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 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.     

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.     

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.     

Trajectory for saving energy of a direct-drive manipulator in throwing motion

In this article, equations of motion of a closed-type manipulator, whose mechanism can easily be made lighter, are derived in consideration of the characteristics of the driving source. Considering the final condition of angular displacement and angular velocity in throwing motion, trajectories of velocity for saving energy are calculated by iterative dynamic programming, and the dynamic characteristics of manipulator control based on the trajectory for saving energy are analyzed theoretically and investigated experimentally. This work was presented in part at the 11th International Symposium on Artificial Life and Robotics, Oita, Japan, January 23–25, 2006     

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     

Dynamic modeling and design optimization of a 3-DOF spherical parallel manipulator

This paper deals with the dynamic modeling and design optimization of a three Degree-of-Freedom spherical parallel manipulator. Using the method of Lagrange multipliers, the equations of motion of the manipulator are derived by considering its motion characteristics, namely, all the components rotating about the center of rotation. Using the derived dynamic model, a multiobjective optimization problem is formulated to optimize the structural and geometric parameters of the spherical parallel manipulator. The proposed approach is illustrated with the design optimization of an unlimited-roll spherical parallel manipulator with a main objective to minimize the mechanism mass in order to enhance both kinematic and dynamic performances.     

Dynamic advantages of singular configurations in moving heavy object by a two-link mechanism

This paper demonstrates dynamic advantages of singular configurations for a two-link mechanism by theoretical analysis and numerical simulations. The advantages can be utilized in moving a heavy object by the mechanism. The theoretical analysis reveals that the configurations of the mechanism near the singular ones are advantageous in generating large acceleration of the object through the joint torques and the kinetic energy of the mechanism. We illustrate the advantages by numerical simulations for two typical motions, that is, a lifting motion of a two-link manipulator and a jumping motion of a two-link legged robot. It is shown that the joint torques necessary to achieve these motions are reduced to a large extent by using the advantages.     

Dragging motion of a two-link mobile manipulator with large pull force through singular configuration: theoretical analysis and experimental verification

This paper reveals the advantageous feature of singular configuration for a two-link mobile manipulator by theoretical analysis, numerical simulations and experiments. When a mobile manipulator drags a heavy object on a flat floor, a large pull force is required to overcome the friction force between the object and the floor. In the motion obtained by numerical optimization, unlike humans, a two-link mobile manipulator pulls the object with a large force by passing through singular configuration. We analyze theoretically the force applied to the object by the manipulator under several assumptions, and show that a large pull force can be generated near singular configuration from the energy stored in the manipulator. The feasibility of the motion obtained by numerical optimization is also shown by experimental results.     

多机械手刚性协调动力学建模与混合控制

从力负载分析开始,阐述多手直辖市中对象的外/内力和外/内运动定义;考虑对象运动受限情况,提出一组描述协调任务的广义运动和力向量;以各机械手及对象的运动方程为基础,建立面向对象的运动学、静力学和动力学模型,该模型与单机械手操作空间的运动方程具有一致的表达形式,据此,该文探讨了多手协调情况下运动、内力和接触力的混合控制问题。     

Research on the inertia matching of the Stewart parallel manipulator

With the development of the parallel manipulator, inertia matching as an essential factor to realize good potentials of the parallel manipulator is taken serious gradually. However, neither definite inertia index nor inertia matching method has been proposed so far. In this paper, the above issues are discussed by taking the Stewart parallel manipulator as a study object. Firstly, adopting limb Jacobian matrices, the concise algebraic expression of the joint–space inertia matrix of the Stewart parallel manipulator is deduced, based on the dynamic modeling. Next, on the basis of the coupling analysis of the joint–space inertia matrix, the inertia index of the parallel manipulator, the Joint-Reflected Inertia, is proposed. Then, the practical inertia matching principles of the Stewart parallel manipulator are concluded on the basis of simulations, considering multiple factors, such as mechanical resonance frequency, acceleration torque and dynamic performance. Finally, the available range of the motor inertia is deduced, and the inertia matching of the Stewart parallel manipulator is finished as the case study. The inertia index and inertia matching method suggested in this paper can be further used in other parallel manipulators for dynamic analysis and motion system design.     

Distribution of dynamic loads for multiple cooperating robot manipulators

For the situation of multiple cooperating manipulators handling a single object, a formulation is presented which allows load distribution of the combined system to be made while taking manipulator dynamics into account. First, object dynamics are used to transform the motion task. An integrated procedure for modeling arm dynamics is detailed. Then a method is introduced which transforms the object load to the joint level. At this level, various methods of load distribution that allow subtask performance are proposed. These methods allow desired object motion while selecting loads desirable to alleviate manipulator dynamic loads.     

Dynamic Analysis and Control Synthesis of Grasping and Slippage of an Object Manipulated by a Robot

Grasping an object by a cooperating system such as multi-fingered hands and multi-manipulator robotic system has received much attention. Research has focused on analysis of force-closure grasps and the synthesis of optimal grasping, when there is no slipping condition. Although the control system is designed to keep the contact force in the friction cone and avoid the slipping condition, slippage can occur for many reasons. In this research, dynamics analysis and control synthesis of a manipulator moving an object on a horizontal surface using the contact force of an end-effector are performed considering the slipping condition. Equality and inequality equations of frictional contact conditions are replaced by a single second-order differential equation with switching coefficients in order to facilitate the dynamic modeling. Accuracy of this modeling is verified by comparing the results of the model with those of SimMech. Using this modeling of friction, a set of reduced order form is obtained for equations of motion of the system. A new method is proposed to control the object motion and the end-effector undesired slippage based on the reduced form. Finally, performance of the method is evaluated both numerically and experimentally.     

