WO2008089591A1

WO2008089591A1 - A control system for a brushless dc motor and a control method thereof

Info

Publication number: WO2008089591A1
Application number: PCT/CN2007/000178
Authority: WO
Inventors: Tiecai Li; Zhaoyong Zhou; Yamei Qi; Xiang Sun; Shuang Wang; Pinghua Tang
Original assignee: Shenzhen Tech-Innovation International
Priority date: 2007-01-18
Filing date: 2007-01-18
Publication date: 2008-07-31

Abstract

By a control system and a control method for a brushless DC motor and an inverter module thereof, it will be realized that a squarewave brushless DC magnetoelectric machine can be controlled in the form of current closed-loop. The cathodes of diodes (D1, D3, D5) in the upper section of the inverter are not connected with the inputs of corresponding transistors and are connected in parallel with each other to a sampling coil (L2), and/or the anodes of diodes (D4, D6, D2) in the lower section are not connected with the outputs of corresponding transistors and are connected in parallel with each other to another sampling coil (L3). Single composite current sensor can be adopted in the control system so as to sample the three-phase current wholly and continuously when the motor is conducting or freewheeling, and the three-phase current can be controlled continuously in the form of closed-loop by single current closed-loop regulator.

Description

Brushless DC motor control system and control method thereof

The present invention relates to a control technique for a three-phase direct current motor, and more particularly to an inverter module for controlling a brushless DC motor, a brushless DC motor control system using the same, and a control method for the system; The solution of the invention is particularly suitable for servo control of a three-phase square wave brushless permanent magnet DC motor. Background technique

The square wave brushless permanent magnet DC motor is a special brushless DC motor whose phase current and air gap magnetic field are approximately square wave or trapezoidal wave. For a three-phase six-state driven brushless DC permanent magnet motor, the forward conduction angle of each phase winding is 120°, stopped at 60°, then reversed to 120°, then stopped 60°, and thus cycled. Among them, the current of each phase winding is discontinuous, and the discontinuous current characteristics make the current closed-loop control very difficult. Therefore, in the conventional square wave brushless DC permanent magnet motor control system, few Current closed loop control.

In the prior art, for a three-phase square wave brushless DC motor, the instantaneous value of the phase current is usually used to achieve current closed loop control. This solution requires three independent current sensors and three independent current regulators, which make the control circuit cumbersome, complicated, difficult to adjust, and poorly reliable, so it is rarely used in the industry. In the prior art, a bridge arm current instantaneous value is also used to implement current closed-loop control, but this current sampling scheme ignores the freewheeling effect of the motor winding inductance, but is an approximate current sampling due to the freewheeling current in the inverter circuit. And the inner loop is formed in the winding of the motor, so the sampling cannot be obtained on the bridge arm (bus bar), and the real current flowing through the winding of the motor and generating the torque cannot be accurately fed, so that the precise control of the torque cannot be realized; The solution will produce an intolerable large value deviation, so it is currently only used for monitoring the current limit value.

On the other hand, in high-performance servo control systems, current closed loop, speed closed loop, and position closed loop control are often essential. However, in the prior art, a good current closed-loop control is not realized for a three-phase square wave brushless DC motor. Therefore, in the existing high performance servo control system, a square wave brushless permanent magnet DC motor is usually not used, but AC servo motor or sine wave brushless permanent magnet DC electric confirmation As a result, the complexity of the control system is greatly increased, and the overall cost remains high. Summary of the invention

In view of the above-mentioned defects of the prior art, the present invention solves the problem that the current closed-loop control is not realized for the three-phase square wave brushless DC motor in the prior art, so that the square wave brushless permanent magnet DC motor can be better applied. .

In order to solve the above technical problem, the present invention firstly provides an inverter module for controlling a brushless DC motor, comprising: a switch tube Ql, Q3, Q5 connected to the upper arm, and a switch tube Q4 connected to the lower arm, Q6, Q2, freewheeling diodes D1, D2, D3, M, D5 and D6 cooperating with the respective switching tubes; wherein the cathodes of the freewheeling diodes D1, D3, D5 of the switching tubes Q1, Q3, Q5 are independent The anodes of the respective switching tubes are connected in parallel with each other; the anodes of the freewheeling diodes D4, D6, D2 of the switching tubes Q4, Q6, Q2 are independent of the output ends of the respective switching tubes and are connected in parallel with each other.

