Claims:WE CLAIM:
1. An excitation control system (100) for an alternator (104) of a vehicle, said system (100) comprising:
a. a plurality of sensor units (202a-n) configured to periodically detect a plurality of parameters associated with said vehicle to generate corresponding sensed signals, and further configured to generate sensed values based on said sensed signals;
b. a driver unit (116) comprising:
i. an identification unit (204) configured to cooperate with said sensor units (202a-n) to receive said sensed values, and further configured to identify vehicle state based on said received sensed values;
ii. a memory (206) configured to store:
• a lookup table having a plurality of vehicle states, parameters associated with each of said vehicle states, and at least one pre-determined value for each of said parameters; and
• a pre-determined set of rules, and
iii. a Pulse Width Modulated (PWM) signal generator unit (208) configured to cooperate with said identification unit (204) and said memory (206) to extract pre-determined values associated with said identified vehicle state from said lookup table, and further configured to cooperate with said sensor units (202a-n) to receive said sensed values and compare each of said extracted pre-determined values with corresponding sensed values to generate a PWM control signal for controlling the excitation of said alternator (104) based on said pre-determined set of rules,
wherein said identification unit (204) and said PWM signal generator unit (208) are implemented using one or more processors.
2. The system (100) as claimed in claim 1, wherein said PWM signal generator unit (208) comprises:
a. a crawler and extractor unit (210) configured to cooperate with said identification unit (204) and said memory (206) to receive said identified vehicle state and crawl through said lookup table to extract pre-determined values associated with parameters of said identified vehicle state;
b. a digital comparator (212) configured to cooperate with said crawler and extractor unit (210) to receive said extracted pre-determined values, and further configured to compare each of said extracted pre-determined values with corresponding sensed values to generate a comparison signal for each of said parameters of said identified vehicle state; and
c. a PWM driver module (214) configured to cooperate with said digital comparator (212) to receive said comparison signals, and further configured to cooperate with said memory (206) to generate said PWM control signal based on said received comparison signals and said pre-determined set of rules,
3. The system (100) as claimed in claim 1, wherein said parameters include vehicle speed, engine RPM (revolutions per minute), battery voltage, engine temperature, RPM settling time, park lamp status, AC compressor status, and glow plug status.
4. The system (100) as claimed in claim 1, wherein said vehicle states include idling, coasting, high speed, low speed, accelerating and braking.

5. The system (100) as claimed in claim 2, wherein said pre-determined set of rules include rules for determining the duty cycle of said PWM control signal based on said identified vehicle state and said comparison signals.
6. The system (100) as claimed in claim 1, wherein said driver unit (116) is configured to supply said generated PWM control signal to a regulator (110), said regulator (110) being configured to switch on/off field current supply to the field winding (108) of said alternator (104) based on the duty cycle of said received PWM control signal.
7. The system (100) as claimed in claim 1, wherein said memory (206) is configured to store a pre-set delay time value.

8. The system (100) as claimed in claim 7, wherein said PWM signal generator unit (208) is configured to cooperate with said memory (206) to generate said PWM control signal after said pre-set delay time when duty cycle of said PWM control signal changes in response to change in detected parameters.

9. The system (100) as claimed in claim 1, wherein said system (100) includes an input module (216) configured to cooperate with said memory (206) to facilitate an operator to define said pre-determined values for each of said parameters.
, Description:FIELD
The present disclosure relates to automotive alternator control systems. More particularly, the present disclosure relates to a system for controlling excitation of an alternator of a vehicle based on parameters such as vehicle speed, engine RPM (revolutions per minute), battery voltage, park lamp status, AC compressor status, glow plug status, and engine temperature.
BACKGROUND
The background information herein below relates to the present disclosure but is not necessarily prior art.

