Spark plug monitoring apparatus and method

Abstract

A control system for performing one or more monitoring cycle to monitor a spark plug 50 during operation of a spark-ignition reciprocating piston internal combustion engine 10 including an ignition co

Description

TECHNICAL FIELD The present disclosure relates to a spark plug monitoring apparatus and method. Aspects of the invention 5 relate to a control system for monitoring a spark plug; a vehicle; a method of monitoring a spark plug; and a non-transitory computer-readable medium. BACKGROUND There is an industry trend towards gasoline hybrid electric vehicles. The vehicles include a spark-ignition 10 reciprocating piston internal combustion engine. The internal combustion engine comprises one or more spark plugs for generating a spark to combust fuel in a combustion chamber. An ignition coil generates a high voltage which arcs across a gap formed in the spark plug to form an ignition spark. Ideally the spark plug gap is set to the largest size possible for a guaranteed high energy spark. This improves combustion stability, emissions and fuel economy. A large (i.e., high energy) spark may increase or extend the operating 15 window for lean operation and / or exhaust gas recirculation for improved fuel economy. An issue arises due to erosion / wear of the spark plugs which may increase the size of the spark plug gap. This problem is particularly prevalent for aggressive or stressed operation of the internal combustion engine. It has been recognised that there is a fine line between delivering a large productive ignition spark [20 and failing to deliver a spark at all when the gap grows too large. The failure to generate a spark may cause a misfire (with may cause problems with driveability, emissions and on-board diagnostics). For this reason, I the spark plug gaps are typically set smaller than ideal to allow for erosion. This ensures that the spark plug gaps do not grow too large between the service intervals. •25 A further issue is that hybrid vehicles will share the powertrain use miles between the internal combustion engine and an electric traction motor. This may further increase the potential for a larger gap size and mileage between gap resetting and / or spark plug replacement. It is an aim of the present invention to address one or more of the disadvantages associated with the prior 30 art. SUMMARY OF THE INVENTION Aspects and embodiments of the invention provide a control system for monitoring a spark plug; a vehicle; 35 a method of monitoring a spark plug; and a non-transitory computer-readable medium as claimed in the appended claims. According to an aspect of the present invention there is provided a control system for performing one or more monitoring cycles to monitor a spark plug during operation of a spark-ignition internal combustion 40 engine, the internal combustion engine comprising an ignition coil having a primary winding and a secondary winding, wherein the control system comprises one or more controllers configured to: determine a first dwell time for a first charging cycle of the primary winding; control a supply of electric current to the primary winding for the determined first dwell time in the first charging cycle; control the supply of electric current to the primary winding after the determined first dwell time to induce a first voltage in the secondary winding; and 5 determine if the first voltage induced in the secondary winding fails to generate a spark or generates a degraded spark, wherein the monitoring cycle comprises: monitoring the current in the primary winding to determine if the first voltage induced in the secondary winding fails to generate a spark or generates a degraded spark; performing a second charging cycle after the first charging cycle; and 10 monitoring the current in the primary winding during the second charging cycle to determine if the first voltage induced in the secondary winding fails to generate a spark or generates a degraded spark, wherein the one or more controllers is configured to implement a time interval between the first charging cycle and the second charging cycle, the time interval being controlled such that the second charging cycle interrupts a spark generated after the first charging cycle. The internal combustion engine 15 may be a reciprocating piston internal combustion engine. LO A |2O The monitoring cycle is performed to monitor an operating condition of the spark plug. The monitoring cycle is implemented during operation of the internal combustion engine. The monitoring cycle may be performed to generate at least one monitoring (non-ignition) spark. The one or more monitoring cycle can be performed during operation of the internal combustion engine. At least in certain embodiments, this facilitates on-going monitoring of the spark plug. The control system is configured to assess the characteristics of the spark generated when the first voltage is induced in the secondary winding following charging of the primary winding for the first dwell time. The control system may monitor the energy (intensity) of the spark. A degraded spark may have a reduced energy (intensity) and, if sufficiently degraded, may adversely affect combustion of fuel. Alternatively, or in addition, the control system may determine if the spark plug fails to generate a spark when the first voltage is induced in the secondary winding following charging of the primary winding for the first dwell time. The failure to generate a spark during the combustion phase may result in a misfire of the internal combustion engine. 30 At least in certain embodiments, the control system may enable dynamic control of a charging cycle to combust fuel in the internal combustion engine. A dwell time for charging the primary winding to generate an ignition spark for combusting fuel may be selectively increased and decreased in dependence on the monitoring of the spark generated by the spark plug. A dwell time for charging the primary winding to generate an ignition spark for combusting fuel may be increased to increase the energy (intensity) of the 35 resulting spark. This may at least partially counteract degradation of the spark, for example caused by erosion of the spark plug. Alternatively, a dwell time for charging the primary winding for combusting fuel may be decreased to reduce the energy (intensity) of the resulting spark. This may reduce erosion of the spark plug. 40 At least in certain embodiments, the control system can detect that the spark plug is worn (eroded) before the internal combustion engine starts to misfire. This can enable servicing to replace the spark plug(s) to reduce or avoid degradation in performance. This may avoid an increase in emissions and / or noise vibration 2 harshness (NVH). The control system may be configured to calibrate a monitoring spark purposely weak (i.e., a low energy or low intensity spark) so that the spark fails during the monitoring cycle in a period between generation of combustion (ignition) sparks. If the plugs are worn, this may provide earlier notice of the need to replace the spark plug before the internal combustion engine starts to misfire. 5 Controlling the supply of electric current to the primary winding after the determined first dwell time to induce a first voltage in the secondary winding may comprise interrupting the supply of current. For example, a current supply circuit may be broken to interrupt the supply of current to the primary winding. A switch may be opened to interrupt the supply of current to the primary winding. The resulting change in the current in 10 the first winding may induce the first voltage in the secondary winding. At least in certain embodiments, the first dwell time applied during the monitoring cycle may be shorter than a dwell time applied to create a spark to combust fuel. This may facilitate identification of erosion of the spark plug before the degradation of the spark. 15 The one or more controllers may comprise at least one electronic processor having an electrical input and an electrical output. At least one memory device may be electrically coupled to the at least one electronic processor and having instructions stored therein. The at least one electronic processor may be configured . to access the at least one memory device and execute the instructions therein to implement the monitoring 0^20 cycle. CM The determined first dwell time is suitable for achieving a first target primary current in the primary winding. The first target primary current may be less than a primary current set-point for generating an ignition spark. The primary current set-point for generating a spark may be predefined. 