Hyun Soo Woo

Exploitation of the Impedance and Characteristics of the Human Arm in the Design of Haptic Interfaces

It is well known that friction in haptic devices plays a key role in dissipating surplus energy to maintain passivity of the haptic system. This paper shows that the surplus energy can also be dissipated by careful exploitation of human operators damping and analyzes the effects of the time-varying human arm impedance on the passivity of a haptic system. The human arm impedance is modeled as a second-order mass-damper-spring system. An impedance model is developed to describe the dynamic behavior of a haptic system that includes the human arm impedance. A new necessary and sufficient passivity condition of the haptic system is derived using an energy-based approach. The analytical results are experimentally validated using a one-degree-of-freedom haptic device. Experimental results show that the maximum achievable stiffness of the haptic system varies widely according to the degree of human arm impedance and is predictable more accurately using the newly derived passivity condition compared to the previous results in the literature.

New colonoscopy simulator with improved haptic fidelity

Colonoscopy is a safe and effective procedure to diagnose and treat the large bowel with the help of the flexible endoscope. This paper presents a new colonoscopy training simulator to help trainees practice and acquire the necessary skills and experiences with no risk to the patients and possibly less cost. The simulator includes a specialized haptic interface to transfer force feedback through a long and flexible tube, and graphics algorithms to display the virtual colon realistically while managing the large number of polygons. A new 2-d.o.f. haptic device with folding guides is developed to transmit large decoupled forces of the colonoscopy simulation to the user. The physicians apply a jiggling motion to the colonoscopy tube to advance the scope. This jiggling is an important skill of colonoscopy and is incorporated for the first time by using the new sensor mechanism. A colonoscope handle that shares the look, feel and functions with an actual colonoscope is developed with the necessary electronics inside. The simulator contains controllers to compensate for the inertia and friction effects, and is evaluated by physicians. New graphics algorithms including polygon reduction, navigation and collision detection are developed to compute the deformation and the corresponding reflective force in real-time.

Haptic Interface of the KAIST-Ewha Colonoscopy Simulator II

This paper presents an improved haptic interface for the Korea Advanced Institute of Science and Technology Ewha Colonoscopy Simulator II. The haptic interface enables the distal portion of the colonoscope to be freely bent while guaranteeing sufficient workspace and reflective forces for colonoscopy simulation. Its force-torque sensor measures the profiles of the user. Manipulation of the colonoscope tip is monitored by four deflection sensors and triggers computations to render accurate graphic images corresponding to the rotation of the angle knob. Tack sensors are attached to the valve-actuation buttons of the colonoscope to simulate air injection or suction as well as the corresponding deformation of the colon. A survey study for face validation was conducted, and the result shows that the developed haptic interface provides realistic haptic feedback for colonoscopy simulations.

Passivity analysis of a 1-DOF haptic system with consideration of human arm impedance

A new passivity condition for designing a 1-DOF haptic system is derived with consideration of human arm impedance. The method includes a human arm impedance model of a newly defined ideal mass-spring system. The developed passivity condition guarantees that the virtual wall requires more work than the ideal mass-spring system to compress. The condition guarantees that extractable energy from the virtual wall is less than the ideal system during the release phase. Eventually, the total energy of the haptic system is guaranteed to be less than or equal to that of an ideal mass-spring system whose passivity is guaranteed for all the possible user movements. The developed condition is also shown to be necessary and sufficient for the passivity of the haptic system.

Model of frictional contact with soft tissue for colonoscopy simulator

This paper presents a model of frictional contact with soft tissue for the colonoscopy simulator with haptic fidelity. The colonoscopy simulator allows the user to navigate the three dimensional virtual colon constructed from CT (computer tomography) data of patients. The frictional contact model is proposed to integrate the therapeutic procedures such as polyp removal. The proposed model uses the finite element method based on the linear static elasticity to simulate deformation and reflective force including friction effects. The variation of the reflective force is computed according to the contact state, stick or slip state, during sliding contact motions. Simulation results show responses following the Coulombs friction law.

