motion_stack.ros2.base_node package

Provides the API template to use the python core through ROS2 nodes.

Create your own node from zero or refer to ros2.default_node for the default implementation

Submodules

motion_stack.ros2.base_node.lvl1 module

Template for a ROS2 node running the python core of lvl1.

class motion_stack.ros2.base_node.lvl1.Lvl1Node

Bases: Node, ABC

Abstract base class for ros2, to be completed by the user.

To see the default behavior implemented using this template, refer to ros2.default_node.lvl1.

core_class

Class from which the core is instantiated. Overwrite this with a modified core to change behavior not related to ROS2.

alias of JointCore

core

Type:    JointCore

Instance of the python core.

abstract subscribe_to_lvl0(lvl0_input)

Starts transmitting incomming sensor data to the python core.

lvl0_input is a function that must be called when new sensor data is available. The data type must be a list of JState.

Tipical steps:

• Subscribe to a topic.

• In the subscription callback:

  • Convert the incomming messages to a List[JState].

  • Call lvl0_input using your processed messages.

Important

This function is called once at startup to setup some kind of continuous process. This continuous process must then call lvl0_input.

Note

lvl0_input is typically JointCore.coming_from_lvl0()

Parameters:

lvl0_input (Callable[[List[JState]], Any]) – Interface function of the joint core, to call (in a callback) when new sensor data is available.

abstract subscribe_to_lvl2(lvl2_input)

Starts transmitting incomming joint targets to the python core.

lvl2_input is a function that must be called when new joint targets (typically resulting from IK) is available. The data type must be a list of JState.

Tipical steps:

• Subscribe to a topic.

• In the subscription callback:

  • Convert the incomming messages to a List[JState].

  • Call lvl2_input using your processed messages.

Important

This function is called once at startup to setup some kind of continuous process. This continuous process must then call lvl2_input.

Note

lvl2_input is typically JointCore.coming_from_lvl2()

Parameters:

• lvl0_input – Interface function of the joint core, to call (in a callback) when new joint targets are available.

• lvl2_input (Callable[[List[JState]], Any])

abstract publish_to_lvl0(states)

This method is called every time some motor commands need to be sent to lvl0.

states should be processed then sent onto the next step (published by ROS2).

Tipical steps:

• Make a publisher in the __init__.

• Process state in a message.

• call publisher.publish with your message

Note

This method will typically be called by JointCore.send_to_lvl0()

Parameters:

states (List[JState]) – Joint states to be sent.

abstract publish_to_lvl2(states)

This method is called every time some joint states need to be sent to lvl2.

states should be processed then sent onto the next step (published by ROS2).

Tipical steps:

• Make a publisher in the __init__.

• Process state in a message.

• call publisher.publish with your message

Note

This method will typically be called by JointCore.send_to_lvl2()

Parameters:

states (List[JState]) – Joint states to be sent.

abstract frequently_send_to_lvl2(send_function)

Starts executing send_function regularly.

Fresh sensor states must be send regularly to lvl2 (IK) using send_function. When using speed mode, it is also necessary to regularly send speed.

Tipical steps:

• Make a timer.

• Call send_function in the timer.

Note

send_function is typically JointCore.send_sensor_up() and JointCore.send_command_down()

Parameters:

send_function (Callable[[], None]) – Function sending fresh sensor states to lvl2

abstract startup_action(core)

This will be executed once during the first ros spin of the node.

You can keep this empty, but typically:

• a message with only joint names and no data is sent to initialise lvl0 (if using Rviz this step is pretty much necessary).

• “alive” services are started to signal that the node is ready.

Parameters:

core (JointCore)

classmethod spin()

Spins the node

motion_stack.ros2.base_node.lvl2 module

Template for a ROS2 node running the python core of lvl2.

class motion_stack.ros2.base_node.lvl2.Lvl2Node

Bases: Node, ABC

Abstract base class for ros2, to be completed by the user.

To see the default behavior implemented using this template, refer to ros2.default_node.lvl1.DefaultLvl2.

core_class

Class from which the core is instantiated. Overwrite this with a modified core to change behavior not related to ROS2.

alias of IKCore

core

Type:    IKCore

Instance of the python core.

abstract subscribe_to_lvl1(lvl1_input)

Starts transmitting incomming state data to the python core.

lvl1_input is a function that must be called when new state data is available. The data type must be a list of JState.

Tipical steps:

• Subscribe to a topic.

• In the subscription callback:

  • Convert the incomming messages to a List[JState].

  • Call lvl1_input using your processed messages.

Important

This function is called once at startup to setup some kind of continuous process. This continuous process must then call lvl0_input.

Note

lvl1_input is typically IKCore.state_from_lvl1()

Parameters:

lvl1_input (Callable[[List[JState]], Any]) – Interface function of the ik core, to call (in a callback) when new state data is available.

abstract subscribe_to_lvl3(lvl3_input)

Starts transmitting incomming ik targets to the python core.

lvl3_input is a function that must be called when new ik target is available. The data type must be a Pose.

Tipical steps:

• Subscribe to a topic.

• In the subscription callback:

  • Convert the incomming messages to a Pose.

  • Call lvl3_input with the processed messages.

Important

This function is called once at startup to setup some kind of continuous process. This continuous process must then call lvl3_input.

Note

lvl3_input is typically IKCore.ik_target()

Parameters:

lvl3_input (Callable[[Pose], Any]) – Interface function of the joint core, to call (in a callback) when new ik target is available.

abstract publish_to_lvl1(states)

This method is called every time some joint targets need to be sent to lvl1.

states should be processed then sent onto the next step (published by ROS2).

Tipical steps:

• Make a publisher in the __init__.

• Process state into a message.

• call publisher.publish with your message

Note

This method will typically be called by IKCore.send_to_lvl1()

Parameters:

states (List[JState]) – Joint states to be sent.

abstract publish_to_lvl3(pose)

This method is called every time some end effector pose needs to be sent to lvl3.

pose should be processed then sent onto the next step (published by ROS2).

Tipical steps:

• Make a publisher in the __init__.

• Process pose into a message.

• call publisher.publish with your message

Note

This method will typically be called by IKCore.send_to_lvl3()

Parameters:

• states – Joint states to be sent.

• pose (Pose)

abstract startup_action(lvl2)

This will be executed once during the first ros spin of the node.

You can keep this empty, but typically:

• a message with only joint names and no data is sent to initialise lvl0 (if using Rviz this step is pretty much necessary).

• “alive” services are started to signal that the node is ready.

Parameters:

lvl2 (IKCore)

classmethod spin()

Spins the node