Sharif Digital Repository

In this thesis, Optimum Counterweight and Spring Balancing of a novel kind of mechanism called a general 3-RPS parallel robot in Dynamic Motion are investigated. Balancing is explained as the set of configurations on robot inertial and dimensional parameters which, when convinced, certify that the weight of the links produce less force at the actuators for any configuration of the robot, under dynamic or static behaviors. In the references, different procedures have been suggested for balancing that consisted of counterweights, springs, and other auxiliary equipments. Study represents the essential information for having optimum spring and counterweight balancing in a new (3RPS) robot using... 

Legged walking and climbing robots have recently achieved important results and developments, but they still need further improvements and study. The spider modeled as an eight-legged system. Legged robots have a body and a number of articulated legs which originate from the body and are put on the ground to hold robot’s weight or are swinging in the air to their new position. Each leg as a kinematic chain can be viewed as a manipulator that acts like a limb and contributes to the overall position and equilibrium of the structure. In order to evaluate and create an effective legged robot, the idea is to draw inspiration from nature. Spider robots present very good performances in terms of... 

In this thesis, a decentralized controller for trajectory tracking of robot manipulators is developed. Proposed control scheme use uncalibrated joint torque sensors. Recently, it has been shown that the use of joint torque sensing results in a simplified manipulator model and reduce the need of dynamic model of links for controlling. In this thesis, we use the special lower triangular structure of this simplified model for decentralized control of manipulator. For the first time a smooth decentralized law is designed which makes both position and velocity tracking errors of robot manipulators globally converge to zero. Against most of previous work in decentralized control of manipulators,... 

Fault detection and identification is one of the major issues and challenges in the field of engineering and currently is considered as an active field of research. As the replacement of human in dangerous or inaccessible environments, robotic mechanical systems can be used which exposes to a variety of stresses and actions that causes faults in the actuators or sensors. Accordingly, detection of fault at the earliest possible time after the fault accurence and its identification such that real flaw waveform is being extracted, can prevent more damage to the system without any need to human immediate interference. Model based approach in recent decades has shown their ability to detection... 

The problem of point to point repetitive time reduction for the rigid manipulators is a major case in industry especially for applications such as point to point welding and part manipulation. These motions are usually repeated for a large numbers of cycles, so that even a minor economization in time can be hugely significant. Nowadays, the time optimal control problem of manipulator with completed theory, is an appropriate solution of the problem. In recent years, with the expansion of design space to structure design, more satisfactory results can be obtained using this method.
Optimal balancing is a new approach based on the optimal control theory in which the balancing unknowns plus... 

In a typical rigid robot manipulator, joint angels and velocities are often considered as system states. Joint angels are usually measured by precise Shaft Encoders. However, lack of velocity measurement sensors “Tachometers” and their undesired characteristics in most of existing robotic systems make it difficult to have access to full system states. As full access to the system states in various applications is inevitable, velocity observers can be used to reconstruct or estimate the unmeasured velocity signals. This thesis presents an observer for global estimation of joint velocities in robot manipulators. A non-minimal model of a robotic manipulator is introduced to design an... 

The goal of controlling robot manipulators is to perform the mission intended for its end effector. Model-based control is a solution that can achieve the control goal with high speed and accuracy in the presence or absence of environmental obstacles by using the knowledge of the robot model. In this thesis, the Armtin 5 robot model parameters were identified in two steps. In the first step, the gravity and friction parameters and in the second step, the dynamic parameters were estimated. In the estimation of gravity and friction parameters, the non-linear behavior of friction causes the estimated parameters to be accompanied by a large amount of error. Estimation of the parameters was...