• 한국정밀공학회지
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• 제15권11호
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• pp.180-188
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• 1998

Z-map is a special form of discrete nonparametric representation in which the height values at grid points on the xy-plane are stored as a 2D array z[i.j]. While z-map is the simplest form of representing sculptured surfaces and it is the most versatile scheme for modeling nonparametric objects, its practical application in industry (eg, tool-path generation) aroused much controversy over its weaknesses ; accuracy, singularity (eg, vertical wall), and some excessive storage needs. Although z-map has such limitations, much research on the application of z-map can be found in various articles. However, research on the systematic analysis of sculptured surface shape representation via z-map model is rather rare. Presented in this paper are the following: shape modeling power of the simple z-map model, exact (within tolerance) B-map representation of sculptured surfaces which have some feature-shapes such as vertical-walls and real sharp-edges by adopting some complementary B-map models, and some application examples.

• 한국멀티미디어학회논문지
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• 제14권2호
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• pp.210-218
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• 2011

일반적으로 GIS 디지털 법의 표현 및 저장 방식에는 아스키(ASCII)와 바이너리(binary) 형식이 있다. 이들 중 대부분 GIS 응용 분야에서는 대용량의 맵 데이터 전송을 위하여 바이너리 형식의 벡터 맵 데이터를 주로 사용한다. 본 논문에서는 다양한 정밀도를 갖는 바이너리 형식의 벡터 맵 데이터의 효율적인 전송 및 저장을 위하여 벡터 맵 데이터의 주요 레이어를 표현하는 폴리라인 및 폴리곤 성분에 대한 계층적 압축 기법을 제안한다. 제안한 기법에서는 정밀 벡터 맵 데이터의 무손실 압축을 위하여 공간 영역 상에서 에너지 집중(energy compaction)을 수행하며, 64bit 부동소수점 좌표에 대하여 정수부와 소수부를 독립적으로 압축 부호화를 수행한다. 실험 결과로부터 제안한 압축 기법이 최소 200% 이상, 최대 900% 이상의 압축 효율을 나타냄을 확인하였으며, 기존의 데이터 압축 기법인 7z, zip, rar 및 gz에 비히여 우수한 압축률을 가지는 것을 확인하였다.

• 한국생산제조학회지
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• 제7권5호
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• pp.38-45
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• 1998

The Z-map model which is quite similar to the non-parametric patch is widely used to describe the shape of a surface because of its simplicity. Despite the inherent advantage of z-map model. it has drawbacks that there exists difficulty in expressing the vertical walls and its related contact treatment method. In the region of vertical walls, there is a convergence problem in searching the contact point. In this study a contact point finding scheme is presented, based on the z value of the z-map model on the sheet normal direction. To show the utility of this scheme a compared with the experimental results. The effects of the Z-map grid distances and the interpolations of the inside Z-map value are also discussed.

• 한국정밀공학회지
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• 제14권3호
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• pp.57-65
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• 1997

In this study, a cutting force in the Ball-end milling process is calculated using Z-map. Z-map can describe any type of cutting area resulting from the previous cutting geometry and cutting condition. Cutting edge of a ball-end mill is divided into infinitesimal cutting edge elements and the position of the ele- ment is projected to the cutter plane normal to the Z axis. Also the cutting area in the cutter plane is obtained by using the Z-map. Comparing this projected position with cutting area, it can be determined whether it engages in the cutting. The cutting force can be calculated by numerical integration of cutting force acting on the engaged cutting edge elements. A series of experiments such as contouring and upward/downward ramp cutting was performed to verify the calculated cutting force.

• 한국컴퓨터정보학회:학술대회논문집
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• 한국컴퓨터정보학회 2014년도 제50차 하계학술대회논문집 22권2호
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• pp.201-202
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• 2014

