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 disclosure relates a controller and method to control Exhaust Gas Recirculation (EGR) for an engine of a vehicle.

Background of the invention:
[0002] An open loop control is usually prone to the disturbances like intake depression, exhaust back pressure and leakages in the Exhaust Gas Recirculation (EGR) system. The EGR is a very important strategy in meeting future emission norms and rate of EGR controlled by means of EGR valve and a throttle valve. The EGR can be close looped with the feedback of any air mass sensor or controlled in open loop without any air mass sensor. The open loop air system is without an air mass sensor i.e., the actuator of the EGR valve position directly through maps based on engine operating points without taking any feedback from the air mass sensor. However, the open loop control of EGR system is less robust against system disturbances in terms of emission and relatively more prone to field failures as there is no correction / close loop possible to actuator positions. With current open loop platform, corrections in the open loop system to minimize the impact of the disturbances like back pressure, intake depression and other tolerances is not available.

[0003] According to a prior art KR20080043663 discloses an exhaust gas recirculation control system for diesel vehicle and method thereof. An exhaust gas recirculation control system for a diesel vehicle and a method thereof are provided to reduce discharge of particulate matter by increasing an air flow rate in case of over boost and reduce discharge of NOx by decreasing an air flow rate in case of under boost. An exhaust gas recirculation control system for a diesel vehicle includes an intake pressure sensor, a memory unit, a control unit, and an exhaust gas recirculation valve. The intake pressure sensor detects the boost pressure charged by a turbo charger. The memory element 122 has a map 124 in which data of reference air pressure are set in accordance with operating condition. The control unit detects the boost pressure charged by the turbo charger, compares the reference pressure of the operating condition and the boost pressure measured actually, and controls opening/closing of the exhaust gas recirculation valve in accordance with the variation. The exhaust gas recirculation valve adjusts an exhaust gas recirculation rate under the control of the control unit.

Brief description of the accompanying drawings:
[0004] An embodiment of the disclosure is described with reference to the following accompanying drawings,
[0005] Fig. 1 illustrates a block diagram of a controller to control Exhaust Gas Recirculation (EGR) for an engine of a vehicle, according to an embodiment of the present invention, and
[0006] Fig. 2 illustrates a flow diagram of a method for controlling Exhaust Gas Recirculation (EGR) for the engine of the vehicle, according to the present invention.

Detailed description of the embodiments:
[0007] Fig. 1 illustrates a block diagram of a controller to control Exhaust Gas Recirculation (EGR) for an engine of a vehicle, according to an embodiment of the present invention. The vehicle comprises an engine 102 connected to a turbocharger 106, an EGR valve 108 positioned in a passage 120 connecting an exhaust conduit 104 to an intake conduit 112 of the engine 102, and a boost pressure sensor 114 positioned in the intake conduit 112. The controller 110 configured to receive input signals from the boost pressure sensor 114, during running conditions of the engine 102, calculate a difference between the actual boost pressure with a reference boost pressure map 124 stored in a memory element 122 of the controller 110 corresponding to a current operating point of the engine 102, and correct a position of the EGR valve 108 based on the difference until the actual boost pressure comes within a threshold range of values, characterized in that, the reference boost pressure map 124 is subject to drift correction based on current environmental pressure before calculation of the difference. The engine 102 in itself is either single cylinder, two cylinder or multi-cylinder.

[0008] According to an embodiment of the present invention, the boost pressure sensor 114 is also subject to offset correction at engine OFF condition before performing the drift correction. The offset correction is performed to adjust any deviation in the boost pressure sensor 114 in no load conditions. Further, the offset correction is done with respect to the environmental pressure or ambient pressure.

[0009] In accordance to an embodiment of the present invention, a calibratable system threshold for the reference boost pressure map 114 is also included in the memory element 124 to accommodate the tolerances of the system 100 or the turbocharger 106. Specifically, for each operating point of the engine 102, the reference boost pressure map 124 comprises minimum and maximum system threshold within which the boost pressure is acceptable, such as +x% of the value in the reference boost pressure map 124. For example, once the difference in boost pressure is calculated (after drift correction due to environmental pressure), then the controller 110 also checks if the boost pressure after drift correction is beyond the system threshold. If outside than the system threshold, then the controller 110 corrects the position of the EGR valve 108 until the boost pressure comes within system threshold. The correction in EGR valve 108 is also limited to permissible limit beyond which the emission are affected and the same is indicated to the user/driver through alert 118.

