Minimal Deviation Paths for Manipulators With Joint Clearances

2014 ◽  
Author(s):  
Ming-Cheng Lai ◽  
Kuei-Yuan Chan
Keyword(s):  
Optimal Path ◽  
Joint Clearance ◽  
Control Effort ◽  
Optimization Framework ◽  
Design Variables ◽  
Additional Equipment ◽  
Angular Velocities ◽  
Minimal Deviation ◽  
Joint Clearances ◽  
Target Locations

Manipulator joint clearance is a natural consequence of manufacturing processes. Although most studies in the literature have assumed zero joint clearance, its existence is unavoidable and thus its impact needs to be evaluated. With the miniaturizing trend in engineering products, errors due to joint clearance have become an increasingly important issue. This study investigates how manipulators deviate from the desired working sites due to joint clearance. Deviations from the target locations can be reduced by properly selecting the working path. The optimal path is obtained by first parameterizing the path based on the required target task locations. Corresponding controlling inputs, namely linear and angular velocities as well as their accelerations, are calculated using inverse kinematics. Joint clearances are then added to obtain the deviations a path will make. An optimization framework with path parameters as the design variables is then formulated to minimize the resulting deviations. The proposed framework is shown to improve accuracy without additional equipment cost or control effort. A five-bar parallel manipulator is used to demonstrate the proposed method.

Identifying joint clearance via robot manipulation

2017 ◽  
Vol 232 (15) ◽  
pp. 2549-2574 ◽  
Author(s):  
Kuan-Lin Li ◽  
Ying-Kuan Tsai ◽  
Kuei-Yuan Chan
Keyword(s):  
Robot Manipulators ◽  
Optimal Path ◽  
Optimal Operation ◽  
Joint Clearance ◽  
Average Error ◽  
Robot Manipulation ◽  
Uncertainty Sources ◽  
Time Calibration ◽  
Joint Clearances ◽  
Improved Accuracy

Inaccuracy in robot manipulation is a result of various uncertainties. Most methods reduce operation errors by calibrating robot parameters, with little attention on understanding the uncertainty sources in the process. This paper investigates how operation accuracy of robot manipulators can be improved by identifying one of the major uncertainty–joint clearance. We first develop the dynamic model of a Delta robot with joint clearance to obtain the operation error of a given trajectory. Errors with different operating procedures can, therefore, be calculated. We then use a Kriging-based model to relate manipulator performances with joint clearance values. Real-time calibration can then be performed by identifying joint clearance via experiments. Errors can also be reduced using optimal path planning with the calibrated joint clearance. Results show that this method reduces the average error at target points from 0.637 to 0.031 mm for robot manipulators with joint clearances of 0.328, 0.171, and 0.483 mm. This is a 95.1% improvement in accuracy over that for the manipulator before optimization. The proposed method can help manufacturers determine robot quality, and achieve optimal operation in a workspace with improved accuracy.

Reduction of Forced Vibration Response by Optimum Balance of Linkage and Optimum Design of System

1997 ◽  
Author(s):  
She-min Zhang ◽  
Nobuyoshi Morita ◽  
Takao Torii
Keyword(s):  
Objective Function ◽  
Root Mean Square ◽  
Forced Vibration ◽  
Vibration Response ◽  
New Method ◽  
Mean Square ◽  
Design Variables ◽  
Calculation Results ◽  
Angular Velocities ◽  
Optimum Balance

Abstract This paper proposes a new method to reduce the forced vibration response of frame of linkage. It is that the root-mean-square (RMS) value of binary maximum (Bmax) of forced vibration response at a series of angular velocities is taken as the objective function, and the counterweight mass parameters of links and the stiffness factors are used as design variables. Then, it is found out that the responses are related not only to the Bmax value of shaking forces, but also to the shape of curve of shaking forces. The calculation results are compared with those of two other methods used in the reduction of forced vibration response by optimized balance of linkages, and it is shown that the new method can significantly reduce the responses of frame of linkage.

