seeker kick-off workshop “state of the art” simon lacroix laboratoire d’analyse et...
TRANSCRIPT
Seeker kick-off workshop
“State of the art”
Simon LacroixLaboratoire d’Analyse et
d’Architecture des SystèmesCNRS, Toulouse
Disclaimer
• Learn last Thursday that I was to give this talk…• Was in Barcelona Thursday / Friday…
• Had a week-end already “burnt” by work
• Plus:• Have not worked on planetary rovers since 2005• Not aware of latest Exomars developments• Knows nothing on Mars Science Laboratory navigation (but who
else than JPL knows?)
What state of what art ?
• MER missions• 2004 baseline stems from mid 90’s research• Has been used as a testbed for improvements
(visOdom, global Nav with D*, target reaching)
• Exomars / MSL navigation approaches
• Publications related to planetary rover navigation
• Huge progresses / publications in vision & navigation in the robotics community
Seeker main axes of development
• Long range navigation
• Mission planning
• Science autonomy
A glimpse at recent publications
• Other essential information sources: • ICRA and IROS space robotics workshops• ASTRA and I-SAIRAS conferences
Related to seeker
• Journal of Field Robotics• 2007: 3 special issues on “Space Robotics”• 2009: 2 special issues on “Space Robotics”• More to come end of this year
• 21 papers• 7 not on rovers (out of Seeker scope)• 2 on rover chassis conception• 4 on locomotion (advanced motion control)• 2 on localization• 2 on navigation• 3 on high level planning• 2 on “target reaching”
Seeker main axes of development
• Long range navigation
• Mission planning
• Science autonomy
Navigation
Three main functionalities:
Perception: data acquisition, environment map building, localization
Decision: path and trajectory determination
Action: locomotion control and monitoring
(plus overall control / supervision)
MER approach
· Main characteristic: validated !· Overview: simple loop
1. Data acquisition: stereovision
2. Environment modelling: local navigation map
3. Decision: elementary trajectory evaluation
4. Trajectory execution (short distance)
· Localization: odometry + IMU (+ sun sensor)· Overall control: sequential loop
MER approach
stereovision
motion selection
Locomotion,then stop
traversability analysis
MER “extended” approach
· VisOdom
· “Itinerary planning” using D*
· Target reaching
CNES approach
· Main characteristic: experimentally validated· Overview: a bit more complex loop
1. Data acquisition: stereovision
2. Environment modelling: navigation map updating
3. Decision:
1. Sub-goal determination
2. Trajectory planning
3. Perception planning
4. Trajectory execution (limited distance)
· Localization: odometry + IMU· Overall control: sequential loop
CNES approach
stereovisiontraversability analysis
Locomotion,then stop
robot
Sub-goal, trajectory and perception task selection
MER vs CNES approaches
In 2004:
· MER approach– The simplest, local navigation (“Obstacle avoidance”
scheme)
· CNES approach– More global reasoning (“Navigation planning”)
Þ Able to more efficiently deal with longer missions
Þ This comparison does not hold since D* integration on MER
(LAAS approach)
Overall loop: sub-goal, trajectory, perception task and motion mode selection
Easy terrain mode Rough terrain mode Mode n
…
But: certainly too complex for Seeker
Lessons learned from MER
· Many easy situations tackled under direct control
· Localisation is a critical issue in some situations
· Better locomotion abilities required (slip detection)
Rover Autonav distance Total distance
Spirit 1253 m 3405 m
Opportunity 224 m 1264 m
As of June 14, 2004 :
Lessons learned from MER
· Higher autonomy required to traverse cluttered areas
· Several ground interactions required to place the instruments
· End of autonomous motions may leave rover in bad attitude (wrt. antenna, solar panel)
Localization
· 3D odometry integrates:– Wheel encoders
– Wheel steering angles
– Chassis angular configuration
· Inertial localization: assess among the following possibilities– Attitude information (at stop and during motions)
– Heading provided by the integration of a gyrometer (what drift? Are there space qualified FOGs ?)
