Workspace Analysis Research Articles

Workspace analysis of an underconstrained cable-driven parallel robot with four cables

Workspace analysis of an underconstrained cable-driven parallel robot with four cables

Output- and state-dependent Riccati equation: An output feedback controller design

An output- and state-dependent Riccati equation (OSDRE) is investigated for a set of coupled k-th order ordinary differential equations (ODEs) in the framework of nonlinear optimal control, in terms of stability, optimality, and application. A state-feedback control is a dominant part of the SDRE in the literature in comparison with an output feedback design. The output feedback design removes outer layers of kinematics or coordinate transformations in some systems and directly controls the output dynamics. This enables efficient control over many systems in which there is an indirect relation between outputs and states such as robots, mobile manipulators, autonomous vehicles, unmanned aerial vehicles, etc. To present the OSDRE, the co-state vector of the optimal control must include both state and output vector; and then the optimality conditions result in a control law and a Riccati equation, which are derived based on the output vector. The application of the OSDRE is devoted to the control of free-floating space manipulators (FFSM). The end-effector position of the FFSM is a function of mobile base coordinates (position and orientation) that are not actuated due to the free-floating condition. Then the output feedback SDRE directly controls the end-effector and guides the mobile base to provide enough reaction force/moment to push the gripper towards the desired end-point. So, the workspace analysis is crucial since the motion of the end-effector depends on the distance and configuration between the initial and final conditions. Simulation results for a mathematical third-order coupled ODE and a three-link FFSM confirm success in the control of the output dynamics. It was shown that the output of the mathematical model successfully tracked the desired output regardless of the individual state regulation. The FFSM has also tracked the desired output position with an accuracy of 0.02% of the travel distance.

Architectural design and development of an upper-limb rehabilitation device: a modular synthesis approach

Purpose Enormous assistance is required during rehabilitation activities, which might result in a variety of complications if performed manually. To solve this issue, several solutions in the form of assistive devices have been presented recently. Another issue highlighted is the lack of kinematic compatibility in low degrees-of-freedom (dof) systems. The proposed approach of developing a human-motion-oriented rehabilitation device deals with the problem through hybrid architectures. A novel modular synthesis approach is used for the purpose to induce generality in the design process. Materials and methods Using a modular strategy, three planar hybrid configurations are generated for two-dof mechanisms for supporting flexion/extension motion. Three such architectures are optimally synthesised and kinematically analysed over the entire workspace. A Genetic Algorithm (GA) is used to synthesise the architecture parameters optimally. Moreover, the outcomes are evaluated against a set of seven poses and posture locations of the wrist to choose the most suitable configuration among the others. Subsequently, kinematic compatibility is analysed for the coupled system – formed by the selected architecture and the human arm – while wearing the proposed mechanism. Results According to the findings of optimal synthesis, workspace and singularity analysis, configuration-III is capable of achieving the optimal postures for all task space locations (TSLs). Further, the work modifies the design by attaching additional three revolute passive joints for correcting misalignment concerns using coupled mobility analysis. Conclusion The modular strategy for hybrid architectures and the subsequent mobility analysis provides an algorithmic framework for synthesising a task-based rehabilitation device. IMPLICATIONS OF REHABILITATION Manual physiotherapy is reported as repeated task, expensive and time-consuming, and considered stressful for the therapist or assistants to provide one-on-one physiotherapy to each patient in the traditional method. Robotic rehabilitation is, therefore, a viable option. In the several reported works on robotic rehabilitation exoskeletons, misalignment of the exoskeleton and the human motion is considered an open challenge. Normally, it is being managed through large number of degrees of freedom, which is certainly expensive and complex in control. The proposed approach of developing a human-motion-oriented rehabilitation device deals with the problem through hybrid architectures and modular strategy to develop them. While focusing upon the emulation of natural human motion trajectory, the compatibility of orthotic joint and human joint motion needs attention. As biological joint possesses complex kinematic characteristics, closed-loops are used in the design. Overall, a complete framework of a cost effective low-dof rehabilitation device is proposed and detailed through coupled analysis.

