Alibre Design

Chapter 19 - Alibre MotionTo completely specify a Sinusoidal function, three things must be known:• Period - The Period is the time taken for one complete cycle. You can enter the Period inseconds, which is the time taken for one complete cycle, or the Frequency in Hertz, whichis the number of cycles per second. Entering one automatically calculates the other.• Amplitude - The Amplitude of a Sinusoidal function is defined as the difference between themid-point and one extreme or the other. In most applications, we know the range of motionor force required, so Alibre Motion allows you to specify the Amplitude by entering theUpper and Lower limits.• Phase - The Phase is most easily thought of as the position within a cycle. In Math andEngineering, Phase is usually specified in Radians or Degrees, but since this may often noteasily translate to the problem at hand, Alibre Motion specifies the Phase as a combinationof the Initial value and whether the value is initially increasing or decreasing. For instance, ifthe Initial Value is half way between the Upper and Lower limits and increasing, this wouldrepresent a Phase of 0. If it is initially decreasing, the Phase would be 180 degrees, or PiRadians.When you first start a Simulation, the positions of the parts, either Linear or Angular, are taken fromyour Assembly Design. If you are specifying a Harmonic Prescribed Motion, you will see that theInitial Value box is disabled. In this case, if you want to specify different initial conditions, ensure thatyou are not in Simulation Mode, change the position of the Part, and regenerate the Simulation.Often you will know the range of motion or force relative to the initial value, rather than as absolutes.Alibre Motion allows you to specify the Limits in either absolute or relative terms. To specify that thevalues you enter should be interpreted as relative to the Initial Value, check the "Limits are relative"check-box.514