Magnetic Condition-Independent 3D Joint Angle Estimation Using Inertial Sensors and Kinematic Constraints

In biomechanics, joint angle estimation using wearable inertial measurement units (IMUs) has been getting great popularity. However, magnetic disturbance issue is considered problematic as the disturbance can seriously degrade the accuracy of the estimated joint angles. This study proposes a magnetic condition-independent three-dimensional (3D) joint angle estimation method based on IMU signals. The proposed method is implemented in a sequential direction cosine matrix-based orientation Kalman filter (KF), which is composed of an attitude estimation KF followed by a heading estimation KF. In the heading estimation KF, an acceleration-level kinematic constraint from a spherical joint replaces the magnetometer signals for the correction procedure. Because the proposed method does not rely on the magnetometer, it is completely magnetic condition-independent and is not affected by the magnetic disturbance. For the averaged root mean squared errors of the three tests performed using a rigid two-link system, the proposed method produced 1.58°, while the conventional method with the magnetic disturbance compensation mechanism produced 5.38°, showing a higher accuracy of the proposed method in the magnetically disturbed conditions. Due to the independence of the proposed method from the magnetic condition, the proposed approach could be reliably applied in various fields that require robust 3D joint angle estimation through IMU signals in an unspecified arbitrary magnetic environment.

Magnetic Condition Flat Core/Shell Nanoparticles

In terms two-phase nanoparticles model, dependence equilibrium position of magnetic moments of parameters size and elongation nanoparticles core is investigated. Phase diagrams of magnetic states were shown and determine geometrical parameters core, in equilibrium states.

VII.—Preliminary Observations on Magnetic Induction in Ferric Oxide at Various Temperatures and in Different States, and on the Possible Chemical Changes indicated by the Observations

In a previous paper by one of us, it was shown that a certain part of rock magnetism was variable and uncertain under the influence of raised temperature. In some instances the rock specimen became permanently more magnetic after it was heated in air, whereas, in the majority of cases, heating caused great loss of magnetic quality. It was suggested that the increase of magnetism observed was caused by the transformation of hæmatite into a more magnetic iron oxide.In order to obtain material which might support this assumption, and also to amplify the work of previous investigators, experiments were undertaken with artificial and natural ferric oxide, in which the transformation of ferric oxide from a non-magnetic into a magnetic condition was observed, while some of the conditions which assist or impede this change were also studied.

XXII.—The Effect of Thermal Treatment and the Effect of Longitudinal Strain in inducing a Sensitive State in certain Magnetic Materials

It has been pointed out by several experimenters, notably by Ewing, and Gray and Ross, that a specimen of steel freshly annealed is in a peculiar magnetic condition. Thus, if a specimen, thoroughly demagnetised, is annealed and then tested, a certain I–H curve is obtained. If it be then demagnetised, and tested again, a second I–H curve is obtained which lies definitely below the first; and any further tests after demagnetisation produce a repetition of the second curve, which is characteristic of the specimen. To obtain the first curve again, the specimen has to be annealed from the same temperature as before, and a test made before demagnetisation.

XXXIX.—Did the Tail of Halley's Comet affect the Earth's Atmosphere?

The return of Halley's Comet in May of this year gave rise to much speculation as to its possible effects on the earth. As it was expected that the earth would pass through the tail of the comet when the comet passed between us and the sun, many observations were arranged for in order to see if the tail, whatever it was composed of, had any effect on the earth or on its atmosphere. If the tail was composed of matter in any form, gaseous, or fine solid or liquid particles, then it seemed possible to get some evidence of its presence in the atmosphere; or if the tail was composed of electrons, then these would disturb the electrical condition of the atmosphere, and also the magnetic condition of the earth.