Mapped Steering

Mapped steering with speed-dependent option

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Libraries:
Vehicle Dynamics Blockset / Steering

Description

The Mapped Steering block implements lookup tables to calculate the right and left wheel angles. Use the Speed dependent parameter to implement a speed-dependent table for the steering angle calculations. The block uses the vehicle coordinate system.

Steering Wheel Angle

If you set Steering type to Steering wheel angle, the block implements these tables.

Speed Dependent	Implementation	Calculations
on (default)	Block uses three tables: fs — Function of vehicle speed fL — Function of superimposed steering wheel angle fR — Function of superimposed steering wheel angle	$$\begin{array}{l}{\delta }_{SpdF}=f_s(v)\\ {\delta }_{SuprImp}={\delta }_{SpdF}\cdot {\delta }_{in}\\ \\ {\delta }_L=f_L({\delta }_{SuprImp})\\ {\delta }_R=f_R({\delta }_{SuprImp})\end{array}$$
off	Block uses two tables: fL — Function of steering wheel angle fR — Function of steering wheel angle	$$\begin{array}{l}{\delta }_L=f_L({\delta }_{in})\\ {\delta }_R=f_R({\delta }_{in})\end{array}$$

Rack Travel Displacement

If you set Steering type to Rack travel displacement, the block implements these tables.

Speed Dependent	Implementation	Calculations
on (default)	Block uses three tables: fs — Function of vehicle speed fL — Function of rack travel displacement fR — Function of rack travel displacement	$$\begin{array}{l}{\delta }_{SpdF}=f_s(v)\\ {\delta }_{SuprImp}={\delta }_{SpdF}\cdot {\delta }_{in}\\ {\Delta }_{Rack}={\delta }_{SuprImp}\cdot Gr\\ {\delta }_L=f_L({\Delta }_{Rack})\\ {\delta }_R=f_R({\Delta }_{Rack})\end{array}$$
off	Block uses two tables: fL — Function of rack travel displacement fR — Function of rack travel displacement	$$\begin{array}{l}{\Delta }_{Rack}={\delta }_{in}\cdot Gr\\ {\delta }_L=f_L({\Delta }_{Rack})\\ {\delta }_R=f_R({\Delta }_{Rack})\end{array}$$

The block uses a gear ratio to adjust the rack travel displacement. To use a

• Constant gear ratio, set Gear ratio parameterized by to Constant.

• Gear ratio as a function of steering angle, set Gear ratio parameterized by to Lookup table.

The equations use these variables.

δin	Steering wheel angle
δSpdF	Steering wheel angle speed factor
δSuprImp	Superimposed steering wheel angle
δL, δR	Left and right wheel angles, respectively
ΔRack	Rack travel displacement
Gr	Gear ratio

Examples

Double Lane Change Reference Application

Simulate a full vehicle dynamics model undergoing a double lane change maneuver standard ISO 3888-2. Use for vehicle dynamics ride and handling analysis and chassis controls development, including yaw stability and lateral acceleration limits.

• Open Script

Ports

Input

AngIn — Steering angle

scalar

Steering angle, δ_in, in rad.

Use the Steering angle breakpoints, StrgAngBpts parameter to specify a steering angle range. By default, the value is set to 1.25*pi, which limits the steering angle to a range of -1.25*pi to 1.25*pi.

VehSpd — Vehicle speed

scalar

Vehicle speed, Veh_spd, in m/s.

Dependencies

To create this port, select Speed dependent.

Output

Info — Bus signal

bus

Bus signal containing these block calculations.

Signal	Description	Variable	Unit
AngLft	Left wheel angle	δL	rad
AngRght	Left wheel angle	δR	rad

AngLft — Left wheel angle

scalar

Left wheel angle, δ_L, in rad.

AngRght — Right wheel angle

scalar

Right wheel angle, δ_R, in rad.

Parameters

Options

Speed dependent — Use speed-dependent tables

on (default) | off

Select to use speed-dependent tables.

Dependencies

Selecting this parameter creates input port VehSpd.

Steering type — Use speed-dependent tables

Steering wheel angle (default) | Rack travel displacement

If you set Steering type to Steering wheel angle, the block implements these tables.

Speed Dependent	Implementation
on (default)	Block uses three tables: fs — Function of vehicle speed fL — Function of superimposed steering wheel angle fR — Function of superimposed steering wheel angle
off	Block uses two tables: fL — Function of steering wheel angle fR — Function of steering wheel angle

If you set Steering type to Rack travel displacement, the block implements these tables.

Speed Dependent	Implementation
on (default)	Block uses three tables: fs — Function of vehicle speed fL — Function of rack travel displacement fR — Function of rack travel displacement
off	Block uses two tables: fL — Function of rack travel displacement fR — Function of rack travel displacement

Steering angle breakpoints, StrgAngBpts — Steering angle breakpoints

[-1.5*pi 1.5*pi] (default) | vector

Steering angle breakpoints, in rad.

Dependencies

If you set Steering type to Rack travel displacement, to enable this parameter, set Gear ratio parameterized by to Lookup table.

Rack travel displacement breakpoints, RackDispBpts — Rack travel displacement breakpoints

[-40 -19.2 -4.53 4.53 19.2 40] (default) | vector

Rack travel displacement breakpoints, in mm.

Dependencies

To enable this parameter, set Steering type to Rack travel displacement and Gear ratio parameterized by to Lookup table.

Gear ratio table, GrTbl — Gear ratio table

[9.87 9.87 7.16 7.16 9.87 9.87]*2*pi (default) | vector

Gear ratio table as a function of rack travel displacement, in mm/rev.

Dependencies

To enable this parameter, set Steering type to Rack travel displacement and Gear ratio parameterized by to Lookup table.

Gear ratio constant, Gr — Gear ratio constant

8.28*2*pi (default) | scalar

Gear ratio constant, in mm/rev.

Dependencies

To enable this parameter, set Steering type to Rack travel displacement and Gear ratio parameterized by to Constant.

Left wheel angle table, WhlLftTbl — Left wheel angle table

[-1.5*pi 1.5*pi]/13.5] (default) | vector

Left wheel angle table, δ_L, in rad.

Right wheel angle table, WhlRghtTbl — Right wheel angle table

[-1.5*pi 1.5*pi]/13.5] (default) | vector

Right wheel angle table, δ_R, in rad.

Vehicle speed breakpoints, VehSpdBpts — Vehicle speed breakpoints

[-1 1] (default) | vector

Vehicle speed breakpoints, in m/s.

Dependencies

To create this parameter, select Speed dependent.

Superimposed speed factor table, SpdFctTbl — Speed factor

[1 1] (default) | vector

Superimposed speed factor table, ƒ_s, dimensionless. The table is a factor of vehicle speed, v.

Dependencies

To create this parameter, select Speed dependent.

References

[1] Crolla, David, David Foster, et al. Encyclopedia of Automotive Engineering. Volume 4, Part 5 (Chassis Systems) and Part 6 (Electrical and Electronic Systems). Chichester, West Sussex, United Kingdom: John Wiley & Sons Ltd, 2015.

[2] Gillespie, Thomas. Fundamentals of Vehicle Dynamics. Warrendale, PA: Society of Automotive Engineers, 1992.

[3] Vehicle Dynamics Standards Committee. Vehicle Dynamics Terminology. SAE J670. Warrendale, PA: Society of Automotive Engineers, 2008.

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using Simulink® Coder™.

Version History

Introduced in R2018a