# Publication

Publication in 2020

### 1. Mechanics Based Design of Structures and Machines, An International Journal

A novel mathematical approach for finite element formulation of flexible robot dynamics

A. M. Chu1*, C. D. Nguyen1 , X. B. Duong2, A. V. Nguyen3, T. A. Nguyen4, C. H. Lee5, Michael Packianather61.Institute of Simulation Technology, Le Quy Don Technical University, Ha Noi, Viet Nam;2. Center of Advanced Technology, Le Quy Don Technical University, Hanoi, Vietnam3. Department of Special Robotics and Mechatronics, Le Quy Don Technical University, Hanoi, Vietnam.4. Department of Physics, Le Quy Don Technical University, Ha Noi, Viet Nam5. Faculty of Engineering and Science, University of Greenwich, Kent ME4 4TB, United Kingdom.6. School of Engineering, Cardiff University, Cardiff CF24 3AA, United Kingdom.*corresponding author: myca@lqdtu.edu.vn

Abstract

In conventional Finite Element – Lagrangian methods, the dynamics model of a flexible robot is usually formulated based on a critical assumption that the kinetic energy of an element is approximately calculated with an integral of mass point energy. Since the energy integral is implicit, the formulation of the dynamics model is also very complex and implicit. Moreover, since the mass point energy is integrated along the length of a link, the formulations used are suitable for flexible robots which consist of infinitely thin links, but not practical for real flexible robots which usually have links with given geometric shapes. Hence, this paper develops a new mathematical approach for the dynamic modelling of a general flexible/rigid robot. The proposed method is more comprehensive and efficient in comparison with the previous ones because it no longer requires the calculation of the symbolic integrals and the implicit expressions of the elemental and global mass matrices. Besides, the proposed approach is applicable for both the flexible robots and the hybrid flexible/rigid robots. To validate the proposed method, numerical simulations and experimental results are presented.

Keywords: Flexible robots, flexible/rigid robots, kinematics of machines, dynamics of machines, finite elements method

### 2. International Journal of Advanced Robotic Systems

New development of the dynamic modeling and the inverse dynamic analysis for flexible robot

Chu A My, Duong X BienDepartment of Special Robotics and Mechatronics, Le Quy Don TechnicalUniversity, Hanoi, Vietnam

Abstract

When a segment of a flexible link of a flexible robot is currently sliding through a prismatic joint, it is usually assumed that the elastic deflections of the segment equal to zero. This involves time-dependent boundary conditions for the dynamic modelling and analysis for the flexible robots. Hence, the dynamic modelling and especially the inverse dynamic analysis of the flexible robots that consist of the prismatic joints are challenging. In this paper, we present a new development of the dynamic modelling and the inverse dynamic analysis for all four configurations of a generalized two-link flexible robot that consists of a prismatic joint and a revolute joint. First, a Finite Element - Lagrangian formulation of the dynamic equations for all the configurations of the robot is addressed. Second, a Bisection method-based algorithm is constructed for finding the root of the inverse dynamic equations. Since the Bisection method is a rapid converging method in mathematics, the proposed algorithm is effectively applicable to solving the inverse dynamic problem in a robust manner. Last, the numerical simulation results show the effectiveness and the robustness of the proposed method.

Keywords: Flexible robot, inverse dynamics, prismatic joint, finite element method

### 3. Applied Sciences

Kinematic and Dynamic Modelling for a Class of Hybrid Robots Composed of m Local Closed-Loop Linkages Appended to an n-Link Serial Manipulator

Anh My Chu1,*, Cong Dinh Nguyen1, Minh Hoan Vu2, Xuan Bien Duong3, Tien-Anh Nguyen4 and Chi Hieu Le5 1 Institute of Simulation Technology, Le Quy Don Technical University, Ha Noi, Viet Nam; myca@lqdtu.edu.vn 2 Department of Mechanical Engineering, Le Quy Don Technical University, Ha Noi, Viet Nam; hoanvm92@gmail.com 3 Department of Aerospace, Le Quy Don Technical University, Ha Noi, Viet Nam; duongxuanbien@lqdtu.edu.vn 4 Department of Physics, Le Quy Don Technical University, Ha Noi, Viet Nam; anhnt@lqdtu.edu.vn 5 Faculty of Engineering and Science, University of Greenwich, Kent, United Kingdom; C.H.Le@greenwich.ac.uk 1 * Correspondence: myca@lqdtu.edu.vn

