Vol.4, No.3, 2016 by International Journal of Robotics K.N. Toosi University of Technology
In this paper, trajectory generation for the 4 DOF arm of SURENA III humanoid robot with the purp... more In this paper, trajectory generation for the 4 DOF arm of SURENA III humanoid robot with the purpose of optimizing energy and avoiding a moving obstacle is presented. For this purpose, first, kinematic equations for a seven DOF manipulator are derived. Then, using the Lagrange method, an explicit dynamics model for the arm is developed. In the next step, in order to generate the desired trajectory for the arm, two different methods are utilized. In the first method, each joint motion is presented by a quadratic polynomial. In the second one, the end effector's path has been considered as 3 polynomial functions. Also, a known moving spherical obstacle with a linear path and constant velocity is considered in robot workspace. The main goal of optimization is to reduce the consumed energy by the arm in a movement between two known points in a specified time frame to avoid the moving obstacle. Initial and final velocities of the arm are set as zero. To this end, the optimization is carried out using Genetic Algorithm. Finally, in order to obtain the most reliable solutions for trajectory generation, many optimizations with various parameters are conducted and the results are presented and discussed.
Although construction has been known as a highly complex application field for autonomous robotic... more Although construction has been known as a highly complex application field for autonomous robotic systems, recent advances in this field offer great hope for using robotic capabilities to develop automated construction. Today, space research agencies seek to build infrastructures without human intervention, and construction companies look to robots with the potential to improve construction quality, efficiency, and safety, not to mention flexibility in architectural design. However, unlike production robots used, for instance, in automotive industries, autonomous robots should be designed with special consideration for challenges such as the complexity of the cluttered and dynamic working space, human-robot interactions and inaccuracy in positioning due to the nature of mobile systems and the lack of affordable and precise self-positioning solutions. This paper briefly reviews state-of-the-art research into automated construction by autonomous mobile robots. We address and classify the relevant studies in terms of applications, materials, and robotic systems. We also identify ongoing challenges and discuss about future robotic requirements for automated construction.
Designing the self-balancing two-wheeled mobile robots and reducing undesired vibrations are of g... more Designing the self-balancing two-wheeled mobile robots and reducing undesired vibrations are of great importance. For this purpose, the majority of researches are focused on application of relatively complex control approaches without improving the robot structure. Therefore, in this paper we introduce a new two-wheeled mobile robot which, despite its relative simple structure, fulfills the required level of self-balancing without applying any certain complex controller. To reach this goal, the robot structure is designed in a way that its center of gravity is located below the wheels' axle level. The attention is more paid to obtaining a self-balancing model in which the robot's arms and other equipment follow relatively low oscillations when the robot is subjected to a sudden change. After assembling the robot using the Sim-Mechanics toolbox of Matlab, several simulations are arranged to investigate the robot ability in fulfilling the required tasks. Further verifications are carried out by performing various experiments on the real model. Based on the obtained results, an acceptable level of balancing, oscillation reduction, and power supply is observed. To promote the self-balancing two-wheeled mobile manipulator, its platform is modified to climb high obstacles. In order to obtain this aim, some transformations are done in mechanical aspects like wheels, arms and main body without any increase in DOFs. The robot is supposed to follow proposed motion calculated according to stability criteria. The kinematic equations are utilized to find a possible motion. In a dynamic simulation, the robot ability in passing over an obstacle is verified.
This research focuses on proposing an optimal trajectory planning and control method of two link ... more This research focuses on proposing an optimal trajectory planning and control method of two link rigid-flexible manipulators (TLRFM) for Dynamic Object Manipulation (DOM) missions. For the first time, achievement of DOM task using a rotating one flexible link robot was taken into account in [20]. The authors do not aim to contribute on either trajectory tracking or vibration control of the End-Effector (EE) of the manipulator; On the contrary, utilizing the powerful tool optimal control accomplishing a point-to-point task for TLRFM is the purpose of the current research. Towards this goal, the pseudospectral method will be developed to meet the optimality conditions subject to system dynamics and boundary conditions. The complicated optimal trajectory planning is formulated as a nonlinear programming problem and solved by SNOPT nonlinear solver. To make robust the response of optimal control against external disturbances as well as model parameter uncertainties, the control partitioning concept is employed. The controlled input is composed of an optimal control-based feedforward part and a PID-based feedback component. The obtained simulation results reveal the usefulness and robustness of the developed composite scheme, in DOM missions.
