With the combined effort of all the team members and experiences gathered from past competitions, we have designed our rover Prochesta V1.0 for University Rover Challenge 2023.
This year the drive system consists of four wheels, each driven by a high torque planetary gear DC motors. These motors are independently controlled by separate BTS-7960 drivers. The motors are housed inside the wheel stator to protect it from external damage.
The complete chassis is made from TIG welded Stainless Steel tubes for greater strength to weight ratio. The Chassis is Modular with separate provisions for Arm and Science Tool attachments. The chassis now has more room for Electronics compared to the previous design. Also space for cable management was considered in the new design.
For the suspension system, we implemented a “Bar Differential Mechanism” with a counter-link at the bottom of the rover. This ensures that when the wheel on the right will go up, the wheel on the left will go down and the body will remain at an average angle between either way. So when the rover goes through rocky terrain, there will be minimum jerking of the body. This suspension system is more lightweight than the six-wheel rocker-bogie mechanism.
We have built a six-degree of freedom rover arm using stainless steel square tubes for better stability and precision. The base of the Rover Arm is located at the front of the body for better reach and maneuverability of the arm. The arm base housed a 6:1 worm gear system powered by a high torque low rpm DC motor for precise movement and minimal backlash. Two Linear Actuators are used for shoulder and elbow movements to withstand high load and prevent backlash. Two digital servo motors are implemented in the lower wrist to achieve precise pitch and yaw mechanism. We have reduced the size of the previous yaw-pitch-roll mechanism by 74% by replacing most of the plastic parts with Aluminum 1100 Alloy.
We have implemented DC Motor Mechanism in order to get the 360 degree roll motion of the end effector. A worm gear dual shaft DC motor with linear rails is used for the 2-claw gripper mechanism.
Our end effector can tighten a screw, undo a switch, turn a knob. We have attached a poly-fiber at the end of our gripper for better grip and stability.
We improved the strength of our 2-claw gripper system, with which we can pick up a container and transport it to another place, open and close a drawer and insert a cache into the drawer. We have implemented AS5600 magnetic encoders on all the joints of the arm so our control system will be closed loop which will help us implement inverse kinematics. The whole arm and manipulator is designed and built aligning with the Inverse Kinematics system that our software team is developing.
For the electric system we used four separate PCBs: Wheels, Arm, Science and Power. Each board is used for controlling and monitoring the respective sub-systems. All boards are equipped with Raspberry Pi Pico for low level control. H-bridge BTS-7960 and L298N motor drivers are used for driving the actuators and DC motors.
For the main computer we used a Nvidia Xavier NX. Intel RealSense D435i stereo camera along with a 9 DoF IMU is used for perception during autonomous navigation. ROS is used with a custom made interface for controlling the rover remotely.
The rover is equipped with a 13 dBi high gain Ubiquiti Airmax Omnidirectional antenna while the base station has a 15 dBi high gain Ubiquiti Airmax 120 degree Sector antenna. Both rover and base station uses Ubiquiti Aimax Rocket M2 routers. This communication setup allows us to control the rover for a No LOS (Line of Sight) distance of one and half kilometers.
For in-situ analysis for an on board science mission, we have designed a customized soil collection and chemical analysis kit. Scopper mechanism is used to collect soil samples from the surface which gain vertical motion using two linear actuators. DS5160 60kgcm servo are used for the angular movement of the scooper. The collected soils are poured into a container opening, mixed with water and later carried into the test tubes where chemicals are present in advance.
Presence of lipid, protein, carbohydrate and carbonate biomolecules are examined to determine if the sample consists of extinct, extant or no life. Foxeer fpv camera is used to observe color change after the chemical reactions. Rock samples are analyzed using a digital microscope. RBD-1042 Capacitive soil moisture sensor and DS18B20 Digital thermal probe are used to measure habitability of the soil sample.
