one: the definition of servo: comes from the Greek "slave" means. People want to take "servo" when a handy obedient tool, obey the control signal requirements and action. Before the signal to the rotor, motionless; signal arrival, rotor rotate immediately; when the signal disappears, the rotor can immediately stop turning. Because of its "servo" performance, hence the name.
Servo system is to make the output: the position of the object, range, state the amount charged to follow the input goal (or a given value) of the automatic control system of arbitrary change. The main task is to control the servo command requirements, amplification, transform and regulation processing of power, the drive device output torque, speed and position control is very flexible and convenient. The working principle of the servo motor servo motor is also known as the executive motor, in the automatic control system, used for the implementation of components, the electric signal is received into the motor shaft angular displacement or angular velocity output. Its main characteristic is that, when the signal voltage zero without rotation phenomenon, the increase in speed and torque with uniform speed descent. Servo motor is a typical closed-loop feedback system, a reduction gear set is driven by a motor, the terminal (output) driven by a linear potentiometer as the proportion of position detection, the potentiometer to corner coordinates into a proportional voltage feedback to the control circuit board, a control circuit board to the input of the control pulse signal comparison, produces the correct pulse, and drives the motor forward or reverse rotation, so that the output position gear set and expectations, make correct pulse tends to 0, so as to achieve the purpose of accurate positioning servo motor. The rotor internal servo motor is a permanent magnet, drive control of the U/V/W three-phase power electromagnetic fields, the rotating rotor under the action of magnetic field, while the motor with encoder feedback signal to the drive, the drive according to the feedback value is compared to a target value, adjusting the angle of the rotor rotation. Servo motor precision depends on the precision of encoder (line number). Structure of AC servo motor, AC servo motor stator basically and phase capacitance type single-phase asynchronous motor is similar. Winding is provided with an two position with 90 deg. the stator excitation winding, one is Rf, it is always connected to the AC voltage Uf; another is the control winding L, connection control signal voltage Uc. So AC servo motor is also called the two servo motor.
The work principle and phase splitting single-phase asynchronous motor AC servo motor rotor resistance although similar, but the former is greater than the latter, so compared to the servo motor and the single asynchronous motor, there are three notable features: 1, large starting torque due to the rotor resistance is large, the torque characteristic curve as the curve 3 in Figure 1 shows, and the torque characteristic curve of the ordinary asynchronous motor compared to 2, there are obvious differences. It can make the critical slip S0 > 1, so not only is the torque characteristics (mechanical properties) is more close to linear, and has large starting torque. Therefore, when a control voltage of stator, rotor rotate immediately, which has characteristics of fast starting, high sensitivity. Servo motor, operating a wide range of 2 3, without rotation phenomenon of the normal operation, as long as out of control voltage, the motor stop immediately. When out of control voltage servo motor, it is in the condition of single-phase operation, because the rotor resistance, two torque characteristics generated rotating magnetic field and the rotor two opposite directions in the stator rotating (T1S1, T2S2 curve) and synthetic torque characteristics (T-S curve) the output power of AC servo motor is generally 0.1-100W. When the power supply frequency is 50Hz, voltage is 36V, 110V, 220, 380V; when the power supply frequency is 400Hz, voltage is 20V, 26V, 36V, 115V etc.. AC servo motor to run a smooth, low noise. But the control characteristics are nonlinear, and because the rotor resistance, high loss, low efficiency, therefore, compared with the same capacity of DC servo motor, large volume, heavy weight, small power so only applies to 0.5-100W control system. |
