Disturbance Forces Research Articles

GENERALIZED MATHEMATICAL MODEL OF VIBRATIONS OF A VERTICAL AXIS ROTARY SYSTEM

The rotor’s response to dynamic actions depends on its physical parameters and the parameters of the supporting structure. The vibration measured on the bearings or on the rotor shaft, in addition to the physical properties of the rotor, also depends on the value of the unbalance, its distribution along the rotor axis, as well as on the rotational speed. These factors influence the choice of the balancing method. This article proposes a dynamic model of a rotary machine with a vertical axis of rotation and six degrees of freedom. Differential equations of free and forced oscillations of the rotor system are compiled. It is shown that when considering the general case of oscillations of the rotor system, there is a high connectivity of oscillations along all generalized coordinates. Based on the analysis of differential equations, ways of reducing vibration activity and connectivity of machine vibrations are shown, which provide for: reduction of the center of mass of the platform to the axis of rotation of the rotor; alignment of the center of stiffness of the elastic support system with the center of gravity of the platform, and the main axes of stiffness and constant viscous friction of dampers with the main central axes of inertia of the platform; the use of vertical suspensions for the oscillating system in the construction of the machine; replacement of the elastic sealing diaphragm of the rotor with a non-rigid one. The above measures to reduce the connectivity of vibrations and vibration activity do not completely eliminate the vibrations of the machine caused by stochastic, variable imbalances. Therefore, a further decrease in the vibration activity of the machine can be associated with the use of auto-ballasting devices, which make it possible to reduce the disturbing forces by reducing the magnitude of the stochastic imbalances of the rotary machine.

An Enhanced Linear Active Disturbance Rejection Controller for High Performance PMBLDCM Drive Considering Iron Loss

The use of position sensors for the variable frequency drive (VFD) has been verified for years. However, more reliable VFDs with smart autonomous systems require side-by-side implementation of sensor and/or sensorless operation. Recently developed active disturbance rejection control (ADRC) provides robustness to VFD uncertainty and its fast response to reject disturbances. Considering the iron loss effect as the disturbance to the permanent magnet brushless dc motor (PMBLDCM) performances, a novel ADRC is proposed in this article. The ADRC current controller considering the iron loss effect is proposed along with an estimation of the back electromagnetic force disturbance used for the position/speed estimation. The proposed controller incorporates a structured inner and outer closed-loop ADRC that considers process delays and extended state observer dynamics. These dual ADRC-based control algorithms are verified for PMBLDCM drive both by simulation study and experimental findings. The improved performance of the proposed method is validated with a laboratory prototype of 2.5 kW PMBLDCM drive system.

К вопросу о расчете продольных колебаний коленчатого вала поршневых двигателей

One of the initial stages of calculating the crankshaft longitudinal vibrations is developing an oscillatory system model, which includes the determination of longitudinal pliability (rigidity) of elastic sections. If it is impossible to determine the pliability experimental, the empiric formulas or the final element method (FEM) are used. There are given the values of crank longitudinal pliability of the crankshafts of different marine engine types found by using the formulas of L. Gugliemotti – R. Machciotta, P. Draminsky, E. Y. Gorbunov, S. F. Dorey, N. S. Skorchev, V. S. Stoyanov, etc. It is shown that the calculation results obtained from these formulas for the same engine significantly differ; therefore, the choice of one or another empirical formula for practical calculations is difficult. The preference of using FEM for determining the longitudinal (axial) compliance of cranks and other areas with complex geometric shapes has been proven. The possibility of its application is also shown to determine the longitudinal disturbing force as the reaction of the crankshaft support against the action of the radial force exerted to the connecting rod journal. It is proposed to use, along with empirical formulas, regression equations connecting the longitudinal compliance of the cranks with a significantly larger number of their design dimensions.

NUMERICAL SIMULATION OF AERODYNAMIC STABILITY OF LONG-SPAN BRIDGES

Statement of the problem. The aim of the work is to simulate the resonant vibrations of the continuous beam span of the bridge in the direction perpendicular to the wind flow by the finite element method. The article deals with a non-standard situation that arose on May 20, 2010 on the bridge over the Volga River in the city of Volgograd.Results. As a result, an effective algorithm for calculating the aerodynamic stability of large-span bridge structures was developed using one of the most widespread software systems in Russia and neighboring countries - "Lira-SAPR". Recommendations for the selection and modeling of dampers are given. Conclusions. The developed algorithm makes it possible to numerically describe the disturbing force of periodic breakdown of wind flow vortices, which causes resonant oscillations of bridge spans, to apply this force to the design model in Lira-SAPR, and to obtain parameters that make it possible to assess the stress-strain state of the system during oscillations and to select the optimal characteristics of the damping devices.

