scholarly journals Architectural singularities of parallel mechanisms with prismatic joints due to special designs of platform shapes

2019 ◽  
Vol 10 (2) ◽  
pp. 449-464 ◽  
Author(s):  
Xiaoyong Wu ◽  
Shaoping Bai
Keyword(s):  
Degrees Of Freedom ◽  
Robotic Manipulators ◽  
Parallel Mechanisms ◽  
Mobile Platforms ◽  
Planar Mechanisms ◽  
Special Shape ◽  
Spatial Mechanisms ◽  
Prismatic Joints ◽  
And Algebra ◽  
Base Platform

Abstract. Singularity is an inherent property of robotic manipulators. A manipulator becomes singular when it gains or losses degrees of freedom at a particular configuration. In this work, a type of singularities caused by special shapes of platforms, either the mobile or the base platform, is addressed. This type of singularities pertains to the architecture singularity, but associated only with special shape designs of base and mobile platforms and spans in the whole workspace, which is referred as shape singularity. The paper provides formulations of shape singularity. The geometry and algebra properties of shape singularity are analyzed. Three examples of shape singularity identification for parallel mechanisms with prismatic joints are included, one for 3-DOF planar mechanisms, the others for 3-DOF and 6-DOF spatial mechanisms. The application of shape singularity in adjustable compliance mechanism design is illustrated.

A Method for Type Synthesis of Mechanisms Using Phase Diagrams

1994 ◽  
Author(s):  
Sio-Hou Lei ◽  
Ying-Chien Tsai
Keyword(s):  
Phase Diagram ◽  
Degrees Of Freedom ◽  
Practical Application ◽  
Type Synthesis ◽  
Planar Mechanisms ◽  
Simple Loop ◽  
Single Degree Of Freedom ◽  
Single Degree ◽  
Spatial Mechanisms ◽  
Synthesis Of Mechanisms

Abstract A method for synthesizing the types of spatial as well as planar mechanisms is expressed in this paper by using the concept of phase diagram in metallurgy. The concept represented as a type synthesis technique is applied to (a) planar mechanisms with n degrees of freedom and simple loop, (b) spatial mechanisms with single degree of freedom and simple loop, to enumerate all the possible mechanisms with physically realizable kinematic pairs. Based on the technique described, a set of new reciprocating mechanisms is generated as a practical application.

A New Family of 4-DOF Parallel Mechanisms (1T-3R and 2T-2R) With Two Platforms and Its Application to a Footpad Device

2004 ◽  
Author(s):  
Jungwon Yoon ◽  
Jeha Ryu
Keyword(s):  
Degrees Of Freedom ◽  
Base Plate ◽  
Driving Mechanism ◽  
Parallel Mechanisms ◽  
Pitch Motion ◽  
Human Foot ◽  
New Family ◽  
Revolute Joints ◽  
Prismatic Joints ◽  
Kinematic Analyses

This paper proposes a new family of four degrees-of-freedom (dof) parallel mechanisms with two platforms and its application to a footpad device that can simulate the spatial motions of the human foot. The new mechanism consists of front and rear platforms, and three limbs. Two limbs with 6-dof serial joints (P-S-P-P) are attached to each platform and are perpendicular to the base plate, while the middle limb (Pe-Re-R or Pe-Pe-R) is attached to the revolute joint that connects the front and rear platforms. The middle limb is driven by the 2-dof driving mechanism that is equivalent active serial prismatic and revolute joints (Pe-Re), or prismatic and prismatic joints (Pe-Re) with two base-fixed prismatic actuators. Therefore, two new 4-dof parallel mechanisms with two platforms can generate pitch motion of each platform, and roll and heave motions (1T-3R) or pitch motion of each platform and two translational motions (2T-2R) at both platforms. Kinematic analyses of the 1T-3R mechanism were performed, including inverse and forward kinematics, and velocity analysis. Based on the 1T-3R mechanism, a footpad device was designed to generate foot trajectories for natural walking. Finally, simulations of the foot trajectories in the normal gait cycle were performed using the proposed footpad device.

