Freezing Gazebo until services are called

[DanielLSM]

We need to freeze Gazebo after calling each service, the ideia should be:

1. Start Gazebo, Reset and Freeze Gazebo
2. Call a Service with a certain Torque, unfreeze gazebo, let pass a certain rate
3. Get angle, Freeze Gazebo

Details of another similar simulated environment https://github.com/openai/gym/wiki/Pendulum-v0

[DanielLSM]

This might solve the problem of resetting the gazebo by calling a service to reset the gazebo world:

• https://www.youtube.com/watch?v=ZSvM7dEilhk

Going to add it in the wrapper.

[oscar-lima]

• As suggested doing:

  rosservice call /gazebo/reset_simulation "{}"

brings the robot back to 90 degree (original) position

• Freezing Gazebo (pausing physics) can be done with:

  rosservice call /gazebo/pause_physics "{}"

• Unpausing physics:

  rosservice call /gazebo/unpause_physics "{}"

• Programatically please do:

Imports:

    from std_srvs.srv import Empty

In constructor:

    self.srv = rospy.ServiceProxy ( '/service_name', Empty)

to call it from code:

    rospy.wait_for_service ('/service_name')
    self.srv()

I suggest to create a class out of it so that many services can be called with no code repetition.

[DanielLSM]

The class is the wrapper I'm doing here we still need to reset the arm under certain constraints everytime it is resetted, to prove the learning is robust.