Recording of the ship’s motion in operation on irregular waves and its processing

The safety of the ship state during the voyage is ensured, among other things, by monitoring the state of the ship’s stability. A device for measuring the parameters of the ship’s motion and software for discrete motion recording into a computer have been developed in Siberian State University of Water Transport. With the use of the device, a full-scale experiment to record the motion of the motor ship “Grumant” during an operational voyage has been carried out. For this, the half-periods of rolling and their amplitudes are obtained. Amplitude-half-period distribution of rolling has been built. According to the maximum probability, the half-period of its own roll has been found from it, which makes it possible to assess the stability state of the vessel during the voyage. The spectrum of motion and rolling dispersion has been obtained. If it is possible to obtain objective information about the actual wave spectrum, this opens the way to obtaining the amplitude-frequency characteristic of the motion based on the Wiener- Khinchin theorem. This task is set as a priority for the development of research in this area with the prospect of optimizing vessel navigation in difficult hydrometeorological conditions.

A Novel sEMG-Based Gait Phase-Kinematics-Coupled Predictor and Its Interaction With Exoskeletons

The interaction between human and exoskeletons increasingly relies on the precise decoding of human motion. One main issue of the current motion decoding algorithms is that seldom algorithms provide both discrete motion patterns (e.g., gait phases) and continuous motion parameters (e.g., kinematics). In this paper, we propose a novel algorithm that uses the surface electromyography (sEMG) signals that are generated prior to their corresponding motions to perform both gait phase recognition and lower-limb kinematics prediction. Particularly, we first propose an end-to-end architecture that uses the gait phase and EMG signals as the priori of the kinematics predictor. In so doing, the prediction of kinematics can be enhanced by the ahead-of-motion property of sEMG and quasi-periodicity of gait phases. Second, we propose to select the optimal muscle set and reduce the number of sensors according to the muscle effects in a gait cycle. Finally, we experimentally investigate how the assistance of exoskeletons can affect the motion intent predictor, and we propose a novel paradigm to make the predictor adapt to the change of data distribution caused by the exoskeleton assistance. The experiments on 10 subjects demonstrate the effectiveness of our algorithm and reveal the interaction between assistance and the kinematics predictor. This study would aid the design of exoskeleton-oriented motion-decoding and human–machine interaction methods.

Chaotic Path Planning for 3D Area Coverage Using a Pseudo-Random Bit Generator from a 1D Chaotic Map

This work proposes a one-dimensional chaotic map with a simple structure and three parameters. The phase portraits, bifurcation diagrams, and Lyapunov exponent diagrams are first plotted to study the dynamical behavior of the map. It is seen that the map exhibits areas of constant chaos with respect to all parameters. This map is then applied to the problem of pseudo-random bit generation using a simple technique to generate four bits per iteration. It is shown that the algorithm passes all statistical NIST and ENT tests, as well as shows low correlation and an acceptable key space. The generated bitstream is applied to the problem of chaotic path planning, for an autonomous robot or generally an unmanned aerial vehicle (UAV) exploring a given 3D area. The aim is to ensure efficient area coverage, while also maintaining an unpredictable motion. Numerical simulations were performed to evaluate the performance of the path planning strategy, and it is shown that the coverage percentage converges exponentially to 100% as the number of iterations increases. The discrete motion is also adapted to a smooth one through the use of B-Spline curves.

Discrete mKdV Equation via Darboux Transformation

We introduce an efficient route to obtaining the discrete potential mKdV equation emerging from a particular discrete motion of discrete planar curves.

sEMG-Based Continuous Estimation of Finger Kinematics via Large-Scale Temporal Convolutional Network

Since continuous motion control can provide a more natural, fast and accurate man–machine interface than that of discrete motion control, it has been widely used in human–robot cooperation (HRC). Among various biological signals, the surface electromyogram (sEMG)—the signal of actions potential superimposed on the surface of the skin containing the temporal and spatial information—is one of the best signals with which to extract human motion intentions. However, most of the current sEMG control methods can only perform discrete motion estimation, and thus fail to meet the requirements of continuous motion estimation. In this paper, we propose a novel method that applies a temporal convolutional network (TCN) to sEMG-based continuous estimation. After analyzing the relationship between the convolutional kernel’s size and the lengths of atomic segments (defined in this paper), we propose a large-scale temporal convolutional network (LS-TCN) to overcome the TCN’s problem: that it is difficult to fully extract the sEMG’s temporal features. When applying our proposed LS-TCN with a convolutional kernel size of 1 × 31 to continuously estimate the angles of the 10 main joints of fingers (based on the public dataset Ninapro), it can achieve a precision rate of 71.6%. Compared with TCN (kernel size of 1 × 3), LS-TCN (kernel size of 1 × 31) improves the precision rate by 6.6%.

