D'carula - by Alex Klein and Sahana Karthik
We present The D’carula - named after Dracula - with the c and the r switched so that the word car is in the name, because much like a vampire bat, the ultrasonic sensor uses waves to detect objects or obstacles in front of it. The D’carula was constructed with two motors, one attached to the left and one to the right side. Each motor controls one wheel and a roller was fixed to to the front at the bottom for more stability. Clip-like fixtures were added to the front of the car. These held the wires (connecting the motor to the brick) out of the ultrasonic sensor’s way, and the sensor was attached to the front of the car.
For the code that uses a bang-bang controller, the wheels moves at a constant power until it detects something that is 20 cm away from it. At this point it will stop. After stopping short, if the sensor still detects something within 20 cm, it will slowly start to back up until it is out of range (Top video). The code for the proportional controller (bottom video) uses an equation that multiplies some input value kp with the distance measured on the ultrasonic sensor. While the bang-bang controller simply makes the robot stop short, the proportional controller causes the car to slow down gradually from its top speed as it approaches an object, proportional to how far away the object is. This equation also ensures that the car stops before it is less than 20 cm away from the object. Further, we moved the box closer than 20 cm (also shown in video) and we can see that the car continued to move back and stop only when it was 20 cm away from the object.
Figure 1: View of the Overall design of The D'carula
Figure 2: Ultrasonic sensor attached to the back of the brick
Figure 3: Clip-like fixture that keeps the wire connecting the motor to the brick from obstructing the view of the sensor. The clip on the other side is used to hold up the ultrasonic sensor.
Figure 4: Side view of the supports that keep the motor stable and connected to the brick.
Figure 5: Front view of The D'Carula, showing the steel ball roller at the front to keep the entire robot level, and additional front supports for the motors (where the red connectors are).