Method and system for estimating motor position offset

Abstract

The invention provides a method and a system for estimating position offset of a motor. Systems and methods for operating an electric drive system of an electric or hybrid vehicle are described. In one example, an angular error between a motor rotor reference position and a motor position sensor reference position is estimated when a high voltage is present and when zero torque is commanded to the motor.

Description

Technical Field

[0001] This specification relates to methods and systems for operating an electric machine. The electric machine may include permanent magnets. Background Art

[0002] Electric and hybrid vehicles include an electric machine that serves as a motor to provide positive torque to a driveline. The electric machine may be a permanent magnet electric machine including a rotor and a stator. The permanent magnets are included in the rotor, and the rotor rotates in response to a rotating magnetic field generated by current flowing through windings of the stator. The current flowing through the stator coils may be decomposed into a torque or quadrature current (i q ) that generates torque in the electric machine and a direct current or flux current (i d ) that tends to pull the rotor magnets in an outward direction. To operate the electric machine effectively, it is desirable to control the quadrature current and the flux current. To accurately control the quadrature current and the flux current, it is desirable to determine the angle between the electric machine rotor flux position and the zero angle reference position of the electric machine position sensor (which may be referred to as "resolver offset"). Additionally, it is desirable to determine the error of such an angle (which may be referred to as "resolver offset error") to appropriately degrade the response to prevent over- or under-delivering torque or vehicle speed. Accordingly, a method is provided herein by which the angle error can be determined with little impact on vehicle operation.

[0003] The above Summary of the Invention is provided to introduce a series of concepts that are further described in the Detailed Description below in a simplified form. This is not meant to identify key features of the claimed subject matter, whose scope is uniquely defined by the claims that follow the Detailed Description. Moreover, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure. Summary of the Invention

[0004] According to the present invention, a method for operating an electric drive system includes: supplying a time-varying flux voltage signal and a zero quadrature voltage signal to a motor controller in a synchronous coordinate system via a controller, the motor controller generating phase voltages for motor phase windings; and estimating an angle error between a motor rotor reference position and a motor position sensor reference position in response to the time-varying flux voltage signal and the zero quadrature voltage signal via the controller.

[0005] In one aspect of the present invention, the method includes operating the electric machine via the motor controller based on the angle error between the motor rotor reference position and the motor position sensor reference position.

[0006] In one aspect of the present invention, the method includes supplying the time-varying flux voltage signal and the zero quadrature voltage signal to an inverse Park and Clark transform.

[0007] In one aspect of the present invention, the method includes generating the phase voltage motor phase windings via the inverse Park and Clark transform.

[0008] In one aspect of the present invention, the method includes stopping the supply of the time-varying flux voltage signal in response to a torque command exceeding a threshold.

[0009] In one aspect of the present invention, the method includes operating a power inverter in accordance with the time-varying flux voltage signal.

[0010] In one aspect of the present invention, the method includes determining a motor torque current (iq) generated from operating the inverter and the motor based on the time-varying flux voltage signal and the zero quadrature voltage signal.

[0011] In one aspect of the present invention, the method includes indicating degradation of the motor in response to a magnitude of the motor torque current exceeding a threshold.

[0012] According to the present invention, there is provided a system having: an electric drive system including an inverter and a motor; and a controller including executable instructions stored in a non-transitory memory, the executable instructions causing the controller to generate an estimated error of an angle between a motor rotor reference position and a motor position sensor reference position.

[0013] According to one embodiment, the motor includes one or more permanent magnets, and wherein the estimated error of the angle between the motor rotor reference position and the motor position sensor reference position is determined when the rotational speed of the motor is zero.

[0014] According to one embodiment, the present invention is further characterized in that while generating an estimated value of an offset angle error, the electric drive system is commanded to generate a time-varying flux voltage signal.

[0015] According to one embodiment, the present invention is further characterized by additional executable instructions for generating a flux current and a torque current from the time-varying flux voltage signal and the zero quadrature voltage signal.

[0016] According to one embodiment, the present invention is further characterized by additional executable instructions for generating a flux voltage from the time-varying flux voltage signal.

[0017] According to one embodiment, the invention is further characterized by additional executable instructions for determining the magnitude of the quadrature current, the quadrature current being based on the time-varying flux voltage signal.

[0018] According to one embodiment, the invention is further characterized by additional executable instructions for operating the motor in response to the estimated error of the angle.

