Pulse motor control

Abstract

Various methods, controllers, and motor systems are described that facilitate pulse control of a motor to increase the energy efficiency of the motor when conditions permit. Selected transitions between pulse output levels are controlled to provide a cubic or higher order transition torque profile. In various embodiments, a cubic, quintic, or higher order transition profile is used. Using such a transition torque profile can improve the NVH characteristics of the motor while providing energy saving pulse transitions.

Description

[0001] Cross-references to related applications

[0002] This application claims priority to U.S. Application No. 16 / 866,917, filed May 5, 2020, which is incorporated herein by reference in its entirety. Background Technology

[0003] This application generally relates to motor control. More specifically, control schemes and controller designs are described that smoothly apply pulses to the operation of the motor during selected operating conditions to facilitate motor operation in a more energy-efficient manner.

[0004] As used in this article, the term "electric motor" is intended to be understood broadly to refer to both electric motors and generators. Electric motors and generators are very similar in structure. Both include a rotor and a stator with multiple poles. When an electric motor operates as a motor, it converts electrical energy into mechanical energy. When operating as a generator, it converts mechanical energy into electrical energy.

[0005] Electric motors and generators are used in a wide variety of applications and under a wide range of operating conditions. Typically, many modern electric motors have relatively high energy conversion efficiencies. However, the energy conversion efficiency of most motors can vary significantly depending on their operating load. In many applications, motors need to operate under a variety of different operating load conditions. As a result, many motors operate at or near their maximum efficiency level at certain times, while at other times they operate at lower efficiency levels.

[0006] Battery-powered electric vehicles provide a good example of an electric motor operating over a wide range of efficiency levels. During a typical drive cycle, an electric vehicle will accelerate, cruise, decelerate, brake, corner, etc. Within certain rotor speed and / or torque ranges, the motor operates at or near its most efficient operating point (i.e., its "sweet spot"). Outside these ranges, the motor operates less efficiently. As drive conditions change, the motor will shift between high and low efficiency levels depending on the rotor speed and / or torque demands. If the motor can operate in its high-efficiency operating region for a larger proportion of drive cycles, the vehicle's range will increase for a given battery charge level. Since the limited range of battery-powered electric vehicles is a major commercial barrier to their use, extending the vehicle's operating range is highly advantageous.

[0007] Although conventional motors generally have good energy conversion efficiency, efforts continue to be made to further improve energy conversion efficiency over a wider range of operating conditions. Summary of the Invention

[0008] Various methods, controllers, and motor systems are described to facilitate pulsed control of motors (e.g., electric motors and generators) to improve the energy conversion efficiency of the motor when conditions permit. More specifically, under selected operating conditions, the motor is intermittently driven (pulsed) to deliver a desired average output. The pulsed operation of the motor causes the motor output to alternate between a first output level above the motor's desired average output and a second output level below the desired average output. The first and second output levels are selected such that at least one of the motor and the system including the motor has a higher energy conversion efficiency during the pulsed operation than the motor would have been operating at a third output level required for continuous driving to deliver the desired average output. In many embodiments, the second output level is zero torque (or substantially zero torque).

[0009] Control at least some transitions between control pulse output levels to provide a transition profile of third or higher order. In various implementations, third, fifth, or even higher order transition profiles are used. Using such transition profiles can improve the NVH characteristics of the motor and / or provide other benefits.

[0010] In various embodiments, different transition curves can be used for specific motors under different operating conditions. For example, different transition curves can be optionally used for different operating speeds, different pulse frequencies, and / or different pulse output levels. These transition curves can also vary based on whether the transition is from a zero output level to a target pulse output level, or vice versa; based on whether the motor is operating as a motor or a generator; based on other design considerations and / or any combination of the foregoing.

[0011] In some embodiments, the motor controller includes a pulse decision module and a pulse controller. The pulse decision module determines when pulsed operation of the motor is desired and when continuous operation of the motor is desired to deliver the desired average output. When the pulse decision module determines that pulsed operation is desired, the pulse controller directs the pulsed operation of the motor. In some embodiments, the pulse controller includes a transition curve generator that controls the transition using a third-order or higher transition curve. In some embodiments, an S-shaped transition curve is used. Attached Figure Description

[0012] The invention and its advantages are best understood by referring to the following description taken in conjunction with the accompanying drawings, in which:

[0013] Figure 1 It is a representative torque / speed / efficiency curve that shows the energy conversion efficiency of a representative motor when it is running as an electric motor under different operating conditions.

[0014] Figure 2It is a graph showing the pulse current signal applied to the motor in response to torque demand when the motor is running as an electric motor.

[0015] Figure 3 This is a block diagram of a motor controller according to a non-exclusive embodiment of the present invention.

[0016] Figure 4A It is a graphical representation of the continuous three-phase AC waveforms provided to the motor.

[0017] Figure 4B and Figure 4C These are different examples of pulsed three-phase AC waveforms with similar duty cycles, which are similar to... Figure 4A The continuous waveform provides the same torque.

[0018] Figure 5 It is a graph showing the efficiency of a representative motor system as a function of motor torque at a fixed motor speed.

[0019] Figures 6A to 6C This is a series of related graphs showing the angular jerk, angular acceleration, and torque curves of an exemplary third-order torque curve.

[0020] Figures 7A to 7E It shows a series of related graphs of the fifth, fourth, and third orders (angular jerk time), angular acceleration, and torque curves of an exemplary fifth-order (five-fold) torque curve.

