Motor drive control system and method

Abstract

A motor drive control system includes an actuator configured to generate a rotational force by driving an applied current, a current provider configured to provide the current to the actuator while repeatedly turning on and off the current with a preset period and duty ratio, and a controller configured to estimate a rotational position or a rotational speed of the actuator in a portion in which the current of the current provider is turned on or off, and to control the current provider to follow a speed command based on the estimated rotational position or rotational speed.

Description

Technical Field

[0001] This disclosure relates to an electric motor drive control system and method, and more specifically, to a system and method for estimating the position and speed of an electric motor when the current applied to the motor is controlled to be switched on and off. Background Technology

[0002] In fuel cell electric vehicles, under operating conditions where cooling performance is reduced, such as when the vehicle is driven at high output from the fuel cell stack (e.g., when the vehicle is driving uphill in hot weather), the operating temperature of the fuel cell stack rises, and the moisture content of the supplied fuel decreases, causing the fuel cell stack to dry out and its operating voltage to drop. In this situation, the calorific value of the fuel cell stack increases due to the decrease in the operating voltage, creating a negative feedback loop that further increases the operating temperature of the fuel cell.

[0003] Recently, to prevent the negative feedback loop of the fuel cell from rising operating temperature, a control technique for increasing the relative humidity at the air electrode (cathode) by increasing the pressure of the air supplied to the air electrode has been applied to vehicle fuel cell systems. Therefore, it is necessary to further increase the compression ratio of the air compressor used to supply air to the air electrode of the fuel cell stack.

[0004] Because there is a need to further increase the compression ratio of the air supplied to the air electrode of the fuel cell stack, an air compressor has been designed to achieve maximum efficiency at the maximum pressure operating point while further increasing the compression ratio of the air compressor. The problem with this design is that the compressor efficiency increases in the section with high flow and high compression ratio, but decreases in the section with relatively low flow. Therefore, when the vehicle is driving in urban areas (e.g., under parking and driving conditions), the power consumption of the air compressor increases in the low-flow section, which is the main driving area, adversely affecting the vehicle's fuel efficiency.

[0005] Specifically, due to the difference in motor drive speed between the low-flow and high-flow sections, pressurized air compressors with a higher air compression ratio than conventional ambient pressure blowers are disadvantageous in improving compressor efficiency because the drive speed of the installed motor needs to be further increased. That is, pressurized air compressors reduce motor inductance to ensure sufficient voltage margin in areas where vehicles travel at high speeds as the motor's revolutions per minute (RPM) increases, and the three-phase ripple current increases, thus reducing motor / inverter efficiency due to the reduced motor inductance. Particularly in the low-flow section requiring relatively low output, the three-phase current is low and the current ripple is increased, resulting in a significant decrease in efficiency. That is, the three-phase ripple current is a secondary component and does not contribute to motor torque; therefore, in the section with low flow and low motor torque, the amount of three-phase ripple current is relatively high compared to the three-phase sinusoidal current component, thus reducing motor / inverter efficiency compared to the section with high output.

[0006] Air foil bearings are used to rotate the electric motor of an air compressor at high speeds to maintain a lifting state. Therefore, when the air foil bearing continuously drives the electric motor at a speed equal to or less than the reference speed used to maintain the lifting state, there is a problem of damage to the air foil bearing due to friction between the air foil bearing and the rotating shaft of the electric motor. Therefore, to prevent damage to the air foil bearing, the air compressor has a minimum drive speed limit. Consequently, when the vehicle needs to be driven at a low fuel cell output, by driving the air compressor at the maximum drive speed or higher, air is also unnecessarily and excessively supplied, thus reducing the efficiency of the fuel cell system.

[0007] Conventionally, a strategy to improve the drive efficiency of the air compressor is employed by repeatedly performing pulse width modulation (PWM) to turn the air compressor on and off in the low-power driven portion of the vehicle. Specifically, position sensors, such as Hall effect sensors, are applied to the electric motor included in the air compressor, and thus the motor is turned on / off by identifying its rotational speed and position, even when it is disconnected.