Accuracy analysis and optimization of an extendible support structure with joint clearances

2020 ◽  
pp. 095440622097305
Author(s):  
Jianzhong Ding ◽  
Chunjie Wang
Keyword(s):  
Monte Carlo ◽  
Reduction Method ◽  
Global Sensitivity Analysis ◽  
Angular Error ◽  
Joint Clearance ◽  
Design Parameters ◽  
Support Structure ◽  
Quasi Monte Carlo ◽  
Joint Clearances ◽  
Independent Parameters

An extendible support structure (ESS) used for unfolding and supporting the antenna array of the Synthetic Aperture Radar (SAR) satellite is reviewed and modeled in this paper. The structure is parameterized by calibrating 12 independent parameters, and following which, angular accuracy of the ESS with joint clearances is modeled. The maximum angular error is obtained by the particle swarm optimization (PSO) and validated by the Monte Carlo simulation. A novel error reduction method is then proposed to improve the accuracy of the structure. In the proposed method, the uncertainty of the joint clearance is eliminated using force constraints by adding small torsional springs. Various joint clearance models with force constraints are proposed to obtain the optimal spring allocation, and based on which, the angular error is further reduced by optimizing the structure of the ESS. The Quasi-Monte-Carlo-based Sobol method for global sensitivity analysis is used to select the design parameters for optimization. Finally, the angular error is greatly reduced.

Error Modeling of a Parallel Wedge Precision Positioning Stage

2012 ◽  
Vol 134 (6) ◽  
Author(s):  
Qiang Zeng ◽  
Kornel F. Ehmann
Keyword(s):  
Virtual Work ◽  
Structural Parameters ◽  
Error Model ◽  
Error Modeling ◽  
Joint Clearance ◽  
Structural Parameter ◽  
Precision Positioning ◽  
Positioning Stage ◽  
Input Variables ◽  
Joint Clearances

The parallel wedge precision positioning stage (PW-PPS) presents a novel configuration of a parallel mechanism for precision positioning applications. Based on its specific parallel configuration, the corresponding inverse and forward kinematic models were developed and used to formulate the volumetric error model of the mechanism. The error model that considers the influence of manufacturing errors is built in two steps. In the first, the structural parameter-induced errors associated with the PW-PPS's structural parameters and input variables were considered, while in the second, the joint clearance-induced errors produced by joint clearances were taken into account. The structural parameter-induced errors were modeled based on complete differential-coefficient theory, while the joint clearance-induced errors due to joint clearances were modeled based on the virtual work and deterministic method. In the latter case, the kinetostatic model and joint error contact modes were analyzed to build a joint clearance-induced error model. The relationship between the different error sources and the output pose error of the mechanism's moving platform was obtained. Finally, considering practical values for the mechanism's parameters and errors, the error distribution in the PW-PPS's workspace was evaluated to determine the distributive rules of the various error components.

scholarly journals A Kriging Model for Dynamics of Mechanical Systems With Revolute Joint Clearances

2014 ◽  
Vol 9 (3) ◽  
Author(s):  
Zhenhua Zhang ◽  
Liang Xu ◽  
Paulo Flores ◽  
Hamid M. Lankarani
Keyword(s):  
Simulation Model ◽  
Contact Force ◽  
Design Parameter ◽  
Joint Clearance ◽  
Design Parameters ◽  
Force Model ◽  
Revolute Joint ◽  
Clearance Joint ◽  
Contact Force Model ◽  
Joint Clearances

Over the past two decades, extensive work has been conducted on the dynamic effect of joint clearances in multibody mechanical systems. In contrast, little work has been devoted to optimizing the performance of these systems. In this study, the analysis of revolute joint clearance is formulated in terms of a Hertzian-based contact force model. For illustration, the classical slider-crank mechanism with a revolute clearance joint at the piston pin is presented and a simulation model is developed using the analysis/design software MSC.ADAMS. The clearance is modeled as a pin-in-a-hole surface-to-surface dry contact, with an appropriate contact force model between the joint and bearing surfaces. Different simulations are performed to demonstrate the influence of the joint clearance size and the input crank speed on the dynamic behavior of the system with the joint clearance. In the modeling and simulation of the experimental setup and in the followed parametric study with a slightly revised system, both the Hertzian normal contact force model and a Coulomb-type friction force model were utilized. The kinetic coefficient of friction was chosen as constant throughout the study. An innovative design-of-experiment (DOE)-based method for optimizing the performance of a mechanical system with the revolute joint clearance for different ranges of design parameters is then proposed. Based on the simulation model results from sample points, which are selected by a Latin hypercube sampling (LHS) method, a polynomial function Kriging meta-model is established instead of the actual simulation model. The reason for the development and use of the meta-model is to bypass computationally intensive simulations of a computer model for different design parameter values in place of a more efficient and cost-effective mathematical model. Finally, numerical results obtained from two application examples with different design parameters, including the joint clearance size, crank speed, and contact stiffness, are presented for the further analysis of the dynamics of the revolute clearance joint in a mechanical system. This allows for predicting the influence of design parameter changes, in order to minimize contact forces, accelerations, and power requirements due to the existence of joint clearance.