025 The one or more controllers may be configured to implement the monitoring cycle during a combustion phase. During the combustion phase, fuel is being introduced into the combustion chamber and ignited to cause the internal combustion engine to generate torque. The monitoring cycle may, for example, be performed after an ignition cycle performed to generate an ignition spark. The monitoring cycle may be 30 performed during a compression stroke (piston ascending), for example after an ignition spark for igniting an air / fuel mixture in the combustion chamber. Alternatively, the one or more controllers may be configured to implement the monitoring cycle during a non-combustion phase. During the non-combustion phase, fuel is not being introduced into the combustion 35 chamber and the internal combustion engine is not generating torque. The monitoring cycle may be performed during a power stroke (piston descending) after the compression stroke. Alternatively, the noncombustion phase may be a ‘fuel-cut’ operating mode, for example when the internal combustion engine is operating in an overrun or a shut-down scenario to conserve fuel. 40 The one or more controllers may be configured to output a first service notification. The first service notification may be output if the spark plug fails to generate a spark following supply of the electric current for the determined first dwell time. The first service notification may be output if the spark plug generates a 3 degraded spark following supply of the electric current for the determined first dwell time. The first service notification may be output to prompt servicing or replacement of the spark plug. The one or more controllers may be configured to implement a plurality of the monitoring cycles in respect 5 of a plurality of determined first dwell times. The determined first dwell times may be different from each other. The characteristics of the sparks generated during the plurality of the monitoring cycles may be compared, for example to determine appropriate dwell time for charging the primary winding. The one or more controllers may be configured to identify the one of the plurality of determined first dwell 10 times having the shortest duration which results in the spark plug generating a spark. The monitoring cycle may comprise monitoring the current in the primary winding to determine if the first voltage induced in the secondary winding fails to generate a spark or generates a degraded spark. 15 The delivery / discharge of the spark may be measured using different techniques, such as one or more current clamps and / or monitoring different stages of the coil drivers. The monitoring cycle may comprise performing a second charging cycle. The second charging cycle may LO be performed after the first charging cycle. The one or more controllers may be configured to monitor the CM20 current in the primary winding during the second charging cycle. A current sensor may monitor the current in the primary winding. The current sensor may output a current signal to the one or more controllers. By CM monitoring the current in the primary winding during the second charging cycle, the one or more controllers may determine if the first voltage induced in the secondary winding fails to generate a spark or generates a degraded spark. 025 The one or more controllers may be configured to implement a time interval between the first charging cycle and the second charging cycle. The time interval may be controlled such that the second charging cycle interrupts a spark generated after the first charging cycle. The time interval may be controlled such that the second charging cycle is initiated before a spark generated after the first charging cycle is naturally 30 extinguished. The one or more controllers may be configured to monitor the current in the primary winding when the second charging cycle starts. The one or more controllers may receive a signal from one or more current sensors. 35 The one or more controllers may be configured to determine that the spark plug fails to generate a spark or generates a degraded spark if the current in the primary winding at the beginning of the second charging cycle is greater than zero. A non-zero current in the primary winding when the second charging cycle is initiated may indicate that at some of the energy stored in the magnetic field was not discharged when the 40 first voltage was induced in the secondary winding. This may indicate that a degraded spark was generated or that the induced voltage failed to generate a spark. The starting current in the primary winding may be inversely proportional to the energy (intensity) of the spark. The greater the current in the primary winding, the smaller the energy (intensity) of the spark. Conversely, the smaller the current in the primary winding, the greater the energy (intensity) of the spark. The one or more controllers may approximate the energy (intensity) of the spark in inverse proportion to the starting current in the primary winding. 5 The one or more controllers may be configured to determine that the spark plug failed to generate a spark or generates a degraded spark if the current in the primary winding at the beginning of the second charging cycle has a magnitude greater than or equal to a first threshold. The one or more controllers may be configured to determine that the spark plug generated a spark if the 10 current in the primary winding at the beginning of the second charging cycle has a magnitude less than the first threshold. The one or more controllers may be configured to determine an error state if the current in the primary winding at the beginning of the second charging cycle has a magnitude less than a second threshold. 15 Alternatively, or in addition, the one or more controllers may be configured to compare a first peak current in the primary winding during the first charging cycle to a second peak current in the primary winding during the second charging cycle. The one or more controllers may determine that the spark plug failed to generate LO a spark if the second peak current is greater than the first peak current. A larger second peak current may CM20 indicate that not all of the energy was dissipated from the primary winding when the spark was generated. CM Alternatively, or in addition, the one or more controllers may be configured to compare a first charging period required to saturate the primary winding during the first charging cycle to a second charging period required to saturate the primary winding during the second charging cycle. The one or more controllers may ^^25 determine that the spark plug failed to generate a spark if the second time period is smaller than the first time period. Alternatively, or in addition, the one or more controllers may be configured to compare a first rate of increase of the current in the primary winding during the first charging cycle to a second rate of increase of the 30 current in the primary winding during the second charging cycle. A smaller second rate of increase may indicate that not all of the energy was dissipated from the primary winding when the spark was generated. According to a further aspect of the present invention there is provided a vehicle comprising a control system as described herein. 35 According to a further aspect of the present invention there is provided a method of monitoring a spark plug in a spark-ignition internal combustion engine, the internal combustion engine comprising an ignition coil having a primary winding and a secondary winding, wherein the method comprises implementing a monitoring cycle during operation of the internal combustion engine, the monitoring cycle comprising: 40 determining a first dwell time for a first charging cycle of the primary winding; controlling a supplying of electric current to the primary winding for the determined first dwell time in the first charging cycle; controlling the supply of electric current to the primary winding after the determined first dwell time to induce a first voltage in the secondary winding; determining if the first voltage induced in the secondary winding fails to generate a spark or generates a degraded spark; 5 monitoring the current in the primary winding to determine if the first voltage induced in the secondary winding fails to generate a spark or generates a degraded spark; performing a second charging cycle after the first charging cycle; and monitoring the current in the primary winding during the second charging cycle to determine if the first voltage induced in the secondary winding failed to generate a spark or generated a degraded spark; 10 and implementing a time interval between the first charging cycle and the second charging cycle, the time interval being such that the second charging cycle interrupts a spark generated after the first charging cycle. 