Design of a Compliant and Force Sensing Hand for a Humanoid Robot

Aaron Edsinger-Gonzales

MIT Computer Science and Artificial Intelligence LaboratoryHumanoid Robotics Group, Prof. Rodney Brooks

edsinger@csail.mit.edu

Hand Design for a Humanoid Robot

Hand Design for a Humanoid

•Motivation•Humanoid Platform•Design Description•Force Sensing Compliant Actuator•Control Architecture

Hand Design for a Humanoid

Constraints:•Size•Weight•Form-Factor•Wrist and Arm design

Motivations:•Unknown environments•Modest dexterity•Modest tactile sensing•Force Sensing•Compliance•Robustness

Hand Design for a Humanoid

Practical concern: Robust, functional hands are often notrealized in practice for many humanoids.

Do we need full human dexterity to understand basic manipulation problems such as visuo-motor integration and preshaping of grasp?

Can we find a balance between complexity andutility?

DomoA research platform for

dexterous manipulation

CardeaMobile ManipulationPlatform

Domo Specification

•2 6 DOF force sensing Arms•2 4 DOF force sensing Hands•9 DOF Active Vision Head•29 DOF Total•51 Proprioceptive/Force Sensors•24 Tactile Sensors•2 Firewire CCD Cameras

Domo Research Direction

•Long timescale manipulation experiments•Unknown environments•Two armed manipulation•A Creature Based approach to learning in manipulation contexts

General need for a robust, always-on, humanoid platform!

Back to the hands…

Hand Specification•4 Force Sensing Compliant Actuators•3 Fingers each with:

•1 active force controlled DOF•1 mechanically coupled DOF•1 passively compliant DOF•3 FSR tactile sensors

•1 DOF for spread between 2 fingers•Mechanically coupled•Force controlled

•Angular and force sensors for each active DOF•Embedded interface electronics•Modular Design

Hand Schematic

Dexterity•Kinematics modeled after the Barrett Hand•A modest variety of grasps•Traded complexity of more humanoid form for robustness, compactness•Provides a functional tool to explore perceptual-motor coordination for preshaping and grasping problems

Force Sensing Compliant Actuator•Springs filter high bandwidth shocks•Springs provide force sensing•Springs provide passive compliance•Very compact packaging•Mechanically simple and robust•Can be difficult to assemble

FSC and SEA Actuators

Series Elastic Actuator

•Used in Domo’s Arms•Linear and Rotary configurations•Limited travel•Small packaging difficult

Force Sensing Compliant Actuator

dF=2k*dtheta

Mechanical Details

Hand SpecificationHand Total Weight

Body Dim. Finger Dim. Finger Tip Force Curl Range Spread Range

18 oz 2.75x2.0x2.0 in 3.66x.83x0.7 in 20 oz 140 deg 160 deg

Actuator Weight SizeTorque StallTorque Continuous Speed Max

3.1 oz 1.0x1.0x2.75 in77 oz-in 28 oz-in 3.1 rev/s

Spring Active CoilsDiameter Wire Diameter Stiffness Deflection Max

3.25 0.70 in .0625 in 3.85 oz-in/deg 20 deg

Hand Controller•Motorola DSP 56F807•4 2.8A H-Bridges•Sensor signal filters•2.8”x1.5”x.85”

Hand Controller

Domo Architecture

Preliminary Videos