Eric L. Faulring

A high performance 6-DOF haptic Cobot

A novel, six-degree-of-freedom active haptic device is introduced. A parallel kinematic design and the use of non-holonomic continuously variable transmissions provide extremely high stiffness in directions that would violate a virtual constraint. At the same time, smooth motion is permitted tangential to virtual constraints and in open space. High quality constraint surfaces having one to five dimensions can be displayed. A notable feature of this device is the mutual coupling of all six linear actuators to a common rotating cylinder, which can, optionally, be powered. The resulting mechanism is simple to control, and allows several new control strategies in Cobotic haptics.

The Cobotic Hand Controller: Design, Control and Performance of a Novel Haptic Display

The design, control and performance of the Cobotic Hand Controller, a novel, six-degree-of-freedom, admittance controlled haptic display is examined. A highly geared admittance architecture is often used to render high impedances with reasonable sized actuators for a haptic display. The Cobotic Hand Controller is an extremely faithful realization of an admittance display, since it is capable of obtaining an infinite gear ratio and can render infinite impedances (up to its own structural stiffness). The incorporation of continuously variable transmissions utilizing hardened steel elements in dry-friction rolling contact provide the Cobotic Hand Controller with high bandwidth, low power requirements, and an extremely wide stable dynamic range. Here, an admittance based control algorithm for powered cobots, a novel solution to the actuation redundancy of this device, and a heuristic to avoid slip in the transmissions are described. The performance of the Cobotic Hand Controller is measured in terms of dynamic range.

Lessons learned from a novel teleoperation testbed

Purpose – Sets out to discuss lessons learned from the creation and use of an over‐the‐internet teleoperation testbed.Design/methodology/approach – Seven lessons learned from the testbed are presented.Findings – This teleoperation interface improves task performance, as proved by a single demonstration.Originality/value – In helping to overcome time‐delay difficulties in the operation, leading to dramatically improved task performance, this study contributes significantly to the improvement of teleoperation by making better use of human skills.

Haptic Display of Constrained Dynamic Systems via Admittance Displays

In the Cobotic Hand Controller, we have introduced an admittance display that can render very high impedances (up to its own structural stiffness). This is due to its use of infinitely variable transmissions. While admittance displays typically excel at rendering high impedances, the incorporation of infinitely variable transmissions in the Cobotic Hand Controller allows the stable display of a wide dynamic range, including low impedances. The existence of a display that excels at rendering high-impedance constraints, but has high-fidelity control of low impedances tangent to those constraints, has led us to describe an admittance control architecture not often examined in the haptics community. In this paper, we develop a comprehensive approach that enables rendering of rigid motion constraints while simultaneously preserving the physical integrity of the intended inertial dynamics tangent to those constraints. This is in contrast to conventional impedance-control algorithms that focus primarily on rendering reaction forces along contact normals with constraints. We present this algorithm here, which is general to all admittance displays, and report on its implementation with the Cobotic Hand Controller. We offer examples of rigid bodies and linkages subject to holonomic and/or nonholonomic constraints

Enhanced teleoperation for D&D

Remote systems are essential for reducing risk to human workers from hazardous radiation and difficult work environments, while improving productivity and reducing costs. The major drawback of currently available remote manipulator systems is that teleoperation is slow and imprecise. The presented work focuses on enhancing remote operation of tools for D&D tasks by introducing teleautonomy and telecollaboration. In teleautonomy, the robot performs a given task autonomously, while the human operator intervenes in the process as a supervisor. In telecollaboration, the human operator is passively constrained by a virtual fixture, but is responsible for the motion. This work, sponsored by the US Department of Energy (DOE) Environmental Management Science Program (EMSP), builds on a reactive, agent-based control architecture and robot control technology.

Haptic Interaction With Constrained Dynamic Systems

In this paper we are concerned with allowing the operator of a haptic display to interact with virtual systems having significant inertial dynamics and realistic constraints. We review the mathematical structure arising from the kinetic energy metric, required to create a virtual dynamics simulation consisting of rigid-body dynamics along with holonomic and/or nonholonomic motion constraints. We develop an admittance controller composed of feedforward and feedback terms, while preserving the integrity of the intended virtual dynamics simulation. This controller is implemented on the Cobotic Hand Controller, an admittance-type haptic display, and two examples are discussed.

Power Efficiency of the Rotational-to-Linear Infinitely Variable Cobotic Transmission

Abstract—Cobots are a class of robots that use infinitelyvariable transmissions to develop high fidelity programmableconstraint surfaces. Cobots consume very little electrical powereven when resisting high forces, and their transmissions arehighly power efficient across a broad range of transmissionratios. We have recently introduced the Cobotic Hand Controller,a haptic display that illustrates the high dynamic range andlow power consumption achievable by cobots. In this paperwe present models of the rotational-to-linear rolling contacttransmissions utilized in the Cobotic Hand Controller. We com-pare their efficiency to fixed ratio gear-trains. We also comparethe overall power efficiency of the cobotic architecture to thepower efficiency of a conventional electro-mechanical actuationscheme, for both constant and dynamic power flows. The coboticarchitecture is shown to be more efficient at frequencies andpower levels characteristic of voluntary human motions. I. I NTRODUCTION C OBOTIC devices control the relative velocities of theirlinks by modulating infinitely variable transmissions(IVTs) with small steering actuators [1]. Cobotic IVTs havebeen developed to relate two translational velocities, tworotational velocities, or a rotational velocity to a translationalvelocity, and have been utilized in a variety of haptic

High performance Cobotics

Cobots are a class of robots that use continuously variable transmissions to develop high fidelity programmable constraint surfaces. Cobots consume very little electrical power even when providing high output forces, and their transmissions are highly efficient across a broad range of transmission ratios. Cobotic transmissions also have the ability to act either as a brake or to become entirely free. The design and performance of the cobotic hand controller, a recently developed six-degree-of-freedom haptic display, is reviewed. This device illustrates the high dynamic range and low power consumption achievable by cobots. A thorough comparison of the power efficiency of a cobotic system versus a conventional electro-mechanical system is provided.

Cobotic Architecture for Prosthetics

We envision cobotic infinitely-variable transmissions (IVTs) as an enabling technology for haptics and prosthetics that will allow for increases in the dynamic range of these devices while simultaneously permitting reductions in actuator size and power requirements. Use of cobotic IVTs eliminates the need to make compromises on output flow and effort, which are inherent to choosing a fixed transmission ratio drivetrain. The result is a mechanism with enhanced dynamic range that extends continuously from a completely clutched state to a highly backdrivable state. This high dynamic range allows cobotic devices to control impedance with a high level of fidelity. In this paper, we discuss these and other motivations for using parallel cobotic transmission architecture in prosthetic devices

A Framework for the Simulation and Haptic Display of Dynamic Systems Subject to Holonomic Constraints

In this paper we present a framework that enables an operator to haptically and visually interact with a simulated dynamic environment subject to virtual holonomic constraints. The framework combines a geometric constraint solver with a constrained dynamics simulation engine that controls an admittance-type haptic display. This system takes on relevant issues in the context of assisted teleoperated tasks, from providing an intuitive interface for creating and combining virtual constraints, to haptically displaying rigid motion constraints in simulated environments subject to desired inertial dynamics. Two experiments carried out using the Cobotic Hand Controller haptic display are presented.