Wheel speed recovery based on traction motor

Abstract

A method and apparatus for wheel speed estimation including an electric powertrain having an electric motor providing a motor speed, a wheel, and a mechanical linkage between the motor and the wheel, and an electronic control unit that calculates an estimated wheel speed based on the motor speed and a mechanical dynamic model of the electric powertrain.

Description

Technical Field

[0001] This disclosure relates to electric vehicles. Background Technology

[0002] Electric vehicles can be equipped with speed sensors at various locations within the electric drive system. Speed ​​can be used for various functions and controls. Speed ​​sensing of the electric drive system motors can be used to control these motors. Speed ​​sensing of the drive wheels can be used for various propulsion, suspension, steering, and braking subsystem-related controls. The absence of drive wheel speed sensing at any wheel of the vehicle can negatively impact the performance of systems that rely on individual drive wheel speed sensing. Furthermore, at low vehicle speeds, wheel speed sensing can have limited resolution, which can negatively impact the performance of systems that depend on accurate wheel speed sensing at low speeds. Summary of the Invention

[0003] In one exemplary embodiment, an apparatus for wheel speed estimation may include an electric powertrain and an electronic control unit, the electric powertrain having an electric motor that provides motor speed, wheels, and a mechanical connection between the motor and the wheels, the electronic control unit calculating the estimated wheel speed based on the motor speed and a mechanical dynamic model of the electric powertrain.

[0004] In addition to one or more features described herein, the electronic control unit can synchronize the motor speed with the sensed wheel speed.

[0005] In addition to one or more of the functions described in this article, the electronic control unit can handle sensing wheel speed.

[0006] In addition to one or more features described herein, the mechanical connection between the motor and the wheel may include a gearbox and a drive axle.

[0007] In addition to one or more features described herein, the mechanical dynamics model of an electric powertrain may include modeling the drive axle as an active component that includes a torsional spring constant, a torsional damping constant, a rotation angle at the gearbox output, and a rotation angle at the wheels.

[0008] In addition to one or more features described in this paper, the mechanical dynamics model of an electric powertrain may also include equivalent rotational models of the motor and gearbox.

[0009] In addition to one or more features described in this paper, the estimated wheel speed can be calculated from the second-order transfer function derived from the mechanical dynamics model of the electric powertrain.

[0010] In addition to one or more features described herein, an electric motor that provides motor speed may include an electric motor that provides motor speed based on a motor encoder.

[0011] In another exemplary embodiment, a method for estimating wheel speed in an electric powertrain may include using an electric motor to drive the wheel, and calculating the estimated wheel speed based on the speed of the electric motor and a mechanical dynamic model of the electric powertrain.

[0012] In addition to one or more features described in this article, the speed of the electric motor can be synchronized with the speed of the sensed wheel.

[0013] In addition to one or more features described herein, an electric powertrain may include a drive axle that is mechanically connected between the wheels and an electric motor, and the mechanical dynamics model of the electric powertrain may include modeling the drive axle as an active component including a torsional spring constant, a torsional damping constant, a rotation angle at the input end of the drive axle, and a rotation angle at the wheels.

[0014] In addition to one or more features described herein, the electric powertrain may also include a gearbox that mechanically connects the electric motor and the drive axle, and the mechanical dynamic model of the electric powertrain may also include an equivalent rotational model of the electric motor and the gearbox.

[0015] In addition to one or more features described in this paper, the estimated wheel speed can be calculated from the second-order transfer function derived from the mechanical dynamics model of the electric powertrain.

[0016] In yet another exemplary embodiment, an electric motor-driven vehicle may include an electric powertrain with an electric drive unit including an electric motor mechanically coupled to an input of a gearbox, and a motor controller that provides motor speed according to an encoder. The electric powertrain may also have wheels and a drive axle that mechanically connects the wheels to the output of the gearbox. The electric motor-driven vehicle may further include an electronic control unit that calculates estimated wheel speeds based on the motor speed and a mechanical dynamic model of the electric powertrain, processes sensed wheel speeds from wheel speed sensors, and provides the sensed wheel speeds and estimated wheel speeds to a vehicle subsystem controlled based on the wheel speed information.

[0017] In addition to one or more features described herein, the vehicle subsystem may include at least one of an electric propulsion subsystem, a suspension subsystem, a steering subsystem, and a braking subsystem.

[0018] In addition to one or more features described herein, the mechanical dynamics model of an electric powertrain may include modeling the drive axle as an active component comprising a torsional spring constant, a torsional damping constant, a rotation angle at the gearbox output, and a rotation angle at the wheels.

[0019] In addition to one or more features described in this paper, the mechanical dynamics model of an electric powertrain may also include equivalent rotational models of the electric motor and gearbox.

[0020] In addition to one or more features described in this paper, the estimated wheel speed can be calculated from the second-order transfer function derived from the mechanical dynamics model of the electric powertrain.

[0021] In addition to one or more features described herein, the vehicle subsystem may use estimated wheel speed when a wheel speed sensing failure occurs.

