Analytically derived three-dimensional reach volumes based on multijoint movements

The main objectives of this study were to quantify the range of reaching for the upper body with eight degrees of freedom (the trunk and shoulder, elbow, and wrist joints) and the lower body with six degrees of freedom (the hip, knee, and ankle joints). A sweeping algorithm that included trunk and foot motions was used to generate the analytical total reach volume of the human body for young men. Three types of reach volume--unconstrained arm reach, shoulder-restricted arm reach, and foot reach--were generated depending on the joint involved in reach activities. The robot kinematics methodology was employed to represent the human body as a multilink system, which was needed for calculating three-dimensional coordinates of the involved joints. The statistical test results showed that the total reach volume analytically generated in this study was nearly identical to that obtained from the direct human body measurements. Applications of this research include generating the human body's reach volume for the purpose of designing work spaces and products.     

A partitioned redundancy management scheme for an eight‐joint revolute manipulator

A partitioned redundancy management approach is developed for a class of eight‐joint manipulators with four‐axis intersecting wrists. Segmenting the excess degrees of freedom at the wrist simplifies the inverse kinematics problem substantially and allows different and often competing schemes to be used for controlling the motion of the arm. In the upper arm, the roll angle of the shoulder–elbow–wrist plane is controlled directly. In the wrist, the spare joint is used to minimize the instantaneous joint velocities. In addition, the partitioning scheme substantially reduces the number of singularities that can be encountered by the arm and thus actively avoided. A new four‐axis “skew” wrist design is also introduced which doubles the workspace size of the traditional orthogonal design while retaining the ability to avoid singularities. Simulations are used to illustrate the redundancy management approach on the dexterous manipulator for a submersible robotic vehicle. © 2000 John Wiley & Sons, Inc.     

人手食指运动学建模

通过分析人手解剖学结构和观察人手运动特性，提出如下观点：（1）食指指掌关节具有两个轴线垂直相交的旋转自由度，两轴线相对于手掌不同的排列顺序对应于两种不同的运动学模型，指掌关节只能是其中的一种；（2）食指指掌关节的两个自由度在运动极限位置具有相关性．通过实验测绘出人手食指的工作空间形状，将之与两种可能的食指运动学模型对应的工作空间相比较，判别出指掌关节的真实运动学结构，并验证了指掌关节极限位置上两个自由度运动相关性．在上述工作基础上建立了符合人手实际结构的手指运动学模型．     

基于Kinect的仿人机器人控制系统

为实现对具有16个自由度仿人机器人的姿态控制,采用Kinect传感器对人体姿态的坐标数据进行采集,根据坐标信息利用Processing软件开发基于SimpleOpenNI库的上位机软件,建立人体关节模型,并利用空间向量法对仿人机器人的步态规划以及重心控制算法分析,解析各关节的转动角度,经由无线WiFi模块向仿人机器人发送指令以控制舵机的运动,最终实现对机器人的控制,搭建了基于Kinect传感器的测试平台.测试结果表明:仿人机器人上肢在运动范围内无死角,通过对重心的控制,下肢可实现简单的步行,符合预期效果.     

Fuzzy-GA-based trajectory planner for robot manipulators sharing a common workspace

This paper presents a novel fuzzy genetic algorithm (GA) approach to tackling the problem of trajectory planning of two collaborative robot manipulators sharing a common workspace, where the manipulators have to consider each other as a moving obstacle whose trajectory or behaviour is unknown and unpredictable, as each manipulator has individual goals and where both have the same priority. The goals are not restricted to a given set of joint values, but are specified in the workspace as coordinates at which it is desired to place the end-effector of the manipulator. By not constraining the goal to the joint space, the number of possible solutions that satisfies the goal increases according to the number of degrees of freedom of the manipulators. A simple GA planner is used to produce an initial estimation of the movements of the robots' articulations and collision free motion is obtained by the corrective action of the collision-avoidance fuzzy units.     

Joint workspace of parallel kinematic machines

Robot workspace is the set of positions a robot can reach. Workspace is one of the most useful measures for the evaluation of a robot. Workspace is usually defined as the reachable space of the end-effector in Cartesian coordinate system. However, it can be defined in joint coordinate system in terms of joint motions. In this paper, workspace of the end-effector is called task workspace, and workspace of the joint motions is called joint workspace. Joint workspace of a parallel kinematic machine (PKM) is focused, and a tripod machine tool with three degrees of freedom (DOF) is taken as an example. To study the joint workspace of this tripod machine tool, the forward kinematic model is established, and an interpolating approach is proposed to solve this model. The forward kinematic model is used to determine the joint workspace, which occupies a portion of the domain of joint motions. The following contributions have been made in this paper include: (i) a new concept so-called joint workspace has been proposed for design optimization and control of a PKM; (ii) an approach is developed to determine joint workspace based on the structural constraints of a PKM; (iii) it is observed that the trajectory planning in the joint coordinate system is not reliable without taking into considerations of cavities or holes in the joint workspace.     