A Hierarchical Anti-Disturbance Path Tracking Control Scheme for Autonomous Vehicles Under Complex Driving Conditions

Path tracking is one of the most crucial issues of autonomous vehicles, but uncertain factors including road roughness and wind gusts could cause lateral deviation and even divergence of the control system. Therefore, this paper proposes a hierarchical anti-disturbance tracking architecture based on the steer-by-wire (SBW) system to improve tracking accuracy and dynamic stability for autonomous vehicles. The proposed architecture is robust strongly against different types of disturbances in the path tracking process by means of hierarchical decoupling. Firstly, in the upper-layer path tracking module, a robust model predictive control (MPC) method with a feedback correction term calculates the expected front-wheel steering angle. Secondly, in the lower-layer SBW module, a nonlinear high gain rack force observer is proposed to compensate for the generalized rack force disturbance. Then, an improved non-singular fast terminal sliding mode auxiliary control law based on the super-twisting algorithm is presented to attenuate the norm-bounded rack disturbance effectively. Simulation and experiment results show that the proposed control architecture can improve the path tracking accuracy and has strong interference resistance and robustness against both modeled and unmodeled disturbances.

Design and Implementation of Integral Backstepping Sliding Mode Control for Quadrotor Trajectory Tracking

A robust trajectory tracking control scheme for quadrotor unmanned aircraft vehicles under uncertainties is proposed herein. A tracking controller combined with the sliding mode and integral backstepping is performed for position and attitude tracking. The stability of the trajectory tracking controller of the quadrotor is investigated via Lyapunov stability analysis. By incorporating force and torque disturbances into numerical simulations, the results demonstrate the effectiveness of the proposed quadrotor trajectory controller. Finally, the experiments validate the feasibility of the proposed controller.

Dynamic walking characteristics and control of four-wheel mobile robot on ultra-high voltage multi-split transmission line

High-voltage lines are an important channel for power transmission, and multi-split transmission lines are the main strength of power transmission. Compared with double-wheel single-wire maintenance robots, ultra-high-voltage multi-split transmission lines and four-wheel mobile robots have a wider application range and greater demand. The maintenance of multi-split transmission lines relies on the stable walking and control of four-wheel mobile robots on heterogeneous multi-split transmission lines. However, uncertain disturbance factors such as wind load in the complex field environment cause vibration of double-split and quad-split lines. The slight change in the line spacing causes the line contact to the edge of the robot’s walking wheel, which increases the friction during the robot’s walking. It also directly hinder the movement of the robot on the multi-split transmission line, thus restricting the completion of the robot’s maintenance operation. Based on the analysis, this paper establishes a mathematical model of the external force disturbance influence on the spacing of the double-split lines. At the same time, the robot walking mechanics characteristics model under the change of the line space has been established. Three different forms of the robot walking online have been obtained through abstraction processing. A method of side friction identification based on fuzzy control has been proposed, through the online monitoring of the friction between line and edge of the walking wheel, the robot walking wheel motor walking force can be intelligently controlled in real time, and effectively avoids the “wheel-line” jam phenomenon under the external uncertain factors in the field environment. Finally, the feasibility and engineering practicability of the method have been verified through MATLAB/ADAMS simulation and field operation experiments. Therefore, the automation and intelligence level of the operation and the transmission system maintenance management has been improved.

Modeling and Vibration Suppression of a Flexible Structure in SimMechanics

In this work, modeling and simulation of a flexible cantilever beam are investigated in SimMechanics and then, vibration results are verified with the finite element (FE) model in ANSYS. Flexible beam model based on SimMechanics is created in MATLAB, while the FE model is established in ANSYS. In the system, inputs are determined as a force base actuator and disturbance force. Outputs of the system are selected as displacement and acceleration responses at the endpoint of flexible beam. Undamped natural frequencies are determined by modal analysis in ANSYS and frequency analysis in MATLAB. Transient analyses are achieved to obtain the vibration responses. For the open loop responses, the displacement and acceleration vibration results are verified using step and harmonic excitations. The closed-loop control with PID controller is applied to the FE and SimMechanics models to control the endpoint position. The open and closed-loop vibration results are indicated for different controller gains. It observed that open and closed-loop results are successfully matched well with the FE model and SimMechanics. The accuracy of flexible beam model based on SimMechanics is verified with the FE model.