[0021] Figures 8A to 8E This is a series of related graphs showing the fifth, fourth, third, angular acceleration, and torque curves of an exemplary fifth-order (five-fold) torque transition curve when the desired off-time of the pulse period is shorter than the torque transition time.

[0022] Figures 9A to 9E This is a series of related graphs showing the fifth, fourth, third, angular acceleration, and torque curves of an exemplary fifth-order (five-fold) torque transition curve when the desired on-time of the pulse period is shorter than the torque transition time.

[0023] In the accompanying drawings, the same reference numerals are sometimes used to designate the same structural elements. It should also be understood that the depictions in the drawings are illustrative rather than to scale. Detailed Implementation

[0024] This application relates to pulse control of various motors (e.g., electric motors and generators) that, in other cases, operate continuously. Pulse motor control is described in U.S. Patent Applications Nos. 16 / 353,159 and 16 / 353,166, filed March 14, 2019, and No. 16 / 818,570, filed March 13, 2020. Each of the foregoing applications is incorporated herein by reference in its entirety. As described in the incorporated applications, pulse control of motors provides the advantage of improving the energy conversion efficiency of the motor's operation.

[0025] When pulses are used, the motor's command output changes frequently. A potential drawback of pulse control is that frequent output transitions can increase the motor's operating noise, vibration, and acoustic harshness (NVH). NVH problems associated with pulses tend to be more severe in motors with higher electrical time constants, as the motor's electrical time constant may impose practical limitations on the frequencies at which pulses can occur. NVH is often greater when the pulse frequency is within the range of frequencies normally perceptible to humans. Therefore, it is desirable to manage pulse transitions in an effective and efficient manner.

[0026] This application proposes the use of third-order or higher pulse transition torque profiles in some motor pulse applications. This control can help mitigate NVH issues while managing transitions efficiently. In some embodiments, a fifth-order pulse transition profile is used.

[0027] refer to Figure 1 Figure 100 illustrates exemplary motor efficiency when operating as an electric motor under different load and speed conditions. Figure 10 plots the torque (N*m) along the vertical axis as a function of the motor speed (RPM) along the horizontal axis. The maximum steady-state output power is given by curve 102.

[0028] The area under the peak torque / speed curve 102 is mapped to multiple regions, each labeled with a percentage of operating efficiency. For the specific motor shown, the following characteristics are evident:

[0029] The most efficient or "optimal point" operating range for this particular motor is the region marked 104, which is typically in the range of 4,500 RPM to 6,000 RPM and has a torque output in the range of approximately 40 N*m to 70 N*m. In region 104, the energy conversion efficiency is approximately 96%, making it the "optimal point," where the motor operates within its most efficient operating range.

[0030] • As the motor speed increases to over approximately 6,000+ RPM, efficiency decreases regardless of the output torque.

[0031] As output torque increases to above 70 N*m or below 40 N*m, the efficiency percentage tends to decrease from its peak, and in some cases quite significantly. For example, when the motor is running at approximately 2,000 RPM and 100 N*m of output torque, the efficiency is approximately 86%. When the torque output decreases to below approximately 30 N*m, the efficiency drops regardless of the motor speed, approaching zero at zero load.

[0032] • At any given motor speed, there will be a corresponding maximum efficiency output torque, which is graphically illustrated by the maximum efficiency curve 106.

[0033] Figure 100 refers to an internal permanent magnet synchronous motor. Specifically, this figure is derived from the traction motor used in the 2010 Toyota Prius. It should be understood that Figure 100 is illustrative only and should not be construed as limiting in any way. Similar figures can be generated for virtually any motor, whether used in vehicles or in certain other applications.

[0034] As can be seen from Figure 100, when driven by an electric motor, the motor is typically most efficient when operating within the speed and torque range of its optimal point 104. If operating conditions can be controlled to allow the motor to operate at or near its optimal point 104 for a larger proportion of the time, the overall energy conversion efficiency of the motor can be significantly improved.

[0035] However, from a practical standpoint, many driving situations require the electric motor to operate outside the optimal speed and torque range of point 104. Electric vehicles typically lack a transmission or gearbox, so the ratio of the electric motor's rotational speed to the wheel's rotational speed is fixed. In this case, the electric motor speed can vary between zero when the vehicle is stationary and the relatively high RPM required for cruising at highway speeds. Torque requirements can also vary significantly depending on factors such as whether the vehicle is accelerating or decelerating, going uphill or downhill, driving on a level surface, braking, etc.

[0036] Similarly, Figure 1 As can be seen, at any given speed, there exists a corresponding maximum efficiency output torque, which is graphically illustrated by the maximum efficiency curve 106. Conceptually, when the desired motor torque is lower than the maximum efficiency output torque at the current motor speed, the overall efficiency of the motor can be improved by applying pulses to the motor. This allows the motor to operate at or near its peak efficiency for a certain proportion of the time at a given speed, and to operate at a low or zero torque output level for the remaining time. Therefore, the generated average torque is controlled by adjusting the duty cycle of the peak efficiency torque applied to the motor.

[0037] It should be understood that the motor will have a similar efficiency diagram, which characterizes its efficiency as a generator.

