Electricity: motive power systems – Positional servo systems – Adaptive or optimizing systems including 'bang-bang' servos
Reissue Patent
1999-11-30
2001-09-18
Ro, Bentsu (Department: 2837)
Electricity: motive power systems
Positional servo systems
Adaptive or optimizing systems including 'bang-bang' servos
C318S568110, C318S649000
Reissue Patent
active
RE037374
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to force feedback and, more particularly, to the use of gyroscopic stabilization to provide an inertial frame against which a force-reflecting device react.
BACKGROUND OF THE INVENTION
Force-feedback technology and related devices may be divided into four broad application areas: medical, entertainment, teleoperations, and virtual reality. Teleoperations, the research of which provided the foundation for the development of force-feedback devices, is the process of locally controlling a remote device. The primary difference between virtual reality and teleoperations is in the objects which they control. With teleoperations, actual physical robots are manipulated in the real world, whereas virtual reality involves simulated devices in synthetic worlds. Force-feedback for telerobotics has evolved large and bulky mechanical arms to more joystick-like designs. In general, these devices are designed for six degree-of-freedom (6DOF) force feedback, and have the capability to provide high levels of force. More recently, finger-operated devices have also been introduced for use in teleoperations applications.
The use of force feedback in medical training, simulation, and teleoperations is also increasing, with the primary application being minimally invasive surgical techniques which use laparscopic tools to perform intricate tasks when inserted into body cavities through small incisions. To realistically simulate laparoscopic tool forces, special-purpose force-feedback devices are currently under development.
The entertainment field is very difficult to address with force-feedback technology, since the applications demand both higher performance and lower costs. There are three primary markets for force feedback devices in entertainment: location-based entertainment (LBE), arcades, and home entertainment. LBE demands the highest performance while home entertainment demands the lowest cost. Despite the conflicting demands, progress is being made in each of these fields.
It may be argued that each of the application domains just described has its roots in virtual reality, which is becoming dominant in all immersive applications. As a consequence, on-going research in immersive applications is often termed “virtual reality,” whereas, when the research is completed, the application is given a specific name, such as a surgical simulator. Overall, virtual reality is becoming increasingly popular as a preferred means of interacting with many scientific and engineering applications. To cite two of many examples, molecular modeling and automobile design are moving from standard graphics, carried out on conventional graphics terminals, to more interactive environments utilizing 3-D stereo graphics, head-mounted displays and force feedback.
As visualization is a very important aspects of these applications, interesting and useful technologies are being developed, including graphical object representations and large working volumes (CAVES). Concurrently, haptic interfaces are being perfected, which enable manual interactions with virtual environments or teleoperated remote systems. The haptic system is a unique sensory system in that is can both sense the environment and allow a user to react accordingly. As a result, haptic devices not only stimulate the user with realistic sensor input (forces, tactile sensations, heat, slip, etc.), but also sense the user's actions so that realistic sensory inputs can be generated. Haptic devices are divided into two classes, depending upon the type of sensory information being simulated. The first, tactile, refers to the sense of contact with the object. The second, kinesthetic, refers to the sense of position and motion of a user's limbs along with associated forces.
Broadly, these approaches point toward the same goal: to immerse a person in a seemingly visual reality, complete with haptic feedback. However, a major deficiency with all existing force-generating devices is the requirement that they be connected to a fixed frame, thus forcing immobility on the user. State-of-the-art force-feedback devices, for example, are table mounted, requiring the device to be mounted to an immobile object in order to generate a fixed point of leverage for forces and/or torques. Consequently, no existing force feedback device allows for easy mobility and force generation. This problem is fundamental, since many virtual reality applications require large working volumes and the ability to move freely within these volumes, to provide realistic visual and audio feedback during walk-through scenarios, for example.
In summary, large, immersive environments such as CAVES currently lack haptic feedback, primarily because the existing technology will not support unrestricted motion. This leads to one conclusion that force-feedback devices must migrate as visual technologies have, that is, from the desktop to large-volume, immersive environments. However, the design of a hand-held, spatially unrestricted force-feedback device is fundamentally different from existing devices, which typically use primarily electromechanical or pneumatic actuators operating against fixed supports to achieve active force feedback. Nor is the realization of such a device intuitively obvious. To construct an n-axis joystick, requiring 1, 2, 3 to n+3 motors, presents significant challenges, for example, since the additional motors may significantly increase the cost and/or weight of the device.
SUMMARY OF THE INVENTION
The present invention addresses the need for force feedback in large, immersive environmentally by providing a device that uses a gyro-stabilization to generate a fixed point of leverage for the requisite forces and/or torques. In one embodiment, one or more orthogonally oriented rotating gyroscopes are used to provide a stable body or platform to which a force-reflecting device can be mounted, thereby coupling reaction forces to the user without the need for connection to a fixed frame. In one embodiment, a user-interactable member is physically coupled to a stabilized body, with the control structure used for stabilization and that used to mitigate force-feedback being substantially independent of one another, enabling different stabilization mechanisms as described herein to be used with existing force-feedback capabilities. In alternative embodiments, inventive apparatus and methods are used which take into account both the movements associated with the gyroscopic stabilization, a user's movements, and the application of torques and forces to realize a spatially unrestricted force-feedback device requiring fewer motors and structural elements. Specifically, an inventive control scheme is used in these cases to accelerate and decelerate the motor(s) associated with providing the gyroscopic stabilization such that only the desired tactile feedback is experienced by the user. All of the various approaches are applicable to single and multiple degrees of freedom.
A three-axis implementation includes a set of three, mutually perpendicular momentum wheels which form the gyro-stabilized platform, an attitude measuring device, and a control system. The attitude measuring device is employed to detect disturbances to the gyro-stabilized platform, including reaction torques due to a user's interactions with the device. The control system varies the speed the momentum wheels in order to maintain the gyro-stabilized platform in a fixed position. In an alternative embodiment, a reaction sphere is used to produce the requisite inertial stabilization. Since the sphere is capable of providing controlled torques about three arbitrary, linearly independent axes, it can be used in place of three reaction wheels to provide three-axis stabilization for a variety of space-based and terrestrial applications.
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patent: 4839838
Jacobus Charles J.
Roston Gerald P.
Cybernet Haptic Systems Corporation
Riegel James R.
Ro Bentsu
Tucker Guy V.
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