[0019] According to the invention, a method for operating an electric drive system includes: when the rotational speed of a motor in the electric drive system is zero and when the torque request of the electric drive system for operating the motor is zero, via a controller, starting to supply a time-varying flux voltage signal to a motor controller; continuously supplying the time-varying flux voltage signal to the motor controller for a predetermined duration as long as there is a predetermined voltage at the electric drive system and the torque request is zero; and estimating, via the controller, an error in the angle between a motor rotor reference position and a motor position sensor reference position in response to the time-varying flux voltage signal.

[0020] In one aspect of the invention, the method includes operating the motor in response to the error.

[0021] In one aspect of the invention, the method includes determining a motor torque current based on the time-varying flux voltage signal.

[0022] In one aspect of the invention, the error is based on the time-varying flux voltage signal and a zero quadrature voltage signal.

[0023] In one aspect of the invention, the method includes indicating degradation of the electric drive system in response to the torque current exceeding a threshold. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The advantages described herein will be more fully understood by reading examples of embodiments herein referred to as specific embodiments, either alone or in reference to the drawings, in which:

[0025] Figure 1 is a schematic diagram of a vehicle including a motor for propulsion;

[0026] Figure 2 shows a graph depicting the angle between a rotor flux reference position and a rotor sensor zero angle reference position;

[0027] Figure 3 is a block diagram for estimating an error in the angle between a rotor flux reference position and a rotor sensor zero angle reference position in a space vector pulse width modulation motor control system; and

[0028] Figure 4A flowchart showing the error of the angle between the rotor flux reference position and the rotor sensor zero angle reference position is presented. Detailed implementation

[0029] This specification relates to detecting the resolver offset error and the error of the angle between the rotor flux reference position of the motor and the rotor sensor zero angle reference position. The motor can be included in the electric drive system of a vehicle. The methods and systems described herein can allow for more accurate estimation of the angle between the rotor flux reference position and the rotor sensor zero angle reference position when the rotor sensor zero reference position has changed, such as when the motor stator moves with the resolver stator for a shrink-fit motor design. In one example, the method includes injecting a signal into an electric drive system including a space vector pulse width modulation driver. The space vector pulse width modulation driver can receive a zero torque request when estimating the error of the angle between the rotor flux reference position and the rotor sensor zero angle reference position. Figure 1 A vehicle including a space vector pulse width modulation drive system and a motor is shown. Figure 2 A graph of the angle between the rotor flux reference position of the motor and the rotor sensor zero angle reference position is shown. Figure 3 A block diagram of a system for estimating the angle error of the angle between the rotor flux reference position of the motor and the rotor sensor zero angle reference position is presented. Figure 4 A flowchart for estimating the angle error of the angle between the rotor flux reference position of the motor and the rotor sensor zero angle reference position is presented.

[0030] The angle between the rotor flux reference position and the rotor sensor zero angle reference position can be determined during the development of an electric vehicle or a hybrid vehicle. This angle can be stored in the memory of the controller, and this angle can be the basis for adjusting the operation of the motor so that the motor can operate more efficiently. However, the vehicle may have a different angle between the rotor flux reference position and the rotor sensor zero angle reference position than the developed vehicle. The different angle can be the result of the movement of the motor stator or resolver stator position for a shrink-fit motor design, or the result of storing an incorrect value in the memory of the controller due to human error. If the motor control system does not compensate for the different angle, a vehicle with a different angle between the rotor flux reference position and the rotor sensor zero angle reference position may not operate as efficiently as desired, and the torque generated may be different from the requested torque.

[0031] The inventors herein have recognized the problems mentioned above and have developed a method for operating an electric drive system, the method comprising: supplying a time-varying flux voltage signal to a motor controller that generates a flux voltage signal via a controller; and estimating an angular error of an angle between a motor rotor flux reference position and a motor position sensor zero angle reference position in response to the time-varying flux voltage via the controller.

[0032] By estimating the angular error by supplying a time-varying flux voltage signal to a motor controller that generates a flux voltage signal, a correction angle between a reference rotor flux position and a rotor sensor zero angle reference position can be determined without using a torque sensor and without driving the vehicle.

[0033] This specification can provide several advantages. Specifically, the method can detect a resolver offset error fault and further provide an appropriate fault response action. The method can provide a more accurate estimate of the angle between a rotor flux reference position and a rotor sensor zero angle reference position. Additionally, the method can be performed unobtrusively and without input from a vehicle user. Furthermore, the method can improve vehicle efficiency.

