Software
The coordinates that are received from the earth computer, are used to build an array.This array contains the steering angle and direction, and the distance that has to be driven.
To calculate the steering angle, the position of the lake is compared to the center of the image. Because the distance from the rover to the lake and the distance from the lake and the deviation of the lake to the straight forward direction of the rover are known, the steering angle can be given. For example: when the deviation to the middle is 10, the steering angle for a lake at 20 is twice as large as the steering angle for the lake at 40. See the figure below for a graphical representation.
During driving the new calculated path, the rover will stop to check whether or not there are new coordinates. When there are, the rover will recalculate the path, and continue driving this new path. When there are no new coordinates, for example because there was no communication, the rover continues driving the old trajectory.
When there is an edge detected, the lake approach software gives a “not finished” command to the strategy software, which determines what to do. When the lake is detected, and when this is confirmed by triggering of the middle light sensor, the lake approach gives the command “finished”, which triggers the strategy to measure the lake temperature.
Function usage
The function lake approach is called by the strategy function, and runs by itself, using the edge detection on the slave brick and the communication with the earth. It also uses the path executer to give the steer and drive commands to the rover.
