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Y.-J. Chiu

Bio: Y.-J. Chiu is an academic researcher from National Tsing Hua University. The author has contributed to research in topics: Acceleration & Hexapod. The author has an hindex of 1, co-authored 1 publications receiving 39 citations.

Papers
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TL;DR: In this paper, a self-calibration strategy for a general hexapod manipulator was proposed to overcome weaknesses and embrace the merits of existing approaches using a commercial trigger probe and a cylindrical gauge block.
Abstract: This paper presents a novel self-calibration strategy for a general hexapod manipulator to overcome weaknesses and embrace merits of existing approaches A commercial trigger probe and a cylindrical gauge block are adopted in the present approach The algorithm is formulated to solve a nonlinear least squares problem that takes all measurement errors into account The simulation results show that the proposed algorithm has the following advantages: (1) it is capable of calibrating the position and orientation of the gripper or spindle on the platform; (2) it completely avoids the unobservability of certain parameters due to mobility constraints on the passive joints; (3) the hardware of the calibration system is more compact and cost-effective than that adopted in the existing approaches; and (4) the algorithm is numerically robust, efficient and effective, while the calibrated parameter errors are expected to be with the same order of the measurement errors Due to these merits, the present scheme is attractive for an autonomous hexapod manipulator when a great precision is required in a workspace of five degrees-of-freedom

43 citations


Cited by
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TL;DR: In this article, a kinematic calibration method was developed to improve the accuracy of a six-axis serial industrial robot in a specific target workspace, using distance and sphere constraints.
Abstract: This paper describes a kinematic calibration method developed to improve the accuracy of a six-axis serial industrial robot in a specific target workspace, using distance and sphere constraints. A simulation study demonstrates the ability of the calibration approach to identify the kinematic parameters, regardless of measurement noise. Experimental validation shows that the robot’s accuracy inside the target workspace is significantly improved by reducing the mean and maximum distance errors from 0.698 to 0.086 mm and from 1.321 to 0.127 mm, respectively. The experimental data are collected using a Renishaw precision touch probe mounted on the flange of a FANUC LR Mate 200iC and a special triangular plate with three datum 2-in spheres 300 mm apart. The calibration method uses an optimization model based on fitting several probed positions on spheres and minimizing the residual of the spheres’ center-to-center distances.

89 citations

Journal ArticleDOI
TL;DR: In this article, a non-kinematic calibration method was developed to improve the accuracy of a six-axis serial robot, in a specific target workspace, using planar constraints, and an experimental validation showed that the robot's accuracy inside the target workspace was significantly enhanced by reducing the maximum distance errors from 1.321mm to 0.274mm.
Abstract: This paper describes a non-kinematic calibration method developed to improve the accuracy of a six-axis serial robot, in a specific target workspace, using planar constraints. Simulation confirms that the stiffness of the robot, as well as its kinematic parameters, can be identified. An experimental validation shows that the robot's accuracy inside the target workspace is significantly enhanced by reducing the maximum distance errors from 1.321 mm to 0.274 mm. The experimental data are collected using a precision touch probe, which is mounted on the flange of a FANUC LR Mate 200iC industrial robot, and a high precision 9-in. granite cube. The calibration method makes use of a linear optimization model based on the closed-loop calibration approach using multi-planar constraints. A practical validation approach designed to reliably evaluate the robot's accuracy after calibration is also proposed.

79 citations

Journal ArticleDOI
TL;DR: In this article, a novel orientation constraint of keeping two attitude angles of the end-effector constant is presented to derive the calibration algorithm with special insight on the effect of using various combinations of two angles.
Abstract: This paper considers the problem of improving the accuracy of parallel kinematics machine tools through a low-cost and effective calibration method. A novel orientation constraint of keeping two attitude angles of the end-effector constant is presented to derive the calibration algorithm with special insight on the effect of using various combinations of two angles. The orientation constraint of the selected combination is realized physically through leveling a commercial biaxial inclinometer installed on the end-effector. Benefits of the proposed method include exempting the needs for precise pose (position and orientation) measurement and for mechanical fixtures, as well as rendering the independence of the measuring range and angular positioning accuracy of the inclinometer. Simulation based on the geometry of the Stewart platform of XJ-HEXA shows the position and orientation accuracy can reach 0.1 mm and 0.01° after calibration, when using an inclinometer with the repeatability of 0.001° and measuring the leg lengths with the precision of 0.002 mm at 80 configurations. Experiments on XJ-HEXA further verify the effectiveness of the proposed method.

68 citations

Journal ArticleDOI
TL;DR: Using the product of exponentials (POE) formula, orthogonal partitioning matrices can be constructed in a straightforward way to determine and eliminate the redundant error components and the maximal number of identifiable parameters for both serial and parallel manipulators can be unified by one unique formula.

62 citations

Journal ArticleDOI
TL;DR: In the approach, a differential error model, an optimized model and a statistical method are combined, and the errors of parallel kinematics machine due to inaccurate motion of joints can be reduced by this approach.
Abstract: Parallel kinematics machine has attracted attention as machine tools because of the outstanding features of high dynamics and high stiffness. Although various calibration methods for parallel kinematics machine have been studied, the influence of inaccurate motion of joints is rarely considered in these studies. This paper presents a high-accuracy and high-effective approach for calibration of parallel kinematics machine. In the approach, a differential error model, an optimized model and a statistical method are combined, and the errors of parallel kinematics machine due to inaccurate motion of joints can be reduced by this approach. Specifically, the workspace is symmetrically divided into four subspaces, and a measurement method is suggested by a laser tracker to require the actual pose of the platform in these subspaces. An optimized model is proposed to solve the kinematic parameters in symmetrical subspaces, and then arithmetical mean method is proposed to calculate the final kinematic parameter. In order to achieve the global optimum quickly and precisely, the initial value of the optimal parameter is directly solved based on the differential error model. The proposed approach has been realized on the developed 5-DOF hexapod machine tool, and the experiment result proves that the presented method is very effective and accurate for the calibration of the hexapod machine tool.

58 citations