جستجوی مقالات مرتبط با کلیدواژه « exoskeleton » در نشریات گروه « مکانیک »

Wearable mechanisms and robots are designed to improve human performance and body shape, and their design aims to help humans interact better with the environment. By using this human-connected mechanism, it is possible to help disabled people in more appropriate performance of movement activities such as walking, sitting and standing up, as well as in lifting objects that they are normally unable to lift. Improving a person's performance can include less fatigue in performing activities, protection against physical injuries resulting from heavy work, a person's capacity to carry more load, or a higher speed in performing movements. The upper body exoskeleton robotic mechanism (UBER) is designed as an easy-to-wear, flexible and adjustable mechanism to prevent common injuries, musculoskeletal, spinal and joint diseases. The purpose of developing this mobility aid robot for a skilled worker is to perform specialized tasks such as assembly operations in a production line in a relatively long period of time, with less fatigue and also to use the tools he needs easily. The stress and strain analysis performed with a load of 5 kilograms shows that the arm, in addition to bearing the weight of the user's hand, can also move a load of up to 3 kilograms. Considering the range of motion of the designed robot and the number of degrees of freedom, using this robot in the long term will maintain the skeletal health of the skilled worker, thus increasing production efficiency by reducing labor health costs.

The Creation of reference trajectories and the ability to track them in the presence of disturbances and uncertainties are important issues in investigating the exoskeleton performance. One of the methods of trajectory planning is the central pattern generation algorithm. This algorithm will behave in a limit cycle and the temporal disturbances have quickly removed the system and create harmonious trajectories. In this paper, for the creation of reference trajectories of each joint, a combination of seven modified Hopfield oscillators is used which provides the ability to change the frequency and domain of walking. Online modification of robot joint reference trajectories is done by using the feedback error signal between desired zero momentum point and zero momentum point of the robot at any moment. In order to cope with the disturbances and uncertainty with the uncertain domain and achieve maximum efficiency in tracking robot reference trajectories, an adaptive dynamic fast terminal sliding mode controller is used due to the elimination of chattering phenomena, and finite-time convergence. Also, by moving the Upper link the maximum stability of the robot based on zero momentum point criterion is guaranteed. To achieve maximum performance, controller parameters, oscillator coefficients, and connections between them are optimized. Finally, the performance of the proposed method is compared with a sliding mode controller. The results demonstrate the superiority of the proposed method.

In the nearly six decades, exoskeletons have progressed from the stuff of science fiction to nearly commercialized products. In addition, the main part in usage of these robots in the medical sciences and particularly for the rehabilitation, specially disabled and elderly people is to help them to do their basic routine activities like walking, sitting and etc. This article represents the design process of a lower limb exoskeleton robot for helping disable people in gait cycle. First, the conceptual design of 7 Degrees of Freedom (DoFs) robot, consist of 3-DoFs in each leg and 1-DoF in hip joint, is presented. Then the dynamic modeling of mechanical system is shown by Lagrange Method. In addition to producing an optimized mechanical model of the exoskeleton, it was necessary to ensure the strength of each component. So that after the force analyzing of the robot components which are designed for the lower limb extremities, the physical output information of the modeling software (CATIA) is used as the dynamic model input and also in order to obtain motion equation in the gait cycle always needed to choose an appropriate coordinate for simulating closer to reality. In continuation of discussion a combined controller is designed to investigate its performance. Finally the system results are shown the maximum torque of 1st joint is 32 N.m, the 2nd joint is 13 N.m and the 3rd joint is 3 N.m. The maximum torques lead to select the suitable actuator for each link of robot.

In this paper, finite-time active fault tolerant control based on adaptive back-stepping nonsingular fast integral terminal sliding mode control is proposed to control a lower limb exoskeleton in the presence of actuator fault. In order to detect, isolate and accommodate the actuator fault, a third-order super twisting sliding mode observer is used. To eliminate the chattering of conventional sliding mode, supper twisting sliding mode algorithm is applied, which leads to finite-time convergence and high precision in tracking the desired trajectories. Back-stepping term guarantees global stability based on Lyapunov theory. Upper limb motion is used to provide stability to robot's motion based on zero-moment point criterion. In order to attain maximum stability based on zero-moment point, minimize error in tracking the desired trajectories, increase the tolerance of the controller against actuator fault, controller, observer and upper limb trajectory parameters are optimally tuned based on harmony search algorithm. Performance of the proposed controller is compared with the performance of sliding mode controller with/without fault information. Simulation results reveal the effectiveness of the proposed controller in the presence of actuator fault, uncertainty and disturbance in comparison with sliding mode controller.

