Systems for a dual-motor powertrain

Abstract

Electric powertrain comprising: a planetary gear set comprising a ring gear, a sun gear and a planet carrier coupled to the ring gear and the sun gear; a first motor having a first output shaft coupled to the ring gear; a second motor having a second output shaft coupled to the sun gear; and a controller having instructions stored in its memory that, when executed, cause the controller to set an operating state of the first motor and to selectively couple the ring gear to a static housing via a clutch based on a speed of the planet carrier.

Description

AREA

[0001] This description relates generally to a dual-motor electric powertrain for a vehicle. BACKGROUND AND OVERVIEW

[0002] Vehicle systems can size a motor to match the power demand. However, a single large motor may be inefficient under certain operating conditions. Therefore, some vehicle systems may include two smaller motors.

[0003] These vehicle systems may include complex gear systems and / or control strategies for motor operation, which can increase vehicle manufacturing costs and complexity. Therefore, there may be a need for systems and methods other than those currently available.

[0004] The problems described above can be solved by an electric drivetrain comprising a planetary gear set with a ring gear, a sun gear, a planet carrier coupled to a differential, a first motor coupled to the ring gear, a second motor coupled to the sun gear, and a controller configured to adjust an operating state of the first motor and selectively couple the ring gear to a static housing via a clutch based on a speed of the planet carrier. In this way, the operation of the motors can be achieved with a compact drivetrain.

[0005] It should be understood that the above summary is intended to introduce, in simplified form, a selection of concepts that are further explained in the detailed description. It is not intended to identify the most important or essential features of the claimed subject matter, the scope of which is clearly defined by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that address the disadvantages noted above or elsewhere in this disclosure. SHORT DESCRIPTION OF THE CHARACTERS Fig. 1 shows example vehicle systems. Fig. Figure 2 shows a cross-section of a powertrain used in the vehicle systems. Fig. 3 shows a schematic representation of the drive train. Fig. Figure 4 shows a table indicating the operation of a clutch and driveline components under different working conditions. Fig. Figure 5 shows the power flow in a first operating state in which only one motor is in operation. Fig. Figure 6 shows the power flow in a second operating state in which both electric motors are in operation. Fig. 7 shows a method for determining the operating state of the vehicle. Fig. Figure 8 shows a method for operating the electric motors based on a carrier speed. Fig. Figure 9 shows diagrams illustrating a limit speed for changing the drive mode of only one motor or both motors based on a comparison of power and speed or torque and speed. Fig. Figure 10 shows increased efficiency of the current powertrain compared to previous powertrain examples. DETAILED DESCRIPTION

[0006] The following description refers to systems for a powertrain with two electric motors. Using two lower-power electric motors instead of a single higher-power motor can optimize energy consumption and reduce overall costs. By optimizing the efficiency of the motors, the two motors can consume less energy at light loads or when driving idle. The service life of the motor and electronic hardware components is increased because one motor is switched off at low loads. The vehicle's range is increased with a sufficiently fully charged battery. Vehicles can continue to operate at lower power even if a motor or electronic hardware fails. The general design can be used for all types of vehicles.

[0007] Fig. 1 shows example vehicle systems. Fig. Figure 2 shows a cross-section of a powertrain used in the vehicle systems. Fig. 3 shows a schematic representation of the drive train. Fig. Figure 4 shows a table indicating the operation of a clutch and driveline components under different working conditions. Fig. Figure 5 shows the power flow in a first operating state in which only one motor is in operation. Fig. Figure 6 shows the power flow in a second operating state in which both electric motors are in operation. Fig. 7 shows a method for determining the operating state of the vehicle. Fig. Figure 8 shows a method for operating the electric motors based on a carrier speed. Fig. Figure 9 shows diagrams illustrating a limit speed for changing the drive mode of only one motor or both motors based on a comparison of power and speed or torque and speed. Fig. Figure 10 shows increased efficiency of the current powertrain compared to previous powertrain examples.