Robust motion control with the consideration algorithm of joint torque saturation for a redundant manipulator

As each joint actuator of a robot manipulator has a limit value of torque, the motion control system should consider the torque saturation. In order to consider the torque saturation in a transient state, this paper proposes a new redundant motion control system using the autonomous consideration algorithm on torque saturation. A Jacobian matrix of a redundant robot manipulator can select the optimal one considering its motion energy in the steady state. When the motion control system carries out fast motion and quick disturbance suppression, a high joint torque is required in a transient state. In the experimental results, under the condition of having a large payload torque and a fast motion reference, the proposed redundant manipulator control realizes the quick robot motion robustly and smoothly.     

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.     

基于泛函梯度优化的运动规划算法

针对高自由度的机械臂的灵活性和自主性问题,提出一种快速且高效的机械臂运动规划算法。通过动态运动基元(DMPs)模型对运动轨迹进行编码提取特征,作为运动轨迹先验知识,基于现在物理环境和目标任务设计无碰撞及高能效的目标泛函,通过对目标泛函进行梯度下降得出在该环境下的最优轨迹。为验证算法的有效性,通过机器人实验平台(v-rep)模拟机械臂的日常操作任务。实验结果表明,在整个工作空间内,机械臂通过少量的迭代(少于6次),便可生成无碰撞的运动轨迹,可降低能耗20%以上。     

Pose Planning for a Mobile Manipulator Based on Joint Motions for Posture Adjustment to End-Effector Error

This paper proposes a motion planning method for a mobile manipulator. In general, humans can grasp an object by various ways which depend on object posture, position and so on. The objective of this paper is to present how to detect the pose of a mobile manipulator under the condition that several ways of grasping are given to the robot. Motion errors and object position errors are considered to detect robot pose in our method because these affect the grasp motion of the robot hand. Coping with these errors, we will propose an effective pose searching method for a mobile manipulator from numerous pose candidates. The performance of the proposed method is illustrated by simulation and experiment.     

Impedance control of industrial robots

Manipulation fundamentally requires the manipulator to be mechanically coupled to the object being manipulated. A consideration of the physical constraints imposed by dynamic interaction shows that control of a vector quantity such as position or force is inadequate and that control of the manipulator impedance is necessary. Techniques for planning and control of manipulator behavior are presented which result in a unified approach to target acquisition, obstable avoidance, kinematically constrained motion, and dynamic interaction. A feedback control algorithm for implementing a cartesian end-point impedance on a nonlinear manipulator is presented. The modulation of end-point impedance independent of feedback is also considered. A method for choosing the impedance appropriate to a task using optimization theory is discussed.     

基于行星齿轮机构的牵引式欠驱动机械手设计

为实现夹持力调节和目标物体抓取功能,设计了一种基于行星齿轮机构的牵引式欠驱动机械手。该机械手采用不固定输出轴和内齿圈的行星齿轮机构来分配2种互斥的运动,一种用于手指的转动,实现机械手的夹持功能;另一种用于皮带轮的无限转动,通过皮带实现目标物体的拉入功能。相对于腱绳式和连杆式欠驱动机械手,这种单输入双输出形式不仅能够保持机械手的自适应性,同时还能降低机械手的耦合程度。根据行星齿轮机构的这种传动特点,设计了阻力矩调节机构,实现了机械手的夹持力调节功能。夹持力测试实验表明,在阻力矩调节机构的作用下,机械手能有效调节夹持力。抓取实验结果表明,机械手能够实现对刚性和柔性目标物体的抓取操作,验证了机械手设计的有效性。     

Methodology for the kinematical selection of a manipulator for a specified task

Manipulator design methodology is a recent and important issue in the robot design research area. Most importantly, to design a robot rationally, one must have a strong understanding of the design parameters of the manipulator, and of the characteristics of the robot relative to its kinematical and dynamical requirements. Development of a robot capable of fast movements or high payloads is progressed by the analysis of dynamic characteristics, DOF positioning, actuator selection, structure of links, and so on. This paper highlights the design of a robot manipulator scaled down from its final form, when it will passively be handled by a human for man-machine cooperation. The requirements of the system include its having 6-DOF and the capacity for a high payload in the condition of its maximum reach. The primary investigation factors are motion range, performance within the motion area, and reliability during the handling of heavy materials. Traditionally, the mechanical design of robots has been viewed as a problem of packaging motors and electronics into a reasonable structure. This process usually transpires with heavy reliance on designer experience. Not surprisingly, the traditional design process contains no formally defined rules for achieving desirable results, as there is little opportunity for quantitative feedback during the formative stages. This work primarily focuses on the selection of proper joint types and link lengths, considering a specific task type and motion requirements of the curtain wall installation process in the construction site based on the result of experiment of proto type system of this study.