M.A. Sahir Arikan

A kinematic structure-based classification and compact kinematic equations for six-dof industrial robotic manipulators

Abstract A kinematic structure-based classification of six degree-of-freedom industrial robotic manipulators is introduced, and a complete set of compact kinematic equations is given according to this classification. For the classification, 100 industrial robots are surveyed. These robots are first classified into main groups and then into subgroups under each main group, and nine kinematic main groups, each having 1–10 subgroups are obtained. The main groups are based on the end-effector rotation matrices and characterized by the twist angles. On the other hand, the subgroups are based on the wrist point positions and characterized by the link lengths and offsets. Compact kinematic equations are derived for all main groups and subgroups by utilizing the properties of exponential rotation matrices, and simplification tools derived by using these properties. Most of these simplified compact equations can be solved analytically and the remaining few of them can be solved semi-analytically through a single univariate equation. In these solutions, the singularities and the multiple configurations of the manipulators can be determined easily. Using these solutions, the inverse kinematics can also be computerized by means of short and fast algorithms.

A method of inverse kinematics solution including singular and multiple configurations for a class of robotic manipulators

A semi-analytical method and an associated computer program are developed for inverse kinematics solution of a class of robotic manipulators, in which four joint variables are contained in the wrist point equations. For this case, it becomes possible to express all the other joint variables in terms of a selected one, and this reduces the inverse kinematics problem to solving a non-linear scalar equation having the selected joint variable as the only unknown. The solution can be obtained by iterative methods and the remaining joint variables can easily be computed by using the solved joint variable. Since the method is manipulator dependent, the equations will be different for kinematically different classes of manipulators, and should be obtained analytically in a similar way as done here, using the suggested algebra based on exponential rotation matrices. A significant benefit of the method is that the singular configurations and multiple solutions indicated by sign ambiguities can be determined while deriving the inverse kinematic expressions. The developed method is applied to a six-revolute-joint industrial robot, FANUC Arc Mate Sr.

Process Simulation and Paint Thickness Measurement for Robotic Spray Painting

Abstract A method and a computer program are developed for modeling of spray painting process, simulation of robotic spray painting, off-line programming of industrial robots and paint thickness measurement for painting of curved surfaces. The computer program enables the user to determine the painting strategies, parameters and paths. Surface models of the parts that are to be painted are obtained by using a CAD software. For paint thickness measurements, probe of the coating thickness measurement gage is attached to the wrist of the robot by using a feedback/safety adapter designed and manufactured for this purpose. Thicknesses are measured and transferred to the computer automatically. Then, obtained thickness data is processed and comparisons between simulated and measured thicknesses are made.

Design by using machining operations

Summary Since every designed part will be manufactured afterwards, it is important to consider also the manufacturing aspects at the design stage. Machining, which is one of the basic manufacturing processes, is the removal of certain selected areas, in order to obtain a desired shape or finish. Therefore, it can be considered as removing some defined geometric elements from a solid object wherein geometries of these elements are determined by the individual machining operations. A database comprising the geometric elements related to machining operations is constructed, and parts are formed by subtracting these elements from a simple solid object, like a rectangular prism or a cylinder. The database comprises the geometric elements related to available operations on a 2 1/2 axis CNC milling machine. For design of the part by using this method, an interactive computer program with graphical input and output is developed. The program also has modules for sequencing the machining operations according to a prescribed decision logic, for automatic or manual selection of cutting tools for corresponding operations, for calculation of machining parameters by using emprical relations, for creation and usage of personal databases for cutting tool and machining data, and for preparing the NC program and transmitting it to the milling machine for machining of the part.

Dynamic Load and Root Stress Analysis of Spur Gears

Summary Dynamic loads on spur gears are calculated by using an analytical model based on torsional vibrations of gears, and dynamic load variations during a mesh cycle of a tooth are determined. Tooth profile modifications, profile and pitch errors are included in dynamic load calculations. Variable stiffnesses of gear teeth, which are required for dynamic load calculations, and tooth root stresses resulting from dynamic loads are found by using the finite element method. Calculated tooth root stresses are used in fatigue failure analysis.