[0034] When understood alone or in conjunction with the drawings, the above and other advantages and features of this specification will be readily apparent from the following detailed description.

[0035] Figure 1 is a block diagram of a vehicle 121 including a powertrain or driveline 100. The front portion of the vehicle 121 is indicated at 110, and the rear portion of the vehicle 121 is indicated at 111. The vehicle propulsion system 100 includes an electric motor 126. The electric motor 126 can consume or generate electrical power depending on its operating mode. Throughout Figure 1 , mechanical connections between various components are shown as solid lines, while electrical connections between various components are shown as dashed lines.

[0036] The vehicle propulsion system 100 includes a rear axle 122. In some examples, the rear axle 122 can include two half shafts, such as a first half shaft 122a and a second half shaft 122b. The vehicle propulsion system 100 also includes front wheels 130 and rear wheels 131. The rear wheels 131 can be driven via the electric motor 126.

[0037] The rear axle 122 is coupled to the electric motor 126. The rear drive unit 136 can transfer power from the electric motor 126 to the axle 122, thereby causing rotation of the rear wheels 131. The rear drive unit 136 can include a low gear 175 and a high gear 177 that are coupled to the electric motor 126 via the output shaft 126a of the electric motor 126. The low gear 175 can be engaged via a fully closed low gear clutch 176. The high gear 177 can be engaged via a fully closed high gear clutch 178. The high gear clutch 178 and the low gear clutch 176 can be disengaged and engaged via commands received by the rear drive unit 136 over a controller area network (CAN) 199. Alternatively, the high gear clutch 178 and the low gear clutch 176 can be disengaged and engaged via a digital output or pulse width provided by the control system 114. The rear drive unit 136 can include a differential 128 such that torque can be provided to the first half shaft 122a and the second half shaft 122b. In some examples, an electronically controlled differential clutch (not shown) can be included in the rear drive unit 136.

[0038] The electric motor 126 can receive power from an on-vehicle electrical energy storage device 132. Additionally, the electric motor 126 can provide a generator function to convert the kinetic energy of the vehicle into electrical energy, where the electrical energy can be stored in the electrical energy storage device 132 for later use by the electric motor 126. The inverter / power converter system controller 134 (ISC1) can convert the alternating current generated by the electric motor 126 into direct current for storage at the electrical energy storage device 132, and vice versa. The electric drive system 135 includes the electric motor 126 and the inverter / power converter system controller 134. The electrical energy storage device 132 can be a battery, a capacitor, an inductor, or other electrical energy storage device. The power flowing into the electric drive system 135 can be monitored via a current sensor 145 and a voltage sensor 146. The position and rotational speed of the electric motor 126 can be monitored via a position sensor 147.

[0039] In some examples, the electrical energy storage device 132 can be configured to store electrical energy that can be provided to other electrical loads (other than the motor) residing on the vehicle, including the cabin heating and air conditioning systems, the engine starting system, the headlight system, the cabin audio and video systems, etc.

[0040] The control system 114 can communicate with the inverter / power converter system controller 134, the energy storage device 132, etc. The control system 114 can receive sensed feedback information from the electric drive system 135, the energy storage device 132, etc. In addition, the control system 114 can send control signals to the electric drive system 135, the energy storage device 132, etc. in response to the sensed feedback. The control system 114 can receive an indication of the output of the operator request for the vehicle propulsion system from the human operator 102 or the autonomous controller. For example, the control system 114 can receive sensing feedback from a pedal position sensor 194 that communicates with a pedal 192. The pedal 192 can schematically refer to the driver demand pedal. Similarly, the control system 114 can receive an indication of the operator-requested vehicle caliper actuation via the human operator 102 or the autonomous controller. For example, the control system 114 can receive sensed feedback from a pedal position sensor 157 that communicates with a caliper pedal 156.

[0041] The energy storage device 132 can periodically receive electrical energy from a power source (such as a fixed power grid (not shown)) that resides outside the vehicle (e.g., is not part of the vehicle). As a non-limiting example, the vehicle propulsion system 100 can be configured as a plug-in electric vehicle (EV), whereby electrical energy can be supplied to the electrical energy storage device 132 via the power grid (not shown).

