Sharif Digital Repository

An autonomous hedge trimmer robot was developed to reduce the harmful effects of traditional hedge trimming method (gasoline-powered hedge trimmer) on operators' bodies and increase the speed and quality of the operation. The robot had five degrees of freedom (PRRRR) structure and was geometrically optimized to simplify the control strategy, enabling it to trim simple, stepped, and circular forms. The control system, consisting of a host computer, servo motors and servo drivers, and controller, guided the robot platform, manipulator, and end-effector as it approached and trimmed the hedge. By using a recognition algorithm and vision-based navigation system, the robot was able to detect the... 

Sophisticated surgeons are widely indicating the use of surgical robots in order to reject human error, increase precision, and speed. Among well-known robotic mechanisms, parallel robots are broadly more investigated regarding their special characters as higher acceleration, speed, and accuracy, and less weight. Specific surgical procedures confine, and restrict their workspace, while controlling and validating the robots are complicated regarding to their complex dynamic. To this end, in this paper, a 6-DOF robot, with rotary manipulators, is designed and controlled. Addressing nonlinearity of parallel robots, an innovative methodology is formulated to robustly penalize the error of... 

Simulation of brittle regime machining of materials (such as ceramics) is often difficult because of the complex material removal mechanisms involved. In this study, the discrete element method is used to simulate the dynamic process for machining of slip-cast fused silica ceramics. Flat-joint contact model is exploited to model contacts between particles in synthetic discrete element method models. This contact model is suitable for modeling of brittle materials with high ratios (higher than 10) of unconfined compressive strength to tensile strength. The discrete element method has the ability to simulate initiation, propagation, and coalescence of cracks leading to chip formation in the... 

We propose a model based on extreme value statistics (EVS) and combine it with different models for single-asperity contact, including adhesive and elasto-plastic contacts, to derive a relation between the applied load and the friction force on a rough interface. We determine that, when the summit distribution is Gumbel and the contact model is Hertzian, we obtain the closest conformity with Amonton’s law. The range over which Gumbel distribution mimics Amonton’s law is wider than that of the Greenwood–Williamson (GW) model. However, exact conformity with Amonton’s law is not observed for any of the well-known EVS distributions. Plastic deformations in the contact area reduce the relative... 

Contact modeling plays a central role in motion planning, simulation and control of legged robots, as legged locomotion is realized through contact. The two prevailing approaches to model the contact consider rigid and compliant premise at interaction ports. Contrary to the dynamics model of legged systems with rigid contact (without impact) which is straightforward to develop, there is no consensus among researchers to employ a standard compliant contact model. Our main goal in this paper is to study the dynamics model structure of bipedal walking systems with rigid contact and a novel compliant contact model, and to present experimental validation of both models. For the model with rigid... 

In recent years, robotic rehabilitation has been utilized in treatment and recovery of patients with disabilities. In this paper, a novel design and kinematic analysis of a 4-DOF robot for upper-limb rehabilitation are proposed. The main novelty of this design is its mechanism for wrist and fingers motions which is added to the shoulder and elbow mechanism without any noticeable weight increase in the moving parts of the robot. For this purpose, a cable driven mechanism is implemented at the robot end-effector to move the wrist and fingers parts, and the corresponding actuators are placed at the base of the robot. © 2018 IEEE  

The position accuracy of the robot end-effector is inherently affected by uncertainties. In order to design and manufacture robots with high accuracy, it is essential to know the effects of these uncertainties on the motion of robots. Uncertainty analysis is a useful method which can estimate deviations from desired path in robots caused by uncertainties. This paper presents an applied formulation for 3D statistical error analysis of open-loop mechanisms and robotic manipulators. In order to have an accurate analysis, uncertainty effects of both the link dimension deviation and the joint clearance in performance of the spatial open-loop mechanisms and the robots are considered. The maximum... 

The purpose of this paper is to design and analyze a 3-link micro-device proposed as a micro-manipulator. This micro-manipulator includes 3 micro-beams as links connected to one another with no conventional or flexural joints. While the structure of the micro-manipulator is monolithic, end-effector workspace is achieved through deflection of links which is actuated by piezoelectric layers. By combining static analysis of the links through a multilayer piezoelectric beam model and kinematic analysis of the micro-manipulator, inverse kinematic has been solved utilizing the Taylor series expansion technique and the perturbation method. The obtained results through the present model reveal that... 

Rehabilitation is the best approach for patients who suffer physical disability of their upper-limbs. Maintaining the intensity of exercise during treatment is the main factor that makes the robots suitable for rehabilitation since robots do not get tired and do the exercises with constant intensity under supervision of the doctor. Two main categories of rehabilitation robots are End-Effector based robots and wearable robots. According to the fact that most problems occur in need of rehabilitation for hand wrist area, in this paper a wearable rehabilitation robot has been developed for the wrist. Nowadays, wearable robots attract more attention than the other group. Wearable robots are... 

In this paper, dynamic modeling and dynamic sensitivity analysis of an n-revolute planar serial robot are investigated. First, a dynamic modeling algorithm is proposed which is based on the concept of the so-called Natural Orthogonal Complement. The main goal of this algorithm consists in deriving the corresponding dynamic equations of a planar serial manipulator systematically. As a comparison study, 3-DOF a planar serial manipulator is modeled and the results of the proposed algorithm is compared with other methods, i.e., Newton-Euler, Lagrange-Euler, Adams software and an Open Dynamics Engine, the so-called MatODE. Then, in order to develop a dynamic sensitivity analysis scheme, Sobol's... 