Mechanism design and workspace analysis of a hexapod robot

Mobile robots are essential for inspection, surveillance, and disaster relief. The legged robot can adapt to challenging terrains such as stairs and debris. The hexapod robot has better stability, payload capability, and fault-tolerant ability than the biped and quadruped robot. This paper proposes a novel hexapod robot composed of two walking platforms and an actively actuated waist joint. The mechanical topology of the robot is determined by comprehensively considering the walking stability, energy consumption, and operating dexterity. The modular leg mechanism is selected by analyzing the reachable workspaces of three typical 2-DOF parallel leg mechanisms. Besides, the analytical method of calculating the reachable workspace of the robot body with shank-ground interferences is studied for the first time, which helps to enhance the efficiency of foothold selection. The feasibility of integrating the analytical workspace in obstacle-surmounting is verified by climbing a 45-degree staircase. Simulations including avoiding obstacles, spot turning, and climbing a staircase are carried out to verify the correctness of the theoretical analysis. A robot prototype is fabricated, and the field experiments corroborate the results of the computational simulations.

Topological design and kinematic analysis of a novel hybrid space control mechanism

In order to meet the demand of space mechanism for Chinese space station, a novel hybrid space control mechanism is designed. The hybrid space control mechanism is made up of a serial mechanism and a parallel mechanism. The serial mechanism realizes large workspace and the parallel mechanism provides excellent position accuracy. The physical prototype of the novel hybrid space control mechanism is built up, and the mobility and foldability of the serial mechanism are exhibited. Its kinematic and workspace analysis are carried out, which correctness is verified through comparison with simulation results. The aforementioned research laid a solid foundation for future study about the hybrid space control mechanism.

Workspace and Accuracy Analysis on a Novel 6-UCU Bone-attached Parallel Manipulator

With the increasingly more extensive application of the medical surgical robot in the clinic, higher requirements have been put forward for medical robots. The bone-attached robot, a popular orthopedic robot in recent years, has a tendency of miniaturization and refinement. Thus, a bone-attached parallel manipulator (PM) based on 6-UCU (universal-cylindrical-universal) configuration is proposed, which is characterized by small volume, compact structure, high precision and six-dimensional force feedback. To optimize the structure and make it more compact, the workspace of the 6-UCU PM is analyzed based on the analysis of three kinds of constraint, and workspace model is established through spherical coordinate search method. This study also analyzes the influence of structural parameters on workspace, which may contribute to improving the efficiency of design and ensuring small-sized robots possess relatively large workspace. Moreover, to improve the motion accuracy, an error modeling method is developed based on the structure of 6-UCU PMs. According to this established error model, the output pose error curves are drawn using MATLAB software when the structure parameters change, and the influence of the structure and pose parameters change on the output pose error of PMs is analyzed. The proposed research provides the instruction to design and analysis of small PMs such as bone-attached robots.

2PPaRR-2PPaRU: Design, analysis, and optimization of a new 3T1R parallel manipulator with rotational pitch motion

A new 3T1R parallel manipulator (PM) 2PPaRR-2PPaRU with rotational pitch motion is proposed in this paper. In such a mechanism, there are four limbs connected to the moving platform (MP) through several revolute joints and universal joints, and all actuated joints are prismatic joints with an axis along a vertical direction. Mobility and motion characteristics are verified by constraint screw theory. The inverse kinematic solutions and the singularity configurations are derived through kinematic analysis. Next, the workspace analysis and the connection between [Formula: see text] and the volume of the reachable workspace are performed. The local motion/force transmission index is selected to evaluate the local transmission performance of 2PPaRR-2PPaRU PM. Finally, the global motion/force transmission index and the volume of reachable workspace are considered simultaneously to optimize the structural parameters. The 2PPaRR-2PPaRU PM with improved local transmission performance and reachable workspace has been achieved after optimization.

