In the past two decades, a large number of robot fishes have been built, though their performances are still far inferior compared with that of the real fish. One of the key reasons is the design. This paper presents a novel robot fish. The key innovation is the combination of an active wire-driven body with a soft compliant tail to accomplish undulatory swimming (i.e., flapping in “S” motion). First, the design is presented. Second, the design and analysis model is given. In particular, it is shown that the compliant tail can be modeled through the proposed multipseudolink model. Then, a prototype and experimental results are presented. The experiment results demonstrate that the kinematics of the robot fish can be predicted by the presented model with reasonable errors. Moreover, it has several advantages; simple in structure, easy to control, capable of high-speed swimming (the maximum speed is 2.15 body lengths/s), and good maneuverability (the average turning speed is 63°/s). Most importantly, it is highly efficient; the swimming performance of the robot fish is close to that of a real fish.

Traditional rigid robot application in the medical field is limited due to the limited degrees of freedom caused by their material and structure. Inspired by trunk, tentacles, and snakes, continuum robot (CR) could traverse confined space, manipulate objects in complex environment, and conform to curvilinear paths in space. The continuum robot has broad prospect in surgery due to its high dexterity, which can reach circuitous areas of the body and perform precision surgery. Recently, many efforts have been done by researchers to improve the design and actuation methods of continuum robots. Several continuum robots have been applied in clinic surgical interventions and demonstrated superiorities to conventional rigid-link robots. In this paper, we provide an overview of the current development of continuum robots, including the design principles, actuation methods, application prospect, limitations, and challenge. And we also provide perspective for the future development. We hope that with the development of material science, Engineering ethics, and manufacture technology, new methods can be applied to manufacture continuum robots for specific surgical procedures.

Due to their high flexibility, large workspace, and high repeatability, industrial robots are widely used in roughing and semifinishing fields. However, their low machining accuracy and low stability limit further development of industrial robots in the machining field, with low stiffness being the most significant factor. The stiffness of industrial robots is affected by the joint deformation, transmission mechanism, friction, environment, and coupling of these factors. Moreover, the stiffness of a robot has a nonlinear distribution throughout the workspace, and external forces during processing cause irregular deviations of the robot, thereby affecting the machining accuracy and surface quality of the workpiece. Many scholars have researched identifying the stiffness of industrial robots and have proposed methods for improving the performance of industrial robots, mainly by optimizing the body structure of the robot and compensating for deformation errors with stiffness models. This paper reviews recent research on the stiffness modelling of industrial robots, which can be broadly classified as finite element analysis (FEA), matrix structure analysis (MSA), and virtual joint modelling (VJM) methods. Each method is studied from three aspects: algorithms, implementation, and limitations. In addition, common measurement techniques have been introduced for measuring deformation. Further research directions are also discussed.

This paper presents an experimental study on how different body flapping patterns affect the performances of fish cruising. First, a biomimetic robot fish is designed and built as the experimental platform, which mimics the skeleton structure and the muscle arrangement of real fish. Moreover, an improved Central Pattern Generator (CPG) is developed to generate different patterns, which are characterized by four control parameters: (1) the amplitude, (2) the frequency, (3) the time ratio between the beating phase and half cycle, (4) the shape parameter. Then, a number of experiments are conducted to investigate the thrust, the recoil, the cruising speed and the swimming efficiency. Based on the experimental results, following conclusions can be drawn: (1) Fish cruising follows the traveling wave model proposed in Lighthill's Elongated Body Theory. This model offers a balance between the thrust generation and the recoil, which results in a good swimming speed and high efficiency. (2) The time asymmetry of the body flapping patterns reduces the thrust. (3) The triangular pattern offers the smallest recoil and the cambering sinusoidal pattern gives the largest thrust. These findings provide better understandings on how fish swims and can be used as guidelines for designing the body flapping patterns for robot fish.