Finite-Time Sideslip Differentiator-Based LOS Guidance for Robust Path Following of Snake Robots

This paper presents a finite-time sideslip differentiator-based line-of-sight(LOS)guidance method for robust path following of snake robots.Firstly,finite-time stable sideslip differentiator and adaptive LOS guidance method are proposed to counteract sideslip drift caused by cross-track velocity.The proposed differentiator can accurately observe the cross-track error and sideslip angle for snake robots to avoid errors caused by calculating sideslip angle approximately.In our method,the designed piecewise auxiliary function guarantees the finite-time stability of position errors.Secondly,for the case of external disturbances and state constraints,a Barrier Lyapunov functionbased backstepping adaptive path following controller is presented to improve the robot’s robustness.The uniform ultimate boundedness of the closed-loop system is proved by analyzing stability.Additionally,a gait frequency adjustment-based virtual velocity control input is derived to achieve the exponential convergence of the tangential velocity.At last,the availability and superiority of this work are shown through simulation and experiment results.

Position Errors and Interference Prediction-Based Trajectory Tracking for Snake Robots

This work presents a trajectory tracking control method for snake robots.This method eliminates the influence of time-varying interferences on the body and reduces the offset error of a robot with a predetermined trajectory.The optimized line-of-sight(LOS)guidance strategy drives the robot’s steering angle to maintain its anti-sideslip ability by predicting position errors and interferences.Then,the predictions of system parameters and viscous friction coefficients can compensate for the joint torque control input.The compensation is adopted to enhance the compatibility of a robot within ever-changing environments.Simulation and experimental outcomes show that our work can decrease the fluctuation peak of the tracking errors,reduce adjustment time,and improve accuracy.

Locomotion of Bioinspired Underwater Snake Robots Using Metaheuristic Algorithm

Snake Robots(SR)have been successfully deployed and proved to attain bio-inspired solutions owing to its capability to move in harsh environments,a characteristic not found in other kinds of robots(like wheeled or legged robots).Underwater Snake Robots(USR)establish a bioinspired solution in the domain of underwater robotics.It is a key challenge to increase the motion efficiency in underwater robots,with respect to forwarding speed,by enhancing the locomotion method.At the same time,energy efficiency is also considered as a crucial issue for long-term automation of the systems.In this aspect,the current research paper concentrates on the design of effectual Locomotion of Bioinspired Underwater Snake Robots using Metaheuristic Algorithm(LBIUSR-MA).The proposed LBIUSR-MA technique derives a bi-objective optimization problem to maximize the ForwardVelocity(FV)and minimize the Average Power Consumption(APC).LBIUSR-MA technique involves the design ofManta Ray Foraging Optimization(MRFO)technique and derives two objective functions to resolve the optimization issue.In addition to these,effective weighted sum technique is also used for the integration of two objective functions.Moreover,the objective functions are required to be assessed for varying gait variables so as to inspect the performance of locomotion.A detailed set of simulation analyses was conducted and the experimental results demonstrate that the developed LBIUSR-MA method achieved a low Average Power Consumption(APC)value of 80.52W underδvalue of 50.The proposed model accomplished the minimum PAC and maximum FV of USR in an effective manner.

Multi-gait snake robot for inspecting inner wall of a pipeline

In the field of pipeline inner wall inspection,the snake robot demonstrates significant advantages over other inspection methods.While a simple traveling wave or meandering motion will suffice for inspecting the inner wall of small-diameter pipes,comprehensively and meticulously inspecting the inner wall of large-diameter pipes requires the snake robot to adopt a helical gait that closely adheres to the inner wall.Our review of existing literature indicates that most research and development on the helical gait of snake robots has focused on the outer surface of cylinders,with very few studies dedicated to developing a helical gait specifically for the inspection of the inner wall of pipes.Therefore,in this study,we propose a helical gait that is suitable for the inner wall of pipes and meets the requirements of gas pipeline engineering.The helical gait is designed using the backbone curve method.First,we create a mathematical model for a circular helix curve with constant curvature and torsion,ensuring it is applicable to a snake robot prototype in a laboratory environment.Subsequently.we calculate the joint angles required for two conical spiral curves with variable curvature and torsion,establish a new model,and define the physical significance of the specific parameters.To ensure the feasibility of the proposed gait,we conduct experiments involving meandering and traveling wave motions to verify the communication and control between the host computer and the snake robot.Building upon this foundation,we further validate the mathematical model of the complex helical motion gait through simulation experiments.Our findings provide a theoretical basis for realizing helical movement with a real snake robot.

