Showing papers by "Maarouf Saad published in 2011"
TL;DR: A novel approach is proposed, which allows chattering reduction on control input while keeping high tracking performance of the controller in steady-state regime by designing a nonlinear reaching law by using an exponential function that dynamically adapts to the variations of the controlled system.
Abstract: In this paper, sliding-mode control is applied on multi-input/multi-output (MIMO) nonlinear systems. A novel approach is proposed, which allows chattering reduction on control input while keeping high tracking performance of the controller in steady-state regime. This approach consists of designing a nonlinear reaching law by using an exponential function that dynamically adapts to the variations of the controlled system. Experimental study was focused on a MIMO modular robot arm. Experimental results are presented to show the effectiveness of the proposed approach, regarding particularly the chattering reduction on control input in steady-state regime.
424 citations
24 Oct 2011
TL;DR: A new form of repelling potential is proposed in order to reduce oscillations and to avoid conflicts when the target is close to obstacles, allowing for a smoother trajectory around the obstacles.
Abstract: This paper deals with the navigation of a mobile robot in an unknown environment. The approach developed is based on the Artificial Potential Field (APF) method in which the target creates a virtual potential that attracts the robot while obstacles create a virtual potential that repels the robot. A new form of repelling potential is proposed in order to reduce oscillations and to avoid conflicts when the target is close to obstacles. A rotational force is integrated as well, allowing for a smoother trajectory around the obstacles. Experiment results show the effectiveness of the proposed approach.
101 citations
TL;DR: The model uses a combination of the Lyapunov technique and graph theory embedded in the virtual structure to create an efficient architecture and control algorithm that enables them to work both individually and in meaningful robot formations.
77 citations
TL;DR: An intelligent cooperative control and path-following algorithm is proposed and tested for a group of mobile robots using a fuzzy model, which mimics human thought to control the robot's velocity, movement, and group behavior.
Abstract: In this paper, an intelligent cooperative control and path-following algorithm is proposed and tested for a group of mobile robots. The core of this algorithm uses a fuzzy model, which mimics human thought to control the robot's velocity, movement, and group behavior. The designed fuzzy model employs two behaviors: path following and group cooperation. Hierarchical controllers have also been developed based on fuzzy and proportional integral derivative to instruct the robots to move in a group formation and follow specific paths. As the robots move along individual predetermined paths, the designed algorithm adjusts their velocities so that the group arrives at their target points within the same time duration regardless of the length of each individual path. The fuzzy rules applied to the robots are defined by the kinematics limitation, which is bounded by both linear and angular velocities and the length and curvature of the individual paths. The experimental results of three mobile robots traveling on different paths are presented to show the accuracy of obtaining control and cooperation by using the fuzzy algorithm.
65 citations
TL;DR: A constructive method to design a cooperative state and output feedback to steer a group of nonholonomic mobile robots in chained form to form a desired geometric formation shape and it is shown that the established cooperative controller work well even in the presence of time delay.
Abstract: This paper presents a constructive method to design a cooperative state and output feedback to steer a group of nonholonomic mobile robots in chained form to form a desired geometric formation shape. The control methodology divides the resulting tracking error dynamics into a cascaded of linear and time-varying subsystems. A basic consensus algorithm is first applied to the linear subsystem which makes the states synchronize exponentially to zero. Once this first linear subsystem has converged, the second cascade can be treated as a linear time-varying subsystem perturbed by a vanishing term from its cascade. A dynamic state and output feedback is constructed to achieve synchronization of the rest of the states. The proof of stability is given using a result from cascade systems. Since time delay appears in many interconnection networks and particularly in cooperative control, its effect on the stability of the closed-loop system is analyzed using Razumikhim theorem. It is shown that the established cooperative controller work well even in the presence of time delay. Numerical simulations are performed on models of car-like mobile robots to show the effectiveness of the proposed cooperative state and output-feedback controllers.
28 citations
01 Dec 2011
TL;DR: Experimental results show that the MARSE-4 can efficiently track the desired trajectories as generated by mExoArm and therefore guarantee to tele-operate theMARSE to deliver passive therapy for wrist, elbow, and forearm movements.
Abstract: A robotic exoskeleton, the MARSE-4 has been developed to provide passive rehabilitation therapy to the physically disabled individuals with impaired upper-limb function. In this paper we focused on the tele-operation of the MARSE-4 using an upper-limb prototype 7DoFs (lower scaled) master exoskeleton arm (mExoArm.) The MARSE-4 has 4DoFs and is able to assist elbow (flexion/extension), forearm (pronation/supination) and wrist joint movements (radial/ulnar deviation, and flexion/extension). Modified Denavit-Hartenberg conventions were used in the kinematic modeling of the exoskeleton. In control, a nonlinear computed torque control and a linear PID control techniques were employed to maneuver the MARSE-4 to follow the desired trajectory. Experimental results show that the MARSE-4 can efficiently track the desired trajectories as generated by mExoArm and therefore guarantee to tele-operate the MARSE to deliver passive therapy for wrist, elbow, and forearm movements.
