Snake-like Robot Research Articles

Navigation with minimal occupation volume for teleoperated snake-like surgical robots: MOVE.

Master-Slave control is a common mode of operation for surgical robots as it ensures that surgeons are always in control and responsible for the procedure. Most teleoperated surgical systems use low degree-of-freedom (DOF) instruments, thus facilitating direct mapping of manipulator position to the instrument pose and tip location (tip-to-tip mapping). However, with the introduction of continuum and snake-like robots with much higher DOF supported by their inherent redundant architecture for navigating through curved anatomical pathways, there is a need for developing effective kinematic methods that can actuate all the joints in a controlled fashion. This paper introduces the concept of navigation with Minimal Occupation VolumE (MOVE), a teleoperation method that extends the concept of follow-the-leader navigation. It defines the path taken by the head while using all the available space surrounding the robot constrained by individual joint limits. The method was developed for the i 2 Snake robot and validated with detailed simulation and control experiments. The results validate key performance indices such as path following, body weights, path weights, fault tolerance and conservative motion. The MOVE solver can run in real-time on a standard computer at frequencies greater than 1kHz.

Design and Fabrication of Bio-Inspired Robotic Systems for Developed Mobility and Functionality in Unstructured Environments

In turn, bio-inspired robotic systems have significantly contributed to the development of well-abled robots capable of moving and manipulating with ease in unknown environments. Imitating biological creatures in their mechanisms of adaptation and effectiveness of design gives these robots enhanced qualities of mobility, functionality, and resilience. In fact, major advances build on flexible joints, controlled underactuation, adaptive control, and sensory arrays of high quality, enabling these robots to traverse rough environments and perform high-precision operations inside the human body. For instance, snake-like robots should be able to move through narrow gaps and debris in some kind of search and rescue task much like a real snake, robotic fish can move effectively across underwater environments while monitoring water quality and marine life. These advancements in technology have broadened the sphere of application and effectiveness of robot applications, proving to be valuable tools in many areas, including disaster response, environmental monitoring, and space exploration. In this regard, one also realizes their significance due to the context of bio-inspired robots regarding the capability of data collection and analyses. The usual methods of data collection are generally limited in reach, recurrence, and resolution. Bio-inspired robots compensate for these inadequacies by continuously gathering various real-time data from environments not easily reachable for humans. More precise and detailed analysis of data resolution collected through these robots supports advanced techniques such as AI and machine learning. This is a very crucial capacity that is central to applications such as following wildlife, assessing the impacts of climate change, and monitoring pollution levels. The capacity of these robots to provide timely and accurate data ensures efforts in environmental management and conservation. The importance of bioinspired robotics, therefore, comes in the solutions associated with unstructured environments. Through the gains of nature, which have been exploited by evolution, these robots present new solutions that overcome the inability of classical robotic systems. The persistence in the performance and development of this field of science will provide ever-greater achievements, with very probably a very important role in the exploration, understanding, and interaction with the natural world played by bioinspired robotics.

A worm-snake-inspired metameric robot for multi-modal locomotion: Design, modeling, and unified gait control

Worm-like and snake-like robots have attracted a great deal of research attention due to their slender bodies and excellent mobility. Based on different locomotion mechanisms, worm-like robots are more suited for movement in restricted environments, while snake-like robots excel in fast movements in open spaces but have limited mobility in confined areas. To complement their advantages, this paper presents a new design and prototype of a Worm-Snake-Inspired Metameric (WSIM) robot with multi-modal locomotion capability, which can execute peristaltic planar locomotion by exploiting the contracting of the worm-like modules and serpentine planar locomotion via active swing of the snake-like joints. We also propose a unified gait control framework that unifies the gait signals of worm-like and snake-like locomotion modes by using the parameter vector, and the conditions that need to be satisfied by the control parameters for generating different gaits are derived. This study also takes a major step forward in establishing dynamic models for the worm-like and snake-like locomotion modes, which can effectively predict the robot's locomotion performance, including the average velocity, slope, and radius of the trajectory. Gait experiments and complex scenario locomotion experiments demonstrate that the WSIM robot indeed has multi-modal locomotion capability and is well suited to execute tasks in complex environments including tubes, open areas, and narrow corridors. The findings of this paper would provide a useful basis for the design, modeling, and control of future bioinspired multi-modal robots.

