阅读说明：本技术 带有功率反馈回路的电机控制器 (Motor controller with power feedback loop ) 是由 吕一松 于 2019-11-26 设计创作，主要内容包括：一种电机控制系统,包括：电机；以及电机控制电路,其被耦合到所述电机以给所述电机供电。所述电机控制电路包括：功率基准环路,其具有用于提供基准功率水平的功率基准电路；以及功率控制电路,其被配置成给所述电机提供恒定的功率水平,使得所述电机以基本恒定的转矩操作。所述恒定的功率水平与所述基准功率水平成比例。因此,当电机处于恒定速度时,电机也提供基本恒定的扭矩。(A motor control system comprising: a motor; and a motor control circuit coupled to the motor to power the motor. The motor control circuit includes: a power reference loop having a power reference circuit for providing a reference power level; and a power control circuit configured to provide a constant power level to the motor such that the motor operates at a substantially constant torque. The constant power level is proportional to the reference power level. Thus, when the motor is at a constant speed, the motor also provides a substantially constant torque.)

1. A system, comprising:

a motor;

a motor control circuit coupled to the motor to power the motor, the motor control circuit comprising:

a power reference circuit for providing a reference power level; and

a power control circuit configured to provide a substantially constant power level to the motor such that the motor operates at a substantially constant torque at a substantially constant motor speed, wherein the constant power level is proportional to the reference power level.

2. The system of claim 1, wherein the motor control circuit comprises a power feedback loop.

3. The system of claim 2, wherein the power feedback loop comprises a differential circuit that generates a signal representative of a difference between the reference power level and a power level applied to the motor.

4. The system of claim 3, wherein the power level applied to the motor is calculated by multiplying a voltage applied to the motor by a current applied to the motor.

5. The system of claim 3, wherein the power level applied to the motor is calculated by multiplying an input voltage input to a motor driver circuit by an input current input to the motor driver circuit.

6. The system of claim 5, further comprising a circuit for measuring the voltage applied to the motor.

7. The system of claim 5, further comprising a circuit for measuring the input current applied to the motor.

8. The system of claim 3, wherein the signal is provided as an input to the power control circuit.

9. The system of claim 1, wherein the motor has three phases.

10. The system of claim 1, wherein the motor control circuit comprises a speed feedback loop.

11. The system of claim 10, wherein the speed feedback loop comprises a differential circuit that generates a signal representative of a difference between a reference speed value and a measured speed of the motor.

12. A circuit, comprising:

a motor driver circuit comprising a plurality of switches coupled to power a motor; and

a motor control circuit, the motor control circuit comprising:

a power reference circuit for providing a reference power level; and

a motor control circuit configured to control the motor driver circuit to apply a constant power level to the motor such that the motor operates at a substantially constant torque, wherein the constant power level is proportional to the reference power level.

13. The circuit of claim 12 wherein the motor control circuit comprises a power feedback loop.

14. The circuit of claim 13, wherein the power feedback loop comprises a differential circuit that generates a signal representative of a difference between the reference power level and a power level applied to the motor.

15. The circuit of claim 14, wherein the power level applied to the motor is calculated by multiplying a voltage applied to the motor by a current applied to the motor.

16. The circuit of claim 15, further comprising a circuit for measuring the voltage applied to the motor.

17. The circuit of claim 15, further comprising a circuit for measuring the current applied to the motor.

18. The circuit of claim 14, wherein the signal is provided as an input to the motor control circuit.

19. The circuit of claim 12, wherein the motor control circuit comprises a speed feedback loop.

20. The circuit of claim 19 wherein the speed feedback loop comprises a differential circuit that generates a signal representative of a difference between a reference speed value and a measured speed of the motor.

21. A method of driving an electric machine at a constant torque, comprising:

measuring a voltage applied to the motor;

measuring a current applied to the motor;

calculating an instantaneous power applied to the motor from the measured voltage and the measured current;

determining a difference between the instantaneous power and a reference power level; and

adjusting the voltage and/or current applied to the motor such that the instantaneous power matches the reference power level.

