brom-drake 0.1.1

A set of convenient logging and testing tools for the Drake robotics toolbox.

brom_drake-py

Brom is a helper library for the Drake robotics simulation and verification library. Its goal is to simplify common debugging and testing activities in Drake (for example, logging the outputs of systems in your block diagrams).

Some of Brom's features:

Feature	Code	Results
The Diagram Watcher (the DiagramWatcher will log + plot all output ports of your Diagram automatically)	add_watcher_and_build()

(More coming soon...)

Installation

brom_drake is available on PyPI and installable with pip:

pip install brom-drake

Developer install

You can also install the package during local development by cloning the repository and running the following commands from inside it:

pip install -r requirements.txt
pip install -e .

Use Cases

Here are a few of the features available in brom_drake and how they work.

Easily Log Your Diagram's Signals

It is recommended that you use the convenience function add_watcher_and_build to add a DiagramWatcher to your diagram.

# Drake imports
from pydrake.all import (
    DiagramBuilder, Simulator,
)
# All your other imports

from brom_drake.all import add_watcher_and_build

# Create a diagram builder
builder = DiagramBuilder()

# Add and connect your systems...

# Add the watcher and build the diagram
watcher, diagram, diagram_context = add_watcher_and_build(builder)

# Set up simulation
simulator = Simulator(diagram, diagram_context)
simulator.set_target_realtime_rate(1.0)
simulator.set_publish_every_time_step(False)

# Run simulation
simulator.Initialize()
simulator.AdvanceTo(15.0)

What will happen whenever you use this function is that:

• The DiagramWatcher will be created.
  • It will search through all systems that the DiagramBuilder has added.
  • For each system, the watcher will add a VectorLogger to each output port that is a kVectorValued port.
  • The DiagramWatcher will connect all loggers to all targeted ports (in the above case, we will target all available output ports).
• After the simulation is run and the script completes, the watcher will save all data traces for each port in .png files. These plots will be in a new .brom directory.

Watching Specific systems

If you only want to watch a specific system, then you can do so by passing in information to the "targets" argument:

watcher, _, _ = add_watcher_and_build(
  builder,
  targets=[
    ("system_name", "port_name"),
    "system_name2",
  ],
)

The above code tells the watcher to watch the port named port_name on the system named system_name. (If you don't know your system's name in Drake, then you can usually find it by using the get_name() method.)

FAQs

Why the name Brom?

Brom the storyteller is a character from the Inheritance series by Christopher Paolini. He is a wise mentor that helps Eragon (the protagonist) master dragons. ;)

Related Work

Some other work in the open-source drake community:

• kinova_drake - A Drake-based library that builds a simple version of the manipulation station for the Kinova Gen3 robot arm. Also works with the hardware.
• airo-drake - A python package meant to simplify working with Drake and the airo-mono repository from the AI and Robotics Lab at Ghent University.

To-Dos

• Figure out how to tell if two systems are connected in Drake.
• Demonstrate how to create a simple Vector logger for the tutorial's diagram.
  • Determine if we can use DiagramTarget objects to do everything (assuming that they are all valid). i.e., with the name and the port # can we do waht we want?
• Add more examples
• Add Code coverage
• Add support for abstract output ports?
• Add more readme explanations of what is going on under the hood.
• Add support for giving DiagramTarget (or simpler objects) to the convenience functions.
• Add to PyPI