Power-based pulse injection control for sr self-sensing

Abstract

By comparing motor power to an injected maximum power, the SR motor control system enables self-sensing of rotor position of a power-based SR motor at medium to high speeds and low torque. In response to the motor power being less than the injected maximum power, a position current pulse is injected to a stator pole. An actual stator current resulting from the position current pulse is compared to an estimated stator current, and if the actual stator current is not equal to the estimated stator current, an estimated rotor position stored in memory is updated to a new estimated rotor position.

Description

Technical Field

[0001] This disclosure generally relates to a control system, and more specifically to a switched reluctance motor control system with rotor position self-sensing. Background Technology

[0002] Many construction machines, such as tracked tractors and excavators, can include a drivetrain connected to a power source to enable the machine to be repositioned or move between positions. With increasing interest in energy conservation and avoiding fossil fuels, the use of electric motors as a power source is becoming more common. Electric motors convert electrical energy from sources such as batteries into mechanical power to drive the construction machine.

[0003] Switched reluctance (SR) motors are a type of electric motor widely used in various applications, such as the aforementioned work machinery, due to their robust and solid construction. An SR motor consists of a rotor and a stator with multiple winding poles. Unlike typical brushed DC motors, power is delivered to the windings in the stator of the SR motor, not the rotor. This arrangement greatly simplifies mechanical design because power does not need to be delivered to the moving parts; however, it complicates electrical design due to the need for some form of switching system to deliver power to the different windings. Some SR motors have a control system with self-sensing operation, which estimates the rotor's position relative to the stator without using a direct angular position sensor. Self-sensing operation is important in many applications due to the need for minimal package size, high reliability, and reduced cost. Accurate determination of the rotor's angular position at all operating speeds is crucial for the motor's performance and efficiency.

[0004] Such a self-sensing control system is described in U.S. Patent No. 10,079,566. However, at medium and high speeds with light loads on SR motors, the low power required to rotate the rotor may not provide sufficient current to the stator for the self-sensing control system to estimate the rotor position. This risks that the command current may not be transmitted to the stator pole windings at the correct timing, adversely affecting the performance and efficiency of the SR motor. Therefore, there remains a need for a control system for SR motors that provides accurate self-sensing operation during medium to high-speed / low torque operation. Summary of the Invention

[0005] In one aspect of this disclosure, a working machine is disclosed. The working machine may include a power supply, a SR motor having a stator and a rotor, an inverter operably connected to the power supply and the SR motor to control power transfer from the power supply to the SR motor, and a controller operably connected to the SR motor and the inverter. The controller may be configured to calculate the motor power output by the SR motor, compare the motor power with a maximum injected power, and, in response to a motor power less than the maximum injected power, determine an estimated stator current of the SR motor based on a position current pulse to be injected into the stator poles of the SR motor to estimate the rotor position. The controller may also be configured to, in response to a motor power less than the maximum injected power, cause the inverter to inject a position current pulse having a position current into the stator poles of the SR motor, determine the actual stator current of the SR motor generated by the position current pulse, compare the actual stator current with the estimated stator current, and, in response to determining an error amount in which the actual stator current differs from the estimated stator current by a predetermined error amount, set a stored estimated rotor position to be equal to the new estimated rotor position.

[0006] In another aspect of this disclosure, a method for determining the rotor position of a self-sensing SR motor is disclosed. The method may include: calculating the motor power output by the SR motor; comparing the motor power with a maximum injected power; in response to a motor power less than the maximum injected power, determining an estimated stator current of the SR motor based on a position current pulse to be injected into the stator poles of the SR motor to estimate the rotor position; in response to a motor power less than the maximum injected power, injecting a position current pulse having a position current into the stator poles of the SR motor; determining the actual stator current of the SR motor generated by the position current pulse; comparing the actual stator current with the estimated stator current; and in response to determining an error amount in which the difference between the actual stator current and the estimated stator current is greater than a predetermined error amount, setting a stored estimated rotor position equal to a new estimated rotor position.

[0007] In another aspect of this disclosure, an electric drive system for a work machine is disclosed. The work machine may have a frame, a traction system supporting the frame, and a power supply mounted on the frame. The electric drive system may include an SR motor having a stator and a rotor, an inverter operably connected to the power supply and the SR motor to control power transfer from the power supply to the SR motor, a current sensor operably connected to the SR motor, and a controller operably connected to the SR motor, the inverter, and the current sensor. The controller can be configured to calculate the motor power output by the SR motor, compare the motor power with the injected maximum power, and, in response to the motor power being less than the injected maximum power, determine the estimated stator current of the SR motor based on the position current of the position current pulse to be injected into the stator pole of the SR motor to estimate the rotor position. In response to the motor power being less than the injected maximum power, cause the inverter to inject a position current pulse with the position current into the stator pole of the SR motor. The controller can also determine the actual stator current of the SR motor generated by the position current pulse based on the current sensor signal from the current sensor. Furthermore, the controller can compare the actual stator current with the estimated stator current, and, in response to determining that the difference between the actual stator current and the estimated stator current is greater than a predetermined error, set the estimated rotor position stored in the memory to be equal to the new estimated rotor position.