22. A system, comprising:

a motor; and

a drive arrangement for driving the motor to a constant power such that a torque output of the motor is substantially constant.

Technical Field

The present disclosure relates to motor control systems and circuits.

Background

In many applications, circuits are required to precisely control, drive and regulate brushless direct current ("BLDC") motors. These circuits often create pulse width modulated ("PWM") drive signals for controlling the power to the motor.

The BLDC motor may include a plurality of coils. These coils, when energized, cause the motor to rotate. However, in order for the motor to rotate continuously, the motor controller circuit must energize one or more of the coils (but not all of the coils) at a time, energize the coils in a particular sequence, energize the coils in forward and backward directions at different times, and so forth. The period of time during which the coil is energized is commonly referred to as the so-called "phase" of the motor. The coil (or coils) that are energized during a phase may be referred to as a phase coil (phase coil).

The sequence and timing at which the coils are energized depends on the design for the BLDC motor. As an example, a BLDC motor may have three coils that must be energized sequentially, i.e., cyclically, to turn the motor. Such a motor may have three "phases". In each phase, a different one or more of the three coils is energized. As the motor turns, the phase will change and the motor driver will energize the next coil or coils to keep the motor rotating.

As each phase is energized, it physically drives the rotor of the motor. The amount of power provided to the coil may be proportional to the amount of torque produced by the motor. In many BLDC motors, the amount of power supplied to the coil increases and decreases over time as the coil is energized. Therefore, the motor does not produce a constant torque output.

In U.S. patent No. 7,590,334 (filed 8/2007); us patent No. 7,747,146 (filed 8/2007), us patent No. 8,729,841 (filed 10/12/2011); U.S. patent application No. 13/595,430 (filed on 8/27/2012); U.S. patent No. 9,088,233 (filed 12/18/2012); U.S. patent No. 9,291,876 (filed on 29/5/2013); and U.S. patent application No. 15/967,841 (filed on 5/1/2018), each of which is incorporated herein by reference, describes various electric motor driver circuits, and is assigned to the assignee of the present patent.

Disclosure of Invention

In an embodiment, a system, comprises: a motor; and a motor control circuit coupled to the motor to power the motor. The motor control circuit includes: a power reference circuit for providing a reference power level; and a power control circuit configured to provide a substantially constant power level to the motor such that the motor operates at a substantially constant torque at a substantially constant motor speed. The constant power level is proportional to the reference power level.

One or more of the following features may be included.

The motor control circuit may include a power feedback loop.

The power feedback loop may include a differential circuit that generates a signal representative of a difference between the reference power level and the power level applied to the motor.

The power level applied to the motor may be calculated by multiplying a voltage applied to the motor by a current applied to the motor.

The power level applied to the motor may be calculated by multiplying an input voltage input to the motor driver circuit by an input current input to the motor driver circuit.

The system may include a circuit for measuring the voltage applied to the motor.

The system may include a circuit for measuring the input current applied to the motor.

The signal may be provided as an input to the power control circuit.

The motor may have three phases.

The motor control circuit may include a speed feedback loop.

The speed feedback loop may include a differential circuit that generates a signal representative of a difference between a reference speed value and a measured speed of the motor.

In another embodiment, a circuit includes: a motor driver circuit comprising a plurality of switches coupled to power a motor; and a motor control circuit. The motor control circuit includes: a power reference circuit for providing a reference power level; and a motor control circuit configured to control the motor driver circuit to apply a constant power level to the motor such that the motor operates at a substantially constant torque. The constant power level is proportional to the reference power level.

One or more of the following features may be included.

The motor control circuit may include a power feedback loop.

The power feedback loop may include a differential circuit that generates a signal representative of a difference between the reference power level and the power level applied to the motor.

The power level applied to the motor may be calculated by multiplying the voltage applied to the motor by the current.

A circuit for measuring the voltage applied to the motor may be included.

A circuit for measuring the current applied to the motor may be included.

The signal may be provided as an input to the motor control circuit.

The motor control circuit may include a speed feedback loop.

The speed feedback loop may include a differential circuit that generates a signal representative of a difference between a reference speed value and a measured speed of the motor.

