Showing papers presented at "Mediterranean Conference on Control and Automation in 2015"

Design, modeling and control of a 5-DoF light-weight robot arm for aerial manipulation

Abstract: The design, modeling and control of a 5 degrees-of-freedom light-weight robot manipulator is presented in this paper. The proposed robot arm, named Prisma Ultra-Lightweight 5 ARm (PUL5AR), is employed to execute manipulation tasks equipped on board of a vertical take-off and landing unmanned aerial vehicle. The arm is compact and light-weight. Its mechanics is designed such that it can fold on itself during landing manoeuvres. Moreover, the design is conceived to constrain the center of gravity of the arm as close as possible to vehicle base, thus reducing the total inertia and static unbalancing of the system. Experimental tests have been carried out in order to validate the dynamic model, the communication library, the developed electronics, and the control schemes implemented for the designed robot arm.

Vision based fuzzy control autonomous landing with UAVs: From V-REP to real experiments

Abstract: This paper is focused on the design of a vision based control approach for the autonomous landing task of Vertical Take-off and Landing (VTOL) Unmanned Aerial Vehicles (UAVs). Here is presented the setup of a simulated environment developed in V-REP connected to ROS, and its uses for tuning a vision based control approach. In this work, a Fuzzy control approach was proposed to command the UAV's vertical, longitudinal, lateral and orientation velocities. The UAV's pose estimation was done based on a vision algorithm and the knowledge of the landing target. Real experiments with a quadrotor landing in a moving platform are also presented.

The Power-over-Tether system for powering small UAVs: Tethering-line tension control synthesis

Abstract: Within this work, a system for remote powering of small-scale hovering Unmanned Aerial Vehicles is developed, aiming to achieve prolonged-endurance flight times in order to address possible civilian applications with such requirements. To this purpose, the key-concept of a Power-over-Tether system is proposed, with the power bank for the UAV's operation located on the ground, and power transferred via a tethering cable. In order for the UAV to be capable of executing hovering trajectories as freely as possible, a long power cable is wound onto a custom-developed base, which is capable of releasing and retracting it when necessary. The Power-over-Tether system base is developed to operate autonomously, locally sensing when the aerial vehicle requires additional length of free cable to move to its intended goal, or when excessive cable length requires retraction, and performs the respective actions. The complete implementation of the system, both hardware and control-wise is elaborated in detail within the scope of this paper. Additionally, experimental evaluation studies are conducted, demonstrating the potential of the proposed Power-over-Tether system.

A proposal of methodology for multi-UAV mission modeling

Abstract: The emergence of multi-UAV missions poses a set of challenges. The control and monitoring of these missions requires to increase the autonomy of fleets and to reduce the workload of operators. The development of an appropriate mission model is fundamental not only for specification and planning but also for control and monitoring. This model allows determining the mission and fleet states and, therefore, providing the operator with adequate information of the mission. This paper poses a methodology to develop multi-UAV mission models and analyzes different modeling techniques, such as Petri nets or hidden Markov models.

Design of a teleoperated wall climbing robot for oil tank inspection

Abstract: This paper presents a climbing robot with wheeled locomotion which uses permanent magnets as adhesion mechanism. The robot designed is intended for the inspection of various types of ferromagnetic structures, such as ship hulls, wind turbine towers, bridges, and fuel tanks, in order to detect surface faults or cracks caused by, for example aging or atmospheric corrosion. The proposed robotic system consists of a cordless teleoperated mobile platform which can move on vertical ferromagnetic walls. The robot can be equipped with the various testing probes and cameras that are necessary for different inspection tasks. First, different prototypes of magnetic wall climbing robots are analyzed in order to establish the current state-of-the-art, and to provide the background required to analyse the main advantages and drawbacks of the prototypes presented. The design of the proposed robotic system is then explained, and details are provided of the new approach for the design of the permanent magnetic adhesion mechanism. Finally the mechanical and electrical construction, the control architecture implemented, and the human-machine interface for its control and teleoperation are presented too.

Flat trajectory generation for way-points relaxations and obstacle avoidance

Abstract: This paper addresses some alternatives to classical trajectory generation for an autonomous vehicle which needs to pass through a priori given way-points. Using differential flatness for trajectory generation and B-splines for the flat output parametrization, the current study concentrates on constraint relaxations and on obstacle avoidance conditions. The results are validated through simulations over standard UAV dynamics.

