System and method for controlling motor during clutch shifts in multi-speed electric driveline

Abstract

A system and method (300) for controlling a motor (110) of an electric driveline (105) having a multi-speed transmission (115) having at least a first clutch (130) and a second clutch (135). The system and method (300) includes initiating a transmission shift requiring engagement of a first clutch (130); applying a synchronization torque command (250) to the motor (110) based on an engagement parameter of the first clutch (130) until the shift is completed; and applying a non-shift torque command (250) to the motor (11) after the shift is completed.

Description

Technical Field

[0001] The present disclosure relates generally to systems and methods for controlling a motor of a multi-speed electric powertrain and, more particularly, to systems and methods for generating and applying a synchronizing torque command to a motor during a clutch shift in such a multi-speed electric powertrain. Background Art

[0002] The use of electric drive trains in mobile industrial machinery such as wheel loaders and motor graders has increased, at least in part due to the reduced drive train complexity and relatively large and relatively better control of electric traction motors compared to combustion engines. Therefore, such electric drive trains can provide a relatively simple design with relatively large torque output and relatively good control. However, during shifting of a multi-speed transmission of the electric drive train, the operation and control of the clutch can be challenging due to the large inertia provided by the traction motor of the electric drive train. Although friction clutch elements can be used to absorb some of the high inertia level of the electric motor during shifting, the clutch elements are subject to operating constraints. For example, when attempting to accelerate or slow the traction motor during a shift, the friction clutch elements and their surrounding components may be subject to adversely increased temperatures and wear.

[0003] U.S. Patent No. 8,145,397 (the '397 patent) discusses a hybrid powertrain system having a transmission with four selectively engageable clutches controlled by a hydraulic control circuit. Controlling and managing the output torque of the transmission includes outputting motor torque commands to two electric machines of the hybrid powertrain system to deliver a net output torque to an output member of the transmission that reacts with the driveline and satisfies an operator torque request. To achieve damping of the driveline, the torque offset of the two electric machines may be determined by monitoring the input speed of the transmission and the clutch slip speed of the clutch, and more specifically, may be based on the difference between an input speed error (the difference between the input speed and an input speed curve) and a clutch slip speed error (the difference between the clutch slip speed and a target clutch slip speed). The target clutch slip speed and the clutch slip curve are used during transitions in the operating range state of the transmission to synchronize the clutch slip speed prior to applying an oncoming clutch. Thus, the system of the '397 patent depends on the clutch speed and the slip curve to calculate the motor torque command.

[0004] However, there is a need for improved control of multi-speed transmissions for electric drivetrains, particularly in terms of eliminating high motor inertia levels during shifting. The systems and methods of the present disclosure may address one or more of the problems set forth above and / or other problems in the art. However, the scope of the present disclosure is defined by the appended claims and is not limited by the ability to address any particular problem. Summary of the invention

[0005] In one aspect, a method for controlling a motor of an electric powertrain having a multi-speed transmission having at least a first clutch and a second clutch is provided. The method includes: initiating a transmission shift requiring engagement of the first clutch; applying a synchronizing torque command to the motor based on an engagement parameter of the first clutch until the shift is complete; and applying a non-shifting torque command to the motor after the shift is complete.

[0006] According to another aspect of the present disclosure, a method for controlling a mobile industrial machine having an electric drive train including a traction motor and a multi-speed transmission having at least a first clutch and a second clutch is provided. The method includes: initiating a transmission shift requiring engagement of a first clutch; applying a motor torque command to a maximum available motor torque during partial engagement of the first clutch; and applying a non-shift torque command to the motor after the shift is completed.

[0007] According to another aspect of the present disclosure, a system for controlling a motor of an electric powertrain having a multi-speed transmission is disclosed. The system includes an electric powertrain having a multi-speed transmission, the multi-speed transmission having at least a first clutch and a second clutch. The system also includes a motor and a motor controller. The motor controller is configured to perform operations including: applying a synchronous torque command to the motor based on an engagement parameter of the first clutch during engagement of the first clutch; and applying a non-shift torque command to the motor after a gear shift is completed. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 shows a schematic diagram of a wheel loader as an example of a machine including a multi-speed electric drive train and a motor controller in which systems and methods according to the present disclosure may be used;

[0009] Figure 2 Shows that it can be installed in Figure 1 A schematic diagram of a motor controller in a wheel loader shown in , which motor controller can be used to store instructions for executing the method according to the present disclosure and to execute the method;

[0010] Figure 3 FIG. 1 is a diagram showing a method for controlling a machine (such as Figure 1 A flow chart of a method for a motor of an electric drive train of a wheel loader as shown in FIG.

