Reverse dead band? Is it Possible??

VEX V5 Technical Support
1

So i was wondering for when you’re programming joystick controls you can set dead bands so that from 0%-10% of the joystick the robot won’t move. But is there a way to say from lets say 80%-100% of the joystick it goes at max speed??

2

This is from robot c

if(vexRT[ch3]>80) {
motor[left drive] =100;
}

edit: I haven’t been to robotics club in a while so sorry if my values are off

3

I modified Dan’s code so that it represents 80% rather than 80 and works in both directions:

if((vexRT[ch3])/127.0 > 0.8) {
motor[left drive] = 127;
}else if((vexRT[ch3])/127.0 < -0.8) {
motor[left drive] = -127;
}

(Edited as per Tabor’s warning)

4

You should be more careful with your integer division. None of that would work.

5

You’ll want at least one change to that, and for best practice you’ll want others. First, you need to get a value even if you don’t exceed those limits. Second, you should really only query in input a single time when expecting the same response from it. Third, you probably want normal headbands as well. Finally, you might really want to make a smooth transition; and if you go over 127 it caps at 127 (likewise on the negative side).

motorSpeed = 1.2*vexRT[ch3]; // anything beyond 104 will make it hit 127, so everything beyond that is capped
if(abs(motorSpeed) < 12) {
   motorSpeed = 0; // deadband to 10, adjusted for the *1.2
}
motor[leftDrive] = motorSpeed;

I also have this feeling I read about the motors not going much faster with values over 100, but I really can’t remember that for sure. If that’s the case, the upper cap may essentially already be there.

6

Would this work

//Test of tank control with reverse deadband
      if (Controller1.Axis3.value() <= 80)
      {
          LeftDrive.spin(directionType::fwd,FullSpeed,velocityUnits::pct);
      }
      
      else
      {
          LeftDrive.spin(directionType::fwd,Controller1.Axis3.value(),velocityUnits::pct);
      }
      
      if (Controller1.Axis3.value() >= -80)
      {
          LeftDrive.spin(directionType::rev,FullSpeed,velocityUnits::pct);
      }
      
      else 
      {
          LeftDrive.spin(directionType::fwd,Controller1.Axis3.value(),velocityUnits::pct);
      }
      
      if (Controller1.Axis2.value()<= 80)
      {
          RightDrive.spin(directionType::rev,FullSpeed,velocityUnits::pct);
      }
      
      else 
      {
          RightDrive.spin(directionType::rev,Controller1.Axis2.value(),velocityUnits::pct);
      }
      
      if(Controller1.Axis2.value() >= -80)
      {
          RightDrive.spin(directionType::fwd,FullSpeed,velocityUnits::pct);
      }
      
      else
      {
          RightDrive.spin(directionType::fwd,Controller1.Axis2.value(),velocityUnits::pct);
      }
7

No, it won’t. The problem is the pair of if-else’s for each axis. You really want if-else if-else once for each axis. Here is what will happen with yours:

Axis 3 reads 50.

That’s under 80, so you set your motor to full speed forward. A moment later you check and 50 is greater than -80, so you now set it to full speed backward.

Hopefully that highlights it. You’re using your >= and <= backward, and you’re using pairs of if-else when you should use a single if-else if-else.

8

IMO a deadband like this looks best as a function:


int deadband(int power) {
    if(abs(power)<15) return 0;
    if(abs(power)>80) return power < 0 ? -80 : 80;
    return power;
}

which can be used like this:


Drive.spin(directionType::fwd, deadband(Controller1.Axis3.value()), velocityUnits::pct);
9

@callen so I changed my code but I’m getting this error

*10:52:34 -- warning -- warning: comparison of constant 80 with expression of type 'bool' is always true -Wtautological-constant-out-of-range-compare] 
      if (10 < Controller1.Axis3.value() < 80) 
          ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ^ ~~ 
./main.cpp:216:42: 
10:52:34 -- warning -- warning: comparison of constant 80 with expression of type 'bool' is always true -Wtautological-constant-out-of-range-compare] 
      if (10 < Controller1.Axis2.value() < 80) 
          ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ *

Here’s the full drive code

//Test of tank control with reverse deadband
      if (10 < Controller1.Axis3.value() < 80)
      {
          LeftDrive.spin(directionType::fwd,FullSpeed,velocityUnits::pct);
      }
      
      else if (-10 > Controller1.Axis3.value() > -80)
      {
          LeftDrive.spin(directionType::rev,FullSpeed,velocityUnits::pct);
      }
      
      else 
      {
          LeftDrive.spin(directionType::fwd,Controller1.Axis3.value(),velocityUnits::pct);
      }
      
      if (10 < Controller1.Axis2.value() < 80)
      {
          RightDrive.spin(directionType::rev,FullSpeed,velocityUnits::pct);
      }
      
      else if(-10 > Controller1.Axis2.value() > -80)
      {
          RightDrive.spin(directionType::fwd,FullSpeed,velocityUnits::pct);
      }
      
      else
      {
          RightDrive.spin(directionType::fwd,Controller1.Axis2.value(),velocityUnits::pct);
      }
10

You’re comparing an axis value to 10 or -10 and getting true or false. You’re then comparing true or false to 80. You want things like this if you want to write your code this way:

if (10 < axis && axis < 80)

11

ok thank you