Electric supercharger control for turbocharger

Abstract

New and / or alternative methods of performance control in an engine system having a compressor configured to receive torque from each of a turbine and an electric motor placed in an exhaust output of the engine. A control unit for the electric motor, referred to as an ETurbo controller, is provided with each of a speed control signal and a torque control signal from an engine control unit. The ETurbo controller is configured to operate the electric motor using the torque control signal and the speed control signal without causing the compressor to exceed a speed boundary.

Description

Technical Field

[0001] This invention generally relates to controllers and configurations for such controllers. Background Technology

[0002] A turbocharger is used to improve engine performance by compressing the intake air supplied to the engine using power derived from the engine's exhaust flow. The basic design includes a turbine positioned in line with the exhaust flow. The turbine rotates as the exhaust flows and transmits torque via the turbocharger shaft to a compressor, which compresses the intake air fed to the engine. This basic design limits responsiveness because the energy available to the turbine is the waste heat of the engine fuel, but the engine's ability to burn fuel is limited by the amount of intake air compressed, which itself is limited by the energy available to the compressor from the turbine.

[0003] When required or needed, an electric motor can be used to enhance responsiveness (and / or other characteristics) by applying torque to the turbocharger shaft. As used herein, ETurbo refers to a system in which the turbocharger shaft is operatively connected to an electric motor configured to provide torque to it. Under certain conditions (e.g., relatively high engine speeds), the electric motor does not need to apply additional torque to obtain the desired boost, while under other conditions (e.g., relatively low engine speeds), the electric motor amplifies the torque generated by the turbine to obtain the desired boost from the compressor. In some ETurbo configurations, the electric motor can also function as a generator, drawing torque from the turbocharger shaft to generate current, for example, to charge a rechargeable battery.

[0004] Many engine control systems are managed by electronic control units (ECUs), which can rely on various control strategies. Methods used can include proportional-integral-derivative (PID) control, model predictive control (MPC), linear quadratic regulators (LQR), and others. One approach to turbocharger control is to evaluate the torque balance on the turbocharger shaft. The sum of torques (output via the compressor, received via the turbine, lost due to friction, and increased or decreased by Eturbo) acts on the inertia of the combined compressor, turbine, and turbocharger shaft assembly, causing variations in the turbocharger shaft speed. System information can be processed, and the torque balance can be used to understand the impact of various actions on the turbocharger shaft speed.

[0005] The compressor has an upper limit on its speed. Operating at or above this limit can damage and / or accelerate the aging of the compressor or other components of the turbocharger. In some model-based engine control strategies, an ETurbo control approach typically provides a setpoint (such as a torque setpoint) for ETurbo operation. ETurbo has its own independent controller that translates the torque setpoint into a controllable metric, such as the current applied to the motor coupled to the turbocharger shaft. Meanwhile, the original equipment manufacturer's (OEM) engine control strategy monitors the compressor speed directly or indirectly in a separate ECU. When the compressor speed approaches its upper limit, the ECU can communicate with the ETurbo controller to lower the used torque setpoint or interrupt ETurbo operation. The separate ETurbo controller and ECU introduce delays to the control system, creating a risk of compressor overspeed. The separate controller also introduces the possibility that communication link failures, ECU malfunctions controlling the torque setpoint, or any errors or faults affecting the inputs used by the ECU to generate the setpoint or monitor the compressor speed can lead to overspeed events. New and alternative methods and systems are needed for controlling ETurbo operation to provide safe, fault-tolerant solutions that are easily compatible with model-based engine control. Summary of the Invention

[0006] The inventors have recognized that the problem to be solved is the need to control ETurbo in different ways at different points in the operating timeline of the turbocharger system.

[0007] The first illustrative non-limiting example takes the form of a system comprising: an engine having an air inlet and an exhaust outlet; a turbocharger having a compressor coupled to the air inlet, a turbine coupled to the exhaust outlet, and an electric motor, wherein the compressor is configured to selectively receive force from either or both of the turbine and the electric motor, the electric motor having an ETurbo controller; an engine control unit (ECU) for controlling the operation of the internal combustion engine and the turbocharger; wherein: the ECU is configured to determine a torque control signal and a speed control signal and provide the torque control signal and the speed control signal to the ETurbo controller to enable the ETurbo controller to manage the operation of the electric motor; and the ETurbo controller is configured to use the torque control signal to manage the operation of the electric motor without allowing the compressor speed to exceed a maximum speed determined by the speed control signal.

[0008] Alternatively, the system can be configured such that the speed control signal is a speed boundary, and the ETurbo controller is configured to operate as follows: if the compressor speed is below the speed boundary, use the force setpoint to control the operation of the motor; and if the compressor speed is at the speed boundary, limit the output force provided by the motor to prevent the compressor speed from exceeding the speed boundary.

[0009] Alternatively, the system can be configured such that the ECU determines the speed control signal by determining the target boost level based on the engine speed and calculating the desired compressor speed at which the target boost level is expected to be provided. Alternatively, the system can be configured such that the ECU is configured to determine the speed control signal to indicate speeds above the desired compressor speed and below the absolute maximum compressor speed. Alternatively, the system can be configured such that the ECU is configured to determine the speed control signal to indicate speeds at the desired compressor speed and below the absolute maximum compressor speed.

[0010] Alternatively, the system can be configured such that the ECU determines the speed control signal to a level equal to the absolute maximum speed of the compressor. Alternatively, the system can be configured such that the speed control signal is a speed setpoint. Alternatively, the system can be configured such that the speed control signal includes an upper speed boundary and a lower speed boundary. Alternatively, the system can be configured such that the speed control signal includes each of the speed setpoint, the upper speed boundary, and the lower speed boundary.

[0011] Alternatively, the ETurbo controller is configured to operate as follows: in a first mode, using a torque setpoint to control motor operation while limiting the compressor speed below the upper speed limit indicated by the speed control signal; and in a second mode, using a speed setpoint indicated by the speed control signal to control motor operation; by: selecting the first mode during an operation period in which communication with the ECU is operable; and selecting the second mode during an operation period in which communication with the ECU is inoperable.

[0012] Alternatively, the system can be configured such that the ETurbo controller stores the maximum safe operating speed limit and is configured to limit the compressor's maximum speed below the maximum safe operating speed limit, regardless of the control signals received from the ECU.

