Workspace Analysis Research Articles

Devising a method to analyze the current state of the manipulator workspace

This paper has proposed a program analysis method over the current state of the workspace of an anthropomorphic manipulator using the Mathcad software application package (USA). The analysis of the manipulator workspace helped solve the following sub-tasks: to calculate the limits of the grip reach, to determine the presence of "dead zones" within the manipulator workspace, to build the boundaries of the manipulator workspace. A kinematic scheme of the manipulator typically provides for at least five degrees of mobility, which is why in the three-dimensional Cartesian coordinate system the work zone boundaries represent the surfaces of a complex geometric shape. The author-devised method makes it possible to construct the projections of the boundaries of the manipulator's work zone onto the coordinate planes in the frame of reference associated with the base of the robot.
 Using Mathcad's built-in features makes it possible to effectively solve the above sub-tasks without wasting time developing specialized software. The Mathcad software application package provides for the possibility of a symbolic solution to the first problem of the kinematics of an industrial robot, that is, the program generates analytical dependences of the coordinates for special point P (pole) of the grip on the trigonometrical functions of the generalized coordinates. The resulting analytical dependences are used for kinematic and dynamic analysis of the manipulator.
 Special features in constructing mathematical models when using the Mathcad software application package have been revealed. Simulating the manipulator movement taking into consideration constraints for kinematic pairs, the drives' power, as well as friction factors, makes it possible to optimize the parameters of the manipulator kinematic scheme.
 An example of the analysis of the working space of an anthropomorphic manipulator with five degrees of mobility has been considered.
 The reported results could be used during the design, implementation, modernization, and operation of manipulators.

Structure synthesis of reconfigurable generalized parallel mechanisms with configurable platforms

This paper presents for the first time the idea of constructing reconfigurable generalized parallel mechanisms (GPMs) by integrating closed-loop kinematotropic linkages with configurable platforms. This leads to a novel way of constructing reconfigurable mechanisms. The geometrical configurations of the closed-loop kinematotropic linkages are analyzed in different working phases. By assembling kinematotropic linkages to moving platforms, the reconfigurable GPMs with configurable platforms are obtained. The kinematic constraints of the reconfigurable GPMs are investigated based on the algebraic structure properties of Lie group. Then a new class of reconfigurable GPMs with configurable platforms is synthesized. The variation of the configurable platforms leads to the reconfigurability of the resulting mechanisms. Consequently, the derived mechanisms can perform several motion models associated with different working phases of the kinematotropic linkages. Finally, a five degree-of-freedom reconfigurable GPM with configurable platform is selected as the typical example to perform the kinematic position analysis. Besides, the workspace analysis of the mechanism is carried out.

Retracted: Design and Workspace Analysis of a Parallel Ankle Rehabilitation Robot (PARR).

[This retracts the article DOI: 10.1155/2019/4164790.].

Kinematics and workspace analysis of 4SPRR-SPR parallel robots.

The 4SPRR-SPR parallel robot, which has considerable potential for application in the field of machining, is a novel closed-loop mechanism with a high rigid-weight ratio. Kinematics and workspace analyses of the 4SPRR-SPR parallel robot are key requirements for its application in machining. In this study, the inverse kinematics of the 4SPRR-SPR parallel robot is analyzed using a geometric method based on the mechanism arrangement of the robot. The forward kinematics model is derived by training the vector-quantified temporal associative memory (VQTAM) network, which originates from a self-organizing map (SOM). Furthermore, an improved algorithm is obtained by combining the locally linear embedding (LLE) and VQTAM methods. A boundary extraction algorithm for the workspace analysis of the parallel robot is proposed. The performance of the boundary extraction algorithm is analyzed and compared with that of a global search algorithm; the result indicates that the novel algorithm has the same computational accuracy in addition to higher efficiency. The workspace of the 4SPRR-SPR parallel robot is analyzed using the boundary extraction algorithm. Finally, the 3D model of the 4SPRR-SPR parallel robot is simulated using the ADAMS software to verify the reliability of the proposed algorithms. The simulation results demonstrate the effectiveness of the methods proposed in this study. In addition, the robot kinematics and workspace analysis methods described herein can be extended to other serial and parallel robots. This research provides a theoretical framework for trajectory planning of mechanisms, workspace optimization of robots, and robotic control.