In the present invention, the above-described inverter module for controlling a brushless DC motor can be made into an integrated circuit chip. In a specific implementation, only the cathodes of the freewheeling diodes D1, D3, and D5 of the upper arm may be independent of the input ends of the respective switching tubes and connected in parallel to each other to form a second inverter for controlling the brushless DC motor. Alternatively, or only the anodes of the freewheeling diodes D4, D6, D2 of the lower arm are independent of the output ends of the respective switching tubes and in parallel with each other to form a third inverter module for controlling the brushless DC motor. On the other hand, corresponding to the above-mentioned first inverter module for controlling a brushless DC motor, the present invention provides a brushless DC motor control system including an inverter circuit for outputting a working power to the three-phase motor And a current sensor for detecting the operating current of the three-phase motor; the inverter circuit includes a switch tube Ql, Q3, Q5 connected to the upper arm, and a switch tube connected to the lower arm to close Q4, Q6, Q2, freewheeling diodes D1, D2, D3, D4, D5, and D6 that cooperate with the respective switching tubes; wherein the current sensor includes three sampling coils L1, L2, and L3 having the same number of turns, and three windings The same core is mounted on the core, and a sensing element for outputting a current sensing result according to the magnetic flux change of the core is mounted on the core; the freewheeling diode D1 of the switching tubes Q1, Q3, and Q5 The cathodes of D3 and D5 are independent of the input ends of the respective switching tubes and are connected in parallel to the same end of the sampling coil L2, and the different end of the sampling coil L2 is connected to the upper arm; the switching tube Q4, Q6, Q2 freewheeling diode The anodes of the tubes D4, D6, and D2 are independent of the output ends of the respective switching tubes and are connected in parallel to each other to the different end of the sampling coil L3, and the same name end of the sampling coil L3 is connected to the lower bridge arm; L1 is connected in series with the upper arm and its same name end is connected to the positive pole of the direct current power source, or is connected in series with the lower bridge arm and its opposite end is connected to the negative pole of the direct current power source.

In the present invention, corresponding to the second inverter module for controlling the brushless DC motor, only two sampling coils L1, L2 may be provided, and the sampling coil L3 may be omitted to obtain a second control system scheme; corresponding to the above Two kinds of inverter modules for controlling the brushless DC motor can be provided with only two sampling coils L1 and L3, and the sampling coil L2 is omitted, and a third control system scheme is obtained.

In the brushless DC motor control system of the present invention, the sensing element for outputting the current sensing result is a linear Hall element.

In the brushless DC motor control system of the present invention, the output voltage amplitude of the linear Hall element is sent to the current regulator as a current feedback signal, and the output of the current regulator is sent to a pulse modulation circuit, the pulse modulation circuit The output is sent to the commutation logic circuit, and the output of the commutation logic circuit is sent to the pre-driver circuit, and the pre-driver circuit outputs corresponding drive pulses to the control terminals of the respective switch tubes in the inverter circuit. a signal; the inverter circuit outputs a working power to the three-phase motor under the control of the driving pulse signal.

The brushless DC motor control system of the present invention further includes a position sensor mounted on the rotating shaft of the direct current motor, the output signal of which is sent to the position/speed interface circuit, and the position/speed interface circuit outputs to the speed regulator. a speed feedback voltage, outputting a position feedback voltage to the position adjuster, and outputting a commutation position signal and a motor direction signal to the commutation logic circuit; the position adjuster according to the position given voltage and the position feedback voltage The speed regulator outputs a speed given signal; the speed regulator outputs a current given signal to the current regulator according to the speed given signal and the speed feedback voltage; the current regulator is given according to the current And a current feedback signal from the linear Hall element, outputting a corresponding control signal to the pulse modulation circuit; the commutation logic circuit is based on a pulse signal from the pulse width modulation circuit, and the position/speed a commutation position signal of the interface and a motor direction signal, output corresponding to the pre-drive circuit Pulse system.

In the brushless DC motor control system of the present invention, the three-phase square wave brushless permanent magnet DC motor may also be a stator coreless linear three-phase square wave brushless permanent magnet DC motor, or a stator coreless core Three-phase square wave brushless permanent magnet DC motor. On the other hand, with respect to the first control system scheme described above, the present invention also provides a control method of a brushless DC motor control system, characterized in that, in each inverse transform logic period, the maximum guide of each switch tube The pass angle is 120°, during the conduction period of any group of switches:

Pulse width modulation is separately performed on the switch connected to the upper arm.

Alternatively, pulse width modulation is performed separately on the bypass tube connected to the lower arm.

Alternatively, pulse width modulation is performed on the switching tube connected to the upper arm and the switching tube connected to the lower arm.

For the second control system scheme described above, since only the sampling coils L1, L2 and the sampling coil L3 are absent, only the switching tube connected to the lower arm can be separately pulse width modulated.

