Showing papers by "Maarouf Saad published in 2015"

Development of a whole arm wearable robotic exoskeleton for rehabilitation and to assist upper limb movements

Abstract: To assist physically disabled people with impaired upper limb function, we have developed a new 7-DOF exoskeleton-type robot named Motion Assistive Robotic-Exoskeleton for Superior Extremity (ETS-MARSE) to ease daily upper limb movements and to provide effective rehabilitation therapy to the superior extremity. The ETS-MARSE comprises a shoulder motion support part, an elbow and forearm motion support part, and a wrist motion support part. It is designed to be worn on the lateral side of the upper limb in order to provide naturalistic movements of the shoulder (vertical and horizontal flexion/extension and internal/external rotation), elbow (flexion/extension), forearm (pronation/supination), and wrist joint (radial/ulnar deviation and flexion/extension). This paper focuses on the modeling, design, development, and control of the ETS-MARSE. Experiments were carried out with healthy male human subjects in whom trajectory tracking in the form of passive rehabilitation exercises (i.e., pre-programmed trajectories recommended by a therapist/clinician) were carried out. Experimental results show that the ETS-MARSE can efficiently perform passive rehabilitation therapy.

A Monitoring Technique for Reversed Power Flow Detection With High PV Penetration Level

Abstract: The integration of renewable energy resources (RESs) in power systems poses many research challenges. Research shows that the RES output may exceed the consumed power during the day. Consequently, the direction of the power flow on distribution lines can be reversed during some periods. As the voltage regulator is normally designed for unidirectional power flow, this may cause voltage violations on the distribution feeder. Therefore, most utilities try to set a penetration level (PL) limit for safe operation. On the other hand, time varying and unbalanced loading are the main characteristics of distribution systems. Moreover installation of intermittent and nondispatchable photovoltaic (PV) devices increases the control problems of distribution system. This paper presents an impedance-based monitoring method for detection of distribution system current behavior. It will be shown that by utilizing this monitoring technique, not only the small variation of PV PL can be easily detected, but also some fast transients such as the effect of cloud movement on PV system can be monitored. This monitoring technique employs only local measurements of bus voltages and line current to measure the apparent impedance seen at the installation point. The practical application of measured impedance as a monitoring technique shows its effectiveness for distribution system monitoring in presence of various PV PL.

EMG based control of a robotic exoskeleton for shoulder and elbow motion assist

Abstract: Torehabilitate individuals with impaired upperlimb functions we have developed an exoskeleton robot, ETS-MARSE. In this paper, we proposed and implemented a control strategy using skin surface electromyogram (EMG) signals of subjects to maneuver the developed exoskeleton robot. A nonlinear sliding mode control technique with exponential reaching law was used for this purpose where EMG signals from shoulder and elbow muscles were used as input information to the controller. To evaluate the performance of the proposed control approach experiments were carried out with the healthy subjects. Experimental results indicate that with the proposed control strategy, ETS-MARSE can be effectively maneuvered with the EMG signals both for the single and multi-joint movement assistance. 

Admittance-Based Upper Limb Robotic Active and Active-Assistive Movements:

Abstract: This paper presents two rehabilitation schemes for patients with upper limb impairments. The first is an active-assistive scheme based on the trajectory tracking of predefined paths in Cartesian space. In it, the system allows for an adjustable degree of variation with respect to ideal tracking. The amount of variation is determined through an admittance function that depends on the opposition forces exerted on the system by the user, due to possible impairments. The coefficients of the function allow the adjustment of the degree of assistance the robot will provide in order to complete the target trajectory. The second scheme corresponds to active movements in a constrained space. Here, the same admittance function is applied; however, in this case, it is unattached to a predefined trajectory and instead connected to one generated in real time, according to the user’s intended movements. This allows the user to move freely with the robot in order to track a given path. The free movement is bounded through the use of virtual walls that do not allow users to exceed certain limits. A human-machine interface was developed to guide the robot’s user.

Sliding Mode with Time Delay Control for MIMO nonlinear Systems With unknown dynamics

Abstract: In this paper, the control problem of Multi-Input Multi-Output (MIMO) nonlinear Systems with unknown dynamics is proposed. A novel method based on the Sliding Mode with Time Delay Control (SMTDC) is proposed by combining a Sliding Mode Control (SMC) with saturation (sat) function and Time Delay Control (TDC). This method (SMTDC), allows chattering reduction on control inputs and estimates the amounts of unknown or unmodeled nonlinear dynamics and unexpected uncertainties and cancels them. This algorithm was simulated on the model of the ANAT robot arm system to demonstrate the effectiveness of the proposed design method.

