Abstract:
A method for optimizing the sensitivity of certain radar sensors that works by placing target objects within a sensor&#39;s field of coverage at strategic locations and adjusting the sensor&#39;s radar parameters as a function of the sensor target location and performance characteristics of the sensor, including bin resolution and spatial constraints. The proposed methods are ideally suited for a wide variety of uses, including for use on production lines. The methods are equally appropriate for use in other areas, including sensor maintenance and recalibration and in the development and validation of sensors.

Description:
TECHNICAL FIELD 
     The present invention relates generally to radar systems, and more specifically, to radar sensor optimization systems. 
     BACKGROUND OF THE INVENTION 
     Warning systems are being used today to alert vehicle operators of objects that may be a collision hazard. Warning systems are typically used as aids in precise parking maneuvers or while vehicles are backing up. Warning systems are desirable to minimize or avoid vehicle damage that may otherwise occur. Conventional warning systems use radar emitter/sensor systems to scan fields of coverage for objects that may be a collision hazard. 
     Most radar systems are threshold-type detection systems. These types of radar systems use a minimum signal target (for example, a 1-meter high, 75-mm diameter PVC pipe) as a threshold to assess the sensor&#39;s inherent capability by placing those target objects at representative positions in the field. By placing these targets at the edge of the detection field, fewer target objects are needed. In addition, these types of radar systems are typically designed to minimize R 4  range losses over all of the range bins by amplifying the signal by an incremental amount so that each effective range bin signal is essentially the same. In this way, the farthest range bin is just as sensitive as a range bin closer to the sensor. 
     To be used on a vehicle, a radar sensor must be adjusted based on a number of characteristics, including mounting location. The sensitivity of certain radar sensors can be adjusted by either regulating the voltage threshold of the return signal or by regulating the integration time of each dwell (or range bin). Because of the significant variation in the signal quality of radar sensors from one vehicle&#39;s mounting configuration to another, each radar sensor must be individually adjusted. Current tuning processes are inefficient, tedious and time consuming. 
     SUMMARY OF THE INVENTION 
     It is highly desirable to create an automated method for optimizing radar sensors. The present invention creates several methods for optimizing the sensors in an efficient manner. 
     The present invention operates by placing target objects in a sensor&#39;s field of coverage at strategic locations and adjusting the radar sensor&#39;s parameters based on the target objects. Three preferred methods are used to optimize the radar sensors. The first method for optimizing sensors is accomplished by the placement of objects within the target area as a function of high bin resolution with no spatial constraints. The second method for optimizing sensors is accomplished by the placement of the objects within a target area as a function of low bin resolution with no spatial constraints. The third method of optimizing sensors is by the placement of objects within the target area with either low or high bin resolution as a function of spatial constraints. 
     In one embodiment, where the target area is a function of high bin resolution and no spatial constraints, a coverage area is defined for the sensor. The coverage area is divided into a series of bins, wherein each bin defines an equal portion of said coverage area at varying distances from the sensor. A target object is placed within each of the bins at a predetermined distance from the sensor. The sensor is then adjusted so that each target object is sensed by the sensor at the edge of a detection area for the sensor within each bin. 
     In a second embodiment, where the target area is a function of low bin resolution and no spatial constraints, a coverage area is defined for the sensor. The coverage area is divided into a series of bins, wherein each bin defines an equal portion of said coverage area at varying distances from the sensor. A target object is placed within every other of the bins at a predetermined distance from the sensor. The sensor is then adjusted so that each target object is sensed by the sensor at the edge of a detection area for the sensor within every other bin. The process is then repeated with the unused bins. 
     In a third embodiment, where the target area is a function of high or low bin resolution with spatial constraints, a coverage area is defined for the sensor. The coverage area is divided into a series of bins, wherein each bin defines an equal portion of said coverage area at varying distances from the sensor. A target object is placed within the furthest of the bins (away from the sensor) at a predetermined distance from the sensor. The object is then moved iteratively towards the sensor by either moving the target object or the sensor relative to each other. The sensor is then adjusted so that each target object is sensed by the sensor at the edge of a detection area for the sensor within each bin. 
     The methods disclosed may also be used for sensor maintenance and re-calibration, as well as for quickly and effectively administering tests for development and validation purposes. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will now be described, by way of examples, with reference to the accompanying drawings, in which: 
     FIG. 1 shows an embodiment of a radar system for use with the present inventive method; 
     FIG. 2 is an optimization graph showing preferred target locations according to one embodiment of the present invention; 
     FIG. 3 is an optimization graph showing preferred target locations according to a second embodiment of the present invention; 
     FIG. 4 is an optimization graph showing preferred target locations according to a third embodiment of the present invention; and 
     FIG. 5 is a validation chart for the method corresponding to FIG.  4 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to FIG. 1, a vehicle  10  is shown having a radar system  12 . The radar systems  12  is conventional and may comprise one or more emitter/sensors  14 A,  14 B that are mounted proximate to the bumper system, although the packaging and mounting system may vary greatly from vehicle to vehicle. The radar system  12  further comprises an electronic control module  16  that is electronically coupled to the emitter/sensors  14  and a driver alert display  18 . 
