scholarly journals Operation Safety of a 2-DoF Planar Mechanism for Arm Rehabilitation

Inventions ◽  
2021 ◽  
Vol 6 (4) ◽  
pp. 85
Author(s):  
Marco Ceccarelli ◽  
Matteo Russo ◽  
Daniele Cafolla ◽  
Betsy D. M. Chaparro-Rico
Keyword(s):  
Degrees Of Freedom ◽  
Fem Analysis ◽  
Point Of View ◽  
Force Transmission ◽  
Good Efficiency ◽  
Planar Mechanism ◽  
Arm Rehabilitation ◽  
Human Arm ◽  
Transmission Index ◽  
Singular Configuration

The operation safety of rehabilitation devices must be addressed early in the development process and before being tested on people. In this paper, the operation safety of a 2-DoF (degrees of freedom) planar mechanism for arm rehabilitation is addressed. Then, the safety and efficiency of the device operation is assessed through the Transmission Index (TI) distribution in its workspace. Furthermore, the produced stresses on the human arm are assessed via the FEM (finite element method) when the rehabilitation device reaches five critical positions within its workspace. The TI distribution showed that the proposed design has a proper behaviour from a force transmission point of view, avoiding any singular configuration that might cause a control failure and subsequent risk for the user and supporting the user’s motion with a good efficiency throughout its operational workspace. The FEM analysis showed that Nurse operation is safe for the human arm since a negligible maximum stress of 6.55 × 103 N/m2 is achieved by the human arm when the device is located on the evaluated critical positions.

scholarly journals Optimum Seeking of Redundant Actuators for M-RCM 3-UPU Parallel Mechanism

2020 ◽  
Author(s):  
Chen Zhao ◽  
Jingke Song ◽  
Xuechan Chen ◽  
Ziming Chen ◽  
Huafeng Ding
Keyword(s):  
Parallel Mechanism ◽  
Degrees Of Freedom ◽  
Singularity Analysis ◽  
Universal Joint ◽  
Prismatic Joint ◽  
Transmission Index ◽  
Redundant Actuators ◽  
Force Transmissibility ◽  
Singular Configuration

Abstract This paper focuses on a 2R1T 3-UPU (U for universal joint and P for prismatic joint) parallel mechanism (PM) with two rotational and one translational (2R1T) degrees of freedom (DOFs) and the ability of multiple remote centers of motion (M-RCM). The singularity analysis based on the indexes of motion/force transmissibility and constraint shows that this PM has transmission singularity, constraint singularity, mixed singularity and limb singularity. To solve these singularproblems, the quantifiable redundancy transmission index (RTI) and the redundancy constraint index (RCI) are proposed for optimum seeking of redundant actuators for this PM. Then the appropriate redundant actuators are selected and the working scheme for redundant actuators near the corresponding singular configuration are given to help the PM go through the singularity.

Singularity, isotropy, and velocity transmission evaluation of a three translational degrees-of-freedom parallel robot

Robotica ◽  
2012 ◽  
Vol 31 (2) ◽  
pp. 193-202 ◽  
Author(s):  
Yongjie Zhao
Keyword(s):  
Performance Evaluation ◽  
Angular Velocity ◽  
Degrees Of Freedom ◽  
Jacobian Matrix ◽  
Parallel Robot ◽  
End Effector ◽  
Transmission Index ◽  
Delta Robot ◽  
Singular Configuration ◽  
Velocity Transmission

