Analysis of a manipulator in consideration of the relative motion between a tray and an object

In this article, equations of motion of a manipulator, whose mechanism has a tray installed with a passive revolute joint, are derived after consideration of the characteristics of the driving source. Considering the relative motion between the tray and the object, the trajectories of the velocity for saving energy are calculated by iterative dynamic programming. Also, the dynamic characteristics of manipulator control based on the trajectory for saving energy are analyzed theoretically and investigated experimentally.     

A study of manipulator with passive revolute joint

In this article, equations of motion of a manipulator, whose mechanism has a passive revolute joint, are derived in consideration of the characteristics of driving source. Considering the fi nal condition of displacement and velocity of the passive joint, trajectories of velocity for energy saving are calculated by iterative dynamic programming. And the dynamic characteristics of manipulator control based on the trajectory for energy saving are analyzed theoretically and investigated experimentally. This work was presented in part at the 13th International Symposium on Artificial Life and Robotics, Oita, Japan, January 31–February 2, 2008     

Analysis of a manipulator in relation to collision between a link and an object

In this article, equations of motion of a manipulator are derived after consideration of the characteristics of the driving source. By considering a collision between a link and an object, and considering the active motion to absorb the kinetic energy of the object, the trajectories for saving energy are calculated by the iterative dynamic programming (IDP) method. The dynamic characteristics of manipulator control based on the trajectory for saving energy are also analyzed theoretically and investigated experimentally.     

Analysis of manipulator in consideration of impact absorption between link and object

In this article, equations of motion of a manipulator are derived in consideration of characteristics of driving source. By considering impact force absorption between a link and an object, trajectories for saving energy are calculated by the iterative dynamic programming method. And, the dynamic characteristics of manipulator controlled based on the trajectory for saving energy are also analyzed theoretically and investigated experimentally.     

Analysis of manipulator in consideration of impact absorption between link and projected object

In this article, equations of motion of a manipulator are derived in consideration of the characteristics of DC servomotors, and a performance criterion for saving energy is defined in consideration of energy consumption of the driving source. When the manipulator is operated in a vertical plane, the system is highly non-linear due to gravity, and an analytical solution cannot be found. By considering for catching the object that moves parabolic, trajectories for saving energy are calculated by iterative dynamic programming method. And, the dynamic characteristics of two-link system controlled based on the trajectory for saving energy are analyzed theoretically. When the object moves parabolic, measurement method for the force of collision between link and object is examined by experiment.     

Autonomous Path Planning and Experiment Study of Free-floating Space Robot for Target Capturing

Space robotic systems are expected to play an increasingly important role in the future. The robotic on-orbital service, whose key is the capturing technology, becomes research hot in recent years. In this paper, the authors propose an autonomous path planning method for target capturing. The task is described in Cartesian space and it can drive the manipulator to approach the target along the closest path. Firstly, the target feature is extracted based on the measured information via the hand-eye camera, and the target pose (position and orientation) and velocities (linear velocity and angular velocity) are estimated using Kalman filtering technology. Then, a numerically feasible approach is presented to plan the manipulator motion and avoid the dynamic singularities, which are transformed into real-time kinematic singularities avoiding problem. Thirdly, the potential disturbance on the base due to the manipulator’s motion is estimated, and the joint rates are autonomously adjusted to reduce the disturbance if it is beyond the allowed bound. At last, a ground experiment system is set up based on the concept of dynamic emulation and kinematic equivalence. With the experiment system, the autonomous target capturing experiments are conducted. The experiment results validate the proposed algorithm.     

基于干扰观测器的机械臂广义模型预测轨迹跟踪控制

为实现对多自由度机械臂关节运动精确轨迹跟踪,提出一种基于非线性干扰观测器的广义模型预测轨迹跟踪控制方法。针对机械臂轨迹跟踪运动学子系统,采用广义预测控制（Generalized Predictive Control,GPC）方法设计期望的虚拟关节角速度。对于机械臂轨迹跟踪动力学子系统,考虑机械臂的参数不确定性和未知外界扰动,利用GPC方法设计关节力矩控制输入,基于非线性干扰观测器方法实时估计和补偿系统模型中的不确定性。在李雅普诺夫稳定性理论框架下证明了机械臂关节角位置和角速度的跟踪误差最终收敛于零的小邻域。数值仿真验证了所提出控制方法的有效性和优越性。     

Theoretical Investigation of Time Suboptimal Control of Industrial Manipulators Along Specified Paths

A method for the time suboptimal control of an industrial manipulator from an initial position and orientation to a final position and orientation as it moves along a specified path is proposed. Nonlinear system equations that describe the manipulator motion are linearized at each time step along the path. A method which gives the control inputs (joint angular velocities) for time suboptimal control of the manipulator is developed. In the formulation, joint angular velocity and acceleration limitations are also taken into consideration. A six degree of freedom elbow type manipulator is used in numerical examples to verify the method developed.     