[0013] Another illustrative, non-limiting example takes the form of a system comprising: an engine having an air inlet and an exhaust outlet; a turbocharger having a compressor coupled to the air inlet, a turbine coupled to the exhaust outlet, and an electric motor, wherein the compressor is configured to selectively receive torque from either or both of the turbine and the electric motor, and the electric motor has an ETurbo controller; an engine control unit (ECU) for controlling the operation of the internal combustion engine and the turbocharger; wherein: the ECU is configured to determine a torque control signal, a speed control signal, and a speed boundary and provide the torque control signal, the speed control signal, and the speed boundary to the ETurbo controller to enable the ETurbo controller to manage the operation of the electric motor; and the ETurbo controller is configured to manage the operation of the electric motor using the torque control signal while not allowing the compressor speed to exceed the speed boundary.

[0014] Alternatively, the ETurbo controller is configured to operate as follows: in a first mode, using a torque control signal to control the operation of the electric motor while limiting the compressor speed below a speed boundary; and in a second mode, using a speed control signal to control the operation of the electric motor; by: selecting the first mode during an operating period when communication with the ECU is operational; and selecting the second mode during an operating period when communication with the ECU is inoperable.

[0015] Alternatively, the system can be configured such that the ECU determines the speed boundary by determining the target boost level based on the engine speed and calculating the desired compressor speed expected to provide the target boost level. Alternatively, the system can be configured such that the ECU determines the speed boundary as a level equal to the compressor's maximum speed. Alternatively, the system can be configured such that the torque control signal indicates the desired torque output from the electric motor. Alternatively, the system can be configured such that the ECU determines the speed control signal by determining the target boost level based on the engine speed and calculating the desired compressor speed expected to provide the target boost level.

[0016] Another illustrative, non-limiting example takes the form of a supercharger system for supplying compressed air to an engine having an air inlet and an exhaust outlet, the system comprising: a compressor having an air inlet for receiving air and an output for sending compressed air to the air inlet of the engine; a turbine having an air inlet for receiving air from the exhaust outlet of the engine to generate torque, the turbine being connected to the compressor to provide the generated torque to the compressor; an electric motor coupled to the compressor and configured to apply force to the compressor to add to the torque provided by the turbine; and an ETurbo controller coupled to the electric motor to control its operation, the ETurbo controller being configured to receive at least a torque control signal and a speed control signal from an engine control unit (ECU), and to use the torque control signal to manage the operation of the electric motor without allowing the compressor speed to exceed a speed boundary determined by the speed control signal.

[0017] Alternatively, the booster system can be configured such that the speed control signal is a speed boundary, and the ETurbo controller is configured to operate such that if the compressor speed is below the speed boundary, the force control signal is used to control the operation of the motor; and if the compressor speed is at the speed boundary, the output force provided by the motor is limited to prevent the compressor speed from exceeding the speed boundary.

[0018] Alternatively, the ETurbo controller is configured to operate as follows: in a first mode, using a force control signal to control the operation of the electric motor while limiting the compressor speed below the upper limit of the compressor speed; in a second mode, using a speed control signal to control the operation of the electric motor; determining whether communication with the ECU is operable; and: selecting the first mode during an operation period when communication with the ECU is operable; or selecting the second mode during an operation period when communication with the ECU is not operable.

[0019] Another illustrative, non-limiting example takes the form of a system comprising: an engine having an air inlet and an exhaust outlet; a turbocharger having a compressor coupled to the air inlet, a turbine coupled to the exhaust outlet, and an electric motor, wherein the compressor is configured to selectively receive force from either or both of the turbine and the electric motor, and the electric motor has an ETurbo controller; an engine control unit (ECU) for controlling the operation of the internal combustion engine and the turbocharger; wherein: the ECU is configured to determine a power control signal and a speed control signal and provide the power control signal and the speed control signal to the ETurbo controller to enable the ETurbo controller to manage the operation of the electric motor; and the ETurbo controller is configured to use the power control signal to manage the operation of the electric motor without allowing the compressor speed to exceed a maximum speed determined by the speed control signal.

[0020] As an addition to or alternative to the above-described system and turbocharged system examples, the ECU can be configured to perform model predictive control calculations to determine the force control signal or power control signal. As an addition to or alternative to the above-described system and turbocharged system examples, the ECU can be configured to perform proportional-integral-derivative analysis to determine the force control signal or power control signal.

[0021] As an addition to or alternative to the above-described system and turbocharging system examples, the engine can be an internal combustion engine. As an addition to or alternative to the above-described system and turbocharging system examples, the ETurbo controller can be configured to implement a lower speed limit.

[0022] The illustrative, non-limiting method example takes the form of an operating system method, the system comprising each of the following: an engine having an air input and an exhaust output; a turbocharger having a compressor coupled to the air input, a turbine coupled to the exhaust output, and an electric motor, wherein the compressor is configured to selectively receive force from either or both of the turbine and the electric motor, the electric motor having an ETurbo controller; an engine control unit (ECU) for controlling the operation of the internal combustion engine and the turbocharger; the method comprising the ECU determining a torque control signal and a speed control signal and providing them to the ETurbo controller to enable the ETurbo controller to manage the operation of the electric motor; and the ETurbo controller using the torque control signal to manage the operation of the electric motor without allowing the compressor speed to exceed a maximum speed determined by the speed control signal.

[0023] Alternatively, the speed control signal is a speed boundary, and the method further includes ETurbo using a force setpoint to control the operation of the motor if the compressor speed is below the speed boundary; and ETurbo limiting the output force provided by the motor to prevent the compressor speed from exceeding the speed boundary if the compressor speed is at the speed boundary.

[0024] Alternatively, the ECU determines the speed control signal by determining the target boost level based on the engine speed and calculating the expected compressor speed that is expected to provide the target boost level.

[0025] Alternatively, the ECU determines a speed control signal to indicate a speed higher than the desired compressor speed but lower than the absolute maximum compressor speed. Alternatively, the ECU determines a speed control signal to indicate a speed at the desired compressor speed but lower than the absolute maximum compressor speed. Alternatively, the ECU determines a speed control signal at a level equal to the absolute maximum speed of the compressor.

[0026] Alternatively, the speed control signal may be a speed setpoint. Alternatively, the speed control signal may include an upper speed boundary and a lower speed boundary. Alternatively, the speed control signal may include each of the speed setpoint, the upper speed boundary, and the lower speed boundary.

