Industrial robots have four major components, namely the body, servo, reducer and controller.
The general structure of an industrial robotic electric servo system is three closed loop control, namely current loop, speed loop and position loop. In general, for the AC servo drive, various functions such as position control, speed control, and torque control can be realized by manually setting the internal function parameters.
So what do you need to know about servo motors?
1. How to choose the servo motor and stepper motor correctly?
A: Mainly depending on the specific application, it is simple to determine: the nature of the load (such as horizontal or vertical load), torque, inertia, speed, accuracy, acceleration and deceleration requirements, upper control requirements (such as port interface And communication requirements), the main control method is position, torque or speed mode. Whether the power supply is DC or AC, or battery powered, voltage range. This is used to determine the model of the motor and the associated drive or controller.
2. Choose a stepper motor or a servo motor system?
A: In fact, what kind of motor should be selected depends on the specific application, each has its own characteristics.
3. How to use a stepper motor driver?
A: According to the current of the motor, a driver with greater than or equal to this current is used. A subdivided drive can be used if low vibration or high precision is required. For high torque motors, use high voltage drives as much as possible to achieve good high speed performance.
4.2 What is the difference between phase and 5-phase stepper motors? How to choose?
Answer: The 2-phase motor has low cost, but the vibration is high at low speed and the torque at high speed is fast. The 5-phase motor has less vibration and high-speed performance, which is 30~50% higher than that of the 2-phase motor. It can replace the servo motor in some occasions.
5. When is the DC servo system selected, what is the difference between it and AC servo?
A: DC servo motors are divided into brushed and brushless motors.
The brush motor has low cost, simple structure, large starting torque, wide speed regulation range, easy control and maintenance, but convenient maintenance (replacement of carbon brushes), electromagnetic interference, and environmental requirements. It can therefore be used in cost-sensitive general industrial and residential applications.
The brushless motor is small in size, light in weight, large in output, fast in response, high in speed, small in inertia, smooth in rotation and stable in torque. The control is complex, and it is easy to realize intelligence. The electronic commutation mode is flexible, and can be square wave commutation or sine wave commutation. The motor is maintenance-free, has high efficiency, low operating temperature, low electromagnetic radiation and long life, and can be used in various environments.
AC servo motors are also brushless motors, which are divided into synchronous and asynchronous motors. At present, synchronous motors are generally used in motion control. It has a large power range and can achieve a large power. High inertia, the highest rotational speed is low, and it decreases rapidly as power increases. Therefore, it is suitable for applications with low speed and smooth operation.
6. What should I pay attention to when using the motor?
A: Check the following before powering up:
1) Is the power supply voltage suitable (overvoltage is likely to cause damage to the drive module); the +/- polarity of the DC input must not be connected incorrectly, and the motor model or current setting value on the drive controller is appropriate (do not start at the beginning) Too big);
2) The control signal line is firmly connected, and the industrial site should preferably consider the shielding problem (such as using twisted pair);
3) Do not connect the wires that need to be connected at the beginning, only connect to the most basic system. After running well, connect them step by step.
4) Be sure to find out the grounding method, or use floating.
5) Closely observe the state of the motor within half an hour of starting operation, such as whether the motion is normal, sound and temperature rise, and immediately stop the adjustment after finding the problem.
7. When the stepping motor starts running, sometimes it will not move or move back and forth in the same place. Sometimes it will lose the step when running. What is the problem?
Generally consider the following aspects for inspection:
1) Whether the motor torque is large enough to drive the load, so we generally recommend that the motor should use a motor with a torque greater than 50%~100% than the actual one, because the stepper motor can't be overloaded, even if it is instantaneous. Causes a loss of step, a serious stop or irregular movement.
2) Whether the current of the input step pulse from the upper controller is large enough (generally >10mA), so that the optocoupler is stably turned on, and the input frequency is too high, resulting in no reception, if the output circuit of the upper controller For CMOS circuits, use a CMOS input driver.
3) Whether the starting frequency is too high, whether the acceleration process is set on the startup program, it is better to start the acceleration from the starting frequency specified by the motor to the set frequency. Even if the acceleration time is short, it may be unstable or even in a passive state. .
4) When the motor is not fixed, this condition sometimes occurs, which is normal. Because, in fact, a strong resonance of the motor is caused at this time, resulting in an out-of-synchronization state. The motor must be fixed.
5) For 5-phase motors, the phase is incorrectly connected and the motor does not work.
8. I want to directly control the servo motor by means of communication, can I?
Yes, it is more convenient, just a speed issue, for applications that require less response speed. If fast response control parameters are required, it is best to use a servo motion control card. Generally, it has a DSP and a high-speed logic processing circuit to achieve high-speed and high-precision motion control. Such as S acceleration, multi-axis interpolation, and so on.
9. Is it good to supply the stepping and DC motor system with a switching power supply?
Generally, it is best not to use a large torque motor, unless a switching power supply that is more than twice as large as the required power is used. Because the motor works as a large inductive load, it will form an instantaneous high voltage on the power supply end. The overload performance of the switching power supply is not good, it will protect the shutdown, and its precision voltage regulation performance is not needed, and sometimes it may cause damage to the switching power supply and the driver. A DC power supply that can be transformed with a conventional toroidal or R-type transformer.
10. I want to use a DC voltage of ±10V or 4~20mA to control the stepper motor. Is it OK?
Yes, but additional conversion modules are required.
11. There is a servo motor with encoder feedback. Can it be controlled by a servo drive with only a speedometer port?
Yes, you need to have an encoder to tachometer signal module.
12. Can the servo motor's code disc part be disassembled?
It is forbidden to disassemble, because the quartz plate in the code wheel is easy to break, and after entering the dust, the life and accuracy will not be guaranteed, and professional maintenance is required.
13. Can the stepper and servo motor be disassembled for repair or modification?
No, it is best to let the manufacturer do it. After disassembling, there is no professional equipment and it is difficult to install it back to the original. The gap between the stator and the stator of the motor cannot be guaranteed. The performance of the magnetic steel material is destroyed, and even the loss of magnetism, the motor torque is greatly reduced.
14. Can the servo controller sense changes in external load?
Stop, return or maintain a certain thrust follow-up if you encounter set resistance.
15. Can I use a domestic drive or motor with a foreign high-quality motor or driver?
In principle, it is ok, but it is necessary to understand the technical parameters of the motor before it can be used. Otherwise, it will greatly reduce the effect and even affect the long-term operation and longevity. It is best to consult with the supplier before deciding.
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