Patent Publication Number: US-2021181337-A1

Title: Distance measurement system for a vehicle

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority from German Patent Application No. 102019219619.5, which was filed on Dec. 13, 2019, and is incorporated herein in its entirety by reference. 
     Embodiments of the present invention relate to a distance measurement system as well as to a vehicle having a distance measurement system. Generally, the invention is in the field of vehicles, such as mobile construction or work machines, elevating work platforms, fire engine turntable ladders or the same. 
     BACKGROUND OF THE INVENTION 
     From WO 2017/178737 A1, a control panel for an elevating platform with protection against crushing of the operator is known. The elevating work platform includes a work cage with rails provided thereon, wherein a control panel for controlling movements of the elevating work platform is arranged on the rails. A system by which it can be determined whether the control panel is mounted on the rails, whether a person is in the work cage next to the control panel or leans in the direction of the control panel or whether an obstacle exists, is arranged on the control panel. For this, the system includes at least one transmitter and one receiver of waves, wherein the system detects an interference by an external object in that the receiver receives the waves emitted by the transmitter by reflection from the interfering object. 
     It is a disadvantage of the known system that depending on the arrangement of the control panel in the work cage, not all objects in the surroundings of the work cage are detected and hence collisions with obstacles that have not been detected can result when the work cage is moving. Further, erroneous measurements can occur, in particular with transmitters and receivers oriented towards the top as, for example, rainwater may not run off but remains on the sensor heads. This can have the effect that a person leaning in the direction of the control panel may not be detected or may not be detected correctly and might get caught. 
     SUMMARY 
     An embodiment may have a distance measurement system for a vehicle, wherein the distance measurement system includes a measurement unit for non-contact determination of a distance to an object, and the measurement unit includes: a sensor unit configured to emit a signal and to receive a signal reflected by the object; an evaluation unit determining a distance between the measurement unit and the object from the signals emitted and received by the sensor unit; and a signal deflection apparatus arranged in the area of the sensor unit with a reflector surface deflecting the signal emitted by the sensor unit in a direction deviating from the propagation direction of the signal, in particular at an essentially right angle to the propagation direction of the signal, in the direction of the object. 
     Another embodiment may have a vehicle with an inventive distance measurement system. 
     According to another embodiment, a measurement unit for a distance measurement system for non-contact determination of a distance to an object may have: a sensor unit configured to emit a signal and to receive a signal reflected by the object; and a signal deflection apparatus arranged in the area of the sensor unit with a reflector surface deflecting the signal emitted by the sensor unit in a direction deviating from the propagation direction of the signal, in particular at an essentially right angle to the propagation direction of the signal, in a direction of the object. 
     Another embodiment may have a vehicle with a measurement unit for a distance measurement system for non-contact determination of a distance to an object including a sensor unit configured to emit a signal and to receive a signal reflected by the object; and a signal deflection apparatus arranged in the area of the sensor unit with a reflector surface deflecting the signal emitted by the sensor unit in a direction deviating from the propagation direction of the signal, in particular at an essentially right angle to the propagation direction of the signal, in a direction of the object; or a vehicle with a measurement unit for non-contact determination of a distance to an object including a sensor unit configured to emit a signal and to receive a signal reflected by the object; an evaluation unit determining a distance between the measurement unit and the object from the signals emitted and received by the sensor unit; and a signal deflection apparatus arranged in the area of the sensor unit with a reflector surface deflecting the signal emitted by the sensor unit in a direction deviating from the propagation direction of the signal, in particular at an essentially right angle to the propagation direction of the signal, in the direction of the object, wherein the vehicle is a mobile construction or work machine. 
     Embodiments of the present invention provide a distance measurement system for a vehicle, wherein the distance measurement system comprises a measurement unit for non-contact determination of a distance to an object, and the measurement unit comprises: 
     a sensor unit configured to emit a signal and to receive a signal reflected by the object; 
     an evaluation unit determining a distance between the measurement unit and the object from the signals emitted and received by the sensor unit; and 
     a signal deflection apparatus arranged in the area of the sensor unit with a reflector surface deflecting the signal emitted by the sensor unit in a direction deviating from the propagation direction of the signal, in particular at an essentially right angle to the propagation direction of the signal, in the direction of the object. 