21 citations
05 Dec 2011
TL;DR: A combination of the virtual vehicle and trajectory tracking approach is used to derive the formation architecture and obstacle avoidance scheme based on sensing the relative distance between follower robots and obstacles is introduced using fuzzy logic.
Abstract: In this paper we investigate the leader follower motion coordination of multiple nonholonomic mobile robots. A combination of the virtual vehicle and trajectory tracking approach is used to derive the formation architecture. A virtual vehicle is steered in such a way it stabilizes to a shifted reference position/heading defined by the leader, the velocity of the virtual vehicle is then provided for further use in designing control law for the follower independent from the measurement of leader's velocity. Position tracking control is then constructed for the follower to track the virtual vehicle using the backstepping and Lyapunov direct design technique. Furthermore and to ensure the safety of robots while moving in a dynamic environment, obstacle avoidance scheme based on sensing the relative distance between follower robots and obstacles is introduced using fuzzy logic. Simulations are provided to show the effectiveness of the proposed approach.
21 citations
TL;DR: In this paper, a Lyapunov-based technique and graph theory are combined to address the problem of coordinated path following where multiple mobile robots are required to follow some prescribed paths while maintaining a desired inter-robot formation pattern.
Abstract: In this study, Lyapunov-based technique and graph theory are combined to address the problem of coordinated path following where multiple mobile robots are required to follow some prescribed paths while maintaining a desired inter-robot formation pattern. The authors address this problem by developing decentralised feedback law that drives each robot to its desired path while adjusting its speed to the nominal velocity profile based on the exchange of information with its neighbours. The decentralised feedback law builds upon a non-linear control strategy with integral actions, that decouples the path following from the coordination control problem, the obtained subsystems are shown to be in a cascade connection of each other and therefore the stability of the entire closed-loop system is guaranteed by the small-gain theorem. The authors explicitly address the situation where the exchange of information among mobile robots takes place according to a quantised communication network and provide conditions under which the complete coordinated path-following closed-loop system is stable. Finally, the theoretical results are validated by simulations on a platform of three mobile robots.
18 citations
TL;DR: Simulated and experimental results show that the controller was able to maneuver the proposed ExoRob efficiently in order to track the desired trajectories, which in this case consisted in passive arm movements, which are widely used in therapy and were performed efficiently with the developed model and controller.
Abstract: Proper functioning of the shoulder, elbow, and wrist movements play a vital role in the performance of essential daily activities. To assist physically disabled people with impaired upper-limb function, we have been developing an exoskeleton robot (ExoRob) to rehabilitate and to ease upper limb motion. The proposed ExoRob will be comprised of seven degrees of freedom (DOFs) to enable natural movements of the human upper-limb. This paper focuses on the kinematic and dynamic modeling of the proposed ExoRob that corresponds to human upper-limbs. For this purpose, a nonlinear computed torque control technique was employed. In simulations, trajectory tracking corresponding to typical rehabilitation exercises were carried out to evaluate the performances of the developed model and controller. For the experimental part, only 3DOFs (elbow, wrist flexion/extension, wrist abduction/adduction) were considered. Simulated and experimental results show that the controller was able to maneuver the proposed ExoRob efficiently in order to track the desired trajectories, which in this case consisted in passive arm movements. Such movements are widely used in therapy and were performed efficiently with the developed ExoRob and the controller.
18 citations
TL;DR: In this article, a 2DOF exoskeleton robot (ExoRob) is used to provide naturalistic range movements of elbow (flexion/extension) and forearm (pronation/supination) motions.