[0022] In addition to one or more features described herein, the vehicle subsystem may also use estimated wheel speeds at low vehicle speeds.

[0023] The above-described features and advantages, as well as other features and advantages, of this disclosure will become clear from the following detailed description when taken in conjunction with the accompanying drawings. Attached Figure Description

[0024] Other features, advantages, and details appear by way of example only in the following detailed embodiments, which are referenced to the accompanying drawings, wherein:

[0025] Figure 1 The schematic diagram illustrates an exemplary vehicle according to this disclosure, which may include an electric propulsion subsystem and other subsystems;

[0026] Figure 2 The diagram illustrates routines for performing various tasks according to this disclosure;

[0027] Figure 3 The figure illustrates a graphical representation of a one-dimensional interpolation according to the present disclosure;

[0028] Figure 4 The figure illustrates a simplified drive system diagram according to the present disclosure; and

[0029] Figure 5 The figure illustrates a rotational model according to this disclosure. Detailed Implementation

[0030] The following description is merely illustrative in nature and is not intended to limit this disclosure, its application, or its use. Throughout the accompanying drawings, corresponding reference numerals denote the same or corresponding parts and features.

[0031] All accompanying drawings are schematic diagrams, and the absolute or relative scaling of the various features shown is meaningless. Similar reference numerals refer to the same or similar parts in several drawings.

[0032] Figure 1The schematic diagram illustrates an exemplary vehicle 101, which may include an electric propulsion subsystem 103. The electric propulsion subsystem 103 may include various control components, electrical and electromechanical systems, including, for example, a rechargeable energy storage system (RESS) 104 and at least one electric drive unit (EDU) 111. The electric propulsion subsystem 103 may be employed in a powertrain to generate propulsion torque, serving as an alternative to or in combination with an internal combustion engine in various electric vehicle (EV) and hybrid electric vehicle (HEV) applications. Vehicle 101 is illustrated as a battery electric vehicle (BEV), with RESS 104 being a battery pack (e.g., powered by 400 volts DC), but other EVs or HEVs may also be used. A control system 115 may provide propulsion torque requests or commands to the powertrain electronics module 113. According to one embodiment, vehicle 101 is depicted as a two-axle, four-wheel vehicle, but it should be appreciated that any other vehicle including one or more axles and one or more wheels, intended for on-road or off-road use, may also be used. An axle may refer to a pair of laterally opposed wheels on a vehicle, without necessarily including a physical bridge between them. A wheel can refer to a single wheel or multiple wheels located on one side of the axle, such as those found on a dual-pickup rear axle. The electric propulsion subsystem 103 can provide propulsion torque or reaction braking torque to one or more wheels 105 located at the front (F) position of the vehicle (i.e., front left (LF) and front right (RF)) and the rear (R) position of the vehicle (i.e., rear left (LR) and rear right (RR)).

[0033] Vehicle 101 may include a front axle 116 corresponding to the front wheels 105. Front wheel steering may be achieved by a front steering mechanism 180, which may include a steering gear and steering linkage. Steering input (i.e., the operator interface) may be made via a mechanical steering shaft that interacts with the steering gear. The mechanical steering effect may be assisted by hydraulic or electric means. Alternatively, a steer-by-wire system that determines the operator's steering intention along with other information such as vehicle speed and yaw rate may drive the steering gear without the mechanical steering shaft interacting with the steering gear. Front steering angle information may be obtained via a front steering angle sensor 181.

[0034] Vehicle 101 may include a rear axle 114 corresponding to the rear wheels 105. Rear wheel steering may be achieved via a rear steering mechanism 106, which may include a steering gear and a steering linkage. The rear steering mechanism 106 may include an actuator 110 that causes the steering gear to turn the rear wheels 105 in a desired direction. In one embodiment, the actuator 110 may be, for example, a rotary or linear electric motor or hydraulic actuator or a combination thereof (such as an electro-hydraulic actuator). Other actuators may be apparent to those skilled in the art. In another embodiment, the rear steering mechanism 106 may include separate wheel actuator mechanisms (such as independent electric actuators). Rear steering angle information may be obtained via a rear steering angle sensor 181.

