A Robust Control Algorithm of a Descent Vehicle Angular Motion in the Earth’s Atmosphere

A new approach to synthesize a robust controller for the angular motion of the Earth lander by decomposition method of output modal control is proposed. A universal analytical solution for the problem of stabilizing the angular position of the lander is obtained. A comparative analysis of the presented algorithm with the currently used onboard algorithm for descent control of the manned spacecraft Soyuz is carried out. The advantages of the new algorithm relative to the existing algorithm are presented, both in terms of stabilization accuracy and the consumption of the working fluid of the control motors.

A Functional Electrical Stimulator to Enable Grasping Through Wrist Flexion

Functional electrical stimulation is an assistive technique that utilizes electrical discharges to produce functional movements in patients suffering from neurological impairments. In this work, a biphasic, programmable current- controlled functional electrical stimulator system is designed to enable hand grasping facilitated by wrist flexion. The developed system utilizes an operational amplifier based current source and is supported by a user interface to adjust stimulation parameters. The device is integrated with an accelerometer to measure the degree of stimulated movement. The system is validated, firstly, on two passive electrical loads and subsequently on four healthy volunteers. The device is designed to deliver currents between 0-30mA, and the error between the measured current and simulated current for two loads were -0.967±0.676mA and -0.995±0.97mA. The angular data from the accelerometer provided information regarding variations in movement between the subjects. The architecture of the proposed system is such that it can, in principle, automatically adjust the parameters of simulation to induce the desired movement optimally by measuring a stimulated movement artifact (e.g., angular position) in real time.

A periodic adaptive current controller for torque ripple reduction in uncertain permanent magnet synchronous motor drives

This paper addresses an adaptive control approach to achieve high-performance response in phase currents and to minimize torque ripples in uncertain permanent magnet synchronous motor drives. In this manner, the electrical part of the permanent magnet synchronous motor drive is considered completely uncertain by taking the inherent characteristic of the parameters into account. A periodic adaptive controller is formulated in order to achieve the torque ripple reduction in the presence of the time-varying periodic uncertainties. In the sense that the periodic uncertainties appearing in permanent magnet synchronous motor drives change by the angular position, a change of the time variable is applied in the formulation of the proposed adaptive controller, and the stability analysis is conducted accordingly utilizing a Lyapunov–Krasovskii functional. Extensive numerical simulations are successfully performed for various operation points to validate the effectiveness of the proposed method.

Moving bar of light evokes vectorial spatial selectivity in the immobile rat hippocampus

Visual cortical neurons encode the position and motion direction of specific stimuli retrospectively, without any locomotion or task demand. Hippocampus, a part of visual system, is hypothesized to require self-motion or cognitive task to generate allocentric spatial selectivity that is scalar, abstract, and prospective. To bridge these seeming disparities, we measured rodent hippocampal selectivity to a moving bar of light in a body-fixed rat. About 70% of dorsal CA1 neurons showed stable activity modulation as a function of the bar angular position, independent of behavior and rewards. A third of tuned cells also encoded the direction of revolution. In other experiments, neurons encoded the distance of the bar, with preference for approaching motion. Collectively, these demonstrate visually evoked vectorial selectivity (VEVS). Unlike place cells, VEVS was retrospective. Changes in the visual stimulus or its trajectory did not cause remapping but only caused gradual changes. Most VEVS-tuned neurons behaved like place cells during spatial exploration and the two selectivities were correlated. Thus, VEVS could form the basic building block of hippocampal activity. When combined with self-motion, reward, or multisensory stimuli, it can generate the complexity of prospective representations including allocentric space, time, and episodes.

CONSTRUCTION OF ROTOR ANGLE IDENTIFIER IN VECTOR CONTROL SYSTEMS OF DOUBLE FEED MACHINES

In asynchronous electric drives with vector control on the rotor, it is necessary to calculate the value of the sine and cosine of the angle of rotation of the rotor relative to the stator to form control actions. When using angle sensors, complex structural tasks can arise — placement and reliable mounting of the sensor on the shaft and, accordingly, the task of the overall layout of the unit. For high-power machines, the tasks of developing and creating the design of the sensor itself arise. If serial rotor angular position sensors can be used, the task of placing and mounting the sensor is no less difficult. In these cases it is necessary to deduce the second end of a shaft from the case of the engine with contact rings that complicates its design. Therefore, the urgent need to create more reliable electric drives with vector control systems on the rotor is the synthesis of identifiers of the angle of rotation of the rotor. Identifiers are known whose calculation algorithms are based on determining the projections of the flow coupling vectors. In the work with the use of coordinate transducers of projections of stator or rotor current vectors and equations of electromagnetic circuits of an asynchronous machine, the synthesis and subsequent analysis of the properties of the rotor position angle identifier in vector control systems of dual power machines is performed. New equations of the identifier of flux couplings are received, its stability is investigated and on conditions of stability types of electric drives in which it is possible to apply the offered identifier are defined. The stability of the vector control system and sufficient identification accuracy when using the proposed equations and functions are confirmed by the method of mathematical modeling of the recommended electric drive systems in different operating modes.

Nussbaum-type Neural Network-based Control of Neuromuscular Electrical Stimulation with Input Saturation and Muscle Fatigue

Neuromuscular electrical stimulation is a promising technique to actuate the human musculoskeletal system in the presence of neurological impairments. The closed-loop control of NMES systems is non-trivial due to their inherent uncertain nonlinearity. In this paper, we propose a Nussbaum-type neural network-based controller for the lower leg limb NMES systems. The control accounts for model uncertainties and external disturbances in the system and, for the first time, provides a solution with rigorous stability analysis to the adaptive NMES tracking problem with input saturation and muscle fatigue. The proposed controller guarantees a uniformly ultimately bounded tracking for the knee joint angular position. To evaluate the control performance, a simulation study is taken, where the adaptation mechanism of the Nussbaum-type gain and the controller's robustness to muscle fatigue and input saturation are discussed.

