Warmup strategies for controlling engine exhaust emissions

Abstract

A control system (200, Fig. 2), a vehicle (1, Fig. 1), a method 500, and computer software (208, Fig. 3), for managing exhaust emissions of a vehicle comprising an internal combustion engine (10, Fig.

Description

30 06 25 TECHNICAL FIELD 5 The present disclosure relates to warmup strategies for controlling engine exhaust emissions. Aspects of the invention relate to a control system, a vehicle, a method, and computer software. BACKGROUND 10 Many vehicles equipped with internal combustion engines (‘engines’ herein) also comprise exhaust gas aftertreatment devices, such as three way catalysts (TWCs), to treat exhaust gases from the engines. The exhaust gas aftertreatment device needs to reach an operating temperature (light-off temperature) at which it is effective to clean exhaust gases. The operating temperature may be in the order of 15 hundreds of degrees Celsius. Therefore, vehicle pollutant emissions are generally highest at the start of a vehicle drive cycle due to the engine running while the temperature of the exhaust gas aftertreatment device is low. To speed up catalyst heating, the engine may be run in a mode that generates higher exhaust gas temperatures, or 20 a heating system can be provided such as a burner system upstream of the exhaust gas aftertreatment device, or an electric heater to heat the exhaust gas aftertreatment device. The electric heater is activated when the engine is running, to heat exhaust gases flowing through the electric heater. The burner system is a separate module with its own air pump, and is activated when 25 the engine is running to inject heated / combusted air towards the exhaust gas aftertreatment device. SUMMARY OF THE INVENTION Aspects and embodiments of the invention provide a control system, a vehicle, a method, and computer 30 software as claimed in the appended claims. According to an aspect of the invention there is provided a control system for managing exhaust emissions of a vehicle, the vehicle comprising an internal combustion engine, an exhaust gas aftertreatment device having an emission control capability dependent on a temperature of the exhaust 35 gas aftertreatment device, the vehicle further comprising a heating system (e.g., fuel burner and / or electric heater) for raising a temperature of the exhaust gas aftertreatment device, wherein the control system comprises one or more controllers, the control system configured to: 30 06 25 । cocivc an input signal indicative of the emission control capability of the exhaust gas aftertreatment device (e.g., proportion of catalytic material of the exhaust gas aftertreatment device which has reached an operating temperature); determine a warmup management strategy in dependence on the input signal, wherein the 5 determined warmup management strategy controls whether the internal combustion engine is to be controlled in dependence on the input signal and whether the heating system is to be controlled in dependence on the input signal; and output at least one control signal in accordance with the determined warmup management strategy, wherein determining the warmup management strategy comprises selecting the warmup 10 management strategy from a plurality of warmup management strategies, in dependence on the input signal, wherein the plurality of warmup management strategies include: a first warmup management strategy configured to control the heating system without controlling the internal combustion engine; and a second warmup management strategy configured to control at least the internal combustion 15 engine, and wherein controlling the internal combustion engine in accordance with the second warmup management strategy comprises controlling the internal combustion engine in a restricted output mode to restrict how much engine torque is demanded in response to a received torque request. 20 An advantage is enabling greater control of light-off of the exhaust gas aftertreatment device. For example, the warmup management strategy may control whether the heating system alone is controlled in dependence on the input signal alone, or is controlled in combination with controlling the internal combustion engine, in dependence on the input signal. In an implementation, if the emission control capability is low, the control system may operate the heating system to pre-heat the exhaust gas 25 aftertreatment device prior to engine-activation. However, if the emission control capability is higher, then a faster and more aggressive warmup management strategy can be used such as operating the heating system while also running the internal combustion engine in a manner that generates elevated exhaust gas temperatures. 30 Determining the warmup management strategy may comprise selecting the warmup management strategy from a plurality of warmup management strategies, in dependence on the input signal, wherein the plurality of warmup management strategies include: a first warmup management strategy configured to control the heating system without controlling the internal combustion engine; and a second warmup management strategy configured to control at least the internal combustion engine. For example, the 35 first warmup management strategy may control the heating system in dependence on the input signal while the internal combustion engine is in a non-running state. The second warmup management strategy may be configured to simultaneously control the heating system and the internal combustion engine. The second warmup management strategy may be configured to control the internal 30 06 25 uuiiiuuouuii engine in dependence on the input signal while controlling the heating system in dependence on the input signal. An advantage is enabling faster light-off of the exhaust gas aftertreatment device when it is needed, 5 because it can be pre-heated by the heating system prior to engine-activation, or heated by both the heating system and the engine if required. The first warmup management strategy may be further configured to inhibit activation of the internal combustion engine in response to requested activation of the internal combustion engine, until a 10 condition for switching to a different one of the plurality of warmup management strategies is satisfied. Inhibiting the activation may comprise applying an engine-activation delay flag. An advantage of requiring the user to wait a short time before departing is that the vehicle is not usable while untreated exhaust emissions would otherwise be at their highest levels. 15 Determining the warmup management strategy may be further dependent on a hybrid vehicle operating mode of the vehicle. For example, the inhibited activation of the internal combustion engine may depend on the hybrid vehicle operating mode. The flag may be applied if the mode comprises an engine only mode but not if the mode comprises a parallel hybrid electric vehicle mode or an e-drive mode. Advantageously, this means that the user is not inconvenienced by the engine-activation delay flag if 20 the vehicle can alternatively be driven under electric propulsion. Controlling the internal combustion engine in accordance with the second warmup management strategy may comprise controlling the internal combustion engine to raise exhaust gas temperature via at least one of ignition timing retardation, fuel enleanment (leaner air-fuel ratio), or exhaust valve timing. 