Total Force Analysis and Safety Enhancing for Operating Both Guidewire and Catheter in Endovascular Surgery

In vascular interventional surgery (VIS), the doctors often need to be exposed to X-ray radiation for a long time, operate surgical instruments (Ex. Guidewires and catheters) to perform the operation, which is difficult to ensure the health of surgeons and the safety of operation. In addition, the force between the blood vessel wall and the surgical instrument is complex and variable, the existence of the external disturbance forces easily affects the judgment of the doctors. In this paper, to ensure the health and reduce the fatigue of the doctors, a novel tactile sensing robot-assisted system for VIS was developed to assist the surgeons to complete the operation. Then, the forces between the blood vessel and the surgical instrument during the surgery were analyzed. Besides, a self-developed force sensor was used to confirm the collision force between the tip of the catheter and the blood vessel wall. Finally, combining the haptic force feedback of the system and the developed force sensor, a series of experiments in “Vitro” were completed, and it was indicated by the experiment results that the accuracy of the force feedback can be improved by using the analysis method proposed in this paper, the collision force between the catheter tip and the blood vessel environment can be confirmed by the self-developed force sensor. Based on the results, the developed robot-assisted system for VIS has high safety.

On maintaining the stability of the equilibrium of nonlinear oscillators under conservative perturbations

Abstract. The problem of Yu.N. Bibikov on maintaining the stability of the equilibrium position of two interconnected nonlinear oscillators under the action of small, in a certain sense, conservative perturbing forces is considered. With different methods of reducing the system to the Hamiltonian form, some features are revealed for the case when the perturbing forces of the interaction of two oscillators are potential. The conditions for preserving the stability and instability of the equilibrium of two oscillators for the case of sufficiently small disturbing forces are obtained. The problem of maintaining the stability of the equilibrium under conservative perturbations is also considered in the more general situation of an arbitrary number of oscillators with power potentials with rational exponents, which leads to the case of a generalized homogeneous potential of an unperturbed system. The example given shows the applicability of the proposed approach in the case when the order of smallness of the perturbing forces coincides with the order of smallness of the unperturbed Hamiltonian.

Study of a Stripper Header for Grain Harvesting as a Vibrating System

Introduction. Grain losses caused by stripping defects are the main problem to be solved in designing a stripper header. To reduce these losses, a design of a stripper header with a vibration drive is proposed. This device combines the processes of stripping grain crops and the vibration effect of the stripping fingers upon the ears of plants. The most important stage of the mathematical description of these processes is composing the differential equation of the stripping fingers motion. Materials and Methods. A computational-graphic diagram of an oscillatory system with one degree of freedom is proposed. To compose the differential equation of the stripping fingers motion, a method based on the application of the Lagrange equation was used. The oscillations of the system under studying arise from the motion of a point in the system according to a given law. The problem of kinematic excitation is reduced to the problem of force perturbation. This stage of the study was carried out without taking into account the resistance forces. Results. An equation for motion of stripping fingers making vibrational reciprocating movements is obtained. It is proposed to select the elastic element in the design scheme and consider a more general case of the stripping fingers movement. In this case, the movement of the stripping fingers is considered to be difficult. A characteristic feature of the mathematical description is the presence of a generalized force of potential forces. The differential equation of motion of a comb in the presence of an elastic element and the solution of this equation are composed. Discussion and Conclusion. Forced oscillations of a system without resistance, excited by a harmonic disturbing force, are harmonic oscillations with constant amplitude. On close values of the angular frequency of vibration of the drive output link and the root of the ratio of the stiffness coefficient of the elastic element to the stripping fingers mass, the case of resonance takes place. The system parameters must be selected so as to avoid this negative phenomenon.

Hydrometeor and Latent Heat Nudging for Radar Reflectivity Assimilation: Response to the Model States and Uncertainties

Radar data are essential to convection nowcasting and nudging-based radar data assimilation through diabatic initialization is one of the most effective approaches for forecasting convective systems with numerical weather prediction (NWP) models, used at several advanced global weather centers. It is desired to assess the uncertainty and physical consistency of this assimilation process. This paper investigated impacts of relaxation coefficient, radar data update intervals and continuous assimilation time duration and addressed the key issues and possible solutions of the radar data assimilation based on the WRF hydrometeor and latent heat nudging (HLHN) developed at the National Center for Atmospheric Research (NCAR). It is revealed that excessively large relaxation coefficient forced the model to observations with a tendency greater than the physical terms of the convection, causing the dynamic imbalances and serious convection “ramp-down” right after the free forecast starts. Assimilating high update frequency radar data can make the tendency terms moderate and sustained thereby maintaining the assimilation effect and reducing fortuitous convection. HLHN requires a minimum continuous assimilation duration to contain the initial forced disturbance of the model. For a summer Meiyu precipitation case studied, the minimum duration is ~1 h. Appropriate selection of the HLHN parameters is able to effectively improve the temperature, humidity, and dynamic fields of the model. In addition, several issues still remain to be solved to further enhance HLHN.