[0008] Fig. 1 shows a reach truck 100 and a heavy forklift 150. The reach truck 100 and the heavy forklift 150 may have an electric drive train coupled to a front axle of the front wheel 102 or the front wheel 152, respectively. The rear axle is a steer axle and is coupled to the rear wheel 104 of the reach truck 100 or to the rear wheel 154 of the heavy forklift 150. The example vehicles from Fig. 1 No gases such as carbon dioxide (CO2), carbon monoxide (CO) or nitrogen oxides (NO x) and can be described as zero-emission vehicles. The reach truck 100 and the heavy forklift 150 are two non-limiting examples of vehicles that can be used with the powertrain described below.

[0009] Fig. 2 shows a cross-section 200 of an electrified powertrain of the front axle 202 with a first electric motor 210, a second electric motor 220, an intermediate planetary system (IPS) 230, and a drive axle 240. The IPS 230 may combine the power of the first electric motor 210 and the second electric motor 220 and transfer the combined power to an input of the drive axle 240. In one example, the input of the drive axle 240 may be a helical bevel gear pair 242. The IPS 230 may be configured as a power mixer to control the power of the first electric motor 210 and / or the second electric motor 220 to the drive axle 240, in one example. The drive axle 240 may include the helical gear pair 242 and a secondary planetary system 250. The power of the IPS 230 is transmitted from the spiral gear pair 242 to the secondary planetary system 250 and then to the wheels, e.g.the front wheel 102 or the front wheel 152 of . Fig. 1, transferred.

[0010] The first and second electric motors 210, 220, and IPS 230 may be mounted on a vehicle chassis. The output of the IPS 230 may be transmitted to an input pinion of the helical gear pair 242, either directly via a dedicated connection or via a drive shaft, depending on the vehicle type, application, and available space on the vehicle chassis.

[0011] Fig. 3 shows a schematic representation of the powertrain of an electric vehicle 300. The powertrain of the electric vehicle may include a battery management system 310, a high-voltage battery 312, a vehicle control unit (VC) 314, a powertrain control unit (DC) 316, a first motor control unit (MC1) 322, a second motor control unit (MC2) 324, the first electric motor (EM1) 210, the second electric motor (EM2) 220, the IPS 230, a clutch system 330, a hydraulic clutch actuation system 332, and the drive axle 240.

[0012] The high-voltage battery 312 may be a primary power source configured to power the electric motors EM1 210, EM2 220, and a third electric motor (EM3) 350 via respective motor controllers MC1 322, MC2 324, and MC3 326. The MCs may include an inverter configured to control the power output of the high-voltage battery 312 to the electric motors. A battery management system (BMS) may provide improved battery operation and protect the batteries from deep discharge and overvoltage caused by extremely rapid charging and extremely high discharge currents.

[0013] The VC 314 can receive various inputs from a driver related to the vehicle's function (e.g., requests to change speed by applying the pedal) and sends signals to the powertrain controller (DC) 316. The functions of the VC 314 can include speed changes, forward and reverse travel, motor optimization, lifting material, turning, and stopping the vehicle. The DC 316 can control the power input of the motor controllers MC1 322 and MC2 324. MC1 322 and MC2 324 can control the speed and direction of rotation of the electric motors based on the DC 316 inputs, resulting in forward and reverse travel and optimization of both motors.

[0014] The vehicle control module (VC) 314 controls the power supply to the third engine control module (MC3) 326. MC3 326 may control the speed and direction of rotation of EM3 350 based on inputs from VC 314. EM3 326 may control a hydraulic pump 334. The hydraulic pump 334 may supply hydraulic pressure to a clutch actuation hydraulic system 332 and other hydraulic fluid-dependent assemblies 336. The clutch actuation hydraulic system 332 may be coupled to a clutch 330 coupled to the ring gear 364. The clutch 330 may be configured to engage and disengage the ring gear 364 from a stationary housing 331.