     The signal emitted by the sensor unit is reflected by the object (obstacle) when impinging on the same. Here, it is advantageous to deflect the signal emitted by the sensor unit in its propagation direction, in particular when a distance to an object above the distance measurement system is to be determined. For this, the sensor unit itself does not have to be oriented toward the top (in the direction of the object or obstacle to be detected) but in horizontal direction, i.e. the sensor unit is oriented such that the signals are emitted in horizontal direction by the sensor unit. Thereby, for example, (rain) water can run off and does not remain on the sensor unit. Hence, even in rainy weather, functionality and availability of the sensor unit are not limited. 
     An evaluation unit consisting of a computing unit, for example a microcontroller system, calculates a distance value from the signals emitted and received by the sensor unit and the result is advantageously output and passed on to a control, for example a vehicle or machine control, for example per field bus message (CAN, LIN or the same). Based on the measured distance value, the control can then react accordingly, for example stop, decelerate, etc., movements of the vehicle or the machine. If the distance measurement system is used, for example, in an elevating work platform or a fire engine turntable ladder, the control can be a safety-oriented control. 
     Advantageously, the signal deflection apparatus is arranged directly in front of the sensor unit or at a (defined) distance to the same in measurement direction, i.e. in transmitting and receiving direction. In distance measurement, the distance to the reflector surface deflecting the signal emitted by the sensor unit in the direction of the object or obstacle has to be included in the calculation. However, this is known when designing the distance measurement system and can be stored (for example saved) as a constant in the evaluation means or the sensor unit. In the context of the present invention, propagation direction of the signals emitted and received by the sensor unit means the measurement direction, or in other words the respective directional vector of the emitted or received signal. The signal deflection apparatus deflects the emitted signal in the direction of the object such that the directional vector of the signal impinging on the object is essentially perpendicular to the directional vector of the signal emitted by the sensor unit. Here, the sensor unit transmits and receives the signal in opposite directions. 
     According to embodiments, the reflector surface deflects the signal reflected by the object in a direction deviating from the propagation direction of the reflected signal, in particular at an essentially right angle to the propagation direction of the reflected signal, in the direction of the sensor unit. The signal deflection apparatus deflects the signal reflected by the object in the direction of the sensor unit such that the directional vector of the signal reflected by the object is essentially perpendicular to the directional vector of the signal received by the sensor unit. 
     According to embodiments, the distance measurement system includes a measurement module on or in which the measurement unit is arranged. Advantageously, the measurement module is configured in a longitudinal manner, for example as measurement beam which can have a round, square, rectangular or similar cross-section. Here, the measurement unit can be arranged on the measurement module, for example screwed, adhered or stuck thereon or the same. However, an integrated variation is also possible, i.e. the measurement unit or parts thereof, for example the evaluation unit and/or the sensor unit are incorporated or integrated in the measurement module. 
     According to embodiments, the signal deflection apparatus is mounted on the measurement unit or on the measurement module in a releasable manner, in particular releasable without any tools. The signal deflection apparatus can, for example, be clicked (click connection), clamped, stuck or mounted by means of Velcro connection or the same on/to the measurement unit or the measurement module. This is particularly advantageous when the signal deflection apparatus is defect as the same can then be exchanged easily and possibly without any tools. However, it is also possible that the signal deflection apparatus is screwed onto the measurement unit or the measurement module. 
     According to embodiments, the signal deflection apparatus includes a holder and a reflector unit that are connected to each other in a releasable manner, in particular releasable without any tools. The holder can also be mounted on the measurement unit or on the measurement module in a releasable manner, however, a fixed mounting on the measurement module or a holder mechanism preformed at the housing of the measurement module is possible, i.e. a holder mechanism integrated in the housing of the measurement module. The reflector unit including the reflector surface is also arranged on the holder in a releasable manner. The reflector unit can, for example, be clicked (click connection), clamped, stuck or mounted by means of a Velcro connection or the same. If the reflector unit is, for example, defect, the same can advantageously be released from the holder and exchanged easily. 
