. Full article
(This article belongs to the Special Issue Soft Robotics: Actuation, Control, and Application)
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