Joint Equivalence Design and Analysis of a Tensegrity Joint

2021 ◽  
pp. 1-12
Author(s):  
Bingxing Chen ◽  
Hongzhou Jiang ◽  
Jingxuan Liu ◽  
Shuaibo Lu
Keyword(s):  
Mechanical Efficiency ◽  
Design Criterion ◽  
Elastic Response ◽  
Rotational Degree ◽  
Robotic Arms ◽  
Large Size ◽  
Compliant Joint ◽  
Deviation Degree ◽  
Rigid Joints ◽  
Robotic Applications

Abstract We propose a method to design a tensegrity joint, making its elastic deformation an accurate joint-like motion, such as a rotation around the designed rotational center. The tensegrity joint can be a three rotational degree-of-freedom (DOF) joint through this method. Axis drift is presented as a design criterion to describe the rotational center's deviation degree concerning the compliance center since the rotational center is not fixed to one point for different positions of the tensegrity joint. The axis drift is designed to be in a prescribed range so that the tensegrity joint is approximately equivalent to a rigid joint. In other words, the tensegrity joint's elastic response under external torque and force becomes precise rigid-joint-like kinematics and can replace rigid joints to transfer motion, force, and energy. A large-size tensegrity joint is developed to verify the joint equivalence experimentally. The experimental results show that the tensegrity joint achieved maximum dimensionless axis drift less than 2%, and indicate an excellent joint equivalence. The tensegrity joints' ability to replace rigid joints as modular joints to construct a hyper redundant serial structure is demonstrated using a tensegrity robotic arm. The proposed tensegrity compliant joint has notable benefits of tensegrity structure such as high mechanical efficiency, modularity, and scalability, and can be extended to many robotic applications, such as large-size serial robotic arms and snake-like robots.

MODEL VALIDATION AND TREND STUDY OF A TWIN ELECTRO-RHEOLOGICAL (ER) CLUTCH MECHANISM FOR ROBOTIC APPLICATIONS

2005 ◽  
Vol 19 (32) ◽  
pp. 4733-4768 ◽  
Author(s):  
K. P. TAN ◽  
R. STANWAY ◽  
A. R. JOHNSON ◽  
W. A. BULLOUGH
Keyword(s):  
Angular Velocity ◽  
Model Validation ◽  
Cogging Torque ◽  
Robotic Arms ◽  
Trend Study ◽  
The Past ◽  
Positioning Errors ◽  
Rapid Reversal ◽  
Clutch Mechanism ◽  
Robotic Applications

Positioning accuracies of the robot arms are important at fast maneuvering speeds of the manipulators. In the past, many researchers had investigated the precisions of the robotic arms. They reported that these robotic positioning errors are caused by the dynamic inefficiencies of the robotic actuators; DC servomotors. Therefore, in order to resolve this actuator's issue, a twin electro-rheological (ER) clutch mechanism that consists of two counter-rotating ER clutches is employed. This is due to its output dynamics being unaffected by the output cogging torque of the driving motors. Also, this clutch mechanism can perform rapid reversal responses in bi-directional mode. In this present paper, two kinematics models that describe the output angular velocity and displacement behaviors of this clutch mechanism undergone validations. Next, the trend studies of these angular kinematics responses are conducted in order to determine the methodology to generate the fastest reversal motions of the clutch mechanism.

scholarly journals Design and Analysis of a Novel Variable Stiffness Joint for Robot

2018 ◽  
Vol 249 ◽  
pp. 03005
Author(s):  
Xiang Zhang ◽  
Twan Capehart ◽  
Carl A. Moore
Keyword(s):  
High Frequency ◽  
Joint Stiffness ◽  
Variable Stiffness ◽  
Robotic Systems ◽  
Compliant Joint ◽  
Variable Transmission ◽  
Application Requirements ◽  
Base Application ◽  
Robotic Applications ◽  
Human Robotic Interaction