Distributed control strategy for flexible link manipulators

Abstract: This paper presents a nonlinear distributed control strategy for flexible-link manipulators to solve the tracking control problem in the joint space and cancel vibrations of the links. First, the dynamic of an n-flexible-link manipulator is decomposed into n subsystems. Each subsystem has a pair of one joint and one link. The distributed control strategy is applied to each subsystem starting from the last subsystem. The strategy of control consists in controlling the nth joint and stabilizing the nth link by assuming that the remaining subsystems are stable. Then, going backward to the (n − 1)th subsystem, the same control strategy is applied to each corresponding joint-link subsystem until the first. Sliding mode technique is used to develop the control law of each subsystem and the global stability of the resulting tracking errors is proved using the Lyapunov technique. This algorithm was tested on a two-flexible-link manipulator and gave effective results, a good tracking performance, and capability to eliminate the links' vibrations.

Three-Dimensional Constrained Tracking Control Via Exact Differentiation Estimator of a Quadrotor Helicopter

Abstract: In this paper, a constructive method is presented to design a three dimensional trajectory tracking controller that forces a quadrotor helicopter to track a bounded and sufficiently smooth reference trajectory asymptotically in the presence of constant force disturbances. The quadrotor helicopter under consideration has fewer independent thrusters than degrees of freedom to be controlled. Motivated by the vehicle's steering practices, the roll and pitch angles are regarded as virtual controls along with four control forces to fulfill the task of position and yaw angle reference tracking. To prevent position constraint violation, the barrier Lyapunov function (BLF) is employed in the vectorial backstepping procedure to guarantee that the position and attitude constraints are not violated. The backstepping procedure employs an exact and robust sliding mode differentiator of order two to facilitate the implementation of the attitude command signal without calculating the virtual control signal derivative analytically.

Application of distance relay for distribution system monitoring

Abstract: The traditional distribution network is primarily composed of radial feeders, designed for unidirectional power flow. Therefore, many operation regulation, protection and control system, in distribution network, are based on the radial distribution systems assumption. The integration of decentralized renewable sources will create a multidirectional power flow condition in the distribution grid which was originally designed for unidirectional power flow only. Integration of that active element increases the importance of new distribution system monitoring. In addition, based on the distributed generation interconnection of some utilities, over current protection is not sufficient for feeder protection in presence of renewable energies integration. Therefore, it is recommended to install a distance relay as the main protection of feeder. This paper presents using the distance relay not only as a protection device, but also as a monitoring tool at presence of renewable energies.

Pilot buses selection based on reduced Jacobian matrix

Abstract: The non-supervised insertion of renewable energy sources into electric power networks causes fluctuations that may lead to voltage instability. The simple and coordinated secondary voltage control systems are used to avoid this instability. To obtain maximum regulation performance with optimized number of controllers, an appropriate selection of pilot buses is suggested. In this paper new algorithm is proposed to select optimal pilot buses. This method is based on the singular decomposition of the reduced Jacobian matrix with the voltage security margin index. To evaluate the efficiency of this algorithm, a comparison with the Bifurcation, Clustering with Node-Partitioning Around Medoids and the Hybrid algorithms is proposed. The simulation results show that the proposed algorithm gives optimal pilot buses according to the selection criteria (explained later in the paper).

Cockpit design for first person view flight for a remotely operated quadrotor helicopter

Abstract: Recently, technological advances have been focused on the cockpit of modern unmanned aerial vehicles (UAVs) in order to reduce pilot requirements and workload to operate them. First person view (FPV) flight represents a key point when UAVs perform tasks beyond the line of sight. This paper presents the design and implementation of a cockpit for a remotely operated quadrotor. We have developed an intuitive graphical user interface (GUI) for piloting the quadrotor encompassing the most relevant flight instruments as an altimeter, attitude, heading, and ground speed indicators. The GUI is developed using the programming development environment LabVIEW®.

A step by step adaptive super twisting controller for mismatched uncertain system

Abstract: In this paper a step by step adaptive super twisting controller is designed for second order nonlinear strict feedback system with mismatched uncertainty. The design procedure is carried out by considering a virtual controller at each step. After obtaining the first step the desired dynamic model for each state is defined by the previous one and finally the actual control law is obtained. The design parameters of super twisting controller are estimated adaptively. The proposed method can be used for disturbance estimation also. The finite time convergence has been obtained by using a strict Lyapunov function. Simulation results demonstrate the efficacy of the proposed controller.

Control of three-level NPC converters in DFIG based off-grid wind energy conversion systems

Abstract: This paper deals with control of three-level neutral point clamped (NPC) voltage source converters (VSCs) for medium rating doubly fed induction generator (DFIG) based off-grid wind energy conversion system. A three-level three-leg insulated gate bipolar transistors (IGBTs) based NPC-VSC is used as a rotor converter (RC). Four-leg three-level IGBTs based NPC-VSC is used as a load converter (LC). A battery energy storage system (BESS) is employed at the DC bus of back to back connected LC and RC in the rotor circuit. The BESS facilitates establishment of off-grid supply using RC control and absorb or supply deficit load power under wind speed variations. A vector-oriented control scheme for RC and LC establishes functions of a load leveler, a load balancer, a harmonic eliminator, a zero sequence load current compensator, a maximum power tracker and a capacitor voltage balancer under dynamic conditions either due to consumer loads or wind. The proposed control scheme for a DFIG based off-grid system is developed and its performance is found satisfactory under steady state and dynamic conditions.

