GB2579356A

GB2579356A - Engine monitoring method and apparatus

Info

Publication number: GB2579356A
Application number: GB1819333.4A
Authority: GB
Inventors: Howard Summers David; Buckingham Richard; Anderson James; McCorrie James; Kennedy Tim
Original assignee: Jaguar Land Rover Ltd
Current assignee: Jaguar Land Rover Ltd
Priority date: 2018-11-28
Filing date: 2018-11-28
Publication date: 2020-06-24
Anticipated expiration: 2038-11-28
Also published as: DE102019129454A1; GB201819333D0; GB2579356B

Abstract

Monitoring an internal combustion engine (7, fig.1) in a hybrid vehicle powertrain, the powertrain including an electric propulsion unit (8, fig.1) and the internal combustion engine, comprises receiving a torque request. A first monitoring phase is implemented comprising controlling the internal combustion engine to provide a first operating condition and monitoring a first group G-1 of engine systems. The electric propulsion unit is controlled such that the total torque generated by the internal combustion engine and the electric propulsion unit at least substantially match the torque request. The first monitoring phase may control the engine to maintain the first operating condition, which may be a first engine set-point or operating range. The first group may comprise a plurality of engine systems which are monitored consecutively or concurrently. A second monitoring phase may be implemented to monitor a second group G-2 of engine systems under a second operating condition.

Description

ENGINE MONITORING METHOD AND APPARATUS

TECHNICAL FIELD

The present disclosure relates to an engine monitoring method and apparatus. Aspects of the invention relate to a method of monitoring an internal combustion engine, to a non-transitory computer-readable medium, to a controller and to a vehicle.

BACKGROUND

The regulatory authorities around the world require the implementation of an On-Board Diagnostic (OBD) system for vehicles that are fitted with an Internal Combustion Engine (ICE). The OBD system is comprised of various monitors, some which operate continuously and some which operate non-continuously. The non-continuous monitors are characterised by a set of parameters that define a window of operation (WOO). The window of operation parameters define the prevailing operating conditions under which the monitor may operate.

The parameters may define a window of operation with reference to one or more of the following: minimum engine speed, maximum engine speed, minimum atmospheric pressure, maximum rate-of-change of air mass flow, etc. Many of the monitors that operate non-continuously must meet In-Use Monitor Performance Ratio (IUMPR) requirements. The IUMPR requirements specify a minimum ratio of monitor operation sufficient to detect a failure during a journey over the number of vehicle journeys meeting the minimum journey standard (engine operation time, minimum vehicle speed plus other characteristics). In practice, the IUMPR can vary by a large amount from vehicle to vehicle due to the influence the driver's behaviour (i.e. how the driver operates the vehicle) has on the monitor window of operation parameters.

The IUMPR requirements for hybridised vehicles are applicable to a minimum journey standard being met with just ten (10) seconds of operation of an internal combustion engine, a significant reduction compared to non-hybridised vehicles. This reduces the windows of operation during which the required monitors may be implemented. Some monitors require longer than ten (10) seconds of operation and some monitors must run in isolation of other monitors. Accordingly, there is a greater risk of not meeting the minimum IUMPR standard on a hybrid vehicle than for a vehicle powered solely by an internal combustion engine.

One solution to the above problem would be to continue operation of the internal combustion engine until all the monitors have had sufficient operation to detect a failure. However, this approach would extend operation of the internal combustion engine.

It is an aim of the present invention to address one or more of the disadvantages associated with the prior art.

SUMMARY OF THE INVENTION

Aspects of the present invention relate to a method of monitoring an internal combustion engine, to a non-transitory computer-readable medium, to a controller and to a vehicle as claimed in the appended claims.

According to a further aspect of the present invention there is provided a method of monitoring an internal combustion engine in a hybrid vehicle powertrain, the hybrid vehicle powertrain comprising an electric propulsion unit and the internal combustion engine. The method comprises receiving a torque request and implementing a first monitoring phase. The first monitoring phase may comprise controlling the internal combustion engine to provide a first operating condition and monitoring a first group of engine systems under the first operating condition. The electric propulsion unit may be controlled such that a total torque generated by the internal combustion engine and the electric propulsion unit at least substantially matches the torque request received during the first monitoring phase. The electric propulsion unit may be controlled to ensure that the combined torque output by the internal combustion engine and the electric propulsion unit at least substantially matches the torque request. At least in certain embodiments, this method makes use of the characteristic of a hybrid vehicle powertrain that allows the energy balance between the internal combustion and the electric propulsion unit propulsion unit to vary, thereby allowing the operation point of the internal combustion to be controlled to provide conditions suitable for monitoring the internal combustion engine while ensuring that the total torque at least substantially matches the received torque request. Other characteristics of a hybridised vehicle powertrain such as engine stop on-the-move (glide) may be altered or suspended during the monitoring phases.

The method may comprise controlling the internal combustion engine to generate the first operating condition. The method may comprise implementing the first monitoring phase when the internal combustion engine is operating under the first operating condition. Alternatively, the method may comprise monitoring the torque request and implementing the first monitoring phase when the torque request is within a first predetermined torque range. The determination that the torque request is within the first predetermined torque range may provide an entry condition for performance of the first monitoring phase. The first predetermined torque range may provide the first operating condition appropriate for performance of the first monitoring phase. The first group of engine systems may be monitored during the first monitoring phase while the internal combustion engine is operating under said first operating condition.

