1. How to select servo motor and step motor correctly?
It mainly depends on the application. Generally, it needs to determine: the nature of the load (horizontal or vertical load), torque, inertia, speed, accuracy, acceleration and deceleration and other requirements, upper control requirements (such as port interface and communication requirements), and the main control mode is the position, torque or speed mode. Power supply is DC or AC power, or battery power, voltage range. To determine the model of the motor and the accompanying drive or controller.
- What is the difference between AC servo motor and DC servo motor?
- Answer: DC servo motor is divided into brush motor and no brush motor.
- The brush motor has the advantages of low cost, simple structure, large starting torque, wide speed range, easy control and maintenance, but it is convenient to maintain, electromagnetic interference and environmental requirements. So it can be used in common industrial and civil occasions sensitive to cost.
- BLDCM has small volume, light weight, large output, fast response, high speed, small inertia, smooth rotation and stable torque. The control is complex, and it is easy to realize intellectualization. The electronic commutation mode is flexible, which can be square wave commutation or sine wave commutation. Motor maintenance free, high efficiency, low operating temperature, electromagnetic radiation is very small, long life, can be used in various environments.
- AC servo motor is also a brushless motor, which is divided into synchronous and asynchronous motor. At present, synchronous motor is generally used in motion control. It has a large power range and can achieve a large power. The maximum rotational speed is low with large inertia, and decreases rapidly with the increase of power. Therefore, it is suitable for the application of low-speed and stable operation; asynchronous motor has high speed and low accuracy than synchronous motor, which is commonly used as the spindle motor of equipment.
- What should be paid attention to when using servo motor?
- Answer: check as follows before power on operation:
a) Whether the power supply voltage is appropriate (over-voltage is likely to cause damage to the drive module); for DC input, + / – polarity must not be connected wrongly, and whether the motor model or current setting value on the drive controller is appropriate (not too large at the beginning);
b) The control signal line shall be firmly connected, and the shielding problem (such as twisted pair) shall be considered at the industrial site;
c) Don’t connect all the wires that need to be connected at the beginning, just connect them to the most basic system, and then connect them gradually after the system runs well. d) Be sure to make sure the grounding method is clear, or use floating air instead of connecting. e) Within half an hour after the start of operation, closely observe the state of the motor, such as whether the movement is normal, sound and temperature rise, and immediately stop the machine for adjustment if any problem is found.
4 is it possible to directly control the servo motor by means of communication?
Yes, it’s also convenient. It’s just a matter of speed. It’s used for applications that don’t require too much response speed. If it requires fast response control parameters, it is better to use servo motion control card. Generally, it has DSP and high-speed logic processing circuit to achieve high-speed and high-precision motion control. Such as s acceleration, multi axis interpolation, etc. 5. Can the encoder part of servo motor be disassembled?
It is forbidden to disassemble, because the quartz chip in the code disk is easy to crack, and after entering the dust, the service life and accuracy will not be guaranteed, which requires professional maintenance.
- Can the servo motor be disassembled for maintenance or refitted?
It’s better to return to the production plant for maintenance. It’s difficult to install the motor back to its original state without professional equipment after disassembling the motor, and the clearance between the rotating stators of the motor can’t be guaranteed. The performance of the magnetic steel material is destroyed, even resulting in loss of excitation, and the motor torque is greatly reduced.
- How to choose the right power supply for the application?
It is recommended that the power supply voltage is 10% – 50% higher than the maximum required voltage. This percentage varies depending on KT, Ke, and the voltage drop in the system. The current value of the driver should be sufficient to deliver the energy required for the application. Remember that the output voltage of the driver is different from the supply voltage, so the output current of the driver is different from the input current. In order to determine the appropriate supply current, it is necessary to calculate all the power requirements of this application, and increase by 5%. According to the formula of I = P / V, the required current value can be obtained.
It is recommended that the power supply voltage is 10% – 50% higher than the maximum required voltage. This percentage varies depending on KT, Ke, and the voltage drop in the system. The current value of the driver should be sufficient to deliver the energy required for the application. Remember that the output voltage of the driver is different from the supply voltage, so the output current of the driver is different from the input current. In order to determine the appropriate supply current, it is necessary to calculate all the power requirements of this application, and increase by 5%. According to the formula of I = P / V, the required current value can be obtained.
- How to ground the servo driver and servo system?
- If there is no isolation between the AC power supply and the driver DC bus (such as transformer), do not ground the non isolated port of the DC bus or the non isolated signal, which may cause equipment damage and personal injury. Because the AC common voltage is not to the earth, there may be a high voltage between the DC bus ground and the earth.
- In most servo systems, all common ground and earth are connected at the signal end. The ground loop generated by multiple connection modes is easily affected by noise and generates flow at different reference points.
- In order to keep the command reference voltage constant, the signal of the driver is connected to the signal of the controller. It will also be connected to the ground of external power supply, which will affect the operation of controller and driver (such as 5V power supply of encoder). d. There are several ways to ground the shield. The correct shielding ground is at the reference potential point inside its circuit. This point depends on whether the noise source and receiver are grounded or floating at the same time. Make sure that the shield is grounded at the same point so that the ground current does not flow through the shield.
- Why can’t the reducer and motor match at the standard torque point?
If considering the maximum continuous torque generated by the motor through the reducer, many reduction ratios will far exceed the torque level of the reducer.
If we want to design each reducer to match the full torque, there will be too many combinations of internal gears of the reducer (large volume and many materials).
This will make the product price high and violate the “high performance, small volume” principle of the product.
The general structure of industrial robot electric servo system is three closed-loop control, namely current loop, speed loop and position loop. In general, for AC servo driver, position control, speed control, torque control and other functions can be realized by manually setting its internal function parameters.
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Post time: Mar-04-2020