For the third control system scheme described above, since only the sample coils L1, L3 and the sampling coil L2 are absent, only the switch tube connected to the upper arm can be separately pulse width modulated. It can be seen from the above technical solution that the present invention solves the problem of achieving good current closed-loop control for a three-phase square wave brushless DC motor, wherein a suitable improvement is made to the conventional inverter circuit, and a composite current sensor is used. The three-phase currents during motor conduction and freewheeling are fully and continuously sampled so that the three-phase current of the motor can be continuously closed-loop controlled by a single current closed-loop regulator. The solution of the invention can greatly improve the dynamic and static indexes of the electric motor. The three-phase square wave brushless permanent magnet DC motor servo control system of the invention can be used in various numerical control systems, such as numerical control machine tools, automated production lines, robots, etc. Performance servo control occasions have the advantages of low cost and high energy performance. DRAWINGS

The present invention will be further described with reference to the accompanying drawings and embodiments. FIG. 1 is a schematic block diagram of a servo control system for a three-phase square wave brushless permanent magnet DC motor in a preferred embodiment of the present invention;

2 is a schematic structural view of a current sensor in a preferred embodiment of the present invention; 3 is a schematic diagram of an embodiment of a first inverter circuit of the present invention;

4 is a schematic diagram of an embodiment of a second inverter circuit of the present invention;

Figure 5 is a schematic view showing an embodiment of a third inverter circuit of the present invention;

6 is a schematic view showing the working state of the switch tubes Q1 and Q6 in FIG. 3 when they are turned on;

7A is a pulse waveform diagram when P-modulation is performed on the upper arm switching transistor Q1 of FIG. 6. FIG. 7B is a schematic diagram showing an operation state when the switching transistor Q1 of FIG. 6 is instantaneously turned off and Q6 is kept turned on; It is a pulse waveform diagram when P-modulation is performed on the lower-arm switch tube Q6 in FIG. 6; FIG. 7D is a schematic diagram showing an operation state when the switch tube Q6 in FIG. 6 is instantaneously turned off and Q1 is kept on; FIG. 7E is a pair FIG. 7 is a pulse waveform diagram of the switching transistors Q1 and Q6 in PWM modulation; FIG. 7F is a schematic diagram showing the operating state of the switching transistors Q1 and Q6 in FIG. 6 simultaneously turned off; FIG. 8 is only the inverter shown in FIG. Schematic diagram of the waveform when the upper arm is PWM modulated in the circuit scheme;

9 is a schematic diagram showing waveforms when only the lower arm of the inverter circuit shown in FIG. 3 is PWM-modulated;

FIG. 10 is a schematic diagram showing a waveform when P-modulation is performed on the upper and lower arms in the inverter circuit scheme shown in FIG. 3;

Figure 11 is a block diagram showing the principle of a position servo control system for a three-phase square wave brushless permanent magnet DC motor in a preferred embodiment of the present invention;

Figure 12 is a step response waveform of the servo control system shown in Figure 11;

Figure 13 is a block diagram showing the principle of a three-phase square wave brushless permanent magnet DC motor torque servo control system in a preferred embodiment of the present invention;

Figure 14 is a schematic view of the torque of the system of Figure 13;

Figure 15, Figure 16, and Figure 17 are circuit diagrams of the inverter module from Figure 3, Figure 4, and Figure 5, respectively. detailed description

In a preferred embodiment of the present invention, a servo control system for a three-phase square wave brushless permanent magnet DC motor is provided, the principle of which is shown in FIG. As can be seen from the figure, the control system includes three phases. The bridge inverter circuit 101, the current sensor 102 connected to the inverter bridge, the current converter 112 that converts the sensing signal of the current sensor, the current regulator 108, the P-modulation circuit 103, and the pre-driver circuit sequentially connected 107. The three-phase bridge inverter circuit 101 outputs a working power to the three-phase square wave brushless permanent magnet DC motor 105. The current converter outputs a sensing signal from the linear Hall element 106. As shown in FIG. 2, in a preferred embodiment of the present invention, the current sensor includes three sampling coils L1, L2, and L3 having the same number of turns, and the three are wound on the same core 201. A sensing element that outputs a current sensing result based on the flux variation of the core is also provided, which is a linear Hall element 202. In the figure, the star with the asterisk W is the same name end of each sampling coil. It can be seen that the three sample coils are wound on the iron core in the same direction. Therefore, the linear Hall element in the current sensor detects three The vector sum of the currents in the sampling coils.

Among them, the linear Hall element has an operating temperature range of -45° to +125°. The output of the linear Hall element varies linearly around the center value as a function of the vector sum of the currents in the three sample coils. When the vector sum of the currents in the three sampling coils is zero, the output of the linear Hall element 202 is its applied voltage; 1/2; when the vector sum of the currents is greater than zero, the output of the linear Hall element increases linearly; When the vector sum of the currents is less than zero, the output of the linear Hall element decreases linearly. As will be understood from the following description, this change reflects the magnitude and direction of the actual current of the brushless motor, so that the present invention is effective for current detection in the four-quadrant operation of the brushless motor. As shown in FIG. 3, in a preferred embodiment of the present invention, the inverter circuit includes switch tubes Q1, Q3, and Q5 connected to the upper arm, and switch tubes Q4 and Q6 connected to the lower arm. Q2, freewheeling diodes D1, D2, D3, D4, D5 and D6 matched with the respective switching tubes.