[0008] However, in the case of a sensorless motor without a position sensor, the motor's rotational speed and position are estimated by estimating the back electromotive force (EMF) when controlling the current applied to the motor. However, the problem with sensorless motors is that it's impossible to identify the motor's rotational speed or position because it's impossible to estimate the current and back EMF based on this information when the PWM is controlled to be off. Therefore, the problem arises from excessive oscillation of the current applied to the motor, and the motor's control becomes unstable.

[0009] It should be understood that the above description in the prior art is only for the purpose of facilitating an understanding of the background of this disclosure and should not be considered as prior art known to those skilled in the art. Summary of the Invention

[0010] Therefore, this disclosure provides a system and method for estimating the rotational speed or rotational position of an electric motor, even in portions where the current applied to the motor is disconnected when the current is controlled to be switched on and off.

[0011] According to one aspect of this disclosure, an electric motor drive control system includes: an actuator configured to generate rotational force by being driven using a received current; a current provider configured to supply current to the actuator while repeatedly switching the current on and off at a preset period and duty cycle; and a controller configured to estimate the rotational position or rotational speed of the actuator during the portion of the current supply being switched on or off, and to control the current provider to follow a speed command based on the estimated rotational position or rotational speed.

[0012] The motor drive control system may also include a sensor configured to sense the current or voltage applied from the current provider to the actuator, wherein the controller may use the current or voltage sensed by the sensor to estimate the back electromotive force generated in the actuator, and may estimate the rotational position or rotational speed of the actuator based on the back electromotive force in the portion of the current provider that is switched on.

[0013] The controller can estimate the rotational position or speed of the actuator based on a motion equation in which the rotational force generated by driving the actuator is assumed to be 0 in the portion where the current from the current provider is disconnected.

[0014] The controller can use the following equation to estimate the actuator's rotational speed in the section where the current supply is disconnected:

[0015]

[0016] Where ω n It is the current rotational speed, ω n-1Where is the previous rotational speed, B is the damping coefficient of the actuator, J is the moment of inertia coefficient of the actuator, and T is the torque coefficient. m Δt is the load torque of the actuator, and Δt is the estimated period of rotational speed.

[0017] The load torque of the actuator can be estimated as a quadratic function of the actuator's rotational speed using the following equation:

[0018]

[0019] Where α is a second-order coefficient and β is a first-order coefficient.

[0020] The actuator can be an electric motor installed in the pneumatic or hydraulic part, and the second-order coefficient α and the first-order coefficient β can be pre-mapped or preset according to the pressure of the pneumatic or hydraulic part.

[0021] The current provider can be a pulse width modulation (PWM) inverter configured to control the current in the three phases (U phase, V phase and W phase) of the actuator.

[0022] The controller can estimate the actuator's rotational position or speed during the pulse width modulation (PWM) cycle in the portion of the current supply that is disconnected.

[0023] The controller may include a speed controller configured to generate a current command based on a speed command and an estimated rotational speed; and a current controller configured to generate a voltage command for the current provider based on a current command and an estimated rotational position.

[0024] According to another aspect of this disclosure, a motor drive control method is provided, the method comprising the steps of: supplying current to an actuator from a current provider, the actuator being configured to generate rotational force from the current provider while repeatedly switching the current on and off at a preset period and duty cycle; estimating the rotational position or rotational speed of the actuator during the portion of the current supply being switched on and off by a controller; and controlling the current provider based on the estimated rotational position or rotational speed to follow a speed command.

[0025] The motor drive control method may also include: checking whether the part is the part where the current supply is turned on or the part where the current is turned off before estimating the rotational position or rotational speed.

[0026] During the inspection, when the current section is the part where the current supply is disconnected, the steps for estimating the rotational position or rotational speed may include: estimating the rotational position or rotational speed of the actuator based on the equation of motion, in which the rotational force generated by driving the actuator is assumed to be 0.