[0027] Alternatively, the method includes the ETurbo controller operating as follows: in a first mode, using torque setpoint operation to control motor operation while limiting the compressor speed below a speed upper boundary indicated by a speed control signal; in a second mode, using speed setpoint operation indicated by a speed control signal to control motor operation; by: selecting the first mode during an operating period in which communication with the ECU is operable; and selecting the second mode during an operating period in which communication with the ECU is inoperable. Alternatively, the ETurbo controller stores a maximum safe operating speed limit and is configured to limit the compressor's maximum speed below the maximum safe operating speed limit, regardless of the control signals received from the ECU.

[0028] Another illustrative, non-limiting example employs an operating system approach, the system comprising: an engine having an air input and an exhaust output; a turbocharger having a compressor coupled to the air input, a turbine coupled to the exhaust output, and an electric motor, wherein the compressor is configured to selectively receive torque from either or both of the turbine and the electric motor, the electric motor having an ETurbo controller; and an engine control unit (ECU) for controlling the operation of the internal combustion engine and the turbocharger; the method comprising the ECU determining a torque control signal, a speed control signal, and speed boundaries and providing them to the ETurbo controller to enable the ETurbo controller to manage the operation of the electric motor; and the ETurbo controller using the torque control signal to manage the operation of the electric motor while not allowing the compressor speed to exceed the speed boundaries.

[0029] Alternatively, the method may include the ETurbo controller operating as follows: in a first mode, using a torque control signal to control the operation of the electric motor while limiting the compressor speed below a speed boundary; and in a second mode, using a speed control signal to control the operation of the electric motor; by: selecting the first mode during an operation period in which communication with the ECU is operable; and selecting the second mode during an operation period in which communication with the ECU is inoperable.

[0030] Alternatively, the ECU determines the speed boundary by determining the target boost level based on engine speed and calculating the desired compressor speed expected to provide the target boost level. Alternatively, the ECU defines the speed boundary as a level equal to the compressor's maximum speed. Alternatively, the torque control signal indicates the desired torque output from the electric motor. Alternatively, the ECU determines the speed control signal by determining the target boost level based on engine speed and calculating the desired compressor speed expected to provide the target boost level.

[0031] Another illustrative, non-limiting example takes the form of a supercharger system for supplying compressed air to an engine having an air input and an exhaust output, the system comprising: a compressor having an air input for receiving air and an output for sending compressed air to the air input of the engine; a turbine having an air input for receiving air from the exhaust output of the engine to generate torque, the turbine being connected to the compressor to provide the generated torque to the compressor; an electric motor coupled to the compressor and configured to apply force to the compressor to add to the torque provided by the turbine; and an ETurbo controller coupled to the electric motor to control its operation, the method comprising the ETurbo controller receiving at least a torque control signal and a speed control signal from an engine control unit (ECU), and the ECU using the torque control signal to manage the operation of the electric motor without allowing the compressor speed to exceed a speed boundary determined by the speed control signal.

[0032] Alternatively, the speed control signal is a speed boundary, and the method includes: if the compressor speed is below the speed boundary, ETurbo uses a force control signal to control the operation of the motor; and if the compressor speed is at the speed boundary, ETurbo limits the output force provided by the motor to prevent the compressor speed from exceeding the speed boundary. Alternatively, ETurbo can further determine whether the compressor speed is below or at the speed boundary.

[0033] Alternatively, the method may include the ETurbo controller determining whether communication with the ECU is operable, and if so, selecting a first operating mode, or if not, selecting a second operating mode, wherein in the first mode, the ETurbo controller uses a force control signal to control the operation of the electric motor while limiting the compressor speed below an upper limit of the compressor speed; and in the second mode, the ETurbo controller uses a speed control signal to control the operation of the electric motor.

[0034] Another illustrative, non-limiting example employs an operating system approach, the system comprising: an engine having an air input and an exhaust output; a turbocharger having a compressor coupled to the air input, a turbine coupled to the exhaust output, and an electric motor, wherein the compressor is configured to selectively receive force from either or both of the turbine and the electric motor, the electric motor having an ETurbo controller; an engine control unit (ECU) for controlling the operation of the internal combustion engine and the turbocharger; wherein the method includes the ECU determining a power control signal and a speed control signal and providing the power control signal and the speed control signal to the ETurbo controller to enable the ETurbo controller to manage the operation of the electric motor; and the ETurbo controller using the power control signal to manage the operation of the electric motor without allowing the compressor speed to exceed a maximum speed determined by the speed control signal.

[0035] As an addition or alternative to these method examples, the method may include the ECU performing model predictive control calculations to determine a force control signal or a power control signal. As an addition or alternative to these method examples, the method may include the ECU performing proportional-integral-derivative analysis to determine a force control signal or a power control signal. As an addition or alternative to these method examples, the engine may be an internal combustion engine. As an addition or alternative to these method examples, the method may also include the ECU implementing the ETurbo controller, which could also implement a lower speed limit.

[0036] This overview is intended to introduce the subject matter of this patent application. It is not intended to provide an exclusive or exhaustive explanation of the invention. A detailed description is included to provide further information regarding this patent application. Attached Figure Description

[0037] In the accompanying drawings, which are not necessarily drawn to scale, similar numbers may describe similar parts in different views. Similar numbers with different letter suffixes may represent different examples of similar components. The accompanying drawings illustrate, by way of example and not limitation, the various embodiments discussed in this document.

[0038] Figure 1 A model of the operation control system is shown;

[0039] Figure 2 A diagram of the compressor is shown;

[0040] Figure 3 The ETurbo system and engine are schematically shown; and

[0041] Figure 4-7 This is a block flowchart illustrating the control method. Detailed Implementation

[0042] Figure 1A general control architecture is shown, which will be described relative to the engine and / or vehicle. The control device, shown as 100, includes a state observer 102 that feeds a set of current state variables x(k) to an optimizer 104. The optimizer calculates solutions that can be applied to a set of process parameters 112, which in turn control the operation of the physical device 114. This set of actuators can be used to control, for example, but not limited to, fuel or other injectors, variable nozzle turbine positions, throttle valves, engine brakes, aftertreatment (including exhaust), exhaust gas recirculation (EGR), turbochargers, wastegate valve (WG) actuator positions (strokes), recirculation valve actuator positions, variable compressor geometry actuator positions; and / or other valves, actuators, etc., and combinations thereof. Some examples may include more than one control unit for separate subsystems, such as controlling the ETurbo motor via a separate controller for the ETurbo subsystem; in the illustrative example, the optimizer 104 provides control signals to the ETurbo controller independently of other actuators.

