ADAMS/Driver

Issues
Resolved

What's New

Notice about ADAMS/Driver

ADAMS/Driver has been shipped with version 4.4.12 of IPG Driver and DriverLite, (the same version that shipped with the 12.0 Service Pack). Efforts were made to integrate the latest version of IPG Driver and DriverLite (Version 4.5) into this release of MSC.ADAMS. Due to failure of our internal validation and quality tests, however, it was decided in the interests of overall quality to remove this functionality from the release.

As a result of these integration problems, the following issues are not resolved:

Poor longitudinal control for models with time delays or high available engine torque (CRs 30680, 30687, 32513, 36537, 41000)
Poor lateral control at low speed and high curvature (CR 37406)
Poor lateral control when Driver controls steering torque (CR 36896)
Odd sensitivity to gear selection (CR 37103)
Brake control initiates at the wrong time (CR 40073)
Poor handling of engine stall conditions by DriverLite (CR 27380)
Driver unable to maintain course on rough roads (CR 28683)
Vehicle occasionally veers off course (CR 36453)
Poor documentation for simple path following (CR 30727)
Poor convergence of preview time when learning (CR 40135)
Location of saving SDC and SDV files

The following enhancements are not implemented:

Improve layout of DIN files (code is ready but compatible only with IPG Driver version 4.5) (CR 38599)
Ensure compatibility (CRs 31047, 30756, 36650)
Improve extraction of parameters from models (also much improved by new DIN file layout developed for Driver version 4.5) (CRs 40117, 40028)

We will be working closely with IPG to rectify these integration issues.

Items introduced in the 12.0 Service Pack and included in this release

The 2003 release of ADAMS/Driver includes items that were first introduced in the 12.0 Service Pack. If you did not install the 12.0 Service Pack for your MSC.ADAMS installation, note that the following items have been included in this release of ADAMS/Driver.

IPG Driver update
Updated ADAMS/Driver to version 4.4.12 of IPG Driver. This update offers many speed and robustness improvements. Upgrading to IPG Driver 4.4.12 exposes a number of new parameters and settings. These include:

MAX_SIDE_SLIP
ADAMS/Driver monitors the slip angles of the front tires. If the slip angle of the loaded front tire (outside tire in a turn) exceeds the MAX_SLIDE_SLIP angle input in the driver input file (.din), then ADAMS/Driver assumes the vehicle is understeering and will not increase the steer angle to attempt to follow the path. For manuevers such as an ISO lane change, this prevents excessive steering-wheel input that must be unwound before counter steering to prevent a spin.

Previously, if the vehicle reached a state of understeer, the driver model would keep dialing in steering wheel angle in an attempt to execute the turn. At the same time, the throttle would often be left open, further exasperating the understeer problem. Now, a new parameter is available. If you are using ADAMS/Car or ADAMS/Chassis interface, this parameter is exposed as MAX_SIDE_SLIP in the driver input file (Din). If you are using the ADAMS/Driver interface, this parameter is exposed as fileKnowl.LatDyn.LimitSideSlip in the knowledge file (.kno). If the parameter is set, on reaching the maximum front wheel side slip angle, the driver will not increase the steering-wheel angle any further, and will back off the throttle in an attempt to make the turn.

GEAR_RATIOS
Previously, it was only possible to set the following parameters for every gear:

MIN_ENG_SPEED   = 2000.0
MAX_ENG_SPEED   = 7000.0
UPSHIFT_RPM     = 10000.0
DOWNSHIFT_RPM   = 3500.0

The interface has now been enhanced so these parameters can be set for each gear. These changes are exposed in the driver input file (Din), if you are using ADAMS/Car or ADAMS/Chassis, or in the knowledge file (.kno), if you are using the ADAMS/Driver interface. Below is an example from each file (Din and .kno, respectively).

Din

[GEAR_RATIOS]
(GEAR_1)
RATIO         = 3.5
MIN_ENG_SPEED = 2000.0
MAX_ENG_SPEED = 7000.0
UPSHIFT_RPM   = 10000.0
DOWNSHIFT_RPM = 3500.0
$-------------------------------------------GEAR_RATIOS
(GEAR_2)
RATIO         = 1.94
MIN_ENG_SPEED = 2000.0
MAX_ENG_SPEED = 7000.0
UPSHIFT_RPM   = 10000.0
DOWNSHIFT_RPM = 3500.0

.kno

  'Minimal engine speed         [1/min] ==> '1000.0 1200.0 1300.0

  'Maximal engine speed         [1/min] ==> '4000.0 4200.0 4300.0

  'Upshift r.p.m at constant... [1/min] ==> '2000.0 2200.0 2300.0

  'Downshifting r.p.m for acc...[1/min] ==> '3000.0 3200.0 3300.0

This is the input for the 1st, 2nd, and 3rd gear. The input for gears greater than 3rd are the same as for the 3rd gear. More columns can be added to represent 4th, 5th, etc.