[0027] The actuator may be an electric motor installed in a pneumatic or hydraulic unit, and the step of estimating the rotational position or rotational speed may include: estimating the rotational position or rotational speed of the actuator using the load torque received by the actuator from the pneumatic or hydraulic unit based on a previously estimated rotational speed of the actuator.

[0028] The steps of providing current to the actuator while repeatedly turning the current on and off may include: controlling the pulse width modulation (PWM) of the current in the three phases (U phase, V phase and W phase) of the actuator.

[0029] The steps for estimating the rotational position or rotational speed may include estimating the rotational position or rotational speed of the actuator during a pulse width modulation (PWM) cycle in the portion of the current supply where the current is disconnected. Attached Figure Description

[0030] The above and other objects, features and advantages of this disclosure will become clearer from the following detailed description taken in conjunction with the accompanying drawings, in which:

[0031] Figure 1 This is a diagram illustrating the structure of a motor drive control system according to an embodiment of the present invention;

[0032] Figure 2A and Figure 2B It is a graph showing the estimated rotational speed and estimated rotational position according to an embodiment of the present disclosure;

[0033] Figure 3 This is a diagram illustrating the configuration of an air supply system for a fuel cell including an actuator according to an embodiment of the present disclosure;

[0034] Figure 4 It is a graph of the load torque at each rotational speed of the actuator according to an embodiment of the present disclosure;

[0035] Figure 5 It is a graph of the primary and secondary coefficients according to embodiments of the present disclosure;

[0036] Figure 6 This is a flowchart illustrating a motor drive control method according to an embodiment of the present disclosure; and

[0037] Figure 7 It is a set of graphs showing the rotational speed of an electric motor following a speed command according to the prior art and this disclosure. Detailed Implementation

[0038] It should be understood that the term "vehicle" or "of a vehicle" or other similar terms as used herein generally include motor vehicles, such as passenger cars (including sport utility vehicles (SUVs), buses, trucks, and various commercial vehicles), watercraft including various boats and vessels, aircraft, etc., and includes hybrid vehicles, electric vehicles, plug-in hybrid electric vehicles, hydrogen-powered vehicles, and other alternative fuel vehicles (e.g., fuels derived from resources other than petroleum). As referred to herein, a hybrid vehicle is a vehicle having two or more power sources, such as both a gasoline-powered vehicle and an electric-powered vehicle.

[0039] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit this disclosure. As used herein, unless the context clearly indicates otherwise, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well. It should also be understood that the terms “comprises” and / or “comprising,” as used in this specification, designate the presence of stated features, integers, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or combinations thereof. As used herein, the term “and / or” includes any and all combinations of one or more associated listed items. Throughout this specification, unless explicitly stated to the contrary, the word “comprise” and variations such as “comprises” or “comprising” are to be understood as implying inclusion of the stated elements, but not excluding any other elements. Additionally, the terms “unit,” “-er,” “-or,” and “module” described in the specification refer to a unit for performing at least one function and operation and may be implemented by hardware components or software components and combinations thereof.

[0040] Furthermore, the control logic of this disclosure may be embodied on a non-transitory computer-readable medium containing executable program instructions that are executed by a processor, controller, etc. Examples of computer-readable media include, but are not limited to, ROM, RAM, optical disc (CD)-ROM, magnetic tape, floppy disk, flash drive, smart card, and optical data storage device. The computer-readable medium may also be distributed across a network-coupled computer system, such that the computer-readable medium is stored and executed in a distributed manner, for example, by a telematics server or a controller area network (CAN).

[0041] The specific structural and functional descriptions of the embodiments disclosed in this specification are for the purpose of describing particular embodiments only. Embodiments of this disclosure are formed in many different forms and should not be construed as limited to the embodiments set forth herein.

[0042] Because this disclosure allows for various changes and numerous embodiments, specific embodiments will be shown in the accompanying drawings and described in detail in the written description. However, this is not intended to limit this disclosure to a particular mode of practice, and it should be understood that all variations, equivalents, and alternatives without departing from the spirit and scope of this disclosure are covered herein.

