Patent Publication Number: US-2013231856-A1

Title: Method and device for fast localization of objects (e.g. vehicles) moving toward a target object

Description:
With an object moving through space, which is to move to a certain target position in order to execute an action, there is the problem that the localization and the feedback indicating that the object has arrived at the target position (e.g. in order to authorize the relevant action) are too slow. 
     The determination of the position is carried out by means of a measurement of the distance from the object to location beacons, the spatial location of which have been determined. The measurement method used between the object and the position beacon can, for example, be a time measurement, a measurement of the time difference, a distance measurement, a measurement of the signal strength, or a combination thereof. The position determined in this manner can be converted to GPS coordinates. 
     This position is subsequently processed in a server-side business application, in order to make a position dependent decision (has, e.g. the object arrived at the target position and is the action permissible at this position?) 
     In a harbor, the moving object may, for example, be a mobile crane, and the action would be the lifting of a container. At the moment in which the mobile crane is located above the container, the taking hold of, and lifting of the container is authorized. 
     The disadvantage with this prior art is, however, that the time required for the localization of the object being driven, including the calculation of the current position and the supplying of the determined position data to the business application is afflicted with a time period of, e.g. 3.5 seconds or more. 
     This is not sufficient, however, for providing the object with a fast feedback and for authorizing the action that is demanded thereof (e.g. the lifting of a container), without noticeably delaying the process. 
     The server calculates the position of the vehicle by means of the location readings. This position is checked in the business application against the current work order of the vehicle, and the corresponding feedback (e.g. the position has been reached, the container is to be deposited, is authorized) is transmitted to the vehicle. Because of the system taking part in the procedure, and the time required for the transmission of the data, a delay of over 10 seconds may occur before the process (loading operation) is completed. 
     In other words, very long time periods are required for the calculation and the decision, which poses a disadvantage. 
     The invention therefore assumes the objective of significantly reducing the duration of the localization confirmation and the authorization of an action for an object that is moving. 
     In order to attain this proposed objective, the invention is characterized by the technical teachings of Claim  1 . 
     The substantial characteristic of the invention is that the target coordinates, to which the object being driven is to move, are already known prior to executing the work order (e.g. for a harbor system). If, for example, a certain container is detected in row 5, column 10 and elevation 8, then its coordinates (e.g. in the form of GPS coordinates) are precisely known in the harbor system and the business application. 
     In this case, it is known that the operator of the harbor crane or similar item is not in possession of the absolute GPS position, but instead, a relative, logical object position (e.g. row 5, column 8, elevation 0); he therefore receives logical coordinates. 
     In so doing, the target coordinates of the target object are stored in the server in advance, such that both the logical position as well as the GPS coordinates are available in the server. 
     The GPS coordinates in the server are converted to distance values, such that said GPS coordinate-defined distances to the stationary location beacons are calculated as a geometric distance in the harbor space. These distance values are converted in the respective localization procedure from the determined measured values (e.g. time measurement, measurement of the time difference, distance measurement, measurement of the signal strength, or a combination thereof; see above). 
     The measured values calculated in this manner are provided to the object being driven, which has received a work order pertaining thereto, instructing said object to move to the position in column 10, row 8, and elevation 5, for example, in order to pick up a container there. At the same time, the location readings of the distance to the position beacon, or to the reference points at the target position that have been previously calculated as permanently established values, are transmitted to the object being driven. 
     After the transmission, the object being driven continuously determines the distances to the stationary radio beacon, wherein the current distances are no longer transmitted to the stationary (e.g. harbor) server for processing and deciding, but instead, the object being driven itself determines the deviation, or the error between the current locations and the location of the target. 
     The computed error is a measurement for the distance from the object to the target coordinates. It is important that the result of the error calculation be a value (e.g. a scale) which one can use for comparison, readily and without extensive computing operations. 
     The size of the error is determined by means of a standard mathematic formula for geometric errors, e.g. in the form of a mean square error (MSE) or the root of the mean square error (RMSE). The method for determining the error is not decisive. In this respect, it is important that the calculation method not require a great deal of computing, and that the error decreases as the target position is approached. 
     Examples for the error calculation are given below: 
     MSE: 
     mi . . . Location reading from the object to a location beacon
 
pi . . . pre-calculated target location reading from the object to a location beacon
 