[0015] Electric motors (EM1, EM2, and EM3) can convert electrical energy into mechanical energy and transmit the power to the individual drive units such as the drive axle, clutch hydraulic systems, lifting system, brakes, and steering. The drive axle 240 can transmit the power to the wheels 302. The IPS 230 is located between the EM1 210 and the EM2 220. The IPS 230 can control and optimize the performance of both the EM1 210 and the EM2 220. The EM1 210 can have a first output shaft 362 that transmits its power to a ring gear 364 of the IPS 230. The EM2 220 can have a second output shaft 366 that transmits its power to a sun gear 368 of the IPS 230. The IPS 230 can mix the power of EM1 210 and EM2 220 via a planet carrier 372 which is coupled to the ring gear 364 and the sun gear 368.A third output shaft 374, concentric with and extending through the body of the second output shaft 366, can transmit power from the IPS 230 to a differential unit 380 that includes the input gear (e.g., the helical bevel gear pair 242). Thus, the second output shaft 366 of the EM2 220 is hollow. The third output shaft 374 can be meshed with the input gear of the differential gear 380.

[0016] In some examples, additionally or alternatively, the third output shaft 374 and the bevel pinion of the drive axle 240 may be connected with a flexible coupling if the vehicle includes shock absorbers. The differential unit 380 may transmit power to both second-stage planetary gear sets 250 via separate axle shafts of the drive axle 240. The power of the second-stage planetary gear set 250 is transmitted to the wheels 302 via wheel hubs.

[0017] One or more of VC 314, DC 316, MC1 322, MC2 324, and MC3 326 may include memory with instructions stored thereon that cause the controller to send signals to actuators and adjust powertrain operating parameters. One or more sensors and actuators may be coupled to and in communication with the control unit(s) so that the controller(s) can adjust the one or more actuators in response to feedback from the one or more sensors.

[0018] Fig. Figure 4 shows a table 400 illustrating four working conditions of a vehicle, e.g., a forklift. A first condition is an empty condition (e.g., no load), a second condition is a low-load condition, a third condition is a medium-load condition, and a fourth condition is a high-load condition. The total weight of the vehicle changes for each loading condition. Table 400 contains general weight values ​​for example purposes and can be modified for different application types.

[0019] The first state (e.g., the empty state) can be a minimum of all load cases, so that the power demand of the vehicle is lower compared to all other load cases. The low power demand of the vehicle is provided by the DC (e.g., DC 316 of Fig. 3) detected when MC1 (e.g. MC1 322 of Fig. 3) and MC2 (e.g. MC2 324 from Fig. 3) less power to the EM1 engines (e.g. EM1 210 from Fig. 3) and EM2 (e.g. EM2 220 from Fig. 3). The DC may send a signal to a solenoid of the hydraulic clutch actuation system (e.g., the hydraulic clutch actuation system 332 in Fig. 3) to close the clutch. In addition, the EM1 can be switched off via MC1. EM2 can continue to operate and supply power to the IPS (e.g., IPS 230 in Fig. 3). The clutch (e.g., clutch 330 in FIG. 3) is mounted on the ring gear (e.g., ring gear 364 in FIG. 3) of the IPS, so that the ring gear no longer rotates and the power transmission between EM1 and the IPS is blocked. In the first state, the IPS can function as a reduction gear with input power to the sun gear (e.g., sun gear 368 in FIG. 3) and output power from the planet carrier (e.g., planet carrier 372 in FIG. 3). In this case, the IPS can be used to increase torque. The power flow of the first state is shown by arrows in FIG. 5. A method executed based on the instructions stored in the DC's memory is described in Fig. 7 shown.

