Motor drive method

Abstract

A motor driving method includes: in an open-loop stage, when the motor is in steady-state operation, calculating, by a controller, an angle difference between an estimated coordinate axis and an actual coordinate axis of the motor based on an estimated voltage value, an estimated current value, and motor parameters feedback on the estimated coordinate axis of the motor; calculating, by the controller, an actual current value of the motor on the actual coordinate axis based on the angle difference; calculating, by the controller, an estimated value of the load torque of the motor based on the actual current value; and when the open-loop stage is switched to a closed-loop stage, compensating, by the controller, the output torque of the motor according to the estimated value of the load torque.

Description

Technical Field

[0001] The present disclosure relates to a motor driving method, and particularly to a motor driving method for load torque estimation and compensation. Background Art

[0002] In the prior art, in applications with load characteristics such as step torque like elevators, torque estimation and compensation are required when switching between open-loop and closed-loop driving methods to avoid no output torque of the motor or electric motor during the switching of the driving method. Moreover, if the speed controller is used to adjust the output torque only after the switching, it will cause a drastic change in speed. Summary of the Invention

[0003] To solve the above problems, an embodiment of the present disclosure provides a motor driving method, including: in the open-loop stage, when the motor is in steady-state operation, calculating, by a controller, an angle difference between an estimated coordinate axis and an actual coordinate axis of the motor based on an estimated voltage value, an estimated current value, and motor parameters feedback on the estimated coordinate axis of the motor; calculating, by the controller, an actual current value of the motor on the actual coordinate axis based on the angle difference; calculating, by the controller, an estimated value of the load torque of the motor based on the actual current value; and when the open-loop stage is switched to the closed-loop stage, compensating, by the controller, the output torque of the motor according to the estimated value of the load torque.

[0004] The motor driving method provided by the present disclosure can compensate for the load torque of the motor to avoid a drastic change in speed when switching driving methods (such as switching from open-loop driving to closed-loop driving), making the system operate smoothly. In addition, since the motor driving method of the present disclosure performs load torque estimation before switching the driving method, no additional transition interval is required when switching the driving method and compensating the motor torque, which can improve system efficiency. Brief Description of the Drawings

[0005] To make the above and other objects, features, advantages and embodiments of the present disclosure more obvious and understandable, the description of the drawings is as follows:

[0006] Figure 1 It is a schematic diagram of a motor driving system shown according to an embodiment of the present disclosure.

[0007] Figure 2 It is a schematic diagram of coordinate conversion shown according to an embodiment of the present disclosure.

[0008] Figure 3 It is a flowchart of a motor driving method shown according to an embodiment of the present disclosure.

[0009] Figure 4A It is a schematic diagram of voltage / frequency (V / f) control experimental data shown according to an embodiment of the present disclosure.

[0010] Figure 4B Schematic diagram of current / frequency (I / f) control experimental data shown in an embodiment of the present disclosure.

[0011] Figure 5A Experimental simulation diagram shown in an embodiment of the present disclosure.

[0012] Figure 5B Regarding Figure 5A Experimental simulation schematic diagram of the first stage P1 in

[0013] Figure 5C Regarding Figure 5B Experimental simulation schematic diagram from 0.8 second to 1.2 seconds in

[0014] Among them, the reference numerals are explained as follows:

[0015] To make the above and other objects, features, and advantages of the present disclosure more obvious and understandable, the descriptions of the attached symbols are as follows:

[0016] 100: Motor drive system

[0017] 110: Controller module

[0018] 112: Controller

[0019] 114: PWM unit

[0020] 116: Coordinate conversion unit

[0021] 118: Position error calculation unit

[0022] 120: Rectifier

[0023] 130: Power module

[0024] 140: Voltage detector

[0025] 150a, 150b, 150c: Three-phase current detectors

[0026] 200: Motor

[0027] 300: Motor drive method

[0028] i a , i b , i c : Current components

[0029] i d : Actual direct-axis current value

[0030] i q : Actual quadrature-axis current value

[0031] Estimate direct-axis current value

[0032] Estimate quadrature-axis current value

[0033] V d : Actual direct-axis voltage value

[0034] V q : Actual quadrature-axis voltage value

[0035] Estimate direct-axis voltage value

[0036] Estimate quadrature-axis voltage value

[0037] L d : Direct-axis inductance

[0038] L q : Quadrature-axis inductance

[0039] Angle difference

[0040] f * : Speed command

[0041] ω th : Speed command threshold

[0042] S302, S304, S306, S308: Steps

[0043] P1: First stage

[0044] P2: Second stage

[0045] P3: Third stage Specific implementation manners

[0046] All the terms used herein have their ordinary meanings. The definitions of the above terms in commonly used dictionaries, and examples of the use of any of the terms discussed herein in the content of this specification are only illustrative and should not limit the scope and meaning of the present disclosure. Similarly, the present disclosure is not limited only to the various embodiments shown in this specification.

