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 electric 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.
Recall that inertia is a measure of an object’s resistance to change in its motion and is a function of the object’s mass and form. The greater an object’s inertia, the more torque is required to accelerate or decelerate the thing. This implies that when the load inertia is much bigger than the engine inertia, sometimes it can cause extreme overshoot or enhance settling times. Both conditions can decrease production collection throughput.
Inertia Matching: Today’s servo motors are producing more torque in accordance with frame size. That’s because of dense copper windings, light-weight materials, and high-energy magnets. This creates higher inertial mismatches between servo motors and the loads they want to move. Using a gearhead to better match the inertia of the electric motor to the inertia of the load allows for utilizing a smaller engine and results in a far more responsive system that’s easier to tune. Again, that is attained through the gearhead’s ratio, where the reflected inertia of the load to the electric motor is decreased by 1/ratio^2.
As servo technology has evolved, with manufacturers generating smaller, yet better motors, gearheads have become increasingly essential partners in motion control. Locating the optimum pairing must take into account many engineering considerations.
So how really does a gearhead start providing the power required by today’s more demanding applications? Well, that all goes back again to the basics of gears and their capability to modify the magnitude or direction of an applied pressure.
The gears and number of teeth on each gear create a ratio. If a engine can generate 20 in-lbs. of torque, and a 10:1 ratio gearhead is attached to its output, the resulting torque will certainly be near to 200 in-lbs. With the ongoing focus on developing smaller footprints for motors and the gear that they drive, the ability to pair a smaller electric motor with a gearhead to achieve the desired torque output is invaluable.
A motor may be rated at 2,000 rpm, but your application may only require 50 rpm. Attempting to perform the motor at 50 rpm may not be optimal based on the following;
If you are operating at an extremely low quickness, such as for example 50 rpm, and your motor feedback resolution is not high enough, the update rate of the electronic drive could cause a velocity ripple in the application form. For example, with a motor feedback resolution of 1 1,000 counts/rev you have a measurable count at every 0.357 degree of shaft rotation. If the electronic drive you are employing to control the motor has a velocity loop of 0.125 milliseconds, it will search for that measurable count at every 0.0375 amount of shaft servo gearhead rotation at 50 rpm (300 deg/sec). When it does not see that count it will speed up the electric motor rotation to find it. At the speed that it finds another measurable count the rpm will become too fast for the application and the drive will sluggish the motor rpm back down to 50 rpm and then the whole process starts all over again. This constant increase and reduction in rpm is exactly what will cause velocity ripple within an application.
A servo motor working at low rpm operates inefficiently. Eddy currents are loops of electrical current that are induced within the electric motor during operation. The eddy currents in fact produce a drag force within the engine and will have a greater negative impact on motor performance at lower rpms.
An off-the-shelf motor’s parameters may not be ideally suited to run at a minimal rpm. When an application runs the aforementioned engine at 50 rpm, essentially it isn’t using most of its offered rpm. Because the voltage constant (V/Krpm) of the engine is set for an increased rpm, the torque continuous (Nm/amp), which is usually directly linked to it-is definitely lower than it requires to be. Consequently the application requirements more current to operate a vehicle it than if the application had a motor particularly created for 50 rpm.
A gearheads ratio reduces the engine rpm, which is why gearheads are sometimes called gear reducers. Using a gearhead with a 40:1 ratio, the motor rpm at the input of the gearhead will be 2,000 rpm and the rpm at the result of the gearhead will be 50 rpm. Operating the motor at the higher rpm will enable you to avoid the problems mentioned in bullets 1 and 2. For bullet 3, it allows the look to use much less torque and current from the engine based on the mechanical benefit of the gearhead.