OPTIMIZED POSITION FOR STOPPING AN ELECTRIC MACHINE TO REDUCE LOSSES AND FOR VEHICLE START

Abstract

Methods and systems for controlling the torque of an electric machine propelling a vehicle when the vehicle is stopped are described. These methods and systems can be applied to synchronous and induction electric machines configured to propel a vehicle. The methods and systems enable the electric machine to output a constant quantity of torque when both the vehicle speed and the speed of the electric machine are zero.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a method and system for positioning an electric machine that powers a vehicle in preparation for starting the vehicle. GENERAL STATE OF THE ART AND OVERVIEW

[0002] An electric vehicle may occasionally stop. After the electric vehicle is stopped, the vehicle may start from zero speed in response to a release of a vehicle brake and / or an increase in torque desired by a driver. The amount of torque required to move the vehicle in a desired forward or reverse direction may be a function of a mass of the vehicle and a slope of a road or surface on which the vehicle is stopped. If a power source (e.g., an electric machine) of the electric vehicle outputs a torque that is lower than the amount of torque that can overcome the mass of the vehicle and the slope of the surface on which the vehicle is resting, the vehicle may not move or may move in an undesirable direction when the vehicle brakes are released.One way to ensure that sufficient starting torque is available to move the electric vehicle in the desired direction is to oversize an electric vehicle inverter, which supplies electrical power to the vehicle's propulsion source, so that the vehicle's propulsion source can be supplied with a larger amount of electrical current. Another possible solution to this problem is to oversize the vehicle's propulsion system's electric motor so that the electric vehicle's propulsion system can produce more torque. However, oversizing the inverter and motor can increase the vehicle's financial costs and increase system losses. Therefore, it may be desirable to provide a way to increase starting torque without having to oversize the inverter or the vehicle's motor.

[0003] The inventors have recognized the above problems and developed a method of operating a vehicle comprising: rotating an electric machine to a predetermined position in response to the vehicle being stopped on a first surface having a first incline greater than a threshold incline.

[0004] By rotating an electric machine in response to an incline of a surface on which a vehicle is stopped, it may be possible to provide the technical solution of generating a uniform torque capacity for an electric machine arranged to propel a vehicle. More specifically, an angular position of a rotor of an electric machine may be adjusted from a position where the electric machine is capable of generating less torque at zero speed, to generating more torque at zero speed. When a rotor of an electric machine assumes a first angular position, the electric machine may, for example, have a torque output capacity (e.g., a capacity to generate an amount of torque) with which it generates 52,000 Newtons of tractive effort at zero vehicle speed.However, if the rotor's angular position is adjusted by 30 (or 15 or 7.5) degrees, the electric machine can have a torque output capacity of 60,000 Newtons at zero vehicle speed. Thus, the rotation angle of the electric machine's rotor can be adjusted when the electric machine's output torque capacity is less than the electric machine's maximum output torque capacity at zero speed.

[0005] The present description can have several advantages. Specifically, the method can generate a high torque output at zero speed for an electric machine. Furthermore, the method can provide a more consistent torque output from an electric machine at zero speed. Furthermore, the method can be applied to differently configured (e.g., 3-phase and 6-phase) synchronous and induction electric machines.

[0006] It should be understood that the above summary is provided to introduce, in simplified form, a selection of concepts further described in the detailed description. It is not intended to identify critical or essential features of the claimed subject matter, the scope of which is defined only by the claims following the detailed description. Furthermore, the claimed subject matter is not limited to implementations that address any disadvantages noted above or in any part of the disclosure. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is an illustration of an example vehicle including an electric machine configured to power a vehicle. Fig. Figure 2 shows a diagram of a hypothetical traction force that can be generated using an electric machine. Fig. 3-8 show examples of operating characteristics for a three-phase electrical machine. Fig. 9 shows an example method for operating an electric machine of a vehicle. Fig. 10 and Fig. 11 show examples of driveline couplings. DETAILED DESCRIPTION

[0007] A method and system for operating an electric power source of a vehicle are described. The method and system are suitable for electric and hybrid vehicles. In one example, the method and system rotate a rotor of an electric machine during selected vehicle conditions such that a consistent traction capacity and a consistent output torque capacity of the electric machine can be provided. Fig. 1 shows a schematic view of an example vehicle. Fig. Figure 2 shows a diagram showing how a vehicle's tractive force can be related to a vehicle's speed. Fig. 3-8 show operating characteristics of an example of an electrical synchronous machine. Fig. 9 shows a flowchart of an example of a method for operating a vehicle and an electric machine. Fig. 10 and Fig. 11 show examples of driveline couplings.

[0008] Fig. 1 illustrates an example of a vehicle propulsion system 199 for a vehicle 10. A front end 110 of the vehicle 10 is indicated, and a rear end 111 of the vehicle 10 is also indicated. The vehicle 10 moves in a forward direction when the front end leads the movement of the vehicle 10. The vehicle 10 moves in a reverse direction when the rear end leads the movement of the vehicle 10. The vehicle propulsion system 199 includes a drive source 105 (e.g., an electric machine, such as a motor), but in other examples, two or more drive sources may be provided. In one example, the drive source 105 may be a synchronous or induction electric machine that can operate as a motor or as a generator. The drive source 105 is attached to an electrified wheel axle 190 and outputs power from its rotor 105a to a gear set 107. In Fig. 1, mechanical connections between the different components are shown as solid lines, while electrical connections between different components are shown as dashed lines.

[0009] The vehicle propulsion system 199 includes an electrified axle 190 (e.g., a axle containing an integrated electric machine that provides propulsion for the vehicle). The electrified axle 190 may include two axleshafts, including a first or right axleshaft 190a and a second or left axleshaft 190b. The vehicle 10 further includes front wheels 102 and rear wheels 103.