Typically, an alternator is used for supplying power to electrical loads and charging a vehicle battery in a motor vehicle. The rotor of the alternator carries field windings. During engine start, the field windings are supplied with power from the vehicle battery via an ignition switch. Once the engine is running and the alternator is generating power, current from the alternator is fed to its field winding through a diode. The excited rotor is driven by the crankshaft of the engine inside the stator of the alternator, thereby inducing a voltage in the stator winding. This induced voltage is rectified to charge the vehicle's battery. A regulator is connected between the alternator and the vehicle battery to regulate current generated by the alternator.

The alternators of existing vehicles are continuously loading the engine to charge the battery. At times, during vehicle operation, the vehicle engine is heavily loaded and the engine RPM (revolutions per minute) is low. This may happen, for example, when the vehicle is climbing a steep hill and demanding continuous acceleration. Under such conditions, the vehicle engine consumes a large amount of fuel, thereby reducing the fuel economy substantially.
Further, when the engine is idling or coasting and the battery voltage is above a required minimum residual voltage level, the alternator shall be switched off to save energy and improve vehicle efficiency. However, the prevailing alternator systems do not have any control means for switching the alternator as per the load requirement. This leads to reduced fuel efficiency and excessive emissions, which is not desired.

Therefore, there is felt a need to provide an excitation control system for an alternator of a vehicle that eliminates the above-mentioned drawbacks.
OBJECTS
Some of the objects of the present disclosure, which at least one embodiment herein satisfies, are as follows:

It is an object of the present disclosure to ameliorate one or more problems of the prior art or to at least provide a useful alternative.

An object of the present disclosure is to provide an excitation control system for an alternator of a vehicle.

Another object of the present disclosure is to provide an excitation control system for an alternator of a vehicle that improves fuel economy of the vehicle.

Still object of the present disclosure is to provide an excitation control system for an alternator of a vehicle that reduces vehicle emissions.

Yet another object of the present disclosure is to provide a system that delivers better acceleration performance during drive as the alternator excitation is cut off when not required.

Still another object of the present disclosure is to provide an excitation control system for an alternator of a vehicle that improves noise, vibration and harshness (NVH) performance of the vehicle during idling by reducing its idling speed.

Other objects and advantages of the present disclosure will be more apparent from the following description, which is not intended to limit the scope of the present disclosure.
SUMMARY
The present disclosure envisages an excitation control system for an alternator of a vehicle. The system comprises a plurality of sensor units and a driver unit. The sensor units are configured to periodically detect a plurality of parameters associated with the vehicle to generate corresponding sensed signals, and are further configured to generate sensed values based on the generated sensed signals. The parameters associated with the vehicle include vehicle speed, engine RPM (revolutions per minute), battery voltage, engine temperature, RPM settling time, park lamp status, AC compressor status, and glow plug status. The driver unit comprises an identification unit, a memory, and a Pulse Width Modulated (PWM) signal generator unit. The identification unit is configured to cooperate with the sensor units to receive the sensed values, and is further configured to identify vehicle state based on the received sensed values. The vehicle states include idling, coasting, accelerating, high speed, low speed, and braking. The memory is configured to store a lookup table having a plurality of vehicle states, parameters associated with each of the vehicle states, and at least one pre-determined value for each of the parameters and a pre-determined set of rules. The PWM signal generator unit is configured to cooperate with the identification unit and the memory to extract pre-determined values associated with the identified vehicle state from the lookup table, and is further configured to cooperate with the sensor units to receive the sensed values and compare each of the extracted pre-determined values with corresponding sensed values to generate a PWM control signal for controlling the excitation of the alternator based on the pre-determined set of rules.

In an embodiment, the identification unit and the PWM signal generator unit are implemented using one or more processors.