This paper initially deals with the design of a new customized reconfigurable mobile parallel mechanism. This mechanism is called "Taar Reconfigurable ParaMobile (TRPM)", consisting of three mobile robots as the main actuators. Then, the kinematics and path planning for this mechanism are represented. The newly proposed mechanism is expected to circumvent some shortcomings of inspection operation in unknown environments with unexpected changes in their workspace, e.g., in a water pipe with non-uniform section area. In this paper, "Artificial Potential Field (APF)" has been assumed to be the path planning algorithm and its resulting attractive and repulsive forces are only applied to the... 

This paper deals with the collision-free path planning of planar parallel robot by avoiding mechanical interferences and obstacle within the workspace. For this purpose, an Artificial Potential Field approach is developed. As the main contribution of this paper, In order to circumvent the local minima problem of the potential fields, a novel approach is proposed which is a combination of Potential Field approach, Fuzzy Logic and also a novel algorithm consisting of Following Obstacle as well as Virtual Obstacle methods, as a hybrid method. Moreover, the inverse kinematic problem of the 3-RRR parallel robot is analyzed and then the aforementioned hybrid method is applied to this mechanism in... 

Kinematic accuracy of the robot end-effector is decreased by many uncertainties. In order to design and manufacture robots with high accuracy, it is essential to know the effects of these uncertainties on the motion of robots. Uncertainty analysis is a useful method which can estimate deviations from desired path in robots caused by uncertainties. This paper presents an applied formulation based on Direct Linearization Method (DLM), for 3D statistical uncertainty analysis of open- loop mechanisms and robots. The maximum normal and parallel components of the position error on the end-effector path are introduced. In this paper, uncertainty effects of both linear and angular variations in... 

Surface electromyogram (sEMG) signals, a noninvasive bioelectric signal, can be used for the rehabilitation and control of artificial extremities. Current sEMG pattern-recognition systems suffer from a limited number of patterns that are frequently intensified by the unsuitable accuracy of the instrumentation and analytical system. To solve these problems, we designed a multistep-based sEMG pattern-recognition system where, in each step, a stronger more capable relevant technique with a noticeable improved performance is employed. In this paper, we utilized the sEMG signals to classify and recognize six classes of hand movements. We employed an adaptive neurofuzzy inference system (ANFIS) to... 

Object handling is one of the most important applications of cable-suspended robots, which can be obtained by use of a gripper as its end-effector. In this paper, a novel cable-driven multi-finger gripper assembled on a cable-suspended robot has been presented. Using lock/unlock mechanisms, the under-actuated finger mechanism has been designed to have a human like motion. A cable-suspended robot structure with 3 position degrees of freedom is also proposed by employing active/passive cables in such a way that makes it capable of resisting external moments, while it may be simplified to a spatial point-mass cable robot during positioning operation. Furthermore, the robot workspace has been... 

The use of human hand gestures as a natural interface tool has motivated researchers to conduct research in the modeling, analyzing and recognition of various hand movements. In particular, human computer intelligent interaction has been a focus for research in vision-based gesture recognition. In this work, we introduce a 3D hand model reconstruction method which offers flexible and elaborate representation of hand gestures. We used 20 landmarked points on tips and joints of the fingers and calculated the 3D coordinates of these points through a stereo vision system. Our results show that such reconstruction provides a precise 3D hand model only to be influenced by intrinsic and extrinsic... 

The general problem of impedance control is addressed for a robotic manipulator with a moving flexible base. Impedance control imposes a relation between force and displacement at the contact point with the environment. The concept of impedance control of flexible base moving manipulators (FBMMs) is rather new and is being considered. The dynamic of the manipulator is decomposed into slow and fast dynamics using the singular perturbation method. A new sliding mode impedance control (SMIC) method using an element on the end-effector is proposed for high-precision impedance control of FBMMs. The SMIC method as a robust impedance control law is derived for the slow dynamics. The asymptotic... 

Electromyogram signal (EMG) is an electrical manifestation of contractions of muscles. Surface EMG (sEMG) signal collected from the surface of skin has been used in diverse applications. One of its usages is in pattern recognition of hand prosthesis movements. The ability of current prosthesis devices has been generally limited to simple opening and closing tasks, minimizing their efficacy compared to natural hand capabilities. In order to extend the abilities and accuracy of prosthesis arm movements and performance, a novel sEMG pattern recognizing system is proposed. To extract more pertinent information we extracted sEMGs for selected hand movements. These features constitute our main... 

In this paper, we propose a decentralized control scheme for combined motion/force control of nonredundant multi-manipulator robotic systems, cooperatively grasping a rigid body in a prespecifled position/force trajectory. The proposed control scheme uses the impedance method for modeling the internal force exerted by the end effectors to the object. The precise mathematical analysis of the overall dynamical system and the proposed controller are presented and the stability of the overall system is studied. The proposed controller, then, is applied to a cooperative system composed of two PUMA560 manipulators and the simulation results are presented to verify the proposed control scheme  

Electromyogram (EMG) signal is an electrical manifestation of muscle contractions. EMG signal collected from surface of the skin, a non-invasive bioelectric signal, can be used in different rehabilitation applications and artificial extremities control. This study has proposed to utilize the surface EMG (SEMG) signal to recognize patterns of hand prosthesis movements. It suggests using an adaptive neuro-fuzzy inference system (ANFIS) to identify motion commands for the control of a prosthetic hand. In this work a hybrid method for training fuzzy system, consisting of back-propagation (BP) and least mean square (LMS) is utilized. Also in order to optimize the number of fuzzy rules, a...