Control system for DC bus regulation

Abstract

Disclosed is an apparatus including a memory and a processor. The processor can be configured to receive control signals for operating a plurality of traction motors of a work machine. The control signals can include information related to an actual speed of the work machine, a target speed of the work machine, and a generator speed of a generator operably coupled to the traction motors. The processor can be configured to determine corresponding torque commands associated with the traction motors based on the actual speed and the target speed, and determine a generator power limit based on the generator speed. The processor can be configured to determine a threshold based on the corresponding torque commands and the generator power limit, adjust the corresponding torque commands based on the threshold, and operate the traction motors based on the adjusted corresponding torque commands.

Description

Technical Field

[0001] The present invention generally relates to electric drive systems and, for example, to a control system for controlling an electric drive system. Background Art

[0002] In on-highway and off-highway applications, electric drive systems are increasingly used to replace mechanical drive systems. Generally, an electric drive system for a work machine includes an engine, a generator, a direct current (DC) bus, and traction motors. The engine may include an internal combustion engine and / or another power source configured to generate mechanical power for rotating a rotor relative to a stator of the generator. The generator may convert the mechanical power into electrical power that can be supplied via the DC bus to different electrical loads of the work machine. The DC bus may include two or more electrical terminals across which multiple loads may be connected (e.g., electrically in parallel) and receive electrical power. For example, the DC bus may be used to provide appropriate electrical power (e.g., via an inverter, a converter, and / or other circuitry) to a traction motor, an auxiliary device, and / or another load of the work machine. The traction motor may convert the electrical power into mechanical power (e.g., rotational power) suitable for propelling the work machine (e.g., via tracks, wheels, and / or other traction means).

[0003] In some cases, such as in a dual-path or multi-path configuration, a work machine may include multiple traction motors that can be independently operated to drive multiple traction means. For example, a tracked tractor may use two parallel tracks (e.g., a left track and a right track) as traction means that can be operated at different speeds and / or torques in order to steer, turn, and / or otherwise propel the tracked tractor in a particular direction. In such a case, each traction motor may need to be sized, rated, and / or capable of propelling the tracked tractor independently. The combined power required for such traction motors can be significant (e.g., when multiple traction motors of the work machine are operating at full load). However, a single generator may not always be sized and / or rated to adequately support the combined power requirements of multiple traction motors. In such a case, when the power required by the traction motors exceeds the power limit of the generator, the bus voltage of the DC bus may collapse (e.g., decrease at a significant rate) or overvoltage (e.g., increase at a significant rate), causing the work machine to stop and / or causing another adverse effect. While using a larger and / or multiple generators may be a possible solution, such a solution is not always feasible due to cost, size, weight, and / or other constraints.

[0004] An attempt to control power on a multi-motion electric drive system is disclosed in U.S. Patent No. 8,415,909, entitled "Method and Apparatus for Controlling Power on a Multi-Motion Electric Drive System," issued to Ramamurthy et al. on April 22, 2010 (the "'909 Patent"). In particular, the '909 Patent discloses a motor control system for controlling two or more motor sets. The '909 Patent discloses that the motor control system includes a power converter that receives power from a power source and converts the power to an intermediate power, and an intermediate power link coupled to the power converter. The '909 Patent discloses a controller configured to cause at least one motor drive to limit the amount of power delivered to one or more motors based on the amount of power that the power converter is capable of generating. However, the '909 Patent does not disclose a generator or a solution that adequately addresses the power limits of the generator as described above. For example, the '909 Patent does not disclose determining the power limit of the generator or adjusting a torque command for one or more traction motors that operate a work machine based on the power limit of the generator.

[0005] The control system of the present invention overcomes one or more of the above disadvantages. SUMMARY OF THE INVENTION

[0006] According to some implementations, a method may include receiving a control signal for operating a plurality of traction motors of a work machine, the plurality of traction motors being in electrical communication with a generator of the work machine, and the control signal including information related to an actual speed of the work machine, a target speed of the work machine, and a generator speed of the generator; determining corresponding torque commands associated with the plurality of traction motors based on the actual speed and the target speed; determining a total power demand associated with the plurality of traction motors based on the corresponding torque commands and corresponding actual motor speeds; determining a generator power limit based on the generator speed; determining a limit ratio based on the total power demand and the generator power limit; adjusting the corresponding torque commands of the plurality of traction motors based on the limit ratio; and performing an action based on the adjusted corresponding torque commands.

