Motor control device and method based on field effect tube on-resistance sampling circuit

Abstract

The present invention discloses a motor control device based on a field effect tube on-resistance sampling circuit, comprising a position sensor and a sampling circuit; the position sensor is installed on the motor, the signal output end of the position sensor is connected to the input end of the Park conversion unit and the input end of the speed loop; the input end of the sampling circuit is connected to the field effect tube in the inverter, the output end of the sampling circuit is connected to the input end of the Clark conversion unit; the output end of the Clark conversion unit is connected to the input end of the Park conversion unit, the output end of the Park conversion unit and the output end of the speed loop are connected to the input end of the current loop, and the output end of the current loop is connected to the motor after passing through the Park inverse conversion unit, the Clark inverse conversion unit, and the inverter in sequence. The present invention saves the traditional alloy sampling resistor by utilizing the on-resistance of the field effect tube itself in the inverter, which not only reduces the heat generation of the PCB, but also improves the efficiency of the entire inverter.

Description

Technical Field

[0001] The present invention relates to the field of motor control, and in particular to a motor control device and method based on a field effect tube on-resistance sampling circuit. Background Art

[0002] Phase current sampling is an essential part in the vector control of permanent magnet synchronous motor (PMSM). At present, current sampling basically uses phase current sampling or lower arm current sampling schemes, such as Figure 1 As shown in the figure, the motor current is detected by a sampling device to obtain a current signal, which is used as the feedback signal of the motor control system; the sampling devices are divided into Hall current sensors and alloy sampling resistors. The Hall current sensor has high sampling accuracy and low heat generation, but the sampling cost is high and the equipment is large. The alloy sampling resistor is much smaller than the Hall current sensor. Due to its own material properties, the resistance changes little with temperature. Because the alloy sampling resistor is low in cost and small in size, it is often used in many current sampling schemes.

[0003] In the current sampling method at this stage, the inverter circuit is composed of an alloy sampling resistor and a field effect transistor. The structure is as follows Figure 2 As shown, the sampling circuit is composed of an operational amplifier circuit and a filter circuit. The operational amplifier in the operational amplifier circuit is used to bias and amplify the sampling signal. The in-phase end is connected to the ground end of the alloy sampling resistor of the lower bridge arm of the three-phase bridge arm in the inverter circuit, and the inverting end is connected to the source (S pole) of the field effect tube of the lower bridge arm of the three-phase bridge arm in the inverter circuit. However, due to the large power consumption of the alloy sampling resistor, it still occupies a considerable space in the printed circuit board (PCB), and also increases the loss of the driver and the heating of the PCB. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides a motor control device based on a field effect tube on-resistance sampling circuit with simple structure, safety and reliability, and provides a motor control method based on the field effect tube on-resistance sampling circuit.

[0005] The technical solution of the present invention for solving the above technical problems is: a motor control device based on a field effect tube on-resistance sampling circuit, comprising a position sensor, a sampling circuit, a Clark conversion unit, a Park conversion unit, a speed loop, a current loop, a Park inverse conversion unit, a Clark inverse conversion unit and an inverter; the position sensor is installed on the motor and is used to measure the angle and angular velocity signals of the motor, and the signal output end of the position sensor is connected to the input end of the Park conversion unit and the input end of the speed loop; the input end of the sampling circuit is connected to the field effect tube in the inverter and is used to measure the on-voltage of the field effect tube, and the output end of the sampling circuit is connected to the input end of the Clark conversion unit; the output end of the Clark conversion unit is connected to the input end of the Park conversion unit, the output end of the Park conversion unit and the output end of the speed loop are connected to the input end of the current loop, and the output end of the current loop is connected to the motor after passing through the Park inverse conversion unit, the Clark inverse conversion unit and the inverter in sequence.