[0047] In this document, the use of terms such as first, second, and third, etc. is understood to be used to describe various elements, components, regions, layers, and / or blocks. However, these elements, components, regions, layers, and / or blocks should not be limited by these terms. These terms are only used to distinguish a single element, component, region, layer, and / or block. Therefore, a first element, component, region, layer, and / or block in the following text may also be referred to as a second element, component, region, layer, and / or block without departing from the meaning of this application. As used herein, "and / or" includes any one and all combinations of one or more associated items.

[0048] Please refer to Figure 1 , Figure 1 which is a schematic diagram of a motor drive system 100 shown according to an embodiment of the present disclosure. As Figure 1 shown, the motor drive system 100 is used to drive a motor 200 and includes a controller module 110, a rectifier 120, a power module 130, a voltage detector 140, and three-phase current detectors 150a, 150b, 150c. The controller module 110 at least includes a controller 112, a pulse width modulation (PWM) unit 114, a coordinate conversion unit 116, and a position error calculation unit 118. In some embodiments, the controller module 110 is used to measure the motor parameters of the motor 200 (such as inductance value, angular rate, flux value, etc.), and after calculating the estimated load torque value based on the above information, transmit the estimated load torque value to the motor 200 to compensate its output torque. In some embodiments, the controller 112 receives a frequency control command f from an upper computer (not shown in the figure) * to perform voltage / frequency control or current / frequency control (detailed later), and the voltage detector 140 is used to receive and detect the voltage value feedback when the motor 200 is running, while the current detectors 150a, 150b, 150c are used to receive and detect the current value feedback when the motor 200 is running. When the motor drive system 100 is running, the rectifier 120 receives an external AC power supply and converts it into a DC power supply to output to the power module 130, and the PWM unit 114 receives the voltage command output by the controller 112 and converts it into a switching signal to provide to the power module 130 for driving control of the motor 200. The coordinate conversion unit 116 can convert the three-phase currents (i a , i b , i c ) measured by the current detectors 150a, 150b, 150c into two-axis current projection values to be provided to the position error calculation unit 118 and the controller 112 for calculation.

[0049] Specifically, in motor applications with load torque characteristics at zero speed, different drive methods are switched (for example, from open-loop drive to sensorless closed-loop drive). At this time, it is necessary to estimate the output torque of the motor to perform torque compensation. In addition, in the control of a permanent magnet synchronous motor (or electric motor), in order to obtain characteristics similar to those of a DC motor, Park's Transformation can be used to establish a coordinate system on the motor rotor that rotates synchronously with the rotor, and transform the original three-phase currents (i a , i b , i c ) into direct-axis (d-axis) current and quadrature-axis (q-axis) current representations. In some embodiments, the rotor magnetic field direction is the direct axis (d-axis), and the direction perpendicular to the rotor magnetic field direction is the quadrature axis (q-axis). The above-mentioned coordinate axis transformation method will be further described with reference to the embodiments shown below Figure 2 .

[0050] In applications where the motor 200 is subject to step loads or sudden loads, such as in elevators or treadmills, if the motor drive system 100 does not know the step load or sudden load during the open-loop drive and fails to compensate for the torque when switching to the closed-loop drive during the above-mentioned drive method change, it will ultimately cause jerks in the operation of the motor 200. Taking the elevator application as an example, the moment of releasing the brake is equivalent to applying a step load to the motor 200 at zero speed. Therefore, a large current is used to drive and output torque during the open-loop stage. Through the method of the present disclosure, the torque can be estimated first, and when the drive method is switched to the closed-loop, the torque can be directly compensated to overcome the step load, so that the output torque of the motor 200 is the same as that during the open-loop period, and further, the acceleration of the motor 200 before and after the drive method change is the same, thereby suppressing jerks.