Direct calculation of AGMA geometry factor J by making use of polynomial equations

Abstract The available sources and procedures for determination of AGMA geometry factor J are tables, charts and semi-analytical methods. When computerized gear design is considered, usage of tables requires a number of interpolations; usage of charts requires curve fitting; and usage of semi-analytical methods needs a numerical algorithm and may have convergence problems. As an alternative to these, polynomial equations for direct calculation of AGMA geometry factor J are derived for external spur gears. Thus, it is made possible to evaluate the J factor easily and with minimum process time. J factors are determined being independent of the highest point of single tooth contact (HPSTC). Derived equations can be used to calculate the tooth root stresses corresponding to loads acting on any point on the involute tooth profile. Thus, cases where the center distance is increased for providing backlash or for operating the gears at a desired exact center distance can easily be handled by determining the corresponding new HPSTC. A computer program is developed to demonstrate the usage of the derived equations. The method can also be used for determination of the J factors for gears with non-standard proportions.

Modeling of paint flow rate flux for elliptical paint sprays by using experimental paint thickness distributions

Purpose – Aims to experimental determination of paint flow rate flux for elliptical paint sprays. Paint flow rate flux distribution is necessary for computer simulation of the spray painting process.Design/methodology/approach – Different painting strokes at different spray distances and painting velocities are made on flat surfaces by using paint sprays with elliptical spray areas. Then, thickness measurements are made across the strokes after the paint dries out completely. Thickness distributions are used for determination of the paint flow rate flux distribution by making use of the developed formulation and algorithm.Findings – Finds that it is possible to determine the paint flow rate flux for elliptical paint sprays by making use of the painting strokes made on flat surfaces at different spray distances and painting velocities.Practical implications – Computer simulation of the spray painting process for elliptical paint sprays is made possible. Simulation software for circular paint sprays has bee...

Determination of Addendum Modification Coefficients for Spur Gears Operating at Non-Standard Center Distances

Although it is possible to find some recommended conventional values both for the sum of the addendum modification coefficients and for the allocation of the sum of the addendum modification coefficients (e.g. ISO/TR 4467), a detailed analysis is necessary to determine the addendum modification coefficient values for the desired optimization criteria and the performance since the main objective of the above mentioned sources is to facilitate practical design of non-standard gear drives which will not have problems while operating. They give practical average values within a safe range. In this study, by considering the required gear ratio, center distance and the desired backlash, alternative gear pairs are determined and corresponding gear performance variables are calculated in order to allocate the addendum modification coefficients for the pinion and the gear by using criteria such as: not having undercut or pointed (or excessively-thinned-tip) tooth, having desired proportions for the lengths of the dedendum and addendum portions of the line of action, having maximum contact ratio, having sufficient bottom clearance, having minimum contact stresses, having balanced pinion and gear tooth root stresses, having equal pinion and gear lives, etc.Copyright

Investigation on replication of microfluidic channels by hot embossing

ABSTRACT In this study, effects of embossing temperature, time, and force on production of a microfluidic device were investigated. Polymethyl methacrylate (PMMA) substrates were hot embossed by using a micromilled aluminum mold. The process parameters were altered to observe the variation of replication rate in width and depth as well as symmetry of the replicated microfluidic channels. Analysis of variance (ANOVA) on the experimental results indicated that embossing temperature was the most important process parameter, whereas embossing time and force have less impact. One distinguishing aspect of this study is that, the channels were observed to be skewed to either side of the channel depending on the location of the protrusions on the mold. The mechanism of the skewness was investigated by finite element analysis and discussed in detail. Results showed that the skewness depends on the flow characteristics of the material and could be reduced by increasing the embossing temperature. The best replication rates were obtained at parameter settings of 115°C, 10 kN, and 8 min for the molds with minimum 56 µm wide features of 120 µm depth. We also showed that the fabricated channels could be successfully sealed by solvent-assisted thermo-compressive bonding at 85°C under 5.5 kN force.

Cam Geometry Generation and Optimization for Torsion Bar Systems

Moment unbalance is a critical issue in many mechanisms rotating around a certain axis. The common element for eliminating the moment unbalance is a spring attached to the rotary system which can nullify it only at a certain angle or position due to the cosine profile of the unbalance. In order to accomplish this at all angles, torsion bar systems following a cam profile are preferred instead. In this paper, a new method has been developed to generate the exact analytical cam profile on which torsion bar system will roll. Using the moment balance equations and the equations related to the geometry of the cam profile at rotated frames and torsion bar parameters, seven nonlinear differential equations with corresponding initial conditions are obtained. Solution of this set of nonlinear equations determined the cam profile, torsion bar torque profile and the overall system layout. Then, the problem transformed into an optimization problem with an objective of minimizing the maximum amount of torque induced on the torsion bar with certain geometrical and structural constraints, with initial conditions forming the search space. Systematical solution to this optimization problem created a blueprint for the design of a generic system in a constrained volume.