System for detecting remaining charge of electrical double layer capacitor

• US 6,664,795 B2
• Filed: 01/23/2002
• Issued: 12/16/2003
• Est. Priority Date: 01/25/2001
• Status: Expired due to Fees

• Current Assignee: Honda Giken Kogyo Kabushiki Kaisha (Honda Motor Company)
• Original Assignee: Honda Giken Kogyo Kabushiki Kaisha (Honda Motor Company)
• Inventors: Imai, Nobuyuki, Tamagawa, Yutaka
• Primary Examiner(s): Le, N.
• Assistant Examiner(s): Nguyen, Vincent Q.
• Application Number:
  US10/052,398
• Publication Number:
  US 20020097053A1
• Time in Patent Office: 692 Days
• Field of Search: 701/22, 701/102, 324/444, 324/446, 324/450, 324/548, 324/658
• US Class Current: 324/548
• CPC Class Codes: B60K 6/485 Motor-assist type
• CPC Class Codes: B60L 50/16 with provision for separate direct mechanical propulsion
• CPC Class Codes: B60L 50/40 using propulsion power supplied by capacitors
• CPC Class Codes: B60L 58/12 responding to state of charge [SoC]
• CPC Class Codes: B60W 10/26 for electrical energy, e.g. batteries or capacitors
• CPC Class Codes: B60W 2050/021 Means for detecting failure or malfunction
• CPC Class Codes: B60W 2510/244 Charge state
• CPC Class Codes: H02J 7/14 for charging batteries from dynamo-electric generators driven at varying speed, e.g. on vehicle
• CPC Class Codes: Y02T 10/62 Hybrid vehicles
• CPC Class Codes: Y02T 10/70 Energy storage systems for electromobility, e.g. batteries
• CPC Class Codes: Y02T 10/7072 Electromobility specific charging systems or methods for batteries, ultracapacitors, supercapacitors or double-layer capacitors

Abstract

A remaining charge detecting system of an electric double layer capacitor to be usable, for example, as an energy source of a hybrid vehicle having an internal combustion engine and an electric motor separately driving wheels. The system includes a current-voltage sensor which generates an output indicative of a terminal voltage across terminals of the capacitor and an output indicative of charge/discharge current charged into and discharged from the capacitor and an electronic control unit, comprising a microcomputer, which inputs the outputs of the current-voltage sensor indicative of the terminal voltage and charge/discharge current and calculates a remaining charge of the capacitor based on a state equation (mathematical model) having the remaining charge of the capacitor as a state variable and an observer that observes the state equation, thereby enabling simple and accurate detection of the remaining charge of the electrical double layer capacitor without need for a high-precision current sensor.

Claims

1. A system for detecting remaining charge of an electric double layer capacitor, comprising:

a current-voltage sensor which generates an output indicative of a terminal voltage across terminals of the capacitor and an output indicative of charge/discharge current charged into and discharged from the capacitor;

an electronic control unit which inputs the outputs of the current-voltage sensor indicative of the terminal voltage and charge/discharge current and calculates a remaining charge of the capacitor based on a mathematical model having the remaining charge of the capacitor as a state variable, wherein the electronic control unit comprises;

remaining charge calculating means for inputting the detected terminal voltage and charge/discharge current to a state equation constituting the mathematical model and for calculating the remaining charge of the capacitor;

estimated terminal voltage calculating means for calculating a voltage drop across the capacitor based on the detected charge/discharge current and an internal resistance of the capacitor and for subtracting the calculated voltage drop from the calculated remaining charge to obtain an estimated terminal voltage of the capacitor; and

remaining charge correcting means for calculating a product obtained by multiplying a difference between the detected terminal voltage and the estimated terminal voltage by a gain of an observer obtained from the state equation that estimates the state variable, and for correcting the remaining charge based on the calculated product.