A packet address driven test strategy for stuck-at faults in networks-on-chip interconnects

Abstract: With the rapid advancements of deep submicron and nano technologies the dimension of a chip is ever shrinking. With continuous shrinking of chip dimensions, immense interconnects are associated on a die to satisfy high bandwidth requirements and make a network-on-chip (NoC) architecture prone to large number of interconnect faults. Therefore the reliability becomes a crucial issue for the communicating parties in a NoC communication fabric. This paper presents a packet address driven test strategy that diagnoses NoC interconnects experiencing stuck-at (stuck-at-0 and stuck-at-1) faults. The proposed strategy is scalable to all sizes and types of mesh NoCs and can be extended to other NoCs. The simulation is done on a number of mesh NoCs to establish the scalability. The simulation results show the performance measured in terms of test and fault coverages that can reach to 100% at the expense of few CPU clocks.

On guaranteeing passivity and performance with a human controller

Abstract: While designing controllers that guarantee the passivity of a closed loop system has a long history, much less attention has been paid to the situation when the control actions are performed by a human. We consider as an example a human who is driving a car. The behavior of human controllers as drivers has been modeled in the literature as a linear time invariant system cascaded with a time delay. We show that such a human model is not passive. In order to guarantee passivity of a closed loop system with a human controller, we use a passivation method. Through an appropriate design of the passivation parameters, positive passivity indices can be guaranteed for the closed loop system. The passivation parameters can be selected by solving an optimization problem such as minimizing the tracking error. To validate our theory, we provide simulation results in CarSim and Simulink.

A PSO-based MPPT re-initialised by incremental conductance method for a standalone PV system

Abstract: This paper presents a modified maximum power point tracker (MPPT) for a standalone PV system. In this research a Particle Swarm Optimization (PSO)-based method is re-initialised by a variable step size (VSS) incremental conductance (IncCond) MPPT. The main motivation in this research is to eliminate the output ripple, and also to shorten the tracking time in rapidly changing insolation condition (RCIC). Used in this study, PSO-based method, precisely designed based on the dynamic behaviors of introduced system. The functionality of proposed method is evaluated by MATLAB/SIMULINK. Compared to IncCond method, the advantage of proposed one is that the PV outputs are more accurate and much less ripple-plotted. In comparison with standard PSO-based MPPT method, the tracking time in this method is much shorter, notably under RCIC.

Energy efficiency of underwater snake robot locomotion

Abstract: Energy efficiency is one of the main challenges for long-term autonomy of underwater robotic systems. In this paper, we present results regarding the power consumption of underwater snake robots. In particular, we investigate the relationship between the parameters of the gait patterns, the consumed energy and the forward velocity for different motion patterns for underwater snake robots. Based on a simulation study, we propose empirical rules to choose the parameters of the gait patterns, taking into account both the desired forward velocity and the power consumption of the system. The simulation results show that with respect to the cost of transportation metric, increasing the number of links the energy efficiency decreases for both lateral undulation and eel-like motion.

Extension of the observability rank condition to nonlinear systems driven by unknown inputs

Abstract: This paper investigates the unknown input observability problem in the nonlinear case under the assumption that the unknown inputs are differentiable functions of time (up to a given order). The goal is not to design new observers but to provide simple analytic conditions in order to check the weak local observability of the state. The analysis starts by providing a new definition of indistinguishable states in the case of unknown inputs. Then, in order to separate the effect of the known inputs from the effect of the unknown inputs on the system outputs, the state is augmented. This allows us to obtain the extension of basic properties, which hold in the case of known inputs. Starting from these properties, the paper provides a sufficient analytic condition for the state observability, which is called the extended observability rank condition. The proposed approach is used to derive the observability properties of two systems. The former is very simple while the latter is very complex and describes the fusion of visual and inertial measurements.

Hybrid visual servoing for aerial grasping with hierarchical task-priority control

Abstract: In this paper a hybrid visual servoing with a dynamic and hierarchical task-priority control framework is proposed for the control of an aerial vehicle endowed with a robot arm. The proposed task composition algorithm retains the main benefits of classical image-based and position-based control scheme, that can be suitably combined in a common hybridcontrol framework.Moreover, the under-actuation of the vehicle base has been systematically taken into account within a general formulation, while a dynamic smooth activation/deactivation mechanism is proposed to avoid discontinuity in the control action. Simulations have been proposed to demonstrate the effectiveness of the proposed approach.

Design, automation and control of a two-stage, two-load-demand experimental refrigeration plant

Abstract: This paper describes the design, implementation and automation of a two-stage, two-load-demand experimental refrigeration plant. The facility is fully configurable, since cycles with one or two compression stages, and one or two load demands can be set up. Detailed description of the experimental facility concerning its physical components, actuators and sensors is addressed, as well as low-level control and communication bus issues. The high-level control environment and its communication with the low-level controller are also approached. Furthermore, a well-known in industry decentralised control strategy is applied to a one-stage, two-load-demand refrigeration cycle, analysing some preliminary control results from an energy efficiency point of view.

