Electric drive unit with planetary gear drive

Abstract

Electric drive unit, comprising: a set of electric machines, each electric machine coupled to a separate pinion device in a first set of pinion devices of a planetary arrangement; and where the planetary arrangement comprises: a support that is mechanically fixed; a ring device; and a solar device; wherein the ring device and / or the sun device act as an output; and wherein the first set of pinion devices is rotationally coupled to the ring device and / or the sun device.

Description

TECHNICAL FIELDThe present description relates generally to an electric drive unit having a plurality of electric machines each driving a pinion device in a planetary arrangement.BACKGROUND AND SUMMARYElectric drives are used in certain vehicles, since the transport sector moves in the direction of electrification of the drive train. Some electric drives use planetary gear sets driven by a single, comparatively large traction motor. Large traction motors are more complex and in some cases more expensive to manufacture than smaller motors. In planetary gear sets where the sun gear is used as the drive of the transmission, and particularly in planetary gear sets with relatively high ratios, the sun gear transmits high input torque of the electric motor under certain operating conditions. Sun-input planetary gear sets may also have noise, vibration, and hardness (NVH) issues as well as manufacturing issues in some cases.U.S. Pat. No. 9,487,084 B2 to Petersen et al. shows an electric drive with a plurality of motors which provide a parallel drive for a Ravigneaux transmission. The Ravigneaux gear set includes summing sun gears coupled to summing differential planet gears.The inventors have recognized several problems with multi-motor electric propulsion patersens. For example, the Ravigneaux gear set of Petersen is complex and can be difficult to manufacture. Also, Petersen is silent on any type of system used for powering the motors. Moreover, the inventors have recognized that other electric drive systems using two motors and inverters have manufacturing and cost issues compared to electric drive systems using only one motor and inverter in electric drive.The inventors have recognized the foregoing challenges and developed an electric drive unit to at least partially overcome the challenges. The electric drive unit, in one example, includes a first set of electric machines each coupled to a pinion device in a first set of pinion devices of a planetary assembly. In such an example, the planetary assembly includes a carrier that is mechanically locked, a ring device, and a sun device. Further, in the electric drive unit, the ring device and / or the sun device may function as an output, and the first set of pinion devices is rotatably coupled to the ring device and / or the sun device. In this way, multiple electric motors are used in the electric drive to reduce the input torque of the individual pinions to the planetary device, thereby reducing the diameters of the components and the size of the bearings, which affects the speed of the components, inertia, wear and other forms of degradation of the drive unit. The longevity of the electric drive unit can thereby be increased. In addition, by using a plurality of relatively small electric machines, in contrast to a single larger machine, the production costs can be reduced by size advantages. Another reason for the construction of the electric drive unit with a pinion-driven planetary arrangement is the relatively high torque multiplication which is possible compared to sun-driven planetary arrangements with an otherwise identical ring-to-sun ratio.In another example, the electric drive unit may further include a clutch that selectively rotatably couples the ring device and the sun device to an output of the drive unit in various positions. When the clutch engages the ring device, the drive unit operates in a lower speed, when the clutch engages the sun device, the drive unit operates in a higher speed. In this way, the electric drive unit is capable of achieving the desired gear ratios in a plurality of electric vehicle platforms.In another example, the planetary assembly may be a compound planetary assembly including a second set of pinion devices rotationally coupled to the first set of pinion devices. In this way, the planetary arrangement is arranged such that the ring device and the sun device rotate in the same direction. If the drive unit has a clutch, the synchronization of the ring and sun device can take place during the shifting process without any change of direction of the drive motors.It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further discussed in the detailed description. It is not intended to identify key or essential features of the claimed subject matter, the scope of which is clearly defined by the claims that follow the detailed description. Moreover, the claimed subject matter is not limited to implementations that address the shortcomings recited above or in other parts of this disclosure.BRIEF DESCRIPTION OF THE FIGURESFIG. 1A is an illustration of an electric vehicle (EV) having an example electric drive unit that includes a planetary arrangement. FIGS. 1B-1C are lever diagrams of the electric drive unit and the planetary assembly shown in FIG. 1A. FIG. 2A shows another example electric drive unit having a planetary gear set. FIGS. 2B-2C are lever diagrams of the electric drive unit and the compound planetary assembly shown in FIG. 2A. FIGS. 3-4 show alternative planetary gear set architectures.FIGS. 5A-5C show various examples of the arrangement of inverters. FIG. 6 is an example illustration of an electric machine. FIG. 7 is an example operating sequence of an electric drive unit according to an example power feedback control scheme.DETAILED DESCRIPTIONDescribed herein are electric drive units and systems that achieve higher performance and manufacturing cost savings due to scale effects. To achieve this increase in performance and manufacturing, multiple motors are incorporated into the drive unit, each coupled to a pinion or planetary roller in a planetary traction drive. By using multiple pinions, each driven by a separate motor, the input torque can be divided among a larger number of components, which reduces the risk of the drive unit being deteriorated and increases the durability of the drive unit.FIG. 1A shows an electric vehicle (EV) 100 having a powertrain 102 that includes an electric drive system 104 having an electric drive unit 106. The EV 100 may be a pure electric vehicle (e.g., a battery-powered electric vehicle (BEV)), in one example, or a hybrid vehicle, in another example. Thus, vehicles using the electric propulsion units described herein may also have an internal combustion engine (e.g., a spark ignition engine, a self-ignition engine, combinations thereof, and the like) in some examples. Thus, the electric drive units described herein may be used in cars, trucks, boats, ATVs, commercial vehicles, light vehicles, off-highway vehicles, mining vehicles, rail vehicles, manufacturing machines, industrial machines, and the like.In the illustrated example, the electric drive unit 106 includes a simple planetary assembly 108 having a sun device 110, a ring device 112, a carrier 114 that is mechanically locked, and a set of pinion devices 116 coupled to the carrier. As described herein, a simple planetary arrangement is an arrangement that includes only a sun device, a ring device, a carrier, and multiple pinion devices. Alternatively, a compound planetary arrangement can also be used in the drive units described here, as will be explained in more detail here.The pinion devices 116 are rotationally coupled to the ring device 112 and the sun device 110 so that torque is transmitted therebetween. The pinion devices may also be referred to as planetary devices. The carrier 114 is mechanically locked in the example shown. The ring device 112 and / or the sun device 110 function as the output of the planetary assembly, as described in detail herein. Conversely, the pinion devices 116 serve as the drive for the planetary arrangement. In one example, the sun device 110 may be hollow to allow a connecting shaft of the powertrain to pass through to an additional downstream transmission.In one application, the pinion devices 116 may be constrained to a maximum relative speed between 10,000 revolutions per minute (U / min) and 12,000 U / min if there is no special lubrication for the bearings (e.g., needle bearings) associated with the pinion devices. The relative speed of the pinion devices refers to the relative speed between the pinion devices and the fixed carrier. However, it should be appreciated that other suitable controllers may be used for electric machines (discussed in more detail herein) having different speed requirements. Factors that may impact speed constraints include the type and size of the electric machines used in the propulsion unit, the type and size of the engine cooling systems used in the propulsion unit, the speed limits of the motor rotor and pinion bearings, and the like.A set of electric machines 118 (e.g., traction motors) with multiple electric machines is included in the electric drive unit 106. Each of the electric machines in the electric machine group 118 is connected to a separate pinion device in the pinion device group 116. The electric machines 118 are schematically illustrated in FIG. 1A. However, it is understood that the machines may have greater complexity, e.g., in terms of form factor. The