scholarly journals Performance Evaluation of a Sensor Concept for Solving the Direct Kinematics Problem of General Planar 3-RPR Parallel Mechanisms by Using Solely the Linear Actuators’ Orientations

Robotics ◽  
2019 ◽  
Vol 8 (3) ◽  
pp. 72 ◽  
Author(s):  
Stefan Schulz
Keyword(s):  
Lower Bound ◽  
Parallel Mechanism ◽  
Degrees Of Freedom ◽  
Parallel Robot ◽  
Parallel Mechanisms ◽  
Revolute Joints ◽  
Prismatic Joints ◽  
Measurement Units ◽  
Linear Actuators ◽  
Direct Kinematics

In this paper, we experimentally evaluate the performance of a sensor concept for solving the direct kinematics problem of a general planar 3-RPR parallel mechanism by using solely the linear actuators’ orientations. At first, we review classical methods for solving the direct kinematics problem of parallel mechanisms and discuss their disadvantages on the example of the general planar 3-RPR parallel mechanism, a planar parallel robot with two translational and one rotational degrees of freedom, where P denotes active prismatic joints and R denotes passive revolute joints. In order to avoid these disadvantages, we present a sensor concept together with an analytical formulation for solving the direct kinematics problem of a general planar 3-RPR parallel mechanism where the number of possible assembly modes can be significantly reduced when the linear actuators’ orientations are used instead of their lengths. By measuring the orientations of the linear actuators, provided, for example, by inertial measurement units, only two assembly modes exist. Finally, we investigate the accuracy of our direct kinematics solution under static as well as dynamic conditions by performing experiments on a specially designed prototype. We also investigate the solution formulation’s amplification of measurement noise on the calculated pose and show that the Cramér-Rao lower bound can be used to estimate the lower bound of the expected variances for a specific pose based exclusively on the variances of the linear actuators’ orientations.

Type synthesis of spatial mechanisms for forging manipulators

2012 ◽  
Vol 226 (9) ◽  
pp. 2320-2330 ◽  
Author(s):  
Yundou Xu ◽  
Jiantao Yao ◽  
Yongsheng Zhao
Keyword(s):  
Degrees Of Freedom ◽  
Screw Theory ◽  
Parallel Mechanisms ◽  
Type Synthesis ◽  
Heavy Duty ◽  
Systematic Method ◽  
Type Selection ◽  
Spatial Mechanisms ◽  
Selection For ◽  
Overconstrained Mechanisms

In this study, a systematic method is proposed to synthesize the parallel and hybrid serial–parallel mechanisms for the forging manipulators based on the screw theory. First, several typical configurations of five-degrees-of-freedom parallel mechanism for the forging manipulators are synthesized, and they are all non-overconstrained mechanisms. Then, two kinds of hybrid serial–parallel mechanisms for the forging manipulators with the advantages of motion decoupling are constructed, which are also not overconstrained. The configurations obtained in this study would provide more type selection for the heavy-duty forging manipulators in engineering.

A modified firefly algorithm for the inverse kinematics solutions of robotic manipulators

2021 ◽  
Vol 28 (3) ◽  
pp. 257-275
Author(s):  
Jesus Hernandez-Barragan ◽  
Carlos Lopez-Franco ◽  
Nancy Arana-Daniel ◽  
Alma Y. Alanis ◽  
Adriana Lopez-Franco
Keyword(s):  
Inverse Kinematics ◽  
Degrees Of Freedom ◽  
Firefly Algorithm ◽  
Statistical Tests ◽  
Robotic Manipulators ◽  
Optimization Techniques ◽  
Multimodal Optimization ◽  
End Effector ◽  
Prismatic Joints ◽  
Joint Limits

