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57 lines
3.4 KiB
Markdown
57 lines
3.4 KiB
Markdown
# ur_robot_driver
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This package contains the actual driver for UR robots. It is part of the *universal_robots_driver*
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repository and requires other packages from that repository. Also, see the [main repository's
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README](../README.md) for information on how to install and startup this driver.
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## ROS-API
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The ROS API is documented in a [standalone document](doc/ROS_INTERFACE.md). It is auto-generated
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using [catkin_doc](https://github.com/fzi-forschungszentrum-informatik/catkin_doc).
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## Technical details
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The following image shows a very coarse overview of the driver's architecture.
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Upon connection to the primary interface the robot sends version and calibration information which
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is consumed by the *calibration_check*. If the calibration reported by the robot doesn't match the
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one configured (See [calibration guide](../ur_calibration/README.md)) an error will be printed to Roslog.
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Real-time data from the robot is read through the RTDE interface. This is done automatically as soon
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as a connection to the robot could be established. Thus joint states and IO data will be immediately
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available.
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To actually control the robot, a program node from the **External Control** URCap must be running on
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the robot interpreting commands sent from an external source. When this program is not running, no
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controllers moving the robot around will be available, which is handled by the
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[controller_stopper](../controller_stopper/README.md). Please see the [initial setup
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guide](../README.md) on how to install and start this on the robot.
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The URScript that will be running on the robot is requested by the **External Control** program node
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from the remote ROS PC. The robot *ur_control.launch* file has a parameter called `urscript_file` to
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select a different program than the default one that will be sent as a response to a program
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request.
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**Custom script snippets** can be sent to the robot on a topic basis. By default, they will
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interrupt other programs (such as the one controlling the robot). For a certain subset of functions,
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it is however possible to send them as secondary programs. See [UR
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documentation](https://www.universal-robots.com/how-tos-and-faqs/how-to/ur-how-tos/secondary-program-17257/)
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on details.
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<br/>
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**Note to e-Series users:**
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The robot won't accept script code from a remote source unless the robot is put into
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*remote_control-mode*. However, if put into *remote_control-mode*, the program containing the
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**External Control** program node can't be started from the panel. If this behavior is required,
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please use the headless mode that does not require having a program running on the teach pendant.
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Note: The current headless mode doesn't offer the full functionality of the teach pendant.
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For using the **tool communication interface** on e-Series robots, a `socat` script is prepared to
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forward the robot's tool communication interface to a local device on the ROS PC. See [the tool
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communication setup guide](doc/setup_tool_communication.md) for details.
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This driver is using [ROS-Control](https://wiki.ros.org/ros_control) for any control statements.
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Therefor, it can be used with all position-based controllers available in ROS-Control. However, we
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recommend using the controllers from the `ur_controllers` package. See it's
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[documentation](../ur_controllers/README.md) for details. **Note: Speed scaling support will only be
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available using the controllers from `ur_controllers`**
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