System and method for calculating distance to empty of green vehicle

Abstract

Disclosed is a system and method for computing distance to empty (DTE) based on available energy computed using a battery soc vs open circuit voltage (OCV) table, battery temperature vs energy efficiency, an energy efficiency vs energy table, etc., to enable a more accurate calculation of the DTE in consideration of the temperature of the battery, which is one of disturbance elements.

Description

CROSS-REFERENCE TO RELATED APPLICATION

This application

In Equation 3, A, B and C denote adjustable weights (coefficients).

Finally, DTE obtained by the multiplication of battery-electric efficiency (km/kwh) and available energy is displayed in a cluster display 50 so that a driver can identify the DTE. Meanwhile, the factors used in the computation, i.e., the real-time SOC, the available energy, etc., including the DTE computed as described above, are stored in a memory or other storage device and then used as initial values in a non-load state after the ignition of the vehicle is on (IG ON).

Non-Load State of Battery

When the battery is in a non-load state in which the battery is not discharged after the ignition of the vehicle is on, the SOC estimated in the load state and then stored in the SOC memory or other storage device is used as an SOC initial value. Next, energy efficiency of the battery is computed by the controller according to the temperature of the battery.

As shown in FIG. 7, data in a map table for battery temperature vs energy efficiency can be obtained through tests, when considering that the energy efficiency exponentially decreases as the temperature of the battery decreases, and the energy efficiency exponentially increases as the temperature of the battery increases. Accordingly, when the temperature of the battery, measured using a temperature sensor, etc., is substituted in a battery temperature vs energy efficiency table, the energy efficiency corresponding to the measured temperature of the battery is extracted.

Next, like the load state of the battery, the available energy as when the SOC is 100% (E_@SOC=100%) is extracted by substituting the extracted energy efficiency of the battery in the energy efficiency vs energy table data-mapped through tests in the available energy computation unit 30, and the available energy is then computed. Subsequently, the current available energy of the battery can be computed using the Equation 2, based on the energy efficiency (η) extracted from the battery temperature vs energy efficiency table, the available energy when the SOC is 100% (E_@SOC=100%) extracted from the energy efficiency vs energy table, and information on real-time SOC (%) extracted from the SOC memory or other storage device in the load state.

Next, DTE is computed based on the available energy of the battery, computed in the DTE computation unit 40 as described above in the same manner as the load state of the battery, and therefore, its detailed description will be omitted. Finally, DTE obtained by the multiplication of battery-electric efficiency (km/kwh) and available energy is displayed in a cluster display 50 so that a driver can identify the DTE.

As described above, the present invention employs a system and method of computing available energy supplied from the battery and computing DTE based on the available energy, so that the DTE can be more accurately computed and displayed even in winter season, etc., in consideration of the temperature of the battery, which is one of disturbance elements affecting battery efficiency.

The invention has been described in detail with reference to exemplary embodiments thereof. However, it will be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.

Claims

1. A method for distance to empty (DTE) computation of a green vehicle, the method comprising:

computing, by a controller, a current available energy of a battery, based on energy efficiency (η) of the battery, available energy when the state of charge (soc) is 100% (E_@SOC=100%) extracted from an energy efficiency vs energy table, and information on real-time soc (%);

computing, by the controller, DTE based on the computed available energy; and

displaying, on a display, the computed DTE in a cluster,

wherein the energy efficiency is computed by:

estimating an soc in a load state in which the battery is discharged;

extracting open circuit voltage and current corresponding to the current soc estimated form from a battery soc versus open circuit voltage (OCV) table; and

computing energy efficiency of the battery by substituting current and the extracted open circuit voltage and current in:

e####

$\mathrm{<span\; class="c0\; g0">energy</span>}\mathrm{<span\; class="c1\; g0">efficiency</span>}\left(\eta \right)=\left(1-\frac{\int i·\left({\mathrm{<span\; class="c13\; g0">v</span>}}_t-{\mathrm{<span\; class="c13\; g0">v</span>}}_e\right)\mathrm{dt}}{\int i·{\mathrm{<span\; class="c13\; g0">v</span>}}_i\mathrm{dt}+\int i·{\mathrm{<span\; class="c13\; g0">v</span>}}_e\mathrm{dt}}\right)·100\left[\right]$ $\mathrm{<span\; class="c0\; g0">energy</span>}\mathrm{<span\; class="c1\; g0">efficiency</span>}\left(\eta \right)=\left(1-\frac{\int i·\left({\mathrm{<span\; class="c13\; g0">v</span>}}_t-{\mathrm{<span\; class="c13\; g0">v</span>}}_e\right)\mathrm{dt}}{\int i·{\mathrm{<span\; class="c13\; g0">v</span>}}_t\mathrm{dt}+\int i·{\mathrm{<span\; class="c13\; g0">v</span>}}_e\mathrm{dt}}\right)·100$

wherein i denotes current, v_t denotes a terminal voltage of the battery, v_e denotes an open circuit voltage of the battery, ∫|i·v_t|dt and ∫|i·v_e|dt denote charging and discharging energy, and ∫|i·(v_t−v_e)|dt denotes heat loss energy generated when the battery is charged and discharged.

