Talking about the application of Emerson EV6000 high-performance inverter in electric spindle

1 Introduction
EV6000 inverter, as a new generation of high-performance inverter of Emerson CT, adopts advanced control strategy to realize the true high-precision magnetic flux vector torque control. Whether it is running with PG or without PG, it has reached the industry-leading control level. . The integration of synchronous motor drive and asynchronous motor drive, and the integration of torque control, speed control, and position control make EV6000 a rare integrated drive with excellent control performance in the industry, meeting the high-performance requirements of customer applications. The electric spindle is an important part of the CNC machine tool. The traditional machine tool spindle works by driving the spindle to rotate through the transmission device. Electric spindle is the abbreviation of motor built-in spindle unit. Its main feature is that the motor is placed inside the spindle, and the spindle is directly driven to work through the drive power supply, which realizes the integrated function of the motor and the spindle for cutting. It has the characteristics of compact structure, high mechanical efficiency, low noise, low vibration, high precision, stable operation and no impact, which can prolong the life of the spindle bearing. Through the built-in machine-specific functions of the EV6000 machine tool-specific version, functions such as dynamic high-precision synchronous tracking, indexing, accurate stop, and zero-speed locking can be completed. Its excellent performance and rich functions can fully meet the process and precision requirements of CNC machining center spindle control.
2 Principle of Servo Spindle System
The AC servo spindle drive system consists of four parts: the spindle controller, the spindle drive unit, the spindle motor and the encoder for detecting the speed and position of the spindle. It mainly completes the closed-loop speed control, but when the spindle stops accurately, it completes the closed-loop position control. The position control and speed control of the spindle drive unit are realized by the internal high-speed signal processor and control system, and its principle block diagram is shown in Figure 1. In the figure, the CNC system sends a speed command or a position command to the spindle drive unit, and the drive unit executes the corresponding speed and position control according to the command. At the same time, the CNC controller also receives the frequency division output from the spindle motor encoder (or the output signal of the terminal sensor) to correct its command. Of course, this signal is also used for the detection of system process deviation, such as speed deviation Too big and so on.
Talking about the application of Emerson EV6000 high-performance inverter in electric spindle
Figure 1 Block diagram of motorized spindle drive (dotted line is optional)
For convenience, we take an actual electro-spindle system as an example to describe. In this system, the CNC controller uses Taiwan LNCT520i spindle controller, the driver uses EV6000 high-performance machine tool special version inverter + PGABS option card (encoder interface card with frequency division output), and the motor uses a manufacturer in Shandong The JSZD150A-8/3C electric motor is equipped with a 2048RPM differential incremental encoder. The wiring diagram of the whole system is shown in Figure 2:
Talking about the application of Emerson EV6000 high-performance inverter in electric spindle
Figure 2: Wiring block diagram of the electro-spindle system
LNCT520i spindle controller sends speed and position signals to EV6000 through PA+/PA- and PB+/PB- quadrature pulse signals, and also includes direction signals. EV6000 is equipped with a PGABS encoder option card, which not only receives the pulse reference of the spindle controller, but also receives the encoder feedback signal from the motor, and divides the encoder signal to feed back to the spindle controller at the same time. EV6000 works in servo mode. The performance of the system is mainly determined by the performance of the drive and motor. The individual components of the system are described in detail below.
(1) Spindle motor: The motor model is JSZD150A-8/3C, with built-in 2048RPM, 5V differential encoder. The technical parameters and curves given by the manufacturer are as follows:
Table 1: Motor manufacturer parameters
Talking about the application of Emerson EV6000 high-performance inverter in electric spindle

Fig. 3 The relationship between power and speed

Talking about the application of Emerson EV6000 high-performance inverter in electric spindle
Fig. 4 Relationship between torque and speed

(2) EV6000 inverter + PGABS speed test card
EV60-PGABS speed measuring card is an option of EV6000 series inverter, which provides the following functions: 1. The encoder interface PG1 supports differential ABZ and UVW signals as speed or position feedback. 2. The pulse frequency division output of PG1 can be used for speed or position synchronization. 3. The pulse command interface PG2 can receive the pulse command of the upper-level device for speed or position synchronization.

