Browsing by Author "Soliman, Ahmed Fahmy"

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Open Access
3-D dynamic walking trajectory generation for a bipedal exoskeleton with underactuated legs: A proof of concept
(IEEE, 2019-06) Soliman, Ahmed Fahmy; Şendur, Polat; Uğurlu, Regaip Barkan; Mechanical Engineering; ŞENDUR, Polat; UĞURLU, Regaip Barkan; Soliman, Ahmed Fahmy
This paper presents a framework to address three dimensional (3-D) dynamic walking for a bipedal exoskeleton with underactuated legs. To achieve this goal, the framework is constructed via a trajectory generator and an optimized inverse kinematics algorithm that can cope with underactuation. In order to feasibly attain task velocities with underactuated legs, the inverse kinematics algorithm makes use of a task prioritization method via the exploitation of null space. In doing so, the tasks with lower priority, e.g., swing foot orientation, are attained as much as possible without disrupting the higher priority tasks, such as CoM trajectory. Meanwhile, the trajectory generator utilizes the ZMP concept analytically and ensures the acceleration continuity throughout the whole walking period, regardless of the contact and phase changes. The proposed method is verified via a lumped human-bipedal exoskeleton model that is developed and simulated in MSC.ADAMS simulation environment. As a result, we obtained feasible and dynamically balanced 3-D walking motion, in which no oblique foot landing or exaggerated torso orientation variations were observed, despite the underactuated nature of the robot legs.
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
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.
Metadata only
Robust locomotion control of a self-balancing and underactuated bipedal exoskeleton: Task prioritization and feedback control
(IEEE, 2021-07) Soliman, Ahmed Fahmy; Uğurlu, Regaip Barkan; Mechanical Engineering; UĞURLU, Regaip Barkan; Soliman, Ahmed Fahmy
This letter presents a study to understand how an underactuated bipedal exoskeleton with an arbitrary human user can exhibit robust dynamic walking behavior despite severe parameter uncertainty and external disturbances. Unlike in the case of classical bipedal robots where each leg possesses 6 or more active joints, it is very challenging to satisfy multiple constraints simultaneously to ensure robust dynamic walking. To overcome this problem, we first propose an optimization algorithm that makes use of a prioritized stack of tasks to satisfy the constraints hierarchically. Furthermore, we synthesized a locomotion controller named ZMP impedance feedback and identified two other state-of-the-art locomotion controllers (admittance control, centroidal momentum control) all of which were built on top of the proposed task prioritization algorithm. In order to verify the validity and robustness of these controllers for a thorough benchmarking, a series of simulation experiments were conducted via MSC ADAMS in which a human-robot coupled model with a 40 kg underactuated exoskeleton and 12 distinct anthropomorphic subjects (66 similar to 102 kg) was considered. As the result, all 3 controllers showed adequate performances to address balanced locomotion behavior when used with the proposed task priority-based optimization algorithm. In addition, the proposed ZMP impedance controller showed statistically significant results, indicating its comparatively more robust feature.
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.
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Towards crutch-free 3-D walking support with the lower body exoskeleton Co-Ex: Self-balancing squatting experiments
(Springer, 2022) Coruk, Sinan; Soliman, Ahmed Fahmy; Dalgıç, Oğuzhan; Yıldırım, M. C.; Uğur, Deniz; Uğurlu, Regaip Barkan; Mechanical Engineering; UĞURLU, Regaip Barkan; Coruk, Sinan; Soliman, Ahmed Fahmy; Dalgıç, Oğuzhan; Uğur, Deniz
In this paper, we succinctly present the hardware properties and capabilities of the lower body exoskeleton Co-Ex, which was developed to attain self-balancing and crutch-free walking support for those experiencing ambulatory difficulties in general. To provide full 3-D walking support while containing the number of required actuators, it includes 4 active joints per leg. Custom-built series elastic actuators enable the torque sensing and controllability at each joint, enhancing the robot’s physical interaction capabilities. While limiting the number of active joints minimizes the weight and energy requirements, the underactuated leg configuration increased the computational load. The preliminary squatting experiments revealed that Co-Ex may provide crutch-free 3-D movement support.