[0008] Additional aspects are defined by the claims of this patent. Attached Figure Description

[0009] Figure 1 This is a side view of an exemplary operating machine in which power-based pulse injection control for an SR motor according to the present disclosure can be implemented;

[0010] Figure 2 yes Figure 1 A block diagram of an exemplary electric drive system for a working machine;

[0011] Figure 3 yes Figure 1 A schematic diagram of the stator and rotor of an SR motor for a work machine;

[0012] Figure 4 Under low speed and high load conditions Figure 3 A graph showing the rotor position of an SR motor versus current and inductance.

[0013] Figure 5 Under medium to high speed and high load conditions Figure 3 A graph showing the rotor position of an SR motor versus current and inductance.

[0014] Figure 5A Under medium to high speed and high load conditions Figure 3 The time versus current and inductance curves of the SR motor;

[0015] Figure 6 yes Figure 3 A graph showing the rotor speed versus motor torque of an SR motor.

[0016] Figure 7 It includes the power-based injection self-sensing region according to this disclosure. Figure 6 A curve graph;

[0017] Figure 8 Under low speed and low load conditions Figure 3 A graph showing the rotor position of an SR motor versus current and inductance.

[0018] Figure 9 Under medium to high speed and low load conditions Figure 3 A graph showing the rotor position of an SR motor versus current and inductance.

[0019] Figure 9A Under medium to high speed and low load conditions Figure 3 The time versus current and inductance curves of the SR motor; and

[0020] Figure 10 Based on this disclosure Figure 3 A flowchart of an exemplary SR rotor position self-sensing routine for an SR motor. Detailed Implementation

[0021] This disclosure relates to an SR motor control system. The SR motor control system is universally applicable to any machinery using such an SR motor control system. The term "machinery" can refer to any machinery performing operations associated with industries such as mining, construction, farming, transportation, or any other industry. As some examples, such machinery can be vehicles, backhoe loaders, cold planers, wheel loaders, compactors, log stackers, forestry machinery, conveyors, harvesters, excavators, industrial loaders, clamp loaders, material handling machines, motorized graders, pipelaying machines, road reclaimers, skid steer loaders, timber harvesters, telescopic forklifts, tractors, bulldozers, tractor-mounted scrapers, etc. Furthermore, one or more implements can be connected to the machinery and controlled using an electric motor associated with the switched reluctance motor control system described herein.

[0022] Figure 1This is a diagram of an exemplary work machine 100 that may include an SR motor control system according to the present disclosure. The work machine 100 is illustrated as a tracked tractor, but may be any type of machine having an SR motor control system capable of controlling a switched reluctance motor of the work machine 100. As shown, the work machine 100 includes a frame 102, a traction system 104 supporting the frame 102, a power source 106 supported on the frame 102, and an electric drive system 108 configured to transfer energy from the power source 106 to the traction system 104. Implements 110, such as, but not limited to, blades as illustrated, may be attached to the frame 102 and may be powered by the electric drive system 108. The work machine 100 may also include an operator's cab 112. The power source 106 is configured to supply power to the work machine 100 and provide operating power for the propulsion of the electric drive system 108. The power source 106 may be a direct current (DC) power supply, an Otto cycle or Diesel cycle engine, etc. Power supply 106 can be operatively arranged to receive control signals from an operator controller (not shown) in the operator's cab 112. Additionally, power supply 106 can be operatively arranged to power other systems of the work machinery 100.

[0023] The electric drive system 108 can be operatively arranged with the power supply 106 to selectively propel the work machinery 100 via control signals from an operator in the operator's cab 112. The electric drive system 108 is operatively connected to a traction system 104, which can be movably connected to the work machinery 100 via shafts, drive shafts, transmissions, and / or other components. In some embodiments, the traction system 104 may be configured as a tracked drive system as shown, although a wheel drive system or any other type of drive system configured to engage the ground and propel the work machinery 100 is also possible.

[0024] In some embodiments, the electric drive system 108 may be additionally or alternatively configured to selectively operate the implement 110, which may be movably connected to the working machinery 100 and the electric drive system 108. The implement 110 illustrated is a blade mounted on the working machinery 100 in the form of a tractor loader; however, other embodiments may include any other suitable implement for various tasks, such as, but not limited to, bulldozing, brushing, compaction, mining, slope reduction, hoisting, turning over soil, plowing, etc. As indicated above, Figure 1 The example provided is a work machine 100 that can utilize the SR motor and SR motor control system according to this disclosure. Other examples are also possible and may differ from the combination. Figure 1 The description explains why the SR motor control system is still implemented.

