Claims:We claim:
1. A system (100) to control operation of an engine (120), said system (100) comprises:
an airflow sensor (104) in an intake path (102) of said engine (120), and
a controller (110) connected to at least one said airflow sensor (104), said controller (110) comprising a memory element (108) storing at least two maps for air mass correction, said controller (110) adapted to
detect a signal (106) to switch from a first map (112), and
select a second map (114) from said at least two maps based on said signal (106), characterized by
switch from a current value of said first map (112) to a predetermined value of selected second map (114) in a linear manner.

2. The system (100) as claimed in claim 1, wherein said signal (106) is triggered on determination of at least one shut-OFF condition of an Exhaust Gas Recirculation (EGR) unit.

3. The system (100) as claimed in claim 1, wherein said switch from said current value of said first map (112) to said predetermined value of said second map (114) is performed by application of pulsating ramp function.

4. The system (100) as claimed in claim 1, wherein said airflow sensor (104) is a Hot Film Air Mass (HFM) sensor.

5. A controller (110) to control operation of an engine (120), said controller (110) comprises a memory element (108) storing at least two maps for air mass correction, said controller (110) adapted to
detect a signal (106) to switch from a first map (112), and
select a second map (114) from said at least two maps based on said signal (106), characterized by
switch from a current value of said first map (112) to a predetermined value of selected second map (114) in a linear manner.

6. The controller (110) as claimed in claim 5, wherein said signal (106) is triggered on determination of at least one shut-OFF condition of an Exhaust Gas Recirculation (EGR) unit.

7. The controller (110) as claimed in claim 5, wherein said switch from said current value of said first map (112) to said predetermined value of said second map (114) is performed by application of a pulsating ramp function.

8. A method for controlling operation of engine (120), said method comprising the steps of:
detect a signal (106) to switch from a first map (112);
selecting a second map (114) from at least two maps based on said signal (106), characterized by
switching from a current value of said first map (112) to a predetermined value of selected second map (114) in a linear manner.

9. The method as claimed in claim 8, wherein said signal (106) is triggered after determining at least one shut-OFF condition of an Exhaust Gas Recirculation (EGR) unit.

10. The method as claimed in claim 8, wherein said switching from said current value of said first map (112) to said predetermined value of said second map (114) is performed by applying a pulsating ramping function.
, Description:Complete Specification:
The following specification describes and ascertains the nature of this invention and the manner in which it is to be performed:

Field of the invention:
[0001] The present invention relates to a system, controller and method for controlling operation of an engine.

Background of the invention:
[0002] Air mass deviation between desired and actual air mass creates impact on NOx emission calculation and governor control parameter. The deviation in air mass was found to be at shut-OFF cases of Exhaust Gas Recirculation (EGR) unit. A change in pulsation correction factor output, due to map switch from a normal map to shut-OFF map lead to air mass deviation in the final value. This air mass deviation usually occurs every time driver press accelerator pedal or releases it. Therefore, air mass deviation throughout drive over a long period in Real Drive Emission (RDE) may lead to different air flow calculation and NOx emissions. There is a need for controlling the engine operation while switching between air mass correction maps.

[0003] A prior art from the similar domain is provided for reference. According to a prior art US2003098014, an EGR control apparatus for internal combustion engine is disclosed. Adequate controllability is ensured when feedback control is provided to both the EGR valve and the intake throttle valve, and switching shock is prevented when control is switched from one to the other. The present apparatus comprises an EGR valve, an intake throttle valve, feedback control means for providing feedback control to the EGR valve and intake throttle valve such that the actual EGR volume approximates the target EGR volume corresponding to the running condition of the engine, and limiting means for limiting the operable opening ranges of the EGR valve and intake throttle valve in accordance with the target EGR volume. During EGR control of one valve, feedback control is provided to the other valve and the target opening is constantly calculated. The actual operations are merely limited, so these operations can start from the optimal opening and the switching shock can be prevented when a switch is made to the control of the other valve.

Brief description of the accompanying drawings:
[0004] An embodiment of the disclosure is described with reference to the following accompanying drawing,
[0005] Fig. 1 illustrates a block diagram of the system to control engine operation, according to an embodiment of the present invention;
[0006] Fig. 2 illustrates waveforms for air mass correction, according to an embodiment of the present invention, and
[0007] Fig.3 illustrates a method for controlling operation of the engine, according to the present invention.

Detailed description of the embodiments:
[0008] Fig. 1 illustrates a block diagram of the system to control operation of an engine, according to an embodiment of the present invention. The system 100 comprises an airflow sensor 104 in an intake path 102 of the engine 120, and a controller 110 connected to at least one airflow sensor 104. The controller 110 is the Engine Control Unit (ECU) which is connected to different components and sensors of a vehicle. The controller 110 is able to diagnose faults (if present) and control the operation of the engine 120 accordingly. The controller 110 comprises a memory element 108 storing at least two maps for air mass correction. The controller 110 adapted to detect a signal 106 to switch from a first map 112, and select a second map 114 from the at least two maps based on the detected signal 106, characterized by, the controller 110 adapted to switch from a current value of the first map 112 to a predetermined value of selected second map 114 in a linear manner. The first map 112 is the current map and the second map 114 is the target map. Once the value is switched to the target map, the controller 110 controls the operation of the engine 120 as per the requirement. Further, the switching is also possible from the second map 114 to the first map 112, in which case the former is the current map and the latter is the target map. The at least two maps comprises correction factors, based on engine operating points (or engine loading) for correcting the detected air mass value to a calibrated/desired air mass value. The system 100 further comprises an Exhaust Gas Recirculation (EGR) unit comprising an EGR path 118, an EGR valve 122 and an EGR cooler 124.