The method may comprise defining one or more groups of the engine systems to be monitored. The engine systems may be grouped according to their respective windows of operation parameters. One or more engine systems having similar or equivalent windows of operation parameters may be allocated to the same group. One or more engine systems having different windows of operation parameters may be allocated to different groups. The groups may be predefined or may be determined dynamically. A set of operating conditions for the internal combustion engine may be assigned for each group. The internal combustion engine and the electric propulsion unit may be balanced to maintain operation of the internal combustion engine substantially equal to the defined operating conditions.

The torque request may comprise a torque set-point. The torque request may be generated by a control system, for example a cruise control or adaptive cruise control system; or a driver of the vehicle.

The method may be initiated following activation of the internal combustion engine. If there is a demand for operation of the internal combustion engine during a journey, the internal combustion engine is activated. The first operating condition may be set and maintained until either all of the monitors in the first group have had a period of operation sufficient to detect a failure or a first time-out period is reached. Alternatively, or in addition, the first monitoring phase may be terminated if the torque request is outside a predefined torque range for performance of the first monitoring phase. This process may be performed in respect of each group. The operation of the internal combustion engine may then be released back to deliver torque under normal operating conditions.

The electric propulsion unit may comprise one or more electric traction motor.

The first group of engine systems may comprise one or more engine systems to be monitored under the first operating condition.

The first monitoring phase may comprise controlling the internal combustion engine to maintain the first operating condition.

The first group may comprise one or more engine systems. The first group may optionally be predefined.

The first operating condition may comprise a first engine set-point or a first engine operating range. The first operating condition may comprise a first target engine set-point or a first target engine operating range. The first target engine operating range may, for example, comprise a first upper engine operating range and/or a first lower engine operating range.

The control of the electric propulsion unit may comprise generating a regenerative torque or a propulsive torque.

The first group may comprise a plurality of engine systems. The engine systems in the first group may be monitored consecutively or concurrently during the first monitoring phase. The concurrent monitoring of the engine systems may comprise monitoring two or more engine systems in parallel. The consecutive monitoring of the engine systems may comprise monitoring two or more engine systems sequentially (i.e. one after the other). It will be understood that some monitors may require operation in isolation (i.e. independently of other monitors). Thus, some of the engine systems in the first group may be monitored consecutively, while others may be monitored concurrently.

The first monitoring phase may be concluded upon completion of the monitoring of the first group of engine systems. A second monitoring phase may be initiated upon conclusion of the first monitoring phase.

The first monitoring phase may be interrupted if the monitoring of the first group of engine systems is not completed within a predetermined first time-out period. Alternatively, or in addition, the first monitoring phase may be interrupted if the monitoring of the torque request is outside a predefined range, for example if the torque request increases above a predefined upper torque threshold and/or decreases below a predefined lower torque.

The method may comprise re-scheduling the first monitoring phase if the monitoring of the engine systems is interrupted or is not completed. If the first monitoring phase is interrupted, the method may comprise continuing to seek to identify opportunities to complete monitoring of the first engine system. Monitoring may be performed independently of the first monitoring phase.

The first monitoring phase may be implemented upon identification of the first operating condition.

The method may comprise implementing a second monitoring phase comprising controlling the internal combustion engine to provide a second operating condition and monitoring a second group of engine systems under the second operating condition. The method may comprise controlling the electric propulsion unit such that the total torque generated by the internal combustion engine and the electric propulsion unit at least substantially matches a torque request received during the second monitoring phase. The second group of engine systems may be monitored during the second monitoring phase while the internal combustion engine is operating under the second operating condition.

The method may comprise controlling the internal combustion engine to generate the second operating condition. The method may comprise implementing the second monitoring phase when the internal combustion engine is operating under the second operating condition. Alternatively, the method may comprise monitoring the torque request and implementing the second monitoring phase when the torque request is within a second predetermined torque range. The determination that the torque request is within the second predetermined torque range may provide an entry condition for performance of the second monitoring phase. The second predetermined torque range may provide the second operating condition appropriate for performance of the second monitoring phase.

The method may comprise monitoring the torque request and implementing the second monitoring phase when the torque request is within a second predetermined torque range.

The second monitoring phase may comprise controlling the internal combustion engine to maintain the second operating condition.

The second operating condition may comprise a second engine set-point or a second engine operating range. The second target engine operating range may, for example, comprise a second upper engine operating range and/or a second lower engine operating range.

The second group may comprise a plurality of engine systems. The engine systems in the second group may be monitored consecutively or concurrently during the second monitoring phase. The concurrent monitoring of the engine systems may comprise monitoring two or more engine systems in parallel. The consecutive monitoring of the engine systems may comprise monitoring two or more engine systems sequentially (i.e. one after the other). It will be understood that some monitors may require operation in isolation (i.e. independently of other monitors). Thus, some of the engine systems in the second group may be monitored consecutively, while others may be monitored concurrently.

According to a further aspect of the present invention there is provided a non-transitory computer-readable medium having a set of instructions stored therein which, when executed, cause a processor to perform the method claimed in any one of the preceding claims.

