The general structure of the electric servo system for industrial robots is three closed-loop control, i.e. current loop, speed loop and position loop. In general, for AC servo drives, a variety of functions such as position control, speed control, torque control, etc. can be realized by manually setting their internal function parameters.
01 How to correctly select the servo motor and stepper motor?
A: Depending on the specific application, simply to determine: the nature of the load (such as horizontal or vertical loads, etc.), torque, inertia, speed, precision, acceleration and deceleration requirements, the upper control requirements (such as the port interface and communication requirements), the main control mode is the position, torque or speed mode. Whether the power supply is DC or AC, or battery power, voltage range. Accordingly to determine the motor and the matching drive or controller model.
02 Selection of stepper motor or servo motor system?
A: In fact, the choice of motor should be based on the specific application, each has its own characteristics.
03 How to match the stepper motor driver?
A: According to the current of the motor, use the driver which is greater than or equal to this current. If low vibration or high precision is required, use an interpolated driver. For large torque motors, use a high voltage type driver as much as possible to get good high speed performance.
04 What is the difference between 042-phase and 5-phase stepper motors and how to choose?
A: 2-phase motor cost is low, but in the low-speed vibration, high-speed torque drop fast. 5-phase motor is less vibration, high-speed performance is good, than the 2-phase motor speed is 30 ~ 50% higher than the servo motor can be replaced in some occasions.
05 when to choose DC servo system, it and AC servo what is the difference?
A: DC servo motors are divided into brushed and brushless motors.
Brushed motors are low cost, simple structure, large starting torque, wide speed range, easy to control, maintenance, but easy to maintain (change carbon brushes), electromagnetic interference, environmental requirements. Therefore it can be used in common industrial and civil occasions which are sensitive to cost.
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 easy to realize intelligentization, and its electronic phase change mode is flexible, which can be square wave phase change or sine wave phase change. The motor is maintenance-free, with high efficiency, low operating temperature, small electromagnetic radiation, long life, and can be used in a variety of environments.
AC servo motor is also brushless motor, divided into synchronous and asynchronous motors, at present, motion control generally use synchronous motors, it has a large range of power, it can do a lot of power. Large inertia, the maximum rotation speed is low and decreases rapidly as the power increases. Thus, it is suitable for low-speed smooth running applications.
06 Problems to pay attention to when using the motor?
A: Make the following checks before powering up and running:
(1) 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 to the wrong, drive the motor type on the controller or whether the current setting value is appropriate (not too large at the beginning);
(2) control signal lines connected securely, the best industrial site to consider shielding (such as the use of twisted-pair cable);
(3) Do not start the need to connect all the lines, only the most basic system, running well, and then gradually connected.
(4) Be sure to find out the grounding method, or the use of floating air is not connected.
(5) start running half an hour to closely observe the status of the motor, such as whether the movement is normal, the sound and temperature rise, found that the problem immediately shut down to adjust.
07 stepper motor start operation, sometimes move a little bit on the immobile or in place to move back and forth, sometimes run out of step, what is the problem?
07 the following aspects should be considered for inspection:
(1) whether the motor torque is large enough to drive the load, so we generally recommend that the user selection of torque than the actual need for 50% ~ 100% of the motor, because the stepping motor can not overload operation, even momentarily, will result in loss of step, serious stalling or irregular in situ repeatedly move.
(2) whether the input stepping pulse current from the upper controller is large enough (generally >10mA) to stabilize the optocoupler conduction, whether the input frequency is too high, resulting in the reception of the upper controller if the output circuit is a CMOS circuit, it is also necessary to use the CMOS input type of driver. Micro-signal technology into the training is worth your attention.
(3) Whether the starting frequency is too high, whether the acceleration process is set on the starting program, it is better to start accelerating to the set frequency from within the starting frequency specified for the motor, even if the acceleration time is short, otherwise it may be unstable or even in an inert state.
(4) When the motor is not fixed properly, this condition sometimes occurs, then it is normal. This is because the motor actually resonates strongly at this time, causing it to enter an out-of-step state. The motor must be secured.
(5) For 5-phase motors, the motor will not work even if the phase is connected incorrectly.
