Fault Detection of a Proposed Three-Level Inverter Based on a Weighted Kernel Principal Component Analysis

Mao Lin,Ying-Hui Li,Liang Qu,Chen Wu,Guo-Qiang Yuan 전력전자학회 2016 JOURNAL OF POWER ELECTRONICS Vol.16 No.1

Fault detection is the research focus and priority in this study to ensure the high reliability of a proposed three-level inverter. Kernel principal component analysis (KPCA) has been widely used for feature extraction because of its simplicity. However, highlighting useful information that may be hidden under retained KPCs remains a problem. A weighted KPCA is proposed to overcome this shortcoming. Variable contribution plots are constructed to evaluate the importance of each KPC on the basis of sensitivity analysis theory. Then, different weighting values of KPCs are set to highlight the useful information. The weighted statistics are evaluated comprehensively by using the improved feature eigenvectors. The effectiveness of the proposed method is validated. The diagnosis results of the inverter indicate that the proposed method is superior to conventional KPCA.

Nonlinear Regression Analysis for Deep Rock Mass Parameters of the Hoek-Brown Failure Criterion Based on the Differential Evolution

Maolin Tian,Lijun Han,Qingbin Meng 대한토목학회 2021 KSCE JOURNAL OF CIVIL ENGINEERING Vol.25 No.8

The Hoek-Brown (H-B) failure criterion is an empirical failure criterion. The estimates of Hoek-Brown criterion parameters, such as the geological strength index (GSI) and the disturbance coefficient (D), are usually subjective. This paper focused on modifying the initial estimates of GSI and D to improve the accuracy of parameters. The nonlinear regression model (NLRM) of the Hoek-Brown failure criterion was proposed to analyze the rock parameters by using the sensitivity analysis and the displacement equation of the surrounding rocks. Then, a reasonable back analysis method was developed by introducing the differential evolution (DE), which was used to accurately obtain the parameters of the Hoek-Brown failure criterion in practical engineering. This method was successfully used to analyze the stability of the roadway in a deep coal mine. The results showed that the NLRM can better reflect the relationship between GSI, D, μ and the displacement of roadways, and the back analysis results are consistent with the filed monitoring results. This method can provide a helpful reference for modifying the influence of empirical and subjective factors on H-B parameters selection, and improving the accuracy of Hoek-Brown criterion parameters in the similar engineering applications.

Experimental Study on the Mechanical Performance of Grouted Specimen with Composite Ultrafine Cement Grouts

Maolin Tian,Lijun Han,Qingbin Meng 대한토목학회 2020 KSCE JOURNAL OF CIVIL ENGINEERING Vol.24 No.1

An experimental investigation was conducted in order to understand properties of grouts and grouted specimens. Three different cement types, i.e., composite ultrafine cement (CUC) that was independently developed, ultrafine cement (UC), and Portland cement (PC) were injected into broken red sandstone specimens on the basis of a self-designed grouting test equipment. After the grouting test, the effects on the mechanical behavior of grouted specimens were studied using an uniaxial compression test, macroscopic failure analysis and mesostructure analysis, as well as a comparison of the mechanical and structural properties of three types of grouted specimens was presented. The test results show that the compressive strength of grouted specimens improved in comparison to the rock residual strength, and the compressive strength of PC, UC and CUC grouted specimens increased by 23.0%, 59.6% and 101.5%, respectively. The failure modes of all grouted specimens were brittle failure, but only the CUC grouted specimen was failed along the new failure surfaces, indicating that CUC grouts can better bond the original cracks. The mesostructure characteristics obtained through the Digital 3D Video Microscope reveal the superior filling effect of the CUC grouts as well as verifying the macroscopic mechanical behavior.

Self-Tuning Control for Articulated Robots Using the Plestan’s Method

Maolin Jin,Jinoh Lee,Kap-Ho Seo,Jin-Ho Suh 한국정밀공학회 2021 International Journal of Precision Engineering and Vol.22 No.4

A self-tuning controller is proposed for an articulated robot using the Plestan’s method. To this end, we reconstruct the articulated robot dynamics exploiting the time-delay estimation (TDE) technique. The closed-loop error dynamics is described with sliding variables and TDE error; then, the Plestan’s sliding mode based gain-adaptation law is incorporated with the TDE technique. The stability of the overall dynamics is proven in the sense of Lyapunov. As a result, self-tuning of the gain is realized through the sliding variable. When the TDE error increases due to the nonlinear effect such as friction, the adaptive gain is automatically adjusted to counteract the TDE error. Chattering can be avoided because the sliding mode based gain dynamics does not allow the gain increase to an excessively high value. The superiority of the proposed self-tuning controller is demonstrated by comparative experiments on a multiple joints robot setup.