[0038] Figure 2 Graph 20 illustrates an example of pulsed motor operation. In this particular example, the desired motor torque is 10 Nm, but the most efficient torque output at the currently operating motor speed is 50 Nm. During normal operation, the motor will continuously generate 10 Nm of torque as long as the desired torque remains at that value. Conceptually, the motor can be driven to deliver a net average torque of 10 Nm by delivering 50 Nm of torque for 20% of the time and then not delivering torque (or delivering zero torque) for the remaining 80% of the time. Therefore, the motor's net output meets the 10 Nm operating requirement. Since the motor is more efficient at delivering 50 Nm than at 10 Nm, conceptually, the overall efficiency of the motor can be improved by applying pulses to the motor's operation in the manner described.

[0039] exist Figure 2 In the middle, curve Figure 2 The total current applied to motor 12 (as a motor) is plotted on the vertical axis, and time is plotted on the horizontal axis. For illustrative purposes, it is assumed that each applied current of amperes will produce an output torque of 1 Nm. In this particular example, the desired motor output torque is 10 Nm, which would require a current of 10 amps, as shown by dashed line 22. Also in this example, the most efficient torque output of the motor is 50 Nm, corresponding to an applied current of 50 amps.

[0040] exist Figure 2 In the example shown, the motor produces a motor output of 50 Nm (labeled 24) for one time unit out of every five time units, and then the motor is turned off (or controlled to produce zero torque) for the intermediate four time units corresponding to a 20% duty cycle. Of course, the duty cycle is not limited to 20%. The desired motor output can be achieved simply by using a wide range of different duty cycles, as long as the desired motor output does not exceed 50 Nm. For example, if the desired motor output changes to 20 Nm, the duty cycle of a motor operating at 50 Nm can be increased to 40%; if the desired motor output changes to 40 Nm, the duty cycle can be increased to 80%; if the desired motor output changes to 5 Nm, the duty cycle can be decreased to 10%, and so on. Generally, the desired motor torque decreases to its maximum efficiency curve (i.e., ...). Figure 1 The pulse motor control can be advantageously used at any time below curve 106.

[0041] On the other hand, when the desired motor torque is at or above the maximum efficiency curve, the motor can operate in a conventional (continuous / non-pulsed) manner to deliver the desired torque. Therefore, for a given motor speed, pulsed operation provides an opportunity to improve efficiency gains when the motor needs to deliver an average torque below the peak efficiency torque.

[0042] It should be noted that the current and torque values, as well as the time scales provided in this article, are illustrative only and are not intended to limit in any way. In practical applications of applying pulses to motors, the duration of the pulses used can vary widely based on the design requirements of any particular system. However, typically, the time period of each pulse cycle is expected to range from 10 microseconds to 10 seconds (i.e., applying pulses at frequencies ranging from 0.5 Hz to 100,000 Hz), for example, between 20 milliseconds and 2 seconds (0.5 Hz to 5000 Hz). Furthermore, a wide variety of motors exist, and each motor has its own unique efficiency characteristics.

[0043] exist Figure 2 In the diagram, the transitions in the commanded drive current and the resulting torque are shown as a step function to explain the benefits of applying the pulse. However, it should be understood that in practice, there will be a time lag between applying voltage to the motor windings and the establishment of the flux linkage required to generate the desired torque. Therefore, in practice, the curve of the generated torque pulse cannot be as shown. Figure 2 The rectangle that is depicted.

[0044] Figure 3 This is a block diagram showing a system with a motor controller 10 capable of pulsed operation of motor 12. Motor 12 can be any type of motor, including induction motors / motors, permanent magnet assisted synchronous reluctance motors, IPM motors, etc. The motor 12 shown is a three-phase motor, although it should be understood that the motor can be designed to utilize any desired number of phases (including single-phase only).

[0045] The motor controller 10 includes a power inverter 14, a pulse controller 30, and a torque control decision module 32. The power inverter 14 can operate as a power inverter or a power rectifier depending on the direction of energy flow through the system.

[0046] When motor 12 operates as a motor, power inverter 14 is responsible for generating three-phase AC power from DC power supply 16 (denoted as 18A, 18B, and 18C for phases A, B, and C, respectively). The three-phase input power is applied to the stator windings of motor 12 to generate a rotating magnetic force (RMF). In an induction motor, this rotating magnetic field induces a current flowing in the rotor windings, which in turn induce a rotor magnetic field. The interaction between the rotor and stator magnetic fields generates an electromagnetic force (EMF), causing the rotor to rotate, which in turn rotates the motor shaft. The rotating shaft provides the motor's output torque. For most common permanent magnet motors, the rotor magnetic field is the magnetic field of the permanent magnets.

[0047] The three-phase 18A-18C are depicted by lines with arrows at both ends, indicating that current can flow in either direction. When used as a motor, current flows from power source 16 to motor 12 through power inverter 14. When used as a generator, current flows from motor 12 to power source 16 through power inverter 14. When operating as a generator, power inverter 14 essentially functions as a power rectifier, and AC power from motor 12 is converted to DC power and stored in a DC power source (such as a battery or capacitor).

[0048] The pulse controller 30 is responsible for selectively applying pulses of three-phase input current 18A-18C to the motor 12. During normal (i.e., continuous) operation, the three-phase input current supplied to the motor 12 is a continuous sinusoidal current signal, each sinusoidal current signal being 120° out of phase with respect to each other. During pulsed operation, the three-phase sinusoidal current signals 18A-18C are selectively pulsed using any of the methods described herein.

[0049] refer to Figures 4A to 4C It provides plots to illustrate the difference between the continuous three-phase current supplied to motor 12 and the pulsed three-phase current supplied by the motor. In each plot, the current is plotted on the vertical axis and the time is plotted on the horizontal axis.