Development of a 4 DOF exoskeleton robot for elbow and wrist rehab

It is important to control impedance between a patient and a robot to maximize the effect of the robot rehabilitation therapy. This paper presents a 4 DOF exoskeleton robot for elbow and wrist rehabilitation, which includes a unified actuator module per each joint. The unified actuator module consists of a frameless motor, an incremental encoder, an absolute encoder, a harmonic drive, a torque sensor, and a motor controller. The interaction force between a patient and the robot can be computed based on the torque signal of each joint. This enables us to design impedance controller to implement proper impedance to the patient. All the components of the unified actuator module were carefully selected to minimize overall weight and size. A second-order state-space model for the unified actuator module is developed via experiments. A H2 optimal controller was designed based on the state-space model.

Improved Haptic Interface for Colonoscopy Simulation

This paper presents an improved haptic interface of the KAIST-Ewha colonoscopy simulator II. The haptic interface enables the distal portion of the colonoscope to be freely bent while guaranteeing enough workspace and reflective forces for colonoscopy simulation. Its force-torque sensor measures profiles of the user. Manipulation of the colonoscope tip is monitored by four deflection sensors, and triggers computation to render accurate graphic images corresponding to the angle knob rotation. Tack switches are attached on the valve-actuation buttons of the colonoscope to simulate air-injection or suction, and the corresponding deformation of the colon.

Control configuration for upper limb rehabilitation robotic systems

It is important to design control configuration for medical robots to allow high fidelity human robot interactions. This paper considers the control configuration for upper limb rehabilitation robotic systems. The considered 11-DOF exoskeleton-type robot enables an grasping motion, an elbow actuation, three wrist actuations, three gleno-humeral joint actuations and another three axis linear actuations corresponds to shoulder joint center movements. The overall control configuration guarantees high-speed control bandwidth of 2 kHz which is enough to algorithm implementations. A position/admittance controllers as well as gravity compensator are developed for each joints to provide high quality therapeutic procedures.

Design of a Haptic Interface for a Gastrointestinal Endoscopy Simulation

Abstract This paper presents a new design and analysis of a haptic interface for a gastrointestinal endoscopy simulation. The gastrointestinal endoscopy is a procedure in which the digestive tract and organs of a patient are diagnosed and treated using a long and flexible endoscope. The developed haptic interface incorporates two degrees of freedom (DOF), each of which is necessary to describe the movements of an endoscope during the actual endoscopy procedures. The haptic interface has a translational motion mechanism to implement the insertion movement of the endoscope, and a rotational motion mechanism to implement the rotational movement of the endoscope. The endoscope included in the haptic interface is supported by a folding guide to prevent the endoscope from buckling. Force feedback in each direction is provided by wire-driven mechanisms. The developed haptic interface has a workspace, sensitivity, and maximum attainable force and torque enough to simulate the endoscopy procedures such as colonoscopy, upper GI (gastrointestinal) endoscopy, and endoscopic retrograde cholangiopancreatography (ERCP). The developed haptic interface is applied to implementation of a colonoscopy simulation. Performance including force bandwidth is evaluated through experiments and simulation.

Colonoscopy Simulator with Enhanced Haptic Realism and Visual Feedback

This paper presents the KAIST-Ewha colonoscopy simulator II with increased haptic fidelity as well as visual feedback. The colonoscopy simulator includes a specially developed haptic interface and optimized colon models constructed from CT data of actual patients. The colonoscopy simulator provides with enhanced haptic realism, which is made possible by employing a haptic device with decoupled translational and roll force-feedback mechanisms. Manipulation of the colonoscope tip is monitored by four deflection sensors, and triggers computation to render accurate graphic images corresponding to the knob rotation. A photo-sensors unit is developed to simulate jiggling motion which is one of the important colonoscopy skills to fold and straighten the colon. Friction in the haptic device is compensated by using force-torque sensors, and the force-torque profile during simulation is also logged by these sensors. The colonoscopy simulator employs a centerline-based parametric modeling of the colon for fast and accurate collision detection and haptic response between the colon and the colonoscope. The developed Colon Modeler provides with patient-customized colon models, and various training scenarios including rare cases.