[0051] Figure 2 FIG. is a schematic diagram of coordinate transformation according to an embodiment of the present disclosure. Figure 2 The i a , i b , i c shown in FIG. respectively represent the components of the current in the a, b, and c three phases. In some embodiments, i d is the actual direct-axis current value on an actual coordinate axis, i q is the actual quadrature-axis current value on the actual coordinate axis, is the estimated direct-axis current value on an estimated coordinate axis, is the estimated quadrature-axis current value on the estimated coordinate axis, is the angle difference between the estimated coordinate axis and the actual coordinate axis. In some embodiments, this angle difference can be the estimated quadrature-axis current value and the actual quadrature-axis current value iq The angular difference therebetween. Based on the above conversion method of projecting three-phase current onto the coordinate axes that rotate with the rotor, the operation analysis of the synchronous motor can be simplified, which is conducive to the following description.

[0052] Figure 3 FIG. 5 is a flowchart of a motor driving method 300 according to an embodiment of the present disclosure. In some embodiments, the motor driving method 300 operates in conjunction with the motor driving system 100, but is not limited thereto. For the sake of clarity and convenience of description, the following motor driving method 300 is described in conjunction with Figure 1 and Figure 2 as an example of the embodiment.

[0053] In step S302, during the open-loop drive control stage of the motor 200 and when the motor 200 operates in a steady state, the controller 112 calculates the angular difference between the estimated coordinate axes and the actual coordinate axes of the motor 200 based on the estimated voltage value, the estimated current value, and at least one motor parameter feedback on the estimated coordinate axes of the motor 200. When the motor 200 is under open-loop drive control, the integral value of the speed command is directly used as the rotor position estimated value. Without considering the difference between the actual speed and the speed command to adjust the control amount, only the previously planned voltage / frequency (V / f) or current / frequency (I / f) control amount is output.

[0054] Next, in step S304, the controller 112 calculates the actual current value of the motor 200 on the actual coordinate axes based on the calculated angular difference. In some embodiments, as Figures 1 to 3 shown, through the controller 112 and the position error calculation unit 118, based on the estimated quadrature-axis current obtained by converting the stator current signal feedback by the motor 200 through the coordinate conversion unit 116 in one direction and the angular difference between the actual quadrature-axis current i q in one direction, the actual current value of the motor 200 is calculated. Calculate the actual current value of the motor 200.

[0055] In some embodiments, the angular difference can be calculated by the controller 112 based on an estimated current value of the motor 200. In some embodiments, through the following derivation process, the estimated voltage value, the estimated current value, and at least one motor parameter of the motor 200 are calculated to obtain the angular difference. In some embodiments, the permanent magnet synchronous motor voltage equation can be expressed as:

[0056]

[0057] Where Vd represents the actual direct-axis voltage value on this actual coordinate axis, V q represents the actual quadrature-axis voltage value on this actual coordinate axis, i d represents the aforementioned actual direct-axis current value, and i q represents the aforementioned actual quadrature-axis current value; and when driving the motor 200, for the aforementioned actual direct-axis voltage value V d 、actual quadrature-axis voltage value V q 、actual direct-axis current value i d and actual quadrature-axis current value i q can be adjusted according to different application scenarios. In addition, in some embodiments, the motor parameters of the motor 200 include, for example, the angular velocity value ω e 、rotor coil resistance r s 、direct-axis inductance L d 、quadrature-axis inductance L q 、equivalent stator flux value λ′ of the rotor m etc. The above motor parameters can be transmitted to the controller 112 through any element in the motor 200 that can be used to transmit data, or the above motor parameters can be input into the controller 112 in advance before the motor 200 is started. Further, the voltage equation carried in the above formula (1) can be transposed and arranged as:

[0058]

[0059] Please refer to Figure 2 , in order to perform the conversion between the actual current value and the estimated current value and between the actual voltage value and the estimated voltage value, the following conversion matrix can be used:

[0060]

[0061] Express the actual voltage values and actual current values of the direct axis and the quadrature axis as:

[0062]

[0063] For the convenience of calculation, the conversion matrix can be simplified to be expressed as:

[0064]

[0065] Next, when the motor 200 is operating in a steady state, there is a characteristic And substitute this characteristic and the above formula (3′) and formula (4′) into formula (2) to simplify the parameters of the inductance and voltage drop in the above voltage equation, which includes the angle difference be expressed as:

[0066]

[0067] After transposing and rearranging it and expanding the transformation matrix, we can obtain:

[0068]

[0069] According to the above formula (6), the angular difference between the actual coordinate axis and the estimated coordinate axis can be calculated from the estimated voltage value (including the components on the estimated coordinate axis, that is, the estimated direct-axis voltage value on the estimated coordinate axis and the estimated quadrature-axis voltage value on the estimated coordinate axis ), the estimated current value (including the components on the estimated coordinate axis, that is, the estimated direct-axis current value and the estimated quadrature-axis current value ) and the motor parameters required in the voltage equation of the above formula (1), and after transposing and rearranging, the trigonometric function values related to the angular difference can be expressed as:

[0070]

[0071] And after transposing and rearranging the above equation (7), the angular difference is as follows:

[0072]

[0073] In step S306, the controller 112 calculates an estimated value of the load torque of the motor 200 based on the calculated actual current value. In some embodiments, since when designing the control parameters of the permanent magnet electric motor, the actual direct-axis current value i d is usually controlled to be zero, the calculation of the load torque of the motor is simplified as follows and becomes only related to the actual quadrature-axis current value i q . In other words, in some embodiments, when the actual direct-axis current value i d is controlled to be zero, the torque equation of the permanent magnet electric motor can be simplified as follows:

[0074]

[0075] Therefore, in some embodiments, as Figures 1 to 3 shows, at this time, as long as the conversion relationship between the actual quadrature-axis current value i q and the estimated direct-axis current value and the estimated quadrature-axis current value (as the following formula (9)) is substituted into formula (8), the controller 112 can calculate the estimated load torque value T e (as the following formula (10)), where λ′ m is the flux of the rotor equivalent to the stator, and P is the number of poles of the motor.

[0076]

[0077] After calculating the estimated value T of the load torque of the motor 200 e in step S308, when the open-loop drive control stage of the motor 200 is switched to the closed-loop drive control stage, the controller 112 can compensate for the output torque of the motor 200 according to the calculated estimated value T of the load torque e . In some embodiments, as Figures 1 to 3 shown, the motor 200 can compensate the original output torque of the motor 200 by using the estimated value T of the load torque calculated by the above process through the controller 112 e .

[0078] In some embodiments, the closed-loop drive control of the motor 200 refers to the rotor position and speed, and uses the estimated rotor position for coordinate axis conversion to complete the current closed-loop control. On the other hand, the speed command is adjusted by comparing the speed estimation result with the speed command to perform speed closed-loop control. The common sensorless control technology uses the back electromotive force as the parameter for rotor position estimation. Since the back electromotive force is approximately proportional to the rotational speed of the motor 200, in practice, the motor 200 needs to operate above a certain rotational speed to successfully capture the back electromotive force signal. Therefore, in order to determine the time point when the drive method switches from open loop to closed loop, the current speed command f * can be compared with a speed command threshold ω th , that is, the controller 112 determines that the current speed command f * is greater than the speed command threshold ω th , and then the drive control method of the motor 200 is switched, which will be described in detail later.

[0079] In some embodiments, the foregoing steps S302 to S304 can be executed multiple times to repeat the calculation to obtain multiple actual current values, and the foregoing step S306 can be repeatedly calculated with multiple actual current values to obtain multiple estimated values T of the load torque e . When compensating the output torque of the motor 200 in step S308, considering the numerical changes in multiple calculations, the estimated values T of the load torque that are too large or too small e may all affect the estimated rotational speed. Therefore, an average value can be calculated from the obtained multiple actual current values, and the average value of the actual current value is used in step S308 to calculate the estimated value T of the load torque e as the compensation amount for the output torque of the motor 200, which will be described in detail later.

[0080] As can be seen from the above, when the motor 200 is operating in the open-loop stage, the controller 112 pre-estimates the load torque value Te Calculation, and when the motor 200 switches from the open-loop stage to the closed-loop stage, the calculated load torque estimation value T is utilized e to compensate the output torque of the motor 200, so that the motor 200 operates smoothly when switching between drive control stages.

