Shape Of Workspace Research Articles

A Three-Actuator Cable-Driven Parallel Robot With a Rectangular Workspace

Abstract In the realm of cable-driven parallel robots (CDPRs), the conventional notion entails that each cable is directly actuated by a corresponding actuator, implying a direct relationship between the number of cables and actuators. However, this article introduces a paradigm shift by contending that the number of cables should be contingent upon the desired workspace, while the number of actuators should align with the robot’s degrees-of-freedom (DoF). This novel perspective leads to an unconventional design methodology for CDPRs. Instead of commencing with the number of actuators and cables in mind, we propose an approach that begins with defining the required workspace shape and determines the requisite number of cables. Subsequently, an actuation scheme is established where each actuator can drive multiple cables. This process entails the formulation of a transmission matrix that captures the interplay between actuators and cables, followed by the mechanical implementation of the corresponding cable-pulley routing. To illustrate this approach, we provide an example involving a 2-DoF CDPR aimed at covering a rectangular workspace. Notably, the resulting wrench-closure workspace (WCW) and wench-feasible workspace (WFW) of the proposed designs exhibit favorable comparisons to existing CDPRs with more actuators.

An Optimal Model for Allocation Readers with Grid Cell Size and Arbitrary Workspace Shapes in RFID Network Planning

RFID Network Planning (RNP) is the problem of deploying RFID readers within a workspace so that each tag can be covered by at least one reader. The objective of RNP is to determine the optimal positions of readers while satisfying certain constraints, such as maximum coverage, minimal interference, load balance among readers, etc. However, most previous studies considered the workspace rectangular or square and assumed a fixed number of readers. They then employed some heuristic methods to find the optimal reader positions. This approach is not practical because the workspace can have any shape, and an approach adaptable to the actual shape of the workspace is needed. This paper proposed an improved adaptive model considering the workspace shape, called RNP-3P. The objectives of RNP-3P are to minimize the number of readers, maximize coverage area, minimize interference, and achieve load balance. RNP-3P optimizes the problem in three phases: Phase 1 involves modeling the workspace with grid cell size, Phase 2 determines the objective function, and Phase 3 proposes the iGAPO algorithm to optimize the number and positions of readers within the workspace. Simulation results demonstrate that the proposed model is more effective compared to other heuristic methods.

Implementing the Analytical Reachable Body Workspace for Calculating the Obstacle-Crossing Ability of a Hexapod Robot

Abstract Calculating the maximum obstacle-crossing ability accurately at the mechanism design stage can better ensure that the manufactured robot prototype meets the predefined indices. The obstacle-crossing task of the legged robot is achieved by the collaborative movement of the leg and body. The reachable workspace constrains the spatial movement boundary of the foot tip and the robot body. The reachable workspace of the foot tip is invariant, while the shape and volume of the reachable body workspace vary with the supporting footholds. In this study, the body movement is modeled as a six-bar mechanism, and the reachable body workspace means the reachable region of the specified target point located on the moving platform of the six-bar mechanism. Unlike the previous work, the analytical method of calculating the reachable workspace for the target point outside the moving platform, named the external target point, is further studied. The influence of supporting footholds and shank-ground interference on the reachable body workspace is considered. The selection of supporting footholds, the collaborative motion sequences of the robot body and legs, and the determination of the maximum ability for crossing a ditch and climbing a step are demonstrated as cases of implementing the analytical reachable body workspace for the internal target point and the external target point, respectively. Finally, simulations verify the correctness of the theoretical analysis.

Haptify: A Measurement-Based Benchmarking System for Grounded Force-Feedback Devices

Grounded force-feedback (GFF) devices are an established and diverse class of haptic technology based on robotic arms. However, the number of designs and how they are specified make comparing devices difficult. We thus present Haptify, a benchmarking system that can thoroughly, fairly, and noninvasively evaluate GFF haptic devices. The user holds the instrumented device end-effector and moves it through a series of passive and active experiments. Haptify records the interaction between the hand, device, and ground with a seven-camera optical motion-capture system, a 60-cm-square custom force plate, and a customized sensing end-effector. We demonstrate six key ways to assess GFF device performance: workspace shape, global free-space forces, global free-space vibrations, local dynamic forces and torques, frictionless surface rendering, and stiffness rendering. We then use Haptify to benchmark two commercial haptic devices. With a smaller workspace than the 3D Systems Touch, the more expensive Touch X outputs smaller free-space forces and vibrations, smaller and more predictable dynamic forces and torques, and higher-quality renderings of a frictionless surface and high stiffness.

