Which one has a larger permissible moment of inertia?
Gain adjustment, in essence, is the adjustment made to achieve optimal control based on the load.
The responsiveness and stability of a servo motor are strongly influenced by the magnitude and variation of the load's moment of inertia, as well as the mechanical rigidity of the device itself. Therefore, when using a servo motor, devices with low mechanical rigidity, such as belt and impeller mechanisms, or those with large inertial loads, may oscillate and fail to operate, necessitating gain adjustment.
While adjusting to the specific mechanism might seem difficult, modern servo motors are equipped with automatic gain adjustment, reducing the time required for adjustments.
According to the organization
For lifting machines with fluctuating working quality, or mechanisms with varying loads such as crank mechanisms and cam mechanisms, gain adjustment can be quite difficult. Stepper motors, on the other hand, are unaffected by the mechanism and achieve high responsiveness without gain adjustment, making them suitable for proposals tailored to the client's specific needs.
Classified by work item
If a servo motor exceeds its recommended load moment of inertia (allowable inertia) torque, it will exceed the range of automatic gain control, leading to unstable operation. This can result in phenomena such as "inability to follow commands and execute agile movements" or "micro-vibration when stationary."
In contrast, the αSTEP has a larger rotor moment of inertia and allowable moment of inertia compared to servo motors of the same size, thus enabling stable operation even under conditions of higher load moment of inertia.
Comparison of allowable moments of inertia
| Installation dimensions | Servo motor※ | αSTEP | ||||
|---|---|---|---|---|---|---|
| Product Series [Output] |
Rotor moment of inertia [×10-4kg·m2] | Allowable moment of inertia [×10-4kg·m2] | Product Series [Servo Equivalent Model] | Rotor moment of inertia [×10-4kg·m2] | Allowable moment of inertia [×10-4kg·m2] | |
| □42mm | 50W | 0.0174 | 0.87 | T3a/T3L Series | 0.055 | 1.65 |
| 100W | 0.029 | 1.45 | T3D Series | 0.115 | 3.45 | |
| □60mm | 200W | 0.162 | 8.1 | T3DF/C30G Series | 0.37 | 11.1 |
| 400W | 0.291 | 14.55 | T5A Series | 0.74 | 22.2 | |
| □85mm | 750W | 0.948 | 47.4 | T5ML (M2)/T6M(M3) Series | 2.2 | 66 |
What is Gain Adjustment?
Gain adjustment is an adjustment made to achieve optimal control based on the load. The magnitude and variation of the load's moment of inertia, as well as the mechanical rigidity of the equipment itself, have a significant impact on the responsiveness and stability of the servo motor. Therefore, gain adjustment is necessary for equipment with low mechanical rigidity or loads with large inertia.
Differences in the Use of Stepper Motors and Servo Motors
Stepper motors may be more suitable for applications with varying load masses, such as hoists, crankshaft mechanisms, and cam mechanisms, or when the load has a large moment of inertia.
Servo motors are suitable for long-stroke, high-speed, and high-precision positioning operations. They can achieve positioning operations with excellent acceleration and reliability.