Tools for quantifying teleoperation system performance and stability when communication delays are present are provided A general multivariable system architecture is utilized which includes all four-types of data transmission between master and slave: force and velocity in both directions It is shown that a proper use of an four channels is of critical importance in achieving high performance telepresence in the sense of accurate transmission of task impedances to the operator It is also shown that transparency and robust stability (passivity) are conflicting design goals in teleoperation systems The analysis is illustrated by comparing transparency and stability in two common architectures, as well as a recent passivated approach and a new transparency-optimized architecture, using simplified one-degree-of-freedom examples >

Stability and transparency in bilateral teleoperation

We survey progress over the past 25 years in the development of microscale devices for pumping fluids. We attempt to provide both a reference for micropump researchers and a resource for those outside the field who wish to identify the best micropump for a particular application. Reciprocating displacement micropumps have been the subject of extensive research in both academia and the private sector and have been produced with a wide range of actuators, valve configurations and materials. Aperiodic displacement micropumps based on mechanisms such as localized phase change have been shown to be suitable for specialized applications. Electroosmotic micropumps exhibit favorable scaling and are promising for a variety of applications requiring high flow rates and pressures. Dynamic micropumps based on electrohydrodynamic and magnetohydrodynamic effects have also been developed. Much progress has been made, but with micropumps suitable for important applications still not available, this remains a fertile area for future research.

https://microfluidics.stanford.edu/Publications/Micropumps_Cooling/Laser%20Review%20of%20Micropumps%20in%20JMM.pdf

A review of micropumps

Bilateral teleoperation: An historical survey

A system for performing minimally invasive cardiac procedures. The system includes a pair of surgical instruments that are coupled to a pair of robotic arms. The instruments have end effectors that can be manipulated to hold and suture tissue. The robotic arms are coupled to a pair of master handles by a controller. The handles can be moved by the surgeon to produce a corresponding movement of the end effectors. The movement of the handles is scaled so that the end effectors have a corresponding movement that is different, typically smaller, than the movement performed by the hands of the surgeon. The scale factor is adjustable so that the surgeon can control the resolution of the end effector movement. The movement of the end effector can be controlled by an input button, so that the end effector only moves when the button is depressed by the surgeon. The input button allows the surgeon to adjust the position of the handles without moving the end effector, so that the handles can be moved to a more comfortable position. The system may also have a robotically controlled endoscope which allows the surgeon to remotely view the surgical site. A cardiac procedure can be performed by making small incisions in the patient's skin and inserting the instruments and endoscope into the patient. The surgeon manipulates the handles and moves the end effectors to perform a cardiac procedure such as a coronary artery bypass graft.

Method and apparatus for performing minimally invasive cardiac procedures

Reports the completion of four fundamental fluidic operations considered essential to build digital microfluidic circuits, which can be used for lab-on-a-chip or micro total analysis system (/spl mu/TAS): 1) creating, 2) transporting, 3) cutting, and 4) merging liquid droplets, all by electrowetting, i.e., controlling the wetting property of the surface through electric potential. The surface used in this report is, more specifically, an electrode covered with dielectrics, hence, called electrowetting-on-dielectric (EWOD). All the fluidic movement is confined between two plates, which we call parallel-plate channel, rather than through closed channels or on open surfaces. While transporting and merging droplets are easily verified, we discover that there exists a design criterion for a given set of materials beyond which the droplet simply cannot be cut by EWOD mechanism. The condition for successful cutting is theoretically analyzed by examining the channel gap, the droplet size and the degree of contact angle change by electrowetting on dielectric (EWOD). A series of experiments is run and verifies the criterion.