[0020] The vehicle load and the relative power consumption of the electric motors can be empirically calibrated by testing vehicles under various load conditions. The threshold power can be determined based on system temperatures, component life, the electric motor, the drive system gear, etc. The DC can be configured to control the operation of the clutch based on the threshold power, where the set threshold power corresponds to the output power of a single electric motor. If the power demand is below the threshold power, the second motor can be activated, the first motor deactivated, and the clutch closed.This can result in energy-efficient operation of the first condition, reducing engine efficiency losses and enabling low operating costs, smooth speed, operation over a required range, and little or no vibration. The first condition also applies to light-load operating conditions when the vehicle's power demand is below the threshold power, as shown with the second condition in Table 400. Under certain operating conditions, such as idling or light load, the vehicle's speed may be higher, resulting in an increase in power above the threshold power. The clutch is then opened, the first electric motor is activated, and the IPS delivers a mix of the power from the first and second electric motors to a differential unit (e.g., the differential unit 380 in FIG. Fig. 3). One such example is given in the Fig. 8 and Fig. 9 and the corresponding descriptions are explained in more detail.

[0021] In one example, these operating conditions can increase the range of the vehicle with a sufficiently fully charged battery. Furthermore, the vehicle can be used even when an engine or electronic hardware is inactive. The arrangement of the present disclosure can be used for all types of vehicles.

[0022] When the vehicle's high power demand detected by the DC is above the threshold power, MC1 and MC2 transfer relatively high power to motors EM1 and EM2 compared to energy-efficient operation. The DC can also determine the motor speed and torque. The DC can provide signals to a clutch actuating solenoid to open the clutch and MC1 to activate EM1. The IPS ring gear can rotate freely with the first output shaft, and the power from EM1 is transferred to the IPS. The DC controls the torque, speed, and power of EM1 and EM2 so that both motors operate at higher efficiency ranges compared to the operation of a single electric motor. The power flow during operation of EM1 and EM2 is shown by arrows in FIGS. 5 and 6.

[0023] As in Fig. As shown in Figure 5, only EM2 is active. The power of EM2 220 is transmitted from the second output shaft 366 to the sun gear 368, to the planet carrier 372, and to the third output shaft 374 toward the differential gear 380. EM1 210 is inactive, and clutch 330 is closed, blocking the rotation of the ring gear 364.

[0024] As in Fig. 6, EM2 and EM1 are active. The power transmission from the EM2 220 is identical to that shown above in Fig. 5. The power of the EM1 210 is transmitted from the first output shaft 362 to the ring gear 364, to the planetary carrier 372, and to the third output shaft 374 to the differential gear 380. In this way, the IPS 230 combines the power of the EM1 210 and the EM2 220.

[0025] Fig. 7 shows a method 700 for adjusting engine operation based on a power demand. The power demand may be determined based on a driver demand. Instructions for performing method 700 and the other methods included herein may be executed by a controller (e.g., DC) based on instructions stored in a memory of the controller and in conjunction with signals received from sensors (e.g., MCs) of the powertrain system. The controller may use the powertrain actuators to adjust operation of the electric motor according to the methods described below.

[0026] At 702, method 700 may include determining the input power of EM1. MC1 may provide feedback to the DC regarding the electrical energy provided to EM1.

[0027] At 704, method 700 may include determining the EM2 input power. The MC2 may provide feedback to the DC regarding the electrical energy provided to the EM2.

[0028] At 706, method 700 may include calculating the total requested power. The total requested power may depend on the vehicle load and the pedal position.

[0029] At 708, method 700 may include determining whether the total requested power is less than the threshold power. The threshold power is based on a positive, non-zero number. The threshold power may be based on the output power of an individual electric motor.

[0030] If the total power required is below the threshold power, the method 700 may include deactivating the EM1 in 710.

[0031] At 712, method 700 may include closing the clutch. This may decouple the ring gear from the planet carrier.

[0032] At 714, the method 700 may include driving the vehicle using only the EM2.

[0033] Returning to 708, if the total power is not below the threshold power, method 700 may include maintaining the clutch open at 716. Thus, the ring gear may be coupled to the planet carrier.

[0034] At 718, method 700 may include driving the vehicle with EM1 and EM2. Thus, the IPS may blend the power from EM1 and EM2 and deliver the blended power to the drive axle.

[0035] In Fig. 8 illustrates a method 800 for actuating the clutch in response to planetary carrier speed. At 802, method 800 may include determining a vehicle speed.