In another embodiment, a method of driving an electric motor with constant torque, comprises: measuring a voltage applied to the motor; measuring a current applied to the motor; calculating an instantaneous power applied to the motor from the measured voltage and the measured current; determining a difference between the instantaneous power and a reference power level; and adjusting the voltage and/or current applied to the motor such that the instantaneous power matches the reference power level.

In another embodiment, a system comprises: a motor; and a drive arrangement for driving the motor to a constant power such that a torque output of the motor is substantially constant.

Drawings

The above features will be more fully understood from the following description of the drawings. The accompanying drawings are included to provide a further understanding of the disclosed technology. The drawings provided depict one or more examples of embodiments, because it is often impractical, or impossible, to illustrate and describe every possible embodiment. Accordingly, the drawings are not intended to limit the scope of the present invention. Like reference symbols in the various drawings indicate like elements.

FIG. 1 is a block diagram of a system for controlling an electric machine.

Fig. 2 is a block diagram of a system for controlling a motor.

Fig. 3 is a motor power diagram for a motor driven by a prior art motor control circuit.

FIG. 4 is a motor power diagram for a motor driven by a motor control circuit providing a substantially constant torque output.

Detailed Description

Fig. 1 is a circuit diagram of a motor control system 100 for controlling a motor 102. The motor control system 100 includes a motor control circuit 104 coupled to a motor driver circuit 106. The motor driver circuit 106 is coupled to the motor 102 and powers the motor 102. In an embodiment, the motor control circuit may be a non-sinusoidal wave brushless dc motor control circuit.

In the example shown in fig. 1, the motor 102 is a three-phase motor. Accordingly, the motor driver circuit 106 has six Field Effect Transistor (FET) switches coupled in pairs between the power supply line 108 and the return line 110. The nodes between the pairs (i.e., nodes A, B and C) are coupled to the coils of the motor 102. When the FET switch is turned on and off, it provides power to the motor 102 and provides a return path from the motor 102. For example, if FET switch 112 and FET switch 114 are closed (e.g., in a conductive state) while the other FET switches are open (e.g., in a non-conductive state), current may flow from power supply line 108, through FET switch 112 to node a, from node a through the internal coils of motor 102 to node B, and from node B through FET switch 114 to ground.

For ease of illustration, only the gate of the FET switch 112 is shown coupled to the motor control circuit 104. However, in an embodiment, the gate of each FET switch within the motor driver circuit 106 may be coupled to the motor control circuit 104. The motor control circuit 104 can drive the gate of each FET switch with a signal 104a to selectively open and close the FET switches. This effectively drives the motor 102 by directing power (electricity) to the coils of the motor 102. Those skilled in the art will recognize that in other embodiments, the FET switch may be replaced by any device capable of acting as a switch, such as a bipolar junction transistor ("BJT"), relay, and the like.

In an embodiment, the signal 104a may be a pulse width modulation ("PWM") signal. As the PWM on-time increases from zero to one hundred percent, the magnitude of the current supplied to the motor scales from zero to its maximum value. Thus, the motor control circuit 104 can control the magnitude of the current supplied to the motor 102 by varying the pulse width of the signal 104 a.

The motor control system 100 may include sensors for measuring the voltage and current supplied to the motor 102. As an example, to measure the voltage supplied to the motor 102, an analog-to-digital converter ("ADC") 116 may be coupled to the node A, B and/or C through a multiplexer 118. The ADC 116 may measure the voltage at the node supplying the motor 102 and generate a signal 116a representative of the voltage supplied to the motor 102. The multiplexer 118 may be controlled by the motor control circuit 104 (or another control circuit) to connect the node that is currently supplying power to the motor 102 (e.g., A, B or C) to the ADC 116. In an embodiment, a processor or circuit may receive signal 116a and use it to calculate an average or RMS value (root mean square value) of the voltage supplied to motor 102.