[0042] The electrical energy storage device 132 includes an electrical energy storage device controller 139 and a power distribution module 138. The electrical energy storage device controller 139 can provide charge balancing between the energy storage elements (e.g., battery cells) and communication with other vehicle controllers (e.g., controller 112). The power distribution module 138 controls the inflow and outflow of electrical power of the electrical energy storage device 132.

[0043] One or more wheel speed sensors (WSS) 195 can be coupled to one or more wheels of the vehicle propulsion system 100. The wheel speed sensors can detect the rotational speed of each wheel. Such examples of WSS can include sensors of the permanent magnet type.

[0044] The controller 112 may include a part of the control system 114. In some examples, the controller 112 may be incorporated into the electric drive system 135. The control system 114 is shown as receiving information from a plurality of sensors 116 (various examples of which are described herein) and sending control signals to a plurality of actuators 181 (various examples of which are described herein). As an example, the sensors 116 may include a tire pressure sensor (not shown), a wheel speed sensor 195, etc. In some examples, sensors associated with the electric machine 126, the wheel speed sensor 195, etc. may transmit information about various states of the electric machine operation to the controller 112. The controller 112 includes a non-transitory (e.g., read-only memory) 165, a random access memory 166, a digital input / output 168, and a microcontroller 167. The controller 112 may receive input data via the CAN 199 and provide the data to the human / machine interface 140.

[0045] Accordingly, Figure 1 The system provides a system that includes: an electric drive system including an inverter and an electric machine; and a controller including executable instructions stored in a non-transitory memory, the executable instructions causing the controller to generate an estimated error of an angle between a motor rotor reference position and a motor sensor reference position when the rotational speed of the electric machine is zero. In a first example, the system includes where the electric machine includes one or more permanent magnets. In a second example that may include the first example, the system further includes commanding the electric drive system to generate a time-varying flux voltage signal while generating an estimated value of an offset angle error. In a third example that may include one or both of the first example and the second example, the system further includes additional executable instructions for generating a flux current and a torque current from the time-varying flux voltage signal and a zero quadrature voltage signal. In a fourth example that may include one or more of the first example to the third example, the system further includes additional executable instructions for generating a flux voltage from the time-varying flux voltage signal. In a fifth example that may include one or more of the first example to the fourth example, the system further includes additional executable instructions for determining a magnitude of a quadrature current based on the time-varying flux voltage signal. In a sixth example that may include one or more of the first example to the fifth example, the system further includes additional executable instructions for operating the electric machine in response to the estimated error of the angle.

[0046] Now referring to Figure 2 , an example graph is shown that depicts the angle between a rotor flux reference position and a rotor sensor reference position. From Figure 2The first curve at the top shows the back electromotive force (BEMF) of each of the phases of the motor as a function of time. The vertical axis represents the BEMF voltage and the horizontal axis represents time. Time increases from the left side of the graph to the right side of the graph.

[0047] from Figure 2 The second curve at the top represents the rotor angle as a function of time as the output of a rotor sensor (e.g., a resolver). The vertical axis represents the rotor angle and the horizontal axis represents time. Time increases from the left side of the graph to the right side of the graph.

[0048] The dashed line 202 represents the BEMF voltage of the vw phase of the motor, the solid line 204 represents the BEMF voltage of the wu phase of the motor, and the dotted line 206 represents the BEMF voltage of the uv phase of the motor. The motor flux axis (BEMF) reference position is the position where the vw phase (BEMF) voltage crosses zero. The angular offset between the motor flux axis reference position and the rotor angle reference position is indicated between the arrows 210. The sum of the angular offset and the rotor sensor sensed angular position is the rotor flux angle, and it can be applied to determine the flux current i d and the quadrature current i q as well as the flux voltage V d and the quadrature voltage V q .

[0049] Now referring to Figure 3 , a block diagram of a controller 300 for determining the angular error between the electrical rotor flux reference position and the rotor sensor zero angle reference position is shown. The controller 300 provides pulse width modulation motor control for the motor 126. The controller 300 may at least partially include executable instructions stored in the non-transitory memory of the controller 112. The controller 300 may also include hardware such as power transistors, inductors, capacitors, etc. In this example, the motor 126 is a three-phase motor supplied with power via an inverter / power converter system controller 134. The amount of current supplied in each of the three phases is input to block 320, where Park and Clarke transforms convert the current from each of the three phases into the measured quadrature current i q and the measured flux current i d .

