Hamed Rahimi Nohooji - Profile on Academia.edu (original) (raw)

Papers by Hamed Rahimi Nohooji

Research Square (Research Square), Dec 4, 2023

This study presents a novel framework that integrates the Universal Gripper (UG) with Unmanned Ae... more This study presents a novel framework that integrates the Universal Gripper (UG) with Unmanned Aerial Vehicles (UAVs) to enable automated grasping with no human operator in the loop. Grounded in the principles of granular jamming, the UG exhibits remarkable adaptability and proficiency, navigating the complexities of soft aerial grasping with enhanced robustness and versatility. Central to this integration is a uniquely formulated constrained trajectory optimization using model predictive control, coupled with a robust force control strategy, underpinning enhanced levels of automation and operational reliability in aerial grasping. This paradigm, while simple, is a powerful conduit for various applications, ranging from material handling to disaster response, propelling advancements toward genuine autonomy in aerial manipulation tasks. The key contributions of this research include the introduction of a constrained trajectory planning algorithm, and a force control strategy ensuring robust grasping, validated through numerical simulations and virtual experiments.

The Comparative Assessment of Modeling and Control of Mechanical Robot Manipulators

Sciyo eBooks, Aug 12, 2010

ABSTRACT

IEEE Access

This work introduces TRIGGER, the first lighTweight univeRsal jammInG Gripper for aErial gRasping... more This work introduces TRIGGER, the first lighTweight univeRsal jammInG Gripper for aErial gRasping. TRIGGER is an omnidirectional, landing-capable aerial grasping system with resilience and robustness to collisions and inherent passive compliance. In particular, this work presents the design, fabrication, and experimental validation of a novel, intelligent, modular, universal jamming gripper specifically designed for aerial applications. Leveraging recent developments in particle jamming and soft granular materials, TRIGGER generates 15 N of holding force with only a relatively small activation force of 2.5 N. Experiments show the relationship between fill ratio and activation force and reveal that adding an additive to the membrane's silicone mixture improves the holding force by up to 52 %. Based on the experimental data, a simulation model for robotic simulators is introduced to facilitate future controller developments. To showcase the concept, TRIGGER is attached to a multicopter platform, performing a pick-and-place task under laboratory conditions. The aerial experiments are concluded by grasping a variety of shapes demonstrating the universal grasping capability.

Actor–Critic Learning Based Pid Control for Robotic Manipulators

Soft robotic grippers have numerous advantages that address challenges in dynamic aerial grasping... more Soft robotic grippers have numerous advantages that address challenges in dynamic aerial grasping. Typical multi-fingered soft grippers recently showcased for aerial grasping are highly dependent on the direction of the target object for successful grasping. This study pushes the boundaries of dynamic aerial grasping by developing an omnidirectional system for autonomous aerial manipulation. In particular, the paper investigates the design, fabrication, and experimental verification of a novel, highly integrated, modular, sensor-rich, universal jamming gripper specifically designed for aerial applications. Leveraging recent developments in particle jamming and soft granular materials, the presented gripper produces a substantial holding force while being very lightweight, energy-efficient and only requiring a low activation force. We show that the holding force can be improved by up to 50 % by adding an additive to the membrane's silicone mixture. The experiments show that our lightweight gripper can develop up to 15 N of holding force with an activation force as low as 2.5 N, even without geometric interlocking. Finally, a pick and release task is performed under real-world conditions by mounting the gripper onto a multi-copter. The developed aerial grasping system features many useful properties, such as resilience and robustness to collisions and the inherent passive compliance which decouples the UAV from the environment. Keywords universal jamming gripper • aerial manipulation • soft gripper • soft aerial robotics License For the purpose of Open Access, the author has applied a CC-BY-4.0 public copyright license to any Author Accepted Manuscript version arising from this submission.

