CONSTRAINT-BASED ANALYSIS OF PARALLEL KINEMATIC ARTICULATED WRIST MECHANISM

2021 ◽  
pp. 1-11
Author(s):  
Revanth Damerla ◽  
Shorya Awtar
Keyword(s):  
Degrees Of Freedom ◽  
Systematic Analysis ◽  
Load Bearing ◽  
Load Transmission ◽  
Pure Rotation ◽  
Parallel Kinematic ◽  
Design Tradeoffs ◽  
Transmission Capability

Abstract This paper presents a systematic constraint-based analysis of the performance attributes of eight parallel kinematic articulated wrist mechanisms from the existing literature. These performance attributes include the number, nature (i.e. pure rotation, or translation, or a combination), and location of a mechanism's Degrees of Freedom (DoFs) in the nominal and displaced configurations, load transmission capability along these DoFs, and load bearing capability along the constraint directions. This systematic analysis reveals performance tradeoffs between these performance attributes for a given mechanism, as well as design tradeoffs across these mechanisms. This analysis also helps inform the suitability of a given mechanism for specific applications.

Constraint-Based Analysis of Parallel Kinematic Articulated Wrist Mechanisms

2020 ◽  
Author(s):  
Revanth Damerla ◽  
Shorya Awtar
Keyword(s):  
Degrees Of Freedom ◽  
Systematic Analysis ◽  
Load Bearing ◽  
Load Transmission ◽  
Pure Rotation ◽  
Parallel Kinematic ◽  
Design Tradeoffs ◽  
Transmission Capability

Abstract This paper presents a systematic constraint-based analysis of the motion attributes of six parallel kinematic articulated wrist mechanisms from the existing literature. These motion attributes include the number, nature (i.e. pure rotation, or translation, or a combination), and location of mechanism’s Degrees of Freedom (DoFs) in the nominal and displaced configurations, range of operation along these DoFs, load transmission capability along these DoFs, and load bearing capability along the constraint directions. This systematic analysis reveals performance tradeoffs between these motion attributes for a given mechanism, as well as design tradeoffs across these multiple mechanisms with respect to these motion attributes. This analysis should help inform the suitability of a given mechanism for specific applications.

An XYZ Parallel Kinematic Flexure Mechanism With Geometrically Decoupled Degrees of Freedom

2011 ◽  
Author(s):  
Shorya Awtar ◽  
John Ustick ◽  
Shiladitya Sen
Keyword(s):  
Degrees Of Freedom ◽  
Element Analysis ◽  
Motion Direction ◽  
Form Analysis ◽  
Flexure Mechanism ◽  
Non Linear ◽  
Decoupled Motion ◽  
Motion Range ◽  
Parallel Kinematic ◽  
Cross Axis

We present the constraint-based design of a novel parallel kinematic flexure mechanism that provides highly decoupled motions along the three translational directions (X, Y, and Z) and high stiffness along the three rotational directions (θx, θy, and θz). The geometric decoupling ensures large motion range along each translational direction and enables integration with large-stroke ground-mounted linear actuators or generators, depending on the application. The proposed design, which is based on a systematic arrangement of multiple rigid stages and parallelogram flexure modules, is analyzed via non-linear finite element analysis. A proof-of-concept prototype of the flexure mechanism is fabricated to validate its large range and decoupled motion capability. The analyses as well as the hardware demonstrate an XYZ motion range of 10 mm × 10 mm × 10 mm. Over this motion range, the non-linear FEA predicts a cross-axis error of less than 3%, parasitic rotations less than 2 mrad, less than 4% lost motion, actuator isolation less than 1.5%, and no perceptible motion direction stiffness variation. Ongoing work includes non-linear closed-form analysis and experimental measurement of these error motion and stiffness characteristics.