6. A non-transitory computer readable medium containing program instructions executed by a processor or controller, the computer readable medium comprising:

program instructions that compute a current available energy of a battery, based on energy efficiency (η) of the battery, available energy when the state of charge (soc) is 100% (E_@SOC=100%) extracted from an energy efficiency vs energy table, and information on real-time soc (%);

program instructions that compute DTE based on the computed available energy; and

program instructions that display the computed DTE in a cluster,

wherein the energy efficiency (η) is computed by estimating an soc in a load state in which the battery is discharged; extracting open circuit voltage and current corresponding to the current soc estimated from a battery soc vs open circuit voltage (OCV) table; and computing energy efficiency of the battery by substituting current and the extracted open circuit voltage and current in:

$\left[\mathrm{<span\; class="c0\; g0">energy</span>}\mathrm{<span\; class="c1\; g0">efficiency</span>}\left(\eta \right)\right]=\left(1-\frac{\int i·\left({\mathrm{<span\; class="c13\; g0">v</span>}}_t-{\mathrm{<span\; class="c13\; g0">v</span>}}_e\right)\mathrm{dt}}{\int i·{\mathrm{<span\; class="c13\; g0">v</span>}}_i\mathrm{dt}+\int i·{\mathrm{<span\; class="c13\; g0">v</span>}}_e\mathrm{dt}}\right)·100$ $\mathrm{<span\; class="c0\; g0">energy</span>}\mathrm{<span\; class="c1\; g0">efficiency</span>}\left(\eta \right)=\left(1-\frac{\int i·\left({\mathrm{<span\; class="c13\; g0">v</span>}}_t-{\mathrm{<span\; class="c13\; g0">v</span>}}_e\right)\mathrm{dt}}{\int i·{\mathrm{<span\; class="c13\; g0">v</span>}}_t\mathrm{dt}+\int i·{\mathrm{<span\; class="c13\; g0">v</span>}}_e\mathrm{dt}}\right)·100$

wherein i denotes current, v_t denotes a terminal voltage of the battery, v_e denotes an open circuit voltage of the battery, ∫|i·v_t|dt and ∫|i·v_e|dt denote charging and discharging energy, and ∫|i·(v_t−v_e)|dt denotes heat loss energy generated when the battery is charged and discharged.

2. The method of claim 1, wherein, in the estimating of the soc, the estimated current soc is stored in an soc memory so as to be used in the computation of the current available energy.

3. The method of claim 1, wherein the energy efficiency (η) is computed by measuring a temperature of a battery in a non-load state in which the battery is discharged; and extracting energy efficiency corresponding to the measured temperature of the battery by substituting the measured temperature of the battery in a battery temperature vs energy efficiency table.

4. The method of claim 1, wherein the available energy is computed by substituting the energy efficiency of the battery in the energy efficiency vs energy table, thereby extracting the available energy when the state of charge (soc) is 100% (E_@SOC=100%); and the energy efficiency (η) of the battery, the available energy when the state of charge (soc) is 100% (E_@SOC=100%), extracted from the soc memory, and the information on real-time soc (%) in:

$\mathrm{<span\; class="c6\; g0">available</span>}\mathrm{<span\; class="c0\; g0">energy</span>}=\frac{E_{@\mathrm{<span\; class="c21\; g0">soc</span>}=100\%}}{\eta }\left\{\mathrm{<span\; class="c21\; g0">soc</span>}-\left(100-\eta \right)\right\}.$

5. The method of claim 1, wherein the DTE is computed by a multiplication of battery-electric efficiency (km/kwh) and available energy.

7. The non-transitory computer readable medium of claim 6, wherein, in the estimating of the soc, the estimated current soc is stored in an soc memory so as to be used in the computation of the current available energy.

8. The non-transitory computer readable medium of claim 6, wherein the energy efficiency (η) is computed by measuring a temperature of a battery in a non-load state in which the battery is discharged; and extracting energy efficiency corresponding to the measured temperature of the battery by substituting the measured temperature of the battery in a battery temperature vs energy efficiency table.

9. The non-transitory computer readable medium of claim 6, wherein the available energy is computed by substituting the energy efficiency of the battery in the energy efficiency vs energy table, thereby extracting the available energy when the state of charge (soc) is 100% (E_@SOC=100%); and the energy efficiency (η) of the battery, the available energy when the state of charge (soc) is 100% (E_@SOC=100%), extracted from the soc memory, and the information on real-time soc (%) in:

$\mathrm{<span\; class="c6\; g0">available</span>}\mathrm{<span\; class="c0\; g0">energy</span>}=\frac{E_{@\mathrm{<span\; class="c21\; g0">soc</span>}=100\%}}{\eta }\left\{\mathrm{<span\; class="c21\; g0">soc</span>}-\left(100-\eta \right)\right\}.$

10. The non-transitory computer readable medium of claim 6, wherein the DTE is computed by a multiplication of battery-electric efficiency (km/kwh) and available energy.

11. The method for distance to empty (DTE) computation of a green vehicle of claim 1, wherein the available energy is expressed as a function using temperature, degradation, state of charge (soc) of the battery as variable factors.