According to a still further aspect of the present invention there is provided a controller for controlling an internal combustion engine and an electric propulsion unit in a hybrid vehicle powertrain. The controller comprises a processor. The processor may be configured to receive a torque request. The processor may generate a first engine control signal to set a first operating condition of the internal combustion engine. The processor may monitor a first group of engine systems under the first operating condition. Optionally, the processor may be configured to generate a motor control signal to control the electric propulsion unit such that a total torque generated by the internal combustion engine and the electric propulsion unit is at least substantially equal to the torque request received during the first monitoring phase.

The first group of engine systems may comprise one or more engine systems to be monitored under the first operating condition. Alternatively, or in addition, the second group of engine systems may comprise one or more engine systems to be monitored under the second operating condition.

The processor may be configured to control the internal combustion engine to generate the first operating condition and then to implement the first monitoring phase. Alternatively, or in addition, the processor may be configured to monitor the torque request and to implement the first monitoring phase when the torque request is within a first predetermined torque range.

The processor may be configured to control the internal combustion engine to maintain the first operating condition throughout the first monitoring phase.

The first group may comprise one or more engine systems.

The first operating condition may comprise a first engine set-point or a first engine operating 35 range.

The motor control signal may be generated in dependence on a torque request signal. The motor control signal may control the electric propulsion unit to generate a regenerative torque or a propulsive torque.

The first group may comprise a plurality of engine systems. The processor may be configured to monitor the engine systems in the first group consecutively or concurrently during the first monitoring phase.

The processor may be configured to generate a second engine control signal to set a second operating condition of the internal combustion engine and to monitor a second group of engine systems under the second operating condition. The motor control signal may control the electric propulsion unit such that the total torque generated by the internal combustion engine and the electric propulsion unit is at least substantially equal to the torque request received during the second monitoring phase.

The processor may be configured to control the internal combustion engine to generate a second operating condition and then to implement a second monitoring phase. Alternatively, or in addition, the processor may be configured to monitor the torque request and to implement the second monitoring phase when the torque request is within a second predetermined torque range.

The processor may be configured to control the internal combustion engine to maintain the second operating condition throughout the second monitoring phase.

The second operating condition may comprise a second engine set-point or a second engine operating range.

The second group may comprise a plurality of engine systems. The processor may be configured to monitor the engine systems in the second group consecutively or concurrently during the second monitoring phase.

The processor may be configured to conclude the first monitoring phase upon completion of the monitoring of the first group of engine systems.

The processor may be configured to interrupt the first monitoring phase if the monitoring of the first group of engine systems is not completed within a predetermined first time-out period. Alternatively, or in addition, the first monitoring phase may be terminated if the torque request is outside a predefined torque range for performance of the first monitoring phase.

The processor may be configured to conclude the second monitoring phase upon completion of the monitoring of the second group of engine systems.

The processor may be configured to interrupt the second monitoring phase if the monitoring of the second group of engine systems is not completed within a predetermined second time-out period. Alternatively, or in addition, the second monitoring phase may be terminated if the torque request is outside a predefined torque range for performance of the second monitoring phase.

The second monitoring phase may be initiated upon conclusion of the first monitoring phase.

The processor may be configured to control the internal combustion engine to generate the first operating condition and then to implement the first monitoring phase.

The processor may be configured to control the internal combustion engine to generate the second operating condition and then to implement the second monitoring phase.

According to a further aspect of the present invention there is provided a vehicle comprising a controller as described herein.

Any control unit or controller described herein may suitably comprise a computational device having one or more electronic processors. The system may comprise a single control unit or electronic controller or alternatively different functions of the controller may be embodied in, or hosted in, different control units or controllers. As used herein the term "controller" or "control unit" will be understood to include both a single control unit or controller and a plurality of control units or controllers collectively operating to provide any stated control functionality. To configure a controller or control unit, a suitable set of instructions may be provided which, when executed, cause said control unit or computational device to implement the control techniques specified herein. The set of instructions may suitably be embedded in said one or more electronic processors. Alternatively, the set of instructions may be provided as software saved on one or more memory associated with said controller to be executed on said computational device. The control unit or controller may be implemented in software run on one or more processors. One or more other control unit or controller may be implemented in software run on one or more processors, optionally the same one or more processors as the first controller. Other suitable arrangements may also be used.

Within the scope of this application it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and/or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. That is, all embodiments and/or features of any embodiment can be combined in any way and/or combination, unless such features are incompatible. The applicant reserves the right to change any originally filed claim or file any new claim accordingly, including the right to amend any originally filed claim to depend from and/or incorporate any feature of any other claim although not originally claimed in that manner.

BRIEF DESCRIPTION OF THE DRAWINGS

One or more embodiments of the present invention will now be described, by way of example only, with reference to the accompanying figures, in which: Figure 1 shows a schematic representation of a vehicle having a controller for controlling a hybrid powertrain in accordance with an embodiment of the present invention; Figure 2 shows a schematic representation of the controller shown in Figure 1; Figure 3 shows a chart representing torque generated by the hybrid powertrain while monitoring operation of an internal combustion engine; Figure 4 shows a block diagram representing operation of the controller according to the present embodiment; and Figure 5 shows a block diagram representing operation of the controller according to a further embodiment of the present invention.

