In this paper, the performance of some evolutionary algorithms on grinding process optimization of silicon carbide (SiC) is investigated. The grinding of SiC is not an easy task due to its low fracture toughness, therefore making the material sensitive to cracking. The efficient grinding involves the optimal selection of operating parameters to maximize the material removal rate (MRR) while maintaining the required surface finish and limiting surface damage. In this work, optimization based on the available model has been carried out to obtain optimum parameters for silicon carbide grinding via three prominent evolutionary algorithms. They are particle swarm optimization (PSO), differential evolution (DE) and genetic algorithm (GA). The objective of this optimization process is to maximize the MRR, subject to surface finish and damage constraints of the grinding process. Numerical results show that PSO is comparatively superior in comparison with DE and GA algorithms for grinding process optimization in terms of its accuracy and convergent capability

In recent years, precise metrology up to nanoscale has attracted substantial attention due to an increasing need for ultra-precision measurement systems for micro electro mechanical systems (MEMS) and nano electro mechanical systems (NEMS) calibration. In this paper, an analytical and numerical investigation for the proposed design of a 6-degree-of-freedom (6-dof) universal measurement system, using a relatively simple and inexpensive but highly sensitive set up, is presented. This system utilizes a convex mirror and two flat mirrors, one angled and one vertical, as targets to reflect laser beams onto photo detectors. These targets, placed on the object of interest for metrology applications, change the direction of the reflected beam when there is any movement in the object, which is detected by the photo detectors. The use of convex and angled mirrors greatly enhances the sensitivity of the system. Geometric relationships are established among all the optical components to predict the final intersection points of the laser beams reflected from the targets with the photo detector planes. These relationships are used to establish a Jacobian partial derivative matrix, which is further used to estimate the target pose when the photo detector outputs are given. Numerical simulation of the measurement process is performed using MATLAB®. Assuming the approximate distance from laser beam origin to target and the target to photo detector as 50 mm, and photo detector resolution as 0.1 µm, translations and rotations less than 50 nm and 2 arc sec, respectively, can be measured accurately. The highest amount of sensitivity in translation is obtained along the Z-axis with minimum a measurement of 3.4 nm; the highest amount of sensitivity in rotation is along the pitch-axis with a minimum measurement of 0.145 arc sec. The corresponding low sensitivity axes are X-axis and yaw-axis, with minimum measurements of 35 nm and 2 arc sec, respectively. The sensitivity and the resolution of the system can be increased many times further by increasing the curvature of the convex mirror or by increasing the distance between the target and the detectors. The analytical and simulation results of this work yield a scientific and engineering guideline for the development of meso, micro, as well as nanoscale metrology systems.

Producing sculptured surfaces of special parts always poses challenges to machining industry. In this paper, an effective tool path error restraining method utilizing adaptive rules for cutting control is proposed for freeform surface machining. Based on the proposed approach an experimental verification is accomplished in milling a sample part with curved surfaces. Specifically, the parametric spatial curves representing the part's sculptured surface are approximated by sequences of connected line segments. From the current reference point of the cutting tool, the method has the capability of predicting the next reference point of the tool for a given feed. If the predicted position is not within the required tolerance, the algorithm will automatically adjust the position of the cutter so as to satisfy the tolerance requirements using feedback control philosophy. It is proved that the developed adaptive cutting laws are robust in achieving the desired freeform surface cutting with pre-specified tolerance requirements. The given tolerance is measured as the angular deviations to which the generated tool path deviates from the desired profile. Feedrate variations have been implemented in the investigation in the range between 5 mm/second and 30 mm/second. The tool paths generated with and without the adaptive mechanisms are compared. The experimental results demonstrate that the proposed tolerance feedback mechanism is very effective for producing parts having curved surfaces.

A framework for integrating the coordinate measuring machine (CMM) into the CAD/CAM environment is developed to automate the process of design, manufacturing and inspection. A concept of automatic generation of optimum and collision free path in 3D space using available CAD database is proposed. A generic algorithm is developed for finding probe path over prismatic polyhedral parts. The algorithm serves as a principal part of the inspection path planning system. It is based on the modified ray tracing technique. To examine and implement the algorithm, a user friendly application is developed employing AutoCAD runtime extension development environment following object oriented programming techniques, running on a Windows NT 4.0 workstation. The effectiveness of the proposed algorithm is verified by the results of the implementation demonstrating optimum collision-free dimensional inspection path generation for four representative prismatic part models.

Presents an investigation of jerk continuity in milling operations for the sculptured surface of parts. It has long been realized that chattering of machine tools during machining operations can cause detrimental effects on the quality of machined parts as well as on the cutting tool's life. One of the major reasons causing chattering is known to be the rough transition of cutter acceleration changes during machining of different part surfaces. The problem becomes serious when machining sculptured surfaces of parts. In this work, an effective computer aided sculptured surface design technique is proposed. The ultimate goal is to achieve a smooth and near chattering-free machining for producing precision parts. The proposed surface design scheme models part's sculptured surfaces in such a way that it warrants a smooth jerk transition at the boundaries of common surface patches on the part. This results in a drastic reduction of large step changes of cutter accelerations during machining operations which will in turn eliminate a good portion of chattering effects. Three theorems concerning the necessary jerk continuity conditions for surface patches connections are developed and their proofs are presented. Examples of an airfoil and a concept car model are implemented using the proposed modeling approach to demonstrate its effectiveness.

In this investigation, a framework for integrating the CMM into the CAD/CAM environment is developed to automate the process of design, manufacturing and inspection. An algorithm to generate an optimum collision free CMM probe path is proposed. This algorithm uses the ray tracing technique to locate the collision of the possible paths, between the initial probe point and the target point, with the workpiece to be inspected. If there is a collision, the algorithm walks through the topological structure of the part and selects the midpoint of the edge, shared by the face with which the path collides and the adjacent face nearest to the target point, as the next probe point. This procedure is followed till the target point is reached. The first half of the proposed algorithm is implemented using Mechanical Desktop and its Runtime Extension (ARX) as the API, running on an Windows NT 4.0 platform. The effectiveness of the proposed algorithm is verified by the results of the implementation demonstrating optimum collision-free dimensional inspection path generation for three prismatic parts.

The method presented can be applied to both closed-chain and open-chain manipulators. It is proved to be more computationally efficient that the conventional Newton-Euler method in inverse manipulator kinetics analysis. The improvement in computational efficiency is due to two factors: First, the method takes advantage of the special geometry of the positioning mechanism of most manipulators. That is, the majority of joint axes are parallel to one another and those few which are not, are perpendicular to the majority of axes. Second, the method uses longitudinal and transverse force components at certain joints. Two examples, one closed-chain and one open-chain, are used as illustrations.>

The kinematics of pantograph type manipulators were studied and found to be very computationally efficient due to the decoupled kinematics of pantograph mechanisms [14]. In this paper, the dynamics of a wrist-partitioned, pantograph type manipulators are studied. Both Lagrange's and an extended D'Alembert's methods are used to derive the equations of motion, in applying the extended D'Alembert's method, a special treatment of the force and moment components in free-body diagrams allows the three dimensional motion of the manipulator to be treated as a two dimensional case. This special treatment also eliminates the need of a simultaneous solution of many equations. The extended D'Alembert's formulation is found to be more computationally efficient than the Lagrange's. Moreover, the inverse dynamics of both methods are found to be more computationally efficient than that of a conventional open-chain manipulator.