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UĞURLU, Regaip Barkan

First Name

Regaip Barkan

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UĞURLU

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Mechanical Engineering

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Now showing 1 - 10 of 45

Open Access
Co-ex: A torque-controllable lower body exoskeleton for dependable human-robot co-existence
(IEEE, 2019-06) Yıldırım, Mehmet Can; Kansızoğlu, Ahmet Talha; Emre, Sinan; Derman, Mustafa; Çoruk, Sinan; Soliman, Ahmed Fahmy; Şendur, Polat; Uğurlu, Regaip Barkan; Mechanical Engineering; ŞENDUR, Polat; UĞURLU, Regaip Barkan; Yıldırım, Mehmet Can; Kansızoğlu, Ahmet Talha; Emre, Sinan; Derman, Mustafa; Çoruk, Sinan; Soliman, Ahmed Fahmy
In this paper, we present our research study concerning the design and development of an exoskeleton that aims to provide 3D walking support with minimum number of actuators. Following a prior simulation study, the joint configuration was primarily determined. In order for the exoskeleton to possess advanced characteristics, the following design criteria were investigated: i) all the actuators (hip/knee/ankle) were deployed around the waist area to decrease leg weight and improve wearability, ii) custom-built series elastic actuators were used to power system for high fidelity torque-controllability, iii) 3D walking support is potentially enabled with reduced power requirements. As a result, we built the first actual prototype to experimentally verify the aforementioned design specifications. Furthermore, the preliminary torque control experiments indicated the viability of torque control.
Open Access
High power series elastic actuator development for torque-controlled exoskeletons
(Springer Nature, 2019) Yıldırım, Mehmet Can; Kansızoğlu, Ahmet Talha; Şendur, Polat; Uğurlu, Regaip Barkan; Mechanical Engineering; Carrozza, M. C.; Micera, S.; Pons, J. L.; ŞENDUR, Polat; UĞURLU, Regaip Barkan; Yıldırım, Mehmet Can; Kansızoğlu, Ahmet Talha
This paper presents the development procedures of a high power series elastic actuator that can be used in torque-controlled exoskeleton applications as a high-fidelity torque source. In order to provide a high torque output while containing its weight, the main objective was to satisfy dimensional and weight requirements within a compact structure. A three-fold design approach was implemented: (i) The torsional spring was designed using finite element analyses and its stiffness profile was experimentally tested via a torsional test machine, (ii) thermal behavior of the actuator was experimentally examined to ensure sufficient heat dissipation, (iii) the fatigue life of the spring was computed to be 9.5 years. Having manufactured the actuator, preliminary torque-control experiments were conducted. As the result, a high-fidelity torque control was achieved with a control bandwidth of up to 12 Hz.
Open Access
Optimal stiffness tuning for a lower body exoskeleton with spring-supported passive joints
(IEEE, 2018-10-09) Yıldırım, Mehmet Can; Şendur, Polat; Soliman, Ahmed Fahmy; Uğurlu, Regaip Barkan; Mechanical Engineering; ŞENDUR, Polat; UĞURLU, Regaip Barkan; Yıldırım, Mehmet Can; Soliman, Ahmed Fahmy
This paper presents a framework to optimally tune the stiffness values of spring-supported passive joints that are included in lower body exoskeletons. First, a dynamic model of a combined human-exoskeleton system was created in MSC.ADAMS software. Second, a gradient-descent based algorithm was used to find the optimum value to minimize the ZMP for a range of ankle stiffness values. In order to corroborate the proposed method, simulation experiments were conducted by considering three cases in which different body mass and heights were assigned to the combined human-exoskeleton system. The simulation results indicate that the proposed methodology is effective in order to find the optimum ankle stiffness for the combined human-exoskeleton systems, resulting in reductions in ZMP variations and therefore increasing the balancing ability. As a consequence, it may be possible to reduce the number of active joints in exoskeletons that aim crutch-free 3-D walking motion support.
Open Access
Variable ankle stiffness improves balance control: experiments on a bipedal exoskeleton
(IEEE, 2016-02) Uğurlu, Regaip Barkan; Doppmann, C.; Hamaya, M.; Forni, P.; Teramae, T.; Noda, T.; Morimoto, J.; Mechanical Engineering; UĞURLU, Regaip Barkan
