John Kenneth Salisbury

The Intuitive/sup TM/ telesurgery system: overview and application

The paper briefly describes daVinci/sup TM/, a surgical telerobot designed to provide enhanced dexterity to doctors performing minimally invasive surgical procedures. The rationale for a full 7-degree-of-freedom master-slave system is presented along with a discussion of the resulting computational architecture and recent clinical applications.

Mechanics Modeling of Tendon-Driven Continuum Manipulators

Continuum robotic manipulators articulate due to their inherent compliance. Tendon actuation leads to compression of the manipulator, extension of the actuators, and is limited by the practical constraint that tendons cannot support compression. In light of these observations, we present a new linear model for transforming desired beam configuration to tendon displacements and vice versa. We begin from first principles in solid mechanics by analyzing the effects of geometrically nonlinear tendon loads. These loads act both distally at the termination point and proximally along the conduit contact interface. The resulting model simplifies to a linear system including only the bending and axial modes of the manipulator as well as the actuator compliance. The model is then manipulated to form a concise mapping from beam configuration-space parameters to n redundant tendon displacements via the internal loads and strains experienced by the system. We demonstrate the utility of this model by implementing an optimal feasible controller. The controller regulates axial strain to a constant value while guaranteeing positive tendon forces and minimizing their magnitudes over a range of articulations. The mechanics-based model from this study provides insight as well as performance gains for this increasingly ubiquitous class of manipulators.

The Black Falcon: a teleoperated surgical instrument for minimally invasive surgery

This paper presents the Black Falcon, an eight degree-of-freedom teleoperator slave with a dextrous wrist for minimally invasive surgery (MIS). We show how teleoperation can address several key problems in MIS by increasing dexterity and degrees of freedom, by giving the surgeon some force feedback to feel instrument-tissue interactions and by eliminating geometric discrepancies between actual and observed tool motions. We discuss relevant design constraints, summarize the mechanism design and give data showing the quality of force reflection achieved. We demonstrate suturing along arbitrarily oriented suture lines in animal tissue, a task essentially impossible using current instruments.

Stability of Haptic Rendering: Discretization, Quantization, Time Delay, and Coulomb Effects

Rendering stiff virtual objects remains a core challenge in the field of haptics. A study of this problem is presented, which relates the maximum achievable object stiffness to the elements of the control loop. In particular, we examine how the sampling rate, quantization, computational delay, and amplifier dynamics interact with the inertia, natural viscous, and Coulomb damping of the haptic device. Nonlinear effects create distinct stability regions, and many common devices operate stably, yet in violation of passivity criteria. An energy-based approach provides theoretical insights, supported by simulations, experimental data, and a describing function analysis. The presented results subsume previously known stability conditions

Interpretation of contact geometries from force measurements

As manipulation practice moves toward greater dexterity through the use of more complex end effectors it becomes necessary to sense more details of the interactions between the manipulator and grasped object. Accurate modeling of grasp kinematics is necessary for high quality control of the force and motion states of the grasped object. To do this one must ascertain the location, orientation and type of contact that occurs between fingers and objects. We present an approach for determining geometric features of certain basic types of contact. The characteristics of forces and moments transmitted through point, line and surface contacts are considered and used to determine the number and placement of sensing elements. Several sensor designs are given that use a minimal number of strain gauge measurements to locate the position and orientation of point and line contacts.

The Effect of coulomb friction and stiction on force control

We have studied the effect of Coulomb friction and stiction on force control with integral feedback. The force is applied through a compliant transmission by a velocity-controlled motor. Our results show that stiction can cause the applied force to enter a limit cycle. Coulomb friction can extend the system stability bounds but may lead to an input-dependent stability. Under certain conditions Coulomb friction causes an actuator limit cycle even though the applied force approaches the desired steady state force. Based on the analysis, we give design guidelines for increasing the performance.

Towards a personal robotics development platform: Rationale and design of an intrinsically safe personal robot

The most critical challenge for Personal Robotics is to manage the issue of human safety and yet provide the physical capability to perform useful work. This paper describes a novel concept for a mobile, 2-armed, 25-degree-of- freedom system with backdrivable joints, low mechanical impedance, and a 5 kg payload per arm. System identification, design safety calculations and performance evaluation studies of the first prototype are included, as well as plans for a future development.

Augmentation of grasp robustness using intrinsic tactile sensing

The authors discuss the application of intrinsic tactile sensing (ITS) to grasp and manipulation control. A brief description of ITS, i.e., contact sensing based on force/torque measurements at fingertips, is provided. A method for using sensory feedback in the control of grasp forces to augment grasp robustness against slippage is discussed with respect to a simple grasp type; simulation and experimental data are provided. The possible generalization of this sensor-driven approach to the control of optimal grasp force in complex grasp configurations is addressed.<<ETX>>

The effect of quantization and Coulomb friction on the stability of haptic rendering

Rendering stiff virtual objects remains a core challenge in the field of haptics. A study of this problem is presented, which relates the maximum achievable object stiffness to the elements of the control loop. In particular, we examine how the sampling rate and quantization of position measurements interact with the inertia, natural viscous, and Coulomb damping of the haptic device. The resulting stability criterion generalizes previously known conditions. Simulations and experimental results support the theoretical analysis based on the passivity and describing function approaches.

In Vivo Micro-Image Mosaicing

Recent advances in optical imaging have led to the development of miniature microscopes that can be brought to the patient for visualizing tissue structures in vivo. These devices have the potential to revolutionize health care by replacing tissue biopsy with in vivo pathology. One of the primary limitations of these microscopes, however, is that the constrained field of view can make image interpretation and navigation difficult. In this paper, we show that image mosaicing can be a powerful tool for widening the field of view and creating image maps of microanatomical structures. First, we present an efficient algorithm for pairwise image mosaicing that can be implemented in real time. Then, we address two of the main challenges associated with image mosaicing in medical applications: cumulative image registration errors and scene deformation. To deal with cumulative errors, we present a global alignment algorithm that draws upon techniques commonly used in probabilistic robotics. To accommodate scene deformation, we present a local alignment algorithm that incorporates deformable surface models into the mosaicing framework. These algorithms are demonstrated on image sequences acquired in vivo with various imaging devices including a hand-held dual-axes confocal microscope, a miniature two-photon microscope, and a commercially available confocal microendoscope.