Simulation Platform of Underwater Quadruped Walking Robot Based on MotionGenesis Kane 5.3 and Central Pattern Generator

It will still in lack of a simulation platform used to learn the walking of underwater quadruped walking robot. In order to alleviate this shortage,a simulation platform for the underwater quadruped walking robot based on Kane dynamic model and CPG-based controller is constructed. The Kane dynamic model of the underwater quadruped walking robot is processed with a commercial package MotionGenesis Kane 5. 3. The forces between the feet and ground are represented as a spring and damper. The relation between coefficients of spring and damper and stability of underwater quadruped walking robot in the stationary state is studied. The CPG-based controller consisted of Central Pattern Generator（ CPG） and PD controller is presented,which can be used to control walking of the underwater quadruped walking robot. The relation between CPG parameters and walking speed of underwater quadruped walking robot is investigated. The relation between coefficients of spring and damper and walking speed of underwater quadruped walking robot is studied. The results show that the simulation platform can imitate the stable walking of the underwater quadruped walking robot.     

On the Survivability of Self-repairing Control System for a Hybrid Underwater Vehicle

A hybrid remotely operated underwater vehicle （HROV） capable of working to the full ocean depth has been developed. In order for the vehicle to achieve a certain survivability level, a self-repairing control system （SRCS） has been designed. It consists of two basic technologies, fault diagnosis and isolation （FDI） and reconfigurable control. For F＇DI, a model-based hierarchical fault diagnosis system is designed for the HROV. Then, control strategies which reconfigure the control system at intervals according to information from the FDI system are presented. Combining the two technologies, it can obtain the fundamental frame of SRCS for the HROV. Considering the hazardous underwater environment at the limiting depth and the hybrid operating modes, an assessment of the HROV＇ s survivability is vitally needed before it enters operational service. This paper presents a new definition of survivability for underwater vehicles and develops a simple survivability model for the SRCS. As a result of survivability assessment for the SRCS, we are able to figure out the survivability of SRCS and make further optimization about it. The methodology developed herein is also applicable to other types of underwater vehicles.     

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.     

SPH-BEM simulation of underwater explosion and bubble dynamics near rigid wall

A process of underwater explosion of a charge near a rigid wall includes three main stages: charge detonation, bubble pulsation and jet formation. A smoothed particle hydrodynamics(SPH) method has natural advantages in solving problems with large deformations and is suitable for simulation of processes of charge detonation and jet formation. On the other hand, a boundary element method(BEM) is highly efficient for modelling of the bubble pulsation process. In this paper, a hybrid algorithm, fully utilizing advantages of both SPH and BEM, was applied to simulate the entire process of free and near-field underwater explosions. First, a numerical model of the free-field underwater explosion was developed, and the entire explosion process–from the charge detonation to the jet formation–was analysed. Second, the obtained numerical results were compared with the original experimental data in order to verify the validity of the presented method. Third, a SPH model of underwater explosion for a column charge near a rigid wall was developed to simulate the detonation process. The results for propagation of a shock wave are in good accordance with the physical observations. After that, the SPH results were employed as initial conditions for the BEM to simulate the bubble pulsation. The obtained numerical results show that the bubble expanded at first and then shrunk due to a differences of pressure levels inside and outside it. Here, a good agreement between the numerical and experimental results for the shapes, the maximum radius and the movement of the bubble proved the effectiveness of the developed numerical model. Finally, the BEM results for a stage when an initial jet was formed were used as initial conditions for the SPH method to simulate the process of jet formation and its impact on the rigid wall. The numerical results agreed well with the experimental data, verifying the feasibility and suitability of the hybrid algorithm. Besides, the results show that, due to the effect of the Bjerknes force, a jet with a high speed was formed that may cause local damage to underwater structures.     

Inverse speed analysis and low speed control of underwater vehicle

Inverse speed is a reversible maneuver.It is a characteristic of underwater vehicle at low speed.Maneuverability in the vertical plane at a speed lower than inverse speed is different from one at higher speed.In the process of underwater working for observation,AUV＇s cruise speed is always low.Therefore,the research on inverse speed is important to AUV＇s maneuverability.The mechanism of inverse speed was analyzed,and then the steady pitching equation was derived.The parameter expression of track angle in vertical plane was deduced.Furthermore,the formula to calculate the inverse speed was obtained.The typical inverse speed phenomenon of the flat body and the revolving body was analyzed.Then the conclusion depicts that,for a particular AUV with flat body,its inverse speed is lower than that of revolving body.After all the calculation and the analysis,a series of special experiments of inverse speed were carried out in the simulation program,in the tank and in the sea trial.     