N . . . Number of measurements
 
       MSE=sum1  . . . N (( mn−pn )2)/ N    
     RMSE: 
       RMSE=SQRT(MSE) 
     For the decision, of whether the object has arrived at the target, the error is checked against a threshold value. The respective selected threshold value is dependent on the respective measurement method, the error method and on the required precision of the positioning at the target. 
     Therefore, a decentralized measurement of the distance from the object being driven to the stationary beacon is made, and a local comparison with the transmitted data of the target object is carried out in the object being driven itself. It is important that the object itself, as soon as the calculated error is less than a previously defined threshold, can decide that the target position has been reached. 
     This results in there no longer being a need for external server assistance, and no need for lengthy computing time, because the actual decision takes place in the moving object itself, specifically by means of the calculation of the error between the readings for the current position, and the target readings at the target position. 
     It is therefore decisive with the invention, that from a known target GPS position of the moving object, readings are derived through a reverse calculation, and that furthermore, the (distance) error is continuously calculated in the object being driven itself, and continuously compared there to the threshold value. 
     The advantage of the invention is that at the point in time of the decision for the execution of the work order in the vehicle being driven, an external computing assistance from the stationary server, which is associated with a computing intensive business application, is no longer required. 
     The data are pre-processed to the extent that the entire distance measuring and the decisions pertaining thereto take place in a decentralized manner in the object being driven, and are carried out in real-time. 
     EXAMPLE 
     Procedural Steps 
     Step 1: The business application decides that the work order is to be sent to the operator of the moving object. 
     Step 2: The target location readings (at the target position) are calculated in the stationary server from the GPS coordinates of the target position. 
     The work order therefore consists of a portion being for the operator, and a portion being for the system in the vehicle, which regulates the execution of the work order. 
     Step 3: The work order is sent to the vehicle. 
     Step 4: The operator receives, in his display, only the notification that he is to drive to lane 35, row 18 and elevation 5 in the grid system of the harbor, in order to pick up a container there. 
     Step 5: The operator begins driving as soon as the work order from step 4 has been received, without waiting for further information, or downloading further data from a server, which in some circumstances would require significant computing time. 
     Step 6: At the same time, readings for the reference points are continuously carried out in the object being driven, and the current error (between the measured location values and the target location values) is calculated. 
     Step 7: As soon as the object being driven has arrived at the location of the target object, all comparison values from the error distance measurement according to step 6 approach zero. 
     As soon as the threshold value for the error is no longer exceeded, the operator receives a visual confirmation that he has arrived at the target object. 
     Step 8: At the same time, the corresponding action (e.g. picking up the container) is authorized. An electronic monitoring regarding the loading operation takes place therefore, in order to prevent the operator from picking up the wrong container. 
     With the invention, the normally occurring procedural time periods are avoided: a decision is made quickly, in a decentralized manner, and the delay for the authorization is significantly shortened thereby. It is decisive that all time-critical calculations are made in real-time in the object being driven. 
     The normal procedural time periods are shortened, which basically take place as follows: 
     A vehicle is equipped with a tag for localization. This tag measures the distance to the reference points and transmits the information via radio signals to a server. Said server calculates the position of the vehicle from the location readings. This position is checked against the current work order of the vehicle in the business application, and a corresponding feedback (e.g. position arrived at, deposit container, is authorized) is transmitted to the vehicle. 
     Due to the system taking part in the procedure, and the transmission times for the data, a delay of over 10 seconds may occur before the procedure (uploading operation) is completed. 
     In order to avoid this undesired lengthy computing time, the invention now provides that the work order, together with the target position, and the pre-calculated location readings at the target position, are delivered in advance to the object being driven at a certain point in time. There is therefore sufficient time in which to execute the necessary computing operations at an external server. In executing the work order, all of the data necessary for a fast decision are already present in the moving object. 
     As a result of the decentralized decision making taking place in the moving object, substantial procedural times are eliminated accordingly. The extensive computations are removed from the time-critical portion of the procedure, and executed prior to starting the procedure (work order). One already prepares the decision long in advance and then decides on a short-term basis. The extensive computations therefore no longer take place during the critical phase. This method therefore functions, when prior to the starting of the procedure, it is already known what the moving object is supposed to do, even though the object still requires a long time in which to do so. 
     If for example, one drives a vehicle at 30 km/h, and said vehicle is to cover a distance of 2 km, one has enough time during the driving period of 10 minutes, in which to prepare the work order and the ensuing decision, with all of the calculations pertaining thereto, during the driving period. As a result, the operator receives authorization for the picking up or depositing of a container as soon as the moving object arrives at its target, without having to wait for a calculation and authorization provided by an external server. 
     This is a substantial difference with respect to the prior art, because with the prior art, it has been known until now that the calculation of the coordinates is executed based on the location readings of the moving object, and all of the computation, or respectively, decisions resulting therefrom, are first carried out when the moving object has arrived at the target object. The invention avoids this. 
     It is important with the invention that the error determination routine carried out in the moving object runs for a time period that is as short as possible, i.e. it does not require an extensive computing time, because otherwise, the advantages of the prior art would still exist, in that time would be used for calculations, which one is actually trying to avoid. The algorithm for the error calculation can be made such that it is dependent on the application, and on the type of distance measurement. For this reason, there are different possibilities for executing an error correction routine of this type. 
     (See Above Examples: MSE, RMSE) 
     The error calculation takes place, however, in the moving object, and for this reason it must be possible to do so with a limited computing expenditure. 
     It is important that the present invention is not limited to one position, but can simultaneously process numerous target positions, or a zone. It is therefore decisive that, due to the short computing times, multiple targets, or even zones, can also be computed and approached. By way of example, the harbor crane could also receive a work order for picking up any one of 3 available containers, and then the other two remaining containers, successively. 
     The invention, however, is not limited to moving objects in the form of a harbor crane or similar item. The moving object can also be a person with a portable display, who carries out certain work orders. Likewise, numerous people can work with the method according to the invention. 
     The invention may be used on a planar surface (2D) or spatially (3D). 
     The subject matter of the invention for the present invention is derived not only from the subject matter of the individual Claims, but also from the various combinations of the individual claims. 
     All of the information and characteristics disclosed in the documents, including the abstract, in particular the spatial design depicted in the drawings, are claimed as substantial to the invention, insofar as they are novel, individually, or in combination, with respect to the prior art. 
    