15 The monitoring cycle may comprise performing a second charging cycle after the first charging cycle. The method may comprise monitoring the current in the primary winding during the second charging cycle to determine if the first voltage induced in the secondary winding failed to generate a spark or generated a degraded spark. 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(s) described herein. , Any control unit or controller described herein may suitably comprise a computational device having one or •25 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 30 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 controllerto 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 35 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 40 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 6 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. 5 BRIEF DESCRIPTION OF THE DRAWINGS One or more embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 shows a schematic representation of a vehicle incorporating a control system configured to implement a monitoring cycle to monitor operation of a spark plug of an internal combustion engine provided 10 in the vehicle; Figure 2 shows a schematic representation of a combustion chamber and a spark plug of the internal combustion engine shown in Figure 1; Figure 3 illustrates a first operating cycle representing conventional operation of a cylinder of the internal combustion engine; 15 Figure 4 shows a schematic representation of a controller of the control system shown in Figure 1; Figure 5 illustrates a second operating cycle representing operation of a cylinderof the internal combustion engine to perform a first monitoring cycle; Figures 6A to 6D illustrate the operating parameters of an ignition coil during the first monitoring cycle LO. shown in Figure 5; CM20 Figure 7 is a first block diagram representing operation of the control system to monitorthe operation of the spark plug; CM Figure 8 illustrates a third operating cycle representing operation of a cylinder of the internal combustion engine to perform a second monitoring cycle. ^^25 DETAILED DESCRIPTION A control system 1 and a method for controlling operation of an internal combustion engine 10 according to an embodiment of the invention will now be described. As shown in Figure 1, the engine 10 in the present embodiment is installed in a road vehicle V, such as an 30 automobile or a sports utility vehicle. It will be understood that the engine 10 may be installed in other types of vehicle. The engine 10 in the present embodiment is a spark ignition, reciprocating piston internal combustion engine. The engine 10 comprises a plurality of cylinders 12. Byway of example, the engine 10 may comprise four (4), six (6) or eight (8) cylinders. As shown schematically in Figure 2, the engine 10 comprises a crankshaft 14 connected to a plurality of pistons 16. The pistons 16 are each associated with 35 a respective one of the cylinders 12. The cylinders 12 and the pistons 16 collectively form combustion chambers 18. The vehicle V may be powered exclusively by the internal combustion engine 10. Alternatively, the vehicle V may be hybrid electric vehicle, for example a plug-in hybrid electric vehicle. The combustion chamber 18 in each cylinder 12 is defined above the piston 16. An intake valve 20 is 40 provided to control the supply of air into the combustion chamber 18 from an inlet port 22. As described herein, the intake valve 20 controls the quantity (trapped mass) of air admitted into the combustion chamber 18 in an air charge. The intake valve 20 in the present embodiment comprises a first poppet valve 20. The 7 inlet port 22 is fed from an inlet manifold 24 having a throttle valve 26. The intake valve 20 is closed by a spring (not shown) and is opened by action of a rotatable cam 28 which is conventionally provided by a lobe of a camshaft (not shown). A first tappet 30 is provided between the intake valve 20 and the cam 28. The first tappet 30 is active, and adjustable in length by relative inward and outward movement of the 5 components thereof, so that the lift of the intake valve 20 may be varied between minimum and maximum. The valve lift may be controllably varied at each successive opening thereof, if required. An exhaust valve 40 is provided to control the exhausting of gases from the combustion chamber 18 from an exhaust port 42. The exhaust valve 40 in the present embodiment comprises a second poppet valve. 10 The exhaust valve 40 is selectively opened and closed. A second tappet (not shown) is provided for controlling operation of the exhaust valve 40. A fuel is injected into the combustion chamber. One or more fuel injector (not shown) is associated with each cylinder 12 and is configured to inject fuel into the cylinder 12 for combustion. The fuel in the present embodiment is gasoline (petrol). In a variant, the fuel could be hydrogen (H2). 15 30 35 40 The engine 10 comprises a plurality of spark plugs 50 for igniting the fuel in respective combustion chambers 18. One of the spark plugs 50 is associated with each cylinder 12. The spark plugs 50 are of conventional design and each comprise a central electrode 52, a side electrode 54 and a core 56. A gap G is formed between the central electrode 52 and the side electrode 54. In use, a spark is created across the gap G to ignite the fuel in the combustion chamber 18. An ignition coil 58 (also known as a spark coil) is provided for supplying electrical current to each spark plug 50. One ignition coil 58 (shown schematically in Figure 2) is associated with each cylinder 12 in the present embodiment. In a variant, one ignition coil 58 could be associated with a pair of the cylinders 12. The ignition coil 58 is an induction coil for inducing a high voltage to generate the electrical spark across the gap G. The ignition coil 58 comprises a primary winding 60 and a secondary winding 62. The primary winding 60 comprises fewer turns than the secondary winding 62. Current is supplied to the primary winding 60 from a current source, such as an on-board battery, to produce a magnetic field in the core 56. The current is supplied to the primary winding 60 during a charging cycle. The current is supplied to the primary winding 60 fora period of time referred to as a dwell time DWT. The supply of current to the primary winding 60 is interrupted (by opening an electrical contact or switching of a transistor) and the resulting changes in the magnetic field induce a high voltage in the secondary winding 62. If the induced voltage is sufficiently high, the electricity arcs across the gap G in the spark plug 50 and generates a spark for igniting fuel in the combustion chamber 18. The amount of energy stored in the magnetic field is dependent on the dwell time DWT of the charging cycle. The voltage induced in the secondary winding 62 and the characteristics of the spark, such as the energy (intensity) and / or duration of the spark, are dependent on the dwell time DWT. Increasing the dwell time DWT increases the energy stored in the magnetic field, thereby increasing the voltage induced in the secondary winding 62. As described herein, the dwell time DWT is controlled to ensure sufficient energy is stored in the magnetic field to induce a voltage in the secondary winding 62 sufficient to produce a spark suitable for igniting the fuel in the combustion chamber 18. The dwell time DWT for generating a spark to ignite the fuel may be referred to as an ignition dwell time DWT. The spark energy and / or the spark duration may influence the combustion of the fuel in the combustion chamber 18. In use, the central electrode 52 and / or the side electrode 54 may erode, especially if the engine 10 is subjected to aggressive / stressed usage cycles. The erosion of the central electrode 52 and / or the side electrode 54 may increase the size of the gap G of the spark plug 50. A change in the size of the gap G (for example, caused by erosion) may affect the characteristics of the spark generated by the spark plug 5 50. If the size of the gap G becomes too large, a spark may not be generated by the spark plug 