It can be seen from FIG. 3 that the cathodes of the freewheeling diodes D1, D3, and D5 of the switching transistors Q1, Q3, and Q5 are independent of the input ends of the respective switching tubes and are connected in parallel with each other, and then pass through the same name end and the different name end of the sampling coil L2. Connected to the upper arm; and the anodes of the freewheeling diodes D4, D6, D2 of the switching tubes Q4, Q6, Q2 are independent of the output ends of the respective switching tubes and connected in parallel with each other, and then pass through the different end of the sampling coil L3, the same name end The sampling coil L1 is connected in series to the upper arm, and the same name is terminated to the positive pole of the power supply. It can be seen that each sampling coil is wound on the iron core on the one hand, and is connected to the inverter circuit on the other hand. Where, sampling The inductance values of the coils L1, L2, L3 are small relative to the motor windings, and the freewheeling effect of the coil inductance can be neglected.

As can be seen from the following description, for the sampling coils L1, L2, and L3, during normal operation, the current flows through only one of the sampling coils at any one time, and both are terminated from the same name, and the different names are terminated. Combined with the connection mode shown in Fig. 2, it is ensured that the current flowing from the same-name end of each of the sampling coils L1, L2, and L3 generates magnetic flux in the same direction in the iron core. In the specific implementation, the sampling coils L1, L2, and L3 of FIG. 3 may all be reversely connected, that is, the same name end and the different name end are exchanged; or the sampling coil L1 is reversed and serially connected to the lower bridge arm, the sampling coil L2. L3 remains unchanged; both of these transformations ensure that the current flowing from the same end of each sampling coil L1, L2, L3 produces the same direction of flux in the core, ultimately ensuring the linear Hall element in the current sensor. What is detected is the vector sum of the currents in the three sample coils.

(1) When the current flows only through the sample coil L1 In Fig. 3, for any of the upper arm switch tubes Q1, Q3, Q5 and the lower arm switch tubes Q4, Q6, Q2, when any one of the switches is turned on The current only passes through the sampling coil L1 and does not flow through other samples. 'Coil; Normally, the current is proportional to the torque of the motor; Under abnormal conditions, such as Q1 and Q4. When passing through, the through current can also be sampled by the coil. L1 is detected, which in turn limits or protects.

In normal operation, any upper arm switch tube plus a lower arm switch tube that is not directly connected to it constitutes a conduction group. For the inverter circuit shown in FIG. 3, when the switching tubes Q1 and Q6 are turned on, the current direction is as shown by the solid thick line in FIG. 6. At this time, the current il enters from the same end of the sampling coil L1, and then It flows through the switching tube Q1, the motor a phase winding, the motor b phase winding, and the switching tube Q6. It can be seen that the current at this time only flows through the sampling coil L1. Similarly, when Q1 and Q2 are on, Q3 and Q4 are on, Q3 and Q6 are on, Q5 and Q4 are on, and Q5 and Q6 are on, current flows only through the sampling coil L1 and does not flow through the other two samples. The circuit voltage equations of coils L2 and L3 at this time are:

U _dc = (A + L _a + L _b )^-+ (R _a + + E. - E _b .

At

(2) When the current only flows through the sampling coil L3

For the state in which the switching transistors Q1 and Q6 shown in FIG. 6 are turned on, when the switching transistor Q1 is PWM During modulation, the control pulses of the two switching tubes are as shown in Fig. 7A. After the switching transistor Q1 is turned off (ie, during the period t2 in Fig. 7A), the current does not jump directly to zero due to the inductance of the motor winding. Instead, the freewheeling is performed according to the line shown by the thick solid line in Fig. 7B. It can be seen from the figure that the freewheeling current i2 flows into the same name end of the sampling coil L3 through Q6, and then flows through the freewheeling transistor D4, the motor a phase winding, and the motor b phase winding in sequence to form a loop. At this time, current flows through the sampling coil L3 and does not flow through the other two sampling coils L1, L2. Similarly, in the conduction period of any group of switching tubes, if PWN modulation is applied to the upper arm switching tube, when the upper arm switching tube is turned off, the freewheeling current only flows through the sampling coil L3, and will not Flow through the other two sampling coils L1, L2. The circuit equation at this point is:

