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CROSS-REFERENCES TO RELATED APPLICATIONS 
     This application claims the benefit of the U.S. Provisional Application No. 61/444,331, filed on Feb. 18, 2011, and of the German patent application No. 10 2011 004 400.0 filed on Feb. 18, 2011, the entire disclosures of which are incorporated herein by way of reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to a door system actuated by an actuator for an aircraft or spacecraft and to an aircraft or spacecraft having at least a door system of this type. 
     Although it can be used in any field, the present invention will be described in greater detail in relation to an aircraft or passenger aircraft. 
     BACKGROUND OF THE INVENTION 
     In current door systems in aircraft, door systems are conventionally used which, for opening and closing the respective door of the aircraft, comprise a manual actuating device for normal use and a pneumatic actuator, for example having a gas pressure cylinder, for emergency use. The conventional manual actuating device is not easy for the operating personnel, in particular the flight attendant, to handle. In the event of strong winds or gusts, the handling of the manual actuating device is also sometimes dangerous for the operating personnel. 
     In addition, the pneumatic actuator specifically for emergency use involves a high level of maintenance. This high level of maintenance results for example from the necessary regular checking of the gas pressure of the gas pressure cylinder of the pneumatic actuator. Furthermore, there is the problem of leakage when a pneumatic actuator is used. This entails increased maintenance outlay and therefore increased expenditure. 
     Furthermore, the conventional pneumatic actuators, including the conventional manual actuating devices, are not equipped to provide a monitoring or error message in the case of a fault or disturbance. For example, if the gas pressure drops below a required minimum level, the conventional pneumatic actuators are not equipped to report a fault of this type. In this case, it is conventional to await the monitoring intervals. However, if a fault occurs at the start of an interval of this type, the door is not equipped with a ready-to-use emergency actuating system for a relatively long period of time. 
     The commercial aircraft Airbus A380 is fitted with electrically actuated door systems, in which electrical actuators integrated in the doors are used for conventional opening and closing of the door for normal use, for example for boarding and disembarkation of the passengers, and also for emergency opening of the door in an emergency. In order to achieve high operational reliability in an emergency, when the connections of the door to the rest of the aircraft could be damaged, emergency electricity supply devices and control devices are provided in the doors themselves, which leads to greater complexity during production and greater weight. While door systems of this type require continuous maintenance, the removal and fitting of components in the event of a fault is very expensive. 
     SUMMARY OF THE INVENTION 
     It is thus an idea of the present invention to provide a less expensive and lighter means of actuating the door of an aircraft with great ease and safety. 
     Another idea is to provide a means of actuating the door of an aircraft which is easy to maintain, and in particular easy to replace in the event of damage. 
     A door system for an aircraft or spacecraft is accordingly proposed, having a door and an actuator for actuating the door. The actuator comprises an actuator drive which moves the door in relation to the aircraft or spacecraft, a detection device which determines movement information of the door and/or of the actuator, an actuator control unit which controls the actuator based on the movement information, and an actuator housing which surrounds the actuator drive and the actuator control unit. 
     Movement information is understood to be information characterising a present state of movement of the door, for example a current opening angle, a pivot speed or pivot acceleration of the door or of an object coupled to the door, such as the actuator actuating the door. In addition to the actuator having the actuator control unit capable of controlling the actuator, and the detection device, the proposed door system comprises a complete control loop which, by monitoring the movement by means of the movement information, allows the movement of the door to be precisely controlled, irrespective of environmental conditions such as strong winds and gusts. It is therefore easy and safe to handle. The fact that the door system comprises said components in a common actuator housing allows the actuation of the door without a separate control unit, which not only means a lower constructional weight, smaller overall size, and lower production costs, but also allows greater reliability. 
     The proposed door system is thus adapted for conventional opening and closing of the door for normal use, for example for boarding and disembarkation of the passengers, and in principle also for emergency opening of the door in an emergency. In addition to a conventional manual actuating device of the door, the door system can thus also replace the conventional pneumatic actuator, for example with a gas pressure cylinder, or it can be used in combination with a pneumatic actuator of this type, the increased reliability of the door system reducing the likelihood of the pneumatic actuator having to be used, and thus allowing a high safety level overall. 
     The door system according to the invention also involves a particularly low level of maintenance, since the components comprised in the actuator housing can be replaced together in a simple, quick manner, and consequently saves costs. Owing to the compact construction, the door system can in addition be adapted particularly easily to different types of aircraft. 