50. In other words, the spark plug 50 will fail to generate a spark. This may cause a misfire of the engine 10 potentially resulting in driveability and emissions issues. The spark plugs 50 may be configured initially such that the gap G is smaller than required, thereby allowing for increases in the size of the gap G caused by erosion of the central electrode 52 and / or the side electrode 54. It would be preferable not to have to reduce the 10 size of the gap G because this reduces the intensity of a spark when generated. During operation of the engine 10, fuel is injected into the cylinders 12 and mixed with air in the combustion chamber 18. The spark plugs 50 generate a spark to ignite the fuel in the combustion chamber 18 and the resulting forces displace the pistons 16 down and rotate the crankshaft 14. Each operating cycle of fuel 15 injection and combustion takes two full revolutions of the crankshaft 14. For a given cylinder 12, the first revolution comprises an intake stroke (piston descending) for taking in air, and a compression stroke (piston ascending) for compressing an air / fuel mixture before ignition. The second revolution starts with a spark and comprises a power stroke (piston descending) for combusting the fuel and forcing the piston LO. downwards, and an exhaust stroke (piston ascending) for expelling exhaust gasses. The full operating cycle CM20 (comprising intake, compression, power and exhaust strokes) is continually repeated during operation of the engine 10. CM A first operating cycle 100 representing cylinder pressure, p, during conventional operation of the cylinder 12 is shown in Figure 3. The intake stroke, I, occurs as the piston 16 travels from top dead centre (TDC) to ^^25 bottom dead centre (BDC). The compression stroke, C, occurs as the piston travels from BDC to TDC Firing (TDCF). The ignition coil 58 supplies current to the primary winding 60 in a charging cycle suitable for generating a combustion spark SP. The charging cycle comprises a dwell time for charging the ignition coil 58 to ensure that the (primary) current in the primary winding 60 is sufficient to generate a spark of sufficient energy (intensity) and / or duration to ignite (i.e. ‘fire’) the fuel in the combustion chamber 18. The 30 ignition coil 58 is controlled such that the spark plug 50 generates the combustion spark SP as the piston 16 approaches TDCF during the compression stroke. The primary winding 60 is opened to interrupt the supply of current to the primary winding 60. The resulting change in the magnetic field induces a high voltage in the secondary winding 62 which generates the spark SP across the gap G in the spark plug 50. The power stroke, P, occurs after ignition of the fuel in the combustion chamber 18 as the piston 16 travels 35 from TDCF to BDC. The operating cycle is completed by the exhaust stroke, E, as the piston 16 returns to TDC. To ensure appropriate combustion of the fuel in the fuel chamber 18, the combustion spark SP generated by the spark plug 50 should have sufficient energy and / or duration. The failure to generate a spark may 40 result in a misfire of the engine 10. A degraded (or weak) spark may have a relatively low energy and / or a short duration. A degraded spark may lead to poor combustion performance via a slow or partial burn but not a complete misfire. The failure to generate a spark or the generation of a degraded spark may be the 9 result of degradation of the spark plug 50. As described herein, the control system 1 is configured to determine if the spark plug 50 generates a spark during operation of the engine 10. The control system 1 may also assess the quality of the spark. 5 The control system 1 comprises an electronic control unit (ECU) 70. As described herein, the ECU 70 is configured to control operation of the engine 10. The ECU 70 is configured to control operation of the or each ignition coil 58 to control the generation of the spark by each spark plug 50. The control system 1 is configured to monitor operation of each of the spark plugs 50. In particular, the ECU 70 is configured to implement a monitoring cycle to monitor operation of the spark plug 50. The ECU 70 implements the 10 monitoring cycle during the power stroke to monitor operation of the spark plug 50. The control system 1 in the present embodiment is configured to control the ignition coil 58 to perform first and second charging cycles to charge the coil 58 to establish operating conditions suitable for generating first and second sparks SP1, SP2 respectively. The first and second sparks SP1, SP2 may be referred to as first and second monitoring sparks SP1, SP2. A time interval is implemented between the first and second charging cycles. 15 At least in certain embodiments, the time interval is sufficiently small that the second charging cycle is initiated while the first spark SP1 is active. The initiation of the second charging cycle extinguishes the first spark SP1. The control system 1 monitors the second charging cycle to infer the properties or characteristics of the preceding first spark SP1. The control system 1 may, for example, monitor the charge LO in the coil 58 to infer the energy and / or the duration of the first spark SP1. The charge in the coil 58 is CM20 monitored with reference to the (primary) current in the primary winding 60 during the second charging cycle. The delivery / discharge of the first spark SP1 may be measured using different techniques, such as CM one or more current clamps and / or monitoring different stages of the coil drivers. At least one first current sensor may be provided for measuring the current in the primary winding 60. At least one second current sensor may be provided for measuring the current in the secondary winding 62. 025 As shown in Figure 4, the ECU 70 comprises a controller 72 having at least one processor 74 and a system memory 76. The processor 74 is an electronic processor and is configured to implement a set of computational instructions stored in the system memory 76. When executed, the computational instructions cause the electrical processor 74 to implement the method(s) described herein. The at least one electrical 30 processor 74 has at least one electrical input 78A for receiving an input signal; and at least one electrical output 78B for outputting one or more output signal. The ECU 70 is configured to monitor a current in the primary winding 60 (referred to herein as a primary current). A primary current signal SC1 is supplied to the electrical input 78A of the at least one electrical processor 74. The primary current signal SC1 indicates the current in the primary winding 60. The at least one processor 74 is configured to monitor the primary current 35 to determine if a spark is generated by the spark plug 50. The monitoring of the spark plug 50 comprises determining if a spark is generated following the supply of electric current to the primary winding 60 for a first dwell time DWT1. The duration of the first dwell time DWT1 may be controlled (i.e., controllably increased or decreased) to assess operation of the spark plug 50. 40 The operation of the ECU 70 will now be described with reference to Figures 5 and 6. The ECU 70 is configured to monitor the current in the primary winding 60 to monitor operation of the spark plug 50. A second operating cycle 200 for monitoring operation of the spark plug 50 is shown in Figure 5. In the present 10 embodiment, the operation of the spark plug 50 is monitored during a combustion phase when fuel has been introduced into the combustion chamber 18 and ignited to drive the crankshaft and cause the engine 10 to generate torque. The ECU 70 controls the ignition coil 58 to cause the spark plug 50 to generate the combustion spark SP to ignite the fuel in the combustion chamber 18 during the compression stroke. The 5 ignition of the fuel in the combustion chamber 18 causes the piston 16 to perform a conventional power stroke after the compression stroke. The ECU 70 is configured to control the ignition coil 58 during the power stroke to monitor operation of the spark plug 50. The ECU 70 controls the ignition coil 58 to supply current to the primary winding 60 for at 10 least one charging cycle during the power stroke. In the present embodiment, the ECU 70 controls the ignition coil 58 to supply current to the primary winding 60 in a first charging cycle suitable for generating the first spark SP1; and to supply current to the primary winding 60 in a second charging cycle suitable for generating the second spark SP2. As illustrated