Sharif Digital Repository

This paper presents inverse dynamics equations for a 3-UPS mechanism using virtual work principle. This mechanism has three UPS legs connecting the base to a triangular platform. By changing the orientation of leg's actuators a non-symmetric mechanism with a suitable workspace near the origin without any singularity is obtained. Direct and inverse kinematics Jacobian matrices of the mechanism are obtained by the Newton-Euler approach. Then the inverse dynamics problem is solved using the principle of virtual work, so that the force and torque of active actuators have been obtained by having external forces (force and torque) acted on the platform. Force analysis of the 3-UPS mechanism has... 

A method is presented to synthesize 5 degrees of freedom (DoFs) of 3 translational and 2 rotational (3T2R) parallel kinematic structures. This method is based on the theory of linear transformation and geometrical analysis. Central to this method is a set of novel 5 DoFs 3T2R parallel mechanisms (PMs). Based on the legs configuration, the generated mechanisms are classified. Moreover, the promising mechanisms of each class are introduced with respect to some criteria, i.e.: (a) degree of coupling between the actuators and degrees of freedom; (b) easy kinematics and control command; (c) easy construction (or low cost construction); and, (d) manufacturability. With reference to these criteria,... 

Workspace of a mechanism is generally defined as the region of space which end-effector of that mechanism can reach. Determination of workspace is an important task in the design of a mechanism. However, for parallel mechanisms, due to the complexity of solving the forward kinematic equations, determination of workspace is much more complicated than for serial mechanisms. In the literature, time-consuming numerical methods, such as point-by-point searching, are usually employed for this purpose. In this paper, an optimization-based algorithm is introduced for the boundary determination of inclusive and constant orientation workspaces of parallel mechanisms. In the proposed algorithm, thanks... 

In this paper, we propose a new 6-DOF parallel mechanism. Due to the fact that degrees of freedom in this robot outnumber the number of kinematic chains, it is not a fully parallel mechanism. This results in a weight and inertia reduction and better dynamic performance, making it ideal for haptic and pole climbing applications. The fact that the mechanism is open on one side enable it to wrap around a pole from one side minimizing the center of gravity distance from the pole and the resulting gripping moments. Both inverse and forward Kinematic and dynamic analysis of the proposed mechanism is addressed. Workspace of the mechanism is compared to that of the Stewart's mechanism and the... 

In this article kinematic analysis of a 3 Leg-Spherically Actuated (3SA) parallel manipulator will be addressed. Since each leg has a spherical actuator (three inputs for each leg) and manipulator has three legs; totally, there are nine inputs. Due to the fact that the manipulator has six degree of freedom, only six independent inputs are needed. Thus actuation could be done in different ways. If the triangles representing base and platform are equilateral, there are twenty different ways of actuation that should be studied during forward kinematic analysis. Rather than adopting the standard Denavit-Hartenberg approach, a simple method for forward kinematic analysis for all these different... 

The objective of this paper is designing, modeling and wrench feasible workspace analysis of a 3D cable suspended robot as IRPM (Incompletely Restrained Positioning Mechanism). This type of robots supports a load platform in space by less than or equal to six spatially arranged cables. We use the model of 6 cables spanned in the same manner as a Stewart parallel mechanism. This mechanism is suitable for the accurate positioning of heavy loads. Concentrating on the operations of heavy loads handling, studying the workspace and ways of increasing it is of high importance. Several workspaces exist amongst which the constant and total orientation statically reachable combined and wrench feasible... 

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... 

This paper initially deals with the design of a new customized reconfigurable mobile parallel mechanism. This mechanism is called the 'Taar Reconfigurable ParaMobile' (TRPM), consisting of three mobile robots as the main actuators. Then, the kinematics and path planning for this mechanism are presented. The newly proposed mechanism is expected to circumvent some shortcomings of inspection operation in unknown environments with unexpected changes in their workspace, for example, in a water pipe with a non-uniform cross-sectional 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... 

The N-3 Revolute-Prismatic-Spherical (N-3RPS) manipulator is a kind of serial-parallel manipulator and has higher stiffness and accuracy compared with serial mechanisms, and a larger workspace compared with parallel mechanisms. The locking mechanism in each joint allows the manipulator to be controlled by only three wires. Modeling the dynamics of this manipulator presents an inherent complexity due to its closed-loop structure and kinematic constraints. In the first part of this paper, the inverse kinematics of the manipulator, which consists of position, velocity, and acceleration, is studied. In the second part, the inverse and forward dynamics of the manipulator is formulated based on... 

The N-3 Revolute-Prismatic-Spherical (N-3RPS) manipulator is a kind of serial-parallel manipulator and has higher stiffness and accuracy compared with serial mechanisms, and a larger workspace compared with parallel mechanisms. The locking mechanism in each joint allows the manipulator to be controlled by only three wires. Modeling the dynamics of this manipulator presents an inherent complexity due to its closed-loop structure and kinematic constraints. In the first part of this paper, the inverse kinematics of the manipulator, which consists of position, velocity, and acceleration, is studied. In the second part, the inverse and forward dynamics of the manipulator is formulated based on... 

The N-3 Revolute-Prismatic-Spherical (N-3RPS) manipulator is a kind of serial-parallel manipulator and has higher stiffness and accuracy compared with serial mechanisms, and a larger workspace compared with parallel mechanisms. The locking mechanism in each joint allows the manipulator to be controlled by only three wires. Modeling the dynamics of this manipulator presents an inherent complexity due to its closed-loop structure and kinematic constraints. In the first part of this paper, the inverse kinematics of the manipulator, which consists of position, velocity, and acceleration, is studied. In the second part, the inverse and forward dynamics of the manipulator is formulated based on... 

A robotic system with 6 DOF mobility was proposed for reduction of femoral shaft fractures based on Stewart platform. A plan for implementing the platform on bone fragments was introduced and a step by step strategy for performing the reduction procedure, based on the system's inverse kinematic solution, was proposed. The efficacy of the system was evaluated in some case studies and it was shown that it can be locked to act as an external fixator