Single Lane Change

Introduction

A Single lane change event drives the vehicle through a single lane change, attempting to follow the centerline of the defined lane. You can define the speed of the lane change, along with the lane dimensions. A steering controller is used to follow the path and a torque controller is used to maintain speed through the event. The event supports right and left lane changes. A plot template is available to plot the results.

A Single lane change does not have specific metrics associated with it. A lane change is typically used as a subjective evaluation test, but it is difficult to create objective metrics of the test.

Note - A Double Lane Change test is also available.

single_lane_change_event_example_mv

Single Lane Change Event

single_lane_change_event_example_top_view_mv

Top View of a Single Lane Change Path

single_lane_change_event_body_with_graphics_example_mv

Vehicle Model with Body Graphics

Detailed Description

The Single lane change event is designed to work with a full vehicle model that has been built through the MotionView Assembly Wizard. The event should attach to the model automatically when added through the Task Wizard. The event can be used with models built manually, as long as the attachment scheme in the event is strictly followed.

The event is comprised of an initial straight section of road, a transition section, and a recovery straight section. In the initial straight section, the vehicle settles into a steady state condition. The transition section is the actual lane change. The vehicle recovers in the final straight section and terminates the simulation. The vehicle maintains a constant velocity (via the torque controller) in the event. The vehicle steering controller is designed to keep the CG of the body on a path at the centerline of the road.

The initial speed, longitudinal and lateral spacing of the cones, and lane graphics can be modified via the event Form (shown below). The Ground z Coordinate is a calculated value (the blue background designates a calculated value) and is calculated by subtracting the front left tire rolling radius from the front left tire CG Z location.

task_wzd_dialog_single_lane_change_event_mv

Single Lane Change Data Dialog

A test model runs this simulation in 60 seconds. Approximately 0.5G lateral is developed by the test vehicle model and default lane change parameters. Increasing the speed and lateral spacing of the cones increases the lateral G forces developed by the vehicle. As the vehicle approaches its limits of handling, the model will yaw excessively or will not complete the lane change. The error Could not Find Ideal SWA in 20 Iterations may be displayed in the log file, indicating that the steering controller is unable to follow the defined path.

The Single lane change event is parametrically defined per the diagram below.

single_lane_change_road_graphics_example_mv

Single Lane Change Event - Road Graphics Parametric Definition

The cone spacing (laterally and longitudinally) and the lane width can be changed, along with the vehicle speed. Use the event Form to change these parameters.

The entities in the event are displayed in the MotionView Project Browser as shown in the image below:

single_lane_change_browser_mv

Project Browser View - Forms - Single Lane Change Analysis

Nine types of modeling element containers (Datasets->templates) are used to define the event (see below). Two sub-systems (a Steer controller and a Drive torque controller) are also included in the event.

The event attaches to the model as shown in the picture below. All of the attachments need to be resolved to write out the model. The attachments are the references in the model required for the event to run.

events_attachment_list_mv

Single Lane Change Event - Attachments

Variable	Label	Description
sys	System	The master system, in this case “Model”.
b_frnt_whl	mot_frnt_wheel	Front wheel body pair.
b_rear_whl	mot_rear_wheel	Rear wheel body pair.
J_frnt_whl	Front Wheel Joint	Revolute joint connecting the front wheels to the knuckle.
J_rear_whl	Rear Wheel Joint	Revolute joint connecting the rear wheels to the knuckle.
J_st_wheel	Steering Wheel Joint	Revolute joint connecting the steering wheel to the body or the steering gear input shaft to the body, if a steering column is not included.
B_body	Vehicle Body	The vehicle body.
Drive_joint	Drive Joint	The joint used to drive the vehicle, which varies depending on the drivetrain. It is typically the revolute joint in the drivetrain closest to the engine.
J_clamp_1_body	Vehicle Body Joint 1	Vehicle body clamp one. One of two clamps used to hold the vehicle fixed during static simulation.
J_clamp_2_body	Vehicle Body Joint 2	Vehicle body clamp two. The second clamp used to hold the vehicle fixed during static simulation.
b_str_dummy	Steering Dummy Body	The Rack in a rack and pinion steering system. The relay rod in a Parallelogram steering system.
J_rackfix_att	Joint Fixed Rack-Body	Rack dummy orient joint in a rack and pinion steering system. Idler Arm ball in a parallelogram system.
J_ball_att	Joint Pitman	The pinion joint in a rack and pinion steering system. The pitman arm ball joint in a Parallelogram system
Tire_dataset	Tire Data	Dataset containing the tire information from the tire system.
b_str_dummy_racksteer	Steering Dummy Body Rack Pinion	Steering dummy body in both parallelogram and rack and pinion steering systems.