[0010] The electrified axle 190 may be an integrated axle that includes a differential gear 106, a gear set 107, and a power source 105. The gear set 107 may be referred to as a geared transmission and may include a plurality of gears and one or more clutches for shifting between gears. In one example, the gear set may include a first gear 108, a second gear 109, and a third gear 131. Further, the electrified axle 190 may include one or more clutch actuators 112 for shifting one or more clutches 145. The clutches 145 may be dog clutches, wet clutches, friction clutches, swaged clutches, or other known configurations. A sensor 168 provides an indication of a motor position and a position of one half of the clutch 145 (e.g.,on an upper side of the clutch 145 relative to a power path), and a sensor 169 provides an indication of a clutch position of the clutch 145 on a lower side of the clutch relative to the power path of the clutch. . Fig. 10 and Fig. 11 shows two examples of clutch configurations. The electrified wheel axle 190 may include a first speed sensor 119 for detecting a speed of a power source 105 on an input side of the clutch 145 and a second speed sensor 122 for detecting a speed on an output side of the clutch 145. An electrical power conversion device, or inverter, 115 is electrically coupled to the power source 105. A wheel axle control unit 116 is electrically coupled to sensors and actuators of the electrified wheel axle 190.

[0011] The power source 105 can transmit mechanical power to or receive mechanical power from the gear set 107. For example, the gear set 107 can be a multi-stage gear set that can be adjusted between gears (e.g., a first gear 108 and a second gear 109) when commanded by the axle control unit 116. The control unit 116 includes a processor 116a and a memory 116b. The memory 116b can include read-only memory, random access memory, and keep-alive memory. The axle control unit 116 can receive a transmission temperature via a sensor 133. The gear set 107 can transmit mechanical power to or receive mechanical power from the differential gear 106. The differential gear 106 can transmit or receive mechanical power to or from rear wheels 103 by means of a right axle shaft 190a and a left axle shaft 190b.The power source 105 may consume alternating current (AC) electrical power provided by the electrical power conversion device 115. Alternatively, the power source 105 may provide AC electrical power to the electrical power conversion device 115. High-voltage direct current (DC) power may be provided to the electrical power conversion device 115 from the battery 160 (e.g., a traction battery, which may also be referred to as an electrical energy storage device or battery pack). The electrical power conversion device 115 may convert the DC electrical power from the battery 160 into AC electrical power for the power source 105. Alternatively, the electrical power conversion device 115 may provide AC power from the power source 105.The electrical power conversion device 115 can convert the AC electrical power from the drive source 105 into DC electrical power for storage in the battery 160.

[0012] Battery 160 may periodically receive electrical energy from a power source, such as a stationary power grid 5, that is external to the vehicle (e.g., not part of the vehicle). As a non-limiting example, vehicle propulsion system 199 may be embodied as a plug-in electric vehicle (EV), in which electrical energy may be delivered to battery 160 via power grid 5 and a charging station 12. Electrical charge may be delivered to battery 160 via a receptacle 100.

[0013] Battery 160 may include a BMS controller 139 (e.g., a battery management system controller) and a power distribution block 162. BMS controller 139 may provide charge balancing between energy storage elements (e.g., battery cells) and communication with other vehicle controllers (e.g., vehicle control unit 152). BMS controller 139 includes a core processor 139a and memory 139b (e.g., random access memory, read-only memory, and keep-alive memory).

[0014] The vehicle 10 may include a vehicle control unit (VCU) 152 that may communicate with the electrical power conversion device 115, the wheel axle control unit 116, a friction or parking brake controller 170, a global positioning system (GPS) 188, a BMS controller 139, and an instrument panel 130 and components therein via a controller area network (CAN) 120. The VCU 152 includes the memory 114, which may include read-only memory (ROM or non-transitory memory) and random access memory (RAM). The VCU also includes a digital processor or central processing unit (CPU) 153 and inputs and outputs (I / O) 118 (e.g., digital inputs, including counters, timers, and discrete inputs, digital outputs, analog inputs, and analog outputs). The VCU can receive signals from sensors 154 and provide control signal outputs to actuators 156.Sensors 154 may include, but are not limited to, lateral accelerometers, longitudinal accelerometers, yaw rate sensors, tilt sensors, temperature sensors, battery voltage and current sensors, and other sensors described herein. Additionally, sensors 154 may include a steering angle sensor 197, a pedal position sensor 141 that communicates a driver demand, vehicle range detection sensors, including a radio-based positioning and ranging (RADAR) sensor, a light-based positioning and ranging (LIDAR) sensor, a sound-based navigation and ranging (SONAR) sensor, and a brake pedal position sensor 151. Actuators may include, but are not limited to, inverters, transmission controllers, displays, human-machine interfaces, friction brake systems, and battery controllers described herein.

[0015] Shown is the driver demand pedal position sensor 141 coupled to a driver demand pedal 140 to determine a degree of human actuation of the driver demand pedal 140. Shown is the brake pedal position sensor 151 coupled to a brake pedal 150 to determine a degree of human actuation of the brake pedal 150. The steering angle sensor 197 is configured to determine a steering angle according to a position of a steering wheel 198.

[0016] The vehicle propulsion system 199 is shown with a global positioning system 188 that receives time and position data from one or more GPS satellites 189. The global positioning system may also include geographic maps in ROM to determine the position of the vehicle 10 and features of roads on which the vehicle 10 may travel.

[0017] The vehicle propulsion system 199 may also include an instrument panel 130 with which a driver of the vehicle can interact. The instrument panel 130 may include a display system 132 configured to display information to the vehicle driver. The display system 132 may, as a non-limiting example, be a touchscreen or human-machine interface (HMI) display that allows the vehicle driver to view graphical information as well as input commands. In some examples, the display system 132 may be wirelessly connected to the internet (not shown) via a VCU 152. Thus, in some examples, the vehicle driver may communicate with an internet site or software application (app) and the VCU 152 via the display system 132.