In this study, a novel variable impedance control for a lower-limb rehabilitation robotic system ... more In this study, a novel variable impedance control for a lower-limb rehabilitation robotic system using voltage control strategy is presented. The majority of existing control approaches are based on control torque strategy, which require the knowledge of robot dynamics as well as dynamic of patients. This requires the controller to overcome complex problems such as uncertainties and nonlinearities involved in the dynamic of the system, robot and patients. On the other hand, how impedance parameters must be selected is a serious question in control system design for rehabilitation robots. To resolve these problems this paper, presents a variable impedance control based on the voltage control strategy. In contrast to the usual current-based (torque mode) the use of motor dynamics lees to a computationally faster and more realistic voltage-base controller. The most important advantage of the proposed control strategy is that the nonlinear dynamic of rehabilitation robot is handled as an external load, hence the control law is free from robot dynamic and the impedance controller is computationally simpler, faster and more robust with negligible tracking error. Moreover, variable impedance parameters based on Interval Type-2 Fuzzy Logic (IT2Fl) is proposed to evaluate impedance parameters. The proposed control is verified by a stability analysis. To illustrate the effectiveness of the control approach, a 1-DOF lower-limb rehabilitation robot is designed. Voltage-based impedance control are simulated through a therapeutic exercise consist of Isometric and Isotonic exercises. Simulation results show that the proposed voltage-based variable impedance control is superior to voltage-based impedance control in therapeutic exercises.
A new type of backbone robot is presented in this paper. The core idea is to use a cross shape me... more A new type of backbone robot is presented in this paper. The core idea is to use a cross shape mechanism with the principle of functioning of the scissors linkages, known as a pantograph. Although this continuum arm acts quite similar to tendon-driven robot, this manipulator does not include any tendon in its structure. This design does not suffer from the weaknesses of the continuum design such as low payload and coarse positioning accuracy. Kinematic model is developed and the equation of motion for this arm is derived by Lagrange's method. The work envelope and the occupied space investigation are supposed to be established on the comparison between tendon-based model as the common backbone models and our proposed idea. The results show the effectiveness of the backbone design.
There are many occasions where the base of a robotic manipulator is attached to a moving platform... more There are many occasions where the base of a robotic manipulator is attached to a moving platform, such as on a moving ship, terrain or space shuttle. In this paper a dynamic model of a robotic manipulator mounted on a moving base is derived using both Newton-Euler and Lagrange-Euler methods. The presented models are simulated for a Mitsubishi PA10-6CE robotic manipulator characteristics mounted on a ship platform that is moving on ocean and the results are verified through both methods. In this simulation it is assumed that the inertia of the base of the robot is large enough and is not affected by the manipulator motion. However, the motion of the ship directly influences the dynamics of the manipulator in movements. Results and computation time of the two methods are compared and it is shown that the Newton-Euler method needs less computation time than the Lagrange method.
Vol.4, No.2, 2015 by International Journal of Robotics K.N. Toosi University of Technology
This paper studies the effect of flexible linear torso on the dynamics of passive quadruped bound... more This paper studies the effect of flexible linear torso on the dynamics of passive quadruped bounding. A reduced-order passive and conservative model with linear flexible torso and springy legs is introduced. The model features extensive spine deformation during high-speed bounding, resembling those observed in a cheetah. Fixed points corresponding to cyclic bounding motions are found and calculated using numerical return map methodologies. Results show that the corresponding robot gaits and the associated performance resemble those of its natural counterparts.
