Showing papers by "Chia-Hsiang Menq published in 1995"

Automated CMM path planning for dimensional inspection of dies and molds having complex surfaces

Abstract: A hierarchical planning system using heuristics for path planning in dimensional inspection using coordinate measuring machines (CMMs) is presented. The objective is to automate the planning of a collision-free inspection path for dies and molds. The proposed system demonstrates that the inspection paths of geometrically complex parts having multiple surfaces can automatically be generated with efficiency. This is made possible by appropriate CMM abstractions, genuine 3D collision detections, and heuristic modifications of reasonably assumed default inspection paths. Automatic generation of probe angles based on a local accessibility analysis of a given surface is also presented. The collision-free inspection path can then be simulated in a CAD environment before it is carried out by the real CMM. Both simulation and experiment show excellent results of the proposed path planning strategies and demonstrate the feasibility of automatic path planning in dimensional inspection of dies and molds using CMMs.

The prediction of dimensional error for sculptured surface productions using the ball-end milling process. Part 1: Chip geometry analysis and cutting force prediction

Abstract: The study of machining errors caused by tool deflection in the balkend milling process involves four issues, namely the chip geometry, the cutting force, the tool deflection and the deflection sensitivity of the surface geometry. In this paper, chip geometry and cutting force are investigated. The study on chip geometry includes the undeformed radial chip thickness, the chip engagement surface and the relationship between feed boundary and feed angle. For cutting force prediction, a rigid force model and a flexible force model are developed. Instantaneous cutting forces of a machining experiment for two 2D sculptured surfaces produced by the ball-end milling process are simulated using these force models and are verified by force measurements. This information is used in Part 2 of this paper, together with a tool deflection model and the deflection sensitivity of the surface geometry, to predict the machining errors of the machined sculptured surfaces.

Precision tracking control of non-minimum phase systems with zero phase error

Abstract: In this paper, a method is proposed for designing the command feedforward controller for zero phase error tracking control of systems having unacceptable zeros. The unacceptable zeros include both non-minimum phase zeros and lightly damped zeros. In the proposed approach, a digital preview filter along with the acceptable part of the system's inverse model is designed to form the command feedforward controller. Using preview information of the input trajectory, the designed tracking controller guarantees zero phase error and high precision tracking performance. In the proposed design, the best tracking performance can be achieved by minimizing a weighted penalty function, which controls the gain error between the desired output and the actual output. Two design cases were examined. The first is the design based on a uniform weighting function. In this study, the optimal solution of the design can be analytically obtained and three prior approaches were shown to be the special cases of the proposed solutio...

The prediction of dimensional error for sculptured surface productions using the ball-end milling process. Part 2: Surface generation model and experimental verification

Abstract: This paper presents a surface generation model for sculptured surface productions using the ball-end milling process. In this model, machining errors caused by tool deflections are studied. As shown in Part 1 of this paper, instantaneous horizontal cutting forces can be evaluated from the cutting geometries using mechanistic force models. In this paper, a tool deflection model is developed to calculate the corresponding horizontal tool deflection at the surface generation points on the cutter. The sensitivity of the machining errors to tool deflections, both in magnitude and direction, has been analyzed via the deflection sensitivity of the surface geometry. Machining errors are then determined from the tool deflection and the deflection sensitivity of the designed surface. The ability of this model in predicting dimensional errors for sculptured surfaces produced by the ball-end milling process has been verified by a machining experiment. In addition to providing a means to predict dimensional accuracy prior to actual cutting, this surface generation model can also be used as a tool for quality control and machining planning.

Integrated laser/CMM system for the dimensional inspection of objects made of soft material

Abstract: The applications of the coordinate measuring machines (CMMs) with a contact trigger probe to the dimensional inspection of manufactured products are restricted to the parts made of hard material, such as steel. By combining the laser and CMM, the applications of the CMMs can be extended to the inspection of objects made of soft materials, such as foils, plastics, wood, wax and clay materials. In this research, replacing the contact probe with an inexpensive laser sensor is attempted so as to eliminate the possible deflection of the component being measured when using contact probe. By combining a laser sensor with the existing automated inspection environment, a CAD-directed, three-dimensional coordinate sampling system which can perform non-contact dimensional inspection is developed.

Robust compensation techniques for DC servomechanisms subject to stiction and parametric uncertainties using sliding mode estimation

Abstract: Sliding mode estimator based control algorithms are presented for compensation of stiction and parametric uncertainties in DC servomechanisms. These estimators utilize the uncertainty information in the present step to generate future control action. The performance of these estimators is verified through experimental investigations, and results indicate that the algorithm provides effective model regulation and stiction compensation.

Design of bi-causal inverse models for non-minimum phase systems and its applications to precision tracking control

Abstract: In this paper, an approach is proposed for the design of approximate inverse models for the controlled systems that have real and/or complex conjugate unacceptable zeros. The proposed approach utilizes a bi-causal formula to construct the inverse model, therefore, it can be applied to the design of both feedforward and feedback controllers. A design example is used to illustrate the proposed design approach. Using the derived optimal solution, a feedback controller and a feedforward controller are designed for an electrical DC servomotor. The tracking performance of the designed system and its robustness to parameter variations are examined through computer simulation and experimental verification.