SUMMARYPerformance evaluation of a parallel robot is a multicriteria problem. By taking Delta robot as an object of study, this paper presents the kinematic performance evaluation of a three translational degrees-of-freedom parallel robot from the viewpoint of singularity, isotropy, and velocity transmission. It is shown that the determinant of a Jacobian matrix cannot measure the distance from the singular configuration due to the existing inverse kinematic singularity of a Delta robot. The determinants of inverse and direct kinematic Jacobian matrices are adopted for the measurement of distance from the singular configuration based on the theory of numerical linear dependence. The denominator of the Jacobian matrix will be lost in the computation of the condition number when the end-effector is on the centerline of the workspace, so the Delta robot may also be nearly at a singular configuration when the condition number of the Jacobian matrix is equal to 1. The velocity transmission index whose physical meaning is the maximum input angular velocity when the end-effector translates in the unit velocity is presented. The evaluation of singularity, isotropy, and velocity transmission of a Delta robot is investigated by simulation. The velocity transmission index can also be used for the velocity transmission evaluation of a parallel robot with pure rotational degrees-of-freedom based on the principle of similarity. The physical meaning is modified to be the maximum input velocity when the end-effector rotates in the unit angular velocity.

Determination of the closed-form workspace area expression and dimensional optimization of planar parallel manipulators

Robotica ◽  
2016 ◽  
Vol 35 (10) ◽  
pp. 2056-2075 ◽  
Author(s):  
M. Ganesh ◽  
Banke Bihari ◽  
Vijay Singh Rathore ◽  
Dhiraj Kumar ◽  
Chandan Kumar ◽  
...  
Keyword(s):  
Closed Form ◽  
Degrees Of Freedom ◽  
Solution Space ◽  
Optimization Procedure ◽  
Parallel Manipulators ◽  
Force Transmission ◽  
Workspace Analysis ◽  
Planar Parallel Manipulator ◽  
Transmission Index ◽  
Planar Parallel Manipulators

SUMMARYOptimization is an important step in the design and development of a planar parallel manipulator. For optimization processes, workspace analysis is a crucial and preliminary objective. Generally, the workspace analysis for such manipulators is carried out using a non-dimensional approach. For planar parallel manipulators of two degrees of freedom (2-DOF), a non-dimensional workspace analysis is very advantageous. However, it becomes very difficult in the case of 3-DOF and higher DOF manipulators because of the complex shape of the workspace. In this study, the workspace shape is classified as a function of the geometric parameters, and the closed-form area expressions are derived for a constant orientation workspace of a three revolute–revolute–revolute (3-RRR) planar manipulator. The approach is also shown to be feasible for different orientations of a mobile platform. An optimization procedure for the design of planar 3-RRR manipulators is proposed for a prescribed workspace area. It is observed that the closed-form area expression for all the possible shapes of the workspace provides a larger solution space, which is further optimized considering singularity, mass of the manipulator, and a force transmission index.

scholarly journals Optimum Seeking of Redundant Actuators for M-RCM 3-UPU Parallel Mechanism

2021 ◽  
Vol 34 (1) ◽  
Author(s):  
Chen Zhao ◽  
Jingke Song ◽  
Xuechan Chen ◽  
Ziming Chen ◽  
Huafeng Ding
Keyword(s):  
Parallel Mechanism ◽  
Degrees Of Freedom ◽  
Singularity Analysis ◽  
Quantitative Criterion ◽  
Singularity Problem ◽  
Transmission Index ◽  
Redundant Actuators ◽  
Open Issue ◽  
Force Transmissibility ◽  
Singular Configuration

AbstractThe singularity problem brings troubles to the design and application for the parallel mechanism. Currently, redundant actuation is one of the useful methods to solve this singularity problem. However, faced to the numerous joints in a parallel mechanism, how to make a quantitative criterion of seeking the most efficient joints added actuators for letting the mechanism passes through singularity is a necessarily open issue. This paper focuses on a 2R1T 3-UPU (U for universal joint and P for prismatic joint) parallel mechanism (PM) with two rotational and one translational (2R1T) degrees of freedom (DOFs) and the ability of multiple remote centers of motion (M-RCM). The singularity analysis based on the indexes of motion/force transmissibility and constraint shows that this PM has transmission singularity, constraint singularity, mixed singularity and limb singularity. To solve these singular problems, the quantifiable redundancy transmission index (RTI) and the redundancy constraint index (RCI) are proposed for optimum seeking of redundant actuators for this PM. Then the appropriate redundant actuators are selected and the working scheme for redundant actuators near the corresponding singular configuration are given to help the PM passes through the singularity. This research proposes a quantitative criterion to optimum seeking of redundant actuators for the parallel mechanism to solve its singularity.

