Abstract:
An improved method and apparatus for drawing energy management circles on electronic flight instrument system displays which includes a microprocessor for making several initial inquiries regarding the orientation of the circle with respect to the display and issuing write or don&#39;t write commands for each point on the circle without the need for individually analyzing each point as to whether it is located on the display screen.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to electronic flight instrument systems and more particularly relates to display devices showing energy management circles (EMCs), and even more particularly concerns an improved apparatus and method for displaying high quality energy management circles on electronic flight instrument systems (EFIS). 
     In today&#39;s aviation industry, it is desirable for aircraft owners and operators to minimize fuel consumption whenever possible. In the past, energy management circles have been proposed to assist pilots in performing economical aircraft descents. These energy management circles have also been proposed for providing pilots with crucial information regarding landing decisions. 
     While these energy management circles have been appreciated as sources of valuable flight information, there has existed some serious drawbacks in their implementation. Typically, the energy management circles have been annoying to pilots, due to the excessive &#34;ratcheting&#34; of the circles as they move across the display. 
     Consequently there exists a need for an improved method and apparatus for displaying energy management circles on EFIS displays which result in improved display characteristics. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide pilots with valuable information in a non-annoying fashion. 
     It is a feature of the present invention to include apparatus and method for displaying energy management circles on EFIS displays which are capable of quick generation and calculation. 
     It is an advantage of the present invention to eliminate the &#34;ratcheting&#34; of energy management circles across the EFIS displays. 
     The present invention provides a method and apparatus for generating energy management circles for EFIS displays which was designed to satisfy the aforementioned needs, achieved the above described objects, include the earlier mentioned features and produce the previously stated advantages. The invention is carried out in an &#34;intermediate inquiry-less&#34; system, in the sense that, the typical intermediate inquiries made regarding each intermediate line point have been eliminated. Instead, several initial inquiries about the orientation of the energy management circles in relation to the display are made, and then the intermediate line points are drawn without the need for individual, display or non-display, inquiries for each intermediate line point. 
     Accordingly, the present invention relates to an improved method and apparatus for drawing energy management circles on EFIS displays where the circles are drawn rapidly after several initial inquiries are made which relate to the circle orientation with respect to the viewing area boundaries. 
     Circles are drawn in response to changes in radius. The new circles must be clipped to the edge of the display to prevent unacceptable circle reflection on the display. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention may be more fully understood by reading the following description of the preferred embodiments of the invention in conjunction with appended drawings 
     FIG. 1 is an EFIS of the prior art which shows the display device and associated control hardware. 
     FIG. 2A is a display device of the prior art showing two energy management circles thereon where the intermittent lines represent portions of the circles not appearing on the display device. 
     FIG. 2B is a display device of the prior art (similar to 2A) except that the energy management circles have larger radii and are focused around a point outside the display device. 
     FIG. 3 is a flow chart of a prior art technique for determining energy management circles to be displayed. 
     FIG. 4 is a flow chart of a preferred embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Now referring to FIG. 1, there is shown a display system of the prior art, generally designated 100, which includes a display device 110 which may be a CRT, TFEL, LCD or any other video type display. Also included in system 100 is system processor 120 and system memory 118, both of which are well known in the art. In a preferred embodiment the system processor may be an Intel 80186 microprocessor. Input/output 116 which may be provided in several well known forms including but not limited to a flight management system or in cockpit pilot controls is also shown. The information from the flight management system or the cockpit controls are input through I/0 116 to system bus 122 where the information is then manipulated by display processor 114 and system processor 120 to generate display commands which are stored in the stroke memory 112 prior to being provided to display 110. Display processor 114 is well known in the art and in a preferred embodiment may be an Intel 80186 micro processor. 
     The I/O 116 is capable of defining energy management circles while the system processor 120 is capable of determining which segments of the energy management circles will be ultimately displayed by 110. 
     Now referring to FIG. 2, there is shown a display device 200 having an interior energy management circle 204 and an exterior management circle 206 disposed about a center point 202. The circle 204 is shown as being completely displayed on the viewing surface 208 while the circle 206 has a segment 207 (shown by the dashed line) which is beyond the viewing area 208. 
     Now referring to FIG. 2B there is shown a display device 200 having a first energy management circle 204 and a second energy management circle 206 surrounding a central point 202 which is located outside of the display 200. Energy management circle 206 has two segments which appear on the viewing screen 208 while energy management circle 204 has only one. Also, shown are view boundary intercepts 209. 
     Now referring to FIG. 3, there is shown a flow chart diagram of a prior art method for displaying energy management circles. 
     Firstly, the energy management circle is defined, by the I/O 116 (FIG. 1). 
     Secondly, the center of the EMC is located by system processor 120 (FIG. 1). 
     Thirdly, the system processor calculates the radius for the energy management circle. 
     Fourthly, the system processor calculates a starting point on the energy management circle. 
     Fifthly, the system processor determines whether the point is located on the display device 110. 
     Sixthly, the system processor determines if the point is on the display and if so provides the appropriate video or deflection (x,y) signal through stroke memory 112 to display 110 and if the point is not to be displayed then the appropriate video or deflection signal is output to display 110. 
     Seventhly, the process continues by individually analyzing the point adjacent to the previous point on the circle until all points have been analyzed. 
     This inquiry into whether or not each individual point on the circle is to be displayed on the display is CPU intensive and greatly affects the overall speed in which an energy management circle can be drawn and consequently updated. 
     Now referring to FIG. 4, there is shown a flow chart of the method of the present invention. 
     Firstly, the energy management circle is defined by a flight management system of the I/O 116 (FIG. 1). 
     Secondly, the system processor 120 then locates the center of the energy management circle. 
     Thirdly, the system processor determines the radius of the energy management circle. 
     Fourthly, the system processor determines view boundary intercepts of the energy management circle and the display boundaries. 
     Fifthly, the system processor 114 determines whether the circle is concave or convex. 
     Sixthly, the circle segments within the display boundary intercepts are drawn without the need for individual determination of whether each point in the segment is located on the display. 
     A more thorough understanding of present invention may be obtained by reviewing the ada source code of the appendix which is implemented by the system processor 120 to essentially perform the following steps: ##SPC1## 
     It is thought that the method and apparatus of the present invention and many of their attendant advantages, will be understood from the foregoing description, and it will be apparent that various changes may be made in the form, construction and arrangements of the parts and steps thereof, without departing from the spirit and scope of the invention, or sacrificing all of their material advantages, forms herein before being merely preferred or exemplary embodiments thereof. It is the intention of the impending claims to cover all of such changes.