Spherical Parallel Mechanism Research Articles

Automatic Lighting System Using Multiple Robotic Lamps

An automatic lighting system using 3-DOF robotic lamps and a laser scanner is proposed in this paper. The 3-DOF robotic lamp, which is designed with a spherical parallel mechanism with a unique forward kinematic solution, has a tilting motion to track a person and zoom-in and zoom-out motions to control the light intensity. In order to minimize the dynamic load, three actuators are installed at the base frame, and a counterbalancing design is considered. The positions of people are detected by a laser scanner, and the Kalman filter and a data association algorithm are applied in order to track the positions of people accurately. Therefore, multiple robotic lamps can track and illuminate each person continuously. We demonstrate experimentally that three robotic lamps mounted on the ceiling illuminate three people independently and control the intensity of the light according to the distance between a person and the robotic lamp.

Kinematic Transmission Analysis of a Novel Spherical 3-RRR Parallel Manipulator

The kinematic transmission property and distributions in workspace of a novel spherical 3-RRR parallel mechanism are given. The orthogonal layout feature of the parallel mechanism is described. The equations for inverse displacement and kinematic transmission property are derived by the relation of geometry. The kinematic transmission evaluation index of a spherical 3-RRR parallel mechanism is defined. Finally, the distribution of the index in workspace was given, which can provide theoretical basis for the application of the spherical mechanism.

Error Analysis of a Manipulators

The forearm is a typical ball and socket joint which have three degrees of freedom rotation. In this case the study of a 3-DOF manipulators is very interesting. In this paper, a novel manipulators based on 3-DOF orthogonal spherical parallel mechanism is proposed. Error analysis play an important role on the design and applications of the manipulators. The error model is derived in closed forms by using differential theory. Error evaluation index is defined. Terminal platform error distribution is analyzed and discussed in detail by using the error model technique. The analytic results indicate error value is smallest in initial position of the manipulators,the bigger value of error distributes in the workspace edge. So, this paper could provide a theoretical foundation for design and application of the manipulators.

One-degree-of-freedom spherical model for the passive motion of the human ankle joint

Mathematical modelling of mobility at the human ankle joint is essential for prosthetics and orthotic design. The scope of this study is to show that the ankle joint passive motion can be represented by a one-degree-of-freedom spherical motion. Moreover, this motion is modelled by a one-degree-of-freedom spherical parallel mechanism model, and the optimal pivot-point position is determined. Passive motion and anatomical data were taken from in vitro experiments in nine lower limb specimens. For each of these, a spherical mechanism, including the tibiofibular and talocalcaneal segments connected by a spherical pair and by the calcaneofibular and tibiocalcaneal ligament links, was defined from the corresponding experimental kinematics and geometry. An iterative procedure was used to optimize the geometry of the model, able to predict original experimental motion. The results of the simulations showed a good replication of the original natural motion, despite the numerous model assumptions and simplifications, with mean differences between experiments and predictions smaller than 1.3mm (average 0.33mm) for the three joint position components and smaller than 0.7° (average 0.32°) for the two out-of-sagittal plane rotations, once plotted versus the full flexion arc. The relevant pivot-point position after model optimization was found within the tibial mortise, but not exactly in a central location. The present combined experimental and modelling analysis of passive motion at the human ankle joint shows that a one degree-of-freedom spherical mechanism predicts well what is observed in real joints, although its computational complexity is comparable to the standard hinge joint model.

Parallel singularity-free design with actuation redundancy: A case study of three different types of 3-degree-of-freedom parallel mechanisms with redundant actuation

Typical parallel mechanisms suffer from parallel singularity due to kinematic coupling of multichains. This paper investigates how to remove parallel singularities by using redundant actuations. First, actuation wrenches and constraint wrenches forming the full direct kinematic Jacobian matrix are derived. After briefly addressing conditions for their constraint singularities, Grassmann–Cayley algebra is employed to identify parallel singularities. Then, employing Grassmann line geometry, the locations and the minimum number of redundant actuators are identified for the parallel mechanisms to have parallel singularity-free workspace. Three different types of 3-degree-of-freedom parallel mechanisms such as planar, spherical, and spatial parallel mechanisms are given as exemplary devices.

Kinematics Analysis of a 3-RRR Spherical Parallel Mechanism with Coaxial Input Shafts

As an important mechanism with special and extensive application, the three degrees of freedom spherical parallel mechanism is always a research hot in the mechanical fields. In this paper, the feature of the 3-RRR spherical parallel mechanism with coaxial input shafts is introduced, and its motion feature is analyzed based on the screw theory. The mobility of the spherical parallel mechanism is calculated by using the Modified Kutzbach-Grübler criterion, and the inverse displacement problem of the mechanism is solved. Then the expression of the Jacobian matrix is deduced based on the kinematics equation and its inverse solution. The contents of this paper should be useful for the further application of the spherical parallel mechanism.