25 The control system may be configured to select the first warmup management strategy in dependence on the emission control capability being less than a first target. The control system may be configured to select the second warmup management strategy in dependence on the emission control capability being greater than the first target and less than a second target. In some examples, determining the 30 warmup management strategy may be dependent on an amount of requested torque. In some examples, determining the warmup management strategy may be dependent on the state of charge of an electrical energy storage means. In some examples, the second warmup management strategy is a more aggressive strategy than the first. Advantageously, the second warmup management strategy may be used only in response to (or in anticipation of) engine-running. 35 Once the emission control capability has reached a value greater than the second target, the control system may be configured to cease outputting the at least one control signal in accordance with the determined warmup management strategy, the determined warmup management strategy being the 30 06 25 OCUUIIU Wdllliup management strategy. The second target may indicate that substantial light-off has been achieved. Therefore, for example, the restricted output mode may be terminated. The heating system may be deactivated. The internal combustion engine may no longer be controlled in dependence on the input signal. Therefore, in an example, full torque is available and normal engine management 5 (e.g., ignition timing, air-fuel ratio, exhaust valve timing) is available, and the heating system is deactivated. This is the most energy-efficient state of the vehicle, while the emission control capability is high. The control system comprises one or more controllers collectively comprising at least one electronic 10 processor having an electrical input for receiving an input signal; and at least one memory device electrically coupled to the at least one electronic processor and having instructions stored therein; and wherein the at least one electronic processor is configured to access the at least one memory device and execute the instructions thereon so as to: receive the input signal, determine the warmup management strategy, and output the control signal. 15 According to an aspect of the invention there is provided a control system for managing exhaust emissions of a vehicle, the vehicle comprising an internal combustion engine, an exhaust gas aftertreatment device, and a system for increasing an emission control capability of the exhaust gas aftertreatment device, wherein the control system comprises one or more controllers, the control system 20 configured to: receive an input signal indicative of the emission control capability; determine a management strategy in dependence on the input signal, wherein the determined management strategy controls whetherthe system is to be controlled in dependence on the input signal; and 25 output at least one control signal in accordance with the determined management strategy. According to another aspect of the invention, there is provided a vehicle comprising the control system. According to a further aspect of the invention, there is provided a method of managing exhaust 30 emissions of a vehicle, the vehicle comprising an internal combustion engine, an exhaust gas aftertreatment device having an emission control capability dependent on a temperature of the exhaust gas aftertreatment device, the vehicle further comprising a heating system for raising a temperature of the exhaust gas aftertreatment device, the method comprising: receiving an input signal indicative of the emission control capability of the exhaust gas 35 aftertreatment device; determining a warmup management strategy in dependence on the input signal, wherein the determined warmup management strategy controls whether the internal combustion engine is to be 30 06 25 UUIILIUIICU III ucpendence on the input signal and whether the heating system is to be controlled in dependence on the input signal; and outputting at least one control signal in accordance with the determined warmup management strategy. 5 According to a further aspect ofthe invention, there is provided computer software that, when executed, is arranged to perform the method. According to a further aspect ofthe invention there is provided a non-transitory computer readable medium comprising computer readable instructions that, when executed by one or more electronic processors, causes the one or more electronic processors to carry 10 out any one or more ofthe methods described herein. BRIEF DESCRIPTION OF THE DRAWINGS 15 One or more embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: FIG. 1 illustrates an example of a vehicle; FIG. 2 illustrates an example of an exhaust system; FIG. 3 illustrates an example of a control system; 20 FIG. 4 illustrates an example of a non-transitory computer-readable storage medium; and FIG. 5 illustrates an example of a state diagram. DETAILED DESCRIPTION 25 FIG. 1 illustrates an example of a vehicle 1 in which embodiments ofthe invention can be implemented. In some, but not necessarily all examples, the vehicle is a passenger vehicle, also referred to as a passenger car or as an automobile. In other examples, embodiments of the invention can be implemented for other applications, such as commercial vehicles. 30 FIG. 2 schematically illustrates an internal combustion engine 10 (‘engine’ herein), an electric machine 14, an electrical energy storage means 16 such as a battery, a control system 200, and a portion of an exhaust system 100. The invention is not limited to the specific layout shown. The illustrated engine 10 is a reciprocating piston engine having a number of combustion chambers 12. 35 In other examples, the engine 10 is any other appropriate type of internal combustion engine. In some, but not necessarily all examples, the vehicle 1 is a hybrid electric vehicle (HEV). The vehicle 1 may be a full HEV or a mild HEV. Full HEVs have an electric-only mode of propulsion ofthe vehicle 30 06 25 uy me eieuuiu machine 14. Mild HEVs do not have an electric-only mode of propulsion, but the electric machine 14 may be configured to provide assistance such as boosting output torque of the engine 10. The vehicle’s powertrain may be a parallel HEV powertrain. A parallel HEV powertrain comprises a 5 torque path between the engine 10 and at least one vehicle wheel, as well as a torque path between the electric machine 14 and at least one vehicle wheel. The torque path(s) may be disconnectable by a torque path connector such as a clutch. The control system 200 is operable to receive a variable signal indicative of an accelerator position, or 10 indicative of how much torque is requested by an autonomous controller in an autonomous driving use case. The control system 200 is operable to determine and output a total drive torque request based at least on the variable signal. In some examples, the control system 200 has a plurality of hybrid vehicle operating modes. In one or 15 more hybrid vehicle operating modes, the engine 10 is in a non-running state and a torque path between the engine 10 and vehicle wheels is disconnected. In another one or more hybrid vehicle operating modes, the engine 10 is in a running state and the torque path is connected. The hybrid vehicle operating mode may be selectable manually, semi-automatically, or automatically. 20 In the running state, the engine 10 generates output torque by injecting fuel and combusting fuel in the engine’s combustion chambers 12. The engine 10 generates exhaust gases requiring aftertreatment. In the non-running state, the engine 10 does not inject and combust fuel in its combustion chambers 12, therefore not generating exhaust gases requiring aftertreatment. The term ‘activating’ the engine 10 describes transitioning the engine 10 from the non-running state to the running state. 