     An aircraft or spacecraft is also proposed which comprises at least a door system of the type according to the invention, the door of the door system being, for example, a passenger door in an outer skin of the aircraft or spacecraft. 
     Advantageous configurations and improvements of the invention are found in the dependent claims. 
     The actuator drive preferably comprises an electric motor, since the door system can thus actuate the door particularly precisely and can be provided in a particularly economical, compact and low-weight manner. Alternatively, a hydraulic actuator drive can, for example, be provided. 
     According to a preferred development, the door system according to the invention comprises a door frame for receiving the door in a closed state and a door fixing arm which can be driven by the actuator drive and is pivotally fixed to the door frame about a first hinge and pivotally fixed to the door about a second hinge. Owing to the direct drive of the door fixing arm, which connects the door and the frame to each other, no parts of considerable size are required for the force transmission from the actuator to the door, which saves weight and costs. 
     According to a preferred development, the actuator is arranged at the first hinge and formed to apply a torque to the door fixing arm in relation to the door frame, about the first hinge. The arrangement at the door frame makes it possible to supply the actuator with electrical (optionally hydraulic) energy from outside the door, without supply lines between the door frame and the door being necessary. This means a lower level of complexity and higher operational reliability, since flexible supply lines are not required and the risk of damage to these supply lines is eliminated. Alternatively, the actuator can however also be arranged at the second hinge and formed to apply a torque to the door fixing arm in relation to the door, about the second hinge. This makes it possible, for example in the case of short line paths, to provide operational controls which are directly integrated in the door. 
     According to a preferred development, the actuator comprises a gear unit which is capable of reducing a rotational speed of the actuator drive by a predetermined ratio to achieve a pivot speed of the door fixing arm. 
     According to a preferred development, the actuator drive can be set in rotation by manual opening of the door. For example, the gear unit is configured so as to have a sufficiently low reduction ratio in such a way that human physical strength is sufficient to move the door while the actuator drive is also rotating. Manual actuation is thus also made possible, and the actuators, for example, electrical actuators, also does not cause any blockage of the shaft in the case of a manual actuation. 
     According to a preferred development, the actuator comprises an electromagnetic coupling which detachably couples the actuator drive to the door. This makes it possible to completely decouple the actuator drive from the door, in such a way that in an emergency, for example, the door can be opened manually without resistance and irrespective of a selected gear transmission ratio. The electromagnetic coupling is preferably arranged between the actuator drive and the gear unit. 
     According to a preferred development, the detection device comprises an angle sensor which detects an angle of the door system, for example an angle of a rotor of the actuator drive, an angle of a gear unit gear wheel, of the door, or of the door fixing arm. The angle sensor is preferably arranged between the gear unit and the door fixing arm in order to detect a pivot angle of the door fixing arm, for example in relation to the door frame or in relation to the door. 
     According to a preferred development, an operating device is also provided which is connected to the actuator control unit to operate the actuator. The operating device preferably comprises an output unit for outputting error messages of the door system. 
     According to a preferred development, a system test interface is also provided for the read-out of system test data by a test system of the aircraft or spacecraft. Interfaces of this type are, for example, referred to as BITE (Built-in test equipment) units. The BITE unit is, for example, capable of carrying out a fault diagnosis as a function of at least an angle signal and providing fault result data as a function thereof. The door system is thus advantageously capable of carrying out a fault diagnosis independently and providing the fault result data to the test system, that is to say to a higher-ranking entity, such as a central processing or control device. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the following, the invention will be described in greater detail on the basis of embodiments with reference to the accompanying figures. 
       In the figures: 
         FIG. 1  is an internal view, open in part, of an embodiment of a door system according to the invention, having an electrical actuator, in an aircraft; 
         FIG. 2  is a perspective view of the electrical actuator from  FIG. 1 ; and 
         FIG. 3  is a schematic block diagram of an embodiment of a door system according to the invention, which is coupled to further on-board systems of an aircraft. 
     
    
    
     In the figures, the same reference numerals denote like or functionally like components, unless stated otherwise. 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  shows an internal view of a portion of an outer wall  103  of a commercial aircraft  101 , in which outer wall a door frame  119  is arranged in addition to an outer wall window  150 . In the state shown, the door frame  119  is completely filled by a matching door  102 , into which a window  151  is also integrated. In order to illustrate the internal structure and the functionality of the door  102 , an inner lining, which typically covers the inside of a commercial aircraft door, has been omitted from the view. Also for clarity, a lever or grip for manual locking and unlocking, opening and closing of the door  102  is not shown. 