[0035] The electric propulsion subsystem 103 may include at least one EDU 111. Each EDU 111 may have different complexities, components, and integrations. In one embodiment, EDU 111 may include at least one electric traction motor (motor) 107, at least one gearbox 109, and at least one power electronics module 113. The EDU 111 is part of an electric powertrain that includes a motor and drivetrain components, including a gearbox, wheel assemblies, and other torque transmission components that mechanically connect the motor to the wheel assemblies. The power electronics module 113 may include a motor controller and a traction power inverter, and may also include other power electronics, such as an auxiliary power module and an on-board charging module. The power electronics module can perform motor control and diagnostics. The motor 107 may be a multiphase AC motor, such as a three-phase AC motor that receives three-phase AC power via a multiphase motor control power bus (AC bus) coupled to the traction power inverter. In one embodiment, the motor 107 may be a three-phase motor, and the traction power inverter may be a three-phase inverter. The traction power inverter may include multiple solid-state switches, such as IGBTs and power MOSFETs. The traction power inverter receives DC power via a high-voltage (HV) DC bus connected to the RESS. The motor controller of the power electronics module 113 can be connected to the traction power inverter for control. The traction power inverter can be electrically connected to the motor 107 via an AC bus, with the current monitored by two or three of its leads. The traction power inverter can be configured with suitable control circuitry, including pairs of power transistors (e.g., IGBTs) for converting high-voltage DC power to high-voltage AC power and vice versa. The traction power inverter can employ pulse-width modulation (PWM) control to convert DC power originating in the RESS into AC power to drive the motor 107 to generate torque. Similarly, the traction power inverter can convert mechanical power transmitted to the motor 107 into DC power to generate electrical energy that can be stored in the RESS, including as part of a regenerative braking control strategy. It is understood that the traction power inverter can be configured to receive motor control commands from the motor controller of the power electronics module 113 and control the inverter state to provide motor drive and regenerative functions.

[0036] exist Figure 1In the illustrated embodiment, the electric propulsion subsystem 103 includes a single-motor front axle configuration and a dual-motor rear axle configuration. The single-motor front axle configuration has an EDU 111 including a motor MA 107 providing propulsion torque to the LF and RF wheels 105. One EDU 111 in the dual-motor rear axle configuration includes a motor MB 107 providing propulsion torque to the LR wheel 105 and a motor MC 107 providing thrust torque to the RR wheel 105. The motors 107 are mechanically coupled to their respective wheels 105 via their respective gearboxes 109. The gearboxes 109 may include reduction gear drives, gear shafts, differential gear drives, and other drivetrain components, such as a drive axle 102, if necessary. The drive axle 102 may be a simple shaft or may include a pair of constant velocity (CV) joints at opposite ends. The drive axle 102 may be fixed at one end to the output end of the gearbox 109 and at the other end to the wheel 105, for example, via a spline coupling. Figure 1 In the illustrated exemplary embodiment, the motor MA 107 is mechanically coupled to the LF and RF wheels 105 via a front gearbox 109 integrating a reduction gear set and a differential gear drive, and to their respective drive axles 102. Such a gearbox can provide a single gear ratio or multiple controllable meshing gear ratios. This gearbox may include an input mechanically coupled to the motor MA 107, an LF output mechanically coupled to the LF wheels 105 via the LF drive axle 102 and corresponding wheel hubs, and an RF output mechanically coupled to the RF wheels 105 via the RF drive axle 102 and corresponding wheel hubs. Figure 1 In the illustrated exemplary embodiment, motor MB 107 can be mechanically coupled to LR wheel 105 via a corresponding rear gearbox 109 (including a reduction gear set) and drive axle 102. Such a gearbox can provide a single gear ratio or multiple controllable meshing gear ratios. Since motor MB 107 is only mechanically coupled to LR wheel 105, this type of gearbox does not include differential gear transmission. Such a gearbox can include an input mechanically coupled to motor MB 107 and an LR output mechanically coupled to LR wheel 105 via LR drive axle 102 and corresponding hub. Similarly, motor MC 107 can be mechanically coupled to RR wheel 105 via a corresponding rear gearbox 109 (including a reduction gear set) and drive axle 102. Such a gearbox can provide a single gear ratio or multiple controllable meshing gear ratios. Since motor MC 107 is only mechanically coupled to RR wheel 105, this type of gearbox does not include differential gear transmission. This gearbox may include an input mechanically coupled to a motor MC107 and an RR output mechanically coupled to an RR wheel 105 via an RR drive axle 102 and a corresponding hub. Figure 1The embodiments described are exemplary and other mechanical arrangements and power split configurations are considered, including single-motor configurations with one or more gearboxes that provide motor torque distribution to one or more wheels, single-motor rear axle configurations, dual-motor front axle configurations, wheel-integrated motor configurations, and various combinations thereof.

[0037] EDU 111 can provide the corresponding motor speed, for example, via a high-resolution motor encoder 108. The motor speed can be provided using alternative methods, including sensorless technology. Encoder 108 can provide rotational information to the corresponding power electronics module 113. The motor encoder information can be processed by the power electronics module 133 to derive the motor speed and related quantities, such as acceleration and angular positioning, angular velocity and angular acceleration, for use by the power electronics module 114 to control the corresponding motor 107.

[0038] Vehicle 101 may include a control system 115, which may include one or more electronic control units (ECUs) 117. The control system 115 may be responsible for functions related to the control and diagnostics of the electric propulsion subsystem 103, including, for example, power mode, torque request acquisition and verification, torque management including limiting, rate, and decision, gear ratio and differential control, RESS charge status, health status, and thermal management. The control system 115 may also be responsible for control functions related to other vehicle 101 subsystems, including, for example, suspension subsystem 50, steering subsystem 60, and braking subsystem 70. Vehicle 101 may include electronic braking control, which may include friction braking application and traction motor control (regenerative braking reaction torque). Electronic braking control may include anti-lock braking functionality. Vehicle 101 may include electronic traction control, which may include friction braking application and traction motor control (propulsion torque). Vehicle 101 may include electronic stability control, which may include friction braking application, traction motor control (propulsion / braking torque), electronic steering control (front and / or rear), and active or semi-active electronic suspension control. Vehicle 101 may include active rear steering control for low-speed maneuverability (reducing turning radius and lateral "tilt" steering) and for high-speed stability, such as when towing. Vehicle 101 may include various levels of advanced driver assistance systems (ADAS), which may include friction braking application, traction motor control (propulsion / braking torque), electronic steering control (front and / or rear), and active or semi-active electronic suspension control.

