Applying force and torque in Gazebo simulation can be done interactively through the graphical user interface (GUI) or programmatically using APIs or plugins.
The most direct way to apply force and torque to a specific object in the Gazebo simulation environment for testing or interaction is using the GUI. This method is straightforward and allows for immediate visualization of the effects.
Here are the steps to apply force or torque using the Gazebo GUI:
- Select the Object: Run your simulation in Gazebo. Navigate to the object you wish to affect (e.g., a box, a robot link).
- Access Apply Menu: Right-click the object in the scene. A context menu will appear.
- Choose Action: From the context menu, select the Apply Force/Torque option.
- Configure Force/Torque: A new dialog window will pop up. This window allows you to specify the force and torque vectors, as well as the point of application for the force.
- Force: Enter the desired force vector in Newtons (N) along the X, Y, and Z axes. For example, under Force, type 1000 N on the X field to apply a force of 1000 N in the positive X direction.
- Torque: Enter the desired torque vector in Newton-meters (Nm) around the X, Y, and Z axes.
- Application Point: For forces, you can specify the point on the object where the force is applied. By default, it's often the object's origin, but you can change this. Under Application point, press the up arrow in the Y field until it reaches 1 m to set the application point 1 meter along the object's local Y-axis. You'll typically see an arrow representing the application point move on the object in the 3D scene as you adjust these values.
- Apply: Click the "Apply" button in the dialog. The specified force and/or torque will be applied to the object for a brief moment, causing it to move or rotate according to its physical properties (mass, inertia, constraints).
This GUI method is excellent for one-off tests or manually interacting with the simulation world.
Example Walkthrough (Applying Force to a Box)
Based on common examples and documentation:
Imagine you have a simple box in your Gazebo world.
- Right-click the box in the scene and choose Apply Force/Torque.
- A new dialog will pop up.
- Under Force, type 1000 N on the X field.
- Then under Application point, press the up arrow in the Y field until it reaches 1 m, you'll see the arrow moving as you do it.
Applying these parameters will push the box strongly in the positive X direction, with the force applied 1 meter up from its origin along its Y-axis.
Programmatic Methods
For dynamic simulations, real-time control, or continuous application of forces and torques, you would typically use programmatic methods:
- Gazebo API: Utilize the C++ or Python bindings to interact with the simulation world, access models and links, and apply forces or torques directly to specific links.
- ROS (Robot Operating System): If using ROS with Gazebo, you can publish messages (e.g.,
geometry_msgs/WrenchStamped) to topics that are monitored by plugins attached to specific robot links. These plugins then apply the received wrench (force and torque) to the link. - Custom Plugins: Write Gazebo plugins that subscribe to topics, read sensor data, or execute control logic, and apply forces/torques to models or links within the simulation steps.
While programmatic methods offer greater flexibility and control for complex scenarios, the GUI method is the most straightforward way to apply force and torque interactively in Gazebo as described in the provided reference.
