DELTA ROBOT INTRODUCTION 1.1

CHAPTER 1 : INTRODUCTION 1.1

 INTRODUCTION

 There are essentially two types of robot manipulators: serial and parallel. Serial manipulators consist of a number of links connected in series to one another to form a kinematic chain. Each joint of the kinematic chain is usually actuated. This type of structure is known as an open chained mechanism. Parallel manipulators, on the other hand, consist of a number of kinematic chains connected in parallel to one another. The kinematic chains work in unison to move a common point. This common point usually consists of a manipulator that performs a certain task. For sake of a 3 DOF1 parallel DELTA robot system which is the main objective of this project, the common point will also be referred to as the end effector. Since the kinematic chains are eventually connected to a common point, a parallel manipulator is considered a closed chained mechanism. The actuators in parallel manipulators are usually located at the base or close to the base of the system, which is in stark contrast to serial manipulators which have actuators at every joint [1]. To illustrate this point consider Figure.1-1.a shows a parallel-architecture robot, used for object loading and unloading. Figure.1-2 shows a SCARA-type serial-architecture robot. By comparing the images it is easy to appreciate the difference between the two types of architecture. In the case of the serial manipulator greater robustness is required, as each link carries not only the weight of the successive links but also the motors and payload. This creates a cantilever effect in each link and, as a result, a greater deformation overall. In contrast, in the parallel architecture the actuators are fixed to the base of the manipulator so that the weight of the motors is not supported by the kinematic chains. In addition, the payload is distributed among the kinematic chains that con-form the manipulator. This leads to thinner and lighter kinematic chains, which in turn results in an increased payload capacity of the manipulator, relative to its total mass.

Figure 1-1- (a) Hexapod Parallel Robot, (b) CODIAN Robotics Parallel robot