User-oriented Natural Human-Robot Control with Thin-Plate Splines and LRCN

We propose a real-time vision-based teleoperation approach for robotic arms that employs a single depth-based camera, exempting the user from the need for any wearable devices. By employing a natural user interface, this novel approach leverages the conventional fine-tuning control, turning it into a direct body pose capture process. The proposed approach is comprised of two main parts. The first is a nonlinear customizable pose mapping based on Thin-Plate Splines (TPS), to directly transfer human body motion to robotic arm motion in a nonlinear fashion, thus allowing matching dissimilar bodies with different workspace shapes and kinematic constraints. The second is a Deep Neural Network hand-state classifier based on Long-term Recurrent Convolutional Networks (LRCN) that exploits the temporal coherence of the acquired depth data. We validate, evaluate and compare our approach through both classical cross-validation experiments of the proposed hand state classifier; and user studies over a set of practical experiments involving variants of pick-and-place and manufacturing tasks. Results revealed that LRCN networks outperform single image Convolutional Neural Networks; and that users' learning curves were steep, thus allowing the successful completion of the proposed tasks. When compared to a previous approach, the TPS approach revealed no increase in task complexity and similar times of completion, while providing more precise operation in regions closer to workspace boundaries.

Conceptual Design and Simulation of Cable-driven Parallel Robot for Inspection and Monitoring Tasks

The paper deals with the conceptual design of cable-driven parallel robot which will be used for inspection and monitoring tasks in production process. The reason and need of vision based control of the production process is described in the introduction. Furthermore, mechanisms with parallel kinematic structure are described, as well as their usage in industry and sports broadcasts. On that basis, there is proposed the conceptual design of the cable driven parallel robot (CDPR) for desired task of visual monitoring of production line. Finally, there is proposed a simulation of designed robotic system and workspace shape analysis.

Workspace Analysis of a Mobile Manipulator with Obstacle Avoidance in 3D Printing Tasks

The knowledge of the workspace for a robotic system on construction sites represents an essential resource to ensure the work progress, guarantee the safety of the construction tasks, and avoid robot damage. Despite the dramatic development of 3D printing technologies with robotic systems in recent years, these are still several challenges to consider, such as the size of the printing profile and obstacles in the construction site. This work presents the results from evaluating the workspace of a mobile manipulator in 3D printing tasks on construction sites. The methodology analyses the printing workspace based on the workspace of the mobile manipulator, considering fixed obstacles and possible collisions between the robot and obstacles during 3D printing tasks. The results showed that the shape of the printing profile defined as a building element changes the shape of the printing workspace. Furthermore, the obstacles in the construction site and height variation of the printing profile cause changes in the displacement of the robotic platform and values of rotation of its joints, which also modify the shape of the printing workspace.

Position, velocity, and acceleration analyses of a reconfigurable parallel mechanism (hexapod) equipped with a single motor

Parallel mechanisms represent complex mechanical systems, which possess several important properties: high load capacity, increased accuracy, multitasking, and high reliability. A class of parallel mechanisms with a circular guide is known in engineering technique. Their design properties provide the end-effector with an increased rotational angle around one of the axes, as well as the ability to manipulate heavy objects. Reconfigurable parallel mechanisms (RPMs) form another class of mechanisms with several distinct features. Such devices can vary their motion pattern, change workspace shape and dimensions, and move avoiding singular configurations. This study provides a novel variation of a reconfigurable parallel mechanism (hexapod) with a circular guide, in which the end-effector movement is controllable by a single drive. The study presents a virtual prototype of this hexapod and shows the solution of the forward and inverse problems on positions, velocities, and accelerations. In addition, the study provides the singularity analysis.