     To operate the radar system  12 , first a signal is sent out from the emitter  14 A in a specific coverage area  22  to sweep for objects  20 . The signal will reflect off of a detected object  20  within the coverage area  22  and be received by the sensor  14 B. The mechanism for sending and receiving signals from emitters  14 A and sensors  14 B is well known in the art. The sensor  14 B may then send a signal to a control module  16 . The returned signals are then processed by the electronic control module  16 , preferably a microprocessor-based control module, to determine the distance between the object  20  and the vehicle  10 . The electronic control module  16  then sends a signal to the driver alert display  24 , which processes the signal to warn the operator of the vehicle  10  of an impending collision. 
     The sensitivity of the radar sensors  14 B is a function of the voltage threshold of the return signal, the integration time of each dwell (or range bin), and the location of the sensor  14 B on the vehicle. Because the sensor  14 B location is typically fixed, the sensitivity of radar sensors  14 B may be adjusted by either regulating the voltage threshold of the return signal or changing the integration time of each dwell. 
     The voltage threshold represents the minimum integration value of a target signal that will indicate a target object  20  has been detected. A voltage value below this threshold value is considered noise or clutter. The voltage threshold analysis is on a per sweep basis and is independent of the individual range bin settings as discussed below. The higher the threshold value set, the less sensitive the radar will appear to be. Conversely, the lower the threshold value set, the more sensitive the radar will appear to be. The threshold voltages are typically in the millivolt range. 
     Bins, or range zones, are distinct areas or regions that the sensor equipment scans for objects  20 . The number and size of bins varies from one configuration of sensing equipment to the next. For example, one sensor may have a bin size of 29 cm in length and have 15 different bins that are capable of being scanned. Bin resolution is the ability of the sensors  14 B to accurately sense target objects  20  within each bin. The integration time is the amount of time that each range bin is allowed to accumulate signal. The longer the time interval of each range bin, the more sensitive the radar sensor  14 B is up to its design limit. Conversely, the shorter the time interval of each range bin, the less sensitive the radar sensor  14 B will appear to be. Integration times are typically in the microsecond range. 
     However, even though the location of the sensor  14 B is fixed, there is significant variation in the signal of the sensor  14 B from one mounting configuration to another. As such, each individual sensor  14 B on each vehicle  10  must be individually adjusted for accuracy. This is a tedious and time-consuming process. 
     The present invention creates an easy, automated procedure for optimizing sensors  14 B in a time efficient manner. The procedure controls the placement of objects in a target area in three distinct ways as a function of bin resolution and spatial constraints. Bin resolution is the ability of the sensors  14 B to accurately sense target objects  20  within each bin. Bin resolution is a function of various practical factors, including the accuracy and differentiating ability of the sensing equipment  14 B and the processing ability of the control module  22 . The higher the bin resolution, the better the ability of the sensor  14 B to place a sensed target  20  within a specific bin. For low bin resolution systems, there may be some overlap between adjacent bins. Spatial constraints are defined as the area that the sensors  14 B will be limited to in scanning for targets  20 . 
     The first method for optimizing sensors  14 B is accomplished by the placement of objects  20  within the target area as a function of high bin resolution with no spatial constraints. The second method for optimizing sensors  14 B is accomplished by the placement of the objects  20  within a target area as a function of low bin resolution with no spatial constraints. The third method of optimizing sensors  14 B is by the placement of objects  20  within the target area with either low or high bin resolution as a function of spatial constraints. Each method is described in detail below. 
     Referring now to FIG. 2, a diagram is shown according to the first embodiment of the invention wherein the sensors are optimized as a function of high bin resolution and no spatial constraints. In this method, targets  20  are first placed at the edge of the desired coverage area at a radial distance equal to the center of each bin. In the example of FIG. 2, the boundary is set for a coverage area width of 2 meters on each side, however, the coverage area width may be of any size. Given these parameters, the sensor  14 B is then calibrated by the electronic control module  16  to prevent the occurrence of any false alarms from the material the sensor  14 B may need to see through. Then, the electronic control module  16  adjusts either the voltage threshold of the return signal or the integration time of each dwell (or range bin), or both, so that the target  20  is at the threshold of detection or no detection. 
     This embodiment of the present invention is a threshold type detection system that also is range optimized via an antenna detection pattern that is an inherent part of the hardware design of the radar system  12 . Because of this feature, and because of the fact that this embodiment has high bin resolution, the assessment of the detection area can be more easily accomplished by assessing the edge of each range bin field. If the target object  20  is just inside the detection field, target objects  20  will be detected by the sensor  14 B. If the target object  20  is outside the detection field, the sensor  14 B will not detect target objects  20 . In this way, the detection field will be properly defined, which is preferred to reduce false alarms. 