[0007] According to some implementations, a device may include one or more memories; and one or more processors communicatively coupled to the one or more memories, the one or more processors configured to receive control signals for operating a plurality of traction motors of a work machine, the control signals including information related to an actual speed of the work machine, a target speed of the work machine, and a generator speed of a generator operatively coupled to the plurality of traction motors; determine corresponding torque commands associated with the plurality of traction motors based on the actual speed and the target speed; determine a generator power limit based on the generator speed; determine a threshold based on the corresponding torque commands and the generator power limit; adjust the corresponding torque commands based on the threshold; and cause the plurality of traction motors to operate based on the adjusted corresponding torque commands.

[0008] According to some implementations, a work machine may include a first traction motor; a second traction motor; a generator operatively coupled to the first traction motor and the second traction motor; and a controller configured to receive information related to an actual speed of the work machine, a target speed of the work machine, and a generator speed of the generator, determine a first torque command associated with the first traction motor and a second torque command associated with the second traction motor based on the actual speed and the target speed, determine a total power demand based on the first torque command and the second torque command, determine a generator power limit based on the generator speed, determine a threshold based on the total power demand and the generator power limit, adjust the first torque command and the second torque command based on the threshold to obtain an adjusted first torque command and an adjusted second torque command, and perform an action based on the adjusted first torque command and the adjusted second torque command. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 is a diagram of an example work machine as described herein.

[0010] Figure 2 is a diagram of an example control system described herein.

[0011] Figure 3A and Figure 3B is a diagram of an example implementation of the control system described herein.

[0012] Figure 4 is a flowchart of an example process for controlling an electric drive system. DETAILED DESCRIPTION

[0013] Figure 1FIG. is a diagram of an exemplary work machine 100 as described herein. The work machine 100 can include a tractor, a bulldozer, a loader, a truck, a motor grader, an excavator, a paver, and / or another work machine 100 configured to perform tasks related to operations. As Figure 1 shown, the work machine 100 includes a frame 102, a traction element 104, a work implement 106, an operator cab 108, an engine 110, and an electric drive system 112. The traction element 104 can include tracks, wheels, and / or other traction devices that are movably coupled to the frame 102 and driven by the electric drive system 112 to propel the work machine 100. The work implement 106 can include a blade, a ripper, a winch, a bucket, a shear, a hammer, and / or another work tool that is movably coupled to the frame 102 and configured to perform tasks associated with the work machine 100. The operator cab 108 can be coupled to the frame 102 and provide a user interface 114 for an operator of the work machine 100. The user interface 114 can include input devices (e.g., joysticks, levers, buttons, dials, steering wheels, pedals, touch screen devices, etc.) and / or output devices (e.g., gauges, displays, speakers, haptic feedback devices, etc.), the input devices being configured to receive information from the operator for operating the work machine 100 (e.g., target travel speed, target track or wheel speed, target engine speed, steering commands, etc.), the output devices being configured to output information to the operator.

[0014] The engine 110 includes a diesel engine, a gasoline engine, a natural gas engine, and / or another power source configured to generate mechanical power that can be used to start the electric drive system 112. The electric drive system 112 can be configured in a dual-path or multi-path arrangement and be capable of simultaneously and independently operating a plurality of traction motors 120 of the work machine 100. The electric drive system 112 can include a generator 116, a common bus 118, a set of traction motors 120, a controller 122, and a set of sensors 124. The generator 116 can include a rotor that is mechanically coupled to the engine 110 and configured to rotate relative to a stator to induce a current (e.g., alternating current (AC)) via one or more windings of the stator. The common bus 118 can include electrical terminals, connectors, capacitors, inverters, converters, and / or other circuit components configured to convert an AC voltage (e.g., three-phase or poly-phase voltage) from the generator 116 into a bus voltage (e.g., DC voltage) that is transmitted to the traction motors 120, the controller 122, and / or another electrical load of the work machine 100. In some examples, the common bus 118 can convert the bus voltage into different DC voltages and / or AC voltages suitable for operating the connected loads. The traction motors 120 can include motors that are configured to convert electrical power from the common bus 118 into mechanical power to cause movement of the traction element 104.