Mechanical Designs for Field Undulatory Locomotion by a Wheeled Snake-Like Robot With Decoupled Neural Oscillators

In this article, we demonstrate the value of using decoupled neural oscillators in conjunction with appropriate mechanical designs for snake-like robots engaging in field locomotion. Even though our typical wheeled snake robot with decoupled neural oscillators incorporating angle joint feedback can generate consistent lateral undulation, it lacks robustness. A purely decoupled actuation strategy is not practical for field locomotion. However, the application of one-way wheels and elasticity between the modules improves robustness, allowing our robot to traverse outdoor open terrain. On the other hand, the physical form of the undulatory motion must be varied to pass through intricate narrow-field environments. The lack of neural constraints between the modules passively enables this variability and also facilitates each module independently gaining propulsion (i.e., by means of reflexive thrust via sensory feedback to the neural oscillator and one-way traction generated by one-way side rollers). The designed robot is able to engage in fast creeping motion through an environment containing randomly distributed logs. The results of the field experiments show that the specially designed mechanisms in conjunction with decoupled oscillators can enhance robustness, variability, and independent local propulsion.

On the Wing

An advanced snake-like robot originally developed for the aerospace sector could ultimately transform in-situ maintenance and manufacturing operations in a range of difficult to access environments

Generalized Design, Modeling and Control Methodology for a Snake-like Aerial Robot.

Snake-like robots have been developing in recent decades, and various bio-inspired ideas are deployed in both the mechanical and locomotion aspects. In recent years, several studies have proposed state-of-the-art snake-like aerial robots, which are beyond bio-inspiration. The achievement of snake-like aerial robots benefits both aerial maneuvering and manipulation, thereby having importance in various fields, such as industry surveillance and disaster rescue. In this work, we introduce our development of the modular aerial robot which can be considered a snake-like robot with high maneuverability in flight. To achieve such flight, we first proposed a unique thrust vectoring apparatus equipped with dual rotors to enable three-dimensional thrust force. Then, a generalized modeling method based on dynamics approximation is proposed to allocate the wrench in the center-of-gravity (CoG) frame to thrust forces and vectoring angles. We further developed a generalized control framework that can handle both under-actuated and fully actuated models. Finally, we show the experimental results with two different platforms to evaluate the flight stability of the proposed snake-like aerial robot. We believe that the proposed generalized methods can provide a solid foundation for the snake-like aerial robot and its applications regarding maneuvering and manipulation in midair.

Modular Morphing Lattices for Large-Scale Underwater Continuum Robotic Structures.

In this study, we present a method to construct meter-scale deformable structures for underwater robotic applications by discretely assembling mechanical metamaterials. We address the challenge of scaling up nature-like deformable structures while remaining structurally efficient by combining rigid and compliant facets to form custom unit cells that assemble into lattices. The unit cells generate controlled local anisotropies that architect the global deformation of the robotic structure. The resulting flexibility allows better unsteady flow control that enables highly efficient propulsion and optimized force profile manipulations. We demonstrate the utility of this approach in two models. The first is a morphing beam snake-like robot that can generate thrust at specific anguilliform swimming parameters. The second is a morphing surface hydrofoil that, when compared with a rigid wing at the same angles of attack (AoAs), can increase the lift coefficient up to 0.6. In addition, in lower AoAs, the ratio improves by 5 times, whereas in higher angles it improves by 1.25 times. The resulting hydrodynamic performance demonstrates the potential to achieve accessible, scalable, and simple to design and assemble morphing structures for more efficient and effective future ocean exploration and exploitation.