[0043] Physical device 114 may be, for example, but not limited to, an internal combustion engine, whether a diesel engine or a gasoline engine, or its subsystems, such as a turbocharger, system air passages as a whole, catalysts, etc.

[0044] Multiple sensors 116 are provided. Throughout the system, sensors 116 may include, for example, but not limited to, sensors that detect manifold absolute pressure (MAP), mass air flow (MAF), EGR flow, turbine speed, exhaust contaminants, engine speed, fuel quantity, boost pressure, etc. Additional monitored parameters may include, for example, wastegate (WG) normalized opening, recirculation valve (RCV) normalized opening, and / or variable geometry compressor configuration. For example, such sensors may be configured to sample the sensed baseline parameters and provide the results of such sampling to a state observer 102. The state observer 102 may record the baseline sensed parameters and actuator position over time to provide a system operating history. In the presence of a separate ETurbo controller, the monitored parameters may also include any parameters reported by the ETurbo controller, such as, for example, torque or current consumption metrics and / or shaft speed.

[0045] In a particular implementation, the output of sensor 116 can be captured in state observer 102 and analyzed based on one or more models of engine behavior. For example, an airflow model can be used to calculate various pressures and temperatures throughout the airflow system without having to measure them at every location within it. By doing so, the number of sensors required can be limited, and the provided sensors can be positioned in standardized locations that provide robust operation. Thus, for example, boost pressure (the pressure downstream of the compressor in a turbocharger system) can be determined using other sensing parameters and an airflow model instead of by direct sensing. The calculated boost pressure can then be used to calculate a control solution in a model-based controller.

[0046] State observer 102 and optimizer 104 can be implemented, for example, in a microcontroller configured to operate on a stored set of instructions to perform state observation and optimization routines. In another example, an application-specific integrated circuit (ASIC) can provide state observer functionality, which may include capturing or accumulating data from actuator 112 and / or sensor 116, which can then be periodically read by a microcontroller configured with a stored instruction set for performing control and / or optimization calculations using, for example, model predictive control (MPC) cost functions, linear quadratic regulator (LQR) control, proportional-integral-derivative (PID) control, or other control algorithms. Optimizer 104 can be integrated into or provided separately from an on-board diagnostic system (not shown) used to record diagnostic variables and present them to a user or store them for later analysis as needed, or, if necessary, both can be additionally integrated into the overall vehicle processing unit.

[0047] The output of the analysis is used to control actuator 112 to operate the device in a manner that minimizes the distance between the operating parameters and one or more target output values ​​of the controllable output or physical device operating characteristics. For example, the target could be any of a target boost pressure, a target pressure differential across the compressor, a target air mass flow rate, or a combination thereof. For example, using the MPC function, the distance to a target or reference value for one or more output values ​​(or the resulting operating characteristics) is minimized, thereby optimizing performance. As an example, a conventional MPC cost function can be represented as shown in Equation 1:

[0048] [Equation 1]

[0049] Where u d,k The desired curve corresponding to the manipulated variable, u k Let represent the manipulated variable, k represent the discrete-time instance, and P represent the prediction range of the predictive controller. In this example, y r,k and y kThese represent the output reference value and the measured value, respectively, and W1 and W2 specify the weighting terms. For simplicity, the k-term can be omitted in the subsequent equations in this paper. The traditional MPC cost function is minimized during operation to provide optimal control to the physical device. This process can be performed by optimizer 104.

[0050] In another example, a PID controller can be used to describe the proportional, integral, and derivative differences from the target operating point. The proportional difference indicates the current state, the integral difference identifies process changes over time, and the derivative difference indicates the direction of these changes. Using PID control, the proportional difference is minimized during monitoring to ensure that the integral and derivative differences do not indicate changing performance that might lead to an increase in the proportional difference after further iterations. For a PID controller, the control parameters output to actuator 112 are adjusted to reduce or minimize the distance between the actual performance and one or more targets based on iterations. For example, optimizer 104 could use PID control instead of MPC. Alternatively, LQR control, applying a similar concept, could be used if desired.

[0051] Figure 2 An illustrative and simplified compressor diagram is shown. The compressor diagram uses the corrected air mass flow rate as the X-axis and the compressor pressure ratio as the Y-axis. Several turbocharger speed lines 150 cross the diagram and are associated with different compressor speeds. Boundary conditions are included, with a surge line 152 on the left side of the diagram and a choke line 154 on the right side. The surge line 152 indicates the maximum pressure the turbocharger can generate at a given mass flow rate. The choke line 154 indicates the maximum mass flow rate at a given pressure ratio. Avoid operation outside these boundaries (i.e., surge line 152, choke line 154) to prevent degraded (and / or unpredictable) operation and potential damage to components. Region 164 is... Figure 2 Highlighted in section 164. Within region 164, surge line 152 is inclined such that when operating near surge line 152, the turbocharger, with its increasing speed, can cross surge line 152, treating (at least temporarily) other variables as constant. Therefore, when operating in region 164, configuring a control system to prevent surge due to variations in turbocharger speed may be useful.

[0052] A turbocharger's efficiency reflects its ability to compress air without adding excessive heat. For a given boost pressure, higher efficiency results in lower outlet temperatures (though still above ambient). Efficiency islands are shown graphically as 160 and 162, each defining a combination of factors that contribute to increased efficiency. For example, operating within efficiency island 160 might be associated with 65% or higher efficiency, while operating within efficiency island 162 might be associated with 75% or higher efficiency. Figure 2The compressor diagram in the image is simplified; a real compressor diagram could include more lines to provide greater granularity.

[0053] For a given turbocharger installation, tests can be performed on a test bench to establish a compressor diagram, and then data representing the compressor diagram can be loaded into the ECU, whether as a lookup table, a set of equations, or in any other suitable manner. The ECU can include programmable parameters (which can be modified without reloading the software) and non-programmable parameters (which are fixed unless the entire software is upgraded). In some installations, the compressor diagram or other calibration-related parameters are treated as programmable parameters; for example, they can be modified on the test bench without reloading the entire software / control package.

[0054] Then, using compressor diagrams and other system characteristics, along with user preferences or inputs (at least in some examples), the factors used in control are derived, such as values ​​used in MPC, PID, and / or LQR. In use, the system is subject to several competing objectives, such as maximizing efficiency at a given turbine speed and air mass flow rate, and a target boost pressure.