DETAILED DESCRIPTION

A controller 1 in accordance with an embodiment of the present invention will now be described with reference to the accompanying figures. The controller 1 is provided in a vehicle 2 which in the present embodiment is an automobile. It will be understood that the controller 1 may be used in other types of vehicle. As described herein, the controller 1 is configured to control vehicle systems to improve determination of an In-Use Monitor Performance Ratio (IUMPR).

As illustrated in Figures 1 and 2, the vehicle 2 comprises four (4) wheels W1-4 and a vehicle body 4. The wheels W1-4 are provided on front and rear axles 5, 6. The first wheel W1 is a front left wheel; the second wheel W2 is a front right wheel; the third wheel W3 is a rear left wheel; and the fourth wheel W4 is a rear right wheel. The vehicle 2 is a hybrid electric vehicle (HEV) having a hybrid drivetrain comprising an internal combustion engine 7 and an electric propulsion unit 8. The electric propulsion unit 8 may comprise or consist of one or more electric traction motor. The vehicle comprises a traction battery 9 and an inverter 10 for controlling the electric propulsion unit 8. The internal combustion engine 7 is connected to an exhaust system 11 (shown in dashed lines in Figure 1) for processing exhaust gases emitted from the internal combustion engine 7. The exhaust system 11 comprises at least one catalyst 12 and at least one oxygen sensor 13 for measuring an oxygen content of the exhaust gases. The internal combustion engine 7 and the electric propulsion unit 8 are operable selectively to generate a torque to propel the vehicle (referred to herein as a positive torque); and a torque to retard the vehicle (referred to herein as a negative torque). The electric propulsion unit 8 can, for example, generate negative torque whilst operating as a generator, for example to perform regenerative vehicle braking to generate electrical energy for charging the traction battery 9. The internal combustion engine 7 is drivingly connected to the front axle 5 for transmitting a torque to the first and second wheels W1, W2. The electric propulsion unit 8 is drivingly connected to the rear axle 6 for transmitting a torque to the third and fourth wheels W3, W4. In alternative implementations, the internal combustion engine 7 and the electric propulsion unit 8 may be drivingly connected to the same axle, i.e. both connected to either the front axle 5 or the rear axle 6.

As described herein, the internal combustion engine 7 and the electric propulsion unit 8 are controllable independently of each other. One or both of the internal combustion engine 7 and the electric propulsion unit 8 may be controlled to generate a torque at least substantially equal to a torque request TQR. A drivetrain control unit 14 is provided for controlling operation of the internal combustion engine 7 and the electric propulsion unit 8 to generate a combined torque at least substantially equal to the torque request TQR. The torque request TQR may be generated by a driver (not shown) of the vehicle 2, for example in dependence on a position of an accelerator pedal (not shown). Alternatively, or in addition, the torque request may be generated by a vehicle controller, for example to implement a cruise control (or adaptive cruise control) function.

The drivetrain control unit 14 is operable to determine one or more of the following operating parameters: a vehicle altitude ALT; a vehicle speed VREF; an engine speed (rpm) ES; an engine load (%) EL; a temperature (°C) T2 of the catalyst 12; a temperature (°C) T3 of the oxygen sensor 13; an exhaust mass flow (kg/h) EMF; and a change (A) in the exhaust mass flow (g/h) AEMF. The operating parameters of the vehicle 2 and the internal combustion engine 7 may be measured or modelled. The catalyst temperature T2 may be modelled in dependence on engine operating parameters; or may be measured by a catalyst temperature sensor (not shown). The oxygen sensor temperature T3 may be modelled in dependence on engine operating parameters; or may be measured by a temperature sensor (not shown). The vehicle altitude ALT and/or the vehicle speed VREF may be measured by one or more on-board sensor; or may be determined indirectly with reference to a navigation system.

The vehicle 2 comprises on-board diagnostic (OBD) system (denoted generally by the reference numeral 15) configured to monitor operation of the internal combustion engine 7.

The OBD system 16 comprises an OBD controller 16 having a processor 17 and a memory 18. As shown in Figure 1, the OBD controller 16 in the present embodiment is discrete from the drivetrain control unit 14. The OBD controller 16 communicates with the drivetrain control unit 14 either directly or over a communication bus (not shown). In a variant, the OBD controller 16 could be incorporated into the drivetrain control unit 11.

With reference to Figure 2, the OBD system 15 is configured to implement a plurality of monitors (denoted by the reference numeral 17-n). In the present embodiment, the OBD system 15 is configured to implement a purge flow monitor 17-1; a catalyst monitor 17-2; an oxygen sensor response monitor 17-3; and a cylinder air-fuel ratio (AFR) imbalance monitor 17-4. The monitors 17-n can only be implemented when the operating parameter(s) of the vehicle 2 and/or the internal combustion engine 7 are within a corresponding window of operation (WOO). The windows of operation define the required operating conditions for performance of the associated monitor 17-n to comply with the In-Use Monitor Performance Ratio (IUMPR) reporting requirement. Different windows of operation may be defined for different monitors 17-n. A window of operation may be predefined for each of the monitors 17-n. The OBD system 15 communicates with the drivetrain control unit 14 to determine when the operating parameters of the vehicle 2 and the internal combustion engine 7 are within the predefined window of operation. Each window of operation may define an upper limit, a lower limit or a range of each operating condition. The operating condition(s) defined in respect of each window of operation should be maintained for a predetermined time period to enable completion of each respective monitor 17-n.