Towards a Discrete Snake-Like Robot Based on SMA-Actuated Tristable Modules for Follow the Leader Control Strategy

Snake-like robots applications include surveillance and exploration of confined environments where human presence is incompatible. The attractiveness of this type of mechatronic structure is notably linked to the modular character and the hyper-redundancy of their architecture, which gives it both mechanical robustness and great manoeuvrability. However, due to the large number of degrees-of-freedom, the use of advanced mathematical models are needed to asses the motion patterns and to simulate it. A new snake-like robot architecture is introduced in this paper together with the development methodology of a replicable multistable module. The interest of this contribution lies in the combination of the mechanical stability of the modules with an easy-to-use direct kinematic model, thus avoiding the need of complex control strategies. The design of one module exploiting the three stable states of a tristable flexible mechanism so as to orient the articulation of the module at three distinct stable angles is first presented. Then a prototype of a modular snake-like robot is built and experimentally evaluated. The prototype consists of 4 modules that can be individually oriented by <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\pm$</tex-math></inline-formula> 7.1 degrees. Each module measures 51.5 × 32 mm and weighs 2.5g. Thereby, this work provides the first results on the feasibility of this robotic architecture which consists of several multistable modules. A good agreement between the working space estimated with the direct kinematic model and experimental measurements is obtained. According to the fact that these are preliminary results, there is a 1.5% error between the experimental results and the models.

A novel position determination method for the modular snake-like natural gas pipeline inspection robot in a GPS denied environment

A novel position determination method for the modular snake-like natural gas pipeline inspection robot in a GPS denied environment

A novel position determination method for the modular snake-like natural gas pipeline inspection robot in a GPS denied environment

A novel position determination method for the modular snake-like natural gas pipeline inspection robot in a GPS denied environment

Dynamic model of a tendon-actuated snake robot using the Newton-Euler formulation

Dynamic models are necessary when dealing with robotic applications where requirements of dexterity, manipulability, payload and compliance have to be satisfied at the same time. This work considers a particular design of tendon-actuated snake-like robots in which links are not coupled through mechanical joints but are free to roll between each other under the effect of cable tension forces. The state of the art in modeling these tendon-actuated rolling-joints systems is limited to kinematic and quasi-static models. In order to simultaneously guarantee modeling accuracy and suitability for model-based control, the Newton-Euler (NE) formulation has been adopted, by taking into account the forces and moments generated by cable tensions, links interactions, inertias, and friction between the rolling surfaces.

Static Modeling of a Class of Stiffness-Adjustable Snake-like Robots with Gravity Compensation

Stiffness-adjustable snake-like robots have been proposed for various applications, including minimally invasive surgery. Based on a variable neutral-line mechanism, previous works proposed a class of snake-like robots that can adjust their stiffness by changing the driving cables’ tensions. A constant curvature hypothesis was used to formulate such robots’ kinematics and was further verified by our previous work via rigorous force analysis and ADAMS simulations. However, all these models and analyses have ignored the effect of the robot links’ gravity, resulting in significant errors in real systems. In this paper, a static model considering gravity compensation is proposed for the stiffness-adjustable snake-like robots. The proposed model adopts a nonlinear Gauss–Seidel iteration scheme and consists of two parts: gravity update and pose estimation. In each iteration, the former updates the payload of each link caused by gravity, and the latter estimates the pose of the robot by refreshing the angle and position values. This iteration stops when the change in the tip position is less than a pre-set error ϵ. During the above process, the only dependent information is each cable’s tension. Simulations and experiments are carried out to verify the effectiveness of the proposed model. The impact of gravity is found to increase with growing material densities in the simulations. The experimental results further indicate that compared with a model without gravity compensation, our model reduces the tip estimation error by 91.5% on average.

Design and Construction of a Snake-Like Robot Implementing Rectilinear and Sidewinding Gait Motions

Bio-inspired robots offer locomotion versatility in a wide variety of terrains that conventional robots cannot access. One such bio-inspired platform is snake-like robots, which are mechanisms designed to move like biological snakes. The aim of this paper was to implement and validate, through comparison in real and simulation tests on flat terrain, the design of a snake robot that allows movements in two perpendicular planes, by the application of three-dimensional locomotion modes. The prototype robot had a modular and sequential architecture composed of eight 3D printed segments. The necessary torques for each motor are found by means of a simulation in Matlab – Simulink and the SimScape tool. The Webots mobile robotics simulator was used to create a parameterized virtual model of the robot, where two types of gaits were programmed: sidewinding and rectilinear. Results showed that the robot undertakes lower than 1 second in execution time to reach the total distance in each of the proposed marches when comparted to the simulation. In addition, mean differences of 6 cm for the distances during the sidewinding mode experiment and 1.2 cm in the deviation in the rectilinear mode on flat terrain were obtained. In conclusion, there is a great similarity between the simulation tests and those performed with the actual robot, and it was also possible to verify that the behavior of the prototype robot is satisfactory over short distances.