[0055] As used herein, ETurbo refers to a system having an electric motor operable to provide torque to the turbocharger shaft. ETurbo can improve the responsiveness, efficiency, or other characteristics of a system and optimize engine performance when conventional turbocharger operation (which relies on exhaust flow for power and / or torque) cannot adequately compress the air entering the engine to achieve the desired boost. For example, at low engine speeds, exhaust flow is relatively low and may not generate sufficient pressure to drive the turbine to effectively rotate the compressor. By using an electric motor to enhance compressor operation, ETurbo provides additional control, efficiency, and responsiveness. Some examples of ETurbo design and uses are shown in US Patent Publication No. 2009 / 0000298 and US Patents 6,637,205 and 6,705,084, the disclosures of which are incorporated herein by reference.

[0056] As used herein, ETurbo differs from a system having a first compressor driven solely by a turbine in the exhaust stream and a second compressor driven solely by an electric motor. In an ETurbo system, the turbocharger shaft is configured to receive torque from both the turbine in the exhaust stream and the electric motor. In some examples, a second compressor may be used in addition to ETurbo, such as a compressor directly driven by the engine's powertrain or driven by a separate electric motor; ETurbo specifically refers to having more than one drive torque source for a single compressor.

[0057] Figure 3 The ETurbo system and engine are schematically illustrated. The system is in... Figure 3 The image is shown at 200, with an engine 210, which is shown having one or more cylinders 212. The engine 210 can be, for example, but not limited to, an internal combustion engine (e.g., diesel, gasoline, propane, natural gas, or any other suitable fuel). The engine 210 receives filtered intake air at 214 and generates an output exhaust 216.

[0058] The control and optimization system of engine 210 includes several components shown; additional components (such as throttle valves and fuel supply) are omitted to focus on the airflow into and out of engine 210. An ETurbo 220 is provided, which includes a compressor 222 coupled to the incoming airflow after an air filter 214, and a turbine 224 in the exhaust flow from engine 210. Basic turbocharger operation causes the turbine 224 to rotate using the air pressure in the exhaust flow and to provide torque to the compressor 222 to compress the incoming air, which improves the efficiency and / or other performance characteristics of engine 210.

[0059] The ETurbo also includes a motor 226, which is coupled to a drive shaft between the turbine 224 and the compressor 222. The motor 226 provides additional torque on the compressor's drive shaft to enhance its operation using energy stored in the battery 230. In some examples, the motor 226 may also be used to slow the drive shaft, thereby recovering energy that can be transferred back to the battery 230; this may be referred to as generator mode. The battery 230 may be a dedicated rechargeable battery for the ETurbo, or it may be used for other electrical applications as needed. The turbocharger 232 may also, or alternatively, use, for example, but not limited to, energy recovered from the exhaust stream, or energy captured from the engine 210 during engine operation, to provide current to the battery 230 to charge it. The motor 226 is coupled to the ETurbo controller 228, which may, for example, but not limited to, a microcontroller, ASIC, or microprocessor.

[0060] The ETurbo controller 228 is connected to the ECU 250 for control purposes. This connection can take any suitable form (e.g., wireless, optical, or wired). In some implementations, communication coupling between the ETurbo controller 228 and the ECU 250 will be provided via a Controller Area Network (CAN) bus, although this is not mandatory. Alternatively, a dedicated connection can be provided between the ETurbo controller 228 and the ECU 250. Communication may include commands, acknowledgments, data, etc., as appropriate for the system.

[0061] Additional components may be provided, including, but not limited to, a wastegate (WG) 242, which allows exhaust flow to bypass turbine 224 under the control of the ECU. A recirculation valve (RCV) 240 may also be provided, allowing the output of compressor 222 to be fed back to its input under certain conditions, such as preventing compressor surge. An exhaust valve (not shown) may be used instead of or in addition to the RCV. A boost air cooler (CAC) 244 may be provided to cool the output from compressor 222 before it enters engine 210; this process can be used to improve engine efficiency.

[0062] In operation, the typical control strategy of ECU 250 is to determine the target boost pressure generated by compressor 222. Various actuators, including WG 242, can be used to control how much force is supplied from the exhaust flow to turbine 224, thereby controlling the torque supplied to compressor 222. At lower engine speeds, ETurbo can be used to apply increased torque from motor 226 to the drive shaft of compressor 222 to increase the rotational speed of compressor 222, increase the provided boost pressure, and optimize the performance of engine 210. At higher engine speeds, turbine 224 can be sufficiently driven by the exhaust flow to rotate compressor 222 fast enough to achieve the target boost pressure without requiring increased torque from motor 226. At even higher speeds, WG 242 can be activated to prevent compressor 222 (or turbine 224) from rotating faster than possibly desired. RCV 240 and WG 242 can be controlled to avoid unnecessarily changing turbocharger speeds, which can lead to low cycle fatigue.

[0063] When excess power is available from the exhaust gas flow, the ETurbo can be used as a generator, for example, to charge the battery powering the ETurbo when needed. However, when using the ETurbo as a generator to draw power from the system, the torque available to rotate the compressor is reduced. For some examples, the inventors have found that, under edge conditions, the ETurbo generator mode can generate a negative feedback loop, where the power drawn by the ETurbo causes a drop in boost pressure, which in turn reduces exhaust flow and further reduces torque on the turbocharger shaft. Therefore, a minimum speed limit associated with using the ETurbo as a generator may be useful.

[0064] Typically, OEMs supply engine systems, while specialized manufacturers supply ETurbo. OEMs can perform various calibration setup operations at the engine test bench and write the calibration settings into the ECU 250, such as modifying programmable parameters stored thereon. However, OEMs have less readily available access to the ETurbo controller 228. Instead, the ETurbo can simply receive control signals from the ECU 250, rather than accessing, for example, the calibration software used at the test bench. This separation of task and control provides various efficiencies in other areas of design and development, but hinders optimal and / or safe operation of the ETurbo. In some examples presented herein, the ETurbo controller 228 is configured to allow calibration of the ECU 250 to be performed in a manner unknown to the ETurbo controller itself, as detailed further below. Furthermore, the control signals provided by the ECU 250 may include operational objectives and one or more secondary factors limiting ETurbo operation. For example, ETurbo can be given a maximum speed, whether related to a safety limit or to avoid compressor surge, and / or a minimum speed to prevent overuse of the ETurbo generator function, as well as an operating target related to the desired boost pressure; in other examples, a combination of two of these three factors (maximum, minimum, and setpoint) can be provided to ETurbo by the ECU. In some examples, ETurbo may also have internally stored limitations, such as a maximum safe operating speed limit.

