Yoshitaka Adachi

Intermediate representation for stiff virtual objects

A method of intermediate space for controlling haptic interfaces is characterized by updating a virtual plane at a low frequency while maintaining a high update rate at force control loop of the interface. By using the virtual plane, the detection of collisions between the tip of finger and virtual objects became independent from the control of the haptic interface. This will enable the haptic interface to display more and more complex surfaces in keeping the same sampling frequency of impedance control. It was revealed by the experiments with a haptic interface SPICE that an operator could touch and trace smoothly on a curved surface of stiff virtual object, even if the update rate of the virtual plane is relatively low.

Real-time interference analysis between a tool and an environment

In applications such as haptic rendering, NC Verification and CAM, it is often necessary to rapidly detect and correct collision between a known tool, such as a cutting tool, and an arbitrary environment, such as the workpiece to be machined. In these situations, the tool can be manually pre-defined, but the workpiece needs a general representation; and careful fulfillment of these requirements enables extremely rapid performance. We describe an algorithm and representations for rapidly detecting and correcting collision between a manually pre-defined tool and an arbitrary workpiece. For the tool, we prescribe a form of CSG consisting of implicit equations separated by binary space partitions. This representation can be enhanced to also yield depth information and exit vector information for many useful solids. The user must hand-construct the tool using this representation. For the environment, we use a cloud of over 10,000 points. This is a general representation. The collision between tens of thousands of points and the implicit representation can be accelerated with a bounding box hierarchy. We show that we can compute collision and correction information at the rate of 1000 times a second, making it possible to perform force control for haptics using the collision detection algorithm in the real-time loop.

Generation of collision-free 5-axis tool paths using a haptic surface

Abstract An intuitive man–machine interface for generating 5-axis tool paths is described in the paper. The system is based on a 5 degree-of-freedom force feedback haptic system, which is used to interface a human with an impenetrable 3D part. In the process of feeling the object, the user ‘teaches’ a milling machine to machine a virtual 3D object. The tool path generation has two phases: recording of access directions at the surface of the object and the post-processing phase. During the recording phase, three functions are carried out simultaneously: first, a fast collision detection algorithm, using hierarchical object representation, to drive the haptic system; second, visual feedback to show the regions that have been accessed by the tool; and third, a system to capture the access directions of the tool as the user touches the object. The post-processing phase involves the use of information generated in the recording phase to generate 5-axis tool paths. First, the access directions at the surface of the part are interpolated; and second, any residual collisions are detected and eliminated. We show the results of the tool path generation for two parts. The system can help an expert user generate, correct and tweak tool paths.

Touch and trace on the free-form surface of virtual object

The Space Perception System with a 3D man-computer interface device, has been built for human factors experiments. An algorithm using a distribution function is utilized to define model shapes in a virtual environment. In this algorithm, the system is able to recognize the interference between the 3D cursor following an operators hand and virtual objects in real time. Impedance control of robotics is utilized to calculate the reaction force which is transmitted in real time from the virtual object to the operators hand through the 3D man-computer interface device. With the combination of the algorithm using the distribution function and the impedance control, the operator can touch and trace the surface of the virtual model which is composed of free-form surfaces in a virtual environment, and can recognize its hardness.<<ETX>>

Simulator for virtual surgery using deformable organ models and force feedback system.

This paper describes a real-time surgery planning system using virtual reality techniques. This system allows us to simulate incision of skin and organs which respond as elastic objects with surgical tools in virtual space. Inner structures such as blood vessels and lesions can be seen and manipulated in the simulation. In addition to these functions we attempted to add a feedback function that responds to the operators hands. We developed a force feedback device to manipulate the elastic organ model based on pressure from the operators fingers.

Virtual Surgery System Using Deformable Organ Models and Force Feedback Systems with Three Fingers

We aimed to develop a virtual surgery system capable of performing surgical maneuvers on elastic organs, the structure of which has been obtained from a patient. We tried to manipulate three dimensional (3D) organs as elastic models by hand or surgical tools in real time in a virtual environment. And we tried to obtain the sense of touch by using force feedback device with manipulator attached to the thumb, forefinger and middle finger of the operator.

Virtual surgery simulator with force feedback function

The authors developed a surgery planning system using virtual reality techniques which allows them to simulate incision of skin and organs which respond as elastic objects with surgical tools in virtual space. The authors also attempted to add a feedback function that responds to the pressure of the operators hand using a force feedback device.

Collaborated surgical works (surgical planning) in virtual space with tactile sensation between Japan and Germany

Surgeons in Japan and Germany applied tele-virtual surgery and a force feedback device during a hepatectomy simulation. Using this system, surgeons in each country were able to perform various surgical maneuvers upon the same patient. They palpated abdominal skin, made electrical scalpel incisions and widened the incision line by using surgical tools in virtual space. While surgeons performed a virtual operation, the force feedback device conveyed tactile sensations. In each location, the force feedback devices and two graphic workstations of equal capability were employed. As each workstation communicated only event signals through an ISDN (64 Kb) line, it was possible to obtain real time tele-virtual surgery without a large capacity communication infrastructure.