Improving Robotic Manipulation Without Sacrificing Grasping Efficiency: A Multi-Modal, Adaptive Gripper With Reconfigurable Finger Bases

This work proposes a framework that improves the dexterous manipulation capabilities of two fingered grippers by: i) optimizing the finger link dimensions and the interfinger distance for a given object and ii) analyzing the effect of finger symmetry and the distance between the finger base frames on their manipulation workspaces. The results of the workspace analysis motivate the development of a multi-modal, adaptive robotic gripper. In particular, the finger link lengths optimization problem is solved by a parallel multi-start search algorithm. The optimal link lengths are then used for the workspace analysis. The results of the analysis demonstrate that different inter-finger distances lead to completely different workspace shapes and that the ratio defined by the area of the optimized workspace (nominator) and the union of all workspaces (denominator), is always significantly less than 1. This means that the area of the union of all workspaces is always larger than the area of the “optimized” workspace. Based on these results the proposed robotic gripper is equipped with reconfigurable finger bases that vary the inter-finger distance as well as with selectively lockable robotic finger joints, offering an increased dexterous manipulation performance without sacrificing grasping efficiency. The device is considered multi-modal as it can be used both as a parallel jaw gripper and as an adaptive robotic gripper.

Workspace analysis in the design parameter space of a 2-DOF spherical parallel mechanism for a prescribed workspace: Application to the otologic surgery

During Otologic surgery, and more broadly during microsurgery, the surgeon encounters several difficulties due to the confined spaces and micro-manipulations. The purpose of the paper is to design a robot with a prescribed regular workspace shape to handle an endoscope to assist the Otologic surgery. A spherical parallel mechanism with two degrees of freedom is analysed in its design parameter space. This mechanism is composed of three legs (2USP-U) to connect the base to a moving platform connected to a double parallelogram to create a remote center of motion (RCM). Its kinematic properties, i.e. the singularity locus and the number of direct kinematic solutions, are investigated. For some design parameters, non-singular assembly modes changing trajectories may exist and have to be investigated inside the prescribed regular workspace shape. Two sets of design parameters are presented with their advantages and disadvantages.

A highly intuitive and ergonomic redundant joint master device for four-degrees of freedom flexible endoscopic surgery robot.

Studies have been conducted on slave-specific master devices with a similar kinematic structure to the slave to enhance intuitiveness. However, for the four-degrees of freedom (DOFs) slave of a flexible endoscopic surgery robot, only four DOFs in the master device causes low ergonomic performance. To enhance ergonomic performance, a second yaw joint was added as a redundant joint after considering the range of wrist motion and the workspace shape. Three experiments were performed to compare the intuitiveness and ergonomic performance of the proposed device with four-DOFs slave-specific and six-DOFs general-purpose master devices. Significant differences were observed in terms of intuitiveness performance between the slave-specific and the general-purposed master device. On the other hand, there was no significant difference in ergonomic performance between the master devices with redundant joint. Compared with a general-purpose master device, the proposed one exhibited noticeably improved intuitiveness performance and comparable ergonomic performance.

Algorithm to Determine the Volume and Shape of Constant Orientation Workspace for a 2(3-RRPS) Parallel Robot

This article describes a geometrical method used to analyze the workspace for parallel robot 2(3-RRPS). The algorithm, implemented in a CAD software, determines the workspace for a constant orientation. Mechanical restrictions of the robot and its influence in the workspace are considered. Actuator stroke, angular stroke of the joints in the base, angular travel of the ball joints on the platform, closing restriction and chain interference are the restrictions considered. Applications of the method are presented, such as the characterization of the workspace, the graphic obtaining of it for a range of orientations and the analysis of the effect that the joint limits have on it. Determination of the workspace for orientations range, shape parameters, quantification of the effect of a restriction on the volume, synthesis and dimensional optimization of the mechanism are examples presented to show the potentiality of the algorithm.

