Chained controller for tiago, based on Crocoddyl

This repo contains the code of a new ros2 controller : cpcc2 (Crocoddyl PVEG(Position Velocity Effort Gains) Chained Controller), added to it, its launch file and config for different actuators characteristics and solver parameters.

Installation

The controllers are based on ros2_control and make use of launch-pal for the launch files:

cd ~/cpcc2_tiago_ws
mkdir ~/cpcc2_tiago_ws/src
cd ~/cpcc2_tiago_ws/src
git clone https://github.com/Gepetto/cpcc2_tiago
cd ~/cpcc2_tiago_ws
rosdep install --from-paths src

Package configuration

The configuration of this package is mandatory for its well functionning, the parameters are easily tunable in cpcc2_tiago_parameters.yaml

First of all the path should be changed to match your directories, you can also enable live and file logging.

By default the torso is disabled for performance evaluation, to enable it, add "torso_lift_joint" in front of "arm_1_joint" and "position" at the beginning of "pveg_joints_command_type"

Building

After cloning the repo in the src folder of the workspace and cd to the root of the workspace

colcon build --symlink-install --cmake-args ' -DCMAKE_BUILD_TYPE=RELEASE'

This should start building the cpcc2_tiago package, it takes a few minutes. After the build is done you can

. ~/cpcc2_tiago_ws/install/setup.bash

Overview

The controller is comprised of 2 smaller ones: one for the high level path planning : Crocoddyl, and the other for the torque to apply calculation : Pveg Chained, those two can be loaded from a single file : cpcc2_tiago.launch.py

Controllers

Pveg Chained Controller

The PvegChainedController is at the lowest level in the command chain : it is connected directly to the robot hardware through a hardware interfaces and sends effort commands to the motors. For communicating it might be tempting to send command through a topic or a service but that would be an unreliable solution for real time and fast control of Tiago, we rather turn this controller into a chained one giving it new and fast communication tools : reference interfaces

Crocoddyl Controller

The CrocoddylController is a used to retrieve the solver results, it computes the command value and send them to the PvegChainedController through the virtual hardware interface. From its side those interfaces have nothing special but their prefix name.

How to launch the controllers ?

The controllers are launched with cpcc2_tiago.launch.py, after sourcing the setup.bash

ros2 launch cpcc2_tiago cpcc2_tiago.launch.py

This scripts loads the controllers, hence the controller manager should have been started earlier. Furthermore the used hardware interfaces (effort for the arm, position for the torso) should not have been claimed. Finally the controllers should have their update frequency above 500Hz, most of the development was done at 1 KHz

Evaluate performance

Python scripts are given to evaluate the performance of Tiago, performance_evaluator.py, it sends Tiago 8 targets being the 8 vertices of a cube and logs many datas (see their docstring).

The performance plotter and full plotter nicely show the results of those studies, the full plotter is used to compare performances between the 3 interpolation types.

All these scripts can be launched with ros2 run cpcc2_tiago scripts.py args, see the scripts' docstring for the required arguments

TODO

Remove the need for absolute paths in the config file
Solve the problem with the warm start of the solver
Find the correct weights for Crocoddyl

Gepetto / cpcc2_tiago