16 research outputs found
Multilayer perceptron adaptive dynamic control of mobile robots : experimental validation
This paper presents experimental results acquired from the implementation of an adaptive control scheme for nonholonomic mobile robots, which was recently proposed by the same authors and tested only by simulations. The control system comprises a trajectory tracking kinematic controller, which generates the reference wheel velocities, and a cascade dynamic controller, which estimates the robot's uncertain nonlinear dynamic functions in real-time via a multilayer perceptron neural network. In this manner precise velocity tracking is attained, even in the presence of unknown and/or time-varying dynamics. The experimental mobile robot, designed and built for the purpose of this research, is also presented in this paper.peer-reviewe
Dual adaptive dynamic control of mobile robots using neural networks
This paper proposes two novel dual adaptive neural control schemes for the dynamic control of nonholonomic mobile robots. The two schemes are developed in discrete time, and the robot's nonlinear dynamic functions are assumed to be unknown. Gaussian radial basis function and sigmoidal multilayer perceptron neural networks are used for function approximation. In each scheme, the unknown network parameters are estimated stochastically in real time, and no preliminary offline neural network training is used. In contrast to other adaptive techniques hitherto proposed in the literature on mobile robots, the dual control laws presented in this paper do not rely on the heuristic certainty equivalence property but account for the uncertainty in the estimates. This results in a major improvement in tracking performance, despite the plant uncertainty and unmodeled dynamics. Monte Carlo simulation and statistical hypothesis testing are used to illustrate the effectiveness of the two proposed stochastic controllers as applied to the trajectory-tracking problem of a differentially driven wheeled mobile robot.peer-reviewe
Unscented transform-based dual adaptive control of nonlinear MIMO systems
The paper proposes a multilayer perceptron neural network controller for dual adaptive control of a class
of stochastic MIMO nonlinear systems subject to functional
uncertainty. The neural network parameters are adjusted in
real-time using the Unscented Kalman filter algorithm and
no pre-operational training phase is required. Dual adaptive control aims to strike a compromise between the two
control characteristics of caution and probing, leading to
an improved overall performance. The system is evaluated
through numerical simulations and Monte Carlo analysis. The
resulting performance of the dual adaptive controller is not only
consistently superior to non-dual adaptive control schemes, but
also surpasses the performance of similar controllers that are
based on Extended Kalman filter estimators. This reflects the
enhanced accuracy of the Unscented Kalman filter estimator,
despite being a local estimation method. In addition, unlike use
of other estimators, the proposed approach neither requires the
computation of complex Jacobian matrices as part of the design,
nor the evaluation of such matrices in real-time. This renders
the proposed controller inherently amenable and practical for
real-time implementation.peer-reviewe
Multi-robot energy-aware coverage control in the presence of time-varying importance regions
Multi-robot systems are becoming widely popular in applications where a rapid response is required or where various different robotic capabilities are required. Applications such as surveillance, or search and rescue, would require an efficient team that can be deployed and optimally dispersed over the environment. This is known as the coverage control problem. The solution to this research optimization problem is affected by several external aspects, such as characteristics of the environment as well as factors that pertain to the robotic team. This work proposes a novel solution to the complete coverage problem where the team of robots is restricted with energy limitations, and must cover an environment that has time-varying regions of importance. Our results show that in a realistic scenario, where the robots have limited energy for the task in question, the proposed solution performs significantly better than a typical coverage algorithm which disregards the energy considerations of the robotic team.peer-reviewe
Non-linear swing-up and stabilizing control of an inverted pendulum system
This paper presents the design and implementation of a complete control system for the swing-up and stabilizing control of an inverted pendulum. In particular, this work outlines the effectiveness of a particular swing-up method, based on feedback linearization and energy considerations. The power of modern state-space techniques for the analysis and control of Multiple Input Multiple Output (MIMO) systems is also investigated and a state-feedback controller is employed for stabilizing the pendulum. Cascade control is then utilized to reduce the complexity of the complete controller by splitting it into two separate control loops operating at well distinct bandwidths.Electrotechnical Association of Slovenia,et al.,IEEE Region 8,IEEE Slovenia Section,Ministry of Education, Science and Sport of the Republic of Slovenia,University of Ljubljana.peer-reviewe
Control of an open-loop hydraulic offshore wind turbine using a variable-area orifice
The research work disclosed in this publication is partly funded by the Malta Government Scholarship Scheme.The viability of offshore wind turbines is presently affected
by a number of technical issues pertaining to the gearbox and
power electronic components. Current work is considering the
possibility of replacing the generator, gearbox and electrical
transmission with a hydraulic system. Efficiency of the
hydraulic transmission is around 90% for the selected
geometries, which is comparable to the 94% expected for
conventional wind turbines. A rotor-driven pump pressurises
seawater that is transmitted across a large pipeline to a
centralised generator platform. Hydroelectric energy
conversion takes place in Pelton turbine. However, unlike
conventional hydro-energy plants, the head available at the
nozzle entry is highly unsteady. Adequate active control at the
nozzle is therefore crucial in maintaining a fixed line pressure
and an optimum Pelton turbine operation at synchronous speed.