The inverse kinematics of robotic manipulators consists of finding a joint configuration to reach a desired end-effector pose. Since inverse kinematics is a complex non-linear problem with redundant solutions, sophisticated optimization techniques are often required to solve this problem; a possible solution can be found in metaheuristic algorithms. In this work, a modified version of the firefly algorithm for multimodal optimization is proposed to solve the inverse kinematics. This modified version can provide multiple joint configurations leading to the same end-effector pose, improving the classic firefly algorithm performance. Moreover, the proposed approach avoids singularities because it does not require any Jacobian matrix inversion, which is the main problem of conventional approaches. The proposed approach can be implemented in robotic manipulators composed of revolute or prismatic joints of n degrees of freedom considering joint limits constrains. Simulations with different robotic manipulators show the accuracy and robustness of the proposed approach. Additionally, non-parametric statistical tests are included to show that the proposed method has a statistically significant improvement over other multimodal optimization algorithms. Finally, real-time experiments on five degrees of freedom robotic manipulator illustrate the applicability of this approach.

The Influence of Non-planar (Spatial) Links in the Static Characteristics Behavior of Planar Parallel Manipulator

2017 ◽  
Vol 6 (3) ◽  
pp. 151
Author(s):  
Ganesh Mangavu ◽  
Karthikeyan. R ◽  
Venkitachalam. P ◽  
Guruguhan . G ◽  
S. Shrinithi ◽  
...  
Keyword(s):  
High Stress ◽  
Mobile Platform ◽  
Parallel Mechanisms ◽  
Vertical Load ◽  
Static Characteristics ◽  
Single Plane ◽  
Planar Manipulators ◽  
Planar Parallel Manipulator ◽  
Prismatic Joints ◽  
Base Platform

<span>Conventional planar manipulators have all their links in a single plane. Increasing payload at the end-effecter/mobile platform can induce high stress in the links due to cantilever nature of links. Thus it limits the total vertical load that can be applied on the mobile platform. In contrast to the links in conventional planar parallel mechanisms, non-planar links are proposed in this paper, i.e., links are made inclined to the horizontal plane and non planar legs are constructed. Although the links are made non-planar, the rotary (or prismatic) joints axes remain perpendicular (or parallel) to the plane of the base platform, which retains the planar motion of the end-effecter. For studying the application of such non planar links in planar manipulators, new models of inertia, stiffness and leg dynamics have to be developed. In this article, these models are developed and with the developed models, the static analysis is done on the planar manipulators with non-planar links and the performance is compared with the corresponding conventional planar manipulators.</span>

scholarly journals A Passive Parallel Master–Slave Mechanism for Magnetic Resonance Imaging-Guided Interventions

2015 ◽  
Vol 9 (1) ◽  
Author(s):  
Santhi Elayaperumal ◽  
Mark R. Cutkosky ◽  
Pierre Renaud ◽  
Bruce L. Daniel
Keyword(s):  
Magnetic Resonance Imaging ◽  
Magnetic Resonance ◽  
Degrees Of Freedom ◽  
Isosceles Triangle ◽  
Parallel Mechanisms ◽  
Force Transmission ◽  
Resonance Imaging ◽  
Robot Architecture ◽  
Prismatic Joints ◽  
Magnetic Resonance Imaging Mri

A passive, parallel master–slave mechanism is presented for magnetic resonance imaging (MRI)-guided interventions in the pelvis. The mechanism allows a physician to stand outside the MRI scanner while manipulating a needle inside the bore and, unlike a powered robot, does not place actuators in proximity to the patient. The manipulator combines two parallel mechanisms based on the Delta robot architecture. The mechanism also includes a two-axis gimbal to allow for tool angulation, giving a total of five degrees of freedom so that the physician can insert and steer a needle using continuous natural arm and wrist movements, unlike simple needle guides. The need for access between the patient’s legs and within the MRI scanner leads to an unusual asymmetric design in which the sliding prismatic joints form the vertices of an isosceles triangle. Kinematic analysis shows that the dexterity index of this design is improved over the desired workspace, as compared to an equilateral design. The analysis is extended to estimate the effect of friction and model the input:output force transmission. Prototypes, with final dimensions selected for transperineal prostate interventions, showed force transmission behavior as predicted by simulation, and easily withstood maximum forces required for tool insertion.

