This project proposes an interval-based approach, to obtain the collision-free workspace of planar parallel mechanisms. This approach is represented through an example for a 3-RPR planar parallel mechanism and 6-UPS spatial parallel mechanisms. Three main feature of the collision-free workspace is taken into account: mechanical stroke of actuators, interference of limbs with the obstacle and interference of end-effector with the obstacle. In this project, a circle shaped obstacle is considered and its mechanical interference with limbs and edges of the end-effector is taken into account.

 

In the most of the works for implementation and control of parallel robots, especially Generally, in parallel robots, solving the forward kinematic problem is much harder than finding the inverse kinematic solution, thus, workspace determination using FKP is a demanding task in most cases. Therefore, in this research, a progressive growing neural gas network algorithm (PGNGN) is proposed, which is a systematic and general approach to obtain the topology of the workspace based on IKP equations.

After establishing a preliminary network with few initial data points, the network starts to develop itself by considering new data points around its border neurons through a boundary data generation procedure.
The proposed algorithm is able to continue learning, adding units and connections, until a performance criterion has been met which leads to a clear workspace topology with minimal errors.

The most important features of this algorithm are the abilities to detect cavities in the workspace, consider singularities and distinguish separated regions of the workspace. Till now, workspace of various parallel robots including 3-RRR, 3-RPR and 3-PRR mechanisms and a Gouph-Stewart platform have been determined. Results reveal the applicability and reliability of this method.

Then upon apply different levels of input voltage on the actuator, different step responses are studied in the presence of dead zone, delay and saturation. Through a linear identification process, a nominal second-order linear model is estimated for the actuator. Based on the identified model, the position (length) of the actuator is controlled by applying some straightforward and reliable control solutions.

 

This project proposes a novel approach to obtain the  maximal singularity-free regions of planar parallel mechanisms which is based on a constructive geometric reasoning. The proposed approach consists of two algorithms. First, the borders of the  singularity-free region corresponding to an arbitrary start point of the moving platform is obtained. Then, the second algorithm aims to find the center of the maximal singularity-free circle which is obtained using the so-called offset curve algorithm.  As a case study, the procedure is applied to a  3-PRR planar parallel mechanism and results are given in order to graphically illustrate the effectiveness of the proposed algorithm. The proposed approach can be directly applied to obtain the maximal singularity-free circle of similar parallel mechanisms, which is not the case for other approaches proposed in the literature which is limited to a given parallel mechanism, namely, 3-RPR. Moreover, as the main feature of  the proposed approach, it can be implemented both in a CAD system or in a computer algebra system where non-convex and re-entrant curves can be considered.

Workspace analysis is one of the most important steps in the procedure of designing industrial robots. The workspace of a robot is defined as the set of all end-effector configurations which can be reached by some choice of joint coordinates.

Various approaches may be used to calculate the workspace of a parallel robot which can be classified by geometrical approaches, discretization method and numerical procedures.

The main features of the geometrical approaches are their fastness and accuracy, which are necessary in efficient calculation of some characteristics of the workspace, such as volume. Moreover, all mechanical and kinematic constraints can be considered using this method.

Using SolidWorks software, the workspace of a 3-DOF decoupled parallel robot, developed in TaarLab, is determined, considering all joint limits and mechanical interface of joints. Since all DOFs are transitional the resulting area is an appropriate representation of the workspace.