[0025] Figure 2This diagram illustrates an exemplary arrangement of components of an electric drive system 108 that can implement the SR motor control system according to this disclosure. The electric drive system 108 may include a controller 200 having one or more processors 202 and a memory 204, a motor 206, an inverter 208, and a plurality of sensors 210. The motor 206 is, for example... Figure 3 The SR motor 206 is shown and described in more detail below. The processor 202 is implemented in hardware, firmware, or a combination of hardware and software. The processor 202 may be a central processing unit (CPU), graphics processing unit (GPU), accelerated processing unit (APU), microprocessor, microcontroller, digital signal processor (DSP), field-programmable gate array (FPGA), application-specific integrated circuit (ASIC), or another type of processing unit. In some embodiments, the processor 202 includes one or more processors that can be programmed to perform functions. The memory 204 may include random access memory (RAM), read-only memory (ROM), and / or other types of dynamic or static storage devices (e.g., flash memory, magnetic storage, and / or optical storage) that store information and / or instructions for use by the processor 202.

[0026] In some embodiments, the controller 200 may be an electronic control unit (ECU), electronic control module (ECM), etc., of the machine tool 100 and / or the SR motor 206. The processor 202 may execute one or more instructions and / or commands to control one or more components of the machine tool 100, such as controlling the operation of the inverter 208, the SR motor 206, etc. The memory 204 may store program code for execution by the processor 202 and / or store data related to the execution of such program code by the processor 202, such as program code for the SR motor control system according to this disclosure.

[0027] The controller 200 can receive one or more input signals from various components of the machine tool 100, can operate on one or more input signals to generate one or more output signals (e.g., to execute a program by using the input signals as input to the program), and can output one or more output signals to various components of the machine tool 100. For example, the controller 200 can be electrically connected (e.g., via wired or wireless connection) to the SR motor 206, to the inverter 208, to one or more sensors 210, etc. The controller 200 is configured to receive inputs from the sensors 210, the operator, and / or other systems of the machine tool 100. Based on these inputs, the controller 200 commands the inverter 208 to provide power to the SR motor 206 as needed. This includes start commands at startup, switching commands during operation, and other commands required by the SR motor control system as described herein.

[0028] Inverter 208 may be electrically connected to power supply 106 and SR motor 206, and supply current to SR motor 206 as commanded by controller 200. In some embodiments, inverter 208 may receive DC current from power supply 106 and may control the phase of the DC current to supply switched DC current to SR motor 206 based on switching commands from controller 200. Additionally or alternatively, inverter 208 may receive commands relating to supplying starting voltage and current or position sensing voltage and current to SR motor 206, enabling the determination of the angular position of SR motor 206 without using a rotational position sensor. In some embodiments, each phase of the current may be controlled in parallel independently. Those skilled in the art will understand that the control functions illustrated and described herein may be centralized at controller 200 or distributed among controller 200 and other “smart” devices. For example, in alternative embodiments, inverter 208 may include control means (e.g., current controller, phase controller, etc.) that control the operation of inverter 208 in response to commands from controller 200. Such variations are contemplated by the inventors.

[0029] Sensor 210 may include a set of sensor devices that provide information about the state of the machine tool 100. For example, sensor 210 may include a current sensor 212 that monitors the current in the SR motor 206 and transmits information about the current in each of several phases of the SR motor 206 to controller 200. Based on the value of the phase current from current sensor 212, the SR motor control system executed by controller 200 can determine an estimate of the angular position of the SR motor 206 without using a position sensor, and can determine a switching command based on the angular position estimate to control the operation of the SR motor 206. In addition to other sensors, sensor 210 may also include a DC link voltage sensor 214 and any other sensors 210 required for the operation of the machine tool 100, the DC link voltage sensor 214 sensing the phase voltage, which is then used to estimate the magnetic flux, which in turn is used to estimate the phase current of the SR motor 206.

[0030] Figure 3The working components of an exemplary SR motor 206 are schematically illustrated. The SR motor 206 includes an outer stator 250 and an inner rotor 252. The stator 250 remains stationary relative to the housing (not shown) of the SR motor 206, while the rotor 252 can rotate therein. The stator 250 has a plurality of stator poles 254A, 254B, 254C circumferentially spaced around the inner surface 256. As illustrated, the stator poles 254A, 254B, 254C are arranged in pairs, diametrically opposed to each other. Unlike brushed DC motors, power is delivered to the stator 250 rather than the rotor 252, which simplifies the mechanical design but complicates the electrical design because the inverter 208 requires a switching system to sequentially deliver power to the stator poles 254A, 254B, 254C. Each pair of stator poles 254A, 254B, and 254C has a corresponding winding (not shown) that receives current from inverter 208 in phase to generate a magnetic field that rotates rotor 252. In the illustrated example, the current to stator pole 254B is 60° out of phase with the current to stator pole 254A, and the current to stator pole 254C is 120° out of phase with the current to stator pole 254A.

