reference gazebo-plugin in urdf-description

edit

I think i solved the Problem, i just changed the plugin-statement to:

<gazebo>
 <controller:pnp-robot name="controller" plugin="/home/user/workspace_ros/pick_place/pnp_robot/lib/libpnp_robot.so">
 <base_turntable>base_turntable</base_turntable>
 <y_first_motor_first_arm>y_first_motor_first_arm</y_first_motor_first_arm>
 <first_arm_y_sec_motor>first_arm_y_sec_motor</first_arm_y_sec_motor>
 </controller:pnp-robot>
</gazebo>

at least, i got some outputs even if it doesn't change the position of my joints.

So I think there must be another problem in my plugin-code:

#include "gazebo.hh"
#include "boost/bind.hpp"
#include "common/common.hh"
#include "physics/physics.hh"
#include <stdio.h>

namespace gazebo
{
    class Controll_Plugin : public ModelPlugin
    {

        private: physics::ModelPtr model;
        private: event::ConnectionPtr updateConnection;

        private: physics::JointPtr turntable;
        private: physics::JointPtr first_arm;
        private: physics::JointPtr sec_arm;


    public : void Load(physics::ModelPtr model, sdf::ElementPtr sdf)
    {
        this->model = model;
        if(this->LoadParams(sdf))
        {
            this->updateConnection = event::Events::ConnectWorldUpdateStart(boost::bind(&Controll_Plugin::OnUpdate, this));
        }   
    }

    public: bool LoadParams(sdf::ElementPtr sdf)
    {
        if(this->findJointByParam(sdf, this->turntable, "base_turntable") &&
            this->findJointByParam(sdf, this->first_arm, "y_first_motor_first_arm") &&
            this->findJointByParam(sdf,this->sec_arm, "first_arm_y_sec_motor"))
        {
            return true;        
        }
        else
            return false;
    }

    public: bool findJointByParam(sdf::ElementPtr sdf, physics::JointPtr &joint, std::string param)
    {
        std::cout << "findJointByParam" << std::endl;
        if(!sdf->HasElement(param))
        {
            return false;
        }
        else
        {
            joint = this->model->GetJoint(sdf->GetElement(param)->GetValueString());

            if(!joint)
                return false;
        }

        return true;
    }

    public: void OnUpdate()
    {
        std::cout << "onUpdate" << std::endl;
        this->turntable->SetAngle(2, 120);
        this->first_arm->SetAngle(0, 120);
        this->sec_arm->SetAngle(2, 120);
    }

};

GZ_REGISTER_MODEL_PLUGIN(Controll_Plugin)
}

It would be great, if anyone can help me!

Thanks a lot

Georg