Showing papers presented at "Mediterranean Conference on Control and Automation in 2013"

Control of quadrotor aerial vehicles equipped with a robotic arm

Abstract: In this paper a novel hierarchical motion control scheme for quadrotor aerial vehicles equipped with a manipulator is proposed. The controller is organized into two layers: in the top layer, an inverse kinematics algorithm computes the motion references for the actuated variables; in the bottom layer, a motion control algorithm is in charge of tracking the motion references computed by the top layer. A simulation case study is developed to demonstrate the effectiveness of the approach in the presence of disturbances and unmodeled dynamics.

EMG based classification of basic hand movements based on time-frequency features

Abstract: This paper proposes an integrated approach for the identification of daily hand movements with a view to control prosthetic members. The raw EMG signal is decomposed into Intrinsic Mode Functions (IMFs) with the use of Empirical Mode Decomposition (EMD). A number of features are extracted in time and in frequency domain. Two different dimentionality methods are tested, namely the Principal Component Analysis (PCA) technique and the RELIEF feature selection algorithm. The outputs of the dimensionality reduction stage are then fed to a linear classifier to perform the detection task. The approach was tested on a group of young individuals and the results appear promising.

Intelligent parking assist

Abstract: In this paper a new parking guiding and information system is described. The system assists the user to find the most suitable parking space based on his/her preferences and learned behavior. The system takes into account parameters such as driver's parking duration, arrival time, destination, type preference, cost preference, driving time, and walking distance as well as time-varying parking rules and pricing. Moreover, a prediction algorithm is proposed to forecast the parking availability for different parking locations for different times of the day based on the real-time parking information, and previous parking availability/occupancy data. A novel server structure is used to implement the system. Intelligent parking assist system reduces the searching time for parking spots in urban environments, and consequently leads to a reduction in air pollutions and traffic congestion. On-street parking meters, off-street parking garages, as well as free parking spaces are considered in our system.

IEC 61851 compliant electric vehicle charging control in smartgrids

Abstract: This paper deals with the problem of controlling electric vehicles charging in a smart grid. We present an event driven model predictive control (MPC) approach, which aims to find a proper trade-off between the needs of minimizing the cost of energy withdrawal and the error in the tracking of a reference aggregated charging power profile. All in respect of drivers' preferences, technical bounds on the control action (in compliance with the IEC 61851 standard) and grid constraints. The proposed control approach allows “flexible” EV users to participate in demand side management programs, which will play a crucial role for stability and efficiency of future smart grids. Simulation results are provided and discussed in details, showing the relevance of our contribution.

A distributed multi-path algorithm for wireless ad-hoc networks based on Wardrop routing

Abstract: Wireless ad-hoc networks are collections of devices which are able to communicate each other through wireless links. Those networks differ from infrastructure-based wireless networks for the absence of a centralized coordinator which handles all the communications among the devices. This leads to higher probability of packets collision, congestion of links, etc. Moreover, wireless links are characterized by an intrinsic high and time varying packet loss ratio, due to external noise and interferences. The objective of this paper is to present a new distributed multi-path algorithm (i.e., traffic is split among multiple paths) for wireless ad-hoc networks with the aims of (i) increasing the throughput of the applications running onto the network (ii) explicitly accounting for the packet loss of the wireless links and (iii) guaranteeing that the routing process converges to stable paths. The algorithm is developed by using the concept of Wardrop equilibrium. Simulation results show the higher throughput achieved by the proposed routing algorithm, compared to shortest path routing protocols, based on hop count and on packet loss metrics.

Power transformer fault diagnosis using fuzzy logic technique based on dissolved gas analysis

Abstract: The most common fault diagnosis method of power transformer is based on the Dissolved Gas-in-oil Analysis (DGA) of transformer oil. It is a sensitive and reliable technique for the detection of incipient fault condition within oil-immersed transformers. There are a number of methods developed for analyzing these gases and interpreting their significance such as Key Gas, Roger gas ratio, Doernenburg, IEC gas ratio and Duval Triangle. Although DGA has widely been used in the industry, this conventional method fails to diagnosis in some cases. This normally happens for those transformers which have more than one type of fault at the same time [6, 7]. To overcome this limitation, an expert system based on DGA for diagnosis of power transformer condition is proposed in this paper. The proposed technique combines three different DGA methods in one diagnosis scheme in order to overcome the limitation of each method stand alone. The three selected methods are Rogers, IEC and Duval. Moreover, this paper investigates the accuracy and consistency of three methods in interpreting the transformer condition by applying fuzzy logic technique in addition to a new final combined fuzzy system. The evaluation is carried out on DGA test data obtained from different literatures as a test data with size 100 cases. Finally, test was applied on DGA data of utility power transformers of MIDOR Refinery Company located in Alexandria, Egypt.

