Stiffness Design for Compliant Manipulators Based on Dynamics Analysis of the Impact Configuration

2011 ◽  
Author(s):  
Dongming Gan ◽  
Nikos G. Tsagarakis ◽  
Jian S. Dai ◽  
Darwin G. Caldwell
Keyword(s):  
Joint Stiffness ◽  
Joint Torque ◽  
Dynamics Analysis ◽  
End Effector ◽  
Joint Torques ◽  
Maximum Value ◽  
Stiffness Design ◽  
Compliant Joint ◽  
Compliant Actuators ◽  
The Impact

This paper presents a study on setting the joint stiffness for compliant robots in order to protect the actuators when the arm comes up against impact. System dynamic equations of compliant manipulators integrated with impact model are linearized to identify the maximum joint torques in the impact. Based on this, different directions of end-effector velocity and impact normal in different configurations in the robot workspace are calculated based on a given magnitude of end-effector velocity. By tuning the stiffness for each compliant joint to ensure the joint torque does not exceed the maximum value of the actuator, candidate stiffness values are obtained to make the compliant actuators safe in all cases when the robot end-effector moves with a velocity within the fixed magnitude value used in the calculation. The theory and procedure are firstly laid and demonstrated in a 1-DOF planar manipulator, then the work is applied to a 2-DOF compliant manipulator and the candidate stiffness is obtained based on the method.

Stiffness Design for a Spatial Three Degrees of Freedom Serial Compliant Manipulator Based on Impact Configuration Decomposition

2012 ◽  
Vol 5 (1) ◽  
Author(s):  
Dongming Gan ◽  
Nikos G. Tsagarakis ◽  
Jian S. Dai ◽  
Darwin G. Caldwell ◽  
Lakmal Seneviratne
Keyword(s):  
Degrees Of Freedom ◽  
General Procedure ◽  
Joint Torque ◽  
End Effector ◽  
Joint Torques ◽  
Serial Manipulators ◽  
Stiffness Design ◽  
Compliant Joint ◽  
The Impact ◽  
Three Degrees Of Freedom

This paper proposes a method of stiffness design for a spatial Three Degrees of Freedom (3DOF) serial compliant manipulator with the objective of protecting the compliant joint actuators when the manipulator comes up against impact. System dynamic equations of serial compliant manipulators integrated with an impact model are linearized to identify the maximum joint torques in the impact. Based on this, a general procedure is given in which maximum joint torques are calculated with different directions of end-effector velocity and impact normal in the manipulator workspace based on a given magnitude of end-effector velocity. By tuning the stiffness for each compliant joint to ensure the maximum joint torque does not exceed the maximum value of the actuator, candidate stiffness values are obtained to make the compliant actuators safe in all cases. The theory and procedure are then applied to the spatial 3DOF serial compliant manipulator of which the impact configuration is decomposed into a 2DOF planar serial manipulator and a 1DOF manipulator with a 2DOF link based on the linearized impact-dynamic model. Candidate stiffness of the 3DOF serial compliant manipulator is obtained by combining analysis of the 2DOF and 1DOF manipulators. The method introduced in this paper can be used for both planar and spatial compliant serial manipulators.

scholarly journals Cobot with Prismatic Compliant Joint Intended for Doppler Sonography

Robotics ◽  
2020 ◽  
Vol 9 (1) ◽  
pp. 14 ◽  
Author(s):  
Juan Sandoval ◽  
Med Amine Laribi ◽  
Saïd Zeghloul ◽  
Marc Arsicault ◽  
Jean-Michel Guilhem
Keyword(s):  
Musculoskeletal Disorder ◽  
Doppler Sonography ◽  
Impact Force ◽  
Variable Stiffness ◽  
Safety Performance ◽  
End Effector ◽  
Force Criterion ◽  
Compliant Joint ◽  
The Impact ◽  
Collaborative Robot