[0011] Figure 4 It is shown that according to the present disclosure Figure 3 A flowchart of additional steps of the method shown in ; and

[0012] Figure 5 Motor torque command and transmission relative speed graphs are provided to illustrate the method of the present disclosure. DETAILED DESCRIPTION

[0013] Both the foregoing general description and the following detailed description are exemplary and illustrative only and do not limit the claimed features. As used herein, the terms "comprise", "comprising", "having", "including" or other variations thereof are intended to cover non-exclusive inclusions, such that a process, method, article or device that includes a list of elements includes not only those elements, but may also include other elements that are not explicitly listed or inherent to such processes, methods, articles or devices. Unless expressly excluded, the use of the singular to describe a component, structure or operation does not exclude the use of a plurality of such components, structures or operations or their equivalents. The use of the terms "a" and "an" and "said" and "at least one" or the terms "one or more" and similar references in the context of describing the present invention (especially in the context of the following claims) should be interpreted as covering both the singular and the plural, unless otherwise specified herein or clearly contradicted by the context. The use of the term "at least one" followed by a listing of one or more items (e.g., "at least one of A and B" or one or more of A and B) should be interpreted to mean one item selected from the listed items (A or B) or any combination of two or more of the listed items (A and B; A, A and B; A, B and B), unless otherwise indicated herein or clearly contradicted by context. Similarly, as used herein, the word "or" refers to any possible permutation of a group of items. In addition, in the present disclosure, relative terms, such as, for example, "about," "substantially," "substantially," and "approximately" are used to indicate a possible variation of ±10% of the stated value.

[0014] Figure 1A schematic diagram of a mobile industrial machine in the form of a wheel loader 100 in which the systems and methods of the present disclosure may be used is shown. Although a wheel loader 100 is shown, other types of mobile industrial machines, such as a tractor or a motor grader, may also use the systems and methods described herein. The machine 100 may be an all-electric drive machine (driven only by one or more traction motors) or a hybrid electric machine. The machine 100 may include an electric drive train 105 including an electric traction motor 110, a multi-speed transmission 115, a ground engaging element such as a wheel 120, and a drive train control system 200. Although the electric drive train 105 of the machine 100 is shown as having a single electric traction motor 110 and an associated multi-speed transmission 115, it should be understood that more electric motors and multi-speed transmissions may be used, such as one traction motor and transmission for each wheel 120. As will be described in more detail below, the drive train control system 200 may receive various inputs and provide various outputs to the electric drive train to provide power to the machine 100.

[0015] The electric traction motor 110 may be any type of suitable electric motor sized to provide power in the form of torque to the input of the multi-speed transmission 115. The electric motor 110 may be powered by any suitable energy source (not shown), such as one or more on-board batteries, an electrical grid, an on-board engine-driven generator, or a fuel cell. The electric traction motor 110 may have motor capacity limits, including torque and speed limits, defined by a continuous curve, an intermittent curve, and / or a peak curve in one or more lookup tables corresponding to a particular electric motor of the electric powertrain system 105.