[0015] The controller 122 includes a processor 126 and a memory 128. The processor 126 is implemented in hardware, firmware, and / or a combination of hardware and software that can be programmed to perform functions associated with the electric drive system 112, the engine 110, and / or the work machine 100. The memory 128 includes random access memory (RAM), read only memory (ROM), and / or another type of dynamic or static storage device that stores information and / or instructions to be executed by the processor 126. The sensors 124 can include a combination of measuring devices, sensing devices, switches, encoders, and / or other devices configured to obtain sensor data (e.g., information related to the operating conditions of the electric drive system 112, the engine 110, and / or the work machine 100). For example, the sensors 124 can be configured to provide information related to the travel speed of the work machine 100, the track or wheel speed, the traction motor speed, the engine speed, the generator speed, the steering angle, the bus voltage, and / or other operating conditions. In some examples, the sensors 124 can include a global positioning system (GPS) device, a global navigation satellite system (GNSS) device, and / or another position sensing device configured to provide the position of the work machine 100. If the work machine 100 includes an implement 106, the sensors 124 can provide information related to the operating conditions of the implement 106.

[0016] As described above, Figure 1 is provided as an example. Other examples may be different from those described in connection with Figure 1 what is described.

[0017] Figure 2 is a diagram of an example control system 200 described herein. As Figure 2As shown, the control system 200 may include a controller 122 that is electrically connected (e.g., via a common bus 118) to a user interface 114, a sensor 124, and a traction motor 120. The controller 122 may include a speed control module 202, a torque control module 204, a limit estimation module 206, and a derating control module 208, which are configured to perform one or more functions associated with operating the electric drive system 112. For example, the controller 122 may be configured to receive a control signal provided by an operator via the user interface 114, determine a total power demand associated with the traction motor 120, determine a power threshold based on the total power demand and a generator power limit, and adjust a corresponding torque command for the traction motor 120 based on the power threshold. In some examples, the controller 122 may be configured with fewer modules, additional modules, and / or a different module arrangement. The controller 122 may be electrically connected to the user interface 114, the sensor 124, and the traction motor 120 via an inverter, a converter, and / or another circuit component of the common bus 118. Additionally or alternatively, the controller 122 may be electrically connected to the engine 110, the generator 116, and / or another electrical load of the common bus 118.

[0018] As Figure 2 As further shown, the speed control module 202 may be configured to receive one or more control signals for operating the traction motor 120 of the work machine 100 via the user interface 114 and / or the sensor 124. For example, the control signals may include a target speed 210 and a steering command 212 (e.g., provided via the user interface 114) and sensor data 214 (e.g., provided via the sensor 124). The target speed 210 may correspond to the travel speed, track speed, wheel speed, and / or engine speed of the work machine 100 requested by the operator. The steering command 212 may correspond to the target direction and / or target steering angle of the work machine 100 requested by the operator. The sensor data 214 may include information related to the travel speed, track speed, wheel speed, traction motor speed, engine speed, generator speed, steering angle, and / or bus voltage of the work machine 100 observed by the sensor 124. In some examples, such as when the sensor 124 is electrically connected to an input device of the user interface 114, the speed control module 202 may obtain and / or derive the target speed 210 and / or the steering command 212 based on the sensor data 214 provided by the sensor 124. In some examples, such as when the user interface 114 includes an output device that provides the sensor data 214 to the operator, the speed control module 202 may obtain the sensor data 214 via the user interface 114.