As people pay more attention to the safety of human-robotic interaction, the flexibility of machine joints is becoming more and more important. To address the needs of future robotic applications, many kinds of variable stiffness mechanisms have been designed by scientists. But most of the structures are complex. By studying and comparing many different mechanism designs of variable stiffness joint, we recognize the need to miniaturization and reduce weight of variable stiffness joints with high frequency operation. To address this, need a continuously Variable Compliant Joint (CVCJ) was designed. The core of the joint is based on the structure of the spherical continuously variable transmission (SCVT) which is the catalyst to change the stiffness continuously and smoothly. In this paper, we present a compact variable stiffness joint structure to meet the volume and weight requirements of the future robotic systems. We show the connection between the joint stiffness coefficient and the structure parameters by making mathematical analysis, modelling and simulation for the system to verify the ability to satisfy the base application requirements of the compliant joint.

scholarly journals Design and Analysis of a Rigid-Flexible Parallel Mechanism for a Neck Brace

2019 ◽  
Vol 2019 ◽  
pp. 1-20
Author(s):  
Jingfang Liu ◽  
Yanxia Cheng ◽  
Shuang Zhang ◽  
Zhenxin Lu ◽  
Guohua Gao
Keyword(s):  
Parallel Mechanism ◽  
Rotational Degree ◽  
Compliance Matrix ◽  
Body Model ◽  
Rotation Measurement ◽  
Rigid Body Model ◽  
Compliant Joint ◽  
Spherical Parallel Mechanism ◽  
Rotation Function ◽  
Flexion And Extension

A rigid-flexible parallel mechanism called 3-RXS mechanism as a neck brace for patients with head drooping symptoms (HDS) is presented. The 3-RXS neck brace has a simple and light structure coupled with good rotation performance, so it can be used to assist the neck to achieve flexion and extension, lateral bend, and axial torsion. Firstly, to prove that the X-shaped compliant joint has a rotational degree of freedom (DoF) and can be used in the 3-RRS spherical parallel mechanism (3-RRS SPM), the six-dimensional compliance matrix, axis drift, and DoF of the X-shaped compliant joint have been systematically calculated. Secondly, the 3-RXS mechanism and its pseudo-rigid-body model (PRBM) are obtained by replacing the revolute pair with the X-shaped compliant joint in the 3-RRS SPM. The rotation workspace of the 3-RXS mechanism is also performed. Finally, to verify the rotation function and effect of 3-RXS mechanism for neck-assisted rehabilitation, the kinematics simulations of the 3-RXS and 3-RRS mechanisms are carried out and compared with the theoretical result, and a primary experiment for rotation measurement of 3-RXS mechanism prototype is carried out. All results prove the feasibility of the 3-RXS mechanism for a neck brace.

Design of Lead Screw Actuators for Wearable Robotic Applications

2005 ◽  
Author(s):  
Kevin W. Hollander ◽  
Thomas G. Sugar
Keyword(s):  
High Weight ◽  
Weight Ratio ◽  
Design Procedure ◽  
Mechanical Efficiency ◽  
Human Muscle ◽  
Wearable Robot ◽  
Screw Design ◽  
Lead Screw ◽  
Standard Lead ◽  
Robotic Applications

A wearable robot is a controlled and actuated device that is in direct contact with its user. As such, the implied requirements of this device are that it must be portable, lightweight and most importantly safe. To achieve these goals an actuator with a good ‘power to weight’ ratio, good mechanical efficiency, good ‘strength to weight’ ratio and that is safe is desired. The design of the standard lead screw does not normally perform well in any of these categories. The typical lead screw has low pitch angles and large radii, thereby yielding low mechanical efficiencies and high weight. However, using the design procedure outlined in this text both efficiency and weight are improved, thus yielding a lead screw system with performances that rival human muscle. The result of an example problem reveals a feasible lead screw design that has a ‘power to weight’ ratio of 277W/kg, approaching that of the DC motor driving it, at 312W/kg, as well as a mechanical efficiency of 0.74, and a maximum ‘strength to weight’ ratio of 11.3kN/kg(1154kgf/kg).