[0016] The multi-speed transmission 115 can receive input torque from the motor 110 and provide output torque to one or more wheels 120 of the machine 100. The multi-speed transmission can be, for example, a two-speed transmission with appropriate gearing (not shown) and two hydraulic clutches 130, 135 in a gearbox 140. The hydraulic clutch 130 can be connected to a pressurized fluid, such as a hydraulic system 140 of the machine 100. Although a two-speed transmission will be described herein, it should be understood that a transmission with more speeds, such as a three-speed or four-speed transmission, can be used. Each of the two clutches 130, 135 can be controlled to move between a fully engaged or "on" state, a partially engaged state, and a disengaged or "off" state. In the fully engaged state, the corresponding clutch plates of the clutches 130, 135 are in mating contact, and all torque is transmitted from the electric traction motor 110 through the multi-speed transmission 115. In the disengaged or "off" state, the corresponding clutch plates are spaced apart from each other, and this particular clutch does not transmit torque from the electric traction motor 110 through the multi-speed transmission 115. Each clutch 130, 135 is configured to engage for a specific speed range of the motor 110. In addition, each clutch 130, 135 operates within operating parameters, such as operating temperature limits or operating pressure limits, both of which can be used to prevent overheating and damage or failure of the clutch 130, 135. When a clutch 130, 135 of two or more clutches 130, 135 moves from a fully engaged state to a disengaged state, the clutch 130, 135 is referred to as an offgoing clutch, and when the clutch 130, 135 moves from a disengaged state to an engaged state, the clutch is referred to as an oncoming clutch.

[0017] refer to Figure 1 and 2 , the powertrain control system 200 may include a controller 205 that receives various inputs 210 from the electric powertrain 105 and provides various outputs 215 to the electric powertrain. For example, the controller 205 may receive a desired torque request signal 220 from an operator, such as in the operator station 150. This desired torque request signal 220 may correspond to a motive request from the operator and is also referred to as a non-shift torque request. The controller 205 of the powertrain control system 200 may also receive a transmission input speed signal 230 and a transmission output speed signal 235 that correspond to the speeds of the input shaft and output shaft of the multi-speed transmission 115, respectively. The transmission input speed signal 230 and the transmission output speed signal 235 may be respectively provided by appropriate real or virtual sensors, such as speed sensors 155 and 160 ( Figure 1 )supply.

[0018] The powertrain control system 200 may provide an output from the controller 205 in the form of a motor torque command 250 that controls the torque output from the electric motor 110. As will be discussed in more detail below, the motor torque command 250 may include a non-shifting motor torque command when a gear shift is not required, and may include a synchronous motor torque command during a gear shift. In addition, as known in the art, the controller 205 may provide a clutch control command 255 for controlling one or both clutches 130, 135.

[0019] The controller 205 may include a memory 240 and one or more processors 245. The memory 240 or a secondary storage device associated with the controller 205 may store data and / or software routines that may assist the controller 205 in performing its functions, such as Figure 3 Method 300 and Figure 4 The functions of the method 315 of the embodiment of the present invention are as follows. In addition, the memory or auxiliary storage device associated with the controller 205 can also store data received from various inputs 210 associated with the electric powertrain 105. Many commercially available microprocessors can be configured to perform the functions of the controller 205. It should be understood that the controller 205 can be easily embodied as a general purpose machine controller capable of controlling many other machine functions. Alternatively, a dedicated machine controller can be provided. Various other known circuits, including signal conditioning circuits, communication circuits, hydraulic or other actuation circuits, and other appropriate circuits, can be associated with the controller 205.

[0020] Industrial Applicability

[0021] The disclosed systems and methods are applicable to electric powertrains 105 having a multi-speed transmission 115. In particular, the disclosed systems and methods are applicable to controlling the traction motor 110 of the electric powertrain 105 to assist in shifting the multi-speed transmission 115 to help avoid adversely high temperatures and wear of components of the multi-speed transmission 115.

[0022] During operation of the machine 100, the multi-speed transmission 115 receives shift commands based on a desired power torque request signal 220 from, for example, an operator of the machine 100 in the operator station 150. The shift commands may be determined automatically, as in the case of an automatic transmission, or manually by an operator of the machine 100. The shift commands may include an upshift of the multi-speed transmission 115, or a downshift of the multi-speed transmission 115. As discussed in more detail below, control of the electric traction motor 110 may be based on the shift commands.

