### Abstract

Comparatively slow growth in power storage and generation makes power-efficient designs desirable for legged robot systems. One important cause of power losses in robotic systems is the mechanical antagonism phenomenon, i.e. one or more motors being used as brakes while the others exert positive energy. This two-part paper first develops a rigorous understanding of mechanical antagonism in multiactuator robotic limbs. We show that, for a 6-DoF robot arm, there exist 4096 distinct regions in the force-velocity space of the end effector (the regions are distinguishable by the sign of the actuator powers). Only sixty-four of these regions correspond with operating points where all actuators exert positive power into the system. In the second part of the paper, we formulate a convex optimization problem which minimizes mechanical antagonism in redundant manipulators. We solve the optimization problem which becomes the derivation for a new, power-optimal, pseudoinverse for non-square Jacobians. In fact, two such pseudoinverses are derived: one for statically determinate systems, such as serial manipulators, and one for statically indeterminate systems, such as parallel manipulators.

Original language | English (US) |
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Title of host publication | 41st Mechanisms and Robotics Conference |

Publisher | American Society of Mechanical Engineers (ASME) |

Volume | 5B-2017 |

ISBN (Electronic) | 9780791858189 |

DOIs | |

State | Published - Jan 1 2017 |

Externally published | Yes |

Event | ASME 2017 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference, IDETC/CIE 2017 - Cleveland, United States Duration: Aug 6 2017 → Aug 9 2017 |

### Other

Other | ASME 2017 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference, IDETC/CIE 2017 |
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Country | United States |

City | Cleveland |

Period | 8/6/17 → 8/9/17 |

### Fingerprint

### ASJC Scopus subject areas

- Mechanical Engineering
- Computer Graphics and Computer-Aided Design
- Computer Science Applications
- Modeling and Simulation

### Cite this

*41st Mechanisms and Robotics Conference*(Vol. 5B-2017). American Society of Mechanical Engineers (ASME). https://doi.org/10.1115/DETC2017-67942

**Understanding power loss due to mechanical antagonism and a new power-optimal pseudoinverse for redundant actuators.** / Cahill, Nathan M.; Sugar, Thomas; Holgate, Matthew; Schroeder, Kyle.

Research output: Chapter in Book/Report/Conference proceeding › Conference contribution

*41st Mechanisms and Robotics Conference.*vol. 5B-2017, American Society of Mechanical Engineers (ASME), ASME 2017 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference, IDETC/CIE 2017, Cleveland, United States, 8/6/17. https://doi.org/10.1115/DETC2017-67942

}

TY - GEN

T1 - Understanding power loss due to mechanical antagonism and a new power-optimal pseudoinverse for redundant actuators

AU - Cahill, Nathan M.

AU - Sugar, Thomas

AU - Holgate, Matthew

AU - Schroeder, Kyle

PY - 2017/1/1

Y1 - 2017/1/1

N2 - Comparatively slow growth in power storage and generation makes power-efficient designs desirable for legged robot systems. One important cause of power losses in robotic systems is the mechanical antagonism phenomenon, i.e. one or more motors being used as brakes while the others exert positive energy. This two-part paper first develops a rigorous understanding of mechanical antagonism in multiactuator robotic limbs. We show that, for a 6-DoF robot arm, there exist 4096 distinct regions in the force-velocity space of the end effector (the regions are distinguishable by the sign of the actuator powers). Only sixty-four of these regions correspond with operating points where all actuators exert positive power into the system. In the second part of the paper, we formulate a convex optimization problem which minimizes mechanical antagonism in redundant manipulators. We solve the optimization problem which becomes the derivation for a new, power-optimal, pseudoinverse for non-square Jacobians. In fact, two such pseudoinverses are derived: one for statically determinate systems, such as serial manipulators, and one for statically indeterminate systems, such as parallel manipulators.

AB - Comparatively slow growth in power storage and generation makes power-efficient designs desirable for legged robot systems. One important cause of power losses in robotic systems is the mechanical antagonism phenomenon, i.e. one or more motors being used as brakes while the others exert positive energy. This two-part paper first develops a rigorous understanding of mechanical antagonism in multiactuator robotic limbs. We show that, for a 6-DoF robot arm, there exist 4096 distinct regions in the force-velocity space of the end effector (the regions are distinguishable by the sign of the actuator powers). Only sixty-four of these regions correspond with operating points where all actuators exert positive power into the system. In the second part of the paper, we formulate a convex optimization problem which minimizes mechanical antagonism in redundant manipulators. We solve the optimization problem which becomes the derivation for a new, power-optimal, pseudoinverse for non-square Jacobians. In fact, two such pseudoinverses are derived: one for statically determinate systems, such as serial manipulators, and one for statically indeterminate systems, such as parallel manipulators.

UR - http://www.scopus.com/inward/record.url?scp=85034835137&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=85034835137&partnerID=8YFLogxK

U2 - 10.1115/DETC2017-67942

DO - 10.1115/DETC2017-67942

M3 - Conference contribution

AN - SCOPUS:85034835137

VL - 5B-2017

BT - 41st Mechanisms and Robotics Conference

PB - American Society of Mechanical Engineers (ASME)

ER -