The window of operation defined for performance of the purge flow monitor 17-1 comprises: the vehicle altitude ALT, the vehicle speed VREF and the engine load EL. The catalyst monitor 17-2, the oxygen sensor response monitor 17-3; and the cylinder air-fuel ratio (AFR) imbalance monitor 17-4 each comprise: the catalyst temperature T2, the oxygen sensor temperature T3, the engine speed ES, the engine load EL, the exhaust mass flow EMF, and the change in the exhaust mass flow AEMF. In accordance with an aspect of the present invention, the OBD system 15 is configured to group the monitors 17-n having windows of operation which at least partially overlap with each other. The monitors 17-n having windows of operation which overlap with each other (either a partial, significant or complete overlap) may be grouped together in one or more groups G-n. The one or more monitor 17-n in each monitor group G-n is then implemented as a batch, either concurrently or consecutively (i.e. sequentially), in a corresponding monitoring phase. A time-out period is defined for completion of each monitoring phase. The time-out period for each monitoring phase is set as the time taken to complete each monitor 17-n in the corresponding monitor group G-n under ideal conditions plus a predetermined margin to allow for non-ideal conditions. In the present embodiment, if the monitoring phase is not completed within the predefined time-out period, the OBD system 15 terminates the current monitoring phase and progresses to the next monitoring phase. In a variant, the time-out periods could be dynamic, for example to increase or decrease the time allocated for each monitoring phase depending on progress.

The OBD system 15 may be configured to implement the groups G-n in a predetermined sequence, for example following start-up of the internal combustion engine 7. In a variant, the OBD system 15 could be configured to implement the groups G-n in a dynamic sequence, for example in dependence on determined operating conditions of the vehicle 2 and/or the internal combustion engine 7.

A summary of the windows of operation defined for the purge flow monitor 17-1, the catalyst monitor 17-2, the oxygen sensor response monitor 17-3; and the cylinder air-fuel ratio (AFR) imbalance monitor 17-4 are provided below.

Purge Flow Monitor Operating window equates to torque c 70nm Catalyst Monitor Operating window equates to torque in the range 80nm to 350nm Oxygen Sensor Response Monitor Operating window equates to torque in the range 80nm to 350nm Cylinder AFR Imbalance Monitor Operating window equates to torque in the range 100nm to 420nm In the present embodiment, the OBD system 15 defines a first monitor group G-1 comprising (or consisting of) the purge flow monitor 17-1. A first monitoring phase having a first time-out period of 40 seconds and a torque set-point of 50nm is defined for completion of the first monitor group G-1. The OBD system 15 defines a second monitor group G-2 comprising (or consisting of) the catalyst monitor 17-2, the oxygen sensor response monitor 17-3; and the cylinder air-fuel ratio (AFR) imbalance monitor 17-4. A second monitoring phase having a second time-out period of 120 seconds and a torque set-point of 120nm is defined for completion of the second monitor group G-2. The first and second time-out periods are fixed in the present embodiment. In a variant, the time-out periods may be modified dynamically, for example to ensure completion of all of the monitors 17-n making up an associated monitor group G-n.

The OBD system 15 allocates an engine operation point for the internal combustion engine 7 for each monitor group G-n. In the present embodiment, the engine operation point comprises an engine torque. The use of the engine torque as the engine operation point is appropriate if, for example, the internal combustion engine 7 is connected directly to the vehicle driveline. Alternatively, or in addition, the engine operation point may comprise the engine speed ES and/or the engine load EL. This may be appropriate if, for example, the internal combustion engine 7 is not connected directly to the driveline.

The OBD system 15 defines a target engine (set-point) torque TQE-n for each monitor group G-n. The target engine torque TQE-n sets a target operating torque for the internal combustion engine 7 to enable implementation of each of the monitors 17-n in that monitor group G-n. The drivetrain control unit 14 is configured to control the internal combustion engine 7 to output the target engine torque TQE-n while the OBD system 15 implements the monitors 17-n in that monitor group G-n. The target engine torque TOE-n is defined to fall within an intersection of the windows of operation for the monitors 17-n in each monitor group G-n. At least in certain embodiments, the target engine torque TQE-n may be defined at or proximal to a middle of the intersection of the windows of operation for the monitors 17-n in that monitor group G-n. The target engine torque TQE-n may be determined in dependence on the engine speed and engine load conditions applicable within each of the monitors 17-n. For example, the target engine torque TQE-n may be determined for steady-state vehicle operation on a flat surface with the vehicle transmission in drive. In the present embodiment, a first target engine torque TQE-1 is defined for the first monitor group G-n; and a second target engine torque TQE-2 is defined for the second monitor group G-n. The first and second target engine torques TOE-1, TQE-2 are different from each other. The drivetrain control unit 14 is configured to control the electric propulsion unit 8 to generate a corresponding target electric motor torque TQM-n to satisfy a current torque request TQR.

