Power-Based Pulse Injection Control for SR Self-Sensing

Abstract

Power-Based Pulse Injection Control for SR Self-Sensing Power-based self-sensing of rotor position of an SR motor at medium to high speed and low torque is achieved in an SR motor control system by comparing the motor power with an injected maximum power. In response to the motor power being less than the injected maximum power, a position current pulse is injected into the stator poles. The actual stator current generated by the position current pulse is compared with an estimated stator current, and if the actual stator current is not equal to the estimated stator current, the estimated rotor position stored in memory is updated with a new estimated rotor position.

Description

[Technical Field]

[0001] The present disclosure relates generally to control systems, and more particularly to switched reluctance motor control systems with rotor position self-sensing. [Background technology]

[0002] Many work machines, such as track tractors, excavators, and the like, may include a transmission connected to a power source that allows the work machine to be repositioned or moved between locations. With increasing interest in energy conservation and avoiding the use of fossil fuels, the use of electric motors as a power source has become more common. Electric motors convert electrical energy from an energy source, such as a battery, into mechanical energy to drive the work machine.

[0003] One type of electric motor known as a switched reluctance (SR) motor is widely used in a variety of applications, including the above-mentioned work machines, due to its rugged and robust construction. An SR motor includes a rotor and a stator with multiple stator poles with windings. Unlike typical brushed DC motor types, power is transmitted to the stator windings of an SR motor rather than to the rotor. This configuration significantly simplifies the mechanical design by eliminating the need for power transmission to moving parts, but complicates the electrical design by requiring some kind of switching system to transmit power to the various windings. Some SR motors have control systems that employ self-sensing techniques to estimate the rotor's position relative to the stator without using a direct angular position sensor. Self-sensing is important in many applications due to the need for minimal package size, high reliability, and low cost. Accurately determining the rotor's angular position at all operating speeds is essential to 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 where the load on the SR motor is small, the power required to rotate the rotor for the self-sensing control system to estimate the rotor position is low, so insufficient current may flow through the stator. As a result, there is a risk that the command current will not be transmitted to the stator pole windings at the correct time, which adversely affects 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-high speed / low torque operation. Summary of the Invention

[0005] In one aspect of the present disclosure, a work machine is disclosed. The work machine may include a power source, an SR motor having a stator and a rotor, an inverter operably connected to the power source and the SR motor and controlling power transfer from the power source to the SR motor, and a controller operably connected to the SR motor and the inverter. The controller may be configured to calculate motor power output by the SR motor, compare the motor power to an injected maximum power, determine an estimated stator current of the SR motor based on a position current of position current pulses injected into stator poles of the SR motor, and estimate a rotor position in response to the motor power being less than the injected maximum power. The controller may be further configured to, in response to the motor power being less than the injected maximum power, cause the inverter to inject position current pulses having a position current into the stator poles of the SR motor, determine an actual stator current of the SR motor generated by the position current pulses, compare the actual stator current with the estimated stator current, and, in response to determining that the actual stator current is not equal to the estimated stator current by an error amount greater than a predetermined error amount, set the estimated rotor position stored in memory equal to the new estimated rotor position.

[0006] In another aspect of the present disclosure, a method for self-sensing a rotor position of a rotor of an SR motor is disclosed. The method may include calculating motor power output by the SR motor, comparing the motor power to an injected maximum power, determining an estimated stator current of the SR motor based on position currents injected into stator poles of the SR motor, estimating a rotor position in response to the motor power being less than the injected maximum power, injecting position current pulses into the stator poles of the SR motor, determining an actual stator current of the SR motor generated by the position current pulses, comparing the actual stator current with the estimated stator current, determining that the actual stator current is not equal to the estimated stator current by an error amount greater than a predetermined error amount, and setting the stored estimated rotor position as a new estimated rotor position.

[0007] In another aspect of the present 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 source attached to the frame. The electric drive system may include an SR motor having a stator and a rotor, an inverter operably connected to the power source and the SR motor and controlling power transfer from the power source 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 may be configured to calculate motor power output by the SR motor, compare the motor power to an injected maximum power, and in response to the motor power being less than the injected maximum power, determine an estimated stator current of the SR motor based on a position current of a position current injected into a stator pole of the SR motor to estimate a rotor position, and in response to the motor power being less than the injected maximum power, cause the inverter to inject position current pulses having the position current into the stator poles of the SR motor, determine an actual stator current of the SR motor produced by the position current pulses based on a current sensor signal from a current sensor, compare the actual stator current with the estimated stator current, and in response to determining that the actual stator current is not equal to the estimated stator current by an error amount greater than a predetermined error amount, set the estimated rotor position stored in the memory as a new estimated rotor position.