Incorporating set-based control within the singularity-robust multiple task-priority inverse kinematics

Abstract: Inverse kinematics is an active research domain in robotics since several years due to its importance in multiple robotics application. Among the various approaches, differential inverse kinematics is widely used due to the possibility to real-time implementation. Redundant robotic systems exhibit more degrees of freedom than those strictly required to execute a given end-effector task, in such a case, multiple tasks can be handled simultaneously in, e.g., a task-priority architecture. This paper addresses the systematic extension of the multiple tasks singularity robust solution, also known as Null-space Based Behavioral control, to the case of set-based control tasks, i.e., tasks for which a range, rather than a specific value, is assigned. This is the case for several variables such as, for example, mechanical joint limits of robotic arms as well as obstacle avoidance for any kind of robots. Numerical validation are provided to support the solution proposed.

Throughput optimality of extended back-pressure traffic signal control algorithm

Abstract: The back-pressure/max-pressure traffic signal control algorithm proposed in the existing literature is distributed, maximizes network throughput, and can be implemented without knowing traffic arrival rates. In this paper, we present an extended back-pressure traffic signal control algorithm, which can further handle bounded measurement/estimation noises in queue lengths and incorporate online estimation of turning ratios and saturated flow rates. Therefore, the extended back-pressure algorithm forms an important step towards the real application of distributed traffic signal control. We prove that under certain conditions, the extended back-pressure algorithm still achieves maximum throughput, i.e., the expected long-term average of total queues is bounded from above under the extended back-pressure algorithm for largest possible set of arrival vectors.

Modelling and control of the UPV/EHU stellarator

Abstract: This paper deals with the state-space modelling of the Ultra-Low Iota Super Elongated Stellarator of the UPV/EHU, using a physical lumped parameter equivalent circuit approach. The model obtained is validated by means of experimental output data showing an excellent matching with the real system. In order to test the proposed model, a MPC scheme is been successfully implemented both in simulation and experimentally using a real-time control platform, providing also a benchmarking with traditionally used PID controllers.

Robust control strategies of stick-slip type actuators for fast and accurate nanopositioning operations in scanning mode

Abstract: This paper deals with robust closed-loop control of a nano-robotic system dedicated to fast scanning probe microscopy. The nano-robotic system is actuated by piezoelectric stick-slip actuators able to produce a millimeter range displacement with a nanometer resolution. In order to meet the requirements of fast scanning in terms of closed-loop bandwidth and vibration damping, robust control strategies are studied. We first show that a commonly used one degree of freedom (1-DOF) H ∞ controller is limited to satisfy robust performances required for fast and accurate positioning of the actuators. As such, the control strategy is defined considering two closed-loops. Results show that the 2-DOF H ∞ control scheme allows robust performances for the positioning of nanorobotic systems and lead to new perspectives for fast scanning probe microscopy using stick-slip actuators.

Real time optimal power flow integrating large scale storage devices and wind generation

Abstract: This paper presents a real time strategy for optimal power flow in presence of storage devices and wind turbine driven by Doubly Fed Induction Generators. These elements work in cooperation defining a dynamic bus where the generated power is subject to temporal constraints, which establish a coupling between traditional power flow problems related to consecutive time periods; further the uncertainty in wind power generation forecasts requires a continuous update of the planned power profiles, in order to guarantee a dynamic equilibrium among demand and supply. Model predictive control is used for this purpose, considering the dynamic equations of the storage and the wind turbine rotor as prediction models. A proper target function is introduced in order to find a trade-off between the need of minimizing generation costs and the excursions of the storage state of charge and the wind turbine angular speed from reference states. In the case study under consideration storage, wind turbines and a traditional synchronous generator are operated by the Transmission System Operator in the form of a Virtual Power Plant working as slack bus to cover network losses. The proposed approach is validated on simulation basis.