[0039] As used herein, the terms Electronic Control Unit (ECU), Control Module, Module, Control, Controller, Control Unit, Processor, and similar terms refer to any one or more combinations of application-specific integrated circuits (ASICs), electronic circuits, central processing units (preferably microprocessors) and associated memories and registers (read-only memory (ROM), random access memory (RAM), electrically programmable read-only memory (EPROM), hard disk drives, etc.) or microcontrollers executing one or more software or firmware programs or routines, combinational logic circuits, input / output circuits and devices (I / O) and appropriate signal conditioning and buffering circuits, high-speed clocks, analog-to-digital (A / D) and digital-to-analog (D / A) circuits, and other components for providing said functionality. ECUs may include various communication interfaces, including point-to-point or discrete-line and wired or wireless interfaces to networks, including wide area networks (WANs) and local area networks (LANs), vehicle controller LANs, and factory and service-related networks. The functionality of the ECU or control system described in this disclosure can be performed in a distributed control architecture among multiple networked ECUs. Software, firmware, programs, instructions, routines, code, algorithms, and similar terms refer to any set of executable instructions for an ECU, including calibrations, data structures, and lookup tables. An ECU may have a set of control routines executed to provide the described functions. These routines, such as those executed by a central processing unit, are operable to monitor inputs from sensors and other networked ECUs and to execute control and diagnostic routines to control actuator operation. Routines may be executed at fixed intervals during ongoing engine and vehicle operation. Alternatively, routines may be executed in response to events, software calls, or on demand via user interface input or requests.

[0040] The vehicle 101 control system 115 may include several ECUs 117, sensors 119, and a vehicle-user interface device 121, which can communicate via a communication network 123 and perform control functions and information sharing, including executing control routines in a local and distributed manner. The communication network may include wired and wireless communications, such as Controller Area Network (CAN) or Short Range Wireless Communication (SRWC) for example, using appropriate communication protocols for information sharing and routing. ECUs 117 may include modules such as a Vehicle Control Module (VCM), Powertrain Control Module (PCM), Power Electronics Module 113, Engine Control Module (ECM), Transmission Control Module (TCM), Body Control Module (BCM), Electronic Brake Control Module (EBCM), Traction Control or Stability Control Module, Cruise Control Module, Chassis / Suspension Control Module, Steering Control Module, etc. ECUs 117 may be indirectly or directly connected to various sensors and actuators, as well as other ECUs 117 (e.g., via the communication network 123). Sensors 119 may include motor encoders and wheel speed sensors, etc. User interface devices may include accelerometers and brake pedals, steering wheels, touchscreens, gesture and dialogue managers, etc.

[0041] Control system 115 can access various information from sensors 119 and various ECUs 117 for use in controlling various vehicle subsystems, including electric propulsion subsystem 103, suspension subsystem 50, steering subsystem 60, and braking subsystem 70, to achieve desired functions. The information accessed by control system 115 can include non-limiting examples such as vehicle dynamics and kinematic information, such as speed, heading, steering angle, multi-axle acceleration, and yaw, pitch, roll, and their derivatives. Such information is typically obtained via communication network 123, originating from, for example, vehicle sensors such as wheel speed sensors 171 that sense the rotation of wheels 105 at each corner of vehicle 101, front and rear steering angle sensors 181, and yaw rate sensors. Sensors 119 can provide information as discrete inputs to various directly coupled ECUs 117, or to communication network 123. Regardless, various ECUs 117 can access sensor information via communication network 123, for example, where sensors may operate as network node devices, or where sensor information is typically available on the communication network via directly connected ECUs 117. In one embodiment, EBCM 118 may directly monitor wheel speed sensor 171, process information (e.g., filter), and provide wheel speed information for other ECUs 117 to access via communication network 123. Wheel speed information based on wheel speed sensor can be referred to as sensed wheel speed or sensed wheel speed information. As used herein, EBCM refers to an ECU that monitors wheel speed sensor 171, processes wheel speed information from wheel speed sensor 71, and provides wheel speed information for use by other ECUs 117, whether or not braking subsystem control is performed in the EBCM. Similarly, motor speed information for each motor 107 may be based on a motor encoder and provided by the corresponding power electronics module 113 for access by other power electronics modules 114 and other ECUs 117 via communication network 123.