[0008] Additional aspects are defined by the claims of this patent. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a side view of an exemplary work machine in which power-based pulse injection control for SR self-sensing of an SR motor according to the present disclosure may be implemented. [Figure 2] FIG. 2 is a block diagram of an exemplary electric drive system for the work machine of FIG. 1. [Figure 3] 2 is a schematic diagram of a stator and a rotor of an SR motor of the work machine of FIG. 1. [Figure 4]4 is a graph plotting rotor position versus current and inductance for the SR motor of FIG. 3 under low speed and high load conditions. [Figure 5] 4 is a graph plotting rotor position versus current and inductance for the SR motor of FIG. 3 under medium-high speed and heavy load conditions. [Figure 5A] 4 is a graph plotting current and inductance for the SR motor of FIG. 3 against time under medium-high speed and high load conditions. [Figure 6] 4 is a graph plotting the rotor speed and the motor torque of the SR motor of FIG. 3. [Figure 7] 7 is the graph of FIG. 6 including a power-based injection self-sensing region according to the present disclosure. [Figure 8] 4 is a graph plotting rotor position versus current and inductance for the SR motor of FIG. 3 under low speed and low load conditions. [Figure 9] 4 is a graph plotting rotor position versus current and inductance for the SR motor of FIG. 3 at medium-high speed and low load conditions. [Figure 9A] 4 is a graph plotting current and inductance for the SR motor of FIG. 3 against time under medium to high speed and low load conditions. [Figure 10] 4 is a flow diagram of an example SR rotor position self-sensing routine according to the present disclosure for the SR motor of FIG. 3. DETAILED DESCRIPTION OF THE INVENTION

[0010] The present disclosure relates to an SR motor control system. The SR motor control system is versatile for any machine using such an SR motor control system. The term "machine" can refer to a machine performing an operation related to an industry, such as mining, construction, agriculture, transportation, or other industries. As some examples, the machine can be a vehicle, backhoe loader, cold planer, wheel loader, compactor, feller buncher, forestry machine, forwarder, harvester, excavator, industrial loader, knuckle boom loader, material handler, motor grader, pipe layer, road recovery machine, skid steer loader, skidder, telehandler, tractor, bulldozer, tractor shovel, etc. Additionally, one or more tools can be connected to the machine and controlled using an electric motor associated with the switched reluctance motor control system described herein.

[0011] FIG. 1 is a diagram of an exemplary work machine 100 that may include an SR motor control system according to the present disclosure. While the work machine 100 is shown as a track-type tractor, it may also be any 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 by the frame 102, and an electric drive system 108 configured to transfer energy from the power source 106 to the traction system 104. A work implement 110, such as, but not limited to, a blade as shown, may be connected to the frame 102 and may be powered by the electric drive system 108. The work machine 100 may further include a working chamber 112. The power source 106 is configured to provide electrical power to the work machine 100 and to provide operating power for propulsion of the power drive system 108. The power source 106 may be a direct current (DC) power source, an Otto-cycle or a Diesel-cycle engine, or the like. Power source 106 is operably positioned to receive control signals from an operator control (not shown) within operating room 112. Power source 106 is also operably configured to provide electrical power to other systems of work machine 100.

[0012] Electric drive system 108 may be operatively configured with power source 106 to selectively propel work machine 100 via control signals from an operator in operating room 112. Electric drive system 108 is operatively connected to traction system 104, which may be movably connected to work machine 100 via axles, driveshafts, transmissions, and / or other components. In some implementations, traction system 104 may be provided in the form of the illustrated track drive system, although a wheel drive system or any other type of drive system configured to engage the ground and propel work machine 100 is also possible.

[0013] In some implementations, the electric drive system 108 may additionally or alternatively be configured to selectively operate the work machine 100 and an implement 110, which may be movably connected to the electric drive system 108. The illustrated implement 110 is a blade attached to the work machine 100 in the form of a tractor loader, but of course, in other embodiments, the implement 110 may include any other suitable implement for various tasks, such as dozing, brushing, compacting, digging, grading, lifting, tearing, plowing, etc. As noted above, FIG. 1 is provided as one example of a work machine 100 that may utilize an SR motor and SR motor control system according to the present disclosure. Other examples are possible, and the reasons for implementing an SR motor control system may differ from those described in connection with FIG. 1.