A Q-Learning based approach to Quality of Experience control in cognitive Future Internet networks

Abstract: The paper describes an innovative and fully cognitive approach which offers the opportunity to cope with some key limitations of the present telecommunication networks by means of the introduction of a novel architecture design in the perspective of the emerging Future Internet framework Within this architecture, the Quality of Experience (QoE) Management functionalities are aimed at approaching the desired QoE level of the applications by dynamically selecting the most appropriate Class of Service supported by the network In the present work, this selection is driven by an optimal and adaptive control strategy based on the renowned Q-Learning algorithm The proposed dynamic approach differs from the traffic classification approaches found in the literature, where a static assignment of Classes of Service to applications is performed

Predictive Cruise Control for energy saving in REEV using V2I information

Abstract: This paper proposes a Predictive Cruise Control for a Range Extended Electric Vehicle that uses the information of upcoming traffic lights to arrive at a green or to reduce idling at a red light. Simultaneously, it is decided in a predictive manner, which is the best energy management strategy to operate the vehicle's powertrain. The main goals are to reduce fuel consumption and to increase energy efficiency. The control algorithm is formulated based on Model Predictive Control theory, which also allows the controller to operate in the absence of traffic light information as an Adaptive Cruise Control with predictive energy management. The controller tracks an optimal velocity trajectory, computed based on current traffic light's timing, and decides how much energy must be provided from the battery and from the generator. The simulation results show a significant reduction in fuel and energy consumption.

Multi-UAV ground control station for gliding aircraft

Abstract: This paper presents a Ground Control Station based on the Robot Operating System (ROS) which has been developed in order to monitor highly automated multi-UAV missions. The proposed system has been designed in order to easily perform Hardware in the Loop (HIL) simulations. This allows to test the desired algorithms in an environment as close as possible to the one found in real experimentation, which will reduce the costs related to field experiments. The architecture of the system is fully based on open source software, protocols and hardware. Furthermore a new user interface has been developed in order to provide relevant information in multi-UAV gliding experiments. This tool allows the operator to allocate tasks to the UAV and to monitor the operational information. This information can be complemented with the use of open source control stations. The proposed system has been demonstrated in both HIL simulation and in field experimentation. These results are compared in order to indicate how close the simulated behaviour was with respect to the real.

Control strategies for ammonia violations removal in BSM1 for dry, rain and storm weather conditions

Abstract: This paper presents a proposal with the objective of eliminating violations of ammonia nitrogen in the effluent (NH e ) of a wastewater treatment process. Furthermore, improving effluent quality and reducing operating costs and the percentage of violations of total nitrogen in the effluent (N tot,e ) are also considered. The evaluation of control strategies are conducted with the Benchmark Simulation Model No 1 (BSM1). Several controllers have been proposed: Model Predictive Control (MPC) with inlet flow rate feedforward compensation (MPCFF), Fuzzy controller and Exponential, Linear and Affine Functions. MPCFF and Fuzzy controller are applied in a hierarchical structure to improve effluent quality, to reduce operational costs and to decrease NHe peaks. Exponential, Linear and Affine Functions are implemented, along with the hierarchical control structure, to avoid NH e violations. The results are presented and compared with the default control strategy of BSM1 for dry, rain and storm weahter conditions. They show that the NH e violation removal is achieved for the three weather conditions. For dry influent also an improvement of effluent quality and a reduction of operational cost are acquired. For the rain and storm cases, an increment of operational cost is required.

Study of dexterous robotic grasping for deformable objects manipulation

Abstract: Most works in dexterous manipulation consider Force Closure Grasp (FCG), not only for rigid object but also, for flexible ones, though in the second case a force readjustment is also necessary. However, there are situations in which FCG is nonviable. This paper deals with the situation of a flexible object that must be necessarily grasped from one of its sides, taking advantage of its flexibility. This situation is common in packaging processes, or other everyday situations carried out by people. The paper presents first a new solution based on a planner that reproduces the actions of a human hand, aided by a database with knowledge about previous tasks. The paper is focused on describing the first tests done to evaluate the effectiveness of the planner for grasping different basic flexible objects, compared to a human hand.

Leak isolation based on Extended Kalman Filter in a plastic pipeline under temperature variations with real-data validation

Abstract: The present work is motivated by the purpose of considering a more realistic scenario than in former studies on the problem of leak isolation within a plastic pipeline, when the water can be affected by temperature changes. In order to address this situation, a state observer approach based on a model including temperature effect and an Extended Kalman Filter is proposed. Noting indeed that temperature affects some equivalent straight length of the pipe, which is used in the model, the observer estimates it together with the leak coefficients. This approach only considers head pressure and flow rate measurements coming from pipeline ends, likewise, water temperature measurement at upstream tank. Results with real data obtained from a pipeline prototype are shown in two different ways in order to illustrate the performance of proposed leak isolation system, as compared to the traditional approaches found at literature.