Abstract: The movements of the shoulder, elbow, and wrist play a vital role in the performance of essential daily activities. We therefore have developed a 2DOF exoskeleton robot ( ExoRob ) to rehabilitate the elbow and forearm movements of physically disabled individuals with impaired upper-limb function. The proposed ExoRob is supposed to be worn on the lateral side of forearm in order to provide naturalistic range movements of elbow (flexion/extension) and forearm (pronation/supination) motions. This paper focuses on the modelling, design (electrical and mechanical components), development, and control of the proposed ExoRob . The kinematic model of ExoRob has been developed based on modified Denavit-Hartenberg notations. Non-linear modified computed torque control technique is employed to control the proposed ExoRob , where trajectories (i.e., pre-programmed trajectories recommended by therapist/clinician) tracking corresponding to typical rehabilitation (passive) exercises has been carried out to evaluate the performances of the developed ExoRob and controller. Furthermore, experiments were carried out with the master exoskeleton arm [ mExoArm , an upper-limb prototype 7DOF (lower scaled) exoskeleton arm] where subjects (robot users) or experimenter operate the mExoArm (like a joystick) to manoeuvre the proposed ExoRob to provide passive rehabilitation. Experimental results show that the controller is able to manoeuvre the ExoRob efficiently to track the desired trajectories. Such movements are widely used in rehabilitation and have been performed efficiently with the developed ExoRob and the controller.
17 citations
13 Apr 2011
TL;DR: In this paper, the leader follower motton coordination of multiple nonholonomic mobile robots is investigated, and a combination of the virtual vehicle and trajectory tracking approach is used to derive the formation architecture.
Abstract: In this paper we investigate the leader follower motton coordination of multiple nonholonomic mobile robots. A combination of the virtual vehicle and trajectory tracking approach is used to derive the formation architecture. A virtual vehicle is steered in such away it stabilizes to a shifted reference position/heading deflned by the leader, the velocity of the virtual vehicle is then provided for further use in designing control law for the follower independent from the measurement of leader's velocity. Position tracking control is then constructed for the follower to track the virtual vehicle using the backstepping and Lyapunov direct design technique. Simulations are provided to show the effectiveness of the proposed approach.
TL;DR: The e-business needs in the e-learning environment using new learning tools and approaches is presented and the steps in the problem-based learning approach are detailed and its use and advantages are presented in some examples.
Abstract: Information and communication technologies (ICT) have affected all areas of our life: from information to recreational games, education, medicine, commerce and many other domains. The impact of these technologies has generated a real revolution in certain sectors and particularly in business. We talk more and more about electronic business (e-business) and training systems where electronic learning (e-learning) has experienced unprecedented development. In practice, these two domains are also interrelated. Several companies and institutions providing services for e-learning have adopted the e-business model for their management. Although the technological aspect of e-learning is efficient, effective e-learning is still strongly dependent on the pedagogical approaches. In fact, at the end of the last century, shortcomings were highlighted in the training of education in various fields. An observation was made of students' performance and attitudes. Students were found to be passive and uncreative, having difficulties in communication and working in teams. Another measured reality was the lack of autonomy in learning, accompanied by low interest and motivation in acquiring knowledge, and more difficulties in solving problems. Globalisation and increased competition among players in the industry have been the source of a profound reflection on training and education methods. Employers do not just require the title of the diploma but have more specific requirements on the profile of a competent graduate. Therefore, for e-learning and classical learning new pedagogical and active approaches are needed. This article presents the e-business needs in the e-learning environment using new learning tools and approaches. It details the steps in the problem-based learning approach and presents its use and advantages in some examples. It is definitely an efficient learning tool or method for e-learning in several disciplines such as business, management, medicine, engineering, economics, social sciences and many others.
26 Jun 2011
TL;DR: This article will show the various components of the environment of a remote laboratory in Electrical Engineering, and results obtained following the implementation of this new concept of Software as Service which adds more flexibility to the existing ones investigated so far.
Abstract: The Evolution of Cloud Computing, decreases the cost of electronic components, and the sizes of devices, and makes possible the emergence of other models for exploitation of remote laboratories. Indeed, until now, most remote laboratories are made available by accessing equipment or the real instruments installed in a remote laboratory room through computer networks and software and hardware interfaces. Now, it is time to allow students to carry out laboratory work from home by using relatively inexpensive compact measuring instruments. The proposed environment will be based on the concept of Software as Service to allow the student to use software tools from the Cloud to perform the tasks in solo or in collaboration with other partners. This article will show the various components of the environment of a remote laboratory in Electrical Engineering, and results obtained following the implementation of this new concept which adds more flexibility to the existing ones we have investigated so far.
01 Dec 2011
TL;DR: Experimental results show that the MARSE-4 can efficiently deliver passive therapy for elbow, forearm and wrist joint movements.
Abstract: To provide passive rehabilitation therapy to individuals with deficits in upper-limb function, we have developed a powered exoskeleton robot, named the MARSE-4. The developed exoskeleton is supposed to be worn on the lateral side of the upper limb and will provide passive arm movement assistance at the level of elbow, forearm and wrist joints. The kinematic model of the exoskeleton was developed based on modified Denavit-Hartenberg notations. In experiments, PID controllers were employed where trajectory tracking that corresponds to typical rehabilitation (passive) exercises were carried out to evaluate the performances of the developed exoskeleton and the controller. Experimental results show that the MARSE-4 can efficiently deliver passive therapy for elbow, forearm and wrist joint movements.