[0018] The instrument panel 130 may further include a user interface 136 through which the vehicle operator can adjust the operating state of the vehicle. More specifically, the user interface 136 may be configured to enable / disable operation of the vehicle powertrain (e.g., the power source 105) based on user input. Further, a user may request a wheel axle mode (e.g., park, reverse, neutral, drive) through the user interface. Various examples of the user interface 136 may include interfaces that utilize a physical device, such as a key, that can be inserted into the user interface 136 to activate the electrified wheel axle 190 and the power source 105 and turn on the vehicle 10, or that can be removed to deactivate the electrified wheel axle and the power source 105 to turn off the vehicle 10.The electrified wheel axle 190 and the power source 105 may be activated by supplying electrical power to the power source 105 and / or the inverter 115. The electrified wheel axle 190 and the electric machine may be deactivated by interrupting the supply of electrical power to the electrified wheel axle 190 and the power source 105 and / or the inverter 115. Still other examples may additionally or optionally utilize a start / stop button manually pressed by the user to start or stop the electrified wheel axle 190 and the power source 105 to turn the vehicle on or off.In other examples, a remote start of an electrified wheel axle or electric machine may be initiated from a remote computing device (not shown), such as a mobile phone or smartphone-based system, where a user's mobile phone sends data to a server, and the server communicates with the vehicle control unit 152 to activate the electrified wheel axle 190, including an inverter and electric machine. A spatial orientation of the vehicle 10 is indicated via the axles 175.

[0019] The vehicle 10 is also shown with a parking or friction brake controller 170. The friction brake controller 170 can selectively apply and release the friction brakes (e.g., 172a and 172b) by allowing hydraulic fluid flow to friction brakes. The friction brakes can be applied and released to avoid locking of the friction brakes on front wheels 102 and rear wheels 103. Wheel position or speed sensors 161 can provide wheel speed data to the friction brake controller 170. The vehicle propulsion system 199 can provide torque to rear wheels 103 to propel the vehicle 10.

[0020] A human or autonomous driver may request wheel torque according to a driver demand, or alternatively, wheel power according to a driver demand, via an actuation of a driver-demanding pedal 140 or via an output to the vehicle control unit 152 of a request for wheel torque / power according to a driver demand. The vehicle control unit 152 may then request torque and power from the drive source 105 via commands from the wheel axle control unit 116. The wheel axle control unit 116 may command the inverter 115 to deliver the wheel torque / power according to a driver demand via the electrified wheel axle 190 and the drive source 105. The inverter 115 may convert the DC electrical power from the battery 160 to AC power and supply the AC power to the drive source 105. The drive source 105 rotates and transmits torque / power to a gear set 107.The gear set 107 can supply torque from the drive source 105 to differential gears 106, and the differential gears 106 transmit torque from the drive source 105 to rear wheels 103 via axle shafts 190a and 190b.

[0021] Under conditions where the driver-demand pedal is fully released, the vehicle control unit 152 may request a small amount of negative or regenerative braking power to gradually decelerate the vehicle 10 when a speed of the vehicle 10 is greater than a threshold speed. The amount of regenerative braking power requested may be a function of a driver-demand pedal position, a battery state of charge (SOC), a vehicle speed, and other conditions. When the driver-demand pedal 140 is fully released and the vehicle speed is lower than a speed threshold, the vehicle control unit 152 may request a small amount of positive torque / power (e.g., drive torque) from the power source 105, referred to as creep torque or creep power.The creep torque or creep power may enable the vehicle 10 to remain stationary when the vehicle 10 is on a small positive gradient.

[0022] The human or autonomous driver may also request negative or regenerative braking torque in accordance with a driver demand, or alternatively, braking power in accordance with a driver demand, via an actuation of a brake pedal 150 or via an output of a braking power request in accordance with a driver demand to the vehicle control unit 152. The vehicle control unit 152 may request that a first portion of the driver-requested braking power be generated via the electrified wheel axle 190 and the power source 105 by means of a command to the wheel axle control unit 116. In addition, the vehicle control unit 152 may request that a portion of the driver-requested braking power be provided via friction brakes 172 by means of a command to the friction brake controller 170 to provide a second portion of the driver-requested braking power.

[0023] After the vehicle control unit 152 determines the braking power demand, the vehicle control unit 152 may command the wheel axle control unit 116 to deliver the portion of braking power allocated to the electrified wheel axle 190 according to a driver demand. The inverter 115 may convert the AC electrical power generated by the power source 105 into DC power for storage in the battery 160. The power source 105 may convert the vehicle's kinetic energy into AC power.

[0024] The axle control unit 116 contains predetermined gear shift schedules for the transmission, allowing gears of the fixed-ratio gear set 107 to be selectively engaged and disengaged. Shift schedules stored in the axle control unit 116 can select gear shift points or conditions as a function of wheel torque and vehicle speed according to driver demand.

