Motion–Force Interaction Performance Analyses of Redundantly Actuated and Overconstrained Parallel Robots With Closed-Loop Subchains

2020 ◽  
Vol 142 (10) ◽  
Author(s):  
Qizhi Meng ◽  
Fugui Xie ◽  
Xin-Jun Liu
Keyword(s):  
Closed Loop ◽  
Interaction Analysis ◽  
Structural Parameters ◽  
Parallel Robot ◽  
Parallel Robots ◽  
Load Carrying Capacity ◽  
Force Interaction ◽  
Load Carrying ◽  
Redundantly Actuated ◽  
Performance Analyses

Abstract Motion–force interaction performance analyses of redundantly actuated and overconstrained parallel robots with closed-loop subchains are an open problem considering two challenges: (a) how to take all the internal wrenches into account at the same level when the mobile platform suffers uncertain loads and (b) how to disclose the influence of the structural parameters inside the closed-loop subchains on the robot’s performance. To tackle this problem, based on the blocking-and-acting strategy, this paper proposes a new screw-based method to analyze the motion–force interaction performance of such parallel robots. Two aspects of performance are focused, i.e., the distal and proximal motion–force interactability. The two proposed indices focus on reflecting the load-carrying capacity and the motion-transmission capacity, respectively. To evaluate the comprehensive performance of the parallel robot at a certain pose, a local interaction index (LII) is defined as the minimum value of indices of the minimized distal and proximal interaction performance. The feasibility and validity of the proposed indices are illustrated by the motion–force interaction analysis of some redundantly actuated and overconstrained parallel robots with closed-loop subchains.

Optimizing the Torque Distribution of a Redundantly Actuated Parallel Robot to Study the Temporomandibular Reaction Forces During Food Chewing

2020 ◽  
Vol 12 (5) ◽  
Author(s):  
Naser Mostashiri ◽  
Jaspreet Dhupia ◽  
Alexander Verl ◽  
John Bronlund ◽  
Weiliang Xu
Keyword(s):  
Inverse Dynamics ◽  
Parallel Robot ◽  
Parallel Robots ◽  
Cost Functions ◽  
Measurement Tool ◽  
Redundancy Resolution ◽  
Theoretical Formulation ◽  
Temporomandibular Joints ◽  
Redundantly Actuated

Abstract Inverse dynamics solution of redundantly actuated parallel robots (RAPRs) requires redundancy resolution methods. In this paper, the Lagrange’s equations of the second kind are used to derive governing equations of a chewing RAPR. Jacobian analysis of the RAPR is presented. As redundancy resolutions, two different optimization cost functions corresponding to specific neuromuscular objectives, which are minimization of effort of the muscles of mastication and temporomandibular joints (TMJs) loads, are used to find the RAPR’s optimized actuation torque distributions. The actuation torques under the influence of experimentally determined dynamic chewing forces on molar teeth reproduced from a separate chewing experiment are calculated for realistic in vitro simulation of typical human chewing. These actuation torques are applied to the RAPR with a distributed-computed-torque proportional-derivative control scheme, allowing the RAPR’s mandible to follow a human subject’s chewing trajectory. TMJs loads are measured by force sensors, which are comparable with the computed loads from theoretical formulation. The TMJs loads for the two optimization cost functions are measured while the RAPR is chewing 3 g of peanuts on its left molars. Maximum and mean of the recorded loads on the left TMJ were higher in both cases. Moreover, the maximum and mean of the recorded loads on both TMJs were smaller for the cost function minimizing the TMJs loads. These results demonstrate validity of the model, suggesting the RAPR as a potential TMJ loads measurement tool to study the chewing characteristics of patients suffering from pain in TMJs.

Determining maximum load carrying capacity of planar flexible-link robot: closed-loop approach

Robotica ◽  
2010 ◽  
Vol 28 (7) ◽  
pp. 959-973 ◽  
Author(s):  
M. H. Korayem ◽  
R. Haghighi ◽  
A. H. Korayem ◽  
A. Nikoobin ◽  
A. Alamdari
Keyword(s):  
Carrying Capacity ◽  
Closed Loop ◽  
Sliding Mode ◽  
Maximum Load ◽  
Open Loop ◽  
Nonlinear Observer ◽  
Flexible Manipulator ◽  
Load Carrying Capacity ◽  
Maximum Payload ◽  
Load Carrying

