Surgery – Diagnostic testing – Measuring anatomical characteristic or force applied to or...
Reexamination Certificate
2000-02-11
2002-08-06
Hindenburg, Max (Department: 3736)
Surgery
Diagnostic testing
Measuring anatomical characteristic or force applied to or...
Reexamination Certificate
active
06428490
ABSTRACT:
INTRODUCTION
1. Background
A growing market has developed for tools and systems that track humans and other bodies at rest and in motion. The applications for such systems vary considerably, and include such areas as the creation of computer-generated and graphical animations, the analysis of human-computer interaction, the assessment of performance athletics and other biomechanics activities, and the evaluation of workplace and other activities for general ergonomical fitness.
The possible sample uses for a body-tracking system are wide and varied. For example, a user interested in creating a realistic computer animation of a gymnast might be interested in tracking the full-body movements of the gymnast during a brief tumbling run characterized by high-velocity, high-acceleration activity. A second sample user might instead be interested in measuring the upper-body movements of a typical clerical worker over a full workday, in order to assess the role of various activities in causing repetitive stress injury. A third sample user might wish to record the motions of a high-performance skier or snowboarder over a mile-long section of mountain in order to study and possibly improve his or her technique.
The most general functional requirement of a body-tracking (or motion-capture) device is that it accurately and reliably measure and report the configuration of the various articulating members (limbs) of the body over a particular duration of interest. In order to be most useful, however, a motion-capture device must also satisfy additional criteria. It must be sufficiently lightweight and unencumbering to allow the free performance of the activity being measured. (A system that prevents an athlete or performer from acting naturally, either due to the addition of weight, to an impeding of balance and flexibility, or to the presence of other physical constraints is clearly of lessened utility as a motion-capture device). It must also allow for a performance space appropriate to the motion being measured, i.e., it must allow the user the freedom to move through space as needed to complete the activity being measured.
Various contributions to the prior art have addressed themselves to the general problem of motion capture. Electromagnetic (E/M) tracking systems, such as those manufactured by Polhemus and Ascension, use multiple elements consisting of three orthogonally wound coils. At least one such element is designated as a transmitter, and at least one such element is designated as a receiver. By energizing, in turn, the coils in a transmitter element, and measuring the signal induced in the receiver elements(s), the relative position of the transmitter and receiver element(s) can be calculated. Such E/M tracking systems are sensitive to the presence of metal in the close surroundings and, in addition, have a workspace limited by the requirement that the receiver(s) remain within several feet of their corresponding transmitter. Another disadvantage of E/M technology is that it typically includes lag time which renders the position data non-real time.
As with E/M position sensing technology, ultrasonic (US) and infrared (IR) position sensing technologies do not require a direct tether between the hand and monitor. US and IR technologies have the disadvantage, however, that they both require direct line of sight. Thus, when one hand passes in front of the other, the position signal can be lost. Additionally, US technology, in particular, is very sensitive to ambient acoustic noise. Both technologies can introduce lag time, again rendering the position data non-real time.
Another example of a prior art solution to the problem of motion capture is a passive, optically-based body-tracking system, such as that produced by Motion Analysis. In such a system, multiple reflective markers are attached to the surface of the limbs of interest, such that these markers are placed on either side of the articulating joints. Multiple cameras record the positions of these markers over time, and this marker position data is used to extract (via “inverse kinematics”) the corresponding configurations of the various limbs and joints of interest. Such optical tracking systems have an inherent workspace limitation that comes from the need to use cameras, namely that the user of the system is limited to the relatively small workspace that is both visible to the cameras and in focus. Tracking problems occur when markers become occluded, since data cannot be recorded. In addition, such a system requires a non-trivial amount of post-processing of the data; while it is expected that computing power and cost efficiency will continue to increase, optical systems still do not deliver on-the-spot, “real-time” data.
Still another example of a prior art solution is an active, optically-based body-tracking system. Such a system is conceptually similar to the passive system described above, but with several differences. The markers in such a system typically actively emit light, instead of being simple, passive reflectors. This allows the controlling software to energize each of the markers in turn, and if properly synchronized with the computer doing the data analysis, can help prevent problems that occur when the control software loses track of “which marker is which.” Otherwise, the workspace, marker-occlusion, and post-processing shortcomings of such active optical systems are similar to that of the passive ones.
A Toronto-based company, Vivid Group, uses camera-based technology called Mandela to monitor human motion without requiring the user to wear any special devices. The system, however, only tracks body movements in two dimensions (2D). Most motion capture (MC) systems require the user to wear some form of element that either is a sensor itself, or is one component of a sensing system where other components are located off the user.
Still another example of a prior art solution is a theoretical simulation of the desired motion. By building a kinematic model of a human, attributing that model with realistic masses, rotational interias and other properties, and specifying all relevant initial-condition and boundary constraints, it is theoretically possible to solve the dynamic equations of motion for a complex body. Once a solution has been generated, such information could be used to create graphical animations or other imagery. There are several drawbacks, however. For example, such algorithmic solutions to motion capture are just now in their infancy and can be applied only in the most limited and constrained of activities. Also for example, the human brain is very good at detecting “incorrect” motion, so the performance demands on such a theoretical simulation will be very exacting. Also for examples such a system does not help at all with the problem of measuring the motion of living humans and is of little utility in biomechanics and ergonomic applications.
There still remains a need for a position-sensing device which is accurate, insensitive to environmental influences, has little lag time and has high data rates.
2. Relevant Literature
U.S. Pat. No. 5,676,157, “Determination of Kinematically Constrained Multi-Articulated Structures”, J. F. Kramer, describes kinematically constrained multi-articulated structures.
SUMMARY OF THE INVENTION
A general overview of the inventive structure and method is now provided. The subject invention provides improvements, enhancements, and additional patentable subject matter to the prior provisional patent application numbers U.S. Patent Application Serial No. 60/044,495, filed Apr. 21, 1997, and No. 60/054,745, filed Aug. 4, 1997, which provisional applications are incorporated herein in their entireties. In particular, the subject invention provides new shoulder- and hip-sensing structures and techniques. In particular for each shoulder sensor assembly, this new structure and technique employs five long, thin, flexible strain-sensing goniometers to measure the overall angle of one or more contiguous parallel-axis revolute joint sets. The shoulder-sensing assembly i
Ananny John M.
Bentley Loren F.
Boronkay Allen R.
Korff Paul L.
Kramer James F.
Hindenburg Max
Riegel James
Thyfault Paul M.
Virtual Technologies, Inc.
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