Experimental and numerical study of the adsorption performance of a vortex suction device using water-swirling flow

An electrically activated underwater suction device is designed to form an amazing amount of negative pressure by generating water swirling flow, which can make underwater wall-climbing robot stick to the wall surface allowing a ground clearance. For the purpose of a full understanding of the mechanism of the suction device, a series of experimental tests are carried out and a computational fluid dynamics(CFD) model is established. The results show that the suction force F is consistent between experimental tests and simulations. An insight into the flow phenomena of vortex suction device, including spatial velocity and pressure distribution, is given through numerical simulation analysis. Furthermore, the crucial parameters, i.e., the rotation speedω and gap clearance h, are studied. Then the relationships of F-ω and F-h are clarified. It reveals that with the increasing of rotation speed, the suction force increases quadratically. And with the increasing of gap clearance, the suction force increases firstly and then decreases, so that a reasonable design interval of gap clearance can be got to obtain the required suction force for the engineering applications.     

Vibration velocity and frequency of underwater short-hole blasting

Based on the measuring data of underwater blasting vibration and the regression analysis results of these data, two formulae usually used of blasting vibration velocity were compared. Factors that can affect blasting vibration and frequency were summarized and analyzed. It is thought that the effect of the number of freedom face and burden direction on blasting vibration should be considered during blasting design. Based on the relevant research results and the regression results of these data, a formula to calculate under water blasting frequency was put forward.     

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.     

Influence of Lithological Characters of Coal Bearing Formation on Stability of Roof of Coal Seams

Lithology is one of the important factors influencing the stability of roof of coal seams. In order to investigate this, the phenomenon of underground pressure and distribution of pressure were studied by using the local observation and simulation test with similar materials. The observation results show that the distance of initial weighting and periodic weighting of the mudstone roof is shorter than that of sandstone roofs. The sandstone roof with a high strength has a longer distance of initial weighting and periodic weighting, the abutment stress on the working face is big and the height of caving and fracture zone is high. The peak point of abutment stress in the sandstone roof is near to the working face and the pressure bump is inclined to occur. The result is contrary to that in case of the mudstone roof with a low strength. While in the transition zone of nipped sandstone, roof rock-mass is broken and is poor in stability, therefore, it is difficult to hold the roof.     

Underwater Distribution Field of Laser Through Wavy Surface of Water

Aimed at the properties of the absorption and the scattering of photons in the water, the process of sim-ulating by Monte Carlo method is analyzed. According to the slope distribution of wavy surface of water, the dis-tribution field of underwater laser is simulated, and some conclusions about the distribution field of laser through wavy surface in two different conditions are obtained. The characteristics of the distribution of laser in the seawa-ter at the same depth with different water qualities and in the seawater at different depths with the same water quality are computed. The results are significant to the design of airborne oceanic lidar.     

Dynamics model of underwater robot motion control in 6 degrees of frccdom

In order to analyze underwater robot control system dynamics features, a system 6-DOF dynamics model was founded. Underwater robot linear and nonlinear hydrodynamics were analyzed by Taylor series, based on general motion equation. Special control system motion equation was deduced by cluster of inertial items and non-inertial items. For program convenience, motion equation matrix format was presented. Experimental principles of screw propellers, rudders and wings were discussed. Experimental data least-square curve fitting, interpolation and their corresponding traditional equation helped us to obtain the whole system dynamic response procedure. A series of simulation experiments show that the dynamics model is correct and reliable. The model can provide theory proof for analyzing underwater robot motion control system physics characters and provide a mathematic model for traditional control method.     

基于神经网络模型的拱泥机器人控制

拱泥机器人是为打捞沉船的关键工序—水下攻打千斤洞而设计的特种机器人.分析了拱泥机器人在水下泥土环境中受力情况,建立了基于MATLAB的拱泥机器人头部的动力学模型.针对拱泥机器人工作环境的不确定性,将传统PID控制与神经网络相结合,建立了一种应用BP神经网络实现PID参数自整定的自适应PID控制模型.控制器由PID控制器、神经网络NNC和NNI组成.神经网络NNC能够根据拱泥机器人动态特性的变化,自动整定PID参数,从而改善了控制性能.神经网络NNI为NNC提供学习的梯度信息.计算机仿真结果表明该方法是有效的.     

面向配电系统的带电抢修作业机器人

面向电力行业应急救援和安全抢修作业装备发展的需求,设计了一种配电系统带电抢修作业机器人,并对其机械结构与控制系统进行了介绍。提出一种基于液压伺服驱动的6自由度机械臂的系统解决方案,通过运动学、动力学和有限元分析优化了部件结构和动力学性能,使其有效负载能力达到最大。针对作业过程中机器人本体与导线发生碰撞等引起的震荡问题,使用非对称控制方法,建立了机械臂的柔顺控制模型,降低了震荡的影响。将整体单目视觉的静态测量与双目手眼视觉系统的动态测量相结合,设计了复杂环境下目标点的高精度动态定位系统,实现了机械臂的局部自主路径规划与运动控制。通过实验验证了所开发的带电抢修作业机器人在10 kV以下配电线路应用的有效性和可行性。     

非驱动关节机器人的位置闭环控制研究

以具有非驱动关节的水平2自由度机器人为研究对象，利用拉格朗日动力学方程，建立了具有非驱动臂的两关节机器人的动力学数学模型，利用求解非线性方程的有效方法——平均值法，对已经建立的二阶非线性微分方程的数学模型进行了平均化处理，实现了数学模型的化简，同时提出了一种非线性闭环反馈的控制方法并对此控制方法进行了仿真，在控制仿真中，实现了对非驱动关节机器人系统的期望控制目标，并验证了模型化简和控制方法的有效性。     

