However, when the motor inertia is larger than the strain inertia, the engine will require more power than is otherwise necessary for this application. This raises costs since it requires spending more for a engine that’s bigger than necessary, and because the increased power intake requires higher operating costs. The solution is to use a gearhead to match the inertia of the engine to the inertia of the load.
Recall that inertia is a way of measuring an object’s resistance to change in its motion and is a function of the object’s mass and shape. The higher an object’s inertia, the more torque is needed to accelerate or decelerate the object. This means that when the strain inertia is much larger than the motor inertia, sometimes it can cause excessive overshoot or boost settling times. Both conditions can decrease production series throughput.
Inertia Matching: Today’s servo motors are generating more torque in accordance with frame size. That’s because of dense copper windings, lightweight materials, and high-energy magnets. This creates higher inertial precision gearbox mismatches between servo motors and the loads they are trying to move. Utilizing a gearhead to better match the inertia of the electric motor to the inertia of the strain allows for using a smaller motor and outcomes 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 electric motor 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. Locating the optimal pairing must consider 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 to the fundamentals of gears and their ability to change the magnitude or direction of an applied pressure.
The gears and number of teeth on each gear create a ratio. If a electric motor can generate 20 in-pounds. of torque, and a 10:1 ratio gearhead is attached to its output, the resulting torque will be near to 200 in-pounds. With the ongoing emphasis on developing smaller footprints for motors and the gear that they drive, the ability to pair a smaller engine with a gearhead to attain the desired torque output is invaluable.
A motor could be rated at 2,000 rpm, but your application may only require 50 rpm. Trying to run the motor at 50 rpm might not be optimal predicated on the following;
If you are working at an extremely low swiftness, 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 digital drive you are using to control the motor has a velocity loop of 0.125 milliseconds, it’ll look for that measurable count at every 0.0375 amount of shaft rotation at 50 rpm (300 deg/sec). When it generally does not see that count it will speed up the engine rotation to find it. At the acceleration that it finds the next measurable count the rpm will become too fast for the application form and then the drive will gradual the motor rpm back down to 50 rpm and then the whole process starts yet again. This constant 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 electrical current that are induced within the engine during operation. The eddy currents in fact produce a drag force within the motor and will have a larger negative effect on motor performance at lower rpms.
An off-the-shelf motor’s parameters may not be ideally suitable for run at a minimal rpm. When a credit card applicatoin runs the aforementioned motor at 50 rpm, essentially it is not using all of its available rpm. Because the voltage continuous (V/Krpm) of the motor is set for a higher rpm, the torque continuous (Nm/amp), which is directly related to it-is usually lower than it needs to be. As a result the application needs more current to operate a vehicle it than if the application had a motor particularly created for 50 rpm.
A gearheads ratio reduces the motor 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 become 2,000 rpm and the rpm at the output of the gearhead will be 50 rpm. Operating the motor at the bigger rpm will permit you to prevent the issues mentioned in bullets 1 and 2. For bullet 3, it enables the design to use much less torque and current from the motor predicated on the mechanical advantage of the gearhead.