Difference between revisions of "ARMD 10.40 (Torque-Based Anti-Jerk Function)"

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2. Evaluation of filter parameters
 
2. Evaluation of filter parameters
  
Low pass filter in 50 ms scan rate: transmission function has the form G(z) = Z(z)/N(z) with
+
For a low pass filter with 50 ms scan rate, the transmission function has the form G(z) = Z(z)/N(z) where
  
 
Z(z) = A0 + A1z<sup>-1</sup> + A2z<sup>-2</sup>
 
Z(z) = A0 + A1z<sup>-1</sup> + A2z<sup>-2</sup>
  
N(z) = 1 + B1z<sup>-1</sup> + B2z<sup>-2</sup>.
+
N(z) = 1 + B1z<sup>-1</sup> + B2z<sup>-2</sup>
  
  

Revision as of 12:27, 22 May 2012

See the funktionsrahmen for the following diagrams:

armd-armd Main function

armd-kifz Subfunction KIFZ (amplification of vehicle model)

armd-flrar Subfunction FLRAR (amplification factor for modelling of external load)

armd-fdar Subfunction FDAR (amplification factor for anti-jerk intervention)

armd-nmoti Subfunction NMOTI

armd-ndfil Subfunction NDFIL (filtered engine speed difference)

armd-frgar Subfunction FRGAR

armd-iniarv Subfunction INIARV

armd-kup gw Subfunction KUPGW

armd-dmar Subfunction DMAR (delta torque anti-jerk)

armd-varss Subfunction VARSS


ARMD 10.40 Function Description

Function purpose

The anti-jerk function detects oscillations of the power train and damps them out by applying opposing-phase torque interventions. The torque intervention is converted into an ignition angle offset by the torque interface.


Desired phase position of the torque intervention

In order to damp the power train oscillation efficiently, the torque intervention should counteract engine speed oscillations. Thereby the same effect is achieved as if the attenuation coefficient of the drive shaft is increased.


Operation pattern of anti-jerk function

Basic idea: a reference speed without oscillation and corresponding to the driver’s demand is evaluated. The difference between desired and actual engine speed isolates the oscillation. A counteracting delta torque is set which is proportional to this oscillation.

The function is realized by a simple vehicle model consisting of an integrator with the constant kifz_w. The input to this integrator is the difference between the driver’s predetermined clutch torque mkar_w and the load torque mlast_w. The output from the integtrator is the modelled engine speed nmod_w. The engine speed difference ndiff_w between the modelled engine speed nmod_w and the actual engine speed nmot_w now forms the basis for the torque intervention as well as for the calculation of the load torque. The load torque is evaluated proportional to the engine speed difference and the factor flrar is taken from the corresponding characteristic line. The engine speed difference ndiff_w contains another offset besides the oscillation part. This offset is filtered on a 50 ms scan timescale through a discrete second order low pass filter. (Coefficients of the nominator polynomial are denoted A0, A1 and A2 and of the denominator polynomial 1, B1 and B2.


The filtered offset ndfil_w is substracted from the differential engine speed and gives the engine speed oscillation ndar_w. Proportionally to this engine speed and using the factor fdar, a delta torque as a torque intervention is calculated. If this intervention lays between the limits KFDMDARU and KFDMDARO, it is set to zero.


Activation Conditions

The model is always active, just the intervention can be switched off.


Application Notes

Conditions for calibration of anti-jerk

The basic calibration of the vehicle must have been done. This includes the transition compensation and all functions for the torque interface.


1. Evaluation of the integrator constant kifz_w and flrar

Coarse application:

Drive on the road (flat surface, no hills) at a constant speed in respective gear with the anti-jerk function deactivated (fdar=0). Then execute a change in load and register the calculated coupling torque mkar_w and the engine speed nmot_w.

Evaluation of integrator constant as follows: at a load step the torque jump is approximately delta M (in %) and the speed approximately rises with constant gradient gradn (in RPM/s). Kifz_w is then calculated from the expression gradn/(delta M). A typical value for second gear is 4.6 x 100/MDNORM [RPM/(sx%)].


Fine application:

Driving on flat surface. Set the product kifz_w x flrar to a fixed value (recommendation: 15). Realization of load jumps with registration of mkar_w, mlast_w, nmot_w and ndiff_w. Vary the couple kifz_w and flrar (maintaining the product constant!) until ndiff_w remains approximately constant during a load jump.

In principle the following process is valid for the amplification factor flrar: high factors cause a reduction of the offset ndfil_w, but also a big phase advance of ndiff_w.


2. Evaluation of filter parameters

For a low pass filter with 50 ms scan rate, the transmission function has the form G(z) = Z(z)/N(z) where

Z(z) = A0 + A1z-1 + A2z-2

N(z) = 1 + B1z-1 + B2z-2


Select one of the low pass filters listed in the table below, according to the appearing jerk frequency:


TP No.

Limit freq.

A0

A1

A2

B1

B2

1

0.67 Hz

0.0095

0.0191

0.0095

-1.7056

0.7437

2

0.80 Hz

0.0134

0.0267

0.0134

-1.6475

0.7009

3

1.00 Hz

0.0201

0.0402

0.0201

-1.5610

0.6414


Low pass filter No. 3 is recommended. The attenuation of the jerk frequency is determined by the margin between the jerk frequency and the filter cut-off frequency. The bigger the filter cut-off frequency, the smaller the time the filter needs to stabilize. Attenuation: modification of a single coefficient of G(z) is not permitted!


