Navigational method for FTF

If a vehicle is to be operated automatically, thus without human driver, navigation is one of the substantial tasks, which must be solved by vehicle computers + software + suitable sensor technology. With navigation - applies original with ships, however likewise to land vehicles - there are the following setting of tasks:

• Positioning ("„where am "“)
• Course regulation:

1. dependent on the current position and the goal, which are to be achieved: Determination of the target driving direction and ideal velocity
2. Statement of the actual values: current driving direction and - speed

The procedure ''' of dead reckoning originating from the navigation ''' is based on the principle to compute by fairs outgoing from driving direction and speed and/or put back distance from a well-known starting point the current position. Dead reckoning is not used a relative procedure for the positioning, it except the starting point absolute (fix) points of reference.

• Advantage of dead reckoning is that it can be accomplished with relatively simple measuring instruments and algorithms.
• Disadvantage is the fact that the accuracy and/or the error of these measuring instruments enters accuracy of the result directly and therefore with increasing distance of the starting point the quality of the determined position worse and worse becomes.

This principle-conditioned disadvantage can be minimized by calibration of the measuring instruments and careful working, but turned off not completely. Additional errors do not result from the influence of unknown quantity, unnoticed and/or measurable variable disturbances.

One calls dead reckoning with land vehicles also Odometrie (English Odometer = equipment for displacement measurement). The determination of the driving direction takes place via measurement () guidance angle (s) of the vehicle. The put back distance can be determined by counting the revolutions of a Rades, whose diameter/circumference admits is.

Admitted problems/possible sources of error of the Odometrie:

• Exactness of the vehicle adjustment at the initial position
• Attitude of the straight line adjustment of the Rades/the wheels (guidance angle measured value 0"° does not lead accurately to travelling straight ahead)
• Guidance angle zero point "„moves "“(changes by mechanical influences)
• Wheel diameter changes, e.g. by wear or different loads
• Wheel slippage: blocking wheel with emergency stop, revving up wheel on wet roads, chutes in too fast driven curve

Result: Odometrie alone is sufficient as navigational methods for transport vehicles without driver under no circumstances!

The problems which is connected with the determination of the driving direction are not longer relevant, if the vehicle with suitable sensor technology pursues a continuous guideline. On the employment site conditions become dependent

• optical,
• magnetic or
• inductive

Guidelines uses and with cameras (color contrast), resounding sensors (magnetic field) or antennas (electrical alternating field) detects.

The second problem of the Odometrie, the accumulating error in the displacement measurement, can be solved by points of reference along the drive: The over driving of soil marks (piece of metal, magnet, transponder), whose distances in the vehicle price increase is deposited, releases a signal in the vehicle price increase and to here developed errors of the displacement measurement one zeroes. Perhaps one at the goal necessary fine positioning of the vehicle takes place likewise relative to an external trigger signal (soil mark, light barrier, etc.).

Predivide this technology:

• for many years in the employment ("„old, but works satisfactorily "“)
• no technology, therefore inexpensive and durably

Disadvantages:

• high expenditure when providing, changing and if necessary repairing the guideline
• dependent on ground condition, not everywhere applicable
• small to no flexibility with driving course changes

In order to reduce the costs connected with the production of the guidance trace, one can make an intermittent guideline, i.e. a consequence of bases from the continuous guideline. This procedure is called raster navigation. Raster points are formed usually through into the soil let in magnets or transponder. Optical rasters (e.g. Through "„chessboard samples "“) are likewise possible for color contrast. The FTF is equipped with suitable sensor technology for recognizing the raster points (magnet sensor, camera) and "„slope ELT itself "“from a raster point to the next.

If - from cost reasons - which should be large distance of the raster points, the Odometrie must and in particular the straight line discharge of the vehicle to be very well calibrated. For the support/improvement frequently a turning rate sensor (gyroscope) is used for the measurement of the change of the turning situation of the vehicle.