[0050] Figure 4A The diagram illustrates the typical sinusoidal three-phase currents 42a, 42b, and 42c delivered to motor 12 / generated by the motor during excitation. Phase B, represented by curve 42b, lags behind phase A, represented by curve 42a, by 120 degrees. Phase C, represented by curve 42c, lags behind phase B by 120 degrees. The sinusoidal period is τ. The three-phase currents 42a, 42b, and 42c are continuous (non-pulsating) and have a specified maximum amplitude of approximately 50 amps. It should be understood that 50 amps is merely a representative maximum current, and the maximum current can have any value.

[0051] Figure 4B and Figure 4CTwo examples of three-phase sinusoidal current waveforms with different pulses are shown: 44a, 44b, and 44c, and 46a, 46b, and 46c. Note that each set of waveforms has a 50% duty cycle and a peak amplitude of approximately 100 amps.

[0052] exist Figure 4A In the example, the period of the sine waves 44a, 44b and 44c is τ; however, each of the sine waves is modulated to be intermittent. Figure 4C The difference between the 44A-C and 46A-C pulsed currents lies in the duration of their respective current pulses and the staggered "off" periods. Figure 4B In this circuit, current pulses 44a-c are interleaved with equal-length "off" time periods. The length of each on and off time period is 2τ. Figure 4C In this example, the current pulses 46a-c and the interleaved "off" time periods also have equal durations. In this case, the duration is τ / 2. In both examples, the duty cycle is 50%. However, the durations of the "on" and "off" time periods differ, i.e., the pulse modulation frequencies are different. The pulse modulation frequency may vary based on the type of motor used, noise and vibration considerations, the speed of the currently operating rotor, and other factors.

[0053] When operating as an electric motor Figure 4B and Figure 4C Excitation current delivery and Figure 4A The average torque is the same when three-phase currents are continuously applied (assuming torque is proportional to current, which is common in surface permanent magnet motors).

[0054] Figure 4B and Figure 4C An application is demonstrated where, while the motor is operating at its desired steady-state output level, the "on" drive pulses are evenly spaced. This method performs well in many cases but is not a requirement. The duty cycle does not need to be 50% but can be adjusted to match the desired average torque. Figure 4B and Figure 4C In this embodiment, the phase of the pulse is synchronized with the applied AC power; however, in some embodiments, the phase of the pulse need not be synchronized with the phase of the applied AC power. Therefore, the relative magnitude and / or timing of the motor drive pulses can vary, as long as their average reaches the desired average torque.

[0055] return Figure 3During motor operation, the torque modulation decision module 32 receives torque demands. In response, the torque modulation decision module 32 determines whether the requested torque demand is greater than or less than a specified “pulse” threshold associated with the current motor speed. In most embodiments, the pulse threshold will vary with the speed of the motor 12. In some embodiments, the pulse threshold for a given speed may be at or near the peak efficiency torque of the motor 12 at that speed. However, this is not a requirement. It should be understood that for any given motor / generator speed, there are many factors that can determine an appropriate pulse threshold. The net operating efficiency of the motor or the larger system including the motor is an important factor in determining the pulse threshold, which will be discussed in more detail below. However, other factors (e.g., NVH mitigation issues) may also be considered.

[0056] When the torque demand exceeds the pulse threshold, the torque modulation decision module 32 instructs the motor 12 to operate in continuous mode. In this case, the torque demand is transmitted to the inverter 14 in a conventional manner as an inverter control signal 39, and the inverter 14 instructs the motor to operate in a continuous manner to deliver the desired torque.

[0057] When the torque demand is less than the pulse threshold, the torque modulation decision module 32 determines the desired pulse control operating state. The desired pulse control operating state is transmitted via 33 to the pulse controller 30, which then directs the operation of the inverter 14 via the inverter control signal 38. In this context, the pulse operating state may include an indication of whether pulse control is enabled, and if so, (a) the desired target output level (sometimes referred to as the target pulse torque) during the torque-on period; (b) the desired pulse duty cycle; and (c) whether the inverter should remain active or deactivated during the torque-off period. In practice, the characteristics of the motor, the combination of the motor and its control system, and / or a larger system including the motor / motor controller can be characterized by creating an operating graph (such as the efficiency graph described above). Based on such a graph, the most efficient operating state for any and all operating conditions (e.g., all possible combinations of motor speeds and output levels) can be determined. In some embodiments, this information may be stored in a data structure such as a lookup table, which the torque modulation decision module 32 can utilize to determine the appropriate operating state for any command output (e.g., torque demand) based on the current motor speed and any other relevant control parameters. In other embodiments, the torque modulation decision module may use an algorithm or other suitable method to make such a decision.

[0058] The pulse controller 30 is responsible for timing the pulses of the motor 12 when pulses are required. In the illustrated embodiment, the pulse controller 30 includes a transition curve generator 34, the purpose of which will be described below.

[0059] Transformation Control

[0060] When implementing pulse motor control, the command torque frequently transitions between low values ​​(typically zero) and higher values ​​with higher energy conversion efficiency, and vice versa. For optimal efficiency, the transition is preferably very rapid. (Reference) Figure 5 Its benefits are understandable. Figure 5 This is a graphical representation of the energy conversion efficiency (vertical axis) of a motor operating at a fixed speed for various torque demands (horizontal axis). It should be apparent that rapid transitions through the low torque / efficiency region help maximize overall energy conversion efficiency.