Hands are complex moveable organs of the human body. some reasons such as stroke can cause the hands disordering. These patients have problem doing their daily routines. Communication between human and robots lead to inventing devices to improving ability. This paper aims to design and prototype a portable wearable robot. This robot has been designed to facilitate the daily routines of patients who are not able to extend their hands. Researchers are facing challenges like high cost due to numerous actuators and innumerous sensors used to control the system. As the number of elements used to build the device increase, the ultimate weight of the device, also, grows, and practically it loses portability. According to the importance of portability of the robot and the need for long-term use by the user, device components with less weight are designed in this work. In this regard, in the introduced mechanism, a torque is applied to the lowest metacarpophalangeal joints simultaneously by only one electric operator; therefore, fingers are opened. The power transmission system is inspired from the hand tendon with the help of the cable length changes. Because of disturbances and nonlinearity of the system, sliding mode controller to minimize the error is designed. The results demonstrate that the joint angle converges to the desired angle, and the error tends to zero. Good results of the practical test, in addition to being low cost, and weight imply that we can trust the extensibility of this project.

Disturbance and bounded uncertainty are the most important factors which can be degrade efficient performance of the lower limb exoskeleton. While sliding mode control is a robust control approach against such disturbances, however, by applying the boundary layer in spite of chattering phenomenon, robust performance becomes feeble. In order to overcome this drawback, high order sliding mode algorithms like supper twisting has been proposed in which, chattering phenomenon is mitigated by eliminating the boundary layer. In this paper, an adaptive supper twisting sliding mode control is proposed for a lower limb exoskeleton robot in which the sliding variable and its derivative tend to zero continuously in presence of the disturbance and bounded uncertainty. In addition, the desired trajectory of the upper limb is determined so that in each moment the stability of the robot is guaranteed based on zero momentum point criterion. To achieve maximum stability and minimum error in tracking of the desired trajectories, the controller parameters and the upper limb desired trajectory parameters are optimized using the Harmony Search algorithm. Robot is modeled in ADAMS and then control inputs are applied to the Adams model. Finally, Performance of two controllers is compared. Simulation results reveal the performance of the proposed controller is better than the optimal sliding mode controller.

Reference trajectory tracking and guarding against system disturbances and uncertainties are the important factors in the realm of lower limb exoskeleton robots control. Sliding mode PID is one of the robust controllers, which has a sliding manifold in the form of the PID controller. Chattering is the substantial predicament of the PIDSMC so that boundary layer around the sliding manifold is applied to eliminate the phenomenon. In this step, not only the chattering phenomenon is not eliminated but the robustness of the controller is also mitigated. In this study, supper twisting PID sliding mode controller (STPIDSMC) was used to eradicate the chattering phenomenon and enhancing controller robustness. The STPIDSMC robustness is protected indigenously and without defining the boundary layer, and the chattering phenomenon is reduced. Furthermore, to meet the external disturbances and uncertainties with unlimited amplitude, adaptive active force control method is combined by STPIDSMC as a modifying input control loop. In the active force control approach, the control input is online modified based on the estimation of moment inertia of the robot links. In order to accomplish maximum performance, control parameters were optimized using harmony search algorithm. In the optimal state, the performance of the proposed controller has been compared with PIDSMC and STPIDSMC that revealed the priority of the proposed controller rather than other controllers. The results indicate that the three error criteria, ITAE, ITASE, and IASE experience significant reduction about 39, 48, and 66 percent respectively compared to STPIDSM.

This paper presents a comprehensive process of designing series elastic actuators to be used in active joints of assistive exoskeleton robots. In this process, the stiffness parameter of torsional spring is selected based on two main criteria to satisfy all the requirements of human motions. The first criterion is an appropriate frequency response for the actuator, according to human motion needs. The second criterion is to provide a sufficient protection of actuator hardware against collision and impact. By determining the desired value for the stiffness parameter, spring architecture is designed to have sufficient mechanical strength and provide the desired stiffness in practice while occupying a minimum space. Along with motor and gearbox, the designed spring is assembled in a module to be used in active joints of exoskeleton robots. The module is designed in a way that the spring can be detached easily and the motor and gearbox can be used as a stiff actuator as well. The considerations in the optimization of the spring and in the design of the module has led to a very compact series elastic actuator which can be used in different human motions such as stair ascend and descend, sit to stand and walking.

Due to the various injuries that because of exercise or stroke occur to people and require rehabilitation treatments the presence of a wearable robot is important. In this paper, assistive robot is designed that consists of a six-bar mechanism. This mechanism has one degree of freedom and is used to perform radial /ulnar movement of the wrist and moves in the form of parallel with the person's body. The design of the robot is somehow that the dimensions of the robot are proportional to the patient's hand, and also provides the natural movement of the hand and helps the patient to perform movements until his recovery .At first by doing the experimentation the direction of movement for doing the radial /ulnar motion was obtained and then the appropriate mechanism was selected and in terms of Kinematics and dynamics have been studied and the accuracy of the obtained equations is evaluated.