A Backdrivable Kinematically Redundant (6+3)-Degree-of-Freedom Hybrid Parallel Robot for Intuitive Sensorless Physical Human–Robot Interaction

A novel backdrivable 3-[ <underline xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">R</u> ( <underline xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">R</u> R- <underline xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">R</u> RR)SR] kinematically redundant (6+3)-degree-of-freedom (DOF) spatial hybrid parallel robot with revolute actuators is proposed for low-impedance physical human–robot interaction. The kinematic model is developed based on the constraint conditions of the robot. It is shown that the type II (parallel) singularities can be completely avoided, thereby yielding a very large translational and orientational workspace. A workspace analysis is presented in order to demonstrate the capabilities of the robot. Mechanisms are then introduced to use the redundant DOF of the robot to operate a gripper with the robot actuators, which are mounted on or close to the base, thus reducing the inertia of the moving parts. The architecture of the robot makes it possible to use direct drive motors, thereby making the robot easily backdrivable and allowing the use of a very simple and effective controller. A prototype of the robot is then designed and built and the large workspace of the robot as well as the effortless physical human–robot interaction are demonstrated. The controller of the robot is then described, including a position control mode and a control mode for physical interaction, which does not require the use of a force/torque sensor or joint torque sensors. Because of its backdrivability and low moving inertia, the robot is particularly well-suited for physical human–robot interaction, as demonstrated in the accompanying videos.

Static workspace analysis of a multi-robot collaborative towing system with floating base

The static workspace of the multi-robot collaborative towing system with floating base was analyzed. The spacial configuration of the system was built, and the system was divided into three types according to the actuation. The kinematic and dynamic models of the floating base and the towing system were established, respectively, by using the Newton-Euler equation. Then the static workspace of the system was analyzed, and the specific steps to solve the workspace with the improved Monte Carlo method were obtained. Finally, the static workspaces of three types of systems were solved though actual simulation calculation, the simulation results show that the improved Monte Carlo method can get a workspace with higher precision compare to the traditional Monte Carlo method. Results of this study lay a basis for the subsequent trajectory plan, stability analysis and configuration optimization of the system.

Konfigurisanje virtuelnog prototipa BiSCARA robota

The paper presents the configuring of a virtual prototype BiSCARA robot generated on the basis of a fully developed kinematic model of the robot. The virtual CAD model developed in this way will enable its implementation in the Python graphical environment as an integral part of the open architecture control system developed on the basis of the presented kinematic model. The developed kinematic model included solving the inverse and direct kinematic problem, determining the Jacobian matrix and workspace analysis. Verification of the kinematic model, i.e. the configured virtual prototype of the robot, was performed by simulations of the end-effector tip movement according to the given program in a CAD / CAM environment.

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.

Kinematics and workspace analysis of a robotic arm for medical delivery robots

For the control of the robot arm of a medical delivery robot, firstly, the forward kinematic equations of this 7-degree-of-freedom redundant robot arm are constructed according to a modified D-H method. Secondly, the analytical solution of the inverse kinematics of the redundant robotic arm is solved using the parameterised arm angle. Thirdly, kinematic simulation experiments were carried out by gazebo and RVIZ in ROS to verify the correctness of the forward and inverse kinematic solution process. Finally, the Monte Carlo method was used to generate the point cloud map of the workspace of the redundant robotic arm within the allowed range of joints, and the boundary points of the workspace were extracted, and the extracted boundary points were fitted with least squares curves to find the workspace of the robotic arm, which laid the foundation for future research directions such as motion control and path planning of medical delivery robots.