Locomotion control of a rigid-soft coupled snake robot in multiple environments

The versatile motion capability of snake robots offers themselves robust adaptability in varieties of challenging environments where traditional robots may be incapacitated.This study reports a novel flexible snake robot featuring a rigid-flexible coupling structure and multiple motion gaits.To better understand the robot's behavior,a bending model for the soft actuator is established.Furthermore,a dynamic model is developed to map the relationship between the input air pressure and joint torque,which is the model base for controlling the robot effectively.Based on the wave motion generated by the joint coupling direction function in different planes,multiple motion gait planning methods of the snake-like robot are proposed.In order to evaluate the adaptability and maneuverability of the developed snake robot,extensive experiments were conducted in complex environments.The results demonstrate the robot's effectiveness in navigating through intricate settings,underscoring its potential for applications in various fields.

Gait fitting for snake robots with binary actuators

Thanks to the special physical architectures and various locomotion gaits,snake robots may offer significant benefits over traditional legged or wheeled locomotion designs in vast types of scenarios.This paper proposes an innovative snake robot with digitally-actuated Stewart platforms as its modules and mainly focuses on the simulations of various snake gaits.Three categories of fitting algorithms are elaborated in simulations of lateral undulation and Configuration-Fitting Algorithm of Four Modules is demonstrated as a universal gait fitting algorithm for all kinds of snake robots with binary actuators.Several typical snake gaits are simulated and the results demonstrate the excellent mobility of the snake robot.

Self-adaptive rolling motion for snake robots in unstructured environments based on torque control

Snake robots have great potential for exploring and operating in challenging unstructured environments,such as rubble,caves,and narrow pipelines.However,due to the complexity and unpredictability of unstructured environments,designing a controller that can achieve adaptive motion is crucial.This paper proposes a self-adaptive torque-based rolling controller for snake robots,enabling compliant motion in unstructured environments.First,a controller is designed to modify the torque of each motor by focusing on the different motion states of the rolling gait.Second,an experimental platform is established for snake robots to verify the effectiveness of the controller.Finally,a series of rolling experiments are conducted using the torque-based rolling controller.In conclusion,the self-adaptive torque-based rolling controller enhances snake robot adaptability and mobility.

Confined spaces path following for cable-driven snake robots with prediction lookup and interpolation algorithms

While cable-driven snake robots are promising in exploring confined spaces, their hyper-redundancy makes the collision-free motion planning difficult. In this paper, by combining the prediction lookup and interpolation algorithms, we present a new path following method for cable-driven snake robots to high-efficiently slither into complex terrains along a desired path. In our method, we first discretize the desired path into points, and develop the prediction lookup algorithm to efficiently find the points matched with joints of the robot. According to geometric relations between the prediction lookup results and link length of the robot, we develop the interpolation algorithm to reduce the tracking errors caused by the discretization. Finally, simulations and experiments of inspections in two confined spaces including the obstacle array and pipe tank system are performed on our custom-built 25 degree of freedoms(DOFs) cable-driven snake robot. The results demonstrate that the presented method can successfully navigate our snake robot into confined spaces with high computational efficiency and good accuracy, which well verifies effectiveness of our development.

Steering motion control of a snake robot via a biomimetic approach

We propose a biomimetic approach for steering motion control of a snake robot. Inspired by a vertebrate biological motor system paradigm, a hierarchical control scheme is adopted. In the control scheme, an artificial central pattern generator(CPG) is employed to generate serpentine locomotion in the robot. This generator outputs the coordinated desired joint angle commands to each lower-level effector controller, while the locomotion can be controlled through CPG modulation by a higher-level motion controller. The motion controller consists of a cerebellar model articulation controller(CMAC) and a proportional-derivative(PD) controller. Because of the fast learning ability of the CMAC, the proposed motion controller can drive the robot to track the desired orientation and adapt to unexpected perturbations. The PD controller is employed to expedite the convergence speed of the motion controller. Finally, both numerical studies and experiments proved that the proposed approach can help the snake robot achieve good tracking performance and adaptability in a varying environment.

