DiffDrive2WKinematics.cpp

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#include <neo_PlatformCtrl/DiffDrive2WKinematics.h>
#include <geometry_msgs/Vector3.h>

#define DIFF_PI 3.14159265

DiffDrive2WKinematics::DiffDrive2WKinematics()
{
        m_dAxisLength = 0;
}

void DiffDrive2WKinematics::execForwKin(const sensor_msgs::JointState& js, nav_msgs::Odometry& odom, OdomPose& cpose)
{
        current_time = ros::Time::now();
        //velocities:
        odom.twist.twist.linear.x = 0.5 * (js.velocity[0] +  js.velocity[1]) * m_dDiam * 0.5;
        odom.twist.twist.linear.y = 0;
        odom.twist.twist.linear.z = 0;
        odom.twist.twist.angular.x = 0;
        odom.twist.twist.angular.y = 0;
        odom.twist.twist.angular.z = (js.velocity[0] -  js.velocity[1]) * m_dDiam /2  / m_dAxisLength;
        //positions:
        double dt = (current_time - last_time).toSec();
        cpose.xAbs += odom.twist.twist.linear.x * dt * cos(cpose.phiAbs);
        cpose.yAbs += odom.twist.twist.linear.x *dt * sin(cpose.phiAbs);
        cpose.phiAbs += odom.twist.twist.angular.z * dt;
        odom.pose.pose.position.x = cpose.xAbs;
        odom.pose.pose.position.y = cpose.yAbs;
        odom.pose.pose.position.z = 0;
        odom.pose.pose.orientation = tf::createQuaternionMsgFromYaw(cpose.phiAbs);
        last_time = current_time;
}

void DiffDrive2WKinematics::execInvKin(const geometry_msgs::Twist& twist, trajectory_msgs::JointTrajectory& traj)
{
        traj.joint_names.clear();
        traj.points.clear();

        //angular velocity in rad
        trajectory_msgs::JointTrajectoryPoint point;
        point.velocities.resize(4);
        // w1:
        traj.joint_names.push_back("wheel_front_left_base_link");
        point.velocities[0] = (twist.linear.x + (twist.angular.z * m_dAxisLength) / 2) * 2 / m_dDiam; 
        // w2:
        traj.joint_names.push_back("wheel_front_right_base_link");
        point.velocities[1] = (twist.linear.x - (twist.angular.z * m_dAxisLength) / 2) * 2 / m_dDiam; 
        traj.points.push_back(point);
}

void DiffDrive2WKinematics::setAxisLength(double dLength)
{
        m_dAxisLength = dLength;
}

void DiffDrive2WKinematics::setWheelDiameter(double dDiam)
{
        m_dDiam = dDiam;
}