Allison M. Okamura

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As a flexible needle with a bevel tip is pushed through soft tissue, the asymmetry of the tip causes the needle to bend. We propose that, by using nonholonomic kinematics, control and path planning, an appropriately designed needle can be steered through tissue to reach a specified 3D target. Such steering capability will enhance targeting accuracy and(More)
The modeling of forces during needle insertion into soft tissue is important for accurate surgical simulation, preoperative planning, and intelligent robotic assistance for percutaneous therapies. We present a force model for needle insertion and experimental procedures for acquiring data from ex vivo tissue to populate that model. Data were collected from(More)
Vibrations can significantly enhance touch perception for virtual environment applications with minimal design complexity and cost. In order to create realistic vibrotactile feedback, we collected vibrations, forces, and velocities during various tasks executed with a stylus: tapping on materials, stroking textures, and puncturing membranes. Empirical(More)
We present the design and implementation of a vision-based system for cooperative manipulation at millimeter to micrometer scales. The system is based on an admittance control algorithm that implements a broad class of guidance modes called virtual fixtures. A virtual fixture, like a real fixture, limits the motion of a tool to a prescribed class or range(More)
The "virtual wall" is the most common building block used in constructing haptic virtual environments. A virtual wall is typically based on a simple spring model, with unilateral constraints that allow the user to make and break contact with a surface. There are a number of factors (sample-and-hold, device dynamics, sensor quantization, etc.) that cause(More)
In this article, we describe and demonstrate control algorithms for general motion constraints. These constraints are designed to enhance the accuracy and speed of a user manipulating in an environment with the assistance of a cooperative or telerobotic system. Our method uses a basis of preferred directions, created off-line or in real-time using sensor(More)
PURPOSE OF REVIEW Robot-assisted minimally invasive surgery (RMIS) holds great promise for improving the accuracy and dexterity of a surgeon and minimizing trauma to the patient. However, widespread clinical success with RMIS has been marginal. It is hypothesized that the lack of haptic (force and tactile) feedback presented to the surgeon is a limiting(More)
We explore motion planning for a new class of highly flexible bevel-tip medical needles that can be steered to previously unreachable targets in soft tissue. Planning for these procedures is difficult because the needles bend during insertion and cause the surrounding soft tissues to displace and deform. In this paper, we develop a planning algorithm for(More)
Haptic virtual fixtures are software-generated force and position signals applied to human operators in order to improve the safety, accuracy, and speed of robot-assisted manipulation tasks. Virtual fixtures are effective and intuitive because they capitalize on both the accuracy of robotic systems and the intelligence of human operators. In this paper, we(More)