Abstract:
A stabilization apparatus and a method for controlling stability of a suspended platform are described. System includes pivotally mounted gyro with an axis of rotation substantially orthogonal to the suspended platform&#39;s plane and adapted with the use of servos to convert precession of the gyro into a tilt of the platform. Described stabilization apparatus works in combination with the platform&#39;s main propulsion system. Apparatus is capable of providing high level stability for pitch, roll and yaw angles. 
     Platform&#39;s orientation control can be optimized by changing modes of operation to control at any time any two of three angles defining position of the suspended platform. 
     It would be advantageous to use such stabilized suspended platform as a camera pod and also in the flying models industry. Idea can be accommodated in the personal transportation vehicles, robotic vehicles both in airspace and outer space.

Description:
BACKGROUND 
       [0001]    Matter in the nature can be found in the form of solid, gas, fluid or plasma. This invention will be dealing with solid bodies suspended in non solid environment or vacuum. The brute force gyro is a large gyro used to directly stabilize a craft that it is mounted on. Unstable environment is environment in which random and unpredictable forces are affecting matter. The suspended platform or the flying platform is a solid object with the propulsion system in the form of a reactionary lifting means. The reactionary lifting means, the lifting means or the lift system is a lift and movement providing apparatus in some form of a fan, a ducted fan, a rocket motor, a jet motor or any other non-direct solid to solid contact. The suspended platform plane or the flying platform plane is the horizontal plane defined by the body of the platform in the state of suspension and motionless in relation to the ground, generally orthogonal to the thrust vector of the platform as a means of suspension. 
         [0002]    Stability of a suspended solid body in a non-solid, unstable environment in reference to another solid body is difficult to achieve. For example, the case of a flying platform and specifically the platform where the center of gravity coincides with the thrust vector. In this invention to the flying platform is attached a stabilization apparatus, heart of which is the brute force gyro pivotally mounted with two degrees of freedom in the pitch and roll axel. In this embodiment vector of momentum of the gyro is kept substantially perpendicular to the plane of the flying platform. This is achieved by varying the thrust vectors of the platforms lift system that in turn will force the brute force gyro to precess in required direction. Pitch and roll of the platform is controlled by at least two servos, mounted nominally perpendicular to each other and in the plane of the flying platform. Servos are placed between the body of the flying platform and the spin axis of the gyro. Overall, the system provides a level of stability for pitch and roll comparable to the accuracy of the servos used. Yaw of the flying platform will be slightly affected by the effort of holding pitch and roll stable but depending on the system that can be minimized or virtually eliminated. 
         [0003]    Prior Art shows many ways of controlling stability of a suspended solid body, most of them are involving changing the direction or magnitude of the vector of thrust, some are using brute force gyros for more direct control. Invention described here is based on the latter method therefore prior art described here concentrates on controlling stability with the use of a large gyro. Generally stabilization of a flying platform is achieved by holding the spin axis of a gyro in near vertical position and along with it plane of the platform is kept horizontal. Most similarities of mentioned idea and this invention are visible in U.S. Pat. No. 3,985,320. Disadvantage of described system is a necessity of holding the craft horizontally and a need for physical shifting ballast. Some devices have gyroscopic air foil attached to the lifting fan. Good example of such device can be found in U.S. Pat. No. 5,421,538. Here gyroscopic device is placed in the air stream of the lifting fan and has slight tilting abilities to work against the crafts fuselage with the use of servos. Control range of the gyroscopic device is limited in the described patent. Thrust vector for lift and stabilizing momentum from the gyro are not independent, thereby difficult to interact with each other. Another example of prior art is U.S. Pat. No. 6,789,437. Device described here is gimbals mounted, with servos purposely precessing the gyro to the required position. Device controls pitch and yaw. 