The operation of the OBD system 15 will now be described with reference to a first chart 100 shown in Figure 3. The first chart 100 provides a graphical representation of the requested torque with respect to time (t) for a journey undertaken by the vehicle 2. A first profile TP1 represents the torque request TQR. A second profile TP2 represents the target engine torque TQE-n for the internal combustion engine 7; and a third profile TP3 represents the target electric motor torque TOM-n for the electric propulsion unit 8. As described herein, the drivetrain control unit 14 controls the internal combustion engine 7 and the electric propulsion unit 8 such that the sum of the target engine torque TQE-n and the target electric motor torque TOM-n is at least substantially equal to the torque request TQR.

The OBD system 15 is configured to implement the monitors 17-n to meet the In-Use Monitor Performance Ratio (IUMPR) reporting requirement. As described herein, the monitors 17-n are performed in the predefined monitor groups G-n. The first monitor group G-1 is performed in a first time period (t1 to t2); and the second monitor group G-2 is performed in a second time period (t2 to t3). It will be understood that one or more additional monitor group G-n may be implemented. The time period for implementation of each monitor group G-n is predefined. The target engine torque TQE-n is controlled to enable implementation of the one or more monitor 17-n in each monitor group G-n. In particular, the drivetrain control unit 14 controls the internal combustion engine 7 to generate torque at least substantially equal to the target engine torque TQE-n defined for the current monitor group G-n. The drivetrain control unit 14 controls the electric propulsion unit 8 to generate a complementary torque to ensure that the total output torque is at least substantially equal to the torque request TQR. In particular, the drivetrain control unit 14 controls the electric propulsion unit 8 to generate the target electric motor torque TQM-n. The target electric motor torque TOM-n being determined by subtracting the target engine torque TQE-n from the torque request TQR. In use, the target engine torque TQE-n and the electric motor torque TOM-n combined are at least substantially equal to the torque request TQR. It will be understood that the electric motor torque TQM-n may be positive or negative to satisfy the torque request TQR.

The OBD system 15 is activated after expiry of an engine start and system stabilisation period (t0 to t1). To implement the purge flow monitor 17-1 (which makes up the first monitor group G-1), the internal combustion engine 7 is controlled to achieve the first engine set point defined for the first monitoring phase (t1 to t2). In the present embodiment, the first engine set point corresponds to the first target engine torque TOE-1. The torque generated by the internal combustion engine 7 is maintained at least substantially equal to the first target engine torque TQE-1 while the OBC system 15 implements the purge flow monitor 171. During the first monitoring phase (t1 to t2), the target electric motor torque TQM-n is set in dependence on a received torque request TQR. The target electric motor torque TQM-n is controlled such that the combined torque generated by the internal combustion engine 7 and the electric propulsion unit 8 is at least substantially equal to the torque request TQR. Thus, even if the torque request TQR changes during the first monitoring phase (t1 to t2), the total torque is at least substantially equal to the torque request TQR. The first target engine torque TQE-1 is maintained until expiry of the first monitoring phase (t2).

The internal combustion engine 7 is then controlled to achieve the second engine set point defined for the second monitoring phase (t2 to t3). In the present embodiment, the second engine set point corresponds to the second target engine torque TQE-2. The torque generated by the internal combustion engine 7 is maintained at least substantially equal to the second target engine torque TQE-2 while the OBD system 15 implements the catalyst monitor 17-2, the oxygen sensor response monitor 17-3, and the cylinder air-fuel ratio (AFR) imbalance monitor 17-4. During the second monitoring phase (t2 to t3), the electric motor torque TOM-n is controlled in dependence on a received torque request TOR. The electric motor torque TQM-n is controlled such that the combined torque generated by the internal combustion engine 7 and the electric propulsion unit 8 is at least substantially equal to the torque request TQR. Thus, even if the torque request TQR changes during the second monitoring phase (t2 to t3), the total torque is at least substantially equal to the torque request TQR. As shown in Figure 3, the torque request TQR decreases during the second monitoring phase (t2 to t3) to a value less than the second target engine torque TQE-2. In order to maintain the combined torque of the internal combustion engine 7 and the electric propulsion unit 8 at least substantially equal to the torque request TQR, the drivetrain control unit 14 sets a negative (-ve) electric motor torque TQM-n such that regenerative braking is performed. The second target engine torque TQE-2 is maintained until expiry of the second monitoring phase (t3). This process is repeated for each monitor group G-n. In the illustrated example, during a subsequent monitoring phase (tn-1 to tn), a negative (-ve) electric motor torque TQM-n is maintained for the duration of the monitoring phase to ensure that the torque request TQR is satisfied. In the illustrated example, the torque request TQR may be satisfied exclusively by the electric propulsion unit 8 and the internal combustion engine 7 may be deactivated when the second monitoring phase is complete (at t3).

A first block diagram 200 representing operation of the OBD system 15 is shown in Figure 4. The process begins when the internal combustion engine 7 is started (BLOCK 205). A system stabilisation is performed (BLOCK 210), for example comprising catalyst heating and closed-loop fuelling control activation. A group counter (n) for the OBD system 15 is set as equal to one (n=1) (BLOCK 215). An engine set-point for the current monitor group G-n is activated and a group timer started (BLOCK 220). A check is performed to determine if all monitors 17-n in the current monitor group G-n have been implemented. In the present embodiment, an OBD numerator increments a counter associated with each monitor 17-n when it is completed. The check subsequently determines whether each monitor 17-n in the current monitor group G-n has been incremented by the OBD numerator (BLOCK 225). If the monitors 17-n have all been incremented, a check is performed to determine if there is another group G-n in the OBD process (BLOCK 230). If the monitors 17-n in the monitor group G-n have not all been incremented, a check is performed to determine if the group timer is less than the time-out period defined for the current monitoring phase (BLOCK 235).

