Work

Design Paradigms Based on Spring Agonists for Underactuated Robot Hands: Concepts and Application

Year: 2021

Type: conference-paper

Abstract: In this paper, we focus on a rarely used paradigm in the design of underactuated robot hands: the use of springs as agonists and tendons as antagonists. We formalize this approach in a design matrix also considering its interplay with the underactuation method used (one tendon for multiple joints vs. multiple tendons on one motor shaft). We then show how different cells in this design matrix can be combined in order to facilitate the implementation of desired postural synergies with a single motor. Furthermore, we show that when agonist and antagonist tendons are combined on the same motor shaft, the resulting spring force cancellation can be leveraged to produce multiple desirable behaviors, which we demonstrate in a physical prototype.

Source: Proceedings - IEEE International Conference on Robotics and Automation/Proceedings

DOI: 10.1109/icra48506.2021.9561832

Authors: Tianjian Chen, Tianyi Zhang, Matei Ciocarlie

Institution: Columbia University

Language: English

Topic: Robotic Mechanisms and Dynamics

Subfield: Control and Systems Engineering

Field: Engineering

Domain: Physical Sciences

Open Access status: green

Funder: National Aeronautics and Space Administration

Award: THE ABILITY TO MANIPULATE THE ENVIRONMENT COULD ADD AN IMPORTANT NEW DIMENSION TO ASSISTIVE FREE-FLYERS (AFF) ROLES IN ORBIT. COLOCATED WITH THE HUMAN CREW AFFS HAVE SHOWN THE POTENTIAL TO ASSIST IN AREAS SUCH AS SURVEILLANCE INSPECTION MAPPING ETC. HOWEVER A PLATFORM WITHOUT MANIPULATION ABILITIES IS RESTRICTED TO TASKS WHERE ITS ROLE CONSISTS OF DELIVERING SENSORS TO A DESIRED LOCATION. THE ENABLING CAPABILITIES FOR SUCH TASKS COMPRISE LOCALIZATION AND NAVIGATION BOTH WELL-STUDIED IN THE CONTEXT OF AFFS. HOWEVER ADDING THE CAPABILITY TO PHYSICALLY INTERACT WITH THE ENVIRONMENT THROUGH MANIPULATION COULD GREATLY INCREASE AFF'S REACH LITERALLY AND FIGURATIVELY. IN THIS PROJECT WE AIM TO DEVELOP THE HARDWARE AND SOFTWARE TOOLS THAT ENABLE VERSATILE MANIPULATION FOR AFFS IN A SMALL LIGHTWEIGHT PACKAGE AND WITH HIGH-DELAY LOW-THROUGHPUT SUPERVISORY CONTROL. WE PLAN TO EQUIP AFFS WITH NEWLY DEVELOPED DEXTEROUS ENDEFFECTORS ALONG WITH THE PLANNING AND CONTROL METHODS TO OPERATE THEM. WE AIM TO DEMONSTRATE NEW CAPABILITIES ON TASKS INVOLVING OBJECT ACQUISITION AND TRANSPORT PART INSERTION AND EXTRACTION BUTTON OR LEVER OPERATION DOCKING AND PERCHING IN REALISTIC ENVIRONMENTS EMULATING AN AFF PLATFORM OPERATING IN CLOSE PROXIMITY TO A HUMAN CREW. WE TAKE A COMBINED APPROACH ADDRESSING BOTH THE HARDWARE AND SOFTWARE COMPONENTS OF THE TASK. WE BELIEVE THAT INNOVATIONS IN THE FOLLOWING AREAS WILL SERVE AS ENABLERS FOR THE DESIRED CAPABILITIES: * COMPACT KINEMATIC CHAINS VIA MULTI-DEGREE-OF-FREEDOM (MULTI-DOF) CABLE-DRIVEN JOINTS. ONE OF THE KEY PROBLEMS FOR MANIPULATION ON AN AFF IS ACHIEVING DEXTERITY IN A SMALL PACKAGE. HIGH CONFIGURABILITY THROUGH SEQUENCES OF TRADITIONAL ONE-DOF JOINTS DRIVEN BY CO-LOCATED MOTORS REQUIRES MULTIPLE SEGMENTS IN A KINEMATIC CHAIN. WE WILL DEVELOP MULTI-DOF JOINTS DRIVEN BY ELASTIC TENDONS AND STABILIZED BY LIGAMENTS AIMING FOR HIGH FLEXIBILITY WITH AS FEW AS TWO SEGMENTS IN A KINEMATIC CHAIN. * UNDERACTUATION AND PASSIVE COMPLIANCE THROUGH HARDWARE IMPLEMENTATION OF SOFT SYNERGIES IN HAND MOVEMENT. PASSIVELY COMPLIANT UNDERACTUATION METHODS FOR DEXTEROUS ROBOT HANDS KNOWN AS "SOFT SYNERGIES" HAVE MULTIPLE ADVANTAGES FOR AFFS. USING FEWER MOTORS THAN DOFS LEADS TO COMPACT LIGHTWEIGHT DESIGNS; PASSIVE COMPLIANCE CAN HELP REGULATE THE FORCES APPLIED TO THE ENVIRONMENT WITHOUT COMPLEX HARDWARE FOR CLOSED-LOOP FORCE CONTROL. WE WILL COMBINE MULTIPLE SOFT SYNERGIES IN A SINGLE END-EFFECTOR DESIGN AIMING TO ACHIEVE THE VERSATILITY NEEDED FOR MULTIPLE MANIPULATION TASKS. * HARDWARE-AWARE SUPERVISORY CONTROL METHODS ABLE TO QUANTIFY ROBUSTNESS TO EXECUTION ERRORS. PASSIVE COMPLIANCE DURING GRASPING CAN INCREASE ROBUSTNESS TO ERRORS DURING THE EXECUTION FOR EXAMPLE BY INCREASING THE "CAPTURE REGION" FOR A TARGET OBJECT WHILE GRASPING. A SUPERVISORY CONTROL AWARE OF THE ERROR-CORRECTING ABILITY OF THE HARDWARE CAN ANALYZE THE TASK AS IT IS BEING EXECUTED AND CALL FOR HUMAN ASSISTANCE ONLY WHEN NEEDED. WE POSIT THAT A TIGHTER INTEGRATION BETWEEN HARDWARE DESIGN AND SUPERVISORY CONTROL METHODS WILL REDUCE THE NEED FOR OPERATOR INTERVENTIONS AND INCREASE OVERALL ROBUSTNESS. BEYOND THE SPECIFIC GOALS OF THIS PROJECT THE TECHNOLOGIES DEVELOPED HERE CAN BE FURTHER EXPLOITED IN SPACE AND OTHER DOMAINS. AS MANIPULATION CAPABILITIES OF AFFS INCREASE IN DEXTERITY AND ROBUSTNESS MORE TASKS WILL BECOME FEASIBLE INCREASING THE ROLE OF THE PLATFORMS IN SUPPORTING THE CREW. ADVANCES IN SENSING REASONING ABOUT THE ENVIRONMENT AND PLANNING WILL PROGRESSIVELY DECREASE THE NEED FOR INTERVENTION BY A HUMAN OPERATOR AIMING TOWARDS FULLY AUTONOMOUS OPERATION. SOME OF THE CORE DESIGNS AND METHODS WE PROPOSE TO DEVELOP HAVE CROSSCUTTING POTENTIAL ACROSS OTHER DOMAINS THAT STAND TO BENEFIT FROM AUTOMATED MANIPULATION SKILLS SUCH AS SURFACE MISSIONS OR EXTRA-VEHICULAR ACTIVITIES.