Oct 11, 2017

Servo Motor General principles of driving

Servo motor driven general principles

The influence of PID adjustment on the system is:

1, P (proportional) is to separate is proportional to the difference in operation, it is that there are the distinctive features of adjustment, there is after the adjustment process, the significance of modulated quantity can't be with equal value accurately, between them, there must be residual, residual concrete values you can calculate the proportion relations, increase the proportion will effectively reduce the residual error and increase the system response, but the fierce turbulence and even easy to cause system instability.

2, separate the I (integral) is to make the controller output signal changes in the speed is proportional to the differential signal, it is easy to understand, if the difference is big, the pace of change is big, in integrating the inverse proportion of proportionality constant at this stage we usually call it in servo system for the integral time constant, the smaller the integral time constant, the faster it means system change, so if the same increase integral speed (i.e., reduce the integral time constant) will reduce the stability of control system, until finally a divergent oscillation process, the link's biggest advantage is that there is no residual amount was finally.

3. PI (scale integral) is the advantage of combining P and I, using P to adjust the influence of fast offset interference, while using I to adjust the elimination of residual.

4, separate D (differential) is adjusted according to the difference of the direction and size of the output of the controller is proportional to the difference of time derivative, the regulation of differential link can only play an auxiliary role, it can combine with other adjustment into the PD and PID to adjust its benefits can be according to the (difference) by regulating quantity to adjust the speed of change, but don't start until after a large deviation, the regulator is endowed with some degree of predictability, can increase the response of the system for small changes.

5. PID synthesis can make the system more accurate and stable to achieve the control expectation.

The PID constant of the servo current ring is generally set in the drive, and the operator does not need to change.

The speed loop mainly focuses on PI (ratio and integral), and the ratio is the gain, so we need to adjust the time constant of the speed gain and speed to achieve the desired effect.

The position ring is mainly regulated by P (proportional), so we just need to set the proportional gain of the position loop.

The parameters of the position loop, speed loop regulation no fixed value, according to the external load, load of mechanical transmission connection ways of speed, acceleration and load inertia, the requirements and the rotor inertia motor itself and the output moment of inertia, and so on many conditions, adjust the simple method is in according to the experience of the general situation of external load range from small to major will gain parameters, integral time constant from major to minor, to not appear overshoot of steady-state vibration value set for optimal value.

When need to adjust the position loop position mode, it's best to adjust the speed loop (the proportion of the position loop gain setting at this time in the experience value of the minimum), after adjusting the speed loop stability, in adjusting the position loop gain, right amount increase gradually, the response of the position loop most like speed ring slowly, otherwise also prone to speed.

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