This paper deals with a collaborative robot, i.e., cobot, coupled with a new prismatic compliant joint (PCJ) at its end-effector. The proposed collaborative solution is intended for Doppler sonography to prevent musculoskeletal disorders issues. On one hand, the Doppler sonographer’s postures are investigated based on motion capture use during the arteries examination. This study highlighted that configurations adopted by angiologists lead to the musculoskeletal disorder. On the other hand, the proposed PCJ with variable stiffness gives an intrinsic compliance to the cobot handling the probe. This feature allows preserving the human safety when both human and cobot share a common workspace. The effectiveness of the proposed solution is experimentally validated through a 7-DoF Franka Emika robot virtually coupled with the PCJ, during the execution of a trajectory performed during a Doppler ultrasound exam. The impact force criterion is considered as a safety performance.

The relationship between controlled joint torque and end-effector force in underactuated robotic systems

Robotica ◽  
2010 ◽  
Vol 29 (4) ◽  
pp. 581-584 ◽  
Author(s):  
Jaeheung Park
Keyword(s):  
Jacobian Matrix ◽  
Joint Torque ◽  
Generalized Jacobian ◽  
End Effector ◽  
Joint Torques ◽  
Floating Base ◽  
Force Moment ◽  
Generalized Jacobian Matrix ◽  
The Relationship ◽  
Jacobian Inverse

SUMMARYThe generalized Jacobian matrix was introduced for dealing with end-effector control in space robots. One of the applications of this Jacobian is to be used in Jacobian transpose control to generate joint torques given end-effector position error. It would be misleading, however, to consider the transpose of this Jacobian as a mapping from end-effector force/moment to controlled joint torques for underactuated systems or floating base robots. This paper explains why it does not represent the mapping and provides a simple example. Later, the correct mapping is provided using the dynamically consistent Jacobian inverse and then a method to compute the actuated-joint torques is explained given the desired end-effector force. Finally, the effect of using the generalized Jacobian in the Jacobian transpose control is analyzed.

Landing Motion of a Legged Robot with Minimization of Impact Force and Joint Torque

2015 ◽  
Vol 27 (1) ◽  
pp. 32-40 ◽  
Author(s):  
Xianglong Wan ◽  
◽  
Takateru Urakubo ◽  
Yukio Tada
Keyword(s):  
Cost Function ◽  
Numerical Optimization ◽  
Impact Force ◽  
Contact Point ◽  
Joint Torque ◽  
Legged Robot ◽  
Joint Torques ◽  
Singular Configuration ◽  
The Cost ◽  
The Impact

<div class=""abs_img""><img src=""[disp_template_path]/JRM/abst-image/00270001/04.jpg"" width=""300"" />Optimal motion of a legged robot</div> This paper deals with an optimal landing motion of a four-link legged robot that minimizes the impact force at the contact point and the joint torques necessary during the motion. The cost function for optimization is given as the weighted sum of the impact force and the joint torques. The configuration of the robot that is close to a singular configuration is advantageous in minimizing the joint torques for a heavy torso, while the configuration where the leg is bent is advantageous in reducing the impact force. This is shown by numerical optimization results with different weights for the cost function and a theoretical analysis of a simplified model of the robot. </span>

On the Use of Induced End Effector Force Analysis for Determining Muscle Roles During Movement

2007 ◽  
Author(s):  
Stephen J. Piazza ◽  
Vladimir M. Zatsiorsky
Keyword(s):  
Electrical Stimulation ◽  
Muscle Function ◽  
Muscle Force ◽  
Human Movement ◽  
The Body ◽  
Joint Torque ◽  
Force Analysis ◽  
End Effector ◽  
Joint Torques ◽  
Muscle Strengthening

It is often of interest in studies of human movement to quantify the function of a muscle force or muscular joint torque. Such information is useful for the identification of the causes of movement disorders and for predicting the effects of interventions including surgical procedures, targeted muscle strengthening, focal treatments for spasticity, and functional electrical stimulation. One useful way to characterize the actions of muscle forces or muscular joint torques is to create linked-segment models of the body and analyze these linkages to determine the joint angular accelerations or end effector forces that result solely from the application of the muscle force or torque in question. Such induced acceleration (IA) analyses or induced end effector force (IEF) analyses have been applied most often to quantify muscle function during normal and pathological walking [1,2].