    
     
       In the following, the invention shall be explained in greater detail based on drawings depicting only one means of execution. In so doing, further characteristics and advantages substantial to the invention are to be derived from the drawings and the descriptions thereof. 
       They show: 
         FIG. 1 : a schematic depiction of the method, 
         FIG. 2 : the same depiction as that in  FIG. 1 , with a depiction of the determined location readings, 
         FIG. 3 : a schematic depiction of the method according to  FIGS. 1 and 3  with other devices, 
         FIG. 4 : a recording as a specific moment of the determination of the distance to the individual radio beacon during the driving operation of the moving object, 
         FIG. 5 : a process design for data collection between the server and the moving object, 
         FIG. 6 : a flow chart for the execution of the method. 
     
    
    
     In a spatially fixed, defined space  28 , e.g. a harbor space, radio beacons  4 ,  5 ,  6 ,  7  are disposed at regular intervals on the border of the space  28 , which can execute distance measurements on an object  1  moving in the space  28 . The object  1  has a particular current GPS position  21  and moves, by way of example, in the direction of the arrow  2  toward a target object  3 . The target object  3  has, for example, the GPS position  31 . 
     According to  FIG. 2 , a continuous measurement takes place between each radio beacon  4 - 7  with respect to the object  1  moving in the direction of the arrow  2 , by means of which the actual location readings  12 - 15  are generated. 
     At the same time, however, the target position of the target object  3  is known, in which the target location readings  8 - 11  of the target object  3  are disposed. 
     The detection of the target coordinates of the target object  3  by means of downloading the target location readings  8 - 11  can be carried out a long time prior to the execution of a work order, and a long time prior to the start-up of the object  1 . 
     According to  FIG. 3 , a continuous distance measurement and downloading of the actual location readings  12 - 15  takes place in relation to the moving object  1 , wherein said location readings are sent via a communication connection  16 , which is preferably wireless, to a stationary reader  17 , which is connected to a stationary server  18 . 
     The server  18  is connected to a device for position determination  19 , in which the current actual coordinates of the moving object  1  are calculated, which are sent to the business application  23  via a data link  20  in the form of position data  22 . 
     Said business application is a software program, which is administered in the server  18 , and which receives data from a localization device  26  via a data link  27 . 
     All current location positions (target location readings  8 - 11 ) for each arbitrary target object  3  in the space  28  are stored in the localization device  26 . 
     Thereby, a work order  24  for the moving object  1  is uploaded in the business application  23 , and stored, via a data link  25 , in the business application  23 . 
     The current position of the object  1  in the space is thus determined in the formula according to  FIG. 3 , and furthermore, the distance is from the object  1  to the target object  3  is determined thereby. 
     These data are sent to the reader  17  via the data link  20 , which transmits the work order  24  generated by the business application  23  to the moving object  1  via the communication connection  16 . 
     At the point in time of the transmission of the work order, the error table depicted in  FIG. 4 , by way of example, applies. It can be seen therein that the target object with respect to the radio beacon  4  is at a distance of 70 m, with respect to the radio beacon  5 , is at a distance of approx. 80 m, and with respect to the radio beacons  6  an  7 , is at distances of 20 and 30 m respectively. 
     Similarly, this table indicates that the current position of the moving object  1  is at a distance of 10 m from the radio beacon  4 , 80 m from the radio beacon  5 , 20 m from the radio beacon  6 , and 30 m from the radio beacon  7 . 
       FIG. 5  again shows in a schematic manner the generation of the work order  24  in the stationary server  18 , wherein the work order  24  is converted using the current GPS coordinates of the target object  3  in a preliminary calculation step  29  to distance values, and said distance values are sent to the moving object  1  as target location readings  8 - 11  via the communication connection  16 . 
     For this reason, a continuous detection of the current actual location readings  12 - 14 , and a comparison with the target location readings  8 - 11  of the target object, takes place in the moving object  1 , and from this an error calculation step  30  is triggered, in which the deviations between the actual position and the target position are calculated according to  FIG. 4 . 
     With reference to  FIG. 4 , the error with respect to the radio beacon  4  is given a difference value of 60 m for this reason, with respect to radio beacon  5 , a difference error of zero, and with respect to radio beacon  3 , also a difference error of zero, and with respect to radio beacon  4 , also a difference error of zero. 