The dataset contains the data used to describe the lane change. The four parameters at the top of the dataset, shown with a white background, can be changed to modify the event using single lane change Form. The six parameters at the bottom of the dataset are calculated parameters and should not be changed. The blue background signifies a calculated parameter. The dataset should not require any user input.

single_lane_change_browser_data_sets_mv

Project Browser View - Datasets - Single Lane Change Analysis

single_lane_change_data_sets_panel_dialog_mv

Datasets Property Data Dialog - Single Lane Change Analysis

The Form is the only place that you should change the lane change event. Vehicle velocity and the lane change geometry are the parameters that can be changed. All lane change data and vehicle path graphics are defined parametrically using these four inputs (shown with a white background). The Ground z Coordinate is a calculated value (designated by a blue background) and is calculated using the left front wheel CG Z location and the tire rolling radius from the Tire Data Form.

single_lane_change_browser_forms_mv

Project Browser View - Forms - Single Lane Change Analysis

single_lane_change_forms_panel_dialog_mv

Single Lane Change Data Analysis - Form Dialog

The road graphics are included to illustrate the path being driven and are defined parametrically using the data in the single lane change Form. All road graphics are used to illustrate the lane dimensions, but they are not of the actual road used for calculating tire forces. Road graphics should never require editing unless the event is being fundamentally changed.

The road used to calculate the tire forces is at the same height as the road graphics and is defined by the road file (.rdf) in the tire system. The default flat road file in the vehicle library is an infinitely large flat road with a coefficient of friction of 1.0. The road file is an ASCII file that can be edited.

single_lane_change_browser_graphics_mv

Project Browser View - Graphics - Single Lane Change Analysis

single_lane_change_cone_graphics_example_mv

Cone Graphics

single_lane_change_road_graphics_example2_mv

Road Graphics

A ball joint is included in the Single lane change event. The joint attaches a dummy body to the steering rack. The joint is included to make certain events work in ADAMS. Attach the dummy body to the steering rack if building a model manually.

single_lane_change_browser_joints_mv

Project Browser View - Joints - Single Lane Change Analysis

events_joints_ball_joint_panel_example_mv

Joints Panel - Single Lane Change Analysis

Nine markers are included in the Single lane change event. The markers are used to define the lane graphics (cones and the lane road surface).

The path outline markers point to the Path Outline points for their XYZ location. The points are parametrically defined using the event input data. Path Origin is the origin of all lane change graphics and is parametrically defined to be the CG of the vehicle body.

None of the markers should require any user input.

single_lane_change_browser_markers_mv

Project Browser View - Markers - Single Lane Change Analysis

Three motions are included in the event. The motion names and a description are shown in the table below.

Name

Variable Name

Description

Steering Wheel Motion

mot_st_wheel

Applies a rotation motion at the steering wheel joint.

The motion is initially set to the linear type of value 0 but is modified through the event template to an expression.

Front Wheel Motion

mot_frnt_wheel

Applied at the front wheel spindle and is of type linear and value 0.

Rear Wheel Motion

mot_rear_wheel

Applied at the rear wheel spindle and is of type linear and value 0.

The steering motion is used by the steering controller to steer the vehicle and acts on a revolute joint that connects the steering column to the vehicle body. If a steering column is not included, the joint acts between the steering rack input shaft and the vehicle body.

