distributed compliance controllers for legged- robot with...
TRANSCRIPT
Distributed Compliance Controllers for Legged-
Robot with Geared Brushless DC Joints
DFKI Bremen & Universität Bremen
Robotics Innovations Center
Director: Prof. Dr. Frank Kirchner
www.dfki.de/robotics
Lan Yue Ji, Sebatian Bartsch, Frank Kirchner
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Overview
• General information of the SpaceClimber project
• Types of Mobility for Crater Exploration
• Technical Aspect of SpaceClimber Robot
• the Controller Design
Actuator
Estimation of the contact torque
Control schematic
Exemplar experimental result
• Conclusion and Outlook
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Project SpaceClimber
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• Goal:
Development of a six-legged, biologically-inspired, energy efficient, and adaptable free climbing robot for extraterrestrial exploration
The system has to be able to
► move freely and securely in crater environment
► cope with inclinations up to 80%
► navigate semi-autonomous
► carry a scientific payload
Future space qualification has to be taken into account
• Funding:
The project SpaceClimber is funded by the German Space Agency (DLR, Grant number: 50RA0705) and the European Space Agency ESA (Contract no.: 18116/04/NL/PA)
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• Multitude of concepts for robots that could provide mobility in crater
environments (e.g. wheels, tracks, legged-wheels and robot teams)
• Walking systems offer the highest mobility
Trajectories with partial ground contact (no bulldozing, negotiate obstacles)
Variable selectable foothold position
High traction in steep terrain
High flexibility
► Various walking pattern and postures
► Omni directional walking
► Multi-functionality
Mobility for crater exploration
Scarab Rover (CMU) [1] Icebreaker (CMU) [2] TRESSA (JPL) [3] CESAR (Uni Bremen / DFKI) [4]
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Evolution of DFKI Legged Robots
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SpaceClimber Prototype
• Technical Data Size [LxWxH]: 820mm x 900mm x 220mm
Weight: 23Kg
Actuators (# = 25 x Body, 1 x Head) :
► Legs: 24x RoboDrive, Harmonic Drive 1:100
(6x Spring in lower legs)
► Body: 1 RoboDrive, Harmonic Drive 1:160
► Head: 1x Dynamixel DX117
Sensors (# = 193) :
► Actuator: Position, speed, current, temperature, noise level
► Foot: 4x pressure, (4x DMS), 3 axes acceleration,
temperature, piston immersion
► Leg mounting: 6 axes force-torque-sensor
► Body: IMU, overall power consumption
► Head: Laser range finder, CMOS camera
Controller: Microblaze (51,96Mhz) on Spartan3A 1200
Communication: Wireless LAN (telemetry, commands), DECT (emergency switch)
Power Supply : 44,4V @ 4000mAh
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Control Hierarchy of SpaceClimber
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Control Frequencies
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Actuator Design
• Selected components
BLDC-motor: RoboDrive ILM 50x8
Gear: 100:1 HarmonicDrive
Rotor position: Digital Hall sensors
Absolute angular sensor: 12bit Hall effect based
• Specification
Dimensions (ᴓ x L): 64mm x 110mm
Weight: 525g
Repeatable torque: 28Nm
Maximum rotational speed: 0,58Hz
Hollow shaft with 8mm diameter for cabling
Different support points on drive side
Multi-turn of each joint: ±360° = 720°
Integrated electronics including
► Power electronics
► FPGA -based control
► LVDS communication
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Compliance Control in General
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In Cartesian Space:
In Joint Space: ?
Springer Handbook of Robotics
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Torque Estimation
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Identification of Torque Constant
Setup2: Motor Test Bench
Setup1: Winch Test
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Estimation of Contact Moment by Current
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Compliance Controller in Joint Space
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Compliance Control using Indirect Method
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In Cartesian Space:
In Joint Space:
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Experiment Video
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Current Estimation for Thorax
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Experiment Result for Thorax
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Experiments on Distal, Basal and Thorax
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Conclusion
With distributed compliance controllers in joint space, the
legged robotic system
can react faster to unexpected obstacle;
can improve locomotion on uneven surfaces;
reduce complexity and integration effort using estimation
Thus they contribute to the improvements in
overall performance: stability, energy-efficiency, …
better protection of the robotic system
level of autonomy and robustness
Immediate Reactive Reflex based on Self-Awareness!
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Outlook and Future Work
• Optimization of compliance settings in various
scenarios
• Design of a general control architecture merging
reflexes, locomotion control and decision-makings
• Improvement in the estimation accuracy
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Thank You!
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