Claims:We claim:
1. A device (100) for controlling coupling of a drive motor (12) to an output shaft (22) of a hybrid vehicle, said hybrid vehicle comprises at least one ultra-capacitor (10) as a main power source, said device (100) comprises
? an input-output (I/O) interface (14) configured to receive
? a State-of-Charge (SOC) value of said ultra-capacitor (10) from a SOC sensor (18); and
? a vehicle speed from vehicle speed sensor (20); and
? a processor (16) configured to
? compute a corrected SOC value using said SOC value and said vehicle speed;
? determine power generated by said drive motor (12) using said corrected SOC value; and
? control a coupling mechanism (24) to couple said drive motor (12) selectively to said output shaft (22) based on the determined power and an engine power.

2. The device (100) of claim 1 wherein said processor (16) decides operating mode of said hybrid vehicle based on said corrected SOC value;

3. The device (100) of claim 1 wherein said processor (16) controls the operation of said drive motor (12) selectively based on the determined power and the engine power.

4. The device (100) of claim 1, wherein said processor (16) computes the corrected SOC value by applying a correction to said SOC value based on kinetic energy of said hybrid vehicle.
5. The device (100) of claim 1, wherein said processor (16) determines the kinetic energy of said hybrid vehicle using the vehicle speed and vehicle mass.

6. The device (100) of claim 1, wherein said processor (16) further computes a fuel-cost optimization model to controls the coupling mechanism to couple said drive motor (12) to the output shaft (22) of said hybrid vehicle.

7. The device (100) of claim 6, wherein said a fuel-cost optimization model uses at least one of variable output voltage, a lower SOC limit, and cycle life of the ultra-capacitor (10).

8. A method for controlling coupling of a drive motor (12) to an output shaft (22) a hybrid vehicle, said hybrid vehicle comprises at least one ultra-capacitor (10) as a main power source, said method comprises
? receiving a State-of-Charge (SOC) value of said ultra-capacitor (10) from a SOC sensor (18) and a vehicle speed from a vehicle speed sensor (20);
? computing a corrected SOC value using said SOC value and said vehicle speed;
? determining power generated by said drive motor (12) using said corrected SOC value; and
? controlling a coupling mechanism (22) to couple said drive motor (12) selectively to said output shaft (22) based on the determined power and an engine power.

9. The method of claim 8, further comprises controlling the operation of said drive motor (12) selectively based on the determined power and the engine power.

10. The method of claim 8, further comprises a step of computing a fuel-cost optimization model to control the coupling mechanism (22) to couple said drive motor (12) to the output shaft (22) of said hybrid vehicle. , Description:Field of the invention:
[0001] The invention relates to a device and a method for controlling coupling of a drive motor to an output shaft of a hybrid vehicle having ultra-capacitor as a main power source.

Background of the invention:
[0002] Parallel hybrid vehicle are already existing in market since long time. These hybrid vehicles uses battery as a main power source for operating a drive motor. WO2005115786 A1 discloses one such parallel hybrid vehicle. Similarly, use of ultra-capacitor as a main power source in parallel hybrid vehicle is also known. US7096985 indicates the possibility of using ultra-capacitor in a parallel hybrid vehicle.
[0003] However, there exists a need to continuously optimize the operation of the hybrid vehicle and minimize the fuel consumption. As the characteristics of the ultra-capacitor and the battery are significantly different, there are lot of opportunities available to control the power distribution between the engine and drive motor, and thereby reducing the fuel consumption to a maximum level.

Brief description of the invention:
[0004] The invention discloses a device for controlling coupling of a drive motor to an output shaft of a hybrid vehicle. The hybrid vehicle comprises one or more ultra-capacitors as main power source. The device comprises an input-output (I/O) interface configured to receive a State-of-Charge (SOC) value of the ultra-capacitor from a SOC sensor and a vehicle speed from a vehicle speed sensor. The device comprises a processor which is configured to compute a corrected SOC value using the SOC value and the vehicle speed. The processor is further configured to determine power generated by the drive motor using the corrected SOC value and control a coupling mechanism to couple the drive motor selectively to the output shaft based on the determined power and an engine power.

[0005] The processor decides operating mode of the hybrid vehicle based on the corrected SOC value and also controls the operation of the driver motor selectively based on the determined power and the engine power. Also, the processor computes the corrected SOC value by applying a correction to the SOC value based on kinetic energy of the hybrid vehicle. The kinetic energy of the hybrid vehicle is determined using the vehicle speed and vehicle mass. The processor further computes a fuel-cost optimization model to controls the coupling mechanism to couple the drive motor to the output shaft of the hybrid vehicle. The fuel-cost optimization model uses at least one of variable output voltage, a lower SOC limit, and cycle life of the ultra-capacitor.
[0006] The invention also discloses a method for controlling coupling of a drive motor to an output shaft a hybrid vehicle. The hybrid vehicle comprises one or more ultra-capacitors as a main power source. The method involves receiving a State-of-Charge (SOC) value of the ultra-capacitor from a SOC sensor and a vehicle speed from vehicle speed sensor. A corrected SOC value is computed using the SOC value and the vehicle speed. Power generated by the drive motor is determined using the corrected SOC value. A coupling mechanism is controlled to couple the drive motor selectively to the output shaft based on the determined power and an engine power. The coupling mechanism is controlled based on a fuel-cost optimization model. Further operation of the drive motor is controlled selectively based on the determined power and the engine power.

Brief description of the accompanying drawings:
[0007] Different embodiments of the invention are described with reference to the following accompanying drawings,
[0008] Fig. 1 illustrates a schematic view of device for controlling coupling of a drive motor to an output shaft a hybrid vehicle, in accordance with an embodiment of the invention; and
[0009] Fig. 2 illustrates a method for controlling coupling of a drive motor to an output shaft a hybrid vehicle, in accordance with an embodiment of the invention.