[0043] Terms such as “first” and “second” are used herein only to describe various constituent elements, but these constituent elements are not limited by these terms. The terms are used only for the purpose of distinguishing one constituent element from another. For example, without departing from the teachings of this disclosure, a first element may be referred to as a second element, and a second element may be referred to as a first element.

[0044] It should be understood that when an element such as a layer, region, or substrate is referred to as "on another element," "connected to," or "coupled to" another element, it can be directly on, connected to, or coupled to another element. Conversely, when an element is referred to as "directly on another element or layer," "directly connected to," or "directly coupled to" another element or layer, there is no intermediate element or layer. Other terms used to describe the relationship between elements or layers should be interpreted in a similar manner, such as "between" versus "directly between," "adjacent," "directly adjacent," etc.

[0045] Unless otherwise defined, all terms used herein, including technical and scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains. It should also be understood that terms such as those defined in common dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant field, and should not be interpreted in an idealized or overly formal sense unless explicitly defined herein.

[0046] In the following, the present disclosure will be described in detail by referring to the accompanying drawings, which illustrate exemplary embodiments of the present disclosure. The same reference numerals in the drawings denote the same elements.

[0047] Figure 1 This is a diagram illustrating the configuration of an electric motor drive control system according to an embodiment of the present disclosure. Figure 2A and Figure 2B It is a graph showing the estimated rotational speed and estimated rotational position according to an embodiment of the present disclosure.

[0048] refer to Figure 1 and Figure 2A-2BAn electric motor drive control system according to an embodiment of the present disclosure may include: an actuator 10 for generating rotational force by driving received current; a current provider 20 for providing current to be applied to the actuator 10 while repeatedly switching the current on and off at a preset period and duty cycle; and a controller 30 for estimating the rotational position or rotational speed of the actuator 10 in one or more portions of the current being switched on and off in the current provider 20, and controlling the current provider 20 to follow a speed command based on the estimated rotational position or rotational speed.

[0049] The controller 30 according to an embodiment of the present disclosure may be implemented using a non-volatile memory (not shown) and a processor (not shown). The non-volatile memory is configured to store an algorithm configured to control the operation of various components of the vehicle or data for reproducing software commands of the algorithm. The processor is configured to use the data stored in the respective memory to perform operations described below. Here, the memory and processor may be implemented as separate chips. Alternatively, the memory and processor may be implemented as a single integrated chip. The processor may be configured as one or more processors.

[0050] The actuator 10 may be an electric motor driven by current applied from the current provider 20, and may generate rotational force when driven. That is, when the electric motor is driven, rotational torque may be generated at the output shaft.

[0051] The current provider 20 can perform control to switch the current on and off during the low-speed rotation of the actuator 10. This increases the driving efficiency for driving the actuator 10. For example, the cycle and duty cycle for controlling the current to switch on and off can be preset, for example, according to a speed command.

[0052] The cycle and duty cycle can be preset to minimize the power consumption for driving actuator 10. That is, when current provider 20 performs control to repeatedly turn the drive current of actuator 10 on and off, the cycle and duty cycle of the repeated on / off control can be set to minimize the power consumption of actuator 10 at each driving speed, as well as the switching losses and three-phase current ripple of current provider 20. The corresponding values ​​can be determined experimentally, and the power consumption at each driving speed can be preset and stored in a map.

[0053] According to another embodiment of this disclosure, the current provider 20 can continuously supply power to the portion of the actuator 10 that is rotating at high speed.

[0054] The controller 30 can control the current applied by the current provider 20. Specifically, the controller 30 can control the current provider 20 to follow speed commands received from a separate higher controller 30. The controller 30 can control the current applied by the current provider 20 based on the rotational position or rotational speed of the actuator 10.

[0055] Here, the rotational position or rotational speed of the actuator 10 may refer to the rotational position or rotational speed of the output shaft or rotor of the actuator 10.