E _b - E _a = (R _a + R _b )i ₂ +(4 +4

At

(3) When the current only flows through the sampling coil L2

For the state in which the switching transistors Q1 and Q6 shown in FIG. 6 are turned on, when the switching transistor Q6 is PWM-modulated, the control pulses of the two switching transistors are as shown in FIG. 7C, after the switching transistor Q6 is turned off (ie, In Figure 7C, the period t2), the current does not jump directly to zero due to the inductance of the motor winding. At this time, it will flow through Q1, the motor phase a winding, the motor b phase winding, the freewheeling diode D3, and then sample. The same name end of the coil L2 returns to Q1 to form a loop, as shown in Fig. 7D. At this time, current flows through the sampling coil L2 and does not flow through the other two sampling coils L1, L3. Similarly, in the conduction period of any group of switching tubes, if PWN modulation is performed on the lower arm switching tube, when the lower arm switching tube is turned off, the freewheeling current only flows through the sampling coil L2, and does not flow. Pass the other two sampling coils Ll, L3 o

It can be seen from the above three cases (1), (2), and (3) that the current sensor can detect the current when it is normally turned on, and can also detect the freewheeling current during the P-modulation. The true current of the three-phase brushless permanent magnet DC motor is detected at any time, and it is suitable for any pulse modulation method and has universality.

(4) P-modulation only for the lower arm switch

As can be seen from the above case (3), when only the lower arm switching tube is pulse width modulated, the freewheeling current flows only through the sampling coil L2 and does not flow through the other two sampling coils L1, L3. If this control mode is always used, the current flows through the sampling coil L1 during normal conduction, and only the switching of the lower arm switching tube During operation, current flows through the sampling coil L2, so the sampling coil L3 in FIG. 2 can be omitted, and accordingly, the inverter circuit shown in FIG. 4 is obtained. As can be seen from comparison with FIG. 3, the freewheeling diode D4 in FIG. D6 and D2 maintain the conventional connection mode, that is, connect the anodes of the freewheeling diodes to the output ends of the respective switching tubes.

It can be seen that for the circuit shown in FIG. 3 and FIG. 4, the pulse width modulation mode can be adopted only for the lower arm switching tube, and the relevant waveform at this time is as shown in FIG. 8, wherein Ea, Eb, and Ec are three motors. The back EMF of the winding, H is the drive pulse of the upper arm switch tube, and L is the drive pulse of the lower arm switch tube. In the embodiment shown in Fig. 8, for the 120° conduction angle of each of the lower arm switching tubes, only the latter 60° is modulated. In the specific implementation, the time of P-modulation can also be increased or decreased.

(5) P-modulation only for the upper arm switch

As can be seen from the above case (2), when only the upper arm switching tube is pulse width modulated, the freewheeling current flows only through the sampling coil L3 and does not flow through the other two sampling coils L1, L2. If this control mode is always used, the current flows through the sampling coil L1 during normal conduction, and the current flows through the sampling coil L3 only during the modulation operation of the upper bridge switching tube, so the sampling coil L2 in FIG. 2 can be omitted, correspondingly The inverter circuit shown in FIG. 5 is obtained. As can be seen from comparison with FIG. 3, the freewheeling diodes D1, D3, and D5 in FIG. 5 maintain the conventional connection mode.

It can be seen that for the circuits shown in FIG. 3 and FIG. 5, the pulse width modulation mode can be adopted only for the upper arm switching tube, and the relevant waveform at this time is as shown in FIG. 9. In the embodiment shown in Figure 9, for the 120° conduction angle of each upper arm switch, only the first 60° of the PWM modulation is performed. In the specific implementation, the time of PWM modulation can also be increased or decreased.

(6) PWM modulation of the upper arm switch tube at the same time

For the circuit shown in Figure 3, since there are three sampling coils L1, L2, L3, in the conduction period of any group of switching tubes, the upper arm switching tube can be pulse width modulated first, and then the lower bridge switching tube Perform pulse width modulation, or vice versa.

During the modulation process, it is best to ensure that when switching a pulse tube, the other switch should be kept constant. If the modulation pulse is as shown in Figure 7E, both switches will be turned off at the same time. Produced in the case shown in FIG. 7F, the diodes D3, D4 ON freewheeling current flows from the end of the coil L2 samples of the same name, then enters the non-dot end of winding L1 is sampled, and then flows through the power supply U _d. After that (at this time, the battery DC power supply can be charged, or the capacitor connected in parallel with the power supply can be charged), and the same name end of the sample coil L3 can be seen, and the freewheeling current passes through the sampling coils L1, L2, and L3. Since the sampling coils L1 and L2 are reversed in the current loop at this time, the currents of the two are the same, and the opposite directions, the magnetic flux generated in the iron core is exactly offset; the actual effect is still equivalent to the current flowing only through the sampling coil. L3.

If it is ensured that the pulse switching of one switching tube should be kept constant, then in the conduction period of any group of switching tubes, when both are conducting at the same time, the current only passes through the sampling coil L1; When the lower arm switching transistor performs pulse width modulation, the current only passes through the sampling coil L2; when the upper and lower arm switching tubes are pulse width modulated, the current only passes through the sampling coil L3. It can be seen that for the circuit shown in FIG. 3, the above three cases (1), (2), and (3) may appear respectively. The relevant waveform at this time is shown in Figure 10. In the embodiment shown in Fig. 10, for each of the 120° conduction angles of the switching transistor, only the front 30° and the rear 30° conduction angle are PWM modulated.