Influence of Contact Geometry on Local Friction Energy and Stiffness of Revolute Joints

2012 ◽  
Vol 134 (2) ◽  
Author(s):  
Alexander Gummer ◽  
Bernd Sauer
Keyword(s):  
Dynamic Behavior ◽  
Contact Zone ◽  
Mechanical Systems ◽  
Contact Geometry ◽  
Rotational Degree ◽  
Multibody Simulation ◽  
Calculation Algorithm ◽  
Robotic Arms ◽  
Revolute Joints ◽  
Friction Energy

Revolute joints (also called pin joints or hinge joints) are used in many different mechanical systems such as robotic arms, door hinges, folding mechanisms, or hydraulic shovels. Since they transmit forces and give a rotational degree of freedom to the connected parts, revolute joints have a major impact on the dynamic behavior of the system into which they are built. Two main characteristics of these elements are their stiffness and their clearance. Both of them change as the wear between the joint’s pin and the rod hole increases during operation. In order to consider these aspects in a multibody simulation an analytical, numerically effective method has been developed to calculate the stiffness of a revolute joint in dependence of the geometry and the wear state. In addition, the calculation algorithm allows for for the analysis of the local friction energy that occurs in the contact zone. In this paper, the calculation approach is presented together with the results for two different steady loaded revolute joints.

Design of Lightweight Lead Screw Actuators for Wearable Robotic Applications

2005 ◽  
Vol 128 (3) ◽  
pp. 644-648 ◽  
Author(s):  
Kevin W. Hollander ◽  
Thomas G. Sugar
Keyword(s):  
Direct Contact ◽  
Weight Ratio ◽  
Design Procedure ◽  
Mechanical Efficiency ◽  
Human Muscle ◽  
Wearable Robot ◽  
Screw Design ◽  
Lead Screw ◽  
Standard Lead ◽  
Robotic Applications

A wearable robot is a controlled and actuated device that is in direct contact with its user. As such, the implied requirements of this device are that it must be portable, lightweight, and most importantly safe. To achieve these goals, an actuator with a good “power to weight” ratio, good mechanical efficiency, good “strength to weight” ratio, and that is safe is desired. The design of the standard lead screw does not normally perform well in any of these categories. The typical lead screw has low pitch angles and large radii, thereby yielding low mechanical efficiencies and heavy weight. However, using the design procedure outlined in this text, both efficiency and weight are improved; thus yielding a lead screw system with performances that rival human muscle. The result of an example problem reveals a feasible lead screw design that has a power to weight ratio of 277W∕kg, approaching that of the dc motor driving it, at 312W∕kg, as well as a mechanical efficiency of 0.74, and a maximum strength to weight ratio of 11.3kN∕kg(1154kgf∕kg).

scholarly journals Transmission Comparison for Cooperative Robotic Applications

Actuators ◽  
2021 ◽  
Vol 10 (9) ◽  
pp. 203
Author(s):  
Mark J. Nandor ◽  
Maryellen Heebner ◽  
Roger Quinn ◽  
Ronald J. Triolo ◽  
Nathaniel S. Makowski
Keyword(s):  
Muscle Activation ◽  
Mechanical Efficiency ◽  
Assistive Devices ◽  
Joint Torque ◽  
Harmonic Drive ◽  
Electromechanical Actuators ◽  
Passive Resistance ◽  
Isometric Torque ◽  
Planetary Transmission ◽  
Robotic Applications

The development of powered assistive devices that integrate exoskeletal motors and muscle activation for gait restoration benefits from actuators with low backdrive torque. Such an approach enables motors to assist as needed while maximizing the joint torque muscles, contributing to movement, and facilitating ballistic motions instead of overcoming passive dynamics. Two electromechanical actuators were developed to determine the effect of two candidate transmission implementations for an exoskeletal joint. To differentiate the transmission effects, the devices utilized the same motor and similar gearing. One actuator included a commercially available harmonic drive transmission while the other incorporated a custom designed two-stage planetary transmission. Passive resistance and mechanical efficiency were determined based on isometric torque and passive resistance. The planetary-based actuator outperformed the harmonic-based actuator in all tests and would be more suitable for hybrid exoskeletons.

scholarly journals Cartesian Aerial Manipulator with Compliant Arm

2021 ◽  
Vol 11 (3) ◽  
pp. 1001
Author(s):  
Alejandro Suarez ◽  
Manuel Perez ◽  
Guillermo Heredia ◽  
Anibal Ollero
Keyword(s):  
Dynamic Models ◽  
Position Control ◽  
Force Sensor ◽  
Monitoring And Control ◽  
End Effector ◽  
Robotic Arms ◽  
Revolute Joints ◽  
Angular Deflection ◽  
Compliant Joint ◽  
And Control

