Revision as of 09:21, 15 April 2014

Helicopter Flight Example

This example demonstrates the control of a toy helicopter. The mission here is to paint a wall with different colors. This can be considered as an analogy to a photography mission where a particular area as to be covered.

Requirements

The requirements below were added incrementally, and b-threads were added to deal with each requirement. In the simulator - the painting of the wall is by drawing a line on the screen.

• The helicopter should go up and down along the wall.
• When the helicopter reaches the ceiling or the floor it should move to the right
• Every fixed number of pixels the paint color should be changed
• Since the line drawn by the helicopter is thin, after every small vertical move, the helicopter should move right and left with horizontal brush strokes, before moving vertically again.
• The helicopter may move from its present location due to wind.
• If the helicopter is moved by wind, it should return to its last known location.

In the integration with LSC, two more requirements were added

• The amount of paint is limited. After a certain number of points is painted - the paint runs out.
• When paint of a certain color runs out, this color can no longer be used.
• When all paint colors run out, the helicopter must stop.
• Paint cans may be re-filled. This is simulated by a user clicking on a button on the screen.

Events

General control events

BeginPainting: Start the painting process StopPainting: End the painting process MoveDown: Move down a fixed number of pixels. EndOfColUp: End painting wall going up DoColDownL Start painting wall going down EndOfColDown: End painting wall going up DoRowRight: Start painting wall going right EndOfRowRight: Stop moving right. ChangeColor: The time has come to change color UpdateArrived: simulate information from a GPS with actual helicopter location

Move Events

The following events indicate the desire to move a fixed number of pixels in the desired direction. These events have a data field - indicating whether the movement is for a mission or for maintenance, which serves in correcting wind shifts.

MoveUp: Move down a fixed number of pixels MoveLeft: Move left a fixed number of pixels MoveRight: Move right a fixed number of pixels DoColUp: Start painting wall going up

BPJ b-threads

General control b-threads

DoColD2U: Controls coloring in the up direction; YAxis: Reports when helicopter reaches top or bottom end of wall (ceiling of floor) EndColUp: Handle reaching of ceiling. Stop moving vertically, start moving right. DoRowL2R: Left to right painting - waits for DoRowRight and then repeatedly requests movement to the right until end of right movement is reached. XAxis: Monitor horizontal coordinates. Report reaching of right and left borders of wall, and report end of movement right to start a new column DoColU2D: Controls coloring in the up direction EndColDown: Handles reaching the floor - requests a movement to the right BrushMove: Move the brush right and left (horizontal moves) to create a thicker line and paint continuous area. This b-thread performs its actions between any two vertical moves.

Actuator b-threads

MovingRight, MovingLeft, MovingDown, MovingUp: These b-threads wait for the corresponding move event and call the helicopter API (or the simulator) to cause the actual movement.

Color control b-threads

ChangePaintingColor: Waits for the need to change color and changes the color randomly.

Location correction b-threads

FixWind: When a report comes in that the helicopter is not where it is supposed to be - stop painting movement and return to last known location.

Environment Simulation

ColorControl: Counts movements and announces the need to change color. Wind: Every certain random number of steps, report a random location of the helicopter