[0065] Figure 4This is a block flowchart of control method 300. At block 302, the ECU calculates the torque setpoint and sends it to the ETurbo, instructing the ETurbo to provide how much torque to the compressor. The torque setpoint can be used to manage the torque applied from the turbocharger shaft to the compressor in several ways. The torque setpoint is designed to influence the applied torque; it does not need to be issued or set in the form or unit of actual torque. Alternatively, the torque setpoint can be defined by the current supplied to the ETurbo motor, for example, for applying added torque to the turbocharger shaft, or it can refer to the actual torque output of the ETurbo motor, or a calculation of the torque consumed by the compressor given a specific input from the turbine and / or the ETurbo motor, again referring to the torque balance on the turbocharger shaft. The torque setpoint can also be calculated based on power; adjusting the power supplied to or from the turbocharger shaft also affects the torque balance, such that a setpoint calculated based on power can also be considered a torque setpoint. Other setpoint types can be used; any setpoint or control signal used by the ETurbo motor to evaluate or modify the torque balance on the turbocharger shaft can be a torque setpoint, except for referencing the turbocharger shaft speed. The torque setpoint can be calculated by the ECU after taking into account the desired boost level to be generated by the compressor, environmental factors (e.g., intake characteristics such as humidity and temperature), measured, predicted, or modeled exhaust pressure or speed, and other states, conditions, or requirements within the system. The ECU may also consider factors such as turbocharger size or other configuration characteristics. PID, MPC, or other control methods, including referencing the compressor diagram, can be used to determine the torque setpoint.

[0066] At box 304, the maximum turbocharger speed is a defined feature of the ECU. More specifically, the compressor is typically rated at a maximum speed that will not be exceeded without the risk of excessive wear or complete failure. Furthermore, regardless of the actual compressor speed, the system's operating point may be close to the surge line on the compressor diagram, meaning that increasing the compressor speed may trigger unwanted surge. Therefore, the ECU can calculate the maximum turbocharger speed by referencing safety boundaries or other factors, such as proximity to the compressor surge line.

[0067] At box 304, the ECU can identify situations where the turbine (or compressor) speed is approaching its maximum limit. The ECU can take one or more corrective actions, including issuing a new force setpoint to the ETurbo, thereby reducing the force, torque, power, or current applied by the ETurbo, as shown in 306. In extreme cases, the ECU may interrupt ETurbo operation, as shown in 308, issuing a command to reduce the motor output to zero; alternatively, the ECU commands the ETurbo to switch to generator mode, thereby counteracting the torque on the turbocharger shaft. This type of abrupt change can subject the compressor to low-cycle fatigue; however, step 308 can be used if overspeed avoidance is required. At box 310, the ECU can also actuate the WG to bypass the exhaust flow to the turbine, again reducing the force supplied to the compressor. Actuating the WG is not necessarily preferred, as the WG is typically rated for a certain number of actuation steps during its lifespan. As the ECU calculates the maximum turbocharger speed by referring to the compressor diagram or surge line, the RCV or exhaust valve can be opened to reduce boost pressure and prevent surge, either as an alternative to or in addition to any of the boxes 306, 308, or 310.

[0068] While both 308 and 310 are available, box 306 will be preferred as the means of providing control of the turbocharger. However, the communication required at box 306 may introduce latency due to system delays; even if the processor or controller operates at a high clock speed, the method shown in 306 will have inherent hysteresis. Communication failures, requiring retries, may add further latency. In this setup, the ECU may need to act early to prevent the compressor from exceeding its maximum speed.

[0069] If the ETurbo controller is also responsible for monitoring the compressor speed, more complex factors arise. In this case, to prevent compressor overspeed, the ETurbo controller will measure the compressor speed and report it to the ECU via the CAN bus. In response, the ECU will determine whether overspeed is a current risk and will modify the control signals sent back to the ETurbo controller, as well as potentially modifying the control signals to another actuator in the system (such as, for example, by turning on WG via box 310). Due to the various dependencies, Figure 4 The solution in this context may not be optimal.

[0070] Figure 5 It can be improved. Figure 4The illustrative method of the process 400 is illustrated in the block flowchart. At block 402, the ECU uses optimization or other control analysis, such as PID or MPC or other control calculation methods, to calculate the compressor speed setpoint. For example, the optimized speed at block 402 could be a speed calculated via MPC analysis, which would achieve the desired boost pressure to optimize engine performance (defined by any of efficiency, power, etc.). As shown at block 404, the ECU also uses references to any suitable inputs (including, for example, but not limited to, safety boundaries and / or compressor diagrams and surge lines) to calculate the speed setpoint relative to the maximum compressor speed. The setpoint at block 404 can be equal to or reduced from the actual maximum compressor speed by a predetermined margin or percentage, as determined by safety or other boundary conditions.

[0071] Next, at box 410, the ECU calculates the speed boundary and transmits it to the ETurbo controller. The speed boundary can be transmitted as a speed control signal. For example, if both 402 and 404 operate in this method, the ECU selects the smaller speed boundary between the setpoints calculated in boxes 402 and 404. The ECU also calculates the torque setpoint and transmits it to the ETurbo, as shown in 412. The torque setpoint can be transmitted as a control signal. As mentioned above, the torque setpoint can be in any suitable form / unit. The torque setpoint can be calculated by the ECU after taking into account the desired boost level to be generated by the compressor, environmental factors (e.g., intake characteristics such as humidity and temperature), measured, predicted, or modeled exhaust pressure or speed, and other states, conditions, or demands within the system. As previously mentioned, the torque setpoint can be determined by referencing the torque balance on the turbocharger shaft. PID, MPC, or other control methods, including referencing the compressor diagram, can be used to determine the torque setpoint. Some examples may reference or otherwise use the power setpoint instead of the torque setpoint if desired.

[0072] At box 420, ETurbo receives a speed control signal (transmitting speed boundaries) and a torque control signal (transmitting torque setpoint) and implements a control solution for the motor, where the torque setpoint controls the motor as long as the compressor speed remains within the speed boundaries. Therefore, the ECU does not need to provide continuous, time-sensitive control to ETurbo to protect the compressor from overspeeding or to avoid harmful conditions such as surge. Furthermore, when operating in response to various ingressed disturbances, the compressor speed (at least to the extent that it is increased by the ETurbo motor force) is limited to an amount close to the speed setpoint determined by the ECU at box 404.