An XYZ Parallel-Kinematic Flexure Mechanism With Geometrically Decoupled Degrees of Freedom

2012 ◽  
Vol 5 (1) ◽  
Author(s):  
Shorya Awtar ◽  
John Ustick ◽  
Shiladitya Sen
Keyword(s):  
Degrees Of Freedom ◽  
Finite Elements Analysis ◽  
Motion Direction ◽  
Flexure Mechanism ◽  
Nonlinear Finite Elements ◽  
Decoupled Motion ◽  
Motion Range ◽  
Stiffness Variation ◽  
Parallel Kinematic ◽  
Cross Axis

A novel parallel-kinematic flexure mechanism that provides highly decoupled motions along the three translational directions (X, Y, and Z) and high stiffness along the three rotational directions (θx, θy, and θz) is presented. Geometric decoupling ensures large motion range along each translational direction and enables integration with large-stroke ground-mounted linear actuators or generators, depending on the application. The proposed design, which is based on a systematic arrangement of multiple rigid stages and parallelogram flexure modules, is analyzed via nonlinear finite elements analysis (FEA). A proof-of-concept prototype is fabricated to validate the predicted large range and decoupled motion capabilities. The analysis and the hardware prototype demonstrate an XYZ motion range of 10 mm × 10 mm × 10 mm. Over this motion range, the nonlinear FEA predicts cross-axis errors of less than 7.8%, parasitic rotations less than 10.8 mrad, less than 14.4% lost motion, actuator isolation better than 1.5%, and no perceptible motion direction stiffness variation.

A novel five-degrees-of-freedom decoupled robot

Robotica ◽  
2009 ◽  
Vol 28 (6) ◽  
pp. 909-917 ◽  
Author(s):  
Jaime Gallardo-Alvarado ◽  
Horacio Orozco-Mendoza ◽  
José M. Rico-Martínez
Keyword(s):  
Machine Tools ◽  
Degrees Of Freedom ◽  
Parallel Manipulators ◽  
Solar Panels ◽  
Spatial Mechanism ◽  
Moving Platforms ◽  
Parallel Kinematic ◽  
Radar Antennas

SUMMARYIn this work a new nonoverconstrained redundant decoupled robot, free of compound joints, formed from three parallel manipulators, with two moving platforms and provided with six active limbs connected to the fixed platform, called LinceJJP, is presented. Interesting applications such as multi-axis machine tools with parallel kinematic architectures, solar panels, radar antennas, and telescopes are available for this novel spatial mechanism.

Potential of the 3-UPU Translational Parallel Manipulator

2010 ◽  
Author(s):  
Ahmed Hachem Chebbi ◽  
Vincenzo Parenti-Castelli
Keyword(s):  
Parallel Manipulator ◽  
Degrees Of Freedom ◽  
Joint Clearance ◽  
General Frame ◽  
Pure Rotation ◽  
Work Done ◽  
Relevant Work ◽  
Three Degrees Of Freedom

The 3-UPU three degrees of freedom fully parallel manipulator, where U and P are for universal and prismatic pair respectively, is a very well known manipulator that can provide the platform with three degrees of freedom of pure translation, pure rotation or mixed translation and rotation according to the relative directions of the revolute axes. Many studies have been reported in the literature on singularities, workspace and joint clearance influence on the platform accuracy of this manipulator. However, much work has still to be done to reveal all the features this topology can offer to the designer. This paper collects the previous most relevant work done on the 3-UPU parallel manipulator and shows the main results in a coherent general frame. The paper proposes new architectures of the 3-UPU manipulator which offer interesting features to the designer. Finally, based on a number of indexes, a procedure is proposed that allows the designer to select the best architecture of the 3-UPU manipulator for a given task.

Kinematics Research for a High-Precise Multi-Gratings Mosaic Mechanism

2012 ◽  
Vol 452-453 ◽  
pp. 1496-1500
Author(s):  
Li Hua Lu ◽  
Ying Chun Liang ◽  
Fu Li Yu ◽  
Bao Ku Su
Keyword(s):  
Degrees Of Freedom ◽  
Design Principle ◽  
Load Capacity ◽  
Dual Mode ◽  
Micro Actuator ◽  
Feed Drives ◽  
Parallel Kinematic ◽  
High Load Capacity ◽  
Novel Design ◽  
Kinematic Properties

A novel design of high load capacity multiaxis positioning stages with accuracy in the range of nanometers is presented. For strokes of 2mm with no play and high stiffness a general design principle supporting five Cartesian degrees of freedom has been developed using a new parallel kinematic topology based on Parallelogram arrangements. The five uniform feed drives are improved dual mode mechanism with servomotor and ballscrew as macro-actuator and piezoelectric transducer (PZT) with resolution of 1.2nm as micro-actuator. The performance of the setup and its kinematic properties are described as well as resolution of the five motions and their crosstalk. The setup has been implemented with outstanding characteristics and excellent reliability for alignment of a multigrating mosaic compressor in a PW-class CPA-laser.