[0050] A zero torque voltage request is input to the inverse Park and Clarke transform 312. Also, a high-frequency time-varying flux voltage supplied from source 350 is input to the inverse Park and Clarke transform 312. At block 312, the quadrature voltage V q command and the time-varying flux voltage command V d are processed into phase voltages. The phase voltages Van, Vbn, and Vcn are input to block 314.

[0051] At block 314, the phase voltages are converted into phase pulses via space vector pulse width modulation. The transistors or switches in the pulse-operated inverter / power converter system controller 134 are operated. The inverter / power converter system controller 134 outputs voltages for each of the phase windings 351 of the motor 126, which can cause the rotor 352 to rotate. The position of the rotor 352 is converted into an angle via the sensor 350, and the angle is supplied to blocks 312 and 320 for inverse Park transformation and Park and Clarke transformations.

[0052] Thus, a time-varying flux voltage can be injected into the controller, and the controller can determine the quadrature current i q , as Figure 4 detailed in the method of. In addition, the controller can estimate an angle error or offset for compensating motor operation.

[0053] Referring to Figure 4 , a flowchart of a method for estimating an angle error for controlling a motor is shown. Figure 4 The method of can be at least partially implemented as executable instructions stored in the controller memory of the system of Figure 1 and Figure 3 . In addition, Figure 4 the method of can include taking actions in the physical world to transform the Figure 1 and Figure 3 operating state of the system of. Additionally, in some examples, Figure 4 the method of can be distributed among several controllers, where each controller executes a portion of the method.

[0054] At 402, method 400 checks the prerequisites for Vd injection. It determines whether there is a high voltage at the inverter / power converter of the motor. The high voltage can be the voltage output of the traction battery. When the vehicle is activated, a high voltage may be present at the inverter / power converter. Method 400 can also determine whether the torque command of the motor is zero or substantially zero (e.g., within ±5 Nm of zero Nm). In addition, method 400 can also determine whether the rotational speed of the motor is zero or substantially zero (e.g., less than 5 revolutions per minute). If method 400 determines that there is a high voltage, the torque request for the motor is zero, and the motor rotational speed is zero, then the answer is yes, and method 400 proceeds to 404. Otherwise, the answer is no, and method 400 proceeds to exit.

[0055] At 404, method 400 injects or supplies a flux voltage command signal to the motor controller, as Figure 3As shown. The flux voltage command signal can vary over time, and the flux voltage command signal can be supplied to the controller within a predetermined amount of time. The flux voltage command signal can be a sinusoidal voltage or other periodic wave signal. The flux voltage can be input into the inverse Park and Clarke transforms to convert the flux voltage V d and the zero quadrature V q voltages into phase voltages Van, Vbn, and Vcn, as shown at boxes 311 and 312 of Figure 3 . The phase voltages can be converted into electrical pulses supplied to the motor 126 via space vector pulse width modulation and the power converter / inverter 134. Method 400 proceeds to 408.

[0056] At 408, method 400 determines whether to continue injecting the time-varying flux voltage V d . If so, the answer is yes, and method 400 proceeds to 406. If not, the answer is no, and method 400 proceeds to 410. Method 400 can inject the time-varying flux voltage V d within a predetermined amount of time.

[0057] At 406, method 400 determines whether there is a high voltage at the inverter / power converter of the motor. The high voltage can be the voltage output of the traction battery. When the vehicle is activated, a high voltage may be present at the inverter / power converter. Method 400 can also determine whether the torque command of the motor is zero or substantially zero (e.g., within ±5 Nm of 0 Nm). If method 400 determines that there is a high voltage and the torque command is zero or substantially zero, the answer is yes, and method 400 proceeds to 404. Otherwise, the answer is no, and method 400 proceeds to exit.

