Determination of worker physiological cost in workspace reach envelopes

Oxygen uptake (VO₂), heart rate (HR) and myoelectric activity (EMG) were measured while performing a repetitive task in the normal, maximum and extreme workspace reach envelopes. The VO₂ and HR increased significantly from the normal to the maximum to the extreme workspace reach envelope. The average increases in VO₂ when compared to the normal workspace were 19 and 52%, respectively. The corresponding average increases in HR were 6 and 14%, respectively. The increase in EMG for anterior deltoid, upper trapezious and erector spinae showed a significant increase from normal to maximum and from maximum to extreme workspaces. The average increases in EMG for anterior deltoid, upper trapezious and erector spinae, compared to the normal workspace were 96, 37 and 48% respectively for the maximum workspace and 193, 95 and 106% for the extreme workspace, respectively. The research indicated for the first time that during task performance, worker physiological cost would increase significantly with the increase in workspace reach levels.     

Determination of the orientation workspace of parallel manipulators

An important step during the design of a parallel manipulators is the determination of its workspace. For a 6-d.o.f. parallel manipulator workspace limitations are due to the bounded range of their linear actuators, mechanical limits on their passive joints and links interference. The computation of the workspace of a parallel manipulator is far more complex than for a serial link manipulator as its translation ability is dependent upon the orientation of the end-effector.We present in this paper an algorithm enabling to compute the possible rotation of the end-effector around a fixed point. This algorithm enables to take into account all the constraints limiting the workspace. Various examples are presented.     

Determination of workspace and required initial position of free-flying space manipulator at target capture

Consideration was given to the issues of computer-aided construction of the workspace of the free-flying space handling robot controlled in the class of feedback systems. In particular, a case was discussed where the information about the direction and distance to the target is acquired with the use of a camcorder with built-in range finder mounted on a gimbal attached to the robot body. The analytical relations obtained enable one to solve the problems of injecting the space robot into the zone of target location and maintaining the desired orientation of the body relative to the direction to the target. The proposed approach to the problem of generation of the workspace was implemented as a computer algorithm in the Matlab-Simulink environment. Operability of the algorithm was exemplified an arbitrary initial configuration of the robot.     

Personality and inter-subject differences in performance and physiological cost during whole-body vibration

When subjects are exposed to whole-body vibration, extra effort is required to maintain pre-vibration standards of performance. Therefore the willingness of subjects to expend this effort might influence both performance and physiological cost. Willingness may be related to a personality variable-score on the locus of control scale. This hypothesis was tested in 12 subjects who performed a simulated driving task during 10 min of vertical (±Gz) whole-body vibration at energy levels of 021,0-28 and 0-35 r.m.s.g using a sinusoidal and a random waveform. Accuracy at a foot-controlled, compensatory tracking task, reaction time, oxygen uptake and heart rate were measured. Subjects with an ‘internal’ locus of control had less tracking error(p<0.001)and higher heart rates (p<0.05) than did subjects with an ‘external’ locus of control. Furthermore, both variables were significantly correlated with the locus of control scores (r= +0.73 and —0.66) respectively. These findings suggest that the inter-subject differences found in investigations using human subjects may be explained in part by personality differences related to locus of control.     

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.     

基于眼固定安装方式的机器人定位系统

研发了基于眼固定安装方式的机器人定位系统,提出了一种方便有效的手眼标定方法。通过最小二乘法求解手眼坐标的变换关系,再根据工作台平面与摄像机成像模型的约束关系,求解出目标物体的三维位姿,并最终实现了机械手的精确定位。     

工作区感知在配置管理中的应用

在配置管理系统中,工作区隔离了开发人员的工作。因此,开发人员在自己的工作区中进行变更时不会受到他人工作的影响。然而,它造成的困难是难以了解到并行存在的变更,所以当变更提交到配置库中时往往会引发很多问题。通过将工作区感知引入配置管理系统可以克服工作区的不足同时保留其优点。工作区感知的实现可以方便开发人员在变更的过程中避免冲突。     

Multi robot collision avoidance in a shared workspace

This paper presents a decentralised human-aware navigation algorithm for shared human–robot work-spaces based on the velocity obstacles paradigm. By extending our previous work on collision avoidance, we are able to include and avoid static and dynamic obstacles, no matter whether they are induced by other robots and humans passing through. Using various cost maps and Monte Carlo sampling with different cost factors accounting for humans and robots, the approach allows human workers to use the same navigation space as robots. It does not rely on any external positioning sensors and shows its feasibility even in densely packed environments.     

Operational and maximal workspace of the thumb

The purposes were to examine the workspace of the thumb during its operational (submaximal and random) movement and to compare the operational workspace with its maximal workspace. Fifteen female subjects with asymptomatic hands performed the thumb circumduction and operational motion. Linear and angular measurements of the thumb were obtained by a marker-based motion analysis system. During the circumduction, the linear ranges of motion of the thumb tip were 102.8 ± 9.9 mm and 130.7 ± 14.1 mm in abduction/adduction and flexion/extension directions, respectively, and the corresponding values for the operational motion were 67.3 ± 16.1 mm and 73.1 ± 18.0 mm, respectively. The angular ranges of motion of the carpometacarpal (CMC) and metacarpophalangeal joints during the operational motion were less than 65% of their maximal motion ranges. In addition, the CMC joint tended to move in directions oblique to its anatomical defined axes. The results of operational motion may provide guidelines for ergonomic design of thumb-operated tools and hand-held electronics devices.     