     According to embodiments, the reflector unit is arranged on the holder in a slidable manner, in particular slidable to the side. Thereby, the measurements direction of the distance measurement can be changed easily or the measurement direction of the measurement module or the measurement unit can be changed and thereby be adapted to the conditions of the vehicle or the machine. If, for example, a measurement module having two measurement units is to be used on the vehicle or the machine for two different measurement directions, for example, in the first measurement unit, the reflector unit can be slid directly in front of the sensor unit, such that the signal emitted by the sensor unit of the first measurement unit is deflected in the direction of the object or the obstacle, whereas in the second measurement unit the reflector unit is slid towards the side, such that the signal emitted by the sensor unit of the second measurement unit is not deflected (and accordingly has a different measurement direction). 
     According to embodiments, the holder comprises a lock for locking the reflector unit and/or the reflector unit  52  comprises a lock for locking the same. Thereby, automatic release of the reflector unit during operation of the vehicle or the machine is advantageously prevented. Advantageously, the lock can be operated easily and quickly with the touch of a finger, such that the reflector unit can be released from the holder and exchanged easily. Here, the lock can be arranged on the holder and/or on the reflector unit. 
     According to embodiments, the signal deflection apparatus comprises at least one opening or at least one gap between the holder and the reflector unit. Thereby, advantageously, for example no (rain) water remains in the signal deflection apparatus, in particular when the measurement unit or the distance measurement system is oriented such that an object (obstacle) above the distance measurement system is to be detected. For this, the sensor unit is oriented in horizontal direction, i.e. the sensor unit is oriented such that the signals are emitted and received in horizontal direction by the sensor unit, whereas the reflector unit of the signal deflection apparatus can act like a funnel, such that without at least one opening or without at least one gap, (rain) water can remain therein and would affect functionality and availability of the sensor unit. 
     According to embodiments, the sensor unit comprises a sensor head configured to emit the signal and to receive the signal reflected by the object. For this, a sensor head is possible, which can both emit as well as receive (with time offset) signals, or a sensor head having a separate transceiver, wherein no switching between transmitting and receiving is needed. 
     According to embodiments, the signals emitted and received by the sensor unit are ultrasound signals, microwave signals or optical signals. Radar signals or the same are possible as microwave signals, for example, light (for example infrared light) or laser or the same can be used as optical signals. The reflector surface of the signal deflection apparatus is configured in an opal, glossy, mirrored or similar manner according to the used measurement technology (signals). 
     According to embodiments, the measurement module includes several measurement units that can be electrically connected to one another by means of a cable connection. Here, the measurement units can be arranged in or on the measurement module, for example screwed, adhered, stuck to/on the same or also completely or partly integrated in the same, i.e. measurement units or parts thereof, such as evaluation units and/or sensor units are incorporated or integrated in the measurement module. Evaluation units, each consisting, for example, of a computing unit, such as a microcontroller system, calculate distance values from the signals emitted and received by the sensor units, and the result is output or passed on to a control, for example a vehicle or machine control, via a cable connection, for example per field bus message (CAN, LIN or the same). Here, the measurement units can perform a respective distance measurement either simultaneously or offset in time, i.e. one after the other or in temporal sequence or in a priority-based manner. Due to the fact that the measurement units are electrically connected to one another and can hence exchange data via field bus messages, it is possible that both simultaneous as well as time-offset or priority-based (i.e. for example depending on the number or arrangement of the measurement units) measurement or measurements of distances is/are performed. 
     According to embodiments, the measurement units of a measurement module have a common evaluation unit. If, for example two or three measurement units are arranged in or on a measurement module, it is possible that the sensor units are electrically connected to a common evaluation unit. Thereby, the measurement module as a whole becomes more cost-effective since electronic components can be saved. However, it is also possible that more than two or three measurement units are electrically connected to a common evaluation unit. It is advantageous and cost-effective when all measurement units arranged in or on a measurement module are electrically connected to the same evaluation unit of a measurement module. 