[0031] The rotor 252 in the illustrated embodiment may be made of ferromagnetic metal, alloy, or other materials and is rotatable about rotor axis 258. The rotor 252 has a plurality of rotor teeth 260A, 260B circumferentially spaced around its periphery and rotor axis 258. The rotor teeth 260A, 260B are arranged in pairs and interact with a magnetic field generated by the current at stator poles 254A, 254B, 254C to control the speed and direction of rotation of the rotor 252 about rotor axis 258 as the rotor teeth 260A, 260B are pulled toward or repelled from stator poles 254A, 254B, 254C, as discussed below. The configuration of stator 250 and rotor 252 is exemplary, and those skilled in the art will understand that SR motor 206 may have alternative combinations of stator poles 254 and rotor teeth 260 to control the rotation of rotor 252, and such alternatives are contemplated by the inventors for use with power-based pulse injection control according to this disclosure.

[0032] The SR motor 206 operates based on the tendency of the rotor 252 to move to a position maximizing inductance relative to the stator 250. This position of maximized inductance occurs when a pair of rotor teeth 260A, 260B are aligned with a pair of energized stator poles 254A, 254B, 254C. This magnetic attraction generates torque that rotates the rotor 252 and moves it toward the position of maximized inductance. As power is delivered to each pair of stator poles 254A, 254B, 254C and the rotor 252 moves to alignment, the next stator pole 254A, 254B, 254C is then sequentially energized to continue the movement of the rotor 252 and maintain angular momentum. This switching mode of energizing and de-energizing stator poles 254A, 254B, 254C, along with which phase, complicates the operation of this type of motor. The correct operation of the SR motor 206 depends on the correct timing of energizing each stator pole 254A, 254B, 254C. The timing is driven by the angular position of the rotor 252 relative to the stator 250.

[0033] Figure 4 The diagram illustrates the control of the SR motor 206 by supplying current to stator poles 254A, 254B, and 254C at specific intervals to cause rotor 252 to rotate counterclockwise as shown. Graph 300 illustrates the relationship between the angular position θ of rotor 252 and the current I transmitted to the windings of stator pole 254A under the condition that the SR motor 206 is operating at low speed under full load. Stator 250 and rotor 252 are shown in series below graph 300, with rotor 252 rotating in 45° increments. At the 0° position, rotor teeth 260A are aligned with stator pole 254A. At this position, due to the alignment of rotor teeth 260A with stator pole 254A, the mechanical inductance L between stator pole 254A and rotor 252 is at its maximum inductance L on inductance curve 302. MAX When the rotor teeth 260A rotate and are not aligned with the stator poles 254A, the inductance L will decrease until it reaches its minimum after rotating 45° when the rotor teeth 260A are equidistant from the stator poles 254A. MIN When rotor 252 is at minimum inductance L MIN and maximum inductance L MAX When rotating between these phases, the SR motor 206 is in the motion torque region MTZ, where the current to the stator poles 254A generates a motion torque in the rotational direction on the rotor 252. Conversely, when the rotor 252 is at its maximum inductance L... MAX and minimum inductance L MINWhen rotating, the SR motor 206 is in the braking torque region RTZ, where the current to the stator pole 254A generates a braking torque on the rotor 252 opposite to the direction of rotation. Those skilled in the art will understand that the motion torque region MTZ and the braking torque region RTZ are directionally related, and they are opposite when the SR motor 206 operates in reverse. When the rotor teeth 260A enter the stator pole 254A but are not aligned with it, the rotor 252 continues to operate at maximum inductance H. MAX and minimum inductance H MIN It cycles between them.

[0034] The counterclockwise rotation of rotor 252 transmits the command current I. CMD The stator pole 254A is sent to the motion torque region MTZ to maintain the torque. The command torque T required to operate the SR motor 206 is... CMD and command current I CMD The SR motor control system at controller 200 can determine this based on operator input and the current operating conditions at the machine 100. When rotor 252 passes the 45° position, rotor teeth 260A rotate away from stator pole 254A and rotor teeth 260B rotate towards stator pole 254A. When rotor 252 reaches the command current-on position θ... 接通 At that time, the controller 200 causes the inverter 208 to transmit the command current pulse 304 to the winding of the stator pole 254A until the command current is disconnected at position θ. 断开 This generates a magnetic field that pulls the rotor teeth 260B toward the stator poles 254A. The controller 200 controls the command current I as needed. CMD Values ​​and positions θ 接通 and θ 断开 The dwell time between these pulses controls whether the angular velocity ω of rotor 252 increases, decreases, or remains constant. When the speed and load of the SR motor 206 remain constant, similar command current pulses 304 will occur at approximately 90° intervals. Stator poles 254B and 254C are similarly controlled by command current pulses 304, which are 60° and 120° out of phase with the command current pulses 304 to stator pole 254A, respectively. Those skilled in the art will understand that the controller 200 changes the timing, duration, and polarity of the command current pulses 304 to accelerate, decelerate, or reverse the rotation of rotor 252, thereby controlling the operation of the SR motor 206.