packaging of the motor in relation to the form factor of the motor is explained in more detail below with reference to FIG. 2A.The electric machines described herein may be polyphase (e.g., three-, four-, six-phase, etc.) The AC machines are, but are not limited thereto. Moreover, in some cases, the electric machines described herein may be configured to operate in both a drive mode and a regeneration mode. In the regeneration mode, the machine generates electrical energy. In particular, the electric machines described here can be induction motors, which are also referred to as asynchronous motors. In other examples, the electric machines described herein may be permanent magnet motors (e.g., PM synchronous motors) that include permanent magnets. The specific types of motors used in the electric drive unit may be selected based on the inverter architecture in the drive unit discussed below with respect to FIGS. 5A-5C.As mentioned above, the group of electric machines 118 is schematically illustrated in FIG. 1A. It will be understood, however, that each of the machines may be positioned coaxial with the pinion apparatus to which it is attached, as shown in FIG. 2A and discussed in more detail herein.The planetary arrangements described herein may be planetary gear sets or traction drive planetary devices. The planetary arrangements and the components contained therein are referred to below as planetary gear sets with gears. However, it should be understood that traction drives having an identical construction to the planetary gear sets may be used in any of the electric drive units described herein.As shown in FIG. 1A, the EV 100 may also include a control system 150 having a controller 152. The controller 152 may include a microcomputer having components such as a processor 154 (e.g., a microprocessor unit), input / output ports, an electronic storage medium 156 for executable programs and calibration values, e.g., a read-only memory chip, a read-only memory, a diagnostic memory, a data bus, and the like. The storage medium may be programmed with computer readable data representing instructions executable by a processor for performing the methods, control techniques, etc. described herein, as well as other variants that are expected but not expressly listed. Thus, the electronic storage medium 156 may store instructions that, when executed by the processor 154, cause the controller 152 to perform the various method steps described herein.The controller 152 may receive various signals from sensors 158 connected to various areas of the vehicle 100, and more specifically the electric drive unit 106. The sensors 158 may include, for example, one or more engine speed sensors (see below), shaft / transmission speed sensors, a pedal position sensor to detect actuation of a driver-actuated pedal (e.g., an accelerator and / or brake pedal), speed sensors at vehicle wheels, and the like. An input device 160 (e.g., accelerator pedal, brake pedal, gear selector, combinations thereof, and the like) may also provide input signals indicative of the driver's intention to control the vehicle.Upon receiving the signals from the various sensors 158 of FIG. 1A, the controller 152 processes the received signals and employs various actuators 162 of vehicle components to adjust the components based on the received signals and the instructions stored in the memory of the controller 152. For example, the controller 152 may receive an accelerator signal indicative of the driver's request for an adjustment to vehicle acceleration. In response, the controller 152 may command operation of inverters electrically connected to the electric machines 118 to increase the power supplied by the motors to the planetary assembly 108. The other controllable components in the vehicle may function in a similar manner, e.g., with respect to sensor signals, control commands, and actuator setting. Moreover, the control system 150 may be employed in any of the electric drive systems and units described herein.A speed sensor 164 may be used in the electric drive unit 106 that is integrated into the set of electric machines 118. In multiple electric machines (e.g., induction or PM motors), a single speed sensor (coupled to one of the motors) may be used to determine engine speed, if desired. The planetary gear forces the electric machines to rotate at the same speed. When using asynchronous motors, the control of the asynchronous motor can only require the speed and position of the motor for an encoder. Thus, the speed sensor in the example of the asynchronous motor can be an encoder. In contrast, in PM motors, the control of the motor may require information about the speed and absolute position (orientation of the d-axis to the magnetic poles), which may require the use of a resolver as a speed sensor and a resolver offset learning routine (ROL). In PM engines, the engines may be sorted into groups with similar ROL values. In the assembly of PM motors, the motors may have a positioning feature and a synchronization mark (schematically shown at 166) on the carrier to enable all d-axes of the motor to be aligned with the single speed sensor. The alignment may be required during the mounting of the carrier of the planetary gear set. The alignment may be requested for coordinated motor control and is independent of the number of speed sensors indicated. The use of a single speed sensor reduces the complexity and cost of the drive unit and thus makes it more attractive to the customer. Alternatively, a plurality of speed sensors can also be used in the electric drive unit.The controller 152 may include a control routine that operates the electric drive system in a full torque control mode in which an equivalent torque request may be requested for all electric machines coupled to the pinion device(s). In this mode of full torque control, the speed of the electric machine results from the torque balance between the electric machines and the demanded torque.Additionally, in one example, the controller 152 may include a control routine that operates the electric drive unit in a speed and torque control mode in which the electric machine is controlled with the primary speed sensor using a speed signal and the other electric machines are controlled via torque signals. The control of speed and torque may be particularly used in electric drive systems using the inverter arrangements shown in FIGS. 5B and 5C and the corresponding electric machines and planetary arrangements.An axis system is shown in FIG. 1A as well as in FIGS. 2A and 3-4 as a reference. In one example, the z-axis may be a vertical axis (e.g., parallel to a gravitational axis), the x-axis may be a lateral axis (e.g., a horizontal axis), and the y-axis may be a longitudinal axis. In other examples, the axes may also have different orientations.FIG. 1B shows a drive torque lever diagram for the electric drive unit 106 with the planetary arrangement 108. In the lever diagram shown in FIG. 1B, as well as in the other lever diagrams in FIGS., the components of the planetary arrangement are shown as nodes. The set of electric machines 118 is shown to drive the pinion set 116. The pinions 116 are rotationally coupled to the ring gear 112 which, in turn, is rotationally coupled to the sun gear 110. In the example shown, the carrier 114 is fixed and the ring gear 112 and sun gear 110 are possible starting points. Specifically, the carrier 114 may be secured via a component 180, which may be, in one example, the housing of a drive unit or, in another example, the front surface of an electric machine. In this way, the carrier is secured mechanically and in a space-saving manner. Equations (1) and (2) representing the correspondence between the transmission ratio of the planetary arrangement, the input torque, and the output torque when using the ring gear and the sun gear as the output of the planetary gear set are listed below.parametersT outR: Output torque, ringT outS: Output moment, sune p1: Ratio of Ring to First Pinione 1: Ring to Sun RatioFIG. 1B shows an optional clutch 170 (e.g., but not limited to a slip clutch mechanism) that may be included in the electric drive unit 106. The clutch 170 is configured to selectively engage the ring gear 112 with an output 172 for the planetary gear set 108 and the sun gear 110 with the output 172 in a first position. As such, clutch 170 is shiftable between a first gear position, in which the ring gear forms the output, and a second gear position, in which the sun gear forms the output. Clutch 170 may also have a neutral position in which neither the ring gear nor the sun gear are engaged. A clutch as described herein may be a friction clutch (e.g., a wet friction clutch), a synchronizer clutch, a dog clutch, combinations thereof, and the like.The output 172 may be in the form of a shaft, sprocket, chain, flange, combination thereof, and the like. The output 172 may be rotationally coupled to a downstream component of the powertrain 174. In one example, the output 172 may be coupled to a drive axle, which may include a differential that provides mechanical power to the drive wheels via axle shafts.In another example, the downstream component 174 rotationally coupled to the output 172 may be a drive wheel. In such an example, two electric drive units (e.g., left and right electric drive units) may independently provide mechanical power to opposing drive wheels (e.g., left and right drive wheels). The dual drive axle architecture may be configured to function as a torque vector control E-axis, in which torque bias