Singularities of a planar 3-RPR parallel manipulator with joint clearance

Robotica ◽  
2018 ◽  
Vol 36 (7) ◽  
pp. 1098-1109 ◽  
Author(s):  
Marise Gallant ◽  
Clément Gosselin
Keyword(s):  
Trajectory Planning ◽  
Parallel Manipulator ◽  
Joint Clearance ◽  
End Effector ◽  
Manipulator Design ◽  
Joint Clearances ◽  
Unconstrained Motion

SUMMARYIf the joint clearances of the joints of a manipulator are considered, an unconstrained motion of the end-effector can be computed. This is true for all poses of the manipulator, even with all actuators locked.This paper presents how this unconstrained motion can be determined for a planar 3-RPR manipulator. The singularities are then studied. It is shown that when clearances are considered, the singularity curves normally found in the workspace of such a manipulator become singular zones. These zones can be significant and greatly reduce the usable workspace of a manipulator. Since a prescribed configuration that would not, in theory, corresponds to a singular pose can become singular due to the unconstrained motion, the results of this paper are relevant to manipulator design and trajectory planning.

Joint Clearances With Lubricated Long Bearings in Multibody Mechanical Systems

1999 ◽  
Vol 122 (4) ◽  
pp. 484-488 ◽  
Author(s):  
P. Ravn ◽  
S. Shivaswamy ◽  
B. J. Alshaer ◽  
Hamid M. Lankarani
Keyword(s):  
Mechanical Systems ◽  
Steady Motion ◽  
Joint Clearance ◽  
Hydrodynamic Theory ◽  
Viscous Effects ◽  
Analysis And Design ◽  
Joint Clearances ◽  
The Impact ◽  
Crank Mechanism ◽  
Hydrodynamic Theory Of Lubrication

Proper modeling of joint clearance is of great importance in the analysis and design of multibody mechanical systems. The clearance may be due to wear or imperfection in manufacturing. When there is no lubricant in the clearance, solid-to-solid contact occurs. The impulse due to contact between the links is transmitted throughout the system. The presence of a lubricant avoids such contact, as the hydrodynamic forces developed by the lubricant film support the loads acting on the bodies and prevent the bodies from coming into contact. In this paper, an analysis of revolute joint clearances in multibody mechanical systems with and without lubricant is presented. Squeeze as well as viscous effects are considered utilizing the hydrodynamic theory of lubrication in long bearings. Unlike the traditional machine design approach, the instantaneous lubricant forces are the unknown and evaluated in terms of the known geometrical position and velocity of the journal and bearing. In the case of analysis of a joint clearance with no lubricant, a modified Hertzian relation is used to model the impact or contact between the journal and bearing, which includes a hysteresis damping term to account for the energy dissipation during impact. The methodology is applied for the analysis of a slider-crank mechanism having a clearance in the piston pin. The simulations are carried out with and without lubricant and the results are compared. It is shown that the lubricant results in a steady motion with fewer peaks in the required cranking moment for the system. [S1050-0472(00)01804-3]

Using Parallel Coordinates in Optimization of Nano-Particle Drug Delivery

2021 ◽  
Author(s):  
Timoleon Kipouros ◽  
Ibrahim Chamseddine ◽  
Michael Kokkolaras
Keyword(s):  
Drug Delivery ◽  
Tumor Model ◽  
Mechanistic Modeling ◽  
Analytical Relationship ◽  
Parallel Coordinates ◽  
Modeling And Optimization ◽  
Optimization Framework ◽  
Design Variables ◽  
Nanoparticle Design ◽  
Nanoparticle Sizes