Two‐handed human reach prediction models for ergonomic evaluation

As an essential function of computerized ergonomic evaluation models based on digital human models, realistic simulation or prediction of human reach profiles is of great importance. Although several human‐modeling efforts have been made to provide the capability of reach simulation, most studies have been limited to the reach of a single extremity. A variety of activities of human operators, however, frequently involve simultaneous positioning of two or more extremities to different target positions. Such a multiple reach problem cannot be satisfactorily resolved by means of conventional single‐extremity reach models because formulation of the problem as a series of single reaches rarely yields accurate trajectory of human‐reach profiles due to interactions of multiple extremities. In this research, a two‐handed reach prediction model was developed. The human upper body was modeled as a seven‐link system with 13 degrees of freedom, being regarded as a redundant open kinematic chain with two end‐effectors. As a way of solving the two‐handed reach problem, the resolved motion method was adopted among several inverse kinematics methods as the technique is fit for real‐time redundancy control. The method is also capable of incorporating the joint range availability criterion as a cost function to minimize excessive deviations of body joints from their neutral positions. Real human‐reach profiles were compared to those obtained from the prediction model and were found to be statistically similar. The methodology is expected to be applicable to the reach simulation of both upper and lower extremities without algorithmic difficulties. © 2010 Wiley Periodicals, Inc.     

On the Workspace of a Free-Floating Space Robot

The planar problem of controlling the motion of a free-floating space robot is investigated. The robot consists of a body and a telescopic manipulator arm. The motion of the manipulator arm changes the body’s center of mass and causes the body to rotate. It is assumed that the length of the manipulator arm and the angle of its turn relative to the body are restricted. It is shown that the workspace of such a robot is significantly larger than the workspace of a robot with a fixed body. Due to the special motions of the manipulator arm, the robot’s body can be turned and the gripper can be moved from an arbitrary position to another arbitrary position if they are within the workspace, which is a ring centered at the robot’s center of mass. In addition, the prescribed angle between the manipulator arm and the body in the terminal position can be ensured.     

具有7自由度和双球型髋关节的仿人机器人下肢运动分析与规划

提出了具有7自由度和双球型髋关节的仿人机器人下肢机构．它和传统的6自由度双足步行机构相比，具有下述两大优点．首先双球型髋关节使机器人在不增加腰部关节的情况下实现腰部的基本运动功能，使机器人能够直立行走；其次在给定腰和足部位置时，它也能和人类一样实现转动双腿的动作．本文还对该复杂机构进行了运动特性分析、运动学求解、运动规划和实验验证．     

Connectionist modeling for arm kinematics using visual information

The self-organizing adaptive map algorithm is adopted to learn all possible postures for an artificial arm of arbitrary configuration placed in a three-dimensional workspace. Arm postures are represented through their projections onto a set of image planes. Based on the link orientation and link length extracted from these images, a topological state space Q is generated. Arm kinematics is expressed as a transformation of topological hypersurfaces, the intersections of which represents the multiple postures of the arm in the workspace for a given end effector position. The self-organizing feature map learns how the topological hypersurfaces transform in the state space during arbitrary movements of the arm in the workspace. During the learning phase, the neural network generates clusters of neurons, each neuron being responsible for reproducing an arm posture in the workspace. The neural clusters map the hypersurfaces' intersection in the topological Q-space to any position of the arm gripper in the workspace. Simulations for planar and nonplanar multiple degrees of freedom arms are presented.     

Autonomous motion planning of a hand-arm robotic system based on captured human-like hand postures

The paper deals with the problem of motion planning of anthropomorphic mechanical hands avoiding collisions and trying to mimic real human hand postures. The approach uses the concept of “principal motion directions” to reduce the dimension of the search space in order to obtain results with a compromise between motion optimality and planning complexity (time). Basically, the work includes the following phases: capturing the human hand workspace using a sensorized glove and mapping it to the mechanical hand workspace, reducing the space dimension by looking for the most relevant principal motion directions, and planning the hand movements using a probabilistic roadmap planner. The approach has been implemented for a four finger anthropomorphic mechanical hand (17 joints with 13 independent degrees of freedom) assembled on an industrial robot (6 independent degrees of freedom), and experimental examples are included to illustrate its validity.     

Application of parallel mechanism in varistructured quadruped/biped human-carrying walking chair robot

For the existing problems of walking chair robot such as simple function,lower bearing capacity and not walking in complex environment,a novel varistructured quadruped / biped human-carrying walking chair robot is proposed.The proposed robot could be used as biped and quadruped walking chair robots.Considering the conversion of the walking chair robot from the quadruped to the biped or vice versa,6-UPS and 2-UPS+UP(U,P and S are universal joint,the prismatic pair,and sphere joint,respectively) parallel mechanisms are selected as the leg mechanism of the biped walking robot and quadruped walking robot,respectively.Combining the screw theory and theory of mechanism,the degrees of freedom of the leg mechanism and the body mechanism in diferent motion states are computed so as to meet the requirements of mechanism design.The motion characteristics of the 2-UPS+UP parallel mechanism which is the key part of the walking chair robot are analyzed.Then,the workspace of the moving platform is drawn and the efect of the structural parameters on the workspace volume is studied.Finally,it is found that the volume of the workspace of the moving platform is bigger when the side length ratio and the vertex angle ratio of the fxed platform and the moving platform which are isosceles triangles are close to 1.This study provides a theoretical foundation for the prototype development.     

