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Rotor spins smooth, But Measure shows DOF = 0, Why ?

CADfan

Member
Dear all,
I have analyzed the Rotor design using both by Kinematic and Dynamic analysis. Before running the those analysis, i created the Degree of Freedom (DOF) measure. While both analysis the Rotor spins smoothly, for the given angular velocity, But if we see the DOF, It shows zero. Why its so?

The following connection used in the Rotor:

Shaft - Pin connection ; DOF =1 (Rotational)
Other parts mounted on the shaft are Rigid and weld connections; DOF = 0
Weld connection used to find the reaction forces

The measure shows:
DOF = 0
Redundancy =0

I think zero redundancy is ok, And its good to get accurate Reaction forces, But why DOF also become zero.
Can anyone tell me, DOF shown by the measure value is correct, Shall i proceed further.


Thanks,

CADfan
 
Dear all,

The DOF for this Rotor Mechanism is 1. I also calculated it as shown below.

DOF = 6 * (No. of bodies not including ground) - Constraints

No. of Bodies not including ground = 16

Constraints on Pin connection = 5 ( one Rotational)

No. of rigid and weld connections = 15 ( Rigid and weld connection has zero DOF)

DOF = 6 (16) - (5+ 15*6)
= 96 - 95
= 1

But the Measure shows 0 (Zero). Any idea. Is there anything going wrong.


Thanks

CADfan
 
Dear all,

As we are all know that Degree of Freedom (DOF) measure is important in a Mechanism Dynamics analysis. I was trying to get the correct DOF for my Rotor mechanism, but i couldn't get.While checking the each steps from beginning i found that, if the Servo motor is removed the Mechanism measure shows the DOF as 1. If the Servo motor is added it again shows the DOF as 0 (zero).

If servomotor added the DOF value got changed. Its puzzling me. Can anybody tell me in what way the Servo motor restricts the DOF measure calculation.

Without servo motor the mechanism runs and shows the measure values and graph. (But no Rotation)
I am trying to get the correct DOF to get the accurate Reaction forces on the mechanism parts.


Thanks

CADfan
 
DOF - Issue solved.

Dear all,

"Because a servo motor defines the absolute rotational motion of a joint axis, the joint axis loses the Degree of freedowm (DOF) associated with that motion."

That is the reason, the Mechanism Dynamics measure showed DOF = 0. (when there is a servo motor)


Thanks,

CADfan
 

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