Design, modeling, and workspace analysis of an extensible rod-driven Parallel Continuum Robot

Rod-driven Parallel Continuum Robots (PCR) are a class of continuum robots (CR) that possess the potential to combine advantages of parallel structure into CRs. However, rod-driven PCRs usually have a limited workspace due to the designed constraints, which restrict the exploitation of their potentials. This paper presents the design, statics modeling, and workspace analysis of a rod-driven PCR for extending its motion range. The proposed design has 5 degrees of freedom (DoFs) for manipulation by reasonably arranging constraints and kinematic pairs. We employ a known modeling method based on the Cosserat equations and a variant of the Levenberg-Marquardt method to solve the model, making the PCR with multi-intermediate constraints approach real-time applications. The design's feasibility is experimentally verified on a developed prototype. We then present a numerical procedure for analyzing partial workspace efficiently. Our results highlight the design's feature to enlarge workspace, of which a set of configurations can reach about 64% of the cube volume of max arm length, and an average of 4 s solving spatial paths, with max errors of 2.5% of max arm length.

Ray-based cable and obstacle interference-free workspace for cable-driven parallel robots

A low computational cost and generalized ray-based interference-free workspace (IFW) analysis method for arbitrary types of CDPRs is proposed in this paper. This work extends the existing ray-based method (RBM) properties to solve the ray-based workspace under cable–cable and cable–obstacle interference-free conditions. The proposed method covers a broader range of obstacles defined by polynomial surfaces than existing methods. After determining the IFW, the ray-based workspace under different workspace conditions can be combined. Path planning can be performed similarly to the existing point-wise approach but with guaranteed connectivity inside the available workspace. Meanwhile, the proposed approach can simultaneously handle different CDPRs with translation and orientation.

Workspace Analysis of Cable-driven Continuum Manipulator with Cable-constrained Synchronous Rotating Mechanism

In this paper, a cable-driven continuum manipulator with cable-constrained synchronous rotating mechanism (CCSRM) is studied. The purpose of this paper is to give the workspace for the cable-driven continuum manipulator, where the friction effects and the allowable range of cable tension are considered. The problem of solving workspace is transformed into a linear programming problem, which is solved by dual-simplex algorithm. On this basis, the influence of the pre-tightening force of the connecting cable on the workspace is analyzed. In addition, the tension of the motor on each driving cable is optimized to minimize the control error. Finally, the load range that the manipulator can withstand within the workspace is analyzed.

Workspace analysis and optimal design of dual cable-suspended robots for construction

Given their advantages of large workspaces and high payload-to-weight ratios, cable-driven parallel mechanisms have great potential for use in on-site autonomous construction. This paper proposes a configuration containing two cable-suspended robots driven by eight cable pairs (four cable pairs each), which form parallelograms, to perform construction efficiently in terms of time and space. A core issue of this system is the collision problems that occur in dynamic construction processes. The use of the distance between two spatial line segments is proposed to calculate collision detection, and the wrench-feasible workspace is examined to analyze the collision-free buildable workplace. The operation mode of dual cable-suspended robots for construction is discussed herein. Further, the design variables of the dual cable-suspended robot are optimized using multi-objective particle swarm algorithm to ensure a sufficiently large collision-free buildable workspace with suitable scale and payload of the frame of the cable robots for construction.

Kinematic and workspace analysis of redundant heterogeneous robot for flat slag of high temperature furnace

Kinematic and workspace analysis of redundant heterogeneous robot for flat slag of high temperature furnace

Development and Validation of a Mixed Reality Configuration of a Simulator for a Minimally Invasive Spine Surgery Using the Workspace of a Haptic Device and Simulator Users.

