Design Assembly

Int J Adv Manuf Technol (****) **: *** ***

DOI **.1007/s00170-006-0407-8

ORIGINA L ARTI CLE

Y. Li . M. Fang . M. L. Feng . S. Frimpong

Three dimensional modeling of the working linkage

of load-haul-dump loader

Received: 17 December 2003 / Accepted: 6 January 2006 / Published online: 11 April 2006

# Springer-Verlag London Limited 2006

Abstract 3-dimensional (3D) modeling approach of the connected together with an articulation joint. Steering is

working linkage of load-haul-dump (LHD) loader has been achieved by changing the articulation angle with hydraulic

presented to implement 3D computer aided design (CAD) actuators. The working linkage of LHD loader is a loader

and manufacture. The modeling approach is described in assembly supported by the front frame of LHD loader.

detail with application examples. The major issues in There is a big bucket mounted on lift arms. The working

implementing modeling are discussed. Research work is linkage provides a function for lifting, lowering and tilting

focused on integration of basic modeling operations in the the bucket during loading operations.

HELIX design system with modeling methods proposed in A lot of effort has been invested to study the navigation

and guidance system for an autonomous LHD loader [1 3].

this work to achieve part modeling, assembly modeling,

and assembly analysis of the working linkage. Part However, there is less study in automation design of LHD

modeling operations in the HELIX design system and loader now. In recent years, 3D CAD has been recognized

proposed compound modeling method are used together to as one of the most important technologies for mechanical

design the parts in 3-dimensions. Assembly modeling product [3]. This technology is also critically important to

operations in the HELIX design system and proposed promote automation design of LHD loader. Traditional

feature-based modeling and assembly method from top to CAD system represents the design in terms of 3D entities

bottom have been integrated to assembly parts into an (wireframe, surface, and solids). Some of them are only a

assembly tree structure in 3-dimensions. Assembly anal- geometric representation of the object for observation.

ysis operations in the HELIX design system have been They do not have enough of the features to allow testing of

proposed to find out the geometric connection, express the the product design against the product requirement. These

spatial dimension and make the interference check in the representations have little significance to the process

assembly model. This approach can be used for all kinds of planner who interprets the design in terms of manufactur-

3D modeling of the working linkage of LHD loader. ing features, e.g., holes, pockets, and fillets [4].

Feature-based 3D modeling is an intelligent form of

Keywords Working linkage . LHD loader . 3D modeling . design representation. One of main advantages of feature

Compound modeling . Feature-based modeling modeling over common geometric modeling is the ability

to associate functional and engineering information to

shape information in a product model. In the manufacturing

1 Introduction domain, a feature representation is in terms of holes, slots,

channels, fillets, and chamfers. The parts of the working

LHD loaders are used to transport ore in underground linkage contained these features. It is necessary to focus

mines. The body of the vehicle consists of two parts research on the creation of 3D model of the working

linkage of LHD loader by using this technology.

HELIX system is a feasible feature-based CAD system.

Y. Li . M. Fang . M. L. Feng It provides feature operations to create feature-based part

School of Resources and Engineering, models. It also provides a tool for assigning 3D geometric

Beijing University of Science and Technology, constrains between components. Even so, it needs to

Beijing 100083, People s Republic of China

combine some particular methods to design the working

Y. Li . S. Frimpong linkage of LHD loader when using this design system. The

part modeling, assembly modeling, and assembly analysis

Department of Civil and Environmental Engineering,

School of Mining and Petroleum Engineering,, of the working linkage can be performed.

University of Alberta, Edmonton, T6G 2G6, Canada

In this work, we focus on 3D modeling of parts,

e-mail: *********@*****.***

components, and assembly of the working linkage of LHD

Tel.: +1-780-***-****

loader. We combine the basic operation functions in

Fax: +1-780-***-****

857

HELIX design system with the modeling methods complex parts, the compound modeling, which integrates

established in this work to model the working linkage in some modeling technologies, such as wire frame, solid,

3-dimensions. surface, and feature-based part modeling, is used. The

following are modeling methods:

2 Modeling

2.2.1 Shell part

2.1 System structure

The system supports two methods to create a model of shell

Figure 1 shows the schematic of the working linkage of a part of the working linkage. They are skinning modeling

typical LHD loader [5]. This mechanism can be assumed to and sweeping modeling.

consist of a front frame to which lift hydraulic linkage and

The sweeping modeling creates a model by specifying

rocker hydraulic linkage are attached. The working linkage

a cross-section curve of an object and a trajectory curve

has provided a system for operating the lift arms and the tilt

of the cross section and then sweeping the cross-

of the bucket.

section curve along the trajectory.

