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root / scout / libscout / src / behaviors / Odometry.cpp @ 339f64d2

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#include "Odometry.h"
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using namespace std;
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/** Set up the odometry node and prepare communcations over ROS */
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Odometry::Odometry(string scoutname, Sensors* sensors):Behavior(scoutname, 
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                                                "odometry", sensors)
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{
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  name = scoutname;
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  scout_pos = new pos;
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  motor_fl_ticks = motor_fr_ticks = motor_bl_ticks = motor_br_ticks = 0;
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}
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/** Query encoders and estimate position based on encoder reading */
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void Odometry::get_position()
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{
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  float left_dist, right_dist, total_dist, theta;
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  encoder_readings scout_enc = encoders->query();
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  motor_fl_dist = scout_enc.fl_ticks - motor_fl_ticks;
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  motor_fr_dist = scout_enc.fr_ticks - motor_fr_ticks;
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  motor_bl_dist = scout_enc.bl_ticks - motor_bl_ticks;
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  motor_br_dist = scout_enc.br_ticks - motor_br_ticks;
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  // Get Left and Right distance
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  left_dist = DIST_PER_TICK*(((float)(motor_fl_dist))/2.0 +
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                             ((float)(motor_bl_dist))/2.0);
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  right_dist = DIST_PER_TICK*(((float)(motor_fr_dist))/2.0 + 
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                              ((float)(motor_br_dist))/2.0);
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  total_dist = (left_dist)/2.0 + (right_dist)/2.0;
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  theta = scout_pos->theta + atan2(right_dist - left_dist, WHEEL_BASE);
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  //Use negative theta because we measure theta from 0 on the
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  //right to 180 on the left counter-clock-wise, but this is
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  //negative theta in the coordinate frame.
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  //Also, subtract the delta from y because positive y is down.
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  scout_pos->x += total_dist*cos(-theta);
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  scout_pos->y -= total_dist*sin(-theta);
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  scout_pos->theta = fmod(theta, (float)(2*M_PI));
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  //Save state for next time in.
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  motor_fl_ticks = scout_enc.fl_ticks;
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  motor_fr_ticks = scout_enc.fr_ticks;
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  motor_bl_ticks = scout_enc.bl_ticks;
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  motor_br_ticks = scout_enc.br_ticks;
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 return;
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}
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void Odometry::run()
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{
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  scout_position = node.advertise< ::messages::ScoutPosition>(name+"/position", 1000); 
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  while(ok())
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  {
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    get_position();
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    position.name = name;
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    position.x = scout_pos->x;
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    position.y = scout_pos->y;
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    position.theta = scout_pos->theta;
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    scout_position.publish(position);
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  }
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}