is generated with unequal torques of the electric drive units. In such an example, a differential on the drive axle may be omitted.In another example, the downstream component 174 may be an auxiliary transmission or a manual transmission (e.g., a multi-speed transmission). In such an example, a continuous shaft engine architecture may be avoided if desired, where the combined engine inputs 118 and the pinion input planetary assembly 108 allow passage of a connecting shaft through a hollow sun gear 110. When the electric drive unit is coupled to a transmission, the motor input assembly may be disposed at any location in the power path and is not limited to one end, as in an electric drive assembly with a motor without a through shaft. Moreover, it can be a multi-speed transmission in which the transmission range of the electric drive can be extended by shifting. Moreover, in such an example, a power take-off 176 may be incorporated into one of the outputs of the electric drive unit.Further, in one example, in the electric drive unit 106, the auxiliary output 176 may be rotationally coupled to the ring gear 112 via one or more shaft(s), gear(s), and the like. A power take-off clutch 178 may be provided in a power take-off assembly 179. The power take-off clutch 178 serves to disconnect the ring gear 112 from the power take-off. For the auxiliary output clutch to operate at a standstill (i.e., when the vehicle is stationary and at a speed of zero), the auxiliary output clutch 178 may be engaged while the clutch 170 is in a neutral position. Alternatively, the auxiliary power take-off 176 can be switched on during travel and therefore shares the drive torque with the ring gear 112. In another mode, the auxiliary output 176 may be engaged via the ring gear 112 to drive an auxiliary load while the drive torque is provided via the sun gear 110. Although coupling the auxiliary output 178 to the ring gear 112 may be desirable with respect to auxiliary output loads as the output of the low speed planetary assembly 106, the previously described auxiliary output clutch 176 and auxiliary output clutch 178 may alternatively be coupled to the sun gear 110 to drive auxiliary loads at high speed and may be operated in one of the three previously described modes of operation, either stationary, load distribution across the sun device 110, or drive torque across the ring device 116 and auxiliary load across the sun device 110.In another example, the electric drive unit 106 may be connected to multiple drive axles (e.g., front and rear drive axles) in an all-wheel drive train (e.g., all-wheel drive train). In such an example, the electric drive unit 106 has a second output 182 connected to the sun gear 110 and a drive axle 184. In this example, the first output 172 is connected to another drive axle. In such an example, the downstream component 174 thus represents a further drive axle. In this way, the drive train is able to achieve a fixed distribution of torque between front and rear axles by using both outputs of the planetary arrangement. In this example, a clutch may be provided at one or both outputs so that at least one of the drive axles may be decoupled for two-wheel operation. In the example of all-wheel drive, the electric drive unit 106 can also be mounted centrally in the vehicle. The auxiliary power take-off 176 may be used in conjunction with this all-wheel architecture.In one example, since the division speeds of the ring gear 112, the sun gear 110, and the pinions 116 are the same, the pinions may have different sizes with different tooth numbers such that the sun gear and ring gear centers have an offset (e.g., eccentricity). An eccentric planetary architecture allows the packaging options of the drive unit to be expanded by different offsets of the output shaft. In another example, a pinion tooth count may be selected that allows for unequal arc spacing of the pinions with respect to placement around the interior of the ring gear.It is understood that the ring gear 112 and the sun gear 110 rotate in opposite directions to each other in the example shown. Thus, a changeover between the use of the ring gear and the sun gear as output can use an electrical synchronization technique in which the changeover is effected by changing the direction of the drive motor. For example, during a shift, clutch 170 may be placed in a neutral position and electric machines 118 controlled to bring the speed of the ring gear and sun gear to zero. The electric machines 118 reverse direction and then the new output (ring gear or sun gear) can be brought within a target speed variance of the output (172 or 182 respectively) and then the clutch 170 is engaged with the corresponding output (172 or 182 respectively).FIG. 1C shows a lever diagram for the speed of the planetary gear set 108 included in the electric drive unit 106 shown in FIG. 1A. As shown in FIG. 1C, the pinions 116 are rotationally coupled to the ring gear 112 which, in turn, is rotationally coupled to the sun gear 110. In the example shown, the carrier 114 is fixed to the component 180, and the ring gear 112 and sun gear 110 are potential sources.Equations (3) and (4) indicate the correspondence between the ratio between the ring and planet of the planetary assembly, the output speed, and the input speed when the ring gear and the sun gear are used as the output.parametersω S: angular velocity, sunω R: angular velocity, ringe p: Ring to Pinion Ratioe 1: Ring to Sun RatioFIG. 2A shows an example of an electric drive unit 200 having a planetary gear set 202. The compound planetary gear set 202 in turn includes a carrier 204 that is fixed, and a ring gear 206 and a sun gear 208, both of which may function as an output. In addition, the planetary gear set 202 includes a first pinion set 210 that meshes with a second pinion set 212. The carrier 204 is connected to the first and second pinion sets 210 and 212. In the example shown, the first pinion set 210 meshes with the ring gear 206 and the second pinion set 212 meshes with the sun gear 208. In other examples, the pinions 212 may be referred to as a first pinion set and the pinions 210 may be referred to as a second pinion set, depending on the order in which they are described. The numbering of the group of electric machines may be reversed according to the order in which they are introduced.The first pinion set 210 rotates in the opposite direction as the second pinion set 212. By using two pinion groups, the direction of rotation is reversed so that the sun gear 208, ring gear 206 and first pinion set 210 rotate in the same direction. Thus, electronic synchronization of the sun gear and ring gear may occur without directional change of the electric machines 218 when the electric drive unit 200 is configured as a multi-speed drive unit having a clutch 214 designed to shift the output of the planetary gear set 202 between the ring gear 206 and the sun gear 208.To ensure backlash between the pinion sets and the non-intermeshing teeth, in one example, equation (5) may be used to determine the maximum size of the pinions. The toothing is expressly used in equation (5) as a measure of the size of the gearwheel. However, it should be understood that the size of the gear may also be expressed as radius, diameter, etc. in other examples.parametersP max: maximum pinion gearR: Ring gear teethS: Sun gear teethFIG. 2A also shows a set of electric machines 216 having individual electric machines 218, 220, 222, and 224. It should be appreciated that the electric machines may be conceptually divided into subgroups as discussed herein with reference to FIGS. 5B-5C.In one example, each of the electric machines 218, 220, 222, and 224 may have a similar axial distance between the machine and the corresponding pinion device. Therefore, in such an example, the size of the housing may be limited by equation (6).parametersr motor max: maximum motor radiusr ring: ring gear radiusr p: pinion radiusN p: number of pinion gearsHowever, in another example, the electric machines may be positioned at different axial distances from the associated pinion gear to accommodate a larger radius electric machine in the electric drive unit. In another example, the electric machines may be connected to the pinion devices via a reduction gear, which however may increase the overall size and complexity of the unit.FIG. 2B shows a drive torque lever diagram for the electric drive unit 200 with the planetary arrangement 202. A set of electric machines 230 are shown driving the first pinion set 210. The first pinion set 210 is rotationally coupled to the ring gear 206, which in turn is rotationally coupled to the sun gear 208. In the example shown, the carrier 204 is fixed to a member 232 and the ring gear 206 and sun gear 208 are possible starting points. The second pinion set 212 is shown in FIG. 2B. The following equations (7) and (8) describe the correspondence between the ring-to-planet ratio of the planetary assembly, the input torque, and the output torque when the ring gear and the sun gear are used as the output.parametersT outR: Output torque, ringT outR: Output moment, sune p1: Ratio of Ring to First Pinione 1: Ring to Sun RatioFor equations (7) and (8), the first pinion set 210 is used as input and the gear ratios of ring gear and pinion gear are assumed to be identical. In such an example, an identical equation may be used when the second pinion set 212 is used as the motor input. However, the ratios of ring gear and pinion gear may vary in alternative examples.FIG. 2B again shows an optional clutch 