Kinetostatic Analysis and Actuation Strategy of a Planar Tensegrity 2-X Manipulator

Abstract A planar tensegrity manipulator made of two X-mechanisms in series is studied in this paper. Contrary to a classical 2-R linkage, the proposed architecture does not contain elements subject to bending and it can be driven with remote actuation and cables in an antagonistic way. Accordingly, it is an interesting candidate for the design of lightweight manipulators with variable stiffness suitable for safe interactions. On the other hand, its kinematics is more challenging because of a variable instantaneous center of rotation of the X-mechanisms. First, the inverse kinematic problem is solved using an adequate methodology, the singularities are determined, and the workspace shape is analyzed as a function of the design parameters. Then, two actuation schemes are studied and the wrench feasible workspace is analyzed for each of them. The second actuation scheme provides a larger wrench feasible workspace and allows for stiffness control.

Determining the effect of multifunctional partitions on noise level at "Open space" offices

Multifunction partitions and their influence on noise levels were explored. It was emphasized that the existing systems of classification of building partitions explore them based on the convenience of their use, material, design, etc. At the same time, not enough attention was paid to their impact on the indicators of a decrease in noise levels in office premises. Partitions are made of different materials, having different properties; they are different in shape and enclosure of premises or workspace at different distances from the floor. In such cases, there arises a complicated problem of selecting certain types of partitions, which, as shown in the research, make it possible to solve the problem of optimizing working conditions and reduce the negative effect of noise on the health of employees. The performed research showed that the set problem of noise reduction through the use of partitions can be solved. The factors that should be especially taken into consideration include the height of a partition (degree of enclosure of the height of premises by a partition), material of partitions, existence of technological openings and the geometry of their location. It was revealed that double-layer walls, made of heavy materials (density ≈2,500 kg/m 3 ) and 100 % premises enclosure by height, can reduce the noise level by 2–3 times (from 90 dBA to 30–45 dBA). Glass partitions (glass pipes) of moderate heaviness (≈1,200 kg/m 3 ) reduce noise by 1.5–1.6 times. If enclosure of premises is not complete or there are openings, ventilation shafts, etc., the effect of influence of partitions decreases considerably, reducing it almost to zero. Significant influence of partitions takes place in the frequency range of 200–3,000 Hz at noise level of 40–60 dBA. Noise was explored in the premises of the Open space type, where various options of partitions were applied (glass pipes in metal casings, ceramic panels, foam plastic panels). The research found that partitions can have a significant impact on noise indicators, but only on condition of complete enclosure of premises by height, closed doors and construction channels in walls. It was established that the material of partitions does not affect noise indicators if the degree of premises enclosure is not complete (less than 100 %). The studies proved the relevance of scientific substantiation of partitions’ application and of determining the relations of premises enclosure with the factors that affect employees with a view to improving their working conditions. Improvement of working conditions, in turn, will make it possible to decrease professional diseases, minimize turnover, and increase work efficiency

Workspace, joint space and singularities of a family of delta-like robot

This paper presents the workspace, the joint space and the singularities of a family of delta-like parallel robots by using algebraic tools. The different functions of SIROPA library are introduced, which is used to induce an estimation about the complexity in representing the singularities in the workspace and the joint space. A Gröbner based elimination is used to compute the singularities of the manipulator and a Cylindrical Algebraic Decomposition algorithm is used to study the workspace and the joint space. From these algebraic objects, we propose some certified three-dimensional plotting describing the shape of workspace and of the joint space which will help the engineers or researchers to decide the most suited configuration of the manipulator they should use for a given task. Also, the different parameters associated with the complexity of the serial and parallel singularities are tabulated, which further enhance the selection of the different configuration of the manipulator by comparing the complexity of the singularity equations.

Spectral Method to Investigate the Dependence of MHD Stability of an Electrolysis Bath on the Shape of the Skull

We consider the dependence of the MHD stability of an electrolysis bath on the shape of the work space. As the optimal work-space shape we choose the one that achieves the best separation of the eigenvalues in the spectrum of the multidimensional problem posed for the kinematic equation for the electrolytealuminum interface in a particular electrolysis bath.