[0035] Effective operation of the SR motor 206 depends on knowing the position of the rotor 252 so that the command current pulses 304A, 304B, and 304C are at the correct command current on position θ during the rotation of the rotor 252. 接通Start-up at the location. Although some SR motors 206 in the art use position sensors to detect the position of the rotor 252 relative to the stator 250, self-sensing operation is important for a variety of applications due to the need for minimal package size, high reliability, and low cost of the SR motor 206. Reliable and accurate position sensing of the SR motor 206 is a key step in developing low-cost, high-performance SR working mechanical drives. One strategy for self-sensing the angular position ω of the rotor 252 involves injecting a position current I during the injection window IW. P Position current pulse 306 is injected into stator poles 254A, 254B, and 254C, wherein command current pulse 304 is not generated by stator poles 254A, 254B, and 254C. The timing of position current pulse 306 is based on the estimated rotor position θ stored in memory 204. EST and the estimated rotor speed ω EST Then, an observer-based estimation method is used to determine the estimated rotor position θ flowing through position current pulse 306. EST The estimated stator current I corresponding to stator poles 254A, 254B, and 254C EST Position current I of position current pulse 306 P It can have a sufficiently large amplitude to cause a measurable change in the current measured by current sensor 212, but will not induce a parasitic braking torque on rotor 252 significant enough to affect the performance of SR motor 206, outweighing the benefits of self-sensing rotor position θ. Controller 200 will estimate the stator current I... EST The actual stator current I received from current sensor 212 ACT A comparison is made to generate an error signal. This error signal is used to calculate an updated estimated rotor position θ for rotor 252. EST and the updated estimated rotor speed ω EST The error signal can be stored in memory 204 for timing subsequent command current pulses 304.

[0036] Used to determine the estimated rotor position θ EST The strategy works well at low speeds, but may have difficulties at higher operating speeds. For example... Figure 5 As shown in graph 300, which represents the stator poles 254A at higher operating speeds of the SR motor 206, and the rotor position θ 接通 The command current appears within the braking torque region RTZ, allowing the command current pulse 304 to reach the command current I at the appropriate rotor position θ. CMD This pulls the corresponding rotor teeth 260A and 260B toward the stator pole 254A. Because the command current is at rotor position θ 接通With proper positioning and timing, the chance of the position current pulse 306 being injected into the injection window IW is greatly reduced or eliminated. Figure 5A Graph 300 is plotted where the rotor position axis is changed to a time axis to represent the rotor speed ω, which is... Figure 4 The rotor speed ω is approximately 5 times that of the rotor. This figure illustrates that the time for injecting the position current pulse 306 can be greatly reduced as the rotor position θ of the injected position current pulse 306 ranges.

[0037] Figure 6 This is curve 320, which shows the known position self-sensing strategy. Curve 320 represents the motor speed ω versus motor torque T of the exemplary SR motor 206. Power curve 322 represents the maximum operating power P of the SR motor 206 for the combination of motor torque T and rotor speed ω. MAX The SR motor 206 has a low-speed range of 322. L The maximum output torque T MAX Medium or intermediate speed range 322 M The constant maximum power output is equal to the motor torque T multiplied by the motor speed ω; and the high-speed range is 322. H Or a continuous conductive region, where the current incompletely changes to zero, resulting in a medium speed range of 322 M Different mechanical power curve geometries are considered. In the exemplary SR motor 206, the position self-sensing described above can be performed in the velocity-based injection self-sensing region 324 until the maximum injected rotor speed ω. IMAX Low speed range 322 L Internal execution. Higher than the maximum injected rotor speed ω. IMAX Motor position self-sensing can be performed in the main current-based self-sensing region 326 using a similar strategy based on the estimated measured inductance H or flux flow, using the main command current pulses 304A, 304B, and 304C.

[0038] This method of position self-sensing based on main current requires a minimum current to the SR motor 206. At very low torque loads and medium to high rotor speeds, the power required to drive this load is relatively low, and it can be achieved with a low command current I. CMD To maintain rotor speed ω. The command current I required to rotate rotor 252. CMD The current level may be too low for the injection, measurement, and comparison processes to function correctly, resulting in a dead zone where the controller 200 cannot determine the position of the rotor 252. Although low power is required under low torque / medium to high speed conditions, it is still desirable to maintain up-to-date information about the rotor position θ for optimal operation of the SR motor 206.

[0039] The SR motor control system for the SR motor 206 according to this disclosure can be implemented by the controller 200 and is configured to determine the estimated rotor position θ when the SR motor 206 operates at medium to high speeds with low torque. EST .like Figure 7 As shown, the position self-sensing strategy of curve 320 is modified to include a power-based injection self-sensing region 328, which injects a speed greater than the maximum rotor speed ω. IMAX The estimated rotor speed ω EST The self-sensing region 326, based on main current, is demarcated where the SR motor 206 is driving a low-torque load. The power-based injection self-sensing region 328 is defined by a self-sensing power curve 330, which indicates the maximum injected power P. IMAX The controller 200 can inject a position current pulse 306 below the maximum injected power, as discussed further below. When the SR motor 206 operates, the motor power P... M It can be calculated as the command torque T used to control the SR motor 206 CMD and the estimated rotor speed ω stored in memory 204 EST The product of ω and ω. If the estimated rotor speed ω EST Greater than the maximum rotor speed ω injected IMAX And the motor power P M Less than the maximum injected motor power P IMAX The estimated motor position θ can then be determined using the position current pulses 306 at stator poles 254A, 254B, and 254C. EST .