Kinematics and workspace analysis of a robotic device for performing rehabilitation therapy of upper limb in stroke-affected patients

Exoskeleton robots generally have multi-functions and one such function is doing rehabilitation therapy in upper limb and lower limb in stroke-affected patients. A novel hybrid (serial-parallel) robot manipulator was proposed in this paper for rehabilitation of upper limb and its kinematics are studied systematically. This robot manipulator intends to perform wrist flexion, wrist extension, wrist radial deviation, wrist ulnar deviation, elbow flexion, elbow extension, elbow pronation and elbow supination motions. The contemporary mechanical designs especially the kinematic structure of upper limb exoskeleton robots have a unique feature that is, almost all of them use serial manipulators, and few others used parallel manipulators. The kinematic structure of the proposed robot is that of a hybrid manipulator (two parallel manipulators connected in series) which has 4-degrees-of-freedom. It is composed of an upper 3SPS-type parallel manipulator and 2SPR-type parallel manipulator connected in series. The Jacobian and Hessian Matrix method was used to derive the manipulator kinematic formula for solving the displacement, velocity and acceleration. A 3D model of the robotic arm was constructed and analyzed by simulation. The positioning workspace of manipulator was constructed and analyzed. The 3SPS-type parallel manipulator has good kinematic characteristics while performing wrist motions. The 2SPR-type parallel manipulator produced singular configuration, while performing the desired rehabilitation elbow motions, it was found to not be suitable for usage in performing rehabilitation therapy in stroke-affected patients.

Configuration Design and Workspace Analysis of Parallel Mechanism Driven by Eight Cables for On-orbit Assembly

Configuration Design and Workspace Analysis of Parallel Mechanism Driven by Eight Cables for On-orbit Assembly

Design and Workspace Analysis of a Differential Motion Rotary Style Breast Interventional Robot.

Introduction Magnetic Resonance Imaging has better resolution for soft tissue; at the same time, the robot can work in a stable manner for a long time. MRI image-guided breast interventional robots have attracted much attention due to their minimally invasive nature and accuracy. In this paper, a hydraulic-driven MRI-compatible breast interventional robot is proposed to perform breast interventional procedure. Methods First is the analysis of the design requirements of the hydraulic-driven MRI-compatible breast interventional robot, and then the design scheme is determined. Second, the three-dimensional model and the link frames are established. The workspace of the robot end point is solved by MATLAB/Simulink software. Then, the 3D printing technology is used to make a physical model of the MRI-compatible breast interventional robot. After assembly and debugging, the physical model is used for workspace verification, and the simulation result of the workspace shows that it is correct. Finally, the experimental research on the positioning error of the hydraulic drive is carried out, which established the theoretical foundation for the follow-up control research of the robot. Results The positioning error has nothing to do with the motion distance, speed, and length of the selected tubing. The errors are 0.564 mm, 0.534 mm, and 0.533 mm at different distances of 40 mm, 80 mm, and 120 mm, respectively. The errors are 0.552 mm, 0.564 mm, and 0.559 mm at different speeds of 3 mm/s, 5 mm/s, and 8 mm/s, respectively. The errors are 0.564 mm, 0.568 mm, and 0.548 mm for different lengths of 0.5 m, 1 m, and 1.6 m, respectively. Then, the robot's working space on the XOZ plane and the XOY plane meets the conditions. Conclusion The structure of a differential rotary breast interventional robot is determined, with the link frames assigned to the mechanism and the Denavit-Hartenberg parameters given. Workspace simulation of MRI-compatible breast interventional robot is done in MATLAB. The 3D printed MRI-compatible breast interventional robot is assembled and debugged to verify that its working space and positioning error meet the requirements.

A Novel End Effector of Environmental Exploring Robot with Fully Spherical Workspace

Yu, S.; Zhang, J., and Li, W., 2020. A novel end effector of environmental exploring robot with fully spherical workspace. In: Hu, C. and Cai, M. (eds.), Geo-informatics and Oceanography. Journal of Coastal Research, Special Issue No. 105, pp. 159–164. Coconut Creek (Florida), ISSN 0749-0208.A large workspace is an important parameter to improve the robot's mobility and flexibility. Based on decoupled 2-degree of freedom spherical parallel mechanism, two novel end effectors of the environmental exploring robot with a fully spherical workspace was presented. Through workspace analysis, the conditions of the end effectors to achieve a fully spherical workspace were determined. Through kinematic analysis, the kinematic equations of the two end effectors were established. After size optimization and performance comparison, the input and output performance of the RR&P5R end effector is better. Then the statics analysis and finite element analysis of the RR&P5R end effector were carried out. The results show that the material selection and structural design are reasonable. This research provides a technical support for complex unknown environment exploration.