Forward displacement analysis of a 3-RPR spherical parallel mechanism

The forward displacement analysis of spherical parallel mechanisms is a nonlinear problem and has attracted the attention of many researchers. A method is proposed to analyze the forward displacement of a 3-RPR spherical parallel mechanism. Firstly, based on spherical geometry and spherical trigonometry theory, a mathematical model is derived for the forward displacement analysis of the spherical parallel mechanism. After simplifying the mathematical model, the kinematical equations are then solved using the resultant elimination method. Using this method, one can obtain the three variables representing the position and pose of the moving platform directly. Finally, a numerical example is presented and Autodesk Inventor software is used to verify all the real solutions. The method of mathematical modeling, equation simplification, resultant elimination presented in this paper can be extended to solve similar problems effectively.

Analysis of Structural Parameter and Design of Elbow Joint Rehabilitation Parallel Robot

Elbow joint is one of the body's important joints, most of the activities of the human body are inseparable from the elbow joint, and including taking and holding movements.In order to increase the workspace of elbow joint, a novel elbow joint rehabilitation parallel robot based on 2-DOF orthogonal spherical parallel mechanism is proposed. First, the position inverse solution equation of elbow joint is established. Further, the workspace of elbow joint is analyzed. The optimal structural parameters are obtained by use of the objective function of optimization method. Finally, the virtual prototype of elbow joint rehabilitation parallel robot is designed using optimal structural dimensions parameters.

Kinematics Performance Analysis of a Robot Hip Joint

Kinematics research of mechanism is very important, the dynamic analysis and the design are based on linematics analysis. In this paper, a novel robot hip joint based on 3-RRR orthogonal spherical parallel mechanism is proposed, and Jacobin matrix is established. Then the linematics transmission performance evaluation index is defined. Furthermore the linematics transmission performance index is analyzed. The hip joint has good linematics transmission performance at the initial position. With the increase of workspace, linematics transmission performance gradually decreased. 3-RRR parallel mechanism is the ideal prototype of bionic robot and rehabilitation robot hip joint.

Parameter Optimization Design of a Novel Robot Shoulder Based on the Workspace

A robot shoulder joint should have good kinematic performance and workspace, but the structural parameters of shoulder joint directly affect the workspace. In order to increase the workspace of shoulder joint, a novel robot shoulder joint based on 3-DOF orthogonal spherical parallel mechanism is proposed. This paper studied the influence on its workspace affected by the variation of structural parameters of the connecting rod, frame connecting rod, rod diameter of this shoulder joint mechanism. Based on the consideration of mechanical constraint, the objective function of the optimal structural parameters of the shoulder joint is established. Having the maximum the workspace, the structural parameters of shoulder joint are gained.

Interference analysis and workspace optimization of 3-RRR spherical parallel mechanism

The causes of restriction on the working scope of spherical parallel mechanism (SPM) were analyzed. A systematic design methodology (Least Interference Design Methodology, LIDeM) for reducing interference among links and increasing workspace of mechanism was also developed in this study. Focusing on 3-RRR SPM, the optimal structure was given according to the LIDeM theory. The optimum values of the modified link ratio β1 and β2 were obtained through numerical simulation of its mathematical model. In addition, the total workspace mapping, singularity loci and interference regions of the optimum 3-RRR SPM were also attained in this study by computational simulation. This work improves the total workspace of 3-RRR SPM and could be applied on some other revolute-joint mechanisms.

Development of a Parallel-Series Stabilized Platform System

This document designed a stabilized platform of 2-DOF spherical parallel mechanism with 1-DOF in series. DC servo motors are adopted as the driver of the mechanism. The system uses an inertial gyro sensor as the feedback of the angular position. Software and hardware of the platform were developed. The full closed-loops control structure based on Advantech IPC with NI multifunction data acquisition card(PCI-6230), including current loop, velocity loop and angular position loop, gets wide speed range and high precision for angular tracking. Control software was the Matlab with embedded real-time QuaRC. Experiment results meet the technical index and precision requirement, and illustrate the practicability and effectiveness of the scheme.

Design of Large Motion Range and Heavy Duty 2-DOF Spherical Parallel Wrist Mechanism

Wrist mechanisms are important elements of robotic arms because they significantly affect the arm’s handling ability. Although various wrist mechanisms have been developed to date, a mechanism with a compact structure, a wide range of motion and a large load capacity has not yet been realized. Thus, in this paper, we propose 2-DOF Spherical Parallel (2DSP) mechanism, a heavy-duty wrist mechanism with a large motion range, and clarify its features both analytically and experimentally. The 2DSP mechanism is driven by a 2-DOF spherical parallel mechanism and is supported by a universal joint located at its center. This structure allows the 2DSP mechanism to realize a large motion range and load capacity and simplifies its kinematic analysis. Based on this analysis, we clarify the design process to maximize the motion range and propose a preferable structure of passive joints from the viewpoint of load capacity and production cost. We also describe the detailed design of a 2DSP mechanism for a rescue robot we developed previously and verify the feasibility of the proposed mechanism.

