You must enter the equations correctly with the correct syntax. The Math FB will check the syntax, but not the equation itself. If you enter a meaningless equation, the output will not be correct.

For example, to find, after a time-period, the displacement of a point that has constant acceleration, if you enter:

•((u*t) + (0.5*a*t), the syntax is correct, but the equation is meaningless

•((u*t) + (0.5*a*t*t) the syntax is also correct, and the displacement of the Point is correct.

Note - a bad example. I would design a motion in MotionDesigner with Constant-Acceleration.

MechDesigner continually calculates the Position, Velocity, and Acceleration of all Points and Parts in your model when all Parts are kinematically-defined.

However, YOU must add the symbolic equation for each motion-derivative.

If you do not add the equations for each motion-derivatives (velocity and acceleration), their values remain equal to those motion-derivatives of the data at the input-connector.

The units inside the Math FB are S.I.. For example:

•50mm at the input-connector becomes 0.05m when applied to an equation inside the Math FB dialog

•50° at the input-connector becomes (50*2*pi/360)rads when applied to an equation inside the Math FB dialog

You can use the Math FB to do:

Simple Algebra

For example: 2+3. The output will be 5, of course.

Parametric Constants

For example, connect the output from a Motion-Dimension FB and the output from a Force-Data FB at the same joint. You can use the Math FB to multiply the Torque(Nm) and the Velocity(rad/sec) values to give the Power(kW) as the output.

Top-Tip: Connect a Gearing FB to the input of a Math FB. You can edit the Gearing FB, so that it becomes a parametric-constant of an equation in the Math FB, for example, a Friction Coefficient.

Change the Units of a Variable

For example, change the units at the input-connector of a Math FB to different units at its output-connector - for example: mm to Newtons.

1.Click Modeling-FB toolbar > Math FB

2.Click the graphics-area

1.Double-click the Math FB.

or

1.See How to edit an Elements.

1.Click Add Input to add one input-connectors to the Math FB.

1.Click Add Output to add one output-connectors from the Math FB.

1.Click the drop-down box to select the Data-Type that applies to all of the output-connectors.

Input-Connector 1 = Wire Number 0 - connected to the TOP input-connector

Input-Connector 2 = Wire Number 1 - connected to the next input-connector, one down from the top

Input-Connector 3 = Wire Number 2 - connected to the next input-connector, one down again

•and so on ...

Each wire has 3(three) data-channels.

In the Math FB, we use a letter for data-channel has a letter - p, v, and a ALWAYS even if data is not motion-data.  

E.g. even if the wire is from the output of a Force-Data FB

•p = Data-Channel 1

•v = Data-Channel 2

•a = Data-Channel 3

p(0) : the p refers to Data-channel 1, and (0) refers to input-connector 1

a(2) : the a refers to Data-channel 3, and (2) refers to input-connector 3

v(1) : the v refers to Data-channel 2, and (1) refers to input-connector 2

P =  Ʈ . ω

Power (N.m./sec) = Torque(N.m.) × Angular Velocity (rad/sec)

Torque data and Angular-Velocity data are the inputs and Power is the output.

Thus, you need two input-connectors and one output-connector.

You get Torque data from a Force-Data FB.

You get Angular-Velocity data from a Motion-Dimension FB.

1.Add a Rocker - see Tutorial 1

2.Edit the CAD-Line of the Rocker, to open the CAD-Line dialog.

In Mass Properties tab > User Mass Properties >
Enter a Mass.
Enter a Center-of-Mass (X-axis) and a Center-of-Mass (Y-axis) to move the Center-of-Mass from the start-Point of the CAD-Line.

Do not enter a value for Inertia or Radius of Gyration.

The mass is at a single point. In cosmology we would use the term Black-Hole! In kinematics and kinetostatics we use the term Point-Mass.

3.Add a Force-Data FB, and open the Force-Data dialog.

4.Select the Pin-Joint, and select the Point in the Base-Part to find the Torque that acts-on the Base-Part.

1.Open the Math FB dialog

2.Add two Input-Connectors with the Add-Input button

3.Select Power as the Output Data Type.

4.Click UPDATE button after we select the Output Data Type and before we add equations.

5.Enter the Equations to calculate Power.

The equation in the Math FB is:

× (see image above)

p(0)*v(1)

p(0): Wire-Number 0 (top wire), Channel 1 (p = Torque)

v(1): Wire-Number 1 (bottom wire), Channel 2 (v = Angular Velocity)

Click the Update after you add the equation to find if its syntax is correct or not correct.

The at the left of each equation confirms that the syntax is correct.

For example, the syntax is not correct if it does not have the correct number of parentheses. The reason is given as a message in the Feedback-Area.