in Figure 5, the first and second charging cycles are both performed during the power stroke after the fuel in the combustion chamber 18 has been combusted. The 15 first and second sparks SP1, SP2 are wasted (non-ignition) sparks as they are not intended to ignite fuel in the combustion chamber 18. As shown in Figure 6, the first charging cycle has a first dwell time DWT1 (tO-t1); and the second charging cycle has a second dwell time DWT2 (t2-t4). The first and second dwell times DWT1, DWT2 may be the |20 same as each other or may be different from each other. In the present embodiment, the first dwell time DWT1 is shorter than the second dwell time DWT2. The ECU 70 may optionally be configured to control I the dwell time DWT dynamically in dependence on the determined operation of the spark plugs 50. A time interval t1-t2 is implemented between the first and second charging cycles, i.e. after the ignition coil 58 is , opened to initiate the generation of the first spark SP1 and before the ignition coil 58 is closed to re-establish •25 the magnetic field for generating the second spark SP2. The time interval t1-t2 may be increased or decreased to monitor changes in the characteristics of the first and second sparks SP1, SP2. The first and second sparks SP1, SP2 generated in the monitoring cycle are used to monitor operation of the spark plug 50. At least in certain embodiments, the control system 1 can differentiate between the 30 following conditions: (a) the first spark SP1 occurred and was of sufficient energy and / or duration for combusting fuel; (b) the first spark SP1 occurred but was degraded, i.e. was of low energy and / or duration; and (c) the first spark SP1 did not occur. The characteristics of the first and second sparks SP1, SP2 generated will now be described with reference to the plots shown in Figures 6A to 6D. In the arrangement illustrated in Figures 5 and 6, the first and second dwell times DWT1, DWT2 result in first and second 35 sparks SP1, SP2. In the present embodiment, the ECU 70 is configured to initiate the second charging cycle to extinguish the first spark SP1. The switching on of the primary winding 60 to initiate the second charging cycle extinguishes the first spark SP1 before all the energy in the primary winding 60 has been expended. The 40 premature extinguishing of the first spark SP1 can be detected in the (primary) current in the primary winding 60 for the second charging cycle. If the first spark SP1 had naturally extinguished, the (primary) current in the primary winding 60 would be fully depleted (i.e., at least substantially zero). Since the first 11 spark SP1 is interrupted by initiating the second charging cycle, the charge in the ignition coil 58 is greater than zero. The ECU 70 is configured to generate the first and second sparks SP1, SP2 close together to achieve this current profile in the primary winding 60 to facilitate monitoring of the spark quality, particularly the quality of the first spark SP1. An elevated (non-zero) current in the primary winding 60 at the beginning 5 of the second charging cycle (t2) may indicate that the first spark SP1 did not occur, or that a degraded first spark SP1 occurred. The ECU 70 is configured to assess the first spark SP1 by measuring the (primary) current in the primary winding 60 during the second charging cycle. A first monitoring cycle will now be described with reference to a spark energy, SE; a discharge current, 10 DC; a (primary) current, PC; and a voltage, GV across the gap G. These operating parameters are illustrated in Figures 6A to 6D. These operating parameters are shown for illustrative purposes only and it will be understood that it is not necessary for the control system 1 to monitor each of these operating parameters. The control system 1 in the present embodiment is configured to monitor only the (primary) current, PC, in the primary winding 60, for example using a current sensor. Alternatively, or in addition, the 15 control system 1 may monitor one or more of the other operating parameters described herein. A first plot 310 representing the spark energy, SE, of the first and second sparks SP1, SP2 is shown in Figure 6A. The first plot 310 comprises first and second peaks 312, 314 representing the energy of the first LO. and second sparks SP1, SP2 respectively. In the present example, the spark energy of the second spark CM20 SP2 is greater than that of the first spark SP1. The peak amplitude and the duration of the second peak 314 are greater than those of the first peak 312 in the present example. CM A second plot 320 representing the discharge current, DC, for the first and second sparks SP1, SP2 is shown in Figure 6B. The second plot 320 comprises first and second peaks 322, 324 representing the ^^25 current discharged by the first and second sparks SP1, SP2 respectively. The second peak 324 extends over a longer period of time than the first peak 322, representing the longer duration of the second spark SP2. The discharge current, DC, of each of the first and second sparks Sp1, SP2 may be measured, for example, using one or more current clamps and / or by monitoring different stages of the coil drivers. 30 A third plot 330 representing the (primary) current, PC, in the primary winding 60 of the ignition coil 58 is shown in Figure 6C. The third plot 330 comprises first and second peaks 332, 334 representing the current in the primary winding 60 during the first and second charging cycles, respectively. The first peak 332 represents the primary current, PC, measured in the primary winding 60 for the first charging cycle. The second peak 334 represents the primary current, PC, measured in the primary winding 60 for the second 35 charging cycle. The current measured in the primary winding 60 is indicative of the energy stored in the magnetic field. When the ignition coil 58 is opened (represented by the vertical profile at the end of the first and second peaks 332, 334), the change in the magnetic field induces a high voltage in the secondary winding 62 which arcs across the gap G to form the first and second sparks SP1, SP2. The second peak 334 represents discharge of current over a longer period of time representing the longer duration of the 40 second spark SP2. The primary current profile for the second peak 334 comprises an inclined section starting from a non-zero value at the beginning of the second dwell time DWT2. The second peak 334 comprises a substantially horizontal section (t3-t4) representing a saturation point for charging of the 12 ignition coil 58. The saturation point may be defined by a controller, for example as a maximum / target current for the ignition coil 58. A fourth plot 340 representing the voltage, GV, across the gap G is shown in Figure 6D. The fourth plot 340 5 comprises first and second troughs 342, 344 occurring during the first and second dwell times DWT1, DWT2 respectively; and first and second peaks 346, 348 representing the voltage during generation of the first and second sparks SP1, SP2 respectively. The at least one processor 74 is configured to control the ignition coil 58 to achieve a set-point current in 10 the primary winding 60 during a charging cycle. The set-point current is sufficient to generate a spark suitable for igniting the fuel in the combustion chamber. The set-point current may, for example, provide particular spark characteristics, such as a minimum peak spark energy and / or a minimum spark duration. The set-point current may be a default or standard current applied during a charging cycle to generate the combustion spark SP to combust the fuel in the combustion chamber 18 during a combustion phase. The 15 set-point current may be predefined, for example in dependence on empirical data. In the present embodiment, the charging cycle to generate the combustion spark SP during the compression stroke is controlled to achieve the set-point current. The at least one processor 74 may determine the dwell time in dependence on the set-point current. The determined dwell time may vary in dependence on a supply voltage to the ignition coil 58. The at least one processor 74 is configured to monitor the operation of the spark plug 50 during a first monitoring cycle. A first target current is defined for the (primary) current in the primary winding 60 in the first monitoring cycle. The first target current in the present embodiment is determined with reference to the set-point current. The first target current could be at least substantially equal to the set-point current. However, in the present embodiment, the first target current is less than the set-point current. Thus, the (primary) current in the primary winding 60 for the first monitoring cycle is less than the target current to ignite the fuel in the combustion chamber 18 during the combustion phase. The reduced first target current may increase the sensitivity of the monitoring of the spark plug 50. In particular, the reduced first target current increases the likelihood of a failed spark event, so that the condition of the spark plug 50 can be 30 monitored. The first dwell time DWT1 is determined in dependence on the first target current. In particular, the first dwell time DWT1 is calculated to achieve the first target current in the primary winding 60. The at least one processor 74 controls the ignition coil 58 to perform the first charging cycle for the first dwell time DWT1. 