[0081] In some embodiments, the open-loop stage in the motor drive method 300 can be controlled by the controller 112 according to the voltage / frequency control method (V / f control) or the current / frequency control method (I / f control). As Figure 4A shown, it is a schematic diagram of voltage / frequency (V / f) control experimental data shown according to an embodiment of the present disclosure. In some embodiments, the estimated direct-axis voltage value and the estimated quadrature-axis voltage value of one of them can be set to zero, and the controller 112 calculates and obtains the estimated direct-axis current value and the estimated quadrature-axis current value by setting the value of the other one of the estimated direct-axis voltage value and the estimated quadrature-axis voltage value For example, in some embodiments, as Figure 4A shown, the voltage / frequency control method (V / f control) is that the controller 112 adjusts the estimated quadrature-axis voltage value of the motor 200 according to the required rotational speed, and sets the estimated direct-axis voltage value to zero, and obtains the estimated quadrature-axis current value and the estimated direct-axis current value through circuit feedback. As Figure 4A shown, the simulation data starts to calculate the rotor angle error at about 0.66 seconds and begins to approach the actual rotor angle error. By about 0.8 seconds, they are close, and until about 0.9 seconds, the two curves roughly coincide, indicating that the estimation method of the present disclosure is highly accurate and fast. In different embodiments, the controller 112 can also adjust the estimated direct-axis voltage value of the motor 200 according to the required rotational speed and set the estimated quadrature-axis voltage value to zero, and obtain the estimated quadrature-axis current value and the estimated direct-axis current value

[0082] In some embodiments, the above-mentioned motor 200 can be an interior permanent magnet (IPM) motor, a surface permanent magnet (SPM) motor, or other types of motors that require torque compensation. The present disclosure is not limited thereto.

[0083] In some embodiments, the current / frequency control method (I / f control) adjusts the estimated quadrature-axis voltage value through the controller 112 and the estimated direct-axis voltage value such that one of the estimated quadrature-axis current value and the estimated direct-axis current value is zero, and the other of the estimated quadrature-axis current value and the estimated direct-axis current value is a predetermined target value (not zero). As Figure 4B shown, it is a schematic diagram of current / frequency (I / f) control experimental data according to an embodiment of the present disclosure. An embodiment of the present disclosure adopts the current / frequency control method (I / f control), estimating the quadrature-axis voltage value and the estimated direct-axis voltage value such that the estimated quadrature-axis current value is zero, and making the estimated direct-axis current value about 20 amperes, and calculating the angle difference with this information. As Figure 4B shown by the simulation data, the rotor angle error calculated starting at about 0.66 seconds is close to the actual rotor angle error, and the two curves almost coincide in subsequent times, indicating that the estimation method of the present disclosure is extremely accurate and fast. For example, in the application of an interior permanent magnet (IPM) motor with the current / frequency control method (I / f control), the estimated quadrature-axis current value is zero, and the estimated direct-axis current value can be set to a predetermined target value, so that the above formula (7) can be expressed as:

[0084]

[0085] Therefore, the angle difference

[0086]

[0087] Substituting the above formula (12) into formula (9) gives the actual quadrature-axis current value i q :

[0088]

[0089] For another example, in the application of a surface permanent magnet (SPM) motor with the current / frequency control method (I / f control), the estimated quadrature-axis current value is zero, and because the direct-axis inductance L d of this type of motor is equal to the quadrature-axis inductance L q , the above formula (7) can be further simplified as:

[0090]

[0091] Therefore, Substituting the above equation (15) into equation (9) gives the actual quadrature-axis current value i q :

[0092]

[0093] For another example, in the application of an interior permanent magnet (IPM) motor or a surface permanent magnet (SPM) motor with a voltage / frequency control method (V / f control), since the estimated quadrature-axis current value is not zero, its value must be considered together, and its calculation method is still the same as that of the foregoing embodiments, that is, the angle difference in the above equation (7) is calculated and then substituted into the above equation (9) to calculate the actual quadrature-axis current value i q , and after multiplying by the constant shown in equation (10), the estimated value of the load torque T e is calculated. For the sake of simplicity, the detailed process is not described herein again.

