D4C-3202 Omron limit switch

Stepper motor

principle 

Stepping motor as a control of the special motor, is the electrical pulse into the angular displacement of the implementing agencies. When the stepper driver receives a pulse signal, it drives the stepper motor to rotate a fixed angle (called the "step angle") in the set direction, and its rotation is run step by step with a fixed step angle The It can control the pulse frequency to control the speed and acceleration of the motor rotation, so as to achieve the purpose of speed control, change the winding power sequence, the motor will Reversal. 

Drive principle 

Stepper motor need to use a dedicated stepper motor driver drive, the drive by the pulse control unit, power drive unit, the protection unit and so on. The power driving unit amplifies the pulse generated by the pulse generating control unit and is directly coupled with the stepping motor, and belongs to the power interface of the stepping motor and the micro controller.

A control command unit, a receiving pulse and a direction signal, and a corresponding pulse generating control unit correspondingly generates a set of pulses of a corresponding number of phases, which are sent to the stepping motor via the power driving unit, the stepping motor turning a step angle in the corresponding direction The The pulse reference mode of the drive determines the mode of operation of the stepper motor as follows:  

(1) m phase single m shoot line  

(2) m-phase double-m run  

(3) m phase single, double m beat run  

(4) subdivided drive, the drive is required to give different amplitude of the drive signal 

Stepper motor has some important technical data, such as the maximum static torque, starting frequency, operating frequency and so on. In general, the smaller the step angle, the greater the maximum static torque, the higher the starting frequency and operating frequency, so the operation mode emphasizes the subdivision drive technology, which improves the rotational torque and resolution of the stepper motor , Completely eliminates the low frequency oscillation of the motor. So the subdivision drives drive better performance with other types of drives.

The rotor inside the servo motor is a permanent magnet, the driver controls the U / V / W three-phase electric field to form an electromagnetic field, the rotor rotates under the action of the magnetic field, and the motor comes with the encoder feedback signal to the driver, the driver according to the feedback value and the target Value to compare, adjust the rotor rotation angle.

servo motor

Principle of Servomotors 

Servo motor, also known as the implementation of the motor, in the automatic control system, used as an actuator, the received electrical signal into the motor shaft angular displacement or angular velocity output. Divided into DC and AC servo motor two categories. 

The servo motor receives a pulse, it will rotate a pulse corresponding to the angle, in order to achieve displacement, because the servo motor itself has the function of issuing a pulse, so the servo motor for each rotation of an angle, will issue a corresponding number of pulses, And the servo motor to accept the pulse to form a closed loop, the system will know how much pulse to the servo motor, while the number of pulses received back, so that you can accurately control the motor rotation, in order to achieve accurate positioning.

In comparison with the performance, AC servo motor is better than DC servo motor, AC servo motor using sine wave control, torque ripple small, the capacity can be relatively large. DC servo motor using trapezoidal wave control, relatively poor. DC servo motor brushless servo motor than the brush servo motor to better performance.

Servo motor drive

The rotor inside the servo motor is a permanent magnet, the driver controls the U / V / W three-phase electric field to form an electromagnetic field, the rotor rotates under the action of the magnetic field, and the motor comes with the encoder feedback signal to the driver, the driver according to the feedback value and the target Value to compare, adjust the rotor rotation angle. 

Brush DC Servo Motor Driver: The working principle of the motor and the ordinary DC motor is exactly the same, the drive for the three closed-loop structure, from the inside out, respectively, the current loop, speed loop, position loop. The output of the current loop controls the armature voltage of the motor and the input of the current loop is the output of the speed loop PID. The input of the speed loop is the PID output of the position loop. The input of the position loop is the given input and the control schematic is shown above. 

Brushless DC servo motor drive: the power supply for the DC, through the internal three-phase inverter inverter U / V / W AC, the supply of motor, the drive also uses three closed-loop control structure (current loop, speed loop, ), Drive control principle ibid.

AC servo motor drive: can be divided into a relatively independent function of the power board and control panel two modules, the control board through the corresponding algorithm output PWM signal, as the drive circuit drive signal, to change the inverter output power to achieve The purpose of controlling three - phase permanent magnet synchronous AC servo motor. 

Power drive unit first through the three-phase full-bridge rectifier circuit input of the three-phase power or electricity to rectify, get the corresponding DC. Through the three-phase rectifier good or the mains, and then through the three-phase sinusoidal PWM voltage inverter inverter to drive three-phase permanent magnet synchronous AC servo motor, simply say AC-DC-AC converter process. 

The control unit is the core of the entire AC servo system, enabling system position control, speed control, torque and current control.

Performance Comparison between Servo Motor and Stepping Motor 

Control accuracy: stepper motor number and beat the more, the higher the accuracy of its servo motor block in the tape comes with the encoder, the more the encoder scale, the higher the accuracy; 

Low-frequency characteristics: stepper motor at low speed prone to low-frequency vibration phenomenon, when it is working at low speed generally use damping technology or sub-technology to overcome the phenomenon of low-frequency vibration, servo motor running very smooth, even at low speed will not appear vibration phenomenon; 

Moment frequency characteristics: Stepping motor output torque decreases with the increase of speed, high speed will drop sharply, the servo motor in the rated speed constant torque output, rated speed for the constant power output;

Overload capacity: stepper motor does not have the overload capacity, servo motor has a strong overload capacity; 

Operating performance: stepper motor control for the open-loop control, the starting frequency is too high or the load is too easy to lose step or stall phenomenon, stop the high speed is prone to overshoot phenomenon, AC servo drive system for closed-loop control, drive Can be directly on the motor encoder feedback signal sampling, the internal configuration of the location ring and speed loop, generally do not appear stepping motor stepping or overshoot phenomenon, control performance is more reliable;

Speed ​​response performance: stepper motor from the static acceleration to the working speed of hundreds of milliseconds, and AC servo system acceleration performance is better, generally only a few milliseconds, can be used for fast start and stop control occasions.