     According to embodiments, the measurement units are arranged on or in a measurement module such that the same determine distances to the same object or distances to different objects. The measurement units can be arranged in the same detection direction in or on a measurement module, such that distances either to the same object (obstacle) or distances to different objects (different obstacles) are determined. On the other hand, the measurement units do not necessarily have to be arranged in the same detection direction in or on a measurement module, but can have different detection directions and can hence determine distances to different objects (different obstacles). 
     According to embodiments, the distance measurement system includes several measurement modules that can be connected to one another by means of an electric cable connection or a wireless connection. Measurement modules can be arranged by means of an electric cable connection or a wireless connection in a cascaded manner in a distance measurement system, i.e. the same can be connected in series or can be connected to one another such that the distance measurement system consists of two or several measurement modules. The measurement modules or the measurement units or the evaluation units arranged in the measurement units can communicate to one another and can output distance values or pass them on to a control, for example to a vehicle or a machine control, for example by means of a field bus system (CAN, LIN or the same). For this, advantageously, the field bus system of the distance measurement system is electrically connected to the field bus system of the machine or the vehicle. This cascading is advantageous since the distance measurement system can be designed or configured with a very flexible structure or design. The same can be individually adapted to different vehicles or machines, i.e. such that, for example, the number of measurement modules or the length of the cable connections between the individual measurement modules can be configured freely and very flexibly. 
     If a wireless connection of the measurement modules is used, a measurement module includes at least one accumulator to ensure the current supply of the individual measurement units. Here, the individual measurement modules in a distance measurement system communicate by means of radio signals, for example WLAN, Bluetooth or the like. A wireless connection of the measurement module is advantageous with regard to an attachment to a vehicle or a machine, since an even more flexible adaptation to the conditions of the vehicle or the machine is possible, for example because no cable routing is needed. 
     The measurement modules can perform a respective distance measurement either simultaneously or offset in time, i.e. one after the other or in temporal sequence or in a priority-based manner. Due to the fact that the measurement modules are electrically connected to one another (either wired or wireless) and can hence exchange data among each other, it is possible that both simultaneous as well as time-offset or priority-based (i.e. for example depending on the number or arrangement of the measurement modules) measurement or measurements of distances is/are performed. 
     A further embodiment relates to a vehicle having a distance measurement system as outlined above. According to embodiments, the vehicle is a mobile construction or work machine. This can, for example, be construction vehicles, construction machines (excavators, cranes, . . . ), road construction machines (finisher, feeder, presser (roller), . . . ) or other mobile vehicles or machines. In this context, vehicles used at airports are also possible (for example mobile stairways pulled up to a parking airplane, etc.). The inventive distance measurement system can be used in all vehicles and machines approximating an obstacle or object during operation where it is important to prevent collision, or where a distance to an obstacle or object is to be measured, detected or determined. 
     According to embodiments, the vehicle is an elevating work platform or a fire engine turntable ladder with a work cage movably arranged on the vehicle, wherein at least one distance measurement system is arranged on the work cage. The elevating work platform is, for example, a work platform having a telescopic crane mechanism or a so-called scissor stage. Fire engine turntable ladders frequently comprise a work cage moved together with the extendable ladder. Here, the distance measurement system is located at any position on the work cage and measures distances to one or several objects or obstacles. 
     According to embodiments, the work cage arranged movably on the vehicle comprises a floor and railings, and at least one distance measurement system is arranged on the floor and/or the railings or integrated in the floor and/or in the railings. If the at least one distance measurement system is mounted on the floor and/or the railings or the rails, this mounting can be releasable, in particular releasable without any tools, for example by means of a Velcro connection, a clamping connection, a plug apparatus, an adhesive apparatus or the same. Alternatively, the distance measurement system can, for example, be screwed, riveted or mounted in any other way on the floor and/or on the railings or the rails. Arranging the at least one distance measurement system or parts of the at least one distance measurement system in the floor and/or in the railings or the rails is possible. The individual parts of the railings or the rails of the work cage can be considered as measurement module in which the measurement units or at least parts thereof are incorporated or integrated such that further mechanisms in the form of separate measurement modules can advantageously be omitted. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the present invention will be detailed subsequently referring to the appended drawings, in which: 
         FIG. 1 a,b    is a schematic illustration of the functional principle of the distance measurement system; 
         FIG. 2  is a schematic illustration (section) of a measurement module; 
         FIG. 3  is a schematic illustration of a measurement module; 
         FIG. 4  is a schematic illustration of a reflector unit and a holder; and 
         FIG. 5  is an elevating work platform with a distance measurement system. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Before embodiments of the present invention will be discussed in more detail below based on the figures, it should be noted that equal elements are provided with the same reference numbers, such that the description of the same is inter-applicable or inter-exchangeable. In distance measurements, the distance to the reflector surface  55  that deflects the signal S 11  emitted by the sensor unit  30  in the direction of the object  70  or the obstacle  70  has to be incorporated in the calculation. Since this distance value should be known when designing the distance measurement system  10 , the value can, for example, be stored (for example saved) as a constant in the evaluation means  40  or the sensor unit  30 . 