If the group timer is less than the time-out period defined in respect of the current monitoring phase, the group timer is incremented (BLOCK 240), and the check repeated to determine if all monitors 17-n in the monitor group G-n have been incremented by the OBD numerator (BLOCK 225). If the group timer is not less than the time-out period defined in respect of the current monitoring phase, a check is performed to determine if there is another group G-n in the OBD process (BLOCK 235). If there are remaining groups G-n, a group counter (n) is incremented (BLOCK 245), and the process repeated for the next monitor group (BLOCK 220). If the check determines that there are no remaining groups G-n (BLOCK 235), the process is terminated (BLOCK 250). The drivetrain control unit 14 can continue to control the internal combustion engine 7 and/or the electric propulsion unit 8 in dependence on the torque request TQR.

In use, the OBD system 15 activates a monitoring phase and sets a target torque set-point for the internal combustion engine 7 which is appropriate for implementation of one or more monitors 17-n associated with that monitoring phase. The electric propulsion unit 8 is controlled to ensure that the torque request TQR is satisfied while the monitors 17-n are implemented. The internal combustion engine 7 may be maintained at the target set point, thereby increasing the likelihood of the monitors 17-n being completed. By forming one or more monitor groups G-n comprising at least one monitor 17-n which require common or overlapping operating parameters, the monitors 17-n may be completed during a shorter operating window of the internal combustion engine 7.

The OBD system 15 is described above as defining a discrete value for the target engine torque request TQE-n. In a variant, the OBD system 15 may define a target engine torque range. For example, the target engine torque request TQE-n may comprise an upper torque limit and/or a lower torque limit. In this arrangement, the target engine torque TQE-n may set a target operating torque range for the internal combustion engine 7 to enable implementation of each of the monitors 17-n in that monitor group G-n. The drivetrain control unit 14 controls the internal combustion engine 7 to operate within the defined target engine torque range while the OBD system 15 implements the monitors 17-n in that monitor group G-n. The target engine torque range may, for example, comprise an intersection of the windows of operation for the monitors 17-n in each monitor group G-n. The first target engine torque TQE-1 may define a first engine torque range for the first monitor group G-1; and the second target engine torque TQE-2 may define a second engine torque range for the second monitor group G-2. The first and second target engine torque ranges in this example may be different from each other. The drivetrain control unit 14 is configured to control the electric propulsion unit 8 to generate a corresponding target electric motor torque TQM-n to satisfy a current torque request TOR. This approach may allow improved integration with other engine control strategies, for example to enable engine stop while the vehicle is on-the-move (a vehicle "glide" function) and/or to disable engine eco-stop functionality within a monitoring phase. The torque request TQR generated in response to a driver-demand will determine which phase is acted upon. If the torque request TQR is substantially different from the conditions demanded for a current monitoring phase, then that monitoring phase will not be serviced.

A further embodiment of the present invention will now be described with reference to a second block diagram 300 illustrated in Figure 5. Like reference numerals are used for like components.

The OBD system 15 according to the present embodiment seeks to determine when a torque request, for example generated by a driver of the vehicle or an on-board vehicle system, is appropriate to perform a monitoring operation. The OBD system 15 may select one of a plurality of monitor groups G-n in dependence on the torque request. For example, the OBD system 15 may select and perform a monitor group G-n having a torque operating set-point or a torque operating window which is coincident with the current torque request. The torque operating window may, for example, define an upper torque limit and/or a lower torque limit.

A second block diagram 300 representing operation of the OBD system 15 is shown in Figure 5. The process begins when the internal combustion engine 7 is started (BLOCK 305). A system stabilisation is performed (BLOCK 310), for example comprising catalyst heating and closed-loop fuelling control activation. The OBD system 15 monitors the torque request, for example by interrogating a network bus on the vehicle 2. The OBD system 15 performs a check to determine if the torque request is coincident within an engine set-point requirement of one of the plurality of monitor groups G-n (BLOCK 315). If one of the plurality of monitor groups G-n is identified, a check is performed to determine if all of the monitors 17-n within the identified group G-n have been completed (BLOCK 320). In the present embodiment, an IMUPR counter is incremented when a monitor 17-n is completed, thereby signalling that the monitor 17-n has been performed. The IMUPR counter is accessed to determine which monitors 17-n within the identified group G-n have been completed. If all the monitors 17-n have been completed, the OBD system 15 proceeds without setting a target engine torque (BLOCK 325). If the OBD system 15 determines that the torque request is coincident within an engine set-point requirement of one of the plurality of monitor groups G-n (BLOCK 315), the OBD system 15 sets the target engine torque for the identified monitor group G-n (BLOCK 345). The monitors 17-n in the identified monitor group G-n are then performed. The monitors 17-n in the first group (G-1) may be performed consecutively or concurrently. The OBD system 15 performs a check to determine if a predefined time limit for completion of the monitor process has elapsed (BLOCK 330). If the predefined time limit has elapsed, the OBD system 15 proceeds without setting the target engine torque (BLOCK 335). The process then ends (BLOCK 340). If the predefined time limit has not expired, the OBD system 15 continues to monitor the torque request to determine when the torque request is coincident with an engine set-point requirement of one of the plurality of monitor groups G-n (BLOCK 315). The process then continues to determine if all of the monitors 17-n within the identified group G-n have been completed (BLOCK 320).

