Cuneyt Oysu

Comparison of inverse kinematics solutions using neural network for 6R robot manipulator with offset

An artificial neural network (ANN) using backpropagation algorithm is applied to solve inverse kinematics problems of industrial robot manipulator. 6R robot manipulator with offset wrist was chosen as industrial robot manipulator because geometric feature of this robot does not allow solving inverse kinematics problems analytically. In other words, there is no closed form solution for this problem. In order to define orientation of robot end-effector, three different representations are used here: homogeneous transformation matrix, Euler angles and equivalent angle axis. These representations were compared to obtain inverse kinematics solutions for 6R robot manipulator with offset wrist. Simulation results show that prediction performance from the approximation accuracy point of view is satisfactory with low effective errors based on 10 degrees data resolution

Application of heuristic and hybrid-GASA algorithms to tool-path optimization problem for minimizing airtime during machining

In this paper, heuristic algorithms such as simulated annealing (SA), genetic algorithm (GA) and hybrid algorithm (hybrid-GASA) were applied to tool-path optimization problem for minimizing airtime during machining. Many forms of SA rely on random starting points that often give poor solutions. The problem of how to efficiently provide good initial estimates of solution sets automatically is still an ongoing research topic. This paper proposes a hybrid approach in which GA provides a good initial solution for SA runs. These three algorithms were tested on three-axis-cartesian robot during milling of wood materials. Their performances were compared based on minimum path and consequently minimum airtime. In order to make a comparison between these algorithms, two cases among the several milling operations were given here. According to results obtained from these examples, hybrid algorithm gives better results than other heuristic algorithms alone. Due to combined global search feature of GA and local search feature of SA, hybrid approach using GA and SA produces about 1.5% better minimum path solutions than standard GA and 47% better minimum path solutions than standard SA.

A support vector machine-based online tool condition monitoring for milling using sensor fusion and a genetic algorithm

In machining systems, the quality of the manufactured part is directly related to the condition of the tool used. Sharp tools are mostly used on the final machining pass to obtain enhanced dimensional accuracy and surface smoothness. Worn tools on the other hand are typically used for coarse machining. The operator usually makes tool assignments based on his experience, the wear levels of the tools and the type of machining task. However, this kind of operator judgment is bound to errors and may not be reliable in processes requiring high precision. Therefore, a tool condition monitoring system is highly desirable to achieve the best results in machining quality. In this study, three-axis cutting forces, torque, three-axis accelerometer and acoustic emission signals were analyzed and used for the development of an online tool condition monitoring system. Various time domain and statistical features extracted from these signals were used to train support vector machine models in a binary decision tree, which was used to predict the condition of the cutting tool. The genetic algorithm was employed for reducing the dimensionality of the feature set by selecting the features that correlates best with the tool condition. Nine experiments were carried out at different cutting conditions. Experimental results demonstrated the efficacy of the proposed scheme. The classification rates for the tool condition monitoring system before and after inclusion of the genetic algorithm step were determined as 89% and 100%, respectively.

Applying Neural Network to Inverse Kinematic Problem for 6R Robot Manipulator with Offset Wrist

An Artificial Neural Network (ANN) using backpropagation algorithm is applied to solve inverse kinematics problems of industrial robot manipulator. 6R robot manipulator with offset wrist was chosen as industrial robot manipulator because geometric feature of this robot does not allow to solve inverse kinematics problems analytically. In other words, there is no closed form solution for this problem. As the number of neurons at hidden layer is varied between 4 and 32, the robot joint angles (θ1θ2… θ6) were predicted with average errors of 8.9°, 7.8°, 8.3°, 13°, 8.5°, and 10.5° for the 1st, 2nd, 3rd, 4th and 6th joint, respectively.

An Assessment of the Methods for Calculating Ampacity of Underground Power Cables

Endurance of an insulation material to high temperatures determines the maximum current-carrying capacity (ampacity) of an underground power cable. Cable ampacity is calculated conventionally using the installation conditions and maximum steady-state operation temperature according to IEC-60287 standard. In this article, finite element method results are compared with IEC-60287. A further verification has also been made with experiments. In this work, ampacity analyzes of 154 kV high voltage XLPE underground power cable are made using ANSYS 5.61 finite element analysis software. An experimental set-up is developed to measure conductor and surface temperature of the cable in underground conditions. The results of experiments and numerical calculations are compared to the IEC-60287 standard. Additionally, the thermal regions of three cables in flat installation are investigated to show the versatility of the finite element method. The effects of insulation thickness and external thermal source on ampacity are also analyzed using the finite element method.

Fuzzy control of a real time inverted pendulum system

In this study, a real-time control of the cart-pole inverted pendulum system was developed using fuzzy logic controller. Swing-up and stabilization of the inverted pendulum were implemented directly in fuzzy logic controller. The fuzzy logic controller designed in the Matlab-Simulink environment was embedded in a dSPACE DS1103 DSP controller board. Swing-up algorithm brings the pendulum near to its inverted position in 10 seconds from downward position. In order to test the robustness of the fuzzy logic controller internal (changing model parameters) and external disturbances (applying external forces) were applied on the inverted pendulum. The inverted pendulum system was shown to be robust to the external and internal disturbances. The maximum errors of the pendulum angle to the impulse input were between 1.89° and 4.6449° in the robustness tests.

Two-dimensional elastic contact analysis by coupling finite element and boundary element methods

Abstract A coupled finite element and boundary element method is introduced for the analysis of two-dimensional elastic contact problems without friction. The Lagrange multiplier method is used to apply the contact constraints. A computer program, which can analyse axisymmetric, plane strain and plane stress problems, has been developed and used to demonstrate the accuracy of the method. The program is applied to a sphere in contact with a flat surface, a rigid punch pressed on to an elastic foundation and an elastic cylindrical punch in contact with an elastic plate. In all cases good agreement is obtained with analytical solutions for stresses near the contact region.

Automation of welding face shaping process for tubular structures

Purpose – The purpose of this paper is to describe the development of a low cost fully automatic computer controlled oxy‐fuel cutting system for tubular members. Operation of the system should be easy even for unskilled technicians.Design/methodology/approach – The robot consists of one revolute axis and two linear axes. As the pipe rotates, two cutting torches move linearly at both ends of the pipe to complete the cutting process in one rotation. Both torchs cutting paths are calculated in a computer offline. Tool paths are then loaded in a micro control unit for each cutting. When the pipe is attached to the system, the whole cutting process can be completed automatically. The mathematical method for calculation of the geometry of intersecting cylinders is also explained in this paper.Findings – The automation of oxy‐fuel cutting process brings enhancement in the final product quality, considerable increase of repeatability, reduction of rework and reduction of the cutting time.Originality/value – The ...

Comparison of stochastic and approximation algorithms for one-dimensional cutting problems

The paper deals with the new algorithm development and comparison of three one-dimensional stock cutting algorithms regarding trim loss. Three possible types of problems used in this study are identified as easy, medium and hard. Approximate method is developed which enables a comparison of solutions of all three types of problems and of the other two stochastic methods. The other two algorithms employed here are Genetic Algorithms (GA) with Improved Bottom-Left (BL) and Simulated Annealing (SA) with Improved BL. Two examples of method implementation for comparison of three algorithms are presented. The approximate method produced the best solutions for easy and medium cutting problems. However, GA works very well in hard problems because of its global search ability.