Stepping motor drive system used in industrial robots
a robot main requirements for joint drive motor,
1, quickness, servo stepper motor from get instructions signal to complete the required working state of time should be short. Response signals of the shorter time, the higher the sensitivity of the electrical servo system, the more rapid response performance good, generally based on the mechanical and electrical time constant of the servo stepper motor servo motor to illustrate the size of the quick response performance.
2, starting torque, moment of inertia than the big, in the case of driving load, the requirement of the robot servo stepper motor's starting torque, moment of inertia is small.
3, the control characteristics of the continuity and linearity, as the change of control signal, the speed of the stepper motor can change continuously, sometimes still need speed is proportional to the control signal is proportional or approximation.
4, wide speed range, can be used in the latter ~ 10000 speed range.
5, small volume, low quality and short axial dimensions.
6, able to withstand harsh operating conditions, can be very frequent direction and deceleration operation, and can withstand overload in short time.
at present, due to the high starting torque and high torque and low inertia of ac and dc servo stepper motor is widely used in industrial robots, average load of 1000 n ( A 100 KGF) The following industrial robots are mostly driven by stepping motor servo system. Joint driving a stepper motor is mainly adopted by the AC servo stepper motor and the DC servo stepper motor. Among them, the ac servo motor, dc servo motor driven directly, adopt position closed loop control, commonly used in high precision, high speed drive system of the robot. Stepping motor driven system more suitable for precision, speed, demand is not high, small simple open loop system of the robot. Ac servo motor with electronic commutation, no commutation spark, has been widely used in the inflammable and explosive environment. Robot joints drive motor power range of 0. 1 ~ 10 kw。 Industrial robot drive system adopted by the planetary gear motor.
2, the motor can be subdivided into several
1, ac servo motor,
including synchronous ac servo motor and reactive stepping motor, etc.
2, dc servo motor
including small inertia permanent magnet dc servo motor, printed circuit dc servo motor, big inertia permanent magnet dc servo motor, hollow glass of armature dc servo motor.
3, stepper motor
include permanent magnetic induction stepping motor. Speed sensor used more tachogenerator and rotating transformer; Position sensor light code disc and rotating transformer. Abroad in recent years, robot manufacturers are already using a set of light code disc and rotating transformer functions as one of the hybrid photoelectric position sensor, servo motor with position and velocity detector, brake, retarding mechanism of servo motor drive unit. Robot driver system requirements drive system, large output torque and high stiffness and small gap reduction ratio.
3, commonly used drive control
1, dc servo motor drives the
with pulse width modulation (dc servo motor driver 脉宽调制) Servo drives, and by changing the pulse width to change on average at the ends of the motor armature voltage, which changes the speed of the motor.
PWM servo driver has a wide range of speed regulation, good low speed performance, fast response, high efficiency, overload ability and other characteristics, in industrial robot as a dc servo motor drive.
2, synchronous ac servo motor drive
compared with dc servo motor drive system, synchronous ac servo motor drive with high torque moment of inertia ratio, brushless and commutation spark and so on merits, is widely used in industrial robots. Synchronous ac servo motor drives are usually USES the current mode pulse width modulation ( 脉宽调制) Phase inverter and the current loop is inner loop, speed loop as the outer ring of the closed loop control system, so as to realize the current of three-phase permanent magnet synchronous servo motor control. According to its working principle, drive current waveform and the different methods of control, it can be divided into two kinds: (servo system 1) Rectangular wave current drive permanent magnet ac servo system. ( 2) Sine wave current drive permanent magnet ac servo system. Driven by square wave current of permanent magnet ac servo motor is called brushless dc servo motor, driven by sine wave current of permanent magnet ac servo motor is called the brushless ac servo motor.
3, stepper motor drives the
step motor is to electrical pulse signal transform into the corresponding angular displacement or linear displacement of the element, its angular displacement and linear displacement quantity is proportional to the number of pulses. Speed or linear velocity is proportional to the pulse frequency. Within the scope of the load capacity, these relationships are not due to the power supply voltage, load size, environmental conditions change, due to the variation of error is not long-term accumulation, stepping motor drive system can be in a wide range of speed regulation by changing the pulse frequency, fast starting, positive and negative conversion. As a kind of open loop digital control system, get more extensive application in the small robot. But due to the existence of overload ability is poor, a relatively small range of speed and low speed movement has the disadvantages such as pulse, unbalanced, generally only used in small or simple robot.
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