     Inside the door  102 , visible, intersecting reinforcing elements  152  give the door  102  mechanical stability. The door  102  is connected to the door frame  119  via a door fixing arm  118  which is pivotally fixed to the door frame  119  about a first hinge  121 , and pivotally fixed to the door  102  about a second hinge  122 . In addition to the door fixing arm, the suspension of the door  102  comprises further mechanical components such as rods  154  inter alia, which, for clarity, are only indicated in this case. These cause the angles of the first  121  and second  122  hinge to be dependent on one another when the door  102  is opened, in such a way that when the door  102  is opened, it performs an outward pivoting movement having only one degree of freedom. On the side of the door fixing arm  118  remote from the viewer, a gas pressure cylinder  156  is installed, which serves as a pneumatic actuator for opening the door  102  in an emergency. 
     An electrical actuator  104  is mounted at the first hinge  121 , which actuator is connected via an operating device feed line  302  to an operating device  398  attached near to the first hinge  121  in the inner lining of the outer wall  103 . In alternative embodiments, the operating device  398 , which, like the door  102 , together with the door frame  119 , door fixing arm  118  and actuator  104 , belongs to the door system  100 , is attached at other locations, for example on the opposite side of the door  102 . In the present case, the operating device  398  is as a touchscreen inserted into the inner lining of the outer wall  103 , which screen can be quickly and simply replaced in the event of damage. 
       FIG. 2  shows the electrical actuator  104  in greater detail, viewed from the side facing the door  102 , the door  102  itself being omitted in  FIG. 2 . The actuator  104  comprises a substantially cylindrical actuator housing  116 , in which a, for example, brushless electric motor  108  as an actuator drive, and an associated actuator control unit  112  are contained. Also located in the actuator housing  116  are an angle sensor  202 , for example a Hall sensor, and a detection device  110 , which during operation determines, by means of the angle sensor  202 , an angle of the electric motor  108 , and transmits this angle to the actuator control unit  112 . 
     A gear unit  124  for the gear reduction of the rotation of the electric motor  108  by a predetermined ratio is also located inside the actuator housing  116 . The actuator housing  116  having the gear unit  124  is connected to the door fixing arm  118  in a non-rotational manner by means of a fixing fitting  253 . A fixing lever  200  is flange-mounted in a non-rotational manner on an output shaft  252  of the gear unit  124  for the likewise non-rotational connection to the door frame  119 . The distal end of the gear unit output shaft  252  is mounted on the door fixing arm  118  in an upper bearing  251  which, together with a lower bearing  254 , is oriented along the pivot axis  250  of the first hinge  121  for the formation of said first hinge. 
       FIG. 3  is a schematic block diagram of an embodiment of a door system  100  according to the invention, which is coupled to further on-board systems  306 ,  308 ,  310  of an aircraft. The on-board systems  306 ,  308 ,  310  comprise a power supply switch  308  which is connected to the secondary energy supply network (not shown) of the aircraft and, when activated, connects a power supply feed line  314 , which leads to the actuator  104 , to this network, in such a way that the actuator  104  and the entire door system  100  is supplied with line voltage  315  of, for example, 115 VAC. 
     The on-board systems  306 ,  308 ,  310  also comprise a central door system  310  for the entire aircraft, which system provides a status signal  316  which indicates whether emergency slides provided at the doors have been deactivated. For example, for this purpose the central door system determines the state of activation of the emergency slides of all doors, or with less complexity, the state of activation of the emergency slide of only one individual door, preferably the door at the front left of the aircraft, which is typically opened at every landing for the disembarkation of passengers, in such a way that, in any case, the crew of the aircraft deactivate the emergency slide of this door before disembarkation. The power supply switch  308  is connected to the central door system  310 , for example via a data bus  399 , which for example operates according to the AFDX or ARINC  429  standard, and said switch is configured in such a way that it connects the line voltage  315  to the actuator  104  if the status signal  316  indicates that the emergency slides have been deactivated. 
     The on-board systems  306 ,  308 ,  310  also comprise a central maintenance system  306  of the aircraft, which is connected to a test data interface  113  of the actuator control unit  112  via a test data line  313  or a suitable data bus, in order to obtain maintenance information  312  such as error messages from the actuator control unit  112 , which information can be centrally used and processed in this central maintenance system. 