Telemanipulation with the DLR/HIT II robot hand using a dataglove and a low cost force feedback device

Abstract: In this paper a series of teleoperation and manipulation tasks are performed with the five fingered robot hand DLR/HIT II. Two different everyday life objects are used for the manipulation tasks; a small ball and a rectangular object. The joint-to-joint mapping methodology is used to map human to robot hand motion, taking into account existing kinematic constraints such as synergistic characteristics and joint couplings. The Cyberglove II motion capture dataglove is used to measure human hand kinematics. A robot hand specific fast calibration procedure is used to map raw dataglove sensor values to human joint angles and subsequently through the mapping procedure, to DLR/HIT II joint angles. A novel low cost force feedback device is developed, in order for the user to be able to detect contact and perceive the forces exerted by the robot fingertips, during manipulation tasks. The design of the force feedback device is based on RGB LEDs that provide visual feedback and vibration motors that provide vibro-tactile feedback.

Distributed solution for the economic dispatch problem

Abstract: A distributed approach for the economic dispatch of generating units is presented. It is assumed that the generators are connected by a communication graph. Each unit has information about itself, and can exchange information only with a few neighboring units in such a graph. Using graph theory and consensus algorithms, the proposed approach solves the economic dispatch problem in a distributed manner instead of existing centralized approaches. The proposed solution is shown to be optimal, independent of the initial power distribution, and to respond automatically to real-time load demand changes. Moreover, it requires only that the communication graph be connected. The effectiveness of the proposed algorithm is verified by simulating a standard IEEE test system.

Modelling and frequency separation energy management of fuel Cell-Battery Hybrid sources system for Hybrid Electric Vehicle

Abstract: This paper presents a hybrid system of fuel cell-battery power sources for electric vehicle Because fuel cell (FC) and battery have advantages and disadvantages of their own, it should be beneficial to have hybrid sources, in which FC supplies the base energy while battery supplies peak power for fast acceleration and captures the braking energy regeneration In this paper a state space model for the Fuel Cell-Battery Hybrid Electric Vehicle (FCEV) power system is given and an energy management based on frequencies separation is discussed and validated by Matlab simulation

On semiclassical solutions of hybrid regulator equations

Abstract: In this paper, a special class of hybrid regulation problems is considered, which can be solved by using a class of steady-state inputs essentially coinciding with the class used in standard output regulation problems (for non hybrid systems), although the corresponding state evolution happens on a genuinely hybrid invariant manifold; hence the name “semiclassical”. The main advantage of using such solutions lies in easier implementation and the possibility of robust design.

Trajectory tracking control for a quadrotor helicopter based on backstepping using a decoupling quaternion parametrization

Abstract: This paper presents a trajectory tracking control for the position and heading angle of a quadrotor helicopter. The control design is based on the backstepping approach and proves the asymptotic stability of the tracking problem. We use a beneficial quaternion-based attitude parametrization, which is composed of two rotations. The first describes the orientation of the thrust vector independently from the second, which describes the quadrotor's heading. As a result, the translational dynamics and the yaw dynamics decouple from each other, which augments the control design. In addition, this decoupling allows an analytical derivation of all control signals within the backstepping procedure with reasonable expense. Experimental results show the practical use of the suggested control design.

Road pavement crack automatic detection by MMS images

Abstract: The research topic was to test different feature extraction methods to localize road pavement cracks useful to construct a spatial database for the pavement distress monitoring. Several images were acquired by means of a line scan camera that assembled in a Mobile Mapping System (MMS) allows tracking directly the position of the images by a GPS-INS system. Following an automatic digital image processing was performed by means of several algorithms based on different approaches (edge detection and fuzzy set theory). The detected cracks were described with some parameters in relation to some shape characteristics (dimension, typology, direction), which are necessary to recognize the gravity of the road pavement conditions. The edge detection techniques tested in this research allowed identifying fatigue cracking or alligator cracking and also thin linear cracks in images with strong radiometric jumps by applying filters, gradient functions and morphological operators. The snake approach was one of them, in particular the type called Gradient Vector Flow (GVF). Another approach was based on the fuzzy theory. The advantage of this method is that the pixels, necessary to identify the cracks in road pavement, are darker than their surroundings in an image. The last stage was the pavement distress spatial database collection. The Mobile Mapping System (MMS) has allowed localizing the raster data and consequently the vector features of the detected cracks, associating into the table their attributes too. The proposed approaches allow to automatically localize and classify the kind of road pavement crack.