[0042] Wheel speed information, along with other sensor information and vehicle parameters, can be used in various vehicle control functions. For example, each of the electric propulsion subsystem 103, suspension subsystem 50, steering subsystem 60, and braking subsystem 70 can use wheel speed information to achieve various desired functions when controlling various actuators. Therefore, the control of the electric propulsion subsystem 103, suspension subsystem 50, steering subsystem 60, and braking subsystem 70 may require or depend on the completeness of wheel speed information. The control of subsystems using wheel speed information can be described as wheel speed-based or based on wheel speed information. For example, the electric propulsion subsystem 103 can use individual wheel speed information at each corner of the vehicle in torque vectoring and electronic differential control. The suspension subsystem 50 can use wheel speed information in roll control, brake descent, and start-up control. During low-speed and high-speed maneuvers, the steering subsystem 60 can use wheel speed information in front and rear steering angle control. And, the braking subsystem 70 can use wheel speed information in traction control, stability control, and anti-lock braking control.

[0043] The control system 115 can execute wheel speed sensing diagnostic and recovery routines, wherein motor speed information from EDU 111 can provide a redundancy source and backup for the wheel speed sensing information. In one embodiment, EBCM 118 can perform, for example... Figure 2The illustrated routine 201. This routine may be stored on a non-transitory computer-readable storage medium and includes computer-readable program instructions for causing a processor to perform aspects of this disclosure. A computer-readable storage medium may be a tangible device capable of residing and storing instructions for use by an instruction execution device. A computer-readable storage medium may be, for example, but not limited to, electronic storage devices, magnetic storage devices, optical storage devices, electromagnetic storage devices, semiconductor storage devices, or any suitable combination of the foregoing. A non-exhaustive list of more specific examples of computer-readable storage media includes: portable computer floppy disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or Flash memory), static random access memory (SRAM), portable compressed optical disc read-only memory (CD-ROM), digital universal disk (DVD), memory sticks, mechanical encoding devices, and any suitable combination of the foregoing. As used herein, a computer-readable storage medium should not be construed as a transient signal, such as radio waves or other freely propagating electromagnetic waves, electromagnetic waves propagating through waveguides or other transmission media (e.g., light pulses through fiber optic cables), or electrical signals transmitted through wires. Computer-readable program instructions can also be loaded onto a computer, other programmable data processing apparatus, or other device to cause a series of operational tasks to be performed on the computer, other programmable apparatus, or other device to produce a computer-implemented process, thereby implementing the instructions that execute on the computer, other programmable apparatus, or other device. Figure 2 The functions / actions illustrated in the flowchart and / or block diagram of routine 201 are shown in one or more boxes.

[0044] Routine 201 is initialized at 203, where motor diagnostic data is provided by the power electronics module 113 of EDU 111 and read into EBCM 118. Although routine 201 can be described for one corner of the vehicle, all corners of the vehicle are evaluated by routine 201. A motor speed fault check is performed at 205 to determine whether the motor speed information is considered good, for example, that there are no open or short circuits in encoder 108 and wiring harness, and that the motor speed information is free of speed errors. Such a fault check may include checking fault flag information transmitted from power electronics module 113 to EBCM 118, or processing the motor speed information at EBCM 118 in a local diagnostic routine. A motor speed fault at 205 causes routine 201 to proceed to 207, while the absence of a motor speed fault causes the routine to proceed to 213. A wheel speed sensing fault check is performed at 207 to determine whether the wheel speed sensing is considered good, for example, that there are no open or short circuits in wheel speed sensor 171 and wiring harness, and that the wheel speed sensing is free of speed errors. Such fault checks may include checking fault flag information passed from the EBCM 118 diagnostic routine to routine 201, or processing sensed wheel speeds in a local diagnostic routine. A sensed wheel speed fault at 207 causes routine 201 to proceed to 209, while a no-sense wheel speed fault causes routine 211. At 209, a fault flag can be set to indicate the simultaneous presence of a motor speed fault and a sensed wheel speed fault. Sensed wheel speeds determined to be good at 207 can be designated at 211 for use in controlling various subsystems using wheel speed information. Each of 209 and 211 proceeds to 235.

[0045] If the motor speed is already considered good at position 205, then synchronization of the motor speed and wheel speed is performed at position 213. Synchronization can be desirable when, for example, the motor speed and the sensed wheel speed use different sampling rates. In one embodiment, the motor speed can be synchronized with the sensed wheel speed through interpolation, for example, by using a pair of time-series samples of the motor speed and placing a given time-series sample of the sensed wheel speed on one side. Other synchronization processes, such as scaling up and scaling down, can also be used.

