An experimental study to swing up and control a pendulum with two reaction wheels

Meccanica - An experimental study is discussed on a strategy that combines on-off and sliding mode control to swing up and control a pendulum with two reaction wheels in the upright position. The...     

A method of torque control for independent wheel drive vehicles on rough terrain

Our previous research has revealed that, for vehicles with independently driven wheels, a torque distribution based on the ratio of the vertical load of each wheel to the total vehicle load is efficient for driving on flat ground. In this research, this method of torque distribution was extended to electric off-road vehicles driving on rough ground. In order to examine the driving efficiency of these vehicles, a numerical vehicle model was constructed in the pitch plane. Simulations using the numerical vehicle model on rough ground were conducted with a proposed torque distribution and control method. The numerical results from these simulations were compared with those of a conventional vehicle to evaluate the driving efficiency and trafficability on ground with various profiles. A comparison between the simulations demonstrated that the proposed method of torque distribution to the front and rear wheels based on the ratio of the vertical load is efficient for driving on rough ground.     

Dynamics analysis of the Minuteman cover drive

Recursive matrix relations in kinematics and dynamics analysis of a 1-DOF compound planetary gear train are established in the paper. The mechanism of the Minuteman cover drive is a system with four moving links and three gear pairs controlled by one electric motor. Knowing the rotation motion of the output link, the inverse dynamic problem is solved using an approach based on the principle of virtual work, but it has been verified the results in the framework of the Lagrange equations. Finally, some simulation graphs for the input and output angles of rotation, the torque and the power of the actuator are obtained.     

Control of a compound wheeled vehicle with two steering wheels

The problem of synthesis of a control system for a wheeled robotic vehicle consisting of two links (driving and driven) is analyzed. The robot is considered to be a controlled system of rigid bodies with nonholonomic constraints and to have two steerable wheels. Additionally, it is necessary to decide where the second steerable wheel is (on the driving or driven link). In this connection, two models of a compound wheeled robotic vehicle with two steerable wheels are considered. For these models, the problem of synthesis of feedback is solved. They are compared by modeling Translated from Prikladnaya Mekhanika, Vol. 44, No. 12, pp. 111–120, December 2008.     

Multi-surface sliding mode control of continuum robots with mismatched uncertainties

Meccanica - In this paper, we tackle the control problem of continuum robots with mismatched uncertainties. Uncertainties that affect systems through any of their states and may not be directly...     

Compact robust FAT control of rigid robots with state constraints

Nonlinear Dynamics - This paper develops a robust regressor-free controller for n-link robots with state constraints. We use the function approximation technique to represent the uncertain robot...     

Motion and shape control of soft robots and materials

Nonlinear Dynamics - A continuum-based approach for simultaneously controlling the motion and shape of soft robots and materials (SRM) is proposed. This approach allows for systematically computing...     

Output-feedback formation control of wheeled mobile robots with actuators saturation compensation

Nonlinear Dynamics - This paper addresses output-feedback formation control of a group of wheeled mobile robots with saturating actuators. A virtual leader–follower strategy and a...     

Dynamics of coaxial torsional resonators consisting or segments with different radii,material properties and surrounding media

High-Q torsional resonators constitute the most sensitive transducers for high frequency dynamic viscoelastic measurements of dilute polymer solutions. Most such resonators described in the literature are segmented. Because of the need for torque and torsional displacement transducers the Q-value of the individual segments most often differ, but normally all segments have the same radius.A detailed analysis of the dynamics of such resonators when both the radii, material properties and surrounding media may be different for each segment, is presented. For resonators where all segment lengths equal an integer multiple of a quarter of the torsional wavelength, we find that the Q-value of the resonator as a whole is mainly determined by the Q-value of the segment with the smallest radius. We further find that reduction of the radius of the segment surrounded by polymer solution results in a stronger mechanical coupling between the resonator as a whole and the polymer solution. These findings suggest that the segment radii are important optimization parameters of segmented torsional resonators used to measure the high frequency dynamic viscoelastic properties of e.g. polymer solutions.     

