MATLAB SIMULINK 3D ANIMATION 5 Bedienungsanleitung PDF herunterladen (Seite 37)

positions of joints between objects. Joints between parts are

usually positioned not in the [0 0 0] of parent’s coordinate

system. To define a center of rotation different from the

default value [0 0 0], define the center field of the child

Transform in the VRML file. Example – define the robot’s

tool center of rotation to be collocated with the joint

connecting the hand and the tool , in the hand’s local

coordinates.

Hint: In the case of hierarchical scene structure, when the parts are connected

by revolute joints, it is very easy to define relative rotations between parts. The

joint axis defines directly the VRML rotation axis, so constructing the [axis

angle] 4-element VRML rotation vector is trivial.

5.3.2. Initial Conditions

Simulink model initial conditions must correspond to the initial object’s

positions and rotations defined in the virtual scene. Otherwise, the object

controlled from Simulink would “jump” from the position defined in the VRML

file to the position dictated from Simulink at the start of the simulation. The

possible offset can be compensated either in the VRML file (by defining another

level of nested Transform around the controlled object) or in the Simulink

model by adding the object initial position to the model calculations before

sending to the VR Sink block.

In order to align Simulink model initial conditions with virtual scene object

positions, while maintaining also correct position of the object relative to the

surrounding scene, it is sometimes necessary to adjust also position of the

object surroundings. Example – move the road position so that the car at

position [0 0 0] stays on the road, the wheels not sinking nor floating above the

road surface.

5.3.3. Use of VR Placeholder and VR Signal Expander

The VR Sink block accepts only inputs that define fully qualified VRML field

values. For dynamic models that describe system’s behaviour only in one

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MATLAB SIMULINK 3D ANIMATION 5 Bedienungsanleitung Seite 37