External disturbances and internal uncertainties with an unknown range, as well as the connection between the human body and robot, are major problems in control and stability of exoskeleton robots. In order to deal with disturbances and uncertainties with the known range of the system, the sliding mode controller is used as a robust approach. The chattering phenomenon is one of the drawbacks of sliding mode controller, which boundary layer is employed to reduce the effects of this phenomenon. In this case, not only the chattering phenomenon is not completely eliminated, but the robust characteristics of the controller are mitigated. In this paper, in order to cope with the disturbances and uncertainties with unknown range, and guard against chattering as a key ingredient of excessive energy consumption and convergence rate reduction, optimal adaptive high-order super twisting sliding mode control has been applied. The dynamic model of a lower limb exoskeleton robot is extracted using the Lagrange method in which four actuators on the hip and knee joints of the left and right legs are considered. To achieve optimal performance, controller parameters are determined using Harmony Search algorithm by minimizing an objective function consisting of ITAE and control signal rate. The proposed controller performance is compared with optimal adaptive supper twisting sliding mode and optimal sliding mode controllers which shows the superiority of the optimal adaptive high-order sliding mode controller rather than other designed controllers.

Anthropomorphic robotic hand has always been one of the interesting topics for researchers in recent decades due to its application range, including space exploration, medicine, military, etc. In this paper, a new plan is designed to drive exoskeleton fingers and by means of which the fingers can not only mimic human-like movements, but also be lightweight and portable. In this way, before implementation of the new plan, the anatomy of index finger and related kinematic were studied to give a hand to the extraction of angle relationships among distal, middle, and proximal phalanges. In upcoming step, theories, and mathematical relations about replacing sheaths and its influence on bending joints, based on the coupling mechanisms, were explained and applied clearly. Additionally, considering extracted relationships and equations in prior section, a new model of robotic finger with mentioned properties was simulated in MSC ADAMS software. In following step, after linking the software with Matlab, the results of the simulation and comparing them with human finger in the configuration and generation of humanoid movements were discussed. In the last step, according to simulation results, an example was constructed and presented, using a 3D printer in accordance with the proposed mechanism.

Lower extremity exoskeleton a motion assistive technology, has been developed in recent years. Generation of gait pattern is a fundamental topic in design of these robots. A usual approach in most of exoskeletons is to use a pre-recorded pattern used as look up table. There are some deficiencies in this method, including data storage limitation and poor regulation according to walking parameters. Therefore, it is required to modeling human walking pattern to use in exoskeletons. There are simple models for walking of healthy person and humanoid robots. Nevertheless, using these models may cause injury to joints of the patient or damage to robot motors due to physical limitation of the user’s body. In this paper, the physical limitations are represented as mathematical constraints. Considering these constraints, appropriate models are proposed for position of the joints. Then, inverse kinematics equations are used to generate joints angles. In this work, the model parameters consist of stride length and height, walking speed and length of user thigh and shin. The performance of the model is evaluated by implementing on Exoped robot. Satisfaction and convenience of the users demonstrates the good performance of the model.

Nowadays the exoskeleton, known as a useful device in robotic rehabilitation and elderly assistance, has been attracted the attention of many researches. One of the most important feathers of the exoskeleton robots are the compliant interaction with patient. The Series Elastic Actuators (SEA) not only interact with human compliantly but also provide several advantaged such as torque measurement and torque control. The pervious researches have used an inner position loop and an outer force loop. In this paper, the motor and power transmission model is also integrated in the controller design. In this paper, the parameters of the SEA, motor and links are identified firstly. Then, two model-based torque control is designed and introduced based on the velocity and current commands. In contrast to previous researched, the controller is proposed for the locked and free condition and the Lyapunov stability analysis is presented. Finally, the experimental validation test on the Sharif lower limb exoskeleton is presented for these controller. The experimental results of the controller show that the accuracy of torque control based on the current and velocity is 1.2 and 0.2 N.m, respectively.

Gait rehabilitation using body weight support on a treadmill is a recommended rehabilitation technique for neurological injuries, such as spinal cord injuries. Over the last few years, the use of robots in gait rehabilitation has been considered. The robots can substitute physiotherapy training, and are particularly suitable when the exercise is very intensive. Moreover, robots can reduce therapist intensity and the exercise time can be increased. This paper introduces a new robotic orthosis for the automation of treadmill training. The robot design basis is body weight supported treadmill training (BWSTT). In doing So, a part of the body weight is balanced using a supporting system. Then, the patient is placed on the treadmill and the walking algorithm is applied to the leg using an exoskeleton to perform the rehabilitation exercises. In the design, many criteria such as the 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 degree of freedom for the knee joint and two degrees of freedom are considered for the pelvis. Different tests are designed to investigate the performance of the robot. Measuring the inertia of this robot reveals that it exhibits less resistive forces compared to other existing rehabilitation robots. Furthermore, different walking algorithms of a healthy human are applied to the robot with an artificial leg on a treadmill. Primitive tests, with artificial legs and healthy humans, indicate that the robot has enough capability of fulfilling the walking algorithms. It can be concluded that the presented robot has the necessary design criteria, such as suitable degrees of freedom, low inertia and high safety, and so, is suitable for use in gait rehabilitation exercises.