25 In an e-drive mode of the hybrid vehicle operating modes, the control system 200 controls torque of the electric machine 14 in dependence on the total drive torque request, while the engine 10 is not controlled based on the total drive torque request. The control system 200 outputs an e-drive torque request based on the total drive torque request, to control the output torque of the electric machine 14. The engine’s 30 torque path may be disconnected. In an internal combustion engine mode (engine only mode, or ‘ICE mode’) of the hybrid vehicle operating modes, the engine 10 is in the running state. The control system 200 controls torque of the engine 10 in dependence on the total drive torque request, while the electric machine 14 is not controlled 35 based on the total drive torque request. The control system 200 outputs an engine torque request based on the total drive torque request, to control the output torque of the engine 10. The engine’s torque path is connected. The electric machine 14 can be said to be in an inactive state, with respect to drive torque, so that it does not generate positive (propulsive) output torque to control wheel torque at the vehicle 30 06 25 wiiccio iii uopoiiuence on the total drive torque request. The electric machine 14 may however provide regenerative braking. In a parallel HEV (PHEV) mode of the hybrid vehicle operating modes, the control system 200 can 5 control torque of the electric machine 14 and torque of the engine 10 simultaneously in dependence on the same total drive torque request, while their torque paths are connected to the vehicle wheels. The control system 200 outputs separate arbitrated e-drive and engine torque requests based on the same total drive torque request, to control the output torques of the electric machine 14 and engine 10 respectively to simultaneously provide wheel torque. Again, electric machine 14 may also provide 10 regenerative braking. The PHEV mode may either be temporary or persistent, and may be user selected. - Temporary PHEV mode can occur when the e-drive mode is selected, but the PHEV mode is temporarily entered for the engine 10 to provide ‘torque fill’ in the event of an accelerator ‘tip-in’. 15 This occurs if the total drive torque request exceeds a torque capability of the electric machine 14. - Persistent PHEV mode can occur when the engine 10 is kept in the running state regardless of whether or not the total drive torque request exceeds the torque capability of the electric machine 14. The vehicle’s responsiveness to fast accelerator inputs is greater in persistent PHEV mode than in temporary PHEV mode. 20 The exhaust system 100 in FIG. 2 comprises an exhaust manifold 110, an optional turbomachine assembly 120, a heating system 130, a canning 150 comprising an exhaust gas aftertreatment device 152, and one or more exhaust pipes 140, 160. 25 The canning 150 houses an exhaust gas aftertreatment device 152, which can comprise a catalytic converter such as a three-way catalytic converter. The exhaust gas aftertreatment device 152 needs to reach an operating temperature (light-off temperature) at which it is effective to clean exhaust gases. The operating temperature may be in the 30 order of hundreds of degrees Celsius. The heating system 130 shown in FIG. 2 is operable to raise the temperature of the exhaust gas aftertreatment device 152 quickly in a cold start situation, to minimise cumulative pollutant emissions. The heating system 130 may comprise a fuel burner 132 as shown, or an electric heater for heating the 35 catalyst, or a combination thereof. The heating system 130 may have a power of several kilowatts, the electrical energy (when it is an electric heater) being supplied by the electrical energy storage means 16. 30 06 25 me iuci uumei 132 receives fresh combustible air from any appropriate source of fresh air. The fuel burner comprises a fuel injector to inject fuel, an igniter, and a housing comprising a burner combustion chamber. The burner combustion chamber can be outside the main exhaust gas path and be connected to the main exhaust gas path via a pipe to a junction upstream of the exhaust gas aftertreatment device 5 152. The junction can be at an oblique angle to direct hot gas from the fuel burner 132 towards the exhaust gas aftertreatment device 152. Separately from the heating system 130, a warmup strategy using the engine 10 to raise the temperature quickly comprises controlling the engine 10 in a CSSRE (Cold Start Spark Retard 10 Enleanment) engine management mode to raise exhaust gas temperature. For a given operating point of the engine 10, CSSRE engine management mode retards ignition timing and leans the air-fuel ratio. It may also advance exhaust valve opening timing if this is controllable. The term ‘modes’ in the context of engine control refers to different sets of maps, curves, or lookup tables interrogated by an engine control unit. 15 Once the operating temperature of the exhaust gas aftertreatment device 152 is reached or approached, the heating system 130 would be deactivated or control of the engine 10 would be switched to a normal engine management mode more thermally efficient than CSSRE engine management mode. 20 FIG. 3 illustrates an example control system 200 configured to implement one or more aspects of the invention. The control system 200 of FIG. 3 comprises a controller 201. In other examples, the control system 200 may comprise a plurality of controllers on-board and / or off-board the vehicle 1. 25 The controller 201 of FIG. 3 includes at least one processor 204; and at least one memory device 206 electrically coupled to the electronic processor 204 and having instructions (e.g. a computer program 208) stored therein, the at least one memory device 206 and the instructions configured to, with the at least one processor 204, cause any one or more of the methods described herein to be performed. The controller 201 may have an interface 202 comprising an electrical input / output I / O 210, 212, or an 30 electrical input 210, or an electrical output 212, for receiving information and interacting with external components. FIG. 4 illustrates a non-transitory computer-readable storage medium 300 comprising the instructions (computer software). 35 The control system 200 is configured to receive input signals including a first input signal indicative of an emission control capability of the exhaust gas aftertreatment device 152. The emission control capability indicates a proportion of catalytic material of the exhaust gas aftertreatment device 152 which 30 06 25 nao luauiicu uic operating temperature. This may be expressed as a percentage, ratio, or any other appropriate variable ranging from minimum-partial-maximum capability. For example, the emission control capability can be described as a percentage of catalyst volume lit-off, where the volume refers to the catalyst-containing volume of the exhaust gas aftertreatment device 152. 5 The first input signal may be received from a predictive temperature model, which is internal or external to the control system 200. The predictive temperature model may be a mathematical algorithm to calculate the current proportion of lit-off catalytic material based on variables such as one or more of: - time since engine entered the running state; 10 - engine power produced; and / or - integration of engine power produced overtime. Alternatively, a reactive model may utilise information from a downstream emissions sensor (e.g., lambda sensor). This indicates when the post-catalyst oxygen (O2) is insufficiently reduced which 15 indicates that the catalyst volume is not lit-off. The control system 200 is configured to determine a warmup management strategy for the exhaust gas aftertreatment device 152, based on the first input signal, and is configured to transmit one or more control signals in accordance with the determined warmup management strategy. 