Kuchenbecker, Katherine J.
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Publication Spectral Subtraction of Robot Motion Noise for Improved Event Detection in Tactile Acceleration Signals(2012-06-01) Kuchenbecker, Katherine J; McMahan, WilliamNew robots for teleoperation and autonomous manipulation are increasingly being equipped with high-bandwidth accelerometers for measuring the transient vibrational cues that occur during con- tact with objects. Unfortunately, the robot's own internal mechanisms often generate significant high-frequency accelerations, which we term ego-vibrations. This paper presents an approach to characterizing and removing these signals from acceleration measurements. We adapt the audio processing technique of spectral subtraction over short time windows to remove the noise that is estimated to occur at the robot's present joint velocities. Implementation for the wrist roll and gripper joints on a Willow Garage PR2 robot demonstrates that spectral subtraction significantly increases signal-to-noise ratio, which should improve vibrotactile event detection in both teleoperation and autonomous robotics.Publication Refined Methods for Creating Realistic Haptic Virtual Textures from Tool-Mediated Contact Acceleration Data(2012-03-01) Culbertson, Heather; Romano, Joseph M; Castillo, Pablo; Mintz, Max; Kuchenbecker, Katherine JDragging a tool across a textured object creates rich high-frequency vibrations that distinctly convey the physical interaction between the tool tip and the object surface. Varying one’s scanning speed and normal force alters these vibrations, but it does not change the perceived identity of the tool or the surface. Previous research developed a promising data-driven approach to embedding this natural complexity in a haptic virtual environment: the approach centers on recording and modeling the tool contact accelerations that occur during real texture interactions at a limited set of force-speed combinations. This paper aims to optimize these prior methods of texture modeling and rendering to improve system performance and enable potentially higher levels of haptic realism. The key elements of our approach are drawn from time series analysis, speech processing, and discrete-time control. We represent each recorded texture vibration with a low-order auto-regressive moving-average (ARMA) model, and we optimize this set of models for a specific tool-surface pairing (plastic stylus and textured ABS plastic) using metrics that depend on spectral match, final prediction error, and model order. For rendering, we stably resample the texture models at the desired output rate, and we derive a new texture model at each time step using bilinear interpolation on the line spectral frequencies of the resampled models adjacent to the user’s current force and speed. These refined processes enable our TexturePad system to generate a stable and spectrally accurate vibration waveform in real time, moving us closer to the goal of virtual textures that are indistinguishable from their real counterparts.Publication Spatially Distributed Tactile Feedback for Kinesthetic Motion Guidance(2010-04-08) Kapur, Pulkit; Jensen, Mallory; Kuchenbecker, Katherine J.; Buxbaum, Laurel J.; Jax, Steven A.Apraxic stroke patients need to perform repetitive arm movements to regain motor functionality, but they struggle to process the visual feedback provided by typical virtual rehabilitation systems. Instead, we imagine a low cost sleeve that can measure the movement of the upper limb and provide tactile feedback at key locations. The feedback provided by the tactors should guide the patient through a series of desired movements by allowing him or her to feel limb configuration errors at each instant in time. After discussing the relevant motion capture and actuator options, this paper describes the design and programming of our current prototype, a wearable tactile interface that uses magnetic motion tracking and shaftless eccentric mass motors. The sensors and actuators are attached to the sleeve of an athletic shirt with novel plastic caps, which also help focus the vibration on the user's skin. We connect the motors in current drive for improved performance, and we present a full parametric model for their in situ dynamic response (acceleration output given current input).Publication GPU Methods for Real-Time Haptic Interaction with 3D Fluids(2009-11-01) Yang, Meng; Safonova, Alla; Lu, Jingwan; Kuchenbecker, Katherine J.Real-time haptic rendering of three-dimensional fluid flow will improve the interactivity and realism of applications ranging from video games to surgical simulators, but it remains a challenging undertaking due to its high computational cost. Humans are very familiar with the look and feel of real fluids, so successful interactive simulations need to obey the mathematical relationships of fluid dynamics with high spatial resolution and fast temporal response. In this work we propose an innovative GPU-based approach that enables real-time haptic rendering of high-resolution 3D Navier-Stokes fluids. We show that moving the vast majority of the computation to the GPU allows for the simulation of touchable fluids at resolutions and frame rates that are significantly higher than any other recent real-time methods without a need for pre-computations. Based on our proposed approach, we build a haptic and graphic rendering system that allows users to interact with 3D virtual smoke in real time through the Novint Falcon, a commercial haptic interface.Publication Quantifying the Value of Visual and Haptic Position Feedback During Force-Based Motion Control(2007-04-02) Kuchenbecker, Katherine J.; Gurari, Netta; Okamura, Allison M.Controlling the motion of a prosthetic upper limb without visual feedback is extremely difficult because the wearer does not know the prosthesis’ configuration. This paper describes an experiment designed to determine the relative importance of visual and haptic position feedback during targeted force-based motion by non-amputee human subjects as an analogy to prosthetic use. Subjects control the angle of a virtual proxy through an admittance relationship by generating torque at the MCP joint of the right index finger. During successive repetitions of a target acquisition task, the proxy’s state is