252 (e.g., a slip clutch mechanism) that may be included in the electric drive unit 200. Clutch 252 is configured to selectively connect ring gear 206 or sun gear 208 to output 254 for planetary gear set 202. Thus, clutch 252 is shiftable between a first gear, where the ring gear is the output, and a second gear, where the sun gear is the output. Clutch 252 may also have a neutral position in which neither the ring gear nor the sun gear is engaged. In this way, the transmission ratio of the electric drive unit can be changed, which enables more efficient operation of the electric machines and thus increases the efficiency and range of the vehicle.The output 254 may be connected to another planetary assembly for a coaxial power path or a transfer case for a multiaxial assembly. In general, the output 254 may in turn be coupled to a downstream component of the powertrain, such as a drive wheel, a drive axle, or a transmission (e.g., a multi-speed transmission). This makes the electric drive unit applicable to a plurality of vehicle platforms, which increases the attractiveness for customers.The electric drive unit 200 may further include a power take-off assembly 260, which may include a power take-off 262 and a power take-off clutch 264. The auxiliary output 262 is coupled to the ring gear 206 in the example shown. Alternatively, however, the auxiliary output 262 may also be coupled to the sun gear 208. The auxiliary output assembly 260 may have similar functionality to the auxiliary output assembly 179 described above with respect to FIG. 1B. Therefore, redundant description is omitted for brevity.FIG. 2C shows a lever diagram for the speed of the compound planetary gear set 202. Again, the first pinion set 210 is rotationally coupled to the ring gear 206 and the second pinion set 212 is rotationally coupled to the sun gear 208. In the example shown, the carrier 204 is fixed and the ring gear 206 and sun gear 208 are possible starting points.Equations (9) and (10) indicate the correspondence between the ring-to-planet ratio of the planetary assembly, the output speed, and the input speed when the ring gear and the sun gear are used as the output.parametersω S: angular velocity, sunω R: angular velocity, ringe p1: Ratio of Ring to First Pinione 1: Ring to Sun RatioFor equations (7)-(10), it is assumed that the gear ratios of ring gear and pinion are identical. However, the ratios of ring gear and pinion gear may vary in alternative examples.FIG. 3 shows another example of a planetary gear set 300 that may be included in an electric drive unit. The planetary gear set 300 in turn includes a ring gear 302, a sun gear 304, and a carrier 306 that is mechanically locked. The planetary gear set 300 also includes a first pinion set 308 and a second pinion set 310. In the exemplary arrangement shown in FIG. 3, the two sets of pinions 308 and 310 mesh with both the ring gear 302 and the sun gear 304. However, the pinion sets 308 and 310 do not mesh with each other in the example shown. The various pinion sets may be driven independently of each other by different inverter components, as discussed in more detail below with respect to FIGS. 5A-5C.FIG. 4 shows another example of a planetary gear set 400. The planetary gear set 400 is a simple planetary gear set that, in the example shown, includes only the ring gear 402, the pinion gears 404, the fixed carrier 406, and the sun gear 408. In particular, as shown in FIG. 4, the planetary gear set 400 may include 28 pinions, which in some cases may be the maximum number of pinion gears that may be included in the gear set. The maximum number of pinion gears may depend, in part, on the selected planetary gear set ratio and a minimum ring-to-sun ratio constraint (e.g., 1.25 in one application) for manufacturing purposes. In one example, the maximum number of pinion gears may be inferred from a geometric test and condition that limits the planetary ratio to a minimum value (e.g., 1.25) for manufacturing purposes. Conversely, the minimum number of pinion gears in the planetary gear sets described herein may be three in one example. In certain practical applications, the planetary gear set may include 3 to 6 pinions to achieve the desired package sizes or to accommodate the limitations of certain vehicle platforms. In one example, the maximum number of sprockets and motors may be 6. In this way, the electric drive unit is capable of achieving packaging and cost objectives for particular vehicles.The electric machines illustrated in FIGS. 1A, 1B, 2A, and 2B, as well as the electric machines that can be coupled to the planetary gear sets illustrated in FIGS. 3 and 4, can receive electrical energy from inverter assemblies, also referred to as power electronics. It will be appreciated that the inverter arrangements may be conceptually integrated into the electric drive units in one example. However, in other examples, the inverter assemblies may be separate from the drive units. Generally, the inverters may be included in the electric drive systems. Also, in some cases, the inverters may be arranged together with the electric machines and the planetary assembly. Alternatively, the inverter arrangements may be spaced apart from the electric machines and / or planetary arrangements. Cables and / or busbars can be used for the connection between the inverters and the electric machines. FIGS. 5A-5C show various inverter arrangements that may be used in conjunction with the electric machines and electric drive units described herein.FIG. 5A illustrates an inverter arrangement 500 in which an inverter arrangement drives each electric machine in parallel. As already mentioned, the electric machine may be a three-phase machine and the inverter arrangement 500 and the other inverter arrangements described here may be three-phase inverters. However, the inverter arrangement architecture shown in FIG. 5A corresponds to a phase in the electric machine. It should be appreciated that the inverter circuit for the other phases in the electric machine may be identical to the inverter circuit shown in FIG. 5A. Moreover, additional bus bars may be required for connecting the inverter assembly to each individual electric machine.The phase electronics 502 for the single phase in the inverter assembly 500 includes an upper switch 504 and a lower switch 506. The phase electronics further include a first set of modules 508 (e.g., power electronics chips) corresponding to the upper switch 504, and a second set of modules 510 corresponding to the lower switch 506.The upper switch 504 and the lower switch 506 are electronically coupled to an output node 512 which may be electronically coupled in parallel with a bus bar in each electric machine. The input nodes 514 for the upper switch 504 and the lower switch 506, which may be electronically coupled to an energy store 507, are further illustrated in FIG. 5A. Similarly, energy stores may be electrically connected to the other inverter arrangements described herein.In the inverter architecture shown in FIG. 5A, the switch portion, the module portion and the total inverter current may be similar to a drive unit having a comparatively large individual motor. However, additional bus bars may also be used to connect each individual motor of the electrical drive units described herein. The inverter assembly 500 shown in FIG. 5A may be coupled to either induction motors or PM motors in various examples.FIG. 5B shows an inverter arrangement 520 where the single inverter unit drives each electric machine in parallel with electrical contactors 522 that can be selectively decoupled to shut down a subset of the electric machines independently of each other, if desired. Illustratively, FIG. 5B shows an upper switch 524 and a lower switch 526 corresponding to a first phase, an upper switch 528 and a lower switch 530 corresponding to a second phase, and an upper switch 532 and a lower switch 534 corresponding to a third phase.The contactors 522 include, in the example shown, a contactor 536 electrically connected to one group of electric machines and a contactor 538 electrically connected to another group of electric machines. Thus, contactors 536 and 538 are associated with two different groups of electric machines. For example, the electric machines 218 and 222 shown in FIG. 2A may belong to the first group of machines and the electric machines 220 and 224 may belong to the second group of electric machines, or vice versa. The electrical input nodes 540 for the inverter assembly 520 are further illustrated in FIG. 5B. The groups of electric machines can be operated depending on the load and torque requirement. Both groups of electric machines can be operated, for example, at high torques and / or loads. Conversely, one of the electric machine groups may be shut down at low load and / or low torque. Alternatively, a single disconnect contactor 542 may be used for one group of electric machines while the other group of electric machines is permanently electrically connected to the inverter (i.e., without disconnect contactor).FIG. 5C shows an inverter arrangement 550 divided into multiple sub-arrangements (e.g., a first sub-arrangement 552 and a second sub-arrangement 554). The first sub-assembly 552 and the second sub-assembly 554 drive different groups of electric machines. For example, the first subassembly 552 may drive a group of electric machines including the electric machines 218 and 222 shown in FIG. 2A, while the second subassembly 554 may drive a group of electric machines including the electric machines 220 and 224 