Abstract Nanoparticle drug delivery better targets neoplastic lesions than free drugs and thus has emerged as safer form of cancer therapy. Nanoparticle design variables are important determinants of efficacy as they influence the drug biodistribution and pharmacokinetics. Previously, we determined optimal designs through mechanistic modeling and optimization. However, the numerical nature of the tumor model and numerous candidate nanoparticle designs hinder hypothesis generation and treatment personalization. In this paper, we utilize the parallel coordinates technique to visualize high-dimensional optimal solutions and extract correlations between nanoparticle design and treatment outcomes. We found that at optimality, two major design variables are dependent, and thus the optimization problem can be reduced. In addition, we obtained an analytical relationship between optimal nanoparticle sizes and optimal distribution, which could facilitate the utilization of tumors models in preclincal studies. Our approach has simplified the results of the previously integrated modeling and optimization framework developed for nanotherapy and enhanced the interpretation and utilization of findings. Integrated mathematical frameworks are increasing in the medical field, and our method can be applied outside nanotherapy to facilitate clinical translation of computational methods.

A Systematic Approach for Optimal Mounting System Design of Truck Body

2005 ◽  
Author(s):  
Dongying Jiang ◽  
Yushun Cui ◽  
Zheng-Dong Ma ◽  
Rod Hadi
Keyword(s):  
System Design ◽  
Design Problem ◽  
Systematic Approach ◽  
Dynamic Stiffness ◽  
Optimal Path ◽  
Optimization Procedure ◽  
The Body ◽  
Design Variables ◽  
Engine Mount ◽  
Stiffness And Damping

Body mount system is utilized for isolating dynamic load and vibration into the cab from the rest of vehicle system. The behavior of the mount system not only depends on the performance of individual mounts but also on the complete system configuration. A systematic approach is proposed for optimal design of the truck body mount system. Design variables include the mount locations and mechanical properties of each individual mount. First, an advanced component mode-based substructuring method is utilized for developing reduced-order models of the cab body and the other related subsystems, such as the chassis frame, from the original detailed finite element models. An optimization procedure is then developed, which can be used to determine the geometric distribution of the mounts and their mechanical characteristics (e.g., dynamic stiffness and damping) for minimizing vibration amplitudes at the given locations in the body structure over a frequency range of interest. To determine the optimal mount distribution, a path variable is introduced at the interface of cab and frame, which allows each individual mount moving along the chassis frame in the permitted range. The optimal mount location design problem is thus transformed to an equivalent problem that determines the optimal path variables of each mount. MATLAB codes are developed for the mount system design problem. An example mount system design is given to illustrate the effectiveness and efficiency of the proposed approach, in which the mount stiffness and the mount locations are optimized simultaneously. The developed optimization tool can be extended for optimizing other general mounting systems, such as an engine mount system.

Multi-Objective Optimization of a Segmented Lunar Wheel Concept

2011 ◽  
Author(s):  
Michele Faragalli ◽  
Damiano Pasini ◽  
Peter Radzizsewski
Keyword(s):  
Optimization Problem ◽  
Element Model ◽  
Multi Objective Optimization ◽  
Stress Concentrations ◽  
Multi Objective ◽  
Optimization Framework ◽  
Multi Objective Genetic Algorithm ◽  
Design Variables ◽  
Rider Comfort ◽  
Original Concept

The goal of this work is to develop a systematic method for optimizing the structural design of a segmented wheel concept to improve its operating performance. In this study, a wheel concept is parameterized into a set of size and shape design variables, and a finite element model of the wheel component is created. A multi-objective optimization problem is formulated to optimize its directional compliance and reduce stress concentrations, which has a direct affect on the efficiency, traction, rider comfort, maneuverability, and reliability of the wheel. To solve the optimization problem, a Matlab-FE simulation loop is built and a multi-objective genetic algorithm is used to find the Pareto front of optimal solutions. A trade-off design is selected which demonstrates an improvement from the original concept. Finally, recommendations will be made to apply the structural optimization framework to alternative wheel conceptual designs.

Sign in / Sign up

Export Citation Format

Share Document