In another embodiment, the PWM signal generator unit comprises a crawler and extractor unit, a digital comparator, and a PWM driver module. The crawler and extractor unit is configured to cooperate with the identification unit and the memory to receive the identified vehicle state and crawl through the lookup table to extract pre-determined values associated with parameters of the identified vehicle state. The digital comparator is configured to cooperate with the crawler and extractor unit to receive the extracted pre-determined values, is further configured to compare the extracted pre-determined values with the sensed values to generate a comparison signal for each of the parameters of the identified vehicle state. The PWM driver module is configured to cooperate with the digital comparator to receive the comparison signals, and is further configured to cooperate with the memory to generate the PWM control signal based on the received comparison signals and the pre-determined set of rules. The pre-determined set of rules include rules for determining the duty cycle of the PWM control signal based on the identified vehicle state and the comparison signals.

In an embodiment, the driver unit is configured to supply the generated PWM control signal to a regulator. The regulator is configured to switch on/off field current supply to the field winding of the alternator based on the duty cycle of the received PWM control signal.

In an embodiment, the memory is configured to store a pre-set delay time value. In an embodiment, the PWM signal generator unit is configured to cooperate with the memory to generate the PWM control signal after the pre-set delay time when duty cycle of the PWM control signal changes in response to change in detected parameters.

Advantageously, the system includes an input module configured to cooperate with the memory to facilitate an operator to define the pre-determined values for each of the parameters.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING
An excitation control system for an alternator of a vehicle of the present disclosure will now be described with the help of the accompanying drawing, in which:
Figure 1 illustrates a schematic circuit diagram of an alternator based battery charging system, in accordance with an embodiment of the present disclosure;
Figure 2 illustrates a block diagram of an excitation control system for the alternator of Figure 1;
Figure 3a illustrates an exemplary flow diagram depicting alternator switching control logic for vehicle idling state;
Figure 3b illustrates an exemplary flow diagram depicting alternator switching control logic for vehicle low-speed state;
Figure 3c illustrates an exemplary flow diagram depicting alternator switching control logic for vehicle high-speed state;
Figure 4a illustrates a graph of battery charging current and voltage on the Y-axis versus time on the X-axis for different vehicle states;
Figure 4b illustrates a bar graph depicting fuel economy measurement with and without the excitation control system of Figure 2 for a diesel engine vehicle; and
Figure 5 illustrates a Pulse Width Modulated waveform for switching on/off alternator excitation.
LIST OF REFERENCE NUMERALS
100 – System
102 – Rectifier
104 – Alternator
106 – Stator winding
108 – Field winding
110 – Regulator
112 – Battery
114 – Loads
116 – Driver unit
202a-n – Sensor units
204 – Identification unit
206 – Memory
208 – PWM signal generator unit
210 – Crawler and extractor unit
212 – Digital comparator
214 – PWM driver module
216 – Input module
DETAILED DESCRIPTION
Embodiments, of the present disclosure, will now be described with reference to the accompanying drawing.
Embodiments are provided so as to thoroughly and fully convey the scope of the present disclosure to the person skilled in the art. Numerous details, are set forth, relating to specific components, and methods, to provide a complete understanding of embodiments of the present disclosure. It will be apparent to the person skilled in the art that the details provided in the embodiments should not be construed to limit the scope of the present disclosure. In some embodiments, well-known processes, well-known apparatus structures, and well-known techniques are not described in detail.
The terminology used, in the present disclosure, is only for the purpose of explaining a particular embodiment and such terminology shall not be considered to limit the scope of the present disclosure. As used in the present disclosure, the forms "a,” "an," and "the" may be intended to include the plural forms as well, unless the context clearly suggests otherwise. The terms "comprises," "comprising," “including,” and “having,” are open ended transitional phrases and therefore specify the presence of stated features, elements, modules, units and/or components, but do not forbid the presence or addition of one or more other features, elements, components, and/or groups thereof. The particular order of steps disclosed in the method of the present disclosure is not to be construed as necessarily requiring their performance as described or illustrated. It is also to be understood that additional or alternative steps may be employed.
An excitation control system (hereinafter referred as “system 100”) for an alternator 104 of a vehicle of the present disclosure is now being described with reference to Figure 1 through Figure 5. The system 100 can be used for controlling the output of the alternator 104 by employing a digital control strategy in order to improve the fuel economy of the vehicle. The digital control strategy produces an output based on vehicle states such as idling, coasting, accelerating, decelerating, braking and cruising.