[0058] At 410, method 400 determines the magnitude of the quadrature current i q . The interior permanent magnet synchronous motor in the synchronous coordinate system is via the following equations:

[0059]

[0060] where R s is the phase winding resistance, λ pm is the permanent magnet flux linkage, L d and L q are the inductances on the d-q axes, i d and i q are the currents on the d-q axes, V d and V q are the voltages on the d-q axes, and ω e is the motor rotor angular velocity. When the rotor rotational speed is zero (ω e = 0), equations (1) and (2) can be simplified to:

[0061]

[0062] The sine wave v′ d can be injected into the estimated synchronous coordinate system of the voltage as follows:

[0063] v′ d = V0*sin(ωt) (5)

[0064] v′ q = 0 (6)

[0065] where ω = 2πf and f is the injection frequency of the injected flux voltage. The actual flux voltage V d and the quadrature voltage V q can be determined as follows:

[0066] V d = v′ d cosα = V0cosα*sin(ωt) (7)

[0067] V q = V0sinα*sin(ωt) (8)

[0068] where α is the resolver offset error (e.g., the angular error between the motor rotor flux reference position and the zero angle reference position of the motor position sensor). Substituting equations (7) and (8) into equations (3) and (4), the true flux current i d and the quadrature current i q can be determined via the following:

[0069]

[0070] where and Therefore, the q-axis current (e.g., the quadrature current) in the estimated synchronous coordinate system can be determined via the following:

[0071]

[0072] For a surface-mounted permanent magnet motor, where L d ≠ L q , i′ q,mag = kV0|sin2α|.

[0073] Equation 11 shows that if α = 0, the magnitude of i′ q = 0, such that the angular error = 0, thereby indicating that there is no error exhibited in the predetermined angle between the motor rotor reference position and the motor rotor position sensor reference position. As the angular error α increases from zero to 45 degrees, i′ qThe value increases from zero to a maximum value. Thus, i′ q The magnitude of can indicate the angular error between the motor rotor flux reference position and the zero angle reference position of the motor rotor position sensor. Method 400 proceeds to 412.

[0074] At 412, method 400 determines whether the estimated quadrature current is greater than a predetermined threshold quadrature current. If so, the answer is yes, and method 400 proceeds to 414. Otherwise, the answer is no, and method 400 proceeds to 416.

[0075] At 414, method 400 indicates the deterioration of the electric drive system. This deterioration can be indicated by displaying a message on a human / machine interface or broadcasting a message to a remote server. Method 400 proceeds to exit.

[0076] At 416, method 400 indicates that the electric drive system has no deterioration. This lack of deterioration can be indicated by displaying a message on a human / machine interface or broadcasting a message to a remote server. Method 400 can also operate the motor based on the angle between the motor rotor reference position and the motor position sensor reference position plus the angular error. The angular error can be estimated via a function that correlates the magnitude of i′ q with the angular error. Method 400 proceeds to exit.

[0077] Therefore, method 400 injects a time-varying flux voltage into the motor controller and estimates the motor position offset angle based on the magnitude of i ′ q when the torque request of the motor is zero.

[0078] Figure 4The method provides a method for operating an electric drive system, which includes: supplying a time-varying flux voltage signal and a zero quadrature voltage signal to a motor controller in a synchronous coordinate system via a controller, the motor controller generating phase voltages for motor phase windings; and estimating an angular error between a motor rotor reference position and a motor position sensor reference position in response to the time-varying flux voltage signal and the zero quadrature voltage signal via the controller. In a first example, the method further includes operating the motor via the motor controller based on the angular error between the motor rotor reference position and the motor position sensor reference position. In a second example that may include the first example, the method further includes supplying the time-varying flux voltage signal and the zero quadrature voltage signal to an inverse Park and Clarke transform. In a third example that may include one or both of the first example and the second example, the method further includes generating the phase voltages for the motor phase windings via the inverse Park and Clarke transform. In a fourth example that may include one or more of the first example to the third example, the method further includes stopping the supply of the time-varying flux voltage signal in response to a torque command exceeding a threshold. In a fifth example that may include one or more of the first example to the fourth example, the method further includes operating a power inverter according to the time-varying flux voltage signal. In a sixth example that may include one or more of the first example to the fifth example, the method further includes determining a motor torque current (iq) generated from operating the inverter and the motor based on the time-varying flux voltage signal and the zero quadrature voltage signal. In a seventh example that may include one or more of the first example to the sixth example, the method further includes indicating deterioration of the motor in response to a magnitude of the motor torque current exceeding a threshold.

