Signal processing method

• US 20010033246A1
• Filed: 01/10/2001
• Published: 10/25/2001
• Est. Priority Date: 07/10/1998
• Status: Active Grant

• Current Assignee: Cambridge Solutions Limited (DXC Technology Company)
• Original Assignee: Cambridge Solutions Limited (DXC Technology Company)
• Inventors: Livesey, Thomas F., Burchett, Michael H.
• Granted Patent: US 6,515,615 B2
• Time in Patent Office: Days
• US Class Current: 342/91
• CPC Class Codes: G01S 13/726 Multiple target tracking
• CPC Class Codes: G01S 3/7864 T.V. type tracking systems
• CPC Class Codes: G01S 3/7865 using correlation of the live video image with a stored image
• CPC Class Codes: G01S 7/2927 by deriving and controlling a threshold value
• CPC Class Codes: G01S 7/4873 by deriving and controlling a threshold value
• CPC Class Codes: G01S 7/527 Extracting wanted echo signals Doppler systems G01S15/50

Abstract

A signal processing method is particularly for use in object detection systems which allows a sensed target signal to be “held” once it has raised above a detection-threshold. The method involves reducing the detection-threshold values of the detection-threshold function within the target region. This method is useful for such applications as automotive radar sensors, airbag deployment systems, communication systems demodulation, security sensor systems, sanitary flushing systems and lighting systems.

Claims

1. A method of processing a signal, such as an output signal of an object detection sensor, which signal comprises a plurality of amplitude values each associated with a respective value along a reference axis which is representative of a physical quantity, such as the distance of an object from an object detection sensor, the method comprising the steps of:

providing a detection-threshold function comprising a plurality of detection-threshold values each associated with a respective value along said reference axis;

comparing the signal to the detection-threshold function;

identifying target regions of the reference axis where the signal exceeds the detection-threshold function;

in response to the identification of a target region, reducing the detection-threshold values of the detection-threshold function within said target region.

2. A signal processing method according to

claim 1

used for processing an output signal from an object detection system, in particular an output signal from a radar sensor system capable of sensing at least one spatial and/or temporal property (e.g. distance, speed/velocity, acceleration ctc.) of an object or objects and of producing at least one output signal which is a function of the or each sensed spatial and/or temporal property thus forming a signal which comprises a plurality of amplitude values each associated with a respective value along a reference axis which is representative of a physical quantity, comprising the additional steps of:

calculating a clutter-threshold level below which the object detection system is unable to distinguish between an output signal caused by a sensed spatial and/or temporal property of an object and a signal caused by clutter;

initially setting the detection-threshold values at a level higher than that of the clutter-threshold value;

wherein, the detection-threshold is only altered within boundaries set at a lower end in relation to the clutter-threshold level and at an upper end by a predetermined variable or fixed upper limit.

3. A signal processing method according to

claim 2

in which after said reduction in the value of the detection-threshold, the detection-threshold function is adapted in the target region to ensure that each detected object is substantially continuously detected while it is in a field of view of the object detection system.

4. A signal processing method according to

claim 3

in which the detection-threshold function is adapted in dependence on predicted changes in a or each sensed spatial and/or temporal property/ies of the detected object or objects.

5. A signal processing method according to

claim 2

in which, once a particular object has left a field of view of the object detection system, the level of the section of the detection-threshold function associated with the particular object is reset to a predetermined variable or fixed level as a function of time.

6. A signal processing method according to

claim 2

in which, when a particular section of the detection-threshold is reduced in response to a detection of an object or multiple objects, the shape of the resulting detection-threshold function at the target region is a predetermined shape, which shape is predetermined to take into account the expected shape of output signal(s) of the sensor.

7. A signal processing method according to

claim 3

in which, when the detection-threshold is altered, it is altered to assume one of a plurality of predetermined shapes or to correspond to a predetermined shape function, which plurality of predetermined shapes or which predetermined shape function is predetermined to take into account the expected shape of output signal(s) of the sensor.

8. A signal processing method according to

claim 1

, in which, in response to the identification of a target region, the level of the detection-threshold is reduced by a predetermined amount or proportion.

9. A signal processing method according to

claim 8

in which the predetermined amount or proportion is approximately 50%.

