Difference between revisions of "MDFAW 12.260 (Driver Requested Torque)"

mdfaw-dmlwhs Sub-function DMLWHS: indicated driver requested torque for

<u>MDFAW 12.260 Function Description</u>

The duty of this function is to calculate the driver’s requested torque as a function of accelerator pedal position (wped_w) and cruise control output (mrfgr_w). Separate values are provided for cylinder charge and ignition influences (mifal_w, mifa_w).

The throttle pedal characteristic is defined by maps, where through pedal position and engine speed, a factor (relative torque) is stored to help scale indicated torque between the minimum and maximum. The relative driver’s requested torque can have values &#8203;&#8203;greater than 100% (pedal crossover). For reverse gear, a separate map is available that can be used on vehicles with automatic transmission. To enhance driving

comfort, a change in the driver’s requested torque limit can take place under certain conditions (load changes, overrun fuel cut-off and reinstatement, transition from part load to idle and vice versa. See sub-function DMFABEG).

The idle condition (B_ll) is set when the relative driver’s requested torque drops below the threshold MRFALLU and is reset when the threshold MRFALLO is exceeded. The cruise control condition (B_fgr) is set when the cruise controller output is greater than the output of the pedal characteristic. The integral component of the idle control (dmllri_w) is included in the driver’s request.

The change limitation for the driver’s requested torque (sub-function DMFABEG) is used to improve ride comfort and overrun fuel cut-off and smooth resumption of positive and negative load changes. With that, a DT1-element filtered torque loss (dmverl_w) is added behind the change limitation around jumps in the clutch torque to damp the connection or disconnection of load.

<u>Overrun fuel cut-off/reinstatement</u>

Via a PT1-filter, down-regulation of the target torques starting from the actual torque at zero takes place by overrun fuel cut-off; smooth resumption by up-regulation of the target torques starting from mizwmn_w to mimin_w. The filter time constants for up-regulation and down-regulation can be chosen independently of each other. One more time constant is made available for hard resumption and leaving idle (under light throttle). The initialization of the filters on the overrun fuel cut-off to the actual torque is needed to avoid a jump in torque on enabling of the ignition angle interventions. The filtering is, or is not cancelled:

- On a steep negative speed gradient (uncoupling of thrust or throttle),

- When the clutch is actuated (configurable via CWDMFAB)

- mrfa gradient at higher threshold (important during hard resumption and when leaving the idle),

The change limitation for negative load changes (dashpot) is implemented using a

The driver’s desired torque for the cylinder charge influence mifal_w is calculated by a dashpot with its own PT1-filter that is initialized when the unfiltered driver’s desired torque drops below the trigger level. In this way, a steep initial drop is reached, which leads to the rapid closing of the throttle. Then a soft change is made to the target value. The dashpot can be active only when:

- The general dashpot-enable is done viaCWDMFAB Bit1,

- There is no commitment to overrun fuel cut-off,

- The cylinder charge is greater than the minimum charge.

The change limitation during positive load changes is realized with the help of a PT2 filter whose damping and time constant are gear- and speed-dependent. The PT2 filter runs with a positive gradient of the unfiltered driver’s requested torque. Load shock damping is triggered when the difference between unfiltered and filtered output value exceeds a gear- and clutch torque-dependent threshold. The PT2 filter is triggered when the load shock absorption is initialized with the actual torque or a speed-and gear-dependent initial value, to avoid a jump in torque upon enabling of the ignition angle interventions and to influence the response behavior. The load shock damping is terminated when the difference between the filtered and unfiltered value drops below a gear-dependent threshold.

The driver’s desired torque for the cylinder charge influence mifal_w with active load shock damping is calculated from a map which depends on the desired torque for the ignition influence (mifa_w) and on the gear, which is a limitation on the unfiltered target. Thus, the cylinder charge can be controlled so that there is no significant ignition angle intervention in order to set the desired torque curve.

The load shock damping can be active only when

- Load shock damping is generally enabled via CWDMFAB Bit 0,

- For vehicles with CVT transmission, the torque gradient limitation is not active and the torque converter clutch is not open,

- The minimum speed for load shock absorption is exceeded,

The PT2 filter is implemented with two integrators and feedback. There is also the possibility that the filter is initialized with a given value (iwflsd_w) if the condition B_iflsd is set.

Bit 0 0: Load shock damping deactivated

Bit 1 0: Dashpot deactivated

Bit 2 0: Load shock damping with B_gwhs inactive

Bit 3 0: Dashpot with B_gwhs inactive

Bit 4 0: Overrun fuel cut-off/reinstatement filter with B_kuppl active

Bit 5 0: Dashpot and load shock damping even with traction control intervention enabled

1: Dashpot and load shock damping with traction control intervention inactive

Bit 6 0: Dashpot triggering independently of B_ll

1: Dashpot triggering on positive edge of B_ll

Bit 7 0: Load shock damping and dashpot triggering via threshold inactive, until cruise control intervention

1: Load shock damping and dashpot triggering via  threshold also possible during cruise control intervention

Bit 0 0: Initialization of migef_w when reinstating with miistoar_w

1: Initialization of migef_w when reinstating with 0 (for sequential reinstatement)

Bit 1 0: Initialization of mifal_w with dashpot with mivbeb_w

1: Initialization of mifal_w with dashpot with mibdp_w - dmdpo_w

Bit 2 0: Load shock damping with B_kupplv or B_gwhs inactive

1: Enable the load and shock damping independent of B_kupplv and B_gwhs

KFPEDL and KFPEDR must contain smaller values than KFPED at the same pedal value and the same speed so that the torque monitoring only depends on KFPED.

Delta indicated torque for change limitation by B_mismeus

Indicated driver requested torque for cylinder charge path during load

Indicated torque initial value for load shock damping

Maximum indicated engine torque

Indicated driver requested torque for cylinder charge path with active