       FIGS. 1 a  and 1 b    show a distance measurement system  10 , each in a schematic illustration, to explain the basic mode of operation of the distance measurement. The distance measurement system  10  comprises a measurement unit  20  for non-contact determination of a distance to an object  70  (an obstacle, such as a wall, a roof, a roof overhang or the same), wherein the measurement unit  20  essentially comprises a sensor unit  30 , an evaluation unit  40  and a signal deflection apparatus  50 . The sensor unit  30  is configured to emit a signal S 11 , S 12  and to receive a signal S 21 , S 22  reflected by the object  70 . The evaluation unit  40  determines a distance between the measurement unit  20  and the object  70  from the signals S 11 , S 12  emitted by the sensor unit  30  and the signals S 21 , S 22  received by the same, for example based on the signal runtime, i.e. based on the time difference between the emitted signals S 11 , S 12  and the received signals S 21 , S 22 . The signal deflection apparatus  50  arranged in the area of the sensor unit  30  comprises a reflector surface  55  that is at an angle of approximately 45° to the sensor unit  30 , such that the signal S 11  emitted by the sensor unit  30 , when impinging on the reflector surface  55 , is deflected in a direction deviating from the propagation direction of the signal S 11 , in particular at an essentially right angle to the propagation direction of the signal S 11 , in the direction of the object  70 . Here, the angle of the reflector surface  55  to the sensor unit  30  can have a range of approximately 40° . . . 50° or a range of approximately 30° . . . 50°. When impinging on the object  70 , the deflected signal S 12  is reflected at the same, and when impinging on the reflected surface  55 , the same is reflected in a direction deviating from the propagation direction of the reflected signal S 21 , in particular at an essentially right angle to the propagation direction of the reflected signal S 21 , in the direction of the sensor unit  30 . Now, the signal S 22  deflected by the deflector surface  55  impinges on the sensor unit  30  and is received there by a sensor head  31  (not illustrated). The sensor head  31  can be configured to emit the signal S 11  and to receive the signal S 22  reflected by the object  70  and deflected by the signal deflection apparatus  50 . Here, both a sensor head that can both emit as well as receive (with time offset) signals or a sensor head having a separate transceiver is possible, wherein no switching between transmitting and receiving is needed. For example, an ultrasound sensor head can be used, where the ultrasound waves propagate in a “lobe-shape”, as illustrated schematically in  FIG. 5 . This “lobe-shaped” propagation is of less significance in signal propagation on the short path (distance) from the sensor unit  30  or the sensor head  31  to the reflector surface  55 , as the ultrasound lobe could not propagate in its cross-section on the short path (distance) such that this has a negative influence on a measurement, i.e. a distance measurement. 
       FIG. 2  shows a schematic illustration (section) of a measurement module  60  with a measurement unit  20  partly arranged therein. The measurement module  60  is configured in a longitudinal manner, for example as measurement beam and formed with a rectangular cross-section according to  FIG. 2 . The evaluation unit  40  and the sensor unit  30  (with the sensor head  31 ) are arranged in the measurement module  60 , i.e. incorporated or integrated in the measurement module  60 . The signal deflection apparatus  50  is arranged on the measurement module  60  in the area in front of the sensor unit  30 . As illustrated in  FIG. 2 , the signal deflection apparatus  50  consists of a holder  51  and a reflector unit  52  which are connected to one another in a releasable manner, in particular releasable without any tools. Here, the holder  51  is mounted either in a fixed manner or also in a releasable manner on the housing of the measurement module  60 . The reflector unit  52  including the reflector surface  55  is arranged on the holder  51  in a releasable manner, for example plugged onto the same. 
