Constant Radius Maneuver

This reference application represents a full vehicle dynamics model undergoing a constant radius test maneuver. For information about similar maneuvers, see standards SAE J266_199601[1] and ISO 4138:2012[2]. You can create your own versions, establishing a framework to test that your vehicle meets the design requirements under normal and extreme driving conditions. Use this reference application in ride and handling studies and chassis controls development to characterize the steering and lateral vehicle dynamics.

You can configure the reference application for open-loop and closed-loop tests:

  • Open-loop — Maintain the target velocity and steering wheel angle to determine the lateral acceleration, side-slip characteristics, and steering angles for specific accelerations and subsequent test maneuvers. For the open-loop test, set the Reference Generator block Maneuver parameter to Increasing Steer.

  • Closed-loop — Use the predictive driver to maintain a prespecified turn radius at different velocities for drivability and handling performance studies. For the closed-loop test, set the Reference Generator block Maneuver parameter to Constant radius.

To create and open a working copy of the constant radius reference application, enter

This table summarizes the blocks and subsystems in the reference application. Some subsystems contain variants.

Reference Application ElementDescriptionVariants

Reference Generator block

Sets the parameters that configure the maneuver and 3D visualization environment. By default, the block is set for the constant radius maneuver with the 3D simulation engine environment disabled.

For the minimum 3D visualization environment hardware requirements, see 3D Visualization Engine Requirements.

To enable 3D visualization, on the 3D Engine tab, select Enabled.

Driver Commands block

Implements the driver model that the reference application uses to generate acceleration, braking, gear, and steering commands.

By default, Driver Commands block variant is the Predictive Driver block.

Environment

Implements wind and road forces.

Controllers

Implements controllers for engine control units (ECUs), transmissions, and brakes

Passenger Vehicle

Implements the:

  • Body, suspension, and wheels

  • Engine

  • Steering, transmission, driveline, and brakes

Visualization

Provides the vehicle trajectory and driver response

Reference Generator

The Reference Generator block sets the parameters that configure the maneuver and 3D simulation environment. By default, the block is set for the constant radius maneuver with the 3D simulation engine environment disabled.

Use the Maneuver parameter to specify the type of maneuver. You can specify the double lane change, swept sine, sine with dwell, and slowly increasing maneuvers.

If you select the Use maneuver-specific driver, initial position, and scene parameter, the reference application sets the driver, initial position, and scene for the maneuver that you specified.

For more information, see Reference Generator.

Driver Commands

The Driver Commands block implements the driver model that the reference application uses to generate acceleration, braking, gear, and steering commands. By default, if you select the Reference Generator block parameter Use maneuver-specific driver, initial position, and scene, the reference application selects the driver for the maneuver that you specified.

Vehicle Command Mode Setting

Implementation

Longitudinal Driver

Longitudinal Driver block — Longitudinal speed-tracking controller. Based on reference and feedback velocities, the block generates normalized acceleration and braking commands that can vary from 0 through 1. Use the block to model the dynamic response of a driver or to generate the commands necessary to track a longitudinal drive cycle.

Predictive Driver

Predictive Driver block — Controller that generates normalized steering, acceleration, and braking commands to track longitudinal velocity and a lateral reference displacement. The normalized commands can vary between -1 to 1. The controller uses a single-track (bicycle) model for optimal single-point preview control.

Open Loop

Implements an open-loop system so that you can configure the reference application for constant or signal-based steering, acceleration, braking, and gear command input.

Environment

The Environment subsystem generates the wind and ground forces. The reference application has these environment variants.

EnvironmentVariantDescription

Ground Feedback

3D Engine

Uses Vehicle Terrain Sensor block to implement ray tracing in 3D environment

Constant (default)

Implements a constant friction value

Controllers

The Controllers subsystem generates engine torque, transmission gear, and brake commands. The reference application has these brake variants.

ControllerVariantDescription

Brake Pressure Control

Bang Bang ABS

Anti-lock braking system (ABS) feedback controller that switches between two states

Open Loop (default)

Open loop braking controller

Passenger Vehicle

The Passenger Vehicle subsystem has an engine, controllers, and a vehicle body with four wheels. Specifically, the vehicle contains these subsystems.

Body, Suspension, Wheels SubsystemVariantDescription

PassVeh7DOF

PassVeh7DOF (default)

Vehicle with four wheels:

  • Vehicle body has three degrees-of-freedom (DOFs) — Longitudinal, lateral, and yaw

  • Each wheel has one DOF — Rolling

PassVeh14DOF

PassVeh14DOF

Vehicle with four wheels.

  • Vehicle body has six DOFs — Longitudinal, lateral, vertical and pitch, yaw, and roll

  • Each wheel has two DOFs — Vertical and rolling

Engine SubsystemVariantDescription

Mapped Engine

SiMappedEngine (default)

Mapped spark-ignition (SI) engine

Steering, Transmission, Driveline, and Brakes Subsystem

VariantDescription

Driveline Ideal Fixed Gear

Driveline model

All Wheel Drive

Configure the driveline for all-wheel, front-wheel, or rear-wheel drive

Specify the type of torque coupling

Front Wheel Drive

Rear Wheel Drive (default)

Transmission

Ideal (default)

Ideal fixed gear transmission

Visualization

When you run the simulation, the Visualization subsystem provides driver, vehicle, and response information. The reference application logs vehicle signals during the maneuver, including steering, vehicle and engine speed, and lateral acceleration. You can use the Simulation Data Inspector to import the logged signals and examine the data.

ElementDescription

Driver Commands

Driver commands:

  • Handwheel angle

  • Acceleration command

  • Brake command

Vehicle Response

Vehicle response:

  • Engine speed

  • Vehicle speed

  • Acceleration command

Steer, Velocity, Lat Accel Scope block

  • SteerAngle — Steering angle versus time

  • <xdot> — Longitudinal vehicle velocity versus time

  • <ay> — Lateral acceleration versus time

Vehicle XY Plotter

Vehicle longitudinal versus lateral distance

ISO 15037-1:2006 block

Display ISO standard measurement signals in the Simulation Data Inspector, including steering wheel angle and torque, longitudinal and lateral velocity, and sideslip angle

References

[1] J266_199601. Steady-State Directional Control Test Procedures for Passenger Cars and Light Trucks. Warrendale, PA: SAE International, 1996.

[2] ISO 4138:2012. Passenger cars — Steady-state circular driving behaviour — Open-loop test methods. Geneva: ISO, 2012.

See Also

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