It will be appreciated that various modifications may be made to the embodiment(s) described herein without departing from the scope of the appended claims.

Claims

CLAIMS: 1. A method of monitoring an internal combustion engine in a hybrid vehicle powertrain, the hybrid vehicle powertrain comprising an electric propulsion unit and the internal combustion engine; the method comprising: receiving a torque request; implementing a first monitoring phase comprising controlling the internal combustion engine to provide a first operating condition and monitoring a first group of engine systems under the first operating condition; and controlling the electric propulsion unit such that a total torque generated by the internal combustion engine and the electric propulsion unit at least substantially matches the torque request received during the first monitoring phase.
2. A method as claimed in claim 1, comprising monitoring the torque request and implementing the first monitoring phase when the torque request is within a first predetermined torque range.
3. A method as claimed in claim 1 or claim 2, wherein the first monitoring phase comprises controlling the internal combustion engine to maintain the first operating condition.
4. A method as claimed in any one of the preceding claims, wherein the first operating condition comprises a first engine set-point or a first engine operating range.
5. A method as claimed in any one of the preceding claims, wherein the first group comprises a plurality of engine systems, the engine systems in the first group being monitored consecutively or concurrently during the first monitoring phase.
6. A method as claimed in any one of the preceding claims, the method comprising: implementing a second monitoring phase comprising controlling the internal combustion engine to provide a second operating condition and monitoring a second group of engine systems under the second operating condition; and controlling the electric propulsion unit such that the total torque generated by the internal combustion engine and the electric propulsion unit at least substantially matches a torque request received during the second monitoring phase.
7. A method as claimed in claim 6, comprising monitoring the torque request and implementing the second monitoring phase when the torque request is within a second predetermined torque range.
8. A method as claimed in claim 6 or claim 7, wherein the second monitoring phase comprises controlling the internal combustion engine to maintain the second operating condition.
9. A method as claimed in claim 8, wherein the second operating condition comprises a second engine set-point or a second engine operating range.
10. A method as claimed in any one of claims 7, 8 or 9, wherein the second group comprises a plurality of engine systems, the engine systems in the second group being monitored consecutively or concurrently during the second monitoring phase.
11. A method as claimed in any one of the preceding claims, wherein controlling the electric propulsion unit comprises generating a regenerative torque or a propulsive torque.
12. A non-transitory computer-readable medium having a set of instructions stored therein which, when executed, cause a processor to perform the method claimed in any one of the preceding claims.
13. A controller for controlling an internal combustion engine and an electric propulsion unit in a hybrid vehicle powertrain, the controller comprising a processor configured to: receiving a torque request; generate a first engine control signal to set a first operating condition of the internal combustion engine and to monitor a first group of engine systems under the first operating condition; and wherein the processor is configured to generate a motor control signal to control the electric propulsion unit such that a total torque generated by the internal combustion engine and the electric propulsion unit is at least substantially equal to the torque request received during the first monitoring phase.
14. A controller as claimed in claim 13, wherein the processor is configured to monitor the torque request and to implement the first monitoring phase when the torque request is within a first predetermined torque range.
15. A controller as claimed in claim 13 or claim 14, wherein the processor is configured to control the internal combustion engine to maintain the first operating condition throughout the first monitoring phase.
16. A controller as claimed in any one of claims 13, 14 or 15, wherein the first operating condition comprises a first engine set-point or a first engine operating range.
17. A controller as claimed in any one of claims 13 to 16, wherein the first group comprises a plurality of engine systems, the processor being configured to monitor the engine systems in the first group consecutively or concurrently during the first monitoring phase.
18. A controller as claimed in any one of claims 13 to 17, wherein the processor is configured to generate a second engine control signal to set a second operating condition of the internal combustion engine and to monitor a second group of engine systems under the second operating condition; wherein the motor control signal controls the electric propulsion unit such that the total torque generated by the internal combustion engine and the electric propulsion unit is at least substantially equal to the torque request received during the second monitoring phase.
19. A controller as claimed in claim 18, wherein the processor is configured to monitor the torque request and to implement the second monitoring phase when the torque request is within a second predetermined torque range.
20. A controller as claimed in claim 18 or claim 19, wherein the processor is configured to control the internal combustion engine to maintain the second operating condition throughout the second monitoring phase.
21. A controller as claimed in claim 20, wherein the second operating condition comprises a second engine set-point or a second engine operating range.
22. A controller as claimed in any one of claims 18 to 21, wherein the second group comprises a plurality of engine systems, the processor being configured to monitor the engine systems in the second group consecutively or concurrently during the second monitoring phase
23. A controller as claimed in any one of claims 13 to 22, wherein the motor control signal controls the electric propulsion unit to generate a regenerative torque or a propulsive torque.
24. A vehicle comprising a controller as claimed in any one of claims 13 to 23.