交流伺服清洗爬壁机器人的姿态控制

城市高层建筑的清洗作业目前主要由人工完成；不仅危险，而且效率低、质量难以保证。清洗爬壁机器人可对各种高层建筑进行高效和安全的清洗工作，由于作业壁面不平，表现摩擦系数不均，车轮转速不同步，搭承负载不平衡等使机器人在运行中难免偏离预定的轨迹发生倾斜，为此在机器人本体上加装了高精度角度倾斜计，微电脑把预定轨迹和倾斜计测量值相比较，当偏差发生时，利用PID控制规律，对交流伺服电机驱动的双轮进行无级调速，使机器人按预定运动轨迹准确移动，在爬壁机器人运动学方程基础上，讨论了机器人的姿态控制规律，并从交流伺服驱动，微电脑控制等方面采取措施保证爬壁机器人姿态控制的准确无误，样机运行证明这些规律和措施都是行之有效的。     

一款微小型球形机器人的动力学分析

利用拉格朗日方程等力学手段,分析了一款微小型球形机器人滚动和转动的运动特点,以及跳跃运动的起跳条件.分析该类机器人的进动形式的运动形态,建立了整合运动的通用动力学模型,实现了机器人沿任意曲线运动.对机器人进行了虚拟样机仿真,实验验证了上述分析的正确性.该研究为机器人非线性控制打下了基础.     

柔顺关节并联机器人固有频率分析

为了解含有片簧式柔顺关节的并联机器人振动特性,基于含有片簧式柔顺关节的并联机器人动力学方程,建立了频率方程,并对系统固有频率在机器人运动过程以及工作空间的变化情况进行分析,同时对理论轨迹、软件仿真轨迹与名义轨迹的差值进行幅频特性分析来说明理论计算结果和软件仿真结果的正确性,也相互验证了频率方程和幅频特性分析方法的正确性。     

基于混合遗传算法的机器人改进摩擦模型辨识

为了解决机器人运动过程中库伦+黏性摩擦模型不能真实反映关节摩擦的非线性特性的问题,采用改进Stribeck摩擦模型对机器人关节摩擦进行建模,提出基于混合遗传算法与余弦轨迹的模型参数辨识方法. 采用不同的余弦轨迹对机器人关节进行激励,利用已知的机器人动力学方程确定关节摩擦力矩,从而建立机器人关节速度与关节摩擦力矩之间的映射关系,并利用模拟退火混合遗传算法对摩擦参数进行辨识. 为了验证所提方法的有效性,以多关节串联型机器人为研究对象,进行摩擦参数辨识实验. 实验结果表明,与传统的库伦+黏性摩擦模型相比,改进的Stribeck摩擦模型可以减少17.7%~33.6%的关节力矩计算误差,并能够进一步提高机器人动力学模型的准确性.     

基于神经网络的四足机器人 SLIP 模型运动控制

根据四足哺乳动物形态设计的四足机器人,能够适应错综复杂的地形,且具有较强的运动属性。 而对于四足机器人而言,运动的控制十分重要,所以对四足机器人运动过程中的跳跃控制问题进行了研究。 首先,采用弹簧负载倒立摆模型（SLIP）对四足机器人结构进行简化处理,建立了简化模型的动力学方程, 并分析了模型的运动过程以及着陆相与腾空相的转换条件。其次,在仿真平台中建立了 SLIP 动力学模型, 通过动力学仿真得到了一份仿真样本数据,并利用这份样本数据训练了一个神经网络,其中样本考虑了四足 机器人在与地面接触过程中由于碰撞和阻尼所消耗的能量。最后,在仿真平台中进行验证,给定模型的初始 高度和水平速度,通过神经网络计算出合适的着陆角,得到期望的水平末速度和弹跳高度。实验结果表明, 基于神经网络的方法可以较精确地实现对 SLIP 模型运动的控制。     

欠驱动异构式下肢康复机器人动力学分析及参数优化

针对现有外骨骼机器人人机自由度不匹配和关节对中性差的问题,提出欠驱动下肢康复机器人. 欠驱动机器人只有4个直线驱动,驱动的直线运动通过推杆和人机连接机构转化为人下肢在矢状面内的屈伸运动,带动人体进行步态康复训练. 建立机器人系统的人机耦合模型,进行模型的动力学分析,对人机耦合模型中影响动力学结果的参数进行分析,建立驱动力与肢体推动力之间的关系模型,并以推力系数最大为目标进行参数分析与优化,得到最佳的结构参数. 根据优化后的结构参数搭建康复机器人实验系统,对髋、膝关节驱动力与角度进行对比. 实验结果表明最大髋关节角度误差为2.9°,最大膝关节角度误差为6.4°,最大误差均约为9%,验证了动力学模型和参数优化结果的正确性.