Most surgical simulators leverage virtual or bench models to simulate reality. This study proposes and validates a method for workspace configuration of a surgical simulator which utilizes a haptic device for interaction with a virtual model and a bench model to provide additional tactile feedback based on planned surgical manoeuvers. Numerical analyses were completed to determine the workspace and position of a haptic device, relative to the bench model, used in the surgical simulator, and the determined configuration was validated using device limitations and user data from surgical and nonsurgical users. For the validation, surgeons performed an identical surgery on a cadaver prior to using the simulator, and their trajectories were then compared to the determined workspace for the haptic device. The configuration of the simulator was determined appropriate through workspace analysis and the collected user trajectories. Statistical analyses suggest differences in trajectories between the participating surgeons which were not affected by the imposed haptic workspace. This study, therefore, demonstrates a method to optimally position a haptic device with respect to a bench model while meeting the manoeuverability needs of a surgical procedure. The validation method identified workspace position and user trajectory towards ideal configuration of a mixed reality simulator.

Reachable workspace with real-time motion capture feedback to quantify upper extremity function: A study on children with brachial plexus birth injury

Clinical upper extremity (UE) functional assessments and motion capture measures are limited to a set of postures and/or motions that may provide an incomplete evaluation of UE functionality. Reachable workspace analysis offers a more global assessment of UE function, but is reliant on patient compliance with instructions and may result in underestimates of a patient’s true UE function. This study evaluated a clinical tool that incorporates real-time visual feedback with motion capture to provide an innovative means of engaging patients to ensure a ‘best effort’ quantification of their available UE workspace. Reachable workspace for 10 children with brachial plexus birth injury was collected with and without real-time feedback on the affected and unaffected limbs. Real-time feedback consisted of subjects reaching for virtual targets surrounding their physical space using a virtual cursor controlled by the real-time location of their hand. Real-time feedback resulted in significantly greater workspace in multiple regions on both the affected (3/6 octants; mean differences 10.8%-20.0%) and unaffected (6/6 octants; mean differences 24.3%-40.0%) limbs. Use of real-time feedback also yielded significant interlimb differences in workspace across more regions (4/6 octants; mean differences 29.0%-39.9% vs. 1/6 octants; mean difference 17%). Finally, real-time feedback resulted in significant interlimb differences in median reach distance across more regions (4/6 octants; mean differences 7.5%-44.8% vs. 1/6 octants; mean difference 11.2%). A reachable workspace tool with real-time feedback results in more workspace and UE function recorded and offers a highly visual and intuitive depiction of a patient’s UE abilities.

Delta Tipi Bir Paralel Robotun Hareket Kontrolü ve Analizi

Parallel robots have natural advantages for many applications thanks to their high rigidity, high accuracy, low inertia of the moving parts and lightness, etc. The goal of this study has performed motion control, the kinematical, and workspace analyses of a Delta-type parallel robot with 3 degrees of freedom (3-DOF). Delta-type parallel actual parameter values were used in the motion control and analyses. Forward and inverse kinematics analysis, as well as workspace analysis of the robot, were carried out. In addition, the motion control of the robot is actualized in Cartesian space. In order for the delta-type parallel robot to have zero oscillation and to have a robust structure against external disturbances, the Sliding Mode Control (SMC) method was preferred. As a result, the motion control, kinematics, and workspace analyses of the delta-type parallel robot were realized and examined.

Kinematic and Workspace Analysis of the Master Robot in the Sinaflex Robotic Telesurgery System.

Robotic telesurgery systems, including master and slave robots, have emerged in recent years to provide benefits for both surgeons and patients. Surgeons use the master manipulator to navigate the slave robot. The Sinaflex telesurgery system introduced recently by Sina Robotics and Medical Innovators Co., Ltd. consists of two main subsystems: master robotic surgery console and slave surgery robots. As the surgeon use the master robot's handles to control the slave surgery robots, it is important for the master robot to provide the ergonomic postures for the surgeon and also providing a large enough workspace and good manipulability for the surgeon to control it. So in this paper, workspace, manipulability and isotropy of each handle at the master robot of the Sinaflex telesurgery system are analyzed. To this end, the kinematic of the master manipulator is derived, and its Jacobian is calculated. Using the simulation environment, the workspace of the master handle is obtained and drawn. The manipulability of the robot for each points of the workspace is computed. According to the results attained from the simulation study, the most manipulability values lie between 0.1 and 0.9 where it is greater than 0.44 for more than 50% of the whole workspace points of the end effector, which is as large as 574×484×560 mm.