[0040] Figure 8 The graph 340 shows the stator pole 254A, where the SR motor 206 can operate at low rotor speed ω and low torque T. If the motor speed ω... M Less than the maximum rotor speed ω injected IMAX Or motor power P M Less than the maximum injected motor power P IMAX Then, position self-sensing using position current pulse 306 can be performed. If the current motor operating conditions are within either injection self-sensing region 324, 328, position current pulse 306 will be injected during the injection window IW discussed above. Position current pulse 306 will be injected into stator poles 254B, 254C in a similar manner.

[0041] For medium to high rotor speeds ω with low torque in SR motor 206 M , Figure 9 The graph 340 shows the stator pole 254A. Because the command current I...CMD The command current is lower than that under high torque conditions, so the rotor position θ used for command current pulse 304 is... 接通 The command current can later appear in the braking torque region RTZ. The later injection of the command current pulse 304 creates a chance that it is large enough to inject into the injection window IW of the position current pulse 306. Even in Figure 9A In the time-domain version of the curve 340 shown, the opportunities are also evident.

[0042] Industrial applicability

[0043] Figure 10 An exemplary SR rotor position self-sensing routine 400 is illustrated, which can be implemented as part of an SR motor control system according to this disclosure. Routine 400 can implement rotor position detection based on self-sensing injection under low rotor speed and low power operating conditions, such as... Figure 7 The curve is depicted in graph 320. Routine 400 can begin at block 402, where controller 200 determines the estimated rotor speed ω of rotor 252 of SR motor 206. EST In some embodiments as discussed above, when the estimated rotor position θ EST When it is last updated and stored in memory 204, the estimated rotor speed ω may have been previously calculated. EST In these embodiments, the stored estimated rotor speed ω can be retrieved from memory 204. EST For use in routine 400. In other embodiments, the estimated rotor speed ω can be determined in real time from available data, such as data from the signal from current sensor 212 or from data provided by other sensors 210, such as a rotational speed sensor (not shown). EST .

[0044] Retrieve or calculate the estimated rotor speed ω at box 402. EST Then, control can be transmitted to block 404 to adjust the estimated rotor speed ω. EST With the maximum rotor speed ω injected Imax A comparison is made to determine whether the SR motor 206 is operating within the speed-based injection self-sensing region 324. If the estimated rotor speed ω... EST Less than the maximum rotor speed ω injected Imax The SR motor 206 operates in the speed-based injection self-sensing region 324, and a position current pulse 306 can be injected to determine the currently estimated rotor speed ω. ESTIs it accurate? In this case, the routine can bypass the step of determining whether the SR motor 206 is operating in the power-based injection self-emission region 328 and proceed to the step of self-sensing the rotor position based on injection.

[0045] If the estimated rotor speed ω EST Greater than the maximum rotor speed ω injected Imax If the SR motor 206 has a medium to high rotor speed ω, it does not operate in the speed-based injection self-sensing region 324. Instead, the SR motor 206 operates in either the main current-based self-sensing region 326 or the power-based injection self-sensing region 328. At the medium to high rotor speed ω, control can be transmitted to block 406, where the current motor power P of the SR motor 206 is... M By adjusting the command torque T CMD Multiplied by the estimated rotor speed ω previously determined at box 402 EST To determine.

[0046] Determine the motor power P at box 406. M Then, control can be transmitted to box 408, where the calculated motor power P is... M With the maximum injected power P IMAX A comparison is made to determine which of the self-sensing regions 326 and 328 the SR motor 206 operates in. If the motor power P... M Greater than the maximum injected power P IMAX Then, the SR motor 206 operates above the self-sensing power curve 330 and in the self-sensing region 326 based on the main current. In this case, control can be transferred from block 408 to block 410, where the controller 200 is based on the command current I of the command current pulse 304 output by the stator poles 254A, 254B, 254C. CMD To determine the estimated stator current I EST To drive rotor 252. Estimate stator current I. EST The current flowing through the SR motor 206 during the command current pulse 304 can be determined by the controller 200 using the observer-based estimation method described above, or by any other suitable method for determining the current flowing through the SR motor 206 during the command current pulse 304. The estimated stator current I, determined at block 410, is used. EST Control can be transmitted to block 412, where controller 200 causes inverter 208 to be in rotor position θ. 接通 At the command current point, the command current pulse 304 is injected into the corresponding stator poles 254A, 254B, and 254C, and at the rotor position θ 断开 Cut off the command current I at the command current point CMD .

