Difference between revisions of "ATR 1.60 (Exhaust Gas Temperature Control)"

Revision as of 09:11, 11 September 2011

See the funktionsrahmen for the following diagrams:

atr-main exhaust gas temperature control overview

atr-atrbb detection of control range

atr-atrb exhaust gas temperature control for cylinder bank 1

atr-atrerb enabling exhaust gas temperature control for cylinder bank 1

atr-atrpi exhaust gas temperature proportional/integral control for cylinder bank 1

atr-atrb2 exhaust gas temperature control for cylinder bank 2

atr-atrerb2 enabling exhaust gas temperature control for cylinder bank 2

atr-atrpi2 exhaust gas temperature proportional/integral control for cylinder bank 2

atr-atrnl limp mode for exhaust gas temperature control

atr-atrko coordination of the control output

ATR 1.60 Function Description

Task:

Protection of components (manifold, turbocharger, etc.) by controlling the exhaust gas temperature. By means of this control, the general enrichment at high load and speed ("full-load enrichment") can be reduced. When general mixture control is insufficient, the exhaust gas temperature control enrichment must also be invoked which leads to reduced fuel consumption.

Principle:

An excessively high exhaust gas temperature can be lowered by enriching the air-fuel mixture. Through this enrichment, more fuel enters the cylinder than is required for stoichiometric combustion of the fuel. The unburned fuel vaporises on the cylinder walls and cools them, whereby the exhaust gas temperature decreases. For this control, the exhaust gas temperature is measured using an exhaust gas temperature sensor or estimated by an exhaust gas temperature model.

As long as the exhaust temperature is below the threshold temperature, there is no control. Thus, there is only a "down regulation" of the exhaust temperature, not an "up regulation". If the desired temperature is reached or exceeded, the control switches. To achieve an enrichment of the mixture, the controller is adjusted to give a desired value of lambda in the "rich" region. This enrichment decreases the exhaust gas temperature, and the controller sets the desired exhaust temperature. When the exhaust temperature drops back below the threshold temperature, the controller takes back the enrichment. If enrichment is no longer required, control is switched off.

Overview of Codeword CATR:

• If the value of bit 0 is set equal to 1, this enables exhaust gas temperature control.

ATRBB: Detection Control Range

This function detects the valid control range. Via the configuration byte CATR, the control can, in principle, be switched off. A valid range is usually present when the end of start conditions is detected (B_stend = 1), and the relative load (rl) lies above an applicable threshold rlatr. This control scheme is only available in the near-full load range (rl > rlatr) is active, since exhaust temperatures are only likely to be high in this range. Once the range is exited, control is switched off, e.g. in the transition to idle to shorten the duration of the enrichment.

The valid control range is indicated by the flag B_atrb = 1.

ATRERB: Enabling Exhaust Gas Temperature Control for Bank 1

The exhaust gas temperature control is a flip-flop on or off. The condition flag B_atr = 1 indicates that control is active. If the exhaust gas temperature (tabg) is greater than or equal to the applicable threshold value TABGSS, the control is switched on. The control is switched off when enrichment is no longer required. This is the case when the regulator output dlatr > 0. The controller output dlatr for the exhaust temperature control is then set to zero. It is possible to set a lean limit for the control scheme via the fixed value LATRO. If the current set-lambda without add. If the current desired lambda value without additional lamvoa parts above the limit LATRO (in the lean range) there will be no control. In addition, there is no control if any of the following conditions are met:

(a) No valid control range is detected (B_atrb = 0)

(b) Fuel injector cut-off condition is true (B_bevab = 1)

(c) The exhaust gas temperature sensor indicates an error (E_ats = 1)

(d) The exhaust gas temperature sensor is not ready (B_atsb = 0)

(e) Significant differences between the bank controller control variables were found (E_atrd = 1).

If the engine reaches the rich running limit (B_lagf = 1) while exhaust gas temperature control is active (B_atr = 1), a further enrichment attempt is prohibited by the control scheme (B_atrsp = 1). The current value of the controller output is recorded. However, an enrichment reduction is allowed.

ATRPI2: Exhaust Gas Temperature Proportional/Integral Control for Cylinder Bank 1

The exhaust gas temperature controller is configured as a PI controller, because the "delta lambda controller" intervenes additively. ATRP and ATRI are applied amplification factors for the P and I components. When control is switched off (B_atr = 0) the controller output is set to zero. The integral component in this case is set to equal the negative value of the proportional component (dlatri = -dlatrp), so it follows that the sum is zero. The controller output (dlatr) will be limited to "rich" by the applicable limit DLATRMN. In this case, the integrator is suspended. The exhaust gas temperature tabg falls below the threshold temperature TABGSS or the control is turned off (B_atr = 0), the integrator will be released. When the controller is inhibited (B_atrsp = 1), the last value of controller output (dlatr) is recorded. The integral part is calculated so that the controller output is constant even when a control error remains (dlatri = dlatr - dlatrp).

ATRERB2: Enabling Exhaust Gas Temperature Control for Cylinder Bank 2

As per cylinder bank 1

ATRPI2: Exhaust Gas Temperature Proportional/Integral Control for Cylinder Bank 2

As per cylinder bank 1

ATRNL: Limp Mode for Exhaust Gas Temperature Control

In the event that an exhaust gas temperature sensor fails or is not ready, a limp mode variable (dlatrnl) is provided. The delta lambda target of interest for the limp mode is in the characteristic DLATRNL.

ATRKO: Control Output Coordination

If there is no error in the exhaust gas temperature sensors before, the controller outputs dlatr or dlatr2 through the function outputs dlamatr or dlamatr2 are transferred to lambda coordination. Once a sensor failure (E_ats = 1 or E_ats2 = 1) or the sensors are not operational (B_atsb = 0), or significant bank differences of the controller variables (E_atrd = 1 or E_atrd2 = 1) is detected, the ATR-control range (B_atrb = 1) the limp mode variable dlatrnl are transferred to both banks of lambda coordination.

ATR 1.60 Application Notes

Requirements:

- Application of lambda control

Applications Tools:

VS100

Preassignment of the Parameters:

Erkennung Regelbereich:

- Codeword CATR = 01 (hexadecimal) = 1 (decimal) enable control

- Minimum load for exhaust gas temperature control map KFRLATR (x: engine speed/rpm, y: intake air temperature/°C, z:%)

Enable exhaust gas temperature control for cylinder bank 1/bank 2:

- Threshold exhaust gas temperature for exhaust gas temperature control: TABGSS(2) = 1000°C

- Desired AFR upper limit for switching off exhaust gas temperature control: LATRO = 16.0

Exhaust gas temperature control for cylinder bank 1/bank 2:

- Threshold exhaust gas temperature for exhaust gas temperature control: TABGSS(2) = 1000°C

- Gain factor for proportional component exhaust gas temperature PI control: ATRP = 0.005 l/K

- Gain factor for integral component for exhaust gas temperature PI control: ATRI = 0.0005 l/(s ´ K)

- Lower limit for exhaust gas temperature control: DLATRMN = -0.3

Exhaust gas temperature control limp mode:

- Delta lambda exhaust gas temperature control limp mode:

Procedure:

Switching off the Function:

To prohibit exhaust gas temperature control set codeword CATR [Bit 0] equal to 0.

Affected Functions:

%LAMKO through dlamatr_w and dlamatr2_w