A two-stage deep transfer learning for localisation of forced oscillations disturbance source

Accurately locating forced oscillations (FOs) disturbance source in a large-scale power system is a challenging task. In this paper, a localisation method featuring system-level and area-level localisation is proposed. Compared with traditional localisation methods which process the FOs signals only in control centre phasor data concentrator (PDC), the proposed method can not only relieve the data communication pressure, but also meets the data privacy and confidentiality requirements of utility companies. Besides, with the two-stage deep transfer learning, high accuracy of localisation can be realised with far less training. Firstly, by adopting principle component analysis (PCA) to extract the most representative information at system-level and smooth pseudo Wigner-Ville distribution (SPWVD) to characterize FOs signals, graphical representations of FOs at system-level and area-level are obtained respectively, transforming the localisation problem to image recognition problem. Subsequently, a two-stage deep transfer learning (DTL) algorithm is developed to locate FOs disturbance source. The first stage involves repurposing the learnt features from a pre-trained deep convolutional neural network (previously trained for universal image recognition) to improve the learning of system-level localisation. In a similar logic, the second stage entails transferring the knowledge acquired from the first stage is exploited to aid area-level localisation learning. Case studies carried out on the WECC 179-bus system demonstrate that the proposed method achieves a significantly higher accuracy in the presence of measurement noise, topology variation and load disturbances of the system with respect to the traditional machine learning method. The proposed method also exhibits a more favorable computational performance and learning efficiency due to the employment of the tactfully designed two-stage DTL approach.

Autonomous landing of a quadrotor on a moving platform using vision-based FOFPID control

AbstractThis research deals with the autonomous landing maneuver of a quadrotor unmanned aerial vehicle (UAV) on an unmanned ground vehicle (UGV). It is assumed that the UGV moves independently, and there is no communication and collaboration between the two vehicles. This paper aims at the design of a closed-loop vision-based control system for quadrotor UAV to perform autonomous landing maneuvers in the possible minimum time despite the wind-induced disturbance force. In this way, a fractional-order fuzzy proportional-integral-derivative controller is introduced for the nonlinear under-actuated system of a quadrotor. Also, a feedback linearization term is included in the control law to compensate model nonlinearities. A supervisory control algorithm is proposed as an autonomous landing path generator to perform fast, smooth, and accurate landings. On the other hand, a compound AprilTag fiducial marker is employed as the target of a vision positioning system, enabling high precision relative positioning in the range between 10 and 350 cm height. A software-in-the-loop simulation testbed is realized on the windows platform. Numerical simulations with the proposed control system are carried out, while the quadrotor system is exposed to different disturbance conditions and actuator dynamics with saturated thrust output are considered.

Energy optimal control of mobile manipulators subject to compensation of external disturbance forces

This study proposes a new class of controllers for mobile manipulators subject to both undesirable forces exerted on the end-effector and unknown friction forces coming from joints directly driven by the actuators as well as undesirable forces resulting from the kinematic singularities appearing on the mechanism trajectory. Based on the suitably defined task space non-singular terminal sliding manifold (TSM) and the Lyapunov stability theory, we derive a class of estimated extended transposed Jacobian controllers which seem to be effective in counteracting the unstructured forces. Due to a redundant nature of the tasks to be accomplished, our controllers also a involve useful criterion function (energy consumption) in optimally tracking a desired trajectory. Moreover, in order to eliminate (or to alleviate) undesirable chattering effects the proposed control laws include second order sliding techniques. The numerical computations, which are carried out for a mobile manipulator consisting of a platform of (2, 0) type and a holonomic manipulator of two revolute kinematic pairs, illustrate the performance of the proposed controllers and simultaneously their minimizing properties. Numerical comparison with other control algorithms well-known in the literature is also given.

