**1. Introduction**

124 Serial and Parallel Robot Manipulators – Kinematics, Dynamics, Control and Optimization

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Wiley & Sons

Vol. 124, Issue 3, 725-733

15–18, Montreal, Quebec, Canada

The robot presented in this chapter is a new binary hybrid (parallel-serial) type climbing system composed by several closed-chains arranged in an open-chain. The originality of the robot resides in the possibility of combining several parallel modules to build a new configuration of the robot according to the intended application. In this chapter, one possible morphology will be covered, destinated to climb metallic cross-linked structures, but we will also study the kinematics and the structure of the simplest modules apart from the final robot.

Hybrid climbing robots are hard to find, but hybrid climbing robots with binary actuators are still less common. In our opinion, binary actuators are interesting, since they allow for an easier control of the robot: only two different positions need to be controlled. This advantage comes at a price, since less points in the workspace can be reached, but hereby, large motion workspace, small volume and multiple degrees of freedom will be some of the new challenges of this kind of robots (Lichter et al., 2002).

In the robot proposed in this chapter, the activation of every lineal actuator of the closedloop generates a planar and rotational movement of the output link respect to the input one. Several parallel modules can be connected in a serial mode. In this sense, the robot is freely reconfigurable, thus, new modules (translational or rotational) can be added.

A great variety of applications can be reached with the final 2+2 closed-chain disposed in a serial mode proposed system.

As it was mentioned above, it is possible to build complex structures combining parallel modules. Attending some researches, it is not difficult to find many papers of climbing or walking robots (Qi et al., 2009; Nagakubo & Hirose, 1994; Aracil et al., 2006b), but mostly adopt serial mechanism, what makes them less robust and with compromised stability. However, few authors have researched about the use of the hybrid mechanisms to add the desired characteristics with a simple and sensor-less control (Lichter et al., 2002; Chen & Yeo, 2002; Lees & Chirikjian, 1996; Erdmann & Mason, 1988; Goldberg, 1989; Craig, 1989).

The mechanism proposed combines parallel modules to set up a climbing robot, in addition with improve the mentioned characteristics, to outfit the robot with best stability and strength.

Another main feature that contributes originality compared with the related works of similar robots, it is aimed to a discrete workspace. Also we will demonstrate that it is possible to reach enough points to accomplish the required application (climb metallic

Design and Postures of a Serial Robot Composed by Closed-Loop Kinematics Chains 127

Similar to parallel robots (Aracil et al., 2006a) this robot can climb the exterior and interior of tubes or metallic structures. According to the kind of structure, the end-effector and the base

In this chapter, we do not dedicate attention to the fixation system of the end-effector and base of the robot, although a suction pad or magnetic feet are recommended. We are going

As it was introduced above, the main goal of this project was to assemble different parallel modules to set up some new more complex serial ones. All of the linear actuators will be binary, and they will work into ON (stretched)/OFF (shrunken) position, to accomplish a

The purpose of this section will be the kinematics study of the closed-chain module, two closed-chain modules to set up a planar serial module, and the 2+2 closed-chain modules to set up a serial open-chain for three-dimensional movements. Another types of structures are

If we focus in the study of a simple closed-chain module, the Figure 2(a) shows such structure, that is composed by two prismatic actuated joints, with two central sliders to limit the lateral movement, and in turn a free rotational joint in the upper side to provide a

As a consequence of the use of a discrete workspace, the actuated joints will be binary, and these modules will have a d1 translation and a 45 degrees rotation (Figure 2(b)), when their

possible to run up with the disposal and the number of the closed-chain modules.

rotational movement of the end-effector of the module.

configuration will be P1 ON, P2 OFF or vice versa.

could carry magnetic foots or suction pads (Kim et al., 2005).

**3. Schematic design of the robot** 

wide workspace.

Fig. 1. Hybrid climbing robot

**3.1 Parallel module** 

to concentrate on the kinematics analysis and the postures it can achieve.

structures for inspection and maintenance tasks, construction, petroleum, bridges, etc.), and to achieve similar characteristics according to usual robots destinated to these tasks.

In order to demonstrate that this robot could be used in a continuous workspace, and could be positioned in different planes and surfaces of the metallic structure, we will study the closed chain forward and inverse kinematics, and direct kinematics of the final system consisting of hybrid leg mechanism.

This chapter reviews related works, main important features and applications of some climbing and walking robots. A description of the geometry of a new developed climbing robot with a discrete hybrid (parallel-serial) moving mechanism composed by a closed kinematic chain and binary actuators will be explained. The schematic design of the robot and main postures will be also provided. Moreover, an analysis of the robot's workspace, forward and inverse kinematics of the parallel module, and forward kinematics of the complete serial robot will be also discussed.