Analysis and Optimization Based on Factors Affecting the Spiral Climbing Locomotion of Snake-like Robot

The snake-like robot is a limbless bionic robot widely used in unstructured environments to perform tasks with substantial functional flexibility and environmental adaptability in complex environments. In this paper, the spiral climbing motion of a snake-like robot on the outer surface of a cylindrical object was studied based on the three-dimensional motion of a biological snake, and we carried out the analysis and optimization of the motion-influencing factors. First, the spiral climbing motion of the snake-like robot was implemented by the angle control method, and the target motion was studied and analyzed by combining numerical and environmental simulations. We integrated the influence of kinematics and dynamics factors on the spiral climbing motion. Based on this, we established a multi-objective optimization function that utilized the influence factors to optimize the joint module. In addition, through dynamics simulation analysis, the change of the general clamping force of the snake-like robot’s spiral climbing motion was transformed into the analysis of the contact force between the joint module and the cylinder. On the basis of the results, the effect of the control strategy adopted in this paper on the motion and change rule of the spiral climbing motion was analyzed. This paper presents the analysis of the spiral climbing motion, which is of great theoretical significance and engineering value for the realization of the three-dimensional motion of the snake-like robot.

Analysis of Existing and Proposed Maintenance Deployment Systems Toward DEMO MPD Development

This article reports on a study of previously existing or proposed maintenance deployment systems with similar functions and structure to that of the proposed multipurpose deployer (MPD) for demonstration (DEMO fusion power plant project). The current MPD design iteration consists of a boom deployment system that is ~30 m long and can support a payload of ~1000 kg, while still being able to access the DEMO vacuum vessel through a 2.78 m high by 1.08 m wide port. The purpose of this work is to benefit from previous experience by comparing the mechanical attributes and performance of systems as well as their advantages and disadvantages and any issues encountered to bring design input to MPD design development. The following systems were investigated: Joint European Torus (JET) in-vessel remote handling booms, telescopic articulated remote mast (TARM), Next European Torus (NET) experimental device for in-torus handling (EDITH), Tokamak Fusion Test Reactor (TFTR) Maintenance Manipulator, and Snake-like Robot Arms in Nuclear Environments. Systems that are currently in development for ITER and Chinese Fusion Engineering Test Reactor (CFETR) were also investigated according to their latest available design iterations. This article concludes that these systems, comprising of articulating links to form long-reach slender structures, give rise to challenges with their payload, stiffness, and control. The straight boom style system would be the most suitable design for the current tasks that a DEMO MPD is expected to perform. However, there is no particularly strong candidate without first fully defining the requirements and constraints that a DEMO MPD must adhere to.

Direction Control and Adaptive Path Following of 3-D Snake-Like Robot Motion.

This work investigates direction control and path following of a 3-D snake-like robot. In order to control such robots accurately, this work researches the relationships between its phase offsets of pitch joints and directions. A new direction control method is proposed for the robot based on these relationships. An adaptive path-following algorithm based on the line-of-sight guidance law is proposed and combined with the direction control method to steer the robot to move forward and along desired paths. Simulation and experimental results are presented to demonstrate the performances of the proposed 3-D model and control methods. They well outperform the classical and commonly used path-following method.

