Guanyang Liu

Stable haptic interaction using a damping model to implement a realistic tooth-cutting simulation for dental training

It is difficult to implement a stable and realistic haptic simulation for cutting rigid objects that is based on a damping model because of an inevitable conflict between stability and high output force. This paper presents passivity techniques to show that an excessive damping coefficient causes the output stiffness to exceed the maximum output stiffness of the haptic device, leading to instability. By analysing the damping model of a haptic dental-training simulator, we construct a relationship among the damping coefficient, position resolution, sampling frequency, human operation, and the maximum achievable device stiffness that will still maintain device stability. A method is also provided to restrict the output stiffness of the haptic device to ensure stability while enabling the realistic haptic simulation of cutting rigid objects (teeth) that is based in a damping model. Our analysis and conclusions are verified by a damping model that is constructed for a dental-training haptic display. Three types of haptic devices are used in our analysis and experiments.

Force modeling for tooth preparation in a dental training system

Feedback force is very important for novices to simulate tooth preparation by using the haptic interaction system (dental training system) in a virtual environment. In the process of haptic simulation, the fidelity of generated forces by a haptic device decides whether the simulation is successful. A force model computes feedback force, and we present an analytical force model to compute the force between a tooth and a dental pin during tooth preparation. The force between a tooth and a dental pin is modeled in two parts: (1) force to resist human’s operation and (2) friction to resist the rotation of the dental engine. The force to resist the human’s operation is divided into three parts in the coordinates that are constructed on the bottom center of the dental pin. In addition, we also consider the effects of dental-pin type, tooth stiffness, and contact geometry in the force model. To determine the parameters of the force model, we construct a measuring system by using machine vision and a force/torque sensor to track the human’s operations and measure the forces between the dental pins and teeth. Based on the measuring results, we construct the relation between the force and the human’s operation. The force model is implemented in the prototype of a dental training system that uses the Phantom as the haptic interface. Dentists performing virtual operations have confirmed the fidelity of feedback force.

Separate DOF control and mutual guidance in networked haptic collaboration maze game: Design and evaluation

In this paper we study on haptic collaboration in a maze game over computer network. Two players located at separated places operate each haptic device to collaboratively finish the game task. Herein, a new collaboration mode of manipulation - separate DOF control is proposed for the first time. Separate DOF control here means each player controls one DOF of an object or a task independently in collaborative virtual environment. Mutual guidance is also proposed which provides guidance force to each player. We setup an experiment to evaluate its efforts on cooperation performance and co-presence. Twelve participants did the experiment. The results revealed that this collaboration mode is effective. Ten of the twelve participants believed that they performed well in the experiment and thought the collaboration way was very interesting. The presented results motivated a new haptic collaboration mode in the fields of game design, education and cooperative assembly.

Cutting force model of dental training system

This paper presents a cutting force model for dental training system with haptic display capability. The force model is proposed by theoretic analysis of the cutting force between dental tools and tooth. A damping matrix is developed for obtaining a unified formulation for all components of cutting forces. All factors that affect the cutting force are considered in the model by including a number of parameters. These parameters are identified by tooth-cut experiments, which measure the cutting force with a six-dimensional force sensor. A prototype system of haptic simulation is developed to test the model. Dentists performing virtual operation on the system have confirmed the realistic sense of cutting force.

Two-mode system for tank gunnery skill training based on haptic interaction

A study on tank gunnery motor skill training is introduced in this paper. We developed a two-mode system used for teaching and training. In the haptic guidance mode, the trainee is passive and experiences position playback of the experts motion with a proportional-derivation (PD) controller. In the path constraining mode, the trainee operates the haptic device actively, and the aiming point in the virtual environment is constrained on the desired path. A new haptic rendering algorithm is introduced in this mode. An experiment for record-play motion of drawing a virtual sine path and path constraining with drawing an envelope path is designed. Results indicate that the haptic rendering algorithm in the two-mode training system is stable.

A modified motion mapping method for haptic device based space teleoperation

This paper presents a modified master-slave motion mapping method for space teleoperation using haptic device with limited workspace. The method combines rate control and a variable scaled position mapping to realize accurate and efficient teleoperation. Haptic feedback in these two mapping modes is designed with emphasis on ergonomics to improve immersion of teleoperation. A dead zone is defined in master side to guarantee system stability when mode switches. We illustrate our method on teleoperation path tracking and target positioning tasks and compare the results with two widely used methods: rate control and scaled position mapping. The comparison experimental results demonstrate that the proposed hybrid motion mapping method is the most efficient method for path tracking and the most accurate one for target positioning.

Grasping Control in Three-Fingered Robot Hand Teleoperation Using Desktop Haptic Device

This paper presents a three-fingered robot hand teleoperation system using desktop haptic device as the master manipulator. The grasp mapping and force feedback methods are developed for the system. Grasp forces of the robot hand are transformed to proper feedback force in master side. Operator controls the robot hand to grasp and hold different objects depending on the force feedback rather than visual feedback. We demonstrated that a wide range of objects, whose properties are well known by operator, were safely and stably grasped and the force based grasping control was more reliable than visual feedback based control. The intuitive and easy-to-realize system raises a new control scheme in robot hand teleoperation.

A study on haptic collaborative game in shared virtual environment

A study on collaborative game in shared virtual environment with haptic feedback over computer networks is introduced in this paper. A collaborative task was used where the players located at remote sites and played the game together. The player can feel visual and haptic feedback in virtual environment compared to traditional networked multiplayer games. The experiment was desired in two conditions: visual feedback only and visual-haptic feedback. The goal of the experiment is to assess the impact of force feedback on collaborative task performance. Results indicate that haptic feedback is beneficial for performance enhancement for collaborative game in shared virtual environment. The outcomes of this research can have a powerful impact on the networked computer games.

More Identifiable Stiffness Feedback for Dexterous Hand Teleoperation in Unknown Environment

In dexterous hand teleoperation, effective forcefeedback is critical for precisely identifying objects in anunknown environment. This paper proposes an object-basedmotion mapping method to provide more identifiable stiffnessperception for an operator to perceive different objects in ateleoperation system. To verify the effectiveness of the proposedmethod, a three-fingered robot hand (BarrettHand BH8-280)teleoperation system is established which uses a commercialdesktop haptic device as the master manipulator. A comparisonexperiment is carried to identify the stiffness of five differentobjects with two different motion mapping methods: constantmotion mapping, and object-based motion mapping. The resultsshow that the object-based motion mapping is more reliable andeffective as compared with constant mapping method.

An artificial neural network based haptic rendering of contact with deformable bodies

This paper presents an artificial neural network based 3-DOF haptic rendering scheme to render the contact force between a rigid object and a deformable body in a virtual environment. The finite-element method (FEM) technique is widely used for solving the deformation problem. However, this method has a heavy computational load to get accurate result, so it is difficult to apply this method to haptic simulating. To solve the challenging problem, in this paper, we presented a new motion control scheme to divide the motion of a rigid virtual object into three sub-movements along the three axes of a Cartesian-coordinate, based on which three single-input and single-output neural networks can be separately used to compute the three feedback force components along all the coordinate axes. The vector composition of the three force components is the feedback force exerted to a user through a haptic device. The proposed method can ensure the high accuracy and the high update rate of 3-DOF haptic rendering of deformable bodies. To testify the accuracy of the artificial neural network for haptic rendering, a medical robot is used to measure the data of the neural network training in the physical world, and a haptic device based experiment with a virtual environment validates the proposed algorithm for 3-DOF haptic rendering.