A low cost smart glove for visually impaired people mobility

Abstract: Degradation of the visual system reduces the mobility of a person that relies only on his sense of touch and hearing. This paper presents the prototype of a low cost smart glove to improve the mobility of the visually impaired people. The glove is equipped with rangefinders to explore the surroundings: it provides a vibro-tactile feedback on the position of the closest obstacles in range by means of vibration motors. The system is designed to operate with the white cane, enhancing the reliability of this traditional tool.

Open cloud solution for integrating advanced process control in plant operation

Abstract: This paper presents a model for integrating an advanced process control library in a cloud-based environment. The aim is to lower the development times, to reduce maintenance effort and decrease the complexity of process control applications by adopting a modular approach consisting of generic, reusable control strategies following an IEC 61499 representation. The solution uses open cloud technologies based on Heroku for the deployment in a public cloud structure and Docker for increased portability of the designed solution. The conceptual architecture of the system is presented, as well as the details of the execution module.

Rolling bearing fault diagnosis techniques - autocorrelation and cepstrum analyses

Abstract: The faulty vibration signals generally represent a combination of source and transmission path effects. For example, internal forces in vehicle gearbox which are the source of vibration act on a structure whose properties may be described by a frequency response function between the point of application and the point of measurements. A conventional frequency analysis of a spectrum will have transmission path effects affecting the true source signature and also cannot pinpoint the defects accurately where the problem is associated with more than one sideband and harmonic in case of vehicle gearbox. In the present paper, the transmission path effects are additive and can be separated in autocorrelation and cepstrum analyses, also it gives an accurate detection of periodic structure in a spectrum associated with many harmonics and sidebands as a single component for each family of sidebands without any difficulty in interpreting the sideband structure like in spectrum. The test stand is equipped with two dynamometers; the input dynamometer serves as internal combustion engine, the output dynamometer introduces the load on the flange of output joint shaft. An artificial fault is introduced in vehicle gearbox bearing: an orthogonally placed groove on the inner race with the initial width of 0.6 mm approximately. The results show the effectiveness of proposed analyses in diagnosis and detection of the rolling bearing condition.

Adaptive control of a master-slave system for teleoperated needle insertion under MRI-guidance

Abstract: This paper presents the control of a master-slave system for teleoperated needle insertion under guidance by Magnetic Resonance Imaging (MRI). The primary aim of our research is the robot-assisted laser ablation of liver tumors. The master-slave system consists of a master unit that sits next to the operator, outside the scanner room, and of a slave unit located inside the cylindrical MRI scanner. The needle insertion force is measured with a specially designed fiber optic force sensor mounted on the slave unit. Pneumatic actuation is employed in both master and slave in order to minimize the interference with the MRI environment. Accurate position control of the slave unit is achieved with a Time Delay Control scheme (TDC). Differently from previous designs, the force feedback on the master unit is provided by an adaptive controller that compensates the friction of the pneumatic actuator. The advantages over a baseline force controller are demonstrated with experiments on silicone rubber phantoms.

Enhancement of a commercial multicopter for research in autonomous navigation

Abstract: Multicopters are lightweight and maneuverable aerial vehicles yet unable to carry heavy payloads, such as large sensors or computers required for indoor autonomous navigation. Therefore, localization is usually performed by using vision-based solutions employing of either lightweight on-board cameras or external fixed cameras and a ground station for data-processing. Nevertheless, the current tendency is to use a low-power on-board computers to perform all computation on the multicopter itself. This paper covers the enhancement of a commercial multicopter, also called drone, with computation ability and sensorial devices for autonomous flight without the need of a ground-station. We describe the hardware and software integrated into the drone, which will be used for the future development of 6DoF navigation algorithms. The resulting system is able to work with most standard sensors and has the possibility to change them as needed. Also, we demonstrate the correct behavior of the drone by using a test navigation program that autonomously follows a moving beacon at constant distance and controlled altitude using an RGB-D camera and a sonar.

Active Tuned Mass Damper

Abstract: The objective of this paper is to demonstrate the design and implementation of an Active Tuned Mass Damper (ATMD) and to determine its effectiveness experimentally and theoretically. ATMDs are damping units placed in structures where a mass is actuated to move out of phase with respect to the movement of the structure to reduce vibrations. In this paper, an ATMD is used to reduce the vibrations of a scaled-down four-story building. The building is subjected to base excitation through a crank-slider motor mechanism on the bottom floor. The ATMD consists of a mass which is actuated through a DC motor. Using feedback from an accelerometer placed on the topmost floor, a proportional gain controller is implemented through LabVIEW to control the motion of the mass. The results show that the ATMD system has damped approximately 49.7% of the vibrational amplitude.