       FIG. 3  shows a schematic illustration of a measurement module  60  having two measurement units  20  partly arranged therein. Plug connectors are arranged on the lateral ends of the measurement module  60 , in order to arrange further measurement modules  60  by means of an electric cable connection in a cascaded manner, i.e. to connect them in series (daisy chain) or to connect them to one another, such that a distance measurement system  10  of two or several measurement modules results. Similar to the description of  FIG. 2 , the measurement module  60  is configured in a longitudinal manner and formed with a rectangular cross-section. Here, it should be noted that the measurement module  60  can also have a round, square or similar cross-section. The measurement module  60  has, for example, a length of 60 cm, or a length in a range of approximately 40 cm . . . 100 cm or in a range of approximately 40 cm . . . greater than 100 cm. The evaluation unit  40  and the sensor unit  30  (not illustrated in  FIG. 3 ) are arranged in the measurement module  60 , i.e. incorporated or integrated in the measurement module  60 . The signal deflection apparatus  50  consisting of a holder  51  and a reflector unit  52  connected to one another in a releasable manner, in particular releasable without any tools, is arranged on the measurement module  60 . The signal deflection apparatus  50  comprises an opening  53  or a gap  53  between the holder  51  and the reflector unit  52 , such that, for example no (rain) water remains in the signal deflection apparatus  50  when the measurement unit  20  or the distance measurement system  10  is oriented such that an object  70  above the distance measurement system  10  is to be detected. 
     If, for example, an ultrasound sensor head is used for distance measurement, the ultrasound waves normally propagate “in a lobe shape” as, for example, illustrated schematically in  FIG. 5  and already briefly described above with respect to  FIG. 1 . The “lobe-shaped” propagation of the ultrasound waves has to be considered when arranging the measurement units  20  in or on a measurement module  60 , since signal overlapping might occur (if, for example, the distance between two measurement units  20  is too low), i.e. that the emitted and/or reflected ultrasound lobes of two measurement units  20  can overlap. 
     Such overlapping of ultrasound lobes occurs (as shown in practical tests), for example starting from a measurement distance (between measurement unit  20  and object  70 ) of approximately 1.80 m, when two adjacent measurement units  20  are arranged at a distance of approximately 40 cm in or on a measurement module  60 . On the other hand, the “lobe-shaped” propagation of ultrasound waves has the advantage that there is a large detection area of the distance measurement system  10 , i.e. as many objects  70  or obstacles  70  as possible are detected by the distance measurement system  10 . 
       FIG. 4  shows a schematic illustration of a reflector unit  52  and an allocated holder  51 . According to  FIG. 4 , the holder  51  is illustrated as releasable unit having a click mechanism  57  by means of which the holder  51  can be attached to the measurement module  60  in a releasable manner. The holder  51  has an opening  56  in the center, which is needed for the sensor unit  30  (not illustrated in  FIG. 4 ). The sensor unit  30  emits the signal S 11 , S 12  through the opening  56  and receives the signal S 21 , S 22  reflected by the object  70 . The reflector unit  52  includes the reflector surface  55  and can be arranged on the holder  51  in a releasable manner. For this, the reflector unit  52  comprises two lateral grooves  59  directed to the inside, whereby the reflector unit  52  can be plugged onto the lateral edges  58  of the holder  51 . As already illustrated in  FIG. 3 , the signal deflection apparatus  50  comprises an opening  53  or a gap  53  when the holder  51  and the reflector unit  52  are connected to one another. 