[0006] The motor control device based on the field effect tube on-resistance sampling circuit, the sampling circuit includes a fourth resistor, a fifth resistor, a sixth resistor, a seventh resistor, an eighth resistor, a ninth resistor, a tenth resistor, an eleventh resistor, a first capacitor, a second capacitor, a seventh field effect tube and an operational amplifier, the drain of the seventh field effect tube is connected to the drain of the field effect tube in the inverter, the gate of the seventh field effect tube is the control end, the source of the seventh field effect tube is connected to one end of the fourth resistor and one end of the eleventh resistor, the other end of the eleventh resistor is connected to one end of the fifth resistor and is connected to the source of the field effect tube in the inverter, the fourth resistor The other end is connected to one end of the seventh resistor and one end of the first capacitor, the other end of the fifth resistor is connected to one end of the eighth resistor and the other end of the first capacitor, the other end of the seventh resistor is connected to the inverting input terminal of the operational amplifier, the other end of the eighth resistor is connected to one end of the sixth resistor and the non-inverting input terminal of the operational amplifier, the other end of the sixth resistor is connected to a reference voltage source, the ninth resistor is connected between the inverting input terminal and the output terminal of the operational amplifier, the output terminal of the operational amplifier is connected to one end of the tenth resistor, one end of the second capacitor is grounded, and the other end of the second capacitor is connected to the other end of the tenth resistor and serves as the output end of the sampling circuit.

[0007] The above-mentioned motor control device based on the field effect tube on-resistance sampling circuit also includes a negative temperature coefficient thermistor, which is arranged close to the field effect tube in the inverter and is used to detect the temperature of the field effect tube in the inverter, and to obtain the resistance of the field effect tube by looking up a table relative to the temperature, thereby obtaining the current of the field effect tube, and the current is sent to the input end of the Clark conversion unit as a feedback signal for motor control.

[0008] A motor control method based on a field effect tube on-resistance sampling circuit, characterized in that it comprises the following steps:

[0009] 1) Obtain the angle θ and angular velocity ω information of the motor through the position sensor;

[0010] 2) Directly detect the on-state voltage V between the source and drain of the field effect tube through the sampling circuit ds , then place the negative temperature coefficient thermistor NTC close to the field effect tube to detect the temperature of the field effect tube, and then look up the table to get the on-resistance R of the field effect tube ds The value of ds =V ds / R ds Get the on-state current I of the field effect tube ds , with I ds As feedback signal for motor control system;

[0011] 3) The angle value θ is converted to the current I after Clark transformation. ds The current signal is transformed into Park coordinates to obtain the current value I of the d and q axes in the rotating coordinate system. d ,I q ;

[0012] 4) Compare the obtained angular velocity value ω with the set velocity value ω s Compare and then use the PI regulator of the speed loop to get the current setting value I q_s ;

[0013] 5) The q-axis current value I after coordinate change q With the current setting value I q_s By comparison, the control signal V is obtained through the current loop PI regulator q ;

[0014] 6) The d-axis current value I after coordinate change d Compare with 0, and get the control signal V through the current loop PI regulator d ;

[0015] 7) Control signal V d and V q Then, Park inverse transform and Clark inverse transform are performed to obtain the duty cycle signal of the set frequency, control the field effect tube, and thus complete the control of the motor.

[0016] In the motor control method based on the field effect tube on-resistance sampling circuit, in step 2), the on-voltage V of the field effect tube is used. ds The current feedback signal for motor control is obtained by using the temperature information to control the motor.

[0017] The beneficial effects of the present invention are:

[0018] 1. The present invention eliminates the traditional alloy sampling resistor by utilizing the on-resistance of the field effect tube in the inverter, which not only reduces the area of ​​the PCB and the cost of the motor control system, but also eliminates the loss on the alloy sampling resistor, which reduces the heat generation of the PCB and improves the efficiency of the entire inverter.

[0019] 2. The present invention is provided with a negative temperature coefficient thermistor for detecting the temperature of the field effect tube in the inverter, and the negative temperature coefficient thermistor is placed close to the field effect tube in the inverter. ds contains the internal temperature information of the field effect tube. When the load remains unchanged, I ds The effective value is unchanged when V ds When the effective value of increases, the on-resistance R ds The internal temperature of the field effect tube can be obtained by looking up the table. This temperature information can be used for real-time temperature identification and over-temperature protection of the field effect tube.

[0020] 3. In the control method of the present invention, V is directly used ds Overcurrent protection is better than using the motor current directly (the motor current is equal to I ds ), this is because as the temperature increases, R ds Increase, when using V ds As a fixed threshold, the allowed I ds This is consistent with the I ds The characteristic that the boundary decreases as the temperature increases is more similar, which is conducive to better protection of the field effect tube. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is the control block diagram of a traditional permanent magnet synchronous motor.

[0022] Figure 2 This is the sampling circuit diagram of the traditional alloy sampling resistor.

[0023] Figure 3 This is a control block diagram of a permanent magnet synchronous motor according to Embodiment 1 of the present invention.

[0024] Figure 4 This is a control block diagram of a permanent magnet synchronous motor according to the second embodiment of the present invention.