TL;DR: A new hybrid force-position control method for uncertain robotic manipulator interacting with its environment is presented and results on a four-degree of freedom robotic system tracking a triangle while maintaining a constant contact force prove the effectiveness of the solution.
Abstract: A new hybrid force-position control method for uncertain robotic manipulator interacting with its environment is presented. First, the system dynamical model in the compliance frame is derived from the usual joint frame model and leads to two sets of equations due to the constraint associated to the contact surface. Next, the two dynamics are separately used for the synthesis of position and force tracking controllers. For the position control part, the design method consists of an estimated-parameters dependent coordinate transformation and a control law derived from a backstepping procedure. The force control law has two aspects: first it compensates the dynamical interaction between the end-effector motion and the force induced by the environment and secondly, it imposes a desired force using a proportional-like equation. Finally, a parameter-adaptation algorithm is derived from a stability criteria and dependent both on the position and force tracking errors. Simulation results on a four-degree of freedom robotic system tracking a triangle while maintaining a constant contact force prove the effectiveness of our solution.
01 Dec 2011
TL;DR: A strategy of control is presented to track a desired trajectory in workspace for a hyper redundant articulated nimble adaptable trunk (ANAT) robot and the pseudo-inverse of the Jacobean is used to ensure the transformation of the desired trajectory from workspace to joint space.
Abstract: In this paper, a strategy of control is presented to track a desired trajectory in workspace for a hyper redundant articulated nimble adaptable trunk (ANAT) robot. The pseudo-inverse of the Jacobean is used to ensure the transformation of the desired trajectory from workspace to joint space. The control strategy consists of controlling the last joint by assuming that the remaining joints follow their desired values. Then we go backward for the (n-1)-th joint by following the same strategy, and so on until the first joint. In each step, the feedback linearization approach is used to develop the control law. This algorithm was experimented on a 7 DOF ANAT manipulator and gave effective results and good tracking in the robot's workspace.
13 Apr 2011
TL;DR: The simulation results of three mobile robots traveling on different paths in unknown environments are presented to show the accuracy of obtaining control, coordination and obstacle avoidance by using the designed fuzzy algorithm.
Abstract: In this paper, the design of an fuzzy intelligent coordination algorithm is introduced for a team of multi mobile robots (MMR) that are confronted with obstacles. As well as obstacle avoidance, the controllers work to make the robots arrive concurrently at their target points by adjusting each of the robot's velocities as they move along their desired paths. The simulation results of three mobile robots traveling on different paths in unknown environments are presented to show the accuracy of obtaining control, coordination and obstacle avoidance by using the designed fuzzy algorithm.
10 Aug 2011
TL;DR: It is proposed that exponential sliding mode control is an effective solution to reduce chattering for the trajectory tracking of a nonholonomic mobile robot and reduces chattering and delivers a high dynamic tracking performance in a steady state mode.
Abstract: This paper considers the problem of improving chattering reduction and trajectory tracking along a desired trajectory for a mobile robot. It is proposed that exponential sliding mode control is an effective solution to reduce chattering for the trajectory tracking of a nonholonomic mobile robot. Compared to conventional and second-order sliding modes, the developed sliding mode control reduces chattering and delivers a high dynamic tracking performance in a steady state mode. The developed algorithm instructs the robot to keep moving continuously on the desired trajectory while reducing tracking errors. Experimental results on a wheeled mobile robot are presented to demonstrate the performance of the exponential sliding mode controller algorithm compared to both conventional and second-order sliding mode algorithms.
01 Dec 2011
TL;DR: Experimental results show that the SMC can effectively maneuver the developed MARSE to follow the reference trajectory, and the concept of boundary layer technique is employed to eliminate the chattering of conventional SMC.
Abstract: To assist or rehabilitate individuals with impaired upper-limb function, we have developed an upper-limb exoskeleton robot, the ETS-MARSE (motion assistive robotic-exoskeleton for superior extremity). The MARSE has seven degrees-of-freedom (DoFs) and is designed to be worn on the lateral side of upper limb. It is able to assist with shoulder, elbow and wrist joint movements. In this paper we implemented a trajectory tracking algorithm using a nonlinear sliding mode controller (SMC). To eliminate the chattering of conventional SMC, we employed the concept of boundary layer technique. Experimental results show that the SMC can effectively maneuver the developed MARSE to follow the reference trajectory.