However, when the motor precision gearbox inertia is bigger than the load inertia, the motor will need more power than is otherwise necessary for the particular application. This improves costs since it requires having to pay more for a electric motor that’s bigger than necessary, and because the increased power usage requires higher operating costs. The solution is by using a gearhead to complement the inertia of the electric motor to the inertia of the load.
Recall that inertia is a measure of an object’s resistance to improve in its movement and is a function of the object’s mass and shape. The greater an object’s inertia, the more torque is needed to accelerate or decelerate the thing. This means that when the load inertia is much bigger than the motor inertia, sometimes it can cause extreme overshoot or boost settling times. Both circumstances can decrease production range throughput.
Inertia Matching: Today’s servo motors are generating more torque relative to frame size. That’s because of dense copper windings, lightweight materials, and high-energy magnets. This creates better inertial mismatches between servo motors and the loads they want to move. Utilizing a gearhead to raised match the inertia of the motor to the inertia of the load allows for utilizing a smaller electric motor and results in a far more responsive system that’s simpler to tune. Again, that is attained through the gearhead’s ratio, where in fact the reflected inertia of the load to the engine is decreased by 1/ratio^2.
As servo technology has evolved, with manufacturers making smaller, yet more powerful motors, gearheads have become increasingly essential companions in motion control. Finding the ideal pairing must consider many engineering considerations.
So how does a gearhead start providing the energy required by today’s more demanding applications? Well, that all goes back again to the basics of gears and their ability to alter the magnitude or direction of an applied power.
The gears and number of teeth on each gear create a ratio. If a electric motor can generate 20 in-lbs. of torque, and a 10:1 ratio gearhead is mounted on its output, the resulting torque can be close 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 motor with a gearhead to attain the desired torque result is invaluable.
A motor may be rated at 2,000 rpm, however your application may only require 50 rpm. Attempting to perform the motor at 50 rpm might not be optimal based on the following;
If you are operating at a very low rate, such as for example 50 rpm, as well as your motor feedback quality is not high enough, the update rate of the electronic drive may cause a velocity ripple in the application. For instance, with a motor opinions resolution of just one 1,000 counts/rev you have a measurable count at every 0.357 amount of shaft rotation. If the digital drive you are employing to control the motor has a velocity loop of 0.125 milliseconds, it will look for that measurable count at every 0.0375 amount of shaft rotation at 50 rpm (300 deg/sec). When it generally does not find that count it’ll speed up the motor rotation to find it. At the acceleration that it finds the next measurable count the rpm will be too fast for the application form and then the drive will slow the engine rpm back off to 50 rpm and the whole process starts yet again. This continuous increase and decrease in rpm is exactly what will cause velocity ripple within an application.
A servo motor running at low rpm operates inefficiently. Eddy currents are loops of electric current that are induced within the motor during operation. The eddy currents actually produce a drag push within the motor and will have a larger negative impact on motor efficiency at lower rpms.
An off-the-shelf motor’s parameters might not be ideally suitable for 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 electric motor is set for an increased rpm, the torque constant (Nm/amp), which is definitely directly linked to it-is lower than it requires to be. Consequently the application needs more current to drive it than if the application had a motor specifically designed for 50 rpm.
A gearheads ratio reduces the motor rpm, which is why gearheads are occasionally called gear reducers. Using a gearhead with a 40:1 ratio, the motor rpm at the insight of the gearhead will become 2,000 rpm and the rpm at the output of the gearhead will be 50 rpm. Working the motor at the bigger rpm will permit you to avoid the issues mentioned in bullets 1 and 2. For bullet 3, it enables the design to use less torque and current from the engine predicated on the mechanical advantage of the gearhead.