DE19707591C1 - Monitoring alignment of beam characteristic of object sensor - Google Patents

Abstract

The method monitors the alignment of an object sensor (10) especially the vertical alignment of a radar sensor, not angle resolving in this plane. The object sensor using measurement waves transmitted, reflected and received again, determining at least one distance (d(t)) of a measurement object in the detection range. A reference reflector (11) serves as the measurement object, which during at least one measuring cycle, moves on a determined track (12a, b) so that different distances (d(t)) and different angle positions (gamma(t)) between the object sensor and the reference reflector are produced. An intensity distribution (P(gamma)) of the measurement wave reflected by the reference reflector is determined (206). Based on the determined intensity distribution, the alignment of the beam characteristic of the object sensor is monitored (207, 208) and a characteristic is produced, based on which a false alignment of the beam characteristic of the object sensor can be identified (210).

Description

The present invention relates to a method and a Device for checking the alignment of a beam characteristic of an object sensor. With the term object The following means or devices are used as sensors referred to using radar, laser, infrared, Detect objects using ultrasound or other waves and at least determine their distance to a reference point can. In particular, the invention relates to a method and a device for checking a vertical Alignment of a not angularly resolving in this plane Radar sensor, which is mounted in or on a motor vehicle is. However, the scope of the invention is not limited to this use alone.

From numerous publications, for example from "Adaptive Cruise Control - System Aspects and Development Trends "by Winner, Witte et al., Published at SAE 1996 in Detroit, is now known to motor vehicles  to be equipped with an object sensor. Such an object sensor can for example as radar, laser, infrared or Ultrasonic sensor can be realized and serves to hinder nisse that are in the route or in the vicinity of the force vehicle are to be detected. Usually this is done at least a distance from the obstacle to the force vehicle determined. Such object sensors are used for example according to the above-mentioned publication in the context of adaptive vehicle speed controls. Other areas of application are parking aids, lane changes help, collision warning system or procedure and pre directions with which a speed of driving stuff is measurable on the ground. All of these areas of application has in common that the object sensor used is sufficient must be precisely adjusted so that his "line of sight" with a direction to be monitored or measured agrees. Adjust the object sensor understood in the following means and procedures with which the beam characteristic of the object sensor into one desired direction is aligned or aligned has been.

Such an object sensor has the ability to to determine the detected object also its direction, d. H. if he has an angular resolution, this ability to Verification of correct alignment can be used. Not least because of cost reasons is such a skill however, usually only realized where it did is actually needed. Accordingly, there are numerous Use cases where the alignment of an object sensors not based on a sensor 's own ability to Direction can be checked. In the case of the above This applies to the aforementioned publication, for example the vertical alignment of the object sensor mentioned there to. However, a check is also made of the vertical off  direction, for example, when installing one Object sensor in the factory and also after every replacement or Repair required in the workshop.

In previously known methods for checking the verti cal alignment (elevation) of such an object sensor becomes a measuring probe or a reflector at the desired height positioned opposite the object sensor. Then the Alignment of the beam characteristic of the object sensor set that the measuring probe or the reflector with maxi painterly transmission power are illuminated. When using a Reflector this can be checked that in a such case with the position of the reflector unchanged Receiving power at the object sensor must be maximum. disadvantage this method is that the course of the transmission power over the elevation angle of the object sensor in the area of the Maximum is relatively flat. This is a detection of the respective maximum very inaccurate and cannot to one insignificant misalignment of the object sensor in the vertical direction. This in turn affects the described use case also disadvantageously on the quality the horizontal angular resolution of the object sensor. In addition, a vertical misalignment of the Object sensor unwanted and disadvantageous target loss occur.

Accordingly, the object of the present invention is a To specify a method and a device based thereon with or with the simple and inexpensive way a reliable check of the alignment of a beam characteristic of an object sensor is possible. Especially the method or the device should then  be suitable if the object sensor in the to be checked Plane has no angular resolution. Preferably with the method or the device at simple and cost favorable way of vertical alignment of a beam character teristics of a motor vehicle radar sensor can be checked.

According to the invention, this object is achieved by a device solved according to claim 6. The device contains a ref reference reflector for measurement emitted by the object sensor waves that can be moved on a determined path. Here there are different distances on this track d (t) and different angular positions γ (t) between the Object sensor and the reference reflector. Preferably, the Reference reflector movable on a circular path, its radius R lies in the plane in which the alignment of the beam characteristic of the object sensor is to be checked.