[0061] exist Figure 2 In the pulse control example shown, the transition between low (e.g., zero) output levels and higher drive pulse levels (and vice versa) is depicted as a step function. However, in practice, such abrupt transitions are practically unattainable for many motors, adversely affecting the motor's energy conversion efficiency and / or potentially generating undesirable NVH (noise, vibration, and harshness).

[0062] More specifically, when voltage is first applied to the motor windings, the establishment of magnetic flux linkage and magnetization... and arouse movement It lags behind the voltage applied in all sensing circuits. If the goal of control is to reach the target pulse torque as quickly as possible, the controller can theoretically be increased by... To compensate for the hysteresis of the magnetizing flux linkage to achieve the desired torque. This has the effect of increasing the applied current and thus increasing the losses in the motor and inverter, which is contrary to the purpose of pulse control, which is to minimize losses. Therefore, it is desirable to control the amplitude and phase of the applied current during the transition to ensure transition with minimal losses. In other words, during the transition, the flux linkage is preferably controlled so that it produces the most efficient overall solution to the torque equation.

[0063] In motors / electric motors with relatively small time constants, which are associated with the flux linkage required to support the target torque, rapid and efficient transitions are relatively easy to achieve. However, as the time constant increases, the speed at which a transition can actually be achieved decreases, limiting the practical pulse frequency. For example, the time constant associated with some induction motors is high enough that applying pulses at relatively low frequencies of approximately 0.5 Hz to 20 Hz may be desirable. Humans are highly sensitive to vibrations in this frequency range, highlighting the need to consider NVH (Noise, Vibration, and Harshness) issues in pulsed motor control.

[0064] To address the competing demands for rapid changeover times, energy-efficient changeovers, and reduced NVH (noise, vibration, and harshness) issues, this disclosure proposes the use of a changeover torque curve with specific characteristics. In various preferred embodiments, the command torque smoothly but slowly transitions from zero, then rapidly increases over a large portion of the lower efficiency area, and finally slowly transitions to the desired pulse torque (e.g., a value at or near the peak efficiency torque at the current motor speed). In some embodiments, this is achieved using an S-shaped changeover torque application curve. This approach has several advantages. These advantages include:

[0065] 1. A smooth initial transition from zero torque is used to establish rotor flux linkage. At the same time, the applied motor phase current is controlled at a low level to minimize losses during this period.

[0066] 2. Minimum losses are achieved by optimizing the rate of change of most of the lower-efficiency areas, regardless of the need to build up rotor flux.

[0067] 3. Smoothly transition to target operating pulse torque while maintaining near-peak efficiency.

[0068] The same (opposite) method is used to transition from running torque to zero torque state, which facilitates the orderly extraction of energy stored in the motor's magnetic field.

[0069] One way to provide a smooth S-curve is by generating a third-order (cubic) transition torque request curve. In various control fields, cubic control is sometimes referred to as “jump” control because jump is the third-order time derivative of position in physics. Similarly, angular jump is the third-order time derivative of angular momentum. In other embodiments, higher-order functions, such as fifth-order (5th order) or higher, are used to generate the transition torque curve. The specific torque curve commanded by the pulse controller 30 during the transition is specified by the transition curve generator 34. The specific transition torque curve used under any given operating condition can be determined in any desired manner. In some embodiments, the curve is generated in real-time by the transition curve generator 34 via an algorithm. In other embodiments, suitable lookup tables or other suitable data structures can be provided so that the transition curve generator can easily look up the appropriate transition torque curve for the current operating state.

[0070] Figures 6A to 6C The diagram illustrates an example of a basic transition torque curve for abrupt changes that can be applied by the torque curve generator 34. More specifically, Figure 6A This is a graph showing the jerk curve (also known as a third-order or cubic curve) associated with the example transition torque curve. Figure 6B This is a graph showing the obtained angular acceleration (second-order curve), which is... Figure 6A The integral of angular jerkness over time is shown in the figure. Figure 6C This is a graph showing the obtained transition torque curve (first-order curve), which is... Figure 6B The integral of angular acceleration over time is shown in the figure. It should be obvious that... Figure 6A The jerk curve shown in the image is Figure 6C The second derivative of the torque with respect to time (and the third derivative of the angular momentum with respect to time, not shown) are illustrated in the figure.

[0071] In the illustrated embodiment, when the torque is initially applied, the angular jerk is set to a first value 611 and remains constant during the initial time period 610. Figure 6A During this time period, the angular acceleration steadily increases, such as Figure 6B As can be seen, and marked as 613. Simultaneously, the torque increases slowly (marked as 615). After the initial time period 610, the jerk is set to zero 621 and remains constant during the second time period (marked as 620). During this time period 620, the angular acceleration remains constant. Figure 6B (623 in the middle) and the torque increases relatively quickly ( Figure 6C (625 in the text). When the torque approaches the target pulse torque, during the third time period 630, the jerk is set to a negative second value 631. During this time period, the angular acceleration decreases ( Figure 6B (633 in the text). When the angular acceleration reaches zero, the target torque 636 is achieved, and the jerk is set to zero during the fourth time period 640 of the pulse duration.

