Papers by Amir A. Ghavifekr
2019 IEEE East-West Design & Test Symposium (EWDTS), 2019
Bookmarks Related papers MentionsView impact
2021 12th International Symposium on Advanced Topics in Electrical Engineering (ATEE), 2021
This paper presents the design, implementation, and characterization of a miniature crab-like wal... more This paper presents the design, implementation, and characterization of a miniature crab-like walking robot. The first prototype developed is a four-legged servomotor actuated machine that exhibits compact dimensions, low mass, and is capable of overcoming obstacles and moving on irregular terrain and confined spaces. Its bio-inspired design ensures the compliance of its locomotion mechanism even in the presence of external disturbances. The mechanical design, the implementation of the prototype, and its electronic control approach are first discussed. Next, a kinematic analysis characterizing its motion is presented. The aim of this device is to serve as an educational supporting platform for understanding robot kinematics and legged locomotion.
Bookmarks Related papers MentionsView impact
This paper addresses the stability conditions of the sampled-data teleoperation systems consistin... more This paper addresses the stability conditions of the sampled-data teleoperation systems consisting continuoustime master, slave, operator, and environment with discrete-time controllers over general communication networks. The output signals of the slave and master robots are quantized with stochastic sampling periods which are modeled as being from a finite set. By applying an input-delay method, the probabilistic sampling system is converted into a continuoustime system including stochastic parameters in the system matrices. The main contribution of this paper is the derivation of the less conservative stability conditions for linear discrete teleoperation systems taking into account the challenges such as the stochastic sampling rate, constant time delay and the possibility of data packet dropout. The numbers of dropouts are driven by a finite state Markov chain. First, the problem of finding a lower bound on the maximum sampling period that preserves the stability is formulated....
Bookmarks Related papers MentionsView impact
This paper presents an analysis of the passivity condition for discrete-time bilateral teleoperat... more This paper presents an analysis of the passivity condition for discrete-time bilateral teleoperation systems. Considering discrete-time controllers for a master-slave teleoperation system can simplify its implementation. Varieties of control schemes have been utilized for the position error based architecture of bilateral teleoperation systems and major concerns such as passivity and transparency have been studied. This paper takes into account the passivity conditions for the discrete counterparts of P-like, PD-like, and PD-like + dissipation controllers. These conditions impose bounds on the controller gains, the damping of the master and slave robots, and the sampling time which help researchers to provide guidelines to have better transparency and passive teleoperation systems. Simulation results are performed to show the effectiveness of the proposed criteria.
Bookmarks Related papers MentionsView impact
Bookmarks Related papers MentionsView impact
Microgrids
Bookmarks Related papers MentionsView impact
ISA Transactions
Bookmarks Related papers MentionsView impact
European Journal of Control
This paper addresses the stability conditions of the sampled-data teleoperation systems consistin... more This paper addresses the stability conditions of the sampled-data teleoperation systems consisting continuous-time master, slave, operator, and environment with discrete-time controllers over general communication networks. The output signals of the slave and master robots are quantized with stochastic sampling periods which are modeled as being from a finite set. By applying an input-delay method, the probabilistic sampling system is converted into a continuous-time system including stochastic parameters in the system matrices. The main contribution of this paper is the derivation of the less conservative stability conditions for linear discrete teleoperation systems taking into account the challenges such as the stochastic sampling rate, constant time delay and the possibility of data packet dropout. The numbers of dropouts are driven by a finite state Markov chain. First, the problem of finding a lower bound on the maximum sampling period that preserves the stability is formulated. This problem is constructed as a convex optimization program in terms of linear matrix inequalities (LMI). Next, Lyapunov-Krasovskii based approaches are applied to propose sufficient conditions for stochastic and exponential stability of closed-loop sampled-data bilateral teleoperation system. The proposed criterion notifies the effect of sampling time on the stability-transparency trade-off and imposes bounds on the sampling time, control gains and the damping of robots. Neglecting this study undermines both the stability and transparency of teleoperation systems. Numerical simulation results are used to verify the proposed stability criteria and illustrate the effectiveness of the sampling architecture.