본 논문에서는 3차원 공간을 시각적으로 표현이 가능한 MAYA의 MEL Script를 통해 미로 찾기 로봇을 3D시뮬레이션으로 구현하는 방법을 제안한다. MAYA에서는 생성된 개체에 대해 X-Y-Z 좌표정보를 적용하고 이 수치를 개체의 속성 값으로 제공한다. 이를 이용하여 랜덤한 미로 맵을 완성하기 위한 규칙으로 행렬을 생성하고 이 행렬의 인덱스와 값에 따라 X-Y-Z 좌표정보를 적용하여 개체를 생성하면 랜덤한 미로 맵이 완성된다. 그 후 길을 찾기 위한 규칙에 의해 이동하는 로봇의 X-Z좌표정보를 각 프레임 별로 저장하여 재생 시키면 미로 찾기 로봇 시뮬레이션을 눈으로 확인 가능하다. 사람이 직접 번거롭게 임의의 미로 맵 을 생성하지 않고 로봇이 없어도 간편하게 미로 찾기를 구현해 볼 수 있는 방법을 제시한다. 본 시뮬레이터는 미로 찾기 알고리즘을 테스트하는데 유용할 것이다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 춘계학술대회 논문집
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• pp.551-554
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• 2002

The paper discusses new approach for machining operation simulation using enhanced Z map algorithm. To extract the required geometric information from NC code, suggested algorithm uses supersampling method to enhance the efficiency of a simulation process. By executing redundant Boolean operations in a grid cell and averaging down calculated data, presented algorithm can accurately represent material removal volume though tool swept volume is negligibly small. Supersampling method is the most common form of antialiasing and usually used with polygon mesh rendering in computer graphics. The key advantage of enhanced Z map model is that the data structure is same with conventional Z map model, though it can acquire higher accuracy and reliability with same or lower computation time. By simulating machining operation efficiently, this system can be used to improve the reliability and efficiency of NC machining process as well as the quality of the final product.

• 한국CDE학회논문집
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• 제8권4호
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• pp.278-288
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• 2003

Presented in this paper is a numerical method for calculating the intersection points between Z-map vectors and the tool swept surface for circularly moving filleted-end mills. In numerically controlled(NC) machining simulation for large moulds and dies, a workpiece is frequently approximated as a set of z-axis aligned vectors, called Z-map vectors, and then the machining processes can be simulated through updating the Z-map with the intersection points. Circular motions are typically used for machining the free-form surfaces. For fast computation, we express each of intersection points with a single-variable non-linear equation and calculate the candidate interval in which the unique solution exists. Then, we prove the existence of a solution and its uniqueness in this candidate interval. Based on these properties, we can effectively apply numerical methods to finally calculate the solution of the nonlinear equation within a given precision. Experimental results are given for the case of a TV monitor and the hood of a car.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 추계학술대회 논문집
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• pp.616-619
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• 2002

The z-map structure is widely used for NC tool path verification as it is very simple and fast in calculation of Boolean operations. However, if the number of the x-y grid points in a z-map is increased to enhance its accuracy, the computation time for NC verification increases rapidly. To reduce this computation time, we proposed a NC verification method using 3-D graphic acceleration hardwares. In this method, the z-map of the resultant workpiece machined by a NC program is obtained by rendering tool swept volumes along tool pathos and reading the depth buffer of the graphic card. The experimental results show that this hardware-based method is faster than the conventional software-based method.

• 한국정밀공학회지
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• 제20권5호
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• pp.47-56
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• 2003

Geometric cutting-simulation and verification play an important role in detecting NC machining errors in mold & die manufacturing and thereby reducing correcting time & cost on the shop floor. Current researches in the area may be categorized into view-based, solid-based, and discrete vector-based methods mainly depending on workpiece models. Each methodology has its own strengths and weaknesses in terms of computing speed, representation accuracy, and its ability of numerical inspection. The paper proposes a hybrid modeling scheme for workpiece representation with z-map model and discrete vector model, which performs 3-axis and 5-axis cutting-simulation via tool swept surface construction by connecting a sequence of silhouette curves.

• 한국생산제조학회지
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• 제8권3호
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• pp.83-91
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• 1999

In this paper, we suggest a virtual machining system that can simulate cutting forces of ball end milling at the stage of part design. Cutting forces, here, are estimated from the machanistic model that uses the concept of specific cutting farce coefficient. To this end, we need undeformed chip thickness which is used for calculating chip load. It is derived from the Z-map data of a CAD model. That is, chip load is the height difference between the cutting tool and the workpiece at an arbitrary position. The tool contact point is referred from the cutter location data. On the other hand, the workpiece height is acquired from the Z-map model of a CAD data. From the experimental verification, we can simulate machining process effectively to the slot and the side cutting of ball end mill.