Research on the Basic Rodrigues Rotation in the Conversion of Point Clouds Coordinate System

Maolin Xu,Jiaxing Wei,Hongling Xiu 한국정보처리학회 2020 Journal of information processing systems Vol.16 No.1

In order to solve the problem of point clouds coordinate conversion of non-directional scanners, this paperproposes a basic Rodrigues rotation method. Specifically, we convert the 6 degree-of-freedom (6-DOF) rotationand translation matrix into the uniaxial rotation matrix, and establish the equation of objective vector conversionbased on the basic Rodrigues rotation scheme. We demonstrate the applicability of the new method by using abar-shaped emboss point clouds as experimental input, the three-axis error and three-term error as validateindicators. The results suggest that the new method does not need linearization and is suitable for optionalrotation angle. Meanwhile, the new method achieves the seamless splicing of point clouds. Furthermore, thecoordinate conversion scheme proposed in this paper performs superiority by comparing with the iterativeclosest point (ICP) conversion method. Therefore, the basic Rodrigues rotation method is not only regarded asa suitable tool to achieve the conversion of point clouds, but also provides certain reference and guidance forsimilar projects.

Time Delay Control of a Pump-controlled Electro-hydraulic Actuator

Maolin Jin,Jinwook Kim,Dang Xuan Ba,Hyung Gyu Park,Kyoung Kwan Ahn,Jong Il Yoon 제어로봇시스템학회 2015 제어로봇시스템학회 국제학술대회 논문집 Vol.2015 No.10

This paper presents an accurate position control for a pump-controlled electro-hydraulic actuator (EHA) using time-delay estimation (TDE). The TDE technique is used to estimate nonlinear terms of EHA, which is a third order nonlinear system. The measured signal of linear encoder, and pressure of the EHA are used to implement the TDE technique. The effectiveness of the proposed controller is verified through experiment using an EHA test bench. The proposed controller shows better tracking performance compared with a PID controller.

SVRT: a decision tree-assisted support vector regression for modeling engineering data with complex regression relationship

Maolin Shi 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.5

Support vector regression has been widely used in engineering data modeling. The regression relationship of engineering data usually varies greatly, which results that it being difficult to evaluate through a unified prediction model. In this work, a decision tree-assisted support vector regression is proposed, which can take advantage of training samples partition to improve prediction accuracy. A decision tree is proposed to partition the training samples in such a way that the samples in the same part have a more similar regression relationship to each other than to those in the other parts. Support vector regression is used to evaluate the regression relationship, and an optimization algorithm is designed to search the best splitting input variable and division point at each node. For a new sample to predict, it is compared from the root node of the decision tree until reaches a certain leaf node, and the response is obtained according to the prediction model contained in the leaf node. Experiments show that the proposed method is able to provide competitive prediction results compared with the conventional prediction methods.

Multidisciplinary design optimization of dental implant based on finite element method and surrogate models

Maolin Shi,Hongyou Li,Xiaomei Liu 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.10

This study aims to propose a Multidisciplinary design optimization (MDO) approach for dental implant based on Finite element method (FEM), surrogate model and a new MDO algorithm. FEM is used to calculate the stress at the implant-bone interface first. Two surrogate models, Support vector regression (SVR) and Kriging (KRG) are built to replace FEM in the following MDO of dental implant, and their verifications indicate their accuracies. A new multidisciplinary design optimization algorithm, named as Homogenizationtarget-values MDO algorithm (HTV-MDO), is established and first tested by a numerical example to demonstrate its effectiveness. After that, it is applied to the MDO of dental implant based on the SVM and KRG. The results indicate that the new MDO approach proposed in this study can effectively deal with the MDO of dental implant. The stress is reduced greatly with other characteristics of dental implant (contact area and volume of implant in this study) optimizing or slightly deteriorating. This approach can be expanded to other MDO of different bio-implants.

Continuous Nonsingular Terminal Sliding-Mode Control of Shape Memory Alloy Actuators Using Time Delay Estimation

Maolin Jin,Jinoh Lee,Kyung Kwan Ahn IEEE 2015 IEEE/ASME transactions on mechatronics Vol.20 No.2

<P>We have developed a continuous nonsingular terminal sliding-mode control with time-delay estimation (TDE) for shape memory alloys (SMA) actuators. The proposed method does not need to describe a mathematical model of a hysteresis effect and other nonlinearities; thus, it is simple and model free. The proposed control consists of three elements that have clear meaning: a TDE element that cancels nonlinearities in the SMA dynamics, an injection element that specifies desired terminal sliding-mode (TSM) dynamics, and a reaching element using a fast terminal sliding manifold that is activated accordingly when the system trajectory is not confined in the TSM. The proposed control has been successfully implemented in an SMA actuated system and experimental results show the proposed control is easily implementable and highly accurate. Once the TSM and the reaching condition are suitably specified, the tracking performance of the proposed control is improved compared with a conventional time delay control with a linear error dynamics.</P>

Practical Nonsingular Terminal Sliding-Mode Control of Robot Manipulators for High-Accuracy Tracking Control

Maolin Jin,Jinoh Lee,Pyung Hun Chang,Chintae Choi IEEE 2009 IEEE transactions on industrial electronics Vol.56 No.9

<P>This paper presents a practical nonsingular terminal sliding-mode (TSM) tracking control design for robot manipulators using time-delay estimation (TDE). The proposed control assures fast convergence due to the nonlinear TSM, and requires no prior knowledge about the robot dynamics due to the TDE. Despite its model-free nature, the proposed control provides high-accuracy control and robustness against parameters variations. The simplicity, robustness, and fast convergence of the proposed control are verified through both 2-DOF planar robot simulations and 3-DOF PUMA-type robot experiments.</P>