Referring to Figure 1 and Figure 2, the excitation control system 100 comprises a plurality of sensor units 202a-n and a driver unit 116. The sensor units 202a-n are configured to periodically detect a plurality of parameters associated with the vehicle to generate corresponding sensed signals, and are further configured to generate sensed values based on the generated sensed signals. The parameters detected by the sensor units 202a-n include, but are not limited to, vehicle speed, engine RPM, battery voltage, engine temperature, RPM settling time, park lamp status, AC compressor status, and glow plug status. In an embodiment, each of the sensor units 202a-n include a sensor and a signal conditioning unit. The sensor is configured to detect parameters associated with the vehicle, and is further configured to generate a sensed signal based on the detected parameter. The signal conditioning unit is configured to cooperate with the sensor to receive the generated sensed signal, and is further configured to generate a digital sensed value form the received analog sensed signal.

The driver unit 116 is configured to generate a PWM control signal to enable or disable the excitation of the alternator 104. The alternator 104 includes a field winding 108 and a stator winding 106. When the alternator field winding 108 is excited, it produces an output power which is rectified using a rectifier 102. A regulator 110 is provided for stabilizing the rectified output power. The rectified power is then used for charging the battery 112 and supplying vehicle loads 114.

As shown in Figure 2, the driver unit 116 comprises an identification unit 204, a memory 206, and a Pulse Width Modulated (PWM) signal generator unit 208. The identification unit 204 is configured to cooperate with the sensor units 202a-n to receive the generated sensed values, and is further configured to identify vehicle state based on the received sensed values. The vehicle state includes, but is not limited to, idling, coasting, accelerating, high speed, low speed, and braking. In an embodiment, the identification unit 204 is configured to determine the state of the vehicle using the received engine RPM value and received vehicle speed value. In another embodiment. the identification unit 204 is configured to determine the state of the vehicle using the received glow plug status value.

The memory 206 is configured to store a lookup table and a pre-determined set of rules. The lookup table includes a plurality of vehicle states, parameters associated with each of the vehicle states, and at least one pre-determined value for each of the parameters. The memory 206 may be, for example, a random-access memory (RAM), a memory buffer, a database, an erasable programmable read only memory (EPROM), an electrically erasable programmable read only memory (EEPROM), a read only memory (ROM), a flash memory, and the like.

The PWM signal generator unit 208 is configured to cooperate with the identification unit 204 and the memory 206 to extract pre-determined values associated with the identified vehicle state from the lookup table, and is further configured to cooperate with the sensor units 202a-n to receive the sensed values and compare each of the extracted pre-determined values with corresponding sensed values to generate a PWM control signal for controlling the excitation of the alternator 104 based on the pre-determined set of rules.

In an embodiment, the identification unit 204 and the PWM signal generator unit 208 are implemented using one or more processors.

In an embodiment, the PWM signal generator unit 208 comprises a crawler and extractor unit 210, a digital comparator 212, and a PWM driver module 214. The crawler and extractor unit 210 is configured to cooperate with the identification unit 204 and the memory 206 to receive the identified vehicle state and crawl through the lookup table to extract pre-determined values associated with parameters of the identified vehicle state. The digital comparator 212 is configured to cooperate with the crawler and extractor unit 210 to receive the extracted pre-determined values, and is further configured to compare each of the extracted pre-determined values with corresponding sensed values to generate a comparison signal for each of the parameters of the identified vehicle state. The PWM driver module 214 is configured to cooperate with the digital comparator 212 to receive the comparison signals, and is further configured to cooperate with the memory 206 to generate the PWM control signal based on the received comparison signals and the pre-determined set of rules. The pre-determined set of rules include rules for determining the duty cycle of the PWM control signal based on the identified vehicle state and the comparison signals. In an embodiment, the pre-determined set of rules is a set of instructions stored in the memory 206. The set of instructions include a control logic for generating the PWM control signal to enable or disable the excitation of the alternator 104. The PWM control signal can accordingly be an active low (enable) or high (disable) signal. The PWM driver module 214 is configured to cooperate with the memory 206 to execute the control logic for generating the enable or disable signal based on the received comparison signals. Figures 3a, 3b, and 3c illustrate a control logic for generating the enable or disable signal for different vehicle states. If all the conditions of the control logic are met, the PWM driver module 214 generates the active low enable (PWM control) signal to switch off the alternator excitation, thereby avoiding unnecessary fuel consumption and wastage.