Journal of Mechanisms and Robotics, 2022

This paper is concerned with the dynamic motion analysis and the planning of maximum payload path... more This paper is concerned with the dynamic motion analysis and the planning of maximum payload path of flexible manipulators. The finite element method was employed for dynamic modelling of the system and the motion of the model was considered as a combination of the rigid displacement and the elastic deformation of each link. Each manipulator link was treated as a finite number of elements and total displacement was derived by means of the shape functions of flexible elements. The problem of maximum payload trajectory planning was formulated as an optimal control problem. An indirect optimal control solution was employed. This method converts an optimality problem to a twopoint boundary value problem. The effect of the number of elements on the dynamic motion, optimal trajectory and maximum allowable dynamic payload of the system was studied. Finally, a number of simulations were performed to verify the applicability and capability of the method for the nonlinear dynamic modelling an...

Robot-assisted therapy can improve motor function in patients recovering from stroke. Assist-as-n... more Robot-assisted therapy can improve motor function in patients recovering from stroke. Assist-as-needed algorithms provide only minimal robotic assistance in the therapy, thus requiring significant effort from the impaired subject. This paper presents an adaptive neural assist-as-needed controller for rehabilitative robots. The controller combines the Lyapunov direct method with the computed torque control and neural networks. Robot assistance is limited to only as needed by adding the force reducing term into the adaptive control law. This paper shows that by the presented method the tracking error converges to a small value around zero while the neural network weights and system uncertainties remain bounded. Simulation on a robot manipulator model is presented to demonstrate the effectiveness of the proposed method.

Journal of Renewable and Sustainable Energy, 2017

Effects of second-order wave forces and aerodynamic forces on dynamic responses of a TLP-type flo... more Effects of second-order wave forces and aerodynamic forces on dynamic responses of a TLP-type floating offshore wind turbine considering the set-down motion

Frontiers of Mechanical Engineering, 2017

Power maximization has always been a practical consideration in wind turbines. The question of ho... more Power maximization has always been a practical consideration in wind turbines. The question of how to address optimal power capture, especially when the system dynamics are nonlinear and the actuators are subject to unknown faults, is significant. This paper studies the control methodology for variable-speed variable-pitch wind turbines including the effects of uncertain nonlinear dynamics, system fault uncertainties, and unknown external disturbances. The nonlinear model of the wind turbine is presented, and the problem of maximizing extracted energy is formulated by designing the optimal desired states. With the known system, a model-based nonlinear controller is designed; then, to handle uncertainties, the unknown nonlinearities of the wind turbine are estimated by utilizing radial basis function neural networks. The adaptive neural fault tolerant control is designed passively to be robust on model uncertainties, disturbances including wind speed and model noises, and completely unknown actuator faults including generator torque and pitch actuator torque. The Lyapunov direct method is employed to prove that the closed-loop system is uniformly bounded. Simulation studies are performed to verify the effectiveness of the proposed method. Keywords wind turbine nonlinear model, maximum power tracking, passive fault tolerant control, adaptive neural control Additionally, as wind turbines are large, expensive and hard-to-maintain structures, the fault diagnosis and isolation (FDI), and fault tolerant control (FTC) concepts can be used to increase the wind turbine reliability . These methods can also help the system to avoid vulnerability in dangerous wind situations . FTC is a new aspect in wind turbines studies . This method tries to keep wind turbine operating, despite the existence of faults . Two different FTC

Finding the full load motion for a point-to-point task can maximize the productivity and economic... more Finding the full load motion for a point-to-point task can maximize the productivity and economic usage of the mobile manipulators. The presented paper proposes a technique to determine the maximum allowable dynamic payload for flexible mobile manipulators along with the obtained optimal trajectories. Non-linear modeling of the mobile robotic manipulators by considering both link and joint flexibility is presented; then, optimal motion planning of the system is organized as an optimal control formulation. By employing indirect solution of the problem, optimal maximum payload path of such robots is designed for a general objective function. The paper specially focuses on effects of various important parameters on the maximum payload determination and analyzes them thoroughly. The effectiveness and capability of the proposed method is investigated through various simulation studies. The obtained results illustrate the influences of the performance index, operating time and robot characteristics on the maximum payload path.

