How to choose servo motors and stepper motors correctly? How to ground the drive and system?

The general structure of the electric servo system of industrial robots is three closed-loop control, namely the current loop, speed loop and position loop. Generally speaking, for AC servo drives, multiple functions such as position control, speed control, torque control, etc. can be achieved by manually setting their internal function parameters.

1. How to choose servo motor and stepper motor correctly?

A: It depends on the specific application. Simply put, we need to determine: the nature of the load (such as horizontal or vertical load, etc.), 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. The power supply is DC or AC, or battery-powered, and the voltage range. Based on this, we can determine the model of the motor and the corresponding driver or controller.

2. Choose a stepper motor or servo motor system?

Answer: In fact, the choice of motor should be determined according to the specific application situation, each has its own characteristics.

3.How to use the stepper motor driver?

A: According to the motor current, use a driver with a current greater than or equal to this current. If low vibration or high precision is required, a subdivision driver can be used. For large torque motors, use a high voltage driver as much as possible to obtain good high-speed performance.

What is the difference between 4.2-phase and 5-phase stepper motors and how to choose?

A: 2-phase motors are low-cost, but they vibrate more at low speeds and their torque drops quickly at high speeds. 5-phase motors vibrate less and have better high-speed performance. They are 30-50% faster than 2-phase motors and can replace servo motors in some situations.

5. When should a DC servo system be chosen? What is the difference between a DC servo and an AC servo?

Answer: DC servo motors are divided into brushed and brushless motors.

Brushed motors have low cost, simple structure, large starting torque, wide speed range, easy control, and require maintenance, but maintenance is convenient (replacing carbon brushes), but they generate electromagnetic interference and have requirements for the environment. Therefore, they can be used in general industrial and civil occasions that are sensitive to cost.

Brushless motors are small in size, light in weight, high in output, fast in response, high in speed, small inertia, smooth in rotation, and stable in torque. The control is complex and easy to realize intelligentization. Its electronic commutation method is flexible, and it can be square wave commutation or sine wave commutation. The motor is maintenance-free, highly efficient, has a low operating temperature, low electromagnetic radiation, and a long life, and can be used in various environments.

AC servo motors are also brushless motors, which are divided into synchronous and asynchronous motors. Synchronous motors are generally used in motion control. They have a wide power range and can achieve very high power. They have large inertia, low maximum rotation speed, and decrease rapidly as power increases. Therefore, they are suitable for applications with low-speed and stable operation.

6.What should I pay attention to when using the motor?

A: Before powering on, make the following checks:

1) Is the power supply voltage appropriate (overvoltage may cause damage to the drive module); the +/- polarity of the DC input must not be connected incorrectly, and is the motor model or current setting value on the drive controller appropriate (not too large at the beginning);

2) The control signal line should be connected securely. It is best to consider shielding issues at industrial sites (such as using twisted pair cables);

3) Don't connect all the necessary wires at the beginning. Just connect the most basic system. Once it is running well, you can connect them step by step.

4) Be sure to understand the grounding method, or choose floating.

5) Within half an hour of starting operation, closely observe the status of the motor, such as whether the movement is normal, the sound and temperature rise. If any problems are found, stop the machine immediately and adjust it.

7. When the stepper motor starts running, sometimes it moves for a while and then stops, or moves back and forth in place. Sometimes it even loses steps during operation. What is the problem?

Generally, the following aspects should be considered for inspection:

1) Whether the motor torque is large enough to drive the load, we generally recommend that users select a motor with a torque 50% to 100% larger than the actual requirement, because the stepper motor cannot be overloaded, even for a moment, it will cause a loss of step, and in severe cases it will stop or move repeatedly in place irregularly.

2) Is the current of the input walking pulse from the upper controller large enough (generally >10mA) to make the optocoupler conduct stably? Is the input frequency too high to cause it to fail to receive? If the output circuit of the upper controller is a CMOS circuit, a CMOS input driver should also be selected. WeChat ID Jicheng Training is worth your attention.

3) Is the starting frequency too high? Is an acceleration process set in the starting program? It is best to start accelerating from the starting frequency specified by the motor to the set frequency, even if the acceleration time is very short. Otherwise, it may be unstable or even in an inert state.

4) This situation may sometimes occur when the motor is not fixed properly, which is normal. This is because it actually causes strong resonance of the motor and causes it to enter a state of loss of step. The motor must be fixed properly.

5) For a 5-phase motor, if the phases are connected incorrectly, the motor will not work.

8.I want to directly control the servo motor through communication, is it possible?

Yes, it is convenient, but it is a speed issue. It is used for applications that do not require high response speed. If fast response control parameters are required, it is best to use a servo motion control card, which generally has DSP and high-speed logic processing circuits to achieve high-speed and high-precision motion control, such as S acceleration, multi-axis interpolation, etc.

9. Is it a good idea to use a switching power supply to power stepper and DC motor systems?

Generally, it is best not to use it, especially for high torque motors, unless you choose a switching power supply that is more than twice the required power. Because the motor is a large inductive load when working, 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 precise voltage stabilization performance is not needed, which may sometimes cause damage to the switching power supply and the driver. You can use a conventional toroidal or R-type transformer-transformed DC power supply.

10.I want to use ±10V or 4~20mA DC voltage to control a stepper motor. Is it possible?

Yes, but an additional conversion module is required.

11. If there is a servo motor with encoder feedback, can it be controlled by a servo drive with only a tachometer port?

Yes, you need to equip it with an encoder to tachometer signal module.

12.Can the encoder part of the servo motor be disassembled?

It is forbidden to disassemble it, because the quartz sheet inside the code disk is easy to break, and once dust enters, the life and accuracy cannot be guaranteed, and it needs to be inspected by professionals.

13.Can stepper and servo motors be disassembled for inspection or modification?

No, it is best to let the manufacturer do it. After disassembly, it is difficult to install it back to the original state without professional equipment. The gap between the rotor and stator of the motor cannot be guaranteed. The performance of the magnetic steel material is destroyed, and even demagnetization is caused, and the motor torque is greatly reduced.

14.Can the servo controller sense changes in external load?

If you encounter set resistance, stop, return or maintain a certain thrust to follow up.

15. Can domestic drivers or motors be used with high-quality foreign motors or drivers?

In principle, it is possible, but you must understand the technical parameters of the motor before using it, otherwise it will greatly reduce the desired effect and even affect long-term operation and life. It is best to consult the supplier before making a decision.

16. Is it safe to drive a motor using a DC power supply voltage greater than the rated voltage?

Normally this is not a problem as long as the motor is running within the set speed and current limits. Since the motor speed is proportional to the motor line voltage, a supply voltage can be selected that will not cause overspeed, but may cause driver failure.

In addition, it is necessary to ensure that the motor meets the minimum inductance requirements of the drive and that the current limit is set to a value less than or equal to the rated current of the motor.

In fact, if you can run the motor slower (below rated voltage) in your design, that's fine.

Running at lower voltage (and therefore lower speed) results in less brush bounce, less brush/commutator wear, lower current draw and longer motor life.

On the other hand, if motor size limitations and performance requirements require additional torque and speed, overdriving the motor is possible, but at the expense of product life.

17. How do I choose the appropriate power supply for my application?

It is recommended to select a supply voltage value that is 10%-50% higher than the maximum required voltage. This percentage varies depending on Kt, Ke, and the voltage drop in the system. The driver current value should be sufficient to deliver the energy required by the application. Remember that the driver output voltage value is different from the supply voltage, so the driver output current is also different from the input current. To determine the appropriate supply current, calculate the total power requirements of the application and add 5%. The required current value can be calculated by the formula I = P/V.