Abstract:
In a method for determining road clearance of a vehicle, the vehicle is moved relative to a measurement configuration with a reference surface. One or more magnets, which are disposed on the vehicle and assigned preferably each to a defined measurement point on the vehicle, is detected by at least one device for magnetic field measurement. With the help of at least one device for separation measurement, the separation between the measurement configuration and the bottom side of the vehicle is determined. In this way, a rapid, reliable, repeatable and flexibly usable method for the determination of the road clearance of a vehicle is provided. A corresponding device is provided for implementing the method.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the priority, under 35 U.S.C. §119, of German application DE 10 2007 027 253.9, filed Jun. 13, 2007; the prior application is herewith incorporated by reference in its entirety. 
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The invention relates to a method for determining road clearance of a vehicle, where the vehicle is moved relative to a measurement configuration. The invention also relates to a corresponding device. 
     It is known to measure the road clearance of vehicles, particularly of trucks, with the help of lathes or gauges. This may be necessary, for example, for safety reasons. In sport racing events, a minimum height is often prescribed for the road clearance of the participating sport racing vehicles. In the measurement of a road clearance with lathes, a vehicle is moved over a lathe having the prescribed minimum height. If the lathe falls over, then at least some parts of the vehicle bottom are lower than the prescribed minimum height. If the lathe remains standing, then the minimum road clearance is considered to have been met. The road clearance can also be determined by moving gauges on a reference surface beneath the vehicle bottom. If the gauges can be moved appropriately freely, then the minimum road clearance is considered to have been complied with. 
     These known methods for verifying the road clearance of a vehicle are time consuming, imprecise, and they require a large expenditure of testing personnel. 
     BRIEF SUMMARY OF THE INVENTION 
     It is accordingly an object of the invention to provide a method and a device for the determination of the road clearance of a vehicle which overcome the above-mentioned disadvantages of the prior art methods and devices of this general type, which allow a more rapid, simpler, and more precise determination of the road clearance of vehicles. 
     With the foregoing and other objects in view there is provided, in accordance with the invention, a method for determining road clearance of a vehicle. The method includes the steps of moving the vehicle relative to a measurement configuration, detecting at least one magnet disposed on the vehicle with at least one device for magnetic field measurement, and providing at least one device for separation measurement for determining a separation between the measurement configuration and a bottom side of the vehicle. 
     In the method of the type mentioned in the introduction, one or more magnets, which are disposed according to the invention on a vehicle, are detected by at least one device for measuring magnetic fields, and the separation between the measurement configuration and the bottom side of the vehicle is determined with the assistance of at least one device for measuring separation. In this way, a rapid, reliable, repeatable and flexibly usable method is provided for the determination of the road clearance of a vehicle. 
     An appropriate device for the determination of the road clearance of a vehicle has a measurement configuration where the vehicle can be moved relative to the measurement configuration. The measurement configuration has one or more devices for magnetic field measurement and one or more devices for measuring separation. The device for magnetic field measurement has one or more magnetic field sensors, and the device for measuring separation has one or more separation sensors configured for contact-free separation measurement. 
     The invention can considerably reduce the time required for the determination of the road clearance of a vehicle. Moreover, the testing personnel no longer need to perform physical work. The determination of the road clearance becomes moreover much more flexible. The determination of the road clearance according to the invention can also be carried out reliably and reproducibly for different vehicle types and under different general conditions. 
     Advantageously, one or more magnets, which may be configured, for example, as permanent magnets, can be assigned in each case to a defined measurement point on the vehicle to be checked. Here, it is advantageous to determine the separation between the measurement configuration and the bottom side of the vehicle at the defined measurement points. 
     The measurement process(es) of the at least one device for separation measurement can be controlled advantageously in dependence on the measurement values determined with the help of the at least one device for magnetic field determination. 
     The measurement configuration used for the determination of the road clearance can be constructed advantageously so it can be driven over. 
     Advantageously, in each case a device for magnetic field measurement and a device for separation measurement are associated with each other. 
     In an advantageous variant of the invention, the at least one device for magnetic field measurement can have several magnetic field sensors that are arranged in a row. 
     Advantageously, the at least one device for separation measurement can have several separation sensors that are arranged in a row and parallel to the magnetic field sensors. 
     Advantageously, the at least one device for separation measurement can have at least one separation sensor that can be shifted parallel to the magnetic field sensors. 
     Advantageously, one or more, or optionally all of the, separation sensors can be configured as optical sensors. 