       SUMMARY OF THE INVENTION 
       [0004]    It is described here how to accurately control angular stability of a solid body, with the use of servos, connected to another solid body suspended in a reference to a third solid body. In the embodiment described here it would be controlling angular stability of a flying platform in reference to the ground. The flying platform would be connected by servo systems to a mechanical damper which in this case is a brute force gyro. The brute force gyro is mounted inside the apparatus with two degree of freedom, one for pitch and other for roll. In this embodiment the axis of rotation of the brute force gyro is constantly kept in a near perpendicular position to the flying platforms plane. The reason for that is need for maximum range of precession of the brute force gyro&#39;s axis when righting moment is applied to the axis. Righting moment is created by one servo motor mounted between the body of the stabilization apparatus and the rotational axis of the brute force gyro. Precession of the rotational axis of the brute force gyro in the perpendicular plane to the righting moment is allowed and followed by the other servo. Prolonged precession movement exhausts mechanical inertia storage capacity of the brute force gyro and affects the yaw, so in order to recover lost capacity, brute force gyro&#39;s axis has to be brought back to perpendicular position in relation to the plane of the suspended platform. That can be done using suspended platform&#39;s propulsion system, purposely creating disturbance that precesses the brute force gyro back to its original position. In the final account propulsion system of the flying platform is used to move or stabilize the craft as required and the gyro stabilizing apparatus is fulfilling role of the mechanical filter. Combinations of the gyro stabilizing apparatus and flying platform&#39;s propulsion system allows for usage of slow response reactionary engines like fans or jets and achieve high quality rigid-like mechanical response of the flying platform. Complicated electromechanical systems like deflectors and spoilers designed for quick reaction can be removed and replaced with simpler lesser quality thrust means coupled with the gyro based stabilizing apparatus. The operation of both systems coupled together will be explained in grater clarity in the next sections. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0005]      FIG. 1  is a perspective view of a stabilizing apparatus shown as a part of a flying platform. Included are angular displacements of a gyro and a platform. 
           [0006]      FIG. 2  is a top view of a stabilizing apparatus shown as a part of flying platform. All major mechanical modules are shown including directions of gyro&#39;s precession. 
           [0007]      FIG. 3  is a block diagram of a control system. Included are interconnections between a flying platform and a stabilizing apparatus. 
           [0008]      FIG. 4  is a graph of instabilities and distribution of forces of a flying platform without a use of a stabilizing apparatus. 
           [0009]      FIG. 5  is a graph of instabilities and distribution of forces of a flying platform with use of a stabilizing apparatus. 
           [0010]      FIG. 6  is a cross sectional view of an embodiment one of a gyro&#39;s pivotal mounting inside stabilization apparatus. 
           [0011]      FIG. 7  is a cross sectional view of an embodiment two of a gyro&#39;s pivotal mounting inside stabilization apparatus. 
       
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0012]      FIG. 1  shows a diagrammatic representation of the present invention. Flying platform  33  includes four lifting devices: front left ducted fan  31 , front right ducted fan  37 , rear left ducted fan  10  and rear right ducted fan  39 . Also devices to detect flying platform&#39;s  33  tilting are shown as pitch gyroscope  15  and roll gyroscope  16 . In the center of the flying platform is shown stabilization apparatus  32 . It includes brute force gyro  30  mounted in the spherical compartment  12 . Sphere  12  pivotally mounted in the stabilizing apparatus  32  includes studs  36  which are collinear with the brute force gyro&#39;s  30  rotational axis.  FIG. 6  and  FIG. 7  will explain in grater detail structure of sphere  12 . Parts of the stabilizing apparatus  32  are servo  34  designed to induce pitch of the flying platform  33  and servo  38  designed to induce roll of the same. Both servos are rigidly connected to studs  36 . Rigid connection is accomplished by using flexible linkages connected to the top and the bottom of stud  36 . Greater detail will be shown on  FIG. 6  and  FIG. 7 . Stabilizing apparatus  32  does not necessarily have to be mounted in the center of flying platform  33  to accomplish its function. It is obvious that part of the flying platform  33  systems will also be yaw control but for better clarity it is not described here.  FIG. 1  also shows illustratively roll angle β of flying platform  33  and corresponding to it precession angle α of brute force gyro  30  enclosed within sphere  12 . Meanings of both angles will be explained on  FIG. 2   