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.

Towards a Snake-Like Flexible Robot for Endoscopic Submucosal Dissection

The advance of flexible robots enables a more efficient and safer way to perform endoscopic submucosal dissection surgery. The robot should be flexible enough for easy insertion and able to maintain a rigid shape to transmit the forces applied on instrumentation during the operation. This article presents a snake-like flexible endoscope design which consists of an active snake robot and a passive flexible body. The active section is composed of metal printed spring-like joints actuated by tendons arranged in a novel fashion. To analyse the performance and clinical feasibility of the proposed flexible robot, Finite Element Analysis, workspace analysis, path following accuracy and force test have been performed. The results have shown that the robot can reach a minimum retro-flex bending radius of 23 mm and the distance errors of each joint when advancing along a simulated colon path are analysed. Validation of the proposed robot demonstrates its potential for ESD surgeries.

Design and experimental study of a novel 7-DOF manipulator for transrectal ultrasound probe.

Traditional hand-held ultrasound probe has some limitations in prostate biopsy. Improving the localization and accuracy of ultrasound probe will increase the detection rate of prostate cancer while biopsy techniques remain unchanged. This paper designs a manipulator for transrectal ultrasound probe, which assists doctors in performing prostate biopsy and improves the efficiency and accuracy of biopsy procedure. The ultrasound probe manipulator includes a position adjustment module that can lock four joints at the same time. It reduces operating time and improves the stability of the mechanism. We use the attitude adjustment module designed by double parallelogram RCM mechanism, the ultrasound probe can realize centering and prevent its radial motion. The self-weight balance design helps doctors operate ultrasound probe without weight. Using MATLAB to analyze the manipulator, the results show that the workspace of the mechanism can meet the biopsy requirements. And simulate the centering effect of the ultrasound probe when the attitude is adjusted at different feeding distances, the results show that the ultrasound probe is centering stability. Finally, the centering and joint interlocking tests of the physical prototype are completed. In this paper, a 7-DOF manipulator for transrectal ultrasound probe is designed. The mechanism is analyzed for kinematics, workspace analysis, simulation of centering effects, development of a physical prototype and related experimental research. The results show that the surgical demand workspace is located inside the reachable workspace of the mechanism and the joint locking of the manipulator is reliable.

Investigation of an Underwater Vectored Thruster Based on 3RPS Parallel Manipulator

Autonomous underwater vehicles (AUVs) are important and useful tool platforms in exploring and utilizing ocean resource. However, the effect of control surfaces would decrease even invalid complete in this condition, and it is very hard for conventional AUVs to perform detailed missions at a low forward speed. Therefore, solving this problem of AUVs becomes particularly important to increase the application scope of AUVs. In this paper, we present a design scheme for the vectored thruster AUV based on 3RPS parallel manipulator, which is a kind of parallel manipulator and has advantages of compact structure and reliable performance. To study the performance and characteristics of the proposed thrust-vectoring mechanism, a series of works about corresponding kinematic and dynamic analysis have been performed through the theoretical analysis and numerical simulation. In the part of kinematics, the inverse, forward kinematics, and workspace analysis of the thrust-vectoring mechanism is presented, and the numerical simulations are accomplished to prove the feasibility and effectiveness of this design in AUVs. In order to further verify feasibility of the thrust-vectoring mechanism, based on the considerations of various affecting factors, a dynamic model of the designed thrust-vectoring mechanism is established according to theoretical analysis, and the driving forces of the linear actuator are presented through a series of numerical simulations. In addition, a control scheme based on PID algorithm is proposed for the designed vectored thruster with considering various affecting factors and the application environment. Meanwhile, the control scheme is also established and verified in MATLAB Simscape Mutibody. A series of numerical simulations of the thrust-vectoring mechanism prove the feasibility of the vectored thruster. According to equipping the designed vectored thruster, the AUVs can overcome the limit of weakening the control ability at zero or low forward speeds, and this improvement also expands the application of it, which has been scaled greatly.

