CN213637560U

CN213637560U - Large-current brushless direct current motor position-free control system

Info

Publication number: CN213637560U
Application number: CN202021896038.9U
Authority: CN
Inventors: 武亚恒; 刘旸; 丁涛杰; 孙晓冬
Original assignee: CETC 58 Research Institute
Current assignee: CETC 58 Research Institute
Priority date: 2020-09-03
Filing date: 2020-09-03
Publication date: 2021-07-06
Anticipated expiration: 2030-09-03

Abstract

The utility model discloses a no position control system of brushless DC motor of heavy current, carry out driven IGBT's driver including host computer, DSP28335 control chip, brushless DC motor and to the power module unit, DSP28335 control chip's SCIA mouth and SCIB mouth through RS422 commentaries on classics USB's data line respectively with the COM1 and the COM2 interconnection of host computer, SCIA mouth work under the realization normal communication state, SCIB mouth is as the backup work of trouble, but the transmission and the acceptance of signal are realized in step to this design full duplex's transmission mode, improve the efficiency of communication.

Description

Large-current brushless direct current motor position-free control system

Technical Field

The utility model relates to a brushless DC motor technical field specifically is a no position control system of heavy current brushless DC motor.

Background

Brushless dc motors (BLDCMs) are becoming increasingly popular in industrial applications because conventional motors have brushes, increasing the cost and complexity of the hardware, and are susceptible to dust and moisture, etc., causing their reliability to decrease, and position-sensorless control methods are becoming a focus of research.

In order to cut down the cost and power consumption of BLDCM in industrial application, the high frequency and large current position-free BLDCM is designed to be the market demand.

SUMMERY OF THE UTILITY MODEL

An object of the utility model is to provide a no position control system of large current brushless DC motor to the problem of the cost and the consumption of BLDCM in order to reduce industrial application who proposes in solving above-mentioned background art.

In order to solve the technical problem, the utility model provides a following technical scheme: a high-current brushless direct current motor position-free control system comprises an upper computer, a DSP28335 control chip, a brushless direct current motor and an IGBT driver for driving a power module unit, wherein an SCIA port and an SCIB port of the DSP28335 control chip are respectively interconnected with COM1 and COM2 of the upper computer through data lines of RS 422-USB conversion, the SCIA port works in a normal communication state, and the SCIB port works as a fault backup.

Preferably, the system also comprises a double closed-loop control system without a position sensor.

Preferably, the double closed-loop control system without the position sensor adopts a double closed-loop control mode of an outer ring rotating speed loop and an inner ring current loop.

Compared with the prior art, the beneficial effects of the utility model are that:

the utility model discloses, select to use IGBT and not MOSFET to power unit, the operating condition of its high frequency can reduce the uneven phenomenon of electromotive force that the abnormal signal input arouses to weaken the motor buffeting, the power drive unit of high voltage and high current is supported in the simultaneous design, and has under-voltage and desaturation protect function. The undervoltage protection is mainly used for enabling the power tube to quickly enter a saturated state due to the fact that grid voltage is too low in the early stage of conduction of the power tube, power consumption of the power tube is enabled to quickly rise, communication between an upper computer (PC) and a lower computer (DSP28335) is achieved through an RS422 communication system, a full-duplex communication mode is adopted for the communication, system communication efficiency is improved, information of starting, stopping, speed regulation and the like of a motor is transmitted to the lower computer through the upper computer, the lower computer sends data such as rotating speed, phase voltage, phase current, overvoltage, overcurrent, undervoltage, undercurrent and the like to the upper computer, system error correction capacity is enhanced through summation check, and a full-duplex transmission mode can synchronously achieve sending and receiving of signals, and communication efficiency is improved.

Drawings

FIG. 1 is a block diagram of a control system of the present invention;

FIG. 2 is a waveform of ABC phase voltages and currents and zero crossings of the current of the present invention;

FIG. 3 is a schematic diagram of a power unit according to the present invention;

fig. 4 is a schematic view of the virtual neutral point of the present invention;

fig. 5 is a schematic diagram of the communication flow of the RS22 of the present invention;

Detailed Description

The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments in the present invention, all other embodiments obtained by a person skilled in the art without creative work belong to the protection scope of the present invention.

Referring to fig. 1-5, the present embodiment provides a high-current brushless dc motor position-less control system, which includes a DSP28335 control chip, a power module unit, a brushless dc motor, and an IGBT driver, where the control mode of the system adopts a position-sensor-less dual closed-loop control system and a three-stage start mode, and a dual redundancy communication design of RS422, so as to ensure reliability and robustness of system communication.