Bookmarks Related papers MentionsView impact
2015 6th International Conference on Modeling, Simulation, and Applied Optimization (ICMSAO), 2015
In this paper, a position and velocity estimation method for robotic manipulators which are affec... more In this paper, a position and velocity estimation method for robotic manipulators which are affected by constant bounded disturbances is considered. The tracking control problem is formulated as a disturbance rejection problem, with all the unknown parameters and dynamic uncertainties lumped into disturbance. Using adaptive robust extended Kalman filter(AREKF) the movement and velocity of each joint is predicted to use in discontinuous Lyapunov-based controller structure. The parameters of the error dynamics have been validated off-line by real data. Computer simulation results given for a two degree of freedom manipulator demonstrate the efficacy of the improved Kalman Filter by comparing the performance of EKF and improved AREKF. Although it is shown that accurate trajectory tracking can be achieved by using the proposed controller.
Bookmarks Related papers MentionsView impact
In this study, an Improved Fuzzy Controller using Sliding Mode Concept (IFCSMC) is employed to co... more In this study, an Improved Fuzzy Controller using Sliding Mode Concept (IFCSMC) is employed to control an underactuated overhead crane system. As we know fuzzy algorithms do not need the complex dynamic model of system, but fuzzy controller of this paper uses trolley position and load swing angle information instead to design the fuzzy controller. Innovation of the proposed controller is using three experimental rules that utilize the appropriate control signal value of last level for determining the control signal value of new level which depends on difference of error (position error) in these levels. The merits of proposed algorithm in comparison with conventional fuzzy control are decreasing the time of reaching to desire value and reducing sensitivity of system when fuzzy rules are changed. External disturbances, such as the wind and the hit, which always deteriorate the control performance, are also considered to verify the efficiency of the proposed improved fuzzy algorithm
Bookmarks Related papers MentionsView impact
2013 21st Iranian Conference on Electrical Engineering (ICEE), 2013
ABSTRACT Robotic laparoscopic grasper is a surgical tool with minimal invasion. In this robot, ac... more ABSTRACT Robotic laparoscopic grasper is a surgical tool with minimal invasion. In this robot, achieve goals like precise tracking, stability and disturbance rejection are very important. In this paper, first the stages of modeling and simulating of laparoscopic robot will be discussed and the reasons for selecting the appropriate materials for different parts of proposed practical robot will be explained. Inverse dynamic controller with integral action is applied to improve the accuracy of tracking procedure for a surgical manipulator to track a specified reference signal in the presence of tremor that is modeled as constant bounded disturbance. Based on the disturbance rejection scheme, tracking controller is constructed which is asymptotically stabilizing in the sense of Lyapunov. It is shown that how under proper assumptions; the selected schemes succeed in achieving disturbance rejection at the input of a nonlinear system. Computer simulation results demonstrate that accurate trajectory tracking can be achieved by using the proposed controller.
Bookmarks Related papers MentionsView impact
Majlesi Journal of Mechatronic Systems, 2012
Bookmarks Related papers MentionsView impact
International Journal of Engineering works, 2014
Gryphon as a 5-DOF robot has the ability to emulate the gestures of human arm and hand. It has pi... more Gryphon as a 5-DOF robot has the ability to emulate the gestures of human arm and hand. It has pivots for rotation around the elbow and wrist. The wrist has two operative pivots, for rotation and elevation. Unlike previous works which concentrate on using WALLI as Gryphon robots own software, in this paper a PC-based and XPC Target's real-time feature has been used.. Recently, techniques based on metaheuristics of natural computing, mainly evolutionary algorithms (EA), have been successfully applied to a large number of robotic applications. The aim of this paper is to evaluate a modified Biogeography-based Optimization (BBO) approach based on mutation operator to solve the trajectory planning of a Gryphon. Computer simulation results and practical experiments demonstrate that accurate trajectory tracking can be achieved by using the proposed method.