This paper proposes a real-time balance control technique that can be implemented to bipedal robots (exoskeletons, humanoids) whose ankle joints are powered via variable physical stiffness actuators. To achieve active balancing, an abstracted biped model, torsional spring-loaded flywheel, is utilized to capture approximated angular momentum and physical stiffness, which are of importance in postural balancing. In particular, this model enables us to describe the mathematical relation between zero moment point (ZMP) and physical stiffness. The exploitation of variable physical stiffness leads to the following contributions: 1) Variable physical stiffness property is embodied in a legged robot control task, for the first time in the literature to the authors' knowledge. 2) Through experimental studies conducted with our bipedal exoskeleton, the advantages of variable physical stiffness strategy are demonstrated with respect to the optimal constant stiffness strategy. The results indicate that the variable stiffness strategy provides more favorable results in terms of external disturbance dissipation, mechanical power reduction, and ZMP/center of mass position regulation.
Open Access
ZMP-based online jumping pattern generation for a one-legged robot
(IEEE, 2010-05-01) Uğurlu, Regaip Barkan; Kawamura, A.; Mechanical Engineering; UĞURLU, Regaip Barkan
This paper is aimed at presenting a method to generate online jumping patterns, which can be applied to one legged jumping robots and optionally to humanoid robots. Our proposed method is based on ensuring the overall dynamic balance through the complete jumping cycle. To be able to reach this goal, we discretized the ZMP equation in polar coordinates so that we are able to include angular momentum information in a natural way. Thus, undesired torso angle fluctuation is expected to be more restrainable comparing to other methods in which angular momentum information is ignored or zero-referenced. Moreover, we unified support and flight phases in terms of motion generation. Having obtained successful simulation results and vertical jumping experiments in our previous work, we conducted forward jumping experiments. As the result, we obtained successful and repetitive jumping cycles, which satisfactorily verify the proposed method.
Open Access
Tepki kuvveti gözetleyici tabanlı tork kontrolü
(Gazi Üniversitesi, 2021-12) Özçınar, Erim Can; Uğurlu, Regaip Barkan; Mechanical Engineering; UĞURLU, Regaip Barkan; Özçınar, Erim Can
In this article, a reaction force observer-based torque controller was designed and experimentally implemented to a non-backdrivable actuator unit. Torque control is of importance when considering physical human-robot interaction and researchers usually use torque sensors or custom-built torsional springs. These elements lead to relatively more complicated systems and increase the total weight. In contrast, reaction force observers can estimate external forces acting on the system and thus enable torque control with no need of torque sensing. The estimation process performs better for backdrivable systems, therefore, its implementation to non-backdrivable systems, e.g., systems with a gear ratio of 1:100, is limited. To remedy this issue, a reaction force observer-based torque controller was designed and implemented. As a result, experimental data showed that reaction force observer leads to favorable torque control performance when supported with friction compensation.
Open Access
Torque and variable stiffness control for antagonistically driven pneumatic muscle actuators via a stable force feedback controller
(IEEE, 2015) Uğurlu, Regaip Barkan; Forni, P.; Doppmann, C.; Morimoto, J.; Mechanical Engineering; UĞURLU, Regaip Barkan
This paper describes a novel controller that is capable of simultaneously controlling torque and variable stiffness in real-time, for actuators with antagonistically driven pneumatic artificial muscles (PAMs). To this end, two contributions are presented: i) A stable force feedback controller that can cope with inherent PAM nonlinearities is synthesized using the dissipativity theory, for each PAM unit. ii) On top of this force feedback controller, a mathematical formulation is developed to compute reference force inputs that correspond to desired joint torque and joint stiffness inputs, concerning both agonist and antagonist PAMs. This strategy enables us to introduce real-time sensory feedback; torque and stiffness control is addressed by means of PAM force feedback control with guaranteed stability. To validate the proposed control scheme, a series of experiments were conducted on an experimental setup. As the result, the controller exhibited favorable torque and stiffness tracking in real-time, demonstrating that it could meet the performance criteria to power exoskeleton systems.
Metadata only