[0023] Figure 3is a flow chart showing a method for controlling a motor of an electric drivetrain 105 having a multi-speed transmission 115 having at least a first clutch 130 and a second clutch 135. The method may include a step 305 of applying a standard motor torque (or a non-shift motor torque command) 250 during operation of the multi-speed transmission 120 when the multi-speed transmission 115 is in a particular gear corresponding to when the clutches 130, 135 are fully engaged or disengaged. The method may also include a step 310 of initiating a gear shift. As described above, the initiation of the gear shift may be performed automatically or manually. The method 300 may also include a step 315 of generating a synchronous shift torque command based on the operation or clutch engagement parameters of the multi-speed transmission 115 and applying the synchronous shift torque command to the traction motor 110 until the gear shift is completed. Reference is made below to Figure 4 and 5 The step 315 of generating the synchronization torque command 250 and applying the synchronization torque command to the motor 110 is discussed in more detail. The method 300 may also include a step 320 of applying the standard or non-shift motor torque command 250 to the motor 110 as in step 305 once the shift is complete (corresponding to fully engaging / disengaging the clutches 130, 135). Although the method 300 is described as including steps 305 to 320, the method may include a subset of these steps, such as only steps 305 to 315, only steps 310 and 315, only steps 310 to 320, or other combinations.

[0024] Steps 310 and 315 of method 300 are performed during a shifting process of the multispeed transmission 115 of machine 100 and are therefore integrated with control of clutches and other components of the multispeed transmission 115 and as part of other methods that may be performed by one or more control systems of machine 100 .

[0025] Figure 4 and Figure 5 Additional details are shown for step 315 of generating the synchronizing torque command 250 based on the operating parameters of the multi-speed transmission 115 and applying the synchronizing torque command to the traction motor 110 until the shift is complete. Figure 5 In the exemplary operation depicted in , an upshift is illustrated. It should be understood that a downshift will operate in the same manner, but with the motor torque command 250 having the opposite sign (positive vs. negative). In addition, Figure 5 The example assumes that the non-shift torque command 250 applied to the motor 110 before the shift and the synchronous shift torque command 250 applied to the motor 110 during the shift are of the same sign, both positive values, such as Figure 5 as shown in .

[0026] As described above, before applying the synchronous shift torque command 250 to the motor 110, a standard non-shift torque command is applied to the motor 110 (step 305). The standard non-shift motor torque command 250 is applied to the motor 110 at step 305. Figure 5 Depicted as 510. Return to reference Figure 4 , applying the synchronous shift torque command 250 to the motor 110 may include a step 405 of changing the motor torque command 250 to the maximum available motor torque. Changing the motor torque command 250 to the maximum available motor torque may be applied in a stepwise manner or in a ramped or linear manner, and Figure 5 515. This ramping change to the maximum available motor torque 515 can be characterized as "ramp-on". As described above, the direction of this "ramp-on" (positive or negative) depends on whether the shift is an upshift as shown or a downshift (not shown).

[0027] In step 410, the motor torque command 250 is maintained at the maximum available motor torque ( Figure 5 520 in the figure) until the particular clutch 130, 135 is close to being fully engaged. In one example, the transmission control system 200 can determine when the clutch 130, 135 is close to being fully engaged ( 520 in the figure) by monitoring the transmission input speed 230 and the transmission output speed 235 via the speed sensors 155 and 160, respectively. Figure 1 ). The transmission input speed 230 and the transmission output speed 235 may be used to calculate the clutch relative speed, and when the clutch relative speed approaches zero, the clutch is close to full engagement. Although other values ​​may be used, the controller 205 may be programmed to identify close to full clutch engagement as when the transmission input speed 230 and the transmission output speed 235 differ by only 10% (when considering the ratio). This predetermined "close to" full clutch engagement is Figure 5 It is shown as a vertical line / time 525 in FIG. It should be understood that near full clutch engagement can be identified by other means other than clutch relative speed. In addition, it should be noted that Figure 5 The maximum available motor torque is depicted as a horizontal line 520 in FIG. 5 , but it should be understood that the maximum available torque of the motor 110 may vary depending on system conditions, and thus the line 520 may or may not be a horizontal line.