[0046] refer to Figure 3 This illustrates a simplified graphical representation of one-dimensional interpolation. From Figure 3 It can be seen that the sampling rate of motor speed (MS) is higher than that of the sensed wheel speed (WS). Motor speed is sampled at time step (i), and sensed wheel speed is sampled at time step (j), where (i) < (j). The motor speed is expected to be synchronized with the sensed wheel speed. Therefore, the synchronized motor speed sample will correspond to the sensed wheel speed sample acquired at time step (j). For example, at the sensed wheel speed sampling time t... WThe synchronous motor speed sampling at (j+1) is 305 based on the motor speed sampling time t. M (i+1) and t M Motor speed samples 309 and 311 at (i+2) are interpolated. The synchronous motor speed (e.g., 305) can be determined by linear interpolation depending on the motor speed samples on both sides, polynomial interpolation requiring additional motor speed samples, nearest value, prior value, or next value interpolation, or any other interpolation technique suitable for the relative sampling rate and expected system performance. A series of synchronous motor speed samples can undergo the same or similar filtering and processing as the sensed wheel speed samples.

[0047] After the motor speed and the sensed wheel speed are synchronized, an estimated wheel speed is calculated at point 215 based on the synchronized motor speed. The estimated wheel speed can be determined as a function of the mechanical ratio of the gearbox that mechanically connects motor 107 and wheel 105. The wheel speed estimated based on the motor speed can be referred to as the estimated wheel speed or estimated wheel speed information. The transfer function of the mechanical dynamic model based on the electric powertrain can be used to illustrate certain effects of the drivetrain components. The mechanical dynamic model can be used to derive the force balance relationships of the electric powertrain (including motor 107 and drivetrain), and more specifically, in the torque domain. The wheel assembly may include a tire, which is mounted on a wheel fixed to a hub. The wheel used herein may refer to the described wheel assembly or its functional equivalent.

[0048] Simplified drive system diagram in Figure 4 The diagram in the middle illustrates and provides the basis for a pair of torque balance relationships, which corresponds to Figure 1 This refers to the front drive system, which includes one of the single-motor front axle EDU 111, the front wheel 105, and the corresponding drive axle 102. (See reference) Figure 4 The mechanical components of the front axle EDU 111 are schematically represented as including the motor MA 107 and the gearbox 109. The effective gearbox output torque (T1) and effective gearbox output speed (ω1) can be determined based on the gearbox gear ratio and the motor input torque (T). i ) and motor input speed (ω) i To determine this. Therefore Figure 4 This illustrates a further simplified equivalence by incorporating the rotating components of motor MA 107 and gearbox 107 into an equivalent rotational model 405, which includes an equivalent moment of inertia (J). e Effective gearbox output torque (T1) and effective gearbox output speed (ω1). Equivalent moment of inertia (J) e ) can be combined Figure 5 An exemplary configuration is represented by the following relationship.

[0049]

[0050] Figure 5 An equivalent rotational model 405 is schematically shown on the gearbox side, which includes an exemplary compound ordinary gear train 505, wherein (g1-g4) represent gearbox gears having an input located at a simple input gear (g1), an output located at a simple output gear (g4), and compound intermediate gears (g2) and (g3). The moment of inertia (J1) represents the combined moment of inertia of the rotor assembly of motor MA107 and the input gear (g1). The moment of inertia (J2) represents the combined moment of inertia of the rotor assembly of the compound intermediate gears (g2) and (g3). And the moment of inertia (J3) represents the moment of inertia of the output gear (g4). The ratio of (g1) to (g2) is represented by i1, and the ratio of (g3) to (g4) is represented by i2. Other gear train arrangements will have other equivalent rotational model representations and may have corresponding equivalent moments of inertia determined according to the respective arrangements, as understood by those skilled in the art.

[0051] Continue to refer to Figure 4 The diagram also schematically illustrates drive axle 102 and wheels 105. Wheel input torque is represented by (T2), and wheel speed by (ω2). The drive axle is modeled as an active component, comprising a measurable torsional spring constant (k), a torsional damping constant (c) that can be adjusted by empirical correlation of wheel speed estimated and sensed in practice, the rotation angle (θ1) at the gearbox output (i.e., the drive axle input), and the wheel rotation angle (θ2). Figure 4 The wheel input torque (T2) is expressed as the product of the tangential road force (F) and the wheel radius (R) in the wheel-side equivalent rotational model 407, which includes the equivalent moment of inertia (J). w The wheel input torque (T2) = (FR) and wheel speed (ω2) are shown, thus demonstrating further equivalence at wheel 105.

[0052] Based on the equivalent rotation model (405, 407) and the drive axle model, Figure 1 The torque balance relationship of the front drive system can be expressed as follows:

[0053]

[0054]

[0055] A single dot symbol represents the first derivative, and a double dot symbol represents the second derivative. Therefore, and These represent the angular velocities on the gearbox side and the wheel side, respectively. and These represent the angular accelerations on the gearbox side and the wheel side, respectively. This represents the friction loss on the gearbox side, (T) f2 ) represents the wheel-side friction loss. It is assumed that the friction loss is irrelevant in the current application and is therefore assumed to be zero. Therefore, a pair of torque balance relationships [2] and [3] can be further simplified to the following torque balance relationship:

[0056]

[0057]