– Integration of 6-axis IMU - fused with odometry
Vision-based localization
· Visual odometry principle
Stereo : 3D points Stereo : 3D points
Motion estimationwith matched 3D
points
Tk Tk+1
Vision-based localization· Numerous progresses since 2004:
· Feature-based SLAM· Single cams, stereo cams, panoramic cams· Efficient EKF or optimization solutions· INS / odometry integration
Vision-based localization· Numerous progresses since 2004:
· Appearance-based localization· E.g. fabMap @ Oxford· Efficient way to detect loop closures
Locomotion control and monitoring· Opportunity in April 2005
Locomotion control and monitoring· Opportunity in April 2005
Locomotion control and monitoring
Locomotion monitoring of essential importance– Position tracking– Attitude and chassis internal angles checking
· Wrt fixed thresholds· Wrt to a “configuration space trajectory”
– Wheel slippage detection– Localisation algorithms monitoring
Plus: Recovery procedure definition required
Essential importance of diagnosis (FDIR)(non only locomotion, but overall navigation)
Seeker main axes of development
• Long range navigation
• Mission planning
• Science autonomy
ESA-driven GOAC project
“Goal Oriented Autonomous Controller”:
Goal-oriented operations:A goal tells the robot what to do, instead of how to do it.
Model-level programming:High-level of abstraction raising the focus to the problem domain: features of the robot mechanisms, available behaviours, task domain.
Robust execution in an uncertain environment:Let the robot decide how best to accomplish an objective, based on situation at hand.
Safe execution:The model used by the planner can capture safety constraints, so that all plans produced are guaranteed to comply with these constraints.
Correct-by-construction functional layer:Only allowed behaviours will be actually executed.
ESA-driven GOAC project
DELIBERATIVE LEVEL
º
TM ACQUISITION AND PROCESSING
SCIENCE DATA
ASSESSMENT AND
PLANNING
SYSTEM DATA ASSESSMENT
PLANNING
ROVER ACTIVITYPLANNING, VALIDATION
AND COMMAND GENERATION
TM
IMAGESIMAGES
NAVIGATIONPRODUCTS
HK PRODUCTS
PLAN EXECUTION REPORT
PRELIM. SCI . PLAN
ACTIVITY PLAN/COMMAND PRODUCTS
SIMULATION DATA
COMMAND PRODUCTS
ROVER STATUS
EVENTS AND COMM.
SKELETON
ON-BOARD SW MANAGEMENT
MEMORY IMAGES
POST-MISSION PRODUCT
GENERATION
SIMULATOR
EQM/MTS
PRELIM. ENG. PLAN
ROVER OPERATIONS CONTROL SYSTEM
EXOMARS MISSION
OPERATIONS CENTRE
FUNCTIONAL LEVEL
EXECUTION CONTROL
SENSORS AND ACTUATORS
NAVIGATION COMMUNICATIONS
POWER
FDIR
PASTEUR P/L
P/L SUPPORT EQUIPMENT
ROVER
GROUND STATIONS
THERMAL
TVCRPLANNING
H/W INTERFACE
MARS ORBITER(MRO)
TM/ TC
TM/ TC
TM/ TC
The level of uncertainty is extremely high
Planning involves ground assessment. Autonomous path
planning is a must!
Communications are scarce due to a narrow comms window and long
distance (latency)
Plan has to merge science activities with engineering
activities
Plan has to be validated by using the Simulator, before being
uplinked
The tactical operation’s process has very strict deadlines that have to be accomplished on a per-sol basis
As a conclusion
Ongoing R&D issues (according to L. Matthies, 2005)– Much faster flight processor
– 3-D perception at night
– Parachute for high elevation landing
– Brushless motors
– Nuclear power
– Locomotion mechanisms for very steep terrain
– Landmark recognition during descent
– Single command target approach and instrument placement
– Path planning for rough and steep terrain
– Position estimation on slippery terrain
– More automated long range position estimation and mapping
– More automated sequence generation for mission planning
Not related to Seeker
Very relevant – but not in Seeker’s scope
Definitely targeted by Seeker, many solutions exist in the literature