As another example, to measure the current flowing through the motor 102, the motor control system 100 may include a shunt resistance 120 in the current path. The inputs of the differential amplifier 122 may be coupled across the shunt resistor 120. Thus, the amplified signal 122a (i.e., the output of the differential amplifier 122) may represent the voltage across the shunt resistor 120. The ADC 124 may convert the amplified signal 122a into a digital signal 124a, which may be used by the motor control circuit 104 (or other circuitry) to calculate the current flowing through the motor 102. In an embodiment, the shunt resistor 120 may be according to kirchhoff current rules, and the calculated current through the shunt resistor 120 may represent the input current to the motor 102 and/or the output current from the motor 102.

Since the resistance of the shunt resistor 120 is known, the motor control circuit 104 can use the voltage across the shunt resistor 120 to measure the current flowing through the motor 102. Thus, the digital signal 124a may also represent the measured current. In an embodiment, shunt resistor 120 may have a very small resistance such that it does not significantly impede current flow and does not dissipate a significant amount of power. Typical values for shunt resistance 120 may be 0.1 ohms or less. Additionally, although shunt resistor 120 is shown coupled to return line 110 to measure the current (I) returning from motor 102_out) However, a shunt resistor may be coupled to the power line 108 to measure the current (I) flowing into the motor 102_in)。

Referring to fig. 2, a motor control system 200 includes a motor control circuit 202, which may be the same as or similar to motor control circuit 104. The motor control circuit 202 is coupled to a motor driver circuit 204, which motor driver circuit 204 may be the same as or similar to the motor driver circuit 106. Similar to the motor driver circuit 106, the motor driver circuit 204 may be coupled to the motor 102 to power the motor 102.

The motor control circuit 202 may receive a reference speed signal 206a (which represents a desired speed of the motor 102) as an input from the reference speed circuit 206. The reference speed circuit 206 may be any external circuit capable of generating a reference speed signal 206a to represent the desired speed of the motor 102. In an embodiment, the reference speed circuit 206 may be an external control circuit, a processor circuit, or the like. In other embodiments, the reference speed signal 206a may be generated internally by the motor control circuit 202.

The motor control circuitry 202 may also include a power reference circuit 208, which may generate a power reference signal 208 a. The power reference signal 208a may represent the amount of power to be applied to the motor 102. In embodiments, the power reference signal 208a may be a constant or variable signal and/or may be generated internally by the power reference circuit 208. In other embodiments, power reference circuit 208 may receive external power control signal 208b from an external source, which may be representative of a desired power level. In this case, the power reference signal 208a may be proportional to the external power control signal 208b or based on the external power control signal 208 b.

The reference speed signal 206a may be generated from outside the motor control circuit 202. The reference speed signal 206a may be fixed or varied during operation to control the speed of the motor 102. The power reference signal 208a may be calculated based on an error (e.g., difference) between the reference velocity signal 206a (e.g., desired velocity) and the signal 102a (actual velocity). Signal 212a may represent the error between the reference speed signal 206a and signal 102 a. The power reference circuit 208 may then use the error to calculate a power reference signal 208 a.

For example, assume that the reference speed signal 206a requires a motor speed of 1000rpm and the measured speed 102a is 980 rpm. The signal 212a may represent an error (e.g., 20rpm) that will be used by the PI loop 208 to increase the power reference signal 208a, thereby causing the motor to accelerate to 1000rpm at a predetermined power level.

Motor control system 200 may include two feedback loops: a speed feedback loop and a power feedback loop. The velocity feedback loop may include a difference circuit 212 and a proportional integral ("PI") controller 214. The difference circuit 212 may receive the reference speed signal 206a and the back emf signal 102a and generate a difference signal 212a representing the difference or "error" between the reference speed signal 206a and the back emf signal 102 a. The back-EMF (back-EMF) may be a signal representative of the back-EMF voltage of the motor 102 or any other type of signal capable of representing the speed of the motor 102.

The PI controller circuit 214 may receive the differential signal 212a and generate a control signal 214 a. In an embodiment, the control signal 214a may be a pulse width modulated signal for controlling the motor 102. For example, the PI controller circuit 214 may increase the pulse width of the control signal 214a to increase the speed of the motor 102 and decrease the pulse width of the control signal 214a to decrease the speed of the motor 102. In this manner, the PI controller circuit 214 may match the speed of the motor 102 to the desired speed represented by the reference speed signal 206 a.