Cooperative object manipulation control of rigid-flexible multi-body systems in space is studied ... more Cooperative object manipulation control of rigid-flexible multi-body systems in space is studied in this paper. During such tasks, flexible members like solar panels may get vibrated that in turn may lead to some oscillatory disturbing forces on other subsystems, and consequently produces error in the motion of the end-effectors of the cooperative manipulating arms. Therefore, to design and develop capable model-based controllers for such complicated systems deriving a dynamics model is required. However, due to practical limitations and real-time implementation, the system dynamics model should require low computations. So, first to obtain a precise compact dynamics model, the Rigid-Flexible Interactive dynamics Modelling (RFIM) approach is briefly introduced. Using this approach, the system is virtually partitioned into two rigid and flexible portions, and a convenient model for control purposes is developed. Next, Fuzzy Tuning Manipulation Control (FTMC) algorithm is developed, and a Space Free-Flying Robotic (SFFR) system with flexible appendages is considered as a practical case that necessitates delicate force exertion by several end-effectors to move an object along a desired path. The SFFR system contains two cooperative manipulators, appended with two flexible solar panels. The system also includes a third and fourth arm, i.e. a turning antenna and a moving camera. To reveal the merits of the developed model-based controller, the manoeuvre is deliberately planned such that flexible modes of solar panels get stimulated due to arms motion. Obtained results show the effective performance of the proposed approach as will be discussed.
A general robotic mechanism was presented for in-pipe inspection of level pipes with varied diame... more A general robotic mechanism was presented for in-pipe inspection of level pipes with varied diameter or curved pipelines. The robot employed three legs comprised of parallelogram linkages mechanism which enables adapting to various elbow joints in the piping systems. The curvatures in pipeline are the most important constraints in front of the robot through navigation process. To study the adaptability of in-pipe robots to the elbow, geometrical analysis was used to determine the minimum required diameter of an assumed resizable cylinder when it traverses through elbows. The contact points of the cylinder and the elbow are located at the medial longitudinal cross section of the elbow. However, for any designed configuration of the robots, the contact points are located at other longitudinal cross sections. For any elbow joint, a 3D space, so-called " curved pipe limited area " was defined using the minimum required width along all longitudinal cross sections in elbows. The traversing robot should be adaptable to this limited area which is a function of robot's length, pipes' diameter and radius of curvature. A set of computer simulation was used to verify the derived analytical equations. The verified equations in this paper enable designers to confirm the dimensions of the robots for guaranteed traversing through standard elbows in pipeline. In addition to optimizing the robot's dimensions in designing process, the proposed equations can be used for active controlling of robot's diameter when it traverses through elbows.
In this paper the problem of 3D scene and object classification from depth data is addressed. In ... more In this paper the problem of 3D scene and object classification from depth data is addressed. In contrast to high-dimensional feature-based representation, the depth data is described in a low dimensional space. In order to remedy the curse of dimensionality problem, the depth data is described by a sparse model over a learned dictionary. Exploiting the algorithmic information theory, a new definition for the Kolmogorov complexity is presented based on the Earth Mover's Distance (EMD). Finally the classification of 3D scenes and objects is accomplished by means of a normalized complexity distance, where its applicability in practice is proved by some experiments on publicly available datasets. Also, the experimental results are compared to some state-of-the-art 3D object classification methods. Furthermore, it has been shown that the proposed method outperforms FAB-Map 2.0 in detecting loop closures, in the sense of the precision and recall.