[0025] Thus, the system of Fig. 1 provides a vehicle system comprising: an electric machine configured to propel a vehicle; a powertrain clutch; an inverter electrically coupled to the electric machine; and a controller including executable instructions stored in non-transitory memory that cause the controller to adjust a rotational position of a rotor of the electric machine in response to a slope of a surface where the vehicle is stopped or a start metric of the vehicle when the vehicle is stopped. In a first example, the vehicle system further includes additional executable instructions that cause the controller to adjust the rotational position of the rotor in further response to a rotational position of the electric machine where power losses of the electric machine are minimized at a zero speed of the electric machine.In a second example, which may include the first example, the vehicle system further includes additional executable instructions that cause the controller to adjust the rotational position of the rotor in further response to a rotational position of the electric machine where a torque output of the electric machine is maximized at a zero speed of the electric machine. In a third example, which may include one or both of the first and second examples, the vehicle system further includes additional executable instructions that cause the controller to apply vehicle brakes in response to the vehicle being stopped.In a fourth example, which may include one or more of the first through third examples, the vehicle system further comprises additional executable instructions that cause the controller, in response to the vehicle being stopped and the surface slope being greater than a threshold amount or a start metric being greater than a threshold amount, to open a clutch prior to adjusting the rotational position of the rotor at which the vehicle is stopped. In a fifth example, which may include one or more of the first through fourth examples, the vehicle system includes where the clutch is a dog clutch. In a sixth example, which may include one or more of the first through fourth examples, the vehicle system includes where the clutch is a friction clutch.

[0026] Now Fig. 2, where a hypothetical engine diagram is presented showing vehicle performance with a two-speed gear set. The diagram 200 includes a vertical axis 201 representing a tractive effort developed by a vehicle. In this diagram, the tractive effort generated by the vehicle and the electric machine when the vehicle speed is zero represents a non-optimized tractive effort for the vehicle at a vehicle speed of zero. The tractive effort for the vehicle increases in the direction of the vertical axis arrow. The diagram 200 also includes a horizontal axis 203 representing a vehicle speed. The vehicle speed decreases from the left side of Fig. 2 to the right of Fig. 2 towards. Fig. Figure 2 also shows lines 250-260, which represent lines of tractive effort required to meet a vehicle performance metric for constant-grade surfaces on which the vehicle is traveling, as a function of vehicle speed. Line 250 represents the amount of tractive effort required to meet a vehicle performance metric when a vehicle is on a roadway with a 35% grade. Line 252 represents the amount of tractive effort required to meet a vehicle performance metric when a vehicle is on a roadway with a 30% grade. Line 254 represents the amount of tractive effort required to meet a vehicle performance metric when a vehicle is on a roadway with a 15% grade. Line 256 represents the amount of tractive effort required to meet a vehicle performance metric when a vehicle is on a roadway with a 5% grade.Line 260 represents the amount of traction required to meet a vehicle performance metric when a vehicle is on a roadway with a 0% grade.

[0027] Line 202 represents a maximum tractive force capacity for the vehicle in first gear at a peak power (e.g., a maximum amount of tractive force that can be generated by the vehicle) for a predetermined period of time (e.g., 10 seconds) while the vehicle's transmission is engaged in first gear. Line 204 represents a maximum tractive force capacity for the vehicle in second gear at a peak power that can be generated for a predetermined period of time while the vehicle's transmission is engaged in second gear. Line 206 represents a maximum tractive force capacity for the vehicle in first gear at a continuous power (e.g., a maximum amount of tractive force that can be continuously generated by the vehicle) while the vehicle's transmission is engaged in first gear.Line 208 represents a maximum tractive force capacity for the vehicle in second gear at a continuous power that can be continuously generated while the vehicle's transmission is in second gear.

[0028] It can be seen that the maximum pulling capacity for the vehicle in first gear at maximum power, when the vehicle speed is zero, is up to 15% lower than when the vehicle speed is between 2 and 20 kilometers / hour (e.g., the power indicated at triangle 213). Likewise, the maximum pulling capacity for the vehicle in second gear at maximum power, when the vehicle speed is zero, is up to 15% lower than when the vehicle speed is between 2 and 20 kilometers / hour. At a vehicle speed of approximately 2 kilometers / hour, the vehicle may have sufficient pulling power to climb a 35% grade according to the vehicle performance metric when the vehicle is in first gear. However, at a vehicle speed of zero, the vehicle does not have sufficient pulling power to climb the 35% grade according to the vehicle performance metric when the vehicle is in first gear.However, the vehicle has a pulling force 213 that is sufficient, according to the vehicle performance metric when the vehicle is in first gear, to negotiate the 30% grade 252. The system and method described herein attempts to eliminate the lack of engine torque and provide it to the vehicle at zero speed. The highlighted area 215 represents a pulling force required in systems that do not include the pulling force optimization method described herein by increasing the output of the electric machine and its associated inverter to meet the vehicle performance metric to allow the vehicle to negotiate the 30% grade. In contrast, the system and method described herein may enable the electric machine and vehicle to provide pulling force to negotiate the 35% grade at zero and higher vehicle speeds.

[0029] Now Fig. 3-8, where operating characteristics for a three-phase synchronous electric machine are shown. Fig. Figure 3 is a graph of three-phase electrical currents versus an electrical current angle. The vertical axis 301 represents the electrical current for the electrical machine on a unit or normalized basis. The horizontal axis 303 represents an electrical current angle, and the electrical current angles are indicated below the horizontal axis.

[0030] Line 302 represents an electric current for a first electric current phase for the electric machine. Line 304 represents the electric current for a second electric current phase for the electric machine. Line 306 represents the electric current for a third electric current phase for the electric machine. The phase currents are separated by 120 degrees.

[0031] Now Fig. 4, where absolute values ​​are shown for each of the three phase currents of the electric machine. The vertical axis 401 represents the electric current for the electric machine on a unit or normalized basis. The horizontal axis 403 represents an angle of electric current, and the angles of electric current are indicated below the horizontal axis.

[0032] Line 402 represents the absolute value of the first phase current for the electrical machine. Line 404 represents the absolute value of the second phase current for the electrical machine. Line 406 represents the absolute value of the third phase current for the electrical machine.

[0033] It will now Fig. 5, where conductive power losses for all phases are shown as a function of current angle for a three-phase electric machine operating at a constant level of torque output. The vertical axis 501 represents power losses on a unit or normalized basis, and the amount of power losses increases in the direction of the vertical axis arrow. The horizontal axis 503 represents an electric current angle, and the current angles of the electric machine are indicated below the horizontal axis.

