Dynamics: Briefcase

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Dynamics: Briefcase

Summary

The Dynamics Briefcase FB is the 'gateway' that connects the kinematic model with the dynamic model.

Input-Connectors

Each degree-of-freedom has one input-connector.

We recommend you experiment with a one degree-of-freedom model before you experiment with a two degrees-of-freedom model.

You connect to its input-connector a wire from the output-connector of a Motion-Dimension FB*.

The Motion-Dimension FB controls the motion of a degree-of-freedom in a kinematic-chain - typically. The motion-values from the output of the Motion-Dimension FB represent the motion-command to which the dynamic model responds.

The label at the input-connector is - it is the symbol for a generalized coordinate.

The input, , is the input to the Dynamic Analysis.

The input is the motion whose dynamic response you want to analyze.

* You must also connect the wires of the other Function-Blocks in the kinematic model in a particular way - see example, later.

Output-Connector

It has one output-connector,

The data at the output-connector is equal to the kinematic motion data at its input-connector.

Dynamics-Briefcase FB and parameters.

Edit the Dynamics Briefcase FB to:

•Add/remove input-connectors (for extra degrees-of-freedom)

•Add to the Briefcase the Spring-Damper, Inertia, and Graph FBs - you must add these FBs to the graphics-area before you can then add them to the Dynamics-Briefcase FB.

•Edit the integration parameters

•Edit display parameters for the Graph FB.

Add Dynamics Briefcase FB

STEP 1:Add a Dynamics Briefcase FB to the graphics-area:

Add Briefcase FB

1.Click Dynamics menu > Dynamics Briefcase

OR

1.Dynamics toolbar > Add Dynamics Briefcase
Dynamics-Briefcase FB in graphic-area

Dynamics-Briefcase FB in graphic-area

Then:

2.Click the graphics-area

The Dynamics Briefcase FB is now in the graphics-area.

We recommend you also add a:

1.Spring-Damper FB from the Dynamics menu/toolbar

2.Inertia FB from the Dynamics menu/toolbar

3.Graph FB from the “standard” Function-Block menu

Then:

1.Open the Dynamics-Briefcase dialog.

2.Add the Spring-Damper FB, Inertia FB, and Graph FB to the Dynamics-Briefcase FB.

STEP 2:Open the Dynamics-Briefcase FB dialog

Doube-click Dynamics Briefcase FB

Doube-click Dynamics Briefcase FB

1.Double-click the Dynamics Briefcase FB in the graphics-area or Assembly-Tree

OR

See How to Open a dialog

The Dynamics Briefcase FB dialog is now open.

STEP 3:See Briefcase FB dialog

Dynamics : Briefcase dialog

Dynamics Briefcase dialog

Dynamics Briefcase dialog

Toolbar:

Red-14-1 Save Inertia Coefficients to a CSV file - see Dynamic Inertia FB

Red-14-2 Rebuild the Dynamics model

When you click the Rebuild button we can reset the parameters and prepare the model to move with the dynamic response when you run the model.

You can plot the dynamic-response with a Graph FB that is 'inside' the Dynamics-Briefcase FB.

You must click again if you edit a parameter in any of the FBs associated with the Dynamics model.

Red-14-3 Add Input-Connector - for kinematic-chains with more than one degree-of-freedom (Motion-Dimension FBs)

Red-14-4 Delete Input-Connector - delete if you add too many input-connectors
tog_minusDisplay OptionS 
MD-17-DYNAMICS-BRIEFCASE-DIALOG-DISPLAY-OPTIONS

Red-14-2 Background color and Transparency

Use the Background Color button to edit the color of the window - see example below.

Use the Transparency slider to edit the transparency/opacity of the window.

Red-14-3 Show Dynamics FBs in a "Window"

After you add Dynamics FBs to the Dynamics-Briefcase FB:

☑Show Dynamics FBs in a window

❑Do not Show Dynamics FBs in a window

Red-14-3 FB Icon Size

◉32 x 32  

◉64 x 64 (recommended).