Talking about the application of Emerson EV6000 high-performance inverter in electric spindle
Its signal is defined as follows:
Talking about the application of Emerson EV6000 high-performance inverter in electric spindle

The wiring of the whole system can refer to Figure 2. EV6000 inverter body is only connected to running signal and reset signal.
3 Debugging steps and key points
Whether it is speed synchronous tracking or zero-speed locking, the whole system logic is very simple, just need to set EV6000 to servo mode in the F13 group function code, and select the extended PG reference as the position command reference source. Therefore, the main work of debugging is to adjust the relevant parameters of the inverter according to the characteristic curve of the motor to obtain the best performance of the drive system. To do this, it is necessary to understand the principle of the servo mode of the drive.
In the above system, the motor characteristics are the basis for the performance assurance of the entire system. In order to achieve the best control effect, parameter identification of the motor is required. Refer to Table 1 and Figure 3 and Figure 4, and input the rated power, rated Voltage, rated current, rated frequency, and rated speed of the motor in the function group F80 in sequence, and then start the motor rotation auto-tuning. Because the spindle motors are basically special motors, sometimes self-tuning failure occurs. In this case, the three parameters of rated voltage, rated frequency and rated speed need to be adjusted until the tuning is passed. After the tuning is passed, it is advisable to let the motor run with no load in the full speed range to ensure that the system has no vibration and the motor current sound is normal.
Talking about the application of Emerson EV6000 high-performance inverter in electric spindle
Figure 5: Schematic diagram of EV6000 servo mode
From Figure 5, the system also has three control loops. The innermost is the current loop, followed by the velocity loop, and the outermost is the position loop. After the motor self-tuning is passed, the main debugging is to adjust the PI parameters of these three parameters. The first is the current loop. This parameter generally adopts the default parameter of the inverter. In the case of no detection instrument on site, the basis for adjustment can be simplified as follows: run at full speed, observe whether the motor vibrates or whistle, and if so, it needs to be adjusted. This situation generally indicates that the parameter is too strong. Carry out zero-speed locking operation, observe whether the locking action is clean and neat, and whether the locking is strong. You can gradually increase the current loop PI until you feel the motor shaft vibrate significantly. At this time, appropriately adjust the PI to a suitable value, and by the way, you can also observe whether the output current is stable. Current loop parameters are located in group F09.Next, adjust the speed loop, the adjustment principle will not be discussed, you can observe[F01.13]Whether the measured frequency of the motor is stable and the response is fast enough. At the same time, whether the locking force is large enough when locking at zero speed, and if it is not large enough, it is necessary to strengthen the PI. As shown in the figure below, it is the step response diagram of the system.
Talking about the application of Emerson EV6000 high-performance inverter in electric spindle
Figure 6: System Step Response Plot
Finally, adjust the position ring. The position loop mainly adjusts the dynamic position deviation, and the general CNC center has a position out-of-tolerance alarm. On the basis of the appearance parameters, it is generally necessary to strengthen the P parameters of the position loop. Figure 7 is the actual detection result of the position difference in a forward and reverse process. It can be seen that the dynamic error of the whole process is less than 25 pulses (after frequency multiplication by 4).

Figure 7 Position out of tolerance results
In addition, parameters that may affect performance that may need to be tuned include[F09.01]carrier frequency,[F63.08]PG signal filtering, etc. Here we give the parameter settings for the above application.

4 Conclusion
EV6000, as a new generation platform inverter product of Emerson CT, has excellent control performance.We will combine the actual needs of customers with general-purpose products, and launch special aircraft for industry-specific customers. We will also closely integrate with major customers and launch some customized products.
effectiveness. As far as the electric spindle is concerned, the inverter has built-in dedicated F13 (servo control), F33 (spindle accurate stop), and F34 (rigid tapping) function groups. It only needs a simple function code setting to achieve high-precision speed. Tracking, zero-speed locking, indexing and other functions are convenient for users to use. At the same time, some simple position control can also be performed. The dynamic position accuracy can be controlled well within 4 pulses, and the steady-state position accuracy can be controlled within one pulse.

The Links:   CM600HU-12F LQ14D311 LCD-COMPANY