[0094] Please refer to Figure 5A . Figure 5A is an experimental simulation diagram shown according to an embodiment of the present disclosure. Figure 5A The dashed part in Figure 5A is the motor operation curve before torque compensation, and the solid line part is the motor operation curve controlled by the motor drive method 300 provided by the present disclosure. As Figure 5B shown, in the first stage P1 of the motor drive control shown according to the time axis, the motor is first driven and controlled in an open-loop manner (for example: current / frequency control method), and then switched to a closed-loop manner (for example: sensorless) for drive control at an appropriate time; in the second stage P2, the motor is driven and controlled in a closed-loop manner without a shaft detection element and operates at the highest target speed; in the third stage P3, the motor is in an unloaded state (no load). It should be noted that during the process of switching the drive method in the first stage P1, if the existing method is used, the speed shown by the dashed part is not estimated and compensated, which will cause a drastic speed change of the motor; on the contrary, using the motor drive method 300 provided by the present disclosure as shown by the solid line part, the motor can adjust the speed in a relatively smooth and stable manner, and the specific implementation can be described by the following

[0095] Figure 5B is an experimental simulation schematic diagram of the first stage P1 in Figure 5A shown according to an embodiment of the present disclosure. As Figure 5BAs shown, at the moment (around 1.06 seconds) when switching from the current / frequency control method (open-loop drive as described above) to the sensorless (closed-loop drive as described above) drive method, the estimated quadrature-axis current value described above can be used. Calculate the actual quadrature-axis current value i q , and then based on the obtained actual quadrature-axis current value i q Calculate the estimated load torque value T e . Torque compensation is provided in a feed-forward control manner at the moment of or before the switching of the drive control method from open-loop to closed-loop, thereby suppressing the jerks that may be caused by the switching of the drive method.

[0096] The determination of the switching time point of the motor's drive method can use, for example, a speed command threshold ω th as a standard. In this embodiment, it is 4 r / min. When the speed command exceeds this value, it is determined that the rotation speed of the motor 200 is fast enough to successfully capture the back electromotive force signal. In some embodiments of the present disclosure, the speed command threshold ω th can take 5% to 10% of the rated rotation speed of the motor 200. As Figure 5B shown, when the speed command f * constantly rises over time and its value exceeds the speed command threshold ω th , at about 0.9 seconds, the controller 112 controls the switching of the drive method of the motor 200. Figure 5C It is also shown that multiple estimations are performed from about 0.9 seconds to 1.06 seconds on the time axis to obtain multiple values of the estimated load torque T e . Therefore, when the drive method is switched, the controller 112 can use an average value calculated from the values of multiple estimated load torques T e as the compensation value for the output torque of the motor 200, avoiding errors between the estimated rotation speed and the speed command caused by the estimated load torque value T e being too large or too small, and preventing the estimated rotation speed from oscillating up and down and causing jerks. Figure 5B It can be seen that there are still several corrections of the estimated rotation speed after the switching at about 1.06 seconds, but after about 2 seconds, the motor 200 is running smoothly, and at this time, the estimated rotation speed is very close to the speed command.

[0097] Figure 5C is an experimental simulation diagram according to an embodiment of the present disclosure showing the Figure 5B from 0.8 seconds to 1.2 seconds. As Figure 5C shown, in an embodiment of the present disclosure, the motor drive system 100 starts to estimate at the estimation point a at about 0.9 seconds. At this time, the actual quadrature-axis current value i obtained according to the foregoing steps S302 to S304 qApproximately 7.22 amperes, and then continue to obtain multiple estimated points b, c, d, e on the time axis and present them in Table 1 as follows. The actual quadrature-axis current value i obtained through multiple calculations as shown in Table 1 q , where the maximum value within the estimated time is obtained corresponding to the estimated point b, the minimum value within the estimated time is obtained corresponding to the estimated point c, the estimated point d is a sampling point close to the average value during the estimated period, and the estimated point e is executed at the last estimated time before the switch. The aforementioned average value of the estimated time is the actual quadrature-axis current value i obtained through simulation analysis in the time range from 0.91 second to 1.06 seconds, with an estimation performed every 1 microsecond q . The average value after summation is approximately 6.69 amperes.

[0098]

[0099] Table 1

[0100] In some embodiments, the aforementioned estimated time can be estimated proportionally based on the speed command value of the motor 200 and the rated speed of the motor 200. For example Figure 5C As shown in the simulation data, the actual quadrature-axis current value i is estimated in the time interval corresponding to the speed command value of the motor drive system 100 reaching from 1 r / min to 4 r / min q . This estimated time range is, for example, the time corresponding to 1% to 10% of the rated speed of the motor 200 corresponding to the speed command. To avoid the aforementioned estimated value being too large or too small and affecting the subsequent calculation of the estimated value of the load torque T e , the aforementioned average value of the estimated period (i.e., the aforementioned 6.69 amperes) or the value of the final estimated point before the switch (i.e., 7.27 amperes corresponding to the estimated point e) can be substituted into Equation (10) to calculate the estimated value of the load torque T e .