外骨骼式遥操作主手设计及主从异构映射算法研究

为了更好地促进机器人适应复杂的遥操作任务,开发了能够精确获取人体上肢运动信息的外骨骼式遥操作主手,并通过异构映射算法,实现对6自由度协作机械臂的遥操作．首先,基于人体仿生结构,设计了可穿戴式8自由度外骨骼主手（臂部7自由度和手部1自由度）;其次,通过改进的D-H（Denavit-Hartenberg）方法建立遥操作系统的运动学模型,基于Matlab的机器人工具箱进行了工作空间仿真,并设计主从异构映射算法;最后,实验验证外骨骼主手在遥操作系统中的可操作性,以及工作空间异构映射算法的可行性．实验表明,外骨骼主手能够控制从端机械手臂,且保证末端位置和姿态一致,可在大范围工作空间内复现人体上肢精细运动,主从跟随误差达2 mm,工作空间类似于直径1.08 m的半球形．因此,可穿戴式的外骨骼主手使操作者能更加直观地参与到遥操作系统当中,辅助操作者更加高效地完成精细复杂任务．     

Improved dynamics model for human standing posture control using functional neuromuscular stimulation

Many studies on the use of functional neuromuscular stimulation for stabilizing the standing posture of paraplegic patients are conducted in computer simulations to minimize possible risks. Here, a five degrees of freedom skeletal-musculotendon muscle activation model of human body dynamics is formulated for the purpose of control effectiveness evaluation. By including the effect of arm rotation about the shoulder plus foot tipping about toe or heel in dynamics models, a more realistic response prediction capability can be achieved compared with previous models. A closed loop control simulation example is presented to demonstrate the significance of adding these features to the human body dynamics model.     

Rotorcraft with a 3DOF Rigid Manipulator: Quaternion-based Modeling and Real-time Control Tolerant to Multi-body Couplings

This paper proposes a simple solution for the stabilization of a mini-quadcopter carrying a 3DoF (degrees of freedom) manipulator robot in order to enhance its achievable workspace and application profile. Since the motion of the arm induces torques which degrade the stability of the system, in the present work, we consider the stabilization of both subsystems: the quadcopter and the robotic arm. The mathematical model of the system is based on quaternions. Likewise, an attitude control law consisting of a bounded quaternion-based feedback stabilizes the quadcopter to a desired attitude while the arm is evolving. The next stage is the translational dynamics which is simplified for control (nonlinear) design purposes. The aforementioned controllers are based on saturation functions whose stability is explicitly proved in the Lyapunov sense. Finally, experimental results and a statistical study validate the proposed control strategy.     

A multi-objective approach for the motion planning of redundant manipulators

Kinematic redundancy occurs when a manipulator possesses more degrees of freedom than those required to execute a given task. Several kinematic techniques for redundant manipulators control the gripper through the pseudo-inverse of the Jacobian, but lead to a kind of chaotic inner motion with unpredictable arm configurations. Such algorithms are not easy to adapt to optimization schemes and, moreover, often there are multiple optimization objectives that can conflict between them. Unlike single optimization, where one attempts to find the best solution, in multi-objective optimization there is no single solution that is optimum with respect to all indices. Therefore, trajectory planning of redundant robots remains an important area of research and more efficient optimization algorithms are needed. This paper presents a new technique to solve the inverse kinematics of redundant manipulators, using a multi-objective genetic algorithm. This scheme combines the closed-loop pseudo-inverse method with a multi-objective genetic algorithm to control the joint positions. Simulations for manipulators with three or four rotational joints, considering the optimization of two objectives in a workspace without and with obstacles are developed. The results reveal that it is possible to choose several solutions from the Pareto optimal front according to the importance of each individual objective.     

Development of vehicles with legs and wheels

This paper deals with the design of the foot trajectory for a quadruped walking machine. Such walking machines should be capable of both uneven terrain walking and high-speed flat surface walking. The static walking method was used for uneven terrain walking and the dynamic walking method was used for plane walking. In the case of dynamic walking, the relative speed between the foot and the ground causes instability in the balance of the body. A foot trajectory is designed based on two points: the kinematics of foot motion and the relationship between joint motion and joint driving torque. A method for reducing the impact force upon initial contact with a floor by designing a periodic foot trajectory based on the wave motion of a cam is discussed. In this method, vertical and horizontal motions of the foot trajectory were generated independently using cycloidic motion. We named this trajectory the composite cycloid foot trajectory. We further developed a modified cycloidic foot trajectory by smoothing the joint angular acceleration.