Analysis of the Impact of Magnetic Materials on Cogging Torque in Brushless DC Motor

The cogging torque is the most significant issue in permanent magnet applications, since it has a negative impact on machine performance. In this article, the impact of magnetic materials on cogging torque is analyzed on brushless DC motors (BLDC). The effect of neodymium magnets (NdFeB), compression molded magnet, and samarium cobalt (SmCo) magnet on the cogging torque is analyzed to the BLDC motor designed for hybrid electric vehicle traction that has the peak power rating of 50 kW motor with 48 stator slots and 8 rotor poles. With the presence of these three magnetic materials, the cogging torque is estimated independently using multiposition simulation. The multiposition is simulated using a transient application that runs at constant speed. The results of cogging torque, rotational speed, angular position of BLDC motor, and magnetic flux density distribution have been presented. Also, the maximal, mean, minimal, rectified mean, and rms values of cogging torque were provided.

Measurement and modeling of a flexible manipulator for vibration control using five-segment S-curve motion

User designed manipulators are widely used in industry as a part of automation. The design of lighter robotic arms is required for less energy consumption. Joints, structural features, and payload affect the dynamic behavior of manipulators. Even if the arms have sufficient structural rigidity, joints, or payloads further increase their flexibility. These factors should be considered at the design stage. Flexibility causes vibrations, and these vibrations negatively affect robot repeatability and processing speed. Reducing the vibration levels of flexible manipulators is an attractive issue for engineers and researchers. Accurate estimation of the mathematical model of flexible manipulators increases the success of vibration control. In this paper, the modeling and experiments for vibration control of a single-axis flexible curved manipulator with payload are considered. The experimental system is introduced to collect vibration responses synchronously at the tip of the curved manipulator for angular velocity input. The mathematical model of the manipulator is estimated using the continuous-time system identification (CTSI) method with a black-box model based on the experimental input/output (I/O) signals. A five-segment S-curve motion input based on the modal parameters is designed to suppress residual vibrations. Vibration control is successfully performed for different deceleration times of the designed S-curve motion input. The results showed that the residual vibrations from experiments and predicted models matched well for different cases depending on payload, angular position, and motion time.

Integrated Pedal System for Data Driven Rehabilitation

We present a system capable of providing visual feedback for ergometer training, allowing detailed analysis and gamification. The presented solution can easily upgrade any existing ergometer device. The system consists of a set of pedals with embedded sensors, readout electronics and wireless communication modules and a tablet device for interaction with the users, which can be mounted on any ergometer, transforming it into a full analytical assessment tool with interactive training capabilities. The methods to capture the forces and moments applied to the pedal, as well as the pedal’s angular position, were validated using reference sensors and high-speed video capture systems. The mean-absolute error (MAE) for load is found to be 18.82 N, 25.35 N, 0.153 Nm for Fx, Fz and Mx respectively and the MAE for the pedal angle is 13.2°. A fully gamified experience of ergometer training has been demonstrated with the presented system to enhance the rehabilitation experience with audio visual feedback, based on measured cycling parameters.

Ways to identify bearings in two-position goniometric airborne radiomonitoring systems.

For aeronautical goniometric systems for radio monitoring of radio emission sources (RES), one of the primary tasks is the identification of bearings. It is especially difficult to solve the problem of identifying bearings if there are several RESs in the observation area in the case when they are located in the same plane with the direction finders. In this case, the problem of identifying bearings in goniometric two-position systems is solved in the process of performing a two-stage procedure. At the first stage, the primary identification of single measurements of bearings is carried out separately at each receiving position (RP) when receiving radio signals from the RES, and at the second stage, the secondary (inter-positional) identification of bearings arriving from both RPs is carried out. In the initial identification, strobe and strobeless identification algorithms are used. In the secondary identification for selection of true and false points of intersection of bearings on the plane, it is proposed to use the kinematic parameters of the relative RES. However, this type of selection does not provide interposition identification with an arbitrary nature of the movement of the RES relative to the RP, and also assumes a constant angular position of the RP base on the plane. More practical are ways of identifying bearings with RES, in which the procedure for constructing a confidence region (CR) in the form of a circle with a certain radius is used. However, a more correct form of CR is an elliptical CR, since the errors in determining the position of the RES are characterized by an error ellipse, a particular case of which is a circle. Therefore, methods for identifying coordinate information have been developed, in which elliptical CRs are used. In this case, not only the bearings of the RES, but also other measured parameters, for example, estimates of the rectangular coordinates of the RES, calculated on the basis of the triangulation method, can be used as coordinate information. The purpose of the article is to systematize and analyze the developed methods for identifying bearings, which allow one to get a fairly general idea of how to solve the problem of identifying bearings and indirect measurements of the coordinates of radio emission sources in aviation goniometric two-position radio monitoring systems. As a result, a classification of identification methods is given. The existing possibilities and limitations of using various identification methods in solving radio monitoring problems are analyzed. The necessary information on the methods and algorithms for interpositional identification of coordinate information about the position of the RES, using ellipsoidal CRs in solving the identification problem, is given. The practical significance of the presented methods is to increase the likelihood of correct identification of coordinate information, as well as the accuracy of the positioning of RES due to the use of elliptical CRs, which more accurately reflect the regularity of the distribution of errors in determining the position of RES.