Wherein the IGBT driver has under-voltage lockout protection and desaturation protection.

In order to improve the power density and the function of fast switching, an IGBT (insulated gate bipolar transistor) is selected to be used for a power unit instead of an MOSFET (metal-oxide-semiconductor field effect transistor), the phenomenon of unbalanced electromotive force caused by abnormal signal input can be reduced under the working state of high frequency, so that the motor buffeting is weakened, and meanwhile, a power driving unit supporting high voltage and high current is designed and has the functions of undervoltage and desaturation protection. The undervoltage protection is mainly used for enabling the power tube to quickly enter a saturated state due to the fact that grid voltage is too low in the early stage of conducting the power tube, and therefore power consumption of the power tube is quickly increased.

The supersaturation protection is mainly that Vce is usually about 3V in normal work of the IGBT, once the Vce voltage rises too high, the IGBT is subjected to overcurrent or stress damage, in order to protect the supersaturation phenomenon, the Vce voltage is compared with a certain reference voltage set by a driver, and if the Vce voltage is greater than the reference voltage value, the output of a corresponding channel is closed by a driving unit, so that the IGBT is ensured not to be damaged.

The method is characterized in that a position-free double closed-loop control mode is adopted, a double closed-loop control mode of an outer ring rotating speed ring and an inner ring current ring is selected, the position of a rotor is detected through a back electromotive force method, 6 times of commutation is needed when the rotor rotates for a circle, one commutation can occur when the rotor rotates for 60 degrees, six times of commutation is needed in one period, namely, two zero points exist in each back electromotive force, and finally, six commutation information is obtained by delaying the zero crossing point by 30 degrees. Aiming at the situation that a signal is difficult to detect due to the fact that the back electromotive force is too small in the initial stage of starting of the motor in a non-position control mode, a three-stage starting mode is selected and mainly comprises three processes of rotor positioning, acceleration and switching.

The dual-redundancy communication design of the RS422 mainly relates to the interaction of signals such as rotating speed, voltage, current and the like of an upper computer and a lower computer, and the full-duplex transmission mode can synchronously realize the sending and receiving of the signals and improve the communication efficiency. The SCIA port and the SCIB port of the DSP28335 are respectively interconnected with COM1 and COM2 of the PC through data lines of RS422 to USB, so that the SCIA port works in a normal communication state, and the SCIB port works as a fault backup. When the SCIA port works normally, control information (such as set rotating speed, three-stage starting time, switching rotating speed, overvoltage and overcurrent information) of the upper computer can be sent to the lower computer, and the DSP controls the starting and stopping of the motor and other working states. After the motor is started and operated, the counter electromotive force, the current and other information detected by the DSP are subjected to algorithm calculation to obtain information such as rotating speed, rotor position angle, torque and the like, and are transmitted to an upper computer through an SCIA port and displayed; and once the system detects that the communication of the SCIA port is abnormal, the system automatically switches to the communication of the SCIA port, red indicator lights of an upper computer corresponding to the SCIA flash, when the two interfaces simultaneously fail, the upper computer displays that the two interfaces simultaneously fail, and the two red indicator lights on the upper computer flash to prompt the failure.

Please refer to fig. 2, which is a waveform diagram of the ABC phase terminal voltage, the ABC phase current and the ABC zero crossing point, it can be known that: the waveform of the voltage at the BLDCM terminal is trapezoidal, when the current flows from A to B phase within 60 degrees, the zero crossing point of the non-conducting phase C phase exists, the zero crossing point is delayed by 30 degrees to obtain the next commutation signal, the current flows from A to C in the next step, the zero crossing point of the non-conducting phase B phase exists, the zero crossing point of the non-conducting phase B phase is delayed by 30 degrees to obtain the next commutation signal, and the rest can be analogized to obtain all information of 6 commutations.

Referring to fig. 3, the sequence of power tube conduction is illustrated from the perspective of power unit device turn-on; in a pairwise intercommunicating form, for example, when the AB phase winding is conducted, current flows to the A phase of the motor winding from the T1, then flows out of the B phase winding and flows back to the negative end of the power supply through the T6, other conduction sequences are similar, for example, the forward conduction sequence is T1T6-T1T2-T3T2-T3T4-T5T4-T5T6-T1T6, the next commutation signal information can be obtained by delaying 30 degrees after detecting the zero-crossing signal of the non-conducting phase, and therefore, the signal commutation sequence table can be inquired after obtaining the zero-crossing signal every time to obtain the conduction phase information required to be controlled.