The foregoing three embodiments of the three inverter circuits of FIG. 3, FIG. 4 and FIG. 5 are described. With respect to FIG. 3, the three control modes (4), (5), and (6) can be simultaneously implemented; , only the (4) control mode can be implemented, that is, only the lower arm switch tube is P-modulated; for FIG. 5, only the (5) control mode can be implemented, that is, only the upper bridge switch tube Perform P-modulation. On the other hand, for the circuit shown in FIG. 3, after removing the peripheral components, the circuit shown in FIG. 15 is obtained, which is fabricated into an integrated circuit (chip), and an inverter module for controlling the brushless DC motor is obtained. . Wherein, the upper arm and the lower arm are respectively connected to the first and second pins P1, P2; the cathodes of the freewheeling diodes D1, D3, D5 are independent of the input ends of the respective switching tubes and are connected in parallel to the third pin P3 The anodes of the freewheeling diodes Q4, Q6, Q2 are independent of the output ends of the respective switching tubes and are connected in parallel to the fourth pin P4; the three output terminals of the inverter circuit are respectively connected to the fifth, sixth and seventh pins P5, P6, P7; The control terminals of the switching transistors Q1 to Q6 are connected to the eighth to thirteenth pins P8-P13, respectively.

Similarly, for the circuit shown in FIG. 4, after the peripheral components can be removed, the circuit shown in FIG. 16 is obtained, which is fabricated into an integrated circuit, and another inverter module for controlling the brushless DC motor can be obtained. With respect to the circuit shown in FIG. 5, by removing the peripheral components, the circuit shown in FIG. 17 can be obtained and made. An integrated circuit provides an inverter module for controlling a brushless DC motor. Figure 11 is a block diagram showing the principle of a position servo control system for a three-phase square wave brushless permanent magnet DC motor in a preferred embodiment of the present invention, wherein the output voltage of the linear Hall element of the current sensor (not shown) is shown. The value is sent to the current regulator 108 as a current feedback signal, the output of the current regulator is sent to the pulse modulation circuit 103, the output of the pulse modulation circuit is sent to the commutation logic circuit 104, and the output of the commutation logic circuit is sent to the pre-driver circuit 107. The pre-driver circuit outputs a corresponding drive pulse signal to the control terminals of the respective switch tubes in the inverter circuit 101; the inverter circuit outputs the operating power to the three-phase motor 105 under the control of the drive pulse signal.

In order to realize the position/speed closed-loop control, a position sensor 115 is mounted on the rotating shaft of the DC motor, and an output signal thereof is sent to the position/speed interface circuit 111, and the position/speed interface circuit outputs a speed feedback voltage to the speed adjuster 109 to the position. The regulator 110 outputs a position feedback voltage and outputs a commutation position signal and a motor direction signal to the commutation logic circuit 114.

Wherein, the position adjuster 110 outputs a speed reference signal to the speed regulator 109 according to the position given voltage (input from the lower right corner in the figure) and the position: feedback voltage; the speed adjuster according to the speed given signal and the speed feedback voltage And outputting a current given signal to the current regulator 108; the current regulator outputs a corresponding control signal to the pulse modulation circuit 103 according to the current given signal and the current feedback signal from the linear Hall element; the commutation logic circuit 114 is based on The pulse signal of the pulse width modulation circuit, and the commutation position signal and the motor direction signal from the position/speed interface 111, the forward drive circuit outputs a corresponding control pulse.

In this embodiment, the three-phase square wave brushless permanent magnet DC motor position servo control is realized by the current regulator 108, the speed regulator 109 and the position adjuster 110; the power of the brushless permanent magnet DC motor is 150W, and the reduction ratio is 100:1. The output torque is 15N.m. Figure 12 shows the step response waveform of the system. The square wave in the figure is the position given curve, and the other is the tracking result curve. When the position is given a step change, only 30 is needed. - Accurate tracking can be achieved in 60 milliseconds. When a step change occurs for each position, the two curves can quickly coincide, and the position tracking characteristics are excellent.

In the specific application, the motor can also adopt the stator ironless linear three-phase square wave brushless permanent magnet DC motor. Since the motor has a flatter phase current and an air gap magnetic field, the square wave waveform is approximated. A flatter torque waveform facilitates precise position servo control. In addition, the motor can also be a stator coreless rotary three-phase square wave brushless permanent magnet DC motor.

The three-phase square wave brushless permanent magnet DC motor position servo control system in the embodiment of the present invention has a great advantage compared with the position servo control system formed by the AC servo motor in the prior art, and is mainly embodied in:

(a) Since the average value of the square wave is larger than the sine wave, the force index of the motor system of the present invention is increased by about 33%. This means that the size, weight and price of the motor can be reduced by 33% when the same function is achieved.