A Compact Surgical Robot System for Craniomaxillofacial Surgery and its Preliminary Study.

Craniomaxillofacial surgery has the characteristics of complex anatomical structure, narrow surgical field, and easy damage to nerves, blood vessels, and other structures. Compared with the traditional bare-hand operation, robot-assisted craniofacial surgery is expected to achieve a more stable and accurate surgical operation. So we have developed a robot-assisted craniofacial surgery system. A compact mechanism design was adopted for the robot system, integrates with visual and force perception modules. The motion analysis and working space analysis are carried out on the mechanical structure. The binocular vision module is integrated and the robot hand-eye calibration process was completed. The target tracking method based on staple is used to achieve tracking and monitoring of the target area. A distributed robot control system based on CAN bus technology is designed, and a position-based visual servo control method is adopted. Then the precision test of the robot system prototype and the drilling experiment of the 3D printed mandible model were carried out. The average pixel error of the vision module is 0.15 pixels. Based on the staple tracking method, the average center error rate of the image is 0.3175 mm, and the overlap rate is 88.76%. The drilling experiment of the mandible model showed that the average entrance position error is 1.76 ± 0.36 mm, the average target position error is 1.62 ± 0.27 mm, and the angle error is 5.36 ± 0.31 degrees. The designed craniofacial robot system can better assist surgeons to complete the mandibular osteotomy.

Kinematic Analysis and Trajectory Planning Simulation of Citrus Picking Manipulator

Trajectory planning is the premise of studying robot control. This study takes PUMA560 robotic arm as the research object and applies it to citrus picking. This research carried out kinematics analysis and simulation on its picking process, and then performed trajectory planning and workspace analysis. Firstly, the kinematics analysis and simulation of the picking robot arm were carried out in the forward and reverse direction, and the kinematics model was established by Denavit-Hartenberg method. Secondly, the trajectory planning of the robotic arm based on quintic polynomial interpolation is performed in the joint space, and the fitting curves of joint angular displacement, angular velocity and angular acceleration are plotted respectively. Finally, the working space of the picking manipulator is analysed and its working space diagram is drawn. The simulation results show that the trajectory planning and workspace drawing methods selected in this study are effective for the trajectory planning of citrus picking manipulator and provide theoretical support for the control research of citrus picking manipulator.

Development and Workspace Analysis of Smart Actuation based Planar Parallel Robotic Motion Stage

The applications of light weight planar parallel robotic manipulators are increasing enormously because of their various desirable characteristics such as low weight, lower inertia, higher stiffness, energy efficiency etc. Higher accelerations and accuracies can be achieved using planar parallel manipulators (PPMs). Also, Shape Memory Alloy (SMA) based actuators are replacing huge and bulky actuators as SMA actuators provide higher work per unit mass as compared to other actuators and also undergoes silent actuation by simple actuation process. In the present study, three configurations (3PRP, PPR-2PRP and PRR-2PRP) of 3 degrees of freedom U-shaped base planar parallel robotic manipulator have been presented using SMA based smart actuators. The manipulator constitutes of one fixed base and one moving platform. The SMA spring acts as linear actuators mounted on the base which is connected to the end effector with the help of three limbs. A detailed experimental study was carried out to understand the workspace associated with each configuration. The movement of manipulators was investigated with the various combinations associated with the input SMA translation joints. And the study showed that the various configurations acquire different areas of workspace in the manipulator region. This study also shows the essence of SMA springs in PPMs for precise and accurate positioning of the end-effector and also its tracking ability for the development of future micro-motion stage. Note: P refers to Passive Prismatic Joint, R refers to Passive Revolute Joint and P refers to Active Prismatic Joint.