[0009] The signal 106 is triggered by determination of at least one shut-OFF condition of the EGR unit. The at least one shut-OFF condition comprises but not limited to an overrun condition, where the engine speed is greater than specified threshold and injection quantity is less than specified some threshold, an error in the EGR unit and/or throttle valve, battery voltage less than certain limit, etc. Further, the airflow sensor 104 is a Hot Film Air Mass (HFM) sensor, whose detected value is corrected. The HFM sensor is given as an example and other type of sensors to detect airflow is well within the scope of the present invention. The same must not be understood in a limiting manner.

[0010] The switch from the current value of the first map 112 to the predetermined value of the target map 114 is performed by application of a pulsating ramp function. The pulsating ramp function introduces a time delay 214 (shown in Fig. 2) to reach the predetermined value.

[0011] In accordance to an embodiment of the present invention, the controller 110 to control operation of the engine 120 is provided. The controller 110 comprises the memory element 108 storing at least two maps for air mass correction. The controller 110 adapted to detect/receive the signal 106 to switch from the first map 112, and select the second map 114 from the at least two maps based on the signal 106, characterized by, the controller 110 further adapted to switch from the current value of the first map 112 to the predetermined value of the selected second map 114 in the linear manner. The signal 106 is triggered on determination of at least one shut-OFF condition of the Exhaust Gas Recirculation (EGR) unit.

[0012] The at least one shut-OFF condition comprises but not limited to an overrun condition, where the engine speed is greater than specified threshold and injection quantity is less than specified some threshold, an error in the EGR unit and/or throttle valve, battery voltage less than certain limit, etc. Further, the switch/transition from the current value of the first map 112 to the predetermined value of the second map 114 is performed by application of the pulsating ramp function. The first map 112 comprises correction factors under normal operating condition of the engine 120, and the second map 114 comprises correction factors under shut-OFF conditions. There is possibility of using other maps based other operating conditions of the engine 120.

[0013] Fig. 2 illustrates a graph for air mass correction, according to an embodiment of the present invention. The graph 200 comprises plurality of waveforms, a detected air mass waveform (detected sensor signal) 210, a desired air mass waveform (desired signal) 212, the signal 106 and a pulsation correction factor signal (correction signal) 220. In the graph 200, a line 218 corresponds to a value from the second map 114 and a line 222 corresponds to a value from the first map 112, for a specific engine speed. At time 202, the signal 106 indicates the need to switch the map, which is shown by raising pulse. At this instant, the detected sensor signal 210 also raises instantly, however the same causes various sub-systems of the engine 120 and the vehicle to respond unexpectedly, causing rise in the emission such as NOx. If the detected sensor signal 210 is controlled in a gradual manner, then the unexpected change in the behavior of the engine 120 and the emission is nullified. In order to achieve the desired signal 212 at the instant of detecting the transition, the controller 110 corrects the detected sensor signal 210 based on the predetermined value of the second map 114, which is the target map. Considering the time instant 202 again, the controller 110 applies the pulsating ramp function, i.e. a time delay 214, to the current value from the first map 112 to the predetermined value of the second map 114.

[0014] Now at time instant 204, on referring the signal 106, a change in state is seen which indicates switching to first map 112. The controller 110 then applies the pulsating ramp function to the current value of the second map 114 to reach the target value of the first map 112. The switch is performed in the linear manner. Similarly, at the time instant of 206 and 208, the controller 110 detects the change in status of the signal 106 and linearly moves to the target value from the current value. The pulsating ramp function introduces time delays 214 which enables the control of the engine function and the corresponding emissions. The graph is illustrated for simple explanation and is not to the scale. The same must not be understood in limiting sense.

[0015] Fig.3 illustrates a method for controlling operation of the engine, according to the present invention. The method comprising the steps of: a step 302 comprises receiving the signal 106 to switch from the first map 112. A step 304 comprises selecting the second map 114 from at least two maps based on the signal 106. The method is characterized by a step 306 which comprises switching from the current value of the first map 112 to the predetermined value of the selected second map 114 in the linear manner.

[0016] The signal 106 is triggered by detecting at least one shut-OFF condition of the Exhaust Gas Recirculation (EGR) unit. The switching from the current value of the first map 112 to the predetermined value of the second map 114 is performed by applying the pulsating ramping function. The pulsating ramping function introduces delay to overcome the issue.

[0017] According to an embodiment of the present invention, a slower change in pulsation correction factor (and therefore the final air mass value) is achieved to reduce air mass deviation and provide accurate NOx flow emission values over long drive cycle.

[0018] It should be understood that embodiments explained in the description above are only illustrative and do not limit the scope of this invention. Many such embodiments and other modifications and changes in the embodiment explained in the description are envisaged. The scope of the invention is only limited by the scope of the claims.