The robotic arm, which is frequently present in our field of vision, is the most critical part of the motion control system's efforts to power industrial production, and the world's most advanced robotic arm currently has seven gearless joints, each motor driving one joint movement. When the robot arm is operating normally, the motion control system coordinates seven motors at the same time, making it easy for the robot arm to grab objects from any position in the space. Not only does it enable other complex functions, it even helps people clean or play musical instruments.
In previous years, the sweeping robot that fires on the Internet was a microcosm of motion control. Sweeping robot to develop a good movement route, motion control system will drive the motor to perform different movements, so that the sweeping robot efficiently complete the task. In factories, robotic arms are widely used in assembly lines, and on automotive assembly lines, they can easily lift tens or even hundreds of kilograms of parts for welding and assembly. As we can see, motion control systems are not only used in industry, but also in our lives.
To understand motion control systems, one thing to focus on is the motor, the executor of motion commands. Most of the motors used in motion control systems are stepper motors and servo motors, and the following small series provides a brief introduction to the two motors.
1 step motor
Stepper motor can convert the input pulse signal into angular displacement, in the case of the normal operation of the stepper motor, the speed, position, increase and decrease speed of the motor depends only on the frequency and number of pulse signals, not affected by changes in load. When the stepper motor driver receives a pulse signal, he drives the stepper motor to turn a fixed angle in the set direction. Called the "step angle" its rotation is step by step, each step turn a step angle, the name of the stepper motor is therefore.
2 Servo motor
The servo motor converts the received electrical signal into the angular displacement output on the motor shaft, and the servo motor driver controls the three-phase electricity to form an electromagnetic field, and the rotor rotates under the action of the magnetic field. The encoder feedback signal that comes with the servo motor is given to the driver, which adjusts the angle at which the rotor rotates according to the feedback value and the target value.
Comparison of the two motors
1 Control is different
Stepper motor using open-loop control, servo motor using closed-loop control, the difference between the two control methods is that closed-loop control will compare the target value and the actual value, adjust the position of the motor, compared with the servo motor control accuracy is better than the stepper motor.
Motion control systems are not just made up of motors and drivers, they are more important than they are to control and coordinate control schemes or algorithms for multiple motor movements. As if there were such a motion system, the turntable driven by two motors was entangled with film, so that the film could be wrapped from one turntable to another at a set film winding speed without breaking. In the process of film winding, the roll diameter of the two turntables will change constantly, in order to ensure that the film does not break and meet the prescribed film winding speed, it is necessary to constantly adjust the speed of the two motors, which requires the use of PID algorithm, do closed-loop control, so that the accused object: the feedback value of tension affects the speed of the motor. As a result, relying on the performance of the servo motor to respond quickly, reduce the speed when the tension is too large, and speed up the speed when the tension is too small. Under constant adjustment, the tension and winding speed of the film meet the requirements.