[0036] At 804, method 800 may include determining the planetary carrier speed. The planetary carrier speed may be determined directly by a sensor. Additionally or alternatively, the planetary carrier speed may be determined indirectly via the power output of EM1 and EM2.

[0037] At 806, method 800 may include determining whether the planet carrier speed is less than a threshold speed. The threshold speed may be based on a non-zero, positive number. In one example, the threshold speed corresponds to 2,000 revolutions per minute. Additionally or alternatively, the threshold speed may be based on a planet carrier speed above which operating both EM1 and EM2 is more efficient than operating only EM2. In one example, the threshold planet carrier speed is determined based on the vehicle type, application, and traction performance requirements.

[0038] If the planet carrier speed is less than the threshold speed, method 800 may include deactivating EM1 at 808.

[0039] At 810, method 800 may include closing the clutch. This may decouple the ring gear from the planet carrier.

[0040] At 812, the method 800 may include driving the vehicle using only the EM2.

[0041] Returning to 806, if the planet carrier speed is not below the threshold speed, method 800 may include maintaining the clutch open at 814. Thus, the ring gear may be coupled to the planet carrier.

[0042] At 816, method 800 may include driving the vehicle with EM1 and EM2. Thus, the IPS may blend the power from EM1 and EM2 and deliver the blended power to the drive axle.

[0043] Thus, in one example, method 800 indicates that when the carrier's speed is below the threshold speed, the hydraulic clutch closes and one electric motor (EM1) is stopped because the ring gear is attached to the housing, which is static. The other electric motor (EM2) drives the carrier via the sun-to-carrier connection. When the carrier's speed increases above the threshold speed, the hydraulic clutch opens, and the two electric motors (EM1 and EM2) are connected to the carrier via the sun-to-carrier and ring-to-carrier connections, and the carrier is connected to the drive pinion of the drive axle.

[0044] Fig. 9 shows a first diagram 900 illustrating the limit speed (e.g., the threshold speed) for changing the drive mode as a function of the torque. Fig. 9 shows a second graph 950 illustrating the threshold speed for changing drive modes versus power. The powertrain system can be evaluated for both power versus speed (e.g., second graph 950) and torque versus speed (e.g., first graph 900). The graphs are divided into two zones, one with the clutch closed (only one motor running) and the other with the clutch open (dual motors running). At threshold speed 902 of the first graph 900 and threshold speed 952 of the second graph 950, the second motor (EM2) exhibits a downward trend in power and torque (row 904 and row 954, respectively) when the clutch opens and the first motor (EM1) engages the power flow, as shown at row 906 and row 956, respectively.In the clutch-disengaged region at speeds above the threshold speed, the output power and torque may be the sum of the torque and power of both motors. Output torque is represented by line 908 in the first graph 900, and output power is represented by line 958 in the second graph 950. The threshold speed may vary depending on vehicle and engine characteristics.

[0045] Fig. Figure 10 shows a prior art example with a plot of the motor torque-speed-power characteristic. When the motors are operated in the continuous torque range, the motors deliver higher power. Typical efficiency ranges of motors are indicated by dotted elliptical shapes. The efficiency values ​​given are for illustrative purposes and may be changed depending on the motor configuration and application. The prior art efficiency ranges have an irregular contour but are shown in elliptical shape for ease of understanding and explanation. DEM1 (N3, T3, P3) & DEM2 (N2, T2, P2) are typical operating points when both motors are operating at no-load. These points are in the 94% and 80% efficiency range, which means a power loss of 6% and 20%, respectively.In the prior art examples, additional power losses occur because the clutch is open, causing the clutch discs, ring gear, EM1 motor shaft, and all bearings associated with these parts to rotate, resulting in friction losses that contribute to the additional power losses.

