Method and device for the recording, presentation and automatic classification of biomechanical load variables measured on a freely moving test person during a work shift

• US 6,152,890 A
• Filed: 10/30/1998
• Issued: 11/28/2000
• Est. Priority Date: 10/30/1997
• Status: Expired due to Fees

• Current Assignee: Hauptverband Der Gewerblichen Berufsgenossenschaften E.V.
• Original Assignee: Hauptverband Der Gewerblichen Berufsgenossenschaften E.V.
• Inventors: Reinert, Dietmar, Kupfer, Jurgen, Ellegast, Rolf-Peter
• Primary Examiner(s): HINDENBURG, MAX F
• Application Number:
  US09/183,097
• Time in Patent Office: 760 Days
• Field of Search: 600/587, 600/592, 600/594, 600/595
• US Class Current: 600/595
• CPC Class Codes: A61B 5/103 Detecting, measuring or recording devices for testing the shape, pattern, colour, size or movement of the body or parts thereof, for diagnostic purposes A61B5/08 takes precedence; measuring aids for tailors A41H1/00; measuring instruments specially adapted for dentistry A61C19/04
• CPC Class Codes: A61B 5/1116 Determining posture transitions
• CPC Class Codes: A61B 5/4528 Joints A61B5/4533, A61B5/4538 take precedence
• CPC Class Codes: A61B 5/6805 Vests
• CPC Class Codes: A61B 5/6828 Leg
• CPC Class Codes: A61B 5/6831 Straps, bands or harnesses
• CPC Class Codes: A61B 5/7264 Classification of physiological signals or data, e.g. using neural networks, statistical classifiers, expert systems or fuzzy systems neural networks per se G06N3/00; expert systems per se G06N5/00
• CPC Class Codes: G16H 50/20 for computer-aided diagnosis, e.g. based on medical expert systems

Abstract

A device and a method for the recording, presentation and automatic classification of biomechanical load variables measured on a freely moving test person during a work shift. The invention consists of a series of electronic sensors and a series of measuring and storage electronics for recording the movement of a person at a work site. The measuring and storage electronics include at least two sensors and at least one gyroscope. The method for recording a person at a work site includes measuring a set of body angles over a period of time, and measuring the ground reaction force in the region of the sole of a test person'"'"'s foot. The next steps involve determining the threshold values for the identification of postures, and comparing of the threshold values determined with the measured body angles to identify motion patterns. Next, the expected total ground reaction force is calculated and then subtracted from the measured total ground reaction force measured to determine externally exerted forces. Next, the process involves identifying the motion patterns and the output of load profiles. After deriving these measurements, the process involves deriving the acceleration and velocity component of the measured body angles and transforming them into individual joint forces and joint moments while taking account of the measured ground reaction force. The final step includes deriving a disc comparison force and presenting the time characteristic of the disk compression force as a load indication.

Claims

1. A method for the recording, presentation and automatic classification of biomechanical load variables for classified postures measured on a freely moving test personal during a work shift, comprising the steps of:

(a) measuring a set of body angles over a period of time, on the freely moving test person during physical activity;

(b) measuring a ground reaction force and the points of force application in a region of a sole of a foot of the test person;

(c) determining threshold values for the identification of postures and comparing of the threshold values determined with the measured body angles to identify a set of motion patterns;

(d) calculating an expected total ground reaction force based on the measured body angles together with a set of corresponding anthropometric data;

(e) subtracting the measured total ground reaction force from the expected total ground reaction force to determine a set of externally exerted forces;

(f) identifying the motion patterns and an output of load profiles;

(g) deriving the acceleration and velocity component of the measured body angles and transforming them into individual joint forces and joint moments while taking account of the measured ground reaction force;

(h) deriving a disc comparison force; and

(i) presenting the time characteristic of the disk compression force as a load indication, so that a set of test numbers is derived for use in the study of load variables on individuals in a work site.

2. The method according to claim 1, wherein the step of measuring the ground reaction force is performed capacitively and the measuring signal is passed on via an amplifier operating on AC voltage to an analog-to-digital converter.

3. The method according to claim 2, wherein the ground reaction force is determined based on the pressure distribution in a measuring sole.

4. The method according to claim 3, wherein the step of calculating the expected total ground reaction force involves determining the individual joint forces by adding up the individual weights and the measured kinematics of the corresponding body parts, and their vertical components.

5. The method according to claim 1, wherein the data measured on the test person is stored temporarily and, at the same time, pre-processed within a time interval which extends up to the end of the measuring period for evaluation.

6. The method according to claim 1, wherein the measured data in this output is presented in the form of a "vector man" representing a sequence of motions.

7. The method according to claim 6, wherein measurements are calibrated by comparing the posture of the test personal with the "vector man" at the start and the end of a measuring series.

8. The method according to claim 1, wherein the step of driving the disc compression force in the region of the lumbar vertebrae includes the steps of determining individual joint forces by taking account a set of relevant lever arms, and determining the moment of equilibrium around the center of gravity of the intervertebral disc.

