Creating Force Dependent on Angular Displacement

Change Preferences to Ignore Units (Optional)

Choosing to Apply or Ignore Units refers to how math functions are read to ensure proper dimensionality. Apply Units automatically converts the Y-type units within math functions into solver units whereas Ignore Units doesn’t use the Y-type units specified in math functions. More information can be found here.

Change the motion preferences to Ignore Units.

File → Preferences → Motion

Click OK

About the Model

This a simple model in which a disk rotates clockwise about the x-axis via a screw joint while a force is simultaneously applied to a “button” in the z-direction. The purpose of this tutorial is to demonstrate how to apply loads based on a measured angular displacement. In this model, a sensor measuring the angular displacement of the screw joint will provide the input necessary for applying the load.

Edit the Joint Driver

Edit the Joint driver in the model so that the screw joint rotates at a certain angular velocity. Therefore, the angular displacement of the screw joint will be changing and thus the force output.

Change the Velocity to -10 degrees/s. The negative ensures the screw turns clockwise about the x-axis.

Create a Profile Angle vs. Force

Creating a profile provides a relationship between angular displacement and force. For a given angular displacement, there is a given force. Using this information, when an angular displacement value is obtained by a sensor, the profile relation allows the appropriate force to be applied as a result of the displacement.

Home → Mechanism → profile

• Change the Profile Input to Manual Input.

Abscissa

                                Data Type: Angular Displacement

                                Unit: Degrees

Ordinate

                                Data Type: Force

                                Unit: N

• Input the values for Angular Displacement and Force.

Create a Sensor to Measure the Angle

In order to apply the profile relationship between angular displacement and Force, the angle will need to be measured via a sensor.

Home → Mechanism → Sensor

• Select the Screw Joint to measure. The Screw joint allows the disk to spin.
•  Select Displacement and RX.
• The sensor will measure the positive angular Displacement about the x-axis (RX).

Create a Spline Function Relating the Profile and Sensor Created

Creating a function will relate the angular displacement measured by the sensor to the output force as dictated by the profile.

Home → Mechanism → Function Manager à New

• Input the following formula.
• Axis Unit

                                X-axis: Time (s)

                                Y-axis: Force (N)

• The sensor is multiplied by -1, this ensures it is measuring in the same range as the rotation.

Create a Scalar Force That Uses the Function to Apply the Correct Force

Home → Load → Scalar Force

• Apply the force to the button in the global Z direction.
• Make sure the origin is in the center of the button.

• Change the Magnitude Type to Function. Select the Function Manager and browse to the function created earlier in the tutorial.

• Click OK

Solve the Solution and Plot the Results

Right click on the solution and select Solve.

Plot of the Applied Scalar Force (F001).

The plot demonstrate that the force applied to the button increases with the linear changes in angular displacement as expected.