This paper presents a novel control scheme that is based on the
combination of proportional feedback control and feed forward
compensation on a variable area nozzle. Transient domain
simulation results are presented for a Pelton wheel supplied by
sea water from an offshore wind turbine-driven pump across a
10 km pipeline.peer-reviewe
The 25th Mediterranean Conference on Control and Automation
The 25th Mediterranean Conference on Control and Automation (MED 2017) was held on July 3-6, 2017 on the island of Malta. The first MED took place in 1993 in Chania, Greece, and a complete list of the
locations of later MED conferences is available at www.med-control.org. The 2017 edition was held for the
first time in Malta, at the University of Malta Valletta Campus. The campus is a 17th century baroque building endowed with striking historical frescoes, portraits, and architectural
features that is also well equipped
with modern conference facilities. The
conference was organized under the
auspices of the Mediterranean Control
Association (MCA) and the technical
cosponsorship of the IEEE Control
Systems Society and the IEEE Robotics
and Automation Society.peer-reviewe
Multilayer perceptron functional adaptive control for trajectory tracking of wheeled mobile robots
Sigmoidal multilayer perceptron neural networks are proposed to effect functional adaptive control for handling the trajectory tracking problem in a nonholonomic wheeled mobile robot. The scheme is developed in
discrete time and the multilayer perceptron neural networks are used for the estimation of the robot’s nonlinear
kinematic functions, which are assumed to be unknown. On-line weight tuning is achieved by employing the
extended Kalman filter algorithm based on a specifically formulated multiple-input, multiple-output, stochastic model for the trajectory error dynamics of the mobile base. The estimated functions are then used on a
certainty equivalence basis in the control law proposed in (Corradini et al., 2003) for trajectory tracking. The
performance of the system is analyzed and compared by simulation.peer-reviewe
A comprehensive review of endogenous EEG-based BCIs for dynamic device control
Electroencephalogram (EEG)-based brain–computer interfaces (BCIs) provide a novel
approach for controlling external devices. BCI technologies can be important enabling technologies for
people with severe mobility impairment. Endogenous paradigms, which depend on user-generated
commands and do not need external stimuli, can provide intuitive control of external devices. This
paper discusses BCIs to control various physical devices such as exoskeletons, wheelchairs, mobile
robots, and robotic arms. These technologies must be able to navigate complex environments
or execute fine motor movements. Brain control of these devices presents an intricate research
problem that merges signal processing and classification techniques with control theory. In particular,
obtaining strong classification performance for endogenous BCIs is challenging, and EEG decoder
output signals can be unstable. These issues present myriad research questions that are discussed
in this review paper. This review covers papers published until the end of 2021 that presented
BCI-controlled dynamic devices. It discusses the devices controlled, EEG paradigms, shared control,
stabilization of the EEG signal, traditional machine learning and deep learning techniques, and user
experience. The paper concludes with a discussion of open questions and avenues for future work.peer-reviewe
Multilayer perceptron dual adaptive control for mobile robots
This paper presents a novel dual adaptive dynamic controller for trajectory tracking of nonholonomic wheeled mobile robots. The controller is developed in discrete-time and the robot's nonlinear dynamic functions are assumed to be unknown. A sigmoidal multilayer perceptron neural network is employed for function approximation, and its weights are estimated stochastically in real-time. In contrast to adaptive certainty equivalence controllers hitherto published for mobile robots, the proposed control law takes into consideration the estimates' uncertainty, thereby leading to improved tracking performance. The proposed method is verified by realistic simulations and Monte Carlo analysis.non peer-reviewe