[0014] FIG. 2 is an example block diagram of components of an electric drive system 108 in which an SR motor control system according to the present disclosure can be implemented. The electric drive system 108 may include a controller 200 having one or more processors 202 and memory 204, a motor 206, an inverter 208, and a number of sensors 210. The motor 206 is, for example, the SR motor 206 shown in FIG. 3 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), a graphics processing unit (GPU), an accelerated processing unit (APU), a microprocessor, a microcontroller, a digital signal processor (DSP), a field programmable gate array (FPGA), an application-specific integrated circuit (ASIC), or other type of processing component. In some implementations, 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 memory, and / or optical memory) that store information and / or instructions for use by the processor 202.

[0015] In some implementations, controller 200 may be an electronic control unit (ECU), electronic control module (ECM), and / or the like of work machine 100 and / or SR motor 206. Processor 202 may execute one or more instructions and / or commands for controlling one or more components of work machine 100, such as controlling the operation of inverter 208, SR motor 206, and / or the like. Memory 204 may store program code for execution by processor 202 and / or data related to the execution of such program code by processor 202, such as program code for an SR motor control system according to the present disclosure.

[0016] Controller 200 may receive one or more input signals from various components of work machine 100, operate on the one or more input signals (e.g., by executing a program using the input signals as inputs for the program) to generate one or more output signals, and output the one or more output signals to the various components of work machine 100. For example, controller 200 may be electronically connected (e.g., wired or wirelessly) to SR motor 206, inverter 208, one or more sensors 210, and / or the like. Controller 200 is configured to receive inputs from sensors 210, an operator, and / or other systems of work machine 100. Based on these inputs, controller 200 commands inverter 208 to provide power to SR motor 206 as needed. This may include priming commands at start-up, switching commands during operation, and other commands required for an SR motor control system, as described herein.

[0017] The inverter 208 is electrically connectable to the power source 106 and the SR motor 206 and supplies current to the SR motor 206 according to instructions from the controller 200. In some implementations, the inverter 208 can receive DC current from the power source 106 and control the phase of the DC current to supply the switched DC current to the SR motor 206 based on switching instructions from the controller 200. Additionally or alternatively, the inverter 208 can receive instructions related to providing priming voltages and currents or position-sensing voltages and currents to the SR motor 206 to enable the angular position of the SR motor 206 to be determined without the use of a rotational position sensor. In some implementations, each phase of current may be controlled independently and in parallel. Those skilled in the art will understand that the control functions shown and described herein may be centralized in the controller 200 or distributed between the controller 200 and other “intelligent” devices. For example, in alternative embodiments, the inverter 208 may include a controller (e.g., a current controller, a phase controller, etc.) that controls the operation of the inverter 208 in response to instructions from the controller 200. Such variations are contemplated by the inventors.

[0018] Sensors 210 may include a set of sensor devices that provide information about the state of work machine 100. For example, sensors 210 may include a current sensor 212 that monitors current in SR motor 206 and communicates information about the current in each of several phases of SR motor 206 to controller 200. An SR motor control system executed by controller 200 can determine an estimate of the angular position of SR motor 206 based on the phase current values ​​from current sensor 212 without using a position sensor, determine switching commands based on the angular position estimate, and control the operation of SR motor 206 using the switching commands. Sensors 210 may include a DC link voltage sensor 214 that senses phase voltages used to estimate magnetic flux, which is then used to estimate phase currents in SR motor 206, in addition to other sensors, and any other sensors 210 necessary for the operation of work machine 100.

[0019] FIG. 3 schematically illustrates the operating components of an exemplary SR motor 206. The SR motor 206 includes an outer stator 250 and an inner rotor 252. The stator 250 remains stationary relative to the SR motor's 206 housing (not shown), while the rotor 252 is rotatable therein. The stator 250 has a plurality of stator poles 254A, 254B, and 254C circumferentially spaced about an inner surface 256. As shown, the stator poles 254A, 254B, and 254C are arranged in radially opposed pairs. Unlike a brushed DC motor, power is transferred to the stator 250 rather than the rotor 252, simplifying the mechanical design but complicating the electrical design because the inverter 208 requires a switching system to sequentially transfer power to the stator poles 254A, 254B, and 254C. Each pair of stator poles 254A, 254B, 254C has a corresponding winding (not shown) that receives an in-phase current from inverter 208 to generate a magnetic field to rotate rotor 252. In the illustrated example, the current to stator pole 254B is 60 degrees out of phase with the current to stator pole 254A, and the current to stator pole 254C is 120 degrees out of phase with the current to stator pole 254A.

