Maximal singularity-free orientation workspace over a position region of Gough–Stewart platform

Maximizing the singularity-free workspace of parallel manipulators is highly desirable in a context of robot design. So far, no work has been found to address the maximal singularity-free orientation workspace over a position region. In practice, this type of workspace is interesting because a mechanism often works in a range of positions. This work focuses on the Gough–Stewart platform. An optimal position at which the mechanism holds the maximal singularity-free orientation workspace is determined. This optimal position lies on the line which is perpendicular to the base and passes the centroid of the base. Considering the symmetry, a parallelepiped with centre at the determined optimal position could be an interesting working position region for the Gough–Stewart platform. Two algorithms are presented to compute the maximal singularity-free orientation workspace over such an interesting position region. An example is provided for demonstration.     

Orientation-Singularity and Nonsingular Orientation-Workspace Analysis of the Semi-Regular Stewart–Gough Platform Manipulator

This paper addresses the orientation-singularity analysis and the nonsingular orientation-workspace computation of the semi-regular Stewart–Gough platform manipulator (SRSGPM). Based on the half-angle transformation, a polynomial expression that represents the orientation-singularity locus of the SRSGPM when the mobile platform of the platform manipulator is fixed to a constant position is derived. It is shown that the orientation-singularity locus of the SRSGPM at a fixed position is a polynomial expression of degree 13 in the mobile platform orientation parameters and graphical representations of the orientation-singularity locus of the SRSGPM are illustrated with examples to demonstrate the theoretical result. Using this half-angle transformation, a new discretization method is proposed for computing the nonsingular orientation-workspace of the SRSGPM in consideration of singularities, limitations of active and passive joints, and link interference. Examples of a SRSGPM are given to demonstrate the results.     

A web-based platform for the simulation–optimization of industrial problems

This study presents a platform for industrial, real-world simulation–optimization based on web techniques. The design of the platform is intended to be generic and thereby make it possible to apply the platform in various problem domains. In the implementation of the platform, modern web techniques, such as Ajax, JavaScript, GWT, and ProtoBuf, are used. The platform is tested and evaluated on a real industrial problem of production optimization at Volvo Aero Corporation, a company that develops and manufactures high-technology components for aircraft and gas turbine engines. The results of the evaluation show that while the platform has several benefits, implementing a web-based system is not completely straightforward. At the end of the paper, possible pitfalls are discussed and some recommendations for future implementations are outlined.     

Multi-objective optimization design of a connection frame in macro–micro motion platform

Connection frame is an essential component to implement high acceleration and ultra-precision positioning motion in a macro–micro motion platform. The performance of the positioning system is mainly affected by two sources which include thermal–mechanical deformation and the natural frequency of connection frame. In the paper, multi-objective optimization and design for the connection frame is constructed and discussed comprehensively by the effects of thermal–mechanical deformation and the natural frequency of the system. The optimization objectives for the connection structure are the minimized displacement when thermal–mechanical deformation is occurred, the maximized natural frequency to avoid system resonance, and the light weight for the connection structure to fulfil high acceleration motion. Using response surface method (RSM) combined with finite element method (FEM), the objective function is formulated as a prediction model. Non-dominated Sorting Genetic Algorithm II (NSGAII) is used to solve the optimization model and attain the matched parameters. A cantilever beam example is tested to examine the validity of the methodology, and the results from prediction model agree well with that from theoretical model. By the above methodology, a high performance with optimal parameters for the connection structure is obtained, and its natural frequency and weight can meet our design expectation.     