[0010] According to an embodiment of the present invention, the environmental pressure is determined using at least one of an ambient pressure sensor 128 and a geolocation position system. A receiver 130 for the geolocation position system is provided in the vehicle and is used to detect the satellite positions of the geolocation position system and determine the current position of the vehicle in a map. A corresponding environmental pressure or altitude for the determined position is retrieved by the controller 110. The controller 110 then applies a correction factor for the retrieved environmental pressure or the altitude is applied to the current boost pressure as per the operating point of the engine 102 and drift correction is performed.

[0011] According to an embodiment of the present invention, the controller 110 is at least one of internal to said vehicle and external to said vehicle. The internal control unit is any one of an Engine Control Unit and an Exhaust Control Unit and the like and those control units which reside within the vehicle, and the external control unit are those which are not part of the vehicle but part of other computing devices or units such as a server, a cloud or a portable device connected to the vehicle through any one of a wired and wireless means. An example of the wired means comprises the Universal Serial Bus (USB) cable based connection to On-Board Diagnostic (OBD) port. An example of the wireless means comprises Bluetooth dongle based connection to OBD port, or the like. The examples are just for clarification and other types well known in the art are equally usable.

[0012] In accordance to an embodiment of the present invention, the controller 110 is provided with necessary signal detection, acquisition, and processing circuits. The controller 110 is the control unit which comprises input/output interfaces having pins or ports, the memory element 122 such as Random Access Memory (RAM) and/or Read Only Memory (ROM), Analog-to-Digital Converter (ADC) and a Digital-to-Analog Convertor (DAC), clocks, timers, counters and at least one processor (capable of implementing machine learning) connected with each other and to other components through communication bus channels. The memory element 122 is pre-stored with logics or instructions or programs or applications or modules/models and/or threshold values/ranges, system threshold, predefined/predetermined criteria/conditions, correction factor-based maps/table which is/are accessed by the at least one processor as per the defined routines. The internal components of the controller 110 are not explained for being state of the art, and the same must not be understood in a limiting manner. The controller 110 may also comprise communication units to communicate through wireless or wired means such as Global System for Mobile Communications (GSM), 3G, 4G, 5G, Wi-Fi, Bluetooth, Ethernet, serial networks, and the like. The controller 110 is implementable in the form of System-in-Package (SiP) or System-on-Chip (SOC) or any other known types. Examples of controller 110 comprises but not limited to, microcontroller, microprocessor, microcomputer, etc.

[0013] According to an embodiment of the present invention, an open loop controller 110 for EGR system 100 is provided which is without an air flow sensor or Manifold Air Flow sensor. The EGR valve 108 is controlled directly through engine operating maps based on operating points. In alternative embodiment, the controller 110 enables control of EGR valve 108 when the MAF sensor malfunctions or becomes faulty.

[0014] According to an embodiment of the present invention, the controller 110 is the Engine Control Unit (ECU) of the vehicle. The ECU receives all the required data in real-time through existing sensors 116 or sub-systems of the vehicle such as engine speed sensor, wheel speed sensor, Manifold Air Pressure (MAP) sensor, temperature sensor, oxygen sensor and the like, processes the data and controls the EGR valve 108 accordingly including drift correction.

[0015] In accordance to another embodiment of the present invention, the controller 110 is part of the cloud and connected to the vehicle through Telematics Control Unit (TCU). The cloud receives all the engine related parameters values through the TCU, processes the same and sends back the processed data to the vehicle. The ECU of the vehicle then controls the EGR valve 108 accordingly including the drift correction.

[0016] In accordance to yet another embodiment, the controller 110 is both the ECU and part of the cloud where the data gets processed in distributed manner. The processing is done partly by the ECU and partly by the cloud.

[0017] According to the present invention, a working of the controller 110 in the vehicle is provided. Before starting the correction to EGR valve 108, the controller 110 checks for proper functioning of the boost pressure sensor 114. The controller 110 performs offset correction/learning. The controller 110 learns the offset of the boost pressure sensor 114 by comparing it with ambient pressure sensor 128 when the engine 102 is OFF, and ignition is ON. It is to be noted that before the check is performed all the necessary release conditions or predetermined conditions are also checked such as engine parameters are satisfied before said EGR valve 108 is controlled, said engine parameters comprises engine speed and engine speed gradient, injection quantity and injection quantity gradient, throttle valve position, EGR valve position, Engine Operating Mode (EOM), boost pressure and the like and any relevant release conditions. The controller 110 then calculates and considers the offset corrected boost pressure signal for further processing. The offset correction is done after every drive cycle or calibratable as required.