10. A method according to

claim 1

, including the steps of

identifying a first target region and reducing the detection-threshold value of the detection-threshold function within said first target region;

and

identifying a second target region and reducing the detection-threshold value of the detection-threshold function within said second target region,

wherein the reduction of the detection-threshold value in said first target region is carried out independently of the reduction of the detection-threshold value in said second target region.

11. A method according to

claim 1

, including the step of adapting the detection-threshold function in dependence on attributes of the signal.

12. A method according to

claim 1

, including the step of determining a change in an object over time and adapting the detection-threshold function in dependence on the change of the object.

13. A method according to

claim 1

, including adapting the detection-threshold function in dependence on predicted changes in a property of the object.

14. A method according to

claim 1

, wherein the detection-threshold function is adapted in dependence on the current value of the detection-threshold function.

15. A method according to

claim 1

, further including the step of determining the position of an object.

16. A method according to

claim 1

, further including identifying sets of target regions and pattern matching a set of identified target regions against a set of previously identified set of target regions.

20. A radar system for detecting at least one spatial and/or temporal property (e.g. distance, speed/velocity, acceleration etc.) of an object or objects in a field of view of the radar system which employs a signal processing method according to

claim 1

.

21. A radar system according to

claim 20

which comprises a short pulse radar sensor with a pulse width of less than 1 ns.

22. A radar system according to

claim 20

in which at least one of the sensed spatial and/or temporal properties is the physical distance of an object from a sensor of the radar system and further characterised in that the radar system is optimised for detecting the physical distances of an object or objects in a range between a lower limit within the range of 0 to 10 meters and an upper limit less than 100 meters.

23. A radar system according to

claim 20

, which comprises a multiplicity of receiving and transmitting antennae to sense a plurality of distances to a detected object, in order to determine at least one two- and/or three-dimensional spatial and/or temporal property of any objects within the field of view of the radar system.

24. A land-based vehicle, such as an automotive vehicle, mounted with a radar system according to

claim 20

.

25. A land-based vehicle according to

claim 24

, comprising a multiplicity of receiving and transmitting antennae which are one of immovably mounted on the land-based vehicle and incorporated into the structure of the land-based vehicle.

26. An airbag deployment system which comprises a radar system according to

claim 20

, wherein the radar system is used to control a deployment of an airbag.

27. A control system for controlling the actuation of an actuator, which control system comprises a radar system according to

claim 20

, wherein the radar system provides a signal on the basis of which the actuator is actuated.

28. A control system according to

claim 27

which is used to control a function from the group consisting of urinal (and other sanitary apparati) flushing control and the switching on/off of a light and security sensing.

31. Computer software, particularly a computer program on a data carrier, which when run on a data processor, carries out the method of

claim 1

.

32. A computer readable medium having stored thereon a program for carrying out a method according to

claim 1

.

17. A method of processing a signal, which signal comprises a plurality of amplitude values each associated with a respective value along a reference axis which is representative of a physical quantity, the method comprising the steps of:

providing a detection-threshold function comprising a plurality of detection-threshold values each associated with a respective value along said reference axis;

comparing the signal to the detection-threshold function;

identifying a target region of the reference axis where the signal exceeds the detection-threshold function; and

in response to the identification of a target region, reducing the detection-threshold values of the detection-threshold function within said target region.

18. Apparatus for processing a signal, which signal comprises a plurality of amplitude values each associated with a respective value along a reference axis which is representative of a physical quantity, the apparatus comprising:

a signal processor for receiving an output signal from an object detection sensor, comparing the signal to a detection-threshold function comprising a plurality of detection-threshold values each associated with a respective value along said reference axis, identifying target regions of the reference axis where the signal exceeds the detection-threshold function, and reducing the detection-threshold values of the detection-threshold function within an identified target region.

19. Apparatus according to

claim 18

, further including at least one detector.

29. A control system for controlling the actuation of an actuator, the system comprising a signal processor for receiving an output signal from an object detection sensor, which signal comprises a plurality of amplitude values each associated with a respective value along a reference axis which is representative of a physical quantity, comparing the signal to a detection-threshold function comprising a plurality of detection-threshold values each associated with a respective value along said reference axis, identifying a target region of the reference axis where the signal exceeds the detection-threshold function, and reducing the detection-threshold values of the detection-threshold function within an identified target region, and producing an output signal in dependence on the identified target region, the control system producing an actuation signal in dependence on the output signal.

30. A control system according to

claim 29

, wherein the actuation signal is adapted to actuate an airbag deployment device.