A case study for hybrid regulation: Output tracking for a spinning and bouncing disk

Abstract: In this paper, a spinning and bouncing disk is used to illustrate some issues in regulation for a class of hybrid systems. The use of variables having a clear physical meaning allows to give a nice interpretation of the mechanism that can be used, for fat plants, to generate admissible trajectories.

Coordinated standoff tracking of groups of moving targets using multiple UAVs

Abstract: This paper presents a coordinated standoff tracking methodology of groups of moving targets using multiple UAVs. The vector field guidance approach is first applied to track a group of targets for a single UAV by defining a variable standoff orbit to be followed, which can keep all targets within the field-of view of the UAV. A new feedforward term is included in the guidance command considering variable standoff distance, and the convergence of the vector field to the standoff orbit is analysed and enhanced by adjusting radial velocity using two active measures associated with vector field generation. Moreover, for multiple group tracking by multiple UAVs, a two-phase approach is proposed as a suboptimal solution for an NP-hard problem, consisting of target clustering/assignment and cooperative standoff group tracking with online local replanning. Lastly, localisation sensitivity to the group of targets is investigated for different angular separations between UAVs and sensing configurations. Numerical simulations are performed using randomly moving ground vehicles with four UAVs to verify the feasibility and benefit of the proposed approach.

Guidance and control of an overactuated autonomous surface platform for diver tracking

Abstract: The high-risk nature of SCUBA diving activities is usually dealt with by pairing up divers and adopting well defined rules for diving operations to reduce the chance of accidents. However, during more challenging dives (such as technical dives) these procedures may not be sufficient to ensure almost accident-free operations, for the divers must manoeuvre in complex 3D environments, carry cumbersome equipment, and focus attention on operational details. Technological advancement and research related to diver safety, navigation and monitoring has been identified as crucial for advancing diving activities. This paper reports current state of research performed at UNIZG-FER related to an autonomous overactuated surface platform used for following divers and transmitting GPS signal to the underwater. The implemented guidance and control algorithms are described and simulations obtained on realistic models developed in the ROS environment are provided. Special attention is given to algorithms for diver tracking by using measurements from a USBL. Diver motion estimators are used to improve the performance of the sparse and noisy USBL measurements. The results presented in this paper are a starting point for in-the-field experiments expected to take place in the real-world environment.

Root locus rules for polynomials with complex coefficients

Abstract: Applications were found recently where the analysis of dynamic systems with a special structure could be simplified considerably by transforming them into equivalent systems having complex coefficients and half the number of poles. The design of controllers for such systems can be simplified in the complex representation, but requires techniques suitable for systems with complex coefficients. In the paper, the extension of the classical root locus method to systems with complex coefficients is presented. The results are applied with some advantages to a three-phase controlled rectifier.

Closed-form solution for absolute scale velocity estimation using visual and inertial data with a sliding least-squares estimation

Abstract: In this paper a method for the on-line absolute-scale velocity estimation of a system composed of a single camera and of an inertial measurement unit is presented. The proposed formulation makes use of spherical image measurements acquired from at least three camera positions and inertial measurements to estimate the system velocity by solving also the absolute scale problem. A new multi-rate formulation based on a sliding least-squares estimation formulation is proposed, which is capable of providing the velocity estimation also in cases of constant and zero velocity. The effectiveness of the proposed approach is shown through extensive simulations.

Formation control of a large group of UAVs with safe path planning

Abstract: In this article we propose a hierarchical control structure for multi-agent systems. The main objective is to perform formation change manoeuvres, with guaranteed safe distance between each two vehicles throughout the whole mission. The key components that ensure safety are a robust control algorithm that is capable of stabilising the group of vehicles in a desired formation and a higher level path generation method that provides all the vehicles with safe paths, based on graph theoretic considerations. The method can efficiently handle a large group of any type of vehicles. As an illustration, the results are applied to a group of quadrotor UAVs.

