METHOD TO ESTIMATE COMPRESSOR INLET PRESSURE FOR A TURBOCHARGER

Abstract

A method of estimating a compressor inlet pressure for a turbocharger includes: measuring an ambient temperature of air flowing into the compressor; measuring a flow rate of the air into the compressor; measuring a boost pressure of the air from the compressor to an engine; determining a speed of a turbine of the turbocharger; defining a pressure ratio as the ratio of the boost pressure to the compressor inlet pressure; defining a function as the function of the compressor flow rate, the ambient temperature, the compressor inlet pressure and the turbine speed; and equating the pressure ratio and the function and recursively solving for the compressor inlet pressure.

Claims

1. A method of estimating a compressor inlet pressure for a turbocharger, the method comprising: measuring an ambient temperature of air flowing into the compressor; measuring a flow rate of the air into the compressor; measuring a boost pressure of the air from the compressor to an engine; determining a speed of a turbine of the turbocharger; defining a pressure ratio as the ratio of the boost pressure to the compressor inlet pressure; defining a function as the function of the compressor flow rate, the ambient temperature, the compressor inlet pressure and the turbine speed; and equating the pressure ratio and the function and recursively solving for the compressor inlet pressure.

2. The method of claim 1 further comprising measuring an exhaust flow rate of exhaust gas from the engine, measuring an exhaust temperature of the exhaust gas, measuring a wastegate position that controls a flow rate of the exhaust gas that bypasses the turbine, and determining the turbine speed as a function of the exhaust flow rate, the exhaust temperature, the compressor inlet pressure, and the wastegate position.

3. The method of claim 1 wherein recursively solving is based on a linear parameter varying (LPV) dynamic model.

4. The method of claim 3 wherein the LPV dynamic model employs a Kalman filter, the estimated compressor inlet pressure being an output of the Kalman filter.

5. The method of claim 1 further comprising measuring an ambient pressure with a sensor, and determining a residual as the difference between the estimated compressor inlet pressure and the ambient pressure, the residual providing fault detection isolation.

6. The method of claim 5 wherein the turbine is a variable geometry turbine.

7. The method of claim 6 wherein when the estimated compressor inlet pressure has abrupt changes within a specified time and is greater than the ambient pressure, the fault detection isolation indicates that the variable geometry turbine is stuck open.

8. The method of claim 6 wherein when the estimated compressor inlet pressure has abrupt changes within a specified time and is less than the ambient pressure, the fault detection isolation indicates that the variable geometry turbine is stuck closed.

9. The method of claim 6 wherein when the estimated compressor inlet pressure is less than the ambient pressure, the fault detection isolation indicates that there is a fault in a sensor measuring the boost pressure.

10. A method of estimating a compressor inlet pressure for a turbocharger, the method comprising: measuring an ambient temperature of air flowing into the compressor; measuring a flow rate of the air into the compressor; measuring a boost pressure of the air from the compressor to an engine; determining a speed of a turbine of the turbocharger; defining a pressure ratio as the ratio of the boost pressure to the compressor inlet pressure; defining a function as the function of the compressor flow rate, the ambient temperature, the compressor inlet pressure and the turbine speed; and equating the pressure ratio and the function and recursively solving for the compressor inlet pressure, wherein recursively solving is based on a linear parameter varying (LPV) dynamic model that employs a Kalman filter, the estimated compressor inlet pressure being an output of the Kalman filter.

11. The method of claim 10 further comprising measuring an exhaust flow rate of exhaust gas from the engine, measuring an exhaust temperature of the exhaust gas, measuring the wastegate position that controls a flow rate of the exhaust gas that bypasses the turbine, and determining the turbine speed as a function of the exhaust flow rate, the exhaust temperature, the compressor inlet pressure, and the wastegate position.

12. The method of claim 10 further comprising measuring an ambient pressure with a sensor, and determining a residual as the difference between the estimated compressor inlet pressure and the ambient pressure, the residual providing fault detection isolation.

13. The method of claim 12 wherein the turbine is a variable geometry turbine.

14. The method of claim 13 wherein when the estimated compressor inlet pressure has abrupt changes within a specified time and is greater than the ambient pressure, the fault detection isolation indicates that the variable geometry turbine is stuck open.

15. The method of claim 13 wherein when the estimated compressor inlet pressure has abrupt changes within a specified time and is less than the ambient pressure, the fault detection isolation indicates that the variable geometry turbine is stuck closed.

16. The method of claim 13 wherein when the estimated compressor inlet pressure is less than the ambient pressure, the fault detection isolation indicates that there is a fault in a sensor measuring the boost pressure.

