This example shows how to use a hitch to tow a two-axle trailer with a two-axle tractor. To steer and drive the tractor, the model uses a sinusoidal wave steering input and an axle torque applied to the rear wheels.
To implement the tractor and trailer, by default, the three degree-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 6DOF hitch subsystem. See Six Degree-of-Freedom Model.
On the Simulation tab, click Run. As the simulation runs, the Vehicle Position window provides the trace of the tractor and trailer.
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. The subsystem includes models for the wheels, suspension, and vehicle body.
The two-axle trailer subsystem includes models for the wheels, suspension, and the trailer body.
The three DOF 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 spring. The spring force is a function of the planar distance from the tractor hitch location to the trailer hitch location in the inertial reference frame. The resulting spring force 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.
The six DOF hitch model accounts for relative translation between the tractor and trailer hitches. To transmit the forces between the tractor and trailer hitches, the hitch model implements stiff translational springs in three dimensions. The effects of hitch moments due to the relative rotations of the hitches are considered negligible.
To implement a six DOF tractor, trailer and hitch model, click Toggle Between 3DOF and 6DOF. Then, on the Simulation tab, click Run.