Designing optimal motion is critical in several applications for mobile robot from payload transp... more Designing optimal motion is critical in several applications for mobile robot from payload transport between two given states in a prescribed time such that a cost functional is minimized. This paper deals with the problem of path design of wheeled non-holonomic robots with flexible joints, based on Pontryagin's minimum principle. The simplified case study of a Four Wheeled, two-link manipulator with joint elasticity is considered to study the method in generalized model. Nonlinear state and control constraints are treated without any simplifications or transforming them into sequences of systems with linear equations. By these means, the modeling of the complete optimal control problem and the accompanying boundary value problem is automated to a great extent. Performance of method is illustrated through the computer simulation.

Nonlinear dynamic analysis for elastic robotic arms

Frontiers of Mechanical Engineering, 2011

The aim of the paper is to analyze the nonlinear dynamics of robotic arms with elastic links and ... more The aim of the paper is to analyze the nonlinear dynamics of robotic arms with elastic links and joints. The main contribution of the paper is the comparative assessment of assumed modes and finite element methods as more convenient approaches for computing the nonlinear dynamic of robotic systems. Numerical simulations comprising both methods are carried out and results are discussed.

Robotica, 2005

A computational algorithm is developed to find a dynamic motion trajectory of a mobile manipulato... more A computational algorithm is developed to find a dynamic motion trajectory of a mobile manipulator with flexible links and joints that will allow the robot to carry a maximum load between two specified end positions. A compact form of the linearized state space dynamic equations is organized as well as constraint equations. Then, the problem of finding a maximum load carrying capacity on flexible mobile manipulators is formulated as a trajectory optimization problem.

International Journal of Advanced Robotic Systems, 2011

Finding optimal trajectory is critical in several applications of robot manipulators. This paper ... more Finding optimal trajectory is critical in several applications of robot manipulators. This paper is applied the open-loop optimal control approach for generating the optimal trajectory of the flexible mobile manipulators in point-to-point motion. This method is based on the Pontryagin's minimum principle that by providing a two-point boundary value problem is solved the problem. This problem is known to be complex in particular when combined motion of the base and manipulator, nonholonomic constraint of the base and highly non-linear and complicated dynamic equations as a result of flexible nature of links are taken into account. The study emphasizes on modeling of the complete optimal control problem by remaining all nonlinear state and costate variables as well as control constraints. In this method, designer can compromise between different objectives by considering the proper penalty matrices and it yields to choose the proper trajectory among the various paths. The effectiv...

Applied Mathematical Modelling, 2012

This paper is concerned with mathematical modeling and optimal motion designing of flexible mobil... more This paper is concerned with mathematical modeling and optimal motion designing of flexible mobile manipulators. The system is composed of a multiple flexible links and flexible revolute joints manipulator mounted on a mobile platform. First, analyzing on kinematics and dynamics of the model is carried out then; open-loop optimal control approach is presented for optimal motion designing of the system. The problem is known to be complex since combined motion of the base and manipulator, non-holonomic constraint of the base and highly non-linear and complicated dynamic equations as a result of the flexible nature of both links and joints are taken into account. In the proposed method, the generalized coordinates and additional kinematic constraints are selected in such a way that the base motion coordination along the predefined path is guaranteed while the optimal motion trajectory of the end-effector is generated. This method by using Pontryagin's minimum principle and deriving the optimality conditions converts the optimal control problem into a two point boundary value problem. A comparative assessment of the dynamic model is validated through computer simulations, and then additional simulations are done for trajectory planning of a two-link flexible mobile manipulator to demonstrate effectiveness and capability of the proposed approach.