Adaptive tracking control of wheeled mobile robots with unknown longitudinal and lateral slipping parameters

An adaptive control approach is proposed for trajectory tracking of wheeled mobile robot (WMR) with unknown longitudinal and lateral slipping. A kinematic model of tracked WMR is established in this paper, in which both longitudinal and lateral slipping are considered and processed as three time-varying parameters. Sliding mode observer is then introduced to real time estimate the slip parameters online. A stable tracking control law for this robot system is proposed by backstepping method, and the asymptotic stability is guaranteed by Lyapunov theory. Meanwhile, the controller gains are determined online by poles placement method. Simulation results show the effectiveness and robustness of the proposed method.     

Controllability of delay degenerate control systems with independent subsystems

IntroductionAsthestudyforthetheoryofcontrolsystemsdeeplygoesonandtheneedforthestudyandtheapplicationofmanypracticalsystemssuchaspowersystems,ecosystems,economicmanagementsystemsandsoon ,peoplerequestthattheprecisionforthedescribing ,analysisanddesignabout…     

Nonlinear fractional optimal control problems with neural network and dynamic optimization schemes

Nonlinear Dynamics - This paper deals with a numerical technique for fractional optimal control problems (FOCPs) based on a neural network scheme. The fractional derivative in these problems is in...     

Interaction dynamics of two coaxial vortex rings in the presence of natural convection

The problem of the interaction of a pair of coaxial initially stationary thermals is investigated numerically on the basis of the Navier-Stokes equations for a compressible heat-conducting gas. It is established that upon transformation of the thermals into vortex rings, slip-through of the latter, limited in time because of the diffusion of vorticity and the action of molecular viscosity, is realized.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 4, pp. 169–171, July–August, 1991.     

Dynamics modeling and stability of robotic systems with discrete-time force control

This paper investigates the dynamic behavior of robotic echanical systems with discrete-time force control. Force control is associated with the constrained motion of a mechanical system. A novel approach is presented to analyze the stability and performance based on the separation of constrained and admissible motions. This results in a model representing the dynamics of the constrained motion of the system. The analysis connects the complex nonlinear model of a mechanical system to a set of abstract delayed oscillators. These oscillator models make it possible to perform a detailed closed-form mathematical analysis of the stability behavior. A planar two-degree-of-freedom (DoF) mechanism is presented as an example to illustrate the material. Results are illustrated by stability charts in the parameter space of mechanical parameters, control gains and the sampling rate.     

Dynamics and control of a self-sustained electromechanical seismographs with time-varying stiffness

This paper is concerned with the nonlinear dynamics and vibration control of an electromechanical seismograph system with time-varying stiffness. The instrument consists of an electrical part coupled to mechanical one and is used to record the vibration during earthquakes. An active control method is applied to the system based on cubic velocity feedback. The electromechanical system is subjected to parametric and external excitations and modeled by a coupled nonlinear ordinary differential equations. The method of multiple scales is used to obtain approximate solutions and investigate the response of the system. The results of perturbation solution have been verified through numerical simulations, where different effects of the system parameters have been reported.     

Dynamics and control of COVID-19 pandemic with nonlinear incidence rates

World Health Organization (WHO) has declared COVID-19 a pandemic on March 11, 2020. As of May 23, 2020, according to WHO, there are 213 countries, areas or territories with COVID-19 positive cases. To effectively address this situation, it is imperative to have a clear understanding of the COVID-19 transmission dynamics and to concoct efficient control measures to mitigate/contain the spread. In this work, the COVID-19 dynamics is modelled using susceptible–exposed–infectious–removed model with a nonlinear incidence rate. In order to control the transmission, the coefficient of nonlinear incidence function is adopted as the Governmental control input. To adequately understand the COVID-19 dynamics, bifurcation analysis is performed and the effect of varying reproduction number on the COVID-19 transmission is studied. The inadequacy of an open-loop approach in controlling the disease spread is validated via numerical simulations and a robust closed-loop control methodology using sliding mode control is also presented. The proposed SMC strategy could bring the basic reproduction number closer to 1 from an initial value of 2.5, thus limiting the exposed and infected individuals to a controllable threshold value. The model and the proposed control strategy are then compared with real-time data in order to verify its efficacy.