     The operating device  398  comprises a touchscreen which, for example, displays two buttons, “OPEN” and “CLOSE”, for opening and closing the door  102 . The control device  398  also comprises a sound generator  305  for outputting warning signals such as a warning sound before the door  102  is opened by the actuator  104 . The touchscreen of the operating device  398  is also formed to display diagnostic information about faults in a status display region  304 , which faults occur in the door system  100 , for example in the actuator  104  or in the operating device  398  itself. The operating device feed line  302  is designed to transmit data  303 , comprising error messages, operating commands and feedback, in both directions between the operating device  398  and the actuator control unit  112 . The operating device  398  is preferably also supplied with power by the actuator  104  via the operating device feed line  302 . 
     During operation, the door  102  is closed and the energy supply switch  308  is opened owing to the status signal  316  which is output accordingly, in such a way that the door system  100  is dead and consumes no energy. In this state, the gear unit  124  of the actuator  104  is decoupled from the electric motor  108  by the electromagnetic coupling. After landing, when the aircraft crew deactivate the emergency slide, for example at the door at the front left of the aircraft, the status signal  316  changes in such a way that the energy supply switch  308  closes and the actuator  104  is supplied with energy  315  via the actuator supply line  314 . The operating device  398  is also supplied with voltage via the operating device feed line  302 . The actuator control unit  112  moves into a defined initial state (reset), starts, and executes a test program which tests whether the actuator control unit  112  and the operating device  398  are functioning without problems. The result is displayed in the status display region  304  of the operating device  398  and transmitted to the central maintenance system  306  of the aircraft. 
     After a member of the aircraft crew has manually unlocked the door  102 , he/she presses the “OPEN” button on the touchscreen of the operating device  398 . This sends a corresponding signal to the actuator control unit  112 , whereupon the actuator control unit  112  controls the electromagnetic coupling  300  in such a way that it closes, and controls the electric motor  108  in such a way that it begins to rotate the door fixing arm  118  outwards in order to open the door  102 . The actuator control unit  112  preferably causes the operating device  398  to emit a warning signal via the sound generator  305  before the door  102  begins to move, accompanied for example by a warning notice in the status display region  304 . 
     During the rotation, the detection device  110  determines an angle signal of the angle sensor  202  and determines therefrom, as movement information of the door  102 , a current pivot position of the door  102  between the completely closed and completely open position, and provides the current pivot position to the actuator control unit  112 . If the current position corresponds to the completely open position, the actuator control device  112  stops the electric motor  108  and opens the electromagnetic coupling  300 . The actuator control device  112  preferably regulates the rotational speed of the electric motor  102  while the door  102  pivots into the open position according to a speed profile which is, for example, predetermined and stored in a memory (not shown) of the actuator control unit  112  in the form of an allocation which allocates a desired speed value to every pivot position of the door  102 . Furthermore, the actuator control unit can be formed to change the speed as a function of obstacles located in the pivot region, which obstacles are identified by monitoring the mechanical loading of the electric motor  108  or via specifically provided obstacle detectors, in order to prevent people from being injured. 
     If the operating personnel press the “CLOSE” button on the touchscreen of the operating unit, the actuator control unit  112  controls the sound generator  305 , the electromagnetic coupling  300  and the electric motor  108  in an analogous manner, in such a way that the door  102  is closed at a pivot speed which is also controlled, and after reaching the closed position, the electromagnetic coupling  300  is opened. 
     Although the present invention has been described on the basis of preferred embodiments, it is not restricted thereto, but can be modified in many different ways. For example, it is conceivable to provide a self-sufficient power supply composed of, for example, ultracapacitors, in order to be able to use the actuator  104  to open the door  102 , even in an emergency. In  FIG. 3  the angle sensor  202  is shown arranged at the gear unit  124 ; it can also be formed, for example, as a Hall sensor at the rotor of the electric motor  108 . 
     As is apparent from the foregoing specification, the invention is susceptible of being embodied with various alterations and modifications which may differ particularly from those that have been described in the preceding specification and description. It should be understood that I wish to embody within the scope of the patent warranted hereon all such modifications as reasonably and properly come within the scope of my contribution to the art.

Summary:
A door system for an aircraft or spacecraft having a door and an actuator for actuating the door. The actuator includes an actuator drive which moves the door in relation to the aircraft or spacecraft, a detection device which determines movement information of the door and/or of the actuator, an actuator control unit which controls the actuator based on the movement information, and an actuator housing which surrounds the actuator drive and the actuator control unit.