     Advantageously, one or more or optionally all of the separation sensors can be constructed as ultrasound sensors. 
     Advantageously, the one or more devices for magnetic field measurement and the one or more devices for separation measurement can be coupled with a control device. 
     Other features which are considered as characteristic for the invention are set forth in the appended claims. 
     Although the invention is illustrated and described herein as embodied in a method and a device for the determination of the road clearance of a vehicle, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims. 
     The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
         FIG. 1  is a diagrammatic, side-elevational view of a vehicle and a measurement configuration; 
         FIG. 2  is a top, plan view of the vehicle and the measurement configuration; 
         FIG. 3  is an illustration of a device for magnetic field measurement; 
         FIG. 4  is an illustration of a separation sensor; 
         FIG. 5  is an illustration of the device for magnetic field measurement and the device for separation measurement; 
         FIG. 6  is an illustration of the device for magnetic field measurement and the device for separation measurement with a movable separation sensor; 
         FIG. 7  is a diagrammatic, top plan view of the vehicle and the measurement configuration; and 
         FIG. 8  is an illustration of a coupling of the measurement configuration with a control device. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to the figures of the drawing in detail and first, particularly, to  FIG. 1  thereof, there is shown a vehicle  1 ,  1 ′ moved over a measurement configuration  2 . An upper side of the measurement configuration  2  forms a reference plane that is located above a bottom  3 . The reference plane extends in a longitudinal direction x and in a transverse direction y. As a measure of the road clearance of the vehicle  1 ,  1 ′, the separation h (see  FIG. 4 ) can be used, which is measured preferably in the height direction z. By moving the vehicle  1 ,  1 ′ during the measurement over the reference plane and over the measurement configuration  2 , the road clearance can be determined more rapidly and in a continuous measuring process. 
       FIG. 2  shows the vehicle  1  seen from above, where the measurement configuration  2  is indicated schematically. In the example shown, the vehicle  1  presents four measurement points, on which magnets  61 ,  62 ,  63 ,  64  are disposed. The magnets  61 ,  62 ,  63 ,  64  can be arranged, for example, at the measurement points or, for example, at a defined separation in the longitudinal direction x in front of the measurement points on the vehicle  1 . In the measurement configuration shown, there is one degree of freedom for the measurement by the movement of the vehicle  1  over the measurement configuration  2  or over the reference plane. Measurement devices  11 ,  12  used are only indicated in  FIG. 2 . An additional degree of freedom can be achieved by moving the measurement devices  11 ,  12 , for example, by swiveling and/or by a translational movement of the measurement devices  11 ,  12 . To provide an additional degree of freedom during the measurement, the measurement devices  11 ,  12  can alternatively or additionally also present several elements in each case. 
     The magnets  61 ,  62 ,  63 ,  64  can be configured as permanent magnets and they generate advantageously as strong as possible a stray field. For example, sintered magnets, for example, neodymium magnets, can be used. Because high temperatures can occur due to the operation of the vehicle  1 , it can be advantageous to use samarium-cobalt magnets. In an alternative embodiment, the magnets  61 ,  62 ,  63   64 , can be configured as electromagnets. Even if electromagnets are used to generate the magnetic field, it is preferred to generate as strong as possible a stray field. The magnets  61 ,  62 ,  63 ,  64  can be attached to the vehicle  1 , particularly to the measurement points, by screw connection or by gluing. The magnets can also adhere by magnetic interaction to the vehicle  1 . It is preferred for the orientation of the magnetic field to be dependent on magnetic field sensors  41 ,  42 ,  43  used (see  FIG. 3 , among others) or dependent on a device  40  used for magnetic field measurement. It is advantageous for the magnetic axis of the magnets to extend parallel to the longitudinal direction x. 
       FIG. 3  shows the device  40  for magnetic field measurement, where the device  40  for magnetic field measurement presents several sensors  41 ,  42 ,  43  for the detection of magnetic fields. The magnetic field sensors  41 ,  42 ,  43  detect changes in magnetic fields by exploiting the magnetoresistive effect. The magnetic field surrounding a magnet  20  is indicated in the drawing. The magnetic field sensors  41 ,  42 ,  43  of the device  40  for magnetic field measurement are arranged parallel to the transverse direction y, in the example shown. If the magnet  20  is moved over such a device  40  for magnetic field measurement, then the starting voltages of the magnetic field sensors  41 ,  42 ,  43  behave proportionally to the field strength, and thus indirectly proportionally to the separation of the magnetic field sensors  41 ,  42 ,  43  from the magnets  20 . The highest voltage level is generated here by the magnetic field sensors that are closest to the magnet. Thus, it is possible, via the measurement of the starting voltages of the magnetic field sensors  41 ,  42 ,  43  and on the basis of the known position of the individual magnetic field sensors  41 ,  42 ,  43 , to determine at least the position of the magnets  20  along the transverse direction. 