This paper presents an aerial manipulation robot consisting of a hexa-rotor equipped with a 2-DOF (degree of freedom) Cartesian base (XY–axes) that supports a 1-DOF compliant joint arm that integrates a gripper and an elastic linear force sensor. The proposed kinematic configuration improves the positioning accuracy of the end effector with respect to robotic arms with revolute joints, where each coordinate of the Cartesian position depends on all the joint angles. The Cartesian base reduces the inertia of the manipulator and the energy consumption since it does not need to lift its own weight. Consequently, the required torque is lower and, thus, the weight of the actuators. The linear and angular deflection sensors of the arm allow the estimation, monitoring and control of the interaction wrenches exerted in two axes (XZ) at the end effector. The kinematic and dynamic models are derived and compared with respect to a revolute-joint arm, proposing a force-position control scheme for the aerial robot. A battery counterweight mechanism is also incorporated in the X–axis linear guide to partially compensate for the motion of the manipulator. Experimental results indoors and outdoors show the performance of the robot, including object grasping and retrieval, contact force control, and force monitoring in grabbing situations.

New Apparatus and Blower Centrifugal Fan Design Features to Improve its Performance

1999 ◽  
Author(s):  
Monier B. Botros ◽  
Dorothy F. Hanna ◽  
Jasmine E. Boulos ◽  
Ming-Chia Lai
Keyword(s):  
Fluid Dynamic ◽  
Suction Side ◽  
Mechanical Efficiency ◽  
Design Criterion ◽  
Air Separation ◽  
Airflow Rate ◽  
Centrifugal Fan ◽  
Computational Fluid Dynamic Analysis ◽  
New Apparatus ◽  
Fan Blade

Abstract Different design philosophies of a blower centrifugal fan blades and hub are evaluated by airflow performance, computational fluid dynamic analysis (CFD) and experimental Laser Doppler Velocimetry (LDV). A design criterion of fan blade, vanes, channels is developed to eliminate or minimize air separation from the blades suction side. The effect of the fan hub design on the air radial velocity profile is discussed. A new apparatus is developed to control the air flow field at the blower inlet ring. It directs the air to flow in radial directions at the entrance of the fan blade passages, channels. The blower systems with the new features operates at high mechanical efficiency over a broad range of airflow rate in different blower scroll sizes. Its peak static efficiency reaches 62% and total mechanical efficiency 68%, which is 5 to 10% above efficiencies of previous designs. As a result, power consumption is reduced by 7–15% through the operating range.

Design of a Dexterous Robotic Arm Manipulator Using Hybrid BCI

2020 ◽  
Author(s):  
Daniel A. Medina Portilla ◽  
Vidya K. Nandikolla
Keyword(s):  
Point Cloud ◽  
Vision System ◽  
Operation Mode ◽  
Robotic Arm ◽  
Robotic Arms ◽  
Software Interface ◽  
Autonomous Operation ◽  
Dexterous Hand ◽  
Robotic Applications ◽  
Bci System

Abstract The paper describes the design of a hybrid Brain Computer Interface (BCI) system that provides control commands to manipulate a robotic arm. The goal is to facilitate BCI controlled real-time robotic applications by using a semi-autonomous operation mode that accepts multiple commands. Simple tasks, like moving forward or turning, are executed based on a single BCI command while more complicated tasks, like grabbing or pushing an object are automated once the task is selected. The robotic arm vision system uses an Intel RealSense D435 camera for image and depth perception where a point cloud generates an interface for the user to select an object. The user selects an object to manipulate, which identifies the goal position and location. After the location and object is determined, the software interface moves the robotic arm to have the selected object in the robotic arms’ workspace. The current robotic arm design utilizes an open bionics Brunel dexterous hand as the end effector which allows for human-like hand actions. A simulation platform is developed to verify the effect of the entire system of a dexterous robotic arm on a mobile platform. The system design and results using a hybrid BCI system is demonstrated.

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