Measuring and testing – Speed – velocity – or acceleration – Response to multiple sensing means or motion conditions
Reexamination Certificate
2001-07-26
2003-02-04
Kwok, Helen (Department: 2856)
Measuring and testing
Speed, velocity, or acceleration
Response to multiple sensing means or motion conditions
C073S865400, C702S160000
Reexamination Certificate
active
06513381
ABSTRACT:
FIELD OF INVENTION
The invention relates to a method and apparatus for measuring gait kinematics such as, for example, acceleration, velocity and position of gait based on foot movement analysis.
BACKGROUND OF THE INVENTION
The measurement and characterization of gait (i.e. human or animal) is performed by a wide range of methods. At one end of the scale is the measurement and analysis possibilities found in a well equipped bio-mechanical lab. The equipment in these labs typically includes automated 3D optical measurement systems, force plates and physiological output indicators. The output from these transducers are fed into a central computer that enables a wide range of analysis and display possibilities. At the other end of the spectrum is the simplified analysis performed with a ruler, stopwatch and trained clinical observations.
The reasons determining gait kinematic properties (such as acceleration, velocity and position) range from: (i) personal interest, (ii) training and performance considerations of the serious athlete, (iii) rehabilitation of the disabled or (iv) for the design and analysis of footwear.
From an athletic point of view, runners, joggers and walkers often like to know how far they have journeyed and how fast they have traveled, but have had only limited cumbersome ways to measure distance and speed. Distance can be measured after the fact with a calibrated bicycle or automobile or by traveling on a known premeasured route. For determining one's speed, a simple approach is to travel a known, fixed distance on a track or road and then record the length of time required to cover the distance. This method suffers from several limitations including (i) limited walking/running routes, (ii) speed indication at measured intervals only and (iii) only an average velocity is determined over the given distance.
There are a number of portable pedometers that attempt to tackle the problem of measuring both distance and velocity. However, they have failed to gain wide spread use, because these devices are essentially limited to stride counting. Distance and speed can only be estimated if stride length consistency is assumed. This approach is inaccurate because an individual's stride length changes considerably from day to day or even within one session due to changes in terrain, fatigue, interval training, or other factors.
U.S. Pat. No. 3,355,942 discloses a pedometer that counts strides based on compression cycles in a bellows under the heel and then estimates distance based on average stride length. The invention described in U.S. Pat. No. 4,741,001 uses a spirit-biased pendulum to count strides. The pedometer disclosed in U.S. Pat. No. 4,649,552 uses a step sensor sealed into an insole to count strides. The pedometer of U.S. Pat. No 4,651,446 counts strides by detecting flexion of the instep. Other counting pedometers include those under U.S. Pat. Nos. 5,117,444, 5,065,414, 4,855,942, 4,510,704, 4,460,823, 4,371,945, 4,322,609, 4,053,755, 3,818,194 and 3,635,399.
The majority of the patented pedometers are simply different methods of stride counting and do not address the problem of varying stride length. However, a pedometer listed under U.S. Pat. No. 4,371,945 uses ultrasonic emitters and sensors on alternate legs to measure the maximum distance between legs during each stride. While this is a significant improvement, this is only suitable for simple, low-speed gait patterns (no flight stage) and requires two sets of transducers; one on each leg.
U.S. Pat. No. 5,097,706 describes a device for taking measurements of various components of the movement of a horse. The device carries six accelerometers disposed to measure accelerations along the x, y and z axis.
Another U.S. Pat. No. 5,724,265 teaches a device that measures distance traveled, speed and height jumped of a person while running or walking. The device includes accelerometers and rotational sensors.
The broad concept of using accelerometers for determining the velocity and distance traveled, for example by athletes, is also described in German Patent 4,222,373. This patent describes the use of an accelerometer and integration to determine velocity and route or position. This device apparently processes acceleration data continuously and thus has an accumulated error from drift so that in very short period of time, the resulting data contains significant inaccuracies. The inventor indicates that this device is useful for skiers, surfers, sailors, cyclists, etc. and thus is not related to a striding device or for measuring the kinematics of striding and would not be effective for that purpose.
The Russian Patents 862074 and 885879 both by Volkov describe the attempts to overcome accumulated error in acceleration measuring devices by using a bar generator in combination with a summator and integrator. This described device does not make use of updated reference points and is thus also prone to accumulated drift.
A paper entitled “Estimation of Speed and Inclination of Walking Using Neural Networks” by Aminian et al., Published in the IEEE,
Tiansactions on Instrumentations and Measurements;
Volume 44#3, Jun. 1995, describes a portable data logger designed to record body accelerations during walking and uses three orthogonal accelerometers placed on the waistbelt to measure forward, vertical and heel acceleration. By means of neural networks, it correlates the recorded signals to the desired gait velocity and angle of incline. The generality of this method is questionable and no other gait information is produced.
BRIEF DESCRIPTION OF THE PRESENT INVENTION
The purpose of the device described herein is to provide a means to measure and display several gait parameters (that may include instantaneous and average accelerations and velocities as well as total distance traveled) by means of a simple, low-cost, portable device that can accommodate a wide variety of gaits and varying stride length. The device can be used for human or animal study.
The present invention measures various results about each individual stride rather than assuming a given fixed length. With suitable signal processing, the device can accurately determine velocity and distance traveled. The present invention can be modified to give many other useful indicators to the user such as pronation angles and impact forces. Because it is based on acceleration measurements and analysis, it inherently contains data that correlate directly to impact forces. When integrated, the acceleration data yields both instantaneous and average velocity. A second integration of these signals yields distance information such as, for example, total distance traveled, stride length and height of foot off the ground. Other relevant pieces of information include stride rate (ie. cadence) and peak foot velocity. The invention also has the potential to measure biomechanic parameters such as force of impact and gait sway and can be used for off-angle feet.
In broad terms, the present invention relates to a method of determining gait kinematics for a subject in each of a plurality of strides comprised during each stride defining a fresh datum plane, determining angles between a pair of accelerometers and said datum plane, said pair of accelerometers being adapted to measure acceleration in two directions, the two directions being separated by a known angle of greater than 0°, and being adapted to measure acceleration in a plane of motion substantially perpendicular to said datum plane, measuring acceleration in said plane of motion in said two directions, converting said accelerations to provide determination of a gait kinematic result for each said stride.
The two directions are preferably separated by an angle of between about 45° to 135° and more preferably are substantially mutually perpendicular to facilitate determination of the gait kinematic result.
The gait kinematic result can be, for example, details of foot motion, acceleration in a selected direction, velocity in a selected direction or distance in a selected direction. The selected directio
Fyfe Kenneth R.
Fyfe Kipling W.
Rooney James K.
Cesari and McKenna LLP
Dynastream Innovations, Inc.
Kwok Helen
LandOfFree
Motion analysis system does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Motion analysis system, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Motion analysis system will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3151711