Further preferred configurations of the invention Device arise from the subclaims.

Furthermore, the task according to the invention by the Ver drive solved according to claim 1. A reference reflector is on a determined path, preferably a circular path, so moves that different distances d (t), under different angular positions γ (t) and in a preferred Aus also different relative speeds vR (t) between the object sensor and the reference reflector surrender. It is from a measuring shaft by the Refe reflected and then received again determines an intensity distribution P (γ) on the basis of which the Alignment of the beam characteristic of the object sensor via is checked. Then an indicator is generated based on this an incorrect alignment of the jet characters ristik can be recognized. It is particularly advantageous that the  Angular positions γ (t) used to form the intensity distribution P (γ) are required based solely on that of the object sensor respectively measured distance d (t) or also based on the measured relative speed and the selected sizes the device can be determined.

Another advantage of the invention is that for through management of the check no special measuring devices such as high frequency, laser or sound measuring devices are required. A Another major advantage is that with the above Device or the method mentioned in addition to the check Alignment function tests of the object sensor possible are. Due to the determined movement of the Reflector and the resulting determined The course of the distance d (t) can, for example basic function of distance measurement checked will. Likewise, a measurement accuracy in the Distance measurement or a spread of measurement accuracy be checked. The object sensor has the capability speed, a relative speed vR (t) of an object can determine this ability due to the deter minimized movement of the reflector with regard to their reason additional function, their measuring accuracy and the scatter of the measured values are checked. Also due to the determined movement of the reflector and thus connected modulation of the reflected measuring wave can unwanted reflections of the measuring wave of objects from the Environment, for example a wall, clear of the Desired reflections of the reflector are separated. Last but not least, the device mentioned is simple Way feasible.

The following is an embodiment of the invention explained using a drawing: show it

Fig. 1 is a sketch of a device according to the invention and Fig. 2 is a flowchart of the method according to the invention.

Fig. 1 shows a schematic sketch of an inventive device. Opposite an object sensor 10 is a reflector 11 , which is preferably designed as a so-called corner or triple reflector. Such a reflector has the property of reflecting measuring waves each reflecting in the direction from which they came. The reflector 11 is attached to two vertically standing, synchronously rotatable wheels 12 a and 12 b. The aim of this construction is that the reflector 11 can be moved on a vertical circular path such that its opening or its effective reflection surface always points in the direction of the object sensor 10 . This can be done without excluding other forms of construction, for example, in that the two wheels 12 a and 12 b are horizontally offset from one another. The reflector 11 is then attached, for example, with its funnel-shaped opening to the wheel 12 a further projecting and with its closed end, which symbolizes the actual reflection point 15 , to the wheel 12 b further back.

Furthermore, various dimensions and orientation lines are drawn in to illustrate the relationships explained below. A first line 13 runs horizontally from the object sensor 10 in the direction of the two wheels 12 a and 12 b. A second line 14 indicates, in relation to this first line 13, an instantaneous angular position γ (t) between the reflector 11 and the object sensor 10 . The line 14 symbolizes the direction from which the object sensor 10 each receiving a light reflected from the reflector 11 measuring shaft. The height at which the object sensor 10 is above the floor is designated by the size zS.

The determination of a respective instantaneous position of the reflector 11 or an effective reflection point 15 is related here to the center of the wheel 12 b. This center, about which the wheel 12 b is rotatable, is at a height z0 above the ground. The size z0 can be identical to the height of the object sensor zS. However, this is not a necessary requirement. An assumed direction of rotation of the two wheels 12 a and 12 b is indicated by an arrow 16 as an example, but it can also be selected in the opposite direction without functional restrictions. The speed of rotation of the wheels is denoted by ω. Starting from a reference line 17 , which runs perpendicularly through the center or pivot point of the wheel 12 b, a coordinate ψ (t) is indicated, which indicates a momentary rotational angle position of the wheel 12 b and thus also of the wheel 12 a and the reflector 11 designated. ψ (t) results from the rotational movement of the wheels 12 a and 12 b and an initial rotational angular position ϕ

ψ (t) = ϕ. t + ϕ (1)

