Overview: The goal of this exercise is very simple: design a system that transports a 1-foot long vertical prismatic bar across a variable distance, from 5-10 ft, and back, stop to stop, without toppling in the fastest time possible.
Note: estimated and total degrees of freedom equal 1
Base = 1 in when square
Ac = (gravity)(base) / (height) = (386.0885in/s^2)(1 in) / (12 in) = 32.1740417 in/s^2
Base = √2 in when diagonal
Ac = (gravity)(base) / (height) = (386.0885in/s^2)(√2 in) / (12 in) = 45.512 in/s^2
According to the Professor, between a 3 and 4in wheel diameter is ideal.
Max acceleration for a bar with a base of 1 in length is 32.17in/s^2. This is used to calculate how much time it takes to travel 10 ft using D=a(T^2 / 4).
Solving for total time T:
T=2√(D/a)=2√(120/32.17) = 3.86 s
After tracking a line on the aluminum bar that makes contact with the cart, the max velocity the cart can reach is 62 in/s in the middle of the track.
The bar is placed with a diamond base to allow for greater acceleration. The wheels are 8cm in diameter and .4in width. The wheels are within the wooden base for a lower center of gravity while leaving room at the top for the Arduino and motor. The wheels have many holes in it to lower the weight of the system.
All above parts were 3D printed. The base of the wooden cart was laser cut to a 4x6in base with holes for M4 size screws to fit through. 3D print was used to lower the weight of the system.
After many test trials, we found our max velocity to be 2 ft/s and max acceleration to be 1 ft/s^2. The code is set up to control the cart’s motion using a trapezoidal velocity profile that smoothly accelerates, cruises, and decelerates over the set distance. It calculates and tracks the velocity and position using encoder feedback to make sure the movement matches the desired acceleration limits. By continuously adjusting the motor’s output, the code maintains a stable speed and achieves the target distance as efficiently as possible.
"Lil Red" consisted of four red 3D printed PLA wheels with a black 3D printed bracket to encase all electronics and wheel axels and a white 3D printed motor bracket. The aluminum bar was set at a 45 degree angle to optimize acceleration and velocity.