[0034] Line 502 represents the conductive power losses for the electric machine for a phase a current (e.g., a first phase current). Line 504 represents the conductive power losses for the electric machine for a phase b current (e.g., the second phase current). Line 506 represents the conductive power losses for the electric machine for a phase c current (e.g., the third phase current). Line 508 represents the average power loss.

[0035] It will now Fig. 6, where maximum conductive power losses for all current phases are shown as a function of current angle for a three-phase electric machine operating at a constant level of torque output. The vertical axis 601 represents power losses on a unit or normalized basis, and the amount of power losses increases in the direction of the vertical axis arrow. The horizontal axis 603 represents an electric current angle, and the electric current angles are indicated below the horizontal axis.

[0036] Line 602 represents the maximum conductive power losses for all current phases of the electric machine. It can be seen that the maximum conductive power losses can be minimized when the electrical angle of the electric machine is 0 degrees, 60 degrees, 120 degrees, 180 degrees, 240 degrees, 300 degrees, and 360 degrees. By positioning the rotor at zero, 60, 120, 180, 240, or 300 degrees, electric machine losses can be minimized, so that the torque output of the electric machine can be maximized. As a result, when the electric machine rotor stops at 140 electrical degrees, the electric machine rotor can be rotated backward by 20 electrical degrees to optimize the electric machine output torque.On the other hand, if the rotor of the electric machine stops at 170 electrical degrees, the rotor can be rotated 10 electrical degrees in a forward direction to maximize the torque and power output of the electric machine, so that the rotor stops at 180 electrical degrees where the maximum power output of the electric machine can be maximized.

[0037] It will now Fig. 7, where maximum amounts of electric current among all phase currents of a three-phase electric machine operating at a constant torque output are shown. The vertical axis 701 represents amounts of electric currents from all phases of a three-phase electric machine on a unit or normalized basis, and the amount of electric current increases in the direction of the vertical axis arrow. The horizontal axis 703 represents an angle of electric current, and the angles of electric current are indicated below the horizontal axis.

[0038] Line 702 represents the maximum electrical current levels under all phase currents of a three-phase electrical machine operating at a constant torque. It can be seen that the maximum electrical currents occur at 30 degrees, 90 degrees, 150 degrees, 210 degrees, 270 degrees, and 330 degrees. The minimum current levels for operating the electrical machine with a constant torque output occur at 0 degrees, 60 degrees, 120 degrees, 180 degrees, 240 degrees, 300 degrees, and 360 degrees. Thus, the electrical current can be minimized by positioning the rotor at 0, 60, 120, 180, 240, or 300 electrical degrees when the electrical machine's speed is zero.

[0039] It will now Fig. 8, where a peak or maximum torque output of an electric machine operating at a constant peak current is shown as a function of current angle for a three-phase electric machine. The vertical axis 801 represents a peak torque output of the electric machine when the electric machine is operating at a constant peak current. The horizontal axis 803 represents an electric current angle, and the electric current angles are indicated below the horizontal axis.

[0040] Line 802 represents the maximum or peak torque at a constant peak electrical current. It can be seen that the maximum or peak torque output of the electric machine occurs at electrical angles of 0 degrees, 60 degrees, 120 degrees, 180 degrees, 240 degrees, 300 degrees, and 360 degrees. By positioning the rotor at 0, 60, 120, 180, 240, or 300 electrical degrees, the torque output of the electric machine can be maximized at zero electric machine speed. As a result, when the electric machine rotor stops at 140 electrical degrees, the electric machine rotor can be reversed by 20 electrical degrees to optimize the electric machine output torque.On the other hand, if the rotor of the electric machine stops at 170 electrical degrees, the rotor can be rotated 10 electrical degrees in a forward direction to maximize the torque and power output of the electric machine, so that the rotor stops at 180 electrical degrees where the maximum power output of the electric machine can be maximized.

[0041] Please note that Fig. 3-8 show operating conditions that can be a basis for adjusting a position where a rotor of a three-phase electrical machine as a drive source is stopped (e.g., not rotating). Operating conditions for adjusting a rotor position of a six-phase electrical machine can also be a basis for adjusting a rotor position of an electrical machine. Diagrams and data for six-phase electrical machines can be determined using similar methods as were used to determine the diagrams and data for Fig. 3-8 to produce.

[0042] It will now Fig. 9, where a flowchart of a method for operating a vehicle including an electric machine is shown. The method of Fig. 9 can be used in conjunction with the system of Fig. 1. One or more controllers may perform at least a portion of the method 900 by changing operating states of one or more actuators in the real world. The method 900 may be implemented, at least in part, as executable instructions stored in a non-transitory memory of a controller in a system such as that shown in Fig. 1 shown are stored.

[0043] At 902, method 900 judges whether or not the vehicle speed (VS) is within a zero speed threshold. In one example, the speed threshold may be 3 kilometers / hour. If method 900 judges that the vehicle speed is within a zero speed threshold, the answer is yes, and method 900 proceeds to 904. Otherwise, the answer is no, and method 900 proceeds to 950.

[0044] At 950, method 900 adjusts a torque output of the electric machine as a function of a requested torque corresponding to a driver demand and a requested braking torque. The torque corresponding to a driver demand may be based on a position of a pedal conveying a driver demand, and the requested braking torque may be based on a position of a brake pedal. Thus, if a position of the pedal conveying a driver demand indicates a request for 100 Newton meters of torque output from the electric machine 105, the electric machine 105 is commanded to output 100 Newton meters of torque. Method 900 ends.