20 FIG. 5 is a state diagram illustrating an implementation of a method 500 for managing a warmup management strategy for raising the temperature of the exhaust gas aftertreatment device 152. The method 500 is a computer-implemented method. The method 500 may be implemented by the control system 200. 25 The illustrated rectangles are states and the circles are conditions. The states and conditions can also be described as operation blocks and decision blocks of a flowchart, respectively. The states collectively represent a plurality of warmup management strategies, including a first (first-30 level) warmup management strategy (518, 532), and a more aggressive second (second-level) warmup management strategy (520, 538). Further, each strategy level may differ depending on the current hybrid vehicle operating mode. The conditions represent arbitration conditions, enabling the control system 200 to arbitrate (select) the 35 type of warmup management strategy to be used. The method 500 may be the same regardless of whether the heating system 130 is a fuel burner 132 or an electric heater (or both). 30 06 25 Further, it is not essential for all of the states and conditions of FIG. 5 to be included and it is not essential for them to be connected in the specific manner shown. 5 The method 500 starts at the entry condition 502. The entry condition 502 can require a prediction that engine running will be required or is predicted to be required. In an example implementation, block 502 comprises receiving an input signal capable of indicating whether a user (driver) is approaching or entering the vehicle 1 or its driver’s seat, and comprises 10 determining based on the input signal whether a user is approaching or entering the vehicle 1 or its driver’s seat. The input signal can be from a departure time function, or from a sensor such as a door sensor, a key fob presence sensor, a seatbelt sensor, or the like. In some examples, the input signal may be received 15 from a machine learning module configured to predict when engine running will be required based on learned user behaviour. The entry condition 502 can be satisfied before engine running is requested. Advantageously, heating of the exhaust gas aftertreatment device 152 can be initiated before engine running is requested, so 20 that the temperature of the exhaust gas aftertreatment device 152 is closer to its operating temperature by the time engine running is requested. If the entry condition 502 is satisfied, an initialised state 504 is entered. In the initialised state 504, the vehicle 1 is in a non-travelable state and no warmup management strategy is active. The heating system 25 130 is inactive (e.g., Burner OFF). The initialised state 504 is a pre-departure state in which the engine 10 is in a non-running state (e.g., Engine OFF). The electric machine 14 may be in the inactive state (E-drive OFF) or active state. The control system 200 may select the state 504 as an initialised state in a cold start use case, as indicated 30 by the emission control capability. For example, the emission control capability may be below a threshold such as 20% volume lit-off. The initialised state 504 is connected to a termination block 508 by an exit condition 506. The exit condition 506 can comprise the entry condition 502 no longer being satisfied, or any other appropriate 35 condition indicating that engine running is not required or will not be required. For example, the indication may be that the user exits the vehicle 1. 30 06 25 hi oumc GAampieS, other states shown in FIG. 5 (rectangular boxes) may be selected, where their respective requirements are satisfied at the time that the entry condition 502 is satisfied. For example, if the vehicle has only been stopped briefly (e.g., to refuel), the emission control capability may be high and so the state 504 may not be selected. 5 The control system 200 can switch from the initialised state 504 to either an e-drive non-heating state 512 or an engine pre-heating state 532, each comprising a different warmup management strategy. The e-drive non-heating state 512 does not require immediate catalyst heating whereas the engine preheating state 532 does require immediate catalyst heating. 10 In the e-drive non-heating state 512, the hybrid vehicle operating mode is the e-drive mode (E-drive ON, Engine OFF) and no warmup management strategy is selected. Catalyst heating is therefore not requested (Burner OFF). This is because there is no expectation of engine emissions. The vehicle 1 can operate (e.g., depart) while in the e-drive non-heating state 512 under electric propulsion without 15 any catalyst heating required. An advantage is that the heating system 130 may not be used at all in a drive cycle consisting entirely of the e-drive mode, such that substantial energy is saved and vehicle range is improved. A ‘drive cycle’ includes periods where the vehicle is moving and periods where the vehicle is stationary in a state of 20 being ready to move. In the engine pre-heating state 532, use of the engine 10 will be required when the vehicle 1 departs or otherwise requires engine running. The vehicle 1 may be in a pre-departure state, so that the engine 10 may be in the non-running state (engine OFF). The engine pre-heating state 532 selects a first-level 25 warmup management strategy: operating the heating system 130 in a catalyst heating mode (Burner ON), which is to say that the heating system 130 is activated; and implementing a later-described engine-activation delay flag. The determination of which state 512 or 532 to select may depend at least on the state of charge of the 30 electrical energy storage means 16. If there is insufficient charge for e-drive mode, the engine preheating state 532 should be used. If there is sufficient charge for e-drive mode, the e-drive non-heating state 512 may be selected or the decision may be up to the user via a manual mode selection interface (not shown). 35 The conditions 510 and 530 for the respective states 512, 532 are described below. 30 06 25 I I IC CUI IUILIWI I U I J for switching from the initialised state 504 to the e-drive non-heating state 512 can comprise a requirement that the vehicle 1 is operable with the engine 10 in the non-running state. This condition 510 can optionally include the following requirements: a1) emission control capability = no requirement, ora requirement that emission control capability 5 is less than a first target (e.g., 20%), indicating a cold start use case; b1) engine torque request = 0, indicating non-use of the engine 10; c1) a torque request is less than or equal to a pre-activation threshold (e.g., e-drive torque request <75%), indicating that the engine 10 is not likely to be required for purposes such as torque boost; and 10 d1) state of charge of the electrical energy storage means 16 is greater than or equal to a threshold fore-drive (e.g., 20%), indicating that the engine 10 is not imminently required to generate electrical energy. The different condition 530 for switching from the initialised state 504 to the engine pre-heating state 15 532 can comprise a requirement that operation of the vehicle 1 requires the engine to be in the running state. This condition 530 can optionally include the following requirements: a2) as a1) above (cold start use case); b2) as b1) above (non-use of the engine 10); c2) e-drive torque request = 0; 20 d2) state of charge of the electrical energy storage means 16 is less than the threshold for e-drive (e.g., 20%). In summary, determining a warmup management strategy comprises determining which condition 510 or 530 is satisfied. 