Device Building

Designing a V5 Mechanism

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Designing a V5 Mechanism This section d escribes escribes t he basic tasks in creating creating an V 5 mechanism. mechanism. Joint Taxonomy in a V5 Mechanism Creating a V5 Mechanism Creating Joints in a V5 Mechanism Defining a Fixed Part in a V5 Mechanism Defining Defining Co mmands mmands fo r a V5 Mechanism Mechanism Editing Joints for a V5 Mechanism Mechanism Defining Home Positions for a V5 Mechanism Defining a Home Position Timetable Using the Update Command Creating a V5 Mechanism with a Joint Axis Command Defining Travel Limits Defining Tool Tips

Designing a V5 Mechanism

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Joint Taxonomy in a V5 Mechanism Device Building lets you define and edit 11 different joint types.

The table below describes describes the joint types and their characteristics. characteristics. Note that only the joints t hat are assigned a command can be manipulated. In addition addition to the methods of jo int creation creation d escribed on this t able, able, Device Device Building Building sup ports creating creating j oints by s electing electing frames. frames. These joints can be revolute, prismatic, cylindrical, spherical, planar or rigid. GRAPHIC REPRESENT ATI ON

JOI NT T YPE

DEGREES OF FRE EDOM

C OM OMMAND T YPE

Revolute

1 Ro tation

Ang le

YES / Left- mo use butt o n

Prismatic

1 T rans latio n

Lengt h

YES / Left- mo use butt o n

Cylindrical

1 Ro tation tation 1 Tr anslation anslation

An gl gle o r L en en gt gt h

Y ES ES / L ef ef tt- mo mo us us e b ut ut to to n

Leng th + Ang le

NO

Spherical

3 Rotations

 _ 

NO

Planar

2 Translations 1 Ro tation tation

 _ 

NO

Rigid

_

_

Roll Curve

1 Ro tation tation 1Translation

Lengt h

NO

Slide Curve

2 Rotations 1 Tr anslation anslation

 _

NO

Point Curve

3 Rotations 1 Tr anslation anslation

Lengt h

NO

Point Surface

2 Translations 3 Rotations

 _ 

NO

Universal Joint

2 Rotations

 _ 

NO

 

DIRECT MANIPULATION

NO

All joint types that can be created in DMU Kinematics, while not available as part of Device Building, are supported in Delmia simulations. simulations. In addition to the joint t ypes listed listed ab ove, additional suppo rted joints are: screw, screw, CV, g ear, rack, rack, cable, etc.

Designing a V5 Mechanism

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 Creating a V5 Mechanism This procedure sho ws how to create a mechanism and define the joint ax is.

Open the rods .CATProduct document from the samples directory.

Create the Mechanism 1. Make sure you are in Design mode. If not, select the ro ot product in the tree and select Edit > Representations > Design Mode.

2. Click New Mechanism

.

The Mechanism is identified in the specification tree.

Define the Joint Axis In this section, you s elect two lines and two p lanes t hat define the joint axis. 1. Select Line 1 in the geometry area. In our example select a cylinder as shown:

The dialog bo x is automatically updated with your selection.

2. Select Line 2 in the geometry area. Select a second cylinder. The dialog box Current selection area is automatically updated.

Designing a V5 Mechanism

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3. Select a plane for each rod. In the dialog bo x, the Current selection: Plane 1 and Plane 2 fields are up dated. The Revolute Joint is created and the sp ecification tree is updated.

4. Click OK to confirm the Revolute Joint creation.

5. Proceed in the s ame manner to create the ot her joints. Remember to define at least one command and a fixed part within your mechanism.

You can also create a new mechanism by selecting Insert > New Mechanism from the menu bar.

Designing a V5 Mechanism

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Creating Joints in a V5 Mechanism This procedure sho ws how t o create joints in a V5 mechanism.

Open the rods+3joints.CATProduct document.

You can create 11 joint types as shown in the fo llowing table:

 Revolute

Roll Curve

Prismatic

Slide Curve Point Curve

 Cylindrical Spherical

Point Surface

 Planar

Universal

 Rigid

In addition to these joint t ypes, there is a method o f creating joints using frames t hat relies on Joint Axis

.

When you create a jo int, you can define the mechanism within the same dialog box. Remember, though, that you can create a mechanism independently from its joints by selecting Insert > New Mechanism from the menu bar or clicking New Mechanism

1. Click Revolute Joint

from the KinematicJoints toolbar (Revolute Joint

is the default joint type).

2. Click the arrow within the icon and und ock the Kinematic Joints toolbar.

3. Select t he joint t ype of your choice. For instance, click Rigid Joint

.