scholarly journals Verification of Finger Joint Stiffness Estimation Method With Soft Robotic Actuator

2020 ◽  
Vol 8 ◽  
Author(s):  
Xiang Qian Shi ◽  
Ho Lam Heung ◽  
Zhi Qiang Tang ◽  
Kai Yu Tong ◽  
Zheng Li
Keyword(s):  
Estimation Method ◽  
Joint Stiffness ◽  
Ground Truth ◽  
Clinical Score ◽  
Metacarpophalangeal Joint ◽  
Finger Joint ◽  
Joint Torque ◽  
Hand Rehabilitation ◽  
Stiffness Characteristic ◽  
Modified Ashworth Scale

Stroke has been the leading cause of disability due to the induced spasticity in the upper extremity. The constant flexion of spastic fingers following stroke has not been well described. Accurate measurements for joint stiffness help clinicians have a better access to the level of impairment after stroke. Previously, we conducted a method for quantifying the passive finger joint stiffness based on the pressure-angle relationship between the spastic fingers and the soft-elastic composite actuator (SECA). However, it lacks a ground-truth to demonstrate the compatibility between the SECA-facilitated stiffness estimation and standard joint stiffness quantification procedure. In this study, we compare the passive metacarpophalangeal (MCP) joint stiffness measured using the SECA with the results from our designed standalone mechatronics device, which measures the passive metacarpophalangeal joint torque and angle during passive finger rotation. Results obtained from the fitting model that concludes the stiffness characteristic are further compared with the results obtained from SECA-Finger model, as well as the clinical score of Modified Ashworth Scale (MAS) for grading spasticity. These findings suggest the possibility of passive MCP joint stiffness quantification using the soft robotic actuator during the performance of different tasks in hand rehabilitation.

scholarly journals Land Subsidence Estimation for Aquifer Drainage Induced by Underground Mining

Energies ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4658
Author(s):  
Artur Guzy ◽  
Wojciech T. Witkowski
Keyword(s):  
Environmental Impact ◽  
Land Subsidence ◽  
Field Data ◽  
Underground Mining ◽  
Small Scale ◽  
Aquifer System ◽  
Maximum Value ◽  
The Impact ◽  
Method Model ◽  
Impact Of Mining

Land subsidence caused by groundwater withdrawal induced by mining is a relatively unknown phenomenon. This is primarily due to the small scale of such movements compared to the land subsidence caused by deposit extraction. Nonetheless, the environmental impact of drainage-related land subsidence remains underestimated. The research was carried out in the “Bogdanka” coal mine in Poland. First, the historical impact of mining on land subsidence and groundwater head changes was investigated. The outcomes of these studies were used to construct the influence method model. With field data, our model was successfully calibrated and validated. Finally, it was used for land subsidence estimation for 2030. As per the findings, the field of mining exploitation has the greatest land subsidence. In 2014, the maximum value of the phenomenon was 0.313 cm. However, this value will reach 0.364 m by 2030. The spatial extent of land subsidence caused by mining-induced drainage extends up to 20 km beyond the mining area’s boundaries. The presented model provided land subsidence patterns without the need for a complex numerical subsidence model. As a result, the method presented can be effectively used for land subsidence regulation plans considering the impact of mining on the aquifer system.

scholarly journals Upper-Limb Isometric Force Feasible Set: Evaluation of Joint Torque-Based Models

Biomechanics ◽  
2021 ◽  
Vol 1 (1) ◽  
pp. 102-117
Author(s):  
Nasser Rezzoug ◽  
Vincent Hernandez ◽  
Philippe Gorce
Keyword(s):  
Upper Limb ◽  
Isometric Force ◽  
Joint Torque ◽  
Force Distribution ◽  
Prediction Errors ◽  
Feasible Set ◽  
Joint Torques ◽  
Motor Abilities ◽  
Capacity Evaluation ◽  
Measured Force

