P11011: Modular Motion Tracking Knee Flexion Unit V1

Competitive Benchmarking

Links to research papers for Head and Knee Device for competitive benchmarking.


House of Quality

Summary Paragraph

Calculation References

Euler Angles

Knee Device

Estimation and Visualization of Sagittal Kinematics of Lower Limbs Orientation Using Body Fixed Sensors

This paper used a combination of accelerometers and gyroscopes. They estimated the acceleration of the knee joint by placing the sensors at the center of rotation. They were able to calculate a stable and drift-free estimate of segment orientation. This device had small errors, it was portable, and could be used for long term monitoring without hindrance to the patients natural activities. Two sensor modules were used, one on the shank and another on the thigh, each containing two accelerometers and one gyroscope. Future recommendations from this paper: Incorporate full 3-D motion into the gait analysis.

Reliability of Measuring Human Segment Three Dimensional Orientation Using Wearable Sensor System

This paper used tri-axial accelerometers, and a high-accuracy camera to compare the sensor system, which was used to obtain error. It was noted that if accelerometers were used, the vector sum includes gravitational and linear accelerations along with noise, so the result can't simply be integrated. The angular velocity captured by a gyroscope integrated result was distorted by offsets and drifts. 8 Subjects were tested, using three tri-axial accelerometers connected to a MCU. Future suggestions from this paper: it is feasible to integrate only two tri-axial accelerometers on one MCU to perform gait analysis.

A Real Time Articulated Human Motion Tracking Using Tri Axis Inertial Magnetic Sensors Package

This paper built a sensor system using tri-axis accelerometers, gyroscopes and magnetometers. Kalman filtering was applied in this project. The accelerometer for this project was used as an inclinometer under the assumption that the magnitude of the acceleration can be neglected. Using the Kalman filtering turned out to give a long time lag. The next step of this project is to include a number of ISP units.

A New Approach to Accurate Measurement of Uniaxial Joint Angles Based on a Combination of Accelerometers and Gyroscopes

This paper used a combination of accelerometers and gyroscopes. The joint angles were found without the need for integration, absolute angles can be obtained which are free from any source of drift. This system provides the joint angles in real time and ready to use in gait analysis. Virtual sensors were used by mathematically shifting the location of the physical sensors. It was found that skin motion artifact is a common source of error, especially for the thigh. This was reduced by using adequate elastic bands to fix the sensors and applying a low-pass filter on the raw signal.

A Low-Cost Motion Tracker and Its Error Analysis

In this paper, they were able to effectively integrate an accelerometer, a magnetometer and two gyroscopes for low-g motion tracking applications. The system breaks down errors contributed by individual components, then determines error elimination methods, self-calibration is done with a feedback loop. Accelerometers, magnetometers and gyroscopes represent a stand-alone technology measured solely relying upon gravitational and geomagnetic fields which gives an absolute coordinate frame of reference. The log-g signal to noise ratio is low for this device. Tri-axis accelerometers were again used for this device. Errors were caused by drift and scale factors for the gyroscopes, but can be continuously corrected by comparing the difference between the calculation and integration results obtained.

Detecting Absolute Human Knee Angle and Angular Velocity Using Accelerometers and Rate Gyroscopes

In this paper, accelerometers and gyroscopes are used to determine the angle of the knee in patients. The tilt of the limb was calculated by combining signals from the accelerometer and the rate gyroscope. Offset and drift of the gyroscope needed to be offset and this was compensated by using auto-reset and auto-null algorithms. The difference of the tilt in the two segments was used to determine the joint angle.

Head Device

Application of a Digital Head Posture Measuring System in Children

This paper used a magentometer, accelerometer, and guroscope from InterSense Inc. to record the anomalous head position in children. The children had ocular torticollis, which is abnormal head position resulting from the child trying to improve their vision. The device continuouly measures head poture at a rate of 20 Hz and presents a real time animation. They reported the repeatability using tests and equations.

Development and Validation of a Digital Head Posture Measuring System

In this paper, the accuracy and repeatability of a head posture systems is observed. The device continuously measures head position at a rate of 20 Hz. 12 human subjects were recorded and the output from the digital measuring system and the actual head position were compared to determine the accuracy of the device. Results of the digital system were compared to the system that used intersecting protractors and a laser pointing at a grid to determine position.

The Usefulness of the Cervical Range of Motion Device in the Ocular Motility Examination

This paper determines if a device can accurately assess the range of motion of the cervical spine of a patient. This paper list the assumed possible abnormal head positions in the amount of head tilt, the range of face turns and the range of the chin position. This paper was testing the ability of a device that had been developed to see if it could meet the necessary specifications to measure abnormal positions.

Electronic Monitoring of Head Position after Vitrectomy

This paper discusses an electronic monitoring system that continuously determines the degrees of head tilt. For this application, if the patient's head goes to a further degree that what the doctor sets, the device will warn the patient. A 3D MEMS accelerometer is used to give the angle of tilt in all axes. Digital signal processing was used to suppress noise and calculate tilt angles.

A Novel Electronic Cervical Range of Motion Measurement System

In this paper, and electronic monitoring system is attached to the top of a hard hat to measure the range of motion of the cervical spine. The device used an accelerometer and gyroscope. It is connected to a personal computer so data can be easily transferred. This device is meant to be portable and to allow the patient to see any improvements from therapy and treatments for neck pain.

Range of Motion Measurement Device (patent)

This paper discusses the measuring of range of motion in a clinical setting. It discusses how goniometers are typically used, but are very unreliable because of the large amount of human error that is present. They also eliminate the use of inclinometers because they are based on gravity and can only measure in one plane. This device works with a series of accelerometers.