Referring to fig. 4, the terminal voltages of the equivalent circuit of the BLDCM are shown as follows from fig. 4:

wherein U is_NIs the neutral point voltage of the motor, U_A～U_CIs the terminal voltage.

When a pairwise intercommunicating form is sampled, namely only two phases of windings are conducted at any time, the third phase floats, and if the A phase and the B phase are conducted and the C phase floats, the third phase has

i_A+i_B＝0,i_C＝0,E_A+E_B＝0

Assuming a virtual neutral point U_N'＝(U_A+U_B+U_C) And/3, as can be seen from the above formula:

E_C＝3/2(U_C-U_N')

therefore, the voltage of the non-conducting phase is compared with the voltage of the virtual neutral point to obtain a signal of the counter electromotive force zero crossing point.

When the brushless direct current motor is at rest or runs at low speed, the back electromotive force of the brushless direct current motor is usually very small, and the zero-crossing signal of the brushless direct current motor is difficult to detect, so that a three-stage starting method is selected, wherein the positioning is mainly to position the rotor to a preset position in an open-loop stage, namely to provide a certain voltage for the motor, and to provide current for the motor by adjusting the duty ratio, so that enough electromagnetic torque is generated, and the rotor reaches a preset position. The acceleration is mainly that after the rotor is positioned in the open-loop stage, the motor is enabled to operate to a certain specific rotating speed by changing the reversing frequency and increasing the external voltage, so that the open-loop acceleration can be smoothly completed. The switching stage is mainly to operate the open loop of the motor to a certain specific rotating speed (the counter electromotive force zero-crossing signal can be stably detected at the moment, and the rotating speed is not high), and to convert the switching state of the motor operation to the closed loop operation state, so as to ensure the stable and reliable operation of the motor. The outer ring in the double closed-loop control is controlled by a rotating speed ring, the rotating speed of the rotating speed ring is controlled by recording the reciprocal of the zero-crossing signal period, namely the rotating speed of the motor, the obtained rotating speed value is compared with the set rotating speed value of the motor, an expected current value is obtained through PID adjustment, the expected current value is compared with the current value, and then the PID adjustment is carried out, so that the switching phase control information of the power tube is obtained, and the normal operation of the motor is realized.

The design uses an RS422 communication system to realize the communication between an upper computer (PC) and a lower computer (DSP28335), the communication adopts a full duplex communication mode, the system communication efficiency is improved, in addition, the start, stop, speed regulation and other information of a motor are transmitted to the lower computer through the upper computer, the lower computer sends data such as rotating speed, phase voltage, phase current, overvoltage, overcurrent, undervoltage, undercurrent and the like to the upper computer, the system error correction capability is enhanced by summation verification, the full duplex transmission mode can synchronously realize the sending and receiving of signals, and the communication efficiency is improved. Mainly by means of SCIA port and SCIB port of DSP28335, through data line of RS422 to USB, the data line is interconnected and communicated with COM1 and COM2 of PC respectively. The SCI A port works in normal communication state, and the SCI B port works as fault backup. The control flow is as follows: as shown in fig. 5, when the SCIA port works normally, the control information (such as set rotation speed, three-stage start time, switching rotation speed, overvoltage and overcurrent information) of the upper computer can be sent to the lower computer, and the start and stop of the motor are controlled by the DSP. After the motor starts to operate, the terminal voltage, the phase current and other information detected by the DSP are subjected to algorithm calculation to obtain information such as rotating speed, rotor position angle, torque and the like, and are transmitted to an upper computer through an SCIA port and displayed; and once the system detects that the communication of the SCIA port is abnormal, the system automatically switches to the communication of the SCIB port, when the two interfaces simultaneously fail, the upper computer displays that the two interfaces simultaneously fail, and two red indicator lights on the upper computer flash to prompt the failure.

Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.

Claims

1. The utility model provides a no position control system of heavy current brushless DC motor which characterized in that: the SCIA port and the SCIB port of the DSP28335 control chip are respectively interconnected with COM1 and COM2 of the upper computer through data lines of RS 422-USB conversion, so that the SCIA port works in a normal communication state, and the SCIB port works as a fault backup.

2. A high current brushless dc motor position free control system as claimed in claim 1, wherein: a double closed-loop control system without a position sensor is also included.

3. A high current brushless dc motor position free control system as claimed in claim 2, wherein: the double closed-loop control system without the position sensor adopts a double closed-loop control mode of an outer ring rotating speed loop and an inner ring current loop.