Differences between Hardware Interfaces

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-Effort Joint Interface
-Velocity Joint Interface
-Position Joint Interface

From the respective class documentation, these interfaces allow reading state and commanding [effort|velocity|position]-based joints.

The same reasoning applies to the actuator-based interfaces. Actuators are connected to joints via mechanical transmissions, and you need to use them if you want ros_control to handle the mapping between joint and actuator spaces.

As to the force-torque and IMU interfaces, it's also in the docs. You can also browse the source and test suite if you need further insights or usage examples.