         [0013]      FIG. 2  and  FIG. 3  explain the control systems of the flying platform  33  working in conjunction with attached to it stabilizing apparatus  32 . To explain transfer functions of the logic block  18  shown on  FIG. 3 , lifting devices of the flying platform  33  are denoted by letters a to d also servos are marked as X and Y. To illustrate mechanical function of brute force gyro  30  mounted within sphere  12  large arrows  13  and  14  are shown on  FIG. 2 . Sphere  12  will precess in the direction of arrow  13  if servo  34  will apply force to stud  36  through linkage  35 . Similarly if force to stud  36  is applied by servo  38  through linkage  11 , sphere  12  will precess in the direction of arrow  14 . Angle α from  FIG. 1  is illustrated on  FIG. 2  as arrow  14  and is generated by force of servo  38  to create roll angle not shown on  FIG. 2 . It is visible that to roll the flying platform  33  set of lifting devices  37  and  39  on the right side and set of lifting devices  31  and  10  on the left side along with the servo  38  shall be used. To pitch the flying platform correspondingly set of lifting devices  31  and  37  in the front and set of the lifting devices  39  and  10  in the back along with servo  34  will be used. System described here can work not only to induce pitch and roll but also can prevent it if the flying platform  33  would be experiencing instabilities coming from the external environment. 
         [0014]      FIG. 3  is showing block diagram of the stabilizing apparatus  32  in the flying platform. Servo  38 , servo  34  and logic module  18  are located on the stabilizing apparatus. Diagram of  FIG. 3  shows interconnections between stabilizing apparatus and components of the flying platform  33 . Control  17  that could be a joy-stick module, receiver or any other device governing tilt control, sends a roll requirement to the roll gyroscope  16 , that signal gets also to the logic module  18 , gyro  16  sends signal to servo  38  to activate it and start roll, the same signal from gyro  16  goes to the logic module  18 . Similar situation takes place with the pitch signal. It leaves control  17  enters the pitch gyroscope  15  and logic module  18 . Pitch signal from gyroscope  15  activates the pitch servo  34  and enters the logic module  18 . Control  17  also sends the thrust signal to the logic module  18 . Logic module  18  is in the heart of the stability apparatus  32 , it sends the signals to the primary pitch, roll and thrust devices, in this case these are lifting devices  31 ,  37 ,  39  and  10 . Transfer functions  19  shown in its most simple but descriptive form govern all the lifting devices. 
         [0015]      FIG. 4  illustrates stability performance of a flying platform without use of described stabilizing apparatus  32 . First waveform illustrates random instability created by the environment. In order to simplify the explanation instability is shown as a constant force attempting to roll the flying platform illustrated by the step function  20 . Lifting devices of the flying platform will respond with a little lag and overshoot demonstrated by waveform  21 . Corresponding change in the roll angle β is shown on the third waveform  22 . Described response is well known in the prior art and its magnitude depends on the quality and complexity of the lifting devices. Using reaction devices like fans or jets may make deviation in β angle smaller but it will never be eliminated. 
         [0016]      FIG. 5  describes stability performance of the flying platform  33  with stabilizing apparatus  32  attached to it. The same as in the previous case first waveform  23  illustrates instability caused by the environment. Second waveform  24  illustrates response of the lifting devices like fans or jets. There is visible lag and overshoot. Third waveform  25  illustrates response of the stabilizing apparatus  32 . Fourth waveform  26  is the sum of waveforms  24  and  25 . It is shown that reaction force Fr (Fr=Fs+Ff) is equal in magnitude and directly opposed to Fi. Therefore Fr=−Fi. Pitch and roll of the flying platform will be minimized to within the measurement error of the stabilization system, which is predominately determined by the accuracies of the major components, the two sensing gyros  15  and  16 , as well as the two servos  38  and  34 . In this case it is illustrated by the waveform  27  showing the β angle change. In the same time a angle of the precession of the sphere  12 , housing brute force gyro  30 , will change in similar fashion as shown by waveform  28 . 