9. The method according to claim 1, wherein the step of determining the body angles related to the vertical axis includes determining the area formed from a combined signal of the inclination velocities measured by gyroscopes and the inclination angles measured by inclinometers, to form the large flexion angles in the regions of the thoracic and lumbar vertebrae.

10. The method according to claim 1, wherein the body angles are measured and related to the vertical axis angle and velocity signals are measured with a sampling rate of 10-100 Hz.

11. The method according to claim 1, wherein the step of determining the body angles are determined using measurements from an instrument selected from the group consisting of a relative potentiometer, goniometer, and inclinometer.

12. The method according to claim 9, wherein the large flexion angle is stabilized using a combined signal produced by adding the numerically integrated gyroscope signal to the inclinometer signal during each sample.

13. The method according to claim 9, wherein the step of identifying motion patterns includes the steps of:

determining a set of individual values, measured by the gyroscope, and inclinometer sensors and the potentiometers and converted to the vertical axis; and

subtracting said individual values from said threshold values.

14. The method according to claim 1, further comprising the step of transforming measured body angles into motive forces by determining the velocities and acceleration based on the mathematical derivatives of the measured angles and calculating the joint forces and the joint moments acting on the center of gravity, taking account of the joint type, the respective position of the center of gravity and the forces due to the weight of the parts of the body concerned.

15. The method according to claim 1, wherein the expected total ground reaction force is determined based on the measured body angles of angular velocity, and angular acceleration and the anthropometry which is the size, weight, position of centers of gravity of the parts of the body.

16. The method according to claim 1, further comprising the step of determining load peaks based on the measured forces due to weight and compared with a peak dose which is the force-time-load.

17. The method according to claim 1, wherein the threshold values are defined as positive and negative angle variables and wherein a signal is triggered to identify a movement when the variables are exceeded or undercut.

18. A measuring system for recording biomechanical load variables for posture and body movement comprising:

a series of angle sensors attached to a test person'"'"'s joints and spine for measuring and recording a person'"'"'s posture and body movement; and

a series of measuring and storage electronics having a series of sensor combinations, wherein said sensor combinations each comprise at least two inclinometers covering an angular range of at least 180 degrees and at least one gyroscope to measure the position of the spine in relation to a fixed vertical axis of at least two points; and

an evaluation unit for weighting a series of output signals said evaluation unit received from said at least two inclinometers and said at least one gyroscope wherein said evaluation unit calculates said output signals as a single value.

19. The measuring system according to claim 18, further comprising a foot pressure distribution measuring system for recording a ground reaction force with a same sampling rate as a set of posture equipment;

wherein said series of angle sensors include knee angle sensors, mounted on a set of rails and adapted to be attached to a test person'"'"'s lower leg over an article of clothing and adjusted in relation to a position of a knee joint;

wherein said series of angle sensors include hip angle sensors that are preferably a series of potentiometers, and are mounted on a series of molded plates and are adapted to be attached to an adjustable hip belt worn over a test person'"'"'s clothing and which can be adjusted as required in relation to the position of a test person'"'"'s hip joints wherein there is at least one hip angle sensor and at least one knee angle sensor each disposed on one side of the system, and said angle sensors being set in accordance with the test person'"'"'s posture by a flexible detachable connection having a quick-release catch;

wherein said system further comprises;

a set of sensor combinations disposed on the hip belt for measuring a flexion in a test person'"'"'s lumbar spine wherein said set of sensor combinations are attached in a sagittal plane relative to a vertical axis wherein said set of sensor combinations are adapted to be attached to a jacket worn over the clothing to measure a flexion of a thoracic spine in said sagittal plane relative to said vertical axis;

an inclinometer for measuring the flexion of the thoracic spine in the lateral plane relative to the vertical axis, and adapted to be attached to said jacket in a region of a test person'"'"'s thoracic vertebrae; and

a potentiometer for measuring a twisting of the spine between the regions of said lumbar vertebrae and said thoracic vertebrae wherein said potentiometer is adapted to be attached to said jacket in the region of said thoracic vertebrae, and set via a torsion-free connection to a guide attached to the hip belt in the region of the lumbar vertebrae which is used to adapt to changes in length.

20. The measuring system according to claim 18, further comprising:

a set of equipment for a synchronous sampling of said series of angle sensors and said foot pressure distribution measuring system wherein said equipment for synchronous sampling comprises an energy supply source, a microcomputer unit for activating and scanning the sensors and a memory unit wherein said equipment is attached to said jacket;

a set of equipment for determining a load handled based on a posture and a ground reaction force data registered by the measuring system wherein said equipment for determining the load handled consists of a control system for receiving said registered posture and said set of ground reaction forces as an input signal and the calculated ground reaction forces as a reference variable;

a set of equipment for a continual comparison of a determined posture and a load weight data and their assignment to a set of predetermined postures and load weights and their weighting;

a set of equipment for determining a set of forces acting on certain parts of the skeleton, especially the spine, and for determining a time characteristic based on the determined posture and load weight data using a dynamic model of the human body; and

a set of equipment for comparing the determined chronological and spatial motion patterns of joints or the spine with specified standard values to establish functional limitations.