ARTISAN ( ) ARTISAN ( ) Human-Friendly Robot Design

Transcription

1 Human-Friendly Robot Design Torque Control: a basic capability dynamic performance compliance, force control safety, interactivity manipulation cooperation ARTISAN ( ) ARTISAN ( ) 1

2 intelligence for mechanisms Safety Human-Friendly Robots Human-Friendly Robots Requirements Safety Performance Competing? Dependable & Safe Soft Actuators Light Structures Impact-Reduction Skin Low Reflected Inertia Distributed Sensing Good Performance Technology Puma Conventional Geared Drive: Lighter structure Large reflected actuator inertia Puma Effective Joint Inertia Effective Inertia (J link + N 2 J motor ) J link Heavy structure J motor N gear A A diag N J 2 rigid body ( i motor i ) 2

3 Safety Metric Normalized Effective Mass Safety Metric Normalized Effective Mass PUMA560 (Payload 20N) 1.16 Human (Payload 60N) 0.04 PUMA560 (Payload 22N) 1.16 Human (Payload 62N) 0.04 DM 2 (Payload 60N) 0.06 Safety Metric Normalized Effective Mass PUMA560 (Payload 22N) 1.16 Human (Payload 62N) 0.04 DM 2 (Payload 60N) Safety Metric Normalized Effective Mass 0.06 s2 (Payload 33N) 0.02 Inertia Property Effective Inertia/mass perceived in a direction u ( ) u T u 1 1 u u E : Acceleration Capacity Torque to Acceleration Transmission 3

4 Acceleration Capacity Optimized Design Initial Design Optimized Design Why Are Robotic Arms Unsafe? Robot Collision Head Injury Criteria (HIC) Actuation Requirements Distributed Macro Mini (DM 2 ) Approach Assumed Torque Requirements Torque Magnitude Frequency Actual Torque Requirements Torque Vs Frequency: Square Wave Parallel Actuation Small Joint Actuator Torque Magnitude + Elastic Coupling Large Base Actuator Frequency Robot Characteristics Robot Collision Effective Inertia at Contact Equivalent Mass-Spring Model Effective Inertia Effective Stiffness Impact Velocity I a 1 T u u 1 v J A J 1 1 T v v 4

5 Effective Stiffness Impact Velocity 2 Ke K cos with k k k a h Manipulator Safety Index (MSI) Manipulator Safety Index (MSI) Variation with contact point Interface Stiffness constant at 20KN/m Manipulator Safety Index (MSI) DM2 - Human-Friendly Robot Variation with Configuration Interface Stiffness constant at 20KN/m the high capacity of a large robot with the fast dynamics and safety of a small one 5

6 Base actuator (low frequency) Joint actuator (high frequency) + DM 2 New Testbed DM2 vs. PUMA 560: Effective Mass Comparison Torque Magnitude Macro actuator Brushed DC motor Maximum effective mass: PUMA 560: kg Mini actuator Brushless motor Elastic Coupler (Torsional Spring) PUMA 560 (link 2 and link 3) HFR (conventional actuation) HFR (DM 2 actuation) HFR (Macro actuation): kg HFR (DM 2 actuation): 2.81 kg DM 2 Performance Distributed Macro-Mini Actuation DM 2 10x reduction in effective inertia 3x increase in position control bandwidth 10x decrease in trajectory tracking error Safety AND Performance 6

7 DM2 - Hybrid Actuation DM2 - Hybrid Actuation artificial muscles with compact pressure regulators pneumatic artificial muscles DM2 - Hybrid Actuation DM2 - Hybrid Actuation pneumatic artificial muscles pneumatic artificial muscles DM2 - Hybrid Actuation DM2 - Hybrid Actuation pneumatic artificial muscles pneumatic artificial muscles 7

8 DM2 - Hybrid Actuation Human-Friendly Robot Design DM2 artificial muscles with compact pressure regulators s2 : Stanford Human-Safe Robot S2. : Stanford Human-Safe Robot S2. muscle 4bar upper arm 34cm lower arm 29cm total mass 1.5kg torque (7.5,5.0)Nm mini (1.0,0.3)Nm force@effector 14N Stanford Human-Safe Robot Torque [ Nm ] Position [ deg ] Desired Torque 0 Macro DM Time [ sec ] U1 Pressure Regulator Desired Position M acro DM Time [ sec ] Ps P1 Load Cells P2 F1 F2 Tj,θ Macro 0.5Hz Macro/Tension 7.0Hz Macro/Mini. 35Hz Pressure Regulator U2 8

9 Virtual Wall (macro only/macro-mini) s2 1.5: New Design s2 1.5 : New Design Safety Comparison s2 : Stanford Human-Safe Robot s2 Effective Mass: 1.2Kg DM 2 Effective Mass: 3.5Kg Human Effective Mass: 2.1Kg PUMA560 Effective Mass: 25Kg 9

10 s2 : Stanford Human-Safe Robot 2 : Stanford Safety Robot Impact-reducing proximity and pressure sensing Skin using SDM : New Design 2 Testbed Pneumatic Muscle (low frequency) Electrical Motor (high frequency) + 2 Experimental Results Macro Macro + Mini Safety Comparison Position Force 6Hz 26Hz 10

11 Safety Comparison 2 : Motion Range(sine wave) 2 : Contact Force Control 11