[0020] The rotor 252 in the illustrated embodiment may be fabricated from a ferromagnetic metal, alloy, or other material and is rotatable about a rotor axis 258. The rotor 252 has a plurality of rotor teeth 260A, 260B spaced circumferentially about the periphery and rotor axis 258. The rotor teeth 260A, 260B are arranged in pairs and interact with magnetic fields generated by currents in the stator poles 254A, 254B, 254C to control the speed and direction of rotation of the rotor 252 about the rotor axis 258 as the rotor teeth 260A, 260B are attracted to or repelled from the stator poles 254A, 254B, 254C. The configuration of the stator 250 and rotor 252 is exemplary, and one skilled in the art will appreciate that the SR motor 206 may have alternative combinations of stator poles 254 and rotor teeth 260 to control the rotation of the rotor 252. The inventors understand that these alternative combinations are expected to be used in conjunction with power-based pulse injection control according to the present disclosure.

[0021] The SR motor 206 operates by causing the rotor 252 to tend to move toward a position of maximum inductance relative to the stator 250. The position of maximum inductance occurs when a pair of rotor teeth 260A, 260B aligns with a pair of energized stator poles 254A, 254B, 254C. This magnetic attraction generates a torque that rotates the rotor 252 and moves it toward the maximum inductance position. As power is transferred to each pair of stator poles 254A, 254B, 254C and the rotor 252 moves accordingly, the next stator pole 254A, 254B, 254C is energized in sequence to continue the rotor 252's movement and maintain angular momentum. This pattern of switching between energized and de-energized stator poles 254A, 254B, 254C and their phases complicates the operation of such motors. Proper operation of the SR motor 206 depends on proper timing of energizing each stator pole 254A, 254B, 254C, which is driven by the angular position of the rotor 252 relative to the stator 250.

[0022] 4 graphically illustrates controlling SR motor 206 by supplying current to stator poles 254A, 254B, and 254C at specific intervals to rotate rotor 252 counterclockwise as shown. Graph 300 illustrates the current I conducted through the winding of stator pole 254A versus the angular position θ of rotor 252 when SR motor 206 is operating at full load and low speed. Stator 250 and rotor 252 are shown below graph 300 in a series of 45° increments of rotor 252 rotation. At the 0° position, rotor tooth 260A is aligned with stator pole 254A. Because rotor tooth 260A is aligned with stator pole 254A at this position, the mechanical inductance L between stator pole 254A and rotor 252 reaches a maximum inductance L on inductance curve 302. 最大 If rotor teeth 260A are equidistant from stator poles 254A, then rotor teeth 260A rotate so that they are not aligned with stator poles 254A, and so inductance L reaches a minimum inductance L after 45° of rotation. 最小 The SR motor 206 operates when the rotor 252 has a minimum inductance L 最小 and maximum inductance L 最大 While the rotor 252 is rotating between the maximum inductance L and the maximum inductance L, the rotor 252 is in the driving torque region MTZ where the current to the stator pole 254A generates a driving torque in the direction of rotation. 最大 and minimum inductance L 最小 While rotating between , SR motor 206 is in a braking torque region RTZ where current to stator poles 254A generates a braking torque on rotor 252 in the opposite direction to the direction of rotation. Those skilled in the art will appreciate that the driving torque region MTZ and the braking torque region RTZ are direction dependent and will reverse when SR motor 206 is operating in the reverse direction. Rotor 252 experiences a maximum inductance H when rotor teeth 260A are aligned or misaligned with stator poles 254A. 最大 and minimum inductance H 最小 The cycle continues between

[0023] Counterclockwise rotation of the rotor 252 causes a command current I to flow to the stator pole 254A in the driving torque region MTZ. 指令 The command torque T required to operate the SR motor 206 is transmitted. 指令 and the command current I 指令 may be determined by the SR motor control system of controller 200 based on operator input and current operating conditions in work machine 100. As rotor 252 passes the 45° position, rotor teeth 260A rotate further away from stator pole 254A and rotor teeth 260B rotate toward stator pole 254A. Controller 200 determines when rotor 252 reaches commanded current-on position θ オン When the command current is turned off, the オフ The controller 200 controls the inverter 208 to conduct a command current pulse 304 through the winding of the stator pole 254A until the command current I 指令 and the position θ オン and θ オフ and the dwell period between them as needed to control whether the angular velocity ω of the rotor 252 increases, decreases, or remains constant. When the speed and load of the SR motor 206 are held constant, similar command current pulses 304 appear at approximately 90° intervals. Stator poles 254B and 254C are similarly controlled by command current pulses 304 that are 60° and 120° out of phase with the command current pulse 304 to stator pole 254A, respectively. Those skilled in the art will appreciate that the controller 200 varies the timing, duration, and polarity of the command current pulses 304 to accelerate, decelerate, or reverse the rotation of the rotor 252 and control the operation of the SR motor 206.