35 The at least one processor 74 determines if the spark plug generates a spark following the supply of electric current for the first dwell time DWT 1. In the present embodiment, the at least one processor 74 initiates the second charging cycle to determine if the first spark SP1 was generated and / or to monitor the characteristics of the first spark SP1. The current in the primary winding 60 during the second charging cycle is monitored. A non-zero current in the primary winding 60 when the second charging cycle is initiated 40 may indicate that the energy in the magnetic field was only partially discharged. This may indicate one or more of the following: the first spark SP1 was not generated; the first spark SP1 had a low spark energy; the first spark SP1 was of a short duration; the second charging cycle was commenced before the first 13 spark SP1 had been allowed to extinguish naturally; and an error state. The ECU 70 may differentiate between one or more of these conditions in dependence on a magnitude of the (primary) current, PC, in the primary winding 60 when the second charging cycle is initiated; and / or in dependence on a profile of the (primary) current in the primary winding 60 during the second charging cycle. 10 15 30 The at least one processor 74 is configured to compare the measured current in the primary winding 60 at the beginning of the second charging cycle (t2) to one or more predetermined thresholds. In the present embodiment, the measured current in the primary winding 60 at the beginning of the second charging cycle is compared to predetermined first and second thresholds TH1, TH2. If the measured current in the primary winding is less than the first threshold value TH1 and greater than the second threshold TH2, the at least one processor 74 determines that the first spark SP1 was generated in the correct manner without error state. If the measured current in the primary winding is greater than the first threshold value TH1, the at least one processor 74 determines that the first spark SP1 was not generated; or that the first spark SP1 was generated but was below a specified performance level. The specified performance level may, for example, indicate the spark energy and / orthe spark duration. The at least one processor 74 may determine that the spark plug 50 has been subject to wear / erosion. If the measured current was below the second threshold TH2, then this may indicate an error state is present. The error state may, for example, represent an electrical short across the secondary circuit resulting in less charge remaining in the coil than would be expected for a healthy system. If the at least one processor 74 determines that the first dwell time DWT1 (and the corresponding first target current) generated a spark, a determination is made that the set-point current applied during the combustion phase is appropriate to generate a spark suitable for igniting the fuel in the combustion chamber 18. If, however, the at least one processor 74 determines that the first dwell time DWT1 (and the corresponding first target current) failed to generate a spark having sufficient spark energy and / or spark duration, a determination is made from the set-point current, that an equivalent combustion spark SP (generated with the same dwell time) would not be sufficient to ignite the fuel in the combustion chamber 18 and / or to propagate the flame at a sufficient rate. The at least one processor 74 may output a service notification to prompt servicing, for example to replace the spark plug 50. Alternatively, or in addition, the at least one processor 74 may increase the set-point current applied during the combustion phase to ignite the fuel in the combustion chamber 18. The increased set-point current should increase the likelihood of the combustion spark SP igniting the fuel in the combustion chamber 18 and / or increasing the flame propagation rate. 35 In the present embodiment, the at least one processor 74 is configured to perform a second monitoring cycle in which a second target current is defined. The second target current is greater than the first target current applied during the first monitoring cycle. The first and second charging cycles are repeated during the second monitoring cycle. The at least one processor 74 controls the ignition coil 58 to perform the first charging cycle for a modified first dwell time DWT1 to achieve the second target current. The at least one 40 processor 74 determines if the spark plug 50 generates a spark of sufficient energy and / or duration. Again, the at least one processor 74 may compare the measured current in the primary winding 60 at the beginning of the second charging cycle to predetermined first and second threshold values TH1, TH2. If the measured 14 current is less than the first threshold value TH1 and greater than the second threshold value TH2, the at least one processor 74 determines that the first spark SP1 wasgenerated. Ifthe measured current isgreater than the predetermined first threshold value TH1, the at least one processor 74 determines that the first spark SP1 was not generated or was degraded. Ifthe measured current is less than the second threshold 5 value TH2, the at least one processor 74 identifies an error state. The process may be repeated for further iterations until it is determined that the first spark SP1 is generated. The monitoring cycle may be repeated to ensure that the first spark SP1 is generated reliably. The at least one processor 74 may thereby determine a target current which is required by the spark plug 50 to generate 10 a spark. The set-point current for that spark plug 50 may then be set as equal to the determined target current. It will be understood that different set-point currents may be defined in respect of different spark plugs 50 in the engine 10, for example to accommodate different levels of erosion. Ifthe at least one processor 74 determines that the first dwell time DWT1 (and the corresponding first target 15 current) does generate a spark, one or more further monitoring cycles may be performed to determine if the combustion dwell time DWT may be reduced. In this scenario, the second target (feedback) current may be smaller than the first target current. The combustion dwell time may be reduced if it is determined that that a lower measured current profile generates a spark sufficient to ignite the fuel in the combustion chamber 18. The monitoring cycles may adjust the first dwell time DWT1 to determine a reliable first spark SP1. The combustion dwell time DWT for generating the combustion spark SP during the combustion phase may be modified in dependence on the adjusted first dwell time DWT1. This may enable performance to be maintained or improved; and / or the condition of the spark plug 50 to be assessed. Ifthe first spark SP1 is degraded or fails during the monitoring cycle, the combustion spark SP may not have failed, for example due to differences in the combustion dwell time DWT and the first dwell time DWT 1. However, this may indicate that the combustion dwell time DWT during the ignition phase should be modified to improve the spark SP. The at least one processor 74 may thereby determine a first dwell time 30 DWT1 which is required by the spark plug 50 to generate a reliable first spark SP1 during the monitoring cycle with a measured / resultant initial current profile in an acceptable range. Based on monitoring of the resultant first spark SP1, the at least one processor 74 may modify the combustion dwell time DWT to maintain the combustion spark SP, thereby compensating for changes in the spark plug 50. The at least one processor 74 may increase the combustion dwell time DWT to maintain