[0056] The controller 30 can estimate the rotational position or speed of the actuator 10 during one or more periods when the current to the current provider 20 is switched on and off. As described below, different corresponding methods can be used to estimate the rotational position or speed of the actuator 10 during one or more periods when the current is switched on and off.

[0057] Conventionally, the rotational position or speed of actuator 10 can be directly sensed using Hall sensors, encoders, etc. However, according to this disclosure, the rotational position or speed of actuator 10 can be estimated when such sensors are absent or malfunction.

[0058] Therefore, even without sensors for sensing the motor's rotational speed and position, it is possible to estimate the motor's rotational speed and position during the portion of the motor where the current is interrupted. This allows for a reduction in motor cost while simultaneously improving motor operating efficiency and the stability of motor control.

[0059] The motor drive control system may also include a sensor 40 for sensing the current applied from the current provider 20 to the actuator 10, and the controller 30 may use the current sensed by the sensor 40 to estimate the back electromotive force generated in the actuator 10, and may estimate the rotational position or rotational speed of the actuator 10 based on the back electromotive force estimated in the portion of the current provider 20 where the current is turned on (where the PWM buffer is enabled).

[0060] Sensor 40 may be a current sensor and may sense the current applied from current provider 20 to actuator 10. In particular, as described below, sensor 40 may sense the three-phase current applied from current provider 20 and may sense the current of two or more of the three phases.

[0061] The controller 30 can estimate the back electromotive force of the actuator 10 during the portion of the current supply 20 when the current is turned on, and can estimate the rotational position or rotational speed of the actuator 10 based on the estimated back electromotive force.

[0062] According to an embodiment, in the high-speed rotating portion of the motor, the back electromotive force generated from the stator coils in each phase when the motor rotates, as well as information about the rotor position and the time of current conversion in each phase using the zero-crossing point (hereinafter referred to as ZC) of the phase back electromotive force, can be estimated.

[0063] The back electromotive force (EMF) can be obtained by measuring the voltage at the three-phase terminals. The average value of the back EMF can be used to calculate the neutral point, and the ZC point where the neutral point and the back EMF intersect can be obtained.

[0064] Because the ZC point is generated six times in each electric rotation (360°) of the BLDC motor, the AC point is based on the position detection at 60° intervals. Therefore, the algorithm that uses the ZC point to detect the position is called the ZC algorithm.

[0065] According to another embodiment, in the section where the motor rotates at a low speed, when the speed of the motor is equal to or less than a predetermined speed, the controller can control the current provider 20 (inverter) to apply a zero (0) vector to the motor.

[0066] The controller can use the current generated when a zero vector is applied to estimate the position of the motor's rotor. In this case, after applying the zero vector, the controller can use the phase value of the current sensed by sensor 40 to estimate the position of the motor's rotor. That is, the controller can estimate the position of the motor's rotor, which corresponds to the phase of the sensed current.

[0067] The controller 30 can estimate the rotational position or rotational speed of the actuator 10 based on a motion equation in which the rotational force generated by driving the actuator 10 is assumed to be 0 in the part where the current supply 20 is disconnected (the part where the PWM buffer is enabled as False).

[0068] Specifically, the controller 30 can use the following equation to estimate the rotational speed of the actuator 10 in the portion of the current supply 20 where the current is disconnected.

[0069]

[0070] Here, ω n It is the current rotational speed, ω n-1 Where is the previous rotational speed, B is the damping coefficient of actuator 10, J is the moment of inertia coefficient of the actuator, and T is the torque coefficient of the actuator. m Δt is the load torque of the actuator, and Δt is the estimated period of rotational speed.

[0071] Furthermore, the rotational speed of actuator 10 can satisfy the following equation of motion.

[0072]

[0073] Here, T e It is the electrical rotational torque of actuator 10, and in the part where the current is disconnected, the torque of actuator 10 is 0, therefore T e It can be assumed to be 0.

[0074]

[0075] The following equations are used to summarize.