[0073] While compressor overspeeding relative to safety boundaries is a risk, other operating conditions exist, among which... Figure 5This approach can be useful. In one example, the ECU can determine that the engine is idling and can effectively issue a speed setpoint to the ETurbo instead of a speed boundary. For example, the issued torque setpoint could be set relatively high, while issuing a relatively low speed boundary (e.g., a speed boundary at 25% or other percentage of maximum compressor speed), which would cause the ETurbo to issue enough torque to operate the compressor at the speed boundary, turning the speed boundary into the setpoint. Doing so reduces lag when increasing engine speed by maintaining the rotational inertia on the turbocharger shaft. In another example, the ECU can specify the output speed control signal as a speed setpoint instead of issuing a speed boundary command.

[0074] Figure 6 Another example is shown. Here, method 500 causes the ECU to send both the speed setpoint and the torque setpoint as speed and torque control signals to ETurbo. At block 502, the ECU uses optimization calculations to calculate the speed setpoint, for example, employing boundary conditions that ensure the speed setpoint is equal to or less than the maximum compressor speed (e.g., a safety setpoint or set to prevent surge). The ECU also calculates the torque setpoint, as shown at block 504, similar to the previous example. As shown at block 510, the ECU transmits the speed and torque setpoints to the ETurbo controller. In normal operating mode, ETurbo uses the torque setpoint to operate within the speed boundaries shown at block 520. The speed setpoint can be used as the speed boundary in block 520. If the CAN system stops normal operation at block 530 (e.g., due to loss of synchronization or other faults), ETurbo can continue operation as shown at block 532 by using the speed setpoint instead of the torque setpoint to control operation.

[0075] In the alternative example, Figure 6 In this configuration, the ECU can send each of the torque and speed setpoints and speed boundaries separately as a torque control signal, a speed control signal, and a speed boundary signal. The speed boundary can be, for example, but not limited to, an upper limit on the compressor speed, or a boundary set near but below the upper limit. Therefore, in block 520, the transmitted speed boundaries are applied to limit the compressor speed. After a CAN fault is identified at 530, the speed setpoint can only be used when block 532 is invoked.

[0076] In the example, the operation in box 520 can be considered or described as a first operating mode of the ETurbo controller, and the operation in box 532 can be considered or described as a second operating mode of the ETurbo controller. The ETurbo controller can then be configured to select the first operating mode (box 520) when communication with the ECU is operable, or to select the second operating mode (box 532) when communication with the ECU is not operable.

[0077] Figure 7 Another example is shown. Here, method 600 begins with the ECU calculating the speed boundaries at 602. In this example, both the upper and lower limits of the turbine speed are generated by the ECU. The upper speed limit can be calculated as described above, for example, by referencing a compressor diagram, surge avoidance, or an operational safety threshold.

[0078] A speed lower limit can also be set. In some examples, a speed lower limit can be set to prevent a negative feedback loop due to insufficient turbocharger shaft speed, which would lead to a decrease in boost pressure and, in response, a decrease in engine output and exhaust pressure, further resulting in a decrease in applied boost pressure. In some examples, a speed lower limit can be set to prevent power loss during, for example, instantaneous changes in engine speed (i.e., gear shifts). In other examples, a speed lower limit can be set to prevent unsafe or undesirable engine operation, such as at high altitudes, or to ensure proper combustion of fuel. Referring to a compressor diagram, a speed lower limit can be set to prevent blockage. For example, a speed lower limit can also be set when using a variable displacement engine; if one or more cylinders of the internal combustion engine are disabled, the exhaust pressure may be insufficient to maintain the desired boost pressure when the cylinders are reactivated. ETurbo can apply torque, including exceeding the torque setpoint, to prevent exceeding the speed lower limit; in some examples, the speed lower limit can be used to determine whether and when to disable the ETurbo generator function, independent of, for example, engine speed reported to ETurbo by the ECU.

[0079] In this example, the ECU also generates a torque setpoint at box 604, similar to... Figure 6 Box 504 in the diagram. Then, the speed boundary, speed setpoint, and torque setpoint can each be transmitted to ETurbo at box 610. As shown in 620, the ETurbo controller uses the torque setpoint within the speed boundary during normal operation. If a CAN fault occurs at 630, the ETurbo controller switches to using the speed setpoint indicated at 632, similar to box 532 above.

[0080] The above detailed description includes reference to the accompanying drawings, which form a part of the detailed description. The drawings illustrate, by way of illustration, specific embodiments in which the invention may be practiced. These embodiments are also referred to herein as “examples.” In this document, as is common in patent documents, the term “a” or “an” is used to include one or more, and is not related to any other example or use of “at least one” or “one or more.” Furthermore, in the following claims, the terms “first,” “second,” and “third,” etc., are used merely as labels and are not intended to impose numerical requirements on their objects. In the event of any inconsistency between the usage in this document and any document incorporated by reference, the usage in this document shall prevail.

[0081] The above description is intended to be illustrative and not restrictive. For example, the above examples (or one or more aspects thereof) may be used in combination with each other. Other embodiments may be used, as will be apparent to those skilled in the art after reading the above description. Some examples may include elements other than those shown or described. The inventors have also contemplated examples of any combination or arrangement of those elements (or one or more aspects thereof) shown or described, relative to a particular example, or relative to other examples (or one or more aspects thereof) shown or described herein.

[0082] The methods described herein can be implemented, at least in part, by a machine or computer. Some examples may include computer-readable or machine-readable media encoded with instructions operable to configure an electronic device to perform the methods described in the examples above. Implementations of such methods may include code, such as microcode, assembly language code, high-level language code, etc. Such code may include computer-readable instructions for performing various methods. This code may form part of a computer program product. Furthermore, in the examples, the code may be tangibly stored on one or more volatile, non-transient, or non-volatile tangible computer-readable media, such as during execution or at other times. Examples of such tangible computer-readable media may include, but are not limited to, hard disks, removable disks or optical discs, magnetic tape cassettes, memory cards or memory sticks, random access memory (RAM), read-only memory (ROM), etc.

