As the second robot we designed for the IGVC, Argos had the benefit of borrowing from the successes of its predecessor, Kratos, as well as learning from its mistakes. We constructed Argos from the ground up, which allowed us to avoid some of the design flaws from our previous entry.
Drivetrain
Argos boasts a new set of motors, powered by a 24-volt electrical system, that enable it to surpass Kratos in acceleration, and reach the maximum allowed velocity for the competition. To prevent slippage, its tires were upgraded to a knobbier tread, allowing for a better grip on the grass.
Chassis
Protected from the elements by joined exterior panels, Argos is also equipped with ventilation ports and exhaust fans to prevent overheating. Though much of the raw material for the frame was recycled from Kratos, the design is brand new. More compact and maneuverable than its predecessor, Argos stores components closer to the drive wheels thanks to its bilevel frame, giving it a lower moment of inertia, while its taller sensor tower affords a better view of lanes and obstacles.
Sensors
Argos uses a Videre stereo-on-chip (STOC) color camera: an improvement upon the Point Grey Bumblebee2, used in Kratos, given its lower computational costs, higher resolution, and increased refresh rate. While Argos uses the same state sensors as its predecessor, it also incorporates a Gladiator G50 MEMS gyroscope, which directly measure the instantaneous yaw rate, in order to correct for slippage.
Electronics and Computer Hardware
The new 24-volt electrical system is supplied by six 12-volt batteries in a series-parallel configuration and a 24-volt charger. With the Videre camera’s FPGA handling a portion of the stereo image processing, Argos is able to operate with a single on-board computer, saving weight, cost, and energy, as compared to its predecessor. Two 802.11g wireless routers provide Internet access to the onboard computer and allow it to be accessed remotely.
E-Stop
Activated by a red button on the back of the tower, or a switch on the wireless transmitter, Argos’s emergency stop system disconnects the control signals to both motors, causing the robot to come to a complete halt. The 2.4 GHz spread-spectrum wireless radio generates and encounters less interference than the 75 MHz analog radio used by Kratos. Furthermore, connecting it directly to the motors allows for human operability even in the case of computer failure.