[0072] The transition from the target torque to the zero "off" time period of pulse control can be achieved in a repetitive manner. At the start of the transition, at point 649, the jerk is set to a negative value 651 and remains constant during the fifth time period 650. During this time period, the angular deceleration steadily increases 653, and the torque begins to decrease slowly 655. After the fifth time period 650 of the transition, the jerk is set to zero 661 and remains constant during the sixth time period (labeled 660). During this time period 660, the angular deceleration remains constant (…). Figure 6B (663 in the middle) and the torque decreases relatively quickly ( Figure 6C (665 in the text). When the torque approaches zero, during the third time period 670, the jerk is set to a positive value of 671. During this time period, the angular deceleration decreases ( Figure 6B(673 in the original text). If properly controlled, the angular deceleration and torque will simultaneously reach zero (point 682), at which point the jerk is set to zero, thus initiating the "off" period 680 of pulse control. Depending on the desired control type for the off period of pulse control, the inverter may shut down during this phase, or it may maintain operation with zero torque. The command torque remains zero until the next pulse is triggered, at which point the process just described is repeated for the next pulse.

[0073] Typically, the goal is to ensure the total torque delivered in the pulse ( Figure 6C The area under the torque pulse curve 601 (600) is basically equal to the total torque expected by the pulse.

[0074] It should be obvious that, Figures 6A to 6C The examples are illustrative in nature. Certainly, the relative magnitude of change in jerk setting can vary widely to meet the needs and design objectives of any particular situation. In the illustrated embodiments, the magnitude of change in jerk setting is shown to be the same for all jerk transitions. This includes transitions from the existing torque level, approaching the new target torque level, and intermediate transitions. Similarly, the jerk setting for transitions from zero to the target torque and from the target torque back to zero is shown to be the same. These are not requirements. Rather, the relative magnitudes (and corresponding durations) of the various transitions can vary to meet the needs of any particular pulse control design implementation. In practice, the specific values ​​for any design will be based on many considerations, including the motor's time constant, NVH considerations, performance requirements, etc.

[0075] While the generation of jerk-based torque curves, as described in many applications, can significantly mitigate NVH (noise, vibration, and harshness), further improvements can be achieved in some cases through the use of higher-order control. More specifically, the jerk-based control presented is characterized by abrupt changes in the resulting angular acceleration (i.e., the corner in calculus), such as... Figure 6B As can be seen. These sudden changes / turns occur at the transitions between different levels of agitation, in... Figure 6B The points are marked as 607, 617, 627, 637, 647, 657, 667, and 677. In practice, such abrupt changes in acceleration can increase the likelihood of generating perceptible NVH (Noise, Vibration, and Harshness). One way to eliminate abrupt changes in angular acceleration (and thus further mitigate NVH) is to utilize curve generation control of even higher orders. In practice, fifth-order (5th order) or higher curve generation can be used to completely eliminate abrupt changes in angular acceleration.

[0076] exist Figures 7A to 7E The diagram illustrates the generation of a quintic curve. More specifically, Figure 7AThis is a graph showing a representative fifth-order (5th-order) curve created by a fifth-order torque curve generator. Figure 7B This shows the quintic curve (shown). Figure 7A The graph shows the time-based integral of the quintic curve and the corresponding quaternary (4th order) response. Figure 7C This shows the obtained cubic or jerk (3rd order) curve. Figure 7B The graph shows the time-based integral of the quartic curve. Figure 7D This shows the obtained angular acceleration ( Figure 7C The graph shown is a time-based integral of the angular jerkness. Figure 7E The obtained torque curve is shown. Figure 7D The graph shows the time-based integral of angular acceleration. It should be obvious that... Figure 7A The quintic curve shown in the image is Figure 7E The fourth time derivative of the torque (and the fifth time derivative of the angular momentum, not shown) is illustrated in the figure.

[0077] A noteworthy characteristic of the quintic curve generation scheme is that, by definition, there are no sudden changes (corners) or discontinuities in the angular acceleration. Figure 7C The absence of abrupt changes often helps to further reduce NVH. It should be understood that generating curves of higher order than the fifth order (e.g., sixth, seventh, etc.) has the advantage of ensuring that there are no discontinuities or abrupt changes in angular acceleration, and therefore can be used for similar purposes, although they tend to add additional complexity to the torque curve generator.

[0078] exist Figures 7A to 7E In the example of five-order torque curve generation shown, the magnitude of change in the five settings is the same for all five transitions. Similar to the abrupt changes discussed above, this is not a requirement, and the relative magnitude and timing of the transitions can be widely varied to meet the needs and design goals of any particular implementation. Typically, the goal is to ensure that the total torque delivered in the pulse ( Figure 7E The area under the torque pulse curve 701 (700) is basically equal to the total torque expected by the pulse.

[0079] There are many other factors to consider when determining when pulsation is advantageous and desirable, and some of these factors may be affected by the transition control scheme employed by the torque curve generator 34 (e.g., step change of the requested torque, cubic curve generation, quintic curve generation, etc.).

[0080] The nature of some of these factors can be understood by grasping the essence of higher-order torque curve generation. For example, if the pulse duty cycle becomes too high relative to the transition time, pulse control may result in the command torque never actually decreasing to zero. This situation occurs in... Figures 8A to 8E The diagram illustrates the effect of generating a fifth-order torque curve when the "off" portion of the pulse duty cycle is shorter than the torque transition time. Figure 8E As can be seen, the command torque never actually reaches zero. From Figure 5 As can be seen from the efficiency diagram, at many motor speeds, the energy conversion efficiency of many motors does not drop too quickly from peak efficiency torque. Therefore, in this case, continuous operation at a slightly lower torque level may be more energy-efficient than pulsed operation at peak efficiency. In this operating region, continuous operation may be superior to pulsed operation. This determination can be made as part of the motor characterization / mapping, and the motor control law can be designed to utilize methods that are considered more energy-efficient and / or originally more desirable for any given operating state of the motor.