Simulation of non-linear flight control using backstepping method

Abstract: This paper describes the design and the simulation of a non-linear controller for an aircraft using the backstepping method. The aim is to find the expressions of the elevator deflection in order to control the flight path angle. Backstepping controller uses the non-linear equations of motion of an aircraft, the Lyapunov analysis and the errors between the real and the desired values. The advantage of the backstepping method is to work with cascaded structures. Compared to the PID method, there is no need of tuning gains to ensure the stability. Furthermore, compared to the dynamic inversion there is no linearization and no approximations of the system; it works with the true non-linear system using virtual controls. Compared to other works, this paper deals with very accurate equations of motion and a very detailed non-linear coefficient aerodynamic model. This technique does not control only the angle of attack or the pitch Euler angle but particularly the flight path angle allowing a steady, climb or descent flight. The controller has been implemented in Matlab/Simulink and FlightGear.

STATCOM application for decentralized secondary voltage control of transmission networks

Abstract: Recent wide-area blackouts throughout the world highlight the need of smart power networks that could eliminate catastrophic outages by having the ability to react fast and efficient to risky operating conditions. Decentralized voltage control using STATCOM based on partitioning algorithm is discussed in this chapter. The partitioning algorithm technique divides power system into partitions to eventually prevent the propagation of disturbances if interaction between partitions is minimized. The optimized number of partitions is found based on the bus voltage sensitivity to disturbances being applied to loads in each partition. Then, a number of representative buses are labelled as pilot (control) buses displaying the critical point for installation of STATCOM for voltage control in each partition. The control uses decentralized controllers to eliminate voltage violations resulting from load variations and disturbances in each partition of the power system. The decentralized controllers are implemented by fuzzy control which is trained via offline simulations. Required reactive power is injected into the partitions by STATCOMs to correct voltage violations.

Useful global model for charging/discharging plug-in Electrical Vehicles in a parking lot

Abstract: Plug-in Electrical Vehicles (PEVs) are nowadays increasingly penetrating the car market. Charging stations are becoming a lucrative business especially for the public parking lot owners where they can be installed and operated. PEVs can be used as energy storage elements during low demand and as energy sources during peak demand. Some technical problems related to the management of the charging stations may arise. Simultaneously charging a large number of PEVs in a parking lot may disturb the power system due to an unexpected peak demand. To overcome this situation, some researchers are suggesting different forms of Charging and Discharging Schedules (CDS). A reliable model for the flow of vehicles entering/leaving the parking is very essential to define an accurate CDS. In this paper, a new approach for modeling the flow of vehicles is developed, and it is shown how a CDS is related to it. In addition, it shows how incentive programs can contribute to increasing the financial benefits and at the same time reducing the disturbances on the power network.

Distributed super twisting controller for multiple quadrotors

Abstract: The distributed cooperative tracking control problem for a group of quadrotors in a three-dimensional space is addressed in this paper. The controller design is divided in two stages. In the first stage, local distributed controllers for the translational dynamics are designed, forcing the quadrotor to asymptotically track the desired trajectory with the required separation and therefore a specific formation. In the second stage, the rotational dynamics is asymptotically stabilized. The controllers implemented in both stages are based in a combination of block control technique and the super twisting control algorithm which ensures robustness with respect to external disturbances and parameter uncertainties. Moreover, a first order exact differentiator is used to estimate the virtual control inputs, simplifying the control law design. The stability proof of the complete closed-loop system is shown to be asymptotically stable. Finally, numerical simulations are carried out to show that theoretical conclusions are effective.

System-Based Safety Tenets Applied to the Extra-High Voltage Transmission Line Design for Common Uses of Highway Right-of-Way

Abstract: The rapidly increasing demand for electricity in recent years resulted in increasing needs of electrical system capacity and deployment for alternate uses of highway right-of-way (ROW) for the purpose of electric power generation, transmission, and distribution. In this framework, a systems approach—fundamental principles of system dynamics for identifying, understanding, and analyzing safety requirements of the extra-high voltage power line (EHV)—is used to objectively focus on two main safety issues related to the design and the risk of the EHV transmission line within highway ROW: (1) assess the design and the operation, and (2) evaluate causally related impacts on the public and workers’ safety that matter. A generalized model of the electromagnetic fields distribution and the clearance model are developed for the analysis of the causally related impacts of a conceptual design and the reliability of materials of construction of the electric systems by introducing the number of exposed individuals and the level of the environmental impacts as a second dimension in addition to the risk factors. A worst-case design scenario is evaluated. Sensitivity analysis of effects of the design attributes such as the route configuration, over voltages, and conductor clearance is performed by determining the magnitude of the electromagnetic field strengths and predicting the resulting maximum voltage. Information obtained on the structural design scenario, conductor size and configuration, insulators, and connectors is of value in determining the safety of the design for operation at extra-high voltages within highway ROW.