Kinematic Synthesis of Spatial in-Parallel Wire-Driven Mechanism With Six Degrees of Freedom With High Force Transmissibility

2000 ◽  
Author(s):  
Yukio Takeda ◽  
Hiroaki Funabashi
Keyword(s):  
Degrees Of Freedom ◽  
Force Transmission ◽  
Kinematic Synthesis ◽  
Parallel Wire ◽  
Six Degrees Of Freedom ◽  
Output Force ◽  
Transmission Index ◽  
Six Dof ◽  
Force Transmissibility ◽  
The Relationship

Abstract We propose an index for evaluating the force transmission characteristics in general N degree-of-freedom (dof) in-parallel wire-driven mechanisms (PWDMs) with N + 1 wires. The relationship between input force and output force in an N dof in-parallel actuated mechanism with only rigid links was used for defining the transmission index for a PWDM. The index has been applied to the kinematic synthesis of spatial six dof PWDM with seven wires, and novel PWDMs with high force transmissibility have been obtained.

Force transmission and constraint analysis of a 3-SPR parallel manipulator

2017 ◽  
Vol 232 (23) ◽  
pp. 4399-4409 ◽  
Author(s):  
Matteo Russo ◽  
Marco Ceccarelli ◽  
Yukio Takeda
Keyword(s):  
Parallel Manipulator ◽  
Degrees Of Freedom ◽  
Single Point ◽  
Open Loop ◽  
Mobile Platform ◽  
Force Transmission ◽  
Singularity Problem ◽  
Kinematic Chains ◽  
Advantages And Disadvantages ◽  
Transmission Index

This paper presents an analysis of a novel 3-SPR parallel manipulator with 3 degrees-of-freedom that is characterized by a mobile platform consisting of a single point where all the three open-loop kinematic chains converge. The constraint singularity problem of the mechanism is solved in closed form by computing the Jacobian of the manipulator. Then, the expression of the transmission index is obtained for the 3-SPR manipulator by using the pressure angle definition. In order to evaluate the influence of secondary parameters, an equivalent 6-SPS mechanism is analyzed and its transmission index is computed in the parameter space. Finally, the proposed manipulator is compared to a standard 3-SPR parallel mechanism to investigate the influence of the mobile platform radius over transmission index and workspace volume. The results are discussed in order to highlight the advantages and disadvantages of the proposed structure of parallel manipulator.

Mobility, Kinematic Analysis, and Dimensional Optimization of New Three-Degrees-of-Freedom Parallel Manipulator With Actuation Redundancy

2017 ◽  
Vol 9 (4) ◽  
Author(s):  
Lingmin Xu ◽  
Qinchuan Li ◽  
Ningbin Zhang ◽  
Qiaohong Chen
Keyword(s):  
Parallel Manipulator ◽  
Degrees Of Freedom ◽  
Parallel Manipulators ◽  
Force Transmission ◽  
Transmission Index ◽  
Prismatic Joints ◽  
Redundantly Actuated ◽  
Force Transmissibility ◽  
Solution Velocity ◽  
Three Degrees Of Freedom

Parallel manipulators (PMs) with redundant actuation are attracting increasing research interest because they have demonstrated improved stiffness and fewer singularities. This paper proposes a new redundantly actuated parallel manipulator that has three degrees-of-freedom (DOFs) and four limbs. The proposed manipulator is a 2UPR-2PRU parallel manipulator (where P represents an actuated prismatic joint, R represents a revolute joint, and U represents a universal joint) that is actuated using four prismatic joints; two of these joints are mounted on the base to reduce the movable mass. Mobility analysis shows that the moving platform has two rotational DOFs and one translational DOF. First, the inverse displacement solution, velocity, and singularity analyses are discussed. Next, the local transmission index (LTI) and the good transmission workspace are used to evaluate the motion/force transmissibility of the 2UPR-2PRU parallel manipulator. Finally, the parameter-finiteness normalization method (PFNM) is used to produce an optimal design that considers the good transmission workspace. It is thus shown that the motion/force transmission of the proposed manipulator is improved by optimizing the link parameters.