The problem of observer design for nonlinear systems has got great attention in the recent litera... more The problem of observer design for nonlinear systems has got great attention in the recent literature. The nonlinear observer has been a topic of interest in control theory. In this research, a modified robust sliding-mode observer (SMO) is designed to accurately estimate the state variables of nonlinear systems in the presence of disturbances and model uncertainties. The observer has a simple structure but is capable of efficient observation in the state estimation of dynamic systems. Stability of the developed observer and its convergence is proven. It is shown that the estimated states converge to the actual states in a finite time. The performance of the nonlinear observer is investigated by examining its capability in estimation of the motion of a two link rigid-flexible manipulator. The observation process of this system is complicated because of the high frequency vibration of the flexible link. Simulation results demonstrate the ability of the observer in accurately estimating the state variables of the system in the presence of structured uncertainties along with different initial conditions between the observer and the plant.
Dimensional synthesis of a parallel robot may be the initial stage of its design process, which i... more Dimensional synthesis of a parallel robot may be the initial stage of its design process, which is usually carried out based on a required workspace. Since optimization of the links lengths of the robot for the workspace is usually done, the workspace computation process must be run numerous times. Hence, importance of the efficiency of the algorithm and the CPU time of the workspace computation are highlighted. This article exerts an improved numerical search method for workspace generation of a Delta robot. The algorithm is based on a methodology applied to a Hexapod manipulator somewhere else, while the improvement utilized here causes a good increase in its speed and efficiency. The results illustrate that the approach is feasible, practical, and more efficient than initial method for the generation and analysis of the workspace of the parallel manipulator, however it is done for a Delta here.
Vol.4, No.1, 2015 by International Journal of Robotics K.N. Toosi University of Technology
Visual Servoing is generally contained of control and feature tracking. Study of previous methods... more Visual Servoing is generally contained of control and feature tracking. Study of previous methods shows that no attempt has been made to optimize these two parts together. In kernel based visual servoing method, the main objective is to combine and optimize these two parts together and to make an entire control loop. This main target is accomplished by using Lyapanov theory. A Lyapanov candidate function is formed based on kernel definition such that the Lyapanov stability can be verified. The implementation is done in four degrees of freedom and Fourier transform is used for decomposition of the rotation and scale directions from 2D translation. In the present study, a new method in scale and rotation correction is presented. Log-Polar Transform is used instead of Fourier transform for these two degrees of freedom. Tracking in four degrees of freedom is synthesized to show the visual tracking of an unmarked object. Comparison between Log-Polar transform and Fourier transform shows the advantages of the presented method. KBVS based on Log-Polar transform proposed in this paper, because of its robustness, speed and featureless properties.
This paper presents the results of a comprehensive study on the efficiency of planar parallel mec... more This paper presents the results of a comprehensive study on the efficiency of planar parallel mechanisms, considering their kinetostatic performance and also, their workspace. This aim is approached upon proceeding single-and multi-objective optimization procedures. Kinetostatic performances of ten different planar parallel mechanisms are analyzed by resorting to a recent index, kinematic sensitivity. Moreover, the greatest possible continuous circle in the constant-orientation workspace of the latter mechanisms is considered as another objective for the optimization procedures. Seeking the set of design parameters which compromises simultaneous optimal values for the two aforementioned objectives, i.e., kinematic sensitivity and workspace, necessitates launching a multi-objective optimization process. The mathematical framework adopted for the optimization problem is based on genetic algorithm. The results of multi-objective optimization are based on the sets of Pareto points, offering the most reliable decisions to reconciliate between some conflicting objectives. To this end, the ten planar parallel mechanisms are sorted into two sets based on their type of actuator, some of them with prismatic actuators and the other ones with revolute actuators. Finally, a comparison between performances of these mechanisms, according to the obtained results, is carried out.