(b) The square wave drive control circuit is relatively simple, and the cost is usually only 50% of the AC servo system.

(c) The torque fluctuation index is equivalent. Especially when the stator coreless three-phase square wave brushless permanent magnet DC motor is used, the torque fluctuation index is even better.

(d) The manufacturing cost of a square wave brushless permanent magnet DC motor is usually about 30% lower than that of an AC servo motor.

(e) Position servo control system composed of square wave brushless permanent magnet DC motor has better servo stiffness and dynamic response characteristics

13 is a schematic block diagram of a torque servo control system for a three-phase square wave brushless permanent magnet DC motor in a preferred embodiment of the present invention, which differs from FIG. 11 in that there is no speed regulator and position adjuster therein, but A torque reference signal is input directly to the current regulator to achieve the desired torque control. In this embodiment, a stator coreless brushless permanent magnet DC motor is used. Since this motor has a flatter phase current and an air gap magnetic field in principle, it approximates a square wave waveform and has a flatter torque waveform. The rated output torque of the motor is 0. INm, rated speed 6000 rpm, Fig. 14 The torque tracking waveform of the torque control system, wherein the torque is given as a sinusoidal curve, and the tracking result is also a smooth sinusoidal curve, the two are completely coincident, and the tracking characteristics are excellent.

As can be seen from the above embodiment, the present invention proposes a new scheme for realizing closed-loop current control of a square wave brushless permanent magnet DC motor, and can further constitute a high performance servo control system. The invention adopts a single combined current sensor to perform complete and continuous sampling of the three-phase current when the motor is turned on and freewheeling, and a closed loop control of the three-phase current by a single current closed-loop regulator, thereby greatly improving the dynamics of the motor. And static indicators. This high-performance servo control system consisting of a square wave brushless permanent magnet DC motor can be used in a variety of CNC systems. Compared with mainstream systems for industrial applications today, the cost is reduced by 50% and the force index is increased by 33°/. .

Claims

Rights request

1. An inverter module for controlling a brushless DC motor, comprising: a switch tube Ql, Q3, Q5 connected to the upper arm, a switch tube Q4, Q6, Q2 connected to the lower arm, and each of the above Freewheeling diodes D1, D2, D3, D4 D5 and D6 with switching tubes;

The cathodes of the freewheeling diodes D1, D3, D5 of the bypass pipes Q1, Q3, Q5 are independent of the input ends of the respective bypass pipes and are connected in parallel with each other;

The anodes of the freewheeling diodes D4, D6, D2 of the switching transistors Q4, Q6, Q2 are independent of the output terminals of the respective switching transistors and are connected in parallel with each other.

2. An inverter module for controlling a brushless DC motor, comprising: a switch tube Ql, Q3, Q5 connected to the upper arm, a switch tube connected to the lower arm Q4, Q6, Q2, and each of the above Freewheeling diodes D1, D2, D3, M, D5 and D6 cooperated with a bypass tube;

The cathodes of the freewheeling diodes D1, D3, D5 of the switching transistors Q1, Q3, Q5 are independent of the input terminals of the respective switching transistors and are connected in parallel with each other.

3. An inverter module for controlling a brushless DC motor, comprising a switch connected to the upper arm. The tubes Ql, Q3, Q5, the switch tube connected to the lower arm are closed Q4, Q6, Q2, and Freewheeling diodes D1, D2, D3, D4, D5 and D6 cooperated with each of the bypass tubes;

The anodes of the freewheeling diodes D4, D6, D2 of the bypass tubes Q4, Q6, Q2 are independent of the output terminals of the respective switching tubes and are connected in parallel with each other.

4. A brushless DC motor control system comprising: an inverter circuit for outputting a working power to the three-phase motor; and a current sensor for detecting an operating current of the three-phase motor; the inverter circuit includes Switching tubes Ql, Q3, Q5 connected to the upper arm, switching tubes connected to the lower arm Q4, Q6, Q2, freewheeling diodes D1, D2, D3, D4, D5 and the respective switching tubes D6-, which is characterized by

The current sensor includes three sampling coils L1, L2, and L3 having the same number of turns, and the three are wound on the same core, and the iron core is further provided with a output according to the magnetic flux change of the iron core. a sensing element for current sensing results; The cathodes of the freewheeling diodes D1, D3, D5 of the switching transistors Q1, Q3, Q5 are independent of the input ends of the respective switching tubes and are connected in parallel to the same end of the sampling coil L2, the different end of the sampling coil L2 Connected to the upper bridge arm;

The anodes of the freewheeling diodes D4, D6, and D2 of the switching transistors Q4, Q6, and Q2 are independent of the output ends of the respective switching tubes and are connected in parallel to each other to the different end of the sampling coil L3, and the same end of the sampling coil L3 Connected to the lower bridge arm;

The sample coil L1 is connected in series with the upper bridge arm and has the same name end connected to the positive pole of the DC power source, or serially connected to the lower bridge arm, and the different name end thereof is connected to the negative pole of the DC power source.