[0019] In some implementations, the speed control module 202 may be configured to determine a speed command 216 based on a target speed 210, a steering command 212, and / or sensor data 214 (e.g., the actual speed of the work machine 100). For example, the speed control module 202 may determine a first speed command 216-1 for operating a first traction motor 120-1 (e.g., coupled to a traction element 104 on the left side of the work machine 100) and a second speed command 216-2 for operating a second traction motor 120-2 (e.g., coupled to a traction element 104 on the right side of the work machine 100). In the case where the steering command 212 is empty (e.g., the operator does not provide a steering input), the first speed command 216-1 and the second speed command 216-2 may be substantially equal (e.g., to cause the work machine 100 to travel along a straight path). In the case where the steering command 212 is a non-zero value (e.g., the operator provides a steering input), the first speed command 216-1 and the second speed command 216-2 may be different (e.g., proportional between the traction motors 120 in a manner that causes the work machine 100 to turn in the direction requested by the operator). Additionally or alternatively, the speed control module 202 may adjust the speed command 216 (e.g., using a smoothing process, an anti-torsion process, a derating process, and / or a similar process) to improve and / or facilitate the operation of the traction motors 120.

[0020] As Figure 2 further shown, the torque control module 204 may be configured to receive the speed command 216 provided by the speed control module 202 and determine corresponding torque commands 218 for operating the traction motors 120. For example, a first torque command 218-1 may correspond to the amount of torque generated by the first traction motor 120-1 to satisfy the first speed command 216-1, while a second torque command 218-2 may correspond to the amount of torque generated by the second traction motor 120-2 to satisfy the second speed command 216-2. The torque commands 218 may cause the traction motors 120 to achieve the travel speed and / or travel direction requested by the operator of the work machine 100. In some examples, the torque control module 204 may use a proportional integral derivative (PID) controller and / or another controller capable of determining appropriate torque commands 218 that enable the traction motors 120 to satisfy the target speed 210 and / or the steering command 212. In some examples, the torque control module 204 may receive the target speed 210 and / or the steering command 212 from the user interface 114, the sensor data 214 from the sensors 124, and / or a single speed command 216 from the speed control module 202, and proportional torque commands 218 between the traction motors 120 based on the steering command 212.

[0021] As Figure 2As further shown therein, the limit estimation module 206 can be configured to receive sensor data 214 from the sensor 124 and determine a generator power limit 220 based on the sensor data 214. For example, the limit estimation module 206 can determine a generator speed (e.g., the rotational speed of the rotor of the generator 116 relative to the stator) based on the information included in the sensor data 214, and / or derive the generator speed based on the engine speed, the travel speed, and / or other information included in the sensor data 214. In some examples, the limit estimation module 206 can determine the bus voltage of the common bus 118 (e.g., the target bus voltage and / or the actual bus voltage) based on the sensor data 214 and determine the generator torque based on the bus voltage. The limit estimation module 206 can use a PID controller and / or another controller configured to determine the generator torque in a specific situation to determine the generator torque. Based on the generator speed and the generator torque, the limit estimation module 206 can be configured to determine the generator power limit 220 (e.g., the maximum amount of electrical power that the generator 116 can output at the generator speed). In some examples, such as when the user interface 114 includes an output device that provides the sensor data 214 to the operator, the limit estimation module 206 can obtain the sensor data 214 via the user interface 114.

[0022] As Figure 2 As further shown therein, the derating control module 208 can be configured to receive the torque command 218 provided by the torque control module 204, receive the generator power limit 220 provided by the limit estimation module 206, and determine a derated torque command 222 for operating the traction motor 120. The derating control module 208 can determine the corresponding traction motor speed of the traction motor 120 (e.g., based on the sensor data 214 provided by the sensor 124) and determine the corresponding power demand of the traction motor 120 based on the torque command 218 and the corresponding traction motor speed (e.g., by multiplying the torque command 218 by the corresponding traction motor speed). For example, the derating control module 208 can determine a first power demand associated with the first traction motor 120-1 based on the first torque command 218-1 and determine a second power demand associated with the second traction motor 120-2 based on the second torque command 218-2. The derating control module 208 can determine the total power demand based on the corresponding power demands (e.g., based on the aggregation or sum of the corresponding power demands), determine a threshold based on the total power demand and the generator power limit 220, and use the threshold to derate and / or otherwise adjust the torque command 218.