[0081] Conversely, when the pulse duty cycle becomes too low relative to the transition time, the command torque may never actually reach the target pulse torque. This situation occurs in... Figures 9A to 9E This is illustrated in the diagram. In this scenario, the overall energy conversion efficiency of the motor may be better than when operating continuously. However, there are several ways to further improve the overall energy efficiency. For example, in some cases, the pulse frequency can be reduced, thereby generating torque pulses over a longer period. Additionally or alternatively, the target torque used by the controller can be increased to a value higher than the peak efficiency torque, so that the torque level actually commanded by the torque curve generator actually reaches (or at least comes closer to) the desired level. Similarly, the relative impact of this control can be determined during the characterization / mapping of the motor, and the control law of the motor can be designed to utilize methods considered more energy-efficient and / or originally more desirable for any given operating state of the motor.

[0082] exist Figure 3 In the illustrated embodiment, the pulse controller is shown as a separate component from the torque modulation decision module 32 to facilitate explanation of its function. However, in various embodiments, the pulse controller may be implemented as part of a motor controller including the torque modulation decision module 32, a separate component, part of the power controller / inverter 14, or in other suitable forms. Some basic functions and operation of a representative pulse controller 30 are described in incorporated U.S. Patent Applications Nos. 16 / 353,159 and 16 / 353,166.

[0083] The pulse frequency for power can be determined by the torque modulation decision module 32 or the pulse controller 30. In some embodiments, the pulse frequency may be fixed for all motor operations, while in other embodiments, the pulse frequency may vary based on operating conditions such as motor speed and torque requirements. For example, in some embodiments, the pulse frequency can be determined by using a lookup table. In this embodiment, an appropriate index, such as motor speed or torque requirements, can be used to look up the appropriate pulse frequency for the current motor operating conditions. The pulse frequency can be determined by the torque modulation decision module 32, the pulse controller, or other suitable components of the motor controller 10. In other embodiments, the pulse frequency is not necessarily fixed for any given operating conditions and may vary with the indication of the pulse controller 30. This type of variation is common when using Σ-Δ conversion in determining the pulse, as is the case in the incorporated patent application.

[0084] During the pulsed operation of motor 12, the inverter is activated during the pulse and ideally deactivated between pulses. Deactivating the inverter is conceptually desirable because it helps reduce inverter losses and inverter-induced losses during torque-free periods. However, it may sometimes be desirable for the inverter to actively issue a zero-torque command during torque-free periods (or at least a portion of them). There are several reasons for doing so. One of the easiest to understand relates to anti-BEMF. When the BEMF of a permanent magnet motor exceeds the supply voltage 16 used by the motor, a decelerating torque is generated that can significantly reduce the motor's efficiency. Magnetic field attenuation is typically used to mitigate or eliminate decelerating torque. The BEMF generated by the motor is primarily a function of the motor speed. Therefore, BEMF remains a problem during the torque-free periods of pulsed motor control. Because magnetic field attenuation is applied by the inverter, deactivating the inverter during the torque-free periods of pulsed control, under motor operating conditions where magnetic field attenuation is desired, will have the effect of causing the BEMF to decelerate the motor during those periods, thereby reducing the overall efficiency of the motor (sometimes quite significantly). To mitigate these effects, in operating regions where the BEMF exceeds the supply voltage, the inverter preferably maintains a zero-torque command during the torque-free period of pulse control. Of course, there may be other situations where it is desirable to keep the inverter on during the torque-free period of pulse operation. In various embodiments, the pulse controller 30 or the torque modulation decision module 32 can instruct the inverter 14 to shut down when necessary.

[0085] Although only a few embodiments of the invention have been described in detail, it should be understood that the invention can be implemented in many other forms without departing from the spirit or scope of the invention. For example, although the generation of third and higher order functions is described for generating torque transition curves, it should be understood that smooth S-shaped transition curves that eliminate discontinuities in angular acceleration or eliminate discontinuities and corners in angular acceleration can also be generated in other ways.

[0086] Most of the discussion above focuses on controlling torque during transition, thus referring to controlling the transition torque curve. Those skilled in motor control will understand that the same or similar results can be achieved by controlling the current in the same way (i.e., using a third-order or higher transition curve). Therefore, it should be understood that, unless the context otherwise requires, the required transition management can be applied regardless of what parameters the controller actually controls.

[0087] In various embodiments, the described motor controller components, including torque modulation decision modules, pulse controllers, transition curve generators, inverter controllers, and other control elements, can be implemented, grouped, and configured in a variety of different architectures. For example, in some embodiments, the pulse control system can be integrated into the motor controller or inverter controller, or it can be provided as a separate component. Similarly, for a generator, the pulse controller can be integrated into the generator controller or rectifier controller, and in a combined motor / generator, the pulse controller can be integrated into a combined motor / generator controller or a combined inverter / rectifier controller. In some embodiments, the described control functions can be implemented algorithmically by software or firmware executing on a processor, which can take any suitable form, including, for example, general-purpose processors and microprocessors, DSPs, etc.

[0088] A pulse control system can be part of a larger control system. For example, in vehicle applications, the described control can be part of a vehicle controller, powertrain controller, hybrid powertrain controller, or ECU (engine control unit) that performs various functions related to vehicle control. In such applications, the vehicle controller or other related controllers can take the form of a single processor performing all the required controls, or can include multiple processors that are commonly located as part of a powertrain or vehicle control module, or distributed throughout the vehicle. The specific functions performed by any of the processors or control units can vary widely.