Abstract

Recently, more and more hybrid robots have been designed to meet the increasing demand for a wide spectrum of applications. However, development of a general and systematic method for kinematic design and dynamic analysis for hybrid robots is rare. Most publications deal with the kinematic and dynamic issues for individual hybrid robots rather than any generalization. Hence, in this paper, we present a novel method for kinematic and dynamic modelling for a class of hybrid robots. First, a generic scheme for the kinematic design of a general hybrid robot mechanism is proposed. In this manner, the kinematic equation and the constraint equations for the robot class are derived in a generalized case. Second, in order to simplify the dynamic modelling and analysis of the complex hybrid robots, a Lemma about the analytical relationship among the generalized velocities of a hybrid robot system is proven in a generalized case as well. Last, examples of the kinematic and dynamic modelling of a newly designed hybrid robot are presented to demonstrate and validate the proposed method

Keywords: Hybrid robot; kinematic design; dynamic modelling; local-closed loop; serial manipulator.

### 4. The 5th International Conference on Research in Intelligent and Computing in Engineering (RICE 2020)

Inverse Kinematics Analysis of Welding Robot IRB 1520ID Using Algorithm for Adjusting the Increments of Generalized Vector

Chu Anh My1, Duong Xuan Bien1, and Le Chi Hieu2 1 Le Quy Don Technical University, Hanoi, Vietnam 2 Faculty of Science and Engineering, University of Greenwich, United Kingdom

Abstract

This paper focuses on presenting an algorithm for adjusting the increments of generalized vector to solve the inverse kinematics problem of welding robot IRB 1520ID which has six degrees of freedom. It means a redundant system. This method allows the end-effector position of robot to follow the desired trajectory and ensure a given tolerance. Values of joint variables are calculated consecutively in corresponding to each position of the end-effector point. These values are ensured within the permitted limits, stick to each other and avoid singular points. The velocity, acceleration and jerk of joints are also calculated based on the results from the algorithm mentioned above combining with the accurate determination of derivative the first and second order Jacobian matrices with respect to time. These values are guaranteed to be within the permitted motion limits of the robot. In addition, the acceleration and the jerk at the end-effector point are determined through the forward kinematics problem.

Keywords: Welding robots, Adjusting algorithm, Redundant system, Inverse kinematics.

### 5. The 5th International Conference on Research in Intelligent and Computing in Engineering (RICE 2020)

Optimize the Feed Rate of 6-DOF Robot in Parametric Domain Based on Kinematics Modeling

Chu Anh My1, Duong Xuan Bien1, and Le Chi Hieu2 1Le Quy Don Technical University, Hanoi, Vietnam 2Faculty of Science and Engineering, University of Greenwich, United Kingdom

Abstract

Nowadays, robots are widely used in welding machining, cutting machining, printing 3D plastic and additive manufacturing metal because of their greatly flexibility. Due to the demand to reduce time costs and increase the manufacturing performance, the issue of optimizing the production process is always concerned. In particular, optimizing the feed rate parameter has received much attention from researchers. This paper presents the method for optimizing feed rate of the cutting tool along the toolpath profile of an industrial robot with six degrees of freedom in parametric domain based on kinematics modeling. The inverse kinematics problems of redundant system are solved by using the algorithms for adjusting the increments of generalized vector. The positions, velocities, accelerations and jerks of joints are determined following the given toolpath in parametric domain. The algorithm is built based on the gradually increase of feed rate values, while ensuring the kinematic limits of the joints. The results of this study play an important role in improving the technological capabilities of machining robots when manufacturing complex toolpaths in space.