shown in FIG. 2A, or vice versa. Thus, the first subassembly 552 and the second subassembly 554 may drive the motor groups independently of each other. Consequently, a load sharing operation with lower than the peak load can be performed. For example, the load between the two engine groups may be balanced when the deviation between the engine load is greater than a threshold. For example, the motors may be operated to reduce the load differences between the motors to reduce the risk of engine damage from uneven load.The first sub-assembly 552 includes the phase electronics 556. The phase electronics 556 for the single phase in the inverter assembly 550 includes an upper switch 558 and a lower switch 560. The phase electronics further include a first set of modules 562 (e.g., power electronics chips) corresponding to the upper switch 558 and a second set of modules 564 corresponding to the lower switch 560. The upper switch 558 and the lower switch 560 are electronically coupled to an output node 566, which may be connected in parallel with a power rail in each electric machine. Input nodes 568 for the upper switch 558 and the lower switch 560, which may be electronically coupled to an energy store, are shown in FIG. 5C. In the illustrated embodiment, the second sub-array 554 has a similar configuration to the first sub-array 552, and redundant description is omitted for brevity.When the inverter array 550 is divided into sub-arrays, the switch and module contents may be larger than a drive unit using a single comparatively large motor. However, the total current of the inverter divided into subassemblies may be similarly high as an electric drive unit using a single, comparatively large motor. The inverter assembly 550 may require additional bus bars to allow the inverter to be electrically connected to each individual motor.The inverter assemblies 520 and 550 shown in FIGS. 5B and 5C may be coupled to induction motors, for example. When asynchronous motors are used in the drive unit, an emergency mode can be used. To explain, the limp home mode may be triggered when one or more motors in one of the motor sets are damaged (e.g., are no longer functional). In such an example, the set of motors may be deactivated with the non-functioning motor while the other set of motors remains in the driving mode. Therefore, when using asynchronous motors in the drive unit, a counter electromotive force (EMF) in the disconnected motors can be avoided, whereby the risk of motor damage caused by the counter EMF is reduced. In this way, the vehicle can be driven even when one or more engines are not in operation, which extends the possible uses of the drive unit.The electric drive units described herein achieve efficiency gains when using a common inverter as shown in FIGS. 5A-5C to drive all motors in parallel. Moreover, the use of parallel switching devices in the inverter architecture shown in FIGS. 5B-5C allows independent motor control to extend the drive unit's control capabilities and increase the drive unit's efficiency by shutting down a selected group of motors at low load or low torque.The planetary gear sets described herein may be configured such that the two pinion sets have asymmetric gear ratios. Both sets of pinions may be used as motor inputs in combination with a split inverter, such as inverter assembly 550 shown in FIG. 5C and described above. Both engine groups may operate at higher load and torque. The engine group with the numerically lower gear ratio may operate alone at lower load conditions or at an increased efficiency control (while the engine group with the higher gear ratio is not operating) when the engine group or combination of engine group loads results in lower (e.g., lowest) power consumption at part load.In the construction of the electric drive unit, cost aspects can also be taken into account in certain cases. For example, asynchronous motors can in some cases be less expensive than PM motors. In addition, the inverter for the induction motor may require more current compared to the PM motor. In addition, the use of a segmented inverter arrangement such as that shown in FIG. 5C may be more expensive than non-segmented inverters.It will be appreciated that electrical drive systems may be formed from combinations of the various inverter assemblies and electrical drive units described herein. Thus, various combinations of the electric drive units shown in FIGS. 1A-1C, 2A-2C, 3 and 4 and the inverter arrangements shown in FIGS. 5A-5C are conceivable.FIG. 6 shows a four quadrant electric machine map 600 that may be used as a control strategy for the electric drive unit 200 shown in FIGS. 2A-2C or other drive units that includes a planetary gear set with two sets of gears and two sets of electric machines. In the graph 600 shown in FIG. 6, the torque is shown on the abscissa (rising from left to right in the reference frame shown in FIG. 6 ) and the motor angular velocity (ω S) is shown on the ordinate (rising from bottom to top in the reference frame shown in FIG. 6 ). The diagram is conceptually divided into four quadrants (I-IV). The first quadrant (I) corresponds to a forward drive mode for the group of motors operating in this quadrant. The second quadrant (II) corresponds to a forward mode for the motor group operating in this quadrant. The third quadrant (III) corresponds to a reverse mode for the group of motors operating in this quadrant. The fourth quadrant (IV) corresponds to a reverse mode for the motor group operating in that quadrant.As shown in FIG. 6, for planetary gear sets, due to the opposite speed signs of the pinions, it may be necessary for the individual motor groups on the four quadrant plan of the electric machine 600 to operate alternately in the quadrants to drive both pinion sets. For example, the motor groups in quadrants I and III may be operated to commonly motor or in quadrants II and IV to commonly generate. Conventionally, speed and torque of the same sign mean that the engine is running, while opposite signs indicate the generator. In FIG. 6, the forward and backward directions refer to the range of the motor speed.The power feedback can additionally be realized in the electric drive unit with a planetary gear set. In a power feedback mode, the electric machines may be operated in quadrant I and IV, respectively, for example. In another mode of energy recirculation, the electric machines may be operated in quadrants II and III, respectively. In this way, the braking power of the propulsion unit is increased under certain circumstances where the battery power or temperature constraints prevent charging of the battery while at the same time achieving a negative electric braking torque. It will be appreciated that this power feedback control (which is extended herein with respect to FIG. 7 ) may be used specifically in electric drive units having groups of independently controllable electric machines. The power feedback control may be used in conjunction with the inverter arrangements shown in FIGS. 5B and 5C and the corresponding electric machines and planetary arrangements.Referring now to FIG. 7, an example vehicle operating sequence is illustrated. The flow of FIG. 7 may be provided via the electric drive units of FIGS. 2A-2C and the corresponding inverter arrangements (e.g., the inverter arrangements shown in FIGS. 5B and 5C ). The curves shown in FIG. 7 are matched in time and occur at the same time. The vertical lines at times t0 - t5 represent interesting times in the sequence.The first plot from the top of FIG. 7 is a plot depicting the state of a vehicle braking request as a function of time. The vertical axis represents vehicle braking state and vehicle braking is requested when trace 702 is at a level that is near the vertical axis arrow. Vehicle braking is not requested when line 702 is at a level near the horizontal axis. The horizontal axis represents time, and time increases from the left side of the waveform to the right side of the waveform. Line 702 represents the braking state of the vehicle. A vehicle brake request may be initiated by actuation of a brake pedal or by an autonomous driver.The second plot from the top of FIG. 7 is a plot illustrating the state of charge of a battery as a function of time. The vertical axis represents the state of charge of the battery (SOC), and the state of charge of the battery increases in the direction of the vertical axis arrow. The state of charge of the battery is equal to zero at the level of the horizontal axis. The horizontal axis represents time, and time increases from the left side of the waveform to the right side of the waveform. Line 704 indicates the state of charge of the battery. Horizontal line 750 represents a threshold that the state of charge of the battery may exceed.The third plot from the top of FIG. 7 is a plot indicating a mode of operation of a first group of electric machines of a vehicle as a function of time. The first electric machine group may be operated in a generator mode in which the first electric machine group generates electrical energy and provides the electrical energy to a power bus. The first electric machine group may also be operated in an engine mode in which the first electric machine group generates mechanical energy for propulsion of a vehicle. The first group of electric machines may be operated in the generator mode when the curve 706 is at a higher level near the vertical axis arrow. The first group of electric machines may operate in engine operation when trace 706 is at a lower level near the horizontal