Orientationability analyses of a special class of the Stewart–Gough parallel manipulators using the unit quaternion representation

This paper addresses the orientation-singularity and orientationability analyses of a special class of the Stewart–Gough parallel manipulators whose moving and base platforms are two similar semi-symmetrical hexagons. Employing a unit quaternion to represent the orientation of the moving platform, an analytical expression representing the singularity locus of this class of parallel manipulators in a six-dimensional Cartesian space is obtained. It shows that for a given orientation, the position-singularity locus is a cubic polynomial expression in the moving platform position parameters, and for a given position, the orientation-singularity locus is an analytical expression but not a polynomial directly with respect to the mobile platform orientation parameters. Further inspection shows that for the special class of parallel manipulators, there must exist a nonsingular orientation void in the orientation space around the orientation origin for each position in the position-workspace. Therefore, a new performance index referred to as orientationability is introduced to describe the orientation capability of the special class of manipulators at a given position. A discretization algorithm is proposed for the computation of the orientationability of the special class of manipulators. Moreover, effects of the design parameters and position parameters on the orientationability are investigated in details. Based on the orientationability performance index, another novel performance index referred to as practical orientationability is presented which represents the practical orientation capability of the manipulator at a given position. The practical orientationability not only can satisfy all the kinematic demands and constraints of such class of manipulators, but also can guarantee that the manipulator is nonsingular.     

Analysis of kinematics/statics and workspace of a 2(SP+SPR+SPU) serial–parallel manipulator

The kinematics/statics and workspace of a 2(SP+SPR+SPU) serial–parallel manipulator are studied systematically. First, a 2(SP+SPR+SPU) manipulator including an upper and a lower SP+SPR+SPU parallel manipulators is constructed, and the inverse/forward displacements, velocity, acceleration and statics of the lower/upper parallel manipulators are studied, respectively. Second, the kinematics and statics of the lower/upper manipulators are combined and the displacement, velocity, acceleration, statics, and workspace of a 2(SP+SPR+SPU) manipulator are analyzed systematically. Third, the analytic solutions’ examples are given and verified by the simulation mechanism. This manipulator has some potential applications for the robot’s arm, leg, and twist, the serial–parallel machine tools, the sensor, the surgical manipulator, the tunnel borer, the barbette of warship, and the satellite surveillance platform.     

A “3-2-1” kinematic configuration of a Stewart platform and its application to six degree of freedom pose measurements

This paper outlines a simple yet accurate approach to measuring the six degree of freedom position and orientation of a robot end-effector. The mechanism, which will be far less costly than currently available devices, can be used to make both static and dynamic measurements for robot calibration as well as real-time endpoint control. The kinematics of the approach stem from a configuration of the Stewart platform. A “3-2-1” kinematic configuration is proposed which results in a closed-form forward kinematic solution for the Stewart platform. The closed-form algorithm can be computed about 100 times faster than conventional iterative algorithms. A prototype system using six string encoders was built and tested. Issues on error compensation were also studied. The presented approach should be useful for a broad range of applications other than robot metrology where convenient, low-cost, six degree of freedom static and/or dynamic pose measurements are required or preffered.     

A two degrees of freedom model–based optimization method for occupant restraint systems in vehicle crash

Structural and Multidisciplinary Optimization - This paper presents a two degrees of freedom model–based optimization method for occupant restraint systems (ORS), applied before the finite...     

Sensor-based force decouple controller design of macro–mini manipulator

A robotic polishing system includes a force-controlled end-effector (mini manipulator) and a position-controlled industrial robot (macro manipulator). This combination mode has a fast response and a large workspace. However, the force-controlled axis component of the macro motions and the geometric of the workpiece surfaces will affect the contact force response rate and tracking accuracy due to the coupling dynamics between the macro and mini, limiting system performance. A new dynamic decoupling method employing dual force sensors (DFSs) is proposed to address these problems. One of the force sensors installed between the endpoint of the macro and the fixed platform of the mini realizes the dynamic decoupling of the macro and mini. The other one is added at the endpoint of the mini to obtain the interaction force in contact with the environment and feed it back to the control loop. When the disturbances produced by the macro trajectories and the uncertainties coming from the workpiece are introduced into the system, the proposed method can improve force response rate and tracking accuracy without knowing the dynamic models and parameters of the macro and the geometric of the workpiece surface. Several experiments are carried out under various conditions. Experimental results indicate that the contact force response rate and tracking error of DFSs are better than those of the conventional force-controlled and impedance matching methods, proving the proposed method’s effectiveness. In addition, the last comparison experiment verifies that the DFSs method applies to different kinds of end-effectors with various dynamics.     