[0045] At 904, method 900 estimates a road grade or a slope of a surface on which the vehicle is traveling. In one example, the road grade or surface grade may be estimated using an inclinometer. In other examples, method 900 may determine a vehicle performance metric according to a mass of the vehicle, including a mass of a load applied to the vehicle, and a road or surface grade. In one example, the performance metric may be a rate of change of vehicle speed for a given torque or power according to a driver demand. Method 900 proceeds to 906 after the road or surface grade is determined and / or the vehicle performance metric is determined.

[0046] At 906, method 900 assesses whether or not the road or surface gradient can be overcome while the vehicle speed is zero and the electric machine rotor is not positioned such that the electric machine produces its maximum torque at zero electric machine speed. In other words, method 900 assesses whether or not the vehicle and its total mass (e.g., the mass of the vehicle plus the mass of any load added to the vehicle) can accelerate in a forward direction from zero speed to a predetermined speed (e.g.,3 kilometers / hour) without traveling in a reverse direction when the vehicle is in first gear while traveling on a road or surface having the particular grade if the electric machine rotor is not positioned such that the electric machine produces maximum torque at zero electric machine speed. If so, the answer is yes and method 900 continues to 952. Otherwise, the answer is no and method 900 continues to 908. Step 906 allows for avoiding electric machine rotor adjustment when vehicle performance can be maintained on a grade.Further, step 906 prevents adjustment of the electric machine rotor position if a vehicle launch metric can be met if the electric machine rotor is not positioned to output maximum torque when the electric machine speed is zero.

[0047] In some embodiments, method 900 may adjust an angular position of the rotor of the electric machine in response to the rotor not rotating and an anticipated rate of change in vehicle speed during a vehicle launch from a zero speed to a predetermined speed being less than a vehicle launch metric. The launch metric may be a rate of change in vehicle speed from a zero vehicle speed to a predetermined vehicle speed.A simplified anticipated rate of change of vehicle speed may be based on a position at which the rotor was stopped (to obtain an electric machine torque at zero vehicle speed, determined from a lookup table containing predetermined torque values), a vehicle mass, and a gear ratio between the electric machine and vehicle wheels (change in vehicle speed = force applied to wheels / mass of vehicle, where force applied to wheels is an electric machine torque at zero speed multiplied by the gear ratio between the electric machine and the wheels divided by the wheel radius).

[0048] At 952, method 900 adjusts electric machine torque according to a creep torque demand and a driver demand torque. The creep torque demand may be a constant torque, which may cause the vehicle to travel at a low speed (e.g., less than 5 kilometers / hour) when the vehicle is on a flat surface shortly after the vehicle is stopped and its brake pedal is released, without providing torque corresponding to a driver demand. The creep torque may be sufficient to maintain vehicle speed at or above zero for roads with low grade levels. Method 900 also adjusts electric machine torque according to a driver demand torque demand.For example, if a torque corresponding to the driver demand is adjusted from 0 to 40 Newton meters, the electric machine output torque may be adjusted from 0 to 40 Newton meters. In other examples, the driver demand may be a requested wheel torque, and the electric machine torque may be adjusted to a torque that produces the requested wheel torque. Method 900 returns to 902.

[0049] At 908, method 900 judges whether or not the vehicle speed is zero. If so, the answer is yes, and method 900 proceeds to 910. Otherwise, the answer is no, and method 900 proceeds to 952. The vehicle's tires, driveline, and gear backlash can affect where the electric machine rotor comes to rest. The position of the electric machine rotor when the electric machine speed is zero can affect the amount of torque that can be produced via the electric machine at zero speed.

[0050] At 910, method 900 applies vehicle brakes to maintain the vehicle at zero speed. Method 900 proceeds to 912.

[0051] At 912, method 900 retrieves one or more target electric machine rotor positions from a memory (e.g., a read-only memory). The one or more target electric machine rotor positions may be determined by modeling or by commanding the electric machine maximum torque at each rotor degree increment while monitoring the electric machine torque while maintaining the electric machine speed at zero. The rotor positions may be rotor positions where maximum output torque is generated by the electric machine or rotor positions where electric machine losses are lowest, as in Fig. 6 and Fig. 8. As shown in Fig. 6 and Fig. As shown in FIG. 8, the rotor positions for a three-phase electric machine may be 0 degrees, 60 degrees, 120 degrees, 180 degrees, 240 degrees, and 300 degrees. Other rotor positions for six-phase electric machines may be generated in a similar manner. Method 900 proceeds to 914.

[0052] At 914, method 900 opens a clutch in the vehicle's driveline to decouple the electric machine from the vehicle's wheels. By decoupling the electric machine from the vehicle's wheels, it may be possible to rotate the electric machine's rotor to a position where maximum electric machine torque output can be produced at zero electric machine speed without moving the vehicle. In some examples, the clutch may be a dog clutch with teeth, while in other examples, the clutch may be a wet friction clutch or other known clutch type. The clutch type may affect which rotor positions are available to increase the electric machine torque output at zero electric machine speed.For example, with a dog clutch with teeth, the number of dog clutch teeth and their angular orientation become part of the equation when considering which rotor positions 912 are available to increase the electric machine torque output at zero electric machine speed. In one case, the rotor positions 912 are calculated using the motor orientation and the last angular orientation of the dog clutch teeth in a condition where the brake is locked 910, a power path is fixed, and a vehicle speed is zero. In another example, the motor has an encoder (e.g., 168 of . Fig. 1) and thus the angular orientation of the motor is known and the angular orientation of the first clutch tooth 1002 (e.g. as in Fig. 10) can be oriented and calibrated to the motor encoder, a encoder (e.g. 169 of Fig. 1), calibrated to the angular orientation of the second clutch tooth 1004, can be added to the second side of the clutch power path to learn the orientation of the partner tooth. Use of both encoders can be used with or without the brake lock 910 to calculate the rotor positions 912 available to calculate an electric machine torque output at zero electric machine speed, for example, if the vehicle were to roll. In cases where the clutch design may limit an electric machine rotor position due to interfering teeth, the rotor can be rotated to a position closest to one of the rotor positions retrieved from memory.The rotor may need to rotate further, skipping a few clutch teeth, to arrive at the best clutch tooth motor angle to increase the electric machine torque output at zero electric machine speed. Method 900 may rotate the rotor to one of the exact rotor positions retrieved from memory if the clutch type does not preclude adjusting the rotor position.