Creating, transporting, cutting, and merging liquid droplets by electrowetting-based actuation for digital microfluidic circuits

Many of the current implementations of exoskeletons for the lower extremities are conceived to either augment the user's load-carrying capabilities or reduce muscle activation during walking. Comparatively little research has been conducted on enabling an exoskeleton to increase the agility of lower-limb movements. One obstacle in this regard is the inertia of the exoskeleton's mechanism, which tends to reduce the natural frequency of the human limbs. A control method is presented that produces an approximate compensation of the inertia of an exoskeleton's mechanism. The controller was tested on a statically mounted, single-degree-of-freedom (DOF) exoskeleton that assists knee flexion and extension. Test subjects performed multiple series of leg-swing movements in the context of a computer-based, sprint-like task. A large initial acceleration of the leg was needed for the subjects to track a virtual target on a computer screen. The uncompensated inertia of the exoskeleton mechanism slowed down the transient response of the subjects' limb, in comparison with trials performed without the exoskeleton. The subsequent use of emulated inertia compensation on the exoskeleton allowed the subjects to improve their transient response for the same task.

http://ambarish.com/paper/ollinger_colgate_peshkin_goswami_leg_swing_agility_exo_Inst_Mech_Eng_Part_H.pdf

A one-degree-of-freedom assistive exoskeleton with inertia compensation: the effects on the agility of leg swing motion

Revolute-jointed cobots depend on continuously variable transmissions (CVTs). CVTs constrain the speed ratio between two shafts to a particular value within a continuous range. The spherical CVT is well suited to cobots, but like other point contact transmissions, achieving good performance is challenging. We have studied the contact mechanics of the spherical CVT under certain simplifying assumptions. Results of the calculations are compared to experimental measurements of an instrumented CVT. Improved CVT performance may require better control of compliance and contact forces in the CVT. Results for the contact forces under load conditions are shown. We conclude with a discussion of design implications for improved CVTs.Copyright © 2002 by ASME

/pdf/toward-improved-cvts-theoretical-and-experimental-results-155j1pdrt0.pdf

Toward improved CVTs: theoretical and experimental results

Of several possible forms of human-robot collaborative manipulation, we focus on the case where the human and the robot jointly manipulate a common load. In our formulation, the robot's role is to provide a constraint surface to guide the motion of the load. The value of this form of interaction, in terms of ergonomics, accuracy, or speed, depends on how humans make use of such constraints. We are studying natural single-arm manipulation of a load constrained to move along a guide rail. In this paper we present results of experiments showing that subjects apply significant forces against the rail, depending on the configuration of the arm and the orientation of the rail. These forces are unnecessary for the manipulation task, and we hypothesize that humans apply forces against the constraint to simplify the manipulation task.

/pdf/kinematic-constraints-for-assisted-single-arm-manipulation-2omqvrhfqt.pdf

Kinematic constraints for assisted single-arm manipulation

A touch interface device that produces tactile and audio output comprising a touch surface, an first electrode coupled to the touch surface that receives a first haptic/audio output potential, a second electrode coupled to a low impedance return path to the device, the first and second electrodes being configured such that when both the first and second electrodes are touched by an appendage of a user, a current flows between the first and second electrodes and the appendage, where the current creates an electric field that imparts a controlled electrostatic force at interfaces of the first electrode and the appendage, and wherein the electrostatic force provides tactile feedback to the appendage of the user and causes vibration in the surrounding air that is audible to the user.

Apparatus for unified audio tactile feedback

Both haptic and visual senses play a role in how we explore our environment. Previous studies have shown that vision plays a very strong role in perception of object stiffness, yet quantification of the contributions of both haptic and visual feedback remains elusive. This study uses a behavioral adaptation approach in order to better understand how humans perceive stiffness. Namely, subjects make targeted reaches across a virtual surface of varying stiffness, adapting to the new environment. The hand's cursor position is visually distorted to seem more stiff for one group, less stiff for another, and no distortion for the control group. Area reaching deviation (ARD) and post-adaptation interface forces, used in previous studies, were the two outcome measures used to determine differences between groups. We compare the slopes of the post-adaptation force-stiffness relations to quantify the effect of visual distortion. Our results indicate that making a stiff surface look more compliant has a greater effect on humans than making a compliant surface look more stiff

/pdf/a-behavioral-adaptation-approach-to-identifying-visual-2ckwizic43.pdf

J.E. Colgate

Papers

A one-degree-of-freedom assistive exoskeleton with inertia compensation: the effects on the agility of leg swing motion

Toward improved CVTs: theoretical and experimental results

Kinematic constraints for assisted single-arm manipulation

Apparatus for unified audio tactile feedback

A Behavioral Adaptation Approach to Identifying Visual Dependence of Haptic Perception