When over driving a raster point the current Lagefehler must be located, computed a correction movement and be supervised their correct execution while driving to the next raster point. In addition exact guidance angular measurement and - regulation as well as the software related processing of mathematical algorithms are necessary, i.e. is necessary a control compared with vehicles with continuous guideline.

Predivide this technology:

• since many years well-known and proven procedure
• Guidance trace production more inexpensive than with continuous guideline
• Production/changes of the guidance trace during operation possible
• Changes of the guidance trace at visible expenditure possible

Disadvantages:

• dependent on ground condition, not everywhere applicable
• reduced flexibility concerning driving course changes

The procedures described so far use a physical guideline in such a way specified for the vehicle guidance, i.e. along the desired drive physical characteristics are installed (colored line, metal strip, wechselstromdurchflossener wire, magnets etc.), which can be detected and pursued by suitable sensor technology at the FTF.

If a physical guideline cannot be used or is gives it alternatively the virtual guideline in such a way specified, which is present in the form of software in the vehicle computer. Then however a not insignificant hard and software expenditure must be driven, in order to shift a vehicle into the situation to reach automatically and with more sufficiently (repeating) accuracy with the help of this virtual guideline the desired goals. As is the case for raster navigation the Odometrie must be supported also here by detection and measurement of absolute points of reference. These points of reference have however no purchase to the drive and to describe in no way a guideline.

The equipment for detecting and measuring absolute points of reference, most frequently assigned with applications of indoors, is a laser scanner, one speaks therefore also of so-called laser navigation (better: Laser triangulation). E.g. a principle is the basis for the evaluation, with which one brings optical pinpointing lines on several, for a long time applied in the navigation, in their position well-known pinpointing objects to the cut ('' Kreuzpeilung ''). A goal and/or result in the navigation is the graphic positioning in the sea chart. In the vehicle computer of the FTF the graphic procedure replaced by algebra, i.e. release of a set of equations with three unknown quantities. The three unknown quantities correspond the three freedom of movement degree of the vehicle in the driving level, i.e. X-value, Y-value and yaw angle to the current vehicle position (S.A. chapter chassis, kinetics).

The measuring system consists of

• the mobile, on the vehicle laser scanners ("„the direction finder "“for angular measurement) installed. The laser scanner consists of laser diode and receivers, which are in a engine-propelled, rotary head, as well as a highly soluble incremental giver for angular measurement.

as well as

• practically of any size a quantity of stationary points of reference ("„the pinpointing objects "“). The points of reference consist of retroflecting material, i.e. the incident laser light is reflected in itself, thus to the transmitter and/or in this case to directly the receiver installed beside it.

Predivide this technology:

• absolutely measuring procedure with sufficient accuracy and measuring rate for FTF applications
• no expenditure for guidance trace production
• high flexibility, driving course changes simply and at small expenditure possible

Disadvantages:

• Costs of laser sensor (precision measuring instrument!) and evaluation computers
• Costs of assembly and measurement of the reflectiv spots
• Soil within the range of the drives must be relatively even
• optical measuring procedure, cannot be everywhere used

Further procedures with absolute correlation:

• Direction finding:

For applications of outdoors (outdoor FTF, stacker, Van Carrier/Straddle carrier and container bridge crane in the port,"…):

• Government inspection department (global Positioning system), accuracy approx. 10 m
• dGPS (differential government inspection department), accuracy approx. 1 m
• dGPS with phase evaluation, accuracy approx. 0.1 m

For applications of indoors:

• "„Indoor government inspection department "“

• Measurement of natural environment characteristics, e.g. by means of camera or laser scanner

Different technical possibilities are available, which permit it to determine the current position and driving direction of a FTF. All procedures described above exist for many years and are successfully in practice used. The procedures with virtual guideline permit relatively more flexibility and reach by it in a larger measure those far mentioned above advantages with the employment of FTF, this however with higher investment demand.

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