SUMMARYMaximum load carrying capacity (MLCC) of flexible robot manipulators is computed based on closed-loop approach. In open-loop approach, controller is not considered, so the end effector deviation from the predefined path is significant and the accuracy constraint restrains the maximum payload before actuators go into saturation mode. In order to improve the MLCC, a method based on closed-loop strategy is presented. Since in this case the accuracy is improved the actuators constraint is not a major concern and full power of actuators can be used. Since controller can play an important role in improving the maximum payload, a sliding mode based partial feedback linearization controller is designed. Furthermore, a fuzzy variable layer is used in sliding mode design to boost the performance of the controller. However, the control strategy required measurements of elastic variables velocity that are not conveniently measurable. So a nonlinear observer is designed to estimate these variables. Stability analysis of the proposed controller and state observer are performed on the basis of Lyapunov's direct method. In order to verify the effectiveness of the presented method, simulation is done for a two-link flexible manipulator. The obtained maximum payload in open-loop and closed-loop cases is compared and the superiority of the method is illustrated and the results are discussed.

Self-excited vibration of a 3-PRR planar parallel robot

2021 ◽  
pp. 095440622110095
Author(s):  
Xuxian Zhu ◽  
Zhicheng Qiu ◽  
Lingbo Xie ◽  
Xianmin Zhang
Keyword(s):  
Vibration Frequency ◽  
Trajectory Tracking ◽  
Coupling Effect ◽  
Structural Parameters ◽  
Self Regulation ◽  
Parallel Robot ◽  
Parallel Robots ◽  
The Self ◽  
Excited Vibration ◽  
Motion Speed

Self-excited vibration of parallel robots can seriously affect the motion performance and damage the mechanical structure. In order to study the self-excited vibration characteristics of a 3-PRR (where P and R represent the prismatic and revolute joints respectively and the underlined letter represents the actuated joint) planar parallel robot, dynamic model is firstly established and the singularity is analyzed theoretically. Then the dynamic characteristics at internal and boundary singularities are both explored experimentally. The motion form and generating mechanism of the self-excited vibration are researched. The influencing factors on vibration frequency are obtained and the self-excited vibration during trajectory tracking motion is analyzed. Finally, a singularity escaping strategy is proposed and tested. Theoretical analysis and experimental results show that the performance of parallel robot deteriorates dramatically at singularities. Nevertheless, the parallel robot can pass through the internal singularity successfully with optimized load and motion speed so that the workspace can be expanded. The 3-PRR planar parallel robot exhibits self-excited vibration at internal singularities, which is mainly caused by the singularity, self-regulation of motors and the closed-chain coupling effect. The vibration frequency is mainly determined by singular configuration and the structural parameters. The parallel robot can maintain self-excited vibration state while carrying out trajectory tracking under a singular attitude angle. Moreover, the proposed singularity escaping strategy is verified to be feasible so that the self-excited vibration can be eliminated effectively.

The QuadroG Robot, a Parallel Robot With a Configurable Platform for Haptic Applications

2015 ◽  
Author(s):  
Salua Hamaza ◽  
Patrice Lambert ◽  
Marco Carricato ◽  
Just Herder
Keyword(s):  
Kinematic Analysis ◽  
Degrees Of Freedom ◽  
Closed Loop ◽  
Parallel Robot ◽  
Parallel Robots ◽  
End Effector ◽  
Contact Points ◽  
Loop Chain ◽  
End Effectors ◽  
4 Degrees Of Freedom

This paper explores the fundamentals of parallel robots with configurable platforms (PRCP), as well as the design and the kinematic analysis of those. The concept behind PRCP is that the rigid (non-configurable) end-effector is replaced by a closed-loop chain, the configurable platform. The use of a closed-loop chain allows the robot to interact with the environment from multiple contact points on the platform, which reflects the presence of multiple end-effectors. This results in a robot that successfully combines motion and grasping capabilities into a structure that provides an inherent high stiffness. This paper aims to introduce the QuadroG robot, a 4 degrees of freedom PRCP which finely merges planar motion together with grasping capabilities.

scholarly journals Motion Reliability Analysis of the Delta Parallel Robot considering Mechanism Errors

2019 ◽  
Vol 2019 ◽  
pp. 1-10 ◽  
Author(s):  
Yu Li ◽  
Deyong Shang ◽  
Xun Fan ◽  
Yue Liu
Keyword(s):  
Reliability Analysis ◽  
Structural Parameters ◽  
Kinematic Model ◽  
Vertical Direction ◽  
Parallel Robot ◽  
Parallel Robots ◽  
Joint Clearance ◽  
Spherical Joint ◽  
Key Factor ◽  
The Relationship