25 Following the left side of the state diagram first, the e-drive non-heating state 512 can remain active during a drive cycle for as long as engine activation is not required. The e-drive non-heating state 512 can switch back to the initialised state 504 upon satisfaction of a condition 516 such as the e-drive torque request being zero fora monitored period of time, such as several minutes. 30 On the other hand, the control system 200 can instead switch from the e-drive non-heating state 512 to an e-drive heating state 518 if a pre-activation condition 514 is satisfied, indicating a high probability of engine activation. 35 In anticipation of the probable engine activation, the e-drive heating state 518 determines a first-level warmup management strategy: activating and operating the heating system 130 (Burner ON) while the engine 10 is in the non-running state. 30 06 25 hi me e-uiive ilooting state 518, the vehicle 1 remains under electric-only propulsion (Engine OFF, E-drive ON). The e-drive heating state 518 is therefore pre-emptive, activating the heating system 130 due to a greater likelihood of user-initiated engine activation. 5 An advantage is that unnecessary use of the heating system 130 is avoided, because the heating system 130 is not activated unless an engine activation is anticipated. The activation of the heating system 130 may occur at any time during a drive cycle when engine activation is anticipated. The pre-activation condition 514 to enter the e-drive heating state 518 can comprise a requirement that 10 the pre-activation threshold (e.g., 75%) is exceeded. Optionally, the pre-activation condition 514 can include the following requirements: a3) as a2) above; b3) as b2) above; c3) the torque request is greater than a pre-activation threshold (e.g., e-drive torque request >15 75%), indicating a high probability that the engine 10 is going to be required for vehicle acceleration purposes; d3) as d2) above. The e-drive heating state 518 can remain active for as long as the electric machine 14 can supply the 20 requested torque. Although the illustrated state diagram shows one-way connections between states, the connections may of course be two-way connections such that state transitions may be in the reverse direction. For example, the control system 200 may transition from the e-drive heating state 518 back to the initialised 25 state 504 if, for example, the state of charge falls below the threshold fore-drive (e.g., 20%) ora different hybrid vehicle operating mode is selected. The control system 200 can switch from the e-drive heating state 518 to a PHEV heating state 520 if an engine activation condition 519 is satisfied, indicating that more torque than the electric machine 14 30 can supply (torque capability) has been requested. The PHEV heating state 520 activates PHEV mode (Engine ON, E-drive ON), either temporarily or persistently. 35 The PHEV heating state 520 is a second-level warmup management strategy: continuing to operate the heating system 130 (Burner ON), while simultaneously controlling the engine 10 in the CSSRE engine management mode, and implementing a later-described restricted output mode of the engine 10. 30 06 25 The second-level warmup management strategy (520, 538) is more aggressive than the first-level warmup management strategy (518, 532), and is determined when the predicted engine activation has been realised. An advantage is therefore that energy for heating the exhaust gas aftertreatment device 5 152 is only consumed at the highest rate when activation of the engine 10 is unavoidable. The engine activation condition 519 to enter the PHEV heating state 520 can comprise a requirement that an engine-activation threshold greater than (e.g., 90%) the pre-activation threshold (e.g., 75%) is exceeded. Optionally, the engine-activation condition 519 can include the following requirements: 10 a4) first target (e.g., 20%) is more than or equal to the emission control capability but less than or equal to a second target (e.g., 50%); b4) engine torque request >0; c4) the torque request is greater than the engine-activation threshold (e.g., e-drive torque request >90%), indicating that engine activation is required; 15 d4) as d3) above. The requirement a4) contributes to the first warmup management strategy of the e-drive heating state 518 because satisfaction of the requirement c4) alone is not sufficient unless at least the first target (20%) of emissions control capability of the exhaust gas aftertreatment device 152 has been reached. 20 The effect is to ignore an engine-activation request unless sufficient catalyst volume light-off has been achieved to enable engine activation. This effectively saturates the available drive torque of the vehicle 1 to the torque capability of the electric machine 14 until a minimum (first target) catalyst light-off has been reached to enable engine activation. 25 The optional second target a4) is higher than the first target, such as 50%. If the second target is exceeded, no further warmup is required, so that the heating system 130 can be deactivated and the engine 10 can be controlled in a normal engine management mode rather than the CSSRE engine management mode. 30 In a use case, if the engine-activation condition 519 is satisfied in the initialised state 504, the control system 200 may progress through states 512 and 518 directly to the state 520. The PHEV heating state 520 further comprises a restricted output mode in the form of an engine torque de-rate loop 521-522. This forms part of the determined second-level warmup management strategy. 35 The loop has an engine torque de-rate condition 521, requiring a determination that the engine torque request is greater than an emissions threshold (e.g., 80% of maximum engine torque). If satisfied, the sub-state 522 applies a torque de-rate to the engine torque request. This can comprise applying a 30 06 25 .............uumer (hard limit or soft limit) to excess values of the engine torque request above the emissions threshold. The engine torque de-rate condition 521 can include the following requirements: 5 a5) as a4) above; b5) engine torque request is greater than the emissions threshold; c5) as c4) above; d5) as d4) above. 10 The requirement a5) of condition 521 means that the torque de-rate is applied until the second target of emissions control capability (e.g., 50%) of the exhaust gas aftertreatment device 152 is reached. It is only after the second target is reached that the torque de-rate is removed enabling full drive torque capability of the engine 10, greater than the emissions threshold. 15 The PHEV heating state 520 can remain active for as long as heating is required and PHEV mode is required. In some examples, the control system 200 may transition from the e-drive heating state 518 back to the initialised state 504 if, for example, the state of charge falls below the threshold for e-drive (e.g., 20%) or a different hybrid vehicle operating mode is selected. 