[0024] Efficient operation of the SR motor 206 requires that the rotor 252 is rotated at the correct command current ON position θ オンThe self-sensing operation of the SR motor 206 is dependent on knowing the position of the rotor 252 so that command current pulses 304A, 304B, and 304C are initiated at ω. While some prior art SR motors 206 use position sensors to detect the position of the rotor 252 relative to the stator 250, self-sensing operation is important for various 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 toward developing low-cost, high-performance SR work machine drives. One strategy for self-sensing the angular position ω of the rotor 252 is to use a position current I 位置 to the stator poles 254A, 254B, 254C during an injection window IW when no command current pulses 304 are generated by the stator poles 254A, 254B, 254C. The timing of the position current pulses 306 is determined by the estimated rotor position θ stored in the memory 204. 推定 and estimated rotor speed ω 推定 Next, the estimated rotor position θ 推定 , the estimated stator current I flowing through the corresponding stator poles 254A, 254B, and 254C 推定 is determined using an observer-based estimation approach. The position current I of the position current pulse 306 位置 can have a magnitude sufficient to cause a measurable change in the current measured by the current sensor 212, but not produce a parasitic braking torque on the rotor 252 significant enough to affect the performance of the SR motor 206 beyond the benefit of the self-sensing rotor position θ. 推定 The actual stator current I received from the current sensor 212 実際 to generate an error signal. The error signal is compared to an updated estimated rotor position θ of the rotor 252, which may be stored in memory 204 for timing subsequent command current pulses 304. 推定 and the updated estimated rotor speed ω 推定 is used to calculate

[0025] Estimated rotor position θ推定 While this strategy for determining the command current-on rotor position θ works well at low speeds, it can become difficult at higher operating speeds. As shown in FIG. 5, which shows a graph 300 of the stator poles 254A at higher operating speeds of the SR motor 206, オン is the command current I at the rotor position θ where the command current pulse 304 is appropriate. 指令 and appears within the braking torque region RTZ so that the command current-on rotor position θ オン The location and timing of θ significantly reduces or eliminates the opportunity for injection window IW of position current pulse 306. FIG. 5A shows graph 300 in which the rotor position axis has been changed to a time axis to represent a rotor speed ω that is approximately five times greater than the rotor speed ω of FIG. 4. This diagram shows that the time for injecting position current pulse 306 can be significantly reduced, along with the range of rotor positions θ over which position current pulse 306 is injected.

[0026] 6 is a graph 320 of a known position self-sensing strategy. Graph 320 depicts the relationship between motor speed ω and motor torque T of an example SR motor 206. Power curve 322 plots the maximum operating power P of the SR motor 206 for a combination of motor torque T and rotor speed ω. 最大 The SR motor 206 has a maximum output torque T 最大 Low speed range 322 L and a medium or intermediate speed range 322 having a constant maximum power output equal to the motor torque T multiplied by the motor speed ω. M The current never becomes completely zero, and the mid-speed range is 322 M High-speed range 322 which results in a different mechanical power curve shape H In the exemplary SR motor 206, the position self-sensing described above is performed in the velocity-based injection self-sensing region 324 during the low-speed region 322. L Maximum rotor speed ω 注入最大 The maximum rotor speed ω can be 注入最大Beyond this, motor position self-sensing can be performed in the main current-based self-sensing region 326 using a strategy similar to evaluating the measured inductance H or magnetic flux flow based on the main command current pulses 304A, 304B, 304C.

[0027] The main current-based method for position self-sensing requires minimal current to the SR motor 206. At very low torque loads and medium to high rotor speeds, the power required to drive the load is relatively low, and the rotor speed ω is low at low command currents I 指令 The command current I required to rotate the rotor 252 can be maintained at 指令 may be too low to operate properly for the injection, measurement, and comparison process, creating a dead zone where the controller 200 cannot determine the position of the rotor 252. For optimal operation of the SR motor 206, even with low power requirements under low torque / medium-high speed conditions, it is desirable to maintain up-to-date information about the rotor position θ.

[0028] The SR motor control system for the SR motor 206 according to the present disclosure can be implemented by the controller 200 and includes a controller for controlling an estimated rotor position θ when the SR motor 206 is operating at medium to high speed and low torque. 推定 7, the position self-sensing strategy of graph 320 is configured to determine the injected maximum rotor speed ω at which the SR motor 206 drives a low torque load. 注入最大 the estimated rotor speed ω is greater than 推定 3B is modified to include a power-based injection self-sensing region 328 cut out from the main current-based self-sensing region 326 at . The power-based injection self-sensing region 328 defines a maximum injected power P at which the controller 200 can inject the position current pulse 306, as discussed further below. 注入最大 When the SR motor 206 is running, the command torque T for controlling the SR motor 206 is 指令 and the estimated rotor speed ω stored in the memory 204. 推定Motor power P as a product of モータ The estimated rotor speed ω can be calculated. 推定 is the maximum rotor speed ω 注入最大 is larger than the motor power P モータ Maximum motor power P 注入最大 If it is smaller than the estimated motor position θ 推定 can be determined using the position current pulses 306 in the stator poles 254A, 254B, 254C.