基于序列图像处理法的机器鱼转向机动性能研究

基于序列图像处理法，对机器鱼的转向性能进行了初步研究．利用高速摄像机记录机器鱼运动过程， 对游动序列图像进行处理，提取机器鱼体干曲线，获取机器鱼转向运动中角度、角速度、角加速度的动态特性．根 据实验结果，给出了机器鱼C 形转向运动的3 个阶段的运动特征，并对理论值和实验测定值之间的差异进行分析． 同时，对静止和运动两种C 形转向运动进行比较，分析了影响C 形转向效果的因素：初始动能以及保持阶段角度大 小，在此基础上，给出了提高机器鱼转向性能的方法．     

Analysis of the two-link manipulator in consideration of the horizontal motion about object

In this article, equations of motion of two-link-manipulator are derived in consideration of characteristics of driving source. By considering for horizontal motion about object, trajectories for saving energy are calculated by iterative dynamic programming method. And, the dynamic characteristics of two-link system controlled based on the trajectory for saving energy are analyzed theoretically. When the object moves parabolic, measurement method for the force of collision between link and object is examined by fundamental experiment.     

Control of a single-link flexibe manipulator fabricated form composite laminates

An experimental investigation on the control performances of a single-link flexible manipulator fabricated from composite laminates is presented. The dynamic modeling of the flexible manipulator is accomplished by employing Hamilton's principle, prior to developing a finite element formulation. An output feedback controller associated with two collocated angular position and velocity sensors is designed and experimentally implemented. Comparative works are undertaken to demonstrate some of the advantages to be accrued from this proposed methodology. It is shown that the manipulator fabricated from composite laminates has superior performance characteristics, such as smaller tip deflections and a smaller input torque relative to the manipulator fabricated from aluminum. © 1995 John Wiley & Sons, Inc.     

Energy Based Indexes for Manipulator Dynamics Improvement

Several indexes for evaluation of nonlinear effects during the motion of rigid multi-body systems are proposed in this paper. All of them are based on the kinetic energy and arise from an analysis of equations of motion expressed in terms of inertial quasi-velocities (IQV). Such equations are first-order and have a diagonal mass matrix of the system. The IQV depend on configuration of the system and take into consideration also its geometrical and inertial parameters. The indexes enable to detect deformation of joint velocity as a consequence of manipulator motion, the kinetic energy resulting from dynamical couplings and the energy transferred by each link individually. Because calculation of these indexes allow to determine influence of couplings on behavior of the manipulator then they can be used in the design phase for analysis and reduction of nonlinear effects in any motion. Simulation and experimental results demonstrate that the proposed indexes are significant for evaluation of nonlinear effects and kinetic energy reduction during the manipulator motion.     

The design of a new remote manipulator for space operation using a 4-cable-driven thrusters-embedded configuration

A new remote manipulator based on cable-driven parallel mechanism (CDPM) is designed for space long-distance operations (e.g. space capture/docking and other long-distance space activities) in this paper. By controlling the cables and thrusters which are equipped on the manipulator simultaneously, the new remote manipulator can achieve expected position, linear velocity, and angular velocity. The new manipulator has a larger controllable workspace compared with usual CDPMs. The structure and characteristics of this manipulator are discussed in this paper. The volume and characteristics of the workspace are also discussed. The influence of the distance on the static equilibrium is studied. The simulation results show that the workspace of this new manipulator is larger than usual CDPM’s. The results also indicate that the cable forces and thruster vectors can completely constrain the manipulator and meet the requirements of space activities. The results of the simulation also show that the controllable workspace of the manipulator is not continuous at some regions. Hence, trajectory planning is necessary.     

A study of the Brownian motion of the non-spherical microparticles on fluctuating lattice Boltzmann method

In this paper, the fluctuating lattice Boltzmann (FLB) model is used to simulate the Brownian motion of spherical and non-spherical particles directly on 3D. The FLB model is validated by comparing the simulation results with theoretical and experimental results. And then the Brownian motion characteristics of different shapes of non-spherical particles are analyzed, which includes some ellipsoidal and cylindrical particles with different aspect ratios. It is found that, although the ellipsoidal and cylindrical particles are anisotropic, they still obey the energy equalization theorem. The velocity and angular velocity autocorrelation functions of the particles still have the “long-time tail” effect. Moreover, the velocity and angular velocity autocorrelation functions are independent of the particle shape, and the diffusion coefficient is insensitive to the shape under a low aspect ratio. This work is a fundamental study for the further research of the motion of microparticles based on Brownian motion.     