17. A method of estimating a compressor inlet pressure for a turbocharger, the method comprising: measuring an ambient temperature of air flowing into the compressor; measuring a flow rate of the air into the compressor; measuring a boost pressure of the air from the compressor to an engine; measuring an exhaust flow rate of exhaust gas from the engine to a turbine; measuring an exhaust temperature of the exhaust gas; measuring the wastegate position that controls a flow rate of the exhaust gas that bypasses the turbine; determining a speed of the turbine as a function the exhaust flow rate, the exhaust temperature, the compressor inlet pressure, and the wastegate position; defining a pressure ratio as the ratio of the boost pressure to the compressor inlet pressure; defining a function as the function of the compressor flow rate, the ambient temperature, the compressor inlet pressure and the turbine speed; and equating the pressure ratio and the function and recursively solving for the compressor inlet pressure.

18. The method of claim 17 wherein recursively solving is based on a linear parameter varying (LPV) dynamic model.

19. The method of claim 18 wherein the LPV dynamic model employs a Kalman filter, the estimated compressor inlet pressure being an output of the Kalman filter.

20. The method of claim 17 further comprising measuring an ambient pressure with a sensor, and determining a residual as the difference between the estimated compressor inlet pressure and the ambient pressure, the residual providing fault detection isolation.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way.

[0027] FIG. 1 is a schematic of a turbocharger system for a motor vehicle in accordance with the principles of the present disclosure;

[0028] FIG. 2 is a graph illustrating a comparison of an estimated boost pressure to inlet compressor pressure ratio to an actual boost pressure to inlet compressor pressure ratio for the turbocharger system shown in FIG. 1;

[0029] FIG. 3 is a process diagram to estimate a compressor inlet pressure for the turbocharger system shown in FIG. 1;

[0030] FIG. 4A is a graph of a calculated boost pressure from the process shown in FIG. 3;

[0031] FIG. 4B is a graph of an estimated compressor inlet pressure from the process shown in FIG. 3;

[0032] FIG. 5 is a process diagram to calculate a residual with the process shown in FIG. 3;

[0033] FIG. 6 is a graph showing a comparison between an actual ambient pressure measurement and an estimated compressor inlet pressure to determine a fault detection isolation of a pressure sensor; and

[0034] FIG. 7 is a graph showing fault detection isolation of a variable geometry turbine and a boost pressure sensor.

DETAILED DESCRIPTION

[0035] The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses.

[0036] Referring to FIG. 1, there is shown a turbocharger system 10 in accordance with the principles of the present disclosure. The turbocharger system 10 includes a turbocharger 12 with a turbine 14 connected to a compressor 16 with a drive link or shaft 18. The turbocharger system 10 further includes one or more sensors 20 that measures the flow rate of air, W.sub.c, into the compressor 16, the ambient temperature T.sub.a and the ambient pressure p.sub.a of the air flowing into the compressor 16, an air cooler 22, a pressure sensor 24 that measures the boost pressure p.sub.i of the air flowing into an engine 28, and a temperature sensor 26 that measures the boost temperature T.sub.i of the air flowing into the engine 28.

[0037] The temperature T.sub.ex and pressure p.sub.ex of the exhaust gas from the engine 28 is measured by a temperature sensor 30 and a pressure sensor 32, respectively. The exhaust gas flows to the turbine 14 with a flow rate W.sub.ex is estimated from the measured flow rate of air and injected fuel flow, and the outlet pressure p.sub.to of the exhaust gas from the turbine 14 is measured by a sensor 42. A waste gate 40 provides a path for a desired amount of the exhaust gas to bypass the turbine 14. The path line for air flowing between the compressor 16 and the engine 28 and the path line exhaust gas flowing from the engine 28 to the compressor 16 are connected by a path line with an exhaust gas recirculation (EGR) cooler 36 and an EGR valve 34 that directs some of the exhaust gas from the exhaust path line to the air path line. This line also includes a path line 38 that allows some of the exhaust gas to bypass the EGR cooler 36.

[0038] In a typical operation of the turbocharger system 10, exhaust gas flows into the turbine 14. As the turbine 14 spins with a speed of N.sub.t, the turbine 14 drives the compressor 16 with the drive link or shaft 18. As the compressor 16 spins, air is drawn into the compressor 16 with a flow rate W.sub.c.