[0076]

[0077] Figure 3 This is a diagram illustrating the configuration of an air supply system for a fuel cell, including an actuator 10, according to an embodiment of the present disclosure. Figure 4 It is a graph of the load torque for each rotational speed of the actuator 10 according to an embodiment of the present disclosure. Figure 5 This is a graph of the primary and secondary coefficients according to embodiments of the present disclosure.

[0078] Further reference Figures 3 to 5 The load torque of actuator 10 can be estimated as a quadratic function of the rotational speed of actuator 10 using the following equation.

[0079]

[0080] Here, α is a second-order coefficient, and β is a first-order coefficient.

[0081] Specifically, the actuator 10 may be an electric motor installed in a pneumatic or hydraulic unit, and the second-order coefficient α and the first-order coefficient β may be pre-mapped or preset according to the pressure of the pneumatic or hydraulic unit.

[0082] According to one embodiment, such as Figure 3 As shown, actuator 10 may be an air compressor included in an air supply system for supplying air to fuel cell 50. When the output shaft of actuator 10 is positioned and driven in the air, actuator 10 can rotate to compress air.

[0083] The air supply system may include a pressure regulating valve 60, which regulates the pressure of the air supplied to the fuel cell 50 by adjusting the opening degree of the pressure regulating valve 60. As the air pressure changes, the coefficients α and β of the rotational speed of the actuator 10 can vary.

[0084] The load torque coefficients α and β can be adjustment coefficients set to appropriate values ​​according to the load model. When the specifications of the air compressor serving as actuator 10 are determined and the pressure range at the outlet of the air compressor is determined, the coefficients α and β can be adjusted and applied according to the pressure supplied by the air compressor.

[0085] According to another embodiment, actuator 10 may be an electric motor for a coolant pump used to circulate coolant to cool fuel cell 50. Actuator 10 can circulate coolant when the output shaft of actuator 10 is positioned and driven in the coolant.

[0086] The current provider 20 may be a pulse width modulation (PWM) inverter used to control the current in the three phases (U phase, V phase and W phase) of the actuator 10.

[0087] The controller 30 can estimate the rotational position or speed of the actuator 10 during the pulse width modulation (PWM) cycle in the portion of the current supply 20 where the current is disconnected.

[0088] In other words, the period Δt for the controller 30 to estimate the rotational speed can be set to be the same as the pulse width modulation (PWM) period.

[0089] The controller 30 may include a speed controller 31 for generating a current command based on a speed command and an estimated rotational speed; and a current controller 32 for estimating a voltage command for the current provider 20 based on the current command and an estimated rotational position.

[0090] The speed controller 31 can generate current commands (Id*, Iq*) to follow the speed commands received from the high-level controller 30, and can perform feedback control to receive feedback of the estimated rotational speed.

[0091] The current controller 32 can generate voltage commands (Vd*, Vq*) for the current provider 20 based on current commands (Id*, Iq*) received from the speed controller 31, and can also generate voltage commands (Vd*, Vq*) based on the estimated rotational position. Additionally, the current controller 32 can perform feedback control to receive feedback from the current sensed by the sensor 40.

[0092] A coordinate converter may be further provided between the current controller 32 and the current provider 20. The current controller 32 may receive the current target values ​​(Id*, Iq*) in the synchronous coordinate system from the speed controller 31, and may transmit the voltage target values ​​(Vd*, Vq*) in the synchronous coordinate system to the coordinate converter, which may convert the voltage target values ​​in the synchronous coordinate system into three-phase voltage target values ​​(U-phase, V-phase, and W-phase) and provide them to the current provider 20.

[0093] The current provider 20 can provide three-phase drive current to the actuator 10 based on the received three-phase voltage target values ​​(U phase, V phase and W phase) through the PWM output duty cycle of the three-phase switching circuit.

[0094] Figure 6 This is a flowchart illustrating a motor drive control method according to an embodiment of the present disclosure.