Bookmarks Related papers MentionsView impact
Robotica, 2018
The possibility of operating in remote environments using teleoperation systems has been consider... more The possibility of operating in remote environments using teleoperation systems has been considered widely in the control literature. This paper presents a review on the discrete-time teleoperation systems, including issues such as stability, passivity and time delays. Using discrete-time methods for a master-slave teleoperation system can simplify control implementation. Varieties of control schemes have been proposed for these systems and major concerns such as passivity, stability and transparency have been studied. Recently, unreliable communication networks affected by packet loss and variable transmission delays have been received much attention. Thus, it is worth considering discrete-time theories for bilateral teleoperation architectures, which are formulated on the same lines as the continuous-time systems. Despite the extensive amount of researches concerning continuous-time teleoperation systems, only a few papers have been published on the analysis and controller design for discrete bilateral forms. This paper takes into account the challenges for the discrete structure of bilateral teleoperation systems and notifies the recent contributions in this area. The effect of sampling time on the stability-transparency trade-off and the task performance is taken into consideration in this review. These studies can help to design guidelines to have better transparency and stable teleoperation systems.
Bookmarks Related papers MentionsView impact
European Journal of Control, 2018
This paper addresses the stability conditions of the sampled-data teleoperation systems consistin... more This paper addresses the stability conditions of the sampled-data teleoperation systems consisting continuous-time master, slave, operator, and environment with discrete-time controllers over general communication networks. The output signals of the slave and master robots are quantized with stochastic sampling periods which are modeled as being from a finite set. By applying an input-delay method, the probabilistic sampling system is converted into a continuous-time system including stochastic parameters in the system matrices. The main contribution of this paper is the derivation of the less conservative stability conditions for linear discrete teleoperation systems taking into account the challenges such as the stochastic sampling rate, constant time delay and the possibility of data packet dropout. The numbers of dropouts are driven by a finite state Markov chain. First, the problem of finding a lower bound on the maximum sampling period that preserves the stability is formulated. This problem is constructed as a convex optimization program in terms of linear matrix inequalities (LMI). Next, Lyapunov-Krasovskii based approaches are applied to propose sufficient conditions for stochastic and exponential stability of closed-loop sampled-data bilateral teleoperation system. The proposed criterion notifies the effect of sampling time on the stability-transparency trade-off and imposes bounds on the sampling time, control gains and the damping of robots. Neglecting this study undermines both the stability and transparency of teleoperation systems. Numerical simulation results are used to verify the proposed stability criteria and illustrate the effectiveness of the sampling architecture.
Bookmarks Related papers MentionsView impact
Majlesi Journal of Mechatronic Systems, 2012
In this paper, we consider the tracking control problem for robot manipulators which are affected... more In this paper, we consider the tracking control problem for robot manipulators which are affected by constant bounded disturbances. Three control schemes are applied for the problem, which composed of integral action and tracking controllers. The goal is improving the accuracy of tracking procedure for a robot manipulator to track a specified reference signal in the presence of constant bounded disturbances. Inverse dynamics controller, improved Lyapunov-based controller with integral action and discontinuous Lyapunov-based controller are three schemes that are evaluated in this paper. Third one is a novel controller that achieves trajectory following without requiring exact knowledge of the nonlinear dynamics. Based on the disturbance rejection scheme, tracking controllers are constructed which are asymptotically stabilizing in the sense of Lyapunov. Furthermore the closed loop system has strong disturbance rejection property. It is shown that how under proper assumptions, the proposed schemes succeed in achieving disturbance rejection at the input of a nonlinear system. Computer simulation results given for a two degree of freedom manipulator with a large payload and fast maneuver, demonstrate that accurate trajectory tracking can be achieved by using the proposed controllers.