The Joint Creation : Rigid dialog box is displayed.

The term "rigid" corresponds to "fully restricted" in the st andard kinematic terminology.

4. Select t he parts either in the g eometry area or in the s pecification tree.

.

Designing a V5 Mechanism

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Your selection is sho wn in the Joint Creation: Rigid dialog box.

5. Click OK to co nfirm your operation. The rigid joint is identified in the specification tree.

For more information, please refer to Jo int Taxono my and Creating a Mechanism.

Designing a V5 Mechanism

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Defining a Fixed Part for a V5 Mechanism This task describes how to define a fixed part.

Open the rods+4joints+cmd.CATProduct document from the samples  directory.

1. Click Fixed Part

from the too lbar or select Insert > Fixed Part... from the menu bar. The New Fixed Part dialog box is

displayed.

2. Select the Fixed Part either in the geometry area or in the specification tree.

3. The fixed part is automatically defined and is identified in the specification tree.

You can use Undo

at any time to modify your selection.

Designing a V5 Mechanism

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Defining Commands for a V5 Mechanism This task describes how to define a command on a cylindrical joint after its creation.

You can define a command either during joint creation or after joint creation.

Open the rods +4joints.CATProd uct document. You created a mechanism in previous tasks.

1. Double-click Joint 4 in the specification tree. The Joint Edition dialog box is displayed. 2. Explore the options by checking D riven angle. The mechanism corresp onds accordingly.

3. Click OK to confirm your operation. The command is identified in the specification tree.

You can also create the command while creating a joint.

Designing a V5 Mechanism

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Editing Joints for a V5 Mechanism This task describes how to edit the properties of a j oint. Editing the properties of a jo int includes: modifying the joint name activating or deactivating its command Open the rods +4joints.CATProduct document from the samples directory.

1. Double-click the joint to be edited in the specification tree, i.e. Joint 1 as shown in the example below.

The Joint Edition dialog b ox is displayed.

2. In the Joint name field, enter a meaningful name, i.e., Revolute 1-3. 3. Check the Driven angle command.

4. Click OK to confirm your operation. The joint is updated and identified in t he specification tree under its new name.

Designing a V5 Mechanism

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Note that you can edit the mechanism name. Double-click the mechanism in the specification tree, enter a new name in the Mechanism Edition dialog box displayed, and click OK.

Designing a V5 Mechanism

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Defining Home Positions for a V5 Mechanism Device Building allows yo u to define one or more standard configurations (or ho me positions) for a mechanism. Each ho me position is characterized by a unique name and a set of command values. Home positions are typically used to define the desired states of a mechanism; for example, the open and closed configurations of a gripper. This procedure describes several methods that you can use to define home positions for a mechanism. See also: Mechanical Specifications.

1. Open the DRESSUP.CATProduct document. 2. Click Home Positions

. The Home Position Viewer dialog box is displayed.

3. Click New. The Home Position Editor dialog b ox is d isplayed with the s tandard jog controls in the upper s ection and a text entry field in the lower section. The jog controls are used t o s pecify the desired set of command values for t he home pos ition, while the text entry field is used to specify its name.

4. For th e first home pos ition, enter a value of 90 d egrees (1.57 radians) in the numeric field for Command.1 and enter the string "Home1" in the Home Position Name: field. Click OK.

Designing a V5 Mechanism

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5. Home1 has been added to the list of ho me positions for th e mechanism.

6. Define a second home pos ition named "Home2". Use th e slider bar to set the value of Command.1 to appro ximately -45 degrees (-0.78 5 radians). C lick OK.

Designing a V5 Mechanism

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7. In the Home Position Viewer, double click on each home position. This has the effect of immediately moving the mechanism to the sp ecified coordinates. 8. In the Home Position Viewer, select Home2 and click Modify. Move the mouse into the geometry area near the joint labeled Joint.3. Use t he manipulator to change the value of Command.1 to approximately -90 degrees (-1.57 radians). C lick OK. 9. Click Close on the Home Pos ition Viewer. For additional information on entering command values, see Jogging a Mechanism.

Designing a V5 Mechanism

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Defining a Home Position Timetable Device Building allows t he user t o d efine the elapsed t ime for a mechanism to move between each of its home po sitions. The set o f all such time values is stored in a timetable. This information is typically used in simulation contexts when commanding a mechanism to move from one configuration to anot her; for example, opening and closing a gripper. This pro cedure describes h ow to define a home position timetable for a mechanism. See also: Mechanical Specifications. The previous task shou ld be completed and loaded or open t he sample document named rods +homes.CATProduct .