[0025] Figure 5 The circuit diagram of the field effect tube on-resistance sampling circuit of the present invention is shown in FIG.

[0026] Figure 6 It is a schematic diagram of the control signal of the field effect transistor in the sampling circuit of the present invention relative to the control signal of the corresponding lower bridge arm field effect transistor. DETAILED DESCRIPTION

[0027] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0028] Internal on-resistance R of field effect tube ds The size of is usually a few milliohms to a few ohms, and can be used as a lower bridge arm sampling resistor to connect to the sampling circuit. ds The change with temperature is more obvious than that of alloy sampling resistance, so the sampling resistance R ds The voltage drop V ds It is impossible to directly calculate the current signal and feed it back to the motor control system. The present invention provides two solutions for obtaining the motor current feedback signal: Figure 3 As shown, the first solution is to add a negative temperature coefficient thermistor to detect the temperature of the field effect tube, and then find V ds Table relative to temperature gives R ds , and then through formula I ds =V ds / R ds The current is obtained and used as the feedback signal for motor control. Figure 4 As shown, the second solution is to directly use V ds As feedback signal for motor control.

[0029] like Figure 3 As shown, a motor control device based on a field effect tube on-resistance sampling circuit includes a position sensor, a negative temperature coefficient thermistor, a sampling circuit, a Clark conversion unit, a Park conversion unit, a speed loop, a current loop, a Park inverse conversion unit, a Clark inverse conversion unit and an inverter; the position sensor is installed on the motor and is used to measure the angle and angular velocity signals of the motor, and the signal output end of the position sensor is connected to the input end of the Park conversion unit and the input end of the speed loop; the input end of the sampling circuit is connected to the field effect tube in the inverter and is used to measure the on-voltage of the field effect tube, and the output end of the sampling circuit is connected to the input end of the Clark conversion unit; the output end of the Clark conversion unit is connected to the input end of the Park conversion unit, the output end of the Park conversion unit and the output end of the speed loop are connected to the input end of the current loop, and the output end of the current loop is connected to the motor after passing through the Park inverse conversion unit, the Clark inverse conversion unit and the inverter in sequence. The negative temperature coefficient thermistor is arranged close to the field effect tube in the inverter, and is used to detect the temperature of the field effect tube in the inverter, and to obtain the resistance of the field effect tube by looking up a table relative to the temperature, thereby obtaining the current of the field effect tube, and the current is sent to the input end of the Clark conversion unit as a feedback signal for motor control.

[0030] like Figure 5As shown, the sampling circuit includes a fourth resistor R4, a fifth resistor R5, a sixth resistor R6, a seventh resistor R7, an eighth resistor R8, a ninth resistor R9, a tenth resistor R10, an eleventh resistor R11, a first capacitor C1, a second capacitor C2, a seventh field effect transistor Q7 and an operational amplifier, the drain of the seventh field effect transistor Q7 is connected to the drain of the field effect transistor in the inverter, the gate of the seventh field effect transistor Q7 is a control terminal, and a microcontroller (Microcontroller Unit, MCU) is controlled by a driving chip; the source of the seventh field effect transistor Q7 is connected to one end of the fourth resistor R4 and one end of the eleventh resistor R11, the other end of the eleventh resistor R11 is connected to one end of the fifth resistor R5 and is connected to the source of the field effect transistor in the inverter, the other end of the fourth resistor R4 is connected to one end of the seventh resistor R7 and one end of the first capacitor C1, the other end of the fifth resistor R5 is connected to one end of the eighth resistor R8 and the other end of the first capacitor C1, the other end of the seventh resistor R7 is connected to the inverting input end of the operational amplifier, the other end of the eighth resistor R8 is connected to one end of the sixth resistor R6 and the non-inverting input end of the operational amplifier, the other end of the sixth resistor R6 is connected to a reference voltage source, the ninth resistor R9 is connected across the inverting input end and the output end of the operational amplifier, the output end of the operational amplifier is connected to one end of the tenth resistor R10, one end of the second capacitor C2 is grounded, and the other end of the second capacitor C2 is connected to the other end of the tenth resistor R10 and serves as the output end of the sampling circuit.

