Transportation has always been one of the most invested topics in modern society. From the conception of social structure, humans have never ceased to strive for improvements in effective distribution and transfer of cargo and passengers.
<aside> 🚎 Whether alive or still, the objects being transferred almost always require stability and safety in the process of transportation. Challenges on the road to this problem include unexpected collisions and uneven terrain, leading to traumatic accidents.
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The final product of CAVS in a travel mission.
CAVS stands for Collision Avoidance Vehicle System.
<aside> 💡 It focuses on:
From roadtripping on bumpy and twisting roads to serving coffee on a robotic waiter, and from filming perfectly stabilized footage to carrying highly explosive chemicals, our vehicle system will stay away from any potential accidents that could happen if using traditional transportation.
The Collision Avoidance Vehicle System can be broken down into three major functional components that will be discussed in detail below: the all-directional movement system, the collision avoidance system, and the balancing platform system. The overall shape of the vehicle body is a circular disk column composed of three pieces of plywood sandwiching the internal electronic components and the Stewart platform rods as shown in the diagram below.
Diagram 1. The overall structure of the vehicle.
The functional units are the Omni wheels that render rotational and translational movements, the ultrasonic distance sensors that prevent collisions, and the Stewart platform design that maintains horizontal balance under various landscapes. Together, these subsystems integrate into a practical vehicle machine that achieves our primary design goals of transportation.
There are a total of three-quarter-inch plywood layers. The upper layer has a diameter of 11.5 inches; for the middle layer and bottom layer, the numbers are 10 inches and 11 inches, respectively. The upper surface of the middle layer holds servos, sensors, and the microcontroller breadboard of the Stewart platform control. The three wheeling components are mounted on the bottom surface of the lower layer, where the microcontroller breadboard of the wheeling and sensor is placed. The 9V battery holders and breadboards are fixed on the surfaces via magic tape (velcro) as we have noticed their slight movements on the vehicle caused great noise and instability. For the other hardware components, bolts and nuts are utilized. The holes for the bolts on the plywood are laser-cut for perfect symmetry and balance, which is important since this is a vehicle requiring stability in movement.
The lower layer and the middle layer are connected with the support of three 5 cm tall bolts and M5 nuts. The top layer, or the platform, is connected to the four supporting rods using four ball-and-socket joints and four 3D-printed holders. The top layer is intended for object placement, whether that be cargo, passengers, or a nice glass of wine. This is the layer where the machine keeps level at all times.
Rods slanted towards the top layer (initial design)
Initially, our design had three equally sized plywood platforms with only their outlines laser-cut. Since our Stewart platform rods are held outside of the middle layer, with the equal-sizing middle and upper layers, the rods are slanted and stuck when reaching certain angles. With an increased upper layer diameter, we solved the problem by aligning the upper layer brim with the platform rods so that they remain straight when moving.
Also, we initially estimated positions for the screwing holes that fasten the ball joint socket, and we drilled them out with an electric drill, which was both imprecise and strenuous. With the new design using laser-cut, our model was more accurate and easier to be balanced.