General Mechanical

General Mechanical

Topics relate to Mechanical Enterprise, Motion, Additive Print and more

Harmonic Response for a test bench being acted upon by two motors.

    • CDeans97

      I am part of a group creating a test bench for a hardware-in-the-loop simulation of an electric vehicles powertrain. 

      We are doing a harmonic response analysis to examine how the bench will vibrate, however we are unsure if we are applying the correct loads or if our model is correct. 

      On top of the bench structure is a running track. The bench and the running track are connected using dampeners; in our Ansys model we have used springs. On the running track are two motors, which can each produce 100 Nm of torque. The motors act in opposite directions as one acts as a brake. They are connected via shafts and a coupling. 

      Below is our completed model where you can see the motor, the brake, the running track and the bench. The bolts present between the running track and the bench are where the dampers shall be. 

      For our Ansys model, we have accounted for the motors by using point masses and moments.

      The bench is created using beam elements. The model is illustrated below.

      We are unsure if the moments we are applying are the correct excitation loads for the harmonic response. We would greatly appreciate suggestions or considerations.

    • peteroznewman

      (1) What is the purpose of this model?  Why do you care how much the running track vibrates relative to the bench frame?

      (2) The motor has inertia properties that are better represented by a mass matrix, rather than a point mass.  There are significant moments of inertia that become zero when the motor is reduced to a point mass. 

      (3) How much harmonic force is created by the out-of-balance mass in the rotor of the motor and brake?

      (4) What is the magnitude of the torque ripple generated by the motor? Is this the harmonic load you are applying?

      (5) The motor frame seems to have substantial mass and stiffness. Why is this not included in the model?

      (6) Are you including the damping properties of the dampeners that connect the running track to the bench?

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