Re: [Playerstage-users] help about shaft encoder

[Brian G. <br...@ge...>]

On Jun 19, 2007, at 6:37 AM, mar...@ti... wrote:

> it is possible to read the readings of the encoder (I need to know the
> velocity of single wheel).

Player does not expose the encoder values, because it's rarely  
useful.  This is the cost of abstraction.

Luckily, if you know the kinematics and dimensions of your robot,  
then it's a simple geometric computation to get the individual wheel  
velocities from the robot's velocity.

 From memory, something like this works for a differential drive  
robot, where tv is the translational velocity and rv is the  
rotational velocity:

rotational_term = rv * axle_length / 2.0;
left_wheel_velocity = tv - rotational_term;
right_wheel_velocity = tv + rotational_term;

	brian.