3. Evaluation of fdar

Recommendation is fdar = 0.67 x 100/MDNORM (%/RPM). Increase of attenuation by enlargement of fdar, reduction of fdar decreases the attenuation.


4. Thresholds KFDMDARO and KFDMDARU

In case the delta torque for the intervention is within these thresholds, it is set to zero. This avoids undesired ignition angle instability. Typical values are: KFDMDARU = -5 x 100/MDNORM [%], KFDMDARO = 5 x 100/MDNORM [%].


Abbreviations

A0

Transmission coefficient

A1

Transmission coefficient

A2

Transmission coefficient

B1

Transmission coefficient

B2

Transmission coefficient

CWARMD

Code word anti jerk function

DMARMX

Maximum limit of the steady-state torque interventions of the anti-jerk function

DNFILO

Upper threshold of filter output gradient ndfil

DVFZAR

Hysteresis for vehicle speed limit during anti-jerk

FLRAWG

Integrator gain factor of the load controller during AT (throttle plate closed)

FLRHG

Integrator gain factor of the load controller

FRARAWG

Integrator gain factor during AT (throttle plate closed)

FRARHG

Integrator gain factor

KFDMDADP

Upper threshold for torque-intervention during dashpot

KFDMDARO

Upper threshold for torque intervention

KFDMDAROS

Upper threshold for steady-state torque intervention

KIFZGAWG

Integrator gain factor in the vehicle model with AT (throttle plate closed)

KIFZGHG

Integrator gain factor in the vehicle model with HG

NARAO

Upper engine speed threshold for anti-jerk function active

NARASTG

RPM threshold in higher gear for anti-jerk active

NARLLGA

Speed threshold for anti-jerk at idle

NDFILOG

Threshold for filter output ndfil

NDIFFOG

Threshold engine speed difference for initialization of anti-jerk during braking

NVG

Factor to calculate engine speed initialization

NVMNG

Minimum speed / velocity ratio

NVMXG

Maximum speed / velocity ratio

SMK08MDSW

Anti-jerk torque dependent basic point (number =8)

TAREIN

Blocking time for anti-jerk function

TMAR

Lower engine temperature threshold for anti-jerk release

TMLAST

Blocking time until the initialization of the anti-jerk is triggered at deceleration

TVARS

Delay time until anti-jerk is inactive again

TVARSS

Delay time for anti-jerk becoming inactive again in steady-state conditions

TVKUPAR

Delay time for clutch for anti-jerk function

TVKUPHS

Delay time for clutch switch during shifting in higher gear

TVKUPRS

Delay time for clutch switch during shifting in lower gear

TZSPINI

Blocking time for filter initialisation

VARAU

Minimum vehicle speed for anti-jerk active

WPEDU

Pedal lower threshold value for anti-jerk function

B_AR

Condition: anti-jerk active

B_ARGF

Condition: anti-jerk transition window

B_AUTGET

Condition: automatic gearbox

B_BREMS

Condition: brake operated

B_DASHV

Condition: dashpot delayed

B_FGR

Condition: driver's set engine torque determined by cruise control

B_GFEN

Condition: transition window

B_GWHS

Condition: gear change on manual transmission vehicle

B_HPNMOT

Condition: high-point speed oscillation

B_INIAR

Condition: initialization of anti-jerk function

B_INIAR1

Condition: provisional initialization of anti-jerk function

B_INIARV

Condition: initialization of the filter function is delayed

B_KUPGW

Condition: clutch applied until shifting of geanti-jerk is detected

B_KUPPL

EGAS Condition: clutch is disengaged

B_LL

Condition: idle

B_LSD

Condition: limitation of positive torque gradient active

B_SA

Condition: fuel cut-off

B_STEND

Condition: end of start reached

B_TPNMOT

Condition: low-point speed oscillation

B_TVARS

Condition: anti-jerking function dynamically active

B_TVARSS

Condition: anti-jerking function steady-state active

B_WK

Condition: converter lockup clutch closed

DMAR_W

Delta torque anti-jerk

FDAR

Amplification factor for anti-jerk intervention

FLRAR

Amplification factor for modelling of external load

GANGI

Engaged gear

KIFZ_W

Amplification of vehicle model

MDBES_W

Acceleration torque

MDVERL_W

Resistant torque of the engine

MIFA_W

Desired indicated engine torque

MISOLV_W

Indicated resultant nominal torque before torque limitation

MKAR_W

Calculated clutch torque for anti-jerk function

MLAST_W

Estimated load moment

NDAR_W

RPM difference for torque control

NDFIL_W

Filtered engine speed difference

NDIFFOG_W

Threshold engine speed difference for reset of anti-jerk during braking

NDIFF_W

Engine speed difference for ISC amplification

NMODIV_W

Engine speed for initialising ARMD calculated from velocity

NMOD_W

Engine speed from model

NMOT_W

Actual engine speed

NVQUOT_W

Quotient engine speed / vehicle speed

TMOT

Engine temperature

VFZG

Vehicle speed (km/h)

VFZG_W

Vehicle speed (km/h, word)

WPED_W

Normalised throttle pedal angle (word)

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