1. Click Timetable

. The Timetable Editor dialog box is displayed. Notice that default time values are zero.

2. Select t he cell corresponding to row Home1 and column Home2. Enter a value of 10 seconds . This value represents t he time required t o move from Home1 to Home2.

3. Complete the timetable as follows:

4. Click OK.

Designing a V5 Mechanism

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Designing a V5 Mechanism

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Using the Update Command This procedure shows you how to use Update Positions

to synchronize the assembly model and the kinematic model. This

command is t ypically used t o impose t he various joint cons traints on a mechanism, after performing so me operations on the assembly component o f the mechanism. Open the rods_with_joints.CATProduct document.

Updating a mechanism 1. Move the Rod.2. and Rod .1 parts in this model:

Point to the compass manipulation handle. Drag and drop the compass ont o Rod .1 in the geometry area and move it away from Rod.4. Move Rod.2 in a similar manner. 2. Reposition the 3D compass as it was. Select View > Reset compass.

3. Click Update Positions

. The Update Mechanism dialog box is displayed.

4. Click OK to confirm your operation. The mechanism is updated and the parts are returned to t heir original locations.

Designing a V5 Mechanism

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5. Now, move Rod.2 and Rod.1 in the s ame way. Reset the compass.

6. Click

.

7. Check the "Take current positions fo r Rigid Joints" op tion. This opt ion allows you to d efine the rigid joint o ffsets in terms o f  the current po sitions o f the mechanism.

The mechanism is updated as s hown below.

Designing a V5 Mechanism

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8. Now simulate the mechanism. Please refer to Jogging a Mechanism.

The current pos ition has b een kept for Joint.2 (Rigid, Rod .4, Rod.1 ).

Deleting an assembly constraint 1. If you need information about this particular constraint, double-click Coincidence.2 (Rod.3, R od.4) in the specification tree to display the Cons traint Definition dialog bo x. C lick OK. 2. Right-click Coincidence.2 (Rod.3, Rod.4) in the specification tree.

Designing a V5 Mechanism

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3. Select Delete from t he context ual menu displayed.

4. Click

. The Update Mechanism dialog box appears .

5. Click OK. The joints within the mechanism are updated. Joint.1 (Revolute, Rod.3, Rod.4) is converted into a Cylindrical joint as shown below. Revolute:

Cylindrical:

Designing a V5 Mechanism

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Designing a V5 Mechanism

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Creating a V5 Mechanism with Joint Axis This pro cedure describes h ow to create a mechanism with a joint axis.

Open the rods.CATProd uct document. Use Defining Frames of Interest to p ut design tags on two of the ro ds in the place on the geometry where you wish to create a joint.

1. Click Joint Axis

from the Kinematics Joints too lbar. A joint creation dialog box appears.

2. Select the New Mechanism but ton if you do not already have a mechanism created. 3. Select t he relevant design tags on each product for axis 1 and ax is 2. 4. Click OK to confirm your operation and the mechanism is created.

Designing a V5 Mechanism

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Defining Travel Limits This task describes how to define travel limits for commands within a mechanism. The limits are used during jogging/simulation of a device or mechanism. The travel limits for robo ts within the robo t catalog are specified by t he robot manufacturer. In certain cases, users may wish to enter modified limits, e.g., to avoid a collision. These modified limits are called soft limits; the original limits are called hard limits. If a user enters s oft limits, thos e limits become the lower and upper limits for a s pecific device; if the user do es no t enter any s oft limits, the lower and upper limits are the hard limits. Limits can be specified using mathematical expressions o r numeric values. So that values can be defined as a relationship to other joint travel limits, mathematical expressions can be used. In addition to limits, users can also create a caution z one. Caution zo nes exist o nly in the world of CAM so ftware; they are not defined within the ro bot controller. The p urpose o f a caution zo ne is to keep a margin so t hat a do wnloaded pro gram will not exceed the limit after calibration or minor changes in the real world.

This arc represents a robot's travel limits. The green area represents the normal travel limits; the gold / yellow area represents the caution zone and the red area shows t he range of s oft t o hard limits. T he white line represents the so ft limit while the black line represents the hard limit. This zon e can be defined by a percentage or a value with respect to the so ft limits. See also: Mechanical Specifications. To s ee how the command works with a device you have created yours elf, use t he rods+4jo ints+cmd.CATProduct document, after you have defined a mechanism for it. To s ee how the command works with a robot f rom the robo t library, use BodySide_Robo t.CATProcess , and double click on the rob ot in th e PPR tree. This will put t he robot into Device Building. You can access the sample file regardless of you r configuration. However, access to the Standard Rob ot L ibrary product d epends on whether you also have purchased this add- on to Device Building's co nfigurations.

