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Minimum Envelope Setup

Set the parameters for the minimum turning envelope simulation.

This function allows you to set the parameters for the minimum turning envelope simulation.

The coordination interval and Simulation type can be set in the same way as in the main setup.  When creating a Reverse envelope, the program automatically calculates the optimum coordination interval for the curve. 

The turning direction can be set to either left or right. The Turn through option can be set to any angle between 0 and 180 degrees.

Absolute Minimum Envelope

The program simulates a turn at low speeds with the steering wheels at the maximum angle, as specified in the vehicle file.  It is assumed that the distance in which the steering wheels are turned is negligibly small because of the low speed at which the vehicle is travelling.

In a manoeuvre like this, it is possible (especially with long trailers) that the maximum specified angle between tractor and trailer might be reached.  When this happens, the program automatically calculates a new steering angle in order to avoid reaching these maximum angles.

The turning angle graph looks as below.

TRH 17 Template

This method creates a minimum turning envelope in such a way that the outer front wheel travels exactly on a circular curve. This means that the vehicle reaches its maximum steering angle close to the crest of such a circle.

The turning angle graph looks as follows.

Around a Kerb

When running this method, the program uses a specified kerb radius and lane width to calculate the minimum turning envelope for a vehicle that has to turn around the specified kerb.

The following formulas is used:

RIR = RK + (W - w) / 2 + 0.6

ROF = [ (RIR + W)² + L1² + L2² ]^0.5

Where:

• L1 = Wheelbase of the tractor.

• L2 = Wheelbase of the semitrailer.

• w = Track width.

• W = Trough lane width.

• RK = Kerb Radius.

• RIR = Inner rear track radius.

• ROF = Outer front track radius.

Because the TRH formulas are used to calculate ROF, it is possible that ROF > RK + W for small kerb radii. The vehicle might, therefore, move outside the specified lane width for small kerb radii.

Procedure

1. The Minimum Turning Envelope setup displays.

2. Click OK and you are prompted to indicate the start point of the envelope, as well as the initial direction of movement, before turning through the specified angle and direction. The envelope is added to the drawing.