End-to-End Design of Bespoke, Dexterous Snake-Like Surgical Robots: A Case Study With the RAVEN II

Keyhole surgery requires highly dexterous snake-like robotic arms capable of bending around anatomical obstacles to access clinical targets that diverge from the direct port-of-access. Design optimization for these robots under patient-specific anatomical constraints is still lacking, particularly concerning the critical metric of dexterity. In this article, we propose an end-to-end design and production workflow for patient-specific surgical manipulators, assessing dexterity using orientability constrained by task space obstacles. In our work, parametric evolutionary optimization maximizes dexterity in patient-specific task spaces for challenging knee arthroscopy operations. We implement our framework in the design of SnakeRaven—a 3-D printed tool to be attached to the RAVEN II surgical robot in a phantom study for knee arthroscopy. The solution achieved more than three times the dexterity of a state-of-the-art rigid instrument and more than twice the dexterity of a volume-based approach for the same task. We further assemble and validate this design by teleoperating the robot to reach the desired clinical targets in a phantom. We also investigate the changes in the design morphology to changes in the task objectives and found an advantage in task specialization. We also observe guidelines for achieving a dexterous design produced by our algorithms.

Spatiotemporal pattern of periodic rhythms in delayed Van der Pol oscillators for the CPG-based locomotion of snake-like robot

This is the further research on the delayed half-center oscillator (DHCO) neural system presented in our previous paper (Song and Xu in Nonlinear Dyn 108:2595–2609, 2022. https://doi.org/10.1007/s11071-022-07222-y). The DHCO is used to construct a CPG (central pattern generator) neural system to control locomotion of a snake-like robot with pitch-yaw connecting configuration. To this end, we firstly give an improved model of the VDP (Van der Pol) oscillator. Employing mutually coupled delay, a pair of VDP oscillator is connected to produce an half-center oscillator (HCO) module with time delay that is called as a DHCO (delayed HCO) model. Based on the analysis of the Hopf bifurcation, periodic rhythm and their spatiotemporal patterns of the DHCO are illustrated in the different regions of parameters. The DHCO presents periodic rhythms with synchronous and anti-synchronous patterns, which is to control joint actuators combined in snake-like robot with pitch-yaw connecting configuration. To realize a backward propulsive wave to promote snake-like robotic locomotion, based on the DHCOs, we construct a chain type of the CPG neural system combined with a new unidirectional delay in which phase difference can be regulated. Numerical simulations are illustrated that the CPG neural system can control snake-like robot to move with serpentine, rectilinear, and side-winding patterns in the forward and backward directions. The results show that the snake-like robot can be controlled in expected locomotion patterns for a region but not a fixed value of the controlling parameters. Further, the corresponding regions of the parameters are obtained by using theoretical dynamical analysis but not a trial-and-error method. The snake-like robot gets smooth and stable gait transition with parameter changing.

Visualization system in a third-person view for the teleoperation of a snake-like robot

This study presents a visualization system in a third-person view for the teleoperation of a snake-like robot. The proposed system visualizes the robot, its surroundings, past path, and predicted path. The visualization is achieved by drawing a robot at self-position and the sensor information, such as a point cloud around the robot, in a virtual 3D space. Therefore, localization plays a key role in visualization. We propose a new localization method that relies only on the information from joint angles and an IMU. We evaluated the proposed method by comparing it with other methods on a flat ground and on a combination of a plane and a slope with a rough surface. The results demonstrated the effectiveness of the proposed method in both cases. Then, we examined the visualization system in room environments. The results showed that the proposed system successfully visualized the robot and its surroundings. We also confirmed the effectiveness of the visual aid by the predicted path.

Numerical simulation of dynamics and fluid dynamics for biomimetic underwater robots

The paper presents the results of modeling dynamics and hydrodynamics for two types of biomorphic robots: a snake-like robot and a fish-like robot. There were obtained detailed data on the transient process, which desribes the acceleration of robots from a stationary state. Mentioned acceleration was due to large-scale deformation of the robot surface shape. Flow fields near the deformable surface of the robot performing acceleration were also obtained. In fact, there was solved conjugate problem of the robot dynamics and the hydrodynamics of the flowing around fluid. The calculation method is based on the method of deformable grids. This method allows us to have a conservative approximation scheme for hydrodynamic calculations and to save significant computational resources in comparison with other approaches of the conjugate problem solving.