the quality of the combustion 35 spark SP to ignite fuel in the combustion chamber 18 during the combustion phase. The at least one processor 74 may calibrate the first dwell time DWT1 such that the first spark SP1 generated during the monitoring cycle fails before the combustion spark SP generated fails during the combustion phase. This may facilitate determination that the spark plug 50 should be replaced to avoid a misfire or loss in performance. The spark plug 50 can be replaced when the at least one processor 74 determines that the 40 spark plug 50 fails to generate a first spark SP1 after charging the primary winding 60 for the first dwell time DWT1. For example, the at least one processor 74 may output a service notification to prompt replacement of the spark plug 50. The at least one processor 74 may be configured to generate a weak, (i.e., a low energy or low intensity) monitoring spark SP1. This may promote failure of the spark SP1 during the monitoring cycle before the combustion (ignition) spark fails. The at least one processor 74 may modify the first dwell time DWT1 to 5 determine a condition of the spark plug 50, for example to estimate an extent of the wear on the spark plug 50. The at least one processor 74 may modify the first dwell time DWT1 to configure the charging cycle to provide a reliable monitoring spark. The dwell time DWT to generate the ignition spark SP can be configured in dependence on the determined first dwell time DWT1. At least in certain embodiments, this may enable the quality of the combustion spark to be maintained or improved, for example to compensate for the wear 10 and avoid performance degradation and / or misfire. By monitoring the quality of the spark, the control system 1 may avoid unnecessarily increasing the dwell time which may prematurely age the spark plug 50 and / or the ignition coil 58. The at least one processor 74 may be configured to monitorthe profile of the (primary) current in the primary 15 winding 60. For example, the at least one processor 74 may identify a saturation point when the primary winding 60 becomes saturated (i.e., when the measured current in the primary winding 60 during the second charging cycle is substantially constant). The saturation point occurs at time t3 in Figure 6C and the measured current is substantially constant forthe remainder of the second charging cycle. This may provide LO. an alternate method or secondary confirmation of an error state or plug wear. If the saturation point occurs CM20 early, then this is an indication that there was more charge remaining in the primary winding 60 than would be expected. This may indicate that the first spark SP1 did not occur, a degraded first spark SP1 occurred CM (i e. of relatively low energy and / or duration). Conversely, if the saturation point is delayed, then this indicates less charge remaining in the primary winding 60 than expected. This may indicate an error state, such as an electrical short in the secondary winding circuit. 025 The operation of the control system 1 according to the present embodiment will now be described with reference to a first block diagram 400 shown in Figure 7. The engine 10 is activated (BLOCK 405). The ECU 70 is configured to monitor the operation of the spark plug 50. A first target current to be achieved in the primary winding 60 of the ignition coil 58 is determined (BLOCK 410). The first target current may be 30 defined as the set-point current. A first dwell time DWT1 is determined in dependence on the first target current (BLOCK 415). The first dwell time DWT1 is calculated to achieve the first target current in the primary winding 60. The at least one processor 74 controls the ignition coil 58 to apply the first dwell time DWT1 in the first charging cycle (BLOCK 420). The primary winding 60 is opened to interrupt the supply of current to the primary winding 60 (BLOCK 425). The resulting change in the electric field induces a voltage 35 in the secondary winding 62. The at least one processor 74 determines if the voltage induced in the secondary winding 62 generated a spark across the gap G (BLOCK 430). If the at least one processor 74 determines that a spark was generated, the process is terminated (BLOCK 435). If the at least one processor 74 determines that a spark was not generated, the process is repeated. A second monitoring cycle may be performed. A second target current may be set forthe second monitoring cycle. The second 40 target current may be greater than the first target current. If the at least one processor 74 determines that a spark is not being generated, a service notification may be output (BLOCK 440). The service notification may, for example, prompt that the engine 10 is serviced, for example by replacing the spark plug 50. The monitoring cycle may be repeated a predetermined number of times. A counter may be incremented each time the process is repeated. If the counter exceeds a counter threshold, the process may be terminated (BLOCK 445). 5 The above embodiment of the control system 1 implements the monitoring cycles during the combustion phase of the operating cycle. The control system 1 may be configured to implement the monitoring cycles during other stages in the operating cycle. The monitoring cycle may, for example, be performed when no spark is required for combustion. The monitoring cycles could, for example, be performed during the exhaust stroke. Alternatively, or in addition, the control system 1 may implement the monitoring cycles 10 during a non-combustion phase of the operating cycle. The engine 10 may be controlled selectively to operate in a fuel-cut mode in which the supply of fuel to the cylinder 12 is inhibited (or reduced). This may be applied to operate the engine 10 in an overrun mode or a shut-down mode. The fuel-cut mode may, for example, be implemented to provide a coasting function to 15 reduce fuel consumption. In the case of a hybrid vehicle, the fuel-cut mode may be active when the engine 10 is being motored when the electric traction motor is operating and / or during braking of the vehicle V. The piston 18 continues to reciprocate during the fuel cut mode and the same nomenclature is used herein in respect of the different strokes of the piston 18 (i.e., intake, compression, power and exhaust strokes). LO However, it will be understood that combustion does not occur in the fuel cut mode as fuel is not introduced CM20 into the combustion chamber 18 during the intake stroke. The dwell time DWT may be reduced towards the point at which the spark SP is expected to fail if the spark plug 50 was good. If the spark fails prematurely, it indicates that the plug gap is becoming too large, and soon requires resetting / replacement before the gap becomes too large for a 'normal' charge / dwell time. This has no effect on the running of the engine 10 since the charge spark capability is determined under a condition where combustion is not required. The need to service the spark plug 50 can be determined proactively before the gap G becomes excessively large due to erosion (and the spark plug 50 fails to generate a spark). At least in certain embodiments, this may extend the useable life of the spark plug 50 while using a relatively large gap G. 30 The control system 1 may implement the monitoring cycles when the supply of fuel to the combustion chamber 18 is inhibited. A third operating cycle 500 for monitoring operation of the spark plug 50 is shown in Figure 8. The monitoring cycles could be performed during the compression stroke. The generation of the first and second sparks SP1, SP2 in the compression stroke when the engine 10 is operating in a fuel 35 cut-off mode is illustrated in the third operating cycle 500. 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. It is not necessary to monitor the spark plugs 50 during each combustion cycle. The or each spark plug 50 may be monitored periodically, for example after expiry 40 of a predetermined time interval. Alternatively, the or each spark plug 50 may be monitored when one or more operating parameters of the engine 10 are within a predetermined range, for example the operating speed is below a predetermined speed threshold. By reducing the monitoring of the spark plugs 50, 17 overheating of the ignition due 58 may be avoided; and / or wear of the spark plug 50 may be reduced. This may, for example, reduce monitoring of the spark plug 50 which may degrade the main spark event, for example at high engine speeds. 5 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. 07 02 25