[0029] 8 shows a graph 340 of the stator poles 254A that allow the SR motor 206 to operate at low rotor speed ω and low torque T. モータ is the maximum rotor speed ω 注入最大 or motor power P モータ Maximum motor power P 注入最大 If the current motor operating state is within either of the injection self-sensing regions 324, 328, position self-sensing can be performed using the position current pulse 306. If the current motor operating state is within either of the injection self-sensing regions 324, 328, the position current pulse 306 is injected during the injection window IW, as described above. The position current pulse 306 is similarly injected into the stator poles 254B, 254C.

[0030] The graph 340 for the stator pole 254A shows the torque of the SR motor 206 at medium to high rotor speeds ω M The command current I 指令 is lower than that in the case of high torque, the command current on rotor position θ オン may appear later in the braking torque region RTZ. The injection after the command current pulse 304 provides an opportunity for a large enough injection window IW to inject the position current pulse 306. This opportunity is also evident in the time domain version of the graph 340 shown in FIG. 9A. [Industrial Applicability]

[0031] 10 illustrates an example SR rotor position self-sensing routine 400 that may be implemented as part of an SR motor control system according to the present disclosure. The routine 400 may enable self-sensing injection-based rotor position sensing at low rotor speeds and low power operating conditions, as shown in graph 320 of FIG. 7. The routine 400 may begin at block 402, where the controller 200 calculates an estimated rotor speed ω of the rotor 252 of the SR motor 206. 推定 In some of the embodiments described above, the estimated rotor position θ 推定 was last updated and stored in memory 204, the estimated rotor speed ω 推定 In these implementations, the stored estimated rotor speed ω 推定 may be retrieved from memory 204 for routine 400. In other implementations, the estimated rotor speed ω 推定 may be determined in real time from available data, such as data from signals from the current sensor 212 or data provided by other sensors 210, such as a rotational speed sensor (not shown).

[0032] In block 402, the estimated rotor speed ω 推定 After is obtained or calculated, control proceeds to block 404, where the estimated rotor speed ω 推定 and the maximum rotor speed ω 注入最大 may be compared to determine whether the SR motor 206 is operating in the speed-based injection self-sensing region 324. 推定 is the maximum rotor speed ω 注入最大 , the SR motor 206 operates in the speed-based injection self-sensing region 324 and injects position current pulses 306 to estimate the current estimated rotor speed ω 推定 is accurate, in which case the routine may bypass determining whether the SR motor 206 is operating within the power-based injection self-sensing region 328 and proceed to the injection-based rotor position self-sensing step.

[0033] Estimated rotor speed ω 推定 is the maximum rotor speed ω 注入最大 If ω is greater than ω, the SR motor 206 has a medium-high rotor speed ω and is not operating in the speed-based injection self-sensing region 324. Conversely, the SR motor 206 operates in the main current-based self-sensing region 326 or the power-based injection self-sensing region 328. At the medium-high rotor speed ω, control proceeds to block 406, where the current motor power P of the SR motor 206 is calculated. モータ is the estimated rotor speed ω previously determined in block 402 推定 The command torque T 指令 It is determined by multiplying

[0034] In block 406, the motor power P モータ After is determined, control proceeds to block 408 where the calculated motor power P モータ Maximum power injected P 注入最大 and determines in which of the self-sensing regions 326, 328 the SR motor 206 is operating. モータ is the maximum power injected, P 注入最大 , the SR motor 206 is operating on the self-sensing power curve 330 and in the main current-based self-sensing region 326. In this case, control proceeds from block 408 to block 410, where the controller 200 adjusts the command current I of the command current pulses 304 output by the stator poles 254A, 254B, 254C to drive the rotor 252. 指令 Estimated stator current I based on 推定 Determine the estimated stator current I 推定 may be determined by the controller 200 using the observer-based estimation method described above, or any other suitable method for determining the current through the SR motor 206 during the command current pulse 304. Block 410 calculates the estimated stator current I 推定 If so, control may proceed to block 412, where the controller 200 determines the command current-on rotor position θ オン, the inverter 208 injects a command current pulse 304 into the corresponding stator poles 254A, 254B, and 254C, and the command current is turned off at the rotor position θ オフ The command current I 指令 Cut off the signal.