[0058] (k(θ1-θ2)) represents the torsional spring reaction torque of the drive axle 102. This represents the torsional damping torque of drive axle 102. Assuming no slippage between the wheels and the road surface, and further assuming a horizontal slope, the tangential road force (F) can follow the relationship F = ηma, where η is the percentage of the total longitudinal force applied to the bridge, m is the vehicle mass, and a is the vehicle's longitudinal acceleration. The following equivalences are assumed in the absence of wheel slippage: Therefore, by substitution, The torque balance relationship [5] can be rewritten as follows:

[0059]

[0060] Therefore, based on the torque balance relationship described in this article... Figure 1 After defining the driving frame, the transfer function can be derived based on the classical Laplace transform, as shown below:

[0061]

[0062] The relationship [7] can be simplified to wheel speed (ω2) and gearbox output speed (ω1), since the wheel speed is an expected estimate and since the angular quantities in θ and their derivatives are not actually measured. Therefore, the second-order transfer function for estimating the wheel speed (ω2) can be solved as follows:

[0063]

[0064] After calculating the estimated wheel speed based on the motor speed at point 215, various additional diagnostics can be performed on the estimated wheel speed. For example, at point 217, an instability diagnostic routine can be executed. At point 219, routine 201 proceeds to point 221 when an instability diagnostic fault exists. At point 221, a wheel speed sensing fault check is performed to determine whether the wheel speed sensing information is considered good, for example, that the wheel speed sensor 171 and wiring harness have no open or short circuits, and that the wheel speed sensing has no speed errors. Such a fault check may include checking fault flag information passed from the EBCM 118 diagnostic routine to routine 201, or processing the wheel speed sensing in a local diagnostic routine. At point 221, a wheel speed sensing fault causes routine 201 to proceed to point 209, while the absence of a wheel speed sensing fault causes routine 211 to proceed. The fault flag can be set at point 209 to indicate simultaneous wheel speed instability and wheel speed sensing fault. The wheel speed sensing determined to be good at point 221 can be specified at point 211 for use in the control of various subsystems using wheel speed information. Each of steps 209 and 211 leads to step 235. At step 219, if no unstable diagnostic fault exists, routine 201 proceeds to step 223. At step 223, correlation and other plausibility diagnostics can be performed, such as determining that all estimated wheel speeds are consistent and plausible in magnitude and direction. At step 225, if a plausibility diagnostic fault exists, routine 201 proceeds to step 227. At step 227, a sensed wheel speed fault check is performed to determine whether the sensed wheel speed is considered good, for example, that the wheel speed sensor 171 and wiring harness have no open or short circuits, and that the sensed wheel speed has no speed errors. Such a fault check may include checking fault flag information passed from the EBCM 118 diagnostic routine to step 201, or processing the sensed wheel speed in a local diagnostic routine. At step 227, a sensed wheel speed fault causes routine 201 to proceed to step 209, while the absence of a sensed wheel speed fault causes the routine to proceed to step 211. At step 209, a fault flag can be set to indicate both an estimated wheel speed plausibility fault and a sensed wheel speed fault. At 227, it has been determined that the wheel speed is being sensed correctly, and it can be specified at 211 for use in the control of various subsystems using wheel speed information. Each of 209 and 211 proceeds to 235. At 225, routine 201 proceeds to 229 when no reasonable diagnostic fault exists.

[0065] A wheel speed sensing fault check is performed at 229 to determine whether wheel speed sensing is considered good, for example, that wheel speed sensor 171 and its wiring harness have no open or short circuits, and that there are no speed errors in the wheel speed sensing. Such a fault check may include checking fault flag information passed from the EBCM 118 diagnostic routine to routine 201, or handling wheel speed sensing in a local diagnostic routine. A wheel speed sensing fault at 229 causes routine 201 to proceed to 231, while the absence of a wheel speed fault causes the routine to proceed to 230.

[0066] When there is no motor speed fault at 205, no instability, rationality, or other estimated wheel speed faults at 217, 219, 223, and 225, and the sensed wheel speed at 229 is not considered a fault, routine 201 proceeds to 230. When the vehicle speed is not low, for example, if it can be determined by comparing the estimated wheel speed or sensed wheel speed with a predetermined threshold, the sensed wheel speed at 211 can be designated for using wheel speed information to control the various subsystems. When the vehicle speed is low, the estimated wheel speed at 232 can be designated for using wheel speed information to control the various subsystems. Each of 211 and 232 proceeds to 235.

[0067] When there is no motor speed fault at point 205, and no unstable, reasonable, or other estimated wheel speed faults at points 217, 219, 223, and 225, but the wheel speed is sensed at point 229, it is considered a fault. At point 231, the estimated wheel speed is designated as the replacement for the faulty sensed wheel speed for use in the control of various subsystems using wheel speed information. At point 233, the system is notified that the estimated wheel speed has replaced the sensed wheel speed by setting an appropriate fault tolerance flag. The fault tolerance flag identifies the faulty sensed wheel speed and the replacement estimated wheel speed.