scholarly journals BIOMIMETIC DESIGN OF LOW STIFFNESS ACTUATOR SYSTEMS FOR PROSTHETIC LIMBS

2011 ◽  
Author(s):  
D. L. Russell ◽  
M. McTavish
Keyword(s):  
Mechanical Properties ◽  
Degrees Of Freedom ◽  
Analytical Techniques ◽  
Energetic Costs ◽  
Multiple Degrees Of Freedom ◽  
Prosthetic Limbs ◽  
Limb Stiffness ◽  
Human Arm ◽  
Biomimetic Approach ◽  
Low Stiffness

The various relationships that are possible between the mechanical properties of single actuators and the overall mechanism (in this case a human arm with or without a prosthetic elbow) are discussed. Graphical and analytical techniques for describing the range of overall limb stiffnesses that are achievable and for characterizing the overall limb stiffness have been developed. Using a biomimetic approach and, considering energetic costs, stability and complexity, the implications of choosing passive or active implementations of stiffness are discussed. These techniques and approaches are particularly applicable with redundant (agonist - antagonist) actuators and multiple degrees of freedom. Finally, a novel biomimetic approach for control is proposed.

scholarly journals From Loschmidt daemons to time-reversed waves

2016 ◽  
Vol 374 (2069) ◽  
pp. 20150156 ◽  
Author(s):  
Mathias Fink
Keyword(s):  
Wave Propagation ◽  
Time Reversal ◽  
Degrees Of Freedom ◽  
Point Of View ◽  
Propagation Time ◽  
Reversal Invariance ◽  
Spatial Boundary ◽  
Dual Approaches ◽  
Spatio Temporal

Time-reversal invariance can be exploited in wave physics to control wave propagation in complex media. Because time and space play a similar role in wave propagation, time-reversed waves can be obtained by manipulating spatial boundaries or by manipulating time boundaries. The two dual approaches will be discussed in this paper. The first approach uses ‘time-reversal mirrors’ with a wave manipulation along a spatial boundary sampled by a finite number of antennas. Related to this method, the role of the spatio-temporal degrees of freedom of the wavefield will be emphasized. In a second approach, waves are manipulated from a time boundary and we show that ‘instantaneous time mirrors’, mimicking the Loschmidt point of view, simultaneously acting in the entire space at once can also radiate time-reversed waves.

scholarly journals Effect of Gluconacetobacter xylinus cultivation conditions on the selected properties of bacterial cellulose

2016 ◽  
Vol 18 (4) ◽  
pp. 117-123 ◽  
Author(s):  
Karol Fijałkowski ◽  
Anna Żywicka ◽  
Radosław Drozd ◽  
Marian Kordas ◽  
Rafał Rakoczy
Keyword(s):  
Bacterial Cellulose ◽  
Bacterial Strain ◽  
Point Of View ◽  
Synthesis Process ◽  
Cellulose Synthesis ◽  
Gluconacetobacter Xylinus ◽  
Water Release ◽  
Good Efficiency ◽  
Cellulose Fibrils ◽  
Culturing Conditions

Abstract The aim of the study was to analyze the changes in the parameters of bacterial cultures and bacterial cellulose (BC) synthesized by four reference strains of Gluconacetobacter xylinus during 31-day cultivation in stationary conditions. The study showed that the most visible changes in the analyzed parameters of BC, regardless of the bacterial strain used for their synthesis, were observed in the first 10–14 days of the experiment. It was also revealed, that among parameters showing dependence associated with the particular bacterial strain were the rate and period of BC synthesis, the growth rate of bacteria anchored to the cellulose fibrils, the capacity to absorb water and the water release rate. The results presented in this work may be useful in the selection of optimum culturing conditions and period from the point of view of good efficiency of the cellulose synthesis process.

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