The ADAMS/Car and ADAMS/Chassis interface have been updated to reflect these changes. If you write a driver input file (Din) from either interface, the new gear parameters will be added.

FW_PYLON_SHIFT_COEFF/BW_PYLON_SHIFT_COEFF
These parameters are only active for the ISO Lane Change event. By shifting pylons either forward or backward it is possible to tighten or loosen the path that the vehicle must follow by shrinking the distance between the pylons.

For example, the X's below represent pylon locations as input using the driver road file and 0.25m is the pylon shift. ADAMS/Driver constructs the static desired course (SDC) as if there were new pylons at the locations marked with the verticals (|). When you have a problem with the lane change where the vehicle is clipping pylons, the pylon shifting coefficient can be used to modify the path.


X     X      X



-------> Direction of travel



X     X     X---|

                0.25m

                                 0.25m

                                      |---X    X    X

 

 



                                          X    X    X

This parameter is only exposed in the ADAMS/Car and ADAMS/Chassis interface, and can only be used in conjunction with these products. It is not exposed from the ADAMS/Driver interface. The following entries can be found in the driver input file (Din).

FW_PYLON_SHIFT_COEFF = 0.25
BW_PYLON_SHIFT_COEFF = 0.35

Values of 0.25 and 0.35, as shown above, would result in the vehicle following the path of the lane change much more closely.

3D_SMOOTH_ROAD
ADAMS/Driver and ADAMS/DriverLite have been enhanced to work with the new 3D smooth road module (see What's New for ADAMS/Tire for additional information). When used with ADAMS/DriverLite, the road data file (.rdf) is used as the input to the steering controller. The centerline of the road is then followed. The following is an extract of the MACHINE_CONTROL block from a driver control file (.dcf).

(MACHINE_CONTROL)
  STEERING_CONTROL   = 'FILE'
  DCD_FILE_STEERING = 'mdids://private/roads.tbl/pk_3d.rdf'
  SPEED_CONTROL      = 'lon_accel'
  LON_ACCEL_TARGET   = 98.07
  START_TIME         = 0.5
  MIN_ENGINE_SPEED   = 1000.0
  MAX_ENGINE_SPEED   = 7000.0
  DCD_FILE_SPEED     = ''

If you are modifying the .dcd file to use the 3D smooth road with the full version of ADAMS/Driver, you must specify the same 3D smooth road for both the road data file (.rdf) and the course data file (the simulation will not run if you use different files).

ADAMS/Car and ADAMS/Chassis generate road graphics from driver road files and 3D smooth road files that include green shoulders and yellow lines at the road edges and center, and a gray road surface. Previously, the road was represented by a white shell.

STOR_SD_FILES
The writer for the sdc (static desired course) and sdv (static desired velocity) has been enhanced to write an ascii file directly. Previously, a binary file was written, requiring an executable to read the binary file and write the ASCII file.

This functionality is accessed using the driver input file (Din) for ADAMS/Car and ADAMS/Chassis, or the knowledge file (.kno) for the ADAMS/Driver interface. The entries are as follows for each file, respectively:

STOR_SD_FILES = 1

'Storing sdc and sdv (1=yes, 0=no) ===> ' 1

Improved image clarity in ADAMS/Driver guide
Images that were unreadable are now readable.

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Changes

External control to adjust the gain of the DriverLite ('MACHINE') longitudinal controller

In this release of ADAMS/Car and ADAMS/Chassis, we implemented an external control to allow you to adjust the gain of the DriverLite ('MACHINE') longitudinal controller. This control was introduced in response to your feedback. Previously, many of you had difficulty achieving stable control for models with time delays and/or high gains between application of an input at the throttle and the responding acceleration (such as with light or powerful vehicles; those with flexible drivelines, throttle lags or tire relaxation; or when driving in low gears).

Normally, a combination of these factors must be present for any instability to occur. When these conditions are met, it is necessary to reduce the gain of the controller and allow the vehicle to take slightly longer to settle to the desired speed. If you experience such instability in DriverLite's longitudinal control of your model, you can access this gain control by setting the environment variable SDI_LONG_GAIN.

Setting SDI_LONG_GAIN = 1.0 will have no effect. It is equivalent to not
setting the variable.

Setting SDI_LONG_GAIN < 1.0 will improve stability at the expense of
response time.

Setting SDI_LONG_GAIN > 1.0 will improve response time at the expense
of stability.

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Known issues

Please go to the Knowledge Base to read all of the Known Issues for
ADAMS/Driver 2003

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Revised: 09/06/05