Keywords: Feed rate, optimize algorithm, machining robots, parametric domain

### 6. The 5th International Conference on Research in Intelligent and Computing in Engineering (RICE 2020)

Cost-Effective Solution for Integration and Control of a Robotic Cell in Hot Forging Industry

Chu Anh My Le Quy Don Technical University, Hanoi, Vietnam

Abstract

This paper presents an effective technical solution for integration and control of a robotic cell in the hot press forging industry. The robot is designed to support workers for transferring hot and heavy billets between a heating furnace and a hydraulic press machine of a hot press forging shop floor. The control system of the robot is designed mainly based on the industrial PLC units, which also plays a role as a central control unit for controlling all the components of the entire forging station. In order to integrate and control smoothly all the actuators of the robot, the hydraulic cylinders actuating the main joints of the robot are validated via an analytical procedure. The control algorithm for the entire system integration is validated through functional tests and experiments that are carried out with a real forging shop floor at The Mechanical Company Ltd. No. 83, Yen Bai Province, Vietnam.

Keywords: Forging Robot; Robot design; Robot control

### 7. The 5th International Conference on Research in Intelligent and Computing in Engineering (RICE 2020)

The Role of Big Data Analytics and AI in Smart Manufacturing: An Overview

Chu Anh My Le Quy Don Technical University, Hanoi, Vietnam

Abstract

In recent years, Smart Manufacturing which is the core idea of the Fourth Industrial Revolution (Industry 4.0) has gained increasing attentions worldwide. Recent advancements of several information technologies and manufacturing technologies, such as Internet of Thing (IoT), Big Data Analytics, Artificial Intelligent (AI), Cloud Computing, Digital Twin, Cyber-physical System, etc. have motivated the development of Smart Manufacturing. This paper presents a comprehensive review of the recent publications related to Smart Manufacturing, especially related to the particular role of Big Data Analytics and AI in optimization of process parameters for smart manufacturing shop floors consisting of CNC machines and robots.

Keywords: Smart manufacturing; Big data analytics; Artificial intelligent; Industrial robot; CNC machine

### 8. The 5th International Conference on Research in Intelligent and Computing in Engineering (RICE 2020)

Forward and Inverse Kinematics Analysis of a Spatial Three-Segment Continuum Robot

Chu Anh My1, Duong Xuan Bien1, and Le Chi Hieu2 1Le Quy Don Technical University, Hanoi, Vietnam 2Faculty of Science and Engineering, University of Greenwich, United Kingdom

Abstract

Recently soft robots have been intensively investigated in robotics research. One of the types of the soft robots is continuum robot which has high degree of freedom or continuous, backbone structures. In this article, a spatial three-segment continuum robot with elastic backbone is considered. The moving of robot is driven by cable wires through the main movement of backbone. The kinematic characteristics of the continuum robot are demonstrated by modeling the kinematics of its flexible backbone. The relationship between the joint variables in joint space and the position variables in workspace is shown by building the kinematic equations. Forward kinematics is the first step towards solving the inverse kinematics and dynamics problem. Inverse kinematics problem plays important role in designing the control system for robots. These problems are solved based on based on D-H techniques and closed-loop inverse kinematics algorithm (CLIK). The workspace of robot is also calculated. The results of this research can be used to design the control system.

Keywords: continuum robots, kinematics analyzing, workspace, soft robots

### 9. International Conference on Computer Science, Applied Mathematics and Applications (ICCSAMA 2019)

New Feed Rate Optimization Formulation in a Parametric Domain for 5-Axis Milling Robots

Chu Anh My1( B), Duong Xuan Bien1 , Bui Hoang Tung1 , Nguyen Van Cong1 , and Le Chi Hieu21. Le Quy Don Technical University, Hanoi, Vietnam; mychuanh@yahoo.com2. Faculty of Science and Engineering, University of Greenwich, London, UK

Abstract

When producing a numerical control (NC) program for a 5-axis CNC machine (the so-called milling robot) to mill a sculptural surface, a constant feed rate value is usually assigned based on the programmer’s experiences. For this reason, the feed rate in most of NC programs is often not optimized, it is much lower than maximum reachable value. To increase the productivity of the machining process, the feed rate in NC programs for the milling robots need to be maximized. This paper proposes a new feed rate optimization model, of which the objective function and all the kinematic constraints are transformed and expressed explicitly in a parametric domain which is commonly used in the tool path generation process performed by current CAM systems. Thus, the optimal feed rate values along a parametric tool path can be computed in an effective and simplified manner. Numerical examples demonstrate the effectiveness of the proposed method.

Keywords: High speed milling, 5-axis milling robot, Kinematic modelling, Feed rate interpolation