Avi Okon

Lemur IIb: a Robotic System for Steep Terrain Access

Purpose – Introduces the Lemur IIb robot which allows the investigation of the technical hurdles associated with free climbing in steep terrain. These include controlling the distribution of contact forces during motion to ensure holds remain intact and to enable mobility through over‐hangs. Efforts also can be applied to further in‐situ characterization of the terrain, such as testing the strength of the holds and developing models of the individual holds and a terrain map.Design/methodology/approach – A free climbing robot system was designed and integrated. Climbing end‐effector were investigated and operational algorithms were developed.Findings – A 4‐limbed robotic system used to investigate several aspects of climbing system design including the mechanical system (novel end‐effectors, kinematics, joint design), sensing (force, attitude, vision), low‐level control (force‐control for tactile sensing and stability management), and planning (joint trajectories for stability). A new class of Ultrasonic/S...

Sustainable cooperative robotic technologies for human and robotic outpost infrastructure construction and maintenance

Robotic Construction Crew (RCC) is a heterogeneous multi-robot system for autonomous acquisition, transport, and precision mating of components in construction tasks. RCC minimizes use of resources constrained by a space environment such as computation, power, communication, and sensing. A behavior-based architecture provides adaptability and robustness despite low computational requirements. RCC successfully performs several construction related tasks in an emulated outdoor environment despite high levels of uncertainty in motions and sensing. This paper provides quantitative results for formation keeping in component transport, precision instrument placement, and construction tasks.

Behavior-based multi-robot collaboration for autonomous construction tasks

The robot construction crew (RCC) is a heterogeneous multi-robot system for autonomous construction of a structure through assembly of long components. The two-robot team demonstrates component placement into an existing structure in a realistic environment. The task requires component acquisition, cooperative transport, and cooperative precision manipulation. A behavior-based architecture provides adaptability. The RCC approach minimizes computation, power, communication, and sensing for applicability to space-related construction efforts, but the techniques are applicable to terrestrial construction tasks.

Precision Manipulation with Cooperative Robots

We present a cooperative approach to robotic precision manipulation tasks in the context of autonomous robotic construction. Precision manipulation requires a firm grasp, which constraints the team to rigidly maintain formation during transport and manipulation. A leader/follower approach with force sensing to provide relative formation information and vision to provide team position relative to construction components is applied. Our approach demonstrates successful, reliable performance of a construction task requiring cooperative transport and placement of structure components. Qualitative and quantitative performance results are provided.

The Lemur II-Class Robots for Inspection and Maintenance of Orbital Structures: A System Description

The assembly, inspection, and maintenance requirements of permanent installations in space demand robots that provide a high level of operational flexibility relative to mass and volume. Such demands point to robots that are dexterous, have significant processing and sensing capabilities, and can be easily reconfigured (both physically and algorithmically). Evolving from Lemur I, Lemur IIa is an extremely capable system that both explores mechanical design elements and provides an infrastructure for the development of algorithms (such as force control for mobility and manipulation and adaptive visual feedback). The physical layout of the system consists of six, 4-degree-of-freedom limbs arranged axisymmetrically about a hexagonal body platform. These limbs incorporate a “quick-connect” end-effector feature below the distal joint that allows the rapid change-out of any of its tools. The other major subsystem is a stereo camera set that travels along a ring track, allowing omnidirectional vision. The current Lemur IIa platform represents the jumping-off point toward more advanced robotic platforms that will support NASA’s Vision for Space Exploration, which calls for a sustained presence in space. This paper lays out the mechanical, electrical, and algorithmic elements of Lemur IIa and discusses the future directions of development in those areas.

Mars Science Laboratory Algorithms and Flight Software for Autonomously Drilling Rocks

One of the goals of the Mars Science Laboratory (MSL) mission is to collect powderized samples from the interior of rocks in order to deliver these samples to onboard science instruments. This paper describes the algorithms and software used to control the drill, which is the component of the sample collection and delivery system that directly interacts with rocks to create and acquire powderized samples from their interior. This is the first time that autonomous drilling of rocks has ever been performed on another planet. One of the most important components of the algorithm used for drilling is a force feedback control system used to regulate the force applied to the rock during drilling. This algorithm and all of the other algorithms and software used to enable the process of robustly, efficiently, and autonomously drilling into rocks with a priori unknown and widely varying properties are described in detail in this paper. Results are shown from drilling rocks using the drill software on testbed hardware on Earth as part of the software development process. Results are also shown from the first holes drilled with the flight vehicle on Mars, thus successfully demonstrating the first extraterrestrial autonomous drilling of a rock.

A comparison of force sensing techniques for planetary manipulation

Five techniques for sensing forces with a manipulator are compared analytically and experimentally. The techniques compared are: a six-axis wrist force/torque sensor, joint torque sensors, link strain gauges, motor current sensors, and flexibility modeling. The accuracy and repeatability of each technique is quantified and compared. The relative complexity and the impact on flight design of each technique are also compared. The results presented can be used in a trade study for missions requiring manipulator force sensing capabilities

Vision-guided self-alignment and manipulation in a walking robot

One of the robots under development at the NASAs Jet Propulsion Laboratory (JPL) is the limbed excursion mechanical utility robot, or LEMUR. Several of the tasks slated for this robot require computer vision, as a system, to interface with the other systems in the robot, such as walking, body pose adjustment, and manipulation. This paper describes the vision algorithms used in several tasks, as well as the vision-guided manipulation algorithms developed to mitigate mismatches between the vision system and the limbs used for manipulation. Two system-level tasks are described, one involving a two meter walk culminating in a bolt-fastening task and one involving a vision-guided alignment ending with the robot mating with a docking station

Optimal force control of a vibro-impact system for autonomous drilling applications

The optimal force control solution for second-order vibro-impact systems with and without friction nonlinearity is introduced and explicitly solved herein. In particular, a finite-step algorithm is developed which generates open-loop force control laws which are designed to minimize the expended control energy per impact cycle, while ensuring that each impact occurs with sufficient impact velocity. When electromagnetic motors are employed to realize the control forces, the performance of the percussive unit becomes heat-limited. The article demonstrates that the controls needed to drive the hammering mechanism with a minimal amount of dissipated energy is a solution that can be derived in closed form. A closed-loop control architecture based on this result is introduced.