[0095] Further reference Figure 6 The motor drive control method according to embodiments of the present disclosure may include providing a current applied to an actuator 10 to generate a rotational force from a current provider 20, while repeatedly switching the current on and off at a preset period and duty cycle (S100), estimating the rotational position or rotational speed of the actuator 10 during one or more portions of the current being switched on and off in the current provider 20 (S300 and S400), and controlling the current provider 20 to follow a speed command based on the estimated rotational position or rotational speed (S400).

[0096] The motor drive control method may also include checking whether the current section is the part where the current supply 20 is turned on or the part where the current supply is turned off before estimating the rotational position or rotational speed (S300) (S200).

[0097] In the inspection step (S200), when the current part is the part where the current of the current provider 20 is disconnected, the rotational position or rotational speed of the actuator 10 can be estimated based on the motion equation. In the motion equation, when estimating the rotational position or rotational speed (S300 and S400), the rotational force generated by driving the actuator 10 is assumed to be 0 (S300).

[0098] In the inspection step (S200), when the current portion is the portion where the current supply 20 is turned on, the back electromotive force generated by the actuator 10 can be estimated using the current or voltage sensed by the sensor 40, and when estimating the rotational position or rotational speed (S300 and S400), the rotational position or rotational speed of the actuator 10 can be estimated based on the back electromotive force estimated in the portion where the current supply 20 is turned on (S400).

[0099] The actuator 10 may be an electric motor installed in the pneumatic or hydraulic part, and when estimating the rotational position or rotational speed (S300 and S400), the rotational position or rotational speed of the actuator 10 may be estimated by using the load torque received by the actuator 10 from the pneumatic or hydraulic part based on the pre-estimated rotational speed of the actuator 10 (S400).

[0100] While providing current to actuator 10 and repeatedly switching the current on and off, the inverter can control the pulse width modulation (PWM) of the current in the three phases (U phase, V phase and W phase) of actuator 10.

[0101] When estimating the rotational position or rotational speed (S300 and S400), the rotational position or rotational speed of the actuator 10 can be estimated at the pulse width modulation (PWM) cycle in the portion where the current from the current provider 20 is disconnected (S300).

[0102] Figure 7 This is a set of graphs showing the rotational speed of an electric motor following a speed command according to the prior art and the present disclosure. In particular, the first graph shows the rotational speed of an electric motor following a speed command according to the prior art, and the second graph shows the rotational speed of an electric motor following a speed command according to the present disclosure.

[0103] Further reference Figure 7 According to the prior art, it can be seen that in the part where the motor rotates at a constant speed, the rotational speed of the motor varies, and in particular, it can be seen that in the part where the motor rotates at a varying speed and the rotational speed follows a speed command, the rotational speed of the motor varies significantly.

[0104] On the contrary, according to this disclosure, it can be seen that the rotational speed of the electric motor steadily follows the speed command.

[0105] The electric motor drive control system and method according to this disclosure can achieve the effect of estimating the rotational speed and rotational position of the electric motor in the portion where the current is disconnected, without the need for sensors to sense the rotational speed and rotational position of the electric motor.

[0106] Therefore, it is possible to reduce the cost of electric motors while simultaneously improving their operating efficiency and the stability of motor control.

[0107] Although preferred embodiments of the present disclosure have been disclosed for illustrative purposes, those skilled in the art will understand that various modifications, additions, and substitutions are possible without departing from the scope and spirit of the present disclosure as disclosed in the appended claims.

Claims

1. A motor drive control system, comprising: An actuator configured to generate rotational force by being driven by a received current; A current provider is configured to supply current to the actuator while repeatedly switching the current on and off with a preset period and duty cycle. as well as A controller is configured to estimate the rotational position or speed of the actuator during the on and off portions of the current supply, and to control the current supply to follow a speed command based on the estimated rotational position or speed. The controller estimates the actuator's rotational speed during the portion of the current supply that is disconnected, based on the actuator's previous rotational speed, damping coefficient, moment of inertia coefficient, load torque, and estimated rotational speed period.