A size d0 indicates the distance between the object sensor 10 and the center of the wheel 12 b. The following mathematical relationships can be derived from the geometric relationships on the basis of these defined variables:

d (t) = d0 + R. sin (ψ (t)) (2)

vR (t) = ω. R. cos (ψ (t)) (3)

z (t) = z0 + R. cos (ψ (t)) (4)

the individual sizes are designated net according to FIG. 1. Based on the height of the object sensor zS, ie in relation to the line 13 , a momentary angular position between the object sensor 10 and the reflector 11 is then obtained from

γ (t) = arctan ((z (t) - zS) / d (t)) (5)

This relationship can also be calculated approximately as follows:

γ (t) = (z (t) - z0) / d0 + (R / d0). cos (Ψ (t)) (6)

To carry out the method according to the invention, the object sensor 10 sends measuring waves in the direction of the reflector 11 . This is moved on the circular path that results from the movement of the two wheels 12 a and 12 b. This movement results in different angular positions γ (t) and different distances d (t) between the object sensor 10 and the reflector 11 . There are also different relative speeds vR (t) in the radial direction. The object sensor 10 determines, for example, at least the different distances d (t) and an intensity P (t) of the received measuring waves on the basis of the transit time of the transmitted and received measuring waves. The vertical alignment of the object sensor 10 can be checked on the basis of these specific variables, as explained below. At the same time, the further functional tests of the object sensor 10 which have already been mentioned are also connected with this.

Fig. 2 shows a flow chart of a method according to the invention. In steps 201 and 202 , which are carried out simultaneously, the instantaneous distance d (t) of the reflector and the intensity P (t) of the received measuring wave are determined according to generally known and customary methods for generic object sensors. This recording of the measured values can take place completely at the beginning of the method or alternatively step by step in an iterative implementation of the method.

In addition, if the object sensor has this capability, a relative speed vR (t) of the reflector 11 relative to the object sensor 10 can also be determined in accordance with step 211 . This additional, but not necessary step is indicated by the dashed line 214 . In step 203 , the instantaneous angle of rotation position ψ (t) of the wheels 12 a and 12 b and thus of the reflector 11 is determined on the basis of equation (2). For this purpose, equation (2) is changed as follows:

ψ (t) = arcsine ((d (t) - d0) / R) (7)

Alternatively, the current angle of rotation position ψ (t) can also be determined in accordance with step 212 on the basis of the measured relative speed vR (t) by changing and applying equation (3) as follows:

ψ (t) = arccos (vR (t) / ω. R)) (8)

In step 204 , a current height z (t) of the reflector 11 is calculated on the basis of the previously determined angle of rotation position ψ (t) and according to equation (4). Alternatively, this can also be determined according to step 213 on the basis of the relative speed vR (t). The equation required in this case is obtained by substituting equation (3) in equation (4)

z (t) = z0 + vR (t) / ω (9)

In step 205 , the instantaneous angular position γ (t) between the object sensor 10 and the reflector 11 is determined based on the previously determined instantaneous height z (t) and on the distance d (t). In this way, a relationship is obtained at which time t the reflector 11 was in which vertical angular position γ with respect to the object sensor 10 . This γ (t) is then related in step 206 to the intensity P (t) measured according to 202 . In other words, an assignment is made based on the respectively identical times t, which intensity P was determined at which angular position γ. The resulting relationship P (γ) corresponds at least in part to a vertical radiation characteristic of the object sensor 10 in this specific exemplary embodiment. This is then evaluated, for example, with regard to its maximum value.

For this purpose, a maximum value P _{max of} the intensity of the received measuring wave is first determined in step 207 , again by way of example. Γ _max is used to denote the angular position at which this maximum intensity P _max resulted. The angular position γ _max corresponds to the main beam direction of the object sensor 10 . For the evaluation or inspection step of the object sensor 10 is in accordance _to 208 γ a difference between the determined angle γ _max and an angle characteristic of a target value of the vertical angle position, and thus the orientation of the beam indicates determined. Furthermore, a check is carried out to determine whether this difference is less than or equal to a predetermined threshold value X. If this is the case, the vertical alignment of the beam characteristic of the object sensor 10 is in accordance with step 209 . This can be signaled by the object sensor 10, for example, via an interface using a digital status word or using an optical signal.