[0018] The controller 110 is pre-stored with reference boost pressure map 124, which is generated in engine test bench (or a model-based approach) with mean samples and boost pressure correction for altitude to be given based on weightage factor using the ambient pressure sensor 128. In the reference boost pressure map 124, X-axis is represented by engine speed, Y-axis is represented by Injection quantity and Z-axis is reference boost pressure from mean sample. Further, environmental pressure-based factor or weightage table 126 is also stored in the memory element 122 which is used to correct the reference boost pressure map 124 based on the current operating point of the engine 102. A calibratable system threshold for the reference boost pressure map 124 is also included to accommodate the tolerances in the system 100.

[0019] In real time, the controller 110 checks the release/predetermined conditions before proceeding with the drift correction such as engine parameters are satisfied before said EGR valve 108 is controlled, the engine parameters comprises engine speed and engine speed gradient, injection quantity and injection quantity gradient, throttle valve position, EGR valve position, Engine Operating Mode (EOM), boost pressure and any other relevant signals or parameters. Based on the predetermined conditions and during the engine running state, difference in boost pressure and the reference boost pressure from the map 124 is calculated. The controller 110 takes the environmental pressure-based weightage factor from the table 126 to accommodate the environmental pressure/ altitude impact on the boost pressure. If the difference is more than the threshold pressure at that operating point, then the controller 110 applies the correction factor for the EGR valve 108 until boost pressure is within the defined threshold range. A separate threshold is considered by the controller 110 for the level of EGR valve 108 corrections allowed in the set point/operating point, above which error is indicated to the driver to take the vehicle to the service station (after threshold number of consecutive check of the factors). Any error beyond the EGR valve 108 control us intimated to the driver and recorded in the vehicle.

[0020] Fig. 2 illustrates a flow diagram of a method for controlling Exhaust Gas Recirculation (EGR) for the engine of the vehicle, according to the present invention. The vehicle comprises the engine 102 connected to the turbocharger 106, the EGR valve 108 positioned in the passage 120 connecting the exhaust conduit 104 to the intake conduit 112 of the engine 102, and the boost pressure sensor 114 positioned in the intake conduit 112. The method comprises plurality of steps of which a step 202 comprises receiving input signals from the boost pressure sensor 114. A step 204 comprises calculating the difference between the actual boost pressure with the reference boost pressure map 124 stored in the memory element 122 of the controller 110 corresponding to the current operating point of the engine 102. A step 206 comprises correcting the position of the EGR valve 108 based on the difference until the actual boost pressure comes within the threshold range of values. The step 204 is characterized by, a step 210 which comprises performing drift correction to the reference boost pressure map 124 based on the current environmental pressure before calculating the difference. A step 208 comprises triggering the alert 118 to the user if position correction of EGR valve 108 is out of the allowable correction value. The method is executed by the controller 110 as explained before and not explained again to avoid repetition.

[0021] According to the present invention, before performing the drift correction, the method also comprises a step 210 comprising subjecting the boost pressure sensor 114 to an offset correction at engine OFF condition.

[0022] According to the present invention, a method for accommodating tolerances of the system 100 on the boost pressure is provided. According to the method, a calibratable system threshold for the reference boost pressure map 114 is included in the memory element 124. The method considers the minimum and maximum system threshold, for each operating point of the engine 102, in the reference boost pressure map 124. If the correction performed by the controller 110 results the boost pressure within the system threshold range, such as +x% of the value in the reference boost pressure map 124, the correction is completed. For example, once the difference in boost pressure is calculated (after drift correction due to environmental pressure), then the method also checks if the boost pressure after drift correction is beyond the system threshold. If outside than the system threshold, then the controller 110 corrects the position of the EGR valve 108 until the boost pressure comes within system threshold. The correction in EGR valve 108 is also limited to permissible limit beyond which if the emission are affected, the same is indicated to the user/driver through alert 118.

[0023] According to the present invention, the method comprises determining the environmental pressure using at least one of the ambient pressure sensor 128 and the geolocation position system.

[0024] According to the present invention, the method also comprises satisfying predetermined conditions (or release conditions) related to engine parameters before controlling the EGR valve 108. The engine parameters comprises but not limited to engine speed and engine speed gradient, injection quantity and injection quantity gradient, throttle valve position, EGR valve position, Engine Operating Mode (EOM), boost pressure and the like.