Claims

1. A control system for performing one or more monitoring cycles to monitor a spark, plug during operation of a spark-ignition internal combustion engine, the internal combustion engine comprising an 5 ignition coil having a primary winding and a secondary winding, wherein the control system comprises one or more controllers configured to:determine a first dwell time for a first charging cycle of the primary winding;control a supply of electric current to the primary winding for the determined first dwell time in the first charging cycle;10 control the supply of electric current to the primary winding after the determined first dwell time toinduce a first voltage in the secondary winding; anddetermine if the first voltage induced in the secondary winding fails to generate a spark or generates a degraded spark,wherein the monitoring cycle comprises:15 monitoring the current in the primary winding to determine if the first voltage induced in thesecondary winding fails to generate a spark or generates a degraded spark;performing a second charging cycle after the first charging cycle; andmonitoring the current in the primary winding during the second charging cycle to determine if the _ first voltage induced in the secondary winding fails to generate a spark or generates a degraded spark, C\]20 wherein the one or more controller is oonfignred to implement a time inteival between the firstcharging cycle and the second charging cycle, the time interval being controlled such that the second CM charging cycle interrupts a spark generated after the first charging cycle.

2. A control system as claimed in claim 1, wherein the one or more controllers is configured to ^^25 determine that the spark plug fails to generate a spark or generates a degraded spark if the current in the primary winding at the beginning of the second charging cycle has a magnitude greater than or equal to a first threshold.

3. A control system as claimed in any one of claims 1 or 2, wherein the one or more controllers is 30 configured to determine that the spark plug generated a spark if the current in the primary winding at the beginning of the second charging cycle has a magnitude less than the first threshold.

4. A control system as claimed in any preceding claim, wherein the one or more controllers is configured to determine an error state if the current in the primary winding at the beginning of the second 35 charging cycle has a magnitude less than a second threshold.

5. A control system as claimed in any one of the preceding claims, wherein the one or more controllers is configured to implement the monitoring cycle during a combustion phase of the engine.40 6. A control system as claimed in any one of the preceding claims, wherein the one or morecontrollers is configured to implement the monitoring cycle during a non-combustion phase of the engine.

7. A control system as claimed in any one of the preceding claims, wherein the one or more controllers is configured to implement a plurality of the monitoring cycles in respect of a plurality of determined first dwell times, the determined first dwell times being different from each other, and optionally wherein the one or more controllers is configured to identify the one of the plurality of determined first dwell 5 times having the shortest duration which result in the spark plug generating a spark.

8. A control system as claimed in any preceding claim, wherein the one or more controllers comprises:at least one electronic processor having an electrical input and an electrical output; and10 at least one memory device electrically coupled to the at least one electronic processor andhaving 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 therein to implement the monitoring cycle.15 9. A vehicle comprising a control system as claimed in any one of the preceding claims.

10. A method of monitoring a spark plug in a spark-ignition internal combustion engine, the internalcombustion engine comprising an ignition coil having a primary winding and a secondary winding, wherein the method comprises implementing a monitoring cycle during operation of the internal combustion engine, |20 the monitoring cycle comprising:determining a first dwell time for a first charging cycle of the primary winding;I controlling a supplying of electric current to the primary winding for the determined first dwell timein the first charging cycle;, controlling the supply of electric current to the primary winding after the determined first dwell time•25 to induce a first voltage in the secondary winding;determining if the first voltage induced in the secondary winding fails to generate a spark or generates a degraded spark; monitoring the current in the primary winding to determine ifthe first voltage induced in the secondary winding fails to generate a spark or generates a degraded spark;performing a second charging cycle after the first charging cycle; and30 monitoring the current in the primary winding during the second charging cycle to determine ifthefirst voltage induced in the secondary winding failed to generate a spark or generated a degraded spark; andimplementing a time interval between the first charging cycle and the second charging cycle, the time interval being such that the second charging cycle interrupts a spark generated after the first charging 35 cycle.

11. 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 claim 10.

Images