Modeling and Control of Head of the Underwater Snake-like Robot Swimming

In order to solve oscillation of head of the underwater snake-like robot,the Central Pattern Generator( CPG)-based control scheme with head-controller was presented. The Kane dynamic model was constructed to be processed with a commercial package MotionGenesis Kane 5. 3,to which the proposed control scheme was applied. The relation between CPG parameters and orientation offset of head was investigated. The target orientation of head-controller was calculated through a convenient method. The advantage of this control scheme is that the head of the underwater snake-like robot remains in the forward direction during swimming. To prove the feasibility of the proposed methodology,two basic motion patterns,swimming along the straight line and swimming along the curved path,had been implemented in our simulation platform. The results showed that the simulation platform can imitate the swimming of the underwater snake-like robot and the head of the underwater snake-like robot remains in a fixed orientation directed towards the target. The oscillation of head's orientation is inhibited effectively.

Knowledge presentation by the MNSM-based controller for swimming motion of a snake-like robot

A MNSM( mirror neuron system mechanism)-based controller is developed to present the swimming rhythm of a snake-like robot in Cartesian space. From engineering viewpoint,the proposed controller is composed of a neuron for rhythm angle and two neurons for motion knowledge in XY plane. The given knowledge is a rhythm curve for swimming motion of a snake-like robot. Experimental results show that the proposed controller can present the knowledge of swimming rhythm,which represents the corresponding control law to drive the snake-like robot to swim with different speeds and turning motion. This work provides a novel method to present the knowledge for swimming motion of snake-like robots.

Head Orientation Stability of Underwater Snake-Like Robot Swimming

In prior research,the orientation of head of the snake-like robot is changed according to the sinusoidal wave. To solve this problem,we propose Central Pattern Generator( CPG)-based control scheme with head-controller to stabilize the head of the underwater snake-like robot. The advantage of the CPG-based control scheme with head-controller is that the head of the underwater snake-like robot is direct to the target orientation during swimming. The relation between CPG parameters and orientation stability of head is discussed.The adaptation of the proposed method to environment changes is tested. The influences of CPG parameters and hydrodynamic forces on the orientation offset of head are investigated. The target orientation( the input of headcontroller) with an experimental optimization is calculated through a convenient method. To prove the feasibility of the proposed methodology,the different swimming modes have been implemented in our simulation platform.The results show that the oscillation of head's orientation is inhibited effectively,and the proposed method has strong adaptation to environment and CPG parameters changes.

Kinematic Control of Wheeled Snake-Like Mobile Robot

From a bionics viewpoint , this paper proposes a mechanical model of a wheeled snake like mobile mechanism. On the hypothesis of the existing non holonomic constraints on the robot kinematics, we set up the relationship among the kinetic control parameters in the snake like movement using Lie group and Lie algebra of the principle fiber bundle and provide some theoretical control methods to realize the snake like locomotion.

Snake模型和遗传算法在特殊焊缝提取中的应用

针对CCD直接拍摄图像的弧焊机器人焊缝视觉检测问题,文中提出了一种精确提取带有较大的间断、尖锐的拐点、较多的干扰等特殊焊缝轨迹的算法.该算法先用小波变换进行焊缝边缘线的平滑,得到与最终焊缝距离很近的初始焊缝轨迹,再用基于Snake模型和遗传算法的进行特殊焊缝的精确匹配和提取.结果表明,该算法能进一步提高特殊焊缝轨迹识别的识别和检测精度,具有较强的适应性,也为弧焊机器人视觉检测的智能化的进一步提高提供一定的技术参考.