[0046] Fig. 2 shows an example configuration with positional relationships of the various components. If these elements are in direct contact with each other or are directly coupled, they may be referred to as being in direct contact or directly coupled, respectively, at least in one example. Similarly, elements shown next to or adjacent to each other may be adjacent to or adjacent to each other, at least in one example. For example, components that are in surface contact with each other may be referred to as being in surface contact. As a further example, in at least one case, elements that are separated from each other with only a space between them and that do not have any other components may be referred to as such.In yet another example, elements depicted above / below, on opposite sides, or to the left / right of each other may be referred to as such, relative to each other. Further, in at least one example, as depicted in the figures, a topmost element or point of an element may be referred to as a "top" of the component, and a bottommost element or point of the element may be referred to as a "bottom" of the component. As used herein, the terms top / bottom, upper / lower, above / below may refer to a vertical axis of the figures and may be used to describe the positioning of elements of the figures relative to each other. For example, in one example, elements displayed above other elements are arranged vertically above the other elements.As another example, the shapes of the elements depicted in the figures may be referred to as such (e.g., circular, straight, flat, curved, rounded, beveled, angled, or the like). Further, in at least one example, depicted elements that intersect each other may be referred to as intersecting elements or as intersecting elements. Furthermore, an element depicted inside another element or outside another element may be referred to as such. It is understood that one or more components described as "substantially similar and / or identical" may vary from one another according to manufacturing tolerances (e.g., within 1-5% variation). Fig. 2 is shown approximately to scale.

[0047] The disclosure also provides support for an electric powertrain comprising: a planetary gear set including a ring gear, a sun gear, and a planet carrier coupled to the ring gear and the sun gear; a first motor including a first output shaft coupled to the ring gear; a second motor including a second output shaft coupled to the sun gear; and a controller having instructions stored in its memory that, when executed, cause the controller to set an operating state of the first motor and selectively couple the ring gear to a static housing via a clutch based on a speed of the planet carrier. In a first example of the system, a third output shaft is coupled to the planet carrier and a gear of a drive axle.In a second example of the system, optionally including the first example, the third output shaft extends through the second output shaft. In a third example of the system, optionally comprising one or both of the first and second examples, the planetary gear set is disposed between the first motor and the second motor. In a fourth example of the system, optionally including one or more or each of the first through third examples, the first motor is an electric motor and the second motor is an electric motor. In a fifth example of the system, optionally including one or more or each of the first through fourth examples, the instructions cause the controller to deactivate the first motor and close the clutch when the speed of the planet carrier is below a threshold speed.In a sixth example of the system, optionally including one or more or each of the first to fifth examples, only the second motor provides power to the planetary gear set. In a seventh example of the system, optionally including one or more or each of the first to sixth examples, the instructions cause the controller to keep the first motor and the second motor active and to open the clutch when the speed of the planet carrier is greater than a threshold speed. In an eighth example of the system, optionally including one or more or each of the first to seventh examples, the planetary gear set blends the power of the first motor and the second motor and delivers the blended power to a drive axle.

[0048] The disclosure also provides support for a system comprising: an interplanetary system (IPS) disposed between a first electric motor and a second electric motor, wherein a ring gear of the IPS is coupled to a first output shaft of the first electric motor and a sun gear of the IPS is coupled to a second output shaft of the second electric motor, and a clutch configured to couple the ring gear to a housing of the IPS. In a first example of the system, the system further comprises: a planet carrier coupled to the sun gear and the ring gear. In a second example of the system, optionally including the first example, the second output shaft is hollow, and a third output shaft of the IPS extends through and is concentric with the second output shaft. In a third example of the system, optionally including one or both of the first and second examples, the housing is stationary.In a fourth example of the system, optionally including one or more or each of the first to third examples, the system further comprises: a controller configured to determine a total requested power based on the input power of the first electric motor and the second electric motor, and to adjust operation of the first electric motor, the second electric motor, and the clutch in response to a comparison of the total requested power to a threshold power. In a fifth example of the system, optionally including one or more or each of the first to fourth examples, the system further comprises: a third electric motor configured to drive a pump of a hydraulic system coupled to the clutch.