[0079] Figure 4The method also provides a method for operating an electric drive system, which includes: when the rotational speed of the motor in the electric drive system is zero and when the torque request of the electric drive system for operating the motor is zero, via a controller, starting to supply a time-varying flux voltage signal to the motor controller; continuously supplying the time-varying flux voltage signal to the motor controller for a predetermined duration as long as there is a predetermined voltage at the electric drive system and the torque request is zero; and estimating an error in the angle between the motor rotor reference position and the motor position sensor reference position in response to the time-varying flux voltage signal via the controller. In a first example, the method further includes operating the motor in response to the error. In a second example that may include the first example, the method further includes determining a motor torque current based on the time-varying flux voltage signal. In a third example that may include one or both of the first example and the second example, the method includes that the error is based on the time-varying flux voltage signal and a zero quadrature voltage signal. In a fourth example that may include one or more of the first example to the third example, the method further includes indicating degradation of the electric drive system in response to the torque current exceeding a threshold.

[0080] It should be noted that the exemplary control and estimation routines included herein can be used with various engine and / or vehicle system configurations. The control methods and procedures disclosed herein can be stored as executable instructions in a non-transitory memory and can be implemented by a control system including a controller in combination with various sensors, actuators, and other engine hardware. The specific programs described herein can represent one or more of any number of processing strategies, such as event-driven, interrupt-driven, multi-tasking, multi-threading, etc. Thus, the various actions, operations, and / or functions shown can be executed in the order shown, executed in parallel, or omitted in some cases. Similarly, the processing order is not necessarily required to implement the features and advantages of the exemplary embodiments described herein, but is provided for ease of illustration and description. One or more of the actions, operations, and / or functions shown can be repeatedly executed according to the specific strategy used. In addition, at least a portion of the actions, operations, and / or functions described can be graphically represented as code to be programmed into the non-transitory memory of a computer-readable storage medium of a control system. When the described actions are executed by executing instructions in a system including various engine hardware components in combination with one or more controllers, the control actions can also transform the operating states of one or more sensors or actuators in the physical world.

[0081] This specification ends here. After reading this description, many variations and modifications will occur to those skilled in the art without departing from the spirit and scope of this description. For example, single-cylinder, I3, I4, I5, V6, V8, V10, and V12 engines operating on natural gas, gasoline, diesel, or alternative fuels can benefit from this specification.

Claims

1. A method for operating an electric drive system, comprising: Supplying a time-varying flux voltage signal and a zero quadrature voltage signal to a motor controller in a synchronous coordinate system via a controller, the motor controller generating phase voltages for motor phase windings; And Estimating an angular error between a motor rotor reference position and a motor position sensor reference position via the controller in response to the time-varying flux voltage signal and the zero quadrature voltage signal.

2. The method according to claim 1, further comprising operating the motor via the motor controller based on the angular error between the motor rotor reference position and the motor position sensor reference position.

3. The method according to claim 1, further comprising supplying the time-varying flux voltage signal and the zero quadrature voltage signal to an inverse Park and Clarke transformation.

4. The method according to claim 3, further comprising generating the phase voltages for the motor phase windings via the inverse Park and Clarke transformation.

5. The method according to claim 4, further comprising stopping the supply of the time-varying flux voltage signal in response to a torque command exceeding a threshold.

6. The method according to claim 5, further comprising operating a power inverter according to the time-varying flux voltage signal.

7. The method according to claim 1, further comprising determining a motor torque current (iq) generated from operating an inverter and a motor based on the time-varying flux voltage signal and the zero quadrature voltage signal.

8. The method according to claim 7, further comprising indicating degradation of the motor in response to a magnitude of the motor torque current exceeding a threshold.

9. A system, comprising: An electric drive system, the electric drive system including an inverter and a motor; And A controller, the controller including executable instructions stored in a non-transitory memory, the executable instructions causing the controller to generate an estimated error of an angle between a motor rotor reference position and a motor position sensor reference position.

10. The system according to claim 9, wherein the motor includes one or more permanent magnets, and wherein the estimated error of the angle between the motor rotor reference position and the motor position sensor reference position is determined when a rotational speed of the motor is zero.

11. The system according to claim 10, further comprising commanding the electric drive system to generate a time-varying flux voltage signal while generating an estimated value of an offset angle error.

12. The system according to claim 9, further comprising additional executable instructions for generating a flux current and a torque current from a time-varying flux voltage signal and a zero quadrature voltage signal.

13. The system according to claim 12, further comprising additional executable instructions for generating a flux voltage from the time-varying flux voltage signal.

14. The system according to claim 13, further comprising additional executable instructions for determining a magnitude of a quadrature current, the quadrature current being based on the time-varying flux voltage signal.

15. The system according to claim 14, further comprising additional executable instructions for operating the motor in response to the estimated error of the angle.

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