[0053] Method 900 rotates the electric machine rotor to a position closest to the positions retrieved from controller memory in step 912, subject to teeth of a dog clutch, if present. If the vehicle includes a dog clutch, the clutch teeth on the side of the dog clutch where the electric machine is located must be aligned for immediate meshing with teeth on the clutch side opposite the electric machine side, without tooth butting, rotation, or skipping, so that the electric machine does not move from closest to its optimal position due to meshing. For example, if an electric machine rotor stops at 100 degrees and the closest location to where the electric machine rotor can be stopped is where the electric machine rotor can be positioned for maximum torque output (e.g.,300 degrees) while dog clutch teeth are engaged is 298 degrees, then the electric machine rotor is rotated to 298 degrees. For friction clutches, the electric machine rotor may be adjusted to the position retrieved from controller memory (e.g., 180 degrees, 240 degrees, 300 degrees, etc.). The electric machine rotor may be rotated clockwise or counterclockwise to adjust the rotor position to the nearest rotor position retrieved from memory. Method 900 proceeds to 918 after the electric machine rotor position is adjusted.

[0054] At 918, method 900 closes the powertrain clutch so that the electric machine is recoupled to the vehicle's wheels after adjusting the position of the electric machine's rotor to maximize the electric machine's torque output at zero speed. Method 900 proceeds to 920.

[0055] At 920, method 900 adjusts electric machine torque and braking torque according to a creep torque demand, a requested torque corresponding to the driver demand, and a requested braking torque. The creep torque demand may be a constant torque, which may cause the vehicle to travel at a low speed (e.g., less than 5 kilometers / hour) when the vehicle is on a flat surface shortly after the vehicle is stopped and its brake pedal is released, without providing torque corresponding to a driver demand. The creep torque may be sufficient to maintain vehicle speed at or above zero for roads with low grade levels. Method 900 also adjusts electric machine torque according to a requested torque corresponding to the driver demand and adjusts friction braking torque according to the requested braking torque.For example, if the requested braking torque is 50 Newton meters and the requested torque corresponding to the driver demand is 40 Newton meters, the vehicle's friction brakes may be adjusted to provide the requested braking torque, and the electric machine output torque may be adjusted to equal the requested torque corresponding to a driver demand. In other examples, the demand corresponding to the driver demand may be a requested wheel torque, and the electric machine torque may be adjusted to a torque that produces the requested wheel torque. Method 900 ends.

[0056] In this way, a position of a rotor of an electric machine can be rotated such that a torque output of the electric machine is optimized when a torque output of the electric machine varies with an angular position of the rotor of the electric machine at a zero speed of the electric machine. The position of the rotor of the electric machine can be adjusted such that an output torque of the electric machine is a maximum available torque of the electric machine when the speed of the electric machine is zero.

[0057] Thus, the procedure of Fig. 9 provides a method for operating a vehicle, comprising: rotating an electric machine to a predetermined position in response to the vehicle being stopped on a first surface having a first slope greater than a slope threshold. In a first example, the method further comprises not rotating the electric machine to the predetermined position in response to the vehicle being stopped on a second surface having a second slope less than a slope threshold. In a second example, which may include the first example, the method includes where the predetermined position is a position within a predetermined range of angular positions of the rotor of the electric machine where a torque output of the electric machine is a maximum torque output of the electric machine at a zero speed of the electric machine.In a third example, which may include one or both of the first and second examples, the method includes where the electric machine is a synchronous machine or an induction machine. In a fourth example, which may include one or more of the first to third examples, the method includes where the predetermined position is stored in a memory of a controller, and where a first encoder and a second encoder provide data to rotate the electric machine to the predetermined position. In a fifth example, which may include one or more of the first to fourth examples, the method includes where the predetermined position is a function of an angle of electrical current supplied to the electric machine. In a sixth example, which may include one or more of the first to fifth examples, the method includes estimating the first inclination using an inclinometer.In a seventh example, which may include one or more of the first to sixth examples, the method further comprises adjusting a torque output of the electric machine in response to a creep torque request, a torque request corresponding to a driver demand, and a brake torque request after rotating the electric machine to the predetermined position.

[0058] In addition, the procedure can be Fig. 9 provide a method of operating a vehicle, comprising: applying vehicle brakes, opening a powertrain clutch, and rotating an electric machine to a predetermined position in response to the vehicle being stopped. In a first example, the method includes where the predetermined position is a closest angular position of a rotor of the electric machine, relative to the position of the electric machine at which the vehicle is first stopped, to where power losses of the electric machine are minimized. In a second example, which may include the first example, the method includes where the predetermined position is a closest angular position of a rotor of the electric machine, relative to the position of the electric machine at which the vehicle is first stopped, to where a torque output of the electric machine is maximized.In a fourth example, which may include one or more of the first to third examples, the method includes where the clutch is a dog clutch including teeth, and wherein the predetermined position is a position within a predetermined range of angular positions of the teeth of the dog clutch where a torque output of the electric machine is equal to a maximum torque output of the electric machine at a zero speed of the electric machine. In a fifth example, which may include one or more of the first to fourth examples, the method includes where the clutch is a friction clutch.