[0023] In some implementations, the derating control module 208 can be configured to define a threshold as a limit ratio (e.g., the ratio between the generator power limit 220 and the total power demand associated with the traction motor 120). Additionally or alternatively, a percentage, fraction, and / or another value defining the relationship between the total power demand and the generator power limit 220 can be used to define the threshold. The derating control module 208 can adjust the torque command 218 by the limit ratio to determine the derated torque command 222. For example, the derating control module 208 can multiply the first torque command 218-1 by the limit ratio to determine the first derated torque command 222-1, and multiply the second torque command 218-2 by the limit ratio to determine the second derated torque command 222-2. The limit ratio can be configured to ensure that the total power demand associated with the traction motor 120 approaches and does not exceed the generator power limit 220. For example, when the total power demand exceeds the generator power limit 220, the limit ratio can correspond to a value less than 1, such that the torque command 218 multiplied by the limit ratio derates the torque command 218. When the total power demand is less than or substantially equal to the generator power limit 220, the limit ratio can saturate to the value 1, such that the torque command 218 multiplied by the limit ratio does not increase or otherwise change the torque command 218.

[0024] In some implementations, the derating control module 208 can be configured to transmit the derated torque command 222 to the corresponding traction motor 120 (e.g., via the common bus 118) and / or otherwise enable the traction motor 120 to operate according to the derated torque command 222. Additionally or alternatively, the derating control module 208 can be configured to compare the total power demand associated with the traction motor 120 with the generator power limit 220 to determine whether the total power demand exceeds the generator power limit 220. If the total power demand exceeds the generator power limit 220, the derating control module 208 can determine the limit ratio and derate the corresponding torque command 218 by the limit ratio. If the total power demand does not exceed the generator power limit 220, the derating control module 208 can pass the torque command 218 to the corresponding traction motor 120 without modification. The derating control module 208 can intermittently, periodically, and / or continuously monitor in real time changes in the total power demand and / or the generator power limit 220 to ensure regulation of the common bus 118 under different operating conditions. Thus, the derating control module 208 can maintain balance on the common bus 118 and prevent collapse or overvoltage of the bus voltage of the common bus 118.

[0025] As described above, Figure 2 is provided as an example. Other examples may be different from those described in connection with Figure 2 which.

[0026] Figure 3A and Figure 3BIt is a diagram of an exemplary implementation 300 of the control system 200 described herein. As Figure 3A shown and denoted by reference numeral 302, the control system 200 can determine the corresponding power demands of the traction motors 120, determine the total power demand based on the aggregation of the corresponding power demands, determine the generator power limit, determine the limit ratio based on the ratio between the generator power limit and the total power demand, and cause an action to be performed in combination with the limit ratio as described above. In a first example 304, the corresponding power demands of the traction motors 120 (e.g., 270 kW) can be balanced (e.g., the operator does not provide a steering input and / or the output load is evenly distributed to each traction motor 120), and the total power demand (e.g., 540 kW) can be within the generator power limit (e.g., 650 kW). Since the total power demand is less than the generator power limit, the limit ratio can saturate to a value of 1, and the control system 200 can not apply derating. In a second example 306, the corresponding power demands of the traction motors 120 (e.g., 270 kW and 320 kW) can be unbalanced (e.g., the operator provides a steering input on one traction motor 120 and / or the output load is greater on one traction motor 120 than the other), and the total power demand (e.g., 590 kW) can be within the generator power limit (e.g., 650 kW). Since the total power demand is less than the generator power limit, the limit ratio can saturate to a value of 1, and the control system 200 can not apply derating.

[0027] As Figure 3A further shown and according to a third example 308, the corresponding power demands of the traction motors 120 (e.g., 540 kW) can be balanced, and the total power demand (e.g., 1080 kW) can exceed the generator power limit (e.g., 650 kW). Since the total power demand is greater than the generator power limit, the limit ratio can be a value less than 1 (e.g., 0.602), and the control system 200 can apply derating. In a fourth example 310, the corresponding power demands of the traction motors 120 (e.g., 540 kW and 270 kW) can be unbalanced, and the total power demand (e.g., 810 kW) can exceed the generator power limit (e.g., 650 kW). Since the total power demand is greater than the generator power limit, the limit ratio can be a value less than 1 (e.g., 0.802), and the control system 200 can apply derating. For illustrative purposes, the generator power limit is shown as a single value (e.g., 650 kW). It should be understood that the generator power limit can vary over time (e.g., based on changes in generator speed, generator torque, engine speed, and / or another operating condition of the work machine 100), and the control system 200 can be configured to update the limit ratio based on changes in the generator power limit.