[0047] If the motor power P at box 410M Less than the maximum injected power P IMAX The SR motor 206 then operates below the self-sensing power curve 330 and within the power-based injection self-sensing region 328. Under these conditions, control can be transferred from block 410 to block 414, where the controller 200 is based on the position current I of the position current pulses 306 output by the stator poles 254A, 254B, 254C. CMD To determine the estimated stator current I EST To determine the estimated rotor position ω EST Estimate the stator current I. EST The current that will flow through the SR motor 206 during the position current pulse 306 can be determined by the controller 200 using the observer-based estimation method described above or any other suitable method for determining the current that will flow through the SR motor 206 during the position current pulse 306. The estimated stator current I determined at block 414 is used. EST Control can be transmitted to box 416, where controller 200 causes inverter 208 to inject position current pulse 306 into the corresponding stator poles 254A, 254B, and 254C within injection window IW.

[0048] Whether a command current pulse 304 is injected at block 412 or a position current pulse 306 is injected at block 416, control can be transmitted to block 418, where controller 200 determines the actual stator current I flowing through SR motor 206 during current pulses 304 and 306. ACT Actual stator current I ACT This can be the current detected by current sensor 212 and transmitted to controller 200 as described above. In an alternative embodiment, the actual current I... ACT This can be determined using other known methods. Determine the actual current I at box 418. ACT Then, control can be transmitted to box 420, where controller 200 can transmit the actual current I. ACT With the estimated current I EST A comparison is then performed. As discussed above, the current comparison can generate an error signal. If the error signal generated at box 420 indicates the current I... ACT I EST If the values ​​are equal or within an acceptable error range, control can be transferred back to block 402 without updating the estimated rotor position θ stored in memory 204. EST And in routine 400, the next cycle of rotor position self-sensing begins. If the error signal generated at box 420 indicates current I... ACT I EST If the values ​​are not equal and the difference is greater than an acceptable error range, control can be transmitted to block 422, where the estimated rotor position θ stored in memory 204 is used. ESTUpdated to be based on the actual stator current I ACT The new estimated rotor position θ is indicated EST The error signal was used to calculate the new estimated rotor position θ of rotor 252. EST And the new estimated rotor speed ω EST Both values ​​can be stored in memory 204 for timing subsequent command current pulses 304. At the estimated rotor position θ EST After being stored in memory 204, control can be transferred back to block 402 to begin the next cycle of rotor position self-sensing under routine 400.

[0049] The SR motor control system disclosed herein has been found to be applicable in many different industries, including but not limited to earthmoving equipment, construction, agriculture, and mining. More specifically, the power-based injected rotor position self-sensing strategy disclosed herein is important for various applications where rotor position self-sensing is desirable due to the need for minimal package size, high reliability, and low cost in SR motor-driven operating machinery. Reliable and accurate rotor position sensing of the SR motor is a key step in developing low-cost, high-performance SR operating machinery drives. The SR motor control system illustrated and described herein extends reliability and accuracy to low-power operating conditions with very low torque loads and medium to high rotor speeds, which produce dead zones in previously known control strategies, where the command current I required to operate the SR motor 206 is limited. CMD The value may be too low to determine the estimated rotor position θ. EST This SR motor control system provides more complete control coverage for the reliable operation of the SR motor 206 within its operating condition range.

[0050] While the preceding text has set forth detailed descriptions of many different embodiments, it should be understood that the legal scope of protection is defined by the wording of the claims set forth at the end of this patent. The detailed descriptions should be interpreted as exemplary only and do not describe every possible embodiment, as describing every possible embodiment would be impractical, if not impossible. Many alternative embodiments may be implemented using current technology or technology developed after the filing date of this patent, and these alternative embodiments still fall within the scope of the claims that define the scope of protection.

[0051] It should also be understood that unless a term is expressly defined herein, there is no intention to explicitly or implicitly limit the meaning of that term beyond its ordinary or common meaning, and such term should not be construed as limiting the scope of any statement made based on any part of this patent (other than the language of the claims). Any term recited herein in accordance with a single meaning in relation to any claim recited at the end of this patent is used solely for clarity so as not to confuse the reader and is not intended to limit such claim terminology to that single meaning by implication or otherwise.