       FIG. 4  shows, for example, a separation sensor  54  of the measurement configuration  2 . With the help of such separation sensors, the separation h between measurement points  99  on the vehicle and the reference surface or the surface of the measurement configuration  2  can be determined. In the example shown, a measurement point  99  is arranged in an area  5  of the vehicle. The measurement point  99  can also be arranged at other defined points of the undercarriage of a vehicle. In  FIG. 4 , a wheel  4  of the vehicle is also indicated. 
     As represented in  FIG. 5 , separation sensors  51 ,  52 ,  53  of a device  50  for separation measurement can be disposed parallel to the magnetic field sensors  41 ,  42 ,  43  of a device  40  for magnetic field measurement. 
     As indicated in  FIG. 6 , the number of separation sensors used can be reduced, if at least one separation sensor  55  is configured so it can be shifted parallel to the magnetic field sensors  41 ,  42 ,  43 . 
     The measurement of the separation h (see  FIG. 4 ) or of the road clearance can be carried out using a triangulation method. For this purpose, a light beam is emitted, and the reflection of this light beam at the measurement point via a mirror configuration is measured with an optical sensor. The measured angle of the projection of the reflected light point on the measurement point is proportional to the separation of the measurement point. The configuration of the optical sensors is carried out preferably in the immediate vicinity of and preferably parallel to the magnetic field sensors (see  FIG. 5 ). One or more optical sensors can be mounted firmly on the reference plane of the measurement configuration  2  or movably, for example, on a sliding carriage. 
     Alternatively or additionally, the measurement of the separation h (see  FIG. 4 ) can occur with the help of one or more ultrasound sensors. Here, an ultrasound pulse is emitted and the echo reflected by the measurement point is received. The travel time of the echo signal is proportional to the separation of the measurement point. The configuration or mounting of the ultrasound sensors can occur in a way that is similar to the configuration or mounting of the optical sensors, for example, as represented schematically in  FIGS. 5 and 6 . 
     Below, an example of a measurement process is described with reference to  FIG. 7 . First, the vehicle  1  is aligned and then it is moved, preferably with the front axle first, over the reference plane of the measurement configuration  2  at as regular a speed as possible. In the process, the measurement points and the magnets  61 ,  62 ,  63 ,  64  associated with them are moved over the sensor fields, i.e., over the devices  40  for magnetic field measurement and over the devices  50  for separation measurement. It is preferred to arrange two measurement points in the area of the front axle and two measurement points in the area of the rear axle. The voltages of the magnetic field sensors are measured, readout and stored after being provided with time data. The storage is preferably only brief. When the measurement points marked with the help of the magnets  61 ,  62 ,  63 ,  64  are brought closer to the device  40  for magnetic field measurement, the voltages of the magnetic field sensors located in the vicinity change. Starting from a preset threshold value, the separation measurement is activated. From the activation time on, the measured separation values are stored and recorded, preferably after having been provided with time data. If the measured voltages of the magnetic field sensors fall below a predetermined threshold value, the separation measurement is terminated. It is preferred to evaluate the data after the end of the measurement, where the location and the height of the measurement points  99  arranged on the vehicle (see  FIG. 4 ) are determined. 
     As represented in  FIG. 8 , the devices  40  for magnetic field measurement and the devices  50  for separation measurement are coupled with a control device  6 , where measurement data of the sensors are delivered to the control device  6 . The activation of the separation sensors is carried out by the control device  6  as a function of the data produced by the magnetic field sensors. The control device  6  presents preferably an evaluation unit and a storage unit for the sensor data. The control device  6  can be coupled to an input device  7 , by which the type of the vehicle to be measured, for example, can be entered. Control commands can also be entered via the input device  7 . The control device  7  is preferably coupled with an output device  8 , with the help of which measurement values and/or status information, for example, can be displayed. The control device  6  can be coupled with an interface device  9 , where the input and output of data can be carried out with the help of this interface device  9 .