Features of switching autowaves of localized plasticity in FCC alloy

The kinetics of deformation processes at the yield plateau in the aluminum alloy 1550 studied. It is established that in the general case, the motion of the Lüders band fronts occurs discretely and only in the phase of sample unloading. Continuous motion of the deformation fronts is possible if the rate of relaxation of the applied stresses due to the test machine is greater than or equal to the rate of their decline, controlled by internal processes at a lower scale level. The discrete motion of the Lüders fronts in the 1550 alloy suggests that they are not pure autowaves of switching.

Research of the polymer granules shape and size influence on their tribological properties

The use of a mathematical model of discrete motion of bulk material were justified for movement of polymer granules in the working channel of feeding zone of the screw extruder as a set of particles moving relative to each other based on the Discrete Element Method taking into account the influence of the shape and the size of polymer granules on their tribological properties on the example of the problem of forming the angle of repose. The study of the interaction among the granules of the following four polymers has been conducted: high-density polyeth-ylene of brand Marlex HHM 5502BN (HDPE), copolymer of ethylene with vinyl acetate (sevilene) of brand 11104-030(CEV), polystyrene of brand Denka Styrol MW-1-301 (PS), polyvinyl chloride of brand SorVyl G 2171/9005 11/01 (PVC), which are selected because they are widely used in industry and at the same time differ from each other in shape, size and physical and mechanical characteristics. The Hertz-Mindlin viscoelastic model was used to de-scribe the interaction between granules, which assumes that the sphere-shaped particles do not deform upon con-tact and overlap each other by a predetermined amount, forming a contact patch. The study was carried out in the EDEM software package. The calculation results for the formation of an angle of repose of natural methods and numerical experiment were given with the two approaches to modeling the shape of pellets were analyzed: the consideration in the form of granules in the form of spheres and in the form of multisphere, when the calculated shape of the pellets as close to real. The results of the calculations on the formation of the angle of repose prove that the discrete motion model of bulk material based on the discrete element method when using the form of gran-ules close to real better reproduces the behavior of bulk materials compared to spherical granules.

Qubit as the natural unit measure of random choice

Einstein wrote his famous sentence "God does not play dice with the universe" in a letter to Max Born in 1920. All experiments have confirmed that quantum mechanics is neither wrong nor “incomplete”. One can says that God does play dice with the universe. Let quantum mechanics be granted as the rules generalizing all results of playing some imaginary God’s dice. If that is the case, one can ask how God’s dice should look like. God’s dice turns out to be a qubit and thus having the shape of a unit ball. Any item in the universe as well the universe itself is both infinitely many rolls and a single roll of that dice for it has infinitely many “sides”. Thus both the smooth motion of classical physics and the discrete motion introduced in addition by quantum mechanics can be described uniformly correspondingly as an infinite series converges to some limit and as a quantum jump directly into that limit. The second, imaginary dimension of God’s dice corresponds to energy, i.e. to the velocity of information change between two probabilities in both series and jump.

A frame-independent comparison metric for discrete motion sequences

To evaluate the kinematic performance of designed mechanisms, a statistical-variance-based metric is proposed in this article to measure the “distance” between two discrete motion sequences: the reference motion and the given task motion. It seeks to establish a metric that is independent of the choice of the fixed frame or moving frame. Quaternions are adopted to represent the rotational part of a spatial pose, and the variance of the set of relative displacements is computed to reflect the difference between two sequences. With this variance-based metric formulation, we show that the comparison results of two spatial discrete motions are not affected by the choice of frames. Both theoretical demonstration and computational example are presented to support this conclusion. In addition, since the deviation error between the task motion and the synthesized motion measured with this metric is independent of the location of frames, those corresponding parameters could be excluded from the optimization algorithm formulated with our frame-independent metric in kinematic synthesis of mechanisms, and the complexity of the algorithm are hereby reduced. An application of a four-bar linkage synthesis problem is presented to illustrate the advantage of the proposed metric.