axis. The horizontal axis represents time, and time increases from the left side of the waveform to the right side of the waveform. Trace 706 indicates the mode of operation of the first group of electric machines. In this example, the first electric machine group may be coupled to a first pinion set in a compound planetary gear set.The fourth plot from the top of FIG. 7 is a plot indicating a mode of operation of a second group of electric machines of a vehicle as a function of time. The second electric machine group may be operated in a generator mode in which the second electric machine group generates electrical power and provides the electrical power to a power bus. The second electric machine group may also be operated in an engine mode in which the second electric machine group generates mechanical energy for propulsion of a vehicle. The second group of electric machines may be operated in the generator mode when the curve 708 is at a higher level near the vertical axis arrow. The second group of electric machines may operate in engine operation when the track 708 is at a lower level near the horizontal axis. The horizontal axis represents time, and time increases from the left side of the waveform to the right side of the waveform. Trace 708 indicates the mode of operation of the second group of electric machines. In this example, the second electric machine group may be coupled to a second planetary gear set.The fifth plot from the top of FIG. 7 is a plot indicating the operating efficiency of the first electric machine group of a vehicle as a function of time. The efficiency of the first electric machine group may be adjusted by changing the speed of the first electric machine group via the planetary gear set. In addition, the operating efficiency of the first electric machine group may be adjusted via adjustment of the output of an inverter electrically connected to the first electric machine group. The vertical axis represents the operating efficiency of the first electric machine group regardless of whether the first electric machine group is operating in motor or generator operation. The horizontal axis represents time, and time increases from the left side of the waveform to the right side of the waveform. Trace 710 represents the operating efficiency of the first group of electric machines.The sixth plot from the top of FIG. 7 is a plot indicating the operating efficiency of the second electric machine group of a vehicle as a function of time. The efficiency of the second electric machine group may be adjusted by changing the speed of the second electric machine group via the planetary gear set. Moreover, the operating efficiency of the second electric machine group may be adjusted via adjustment of the output of an inverter assembly electrically connected to the second electric machine group. The vertical axis represents the operating efficiency of the second electric machine group regardless of whether the second electric machine group is operating in motor or generator operation. The horizontal axis represents time, and time increases from the left side of the waveform to the right side of the waveform. Curve 712 shows the efficiency of the second group of electric machines.The seventh plot from the top of FIG. 7 is an electric brake torque (e.g., brake torque provided by electric machines) versus time plot. The vertical axis represents a magnitude of the braking torque, and the magnitude of the braking torque increases in the direction of the vertical axis arrow. The horizontal axis represents time, and time increases from the left side of the waveform to the right side of the waveform. Line 714 represents the magnitude of the electric brake torque.At time t 0, vehicle braking is not required and the battery SOC is below threshold 750. The first and second electric machine groups operate in engine operation to propel the vehicle with torque. The operating efficiency of the first and second electric machine groups is high and the braking torque of the vehicle is equal to zero.At time t 1, vehicle braking is requested. The SOC is low so that the first electric machine group and the second electric machine group are operated in a generator mode to increase the SOC of the battery and provide a braking torque for braking the vehicle. The first and second groups of electric machines continue to operate at a high efficiency and the electric brake torque is a low brake torque.At time t 2, the braking request of the vehicle is released and the SOC of the battery starts to decrease. The first electric machine group and the second electric machine group are operated in a motor mode. The efficiency of the first and second groups of electric machines remains at a higher level. The electrical braking torque is reduced to zero.At time t 3, vehicle braking is requested a second time in the sequence. The SOC of the battery is below the threshold of 750 such that both the first electric machine and the second electric machine are operated in the generator mode to charge the battery. The efficiency of the first and second groups of electric machines is high and the braking torque lies in the middle range.At time t 4, the vehicle brake request remains and the battery SOC reaches threshold 750. Therefore, the first electric machine group switches to engine operation and the second electric machine group remains in generator operation. The efficiency of the first electric machine group is maintained and the efficiency of the second electric machine group is reduced. In this example, the total braking torque is decreased, but the electric braking is maintained. The required braking torque can be applied by a combination of an electric brake and a friction foundation brake.At time t 5, the request to decelerate the vehicle is deasserted, and the first and second electric machine groups are both operating in engine operation. The battery SOC is high and the efficiency of the first and second electric machine groups is at a high level. The vehicle braking torque is also reduced to zero.By operating the first electric machine group in the engine mode and the second electric machine group in the generator mode, the first electric machine group may consume all of the electrical power generated and output by the second electric machine group such that the net power flow to / from the battery is zero, such that the battery's SOC cannot increase above a desired value. For example, if the second electric machine group has an output of 100 kilowatts, the first electric machine group may consume 100 kilowatts. The sequence in FIG. 7 is only one example of how the first and second groups of electric machines may be operated. In other examples, the second electric machine group may be operated as a motor and the first electric machine group may be operated as a generator when the battery SOC reaches a threshold.FIGS. 1-7 show a control strategy for an electric drive unit in which during a low gear condition the clutch in the planetary gear assembly is operated to rotationally couple the ring device to the output of the planetary gear set. Conversely, in the high gear state, the clutch gear is actuated to rotationally couple the sun device to the output. The low gear can be selected by the vehicle driver, for example, or automatically engaged at start, at higher load of the vehicle, etc. Conversely, high gear may be selected by the vehicle operator or automatically engaged when the vehicle is driving at higher speed, lower load, etc. The electric drive unit may also operate the clutch to transition between high and low gear states depending on operating conditions. The electric drive unit may also be operated to synchronize the speeds of the ring device and the sun device during a shift operation to enable a smooth gear change when the drive unit uses a simple planetary gear set. In addition, during operation of the electric drive unit, the mechanical power is transmitted from the electric machines to the pinions in the planetary gear set. When using a planetary gear set in the drive unit, the electric machines can also be rotated in opposite directions.FIGS. 1 to 7 also show a control technique in which electrical energy is transmitted from the inverter arrangement in parallel to the electric machines. Moreover, in the configuration of the compound planetary drive, the motor groups can be selectively decoupled from the converter arrangement depending on the operating states of the vehicle, in order to save energy. For example, the first or second electric machines can be decoupled from the inverter if the drive unit experiences loads which are below a threshold value.The planetary arrangements shown in FIGS. 1A, 2A, 3 and 4 are drawn approximately to scale. In addition, the electric machines illustrated in FIG. 2A are drawn approximately to scale. However, in other embodiments, the components may have different relative dimensions.Figures 1A, 2A, 3-4 and 5A-5C show example configurations with relative positioning of the various components. When these elements are in direct contact with or directly coupled to each other, they may be referred to as being in direct contact or directly coupled, respectively, at least in one example. Similarly, elements depicted adjacent or adjacent to each other may be adjacent or adjacent to each other, at least in one example. For example, components which are in planar contact with one another can be referred to as being in planar contact. As another example, in at least one case, elements that are separated from each other and between which only