08 I want to control the servo motor directly through communication, is it possible?
Yes, it is possible and convenient. It is just a matter of speed, for applications that do not require too high a response speed. If you require a fast response to the control parameters, it is best to use a servo motion control card, which generally has a DSP and high-speed logic processing circuitry to achieve high-speed and high-precision motion control. Such as S acceleration, multi-axis interpolation, etc..
09 Is it good to use switching power supply to power stepping and DC motor system?
Generally it is better not to, especially for large torque motors, unless you choose a switching power supply that is more than double the required power. Because, when the motor is working, it is a large inductive load, which will form an instantaneous high voltage on the power supply side. The overload performance of the switching power supply is not good, it will protect the shutdown, and its precision voltage regulator performance is not required, sometimes may cause damage to the switching power supply and driver. You can use a conventional toroidal or R-type transformer to transform the DC power supply.
10 I want to use ±10V or 4~20mA DC voltage to control the stepper motor, can I?
Yes, but another conversion module is required.
11 There is a servo motor with encoder feedback, can it be controlled by a servo driver with a tacho port only?
Yes, an encoder to tacho signal module is required.
12 Can the code disk of servo motor be disassembled?
It is forbidden to dismantle it, because the quartz piece inside the code disk is easy to break, and after entering dust, the life and precision will not be guaranteed, and professional personnel are needed to overhaul it.
13 Can the stepper and servo motors be disassembled for overhaul or modification?
Do not, it is best to let the manufacturer to do, disassembled without professional equipment is difficult to install back to the original, the motor can not be guaranteed clearance between the rotor stator. The performance of the magnet steel material is destroyed, and even cause demagnetization, the motor torque is greatly reduced.
14 Can the servo controller sense changes in the external load?
Such as stopping, returning or maintaining a certain thrust follow-up when encountering a set resistance.
15 can the domestic drive or motor and foreign quality motor or drive with?
In principle, it is possible, but it is necessary to find out the technical parameters of the motor before mating, otherwise it will greatly reduce the desired effect, and even affect the long-term operation and life. It is better to consult with the supplier before deciding.
16 Is it safe to use a DC supply voltage greater than the rated value to drive the motor?
Normally this is not a problem, as long as the motor runs within the set speed and current limits. Since motor speed is proportional to motor line voltage, selecting a certain supply voltage will not cause overspeed, but failures such as drive failures may occur.
In addition, it is important to ensure that the motor meets the minimum inductance factor requirements of the drive, and also that the current limits set are less than or equal to the current rating of the motor.
In fact, if you can get the motor to run slower ( below rated voltage) in the setup you are designing, this is good.
Running at a lower voltage (and therefore lower speed) will result in less brush run bounce and 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 select the proper power supply for my application?
It is recommended to select a supply voltage value 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 by the application. Remember that the output voltage of the driver is not the same as the supply voltage, so the output current of the driver is not the same as the input current. To determine the proper supply current, calculate all the power requirements for the application and add 5%. The I = P/V formula will give you the required current value.
It is recommended to select a supply voltage value 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 by the application. Remember that the output voltage of the driver is not the same as the supply voltage, so the output current of the driver is not the same as the input current. To determine the proper supply current, calculate all the power requirements for the application and add 5%. The I = P/V formula will give you the required current value.
18 Which mode of operation can I choose for a servo drive?
The different modes are not all present in all drive models.
19 How is the drive and system grounded?
a. Do not ground the non-isolated ports of the DC bus or the non-isolated signals of the DC bus to earth ground if there is no isolation between the AC power supply and the drive's DC bus (e.g., transformer), as this may result in damage to the equipment and injury to personnel. Because the AC common voltage is not to earth, there may be a high voltage between the DC bus ground and earth.
b. In most servo systems, all common and earth grounds are connected together at the signal end. The ground loops created by the multiple ways of connecting to earth are susceptible to noise that can create currents at different reference points.
c. To keep the command reference voltage constant, connect the drive's signal ground to the controller's signal ground. It will also be connected to the ground of an external power supply, which will affect the operation of the controller and the driver (e.g., 5V power supply for an encoder).