Interface to SDF Functions in msautotils
A description of MotionSolve .xml statements needed to generate SDFs.
The data to compute the SDFs depend mostly on runtime
measurements, based on markers in the suspension. But some SDFs, for example, anti-lift or
anti-dive, require information about the full vehicle, like the height of the vehicle center
of gravity. To simplify usage the SDF output requests employ the same user function and
inputs, even though only a subset of the inputs are needed for a specific SDF. The form of
all output requests for SDFs is:
<Post_Request
id = "80000000"
comment = "Wheel Vert. Displacement and Vert. Force"
type = "USERSUB"
usrsub_param_string = "USER(0,0,1,31000200,0,31000100)"
usrsub_dll_name = "msautoutils"
usrsub_fnc_name = "sdfrequest"
/>
The
‘user_param_string’ attribute of the Post_Request element defines the data, that is passed
into the subroutine. The members of the USER-array are defined according to the following
table:
| Index | Name | Assumed Type | Example | Purpose |
|---|---|---|---|---|
| 0 | Axle ID | unsigned int | 0 | Provides a unique identifier to the axle. The axle index (counted from front
to rear, where 0 is the index of the first axle) is usually a good unique
identifier. This value is used to assign any registered steering or travel
lock, which has the same id to the suspension. Note: The current implementation
will assume the suffixes “front” and “read” from this value to distinguish
output values. |
| 1 | Branch ID | unsigned int | 350 | Identify the request to compute according to the table on SDF Output. |
| 2 | Testrig-Param-Array Version | unsigned int | 1 | Specifies, which version of the following array to assume. Version 0 refers to a version before v2020. The most recent is version 1. |
| 3 | Testrig-Param-Array | int/array-id | 31000200 | Solver ID of the array, that contains information about the testrig and how it applies measurement to the suspension. |
| 4 | Vehicle-Param-Array Version | unsigned int | 0 | Specifies which version of the following array to assume. The most recent is version 0. |
| 5 | Vehicle-Param-Array | int/array-id | 31000100 | Solver ID of the array, that contains information about the vehicle and how the suspension relates to it. |
Testrig Parameters Array
The ID in USER-array element #2 refers to a solver-array of the following layout:
| Index | Name | Assumed Type | Example | Purpose |
|---|---|---|---|---|
| 0 | Left Wheel Center Marker | int/marker-id | mrk_wc.l.id | The marker should be located on the wheel center, but should be defined on the knuckle. The marker must have no freedom to spin with the wheel. |
| 1 | Right Wheel Center Marker | int/marker-id | mrk_wc.r.id | |
| 2 | Left Lower Marker on Steer-Axis | int/marker-id | mrk_kp.l.id | If the upper and lower steer axis markers are connected to the
same body, the marker should be defined on this body at the location of the steer
axis. This is usually the lower kingpin. In this case, the z-axis of the marker
should point to the direction of the steer axis (upper kingpin). If the two markers are not connected to the same body (McPherson strut), then direction and body of this marker has no effect, but a second marker must be defined in #13 and #14. |
| 3 | Right Lower Marker on Steer-Axis | int/marker-id | mrk_kp.r.id | |
| 4 | Left Ground Reference Marker | int/marker-id | mrk_gnd.l.id | This marker should be located on the wheel center, but defined on ground. It serves as a reference for the measurement of wheel travel and steer. |
| 5 | Vehicle-Param-Array | int/marker-id | mrk_gnd.r.id | |
| 6 | Left Marker on Jack | int/marker-id | sfo_jack_actuator.l.i.id | This marker should be defined on the jack. It serves to measure the jack motion. |
| 7 | Right Marker on Jack | int/marker-id | sfo_jack_actuator.l.r.id | |
| 8 | Left Jack reference Marker on Ground | int/marker-id | sfo_jack_actuator.l.j.id | This marker should be defined on the ground at the same location as the Marker on Jack. It serves as a reference to measure the jack motion. |
| 9 | Right Jack reference Marker on Ground | int/marker-id | sfo_jack_actuator.r.j.id | |
| 10 | Steering Actuation Input Marker | int/marker-id | j_st_wheel_i_id | The marker serves to apply virtual steering input for the computation of
steering relevant values, such as scrub radius and caster trail. In the simplest case, it is a marker on the steering wheel or pinion and its z-axis points along the rotation axis. |
| 11 | Steering Actuation Orientation Marker | int/marker-id | -1 | This marker can be skipped (-1), if the marker in the previous field is oriented to the steering axis or rack. If this marker is specified, the direction will be assumed as the line between the markers. |
| 12 | Steering Actuation Mode | int | 6 | This value defines the mode (1 = TX, 2 = TY, 4 = RX, 6 = RZ) of the steering
input orientation. This is only used, if the second marker is not defined
(=-1). In case of two markers, a negative value indicates, that the two markers are swapped and the marker in #11 defines the application of the steering input. |
| 13 | Left Upper Marker on Steer-Axis | int/marker-id | mrk_upr_mnt.l.id | If this marker is defined (!=-1), then it is used together with
marker #2/#3 to compute the steer axis. Steer axis is assumed to be the line, that
passes the two markers #2-#13 for the left and #3-#14 for the right side. If this marker is not defined, the markers #2/#3s z-axis is used to assume the steer axis. |
| 14 | Right Upper Marker on Steer-Axis | int/marker-id | mrk_upr_mnt.r.id | |
| 15 | Left Ground Level and Orientation Marker | int/marker-id | mrk_jack_cp.l.id | This marker is used to measure the ground plane for each wheel. It supports ground plane inclination for scrub radius and caster trail computation. |
| 16 | Right Ground Level and Orientation Marker | int/marker-id | mrk_jack_cp.r.id |
Vehicle Parameters Array
| Index | Name | Assumed type/dimension | Example | Purpose |
|---|---|---|---|---|
| 0 | Vehicle End/role | unsigned int | ds_vehpar.veh_end.ival | Provides information, if the axle is at the front end or read end of the vehicle. |
| 1 | Type of suspension | unsigned int | ds_vehpar.dif_mnt.ival | Provides information, if the suspension is independent (0) (left/right don’t influence each other) or not (1). |
| 2 | Tire Static Loaded Radius (mm) | Float [L] | ds_vehpar.tire_slr.value | Provides location and body to lock, if #4 is positive. Provides direction to from z-axis, if #3 is not given (-1) and #4 is positive. Provides reference point for direction, if #3 is defined (second marker). |
| 3 | Tire Vertical Spring Rate (N/mm) | Float [F/L] | ds_vehpar.tire_rate.value | Provides location and body to lock, if #4 is negative. Provides second point for direction, if defined (second marker). |
| 4 | Vehicle CG Height (mm) | Float [L] | ds_vehpar.cg_height.value | Height of the center of gravity over ground. |
| 5 | Wheel Base (mm) | Float [L] | ds_vehpar.wheel_base.value | Distance between front and rear wheel centers. |
| 6 | Front Braking Ratio (-) | Float [-] | ds_vehpar.front_brake.value | The brake force distribution at the front wheels. A value of 1 indicates 100% braking on the front. |
| 7 | Front Drive Ratio (-) | Float [-] | ds_vehpar.front_drive.value | The percentage engine power distributed to the front axle. A value of 1 indicates all power is sent to the front. |
| 8 | Axle Ratio (-) | Float [-] | ds_vehpar.axle_ratio.value | The ratio between the angular velocity of the input gear to the angular velocity of the output gear. It is also commonly known as gear or speed ratio. |
| 9 | Vehicle Weight (N) | Float [F] | ds_vehpar.veh_weight.value | Total mass of the vehicle. |