水下蛇形机器人建模与运动控制

针对水下蛇形机器人在复杂水下环境自主游动难问题,设计了一种水下蛇形机器人机构。基于蛇类运动机理建立运动学模型,提出一种基于模糊控制和中枢模式生成(CPG)的运动控制方法,通过对单个Hopf振荡器模型中极限环的稳定性进行分析,搭建由多个Hopf振荡器构建形成的具有双耦合链条网拓结构的CPG模型,引入模糊控制器与CPG模型一起构成闭环控制网络。对水下蛇形机器人进行仿真和实验结果表明,样机可实现直线蜿蜒运动、左右转弯运动和U型运动实验,在3种运动模式中,水下蛇形机器人不仅拥有良好的稳定性,而且能够保持优越的灵活性与机动性。

基于ISO-TW算法的多仓储机器人路径规划研究

针对当前智能仓库中多仓储机器人协同规划效率低下、动态性不足等问题,提出了一种融合改进蛇优化(Improved Snake Optimizer,ISO)算法和时间窗(Time Window,TW)模型的路径规划方法。首先,在静态规划阶段,利用考虑阻塞因素的改进蛇优化算法为多仓储机器人规划出全局最优路径,同时计算出各机器人的时间窗,从而提升仓储机器人的规划效率;其次,在动态规划阶段,通过建立的多仓储机器人时间窗模型并引入动态调节策略,以消解冲突提升算法的动态性能;最后,进行仿真及实验。仿真结果表明,ISO-TW算法相较其他算法在阻塞点数量上最多可减少27~43个,减少幅度达22.50%~31.62%(机器人规模为80个);重规划路径比重可降低39.82%~41.05%(机器人规模为40个);平均运行时长最多可缩短38~40 s,缩短幅度约为18.27%~19.05%(机器人规模为60个)。实验结果表明,ISO-TW算法较其他算法平均运行时长减少8.53%~9.23%,冲突次数减少11.63%~15.56%,能够在真实场景中实现多仓储机器人的高效协同规划。

模块化蛇形机器人运动控制系统研究

近年来,人工智能技术得到了广泛的应用和发展,其中机器人技术已经取得了长足进步。而蛇形机器人因其高度仿真的蛇形动态及运动特性而备受瞩目。以锥齿传动结构蛇形机器人为载体,以STM32为主控制器,采用开环控制和闭环控制相结合的方式控制其运动,通过位置式PID控制算法解算装置姿态,提出一种适用于蛇形机器人灵活运动的控制算法。

基于CoppeliaSim的蛇形机器人建模与运动仿真

在进行蛇形机器人的结构设计及控制算法研究时,需要建立合理的仿真模型和良好的测试环境,便于研究人员有效评估。以课题组自主研发的蛇形机器人为例,基于CoppeliaSim和ROS设计了仿真模型及其运动控制系统,并进行了虚拟仿真,测试了蛇形机器人的蜿蜒运动和侧移运动。结果表明,仿真环境中模型的运动状态良好,机器人与环境交互正常,为蛇形机器人结构和控制算法的测试提供了理想的评估环境。

弯-扭型绳驱蛇形臂的结构设计与运动学分析

为了进一步提升蛇形机械臂的工作效率,建立一种具有扭转关节的多自由度绳驱蛇形机械臂,为其运动学建模奠定基础。所述蛇形臂(摆动+扭转)将传统蛇形臂(摆动+俯仰)的俯仰关节替换为扭转关节,在不同姿态变化中分析其末端执行器能够到达的空间范围,并研究达到目标姿态的连贯性。研究结果表明:文中所述蛇形臂末端执行器与传统蛇形臂具有相同的工作空间;在切换特殊位置时,利用特有的扭转自由度,替代了现有蛇形臂利用俯仰和摆动联动来解算绳索伸缩量,提高了机械臂的反应速度及工作效率。

多蛇形机器人编队路径跟踪控制

为了实现多个蛇形机器人的编队控制,该文提出一种基于误差约束的抗干扰路径跟随方法。该方法使用高度耦合的动态频率补偿器来调整每个机器人的运动速度,以确保编队成员之间位置和速度的一致性。在动力学控制中,通过障碍函数的等效原则消除了虚拟变量的奇异现象,提高了路径跟随的稳定性。此外,该文设计了模型不确定性和外界干扰的预测值,以此来提前补偿机器人的关节偏移量和扭矩输入,从而进一步提高了跟随误差的收敛速度和稳态性能。最后,利用Lyapunov理论证明了该方法的一致最终有界性(UUB)。仿真数据表明,相对于其他经典方法,该文所提模型和控制策略具有更高的跟随精度。