The lift hydraulic linkage provides a function for

The skinning modeling creates a model by specifying

lowering and raising the bucket to a position. It consists

several cross-section curves of an object and then

of hydraulic actuators, lift arm and bar linkages. The bar

connecting them smoothly.

linkages are joined on a pair of the lift arms, which is

pivotally mounted on the front frame. The lift arms may In the above two methods, choosing which method

automatically be raised and lowered by means of extensible depends on the requirements of how the surface should.

hydraulic actuator. The lift arms continue to raise or lower Figure 2 illustrates the latter method. In designing the

to support a work implement when the pistons of actuators bucket model, its shapes are defined by the cross-section

are moved along the chamber. The rocker hydraulic linkage data. The procedure is: (1) create two cross-section curves

provides a function for rotating the bucket from first as basic shape (Fig. 2a); (2) use the operation TRANS-

position to second position. It consists of hydraulic FORM/TRANSLATE, to move smallest cross-section to

actuators and a bucket. The bucket is mounted on lift defining position (Fig. 2b); (3) use the operation SUR-

arms and rock hydraulic actuators. As the lift arms are FACE/SKIN, to connect vertices of adjacent laminas to

raised and lowered, the attitude of the bucket relative to the form surface of bucket (Fig. 2c); (4) use the operation

ground level is controlled through actuation of extensible OFFSET or PARAMETIC, to add or modify thickness to

actuator on the lift hydraulic linkage. Extension and the bucket (Fig. 2d).

retraction of actuator on the rocker hydraulic linkage By interpolating the surface created via the above

operates and controls the bucket. procedure, a bucket model whose cross-section curves are

According to the structures of the working linkage, it can smoothly connected can be obtained. In the bucket

be regarded as a mechanism consisting of components,

such as hydraulic cylinders, lift arm, bar linkage, and a

bucket. All components are assembled by parts.

2.2 Part modeling

In the design system, the parts assembled into the working

linkage can be built into 3D models of solid, wireframe,

and surface by appropriate modeling methods. For feature-

based parts, the feature-based part modeling [6], which

offers parametric and feature-based modeling in addition to

the common geometric modeling facilities, is used. For

Fig. 1 Design system Fig. 2 Bucket model modeling

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operation, cross-section curves are created as laminas, on

condition that the number of vertices of each lamina is

equal. However in part operations, the laminas have

different numbers of vertices, their edges should be

properly divided so that the number of vertices is equal.

2.2.2 Cylinder part

The system supports two methods to create a model

cylinder part. They are extruding modeling and rotating

modeling.

The extruding modeling creates a model by extruding

curves defined in the XY-plane about the Z-axis.

The rotating modeling creates a model by rotating

curves defined in the XY-plane (definition curve) about

the Z-axis. The steps to create sleeve by this method

are: (1) create definition curve of sleeve (Fig. 3a); (2)

use the feature operation REVOLVE, to rotate defini-

tion curve about the z-axis 360 (Fig. 5b) to form solid

model (Fig. 3c); (3) use the feature operation HOLE, to

hole in solid model so that the sleeve model is formed

(Fig. 3d).

A cylinder model can also be created by extruding

modeling. However, two things differ: to create simple

cylinder models, such as a parallelepiped and cylinder,

the most used method is extruding modeling; instead,

Hydraulic cylinder-black modeling

Fig. 4

to create complex cylinder models, the most used

method is rotating modeling. The former creates a

model by extruding the cross-section curve and the

latter does it by revolving definition curve. Figure 4

Fig. 3 Sleeve modeling Fig. 5 Connect plate modeling

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shows the modeling procedure of a hydraulic cylinder 2.3.1 Assembly modeling

by extruding modeling.

This subsection introduces assembly modeling methods of

the working linkage. The task involves 3D assembly

modeling of components, such as hydraulic cylinders, lift

2.2.3 Sheet-metal part

arm or rocker arm, bar linkages, and a bucket. The design

and interaction tools provide feature-based part modeling

Sheet-metal parts are very popular in parts of the working

operations that are necessary to create the components of

linkage. The building models of sheet-metal parts are

an assembly. In addition, they provide a tool for assigning

performed in two cases:

3D geometric constraints between components. Feature-

1 To complicated shapes, SURFACE function can be

based modeling [6], which includes parametric and

used to create simple small curve surfaces, such as

constraint-based assembly modeling [6, 7], assembly

boundary curve surfaces, planes, and sweeping

method from top to bottom and the assembly tree structure

surfaces. Then, by using the Boolean operations to

[8], have been suggested for assembly modeling, modifi-

combine these small curve surfaces, a complicated

cation, and to optimize their configuration. The assembly

surface can be created. Finally, by adding thickness, a

modeling consisting of three stages is described below:

sheet-metal part solid model can be formed.