A force capacity evaluation for a given posture may provide better understanding of human motor abilities for applications in sport sciences, rehabilitation and ergonomics. From data on posture and maximum isometric joint torques, the upper-limb force feasible set of the hand was predicted by four models called force ellipsoid, scaled force ellipsoid, force polytope and scaled force polytope, which were compared with a measured force polytope. The volume, shape and force prediction errors were assessed. The scaled ellipsoid underestimated the maximal mean force, and the scaled polytope overestimated it. The scaled force ellipsoid underestimated the volume of the measured force distribution, whereas that of the scaled polytope was not significantly different from the measured distribution but exhibited larger variability. All the models characterized well the elongated shape of the measured force distribution. The angles between the main axes of the modelled ellipsoids and polytopes and that of the measured polytope were compared. The values ranged from 7.3° to 14.3°. Over the entire surface of the force ellipsoid, 39.7% of the points had prediction errors less than 50 N; 33.6% had errors between 50 and 100 N; and 26.8% had errors greater than 100N. For the force polytope, the percentages were 56.2%, 28.3% and 15.4%, respectively.

scholarly journals Optimization of Dynamic Task Location within a Manipulator’s Workspace for the Utilization of the Minimum Required Joint Torques

Electronics ◽  
2021 ◽  
Vol 10 (3) ◽  
pp. 288
Author(s):  
Adam Wolniakowski ◽  
Charalampos Valsamos ◽  
Kanstantsin Miatliuk ◽  
Vassilis Moulianitis ◽  
Nikos Aspragathos
Keyword(s):  
High Performance ◽  
Human Robot Interaction ◽  
Optimal Position ◽  
End Effector ◽  
Joint Torques ◽  
Dynamic Task ◽  
Arbitrary Position ◽  
Simulation Results ◽  
Set Up ◽  
Task Placement

The determination of the optimal position of a robotic task within a manipulator’s workspace is crucial for the manipulator to achieve high performance regarding selected aspects of its operation. In this paper, a method for determining the optimal task placement for a serial manipulator is presented, so that the required joint torques are minimized. The task considered comprises the exercise of a given force in a given direction along a 3D path followed by the end effector. Given that many such tasks are usually conducted by human workers and as such the utilized trajectories are quite complex to model, a Human Robot Interaction (HRI) approach was chosen to define the task, where the robot is taught the task trajectory by a human operator. Furthermore, the presented method considers the singular free paths of the manipulator’s end-effector motion in the configuration space. Simulation results are utilized to set up a physical execution of the task in the optimal derived position within a UR-3 manipulator’s workspace. For reference the task is also placed at an arbitrary “bad” location in order to validate the simulation results. Experimental results verify that the positioning of the task at the optimal location derived by the presented method allows for the task execution with minimum joint torques as opposed to the arbitrary position.

Study on the Operation Model of Colleges Network Learning Propaganda and Public Opinion Guidance Based on the Internet

2013 ◽  
Vol 380-384 ◽  
pp. 2104-2108
Author(s):  
Chen Liang Li ◽  
Ming Xia Zhu
Keyword(s):  
Public Opinion ◽  
Information Science ◽  
Internet Technology ◽  
The Internet ◽  
C Language ◽  
Network Learning ◽  
Maximum Value ◽  
Network Transmission ◽  
The Impact ◽  
Important Significance

With the development of computer information science and technology, Internet has a large number of network propaganda and public opinion page every day. Through the network micro message and the micro-blog forwarding, network propaganda and public opinion have the impact on the development and stability of colleges, so the study network propaganda and public opinion has important significance for the development of colleges. Under this background, based on the computer Internet technology, the Internet erection of network propaganda guidance mode are analyzed, and compared with the fuzzy minimum production tree theory and the C language software, the network construction is verified. Finally the iterative process of finding the network transmission is relatively stable, after 800 iterative steps, numerical is slowly increasing, in which the maximum value is about 0.0001. The seven school propaganda is been as the minimum spanning of tree main network, its sum of weighted has been up to 1606.

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