1. Select the device. 2. Click Travel Limits

. The dialog box appears.

3. Alter the upper and lower joint limits using specific numeric values or a mathematical expression. Mathematical Expression: An arithmetic statement that contains p re-defined functions and/or op erators. Fo r details, s ee Operators and Functions.

Rules for Co nstant and Variable joint limits : 1.  Specific numeric values imply that the joint limit is a constant. The units ass umed during entry o f const ant joint limits are the current dialog units such as degrees in the example for Joint 1 above.

Designing a V5 Mechanism

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2. By contrast, a mathematical expression implies that the joint limit is a variable function. Such expressions are used when typically the joint limits for o ne joint are functions o f oth er joint current values. In the example above, the Joint 3 limits are a variable function of the Joint 2 current value. Mathematical expressions MUST always be started with an "=" sign. This informs the system that the following text is a variable joint limit. If a mathematical expression is entered without the st arting "=" sign then the expression will be automatically prefixed and saved with an "=" sign on entering OK for the "Modify Command Limits" dialog. The units assumed within a mathematical expression are by definition always radians and millimeters. Hence, for example, degree values specified in mathematical expressions, such as "=90+dof(2)" with 90 is to be 90 degrees, must be multiplied by t he built in const ant RAD s o t he expression sho uld be entered as "=90*RAD+dof(2)". 4. (Optional) Alter the caution zo ne limit by using the s pinners. You can choos e to define the caution z one in terms of absolute values or in terms of a percentage of the joint limits. The caution zon e, whether specified in percentage terms or in abso lute values, cannot b e greater than 50% of the tot al hard limits range. If you attempt to set a range exceeding 50% of hard limits range for any joint, you will get a warning message, and previous caution zone values of all the joints will be retained. 5. Click OK.

To return to the hard limits set by the robot manufacturer, press the Reset butt on. The caution zo ne will return to zero, and any s oft limits previously entered for any of the jo ints will return to t he manufacturer's sp ecifications. If  the limits have not been altered, the Reset butto n will appeared grayed out, as s hown on t he image above.

Operators, Functions, and Constants for Mathematical Expressions Operators ;

Math

Functions

abs

SASA

,

acos, asin, atan

SASS

=

acosr, asinr, atanr

SSSA

+

cos, sin, tan

RANGE

-

cosr, sinr, tnr

INRANGE

*

exp

SASASA

 /

Int

SASASS

^

sqrt

SASSSA1

%

floor, ceil

SASSSA2

(

log, log10

RAMP

)

Operators ;

Usage Separator for exp ressions. Useful in case of  multiple expressions fo r a nono -command  joint.

,

Arguments separator in a function.

=

Assignment

+

Unary plus / binary addition

-

Unary minus / binary subtraction

*

Binary multiplication

 /

Binary division

^

Exponent

%

Modulo operator

(

Opening parenthesis

)

Closing parenthesis

Math abs(x)

Usage Returns absolute value

acos(x), asin(x), Returns arc cos, s in, tan in degrees atan(x) acosr(x), Returns arc cos , sin, tan in radians asinr(x), atanr(x) cos(x), sin(x), tan(x)

Returns cos , sin, tan in degrees

Designing a V5 Mechanism

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cosr(x), sinr(x), tnr(x)

Returns cos , sin, tan in radians

exp(x)

Returns e raised to power x

int (x )

Ret urns integ er value res ulting fro m t runcat io n

sqrt(x)

Returns square root

floor(x), ceil(x)

Returns floor, ceiling of x

log(x), log10(x)

Returns natural logarithm, logarithm base 10

Constant Name

Value Used for Conversion

PI

3.14159

RAD

0.0174533 (to convert degrees to radians)

DEG

57.29578 (to convert radians to degrees)

Designing a V5 Mechanism

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Defining Tool Tips This task d escribes ho w to d efine too l tips on a mechanism. The too l tips are the parts of the d evice that are suppo sed to be in contact with the p roduct for a given home pos ition. The to ol tips are excluded fro m the clash analysis in too ls like DPM Body-in-W hite's weldgun search. 1. Click Define Tool Tips

.

2. Select t he product. The dialog box below appears.

3. From the pulldown menu, select the home position for which you will define the tool tips. The default value is All Positions, although if you have home positions defined, you may select among those. 4. On the part geo metry, select the part that is a to ol tip.

In some cases, such as weld guns, the parts may have two or more tips. You can select as many parts as are applicable, one at a time. The part name appears in the dialog b ox.

5. When you have selected all the parts that make up the tool tip, click OK.