2A2-K04 回転中心位置を変更可能な大傾斜角球面パラレル機構の開発(パラレルロボット・メカニズム)

2A2-K04 回転中心位置を変更可能な大傾斜角球面パラレル機構の開発(パラレルロボット・メカニズム)

Kinematics Analysis and Design of a Novel Robot Shoulder Joint

Kinematics research of mechanism is very important, the dynamic analysis and the design are based on kinematical analysis. In this paper, a novel robot shoulder joint based on 3-RRR orthogonal spherical parallel mechanism is proposed, and the kinematics transmission equation of shoulder joint is derived by using the kinematics inverse solution, and Jacobin matrix is established. Then Jacobin matrix is introduced into the global performance index, and the velocity of global performance evaluation index is defined. Furthermore, the shoulder joint dimensions are changed, and the global performance index is analyzed, then a performance atlas is given at the work spaces of shoulder joint with different dimension. It is found that the Jacobin matrix has more important influence on the kinematics performance of the shoulder joint. Having a good kinematics performance, structure dimensions ranges of shoulder joint are gained, thus the evaluation of kinematics of shoulder joint is more comprehensive. Finally, a novel robot shoulder joint is designed with the kinematics performance evaluation index.

2A2-K03 2自由度球面リンク機構の可動範囲最大化に関する検討(パラレルロボット・メカニズム)

2A2-K03 2自由度球面リンク機構の可動範囲最大化に関する検討(パラレルロボット・メカニズム)

Contribution to the design of robotized tele-echography system

This paper introduces the design of a master-slave robotized system for tele-ultrasound application. The objective of these researches is to design the slave manipulator of this system and its control device (master part). The specification process of the architecture kinematic is based on the analysis of expert’s gesture during ultrasound examinations. These studies have been carried out using a motion capture system. The medical gestures were analyzed in terms of ultrasound probe attitude and used in the definition of the kinematics specifications of the proposed manipulator. The Spherical Parallel Mechanism is selected because its characteristics meet the constraint requirements. The optimal synthesis of spherical parallel manipulators is performed using a realcoded Genetic Algorithm based method. Simulations on the actuator responses of the structure allowed us the validate it. In order to control this robot, we have also designed a haptic device that provides easiness to use as well as force feedback. Its orientation control strategy is based on a use of an adaptative kalman filter which efficiency was demonstrated during experimentations.

A Fast Forward Kinematics Algorithm for 3-PRS Parallel Mechanism

Parasitic motion of 3-PRS (prismatic-revolute–spherical) parallel mechanism is discussed, inverse kinematics model of this mechanism is established. Based on the structure feature of 3-PRS parallel mechanism, a new forward kinematics algorithm for this mechanism is presented. The algorithm consists of approximate calculation and iterative calculation. The mathematical model of the proposed algorithm is clear simple, no derivative operation or Jacobi matrix inverse operation is needed, so computation is less. The experiment shows that in the same computing environment, the calculation speed of the proposed algorithm is about 2 times of the existing algorithms to achieve the same accuracy, so it can be applied to real-time control. Complexity and workload of programming is less than half of before. The algorithm is based on 3-PRS parallel mechanism, but it is also applicable for other parallel mechanism.

2A1-P08 アームレストジョイスティックの開発 : 手先姿勢操作機構の設計と製作(サーチ&レスキューロボット・メカトロニクス(1))

A robot manipulator in fields has to be remotely controlled when doing difficult works. We have already proposed a remote controller of the Master-Slave system with mobility and good operability, Armrest Joystick. It consists of a 3DOF position controller, a 3DOF posture controller and a gripper controller. In this paper, we develop the 3DOF posture controller that consists of 2DOF spherical parallel link mechanism and 1DOF mechanism at the tip. It achieves a wide movable range, smooth and light operation, and a force feedback. And we confirm the effectiveness and operability of this controller by some experiments.

Kinematic and Modal Simulation Analysis of the Bionic Eye Based on Spherical Parallel Mechanism (SPM)

In order to realize stable tracking under bumpy environment, the robot bionic eye constructed by spherical parallel mechanism with 3 DOF is designed based on the characteristics of human being’s eyes. ANSYS and ADAMS are utilized to conduct modal and kinematics property analysis respectively. According to the result of ANSYS modal analysis, the structure highly meets the demands of function and reliability, which lays the foundation for optimization and bump-resistance design. Through ADAMS kinematics analysis, displacement, velocity and acceleration curves of mechanism end effector were obtained, which provides reference for motion control and optimization design.