5. A system according to claim 1, wherein the capacitor is used as an energy source of a hybrid vehicle.

6. A system according to claim 5, wherein the hybrid vehicle includes:

an internal combustion engine connected to driven wheels through a transmission to drive the wheels;

an electric motor connected with the driven wheels through the transmission to drive the vehicle independently of the engine; and

a battery connected to the capacitor;

wherein the capacitor is connected to the motor to supply a current to the motor and is connected to the battery to discharge to and to be charged from the battery.

2. A system for detecting remaining charge of an electric double layer capacitor, comprising:

a current-voltage sensor which generates an output indicative of a terminal voltage across terminals of the capacitor and an output indicative of charge/discharge current charged into and discharged from the capacitor;

an electronic control unit which inputs the outputs of the current-voltage sensor indicative of the terminal voltage and charge/discharge current and calculates a remaining charge of the capacitor based on a mathematical model having the remaining charge of the capacitor as a state variable; and

sensor failure discriminating means for discriminating whether or not the sensor is faulty based on the remaining charge.

3. A system according to claim 2, wherein the sensor failure discriminating means includes:

maximum value comparing means for comparing the remaining charge with a maximum value of a voltage range of the capacitor; and

failure determining means for determining that the sensor is faulty when the remaining charge is greater than the maximum value.

4. A system according to claim 2, wherein the sensor failure discriminating means includes:

minimum value comparing means for comparing the remaining charge with a minimum value of a voltage range of the capacitor; and

failure determining means for determining that the sensor is faulty when the remaining charge is less than the minimum value.

7. A method of detecting remaining charge of an electric double layer capacitor, having a current-voltage sensor which generates an output indicative of a terminal voltage across terminals of the capacitor and an output indicative of charge/discharge current charged into and discharged from the capacitor:

comprising the step of;

(a) inputting the outputs of the current-voltage sensor indicative of the terminal voltage and charge/discharge current and calculating a remaining charge of the capacitor based on a mathematical model having the remaining charge of the capacitor as a state variable wherein step (a) includes the steps of;

(b) inputting the detected terminal voltage and charge/discharge current to a state equation constituting the mathematical model and calculating the remaining charge of the capacitor;

(c) calculating a voltage drop across the capacitor based on the detected charge/discharge current and an internal resistance of the capacitor and subtracting the calculated voltage drop from the calculated remaining charge to obtain an estimated terminal voltage of the capacitor; and

(d) calculating a product obtained by multiplying a difference between the detected terminal voltage and the estimated terminal voltage by a gain of an observer obtained from the state equation that estimates the state variable, and correcting the remaining charge based on the calculated product.

11. A method according to claim 7, wherein the capacitor is used as an energy source of a hybrid vehicle including an internal combustion engine connected to driven wheels through a transmission to drive the wheels;

an electric motor connected with the driven wheels through the transmission to drive the vehicle independently of the engine; and

a battery connected to the capacitor;

wherein the capacitor is connected to the motor to supply a current to the motor and is connected to the battery to discharge to and to be charged from the battery.

8. A method of detecting remaining charge of an electric double layer capacitor, having a current-voltage sensor which generates an output indicative of a terminal voltage across terminals of the capacitor and an output indicative of charge/discharge current charged into and discharged from the capacitor:

comprising the steps of;

(a) inputting the outputs of the current-voltage sensor indicative of the terminal voltage and charge/discharge current and calculating a remaining charge of the capacitor based on a mathematical model having the remaining charge of the capacitor as a state variable; and

(e) discriminating whether or not the sensor is faulty based on the remaining charge.

9. A method according to claim 8, wherein the step (e) includes the steps of:

(f) comparing the remaining charge with a maximum value of a voltage range of the capacitor; and

(g) determining that the sensor is faulty when the remaining charge is greater than the maximum value.

10. A method according to claim 8, wherein the step (e) includes the steps of:

(h) comparing the remaining charge with a minimum value of a voltage range of the capacitor; and

(i) determining that the sensor is faulty when the remaining charge is less than the minimum value.