[0025] According to an embodiment of the present invention, a boost pressure based correction for EGR without (or with faulty) air mass sensor is provided. The controller 110 and method performs corrections to the EGR valve 108 due to changes in the back pressure, intake depressions and the leakages or any other EGR system disturbances. The correction is given based on the boost pressure sensor 114 which is part of almost all the On road and Off road engines and the applications where boost pressure sensor 114 is available and EGR control is required. Along with the correction based on boost pressure sensor 114, the offset correction and drift correction of the boost pressure sensor 114 is also done to ensure the robustness of the pressure signal used for correction. A reference boost pressure values along with tolerances are mapped for a particular engine 102 for all operating points, along with correlation of the same with ambient conditions and threshold calibration for the reference boost pressure to accommodate the tolerances of the system 100. Whenever there is a deviation of boost pressure in field, due to any of the system disturbances (with reference boost pressures mapped), a correction to EGR valve / throttle valve position is given based on the boost pressure difference until boost pressure comes within threshold tolerance band. An upper and lower threshold for EGR valve position correction is given beyond which driver/user is indicated on dashboard or other means such as audio, light, vibration and the like, to take the vehicle to service station for a detailed checkup.

[0026] 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.
, Claims:We claim:
1. A controller (110) to control Exhaust Gas Recirculation (EGR) for an engine (102) of a vehicle, said vehicle comprises an engine (102) connected to a turbocharger (106), an EGR valve (108) positioned in a passage (120) connecting an exhaust conduit (104) to an intake conduit (112) of said engine (102), and a boost pressure sensor (114) positioned in said intake conduit (112), said controller (110) configured to
receive input signals from said boost pressure sensor (114);
calculate a difference between the actual boost pressure with a reference boost pressure map (124) stored in a memory element (122) of said controller (110) corresponding to a current operating point of said engine (102), and
correct a position of said EGR valve (108) based on said difference until said actual boost pressure comes within a threshold range of values, characterized in that,
said reference boost pressure map (124) is subject to drift correction based on current environmental pressure before calculation of said difference.

2. The controller (110) as claimed in claim 1, wherein said boost pressure sensor (114) is also subject to offset correction at engine OFF condition before performing said drift correction.

3. The controller (110) as claimed in claim 1, wherein said environmental pressure is determined using at least one of an ambient pressure sensor (128) and a receiver (130) of a geolocation position system.

4. The controller (110) as claimed in claim 1, wherein an alert (118) is triggered to a user if position correction of said EGR valve (108) is out of the allowable correction value.

5. The controller (110) as claimed in claim 1, wherein predetermined conditions related to engine parameters are satisfied before said EGR valve (108) is controlled, said engine parameters comprises engine speed and engine speed gradient, injection quantity and injection quantity gradient, throttle valve position, EGR valve position, Engine Operating Mode (EOM), boost pressure and the like.

6. A method for controlling Exhaust Gas Recirculation (EGR) for an engine (102) of a vehicle, said vehicle comprises an engine (102) connected to a turbocharger (106), an EGR valve (108) positioned in a passage (120) connecting an exhaust conduit (104) to an intake conduit (112) of said engine (102), and a boost pressure sensor (114) positioned in said intake conduit (112), said method comprising the steps of:
receiving input signals from said boost pressure sensor (114);
calculating a difference between the actual boost pressure with a reference boost pressure map (124) stored in a memory element (122) of said controller (110) corresponding to a current operating point of said engine (102), and
correcting a position of said EGR valve (108) based on said difference until said actual boost pressure comes within a threshold range of values, characterized by,
performing drift correction to said reference boost pressure map (124) based on a current environmental pressure before calculating said difference.

7. The method as claimed in claim 6, comprises subjecting said boost pressure sensor (114) to an offset correction at engine OFF condition before performing said drift correction.

8. The method as claimed in claim 6, comprises determining said environmental pressure using at least one of an ambient pressure sensor (128) and a receiver (130) or a geolocation position system.

9. The method as claimed in claim 6, comprises triggering an alert (118) to a user if position correction of said EGR valve (108) is out of the allowable correction value.

10. The method as claimed in claim 6, comprises satisfying predetermined conditions related to engine parameters before controlling said EGR valve (108), said engine parameters comprises engine speed and engine speed gradient, injection quantity and injection quantity gradient, throttle valve position, EGR valve position, Engine Operating Mode (EOM), boost pressure and the like.