Bookmarks Related papers MentionsView impact
International Journal of Electrical, Electronics and Data Communication (IJEEDC), 2016
In redundant manipulators, there are infinite numbers of joint space velocities that lead to a sp... more In redundant manipulators, there are infinite numbers of joint space velocities that lead to a specific task space velocity. Thus, the main problem is calculating a local maximum for null space joint velocity regarding to physical constraints of a robotic manipulator. The manipulability measure, the distance from mechanical joint limits and the distance from the obstacles are three different cost functions which are evaluated in this paper to find a local maximum for null space joint velocity. It is represented that by using these functions, the redundancy may be exploited to overcome singularities. Furthermore, redundancy can be used to keep the joints of the 5-bar linkage in an acceptable range and can be used to avoid collisions with constant obstacles. Computer simulation results given for a 5-bar linkage manipulator, demonstrate the efficacy of the proposed null space joint velocities. Also it is extracted that accurate trajectory tracking can be achieved by using the well-known controllers.
Bookmarks Related papers MentionsView impact
International Journal of Electrical, Electronics and Data Communication (IJEEDC), 2018
This paper presents an analysis of the passivity condition for discrete-time bilateral teleoperat... more This paper presents an analysis of the passivity condition for discrete-time bilateral teleoperation systems. Considering discrete-time controllers for a master-slave teleoperation system can simplify its implementation. Varieties of control schemes have been utilized for the position error based architecture of bilateral teleoperation systems and major concerns such as passivity and transparency have been studied. This paper takes into account the passivity conditions for the discrete counterparts of P-like, PD-like, and PD-like + dissipation controllers. These conditions impose bounds on the controller gains, the damping of the master and slave robots, and the sampling time which help researchers to provide guidelines to have better transparency and passive teleoperation systems. Simulation results are performed to show the effectiveness of the proposed criteria.
Bookmarks Related papers MentionsView impact
Majlesi Journal of Mechatronic Systems, 2012
This paper evaluates Adaptive Genetic Algorithm (AGA) and Particle Swarm Optimization (PSO) to fi... more This paper evaluates Adaptive Genetic Algorithm (AGA) and Particle Swarm Optimization (PSO) to find a time optimal quadratic polynomial trajectory of an anthropomorphic manipulator. This robot that is used in minimally invasive surgery (MIS) must achieve motions under the constraints of displacement, velocity, acceleration and jerk of each joint. The modeling and resolution of the constraints are presented. PSO and different selection methods of the genetic algorithm are evaluated and compared in order to define the best one according to convergence speed and optimal time. These methods can solve the premature convergence and slow convergence problems in MIS. Simulation and experimental results for the grasper of a compact laparoscopic surgical robot prototype system validate the algorithms.
Bookmarks Related papers MentionsView impact
Conference Presentations by Amir A. Ghavifekr
2013 21st Iranian Conference on Electrical Engineering (ICEE), 2013
In this paper, the tracking control problem for 5 DOF surgical robot which is affected by tremor ... more In this paper, the tracking control problem for 5 DOF surgical robot which is affected by tremor of surgeons' hand is considered. Mechanical modeling and dynamic analysis of a robotic arm in slave subsystem of a telesurgery system will be discussed and the reasons for selecting the appropriate materials for different parts of robot will be explained. It would be required this robot, which will do the main part of the surgery, be controlled based on the uncertain properties of the tissues of patients body. Improved Lyapunov Based control method with uncertainty observer is applied to improve the accuracy of tracking procedure for a surgical manipulator to track a specified reference signal in the presence of tremor that is modeled as constant bounded disturbance. Based on the disturbance rejection scheme, tracking controllers are constructed which are asymptotically stabilizing in the sense of Lyapunov. The control strategy was implemented using a PC interface. Computer simulation results demonstrate that accurate trajectory tracking can be achieved by using the proposed controllers.
Bookmarks Related papers MentionsView impact
Uploads
Papers by Amir A. Ghavifekr
Conference Presentations by Amir A. Ghavifekr