[0083] An abstract is provided to conform to 37 CFR § 1.72(b) to enable the reader to quickly determine the nature of the technical disclosure. It is understood that this submission is not intended to construe as limiting the scope or meaning of the claims. Furthermore, in the detailed description above, various features may be grouped together to simplify this disclosure. This should not be construed as meaning that unclaimed features are essential to any claim. Rather, the subject matter of the invention may not be limited to all features of a particular disclosed embodiment. Therefore, the following claims are incorporated herein by way of example or embodiment, each claim existing independently as a separate embodiment, and these embodiments are contemplated to be combined with each other in various combinations or arrangements. The scope of the invention should be determined by reference to the appended claims and the full scope of their equivalents.

Claims

1. A system for controlling an electric supercharging device for a turbocharger, comprising: An engine, which has an air input end and an exhaust output end; A turbocharger having a compressor coupled to the air input, a turbine coupled to the exhaust output, and an electric motor, wherein the compressor is configured to selectively receive force from either or both of the turbine and the electric motor, and the electric motor has an ETurbo controller; and An engine control unit is used to control the operation of the engine and the turbocharger; in: The engine control unit is configured to determine torque control signals and speed control signals and provide them to the ETurbo controller, enabling the ETurbo controller to manage the operation of the electric motor; and The ETurbo controller is configured to use the torque control signal to manage the operation of the electric motor without allowing the compressor speed to exceed the maximum speed determined by the speed control signal.

2. The system according to claim 1, wherein, The speed control signal is a speed boundary, and the ETurbo controller is configured to operate as follows: If the compressor speed is below the speed boundary, the force setpoint is used to control the operation of the motor; and If the compressor speed is at the speed limit, the output force provided by the electric motor is limited to prevent the compressor speed from exceeding the speed limit.

3. The system according to claim 1, wherein, The engine control unit determines the speed control signal by determining the target boost level based on the engine speed and calculating the expected compressor speed that is expected to provide the target boost level.

4. The system according to claim 3, wherein, The engine control unit is configured to determine the speed control signal to indicate a speed that is higher than the desired compressor speed and lower than the absolute maximum compressor speed.

5. The system according to claim 3, wherein, The engine control unit is configured to determine the speed control signal to indicate a speed at the desired compressor speed and below the absolute maximum compressor speed.

6. The system according to claim 1, wherein, The engine control unit determines the speed control signal to be equal to the absolute maximum speed of the compressor.

7. The system according to claim 1, wherein, The speed control signal is the speed setpoint.

8. The system according to claim 1, wherein, The speed control signal includes an upper speed boundary and a lower speed boundary.

9. The system according to claim 1, wherein, The speed control signal includes each of the speed setpoint, the upper speed boundary, and the lower speed boundary.

10. The system according to claim 1, wherein, The ETurbo controller is configured to operate as follows: In the first mode, torque setpoint operation is used to control the motor operation while limiting the compressor speed below the upper speed limit indicated by the speed control signal; and In the second mode, the speed setpoint indicated by the speed control signal is used to operate and control the operation of the motor; pass: Select the first mode during the operational period in which communication with the engine control unit is possible; and The second mode is selected during an operation period when communication with the engine control unit is inoperable.

11. The system according to claim 1, wherein, The ETurbo controller stores a maximum safe operating speed limit and is configured to set the compressor's maximum speed limit below the maximum safe operating speed limit, regardless of control signals received from the engine control unit.

12. A system for controlling an electric supercharging device for a turbocharger, comprising: An engine, which has an air input end and an exhaust output end; A turbocharger having a compressor coupled to the air input, a turbine coupled to the exhaust output, and an electric motor, wherein the compressor is configured to selectively receive torque from either or both of the turbine and the electric motor, and the electric motor has an ETurbo controller; and An engine control unit is used to control the operation of the engine and the turbocharger; in: The engine control unit is configured to determine torque control signals, speed control signals, and speed limits, and to provide these signals to the ETurbo controller, enabling the ETurbo controller to manage the operation of the electric motor; and The ETurbo controller is configured to use the torque control signal to manage the operation of the electric motor without allowing the compressor speed to exceed the speed limit.

13. The system according to claim 12, wherein, The ETurbo controller is configured to operate as follows: In the first mode, the torque control signal is used to control the operation of the electric motor while limiting the compressor speed below the speed boundary; and In the second mode, the speed control signal is used to control the operation of the motor; pass: The first mode is selected during the operational period when communication with the engine control unit is possible; as well as The second mode is selected during an operation period when communication with the engine control unit is inoperable.

14. The system according to claim 12, wherein, The engine control unit determines the speed boundary by determining the target boost level based on the engine speed and calculating the expected compressor speed to deliver the target boost level.

15. The system according to claim 12, wherein, The engine control unit defines the speed boundary as a level equal to the maximum speed of the compressor.

16. The system according to claim 12, wherein, The torque control signal indicates the desired torque output from the electric motor.

17. The system according to claim 12, wherein, The engine control unit determines the speed control signal by determining the target boost level based on the engine speed and calculating the expected compressor speed that is expected to provide the target boost level.

18. A booster system for supplying compressed air to an engine having an air inlet and an exhaust outlet, comprising: A compressor having an air inlet for receiving air and an output for sending compressed air to the engine; A turbine having an air inlet for receiving air from the exhaust outlet of the engine to generate torque, the turbine being connected to the compressor to provide the generated torque to the compressor; An electric motor is coupled to the compressor and configured to apply force to the compressor to add to the torque provided by the turbine; as well as An ETurbo controller, coupled to the electric motor to control its operation, is configured to receive at least a torque control signal and a speed control signal from the engine control unit, and to use the torque control signal to manage the operation of the electric motor without allowing the compressor speed to exceed a speed boundary determined by the speed control signal.

19. The system according to claim 18, wherein, The speed control signal is a speed boundary, and the ETurbo controller is configured to operate as follows: If the compressor speed is below the speed limit, a force control signal is used to control the operation of the electric motor; and If the compressor speed is at the speed limit, the output force provided by the electric motor is limited to prevent the compressor speed from exceeding the speed limit.

20. The system according to claim 18, wherein, The ETurbo controller is configured to operate as follows: In the first mode, a force control signal is used to control the operation of the electric motor, while limiting the compressor speed below the upper limit of the compressor speed. In the second mode, the speed control signal is used to control the operation of the electric motor; Determine whether communication with the engine control unit is operable, and: Select the first mode during the operational period in which communication with the engine control unit is possible; or The second mode is selected during an operation period when communication with the engine control unit is inoperable.

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