[0035] In block 410, the motor power P モータ is the maximum power injected, P 注入最大 , the SR motor 206 is operating below the self-sensing power curve 330 and in the power-based injection self-sensing region 328. In these conditions, control proceeds from block 410 to block 414, where the controller 200 calculates the estimated rotor position ω 推定 To determine the position current I of the position current pulses 306 output by the stator poles 254A, 254B, and 254C, 指令 Estimated stator current I based on 推定 Determine the estimated stator current I 推定 may be determined by the controller 200 using the observer-based estimation method described above, or any other suitable method for determining the current flowing in the SR motor 206 during the position current pulse 306. A block 414 calculates the estimated stator current I 推定 If so, control may proceed to block 416, where the controller 200 causes the inverter 208 to inject position current pulses 306 into the corresponding stator poles 254A, 254B, 254C within the injection window IW.

[0036] Whether the command current pulse 304 is injected in block 412 or the position current pulse 306 is injected in block 416, control may proceed to block 418, where the controller 200 calculates the actual stator current I flowing through the SR motor 206 during the current pulses 304, 306. 実際 Determine the actual stator current I 実際 may be the current detected by current sensor 212 and conducted to controller 200, as described above. In an alternative embodiment, the actual current I 実際may be determined by other known methods. At block 418, the actual current I 実際 After is determined, control may proceed to block 420, where the controller 200 determines the actual current I 実際 Estimate the current I 推定 As described above, the current comparison can generate an error signal. The generated error signal is then compared to the current I in block 420. 実際 , I 推定 If the values ​​are equal to or within the tolerance, the control calculates the estimated rotor position θ stored in the memory 204. 推定 , may return to block 402 without updating the rotor position self-sensing routine 400 to begin the next cycle of rotor position self-sensing. 実際 , I 推定 are not equal and the difference is greater than the tolerance range in block 420, control may proceed to block 422, where the estimated rotor position θ stored in memory 204 is 推定 The actual stator current I 実際 The new estimated rotor position θ is given by 推定 The error signal is updated to the new estimated rotor position θ of the rotor 252. 推定 and the new estimated rotor speed ω 推定 and these two values ​​may be stored in memory 204 for timing subsequent command current pulses 304. 推定 After is stored in memory 204, control may return to block 402 to begin the next cycle of rotor position self-sensing in routine 400.

[0037] The SR motor control system according to the present disclosure can be applied to many different industries, including, but not limited to, earthmoving equipment, construction, agriculture, mining, etc. More specifically, the power-based injection rotor position self-sensing strategy disclosed herein is important in a variety of applications where rotor position self-sensing is desirable due to the need for minimal package size, high reliability, and low cost of SR motor-driven work machines. Reliable and accurate rotor position sensing of SR motors is a key step toward developing low-cost, high-performance SR work machine drives. The SR motor control system shown and described herein extends reliability and accuracy to low-power operating conditions with very low torque loads and medium-to-high rotor speeds, and in such low-power operating conditions, the command current I required to operate the SR motor 206 is reduced. 指令 is the estimated rotor position θ 推定 The SR motor control system of the present disclosure provides a more complete control range for reliably operating the SR motor 206 over the entire range of operating conditions.

[0038] Although the foregoing provides detailed descriptions of many different implementations, it should be understood that the scope of legal protection is defined by the claims set forth at the end of this patent. The detailed description should be construed as exemplary only and does not describe every possible implementation, as describing every possible implementation would be impractical, if not impossible. Many alternative implementations can be implemented using current technology or technology developed after the filing date of this patent, and they would still be intended to fall within the scope of the claims, which define the scope of protection.

[0039] It should also be understood that unless a term is expressly defined herein, the meaning of a term is not intended to be limited, whether expressly or impliedly, to its plain or ordinary meaning, and such terms should not be construed as having limited scope based on statements made anywhere in this patent (except in the language of the claims). To the extent that any term recited in the claims at the end of this patent is referred to in a manner consistent with a single meaning herein, this is done solely for clarity to avoid confusing the reader, and such claim term is not intended to be limited, by implication or otherwise, to that single meaning.