First, the assembly design of the working linkage involves

2 To simple shapes, SHEET METAL function can be

the creation of assembly models that specify the relative

used to create solid model directly. Figure 5 shows an

location and orientation of components. In the design

example of sheet metal function. In this figure, connect

activity, components are assembled together to create an

plate of lift arm is spread into a plane plate by

assembly model. Surface mating constraints are used to

calculating its sizes (Fig. 5a). Use feature operation

locate and orient components with respect to each other.

HOLE, to hole in the plane plate (Fig. 5b). Use the

There are three major types of mating conditions: distance,

sheet metal function, to bend the plane plate and create

angle, and alignment. This design activity is supported by

connect plate model (Fig. 5c,d).

constraint-based assembly modeling. Figure 6a and b show

the mating piston with respect to the cylinder by this

operation. The base component cylinder is a cylinder with a

blind hole and the mate component piston is a cylinder with

2.2.4 Complex part

a cylindrical shaft. Figure 6a shows that two local

coordinate systems are defined for the piston and the

In the above three ways, surface models are designed by

cylinder, respectively. Figure 6a also shows that the

surface modeling operations and solid models by solid

position and orientation of the above two coordinate

modeling operations. For complex parts, compound mod-

eling methods need be used.

When designing complex parts containing free-form

curves or surfaces, which the features for surface proces-

sing are incorporated in the solid modeling, we need to

integrate functions of solid and surface modeling technol-

ogies. The procedure creating complex part model is: (1)

build basic solid model by solid modeler and build surface

shape by surface modeler; (2) create features by feature

functions EX-TRUDE, HOLE, SHELL, BOUNDARY, etc.

if model includes features; (3) generate and modify model

by local modification operations ROUND, CHAMFER,

and CUT.

2.3 Assembly modeling and analysis

The 3D part models designed above can be assembled into

a 3D model of the working linkage by use of assembly

constrains, features, parameters, etc. Assembly modeling

methods have been suggested in this section. Various

processing tools, such as design, interaction, and analysis

tools have been used for assembly modeling and analysis.

The methods of assembly modeling and analysis are

considered in the following subsection. Fig. 6 Hydraulic cylinder assembly modeling

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systems are assigned for constraining the two components.

Figure 6b illustrates that the piston is inserted into the

cylinder after aligning two components.

Second, in 3D assembly modeling design of the working

linkage by using assembly method from top to bottom, the

assembly procedure of the working linkage forms an

assembly tree structure (Fig. 7). In this structure, parts are

assembled into a component (e.g., hydraulic actuator or lift

arm), components are assembled into a subassembly (e.g.,

lift hydraulic linkage or rocker hydraulic linkage), and

subassemblies are assembled into an assembly: the work-

ing linkage. In this assembly tree structure, the parts are

defined by various feature parameters, and these para-

meters can be connected. The parts given some form of

Fig. 8 Real 3D modeling of bucket

constraints are also connected. Therefore, after constraint-

based assembly modeling, assembly can be linked with

part and component models consisting of the assembly

1. Use the function WINDOW TREE, to show the

model. This assembly model can contain a set of an

assembly tree structure of the working linkage. As

assembly hierarchy, assembly parts, relative placements

shown in Fig. 8, by pointing and clicking on any one of

among parts, and other geometric and non-geometric

part names listed on the left with mouse, this part on

information.

the right becomes light and the structure of the bucket

Last, the assembly modification of the working linkage

can be analyzed.

can be carried out. The feature-based modeling of the

2. Use the function DISPLY SHOW or NO SHOW, to

working linkage makes assembly model, part models, and

simulate various assembling stages of the working

component models be modified parametrically and allows

the values of attributes to be inherited from the object s linkage.

3. Use the function EXPLODE, VIEW ROOM, and

context. When the models need to be modified, this

Boolean intersection operations, to check the interfer-

approach allows automatic sizing of the their structural

ence between two assembly components. If interfer-

components by modifying the part model only. Therefore,

ence is happening, the interfering area is displayed on

there is no need to modify the components directly. For

the screen. Errors can be corrected with the feature tree

example, create two parts, say a piston and a cylinder

edit function and parametric function, and the relation-

(Fig. 6). In a very simple model we can set the diameters of

ship between components can also be automatically

the piston and the cylinder bore to be equal. Constraining

updated when the topology of the model changes

two parameters to be equal results in an update for the

without recreating assembling parts consisting two

piston if the cylinder-bore is changed.

assembly components.

