What does servo motor crossover ratio mean

The vast majority of servo systems.

When there is no crossover function, the crossover multiple is 1 by default;

If the servo does not have a frequency division function, the actual number of pulses required for one revolution of the motor is equal to that of the encoder.

The resolution, which is fixed; If there is a frequency division function, then the actual number of pulses required for one turn of the motor = the resolution of the encoder Frequency division multiple, for example, the resolution of the encoder is 2048 lines, and the frequency division multiple is 2, then the actual number of pulses required for one turn of the motor = 2048 2 = 4096, that is, if the frequency is not divided, 2048 pulses can make the motor rotate once, and after the frequency division, 2048 pulses can only make the motor rotate half a turn;

From this, it can be concluded that the frequency division is for the resolution of the encoder, and the frequency division is for the feedback of the encoder to the servo drive.

The number of pulses is further subdivided (i.e., the resolution of the encoder is amplified), so the angular accuracy of the motor can be improved by using frequency division. The larger the frequency division multiple, the more pulses the motor needs to be compared to the non-frequency division, and the motor speed will be slower. The opposite is the faster, so the use of frequency division can also be on the servo motor.

Speed regulation (but if you do not modify the number of pulses sent by the host computer, the positioning will be inaccurate, and the position will be deviated).

A differential circuit is only used for more precise control.

It's how many times the output of the frequency divider,

The response frequency of the servo is also called the call bandwidth frequency.

Determination method: apply a sinusoidal signal of a certain frequency amplitude, slowly increase the frequency of the sinusoidal signal, when the actual amplitude attenuates to -3 decibels (equivalent to only 70% of the command amplitude), so that the frequency range is called bandwidth. The bandwidth is determined by the combined characteristics of the entire loop of system sampling, calculation cycle, and load.

The corresponding frequency bandwidth reflects the system's ability to respond to commands, and the higher the bandwidth, the better the speed (rigidity).

For servos, the bandwidth of the current loop and the speed loop is important. The adjustment of the PID affects the response frequency (bandwidth).

The current loop is only related to the characteristics of the driver and the motor, and the current loop PID is generally solidified in the driver and basically does not need to be adjusted by the user.

The velocity loop, the bandwidth is determined by the current loop, plus the external load and the transfer stiffness. The higher the bandwidth of the speed loop, the better the responsiveness of the system, the higher the rigidity, the high-speed response, the smooth operation, and the small follow-up deviation. The quality of the speed ring directly affects the operation of the motor, high-frequency vibration in situ, and the speed ring is not good when it shakes during movement, and the response frequency at this time is also very low.

Because the speed loop is highly affected by external loads and transmission stiffness, the speed loop PID often needs to be adjusted.

If the servo system requirements are not high, there is no need to understand these parameters, as long as the PID can be adjusted to start and stop smoothly and run it.

Comes with a message: if the actual amplitude is found to be greater than the command amplitude during the frequency test, then this frequency corresponds to the resonance frequency, and the command of this frequency needs to be filtered out with a notch filter. The resonant frequency can cause the system to be unstable, or not to function at all, and commands for this frequency must be filtered out.

1. Distinguish on the surface.

1. There is an encoder behind the servo motor, but there is no frequency conversion motor.

2. In terms of appearance, the servo motor is mostly based on the square appearance, and the frequency conversion motor is round.

Second, the performance is differentiated.

There are a lot of fake servos out there, and they look the same as we think they are, but they also have encoders.

In terms of performance, the servo motor should mainly achieve the following points:

1. The overload capacity is generally double, triple or even quadruple.

2. Low-speed performance, can rotate at a very low speed and achieve constant torque 3. The constant power section should be long, generally 4 times the rated speed.

The frequency conversion in the AC motor is not equal to the servo, and the frequency conversion motor is used more in the occasions where the speed control and torque control requirements are not high, and there are also frequency conversion motors that form position closed-loop control after adding position feedback signals, but their accuracy and response are not high, and servo motors are generally used in occasions with high accuracy and response requirements; Almost all places that can be controlled by frequency conversion can be replaced by servo control, but there are two obvious differences between servo motors and frequency conversion motors in practical applications, one is that servo motors are more expensive than frequency conversion motors; Second, the power of the inverter can reach hundreds of kW, or even higher, and the servo can reach tens of kW. The power of the servo motor used in the MPT motor test system of domestic ZLG Zhiyuan Electronics is generally in the tens of kW.

The servo motor has feedback, and the inverter motor has no feedback, and it is because of the feedback that the servo motor is more powerful.

The servo motor has three working modes, when working in position mode, each revolution needs thousands of pulses (can be increased or decreased according to the situation), so a special upper computer (such as PLC) that can send pulses is required, with very high precision, with the screw can reach the positioning; When the servo motor is working in speed mode, its working speed can be set (similar to the inverter + three-phase motor, but its speed response is extremely fast and rigid), at this time, priority is given to ensure the working speed, and when working in torque mode, priority is given to ensuring the rotor output torque (constant torque).

When the inverter motor is used with the inverter, it can generally only be used in places where the speed needs to be adjusted, such as acceleration or deceleration during operation, but the response to acceleration and deceleration is not high. Now some inverters also have positioning functions, but the positioning accuracy is not too high!

Of course, it is more accurate than the accuracy of frequency conversion control The simplest analogy is that if you brake, the frequency conversion can only stop, and the servo, if you want him to stop 2m, he will stop 2m,

The servo motor consists of AC servo and DC servo, and the variable frequency motor is the same as the ordinary motor.