scholarly journals Accuracy Improvement Calibrations for the Double-Position 4-PPPS Aircraft Docking System

2020 ◽  
Vol 2020 ◽  
pp. 1-14
Author(s):  
Ruolong Qi ◽  
Yuangui Tang ◽  
Ke Zhang
Keyword(s):  
Parallel Mechanism ◽  
Calibration Method ◽  
Labor Intensity ◽  
Kinematic Calibration ◽  
Kinematic Parameters ◽  
Accuracy Improvement ◽  
Pointing Error ◽  
Accuracy Measurement ◽  
Aircraft Fuselage ◽  
Docking Experiment

A double-positions 4-PPPS parallel mechanism is used for the aircraft fuselage assembly process to improve the docking efficiency and reduce the labor intensity. However, the accuracy is hard to guarantee, for the mechanism is large and redundant and has manufacturing and assembly errors. To improve the accuracy of the 4-PPPS parallel aircraft fuselage docking system, firstly, an averaging iteration method is proposed to calibrate the datum points in the airplane coordinate which are the references of the entire docking system. And secondly, a kinematic calibration method based on the derivative of the spatial pose transformation is proposed to calibrate up to 42 kinematic parameters. By these two methods, the final maximum position error reduced from 2.2 mm to 0.035 mm and the maximum pointing error reduced from 0.08 degree to 0.018 degree. The accuracy measurement and docking experiment prove the efficiency of the proposed methods.

Dynamic Calibration for Serial Robotic Manipulators Based on the Zero Position Analysis Method

1989 ◽  
Author(s):  
G. Z. Qian ◽  
K. Kazerounian
Keyword(s):  
Robotic Manipulators ◽  
Calibration Method ◽  
Dynamic Calibration ◽  
Calibration Model ◽  
Kinematic Calibration ◽  
Dynamic Parameters ◽  
Analysis Method ◽  
Kinematic Parameters ◽  
Position Analysis ◽  
Zero Position

Abstract In the continuation of a kinematic calibration method developed in a previous report, a new dynamic calibration model for serial robotic manipulators is presented in this paper. This model is based on the Zero Position Analysis Method. It entails the process of estimating the errors in the robot’s dynamic parameters by assuming that the kinematic parameters are free of errors. The convergence and effectiveness of the model are demonstrated through numerical simulations.

Self-Calibration of XY-Stage with Parallel Mechanism

2014 ◽  
Vol 590 ◽  
pp. 126-129
Author(s):  
Ryoshu Furutani ◽  
Satoshi Yokouchi ◽  
Miyu Ozaki
Keyword(s):  
High Precision ◽  
Parallel Mechanism ◽  
Least Squares Method ◽  
Calibration Method ◽  
Measuring Instruments ◽  
Precision Manufacturing ◽  
Kinematic Parameters ◽  
Self Calibration ◽  
Simulation And Experiment ◽  
Experimental Process

It is important to calibrate the straightness and the squareness of the XY-stage for precision manufacturing and measurement. Normally it is calibrated using much higher precise and accurate measuring instruments and/or artifacts. The high precision and accurate instruments and artifacts are expensive. So, in this paper, Self-calibration method is applied to XY-stage. This method does not require any much high precision and accurate instruments and artifacts. The normal XY-stage moves to the location at the unique coordinates. In this case, it is difficult to apply self-calibration method. Therefore, XY-stage is expanded to XYθ-stage with parallel mechanism. As this stage moves to the location at a lot of coordinates, self-calibration method is applied. This method is confirmed in simulation and experiment. In simulation, the extension lengths of mechanism are estimated from known kinematic parameters and the target coordinates. After that, estimated kinematic parameters are calculated by least-squares method from the extension lengths and the target coordinates. Finally, the positioning coordinates are calculated from the estimated kinematic parameters and the extension lengths. It is proved that the calibration method is effective by comparing the target coordinates and the positioning coordinates. In experiment, the experimental process is similar to the simulation without the estimation of extension lengths. The results of simulation and experiment are shown in this paper.