Anti-swing radial basis neuro-fuzzy linear quadratic regulator control of double link rotary pendulum

In this article, a radial basis neuro-fuzzy linear quadratic regulator controller is developed for the anti-swing control of a double link rotary pendulum system. The objective of this work is to study the radial basis neuro-fuzzy linear quadratic regulator controller and to compare it with a fuzzy linear quadratic regulator and the linear quadratic regulator controllers. In the proposed radial basis neuro-fuzzy linear quadratic regulator controllers, the positions and velocities of state variables multiplied by their linear quadratic regulator gains are trained using two radial basis neural networks architecture. The output of the two radial basis neural networks is used as the input variables of the fuzzy controller. The novel architecture of the radial basis neuro-fuzzy controller is developed in order to obtain better control performance than the classical adaptive neuro-fuzzy controller. To determine the control performance of the anti-swing controllers, different control parameters are computed. According to the comparative results, the anti-swing radial basis neuro-fuzzy linear quadratic regulator controller yields improved results than fuzzy linear quadratic regulator and linear quadratic regulator. Furthermore, the performance of the three controllers developed was compared based on robustness analysis under external force disturbance. The results obtained here indicate that the anti-swing radial basis neuro-fuzzy linear quadratic regulator controller product has better performance than other controllers in terms of vibration suppression ability.

Group interaction of robots with an arbitrary kinematic diagram of manipulators during synchronous execution of technological operations

The stabilization of the manipulated object near the position of static equilibrium under kinematic and force disturbances during cooperative transportation by two robots of arbitrary structure is considered. The dynamic balance of an object in grippers is described by the Mathieu equation. The controlled executive system of the coupled robot provides adjustment of the manipulation system with minimal potential energy in the grippers. A variant of the optimal control in terms of speed is considered when transferring the system to a position close to static equilibrium. Keywords: robot, group control, controlled generalized coordinates, continuity of connections, cooperative work. vichizhikov@gmail.com

Robust Controller Design for Maglev Suspension Systems Based on Improved Suspension Force Model

The electromagnetic suspension-type maglev train can reach ultrahigh-speed using long stator linear synchronous motors; however, slot effect makes the motors suffer from suspension force ripple, since it causes the nonsinusoidal airgap magnetic field distribution. It has been expounded that the suspension electromagnet system is highly nonlinear and unstable in open loops. Additionally, maglev trains experience disturbances and uncertainties in service. Therefore, the robust disturbance-rejection control for electromagnet suspension system is highly necessary to maintain a constant airgap position. In this article, it is intended to propose a novel robust controller for suspension systems which ensures superior system performances despite suspension force ripple, disturbances, and uncertainties while sustaining stable suspension despite system nonlinearity. First, field harmonics are investigated along with slot effects, and an improved nonlinear mathematical model of electromagnetic force is derived. Second, the controller based on the improved force model is formulated. Then, the performance of the designed controller is evaluated on a maglev suspension system with disturbances and uncertainties. Simulation and hardware-in-the-loop experimental results demonstrate that the improved suspension force model is more accurate than the conventional models, and the corresponding controller excels in attenuating larger disturbance without sacrificing tracking performances at different speeds.

Study Simulation of Umbilical Cable for Underwater Vehicle

Abstract This paper presents a series of analyses regarding the tethered umbilical cable in uniform current cable from the composition of the underwater remotely operated vehicle (ROV). The remotely operated vehicle is used in different undersea operation when it is important to control and determine precisely the disturbance forces generated by drag due to currents that act either on the vehicle directly or indirectly on the tether umbilical cable. The dynamics of umbilical cable represent an important part in ocean environment being used for signal and power transmission application. To perform the simulation in Ansys Aqwa, two axis systems are considered. A coordinate system related to the earth, represented by the key in front of which the measurements are made and a second coordinate system related to the vehicle at a set depth relative to the surface of the key. The results obtained from the simulation show us the drag forces that are exerted on the chosen cable for a given length, drag that appear both the seaborne platforms and underwater remotely vehicle contact.

Method of estimation of dynamic properties of transmissions of forestry units

When performing energy-intensive work in forestry related to the processing of stumpy soil, it is necessary to substantiate new requirements for forestry tractors in terms of weight, energy and dynamic parameters. Their change will cause a change in the disturbing forces acting on the transmission shafts of the unit, which can excite torsional vibrations in its dynamic system. When the natural frequencies of the oscillations coincide with the disturbing ones, unwanted resonant oscillations may occur. The most common models for studying dynamic properties are models in the form of complex multi-mass torsional dynamical systems. To calculate the vibrations of torsional systems, an algorithm and a program for solving a system of differential equations were drawn up. Their solution made it possible to calculate the amplitude-frequency characteristics (AFC) of the dynamic systems of tractor units. The allocation of zones of forced oscillations in transmissions from the working bodies on the frequency response, as well as the coordination of the parameters of the working bodies with the parameters of the transmissions is a necessary condition for ensuring the effective operation of forestry units. When changing the moments of inertia of rotating masses, it is necessary to analyze the vibrations that occur in branched transmissions with active working bodies with significant moments of inertia. To determine their optimal parameters, the presented mathematical models can be used.