     While FIG. 2 diagrams an arrangement showing one sensor  14 B, it is contemplated that the present invention may be used with more than one sensor  14 B. For example, if the system had two sensors  14 B, the optimization method described above would be required for each sensor. 
     Referring now to FIG. 3, a diagram is shown wherein the sensors are optimized as a function of low bin resolution and no spatial constraints according to another preferred embodiment of the present invention. Targets  20  are placed at the edge of the desired coverage area at a radial distance equal to the center of every other bin. In the example of FIG. 3, the boundary was set for a coverage area width of 2 meters on each side, however, the coverage area width may be of any size. Given these parameters, the sensors  14 B are calibrated to prevent the occurrence of any false alarms from the material the sensor  14 B may need to see through. Then, the electronic control module  16  adjusts the voltage threshold of the return signal or the integration time of each dwell (or range bin), or both, so that the target  20  is at the threshold of detection or no detection. The process as described above is done twice, once for even numbered bins and once for odd numbered bins. 
     This embodiment of the present invention is a threshold type detection system that also is range optimized via an antenna detection pattern that is an inherent part of the hardware design of the radar system  12 . Because of this feature, and because of the fact that this embodiment has low bin resolution wherein the process is done twice for even numbered bins and odd numbered bins, the assessment of the detection area can be more easily accomplished by assessing the edge of each range bin field. If the target object  20  is just inside the detection field, targets objects  20  will be detected by the sensor  14 B. If the target object  20  is outside the detection field, the sensor  14 B will not detect target objects  20 . In this way, the detection field will be properly defined, which is crucial to reducing false alarms. 
     While FIG. 3 diagrams an arrangement showing one sensor  14 B, it is contemplated that the present invention may be used with more than one sensor  14 B. For example, if the system had two sensors  14 B, the optimization method described above would be required for each sensor. 
     Referring now to FIG. 4, a diagram is shown wherein the sensors are optimized as a function of low or high bin resolution and as a function of spatial constraints according to a third preferred embodiment of the present invention. One target object  20  is placed at the edge of the desired coverage area at a radial distance equal to the center of one bin. In the example of FIG. 4, the boundary was set for a coverage area width of 2 meters on each side, however, the coverage area width may be of any size. Then, either the target object  20  or the vehicle  10  containing the sensor  14 B is moved relative to each other to a position at the edge of the desired coverage area at a radial distance equal to the center of the next adjacent bin. The process is repeated for each adjacent bin. Given these parameters, the sensor  14 B is calibrated to prevent the occurrence of any false alarms from the material the sensor  14 B may need to see through. Then, the electronic control module  16  adjusts the voltage threshold of the return signal or the integration time of each dwell (or range bin), or both, so that the target object  20  is at the threshold of detection or no detection within each bin. 
     This embodiment of the present invention is a threshold type detection system that also is range optimized via an antenna detection pattern that is an inherent part of the hardware design of the radar system  12 . Because of this feature, and because of the fact that this embodiment has either low or high bin resolution with spatial constraints, the assessment of the detection area can be more easily accomplished by assessing the edge of each range bin field. If the target object  20  is just inside the detection field, targets objects  20  will be detected by the sensor  14 B. If the target object  20  is outside the detection field, the sensor  14 B will not detect target objects  20 . In this way, the detection field will be properly defined, which is crucial to reducing false alarms. 
     While FIG. 4 diagrams an arrangement showing one sensor  14 B, it is contemplated that the present invention may be used with more than one sensor  14 B. For example, if the system had two sensors  14 B, the optimization method described above would be required for each sensor. 
     Referring now to FIG. 5, a validation chart is shown corresponding to the method of FIG. 4, wherein the sensors  14 B are calibrated as a function of low or high bin resolution with spatial constraints. The chart shows three separate graphs showing a coverage area of 6.0 meters. Target objects  20  were placed in approximately 0.3-meter increments at a distance approximately 1 meter from a center baseline (designated 0 meters on the y-axis). Under ideal conditions, as indicated by  100  on the graph, the sensors  14 B would read a straight line approximately 1.0 meter left and right of the center baseline for the entire 6.0-meter coverage area. Prior to optimization, as indicated by  110  on the graph, the sensor  14 B experienced significant variation from the ideal response. After optimization, as indicated by  120  on the graph, the sensor  14 B response more closely resembled ideal response, as the average variation from ideal response varied less than before optimization. For example, at approximately 0.75 meters, the sensor read approximately 0.6 meters before optimization and approximately 0.8 after optimization. Also, at 4.5 meters, the sensor  14 B read approximately 1.4 meters prior to optimization and approximately 1.1 after optimization. 
     The methods of the present invention as described in FIGS. 2,  3  and  4  provide an efficient, accurate and repeatable process for optimizing radar sensor performance. The present invention may be used on a production line, for sensor maintenance or recalibration, or for quickly and effectively administering tests for development and validation purposes. 
     While the invention has been described in connection with three methods, it will be understood that the invention is not limited to those methods. On the contrary, the invention covers all alternatives, modifications, and equivalents as may be included within the spirit and scope of the appended claims.