     This means that the moving object  1  must only move in a certain direction with respect to radio beacon  4 , in order to bring the existing difference error with respect to a predetermined threshold value to within the proximity of zero. 
       FIG. 6  shows a flow chart for the method according to the invention, wherein, based on the business application  23 , first the target location readings for the target object are detected as GPS positions  31 , and at the same time the current GPS position  21  of the object  1  is known, and it is decided in a preliminary calculation step  29  which moving object is to receive the work order  24 . 
     This is transmitted to the moving object  1  via the communication connection  16  and displayed on a display screen  33 . 
     The operator can, therefore, begin driving, and by means of observing the display screen  33 , immediately begin to search for the target object, as the moving object  1  first moves with a large error deviation toward the target object  2 , while said error, however, approaches zero as the target object  3  is approached. 
     In block  35 , an optical signal is provided to the operator, indicating the arrival at the target object  3 , and in block  36 , he receives the authorization for the execution of the work order. 
     A difference calculation, between the target location readings  8 - 11  of the target object and the actual location readings  12 - 15  of the moving object, takes place continuously in the error calculation step  30 , in the moving object itself, and based on this, a threshold value is created. As soon as this threshold value approaches zero, the decision step  32  is triggered. This activates an electronic checking routine via a data link, which decides whether or not the work order should now be executed, and then authorizes said work order. 
     
       
         
           
               
             
               
                   
               
               
                 Reference Symbol Key for the Drawings 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
            
               
                 1 
                 object 
               
               
                 2 
                 direction of arrow 
               
               
                 3 
                 target object 
               
               
                 4 
                 beacon 1 
               
               
                 5 
                 beacon 2 
               
               
                 6 
                 beacon 3 
               
               
                 7 
                 beacon 4 
               
               
                 8 
                 target location reading p1 
               
               
                 9 
                 target location reading p2 
               
               
                 10 
                 target location reading p3 
               
               
                 11 
                 target location reading p4 
               
               
                 12 
                 actual location reading m1 
               
               
                 13 
                 actual location reading m2 
               
               
                 14 
                 actual location reading m3 
               
               
                 15 
                 actual location reading m4 
               
               
                 16 
                 communication connection 
               
               
                 17 
                 reader 
               
               
                 18 
                 server 
               
               
                 19 
                 position determination 
               
               
                 20 
                 data link 
               
               
                 21 
                 GPS position (of object 1) 
               
               
                 22 
                 position data 
               
               
                 23 
                 business application 
               
               
                 24 
                 work order 
               
               
                 25 
                 data link 
               
               
                 26 
                 localization device 
               
               
                 27 
                 data link 
               
               
                 28 
                 space 
               
               
                 29 
                 preliminary calculation step 
               
               
                 30 
                 error calculation step 
               
               
                 31 
                 GPS position (of target 3) 
               
               
                 32 
                 decision step 
               
               
                 33 
                 display screen (in object 1) 
               
               
                 34 
                 drive search 
               
               
                 35 
                 arrival 
               
               
                 36 
                 execution of work order