20 The control system 200 can switch from the PHEV heating state 520 to a charge-deplete fully-heated state 526 if a heating-complete condition 524 is satisfied. The charge-deplete fully-heated state 526 is in PHEV mode (Engine ON, E-drive ON). A warmup management strategy is no longer needed because the emission control capability of the exhaust gas 25 aftertreatment device 152 is sufficiently high. The heating system 130 is deactivated (Burner OFF), the engine 10 is controlled in a normal engine management mode rather than the CSSRE engine management mode, and no de-rates are applied. The charge-deplete fully-heated state 526 acts as a ‘charge deplete’ state which enables the state of 30 charge of the electrical energy storage means 16 to be depleted for electric driving, without requiring the engine 10 to generate electrical energy to sustain a particular state of charge or increase the state of charge. The heating-complete condition 524 can comprise a determination that the emission control capability 35 of the exhaust gas aftertreatment device 152 has reached (e.g., exceeded) the second target (e.g., 50%). Optionally, the heating-complete condition 524 can include the following requirements: a6) emission control capability is greater than the second target (e.g., 50%); b6) engine torque request is less than or equal to the maximum (e.g., wide open throttle, WOT); 30 06 25 uuy me iuiqu6 request >0; d6) as d5) above. The control system 200 can switch from the charge-deplete fully-heated state 526 back to the initialised 5 state 504 upon satisfaction of a condition 528 such as the vehicle 1 entering a non-driving mode, perhaps in response to a driver action (e.g., driver presses a ‘Start / Stop’ button, or driver opens a vehicle door). In the initialised state 504, the vehicle 1 may be in an ‘accessory mode’ (i.e., able to operate infotainment / climate controls but not drive). 10 Turning now to the right-hand side of the state diagram in FIG. 5, specifically to the engine pre-heating state 532, a determined first-level warmup management strategy (state 532) operates the heating system 130 before the engine 10 is activated. FIG. 5 further illustrates an engine-activation delay loop (534-535) forming part of the determined first-15 level warmup management strategy / part of the engine pre-heating state 532. The engine-activation delay loop has an engine-activation delay condition 534, requiring a determination that the engine torque request is greater than zero while the emission control capability of the exhaust gas aftertreatment device 152 is below the first target (e.g., 20%). 20 If satisfied, the sub-state 535 applies an engine-activation delay flag inhibiting engine activation. The engine-activation delay flag may inhibit (prevent) activation of the engine 10 in response to an ignition-on request initiated by the driver. If the driver wishes to depart immediately, they should wait for sufficient catalyst volume light-off (emission control capability) to treat the initial emissions of the engine 25 10. The engine-activation delay condition 534 can include the following requirements: a7) as a2) above; b7) engine torque request >0; 30 c7) as c2) above; d7) as d2) above; e7) as e2) above. The engine pre-heating state 532 can remain active until sufficient catalyst volume light-off has occurred 35 to enable the engine 10 to be activated. The control system 200 may transition from the engine preheating state 532 back to the initialised state 504 if, for example, the state of charge rises above the threshold fore-drive (e.g., 20%) ora different hybrid vehicle operating mode is selected. 30 06 25 i i ic uui ill ui oyoicin 200 can switch from the engine pre-heating state 532 to an engine-on heating state 538 if an initial light-off condition 536 is satisfied, indicating that the emission control capability of the exhaust gas aftertreatment device 152 has reached a sufficiently high value. 5 Satisfaction of the initial light-off condition 536 enables the engine 10 to be activated. The control system 200 may remove the engine-activation delay flag if it is currently active. Satisfaction of the initial light-off condition 536 may enable the engine 10 to be activated by another means, for example in response to a nonzero engine torque request or ignition-on signal initiated by the user. 10 The engine-on heating state 538 is a second-level warmup management strategy: continuing to operate the heating system 130 (Burner ON), while simultaneously controlling the engine 10 in the CSSRE engine management mode, and implementing a later-described restricted output mode of the engine 10. 15 An advantage of the states 532 and 538 is that use of the more efficient heating system 130 is prioritised, resulting in lower energy consumption and emissions. This is because activation of the less-efficient engine 10 is delayed until the user requests pull-away (departure) of the vehicle 1 once the emission control capability has reached the first target. This may even provide sufficient time for the heating system 130 to perform full heating of the exhaust gas aftertreatment device 152. 20 The initial light-off condition 536 to enter the engine-on heating state 538 can comprise a requirement that the emission control capability of the exhaust gas aftertreatment device 152 has at least reached the first target. Optionally, the initial light-off condition 536 can include the following requirements: a8) first target (e.g., 20%) is greater than or equal to the emission control capability but less than 25 or equal to the second target (e.g., 50%); b8) engine torque request >0; c8) same as c7); d8) same as d7). 30 The engine-on heating state 538 further comprises a restricted output mode in the form of an engine torque de-rate loop 539-540, forming part of the determined second-level warmup management strategy. The loop has an engine torque de-rate condition 539, requiring a determination that the engine torque request is greater than an emissions threshold (e.g., 80% of maximum engine torque). If satisfied, the sub-state 540 applies a torque de-rate to the engine torque request. This can comprise 35 applying a saturation modifier (hard limit or soft limit) to excess values of the engine torque request above the emissions threshold. The engine torque de-rate condition 539 can include the following requirements: 30 06 25 cw; do auj aOOVe; b9) engine torque request is greater than the emissions threshold; c9) as c8) above; d9) as d8) above. 5 The requirement a9) of condition 539 means that the torque de-rate is applied until the second target of emissions control capability of the exhaust gas aftertreatment device 152 is reached. It is only after the second target is reached that the torque de-rate is removed enabling full drive torque capability of the engine 10. 10 The engine-on heating state 538 can remain active for as long as heating is required. The control system 200 may transition from the engine-on heating state 538 back to the initialised state 504 if, for example, the state of charge rises above the threshold for e-drive (e.g., 20%) or a different hybrid vehicle operating mode is selected. 15 The control system 200 can switch from the engine-on heating state 538 to an ICE-only fully-heated state 544 if a heating-complete condition 542 is satisfied. The ICE-only fully-heated state 544 is in ICE mode (Engine ON, E-drive OFF). No warmup management 20 strategy is selected. The heating system 130 is deactivated (Burner OFF), the engine 10 is controlled in a normal engine management mode rather than the CSSRE engine management mode, and no derates are applied. The heating-complete condition 542 can comprise a determination that the emission control capability 25 of the exhaust gas aftertreatment device 152 has reached (e.g., exceeded) the second target (e.g., 50%). Optionally, the heating-complete condition 542 can include the following requirements: a10) emission control capability is greater than the second target (e.g., 50%); b10) engine torque request is less than or equal to the maximum (e.g., wide open throttle, WOT); c10) as c9) above; 30 d10) as d9) above. Further, the control system 200 can switch from the ICE-only fully-heated state 526 to a charge-sustain fully-heated state 548 upon satisfaction of a condition 546 such as the state of charge of the electrical energy storage means 16 being above the threshold fore-drive. In the charge-sustain fully-heated state 35 548, PHEV mode may be selected (Engine ON, E-drive ON), and the engine 10 may be controlled to generate electrical energy to maintain or increase the state of charge of the electrical energy storage means 16. Optionally, the condition 546 can include the following