Trajectory optimization of nonholonomic mobile manipulators departing to a moving target amidst moving obstacles

Acta Mechanica, 2013

ABSTRACT How to plan the optimal trajectory of nonholonomic mobile manipulators in dynamic enviro... more ABSTRACT How to plan the optimal trajectory of nonholonomic mobile manipulators in dynamic environments is a significant and challenging task, especially in the system with a moving target. This paper presents trajectory optimization of a nonholonomic mobile manipulator in dynamic environment pursuing a moving target. Full nonlinear dynamic equations of the system considering the nonholonomic constraints of wheels are presented. Then, dynamic motion planning of the system is formulated as an optimal control problem considering moving obstacle avoidance conditions. Accordingly, a new formulation of dynamic potential function was proposed based on the dynamic distance between colliding objects. In addition, an appropriate boundary value for a moving target was defined, and the resulted boundary value problem was solved to optimize the trajectory of the system. To solve the problem, an indirect solution of optimal control was applied which leads to transform the optimal control problem into a set of coupled differential equations. To demonstrate the efficiency and applicability of the method a number of simulations and experiments was performed for a spatial nonholonomic mobile manipulator.

International Journal of Advanced Robotic Systems, 2012

In this work, a computational algorithm is developed for the smooth-jerk optimal path planning of... more In this work, a computational algorithm is developed for the smooth-jerk optimal path planning of tricycle wheeled mobile manipulators in an obstructed environment. Due to a centred orientable wheel, the tricycle mobile manipulator exhibits more steerability and manoeuvrability over traditional mobile manipulators, especially in the presence of environmental obstacles. This paper presents a general formulation based on the combination of the potential field method and optimal control theory in order to plan the smooth point-to-point path of the tricycle mobile manipulators. The nonholonomic constraints of the tricycle mobile base are taken into account in the dynamic formulation of the system and then the optimality conditions are derived considering jerk restrictions and obstacle avoidance. Furthermore, by means of the potential field method, a new formulation of a repulsive potential function is proposed for collision avoidance between any obstacle and each part of the mobile mani...

Constrained control of wind turbines for power regulation in full load operation

2017 11th Asian Control Conference (ASCC), 2017

The safe operation of wind turbines is a vital criterion which should be considered in the contro... more The safe operation of wind turbines is a vital criterion which should be considered in the controller design to avoid rotor over speeding and hazardous operation. In this regard, the main focus of this paper is to keep the wind turbine operating within given limits by considering constrained control concepts using the barrier Lyapunov function. The nonlinear model of a benchmark wind turbine is considered and the wind speed variation is assumed to be unmeasurable disturbance and consequently, utilising the radial basis function neural network, an aerodynamic torque estimator is designed. The proposed controller is evaluated via numerical simulations and its performance is compared to a practical industrial wind turbine controller and a quadratic Lyapunov-based controller.

Journal of Mechanisms and Robotics, 2021

This paper proposed a systematic framework to automatically design and fabricate optimized soft r... more This paper proposed a systematic framework to automatically design and fabricate optimized soft robotic fingers. The soft finger is composed of a soft silicone structure with inner air chambers and a harder outer layer, which are fabricated by molding process and 3D printing, respectively. The softer layer is utilized for actuation while the supportive hard structure is used to impose constraints. The framework applies a topology optimization approach based on RAMP method to obtain an optimal design of the outer layer of the soft fingers. Two basic motion primitives (bending and twisting) of the soft finger were explored. A multi-segmented soft bending finger and a soft twisting finger were designed and fabricated through the proposed framework. This work also explored the combination of bending and twisting primitives by developing a combined bending-twisting soft finger. The soft fingers were characterized by free and blocked movement tests. The experiments showed that the triplesegmented soft finger can achieve a maximum of 50.5 • no-load bending under the actuation pressure of 53 kPa. The blocked movement test on the multi-segmented soft actuating finger showed that this finger could generate up to a maximum of 0.63 N force under 57 kPa actuation pressure in 7 seconds of inflating time. The developed twisting soft finger was shown to achieve tip rotation of up to 219 degrees under 29 kPa actuation pressure. Finally, the potential capability of the bending-twisting soft fingers was verified through applications like screwing and object grasping.