a space is located and that do not have other components may be referred to as such. In yet another example, elements depicted above / below each other, on opposite sides or left / right of each other may be referred to as such relative to each other. Further, in at least one example, as shown in the figures, a top element or point of an element may be referred to as a "top" of the component and a bottom element or point of the element may be referred to as a "bottom" of the component. As used herein, the terms top / bottom, top / bottom, top / bottom may refer to a vertical axis of the figures and be used to describe the positioning of elements of the figures relative to each other. Thus, in one example, items displayed above other items are vertically disposed above the other items. As another example, the shapes of the elements depicted in the figures may be referred to as such (e.g., circular, straight, planar, curved, rounded, beveled, angled, and the like). Moreover, in one example, elements that are coaxial with each other may be referred to as such. Further, the illustrated elements that intersect one another may be referred to as intersecting elements or intersecting elements in at least one example. Moreover, an element shown inside another element or outside another element may be referred to as such. In other examples, elements offset from one another may also be referred to as such.The invention is further described in the following paragraphs. In one aspect, an electric drive unit is provided that includes a set of electric machines, each electric machine coupled to a separate pinion device in a first set of pinion devices of a planetary assembly; and wherein the planetary assembly includes: a carrier that is mechanically locked; a ring device; and a sun device; wherein the ring device and / or the sun device function as an output; and wherein the first set of pinion devices is rotationally coupled to the ring device and / or the sun device. In one example, the planetary assembly may include a second set of pinion devices rotationally coupled to the first set of pinion devices. Moreover, in one example, the first group of pinion devices and the second group of pinion devices may have asymmetric gear ratios. In another example, the electric drive unit may further include a clutch configured to rotationally couple: the ring device with the output in a first position; and the sun device with the output in a second position. In another example, the electric drive unit may further include a controller including instructions stored in memory that, when executed, cause the controller to actuate the clutch to rotationally couple the ring device to the output during a low gear state; and instructions stored in memory that, when executed, cause the controller to actuate the clutch to rotationally couple the sun device to the output during a high gear state. In another example, the controller includes instructions stored in memory that, when executed, cause the controller to: synchronize a speed of the ring device or the sun device with the output speed during a shift. In another example, the sun device or the ring device may function as an output and the ring device or the sun device is rotatably coupled to a power take-off (PTO). In another example, the electric drive unit may further include a power take-off clutch configured to decouple the power take-off from the ring device or the sun device. In another example, the ring device may be rotationally coupled to a first drive axis and the sun device may be rotationally coupled to a second drive axis. In another example, the output may be rotationally coupled to a multi-speed transmission or an auxiliary transmission. In another example, the output may be rotationally coupled to a drive wheel. In another example, the planetary assembly may be a planetary gear set or a planetary traction drive.In another aspect, a method of operating an electric drive unit is provided that includes transferring mechanical power from a set of electric machines to a first pinion set; wherein the electric drive unit includes: the set of electric machines; and a planetary gear set including: the first pinion set; a carrier mechanically fixed; and a ring gear; and a sun gear; and wherein the ring gear and / or the sun gear function as an output; and wherein the first pinion set meshes with the ring gear and / or the sun gear. In one example, the planetary gear set may be a compound planetary gear set including a second pinion set that meshes with the sun gear and is rotationally coupled to the first pinion set; and the ring gear and the sun gear may rotate in the same direction. In another example, the method may further include operating a clutch to transition between a lower gear mode where the ring gear is connected to the output and a higher gear mode where the sun gear is connected to the output. In another example, the output may be rotationally coupled to: a drive axle; a drive wheel; a multi-speed transmission; or an auxiliary transmission.In another aspect, an electric drive unit is provided that includes a set of traction motors each rotationally coupled to a separate pinion in a first pinion set; and a planetary gear set that includes: a carrier mechanically fixed and rotationally coupled to the first pinion set and a second pinion set; the first pinion set that meshes with a ring gear and / or a sun gear; and the second pinion set that meshes with a sun gear and the first pinion set. In one example, the planetary gear set may be a multi-speed planetary gear set. In another example, the multi-speed planetary gear set may include a clutch configured to selectively couple the sun gear and the ring gear to an output in different gear types. In another example, the ring gear and / or the sun gear may function as an output and be configured to rotationally couple to: a drive axle; a drive wheel; a multi-speed transmission; or an auxiliary transmission.In another aspect, an electric drive system is provided that includes a first set of electric machines, each of which is rotatably coupled to a pinion device in a first set of pinion devices; a planetary assembly including: the first set of pinion devices; a carrier mechanically fixed; a ring device; and a sun device; and an inverter assembly electrically coupled in parallel with the first set of electric machines; wherein the first set of pinion devices is rotatably coupled to the ring device and / or the sun device. In another example, the planetary assembly may include a second group of pinion devices rotationally coupled to the ring device or the sun device; and the second group of pinion devices may be rotationally coupled to a second group of electric machines. In another example, the inverter assembly may further include: a first set of electrical contactors configured to selectively electrically decouple the inverter assembly from the first set of electrical machines independently of one another; and a second set of electrical contactors configured to selectively electrically decouple the inverter assembly from the second set of electrical machines independently of one another. In another example, the inverter assembly may further include: a first sub-assembly configured to independently electrically drive the first set of electric machines; and a second sub-assembly configured to independently electrically drive the second set of electric machines. In another example, each of the electric machines in the first group of electric machines and the second group of electric machines may be a permanent magnet motor. In another example, the first group of pinion devices and the second group of pinion devices may have asymmetric ratios. In another example, the electric drive system may further comprise a controller including instructions stored in a memory that, when executed during a drive state, cause the controller to operate the first set of electric machines to rotate in a first direction and to operate the second set of electric machines to rotate in a second direction opposite the first direction. In another example, the electric drive system may further include a speed sensor configured to determine the operating speed of all electric machines in the first group of electric machines. In another example, the electric machines of the first group of electric machines may be permanent magnet motors or induction motors. In another example, the planetary assembly may be a planetary gear set or a planetary traction drive.In another aspect, there is provided a method of operating an electric drive system comprising transferring electrical energy from an inverter assembly to a first set of electric machines in parallel; the electric drive system comprising: the first set of electric machines, each of which is rotationally coupled to a pinion device in a first set of pinion devices; and a planetary assembly comprising: the first set of pinion devices; a carrier mechanically fixed; and a ring device; and a sun device; and the inverter assembly; wherein the first set of pinion devices is rotationally coupled to the ring device and / or the sun device. In another example, the electric drive system may further include a second set of electric machines electrically rotationally coupled to the inverter assembly and to a second set of pinion devices rotationally coupled to the ring device or the sun device, and the method further includes parallel transferring electrical energy from the inverter assembly to the second set of electric machines. In another example, the method may