The Front and Rear Wheel Motions act on the wheel spindle revolute joints that connect the wheel hub to the knuckle. The motion is initially zero (fixing the wheels to the knuckle) so the model converges statically. The motions are deactivated after static convergence to allow the tires to rotate.

single_lane_change_browser_motions_mv

Project Browser View - Motions - Single Lane Change Analysis

Seventeen points are defined in the event. All points are used to create the lane graphics and cones graphics used to illustrate the lanes. The points contain parametric logic to define their X, Y, and Z locations. You should not need to modify any points.

single_lane_change_browser_points_mv

Project Browser View - Points - Single Lane Change Analysis

Name	Variable Name	Description
Path Origin	p_pathor	Point that locates the origin of the path from where the vehicle starts. This is parametrically set to the vehicle body CG location.
Path Outline1	p_path1	Point used for path graphics; defined parametrically using a variety of data from the model.
Path Outline2-N	p_path2-N	Additional points used for path graphics; defined parametrically in a similar scheme to Path Outline 1.
Cone1	p_cone1	Point used to define the cone graphics; defined parametrically to sit at the edge of the road surface along the path to illustrate the road.
Cone2-N	P_cone2-N	Additional points used to define the cone graphics; defined parametrically to sit at the edge of the road surface along the path to illustrate the road.

There is one solver variable in the Single lane change event. The Steer Path Variable is a user-written subroutine call which returns the steering wheel angle that should be applied to follow the desired path. The motion of the steering wheel is set to this variable in the lane change template. You should not need to edit any portion of the Steer Path Variable.

single_lane_change_browser_solver_variables_mv

Project Browser View - Solver Variables - Single Lane Change Analysis

single_lane_change_solver_variables_panel_mv

Solver Variable Panel - Steer Path Variable

The numbers in the solver variable USER subroutine call are as follows:

Number	Description
5010	The Branching ID. 5010 is a Single lane change event.
70000000	The ID of a solver array containing Driver Model Controller data. The array is in the Steer controller system.
70000100	The ID of a Vehicle Data Array containing vehicle information. The array is in the Steer controller system.
30.5	The lane change transition section length in meters.
3.66	The lane change width in meters.

Additional information on the steering controller is contained in the steering controller documentation section.

A template is included in the Single lane change event task. The template is solver specific and only the MotionSolve template is documented. The template is inserted in the solver deck after the </Model> command and controls the execution of the event. The first four commands define different output datasets. More information about these commands can be found in the MotionSolve XML Reference Guide.

The if (tire_dataset.opt_omega.ival) logic is included to handle legacy models which used the omega method of tire rotation. This method is obsolete and the value will always be equal to 1. The logic will be removed in a future release.

The first four deactivate commands deactivate the motion between the wheels and the knuckle, allowing them to rotate. The last two deactivate commands turn off the body clamps. Body clamps hold the body rigid during static analysis.

The Motion_Joint command reassigns the value of the steering wheel joint from zero to the value calculated by the steering controller, essentially turning on the steering controller.

The Simulate transient command starts the transient simulation and establishes the output time step and end time of the simulation. The data can be edited to change the event. Additional XML commands can be added to enhance the solution. The commands are described in the MotionSolve Reference Guide > Command Statements.

single_lane_change_browser_templates_mv

Project Browser View - Templates - Single Lane Change Analysis

The template for this event is shown below:

<ResOutput

angle_type = "YPR"

<ResOutput

mrf_file = "TRUE"

<ResOutput

plt_file = "TRUE"

<H3DOutput

switch_on = "TRUE"

increment = "1"

<ResOutput

abf_file = "TRUE"

{if (tire_dataset.opt_omega.ival ==1)}

<Simulate

analysis_type = "Static"

end_time = "0.0"

{endif}

<Deactivate

element_type = "MOTION"

element_id = "{mot_frnt_wheel.l.idstring}"

<Deactivate

element_type = "MOTION"

element_id = "{mot_frnt_wheel.r.idstring}"

<Deactivate

element_type = "MOTION"

element_id = "{mot_rear_wheel.l.idstring}"

<Deactivate

element_type = "MOTION"

element_id = "{mot_rear_wheel.r.idstring}"

{if (tire_dataset.opt_omega.ival ==2)}

<Simulate

analysis_type = "Static"

end_time = "0.0"

{endif}

<Deactivate

element_type = "JPRIM"

element_id = "{j_clamp_1_body.idstring}"

<Deactivate

element_type = "JPRIM"

element_id = "{j_clamp_2_body.idstring}"

<Motion_Joint

id = "{wh_motion.idstring}"

expr = "VARVAL({sv_path.idstring})"

<Simulate

analysis_type = "Transient"

end_time = "6"

print_interval = "0.05"

<Stop/>

References:

ISO 3888-2-2011 Passenger cars — Test track for a severe lane-change maneuver.

NATO Allied Vehicle Testing Publication AVTP: 03-160 Sep. 1991.