[Ether]

Originally Posted by johncap100

my understand is that we need to specify each motor/wheel assembly , ie all four individually as each wheel is connected indepedently to a single motor.

so then do we use the above statements for each motor/wheel assembly?

thanks

have you actually written some code just to move the bot with mechanum wheels?

You take the commands from the joysticks and you process them (it's called inverse kinematics) to create the 4 wheel speeds.

The drive interface could be a single 3-axis joystick, or two 2-axis joysticks, or any other input device(s).

Mecanum has three completely independent degrees of freedom:

fore/aft
strafe (right/left)
rotate (turn, yaw)

A mecanum vehicle can perform all three of these motions simultaneously.


Here's some reference C code for you:

// 3-axis joystick interface to a mecanum drive

// define your driver interface,
// in this case a 3-axis joystick:

forward = -Y;
right = X;
clockwise = Z;

// put any drivability adjustments here for forward, right, and clockwise,
// for example gain, deadband, etc:

// if rotate gain is too hot, tweak it down:

clockwise /= 2;  

// add deadband so you don't get strafe when you don't want it:

if ((right>-0.1)&&(right<0.1)) right = 0; 


// now apply the inverse kinematic tranformation:

front_left = forward + clockwise + right;
front_right = forward - clockwise - right;
rear_left = forward + clockwise - right;
rear_right = forward - clockwise + right;


// finally, normalize so that no wheel speed command
// exceeds magnitude of 1:

max = abs(front_left);
temp = abs(front_right);
if (temp>max) max = temp;
temp = abs(rear_left);
if (temp>max) max = temp;
temp = abs(rear_right);
if (temp>max) max = temp;

if (max>1) 
  {front_left/=max; front_right/=max; rear_left/=max; rear_right/=max;}


// you're done. send these four wheel commands to their respective wheels

Questions? Fire away.