[0101] In summary, the motor drive method provided by the present disclosure can estimate and compensate for the load torque of the motor to solve the problem of the drastic change in the speed of the motor during the switching of the drive method, especially when switching from open-loop drive control to closed-loop drive control (such as drive without a shaft detection element), so as to make the system operate smoothly. In addition, since the motor drive method provided by the present disclosure performs load torque estimation before the drive method is switched (for example, during the open-loop drive stage), no additional transition interval is required when switching the drive method and compensating for the motor torque, which can improve the system efficiency.

[0102] Although this application has been disclosed in the above embodiments, it does not limit this application. Any person skilled in this art can make various changes and modifications without departing from the spirit and scope of this application. Therefore, the protection scope of this application shall be subject to that defined by the appended claims.

Claims

1. A motor driving method, comprising: In an open-loop stage, and when a motor is in a steady-state operation, a controller calculates an angle difference between an estimated coordinate axis and an actual coordinate axis of the motor according to an estimated voltage value, an estimated current value, and at least one motor parameter feedback on the estimated coordinate axis of the motor; The controller calculates an actual current value of the motor on the actual coordinate axis according to the angle difference; The controller calculates an estimated value of the load torque of the motor according to the actual current value; And When the open-loop stage is switched to a closed-loop stage, the controller compensates an output torque of the motor according to the estimated value of the load torque.

2. The motor driving method according to claim 1, wherein, The angle difference can be expressed as: The actual current value can be expressed as: and The estimated value of the load torque can be expressed as: where ω e is the angular rate value, is an estimated direct-axis voltage value on the estimated coordinate axis, is an estimated quadrature-axis voltage value on the estimated coordinate axis, is an estimated direct-axis current value on the estimated coordinate axis, is an estimated quadrature-axis current value on the estimated coordinate axis, L d is the direct-axis inductance of the motor, L q is the quadrature-axis inductance of the motor, λ′ m is the rotor equivalent to the stator flux and P is the number of poles of the motor.

3. The motor driving method according to claim 2, further comprising: Setting one of the estimated direct-axis voltage value and the estimated quadrature-axis voltage value to zero; and The controller obtains the estimated direct-axis current value and the estimated quadrature-axis current value by setting the other of the estimated direct-axis voltage value and the estimated quadrature-axis voltage value.

4. The motor driving method according to claim 2, further comprising: Adjusting the estimated quadrature-axis voltage value and the estimated direct-axis voltage value so that one of the estimated quadrature-axis current value and the estimated direct-axis current value is zero.

5. The motor driving method according to claim 2, wherein, The motor is a surface-mounted permanent magnet motor, and the direct-axis inductance is equal to the quadrature-axis inductance. The relationship between the angle difference, the estimated direct-axis voltage value, and the estimated direct-axis current value can be expressed as: And the actual quadrature-axis current value can be expressed as:

6. The motor driving method according to claim 1, wherein, The at least one motor parameter includes an angular rate value ω e , a rotor coil wire resistance r s and a quadrature-axis inductance L q in combination, or the angular rate value ω e , the rotor coil wire resistance r s , the quadrature-axis inductance L q , a direct-axis inductance L d and an equivalent stator flux value λ′ of a rotor m in combination.

7. The motor driving method according to claim 1 further includes: Before the open-loop stage is switched to the closed-loop stage, the controller determines that a speed command input to the motor is greater than a speed command threshold, where the speed command threshold is 5% to 10% of the rated speed of the motor.

8. The motor driving method according to claim 1, wherein, The steps of calculating the angle difference and the actual current value of the motor can be repeatedly executed to obtain multiple actual current values, and the motor driving method further includes: calculating the estimated value of the load torque according to an average value of the multiple actual current values obtained during an estimation period.

9. The motor driving method according to claim 8, wherein, The estimation period is determined by the time when a value of a speed command of the motor reaches, and the value of the speed command is between 1% and 10% of the rated speed of the motor.

10. The motor driving method according to claim 8, wherein, The motor driving method further includes: calculating the estimated value of the load torque according to the actual current value obtained at an end point of the estimation period.

11. The motor driving method according to claim 1, wherein, During the open-loop stage, the motor is subjected to a step load or a sudden load addition, and the motor driving method further includes: compensating the output torque of the motor with the estimated value of the load torque and the step load or the sudden load addition.

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