       FIG. 5  shows an elevating work platform  1  with a crane mechanism  2  movably arranged on the elevating work platform  1  and a work cage  80 , wherein the work cage  80  can be moved by means of the crane mechanism  2 . The work cage  80  comprises a floor  81  and railings  82  as well as a control panel  83  by means of which a person  71  in the work cage can move the work cage. Further, a distance measurement system  10  consisting of two measurement modules  60  is arranged on the work cage  80  of the elevating work platform  1 , more exactly on the railings  82 . The distance measurement system  10  or the two measurement modules  60  detect or measure distances to two objects  70  as illustrated in  FIG. 1 , to a wall  70  and to a roof overhang  70 . The distance measurement system  10  or the measurement modules  60  mounted to the railings  82  or to the rails  82  according to  FIG. 5  can be mounted in a releasable manner, in particular releasable without any tools, for example by means of a Velcro connection, a clamping connection, a plug apparatus, an adhesive apparatus or the same. Alternatively, the distance measurement system  10  or the measurement module  60  can also be screwed, pivoted or mounted otherwise on the railings  82  or the rails  82 . Arranging the distance measurement system  10  or parts of the distance measurement system  10  on or in the floor  81  and/or in the railings  82  or the rails  82  is also possible. 
     It would also be possible that further measurement modules  60 , which extend the distance measurement system  10 , are arranged on the elevating work platform  1  according to  FIG. 5 , since all measurement modules  60  arranged on the elevating work platform  1  can be connected to one another by means of an electric cable connection or a wireless connection. This means further measurement modules  60  can be arranged on the work cage  80 , for example in or on the floor  81 , in or on the rails  82 , but also in or on the crane mechanism  2  or other movable machine parts. A “virtual space” results by a respective arrangement of one or several measurement modules  60  or one or several distance measurement systems  10  on the vehicle or on the machine, which means that, for example, all or at least most areas around the work cage  80  of an elevating platform  1  are detected by the measurement modules  60  or distance measurement systems  10  (if several separate systems  10  are arranged on the vehicle or on the machine). This is advantageous since, for example, a work cage  80  of an elevating work platform  1  can move in all possible directions, wherein obstacles  70  cannot be seen or detected by the person standing on the work cage  80 . The measurement module  60  can be arranged freely in their orientation on the machine  1 , i.e. perpendicularly or horizontally as well as in all directions. There are no limitations. All measurement modules  60  can be electrically connected to one another and can hence form an entire distance measurement system  10 . Due to the fact that the measurement modules  60  can be arranged in a cascaded manner, i.e. connected in series (daisy chain) or connected to one another by means of an electric cable connection or a wireless connection, it is possible that the measurement modules  60  or the measurement units  20  or the evaluation means  40  arranged in the measurement unit, communicate with one another by means of a field bus system (CAN, LIN or the same), and/or output or pass on distance values to a control, for example to a vehicle or machine control. For this, advantageously, the field bus system of the distance measurement system  20  is electrically connected to the field bus system of the machine or the vehicle. Cascading measurement modules  60  as described above is advantageous since the distance measurement system can be designed or configured with a very flexible structure. The same can be individually adapted to different vehicles or machines, i.e. the number of measurement modules  60  or the length of the cable connections between the individual measurement modules can be designed freely and very flexibly. If a wireless connection of the measurement module  60  is used, the individual measurement modules  60  in a distance measurement system  10  communicate with one another via radio signals, for example WLAN, Bluetooth or the like. A wireless connection of the measurement modules  60  is advantageous with regard to an attachment to a vehicle or a machine, since here, for example, a more flexible adaptation to the circumstances of the vehicle or the machine is possible because no cable routing is needed. 
     The above-described embodiments are merely illustrative for the principles of the present invention. It is understood that modifications and variations of the arrangements and the details described herein will be apparent to others skilled in the art. It is the intent, therefore, that the invention is limited only by the scope of the appended patent claims and not by the specific details presented by way of description and explanation of the embodiments herein. 
     While this invention has been described in terms of several advantageous embodiments, there are alterations, permutations, and equivalents which fall within the scope of this invention. It should also be noted that there are many alternative ways of implementing the methods and compositions of the present invention. It is therefore intended that the following appended claims be interpreted as including all such alterations, permutations, and equivalents as fall within the true spirit and scope of the present invention.