Kinematic Calibration for Redundantly Actuated Parallel Mechanisms

2004 ◽  
Vol 126 (2) ◽  
pp. 307-318 ◽  
Author(s):  
Jay il Jeong ◽  
Dongsoo Kang ◽  
Young Man Cho ◽  
Jongwon Kim
Keyword(s):  
Optimization Algorithm ◽  
Parallel Mechanism ◽  
Kinematic Calibration ◽  
Parallel Mechanisms ◽  
Geometrical Constraint ◽  
Kinematic Parameters ◽  
Angle Error ◽  
Calibration Algorithm ◽  
Redundantly Actuated

We present a new kinematic calibration algorithm for redundantly actuated parallel mechanisms, and illustrate the algorithm with a case study of a planar seven-element 2-degree-of-freedom (DOF) mechanism with three actuators. To calibrate a nonredundantly actuated parallel mechanism, one can find actual kinematic parameters by means of geometrical constraint of the mechanism’s kinematic structure and measurement values. However, the calibration algorithm for a nonredundant case does not apply for a redundantly actuated parallel mechanism, because the angle error of the actuating joint varies with position and the geometrical constraint fails to be consistent. Such change of joint angle error comes from constraint torque variation with each kinematic pose (meaning position and orientation). To calibrate a redundant parallel mechanism, one therefore has to consider constraint torque equilibrium and the relationship of constraint torque to torsional deflection, in addition to geometric constraint. In this paper, we develop the calibration algorithm for a redundantly actuated parallel mechanism using these three relationships, and formulate cost functions for an optimization algorithm. As a case study, we executed the calibration of a 2-DOF parallel mechanism using the developed algorithm. Coordinate values of tool plate were measured using a laser ball bar and the actual kinematic parameters were identified with a new cost function of the optimization algorithm. Experimental results showed that the accuracy of the tool plate improved by 82% after kinematic calibration in a redundant actuation case.

Kinematic Calibration of a 3rRPS Metamorphic Parallel Mechanism

2020 ◽  
Author(s):  
Xuheng Chai ◽  
Latifah Nurahmi ◽  
Jian S. Dai ◽  
Dongming Gan
Keyword(s):  
Motion Capture ◽  
Parallel Mechanism ◽  
Optimization Problems ◽  
Calibration Method ◽  
Kinematic Calibration ◽  
External Device ◽  
Unknown Parameters ◽  
Constraint Equations ◽  
Search Optimization ◽  
Base Platform

Abstract In this paper, a kinematic calibration method is developed for a 3rRPS metamorphic parallel mechanism with respect to all unknown parameters. Each limb of the 3rRPS mechanism is composed of (rR), P, and S joints. Two joints are actuated, namely P and r joints, hence the mechanism is able to switch between the 3RPS parallel mechanism and 3US parallel mechanism. The geometric constraint equations of the 3rRPS mechanism are initially established. Then, the optimization problems for the base, platform and actuated prismatic lengths during given trajectory are formulated by using the global search optimization algorithm. A physical model of the 3rRPS metamorphic parallel mechanism is built and an experiment is setup to validate the proposed calibration and optimization models. The external device, i.e., the OptiTrack is used during the experiment for motion capture system. All unknown parameters are identified and optimized by dint of the geometric properties of this mechanism and nonlinear optimization algorithms. The experimental results demonstrate that the proposed calibration method is valid and effective.

Kinematic calibration of the Gough Platform

Robotica ◽  
2003 ◽  
Vol 21 (6) ◽  
pp. 677-690 ◽  
Author(s):  
David Daney
Keyword(s):  
Calibration Method ◽  
Parallel Robots ◽  
The State ◽  
Kinematic Calibration ◽  
Basic System ◽  
Initial Error ◽  
Kinematic Parameters ◽  
Constraint Equations ◽  
Machining Center ◽  
Industrial Context

Kinematic calibration is essential to improve the accuracy of the manipulator. This paper presents a complete description of the Gough platform modeling and a unified scheme to identify its kinematic parameters. The interest of this formulation is that it may be applied whatever information is available on the state of the robot (measurement or constraints) without using the kinematics to obtain the basic system of constraint equations. Moreover, the scheme may be applied for all parallel robots. We propose to experiment and compare three methods of calibration, using either (or both) external measurement and internal redundant sensors. Finally, we show how to reduce the initial error in pose determination by 99% for the Hexapode 300, CMW's machining center, and validate the choice of a self-calibration method in an industrial context.