5. A brushless DC motor control system comprising: an inverter circuit for outputting a working power to the three-phase motor; and a current sensor for detecting an operating current of the three-phase motor; the inverter circuit includes Switching tubes Ql, Q3, Q5 connected to the upper arm, switching tubes connected to the lower arm Q4, Q6, Q2, freewheeling diodes D1, D2, D3, D4, D5 and the respective switching tubes D6 _; characterized in that

The current sensor includes two sampling coils L1, 12 having the same number of turns, both of which are wound on the same core, and the core is further provided with an output current according to the magnetic flux change of the core. Sensing junction ^.: sensor element of fruit;

The cathodes of the freewheeling diodes D1, D3, D5 of the switching transistors Q1, Q3, Q5 are independent of the input ends of the respective switching tubes and are connected in parallel to the same end of the sampling coil L2, the different end of the sampling coil L2 Connected to the upper bridge arm;

The sampling coil L1 is connected in series with the upper arm and its same name end is connected to the positive pole of the DC power source, or is connected in series with the lower arm and its different name end is connected to the negative pole of the DC power source.

6. A brushless DC motor control system comprising: an inverter circuit for outputting a working power to the three-phase motor; and a current sensor for detecting an operating current of the three-phase motor; wherein the inverter circuit includes Switching tubes Ql, Q3, Q5 connected to the upper arm, switching tubes connected to the lower arm Q4, Q6, Q2, freewheeling diodes D1, D2, D3, D4, D5 and the respective switching tubes D6; characterized in that

The current sensor includes two sampling coils L1, L3 having the same number of turns, both of which are wound on the same core, and the core is further provided with a current output according to the magnetic flux change of the core. Feeling Sensing element

The sampling coil L1 is serially connected to the upper bridge arm and has the same name end connected to the positive pole of the DC power source, or serially connected to the lower bridge arm, and the different name end thereof is connected to the negative pole of the DC power source.

The brushless DC motor control system according to any one of claims 4-6, wherein the sensing element for outputting the current sensing result is a linear Hall element.

8. The brushless DC motor control system according to claim 7, wherein the output voltage amplitude of the linear Hall element is sent to the current regulator as a current feedback signal, and the output of the current regulator is sent to Pulse modulation circuit,

The output of the pulse modulation circuit is sent to a commutation logic circuit,

The output of the commutation logic circuit is sent to the pre-driver circuit.

The pre-drive circuit further outputs a corresponding driving pulse signal to the control ends of the respective switch tubes in the inverter circuit;

The inverter circuit outputs a working power source to the three-phase motor under the control of the driving pulse signal.

9. The brushless DC motor control system according to claim 8, further comprising a position sensor mounted on a rotating shaft of said direct current motor, wherein an output signal is sent to a position/speed interface circuit, said position / The speed interface circuit outputs a speed feedback voltage to the speed regulator, outputs a position feedback voltage to the position adjuster, and outputs a commutation position signal and a motor direction signal to the commutation logic circuit;

The position adjuster outputs a speed given signal to the speed regulator according to the position given voltage and the position feedback voltage; the speed adjuster according to the speed given signal and the speed feedback voltage, to the current The regulator outputs a current given signal; the current regulator outputs a corresponding control signal to the pulse modulation circuit according to the current given signal and a current feedback signal from the linear Hall element;

The commutation logic circuit outputs a corresponding signal to the pre-driver circuit according to a pulse signal from the pulse width modulation circuit and a commutation position signal and a motor direction signal of the position/speed interface Control pulse.

The brushless DC motor control system according to claim 9, wherein the square wave brushless permanent magnet DC motor is a stator coreless linear three-phase square wave brushless permanent magnet DC motor, or a stator without Iron core rotating three-phase square wave brushless permanent magnet DC motor.

A control method for a brushless DC motor control system according to claim 4, wherein in each of the inverse transformation logic periods, the maximum conduction angle of each of the switching tubes is 120°, in any group of switches During the conduction period of the tube:

Or, separately, pulse width modulation is performed on the switch tube connected to the lower arm.

12. The control method of the brushless DC motor control system according to claim 5, wherein in each of the inverse transformation logic periods, the maximum conduction angle of each of the switching tubes is 120°, in any group of switches During the conduction period of the tube, the switch tube connected to the lower arm is separately pulse width modulated.

A control method for a brushless DC motor control system according to claim 6, wherein in each of the inverse transformation logic periods, the maximum conduction angle of each of the switching tubes is 120°, in any group of switches During the conduction period of the tube, the switch tube connected to the upper arm is separately pulse width modulated.