[0028] As Figure 3BAs shown, and by reference numeral 312, the control system 200 can adjust the respective torque commands of the traction motor 120 based on the limit ratio as described above. In the first example 304, the control system 200 may not apply derating, or use the limit ratio (e.g., 1.000) to provide a derated torque command that is actually not modified (e.g., 600 Nm). In the second example 306, the control system 200 may not apply derating, or use the limit ratio (e.g., 1.000) to provide derated torque commands that are actually not modified (e.g., 600 Nm and 711 Nm). In the third example 308, the control system 200 may apply derating based on the limit ratio (e.g., 0.602) and adjust the torque command (e.g., 1200 Nm) to provide a derated torque command (e.g., 722 Nm). In the fourth example 310, the control system 200 may apply derating based on the limit ratio (e.g., 0.802) and adjust the torque commands (e.g., 1200 Nm and 600 Nm) to provide derated torque commands (e.g., 963 Nm and 481 Nm). In this way, the control system 200 can provide derated torque commands configured to deliver an amount of power to the traction motor 120 that is close to and does not exceed the power limit of the generator 116.

[0029] As described above, provide Figure 3A and Figure 3B as an example. Other examples may be different from those described in connection with Figure 3A and Figure 3B described.

[0030] Figure 4 is a flowchart of an example process 400 for controlling an electric drive system (e.g., the electric drive system 112 of the work machine 100). Figure 4 One or more of the processing blocks of

[0031] such as Figure 4As shown, process 400 may include receiving control signals for operating a plurality of traction motors of a work machine, the plurality of traction motors being electrically connected to a generator of the work machine, and the control signals including information related to the actual speed of the work machine, the target speed of the work machine, and the generator speed of the generator (block 402). For example, as described above, a controller (e.g., using processor 126, memory 128, etc.) may receive control signals for operating a plurality of traction motors of a work machine. The plurality of traction motors may be electrically connected to a generator of the work machine. The control signals may include information related to the actual speed of the work machine, the target speed of the work machine, and the generator speed of the generator.

[0032] As Figure 4 further shown, process 400 may include determining corresponding torque commands associated with the plurality of traction motors based on the actual speed and the target speed (block 404). For example, as described above, a controller (e.g., using processor 126, memory 128, etc.) may determine corresponding torque commands associated with the plurality of traction motors based on the actual speed and the target speed.

[0033] As Figure 4 further shown, process 400 may include determining a total power demand associated with the plurality of traction motors based on the corresponding torque commands (block 406). For example, as described above, a controller (e.g., using processor 126, memory 128, etc.) may determine a total power demand associated with the plurality of traction motors based on the corresponding torque commands.

[0034] As Figure 4 further shown, process 400 may include determining a generator power limit based on the generator speed (block 408). For example, as described above, a controller (e.g., using processor 126, memory 128, etc.) may determine a generator power limit based on the generator speed.

[0035] As Figure 4 further shown, process 400 may include determining a limit ratio based on the total power demand and the generator power limit (block 410). For example, as described above, a controller (e.g., using processor 126, memory 128, etc.) may determine a limit ratio based on the total power demand and the generator power limit.

[0036] As Figure 4 further shown, process 400 may include adjusting the corresponding torque commands of the plurality of traction motors based on the limit ratio (block 412). For example, as described above, a controller (e.g., using processor 126, memory 128, etc.) may adjust the corresponding torque commands of the plurality of traction motors based on the limit ratio.

[0037] As Figure 4As further shown in FIG. 400, process 400 may include causing an action to be performed based on the adjusted respective torque commands (block 414). For example, as described above, a controller (e.g., using processor 126, memory 128, and / or the like) may perform an action based on the adjusted respective torque commands.

