The large number of sensors and actuators in Ranger NBV's flight system, along with the number of trajectory and control modes (which will be introduced in Chapter 4) make the job of controlling Ranger NBV in free flight quite complex. Also, when piloting a large powerful vehicle such as Ranger, the pilot must pay constant attention to the location of the vehicle with respect to its surroundings. The pilot can not afford to spend a lot of time monitoring complex displays of vehicle state or changing modes or parameters. This is especially important with Ranger NBV because it is often working in the immediate vicinity of scuba divers or even EVA subjects in the underwater environment. During these operations the ability to rapidly access the current situation and initiate the appropriate responses is absolutely crucial for maintaining the necessary level of safety.
Data characterizing vehicle state, or system performance must be represented in such a way that it is quickly and easily understood by the pilot. The form in which the data is portrayed should also be easily modifiable to meet the demands of a constantly changing operations environment. Not only is data representation important for informing the pilot of vehicle state, but it is also useful when investigating flight control system performance. Sometimes, representing the data in ways that give a more intuitive understanding of the operation of the vehicle can give new insight for modifying controller design. Having this data available real time allows easy identification of relationships between particular commands from the operator, and characteristic behaviors of the control system.
Changing demands of the operating environment may call for rapid chances of flight control mode. Realistically, these changes require significant restructuring of the software execution patterns. If these changes are to be easily available to the pilot during flight operations the mode changes must be seamless and transparent to the operator. Additionally, changes to control mode should not produce sudden unexpected changes in vehicle state.
Most of the time, only a small subset of the data available from the vehicle is necessary for its operation. Occasionally situations arise in which a particular set of data becomes particularly important. The flight control displays should be able to easily augment the standard data set with the particular set of information of immediate interest to the pilot.
This chapter will describe the Ranger NBV flight control interface, and the methods it uses to handle the many complexities of the real time flight control environment.