Claims

1. 1. An electric drive system (108) for a work machine (100) having a frame (102), a traction system (104) supporting the frame (102), and a power source (106) attached to the frame (102), the electric drive system (108) comprising: a switched reluctance (SR) motor (206) having a stator (250) and a rotor (252); an inverter (208) operably connected to the power source (106) and the SR motor (206) and configured to control power transfer from the power source (106) to the SR motor (206); a controller (200) operatively connected to the SR motor (206) and the inverter (208); Including, The controller (200) calculating the product of a command torque for controlling the SR motor (206) and an estimated rotor speed stored in the memory (204) of the controller (200) as the motor power output by the SR motor (206); comparing the motor power with the maximum power that the controller (200) can inject with a position current pulse (306); determining an estimated stator current of the SR motor (206) based on a position current of the position current pulse (306) injected into a stator pole (254) of the SR motor (206) in response to the motor power being less than the maximum injected power, thereby estimating a rotor position; causing the inverter (208) to inject the position current pulses (306) having the position current into the stator poles (254) of the SR motor (206) in response to the motor power being less than the maximum injected power; determining an actual stator current of the SR motor (206) produced by the position current pulse (306); comparing the actual stator current with the estimated stator current; In response to determining that the difference between the actual stator current and the estimated stator current is greater than an acceptable error range, updating the estimated rotor position stored in the memory (204) to a new estimated rotor position indicated by the actual stator current. an electric drive system (108) configured to:

2. The controller (200) determining an estimated rotor speed of the rotor (252) of the SR motor (206); comparing the estimated rotor speed with an injected maximum rotor speed; performing the step of calculating the motor power in response to determining that the estimated rotor speed is greater than the injected maximum rotor speed. It is configured as follows: The electric drive system (108) of claim 1.

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

4. The controller (200) determining the estimated rotor speed of the rotor (252) of the SR motor (206); determining a motor torque of the SR motor (206); Calculating the motor power by multiplying the estimated rotor speed by the motor torque. It is configured as follows: The electric drive system (108) of claim 1.

5. The controller (200) is configured to determine the estimated rotor speed by reading the estimated rotor speed stored in the memory (204). The electric drive system (108) of claim 4.

6. The controller (200) determining the estimated stator current of the SR motor (206) based on a command current of a command current pulse (304) injected into the stator poles (254) of the SR motor (206) in response to the motor power being greater than the maximum injected power, thereby estimating the rotor position; causing the inverter (208) to inject the command current pulses (304) having the command current into the stator poles (254) of the SR motor (206) in response to the motor power being greater than the maximum injected power; determining the actual stator current of the SR motor (206) produced by the command current pulse (304); It is configured as follows: The electric drive system (108) of claim 1.

7. The controller (200) is configured to determine the actual stator current of the SR motor (206) produced by the command current pulse (304). The electric drive system (108) of claim 6.

8. A work machine (100), A frame (102); a traction system (104) supporting the frame (102); a power source (106) attached to the frame (102); An electric drive system (108) according to claim 1; A work machine (100) comprising:

9. A method for self-sensing rotor position of a rotor (252) of a switching reluctance (SR) motor (206), comprising: calculating a product of a command torque for controlling the SR motor (206) and an estimated rotor speed stored in a memory (204) of a controller (200) as a motor power output by the SR motor (206); comparing the motor power with a maximum power that the controller (200) can inject a position current pulse (306); determining an estimated stator current of the SR motor (206) based on a position current of a position current pulse (306) injected into a stator pole (254) of the SR motor (206) in response to the motor power being less than the maximum injected power, thereby estimating the rotor position; injecting the position current pulse (306) having the position current into the stator poles (254) of the SR motor (206) in response to the motor power being less than the maximum injected power; determining an actual stator current of the SR motor (206) produced by the position current pulse (306); comparing the actual stator current with the estimated stator current; in response to determining that the difference between the actual stator current and the estimated stator current is greater than an acceptable error range, updating the estimated rotor position stored in the memory (204) to a new estimated rotor position indicated by the actual stator current; A method comprising:

10. determining an estimated rotor speed of the rotor (252) of the SR motor (206); comparing the estimated rotor speed with an injected maximum rotor speed; performing the step of calculating the motor power in response to determining that the estimated rotor speed is greater than the injected maximum rotor speed; Including, 10. The method of claim 9.

11. 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. The method of claim 10.

12. determining an estimated rotor speed of the rotor (252) of the SR motor (206); determining a motor torque of the SR motor (206); Including, the step of calculating the motor power includes multiplying the estimated rotor speed by the motor torque; 10. The method of claim 9.

13. determining the estimated rotor speed includes reading an estimated rotor speed stored in the memory (204); The method of claim 12.

14. determining the estimated stator current of the SR motor (206) based on a command current of a command current pulse (304) injected into the stator poles (254) of the SR motor (206) in response to the motor power being greater than the maximum injected power, thereby estimating the rotor position; injecting the command current pulse (304) having the command current into the stator poles (254) of the SR motor (206) in response to the motor power being greater than the maximum injected power; determining the actual stator current of the SR motor (206) produced by the command current pulse (304); Including, 10. The method of claim 9.

15. determining the actual stator current of the SR motor (206) produced by the command current pulse (304); 15. The method of claim 14.

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