As an example, look at a person riding a bicycle, with the individual acting like the electric motor. If that person tries to trip that bike up a steep hill in a gear that’s made for low rpm, he or she will struggle as
they try to maintain their stability and achieve an rpm which will allow them to climb the hill. However, if indeed they change the bike’s gears right into a acceleration that will produce a higher rpm, the rider will have
a much easier time of it. A constant force can be applied with easy rotation being provided. The same logic applies for industrial applications that want lower speeds while maintaining necessary
torque.
• Inertia complementing. Today’s servo motors are producing more torque relative to frame size. That’s due to dense copper windings, lightweight materials, and high-energy magnets.
This creates greater inertial mismatches between servo motors and the loads they want to move. Using a gearhead to better match the 
inertia of the motor to the inertia of the load allows for utilizing a smaller electric motor and results in a more responsive system that is simpler to tune. Again, that is achieved through the gearhead’s ratio, where the reflected inertia of the strain to the motor is decreased by 1/ratio2.
Recall that inertia is the way of measuring an object’s level of resistance to change in its motion and its own function of the object’s mass and form. The higher an object’s inertia, the more torque is required to accelerate or decelerate the thing. This implies that when the load inertia is much larger than the electric motor inertia, sometimes it could cause excessive overshoot or increase settling times. Both circumstances can decrease production line throughput.
On the other hand, when the motor inertia is bigger than the load inertia, the electric motor will require more power than is otherwise necessary for this application. This improves costs because it requires having to pay more for a motor that’s larger than necessary, and because the increased power intake requires higher operating costs. The solution is by using a gearhead to complement the inertia of the motor to the inertia of the load.
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