[0039] The dynamics of the air flow and exhaust flow through the turbocharger system 10 can be described by the following set of expressions:

[00001]$\begin{array}{cc}\begin{array}{c}{p}_{\mathrm{rc}}=.Math.\frac{p_i}{p_a}=f\left(\frac{W_C.Math.\sqrt{T_a}}{p_a},N_t\right)\\ .Math.f\left(\frac{W_C.Math.\sqrt{T_a}}{p_a},g\left(\frac{W_{\mathrm{ex}}.Math.\sqrt{T_{\mathrm{ex}}}}{p_a},\mathrm{WG}\right)\right)\\ =.Math.H\left(\frac{W_C.Math.\sqrt{T_a}}{p_a},\frac{W_{\mathrm{ex}}.Math.\sqrt{T_{\mathrm{ex}}}}{p_a},\mathrm{WG}\right)\\ =.Math.H\left(x_1\left(p_a\right),x_2\left(p_a\right),x_3\right)\end{array}& \mathrm{Eq}..Math.1\end{array}$

where p.sub.rc is the pressure ratio of p.sub.i and p.sub.a, is a function of W.sub.c, T.sub.a, p.sub.a, and N.sub.t, and where N.sub.t is written as a function g of W.sub.ex, T.sub.ex, p.sub.a, and WG, which is the position of the wastegate 40. Hence, the pressure ratio p.sub.rc can be expressed as a function H, which is a function of x.sub.1(p.sub.a), x.sub.2(p.sub.a), x.sub.3 as shown above.

[0040] Referring to FIG. 2, there is shown a comparison of the actual pressure ratio (p.sub.i/p.sub.a).sub.act measured with the sensors 20 and 24 to the estimated pressure ratio (p.sub.i/p.sub.a).sub.est obtained with the expressions shown in Eq. 1 described above for various ambient pressure at 100 kPa, 90 kPa; 80 kPa; and 70 kPa.

[0041] Referring to FIG. 3, there is shown a process 100 that implements the expressions Eq. 1 to estimate a compressor inlet pressure p.sub.a(k).sub.est for a step k in a recursive analysis. Specifically, the processes 100 employs a linear parameter varying (LPV) model that relates engine air and exhaust gas flow with the ambient pressure. The estimated ambient pressure or compressor inlet pressure can then be utilized to diagnose the operation of the sensor 20 that measures the actual ambient pressure. As such, the H function (114)

[00002]$\begin{array}{cc}H\left(\frac{W_C.Math.\sqrt{T_a}}{p_a},\frac{W_{\mathrm{ex}}.Math.\sqrt{T_{\mathrm{ex}}}}{p_a},\mathrm{WG}\right)& \mathrm{Eq}..Math.2\end{array}$

is provided as inputs 102 to the process 100. Note that in Eq. 2, the barred values of p.sub.a are moving averages of the estimated ambient pressure. That is the output 110 of the process 100 generates moving averages 112 that are incorporated into the H function 114.

[0042] The inputs 102 are implemented into the process 100 as the recursive expressions

p.sub.a(k+1)=p.sub.a(k)

p.sub.i(k)=H(x.sub.1(p.sub.a)),x.sub.2(p.sub.a),x.sub.3)p.sub.a(k) Eq. 3

in a step 104, where again k is the kth step of the recursive calculation. The step 104 calculates a boost pressure p.sub.i(k). Example calculations of the boost pressure p.sub.i in kPa are shown in FIG. 4A. The process 100 proceeds to a step 108, which is a Kalman filter. The Kalman filter 108 then provides an estimated ambient pressure or compressor inlet pressure p.sub.a(k).sub.est as an output 110. Example calculations of the output 110 are shown in FIG. 4B. More specifically, FIG. 4B shows a comparison of the measured ambient pressure 202 to the estimated ambient pressure 204.

[0043] Turning now to FIG. 5, there is shown that the output p.sub.a(k).sub.est from the Kalman filter 108 and the measured ambient pressure p.sub.aact can be utilized to determine a residual R, which in turn can be employed for system diagnostics to isolate a fault detection. For example, as shown in FIG. 6, if the measured ambient pressure 302 diverges from the estimated ambient pressure 304 within a specified vehicle travel distance where the ambient pressure is not expected change much as indicated by its estimated value. then residual or difference between the estimated ambient pressure 304 and the measured ambient pressure 302 may indicated that the sensor 20 that measures the ambient pressure may have a fault or is defective.

[0044] As shown in FIG. 7, the system diagnostics can be utilized for other purposes as well. For example, the non-varying measured ambient pressure 402 indicates that the sensor 20 is working properly within a limited vehicle travel distance. The estimated ambient pressure 404, however, shows a larger change in value, which may indicate that a variable geometry turbine (VGT) is stuck open, whereas the estimated ambient pressure 406 may indicate that the VGT is stuck closed. Further, the estimated ambient pressure 408 may indicate that the sensor 24 is not operating properly.

[0045] The description of the present disclosure is merely exemplary in nature and variations that do not depart from the gist of the present disclosure are intended to be within the scope of the present disclosure. Such variations are not to be regarded as a departure from the spirit and scope of the present disclosure.