In the procedure of designing an underwater vehicle or robot, its maneuverability and controllabi... more In the procedure of designing an underwater vehicle or robot, its maneuverability and controllability must be simulated and tested, before the product is finalized for manufacturing. Since the hydrodynamic forces and moments highly affect the dynamic and maneuverability of the system, they must be estimated with a reasonable accuracy. In this study, hydrodynamic coefficients of an autonomous underwater vehicle (AUV) are identified using velocity and displacement measurements, and implementing an Extended Kalman Filter (EKF) estimator. The hydrodynamic coefficients are included in the augmented state vector of a six DOF nonlinear model. The accuracy and the speed of the convergence of the algorithm are improved by selecting a proper covariance matrix using the ARMA process model. This algorithm is used to estimate the hydrodynamic coefficients of two different sample AUVs: NPS AUV II and ISIMI. The comparison of the outputs of the identified models and the outputs of the real simulated models confirms the accuracy of the identification algorithm. This identification method can be used as an efficient tool for evaluating the hydrodynamic coefficients of underwater vehicles (robots), using the experimental data obtained from the test runs.
This paper presents the kinematic analysis and the development of a 4-degree-of-freedom serial-pa... more This paper presents the kinematic analysis and the development of a 4-degree-of-freedom serial-parallel mechanism for large commercial vehicle driving simulators. The degrees of freedom are selected according to the target maneuvers and the structure of human motion perception organs. Several kinematic properties of parallel part of the mechanism under study are investigated, including the inverse and the forward kinematics problems, workspace determination, singularity, and kinematic sensitivity analysis. The workspace of the parallel part of the mechanism is obtained by interval analysis. Moreover, using elimination theory, a univariate expression representing the forward kinematics solution of the parallel part is obtained.
In this paper, a nonlinear model of the underactuated six degrees of freedom (6 DOF) quadrotor he... more In this paper, a nonlinear model of the underactuated six degrees of freedom (6 DOF) quadrotor helicopter was derived based on the Newton-Euler formalism. A new nonlinear robust control strategy was proposed to solve the stabilizing and path following problems in presence of external disturbances and parametric uncertainties. The proposed control structure consist of a sliding mode control based on disturbance observer (SMDO) to track the reference trajectory together with a nonlinear H∞ controller to stabilize the rotational movements. Simulation results in the presence of aerodynamic disturbances and parametric uncertainties are presented to corroborate the effectiveness and the robustness of the proposed strategy.
In this paper standing balance control of a biped with toe-joint is presented. The model consists... more In this paper standing balance control of a biped with toe-joint is presented. The model consists of an inverted pendulum as the upper body and the foot contains toe-joint. The biped is actuated by two torques at ankle-joint and toe-joint to regulate the upper body in upright position. To model the interaction between foot and the ground, configuration constraints are defined and utilized. To stabilize the biped around upright position, model predictive control (MPC) is implemented by which the constraints can be incorporate to the optimal control algorithm properly. To assess stability of system and to find domain of attraction of the fixed point, concept of Lyapunov exponents is utilized. Using the proposed control and stability analysis, we studied the effect of toe-joint in improving the stability of the biped and in decreasing actuator demand, necessary for stabilizing the system. In addition, effect of toe-joint is studied in improving domain of attraction of the stabilized fixed pint.
Gait rehabilitation using body weight support on a treadmill is a recommended rehabilitation tech... more Gait rehabilitation using body weight support on a treadmill is a recommended rehabilitation technique for neurological injuries, such as spinal cord injury. In this paper, a new robotic orthosis is presented for treadmill training. In the presented design the criteria such as low inertia of robot components, backdrivability, high safety and degrees of freedom based on human walking are considered. This robot is composed of a leg exoskeleton for leg control and a segment for pelvis control. In the exoskeleton two degrees of freedom are considered for the hip joint and one for the knee joint. Also two degrees of freedom are considered for the pelvis joints. The inertia of moving components and the required force for the robot motion are measured to evaluate the robot backdrivability and transparency. Further, a walking algorithm is implemented on the robot and is tested on a human subject. Evaluation of the design showed that the robot is suitable for gait rehabilitation exercises.
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Vol.4, No.3, 2016 by International Journal of Robotics K.N. Toosi University of Technology
Vol.4, No.2, 2015 by International Journal of Robotics K.N. Toosi University of Technology
Vol.4, No.1, 2015 by International Journal of Robotics K.N. Toosi University of Technology