Two-Axle Tractor Towing a Two-Axle Trailer

This example shows how to simulate a two-axle tractor towing a two-axle trailer for a commercial trucking application. The model implements a hitch subsystem, sinusoidal wave steering input, and an axle torque applied to the rear wheels of the tractor.

To implement the tractor and trailer, by default, the three degrees-of-freedom (DOF) model uses the Vehicle Body 3DOF and Trailer Body 3DOF blocks. You can use the Toggle Between 3DOF and 6DOF button to configure a six DOF model that uses the Vehicle Body 6 DOF block, Trailer Body 6DOF block, and a hitch subsystem. See Six Degrees-of-Freedom Model.

Model

Run Simulation

On the Simulation tab, click Run. As the simulation runs, the Vehicle Position window provides the trace of the tractor and trailer.

Two-Axle Vehicle Subsystem

To steer and drive the tractor, the two-axle tractor subsystem uses a sinusoidal wave steering input and an axle torque applied to the rear wheels of the tractor. The subsystem includes models for the tires, wheels, suspension, and vehicle body.

Two-Axle Trailer Subsystem

The two-axle trailer subsystem includes models for the wheels, suspension, and the trailer body.

Hitch Subsystem

When you select the three DOF model variant, the hitch model allows relative longitudinal, lateral, and yaw motion between the tractor and trailer. To limit the longitudinal and lateral motion, the hitch model implements a stiff translational spring-damper in the xy plane of the vehicle-fixed reference frame. The resulting spring-damper forces approximately limits the relative motion between the tractor and trailer to yaw rotation about a vertical axis at the hitch connection point. The hitch model transfers the vertical hitch force from the trailer to the tractor.

When you select the six DOF model variant, the hitch model allows relative longitudinal, lateral, vertical, and yaw motion between the tractor and trailer. The hitch model implements another translational spring-damper along the z -axis of the vehicle-fixed reference frame. The effects of hitch moments due to the relative rotations of the hitches are considered negligible.

• Spring forces are linear functions of the planar distance from the tractor hitch location to the first trailer front hitch location in the inertial reference frame.

• Damper forces are linear functions of the planar velocity from the tractor hitch location to the first trailer front hitch location in the inertial reference frame.

Six Degrees-of-Freedom Model

To implement a six DOF tractor, trailer, and hitch model, click Toggle Between 3DOF and 6DOF. Then, on the Simulation tab, click Run.