1. Choice of a point and time of landing in view of an opportunity of ekranoplane to arrive in the specified point in time, and the calculation of the trajectory of ASP descanting.
2. Fulfillment of standard operations of ASP entrance in atmosphere and braking up to subsonic speed.
3. Coordinated control of ASP absolute motion and ekranoplane absolute motion with the purpose of maintenance of their mutual close parallel motion with a difference of altitudes about 200m and mutual mismatch in horizontal plane no more than 100m.
4. Relative motion control system loops closure, and reduction of mutual mismatch of two craft in horizontal plane up to several meters and further - up to 2σ=1m, reduction of difference in their flight altitudes up to 3-5 m at the expense of ASP descending.
5. Engaging the mechanism of docking, exact positioning of mating elements by a special quick-response automatic system, the mating (partial or complete), the attracting of ASP to ekranoplane.
6. The completion of ASP docking with ekranoplane, centering of ASP on the landing deck of ekranoplane, blocking of mating elements, ekranoplane returning to the port.
At a stage of aerodynamic braking the inertial system should keep the correct information on angular orientation and supervise a trajectory of motion, not admitting accumulation of too large errors in definition of position to the moment of the beginning of GPS receiver functioning. After ending of this stage the trajectories of rapprochement of ASP and ekranoplane should be synthesized in view of estimations of their actual positions. It is necessary for it the switching on and further continuous work of the noiseproof radio channel for data exchange between ASP and ekranoplane, uniting their control system in an integrated complex.
On a stage of ASP and ekranoplane rapprochement the high accuracy of definition of coordinates (at a level 2σ=50-100 m) of both flying craft in Earth frame and body frame is necessary. The main contribution to its maintenance should give GPS.
At a final stage of ASP and ekranoplane docking the high accuracy of holding of a difference of linear coordinates on all three axes is required within the limits of shares of meter and difference of speeds - within the limits of shares of m/sec. Besides, in this case it is required a precision (within the limits of 20") of stabilization of pitch, roll and yaw of both flying craft. On the stage of direct approach (before contact) movement of both craft should be close to synchronous flat-parallel. At low power of the landing engine, it is possible to ensure such a mode only within the limits of a short time interval, in this connection the mating system should be rather high-speed.
According to the fulfilled researches, the most suitable method of reception the information on parameters of linear and angular relative motion of two wing craft is the use of digital television optical navigating system. In this case at a final stage of approach when ASP relative altitude become equal 5m the errors of relative motion parameters measuring will be no more than 2σ=10cm in horizontal plane, 2σ=10cm in altitude and 2σ=20' in angles.
With research of the requirements to motion control systems at docking and opportunity of their performance it is important to have good examples in the form of actualized prototypes.
The landing system of ASP《Space Shuttle》for long term of operation has proved the high efficiency and reliability, however it is not completely automatic, and the large sizes of a special landing strip used at landing of《Space Shuttle》admit rather significant errors of control in longitudinal and transversal planes. Nevertheless, this experience is extremely important for forming the concept of landing on ekranoplane at all stages of such landing, except finishing one.
The automatic landing system of ASP《Buran》in potential, probably, is capable to ensure higher accuracy of landing on stationary airdrome on account of more advanced means of forming the controlling radio field, however, its numerous landing beacons and other special means of radionavigation must be placed in large territory and cannot be belongings of one ekranoplane.
It is clear, that the special integrated system of navigation and motion control is necessary for ASP landing on ekranoplane, the main position gauges of which on both craft should be GPS receivers at stages of approach and rapprochement and precise microwave or optic systems of local navigation at the stage of docking directly. The experience of the development of modern landing systems for deck aircraft seems to be very useful. In a part of other components (means of inertial navigation. Air Data System, altimeters) basically the requirements at a level《Space Shuttle》and《Buran》, extrapolated in view of modern achievement in the appropriate technologies, are generally kept. The important modern experience of construction of an onboard control complex of ASP has been gained in Japan during preparation and realization in 1996 the experiment ALFLEX (Automatic Landing Flight Experiment) within the framework of the national program of ASP creation.
The system of a mutual motion control at craft docking has to be an automatic control multi-dimension digital system, It is clear that for arising the quality and reliability of control it is expedient to consider both craft as elements of closed loops of such a dynamic system. A generalized scheme of the system is shown at Fig.10.
As it follows from the diagram, the docking process of ASP and ekranoplane must be operated under motion control complex which involves closed control loops for ASP and ekranoplane absolute motion with controlled values matrices λASP and λEKR consequently, relative motion closed control loop with the controlled value matricesλASP - λEKR and an additional open loop channel for local shifting the docking element along and thwart landing deck with output coordinates matrix λM. The correct interaction of these four interconnected muitidimenslonal loops and control algorithms optimization in each controlled linear and angular coordinate is a complicated problem of analysis and modeling.
The ASP absolute motion control loop for landing trajectory will be initiated by preparing the landing onto ekranoplane. The required landing trajectory is determined by synthesizer priory and described by the given functional matrix λ(t). The navigation system of ASP generates an estimation of an actual motion trajectory λASP(t). The residual λ(t) - λASP(t) is used in control law; it determines the action produced by steering mechanisms. A control law optimization allows to reduce a norm of the matrix λ(t) - λASP(t) and to provide the rather high accuracy in holding the required landing trajectory. At the final stage of approach the errors of relative positioning may be within 2-3m, and the local positioning of matting elements (especially, nose element) could have reduced the errors to 30 cm.
The ekranoplane absolute motion control system has to ensure the required trajectory of its flight to the point of proposed landing of ASP, approach. to this point from given direction at required moment of time, and the capture of ASP by the shot-range optic navigation system. The ekranoplane altitude at ASP landing must be strictly stabilized. Then the approaching of ASP and ekranoplane in vertical plane and lateral shift compensation will occur with a great influence of ASP and their approach in longitudinal plane can influence of ASP and their approach in longitudinal plane can be corrected by ekranoplane speed control.