Kinetostatic Performance Analysis of a Redundantly Driven Parallel Kinematic Manipulator

2014 ◽  
Author(s):  
Michael Lorenz ◽  
Burkhard Corves ◽  
Martin Riedel
Keyword(s):  
Energy Efficiency ◽  
Energy Efficient ◽  
Degrees Of Freedom ◽  
Mathematical Optimization ◽  
Control Methods ◽  
Drive Power ◽  
Maximum Torque ◽  
Torque Distribution ◽  
Mechanical Handling ◽  
Parallel Kinematic

In general the mechanical handling of objects in space is performed by manipulators, whose number of actuators is consistent with the number of required degrees of freedom. In addition, manipulators can be equipped with redundant drives, providing the manipulator with more actuators than the mobility actually requires. Thus, an active distribution of drive torques is enabled. Accordingly, this research intends to analyze the effects of torque distribution in over-actuated manipulators relating to load-optimized and energy-efficient handling. By developing torque distribution strategies the maximum torque levels can be reduced and the required drive power thus be decreased. This results in an increased drive utilization, which improves the energy-efficiency of the handling system. On this basis, an innovative handling concept is analyzed, which represents an over-determined system given the number of actuators. Hence, it is shown that the drive utilization of manipulators can be significantly improved by means of actuation redundancy. For this purpose different mathematical optimization approaches are analyzed, which solve the over-actuated system with defined optimization targets. Here, the optimal torque distribution is found using an algorithm, which minimizes the maximum torque for each object position. The results demonstrate the efficiency of active torque distribution in terms of over-actuated manipulators. For a further approach it is planned to develop control methods including optimized torque distribution strategies in order to improve the performance and the energy efficiency of the entire manipulator.

Design of an Ankle Rehab Robot With a Compliant Parallel Kinematic Mechanism

2020 ◽  
Author(s):  
Nishant Jalgaonkar ◽  
Adam Kim ◽  
Shorya Awtar
Keyword(s):  
Degrees Of Freedom ◽  
Functional Requirements ◽  
Key Factors ◽  
Center Of Rotation ◽  
Ankle Motion ◽  
Natural Motion ◽  
Parallel Kinematic Mechanism ◽  
Parallel Kinematic ◽  
Kinematic Mechanism ◽  
Clinical Adoption

Abstract In this paper, we present the design of a novel ankle rehabilitation robot (ARR), called the Flex-ARR, that employs a compliant parallel kinematic mechanism (PKM) with decoupled degrees of freedom. The Flex-ARR is designed to collocate the biological center of rotation of the ankle with that of the robot’s center of rotation to allow natural ankle motion. While multiple ARR designs have been developed in research labs and some are commercially available, their clinical adoption has been limited because they do not emulate the natural motion of the ankle. The Flex-ARR leverages a unique PKM design that uses compliance to absorb minor misalignments between the center of rotation of the ankle and the robot, thereby allowing natural ankle motion. Also, because of its unique design, the PKM inherently accommodates variations in user foot sizes with minimal adjustments. The Flex-ARR is designed to provide multiple training modes that allow for both rehabilitation and assessment modalities. This paper provides a review of the literature to identify the key factors that have limited the clinical adoption of existing ARRs. Based on this, functional requirements and design specifications for an optimal ARR are defined. This is then used to develop a design strategy, followed by conceptual and detailed design.

Rhombohedral Twin Structure in Hematite (α-Fe2O3)

1992 ◽  
Vol 45 (9) ◽  
pp. 1527 ◽  
Author(s):  
LA Bursill ◽  
JL Peng ◽  
XD Fan
Keyword(s):  
Image Matching ◽  
Structural Models ◽  
Nearest Neighbour ◽  
Twin Structure ◽  
Systematic Analysis ◽  
Coherent Interface ◽  
Pure Rotation ◽  
Twinning Plane ◽  
Twinning Direction ◽  
Edge Shared Octahedra

Electron optical imaging of the structure of haematite ( α-Fe2O3) in two projections has allowed the microscopic twinning elements of rhombohedral twins to be determined. A systematic analysis of alternative structural models, using computer-simulation and image-matching considerations, as well as crystallochemical arguments, is presented. The twin has a screw operation consisting of a pure rotation of 180� about [0111], the twinning direction, combined with a parallel translation of (1/22) [0111]. The twinning plane (0112) forms a coherent interface, consisting of face-and edge-shared octahedra , with no change in the normal nearest-neighbour coordination.

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