System and method for estimating turbo speed of an engine

Abstract

The speed of a turbocharger may be estimated using data from sensors that are readily available in most engine management systems. In some cases, a pressure measurement from a MAP sensor may be used, in combination with one or more computational models, to provide an efficient, lower cost estimate of turbo speed that can be used to control operation of the engine and/or the turbocharger.

What is claimed is: 
     
         1 . A controller for estimating an operating speed of a turbocharger that has a compressor with an air inlet and an air outlet, the compressor feeding compressed air to a downstream throttle that provides a throttled air flow to an air intake manifold of an engine, the controller configured to receive:
 a compressor air flow signal that represents a measure of air flow through the compressor;   a compressor air inlet pressure signal that represents a measure of pressure at the air inlet of the compressor;   an intake manifold pressure signal that represents a measure of pressure at the air intake manifold of the engine; and   a throttle signal that represents the throttle position of the throttle;   wherein the controller includes a processor and a memory having instructions stored therein that are executable by the processor to:   estimate an air pressure at the air outlet of the compressor using a throttle model expressed as a continuous function;   estimate an operating speed of the turbocharger using a turbocharger model expressed as a continuous function obtained by fitting compressor map data; and   provide one or more control signals to control an operation of the turbocharger and/or the engine in response to the estimated operating speed of the turbocharger.   
     
     
         2 . The controller of  claim 1 , wherein the throttle model is expressed as a continuous function including a throttle discharge coefficient modeled as a function of the throttle command signal. 
     
     
         3 . The controller of  claim 1 , wherein the turbocharger model further references a measure of temperature of the air at the air inlet of the compressor. 
     
     
         4 . The controller of  claim 1 , wherein the throttle model further references a measure of temperature of the air at the throttle. 
     
     
         5 . The controller of  claim 1 , wherein the throttle model further references the measure of air flow through the compressor. 
     
     
         6 . The controller of  claim 1 , wherein a charge air cooler is interposed between the air outlet of the compressor and the downstream throttle, wherein the throttle model also models the effects of the charge air cooler. 
     
     
         7 . The controller of  claim 6 , wherein the throttle model further references a measure of temperature of the air in the throttle, wherein the measure of temperature is taken downstream of the charge air cooler and upstream of the throttle. 
     
     
         8 . An air inlet system for use with an engine having an intake manifold, comprising:
 a turbocharger that has a compressor with an air inlet and an air outlet, the air outlet feeding compressed air therefrom;   a throttle downstream of the turbocharger and upstream of the intake manifold;   a plurality of sensors;   a controller for estimating an operating speed of the turbocharger, wherein controller is coupled to the sensors and receives each of:   a compressor air flow signal that represents a measure of air flow through the compressor from a first sensor;   a compressor air inlet pressure signal that represents a measure of pressure at the air inlet of the compressor from a second sensor;   an intake manifold pressure signal that represents a measure of pressure at the air intake manifold of the engine from a third sensor;   a throttle signal that represents the throttle position of the throttle;   wherein the plurality of sensors includes at least the first, second and third sensors, and the controller comprises a processor and a memory having instructions stored therein that are executable by the processor to:
 estimate an air pressure at the air outlet of the compressor using a throttle model expressed as a continuous function; 
 estimate an operating speed of the turbocharger using a turbocharger model expressed as a continuous function obtained by fitting compressor map data; and 
 provide one or more control signals to control an operation of the turbocharger and/or the engine in response to the estimated operating speed of the turbocharger. 
   
     
     
         9 . The system of  claim 8 , wherein the controller is configured to receive a temperature signal from a fourth sensor providing a measure of temperature of the air at the air inlet of the compressor, and the instructions stored in the memory are such that the temperature of the air at the air inlet of the compressor is also used to estimate the operating speed of the turbocharger. 
     
     
         10 . The system of  claim 8 , wherein the controller is configured to receive a temperature signal from a fourth sensor providing a measure of temperature of the air at the throttle, and the instructions stored in the memory are such that the temperature of the air at the throttle is also used to estimate the operating speed of the turbocharger. 
     
     
         11 . The system of  claim 8  wherein the third sensor is a Manifold Air Pressure (MAP) sensor. 
     
     
         12 . The system of  claim 8  wherein the second sensor is a pressure sensor located at the air inlet of the compressor. 
     
     
         13 . The system of  claim 8  wherein the first sensor is a flow sensor located upstream of the air inlet of the compressor. 
     
     
         14 . The system of  claim 8  wherein the throttle signal is a throttle command signal. 
     
     
         15 . The system of  claim 8  wherein the instructions stored in the memory are such that the throttle model is expressed as a continuous function including a throttle discharge coefficient modeled as a function of the throttle signal. 
     
     
         16 . A method for estimating an operating speed of a turbocharger that has a compressor with an air inlet and an air outlet, the compressor feeding compressed air to a downstream throttle that provides a throttled air flow to an air intake manifold of an engine, the method comprising:
 estimating the operating speed of the turbocharger based at least in part on:
 a measure of air flow through the compressor; 
 a measure of pressure at the air inlet of the compressor; 
 a measure of pressure at the air intake manifold of the engine; 
 a throttle signal that represents the throttle position of the throttle; 
   by solving a turbocharger model expressed as a continuous function obtained by fitting compressor map data, the continuous function referencing at least a current value of the measure of air flow through the compressor and a current value of the measure of pressure at the air inlet of the compressor; and   controlling an operation of the turbocharger and/or the engine in response to the estimated operating speed of the turbocharger.   
     
     
         17 . The method of  claim 16 , wherein the estimating the operating speed of the turbocharger is also based on a measure of temperature of the air at the air inlet of the compressor. 
     
     
         18 . The method of  claim 16 , wherein the estimated operating speed of the turbocharger is also based on a measure of temperature of the air at the throttle. 
     
     
         19 . The method of  claim 16 , wherein the estimated operating speed of the turbocharger is also based on a measure of temperature of the air at the air inlet of the compressor and a measure of temperature of the air at the throttle. 
     
     
         20 . The method of  claim 16  further comprising estimating an air pressure at the air outlet of the compressor using a throttle model expressed as a continuous function of the throttle signal.