[0059] In another representation, the process of Fig. 9 provide a method of operating a vehicle, comprising: adjusting an angular position of a rotor of an electric machine in response to the rotor not rotating and an anticipated rate of change of vehicle speed from a zero vehicle speed to a predetermined vehicle speed being less than a starting metric of a vehicle. In a first example, the starting metric may be a rate of change of vehicle speed from a zero vehicle speed to a predetermined vehicle speed (e.g., five kilometers per hour).

[0060] It will now Fig. 10, which shows a perspective view of halves of a clutch 145. In this example, the clutch 145 is a jaw clutch having teeth 1002 on a first side of the clutch 145 that mesh with teeth 1004 on a second side of the clutch 145.

[0061] It will now Fig. Referring to Figure 11, a perspective view of clutch 145 is shown. In this example, clutch 145 is a wet friction clutch. Clutch 145 includes friction linings 1102 for transmitting torque across clutch 145.

[0062] Note that the example control and estimation routines included herein may be used in various configurations of powertrains and / or vehicle systems. The control methods and routines disclosed herein may be stored as executable instructions in non-transitory memory and may be executed by the control system including the controller in combination with the various sensors, actuators, and other hardware of the transmission and / or vehicle. Further, portions of the methods may be physical actions taken in the real world to change a state of a device. Thus, the described actions, operations, and / or functions may graphically represent code to be programmed into non-transitory memory of the computer-readable storage medium in the vehicle and / or transmission control system.The specific routines described herein may employ one or more of a variety of processing strategies, such as event-driven, interrupt-driven, multi-tasking, multi-threading, and the like. Thus, various illustrated actions, operations, and / or functions may be performed in the order presented, in parallel, or in some cases omitted. Likewise, the order of processing is not essential to achieving the features and advantages of the examples described herein, but is provided for ease of illustration and description. One or more of the illustrated actions, operations, and / or functions may be performed repeatedly depending on the particular strategy employed. One or more of the method steps described herein may be omitted if desired.

[0063] Although various embodiments have been described above, it should be understood that they have been presented as examples, not by way of limitation. It will be apparent to one skilled in the art that the disclosed subject matter may be embodied in other specific forms without departing from the spirit of the subject matter. The embodiments described above are, therefore, to be considered in all respects as illustrative, not restrictive. Thus, the configurations and routines disclosed herein are exemplary, and these specific examples are not to be considered in a limiting sense, as numerous variations are possible. For example, the technology described above may be applied to electric vehicles and hybrid vehicles that include induction and synchronous electric machines.The subject matter of the present disclosure includes all novel and non-obvious combinations and sub-combinations of the various systems and configurations and other features, functions and / or properties disclosed herein.

[0064] The following claims particularly point out certain combinations and subcombinations that are considered novel and non-obvious. These claims may refer to "a" element or "a first" element, or an equivalent thereof. These claims may be construed as including incorporation of one or more of such elements, but two or more of such elements are neither required nor precluded. Other combinations and subcombinations of the disclosed features, functions, elements, and / or properties may be claimed by amending the present claims or by presenting new claims in this or a related application. Such claims, whether broader, narrower, of the same or different breadth as the original claims, are also contemplated as being included within the subject matter of the present disclosure.

Claims

[1] A method of operating a vehicle, comprising: Rotating an electric machine to a predetermined position in response to the vehicle being stopped on a first surface having a first slope greater than a slope threshold. [2] The method of claim 2, further comprising not rotating the electric machine to the predetermined position in response to the vehicle being stopped on a second surface having a second slope that is less than the slope threshold. [3] A method according to any one of the preceding claims, wherein the predetermined position is a position within a predetermined range of angular positions of a rotor of the electric machine where a torque output of the electric machine is a maximum torque output of the electric machine at a zero speed of the electric machine. [4] Method according to one of the preceding claims, wherein the electrical machine is a synchronous machine or an induction machine. [5] A method according to any one of the preceding claims, wherein the predetermined position is stored in a memory of a controller, and wherein a first encoder and a second encoder provide data to rotate the electric machine to the predetermined position. [6] The method of claim 5, wherein the predetermined position is a function of an angle of electric current supplied to the electric machine. [7] A method according to any one of the preceding claims, wherein the first inclination is estimated using an inclinometer. [8] The method of any preceding claim, further comprising adjusting a torque output of the electric machine in response to a creep torque request, a driver requested torque request, and a brake torque request after rotating the electric machine to the predetermined position. [9] Vehicle system comprising: an electrical machine designed to drive a vehicle; a driveline clutch; an inverter electrically coupled to the electric machine; and a controller including executable instructions stored in non-transitory memory that cause the controller to adjust a rotational position of a rotor of the electric machine in response to an incline of a surface where the vehicle is stopped or a start metric of the vehicle when the vehicle is stopped. [10] The vehicle system of claim 9, further comprising additional executable instructions that cause the controller to adjust the rotational position of the rotor in further response to a rotational position of the electric machine rotor at which electric machine power losses are minimized at a zero electric machine speed. [11] The vehicle system of claim 9 or 10, further comprising additional executable instructions that cause the controller to adjust the rotational position of the rotor in further response to the rotational position of the electric machine rotor at which a torque output of the electric machine is maximized at a zero speed of the electric machine. [12] The vehicle system of any one of claims 9 to 11, further comprising additional executable instructions that cause the controller to apply vehicle brakes in response to the vehicle being stopped. [13] The vehicle system of claim 12, further comprising additional executable instructions that cause the controller, in response to the vehicle being stopped and the surface slope being greater than a threshold amount, to open a clutch prior to adjusting the rotational position of the rotor at which the vehicle is stopped. [14] The vehicle system of claim 13, wherein the clutch is a dog clutch. [15] The vehicle system of claim 14, wherein the clutch is a friction clutch.

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