[0049] The disclosure also provides support for an electric powertrain system comprising: a first electric motor including a first output shaft, a second electric motor including a second output shaft, a planetary gear set disposed between the first electric motor and the second electric motor, the planetary gear set including a ring gear coupled to the first output shaft, a sun gear coupled to the second output shaft, and a planet carrier coupled to the ring gear and the sun gear, and a clutch configured to control a coupling between the ring gear and a stationary housing of the planetary gear set. In a first example of the system, the system further comprises: a controller configured to control engagement and disengagement of the clutch in response to a comparison of a speed of the planet carrier to a threshold speed.In a second example of the system, optionally including the first example, the controller is further configured to open the clutch when the speed of the planet carrier is greater than the threshold speed and to close the clutch when the speed of the planet carrier is less than the threshold speed. In a third example of the system, optionally comprising one or both of the first and second examples, the second output shaft is hollow, and wherein a third output shaft is coupled to the planet carrier and extends through the second output shaft toward a drive axle. In a fourth example of the system, optionally including one or more or each of the first through third examples, the clutch is coupled to a hydraulic system pressurized by a pump driven by a third electric motor.

[0050] The following claims particularly highlight certain combinations and subcombinations that are considered novel and non-obvious. These claims may refer to "a" element or "a first" element, or the equivalent thereof. Such claims are to be construed as including the inclusion of one or more such elements, neither requiring nor excluding two or more such elements. Other combinations and subcombinations of the disclosed features, functions, elements, and / or properties may be claimed by amending the present claims or by filing new 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.

Claims

[1] Electric powertrain, comprising: a planetary gear set comprising a ring gear, a sun gear and a planet carrier coupled to the ring gear and the sun gear; a first motor with a first output shaft coupled to the ring gear; a second motor with a second output shaft coupled to the sun gear; and a control unit with instructions stored in its memory which, when executed, cause the control unit to set an operating state of the first motor and to optionally couple the ring gear to a static housing via a clutch based on a speed of the planet carrier. [2] Electric drive train according to claim 1, wherein a third output shaft is coupled to the planet carrier and a gear of a drive shaft. [3] Electric drive train according to claim 2, wherein the third output shaft extends through the second output shaft. [4] Electric drive train according to one of the preceding claims, wherein the planetary gear set is arranged between the first motor and the second motor. [5] Electric drive train according to any of the preceding claims, wherein the first motor is an electric motor and the second motor is an electric motor. [6] Electric drive train according to any of the preceding claims, wherein the instructions cause the control to deactivate the first motor and close the clutch when the speed of the planet carrier is below a threshold speed. [7] Electric drive train according to claim 6, wherein only the second motor supplies power to the planetary gear set. [8] Electric drive train according to any of the preceding claims, wherein the instructions cause the control to keep the first motor and the second motor active and to open the clutch when the speed of the planet carrier is greater than a threshold speed. [9] Electric drive train according to claim 8, wherein the planetary gear set mixes the power of the first motor and the second motor and delivers the mixed power to a drive axle. [10] System, encompassing: an intermediate planetary gear system (IPS) arranged between a first electric motor and a second electric motor, wherein a ring gear of the IPS is coupled to a first output shaft of the first electric motor and a sun gear of the IPS is coupled to a second output shaft of the second electric motor; and a coupling designed to couple the ring gear to a housing of the IPS. [11] System according to claim 10, further comprising a planet carrier coupled to the sun gear and the ring gear. [12] System according to claim 10 or 11, wherein the second output shaft is hollow and a third output shaft of the IPS passes through the second output shaft and is concentric to it. [13] System according to any one of claims 10 to 12, wherein the housing is stationary. [14] System according to one of claims 10 to 13, further comprising a control system, is configured to determine a required total power on the basis of the input power of the first electric motor and the second electric motor and to adjust the operation of the first electric motor, the second electric motor and the coupling in response to a comparison of the required total power with a threshold power. [15] System according to any one of claims 10 to 14, further comprising a third electric motor configured to drive a pump of a hydraulic system connected to the coupling.

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