For locomotion, Theia has 6 independent wheels in order to traverse on rough terrain without affecting the center of mass. Theia’s locomotion has 3 main parts; base and middle legs, front legs and rear legs. These 3 parts can move individually according to the terrain so that rover will not tilt over. As total there are 6 legs which has bicycle wheel design which prevents motors from any harm. Pulley rate of bicycle wheels are 1:2 so that rover is powerful enough to climb rough and inclined terrains. Loaded parts that needs to be durable are manufactured from aluminum and leg shafts are manufactured from steel. Parts that are not loaded are manufactured from 3D printers as PLA or ABS in order to lighten the rover. Tires are made from a elastic 3D printed material which is TPU-95 with a specific pattern that helps the rover to grip the surface better.
Theia also has a robotic arm with 5 DoF(Degrees of Freedom) which can reach 1 meter away from arm’s base. For end-effector, there are several options with several designs. Gripper can be modified according to the given tasks. 2 or 3 finger grippers will be used accordingly while fingers can be either elastic material or stiff. If needed, gripper will be modified as shovel which can collect surface soil samples. The final weight of Theia is approximately 50 kg with arm.
Electronics Division focused mainly on the modularity of the design while the safety, compactness and the demand of the whole system were kept in constant check. Custom PCBs were designed to carry out the tasks at hand. There are specific PCBs for controlling the arm motors, measuring the movement and controlling the locomotion, getting the necessary data for the locomotion from the sensors and for our drill. For the necessary power for the rover, 4 different 4 Cell LiPo batteries were used for the main system; and for the communication to continue without interference by the system, a 5 Cell LiPo battery was used. And an omnidirectional 2.4 GHz antenna with 5km range was used on-board for the communication. An emergency button is included on-board the rover to stop the main system without stopping the communication in case of an emergency.
Software division mainly focused on communication, arm control of Theia and autonomous traversal. A complete and easily updatable system for Theia was created. Raspberry Pi 3 and Linux PC in the control station are connected to each other through Wi-Fi with different high power access points, and exchange commands and sensor readings through Robot Operating System. The programs are written in Python, Arduino programming language, and C++. Control of Theia can be divided into 3 parts: locomotion control, arm control, and autonomous control.
Theia ( /θiːə/) is a hypothesized ancient planetary-mass object in the early Solar System that, according to the giant impact hypothesis, collided with another planetary-mass object, Gaia (the early Earth) around 4.51 billion years ago.