4. Also, use the function EXPLODE, to disassemble

some parts from the assembly model. As shown in

2.3.2 Assembly analysis

Figs. 6c,d, the structure relationship of the hydraulic

cylinder can be analyzed by disassembling the piston

At the assembly design stage of the working linkage, the

from the cylinder.

analysis of assembly models is necessary. Assembly

5. Use function VIEW SHADE, to check if curved

analysis can be carried out by the combination of the

surfaces are smoothly connected. When different

basic functions of the design system. This work involves

colors are mapped to the parts consisting of assembly

using different methods to check the interference between

model of the working linkage, the boundary between

the components, calculate mass property of assembly

parts can be expressed. If interference happens, parts

model, and analyze structure of assembly model. Espe-

can be modified parametrically by adding the relation-

cially, by changing the value of constraints, simulation of

ship between the elements of the boundary representa-

assembly can be implemented. These methods are

tions. The contents of the working linkage and its

described below:

surface can be expressed.

Fig. 7 Assembly tree structure Working linkage

of the working linkage

Lift hydraulic linkage Rocker hydraulic linkage

Hydraulic actuator Lift arm Bar linkage Hydraulic actuator Bucket

Cylinder Piston ... ... ... ... Cylinder Piston ... ...

861

Fig. 9 Real 3D modeling of lift

arm

6. Use function EDIT ANALYSIS, to calculate the mass Feature-based modeling is more powerful than common

properties of components assembled in the working geometric modeling in 3D modeling of the working

linkage automatically. For example, in Fig. 9, the mass linkage. It offers parametric and constraint-based modeling

properties of lift arm have been obtained easily during facilities in addition to the common geometric modeling

the design stage. It helps to check if the volume, facilities. So, feature-based modeling possesses good

surface area, and center of gravity are reasonable. properties in creating feature-based part models and

modifying component models of assembly model. This

helps in steering the common geometrical design of the

3 Results and discussion working linkage toward parametric design. In addition, the

common geometrical design can not convey sufficient

information. The combination of the above two methods

The modeling procedure of the working linkage of LHD

gives feature-based parametric models for the working

loader takes the steps: (1) design the part models of the

linkage. These models are more reliable to assembly

working linkage; (2) create the component models of the

analysis.

working linkage by feature-based part modeling opera-

The use of constraint-based assembly modeling and

tions; (3) add assembly constrains to components of the

assembly tree structure of the working linkage admits

subassembly model by the constrain-based assembly

assembly to link with part and component models

modeling operations; (4) assemble subassemblies into

consisting of assembly. This is different from the common

assembly model for making the assembly structure form

geometric modeling methods of the working linkage, by

an assembly tree structure by using the assembly method

which parts and assembly are not connected.

from top to bottom; (5) perform assembly analysis that

However, the approach presented in this paper suffers

includes simulating various assembling stages, checking

from some potential problems. One known problem is:

the interference between the parts, modifying components

feature-based part and assembly modeling of working

of assembly model, calculating mass property of assembly

linkage lacks a complete specification of feature semantics,

model, and analyzing structure of the assembly model; (6)

and therefore fails to maintain the meaning of the features

optimize configuration of the assembly model by modify-

during modeling. Future work will integrate more

ing the model structure parametrically using feature-based

advanced modeling methods, such as the semantic feature

modeling technology.

modeling with the progress of feature modeling systems.

The 3D design of the working linkage should always be

associated with the approach proposed. Even though the

HELIX design system can be used in modeling of different

4 Conclusions

mechanical products, the modeling method used in every

mechanical product will be different. The modeling of the

working linkage need use not only advanced design This article has presented a new approach to create a 3D

systems but also new modeling methods. The approach model of the working linkage. It has focused on the

proposed here is based on research of 3D modeling modeling of part, subassembly, and assembly of the

methods of part and assembly of the working linkage. working linkage, respectively. Especially, there are new

Though modeling methods are used to construct basic methods that distinguish from current 3D modeling meth-

models, such as wierframe, surface and solid models, ods in LHD loader in this article. These new modeling

which are used to create part models of the working methods are well used to part and assembly modeling of the

linkage, new modeling models should be integrated to working linkage. It also described how new modeling

generate complex parts. For example, the compound methods should be used for the modeling of the working

modeling solved the complex part modeling problems. linkage by combination of basic operation functions in

Since the complex part consists of a complex shape, its HELIX system.

structures are not uniform. As a result, conventional In this work, the 3D modeling approach proposed here

modeling methods cannot be applied directly to build this has been successfully implemented in industrial models for

part model. designing the working linkage of an LHD loader. It offers a

862

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