Trajectory control of multirotor helicopters with thrust vector constraints

Abstract: The multirotor control system structure that has mostly been adopted is constituted by an inner and an outer control loop. In this scheme, the inner loop carries out attitude control while the outer loop is responsible for trajectory control. The present work addresses the problem of safely controlling the trajectory of a multirotor helicopter by taking into account specified constraints on both the total thrust magnitude and the inclination of the rotor plane. The proposed solution partitions the whole problem into an altitude and an horizontal position control. The control laws of the two parts combine the feedback linearization principle with saturated proportional-derivative controllers. The proposed method is evaluated by computational simulations, which show its effectiveness to control the vehicle along a spiral trajectory as well as respond to abrupt position commands.

Assessing control performance in closed-loop anesthesia

Abstract: Recently, several control systems for closed-loop anesthesia have been demonstrated both in simulation and clinical studies. A set of performance measures, proposed by Varvel et al., have constituted the standard means of comparing such systems. This paper debates the adequacy of the Varvel measures, as applied to closed-loop anesthesia, and proposes an alternative set of measures. Key features of the proposed measures are: wide acceptance within the control community; reflection of clinical feasibility; separate measures for induction and maintenance of anesthesia; separation of outlier detection and performance evaluation. The proposed measures are descriptive, few, and easy to compute.

Regions of attraction and recursive feasibility in robust MPC

Abstract: For linear systems with multiplicative uncertainty, a formulation of robust model predictive control in a lifted space is given and is proven to give better or equal performance to any tube MPC approach that uses the same parameterisation of the input. Then a tube MPC controller is formulated that ensures recursive feasibility through the use of terminal sets in the degrees of freedom available to the controller. This is shown to give performance comparable to the lifted approach while avoiding an exponential growth in computation.

Optimal fully electric vehicle load balancing with an ADMM algorithm in Smartgrids

Abstract: In this paper we present a system architecture and a suitable control methodology for the load balancing of Fully Electric Vehicles at Charging Station (CS). Within the proposed architecture, control methodologies allow to adapt Distributed Energy Resources (DER) generation profiles and active loads to ensure economic benefits to each actor. The key aspect is the organization in two levels of control: at local level a Load Area Controller (LAC) optimally calculates the FEV's charging sessions, while at higher level a Macro Load Area Aggregator (MLAA) provides DER with energy production profiles, and LACs with energy withdrawal profiles. Proposed control methodologies involve the solution of a Walrasian market equilibrium and the design of a distributed algorithm.

Ultimate boundedness conditions for a hybrid model of population dynamics

Abstract: This paper addresses the ultimate boundedness and permanence analysis for a Lotka-Volterra type system with switching of parameter values. Two new approaches for the constructing of common Lyapunov function for the family of subsystems corresponding to the switched system are suggested. Sufficient conditions in terms of linear inequalities are obtained to guarantee that the solutions of the considered system are ultimately bounded or permanent for an arbitrary switching signal. An example is presented to demonstrate the effectiveness of the proposed approaches.

Fuzzy robust tracking control with pole placement for a Turbocharged diesel engine

Abstract: This paper addresses the modeling and control of the air path system of diesel engines. We propose robust control for the diesel engine equipped with Exhaust Gas Recirculation (EGR) and Variable Geometry Turbocharger (VGT) systems. The goal is to control carefully the air flow for a diesel engine to reduce emissions of pollutant particles and fuel consumption. A mean value model of the air loop is considered and rewriten using fuzzy Takagi-Sugeno (TS) approach. A control strategy based in Lyapunov function and pole placement in LMI regions (Linear Matrix Inequalities) is developed. It takes into account the variation of the engine speed. The goal is to design a robust control law that tracks some reference signals. The effectiveness of the proposed fuzzy tracking controllers in the system diesel engine is demonstrated through numerical simulations.