[0038] Process 400 may include variations and / or additional implementations that incorporate Figure 4 those described, such as any single implementation or any combination of implementations described elsewhere herein. Although Figure 4 example blocks of process 400 are shown, in some examples, process 400 may include more blocks, fewer blocks, different blocks, or differently arranged blocks than Figure 4 those depicted. Additionally, or alternatively, two or more blocks of process 400 may be performed in parallel.

[0039] Industrial Utility

[0040] In on-highway and off-highway applications, electric drive systems are increasingly being used in place of mechanical drive systems. Generally, an electric drive system for a work machine includes an engine, a generator, a DC bus, and a traction motor. The engine may include an internal combustion engine and / or another power source configured to generate mechanical power for rotating a rotor relative to a stator of the generator. The generator may convert the mechanical power into electrical power that can be supplied via the DC bus to different electrical loads of the work machine. The DC bus may include two or more electrical terminals across which multiple loads may be connected and receive electrical power. For example, the DC bus may be used to supply appropriate electrical power (e.g., via an inverter, a converter, and / or other circuitry) to the traction motor, auxiliary devices, and / or another load of the work machine. The traction motor may convert the electrical power into mechanical power (e.g., rotational power) suitable for propelling the work machine (e.g., via tracks, wheels, and / or other traction devices).

[0041] In some cases, such as in a dual-path or multi-path configuration, a work machine may include multiple traction motors that can be operated independently to drive multiple traction devices. For example, a tracked tractor may use two parallel tracks (e.g., a left track and a right track) as traction devices that can be operated at different speeds and / or torques to steer, turn, and / or otherwise propel the tracked tractor in a particular direction. In such a case, each traction motor may need to be sized, rated, and / or capable of propelling the tracked tractor independently. The combined power required for such traction motors can be significant (e.g., when multiple traction motors of the work machine are operating at full load). However, a single generator may not always be sized and / or rated to adequately support the combined power requirements of multiple traction motors. In such a case, when the combined power required by the traction motors exceeds the power limit of the generator, the bus voltage of the DC bus may collapse or overvoltage, causing the work machine to stop and / or causing another adverse effect. While using a larger and / or multiple generators may be a possible solution, such a solution is not always feasible due to cost, size, weight, and / or other constraints.

[0042] The control system described herein provides a solution for regulating a common bus of an electric drive system that has a single generator and multiple traction motors (e.g., in a dual-path or multi-path configuration). For example, the control system can be configured to determine a total power demand associated with the traction motors in the electric drive system, determine the power limit of the generator, determine a threshold based on the total power demand and the generator power limit, and regulate the corresponding torque commands of the traction motors based on the threshold. In some examples, the control system can use a limit ratio based on the ratio between the generator power limit and the total power demand to define the threshold and derate the corresponding torque commands of the traction motors by the limit ratio. For example, when the total power demand exceeds the generator power limit, the limit ratio can correspond to a value less than 1, while when the total power demand is less than or substantially equal to the generator power limit, the limit ratio saturates to a value of 1. Thereby, the control system can be configured to balance the total power demand relative to the generator power limit during operation of the electric drive system.

[0043] Accordingly, the control system described herein overcomes one or more problems associated with currently available electric drive systems. For example, by determining a limit ratio based on the power limit of the generator and the total power demand of the traction motors, and by derating the corresponding torque commands of the traction motors based on the limit ratio, the control system ensures that the total power demand remains balanced with the generator power limit. Additionally, by adjusting the limit ratio based on changes in the total power demand and / or the generator power limit, the control system is able to effectively regulate and prevent the collapse or overvoltage of the common bus of the electric drive system under varying operating conditions. The control system also enables generators with limited and / or variable capacity to be effectively used in a multi-path configuration, and thereby overcomes the need to implement larger generators to support multiple traction motors. The control system further overcomes the need to implement multiple generators in the electric drive system, and thereby saves computational resources that would otherwise be required to control multiple generators.

