Category: Hardware Tech

On the third round of the exploration in year six, VEX Robotics is my exploration. It was introduced to me since last year, Liger Advanced Robotics Competition, where we participate in a VEX Robotics Competition 2016-2017. This year, it is the same competition but different challenge calls  In the Zone. Last year the competition took place at Taiwan while this year it is in Bangkok Thailand. Another difference is the teammate, now Liger team divides into two teams boys and girls. The two teams represent Liger and Cambodia; we worked together really well representing Liger and Cambodia at the competition. It turns out really great success compare to any other robotics competition that Liger had. Well, the girls’ team got First Place and the boys’ team got Third Place. 

I was one of the boys’ team, Botijsu. Not to brag, but at the beginning of the competition, our team seems very outstanding compared to other teams. Our robot can do mobile goals lift, low cone stack, and high cone stack. Our mechanics also seem complex. Sadly, when the game starts the robots stopped working because of the floor of the competition, IT HAS A LOT OF FRICTION! We were frustrated, after one game to another we always loose. It was our last match while we changed our robots a lot, but it was a good change. We won the last game, yey, but we were at the bottom of the table. Botjisu were hopeless the only hope that we had were to get selected from the top team at the selection stage (were the top six high point team have to select their alliance). Yes! We got selected from the four top team and we lead them until they get to the third place at the end of the competition.  

This video is one of elimination stage!

As part of the robotics exploration, I was on a team call the programming team. In this team, our role is to get the code ready for the competition and for testing. In the process of building the robot, we found out that our robot doesn’t go to the point that we need it to be. So we research about different controlling systems that is easy and give more accuracy; we found out a control system calls PID. The full word of PID is Proportional, Integral, and Derivative; each letter represents different equation.

After doing the research we then start to test those system on real robot. On the first day of the testing, we didn’t get anything, the robot went crazy! It took us about 5 days to work on that control system, and it didn’t work then we decided to give up on it and begin to focus on other tasks. We were really ashamed of the time that we put into it. Luckily, I was still learning at Arrowdot (a class that I took for about 8 months) and they teaches us about PID! I was really happy to hear that and at last I finally understand the concept of PID. In the robot we actually use only proportional and integral.

float Kp = 0.25;
float Ki = 0.01;

int encoder = 0;

int totVal1, totVal2 = 0;
int average1, average2 = 0;

int err1, output1 = 0;
int err2, output2 = 0;

int currentPos1 = 0; // To display the
int currentPos2 = 0;

int sp = 500; // Set Point
int p1,i1 = 0;
int p2,i2 = 0;

void pid(){
  int motorLimit = 80; //Limit Speed
  for(int i = 0; i < 10; i++){
    totVal1 += SensorValue[potentiometerScissorsLeft]; // left potentiometer
    totVal2 += SensorValue[potentiometerScissorsRight]; // right potentiometer
  }

  average1 = totVal1/10;
  average2 = totVal2/10;

  err1 = -1 * (sp - average1); // -1 because when go up the value is smaller
  err2 = -1 * (sp - average2);

  p1 = Kp * err1;
  p2 = Kp * err2;

  i1 = Ki * (i1 + err1);
  i2 = Ki * (i2 + err2);

  currentPos1 = average1; // just to display
  currentPos2 = average2; // just to display

  output1 =  p1 + i1;
  output2 =  p2 + i2;

  if(output1 > motorLimit)  output1 = motorLimit;
  else if(output1 < -motorLimit)  output1 = -motorLimit;

  if(output2 > motorLimit)  output2 = motorLimit;
  else if(output2 < -motorLimit)  output2 = -motorLimit;

  totVal1 = 0; totVal2 = 0;
  average1 = 0; average2 = 0;

}