A Parallely Actuated Work Support Module for Reconfigurable Machining Systems

1998 ◽  
Author(s):  
Venkat Gopalakrishnan ◽  
Sridhar Kota
Keyword(s):  
Machine Tool ◽  
Machine Tools ◽  
Degrees Of Freedom ◽  
Mechanical Design ◽  
Performance Criteria ◽  
Machining Accuracy ◽  
Parallel Mechanisms ◽  
Element Analysis ◽  
Work Support ◽  
Reconfigurable Machining

Abstract In order to respond quickly to changes in market demands and the resulting product design changes, machine tool manufacturers must reduce the machine tool design lead time and machine set-up time. Reconfigurable Machine Tools (RMTs), assembled from machine modules such as spindles, slides and worktables are designed to be easily reconfigured to accommodate new machining requirements. The essential characteristics of RMTs are modularity, flexibility, convertibility and cost effectiveness. The goal of Reconfigurable Machining Systems (RMSs), composed of RMTs and other types of machines, is to provide exactly the capacity and functionality, exactly when needed. The scope of RMSs design includes mechanical hardware, control systems, process planning and tooling. One of the key challenges in the mechanical design of reconfigurable machine tools is to achieve the desired machining accuracy in all intended machine configurations. To meet this challenge we propose (a) to distribute the total number of degrees of freedom between the work-support and the tool and (b) employ parallely-actuated mechanisms for stiffness and ease of reconfigurability. In this paper we present a novel parallely-actuated work-support module as a part of an RMT. Following a brief summary of a few parallel mechanisms used in machine tool applications, this paper presents a three-degree-of-freedom work-support module designed to meet the machining requirements of specific features on a family of automotive cylinder heads. Inverse kinematics, dynamic and finite element analysis are performed to verify the performance criteria such as workspace envelope and rigidity. A prototype of the proposed module is also presented.

Unified Rotational and Translational Stiffness Characterization of Compliant Shell Mechanisms

2018 ◽  
Author(s):  
Joost R. Leemans ◽  
Charles J. Kim ◽  
Werner W. P. J. van de Sande ◽  
Just L. Herder
Keyword(s):  
Degrees Of Freedom ◽  
Compliant Mechanisms ◽  
Screw Theory ◽  
Characterization Methods ◽  
Six Degrees Of Freedom ◽  
Thin Walled Structures ◽  
Spatial Mechanisms ◽  
Eigen Decomposition ◽  
Comprehensive Characterization

Compliant shell mechanisms utilize spatially curved thin-walled structures to transfer or transmit force, motion or energy through elastic deformation. To design with spatial mechanisms designers need comprehensive characterization methods, while existing methods fall short of meaningful comparisons between rotational and translational degrees of freedom. This paper presents two approaches, both of which are based on the principle of virtual loads and potential energy, utilizing properties of screw theory, Plücker coordinates and an eigen-decomposition, leading to two unification lengths that can be used to compare and visualize all six degrees of freedom directions and magnitudes of compliant mechanisms in a non-arbitrary physically meaningful manner.

Assembly Configurations of Planar Multi-Loop Mechanisms With Kinematic Limitations

2005 ◽  
Vol 128 (4) ◽  
pp. 747-754 ◽  
Author(s):  
David E. Foster ◽  
Raymond J. Cipra
Keyword(s):  
Degrees Of Freedom ◽  
Planar Mechanisms ◽  
Two Degrees Of Freedom ◽  
Stationary Obstacles ◽  
Joint Limits

This paper examines the problem of identifying the assembly configurations (ACs), also called circuits, of planar multi-loop mechanisms with kinematic limitations, such as joint limits, link interference, collision with stationary obstacles, and constraint regions. First, a technique is given to describe numerically the satisfaction or violation of these kinematic limitations, and then it is applied to find the ACs of mechanisms with kinematic limitations. The method is valid for planar mechanisms with one or two degrees of freedom, and is illustrated with two examples.

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