Parameter optimization of modern machining processes using teaching–learning-based optimization algorithm

Modern machining processes are now-a-days widely used by manufacturing industries in order to produce high quality precise and very complex products. These modern machining processes involve large number of input parameters which may affect the cost and quality of the products. Selection of optimum machining parameters in such processes is very important to satisfy all the conflicting objectives of the process. In this research work, a newly developed advanced algorithm named ‘teaching–learning-based optimization (TLBO) algorithm’ is applied for the process parameter optimization of selected modern machining processes. This algorithm is inspired by the teaching–learning process and it works on the effect of influence of a teacher on the output of learners in a class. The important modern machining processes identified for the process parameters optimization in this work are ultrasonic machining (USM), abrasive jet machining (AJM), and wire electrical discharge machining (WEDM) process. The examples considered for these processes were attempted previously by various researchers using different optimization techniques such as genetic algorithm (GA), simulated annealing (SA), artificial bee colony algorithm (ABC), particle swarm optimization (PSO), harmony search (HS), shuffled frog leaping (SFL) etc. However, comparison between the results obtained by the proposed algorithm and those obtained by different optimization algorithms shows the better performance of the proposed algorithm.     

Fixed-mesh curvature-parameterized shape optimization of an acoustic?horn

We suggest a boundary shape optimization approach in which the optimization is carried out on the coefficients in a boundary parameterization based on a local, discrete curvature. A fixed mesh is used to numerically solve the governing equations, in which the geometry is represented through inhomogeneous coefficients, similarly as done in the material distribution approach to topology optimization. The method is applied to the optimization of an acoustic horn in two space dimensions. Numerical experiments show that this method can calculate the horn’s transmission properties as accurately as a traditional, body-fitted approach. Moreover, the use of a fixed mesh allows the optimization to create shapes that would be difficult to handle with a traditional approach that uses deformations of a body-fitted mesh. The parameterization inherently promotes smooth designs without unduly restriction of the design flexibility. The optimized, smooth horns consistently show favorable transmission properties.     

Development of an IS change reason–IS change type combinations matrix

Firms change their information systems (IS) for various reasons, ranging from compliance with government regulations to the development of new capabilities. When making these changes a firm can choose between four different IS change types: IS introduction, IS extension, IS replacement, and IS merger. This paper proposes that change reasons and change types are interrelated, and that certain reason-type combinations are more likely than others to result in a successful IS change. To identify these combinations, an IS change reason–IS change type matrix is developed. While the matrix is created from prior IS research, we conducted a focus group study of IS professionals to further explore and refine the matrix. The findings from the focus group study reveal that some IS change reason–IS change type combinations are more appropriate than others to carry out the IS change project successfully. We also present three examples of IS change projects to illustrate the use and value of the matrix in practice.     

Embodied cognition of information visualization: Human–computer interaction with six degrees of freedom in movement of an information space

Mental healthcare has been identified as one of the major social and economic challenges that society will face in the coming decades. In this paper, we explore the potential of technology to improve people’s access to and engagement in, as well as the effectiveness and affordability of, mental healthcare services while interacting with computers. Information visualization plays a crucial role in people’s interaction with computers. Specifically, information visualization represents data or concepts graphically and helps people construct cognitive maps i.e., mental representations of the information space. Well-designed information visualization methods enable users to employ their mental capabilities to manipulate an information space and perceive it based on good mental health. According to the latest study of mental capability, movement will guide insight in problem solving situations. Movement in the 3D world is a crucial part of our mental capability, but traditional information visualization approaches fail to consider it. In an attempt to fill this research gap, we propose a new information visualization method that integrates a user’s visual perception and his/her ergonomic perception. Specifically, the approach enables users to manipulate an information space to follow the behavior of human movement in the 3D world with six degrees of freedom. Users can move an information space along the x-, y-, and z-axes as well as rotate it-giving six degrees of freedom. Manipulating the information space in this way provides users with a more comprehensive understanding of the space, and integrates their visual capability and ergonomic perception so that they can fully utilize their mental capabilities.     