[0028] Once the controller identifies that the clutch is close to full engagement, the motor torque command is changed toward zero (step 415). Similar to step 405, changing the motor torque command 250 toward zero can be applied in a stepwise or ramped manner and at Figure 5530 in a ramped or linear manner. This ramping change of the motor torque command 250 toward zero can be characterized as a “ramp-off”. This change of the motor torque command 250 toward zero can continue until the clutches 130, 135 are fully engaged, for example, the transmission relative speed is zero ( Figure 5 At time 535 in the figure), a new standard non-shift torque command 250 corresponding to the new gear of the multi-speed transmission 115 is applied to the motor 110. This corresponds to Figure 3 Step 320, and by Figure 5 However, in some "non-typical" shifts, when the motor ramp off is complete (ie, when the ramp off torque command is equal to the appropriate torque command 250 for the new gear ( Figure 5 40), the transmission relative speed may not be zero. In this case, the motor torque command 250 will remain stable at the torque command 540 for the new gear until the full clutch is engaged, i.e., the transmission relative speed is zero. Thereafter, the standard non-shift torque command 250 may vary based on the operator's desired torque or other system conditions. In addition, if the new gear motor torque command (line 450) is negative, the torque command 250 will remain stable at zero until the full clutch is engaged, and then move to the non-shift torque command 250.

[0029] It should be noted that in some cases, the initial standard non-shift torque command ( Figure 5 510) may have an opposite sign to the maximum available torque 520. In such a case, an additional control step is included, which corresponds to adjusting the motor torque command to zero before starting the ramp up to the maximum available torque. Figure 5 5 is shown in dashed line 550. The adjustment of the motor command may be done in a step manner or a ramp manner or in an alternative manner.

[0030] The powertrain control system 200 described herein can help reduce high traction motor inertia loads on the clutches 130, 135 during gear shifts. This can help reduce elevated temperatures and wear on the clutches 130, 135 and associated components of the electric multi-speed transmission. The methods and operations performed by the controller 205 can also help reduce the time to eliminate traction motor inertia when shifting gears. In addition, with the clutch control provided herein, the system and method manages relatively large amounts of electric motor inertia, and therefore can implement clutch control in an electric powertrain 105 having a multi-speed transmission 115, and provide relatively large torque output by the electric motor in machines such as wheel loaders and motor graders.

[0031] It will be apparent to those skilled in the art that various modifications and variations may be made to the disclosed system and method without departing from the scope of the present disclosure. Other embodiments of the system and method will be apparent to those skilled in the art by considering the specification and the accompanying drawings. This specification, and in particular the examples provided herein, are intended to be considered as exemplary only, with the true scope of the present disclosure being indicated by the following claims and their equivalents.

Claims

1. A method (300) for controlling a motor of an electric powertrain (105) having a multi-speed transmission (115), the multi-speed transmission having at least a first clutch (130) and a second clutch (135), the method (300) comprising: initiating a transmission shift requiring engagement of the first clutch (130); applying a synchronizing torque command (250) to a motor (110) based on an engagement parameter of the first clutch (130) until the shift is complete; as well as A non-shift torque command (250) is applied to the motor (110) after the shift is completed.

2. The method (300) of claim 1, wherein applying the synchronizing torque command (250) to the motor (110) comprises changing the motor torque command to a maximum available motor torque during partial engagement of the first clutch (130).

3. The method (300) of claim 2, wherein changing the motor torque command to a maximum available motor torque is accomplished in a linear manner.

4. The method (300) of claim 2, wherein the motor torque command is set to zero before changing the motor torque command to the maximum available motor torque.

5. The method (300) of claim 2, wherein applying the synchronizing torque command (250) to the motor (110) further comprises changing the motor torque command toward zero when the first clutch (130) approaches full engagement.

6. The method (300) of claim 5, wherein changing the motor torque command toward zero begins upon a predetermined portion of engagement of the first clutch (130).

7. The method (300) of claim 6, further comprising steadily maintaining the synchronizing torque command equal to the desired non-shift torque command until the first clutch (130) is fully engaged.

8. The method (300) of claim 1, wherein the electric drive train (105) is used on an all-electric mobile industrial machine (100), and the machine (100) is driven only by the motor (110).

9. The method (300) of claim 1, wherein the first clutch and the second clutch (130, 135) are hydraulic clutches.

10. A method (300) for controlling a mobile industrial machine (100) having an electric drive train (105) including a traction motor (110) and a multi-speed transmission (115) having at least a first clutch (130) and a second clutch (135), the method (300) comprising: initiating a transmission shift requiring engagement of the first clutch (130); applying a motor torque command that achieves a maximum available motor torque during partial engagement of the first clutch (130); as well as A non-shift torque command (250) is applied to the motor (110) after the shift is completed.

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