Erratum to “Comparative study on the reachable workspaces of regular and irregular axially symmetric hexapod robots”

Six-legged hexapod walking robots are well-known for their intrinsic stability during navigation and 6-DoF object manipulation. The robot must be operated under a stable workspace envelope to attain effective manipulation. The structural parameters of the robot dramatically influence the characteristics of the workspace. Most studies analyze the workspace only by varying the leg parameter of the robot, maintaining the base configuration constant. This study aims to investigate the effect of change in the base plate characteristics on the workspace for an axially symmetric hexapod robot with cyclic and elliptical configurations. Superimposing the lateral 2D workspace of each pair of legs evolved to obtain a 3D workspace. The quantitative data analysis of the workspace shows that the cyclic configuration has an average increase of 23.74 %, and the elliptical configuration has a reduction of 1.97 % reachable workspace volume compared with regular hexapods. Furthermore, regular, cyclic, and elliptical hexapods are fabricated and validated with the selective workspace analysis data to reinforce the results. This study shows that the change in the hexagonal base plate configuration has a significant influence on workspace characteristics.

Computational design and workspace analysis of a passive motion-scaling mechanism based on pantograph for microsurgery

Abstract Robot-assisted surgery has been extensively applied in various microsurgical disciplines owing to its enhanced accuracy and dexterity based on the motion-scaling function between a hand and a surgical instrument. However, the surgical robot system developed thus far incurs high manufacturing costs and restricted compatibility due to the complicated control system, including many actuators and sensors. This paper proposes a novel passive mechanism for motion scaling based on the pantograph structure to resolve these drawbacks of robotic assistance devices. As a first step, a design configuration featuring gravity compensation and the duplication of directional motion is suggested. Subsequently, the geometric dimensions required to satisfy the surgical space and structural constraints are defined. Moreover, the mass of elements required to enable gravity compensation is calculated using moment equations. After determining the principal design parameters, the motion scaling of the proposed passive model is identified using a three-dimensional computer-aided design. In addition, for an extremely precise operation in microsurgery, the dynamic reaction force is expected to be constant in any location. Therefore, to investigate dynamic dexterity, the mathematical model is formulated based on the Lagrangian dynamic equation. Then, the dynamic workspace range is analysed from the determinant of the mass matrix. In addition, the analysis results are evaluated through comparative simulations in different workspace ranges; hence, a constant reaction force can be achieved only in the dynamic workspace range.

Teleoperated Puncture Robot System: Preliminary Design and Workspace Analysis

Teleoperated Puncture Robot System: Preliminary Design and Workspace Analysis

Infrared thermography for a quick construction progress monitoring approach in concrete structures

Construction progress monitoring ensures the construction project is consistent with the schedule and enables the detection of any deviations in the geometry and/or any variation in the schedule. The traditional progress monitoring requires specialized personnel to walk around on the construction site to manually collect data and verify the progress of activities, which is time consuming, costly and/or error prone. Image-based technology is effective for recording on-site data geospatially and chronologically. It has gained increasing attention in the construction field for progress monitoring, work space analysis and quality assurance. However, a notable downside of image processing is the light condition, particularly for noisy environments such as construction sites. Poor or undesirable ambient light conditions produce low quality images that significantly affect the accuracy of data extracted from related images and lead to a high level of errors. This paper presents an innovative approach based on thermal image analysis to overcome problems related to the image quality. Thirty preliminary tests and three case studies have been implemented to show the feasibility of the method. A range of improvement between 8 to 48% has been attained that confirms the great potential of thermal images to overcome the limitation of image-based approaches.