Performance evaluation of neural network based approaches for airspeed Sensor Failure Accommodation on a small UAV

Abstract: Traditional approaches to sensor fault tolerance for flight control systems have been based on triple or quadruple physical redundancy. However, recent events have highlighted the criticality of "common mode" failures on the Air Data System (ADS). In fact, since the parameters of flight control laws are typically scheduled as a function of airspeed, incorrect readings from the ADS can lead to potentially catastrophic conditions. In this paper, we describe the evaluation of an analytical redundancy-based approach to the problem of Sensor Failure Accommodation following simulated failures on the ADS of a research UAV, using Artificial Neural Networks (ANNs). Specifically, two different neural networks are evaluated - the Extended Minimal Resource Allocating Network and a Multilayer Feedforward NN. These neural networks are trained and validated using experimental flight data from the WVU YF-22 research aircraft which was designed, manufactured, instrumented, and flight tested by researchers at the Flight Control Systems Laboratory at West Virginia University. The performance of the two approaches is evaluated in terms of the statistics of the tracking error in the estimation of the airspeed, as compared to actual measurements from the ADS, operating under nominal conditions.

Decentralized control for maintenance of strong connectivity for directed graphs

Abstract: In order to accomplish cooperative tasks, decentralized systems are required to communicate among each other. Thus, maintaining the connectivity of the communication graph is a fundamental issue. Connectivity maintenance has been extensively studied in the last few years, but generally considering undirected communication graphs. In this paper we introduce a decentralized control and estimation strategy to maintain the strong connectivity property of directed communication graphs. The control strategy is initially developed for balanced digraphs, and is then extended to generic strongly connected digraphs, introducing a decentralized balancing algorithm. The control strategy is validated by means of analytical proofs and simulation results.

An architecture for solving quadratic programs with the fast gradient method on a Field Programmable Gate Array

Abstract: In this paper an architecture for the implementation of gradient-based optimisation methods on a Field Programmable Gate Array (FPGA) is proposed. Combining the algorithmic advantages of gradient-based algorithms with the computational strengths of a tailored FPGA implementation allows to solve quadratic programs occurring, for example, in Model Predictive Control (MPC) applications in the microsecond range. The experimental comparisons show a computational advantage of the proposed FPGA implementation against parallel software versions ranging between one and two orders of magnitude. The proposed FPGA-based solution can broaden the applicability of MPC to problems that were considered out-of-reach till recent years.

Design of an innovative prosthetic hand with compact shape memory alloy actuators

Abstract: Shape memory alloy actuation is one of the emerging technologies that shows up remarkable advantages compared to conventional actuation. In this research work, this technology is exploited in driving an innovative prosthetic hand designed to meet most of the requirements of the upper limb amputees. Compact and totally silent linear actuation units are developed and integrated within a lightweight housing closely replicating the shape and size of the average human hand. In addition, a tendon-driven underactuated mechanism provides the necessary dexterity without compromising the simplicity of the device. The physical implementation of the hand chassis is accomplished using rapid prototyping techniques. Experiments with a single-finger testbed are conducted in order to evaluate speed performance and investigate the feasibility of a resistance feedback control scheme.

A two-step procedure for optimal constrained stabilization of linear continuous-time systems

Abstract: This paper considers the problem of constrained stabilization of linear continuous-time systems when a quadratic cost criterion is imposed in the design of the state feedback control law. The linear quadratic regulator (LQR) is solved under positivity constraint, which means that the resulting closed-loop systems are not only optimally stable, but also positive. We focus on the class of linear continuous-time positive systems (Metzlerian systems) and use the interesting properties of Metzler matrices to provide the necessary ingredients for the main results of the paper. A two-step procedure is proposed to solve the problem. First, some necessary and sufficient conditions are presented for the existence of controllers satisfying the Metzlerian constraint, and the constrained stabilization is solved using linear programming (LP) or linear matrix inequality (LMI). Second, a sufficient condition is outlined for the existence of a solution to maintain the positivity of the first step while achieving the optimality of LQR. Finally, the robustness of the design is analyzed and possible extension of the design is proposed for an uncertain interval systems. A numerical example is included to illustrate the procedure.

Stabilizing a quadruped robot locomotion using a two degree of freedom tail

Abstract: This paper investigates how to improve locomotion stability of a dynamical system composed of four spring-mass subsystems by using a tail-like inertial appendage. The paper presents a Denavit-Hartenberg parameterization based kinematic model combined with a Newton-Euler based dynamic model of a two degree of freedom tail. Impedance based leg control simplifies the leg motion so that it can be modeled as a damped spring-mass system. The tail presented in the paper is used as a counterweight, capable of shifting its center of mass so as to balance the body of the robot. To that end, a recursive algorithm that moves the tail in order to balance the robot is proposed. A realistic robot model is built in the Open Dynamic Engine environment and is used to conduct a series of tests proving the effectiveness of the proposed algorithm.