requirements: a11) as a10) above; u i i) ad u i u; above; c11) as c10) above; d11) state of charge of the electrical energy storage means 16 is greater than or equal to the threshold for e-drive (e.g., 20%). Although not shown, the control system 200 may be configured to switch between the charge-deplete fully-heated state 526 and the charge-sustain fully-heated state 548 in dependence on factors such as the state of charge or a manual user selection. One or both of the fully-heated state(s) 544, 548 can switch back to the initialised state 504 upon satisfaction of a condition 550 such as the vehicle 1 entering a non-driving mode, perhaps in response to a driver action (e.g., driver presses a ‘Start / Stop’ button, or driver opens a vehicle door). In summary, the state diagram described in FIG. 5 provides several advantages as identified above. An 30 06 25 e-drive use case is illustrated in Table 1 below, representing a drive cycle: Context: Vehicle off User enters vehicle User starts driving Userdemands engineactivation Normal user driving Emission control capability: 0% at 400 Celsius target 0% 10% 20% 50% Electric machine state: Off Ready Running Running Running State of charge: Above 80% Above 80% Above 80% Above 80% Above 80% Engine state: Off Off Off Activated, with de-rate and CSSRE Running, without derate or CSSRE Heating system state: Ready Running Running Running Off State in FIG. 5: 502 504 518 522 526 It is to be understood that the or each controller 201 can comprise a control unit or computational device having one or more electronic processors (e.g., a microprocessor, a microcontroller, an application specific integrated circuit (ASIC), etc.), and may comprise a single control unit or computational device, or alternatively different functions of the or each controller 201 may be embodied in, or hosted in, 19 30 06 25 uiiiciciii uuiiuui units or computational devices. As used herein, the term “controller,” “control unit,” or “computational device” will be understood to include a single controller, control unit, or computational device, and a plurality of controllers, control units, or computational devices collectively operating to provide the required control functionality. A set of instructions could be provided which, when executed, 5 cause the controller 201 to implement the control techniques described herein (including some or all of the functionality required for the method described herein). The set of instructions could be embedded in said one or more electronic processors of the controller 201; or alternatively, the set of instructions could be provided as software to be executed in the controller 201. A first controller or control unit may be implemented in software run on one or more processors. One or more other controllers or control 10 units may be implemented in software run on one or more processors, optionally the same one or more processors as the first controller or control unit. Other arrangements are also useful. In the example illustrated in FIG. 3, the or each controller 201 comprises at least one electronic processor 204 having one or more electrical input(s) 210 for receiving an input signal 211 indicative of 15 the emission control capability of the exhaust gas aftertreatment device 152, and one or more electrical output(s) 212 for outputting a control signal 213 in accordance with the determined warmup strategy which is based on the input signal. The or each controller 201 further comprises at least one memory device 206 electrically coupled to the at least one electronic processor 204 and having instructions 208 stored therein. The at least one electronic processor 204 is configured to access the at least one 20 memory device 206 and execute the instructions 208 thereon so as to determine the warmup management strategy in dependence on the input signal, wherein the determined warmup management strategy controls whether the internal combustion engine 10 is to be controlled in dependence on the input signal and whether the heating system 130 is to be controlled in dependence on the input signal. 25 The, or each, electronic processor 204 may comprise any suitable electronic processor (e.g., a microprocessor, a microcontroller, an ASIC, etc.) that is configured to execute electronic instructions. The, or each, electronic memory device 206 may comprise any suitable memory device and may store a variety of data, information, threshold value(s), lookup tables or other data structures, and / or instructions therein or thereon. In an embodiment, the memory device 206 has information and 30 instructions for software, firmware, programs, algorithms, scripts, applications, etc. stored therein or thereon that may govern all or part of the methodology described herein. The processor, or each, electronic processor 204 may access the memory device 206 and execute and / or use that or those instructions and information to carry out or perform some or all of the functionality and methodology describe herein. 35 The at least one memory device 206 may comprise a computer-readable storage medium (e.g. a non-transitory or non-transient storage medium) that may comprise any mechanism for storing information in a form readable by a machine or electronic processors / computational devices, including, without 30 06 25 ill I iiianui I. a 11 iciyi ietic storage medium (e.g. floppy diskette); optical storage medium (e.g. CD-ROM); magneto optical storage medium; read only memory (ROM); random access memory (RAM); erasable programmable memory (e.g. EPROM ad EEPROM); flash memory; or electrical or other types of medium for storing such information / instructions. 5 Example controllers 201 have been described comprising at least one electronic processor 204 configured to execute electronic instructions stored within at least one memory device 206, which when executed causes the electronic processor(s) 204 to carry out the method as hereinbefore described. However, it will be appreciated that embodiments of the present invention can be realised in any suitable 10 form of hardware, software or a combination of hardware and software. For example, it is contemplated that the present invention is not limited to being implemented by way of programmable processing devices, and that at least some of, and in some embodiments all of, the functionality and or method steps of the present invention may equally be implemented by way of non-programmable hardware, such as by way of non-programmable ASIC, Boolean logic circuitry, etc. 15 It will be appreciated that various changes and modifications can be made to the present invention without departing from the scope of the present application. The blocks illustrated in the FIG. 5 may represent steps in a method and / or sections of code in the 20 computer program 208. The illustration of a particular order to the blocks does not necessarily imply that there is a required or preferred order for the blocks and the order and arrangement of the block may be varied. Furthermore, it may be possible for some steps to be omitted. Although embodiments of the present invention have been described in the preceding paragraphs with 25 reference to various examples, it should be appreciated that modifications to the examples given can be made without departing from the scope of the invention as claimed. Features described in the preceding description may be used in combinations other than the combinations explicitly described. 30 Although functions have been described with reference to certain features, those functions may be performable by other features whether described or not. Although features have been described with reference to certain embodiments, those features may also 35 be present in other embodiments whether described or not.

