Mechanism Design and Mechanism Dynamics > Mechanism Dynamics > Modeling Entities > Forces and Torques > To Create a Force or a Torque
  
To Create a Force or a Torque
1. Click Force/Torque. The Motor tab opens. The Driven Quantity is set to Force.
2. Select references, set the motion type and direction.
3. Set the force torque profile details.
4. View the graph display.
5. Click .
Selecting References
Use the References tab to select references, set the motion type, and set the motion direction.
1. Select a reference entity on the model. To apply a point force, select a point or a vertex. For a body torque, select a body. For a point to point force, select two points or vertices on different bodies
2. The Motion Type is automatically determined by the Driven Entity reference selected. A point or a point-to-point force implies translational motion. A body torque always implies rotational motion.
3. In the Motion Direction area, specify the direction of the force or the torque vector.
a. Select the type of motion direction from the following options:
▪ Explicit Vector—Select a Reference Frame for the vector. Leave the box empty to use the world coordinate system. Enter explicit X, Y, and Z values.
▪ Straight Line or Plane Normal—Select a motion reference. Click Flip to reverse the direction of the force or the torque.
▪ Point-to-Point—Select 2 points to specify the direction.
b. Select either Ground or Body from the Direction is Relative to area.
Setting Profile Details
When you define a force or torque, the Driven Quantity is set to Force. Follow the steps below to set the other options. The Primary Variable is set to t (time).
1. To define the type of the force or torque, select a Function Type from the list.
Function Type
Description
Coefficients
Constant
Creates a constant profile.
q= A
where
A = Constant
Ramp
Creates a profile that changes linearly over time.
q= A + B*x
where
A = Constant
B = Slope
Cosine
Assigns a cosine wave value to the motor profile.
q= A*cos(360*x/T + B) + C
where
A = Amplitude
B = Phase
C = Offset
T = Period
Cycloidal
Simulates a cam profile output.
q = L*x /T - L*sin(360*x/T)/(2*pi)
where
L = Total rise
T = Period
Parabolic
Simulates a trajectory for a motor.
q = A*x + 1/2 B(x2)
where
A = Linear coefficient
B = Quadratic coefficient
Polynomial
Defines third degree polynomial motor profiles.
q = A + B*x + C*x2+ D*x3
where
A = Constant term coefficient
B = Linear term coefficient
C = Quadratic term coefficient
D = Cubic term coefficient
Table
Generates the motor motion with values from a four-column table. You can use a table of output measure results.
For more information, see To Define a Table Motor Function.
User defined
Specifies any kind of complex profile defined by multiple expression segments.
For more information, see To Define a User-Defined Motor Function.
Custom load
Applies a complex, externally-defined set of loads to your model. This option is only available for the force motor definition.
For more information, see Custom Load.
2. Set the coefficients for the selected type of motor function.
Setting the Graph Display
Use the Graph section to show the force torque profile in the Graphtool.
1. The Force graph profile is selected by default, click the Derivative check box to add the profile to the graph. Clear a check box to remove the profile from the graph.
2. When you define a table profile, you can modify settings related to the display and number of interpolated points.
3. To display each graph in a separate window, click to select the In separate graphs check box.
4. Click to open the Graphtool window.
Changing Properties
To change force torque feature properties, use the Properties tab.
1. To edit the name, type a new one in the Name box.
2. To display feature information in the browser, click .