Claims

1. An apparatus (122) for controlling a work machine, comprising: one or more memories (128); and one or more processors (126) communicatively coupled to the one or more memories (128) and configured to: receive control signals for operating a plurality of traction motors (120) of the work machine (100), the control signals including information related to an actual speed of the work machine (100), a target speed (210) of the work machine (100), and a generator speed of a generator (116) operably coupled to the plurality of traction motors (120); determine corresponding torque commands (218) associated with the plurality of traction motors (120) based on the actual speed and the target speed (210); determine a generator power limit based on the generator speed; determine a threshold based on the corresponding torque commands (218) and the generator power limit; adjust the corresponding torque commands (218) based on the threshold; and cause the plurality of traction motors (120) to operate based on the adjusted corresponding torque commands (218).

2. The apparatus (122) according to claim 1, wherein the one or more processors (126) are configured, when determining the corresponding torque commands (218), to: determine a steering command (212) based on the control signals; determine corresponding speed commands (216) associated with the plurality of traction motors (120) based on one or more of the actual speed, the target speed (210), or the steering command (212), the corresponding speed commands (216) being proportional among the plurality of traction motors (120) to steer the work machine (100) according to the steering command (212); and determine the corresponding torque commands (218) based on the corresponding speed commands (216).

3. The apparatus (122) according to any one of claims 1-2, wherein the one or more processors (126) are configured, when determining the threshold, to: determine corresponding power demands of the plurality of traction motors (120) based on the corresponding torque commands (218) and corresponding speeds of the plurality of traction motors (120); determine a total power demand based on an aggregation of the corresponding power demands; and determine the threshold as a limit ratio, the limit ratio being determined based on a ratio between the generator power limit and the total power demand.

4. The apparatus (122) according to any one of claims 1-2, wherein the one or more processors (126) are configured, when adjusting the corresponding torque commands (218), to: derate the corresponding torque commands (218) by a limit ratio, the limit ratio being determined based on a ratio between the generator power limit and a total power demand of the plurality of traction motors (120).

5. The apparatus (122) according to any one of claims 1-2, wherein the one or more processors (126) are further configured to: Determine the respective power requirements of the plurality of traction motors (120) based on the respective torque commands (218) and respective speeds of the plurality of traction motors (120); Determine the total power requirement based on the aggregation of the respective power requirements; Compare the total power requirement with the generator power limit; and Derate the respective torque commands (218) by a limit ratio based on determining that the total power requirement exceeds the generator power limit, Determine the limit ratio based on the ratio between the generator power limit and the total power requirement.

6. An operating machine (100), comprising: A first traction motor; A second traction motor; A generator (116) operably coupled to the first traction motor and the second traction motor; and A controller (122) configured to: Receive information related to the actual speed of the operating machine (100), the target speed (210) of the operating machine (100), and the generator speed of the generator (116), Determine a first torque command associated with the first traction motor and a second torque command associated with the second traction motor based on the actual speed and the target speed (210), Determine the total power requirement based on the first torque command and the second torque command, Determine the generator power limit based on the generator speed, Determine a threshold based on the total power requirement and the generator power limit, Adjust the first torque command and the second torque command based on the threshold to obtain an adjusted first torque command and an adjusted second torque command, and Cause an action to be performed based on the adjusted first torque command and the adjusted second torque command.

7. The operating machine (100) according to claim 6, wherein the controller (122) is configured, upon receiving the information, to: Receive the target speed (210) from a user interface (114) of the operating machine (100), and Receive one or more of the actual speed or the generator speed from a set of sensors (124) associated with the operating machine (100).

8. The operating machine (100) according to any one of claims 6-7, wherein the controller (122) is configured, when determining the total power requirement, to: Determine a first power requirement of the first traction motor based on the first torque command and a first speed of the first traction motor, Determine a second power requirement of the second traction motor based on the second torque command and a second speed of the second traction motor, and Determine the total power requirement based on the aggregation of the first power requirement and the second power requirement.

9. The operating machine (100) according to any one of claims 6-7, wherein the controller (122) is configured, when determining the generator power limit, to: Determine the generator power limit based on the generator speed and a generator torque limit.

10. The operating machine (100) according to any one of claims 6-7, wherein the controller (122) is configured, when determining the threshold, to: Determine the threshold as a limit ratio, A limit ratio is determined based on a ratio between a generator power limit and a total power demand, and the limit ratio is configured to saturate to a value of 1.

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