GB2259823A

GB2259823A - Navigation system

Info

Publication number: GB2259823A
Application number: GB9119860A
Authority: GB
Inventors: Keith Lawrence Wright; Harvey Alan Thompson
Original assignee: Radamec EPO Ltd
Current assignee: Radamec Broadcast Systems Ltd
Priority date: 1991-09-17
Filing date: 1991-09-17
Publication date: 1993-03-24
Also published as: GB9119860D0

Abstract

A navigation system carried on board a remotely controlled robotic vehicle comprises a TV camera 3 whose output is processed by computer 5 to provide the position of the vehicle with respect to coded reflectors 2. The reflectors are illuminated by lights 1 whose output intensities are controlled by computer 5. The system provides the vehicle's control system with information relating to its physical location with respect to a fixed origin and also measures the angle of orientation of the vehicle. Reflector, operational boundary and obstacle position data relating to a number of possible operating environments may be stored in a memory. <IMAGE>

Description

NAVIGATION SYSTEM This invention relates to a navigation system able to determine the position and orientation of a remotely controlled vehicle.

Remotely controlled robotic vehicles require a means to navigate their movements on a surface. To do this effectively, a navigation system is required, to allow the vehicle's control system to determine its X and Y co-ordinates and in some cases the orientation of the vehicle. In applications, where the vehicle is carrying other directionally sensitive equipment, the orientation angle produced by the navigation system is used to determine a reference for the on board equipment.

According to the present invention there is provided an optical scanning sensor in the form of a television camera, variable ntensity illuminators to illuminate fixed reference targets positioned around the perimeter of the vehicle's area of movement and a computer system to process image information from the camera sensor.

A specific embodiment of the invention is no described by war of example with reference to the accompanying of drawings in which Figure 1 shows a general arrangement of the navigation system.

Figure 2 shows the geometric relationship between targets and sensor.

Figure 3 shows an application of the system for rsbctlca,'y controlled cameras in television studios.

Referring to Figure 1 which shows a general arranqement of true system the principle of operation is as follows.

An illumination system 1 is used to illuminate an array of fixed reference targets 2 which are designed in such a way as to be individually recognisable by the navigation system using a pattern of reflective elements arranged to form a code. The positions of each of the targets with respect to an origin is known precisely and stored within the computer system. The illumination is arranged to ensure that all targets within the field of view of sensor ç are adeuately illuminated. It is also arranged so that as the vehicle approaches the targets, the power to the illuminators is reduced so that the brihtness of the targets appear constant to the sensor. This is used to conserve power and to obtain consistent results from the sensor.

The computer system is pre-programmed with the X and Y positions together with the code identity of each of the targets. The positions of obstacles, boundaries, no-go areas and other reference points are also stored. A set of stored targets and other positions is referred to as a map. Different arrangements of targets and reference points used for different applications are stored on other maps within the computer. The map for the particular application is referred to by the computer when the navigation calculations are performed.

The sensor is fitted with a lens whose focal length and optical characteristics are known and stored within the computer system so that the position of the images of the targets formed on the sensor image plane can be used to precisely determine the angles subtended from the targets to the sensor, see Figure 2.

The angles subtended by the targets (represented by A and B in Fire 2 at the sensor and with respect to the sensor are measured by the sensor and by the use of trigonometrical relationships, in conjunction with the target positions as identified by the sensor system, the X and Y coordinates and orientation angle can be calculated.

To illustrate the navigation system's use more fu'..y a specifIc application is described where it is used to navir control led television camera about a studic floor.

Figure 3 shows an arrangement of a robotic controlled pedesta used to position a broadcast television camera remotely in a television studio.

The targets 2 are positioned around the perimeter cf the studie -loor and specifically in positions easily viewable by the navigation sensor 4 mounted on the pedestal 6. in this example a linear array cr in soan camera is used as the sensor. It is common practice to arrange the steering mechanism of the pedestal base se that it crabs whist it moves around the floor. The crabbing movement ensures that the pedestal always points in the same direction whilst moving. The pedestal usually carries a remotely controlled pan and tilt head cnto which the broadcast camera is mounted so that it can be pointed onto the subject being televised.Because this head is also under remote control, it requires a reference position so that camera shots can be repeated accurately.

This reference is with respect to the pedestal base, and will be fixed provided the pedestal does not rotate as provided by the crabbing motion.

Due to floor imperfections and other causes, slight rotation is usually experienced. The navigation system can detect this rotation and compensation is applied to the pan and tilt head so that the true reference is restored.

The inclusion of obstacle positional data within the compute' system s used for example to prevent the robotic pedesta: from running it tre obstacles.

The inclusion of boundary and "no-go" positions is used for example to prevent the robotic pedestal from leaving a specified area of operation, or from entering a restricted area.

The inclusion of specific reference positions are used for example to :1. Control the pan position cf the on-board pan and tilt head so that the subject, used as a reference, is kept in view whilst the pedestal moves about the floor.

2. Control the tilt position of the on-beard pan and t@lt head so that the subject, used as a reference, is kept in view whilst the television camera is raised or lowered by an on-board height contro system.

3. Control the focus setting cf the televIsIon camera automatically as the pedestal distance from the subject changes.

4. Control the movement of the pedestal from one location to the locations. All locations used as multiple reference references can be selected in any desired order.

Obstacle positional data, boundary data and reference positions as described above are either permanently stored within the computer system, manually entered from time to time by an operator or generated and entered from an external control system.

Claims

1. A remotely controlled vehicle navigation system comprising an optical scanning sensor in the form of a television camera, a means of variable intensity illumination to illuminate fixed reference targets positioned around the vehicles area of movement and a computer system to process image information from the camera.

2. A navigation system as claimed in Claim 1 wherein a television camera in the form of a multi element sensor line scan camera is used to view fixed reference targets.

3. A navigation system as claimed in ClaIm 1 or Claim ; wherein an illumination system is used whose brightness is controlled by a computer system.

4. A navigation system as claimed in any preceding claim wherein X and Y co-ordinates giving position on a surface are produced.

5. A navigation system as claimed in any preceding claim wherein orientation angle of the sensor with respect to a reference is produced.

6. A navigation system as claimed in Claim 1 or Cl air.' 2 or Claim 3 wherein the target positions necessary to perform the navigation calculations are stored in a memory system and that several sets of target positions are stored in separate arrangements re that the navigation system can navigate in several envIronments.

7. A navigation system as claimed in any preceding clam wherein obstacle positional data is stored in a memory system and that several sets of obstacle positional data is stored so that the navigation system can navigate in several environ.m,ents.

8. A navigation system as claimed in any preceding claim wherein boundary positional data is stored in a memory system and that several sets of boundary positional data is stored so that the navigation system can navigate in several environments

9. A navigation system as claimed in any preceding claim wherein reference positional data is stored in a memory system and that several sets of reference positional data is stored.

10. A navigation system as claimed in any preceding claIm wherein the data concerning obstacles boundaries and reference points is permanently stored in a memory system, manually entered by an operator or entered from an external control system.

11. A navigation system as described wherein with reference to F-gures 1, 2 and 3 accompanying this description.