[0089] The invention has been described primarily in the context of motor control and / or inverter / motor control. However, it should be understood that the described methods are equally applicable to generator and / or generator / rectifier control. Therefore, at any point in the description of motor control, it should be understood that similar techniques can be applied to generator control. Thus, unless the context requires a different interpretation, the description of the features of pulse motor control, pulse generator control, or pulse motor / generator control should be understood to be equally applicable to pulse motor control, pulse generator control, and pulse control of combined motor / generators.

[0090] Various control schemes can be implemented within the pulse controller. Typically, these control schemes can be implemented digitally or algorithmically using analog components or a hybrid approach. The pulse generator and / or motor controller can be implemented as code that executes on a processor, on programmable logic such as an FPGA (Field-Programmable Gate Array), on a circuit system such as an ASIC (Application-Specific Integrated Circuit), or on a digital signal processor (DSP), using analog components or any other suitable hardware. In some implementations, the described control scheme can be incorporated into target code to be executed on a digital signal processor (DSP) incorporated into an inverter controller (and / or a rectifier controller in the context of a generator, and / or a combined inverter / rectifier controller).

[0091] In various embodiments, pulse width modulation, delta conversion, or other techniques can be used to generate the pulse inverter control signal 38. Regardless of the modulation type used, the transitions between pulse levels can be managed in the manner described. Similarly, the described pulse transition management can be used on any type of motor using pulse control, regardless of the motor's time constant and / or the switching frequency used. Therefore, this embodiment should be considered illustrative rather than restrictive, and the invention is not limited to the details given herein, but can be modified within the scope and equivalents of the appended claims.

Claims

1. A method for controlling the operation of a motor, the method comprising: The pulsed operation of the motor is directed to deliver a desired average output, wherein the pulsed operation causes the motor to alternate between a first output level greater than the desired average output and a second output level less than the desired average output; and Use a third or higher order transition curve to control the transition from the first output level to the second output level, or from the second output level to the first output level.

2. A method for controlling the operation of a motor, the method comprising: The pulsed operation of the motor is directed to deliver a desired average output, wherein the pulsed operation causes the motor to alternate between a first output level greater than the desired average output and a second output level less than the desired average output; and The transition curve of the S-shaped command is used to control the transition from the second output level to the first output level.

3. The method as described in claim 1 or 2, wherein, The transition curve is a quintic function curve.

4. The method as described in claim 1 or 2, wherein, The transition curve is a cubic function curve.

5. The method as described in claim 1 or 2, wherein, The transition curve is a curve with an order higher than the fifth degree.

6. The method as described in claim 1 or 2, wherein, The second output level is zero torque.

7. The method of claim 6, wherein, The motor is controlled by an inverter, and in at least some operating states, the inverter is turned off for at least a portion of the time during which the motor outputs zero torque.

8. The method of claim 1, wherein, The transitions between these output levels are controlled by using a third-order or higher-order transition curve to control the torque generated by the motor.

9. The method as claimed in claim 1 or 2, wherein, These transition curves are transition torque curves.

10. The method of claim 1, wherein, The transitions between these output levels are controlled by using a third-order or higher-order transition curve to control the current supplied to the motor.

11. The method as claimed in claim 1 or 2, wherein, These transition curves are transition current curves.

12. The method of claim 1, wherein: The second output level is zero torque; The motor is controlled by an inverter; and In at least some operating conditions, the inverter is turned off for at least a portion of the time during which the motor outputs zero torque.

13. The method as claimed in claim 1 or 2, wherein, The transition from the first output level to the second output level is controlled according to a first transition curve, and the transition from the second output level to the first output level is controlled according to a second transition curve different from the first transition curve, wherein both the first transition curve and the second transition curve are third-order or higher transition curves.

14. A motor controller configured to perform the method as claimed in any one of claims 1 to 13.

15. An electric motor comprising the motor controller as claimed in claim 14.

16. A motor controller arranged to direct the operation of a power converter of a motor, the motor controller comprising: A pulse decision module determines when pulsed operation of the motor is desired and when continuous operation of the motor is desired, in order to deliver the desired average output; as well as A pulse controller, which directs the pulse operation of the motor when the pulse decision module determines that the pulse operation of the motor is desired, wherein the pulse operation causes the motor to alternate between a first output level greater than the desired average output and a second output level less than the desired average output, the pulse controller including a transition curve generator that uses a transition curve of third or higher order to control the transition from the second output level to the first output level.

17. The motor controller as claimed in claim 16, wherein, The transition curve generator uses a fifth-order or higher transition curve to control the transition from the second output level to the first output level.

18. The motor controller as claimed in claim 16 or 17, wherein, The transition curve generator uses third-order or higher-order transition curve control to further control the transition from the first output level to the second output level.

19. The motor controller as claimed in claim 16 or 17, wherein, The second output level is zero torque, and the power converter is turned off during pulses in at least some operating states, for at least a portion of the time that causes the motor to output zero torque.

20. The motor controller as claimed in claim 16 or 17, wherein, These transition curves are transition torque curves.

21. The motor controller as claimed in claim 16 or 17, wherein, These transition curves are transition current curves.

22. An electric motor comprising a motor controller as claimed in any one of claims 16 to 21.

23. The motor as claimed in claim 22, wherein, This motor is an induction motor.

24. The motor as claimed in claim 22, wherein, The motor is an electric motor, a generator, or an electric motor / generator.

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