[0031] The operational amplifier in the sampling circuit is used to bias and amplify the sampling signal, and the in-phase input terminal is connected to the source (S pole) of the lower bridge arm field effect transistor of the three-phase bridge arm in the inverter circuit through a resistor-capacitor network, and the inverting input terminal is connected to the drain (D pole) of the lower bridge arm field effect transistor of the three-phase bridge arm in the inverter circuit. Compared with the sampling circuit of the traditional sampling method, in the sampling circuit of the new sampling method, in order to avoid a large voltage being applied to both ends of the operational amplifier when the lower bridge arm field effect transistor is turned off, a seventh field effect transistor Q7 and an eleventh resistor R11 are added here, and the control signal of Q7 is the same as the control signal of the lower bridge arm field effect transistor Q2, or the turn-on signal of Q7 is made later than the turn-on signal of Q2 by a short period of time and the turn-off signal of Q7 is made earlier than the turn-off signal of Q2 by a short period of time Δt, and the length of this short period of time Δt can usually be a few nanoseconds to a few microseconds, such as Figure 6 As shown, Figure 6The solid line in the middle is the control signal of Q7 in the U-phase sampling circuit, which is valid at a high level; the dotted line is the control signal of the corresponding lower bridge arm field effect tube Q2, which is valid at a high level. The field effect tube Q7 in the sampling circuit does not flow through a large current like the lower bridge arm field effect tube Q2 corresponding to Q7. Its current during normal operation is very small, less than tens of milliamperes, and can even reach the microampere level. Therefore, the field effect tube Q7 in the sampling circuit only needs to select a field effect tube with sufficient withstand voltage and very small current. This can greatly reduce the size of Q7, even if the on-resistance of the field effect tube is large (for example, reaching several ohms), because its on-resistance is negligible relative to the resistors R4 and R7 in the resistor network of the subsequent stage (generally up to hundreds of ohms to tens of kiloohms). The withstand voltage value of Q7 is selected to be the same as or close to the withstand voltage value of the lower bridge arm field effect tube Q2 corresponding to Q7. R11 can usually be hundreds of ohms to tens of kiloohms. When Q2 and Q7 are turned off, R11 divides the voltage with Q7 to make the voltage between the two input terminals of the operational amplifier circuit close to 0.

[0032] The sampling signal in the present invention is the current flowing through the field effect tube on-resistance R ds The voltage drop generated is the on-resistance R of the field effect tube when the lower bridge arm field effect tube in the inverter circuit is turned on. ds Voltage drop across both ends. ds Using the voltage drop across the two ends as the sampling signal can reduce the loss of the inverter compared to using the voltage drop across the two ends of the alloy sampling resistor as the sampling signal, and is suitable for low voltage and high current working scenarios.

[0033] A motor control method based on a field effect tube on-resistance sampling circuit, characterized in that it comprises the following steps:

[0034] 1) Obtain the angle θ and angular velocity ω information of the motor through the position sensor;

[0035] 2) Directly detect the on-state voltage V between the source and drain of the field effect tube through the sampling circuit ds , then place the negative temperature coefficient thermistor NTC close to the field effect tube to detect the temperature of the field effect tube, and then look up the table to get the on-resistance R of the field effect tube ds The value of ds =V ds / R ds Get the on-state current I of the field effect tube ds , with I ds As feedback signal for motor control system;

[0036] 3) The angle value θ is converted to the current I after Clark transformation. ds The current signal is transformed into Park coordinates to obtain the current value I of the d and q axes in the rotating coordinate system. d ,I q ;

[0037] 4) Compare the obtained angular velocity value ω with the set velocity value ω s Compare and then use the PI regulator of the speed loop to get the current setting value I q_s ;

[0038] 5) The q-axis current value I after coordinate change q With the current setting value I q_s By comparison, the control signal V is obtained through the current loop PI regulator q ;

[0039] 6) The d-axis current value I after coordinate change d Compare with 0, and get the control signal V through the current loop PI regulator d ;

[0040] 7) Control signal V d and V q Then, Park inverse transform and Clark inverse transform are performed to obtain the duty cycle signal of the set frequency, control the field effect tube, and thus complete the control of the motor.

[0041] In the second embodiment of the control method of the present invention, in step 2), directly V ds As the feedback signal of the motor control, coordinate transformation is performed using the V of the rotor dq axis system. ds Closed-loop control replaces the traditional rotor dq shaft current closed-loop control to control the motor. Although there is no precise current control, it can still achieve normal speed regulation function under the control of the speed outer loop.