Effects of turning gait parameters on energy consumption and stability of a six-legged walking robot

Minimization of energy consumption plays a key role in the locomotion of a multi-legged robot used for various purposes. Turning gaits are the most general and important factors for omni-directional walking of a six-legged robot. This paper presents an analysis on energy consumption of a six-legged robot during its turning motion over a flat terrain. An energy consumption model is developed for statically stable wave gaits in order to minimize dissipating energy for optimal feet forces distributions. The effects of gait parameters, namely angular velocity, angular stroke and duty factors are studied on energy consumption, as the six-legged robot walks along a circular path of constant radius with wave gait. The variations of average power consumption and energy consumption per unit weight per unit traveled length with the angular velocity and angular stroke are compared for the turning gaits of a robot with four different duty factors. Computer simulations show that wave gait with a low duty factor is more energy-efficient compared to that with a high duty factor at the highest possible angular velocity. A stability analysis based on normalized energy stability margin is performed for turning motion of the robot with four duty factors for different angular strokes.     

Review of: ‘ Programmed Instruction in the British Armed Forces’. By D. WALLIS,K. D. DUNCAN and M. A. G. KNIGHT. ( H.M.S.O., 1966.) [Pp. iv+49.] 4s. 6d.

A mathematical model for studying head protection in static is presented and its application to the design of ice hockey helmets is discussed. Static load and dynamic impact tests indicate that dynamic tests are to be preferred when estimating the stiffness of the materials used ns helmet liners. Solutions to the differential equations governing the linear motion of the head under a sideboard collision provide information regarding the thickness of the energy absorbing helmet liner and the tolerance level to which the helmet can be expected to perform. The model also provides a useful estimate of the angular velocity of the head imparted by the rebound from the sideboard. Although the helmet cannot prevent angular motion of the head, an estimate of the expected angular velocity may indicate that additional measures must be taken to prevent head injury from such angular motion. The study also indicates that the problem of providing head protection in ice hockey is of such magnitude that a helmet alone cannot be expected to provide total protection and additional modification to the playing environment must also be undertaken.     

Dynamic Modeling and Experimental Validation of a 3-PRR Parallel Manipulator with Flexible Intermediate Links

This paper presents the development of structural dynamic equations of motion for a 3-PRR parallel manipulator with three flexible intermediate links, based on the assumed mode method. Lagrange’s equation is used to derive the dynamic model of the manipulator system. Flexible intermediate links are modeled as Euler–Bernoulli beams with pinned–pinned boundary conditions. Dynamic equations of motion of a 3-PRR parallel manipulator with three flexible links are developed by adopting the assumed mode method. The effect of concentrated rotational inertia at both ends of intermediate links is included in this model. Numerical simulations of vibration responses, coupling forces and inertial forces are presented. The corresponding frequency spectra analysis is performed using the Fast Fourier Transform (FFT). Experimental modal tests are performed to validate the theoretical model through comparison and analysis of modal characteristics of the flexible manipulator system.     

Motion planning in velocity affine mechanical systems

We address the motion planning problem in specific mechanical systems whose linear and angular velocities depend affinely on control. The configuration space of these systems encompasses the rotation group, and the motion planning involves the system orientation. Derivation of the motion planning algorithm for velocity affine systems has been inspired by the continuation method. Performance of this algorithm is illustrated with examples of the kinematics of a serial nonholonomic manipulator, the plate-ball kinematics and the attitude control of a rigid body.     

Motion Control of a Nonholonomic Mobile Manipulator in Task Space

In this paper, the motion control of a mobile manipulator subjected to nonholonomic constraints is investigated. The control objective is to design a computed‐torque controller based on the coupled dynamics of the mobile manipulator. The proposed controller achieves the capability of simultaneous tracking of a reference velocity for the mobile base and a reference trajectory for the end‐effector. The aforementioned reference velocity and trajectory are defined in the task space, such task setting imitates the actual working conditions of a mobile manipulator and thus makes the control problem practical. To solve this tracking problem, a steering velocity is firstly designed based on the first‐order kinematic model of the nonholonomic mobile base via dynamic feedback linearization. The main merit of the proposed steering velocity design is that it directly utilizes the reference velocity set in the task space without requiring the knowledge of a reference orientation. A torque controller is subsequently developed based on a proposed Lyapunov function which explicitly considers the coupled dynamics of the mobile manipulator to ensure the mobile base and end‐effector track the reference velocity and trajectory respectively. This proposed computed‐torque controller is able to realize asymptotic stability of both the base velocity tracking error and the end‐effector motion tracking error. Simulations are conducted to demonstrate the effectiveness of the proposed controller.