Design and development of a durable series elastic actuator with an optimized spring topology
(Sage, 2021-12) Yıldırım, M. C.; Şendur, Polat; Kansızoğlu, Mehmet Taha; Uras, U.; Bilgin, Onur; Emre, Sinan; Yapıcı, Güney Güven; Arık, Mehmet; Uğurlu, Regaip Barkan; Mechanical Engineering; ŞENDUR, Polat; YAPICI, Güney Güven; ARIK, Mehmet; UĞURLU, Regaip Barkan; Kansızoğlu, Mehmet Taha; Bilgin, Onur; Emre, Sinan
This paper aims to present the integrated design, development, and testing procedures for a state-of-the-art torsion-based series elastic actuator that could be reliably employed for long-term use in force-controlled robot applications. The main objective in designing the actuator was to meet weight and dimensional requirements whilst improving the long-term durability, ensuring high torque output, and containing its total weight. A four-fold design approach was implemented: (i) following recursive design-and-test procedures, an optimal torsional spring topology was unveiled with the help of SIMP (Solid Isotropic Material with Penalization) topology optimization method, (ii) the proposed spring was manufactured and multiple specimens were experimentally tested via a torsional test machine to validate linearity, loading rate response, and mechanical limits, (iii) the actuator’s thermal response was experimentally scrutinized to ensure that the generated heat was dissipated for long-term use, and (iv) the fatigue life of the spring was computed with the help of real-life experiment data. Having concluded the development and verification procedures, two different versions of the actuator were built, and preliminary torque control experiments were conducted. In conclusion, favorable torque tracking with a bandwidth of 19 Hz was achieved while peak-to-peak torque input was 20 Nm.
Open Access
A stability analysis for the acceleration-based robust position control of robot manipulators via disturbance observer
(IEEE, 2018-10) Sarıyıldız, E.; Sekiguchi, H.; Nozaki, T.; Uğurlu, Regaip Barkan; Ohnishi, K.; Mechanical Engineering; UĞURLU, Regaip Barkan
This paper proposes a new nonlinear stability analysis for the acceleration-based robust position control of robot manipulators by using disturbance observer (DOb). It is shown that if the nominal inertia matrix is properly tuned in the design of a DOb, then the position error asymptotically goes to zero in regulation control and is uniformly ultimately bounded in trajectory-tracking control. As the bandwidth of a DOb and the nominal inertia matrix are increased, the bound of error shrinks, i.e., the robust stability and performance of the position control system are improved. However, neither the bandwidth of the DOb nor the nominal inertia matrix can be freely increased due to practical design constraints, e.g., the robust position controller becomes more noise-sensitive when they are increased. The proposed stability analysis provides insights into the dynamic behavior of DOb-based robust motion control systems. It is theoretically and experimentally proved that non-diagonal elements of the nominal inertia matrix are useful in improving the stability and in adjusting the tradeoff between robustness and noise sensitivity. The validity of the proposal is verified by simulation and experimental results.
Metadata only
Simulation-based design and locomotion control implementation for a lower body exoskeleton
(IEEE, 2022) Derman, Mustafa; Soliman, Ahmed Fahmy; Kuru, Alihan; Çevik, Süleyman Can; Ünal, Ramazan; Bebek, Özkan; Uğurlu, Regaip Barkan; Mechanical Engineering; ÜNAL, Ramazan; BEBEK, Özkan; UĞURLU, Regaip Barkan; Derman, Mustafa; Soliman, Ahmed Fahmy; Kuru, Alihan; Çevik, Süleyman Can
This paper proposes a simulation-based design and locomotion control methodology for an exoskeleton that is aimed at providing assistance to users with ambulatory difficulties. To increase the power-to-weight ratio while satisfying design constraints, we made use of simulation tools to recursively update the initial mechanical design for a finer solution. To this end, a coupled human-exoskeleton model was constructed in MSC ADAMS environment using an average human model and the initial design of the robot. Following this step, dynamic walking control simulations were carried out to determine actuator torques and loading. Using the loading data obtained via simulation experiments, certain mechanical links were optimized such that the portions with no stress concentration were removed without violating safety. Finally, two distinct control implementations were conducted: i) stand-to-sit motion, ii) dynamic walking. As a result, we obtained dynamically consistent motion behavior for both cases, adequately validating the proposed methodology.