Claims

1. A motor control device based on a field effect tube on-resistance sampling circuit, characterized in that: The invention comprises a position sensor, a sampling circuit, a Clark conversion unit, a Park conversion unit, a speed loop, a current loop, a Park inverse conversion unit, a Clark inverse conversion unit and an inverter; the position sensor is installed on the motor and is used to measure the angle and angular velocity signal of the motor; the signal output end of the position sensor is connected with the input end of the Park conversion unit and the input end of the speed loop; the input end of the sampling circuit is connected with the field effect tube in the inverter and is used to measure the conduction voltage of the field effect tube; the output end of the sampling circuit is connected with the input end of the Clark conversion unit; the output end of the Clark conversion unit is connected with the input end of the Park conversion unit; the output end of the Park conversion unit and the output end of the speed loop are connected with the input end of the current loop; the output end of the current loop is connected to the motor after passing through the Park inverse conversion unit, the Clark inverse conversion unit and the inverter in sequence.

2. The motor control device based on the field effect tube on-resistance sampling circuit according to claim 1, characterized in that: The sampling circuit includes a fourth resistor, a fifth resistor, a sixth resistor, a seventh resistor, an eighth resistor, a ninth resistor, a tenth resistor, an eleventh resistor, a first capacitor, a second capacitor, a seventh field effect transistor and an operational amplifier. The drain of the seventh field effect transistor is connected to the drain of the field effect transistor in the inverter, the gate of the seventh field effect transistor is a control terminal, the source of the seventh field effect transistor is connected to one end of the fourth resistor and one end of the eleventh resistor, the other end of the eleventh resistor is connected together with one end of the fifth resistor and connected to the source of the field effect transistor in the inverter, the other end of the fourth resistor is connected to one end of the seventh resistor and one end of the first capacitor, the other end of the fifth resistor is connected to one end of the eighth resistor and the other end of the first capacitor, the other end of the seventh resistor is connected to the inverting input terminal of the operational amplifier, the other end of the eighth resistor is connected to one end of the sixth resistor and the non-inverting input terminal of the operational amplifier, the other end of the sixth resistor is connected to a reference voltage source, the ninth resistor is connected across the inverting input terminal and the output terminal of the operational amplifier, the output terminal of the operational amplifier is connected to one end of the tenth resistor, one end of the second capacitor is grounded, and the other end of the second capacitor is connected together with the other end of the tenth resistor and serves as the output terminal of the sampling circuit.

3. The motor control device based on the field effect tube on-resistance sampling circuit according to claim 1, characterized in that: It also includes a negative temperature coefficient thermistor (Negative Temperature Coefficient, NTC), which is arranged close to the field effect tube in the inverter and is used to detect the temperature of the field effect tube in the inverter, and to find the resistance of the field effect tube by looking up a table relative to the temperature, thereby obtaining the current of the field effect tube, and the current is sent to the input end of the Clark conversion unit as a feedback signal for motor control.

4. A motor control method based on a field effect tube on-resistance sampling circuit of a motor control device according to any one of claims 1 to 3, characterized in that: The following steps are involved: 1) Obtain the angle θ and angular velocity ω information of the motor through the position sensor; 2) Directly detect the on-state voltage V between the source and drain of the field effect tube through the sampling circuit ds , then place the negative temperature coefficient thermistor NTC close to the field effect tube to detect the temperature of the field effect tube, and then look up the table to get the on-resistance R of the field effect tube ds The value of ds =V ds / R ds Get the on-state current I of the field effect tube ds , with I ds As feedback signal for motor control system; 3) The angle value θ is converted to the current I after Clark transformation. ds The current signal is transformed into Park coordinates to obtain the current value I of the d and q axes in the rotating coordinate system. d ,I q ; 4) Compare the obtained angular velocity value ω with the set velocity value ω s Compare and then use the PI regulator of the speed loop to get the current setting value I q_s ; 5) The q-axis current value I after coordinate change q With the current setting value I q_s By comparison, the control signal V is obtained through the current loop PI regulator q ; 6) The d-axis current value I after coordinate change d Compare with 0, and get the control signal V through the current loop PI regulator d ; 7) Control signal V d and V q Then, Park inverse transform and Clark inverse transform are performed to obtain the duty cycle signal of the set frequency, control the field effect tube, and thus complete the control of the motor.

5. The motor control method based on the field effect tube on-resistance sampling circuit according to claim 4, characterized in that: In step 2, directly use V ds As the feedback signal of the motor control, coordinate transformation is performed using the V of the rotor dq axis system. ds The closed-loop control replaces the traditional rotor dq axis current closed-loop control to control the motor.

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