         [0017]    Note that lag and overshoot of the primary lifting devices  31 ,  37 ,  39  and  10  is minimized by the servos  34  and  38 . If the inherent lag of lifting devices is small, the size of the brute force gyro  30  can be reduced. There is a proportional relationship between the size of the brute force gyro  30  and the efficiency of the lifting devices  31 ,  37 ,  39  and  10 . Purposeful overshoot of the lifting devices  31 ,  37 ,  39  and  10  in the effort to stabilize flying platform  33  is used to return the rotational axis of the brute force gyro  30  and along with it stud  36  to its original prior of instability position in relation to the flying platform  33 . The home position of the brute force gyro  30  in this embodiment is substantially orthogonal to the plane of the flying platform  33  regardless of its position in relation to the ground. 
         [0018]      FIG. 6  is the cross-sectional view of the representation of the stabilizing apparatus  32 . In this embodiment brute force gyro  30  is mounted inside the sphere  12  with the rotational axis mounted collinear with the studs  36 . Prior art describes in great detail ways of powering the brute force gyro  30 , so it is not described here. Way of suspending pivotally and with low friction is unique. The air film  29  between the sphere  12  and the stabilizing apparatus  32  is created. It is enabled in the similar form as the ball joints are designed, only in place of liquid lubricant, air film is used. Its use provides required two degree of freedom for the sphere  12 , large range of movement and low friction. Means of producing air film  29  are described by prior art. As shown earlier, servo  34  will work against the brute force gyro  30  via the linkage  35  tilting the stabilizing apparatus  32  and in the same time precessing axis of the brute force gyro  30  in the plane perpendicular to the plane showing the cross-sectional view of  FIG. 6 . 
         [0019]      FIG. 7  presents cross-sectional view of the representation of another embodiment of mounting sphere  12  within the stabilizing apparatus  32 . This involves using omni-directional wheel  40  similar to one described by U.S. Pat. No. 3,789,947. Omni-directional wheel  40  allows having free movements of sphere  12  in two directions with minimal friction. It would also be advantages to connect servo  34  and servo  38  to some of the omni-directional wheels  40 . This function would replace linkage  35  and linkage  11 . Third servo, orthogonal to servo  34  and servo  38 , could be used to gain full three dimensional orientation control of brute force gyro  30 . 
         [0020]    This configuration has an advantage of easy disconnecting suspended platform  33  from the sphere  30  if required. Also there is no need for studs  36 , so brute force gyro  30  could be enclosed inside the perfect sphere  12  and capable to move with no hard-coded stop. That would allow for capability of changing the modes of angular control of the suspended platform  33  by reprogramming the system. It means that apparatus would be capable of directly controlling at any time any two of three orthogonal angles defining position of flying platform  33  in the space. These angles may or may not be yaw, pitch and roll. 
         [0021]    Stabilization apparatus  32  comprises at least two servo systems with the vectors of force substantially perpendicular to each other, working simultaneously to control orientation of the flying platform  33 . Operational envelope of each servo in part affects operational envelope of the other servo, so it is necessary to build into the logic module of the servos that relationship. 
         [0022]    Described embodiment of stabilization apparatus  32  shows pitch and roll control, it is understood that part of the propulsion system of flying platform  33 , not shown here, is also a yaw control and in case of using mounting configuration for brute force gyro  30  shown on  FIG. 7 , that angle can also be controlled. 
         [0023]    Obviously many modifications and variations of the present invention are possible in the light of above teachings. For example lifting devices can be jets, rocket motors, ducted fans, fans or other reactionary devices. Any number of lifting devices could be used. Also servos can be electrically or hydraulically operated. Feedback loops can vary as a result of using number of different possible transfer functions. Described invention proposes to stabilize pitch and roll but another possible embodiment can control in similar way pitch and yaw or roll and yaw or any two of three orthogonal angles selected to define orientation of flying platform  33  in the space. 
         [0024]    It is possible to use many technological concepts to accomplish described here results. It is therefore understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.