Zürich Autonomous Systems Lab Cedric Pradalier Cedric.pradalier@mavt.ethz.ch ICRA Workshop on Planetary Rovers, May 2010.

ZürichAutonomous Systems Lab

Cedric PradalierCedric.pradalier@mavt.ethz.ch

ICRA Workshop on Planetary Rovers, May 2010

Zürich

Welcome to Anchorage

Zürich

Outline Autonomous Systems Lab

Brief summary of the space-related activities

Hardware platforms◦ Eurobot EGP Prototype◦ ExoMars breadboard

Embedded Software◦ Lowering friction requirements using optimised

torque distribution◦ Learning what’s come ahead

Zürich

Lab of Pr. Siegwart◦ www.asl.ethz.ch◦ ETH Zürich – Switzerland◦ 20 PhD / 40 Total

Education◦ Lectures: Bachelor / Master◦ Project supervision

Research◦ Vision: Create machines that know what they do◦ Three research line:

The design of robotic and mechatronic systems Navigation and mapping Product design methodologies and innovation

Autonomous Systems Lab

Overview, Crab, Eurobot EGP Prototype

Exomars Breadboard

Zürich

◦ Micro Air Vehicles◦ Walking and Running

Quadruped Robots◦ Service Robots◦ Autonomous Robots/Cars

for Inner City Environments◦ Inspection Robots◦ Space Robots for Planetary

Exploration◦ Autonomous sailing/electric

ASL – ETH Zurich

Zürich

Nanokhod

Shrimp & Solero◦ Passive suspension

systems◦ 6 motorized wheels◦ 2 steering

◦ Very good terrainability!

ASL rovers background

Zürich

Exomars: Pre-study phase A

Zürich

Platform◦ Passive suspension◦ 6 Motorized wheels◦ 4 Steering

Mobile robots◦ Confronted to environments

which are unknown◦ Difficulty to: Model before-hand the

environment of the rover. Predict its terrain interaction

characteristics.

CRAB rover

Zürich

ExoMars Breadboard

Zürich

ExoMars Breadboard

Zürich

Authorization denied…

Test plan and results

Zürich

Eurobot: ◦ Multi-arm astronaut assistant◦ Developed by Thales (and others?) for ESA

EGP = Eurobot Ground Prototype◦ Put some wheels and perception under the Eurobot◦ Experiment on the concept of an astronaut assistant

EGP Rover Prototype

Picture from Didot et al. IROS’07

Zürich

Ability to carry and power Eurobot (150Kg)

Ability to transport an astronaut in full EVA (100Kg)

Power autonomy for multiple hours, fast recharge

◦ 150kg of lead-acid batteries

Ability to perceive its surrounding, plan path, follow

an astronaut, using a stereo-pair

Rough terrain capabilities (15 deg slopes, 15cm

steps)

Cheap !!!

EGP Rover – Requirements

Zürich

Mechanical design

Zürich

Mechanical design

Zürich

Implementation

Zürich

Suspension

Zürich

Integration

880kg, without astronaut…

Zürich

Integration

Optimised Torque ControlLearning what comes ahead

Zürich

Optimised torque control Principle

◦ It is possible to put more torque on wheel with more load

Requirements◦ Measurement of contact

point on each wheel

◦ Static model to deduce the wheel load from the contact points and the rover state

Results submitted to IROS’10

Zürich

Control loop

Zürich

Test setup and hardware

Zürich

Results

Zürich

Results

Ambroise Krebsambroise.krebs@mavt.ethz.ch

Zürich

Two types of sensors needed◦ Remote sensors → Remote Terrain Perception data◦ Local sensors → Rover-Terrain Interaction

data Data association Prediction

◦ What are the Rover-Terrain Interaction characteristics?

Approach: Basic concept

Zürich

Approach: Architecture overview RTILE Rover-Terrain Interactions Learned from

Experiments

SOFTWARE

HARDWARE Actuators

Controller

Path Planning Prediction

Learning

Database

Near to far

Local Sensors Remote Sensors

Obst. Det.

Trafficability & Terrainability

Traversability

Zürich

Outline

SOFTWARE

HARDWARE Actuators

Controller

Learning

Database

Near to farDelay

Obst. Det.

Zürich

Data acquisition: 2D example

Grid based approach◦ Remote Image acquisition◦ Local Position of the wheels◦ Samples When learning occurs

Near to far

Samples can be used for the learning mechanism.

Remote

Features association

Zürich

Bayesian model Goal

◦ Local features predicted based on remote features

Bayesian model◦ Joint distribution and decomposition◦ Introduce abstraction classes and

Question

Class association

Local classification

Remote classification

Zürich

Outline

SOFTWARE

HARDWARE Actuators

Controller

Learning

Database

Near to farDelay

Obst. Det.

Zürich

Prediction Process

Remote Subspace Local Subspace

Fr = 0.5

Prediction

20% 50% 30%

Zürich

Path planner – E*◦ Wavefront propagation

Navigation function◦ Gradient descent◦ Propagation cost

Process

Adaptive navigation

assumption T = 1

Image acquisition

Fl prediction Propagation costs

Zürich

Outline

Zürich

Rover-Terrain Interaction metric◦ ◦ The smaller, the better

Remote feature space◦ Camera◦ Color description

Trajectory adaptation

Absolute cost method◦ Idea of tradeoff between

What can be gained in terms of , meaning The deviation it imposes from the default trajectory

◦ Dynamically adapts to the terrain representation

Propagation costs function

Very bad

Very good

Start Goal

Zürich

RTILE: Results Adaptive navigation Test environment in Fluntern

◦ 3 terrains Grass softest (best) Tartan Asphalt hardest (worst)

•Automatically driven

•6 cm/s

•No prior

•Learning every 6 m

Zürich

RTILE: Results “complete” Test of the complete approach

Waypoints x [m] y [m]

0 0.0 0.0

1 15.0 0.0

2 15.0 -15.0

3 0.0 -15.0

4 0.0 -2.5

5 12.5 -2.5

6 12.5 -15.0

Zürich

Summary RTILE: Rover-Terrain Interactions Learned from

Experiments◦ End-to-end approach

Online learning Navigation adapted accordingly Integrated within the CRAB platform

◦ Tradeoff distance vs MRTI

20% MRTI improvement 10% longer distance

◦ Terrain description Consistent interaction with E* Dynamical adaptation of the propagation costs

RTILE improves the rover behavior

Zürich

Future work Improvements

◦ Add feature spaces (subspaces) for a better terrain description

◦ Use additional sensors Local: Tactile wheels, Microphones, and so on… Remote: Google earth map (increase FOV), Lidar

◦ Improved features Remote: Fourier based, Co-occurrence matrix, and

so on…◦ Learning

Clustering step (GWR)

Outlook◦ Energetic description◦ Learn as well the behavior of the rover

Zürich

Questions?

Zürich Autonomous Systems Lab Cedric Pradalier Cedric.pradalier@mavt.ethz.ch ICRA Workshop on Planetary Rovers, May 2010.

lab of

astronaut slide

crab slide

suspension slide

hardware slide

integration slide

iros07 slide

anchorage slide

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