Thermodynamic optimization of the As–S system

Literature review, critical assessment and thermodynamic modeling of the liquid and solid phases in the As–S system are presented. A set of optimized model parameters was obtained to reproduce previously published experimental data. The literature data included enthalpies of formation, heat capacity, vapor pressure and phase equilibrium data. A significant discrepancy among different sets of literature data was revealed. The model for the liquid phase was developed within the framework of the Modified Quasichemical Model (MQM) in pair approximation. The resulting set of model parameters was merged and tested within a larger multicomponent thermodynamic database for pyrometallurgical copper, lead and recycling industrial operations.     

QoE–aware optimization of multimedia flow scheduling

This paper deals with the subjective quality maximization problem when scheduling multimedia traffic flows in a shared channel. In order to quantify such user satisfaction a utility function dependent on flow transfer delay is used. In this context, we formulate the Quality of Experience aware resource allocation optimization problem as a Markov Decision Process. This model is analytically unsolvable in general, and as an approximate solution we develop a simple and tractable index rule based on Gittins approach, originally aimed just at minimizing mean flow delay. As concluded from simulation results, when evaluating subjective quality performance this novel index rule proposal outperforms the most relevant existing scheduling disciplines.     

Trajectory tracking control of a pneumatically actuated 6-DOF Gough–Stewart parallel robot using Backstepping-Sliding Mode controller and geometry-based quasi forward kinematic method

In this paper, the trajectory tracking control of a 6-DoF pneumatically actuated Gough–Stewart parallel robot is investigated. The dynamic model of each link, comprising of a pneumatic actuator and a proportional electrical valve is extracted with the aim of obtaining the corresponding state space representation of the pneumatic system. Unknown parameters of the dynamic model consisting friction force of the cylinder and parameters of the proportional valve are identified by employing genetic algorithm. Position control of the pneumatic actuator is performed based on Back-Stepping Sliding Mode controller according to the dynamic model of the system. As such trajectory tracking control is performed for different trajectories by employing a rotation sensor and calculated position based on joint space and task space simultaneously. Desired sinusoidal trajectories with pure motions are tracked with root mean square error of the pure translations and rotations lower than 0.85 (cm) and 1.9 (deg), respectively. The results reveal that the trajectory is tracked by the Back-Stepping Sliding Mode controller properly. This shows the efficiency of the control strategy and the proposed method for calculating the position of the end-effector.     

Thermodynamic optimization of the Ni–Al–Nd ternary system

Thermodynamic optimization of the Ni-Al-Nd ternary system and Al-Nd binary systems have been conducted in the present work. A self-consistent set of thermodynamic parameters for the Al-Nd binary system and Ni-Al-Nd ternary system have been optimized using CALPHAD method. Isothermal sections at 600 and 700 °C as well as the liquidus projection have been reproduced. Isopleths with 93 at% Al, 9 at% Ni and 3 at% Nd, have been calculated also. The calculated thermodynamic and phase equilibria data for both the binary and the ternary systems agree fairly well with the experimental data. This work can be used as multi-component thermodynamic database for Ni-based alloys.     

In situ colorimetric detection and mixing of glucose–enzyme droplets in an open-surface platform via Marangoni effect

Precise detection of glucose concentration in blood is critical in health monitoring and medical research. This paper describes a novel approach for enzymatic glucose sensing (glucose oxidase based) using thermal gradient in an open-surface platform. In order to obtain glucose concentration, droplets of enzyme and glucose with various concentrations are dispensed on a thin layer of fluorinert oil. By engineering the location of the droplet on the fluid surface and controlling the surface temperature drop of the fluid, surface deformation is created with fluid recirculating due to Marangoni convection. The surface deformation allows the microliter droplets to collide and mix at the hot spot. Image processing of the colorimetric reaction of the glucose and enzyme allows accurate determination of glucose concentration. The designed biosensor offers high repeatability, and concentration is measured within ±9.5 % of standard absorptiometry method. Contact-free manipulation of droplets, in situ measurement of glucose concentration, fast response time and high sensitivity are the key advantages of this device.