Claims

30 06 251. A control system for managing exhaust emissions of a vehicle, the vehicle comprising an internal combustion engine, an exhaust gas aftertreatment device having an emission control capability5 dependent on a temperature of the exhaust gas aftertreatment device, the vehicle further comprising a heating system for raising a temperature of the exhaust gas aftertreatment device, wherein the control system comprises one or more controllers, the control system configured to:receive an input signal indicative of the emission control capability of the exhaust gas aftertreatment device;10 determine a warmup management strategy in dependence on the input signal, wherein thedetermined warmup management strategy controls whether the internal combustion engine is to be controlled in dependence on the input signal and whether the heating system is to be controlled in dependence on the input signal; andoutput at least one control signal in accordance with the determined warmup management15 strategy, wherein determining the warmup management strategy comprises selecting the warmup management strategy from a plurality of warmup management strategies, in dependence on the input signal, wherein the plurality of warmup management strategies include:a first warmup management strategy configured to control the heating system without controlling the internal combustion engine; and20 a second warmup management strategy configured to control at least the internal combustionengine,wherein controlling the internal combustion engine in accordance with the second warmup management strategy comprises controlling the internal combustion engine in a restricted output mode to restrict how much engine torque is demanded in response to a received torque request.

252. The control system of claim 1, wherein the first warmup management strategy is further configured to inhibit activation of the internal combustion engine in response to requested activation of the internal combustion engine, until a condition for switching to a different one of the plurality of warmup management strategies is satisfied.

303. The control system of claim 1 or 2, wherein the second warmup management strategy is configured to simultaneously control the heating system and the internal combustion engine.

4. The control system of any previous claim, wherein controlling the internal combustion engine35 in accordance with the second warmup management strategy comprises controlling the internal combustion engine to raise exhaust gas temperature via at least one of ignition timing retardation, fuel enleanment, or exhaust valve timing.30 06 255. The control system of any one of any previous claim, configured to select the first warmup management strategy in dependence on the emission control capability being less than a first target.5 6. The control system of claim 5, configured to select the second warmup management strategyin dependence on the emission control capability being greater than the first target and less than a second target.

7. The control system of claim 6, wherein once the emission control capability has reached a value 10 greater than the second target, the control system is configured to cease outputting the at least one control signal in accordance with the determined warmup management strategy, the determined warmup management strategy being the second warmup management strategy.

8. The control system of any preceding claim, wherein determining the warmup management 15 strategy is further dependent onon a hybrid vehicle operating mode of the vehicle; and / oran amount of requested torque.

9. The control system of any preceding claim, wherein the heating system comprises one or more 20 of a fuel burner or an electric heater.

10. The control system of any preceding claim, wherein the emission control capability indicates a proportion of catalytic material of the exhaust gas aftertreatment device which has reached an operating temperature.2511. A vehicle comprising the control system as claimed in any one of the preceding claims.

12. A method of managing exhaust emissions of a vehicle, the vehicle comprising an internalcombustion engine, an exhaust gas aftertreatment device having an emission control capability 30 dependent on a temperature of the exhaust gas aftertreatment device, the vehicle further comprising a heating system for raising a temperature of the exhaust gas aftertreatment device, the method comprising:receiving an input signal indicative of the emission control capability of the exhaust gas aftertreatment device;35 determining a warmup management strategy in dependence on the input signal, wherein thedetermined warmup management strategy controls whether the internal combustion engine is to be controlled in dependence on the input signal and whether the heating system is to be controlled in dependence on the input signal; andouipuuing at least one control signal in accordance with the determined warmup management strategy,wherein determining the warmup management strategy comprises selecting the warmup management strategy from a plurality of warmup management strategies, in dependence on the input5 signal, wherein the plurality of warmup management strategies include:a first warmup management strategy configured to control the heating system without controlling the internal combustion engine; anda second warmup management strategy configured to control at least the internal combustion engine,10 and wherein controlling the internal combustion engine in accordance with the second warmupmanagement strategy comprises controlling the internal combustion engine in a restricted output mode to restrict how much engine torque is demanded in response to a received torque request.

13. Computer software that, when executed, is arranged to perform a method according to claim15 12.30 06 25

Images