selectively conveyed to the user through graphical display, finger motion, and tactile stimulation. Performance metrics for each feedback condition will provide insights on the role of haptic position feedback and may help guide the development of future upper-limb prostheses.Publication Haptically Assisted Golf Putting Through a Planar Four-Cable System(2011-06-01) Kuchenbecker, Katherine J; Huang, Peter Y; Kunkel, Jacquelyn A; Brindza, JordanIndividuals learning a new sport often repeat a motion hundreds or thousands of times to try to perfect their form. The quintessential example of this process may be a beginning golfer struggling to learn to putt, where strokes must be precise and consistent in order to place the ball in the hole. This paper presents a four-cable haptic device designed to help golfers learn to improve their putting accuracy. This planar three-DOF system provides feedback that consists of two Cartesian forces and one angular moment. We present the system’s design and kinematics, along with a closed-loop controller that helps the user keep the putter head at the correct angle in the plane. We evaluated our design through a study in which five subjects used the system to repeatedly putt at a target both with and without assistance. While assistance did not change the mean of the putting distribution, it did significantly affect the variance for some subjectsPublication The Touch Thimble: Providing Fingertip Contact Feedback During Point-Force Haptic Interaction(2008-03-14) Kuchenbecker, Katherine J; Ferguson, David; Kutzer, Michael; Moses, Matthew; Okamura, Allison MTouching a real object with your fingertip provides simultaneous tactile and force feedback, yet most haptic interfaces for virtual environments can convey only one of these two essential modalities. To address this opportunity, we designed, prototyped, and evaluated the Touch Thimble, a new fingertip device that provides the user with the cutaneous sensation of making and breaking contact with virtual surfaces. Designed to attach to the endpoint of an impedance-type haptic interface like a SensAble Phantom, the Touch Thimble includes a slightly oversize cup that is suspended around the fingertip by passive springs. When the haptic interface applies contact forces from the virtual environment, the springs deflect to allow contact between the user's fingertip and the inner surface of the cup. We evaluated a prototype Touch Thimble against a standard thimble in a formal user study and found that it did not improve nor degrade subjects' ability to recognize smoothly curving surfaces. Although four of the eight subjects preferred it to the standard interface, overall the Touch Thimble made subjects slightly slower at recognizing the presented shapes. Detailed subject comments point out strengths and weaknesses of the current design and suggest avenues for future development of the device.Publication Haptic Displayof Realistic Tool Contact via Dynamically Compensated Control of a Dedicated Actuator(2009-12-15) McMahan, William; Kuchenbecker, Katherine J.High frequency contact accelerations convey important information that the vast majority of haptic interfaces cannot render. Building on prior work, we present an approach to haptic interface design that uses a dedicated linear voice coil actuator and a dynamic system model to allow the user to feel these signals. This approach was tested through use in a bilateral teleoperation experiment where a user explored three textured surfaces under three different acceleration control architectures: none, constant gain, and dynamic compensation. The controllers that use the dedicated actuator vastly outperform traditional position-position control at conveying realistic contact accelerations. Analysis of root mean square error, linear regression, and discrete Fourier transforms of the acceleration data also indicate a slight performance benefit for dynamic compensation over constant gain.Publication VerroTouch: High-Frequency Acceleration Feedback for Telerobotic Surgery(2010-07-01) Kuchenbecker, Katherine J; Gewirtz, Jamie; Mendoza, Pierre J; McMahan, William; Lee, David I; Standish, DorseyThe Intuitive da Vinci system enables surgeons to see and manipulate structures deep within the body via tiny incisions. Though the robotic tools mimic one's hand motions, surgeons cannot feel what the tools are touching, a striking contrast to non-robotic techniques. We have developed a new method for partially restoring this lost sense of touch. Our VerroTouch system measures the vibrations caused by tool contact and immediately recreates them on the master handles for the surgeon to feel. This augmentation enables the surgeon to feel the texture of rough surfaces, the start and end of contact with manipulated objects, and other important tactile events. While it does not provide low frequency forces, we believe vibrotactile feedback will be highly useful for surgical task execution, a hypothesis we we will test in future work.Publication Haptography: capturing the feel of real objects to enable authentic haptic rendering (invited paper)(2008-02-14) Kuchenbecker, Katherine JHaptic interfaces are designed to allow humans to touch virtual objects as though they were real. Unfortunately, virtual surface models currently require extensive hand tuning and do not feel authentic, which limits the usefulness and applicability of such systems. The proposed approach of haptography seeks to address this deficiency by basing models on haptic data recorded from real interactions between a human and a target object. The studio haptographer uses a fully instrumented stylus to tap, press, and stroke an item in a controlled environment while a computer system records positions, orientations, velocities, accelerations, and forces. The point-and-touch haptographer carries a simply instrumented stylus around during daily life, using it to capture interesting haptic properties of items in the real world. Recorded data is distilled into a haptograph, the haptic impression of the object or surface patch, including properties such as local shape, stiffness, friction, and texture. Finally, the feel of the probed object is recreated via a haptic interface by accounting for the device's natural dynamics and focusing on the feedback of high-frequency accelerations.