Dimensional synthesis of the single-loop translational parallel manipulator PRRR-PRPU

The dimensional synthesis of translational parallel manipulators (TPMs) of type PRRR-PRPU is addressed by using an overall novel method. Addressing this design step on such TPMs is interesting for the scientific community since, in a previous paper, one of the authors showed that it has the following promising features: a single-loop not-overconstrained architecture with all the actuators on or near to the base, a simple position analysis, easy-to-find workspace boundaries, no constraint singularity, a type-II singularity locus that is a plane easy to keep far from the useful workspace, and a double infinity of isotropic configurations. The presented synthesis includes the analysis of isotropy and dexterity by local and global conditioning indexes, the useful workspace optimization, and the accuracy and stiffness analyses. The result is the identification of a normalized TPM of type PRRR-PRPU with performances that are comparable with those of commercial TPMs. The identified normalized TPM yields a set of actual TPMs with the same performances by changing the value of a reference geometric length. Also, the chosen shape of the useful workspace (i.e., a cuboid) matches the needs of many industrial applications.

Determination of the closed-form workspace area expression and dimensional optimization of planar parallel manipulators

SUMMARYOptimization is an important step in the design and development of a planar parallel manipulator. For optimization processes, workspace analysis is a crucial and preliminary objective. Generally, the workspace analysis for such manipulators is carried out using a non-dimensional approach. For planar parallel manipulators of two degrees of freedom (2-DOF), a non-dimensional workspace analysis is very advantageous. However, it becomes very difficult in the case of 3-DOF and higher DOF manipulators because of the complex shape of the workspace. In this study, the workspace shape is classified as a function of the geometric parameters, and the closed-form area expressions are derived for a constant orientation workspace of a three revolute–revolute–revolute (3-RRR) planar manipulator. The approach is also shown to be feasible for different orientations of a mobile platform. An optimization procedure for the design of planar 3-RRR manipulators is proposed for a prescribed workspace area. It is observed that the closed-form area expression for all the possible shapes of the workspace provides a larger solution space, which is further optimized considering singularity, mass of the manipulator, and a force transmission index.

Optimal dimension of redundant manipulator using the workspace density function

The redundant manipulator has been broadly applied to various fields including industrial manufacturing, surgical manipulation and space exploration by providing high accuracy, flexibility, and efficiency. Particularly, the technology is capable of improving the assembling precision while simplifying the operation in complicated environments, and therefore of intense interest in industrial settings. For manipulator design, space occupation optimizing is a critical step and parameters of the flexible area, the shape and size of workspace have been commonly employed to evaluate the optimizing performance. In this paper, by combining the Fourier transform with the convolution theorem, we presented a workspace density function of redundant manipulator to describe the shape and size of workspace and flexibility. The workspace density function is an evaluation criterion to select the optimal geometric parameters for the manipulator. Based on the workspace density function shown in the simulation results section, the optimal design parameters were obtained. The approach presented in this paper holds the potential to improve the redundant manipulator design.

Workspace Shape and Characteristics for Human Two- and Three-Fingered Precision Manipulation.

To study precision manipulation, which involves repositioning an object in the fingertips and is used in everyday tasks such as writing and key insertion, and also for domain-specific tasks such as small scalpel cuts, using tweezers, and hand soldering. In this study, the range of positions (workspace) through which 19 participants manipulated a 3.3-4.1 cm-diameter object are measured with a magnetic tracker. Each participant performed two conditions: a two-finger thumb-index finger condition and a three-finger thumb-index-middle finger condition. The observed workspaces, normalized to a 17.5 cm hand length, are small compared to free-finger trajectories; for the two-finger trials, 68% of points are within 1.05 cm of the centroid and 95% are within 2.31 cm, while the three-finger case shows a narrower distribution, with 68% of points within 0.94 cm of the centroid and 95% of points within 2.19 cm. The longest axis is a long thin arc in the proximal-palmar plane. Analysis of fingertip workspaces shows that the index fingertip workspace volume is the most linear predictor of object workspace (R(2) = 0.98). Precision manipulation workspace size and shape is shown, along with how the fingers are used during the manipulation. The results have many applications, including normative data for rehabilitation, guidelines for ergonomic device design, and benchmarking prosthetic and robotic hands.