COMPONENTS
Below are the main components that will be used in the autonomous shadowing robot. Each component includes a "Learn More" link that will take the user to the website the component was purchased at.
We have previously used Arduino before in other school projects, so we are familiar with the language and some of the Arduino products. For us, it was an easy choice to use an Arduino Mega 2650 as our microcontroller. We needed something with several ground, 5V, analog and digital pins. We also needed an ICSP header for the Pixy CMUcam5.
We used a Pixy CMUcam5 as our image sensor. This sensor easily connects to the Arduino microcontroller via a ribbon cable that came with the sensor. This camera uses a software called PixyMon in order to set parameters for the Pixy. It also allows you to see what the camera sees. This makes it easier to troubleshoot. We have had very little issues working with the Pixy camera, so it was a good choice for our project.
We received the RoboteQ AX2550 Motor Controller from a professor. We realize that this product is currently discontinued. However, since it was given freely, it helped out with our budget. This motor controller can withstand a peak current spike of 150A. Our wheelchair motors have a stall current of 75 A. Therefore, we needed a very strong motor controller that could take a large current spike. When looking at other motor controllers, we realized that we would also have to make a protection circuit so that we wouldn't damage any of the electrical components. This motor controller is strong enough that we don't have to be concerned about a protection circuit. Anyone else replicating this project would, however, need to look into these circuits. We have also looked at using several different modes on the motor controller. We chose R/C for the input mode and open loop mixed mode for motor operations. This allows us to drive the test vehicle using a "joystick."
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Since this robot will be following people, we decided to have some type of collision avoidance. Our professor gave us the infrared sensors to use as our distance sensors. These sensors indicate if there is an obstacle and stops the vehicle.
The wheelchair motors and batteries were donated to us by Lonnie Pope, an alumni of Georgia Southern University. As previously mentioned, these motors have a stall current of 75 A and they require 24 V. They are also used to carry heavy loads. This test vehicle has the capability to hold 500 lbs or 225 kg.
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We were given two sealed lead acid batteries. We currently have them wired in series to achieve the 24 V needed by the motors. These batteries power the motor controller, which in turn provides power to the motors to move them.
The 15-pin breakout board is what connected the Arduino Mega to the RoboteQ AX2550 Motor Controller. The breakout board is plugged into the motor controller and matches with the output/input pins it has. This allowed the connecting wires to be screwed down to be more secure and provide better connections. ​
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We implemented an emergency stop button for safety. This is for the user if the robot starts to malfunction or on a path to hurt someone. The button will be pushed and immediately cut power to the entire robot. It is reset by pulling the button back out.