In an embodiment, the driver unit 116 is configured to supply the generated PWM control signal to a regulator 110. The regulator 110 is configured to switch on/off field current supply to the field winding 108 of the alternator 104 based on the received PWM control signal. As shown in Figure 5, the PWM control ensures smooth transition during enable/disable of the alternator excitation at the regulator 110. This helps in avoiding unwanted function variation during transition. In an embodiment, super capacitors may be used to avoid further OFF time delay/function variation.

In an embodiment, the memory 206 is configured to store a pre-set delay time value. The PWM signal generator unit 208 is configured to cooperate with the memory 206 to generate the PWM control signal after the pre-set delay time when duty cycle of the PWM control signal changes in response to change in detected parameters.

Advantageously, the system 100 includes an input module 216 configured to cooperate with the memory 206 to facilitate an operator to define the pre-determined values for each of the parameters. In another embodiment, the input module 216 is configured to facilitate the operator to define the pre-set delay time value. Thus, the pre-determined values for each of the vehicle parameters can be calibrated based on vehicle category and model.

A diesel engine vehicle was driven over the New European Driving Cycle (NEDC) to verify its emission performance with and without the alternator excitation system 100. It was found that, the alternator cut-off strategy of the system 100, helped in increasing the fuel economy from 20.46 Km/L to 20.88 Km/L as shown in Figure 4b.

Further, the variation of battery charging current with respect to time for different vehicle states was determined. A graph of battery charging current and voltage on the Y-axis and time on the X-axis for different vehicle states was plotted as shown in Figure 4a. A control pin was used for providing enable/disable excitation control signal to the regulator 110. It can be seen that, in state 1 of the graph, the control pin is open and the alternator 104 is ON. During this state, the battery 112 is charged via the alternator 104. In state 2, the control pin is grounded. Therefore, the alternator 104 is cut-off and the battery 112 does not charge. In state 3, the control pin is still grounded, but since the battery voltage is below a minimum residual voltage value, the alternator 104 is switched ON to supply residual charging current to battery 112. In state 4, the control pin is open and the battery 112 again charges via the alternator 104.

The foregoing description of the embodiments has been provided for purposes of illustration and not intended to limit the scope of the present disclosure. Individual components of a particular embodiment are generally not limited to that particular embodiment, but, are interchangeable. Such variations are not to be regarded as a departure from the present disclosure, and all such modifications are considered to be within the scope of the present disclosure.
TECHNICAL ADVANCEMENTS
The present disclosure described herein above has several technical advantages including, but not limited to, the realization of an excitation control system for an alternator of a vehicle that:
• that improves fuel economy of the vehicle;
• that reduces vehicle emissions;
• that delivers better acceleration performance during drive as the alternator excitation is cut off when not required; and
• that improves noise, vibration and harshness (NVH) performance of the vehicle during idling by reducing the idling speed of the engine.
The embodiments herein and the various features and advantageous details thereof are explained with reference to the non-limiting embodiments in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.

The foregoing description of the specific embodiments so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein.

While considerable emphasis has been placed herein on the components and component parts of the preferred embodiments, it will be appreciated that many embodiments can be made and that many changes can be made in the preferred embodiments without departing from the principles of the disclosure. These and other changes in the preferred embodiment as well as other embodiments of the disclosure will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the disclosure and not as a limitation.