A Simple Two-step Geometric Approach for the Kinematic Calibration of the 3-PRS Parallel Manipulator

Robotica ◽  
2019 ◽  
Vol 37 (5) ◽  
pp. 837-850
Author(s):  
Genliang Chen ◽  
Lingyu Kong ◽  
Qinchuan Li ◽  
Hao Wang
Keyword(s):  
Parameter Identification ◽  
Parallel Manipulator ◽  
Parallel Manipulators ◽  
Calibration Method ◽  
Kinematic Parameter ◽  
Geometric Constraints ◽  
Kinematic Calibration ◽  
Kinematic Parameters ◽  
Positioning Accuracy ◽  
Kinematic Parameter Identification

SummaryKinematic calibration plays an important role in the improvement of positioning accuracy for parallel manipulators. Based on the specific geometric constraints of limbs, this paper presents a new kinematic parameter identification method for the widely studied 3-PRS parallel manipulator. In the proposed calibration method, the planes where the PRS limbs exactly located are identified firstly as the geometric characteristics of the studied parallel manipulator. Then, the limbs can be considered as planar PR mechanisms whose kinematic parameters can be determined conveniently according to the limb planes identified in the first step. The main merit of the proposed calibration method is that the system error model which relates the manipulator’s kinematic errors to the output ones is not required for kinematic parameter identification. Instead, only two simple geometric problems need to be established for identification, which can be solved readily using gradient-based searching algorithms. Hence, another advantage of the proposed method is that parameter identification of the manipulator’s limbs can be accomplished individually without interactive impact on each other. In order to validate the effectiveness and efficiency of the proposed method, calibration experiments are conducted on an apparatus of the studied 3-PRS parallel manipulator. The results show that using the proposed two-step calibration method, the kinematic parameters can be identified quickly by means of gradient searching algorithm (converge within five iterations for both steps). The positioning accuracy of the studied 3-PRS parallel manipulator has been significantly improved by compensation according to the identified parameters. The mean position and orientation errors at the validation configurations have been reduced to 1.56 × 10−4 m and 1.13 × 10−3 rad, respectively. Further, the proposed two-step kinematic calibration method can be extended to other limited-degree-of-freedom parallel manipulators, if proper geometric constraints can be characterized for their kinematic limbs.

CALIBRATION OF THE 3-PRS PARALLEL MANIPULATOR USING A MOTION CAPTURE SYSTEM

2005 ◽  
Vol 29 (4) ◽  
pp. 645-654
Author(s):  
C.G. van Driel ◽  
Juan A. Carretero
Keyword(s):  
Motion Capture ◽  
Parallel Manipulator ◽  
Kinematic Model ◽  
Calibration Method ◽  
Kinematic Calibration ◽  
Virtual Model ◽  
Motion Capture System ◽  
Parallel Mechanisms ◽  
Kinematic Parameters ◽  
Preliminary Testing

In this paper, a kinematic calibration method for the 3-PRS parallel manipulator using a motion capture system is presented. Although parallel mechanisms present numerous advantages over their serial counterparts, an accurate kinematic model must be developed to facilitate their operation. Kinematic calibration is used to accurately determine the kinematic parameters of the kinematic model to improve the overall accuracy of the mechanism. The kinematic calibration of the 3-PRS parallel manipulator will be examined by identification of the manipulator's kinematic parameters, an introduction to the motion capture system used, and the presentation of die calibration method itself. For preliminary testing purposes, a virtual model of the manipulator has been generated in CAD to validate the calibration method. The calibration method initially determines the joint locations and orientations, from which the remaining kinematic parameters can be resolved. Preliminary testing using the virtual model indicates the method is valid and can accurately determine the modelled parameters. Once the physical manipulator is operational, alterations the calibration method will be required to account for manufacturing and assembly tolerances/errors, joint offsets and noise during the static captures.

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