cartesian_controllers
Stefan Scherzinger
FZI Research Center for Information TechnologyROSCon 2019, Macao
November, 1stWhy this package?

Closed loop force control

Direct teaching

Contact-rich manipulationo You want task space control
o You don‘t need collisionchecking or planning

Manual guidancecartesian_controllers

Tele-operation
ROSCon 2019, Macaoo You want to use ROS-control

Stefan Scherzinger

FZI Forschungszentrum Informatik

2The setting within
You have:o Joint position/velocity
streaming interface
Roboto ROS control
HW abstractiono This cartesian_controllers
packageo Application with real-timeend effector control

ROS control HW abstraction

cartesian_controllers

User application

VelocityJointInterface

cartesian_motion_controller

PositionJointInterface

cartesian_force_controller

EffortJointInterface

cartesian_compliance_controller
cartesian_controller_handle

Other controllers
Joint Trajectory Controller

ROSCon 2019, Macao

Stefan Scherzinger

FZI Forschungszentrum Informatik

3Three main controllers

cartesian_motion_controller

o You want to follow
a moving target
o The targets might besparsely sampled
o You prefer smoothness
over accuracy

ROSCon 2019, Macao

cartesian_force_controller

o You want to control therobot with a wrench incontacts
o You have a wrist ft
sensorStefan Scherzinger

cartesian_compliance_controller

o You want to follow
a moving target
o You want to react toexternal disturbanceso You have a wrist ft
sensorFZI Forschungszentrum Informatik

4How do they work?
Cartesian input

cartesian_motion_controller

Pose error

oApply PD gains andinterpret this as a wrenchoMapping from wrench to joint spaceoIterative, forward dynamics solver,
based on virtually conditioned twin

ROSCon 2019, Macao

Stefan Scherzinger

cartesian_force_controllercartesian_compliance_controller

Net force

BothRobot

FZI Forschungszentrum Informatik

5How to use them?
12

Before startup

ooo4

Kinematic chain (base, tip)
Sensor & compliance frame
Controllable joints

Startup and switchingoController manager

Control interfaces

cartesian_motion_controller

oUser target

geometry_msgs/PoseStamped

oSensor input

ROSCon 2019, Macao

Stefan Scherzinger

cartesian_force_controller

3

Online ConfigurationoGains, stiffness, solver

cartesian_compliance_controller

geometry_msgs/WrenchStamped

geometry_msgs/PoseStamped
geometry_msgs/WrenchStamped

geometry_msgs/WrenchStamped

geometry_msgs/WrenchStamped

FZI Forschungszentrum Informatik

6

Recent works using cartesian_controllers

cartesian_motion_controller
ooTeleoperation withuser motion tracking
Pilz PRBT

Further reading
ROSCon 2019, Macaooocartesian_force_controller

cartesian_compliance_controller

Deep-learned contact skill
model with force control
Universal Robots UR10o

IK solving for sparse targets
arXiv: 1908.06252

Stefan Scherzingero

Add-on compliance control
for door sealing assembly
KUKA KR16

Contact skills with force control
arXiv: 1908.06272(IROS 2019)

Initial idea
DOI: 10.1109/IROS.2017.8206325

FZI Forschungszentrum Informatik

7SummaryYou haveo

Joint position/velocity ostreaming interface

ROS control
pipelineocartesian_controllers

Application with real-time,
direct, task space control

cartesian_motion_controller
cartesian_force_controller
cartesian_compliance_controller

Task space control

Add-on compliance

Closed loop force control

Object manipulation

Thank yougithub.com/fzi-forschungszentrum-informatik/cartesian_controllers
scherzin@fzi.deROSCon 2019, Macao

Stefan Scherzinger

FZI Forschungszentrum Informatik8