### Accurate Servo System Control Method

- Oct 20, 2017-

Accurate Servo System Control Method

How to achieve accurate servo system control:

1) AC power has over-zero problem, so AC current can be half a round as a pulse to do relevant control;

2) AC motor,have problem on magnetic pole and phase,the polar phase as a unit for communication,can accurately achieve phase control;

3)DC motor,coil as the unit for the direction,coil slot can be used as a unit to control the DC motor;

Above factors,are the basic basis of servo control to motor;we know that in order to achieve the needs of servo control,people have invented the stepper motor, pulse motor for long time.The core technology to achieve servo control is to allow motor stepping ,no stepping motor can not achieve servo control;

Stepping servo control principle:

1) For example,a DC motor,a pulse current in units of slots,will cause the motor rotor to turn an angle,this angle = 360 / slot number;

2) For example,an AC motor,a pulse current in the form of a pole phase group,will cause the motor rotor to turn an angle,

this angle = 360 / (number of poles 2P&times;phase number m);

3) Although we can not achieve "a pulse of instruction accurate to run 1/10 rounds, 1/100 rounds, 1/1000 rounds, 1/10000

rounds ...", we can achieve a current pulse make DC motor run 1/16 rounds accurately (slot number 16);

4) Although we can not achieve "a direct pulse command accurately run 1/10 rounds, 1/100 rounds, 1/1000 rounds, 1/10000

rounds ...",we can achieve to make an AC motor current pulse run 1/12 rounds accurately (4 poles, 3 phase);

Of course stepping pulse motor,a current pulse can accurately turn 1/36 rounds or more; So how to achieve high precision translation control of the workpiece?

We all know that the instrument manual adjustment knob has a coarse tune knob and fine tune knob;We also know the exact

measuring tool micrometer;

Then we know that use an AC pulse accurately turn 1/12 rounds AC motor to precise control the workpiece translation method:

① between the motor and the ball screw use a reducer to drive,increase motor speed,in order to achieve a current pulse make ball screw run 1/10 rounds, 1/100 rounds, 1/1000 rounds,1/10000 rounds accurate control;

② For example,a 4-pole 3-phase AC motor,in accordance with the phase sequence of three-phase alternating current,each pass

12 AC half cycle pulse,turn a round;

③ motor and ballscrew  reduction ratio is 500,that is,each access to 12 × 500 AC half cycle pulse, motor run 500 round, the ball screw turn a round;

④ ballscrew turn a round,the workpiece translates a pitch of 6mm;

⑤ so we achieve an AC pulse that make the ball screw run 12 × 500 = 1/6000 rounds,the workpiece translation 1 pitch / 6000= 6mm / 6000=0.001mm precise control;

⑥ we really did a current pulse,the workpiece accurately shifted 0.001mm;