2. The electric motor drive control system according to claim 1, further comprising: A sensor is configured to sense the current or voltage applied from the current provider to the actuator. The controller uses the current or voltage sensed by the sensor to estimate the back electromotive force generated in the actuator, and estimates the rotational position or rotational speed of the actuator based on the back electromotive force in the portion of the current provider that is switched on.

3. The motor drive control system according to claim 1, wherein the controller estimates the rotational position or rotational speed of the actuator based on a motion equation, wherein in the portion of the motion equation in which the current supply is disconnected, the rotational force generated by driving the actuator is assumed to be 0.

4. The electric motor drive control system of claim 3, wherein the controller uses the following equation to estimate the rotational speed of the actuator in the portion of the current supply where the current is disconnected: in It is the current rotation speed. Where is the previous rotational speed, B is the damping coefficient of the actuator, and J is the moment of inertia coefficient of the actuator. It is the load torque of the actuator, and It is the estimated period of rotational speed.

5. The electric motor drive control system of claim 4, wherein the load torque of the actuator is estimated as a quadratic function of the rotational speed of the actuator using the following equation: Where α is a second-order coefficient and β is a first-order coefficient.

6. The electric motor drive control system according to claim 5, wherein the actuator is an electric motor installed in a pneumatic or hydraulic unit, and the second-order coefficient α and the first-order coefficient β are pre-mapped or preset according to the pressure of the pneumatic or hydraulic unit.

7. The motor drive control system according to claim 1, wherein the current provider is a pulse width modulation inverter configured to control the current in three phases of the actuator, the three phases being U phase, V phase and W phase.

8. The motor drive control system of claim 7, wherein the controller estimates the rotational position or rotational speed of the actuator at a pulse width modulation period in the portion of the current provider where the current is disconnected.

9. The motor drive control system of claim 1, wherein the controller comprises a speed controller configured to generate a current command based on the speed command and the estimated rotational speed; and a current controller configured to generate a voltage command for the current provider based on the current command and the estimated rotational position.

10. A method for controlling a motor drive, comprising the following steps: A current is supplied to an actuator by a current provider, the actuator being configured to generate rotational force from the current provider while repeatedly switching the current on and off with a preset period and duty cycle; The controller estimates the rotational position or speed of the actuator during the portion of the current supply that is switched on and off; as well as The controller controls the current provider to follow the speed command based on the estimated rotational position or rotational speed; The controller estimates the actuator's rotational speed during the portion of the current supply that is disconnected, based on the actuator's previous rotational speed, damping coefficient, moment of inertia coefficient, load torque, and estimated rotational speed period.

11. The motor drive control method according to claim 10 further includes the following steps: Before estimating the rotational position or the rotational speed, check whether the portion is the part where the current supply is turned on or the part where the current is turned off.

12. The electric motor drive control method according to claim 11, wherein, In the inspection, when the portion is the portion where the current to the current provider is disconnected, the step of estimating the rotational position or the rotational speed includes: estimating the rotational position or the rotational speed of the actuator based on a motion equation, in which the rotational force generated by driving the actuator is assumed to be 0.

13. The electric motor drive control method according to claim 12, wherein: The actuator is an electric motor installed in a pneumatic or hydraulic unit; as well as The step of estimating the rotational position or the rotational speed includes: estimating the rotational position or the rotational speed of the actuator using the load torque received by the actuator from the pneumatic part or the hydraulic part, based on a previously estimated rotational speed of the actuator.

14. The electric motor drive control method according to claim 10, wherein, The step of providing the current applied to the actuator while repeatedly turning the current on and off includes: controlling the pulse width modulation of the current in three phases of the actuator, the three phases being U phase, V phase, and W phase.

15. The electric motor drive control method according to claim 14, wherein the step of estimating the rotational position or the rotational speed comprises: The rotational position or rotational speed of the actuator is estimated at the pulse width modulation period in the portion of the current supply where the current is disconnected.

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