JohnnyAction
Mechanical
- Oct 5, 2012
- 4
Hi all,
The following was originally posted in the Robotics forum. Please excuse any duplication via cross-posting.
First time posting to this forum. I have a mechanical engineering credential from long ago, but the following ideas were never dealt with in great detail in my studies. As of now this is sort of hobby / avocation for me.
My questions relate to reflected inertia of a geared system. I understand the basics of inertia and mass moment of inertia, and that load inertia is what the motor sees and that total system inertia includes the load inertia, plus all gears, shafts, linkages and the motor inertia itself.
Further, I understand that (for example --- in a simple system) a load driven by, say, a 3:1 gear set demonstrates a ratio of N = Nl/Nm (60 teeth driven load gear / 20 teeth pinion driver). Torque is increased at the driven gear, and this increased torque is carried forward to the payload.
My question is this: given that reflected load inertia is (Jr = Jl/N^2); the denominator of the gear ratio squared (N^2) implies that the MOI is acting in reverse. That is, it is feeding back to the motor such that N = 1:3 thereby decreasing the torque at the pinion gear. So, I am imagining that, in reverse (if you will), the concept of reflected inertia carries with it the idea that the load inertia is now "felt" through the system, but directed in reverse, and it is tending to drive the pinion-motor rather than the motor driving the load.
Is this correct thinking? Any additional thoughts would be appreciated. Thanks for reading.
JA
The following was originally posted in the Robotics forum. Please excuse any duplication via cross-posting.
First time posting to this forum. I have a mechanical engineering credential from long ago, but the following ideas were never dealt with in great detail in my studies. As of now this is sort of hobby / avocation for me.
My questions relate to reflected inertia of a geared system. I understand the basics of inertia and mass moment of inertia, and that load inertia is what the motor sees and that total system inertia includes the load inertia, plus all gears, shafts, linkages and the motor inertia itself.
Further, I understand that (for example --- in a simple system) a load driven by, say, a 3:1 gear set demonstrates a ratio of N = Nl/Nm (60 teeth driven load gear / 20 teeth pinion driver). Torque is increased at the driven gear, and this increased torque is carried forward to the payload.
My question is this: given that reflected load inertia is (Jr = Jl/N^2); the denominator of the gear ratio squared (N^2) implies that the MOI is acting in reverse. That is, it is feeding back to the motor such that N = 1:3 thereby decreasing the torque at the pinion gear. So, I am imagining that, in reverse (if you will), the concept of reflected inertia carries with it the idea that the load inertia is now "felt" through the system, but directed in reverse, and it is tending to drive the pinion-motor rather than the motor driving the load.
Is this correct thinking? Any additional thoughts would be appreciated. Thanks for reading.
JA