[0068] Then, at 235, the specified estimated wheel speed, specified sensed wheel speed, motor speed fault flag, wheel speed fault flag, and fault tolerance flag are output for use and by various subsystems in their control. Therefore, the estimated wheel speed based on motor speed information can be used wherever wheel speed information might be used. The estimated wheel speed can replace the sensed wheel speed diagnosed as faulty. The estimated wheel speed can also be used instead of the sensed wheel speed based on other conditions or considerations. For example, regardless of the fault state of the sensed wheel speed, the estimated wheel speed can be used instead of the sensed wheel speed at low vehicle speeds. The estimated or sensed wheel speed can be used to control various vehicle subsystems, including the electric propulsion subsystem 103, suspension subsystem 50, steering subsystem 60, and braking subsystem 70. Therefore, the electric propulsion subsystem 103 can use the estimated or sensed wheel speed at every corner of the vehicle in torque vectoring and electronic differential control. The suspension subsystem 50 can use the estimated or sensed wheel speed in roll control, brake descent, and start-up control. During low-speed and high-speed maneuvers, the steering subsystem 60 can use the estimated or sensed wheel speed in front and rear steering angle control. The braking subsystem 70 can use the estimated or sensed wheel speed at every corner of the vehicle in traction control, stability control, and anti-lock braking control.

[0069] Whether explicitly stated or not, all numerical values ​​herein are assumed to be modified to the term "about". For the purposes of this disclosure, a range may be expressed as from one particular value to another particular value. The term "about" generally refers to a range of values ​​that a person skilled in the art would consider equivalent to the listed values, have the same function or result, or are generally within the reasonable manufacturing tolerances of the listed values.

[0070] Unless explicitly described as “direct,” when the relationship between the first and second elements is described in the above disclosure, the relationship can be a direct relationship in which no other intervening element exists between the first and second elements, or it can be an indirect relationship in which one or more intervening elements (spatial or functional) exist between the first and second elements.

[0071] It should be understood that one or more steps in a method may be performed in a different order (or simultaneously) without altering the principles of this disclosure. Furthermore, although each of the above embodiments is described as having certain features, any one or more of those features described in connection with any embodiment of this disclosure may be implemented in any of the features of other embodiments and / or in combination with any one or more of those features, even if the combination is not explicitly described. In other words, the described embodiments are not mutually exclusive, and substitutions between one or more embodiments remain within the scope of this invention.

[0072] While the foregoing disclosure has been described with reference to exemplary embodiments, those skilled in the art will understand that various changes can be made without departing from its scope, and its elements can be substituted with equivalents. Furthermore, many modifications can be made to adapt particular situations or materials to the teachings of the invention without departing from its essential scope. Therefore, this disclosure is intended to be limited to the specific embodiments disclosed, but to include all embodiments falling within its scope.

Claims

1. A device for wheel speed estimation, comprising: An electric power system, comprising an electric motor that provides motor speed, wheels, and a mechanical connection between the motor and the wheels; as well as An electronic control unit calculates an estimated wheel speed based on the motor speed and the mechanical dynamic model of the electric powertrain. The mechanical dynamic model of the electric powertrain includes modeling the drive axle as an active component comprising a torsional spring constant, a torsional damping constant, a rotation angle at the gearbox output, and a rotation angle at the wheels. The mechanical dynamic model of the electric power system also includes the equivalent rotational model of the electric motor and the gearbox. The torque balance relationship is obtained based on the equivalent rotational model and the mechanical dynamic model, thereby obtaining the second-order transfer function of the wheel speed.

2. The apparatus according to claim 1, wherein, The electronic control unit synchronizes the motor speed with the sensed wheel speed.

3. The apparatus according to claim 2, wherein, The electronic control unit processes the sensed wheel speed.

4. The apparatus according to claim 1, wherein, The mechanical connection between the motor and the wheel includes a gearbox and the drive axle.

5. The apparatus according to claim 1, wherein, The estimated wheel speed is calculated based on a second-order transfer function derived from the mechanical dynamic model of the electric powertrain.

6. The apparatus according to claim 1, wherein, The electric motor that provides motor speed includes the electric motor that provides motor speed based on a motor encoder.

7. A vehicle driven by an electric motor, comprising: An electric powertrain, comprising: An electric drive unit, comprising an electric motor and a motor controller, wherein the electric motor is mechanically connected to the input of a gearbox, and the motor controller provides the motor speed according to an encoder; Wheels; and Drive axle, which mechanically connects the wheels to the output of the gearbox; and Electronic control unit, the electronic control unit: The estimated wheel speed is calculated based on the motor speed and the mechanical dynamic model of the electric power system; Processing the sensed wheel speed from the wheel speed sensor; and The sensed wheel speed and the estimated wheel speed are provided to the vehicle subsystem controlled based on the wheel speed information. The mechanical dynamic model of the electric powertrain includes modeling the drive axle as an active component comprising a torsional spring constant (k), a torsional damping constant (c), a rotation angle (θ1) at the output of the gearbox, and a rotation angle (θ2) at the wheels. The mechanical dynamic model of the electric power system also includes the equivalent rotational model of the electric motor and the gearbox. The torque balance relationship is obtained based on the equivalent rotational model and the mechanical dynamic model, thereby obtaining the second-order transfer function of the wheel speed.

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