Otherwise, according to a preferred embodiment of the method, the difference between the angles γ _max and γ setpoint _is output in step 210 . Based on the sign of this difference, it can then be recognized, for example, whether the alignment of the beam characteristic is too high or too low. Alternatively, for example, two light sources can be controlled so that one indicates a too high and the other a too low orientation.

As an alternative to evaluating the beam characteristic P (γ) An evaluation can also be made of its maximum value regarding two or more intensity values gene, for example by 3 dB compared to the measured Maximum value have dropped. Choosing the one concrete application of a more suitable alternative Leave to a specialist.

Even if the exemplary embodiment described here is preferably used to check a vertical alignment of a beam characteristic of an object sensor which is attached to or in a motor vehicle, this method is not restricted to this application case alone. It is readily possible for a person skilled in the art to apply the basic principle of the invention to other areas of application. For example, a horizontal or any inclined orientation of an object sensor 10 can also be checked by tilting the device consisting of the reflector 11 and the two wheels 12 a and 12 b in the direction to be checked. A horizontal alignment can therefore be checked by moving the reflector 11 on a horizontal circular path. Of course, the device can also be used to check object or distance sensors that are not mounted in or on a motor vehicle.

Variations of the basic method according to the invention result, as already indicated in FIG. 2 by means of the dashed lines, when a relative speed vR (t) is determined according to step 211 .

The method according to the invention can optionally be implemented either in a control unit of the object sensor 10 or, for example, in a separate diagnostic medium, which is then connected to the object sensor 10 via a suitable interface.

Claims (9)

1. A method for checking the orientation of a beam characteristic of an object sensor ( 10 ), in particular the vertical orientation of a radar sensor that does not resolve the angle in this plane, the object sensor using transmitted and received reflected measuring waves at least a distance d (t) of a measuring object in Detection area of the object sensor determined, characterized in that

• 1. that a reference reflector ( 11 ) is used as the measurement object, which moves during at least one measurement cycle on a determined path ( 12 a, b), so that different distances d (t) and different angular positions γ (t) between the object sensor and the reference reflector,
• 2. that an intensity distribution P (γ) of the received measurement wave reflected by the reference reflector is determined ( 206 ),
• 3. that the alignment of the beam characteristic of the object sensor is checked on the basis of the determined intensity distribution P (γ) ( 207 , 208 ) and
• 4. that an indicator is generated, based on which an incorrect alignment of the beam characteristic of the object sensor can be recognized ( 210 ).

2. The method according to claim 1 , characterized in that the reference reflector ( 11 ) moves on a circular path, the radius of which lies in the plane in which the alignment of the beam characteristic is to be checked. 3. The method according to claim 1 or 2, characterized in that the angular positions γ (t) are determined at least on the basis of the distance d (t) ( 203-205 ). 4. The method according to claim 1 or 2, characterized in that the angular positions γ (t) are determined at least on the basis of a relative speed vR (t) ( 203-205 ). 5. The method according to claim 3 or 4, characterized in that the intensity distribution P (γ) on the basis of a measured intensity distribution P (t) and on the basis of the determined angular positions γ (t) is determined ( 206 ). 6. Device for checking the alignment of a beam characteristic of an object sensor ( 10 ), in particular the vertical alignment of a radar sensor in or on a motor vehicle, the object sensor ( 10 ) with the aid of transmitted and received measuring waves at least a distance d (t) one Measuring object in the detection range of the object sensor ( 10 ), characterized in that the device contains a reference reflector ( 11 ) for the transmitted measuring waves, which can be moved on a determined path ( 12 a, b), with different distances d ( t) and different angular positions γ (t) between the object sensor ( 10 ) and the reference reflector ( 11 ) result. 7. The device according to claim 6, characterized in that the reference reflector ( 11 ) is movable on a circular path whose radius R lies in the plane in which the alignment of the beam characteristic is to be checked. 8. Apparatus according to claim 6 or 7, characterized in that the reference reflector ( 11 ) can be fastened to two equally large, synchronously rotatable, eccentrically arranged wheels so that its effective reflection surface at any location of the path to be traversed in the direction of the object sensor ( 10 ) shows. 9. Device according to one of claims 6 to 8, characterized in that the reference reflector ( 11 ) is a corner or a triple reflector.