further comprise selectively, independently electrically decoupling the first or second set of electric machines from the inverter assembly based on one or more operating conditions. In another example, the parallel transfer of electrical energy from the inverter assembly to the first set of electric machines may include the independent transfer of electrical energy from a first inverter subassembly to the first set of electric machines; and the parallel transfer of electrical energy from the inverter assembly to the second set of electric machines includes the independent transfer of electrical energy from a second inverter subassembly to the second set of electric machines. In another example, the first and second sets of pinion devices may have asymmetric ratios, and the method further includes driving the first set of electric machines in a first rotational direction and driving the second set of electric machines in a second rotational direction opposite the first rotational direction. In another example, the method may further include operating the first set of electric machines in a drive mode while the second set of electric machines is operated in a regeneration mode, wherein the first and second sets of electric machines have opposite rotational directions.In another aspect, an electric drive system is provided that includes a first set of traction motors, each of which is rotationally coupled to a pinion in a first set of pinions; a second set of traction motors, each of which is rotationally coupled to a pinion in a second set of pinions; a planetary gear set including the first set of pinions; the second set of pinions; a carrier mechanically fixed; and a ring gear; and a sun gear; and an inverter assembly electrically coupled in parallel with the first set of traction motors and the second set of traction motors; wherein the first set of pinions meshes with the ring gear and / or the sun gear. In one example, the electric drive system may further include a speed sensor coupled to one of the traction motors in the first set of traction motors and configured to determine an operating speed of all of the traction motors in the first set of traction motors. In another example, the traction motors in the first and second sets of traction motors may be permanent magnet motors or induction motors. In another example, the inverter assembly may further comprise: a first set of electrical contactors configured to selectively electrically decouple the inverter assembly from the first set of traction motors independently of one another; and a second set of electrical contactors configured to selectively electrically decouple the inverter assembly from the second set of traction motors independently of one another; and wherein the electrical drive system further comprises a controller including instructions that, when executed while the electrical drive system is operating at less than the peak load, cause the controller to: implement a load distribution between the first set of traction motors and the second set of traction motors.The control methods and routines disclosed herein may be stored as executable instructions in non-transitory memory and may be executed by an electric drive unit and / or a system including the controller in combination with the various sensors and actuators. In addition, portions of the methods may be physical actions taken in the real world to change the state of a device. The specific routines described herein may represent any one or more processing strategies such as event-driven, interrupt-driven, multi-tasking, multi-threading, and the like. Thus, the various actions, operations, and / or functions depicted may be performed in the order depicted, in parallel, or in some cases, without them. Accordingly, the order of processing is not necessarily required to achieve the features and advantages of the examples described herein, but is for convenience of illustration and description only. One or more of the illustrated actions, operations, and / or functions may be repeatedly performed depending on the strategy being used. Further, the described actions, operations, and / or functions may graphically represent code to be programmed into the non-transitory memory of the computer readable storage medium in the control system, wherein the described actions are performed by executing the instructions in a system including the various hardware components in combination with the electronic controller. One or more of the method steps described herein may also be omitted, if desired.While various embodiments have been described above, these are to be considered as examples and not as limitations. It should be understood that the configurations and procedures disclosed herein are exemplary in nature and that 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 powertrains that include various types of propulsion sources, including various types of electric machines, internal combustion engines, and / or transmissions. The technology may be used as a stand-alone system or in combination with other power transmission systems, including, but not limited to, machines and propulsion systems for tandem axles, electric trailer axles, P4 axles, hybrid vehicles, battery vehicles, agriculture, marine travel, motorbikes, recreational vehicles, and road and off-road vehicles. The subject matter of the present disclosure includes all novel and non-obvious combinations and sub-combinations of the various systems and configurations, as well as other features, functions, and / or characteristics disclosed herein. It will be apparent to those 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 following claims particularly emphasize certain combinations and sub-combinations that are considered novel and not obvious. These claims may refer to "a" element or "a first" element or the equivalent thereof. Such claims are to be understood to include inclusion of one or more such elements, with neither requiring nor excluding two or more such elements. Other combinations and sub-combinations of the disclosed features, functions, elements, and / or characteristics may be claimed by altering the present claims or by filing novel claims in this or a related application. Such claims, whether broader, narrower, equal or different in scope than the original claims, are also considered to be included within the subject matter of the present disclosure.The term "about" means plus or minus one percent of the range unless otherwise specified.References included in the specificationThis list of documents cited by the applicant has been produced in an automated manner and is only included for the better information of the reader. The list is not part of the German patent application or utility model application. The DPMA does not take any adhesion for any faults or omissions.Patent Literature citedU.S. Pat. No. 9,487,084 B2

[0003]

Claims

An electric drive unit comprising: a set of electric machines, each electric machine coupled to a separate pinion device in a first set of pinion devices of a planetary assembly; and wherein the planetary assembly comprises: a carrier mechanically locked; a ring device; and a sun device; wherein the ring device and / or the sun device function as an output; and wherein the first set of pinion devices is rotationally coupled to the ring device and / or the sun device.The electric drive unit of claim 1, wherein the planetary assembly comprises a second set of pinion devices rotationally coupled to the first set of pinion devices.The electric drive unit of claim 2, wherein the first set of pinion devices and the second set of pinion devices have asymmetric gear ratios.The electric drive unit of any preceding claim, further comprising a clutch configured to rotationally couple: the ring device with the output in a first position; and the sun device with the output in a second position.The electric power unit of claim 4, further comprising a controller having instructions stored in a memory that, when executed during a low gear state, cause the controller to: actuate the clutch to rotationally couple the ring device to the output; and instructions stored in the memory that, when executed during a high gear state, cause the controller to: actuate the clutch to rotationally couple the sun device to the output.The electric drive unit of claim 5, wherein the controller comprises instructions stored in the memory that, when executed, cause the controller to: synchronize a speed of the ring device or the sun device with the output speed during a shift.The electric drive unit according to any of the preceding claims, wherein the sun device or the ring device acts as an output and the ring device or the sun device is rotatably coupled to a power take-off (PTO).The electric drive unit according to claim 7, further comprising a power take-off clutch configured to decouple the power take-off from the ring device or the sun device.The electric drive unit of any preceding claim, wherein the ring device is rotatably coupled to a first drive axle and the sun device is rotatably coupled to a second drive axle.The electric drive unit of any preceding claim, wherein the output is rotationally coupled to a multi-speed transmission or an auxiliary transmission.The electric drive unit of any preceding claim, wherein the output is rotatably coupled to a drive wheel.An electric drive unit according to any preceding claim, wherein the planetary arrangement is: a planetary gear set; or planetary traction drive.

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