Claims

1. An electric drive system (108) for a work machine (100), the work machine (100) having a frame (102), a traction system (104) supporting the frame (102) and a power supply (106) mounted on the frame (102), the electric drive system (108) comprising: A switched reluctance motor (206) having a stator (250) and a rotor (252); An inverter (208) operably connected to the power supply (106) and the switched reluctance motor (206) to control power transfer from the power supply (106) to the switched reluctance motor (206); and A controller (200), operably connected to the switched reluctance motor (206) and the inverter (208), is configured to: The motor power output by the switched reluctance motor (206) is calculated, wherein the motor power is calculated as the product of the command torque used to control the switched reluctance motor (206) and the estimated rotor speed of the rotor (252). The motor power is compared with the maximum injected power. In response to the motor power being less than the injected maximum power, the estimated stator current of the switched reluctance motor (206) is determined based on the position current of the position current pulse (306) to be injected into the stator poles (254) of the switched reluctance motor (206) to estimate the rotor position. In response to the motor power being less than the injected maximum power, the inverter (208) injects the position current pulse (306) having the position current into the stator pole (254) of the switched reluctance motor (206). Determine the actual stator current of the switched reluctance motor (206) generated by the position current pulse (306). The actual stator current is compared with the estimated stator current, and In response to determining that the difference between the actual stator current and the estimated stator current is greater than a predetermined error amount, the estimated rotor position stored in the memory (204) is set to be equal to the new estimated rotor position.

2. The electric drive system (108) according to claim 1, wherein the controller (200) is configured to: Determine the estimated rotor speed of the rotor (252) of the switched reluctance motor (206); The estimated rotor speed is compared with the injected maximum rotor speed; and The step of calculating motor power is performed in response to determining that the estimated rotor speed is greater than the injected maximum rotor speed.

3. The electric drive system (108) according to claim 2, wherein the controller (200) is configured to omit the step of calculating the motor power in response to determining that the estimated rotor speed is less than the injected maximum rotor speed.

4. The electric drive system (108) according to any one of claims 1 to 3, wherein the controller (200) is configured to determine the estimated rotor speed by reading the memory (204) for storing the estimated rotor speed.

5. The electric drive system (108) according to claim 1, wherein the controller (200) is configured to: In response to the motor power being greater than the injected maximum power, the estimated stator current of the switched reluctance motor (206) is determined based on the command current of the command current pulse (304) to be injected into the stator pole (254) of the switched reluctance motor (206) in order to estimate the rotor position; In response to the motor power being greater than the injected maximum power, the inverter (208) injects the command current pulse (304) having the command current into the stator pole (254) of the switched reluctance motor (206). as well as Determine the actual stator current of the switched reluctance motor (206) generated by the command current pulse (304).

6. The electric drive system (108) according to claim 5, wherein the controller (200) is configured to determine the actual stator current of the switched reluctance motor (206) generated by the command current pulse (304).

7. A type of work machinery (100), comprising: Rack (102); A traction system (104) that supports the frame (102); A power supply (106) mounted on the rack (102); and The electric drive system (108) according to claim 1.

8. A method for determining the rotor position of a rotor (252) of a self-sensing switched reluctance motor (206), comprising: Calculate the motor power output by the switched reluctance motor (206), wherein the motor power is calculated as the product of the command torque for controlling the switched reluctance motor (206) and the estimated rotor speed of the rotor (252); Compare the motor power with the maximum injected power; In response to the motor power being less than the injected maximum power, the estimated stator current of the switched reluctance motor (206) is determined based on the position current of the position current pulse (306) to be injected into the stator pole (254) of the switched reluctance motor (206) to estimate the rotor position; In response to the motor power being less than the maximum injected power, the position current pulse (306) having the position current is injected into the stator pole (254) of the switched reluctance motor (206). Determine the actual stator current of the switched reluctance motor (206) generated by the position current pulse (306); The actual stator current is compared with the estimated stator current; as well as In response to determining that the difference between the actual stator current and the estimated stator current is greater than a predetermined error amount, the stored estimated rotor position is set to be equal to the new estimated rotor position.

9. The method of claim 8, comprising: Determine the estimated rotor speed of the rotor (252) of the switched reluctance motor (206); The estimated rotor speed is compared with the injected maximum rotor speed; as well as The step of calculating the motor power is performed in response to determining that the estimated rotor speed is greater than the injected maximum rotor speed.

10. The method of claim 9, further comprising omitting the step of calculating the motor power in response to determining that the estimated rotor speed is less than the injected maximum rotor speed.

11. The method of claim 8, comprising: Determine the estimated rotor speed of the rotor (252) of the switched reluctance motor (206); as well as Determine the motor torque of the switched reluctance motor (206). Calculating the motor power involves multiplying the motor torque by the estimated rotor speed.

12. The method of claim 11, wherein determining the estimated rotor speed comprises reading a memory (204) for storing the estimated rotor speed.

13. The method of claim 8, comprising: In response to the motor power being greater than the injected maximum power, the estimated stator current of the switched reluctance motor (206) is determined based on the command current of the command current pulse (304) to be injected into the stator pole (254) of the switched reluctance motor (206) in order to estimate the rotor position; In response to the motor power being greater than the injected maximum power, the command current pulse (304) having the command current is injected into the stator pole (254) of the switched reluctance motor (206). as well as Determine the actual stator current of the switched reluctance motor (206) generated by the command current pulse (304).

14. The method of claim 13, comprising determining the actual stator current of the switched reluctance motor (206) generated by the command current pulse (304).

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