An indoor localization system in a multiblock workspace

As service robots and other ubiquitous technology have evolved, an increasing need for the autonomous navigation of mobile objects has arisen. In a large number of localization schemes, the absolute-position estimation method, which relies on navigation beacons or landmarks, has been widely used as it has the advantages of being economical and accurate. However, only a few of these schemes have expanded their application to complicated workspaces, or those that have many rooms or blocks. As the navigation of mobile objects in complicated workspaces is vital for ubiquitous technology, multiblock navigation is necessary. This article presents methodologies and techniques for the multiblock navigation of the indoor localization system with active beacon sensors. This new indoor localization system design includes ultrasonic attenuation compensation, dilution-of-precision analysis, and a fault detection and isolation algorithm using redundant measurements. This work was presented in part at the 13th International Symposium on Artificial Life and Robotics, Oita, Japan, January 31–February 2, 2008     

Operational and maximal workspace of the thumb

The purposes were to examine the workspace of the thumb during its operational (submaximal and random) movement and to compare the operational workspace with its maximal workspace. Fifteen female subjects with asymptomatic hands performed the thumb circumduction and operational motion. Linear and angular measurements of the thumb were obtained by a marker-based motion analysis system. During the circumduction, the linear ranges of motion of the thumb tip were 102.8 +/- 9.9 mm and 130.7 +/- 14.1 mm in abduction/adduction and flexion/extension directions, respectively, and the corresponding values for the operational motion were 67.3 +/- 16.1 mm and 73.1 +/- 18.0 mm, respectively. The angular ranges of motion of the carpometacarpal (CMC) and metacarpophalangeal joints during the operational motion were less than 65% of their maximal motion ranges. In addition, the CMC joint tended to move in directions oblique to its anatomical defined axes. The results of operational motion may provide guidelines for ergonomic design of thumb-operated tools and hand-held electronics devices.     

六自由度机械臂建模与工作空间分析

在危险环境条件下,为确保人员安全,考虑使用机械臂代替人类的工作,针对以上需求设计一种六自由度机械臂。根据D-H多体运动学建模方法,分析建立机械臂各关节坐标系并确定连杆参数,建立机械臂的运动学模型;通过齐次变换推导末端执行器的姿态和位置,通过仿真和数学计算结果比较证明建模的准确性。根据关节空间到工作空间的映射关系,采用蒙特卡洛法分析、求解机械臂的工作空间,在MATLAB中描绘出工作空间的三维云图。为后续的机器人轨迹规划、运动控制和参数优化提供参考。     

On the connectivity of manipulator free workspace

This article presents a new topological characterization of the free workspace of manipulators moving among obstacles. The free workspace is the set of positions and orientations that the end-effector of the manipulator can reach, according to the joint limits of each of its links, and taking into account the obstacles of the environment. A classification of new connectivity properties of the free workspace is proposed, corresponding to different types of motions (point-to-point motions, following of continuous trajectories) that the manipulator can perform in the Cartesian space. For each property, a necessary and sufficient condition is given, which permits verification of the connectivity of the whole free workspace and leads to all the connected subspaces in it. These properties have been implemented in a Robotics C.A.D. system using octree representation of spaces. Some applications are presented, which show that this work is of primary interest for preparing off-line tasks, and is a new contribution to the problem of robotic cell layout design.     

The power of the private workspace model

In the private workspace model of concurrency control the transaction management component of a database management system maintains a private workspace for each transaction. Data items accessed by a transaction, regardless of the access mode, are cached in the workspace. At transaction commit time, its updates are made permananet in the database. In this paper we want to focus our attention on the private workspace model as a framework for the design of concurrency control algorithms which do not require ww synchronization. We present a Two Phase Locking (2PL) derivative called Workspace 2PL (W2PL) and show that in a system employing W2PL no ww synchronization is needed and more importantly, no transaction will restart on a READ request. Furthermore, under the No Blind Writes assumption we can guarantee that no READ request will cause a transaction to starve, thus no Reader will be restarted or starved.     

Computing envelopes in dynamic geometry environments

We review the behavior of some popular dynamic geometry software when computing envelopes, relating the diverse methods implemented in these programs with the various definitions of envelope. Special attention is given to the new GeoGebra 5.0 version, that incorporates a mathematically rigorous approach for envelope computations. Furthermore, a discussion on the role, in this context, of the cooperation between GeoGebra and a recent parametric polynomial solving algorithm is detailed. This approach seems to yield accurate results, allowing for the first time sound computations of envelopes of families of plane curves in interactive environments.     

The effects of the reach and level of lifting/lowering tasks on metabolic cost in symmetric and asymmetric planes

The energy consumption in the workspace envelope around operators was studied for lifting and lowering tasks. The entire working space was bisected into two identical halves. Within one, 81 target locations were selected. Six male young adults (mean age 27.3 years and mean weight 73.8 kg) stoop lifted and lowered 2.5, 5.0, and 10.0 kg loads from floor to their respective knee, hip, and shoulder heights in mid-sagittal, 30° lateral, and 60° lateral planes at half, three-quarters, and full reach distances. The steady state oxygen uptake was measured for quiet standing and the 81 activities. The energy expenditure and inspiratory ventilation volume was subjected to analysis of variance and post hoc analysis. The ANOVA revealed a significant effect of the task reach distance, level of lift and the magnitude of weight (p < 0.001). The plane of activity had no significant effect on metabolic cost. The increased reach of the task required 11–41% more energy and the increased load required 28–100% more energy. A high multiple correlation (r = 0.86, p < 0.001) was achieved for the energy cost of lifting/lowering.