Mecanum4WKinematics.cpp

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

#define DIFF_PI 3.14159265

Mecanum4WKinematics::Mecanum4WKinematics()
{
        m_dAxis1Length = 0.5;
        m_dAxis2Length = 0.7;
}

void Mecanum4WKinematics::execForwKin(const sensor_msgs::JointState& js, nav_msgs::Odometry& odom, OdomPose& cpose)
{
        current_time = ros::Time::now();

        /* See "Omnidirectional Mobile Robot -Design and Implementation": Ioan Doroftei, Victor Grosu and Veaceslav Spinu

                l = l1 + l2

                             |                      |   | w1 |
                | vx |       |  1     1    1    1   | . | w2 |
                | vy | = R/4 | -1     1    1   -1   |   | w3 |
                | wz |       | -1/l  1/l -1/l  1/l  |   | w4 |
        */
        //velocities:
        odom.twist.twist.linear.x = (js.velocity[0] +  js.velocity[1] + js.velocity[2] +  js.velocity[3]) * m_dDiam / 8;
        odom.twist.twist.linear.y = (js.velocity[1] -  js.velocity[0] - js.velocity[3] +  js.velocity[2]) * m_dDiam / 8;
        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]-js.velocity[2]+js.velocity[3]) * m_dDiam / 4 / (m_dAxis1Length + m_dAxis2Length);
        //positions:
        double dt = (current_time - last_time).toSec();
        cpose.xAbs += (odom.twist.twist.linear.x * cos(cpose.phiAbs) - odom.twist.twist.linear.y * sin(cpose.phiAbs)) * dt;
        cpose.yAbs += (odom.twist.twist.linear.x * sin(cpose.phiAbs) + odom.twist.twist.linear.y * cos(cpose.phiAbs)) * dt;
        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 Mecanum4WKinematics::execInvKin(const geometry_msgs::Twist& twist, trajectory_msgs::JointTrajectory& traj)
{
        //make sure that there's no old command in the message.
        traj.joint_names.clear();
        traj.points.clear();
        /* See "Omnidirectional Mobile Robot -Design and Implementation": Ioan Doroftei, Victor Grosu and Veaceslav Spinu

                | w1 |       | 1 -1 -(l1+l2) |   
                | w2 | = 1/R | 1  1  (l1+l2) | . | vx |
                | w3 |       | 1  1 -(l1+l2) |   | vy |
                | w4 |       | 1 -1  (l1+l2) |   | wz |
        */
        trajectory_msgs::JointTrajectoryPoint point;
        point.velocities.resize(4);
        // w1:
        traj.joint_names.push_back("wheel_front_left_base_link");
        point.velocities[0] = 2 / m_dDiam * ( twist.linear.x - twist.linear.y - (m_dAxis1Length + m_dAxis2Length) / 2 * twist.angular.z); 
        // w2:
        traj.joint_names.push_back("wheel_front_right_base_link");
        point.velocities[1] = 2 / m_dDiam * ( twist.linear.x + twist.linear.y + (m_dAxis1Length + m_dAxis2Length) / 2 * twist.angular.z); 
        // w3:
        traj.joint_names.push_back("wheel_back_left_base_link");
        point.velocities[2] = 2 / m_dDiam * ( twist.linear.x + twist.linear.y - (m_dAxis1Length + m_dAxis2Length) / 2 * twist.angular.z); 
        // w4:
        traj.joint_names.push_back("wheel_back_right_base_link");
        point.velocities[3] = 2 / m_dDiam * ( twist.linear.x - twist.linear.y + (m_dAxis1Length + m_dAxis2Length) / 2 * twist.angular.z); 
        traj.points.push_back(point);
        
}



void Mecanum4WKinematics::setAxis1Length(double dLength)
{
        m_dAxis1Length = dLength;
}

void Mecanum4WKinematics::setAxis2Length(double dLength)
{
        m_dAxis2Length = dLength;
}


void Mecanum4WKinematics::setWheelDiameter(double dDiam)
{
        m_dDiam = dDiam;
}