Although not shown, the motor control system 100 may include signal shaping circuitry, such as amplifiers, filters, and the like, to condition the back emf signal 102a prior to being received by the difference circuitry 212.

The power feedback loop may include a difference circuit 216, a PI controller 218, and a multiplier circuit 220. The multiplier circuit 220 may multiply a signal representative of the voltage of the motor 102 (e.g., the signal 116a in fig. 1) with a signal representative of the current through the motor 102 (e.g., the digital signal 124a in fig. 1). The power signal 220a of the multiplier circuit 220 may represent the instantaneous power (e.g., the present power) being applied to the motor 102. In an embodiment, the multiplier circuit 220 may input an input voltage (V) to the motor 102_in) With the input current (I) to the motor 102_in) To generate the power signal 220a, as shown in fig. 1. In other embodiments, the multiplier circuit 220 may multiply the output voltage (V) from the motor 102_out) And the output current (I) from the motor 102_out) To generate power signal 220 a.

The difference circuit 216 may receive a current (e.g., instantaneous) power signal 220a and a desired power reference signal 208a and generate a difference signal 216a that represents a difference or "error" between the power signal 220a and the power reference signal 208 a. The PI controller 218 may receive the differential signal 216a and generate a control signal 218 a. The control signal 218a may be a pulse width modulated signal to control the motor 102. For example, the PI controller 218 may increase the pulse width of the control signal 218a to increase the power applied to the motor 102 and decrease the pulse width of the control signal 218a to decrease the power applied to the motor 102. In this manner, the PI controller 218 is able to match the power applied to the motor 102 to the desired power represented by the power reference signal 208 a. In an embodiment, the control signal 218a may be the same as or similar to the signal 104a (see fig. 1).

In an embodiment, the power supplied to the motor 102 may be proportional to the power reference signal 218 a. Proportional means that a change in the value of the power reference signal 218a can result in a change in the power applied to the motor 102. For example, if the power reference signal 218a increases, the power applied to the motor 102 may increase. In an embodiment, the power reference signal may have a constant value such that the power provided to the motor 102 is a constant power level. In some cases, the power provided to the motor 102 may be a scalar multiple (scalarm) of the value of the power reference signal 218 a.

Referring to fig. 3, a graph 300 illustrates a prior art motor power curve. The horizontal axis represents arbitrary units of time and the vertical axis represents arbitrary units of power. Graph 300 shows a torque curve for a three-phase motor driven by a prior art motor control circuit.

Bottom waveforms 304, 306, and 308 each represent the output power of the motor when driven by one of the three motor phases. When each phase is activated (e.g., when current is driven through the phase coil), the power increases to a peak and then decreases with inactivity of the phase. Adding these three torque curves results in curve 310, which represents the overall output power of the prior art three-phase motor. As shown, the overall power curve is not constant; the function of its peak and fall is similar to the change in amplitude (or absolute value) of a sine wave over time. This may occur, for example, if the motor is driven by a non-sinusoidal wave brushless dc motor controller. Because motor power is the product of torque times motor speed, the torque of the motor will not remain constant when the motor reaches a steady state motor speed, driven by a power curve like curve 310.

Referring to fig. 4, a graph 400 illustrates a power output curve of the motor 102. The horizontal axis represents arbitrary units of time and the vertical axis represents arbitrary units of power. The waveform is an experimental result of the motor input power and the motor output power as the motor is controlled by the motor control circuit 104 (or the motor control circuit 202).

Waveform 402 represents the input power to the motor 102, which may be calculated by multiplying the input voltage and current, as described above. The output power waveform 404 represents the output from the motor 102. As shown, the output power waveform 404 is relatively constant across all three motor phases A, B and C and exhibits a reduced sinusoidal pattern. As a result, the output torque of the motor is constant for any constant motor speed, since the torque is the quotient of the power divided by the motor speed.

Various embodiments are described in this patent. The scope of this patent, however, should not be limited to the described embodiments, but should be limited only by the spirit and scope of the appended claims. All references cited in this patent are incorporated herein by reference in their entirety.