P 545 Final Report

The experimental component of P545 consisted of writing software to control an autonomous golf cart. Sensors on the cart included a GPS tracker, steering sensor, compass, and vision and ranging sensors Actuators included steering control, throttle, and braking. I did not utilize the cart’s braking capability in any of my experiments. Software was run on a full workstation, a Dell GX270, harnessed to the cart and running desktop linux. An onboard embedded computer and other dedicated hardware act as the interface between the workstation and the control mechanisms of the cart. CartFS[1], a synchronous sensor network built on top of the SyncFS file system, was used to connect the software components. The ultimate goal of the experiments was to write a CartFS component that, when provided a list of waypoints, would cause the cart to repeatedly navigate a closed path. While driving, it also was required to avoid detected obstacles and hopefully optimise its path as it reached the same general location on a second and third lap. A waypoint is defined in RDDF format[2] and includes three things: a latitude/longitude pair, a radial boundary, called a lateral boundary offset (LBO), and a recommended speed. A waypoint’s LBO defines a circle surrounding it. A corridor consists of two line segments each tangent to the circles of two consecutive waypoints, connected on opposite sides. Figure 1 shows two such consecutive waypoints, their LBOs and connecting corridor. Given an enclosed path described by a ordered sequence of waypoints, my objective was to write a program that would drive the cart around the waypoints, at all times remaining within the waypoints’ LBOs or the corridors between waypoints. Obstacles appeared dynamically as labeled GPS coordinates and were generated from a synthetic laser component every clock tick when they are within four meters of the cart’s current position. There is no noise in the simulated laser, a given obstacle’s reported position is the same each time it is sensed.