Creating Force Dependent on Angular Velocity

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 velocity. In this model, a sensor measuring the angular velocity 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 acceleration.

Therefore, the angular velocity of the screw joint will be changing and thus the force output.

Change the Acceleration to -200 rev/min^2.  The negative ensures that the screw joint turns clockwise.

Create a Profile Angle vs. Force

 Create a Profile Angle vs. Force

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

Home → Mechanism → profile

• Change the Profile Input to Manual Input.

Abscissa

                                Data Type: Angular Velocity

                                Unit: rev/min

Ordinate

                                Data Type: Force

                                Unit: N

• Input the values for Angular Velocity and Force.

Create a Sensor to Measure the Angle

In order to apply the profile relationship between angular velocity 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 Velocity and RX.
• The sensor will measure the positive angular Velocity about the x-axis (RX).

Create a Spline Function Relating the Profile and Sensor Created

Creating a function will relate the angular velocity 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 velocity as expected.