Over the last decade, many bio-inspired crawling robots have been proposed by adopting the principle of two-anchor crawling or anisotropic friction-based vibrational crawling. However, these robots are complicated in structure and vulnerable to contamination, which seriously limits their practical application. Therefore, a novel vibro-impact crawling robot driven by a dielectric elastomer actuator (DEA) is proposed in this paper, which attempts to address the limitations of the existing crawling robots. The novelty of the proposed vibro-impact robot lies in the elimination of anchoring mechanisms or tilted bristles in conventional crawling robots, hence reducing the complexity of manufacturing and improving adaptability. A comprehensive experimental approach was adopted to characterize the performance of the robot. First, the dynamic response of the DEA-impact constraint system was characterized in experiments. Second, the performance of the robot was extensively studied and the fundamental mechanisms of the vibro-impact crawling locomotion were analyzed. In addition, effects of several key parameters on the robot’s velocity were investigated. It is demonstrated that our robot can realize bidirectional motion (both forward and backward) by simple tuning of the key control parameters. The robot demonstrates a maximum forward velocity of 21.4 mm/s (equivalent to 0.71 body-length/s), a backward velocity of 16.9 mm/s, and a load carrying capacity of 9.5 g (equivalent to its own weight). The outcomes of this paper can offer guidelines for high-performance crawling robot designs, and have potential applications in industrial pipeline inspections, capsule endoscopes, and disaster rescues.

The application of shape memory alloy (SMA) actuated soft grippers is limited by their slow recovery speed. In order to further expand their application range, as one of the solutions to address this limitation, this paper proposes a fast actuated soft gripper based on SMA wire active heat dissipation and elastic rib combination to meet the rapid actuation and recovery. The structure primarily consists of a heat dissipation module capable of winding SMA wire and a soft structure resembling a scorpion tail with embedded supper elastic SMA wire. The geometric structure model, dynamics and SMA constitutive model and finite element model of the soft gripper are established, and the lateral deformation of soft bionic scorpion tail end is analyzed through simulations and experiments. In addition, the force in designed soft gripper tip and its ability to grasp different objects are also studied through experiments. The results show that the addition of a cooling fan increased the recovery rate by about 25%, and the force in soft bionic scorpion tail end can reach about 0.12 N. The designed soft gripper can successfully grasp objects with different softness, shape, size and weight. It lays a theoretical foundation and technical support for the development of soft grippers actuated by SMA in the future.

Vibro-impact crawling robots driven by the emerging dielectric elastomer actuators (DEAs) feature the advantages of reduced system complexity and bidirectional locomotion capability. However, due to the lack of systematic dynamic models and in-depth investigations, the fundamental locomotion principles of the robots are still unclear and therefore their applications in real-world scenarios remain hindered. In this paper, a comprehensive dynamic model of this robot is developed by considering the complex interactions between the electro-mechanical coupling, impact mechanism, and multiple nonlinear friction characteristics. By incorporating extensive modeling and experimental studies, we explain the fundamental principles that lead to the bidirectional locomotion of the robot. The actuation strategies for both forward and backward locomotion are characterized in-depth, which include the actuation frequencies, relative phases, and waveforms. Three typical contact surface cases (i.e. rigid & dry, rigid & viscous, compliant & viscous) are considered in this paper, where we report the changes in the optimal actuation strategies for bidirectional locomotion with the contact surfaces and reveal the influences of key factors of friction coefficient, viscosity, and material compliance. The key findings reported in this work can build foundations for developing a highly robust and efficient DEA-driven vibro-impact crawling robot for broad applications.

The resonant actuation of dielectric elastomer actuators (DEAs) can greatly amplify the power outputs and energy efficiencies and has facilitated numerous applications in soft robotics. In many circumstances, the DEAs are mounted on robotic bodies that are made of soft materials or compliant structures. Such compliant supports can demonstrate an equivalent stiffness and inertia comparable to the DEAs, thereby complicating the dynamics of the DEAs and threatening the performance and controllability of the soft robots by introducing additional degrees of freedom to the systems. Toward the goal of achieving reliable and controllable resonating actuation of the DEAs on soft robots, the effects of compliant supports on the dynamics of DEAs require dedicated investigations. By adopting a double cone DEA configuration, this work conducts a comprehensive study on the dynamics of a double cone DEA-compliant support system. A nonlinear dynamic model of the double cone DEA-compliant support system is developed. Together with experimental studies, the dynamics of the system in different support configurations are characterized and the influences of the key parameters in the system are clarified. The key findings of this work can potentially guide the designs of future high-performance DEA-driven soft robots.

In recent years, with the rapid development of soft robots, dielectric elastomer actuators (DEAs) as a novel type of soft actuators have been widely studied. However, DEAs often suffer from low instantaneous output force/power, especially in high payload damping conditions, which limits their applications in certain scenarios. Inspired by the vibro-impact mechanisms found in many engineering systems (e.g., pile driving and percussive drilling), a resonant-impact DEA system was proposed in the authors’ previous work to potentially address this limitation. However, due to the complex nonlinearities and unique electromechanically coupled forcing mechanism of DEAs, no nonlinear dynamic model was developed to perform systematic investigations and optimization. In this paper, a nonlinear dynamic model of the resonant-impact DEA system is developed by considering multiple nonlinearities, viscoelasticity, and electromechanical coupling. Using both a numerical model and extensive experiments, the nonlinear dynamics of the resonant-impact DEA system are studied in depth. The effects of several key parameters, including excitation voltage amplitude, constraint gap, constraint stiffness, and number of DEA layers, on the dynamic response of the system are characterized. The findings reported in this paper can provide guidance for the performance optimization of resonance-impact DEA systems and their applications.