Detailed description of the embodiments:
[0010] Fig. 1 illustrates a schematic view of device for controlling coupling of a drive motor to an output shaft a hybrid vehicle, in accordance with an embodiment of the invention. The device 100 can be an Electronic Control Unit (ECU) or an energy management unit.
[0011] The hybrid vehicle can be a mild parallel hybrid vehicle or a series hybrid vehicle. For illustrative purpose, use of the device 100 in the mild parallel hybrid vehicle is shown as an example in the figure. The hybrid vehicle comprises one or more ultra-capacitors 10 as main power source. In other words, the ultra-capacitor 10 is used in place of a main battery to supply power to a drive motor 12. The ultra-capacitor 10 can be otherwise called as super-capacitor, hybrid capacitor, etc. The ultra-capacitor 10 has several advantages over battery like higher power density, longer cycle life, faster charge-discharge cycles, etc.
[0012] The device 100 comprises an input-output (I/O) interface 14 to receive different signals from different sensors. The I/O interface 14 can also be called as I/O port(s). The device 100 also comprises a processor 16 which is configured to perform various functions. The processor 16 can be a microcontroller. Further device 100 can have other components like power supply, memory units, etc. which are not elaborately explained here for simplicity.
[0013] The I/O interface 14 receives a State-of-Charge (SOC) value of the ultra-capacitor 10 from a SOC sensor 18. Similarly, the interface 14 also receives a vehicle speed information from a vehicle speed sensor 20. The processor 16 computes a corrected SOC value of the ultra-capacitor 10 using the SOC value measured by the SOC sensor 18 and the vehicle speed. To elaborate, the processor 16 determines the kinetic energy of the hybrid vehicle using its mass and the vehicle speed (i.e. KE=1/2MV2). Using the determined kinetic energy of the hybrid vehicle, the processor 16 applies correction to the SOC value to compute the corrected SOC value.
[0014] Additionally, the processor 16 decides the operating mode of the hybrid vehicle based on the corrected SOC value. In other words, the processor 16 can make-out if electric assist mode is possible or not, by checking whether the corrected SOC value of the ultra-capacitor 10 is more than a threshold value. In some cases, when the corrected SOC value is lesser than the threshold value, it indicates that the ultra-capacitor 10 can’t provide sufficient power to the drive motor 12 to assist the engine in driving the hybrid vehicle. In such cases, the processor 16 decides to operate the hybrid vehicle in engine mode.
[0015] Further, the processor 16 determines power that can be generated by the drive motor 12 using the corrected SOC value. Based on the determined power and an engine power, the processor 16 decides whether the drive motor 12 needs to be operated or not. Accordingly, it controls the operation of the drive motor 12.
[0016] To operate the hybrid vehicle in electric assist mode, the drive motor 12 needs to be coupled to an output shaft 22 of the vehicle. That is, the wheels will be driven not only by the engine power but also by the drive motor 12. A coupling mechanism 24 such as an electromagnetic clutch is being used to selectively couple or decouple the drive motor 12 from the output shaft 22. The processor 16 controls the coupling mechanism 24 to couple the drive motor 12 selectively to the output shaft 22 based on the determined power and the engine power.
[0017] The processor 16 controls the coupling mechanism 24 using a fuel-cost optimization model, which uses parameters such as variable output voltage, a lower SOC limit, cycle life of the ultra-capacitor 10 so that fuel cost is minimized. To explain in detail, the processor 16 computes the fuel-cost optimization model which considers different parameters.
[0018] There are some traditional models being used for power distribution between the engine and the drive motor 12. However, these models assume the battery as the energy storage system, hence the characteristics of the same can’t be used for the hybrid vehicle having ultra-capacitor as main power source.
[0019] The processor 16 uses a modified cost-optimization model which tries to maximize the fuel economy benefit using ultra-capacitors as energy storage system. The model utilizes the fact that ultra-capacitors have a high power density and can sustain a large number of charge-discharge cycles.

[0020] Fig. 2 illustrates a method for controlling coupling of a drive motor to an output shaft a hybrid vehicle, in accordance with an embodiment of the invention. The hybrid vehicle uses ultra-capacitor as a main power source. The method involves receiving a State-of-Charge (SOC) value of the ultra-capacitor 10 from a SOC sensor 18 and a vehicle speed from vehicle speed sensor 20 by a control device 100 or an ECU at step S1. A corrected SOC value is computed by a processor 16 in the control device 100 using the SOC value and the vehicle speed at step S2. Power generated by the drive motor 12 is determined using the corrected SOC value at step S3. A coupling mechanism is controlled at step S4 by the processor 16 to couple the drive motor 12 selectively to the output shaft 22 based on the determined power and an engine power.
[0021] After determining the power generated by the drive motor 12 using the corrected SOC value, the processor 16 decides the operating mode of the hybrid vehicle. In other words, the processor 16 determines whether the hybrid vehicle can be operated in electric assist mode. Accordingly it controls the operation of the drive motor 12 selectively. Further, the coupling mechanism 24 is controlled by the processor 16 based on a fuel-cost optimization model to couple the drive motor 12 to the output shaft 22.
[0022] The invention enables use of ultra-capacitor instead of battery, which has many benefits like higher power density, longer cycle life, faster charge-discharge cycle(s) etc. The use of ultra-capacitor is more suitable and economical for city driving conditions. This invention selectively controls coupling of the drive motor to the output shaft based on the corrected SOC value of the ultra-capacitor, thereby saving fuel cost.
[0023] 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.