SHORT-CUT - To toggle Show and Hide Dynamics FB in a Window Frame

1.Press your SHIFT key on your keyboard

2.Move your mouse above a Dynamics-Briefcase FB

3.Click your mouse

4.Move your mouse away from the Dynamics-Briefcase FB
tog_minusAdd / Remove Function-Blocks
MD-17-DYNAMICS-BRIEFCASE-DIALOG-Add-RemoveFBs

 

 

Add FBs to the Briefcase

1.Click the PadlockRed-14-5 to unlock the Briefcase FB

2.Click the Spring-Damper FB, Inertia FB and Graph FB that are in the graphics-area.

We move each the FBs to the Function-BlocksRed-14-10a box in the Briefcase FB.

3.Click the PadlockRed-14-5 to lock the Briefcase FB

The buttons Red-14-6,Red-14-7, Red-14-8, Red-14-9 are not so important in the Dynamics-Briefcase
tog_minusInegration ParameterS 
MD-17-DYNAMICS-BRIEFCASE-DIALOG-Integration-Parameters

 

These parameters apply to the numerical integration of the differential equations.

Start Recording Time

When you want the numerical integration to start.

0 is when the MMA =0

Note:

Finish Recording Time

When you want the numerical integration to stop.

You usually want to make sure the time is more than 1 machine-cycle, more typically 2-3 machine-cycles.

Note:

Step Size

The nominal Integration Step-Size for the numerical integration.

If the Dynamics are fast (stiff, low inertia, backlash free, low damping), then this must be small.

Typically 1/10 of the period of the Natural Frequency.

Internally, we decrease the step size if the response is very stiff.

Experiment.

Accuracy

Maximum error of the Dynamic-Response.

Minimum Range

If Continuous (Graph Parameters (below)) is not enabled, the Time axis (x) of the simulation graph will only increase up to the Minimum-Range. Then the simulation stops.

If If Continuous (Graph Parameters (below)) is  enabled, then Minimum-Range is ignored.
tog_minusGraph parameters 
MD-17-DYNAMICS-BRIEFCASE-DIALOG-Graph-Parameters

 

 

Theses parameters apply to Graph FB and how to plot the Motion-Command, Motion-Response, Force Command and Force Response over a period of time.

Graph Display Range [s]

The width of the plot in seconds.

There is no maximum time if Continuous is enabled.

Update Range [s]

When you enable Scrolling (see below), and the plot reaches the end of the Graph-Display Range, the Graph will shift to the left by the Update Range, and continue to calculate the Dynamic-Response. Again, when the plot has continued for the Update Range to reach the right-hand-side of the Graph plot area, the whole plot shifts to the left again by the Update Range.

and when the the plot reaches the maximum time axis:

the plot moves (scrolls) across the time axis by the Update-Range.

Decimation

How many points that we calculate before we plot a point with a Graph FB

E.g - if Decimation = 5, then we calculate 4 points, then plot point #5, then we calculate 6 to 9, and plot point #10, and so on.

◉ Continuous

◉ Scrolling

Enable Continuous + Clear Scrolling

Enable Continuous = the simulation plot increases endlessly.

Clear Scrolling = the time axis compresses endlessly, from 0-seconds, until you press the Pause or the Home icons in the Dynamics menu.

Enable Continuous + Enable Scrolling

Enable Continuous = the simulation plot increases endlessly.

Enable Scrolling =

•The range of the time axis is equal to the Graph Display Range

•AND, when the simulation reaches the maximum of the time axis, the time-axis and the plot shifts to left by Update Range in seconds.

•the simulation continues.

Clear Continuous + Clear Scrolling

Clear Continuous = the simulation will increase from 0 seconds to the time equal to the Graph Display Range, and then stop.

Clear Scrolling = The time axis compresses until the maximum time is Maximum Range and the simulation stops.

Clear Continuous + Enable Scrolling

Clear Continuous = the simulation will increase from 0 seconds to the time equal to the Graph Display Range, and then stop.

•The range of the time axis is equal to the Graph Display Range

•AND, when the simulation reaches the maximum of the time axis, the time-axis and the plot shifts to left by Update Range. to continue the simulation.

•when the simulation reaches a time equal to the Maximum Range, the simulation stops.

◉ Scrolling