Delta parallel robots are widely used in assembly detection, packaging sorting, precision positioning, and other fields. With the widespread use of robots, people have increasing requirements for motion accuracy and reliability. This paper considers the influence of various mechanism errors on the motion accuracy and analyzes the motion reliability of the mechanism. Firstly, we establish a kinematic model of the robot and obtain the relationship between the position of the end effector and the structural parameters based on the improved D–H transform rule. Secondly, an error model considering the dimension error, the error of revolute joint clearance, driving error, and the error of spherical joint clearance is established. Finally, taking an actual robot as an example, the comprehensive influence of mechanism errors on motion accuracy and reliability in different directions is quantitatively analyzed. It is shown that the driving error is a key factor determining the motion accuracy and reliability. The influence of mechanism errors on motion reliability is different in different directions. The influence of mechanism errors on reliability is small in the vertical direction, while it is great in the horizontal direction. Therefore, we should strictly control the mechanism errors, especially the driving angle, to ensure the motion accuracy and reliability. This research has significance for error compensation, motion reliability analysis, and reliability prediction in robots, and the conclusions can be extended to similar mechanisms.

scholarly journals Visual Closed-Loop Dynamic Model Identification of Parallel Robots Based on Optical CMM Sensor

Electronics ◽  
2019 ◽  
Vol 8 (8) ◽  
pp. 836 ◽  
Author(s):  
Pengcheng Li ◽  
Ahmad Ghasemi ◽  
Wenfang Xie ◽  
Wei Tian
Keyword(s):  
Dynamic Model ◽  
Visual Servoing ◽  
Closed Loop ◽  
Model Identification ◽  
Parallel Robot ◽  
Parallel Robots ◽  
Model Parameters ◽  
Error Identification ◽  
Output Error ◽  
Identification Method

Parallel robots present outstanding advantages compared with their serial counterparts; they have both a higher force-to-weight ratio and better stiffness. However, the existence of closed-chain mechanism yields difficulties in designing control system for practical applications, due to its highly coupled dynamics. This paper focuses on the dynamic model identification of the 6-DOF parallel robots for advanced model-based visual servoing control design purposes. A visual closed-loop output-error identification method based on an optical coordinate-measuring-machine (CMM) sensor for parallel robots is proposed. The main advantage, compared with the conventional identification method, is that the joint torque measurement and the exact knowledge of the built-in robot controllers are not needed. The time-consuming forward kinematics calculation, which is employed in the conventional identification method of the parallel robot, can be avoided due to the adoption of optical CMM sensor for real time pose estimation. A case study on a 6-DOF RSS parallel robot is carried out in this paper. The dynamic model of the parallel robot is derived based on the virtual work principle, and the built dynamic model is verified through Matlab/SimMechanics. By using an outer loop visual servoing controller to stabilize both the parallel robot and the simulated model, a visual closed-loop output-error identification method is proposed and the model parameters are identified by using a nonlinear optimization technique. The effectiveness of the proposed identification algorithm is validated by experimental tests.

Isotropic Analysis of Line Vector Forces and its Application in the Type Synthesis of Redundantly Actuated 3-DOF Translational Parallel Mechanisms

2016 ◽  
Author(s):  
Yundou Xu ◽  
Xin Zhou ◽  
Ling Lu ◽  
Jiantao Yao ◽  
Yongsheng Zhao
Keyword(s):  
Carrying Capacity ◽  
Kinematic Chain ◽  
Conical Surface ◽  
Load Carrying Capacity ◽  
Parallel Mechanisms ◽  
Type Synthesis ◽  
Active Joint ◽  
Isotropic Line ◽  
Load Carrying ◽  
Redundantly Actuated

The load-carrying capacity of a mechanism is closely related to its line vector force. This article presents a thorough isotropic analysis of line vector forces. The results show that the isotropic condition can be satisfied when the line vector forces are evenly distributed on a conical surface with a cone-top angle of 109.472 degrees. By combining the isotropic line vector forces, a method for the type synthesis of 3-DOF, redundantly actuated translational parallel mechanisms (PMs) is proposed, in which the arrangement of the active joints is taken into account in advance. Using this method, a kinematic chain with a twist system reciprocal to both the constraint and actuation wrenches is constructed firstly, and then the active joint reciprocal to the constraint wrenches but not to the actuation wrench is constructed. Thus, a series of typical redundantly actuated PMs with isotropic actuation forces are obtained. Finally, the 4-PRRR PM is analyzed as an example, and the results show that the isotropy of the load-carrying capacity can always be satisfied during its movement.

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