1 Design and Simulation of a Human-like Robot Neck Mechanism E.A.N.S. Edirisinghe, R.A.P. Lakmal, T.G.G. Lakshitha, S.W.D.T.S. Sirimanna and A.G.B.P. Jayasekara Robotics and control laboratory, Department of Electrical Engineering University of Moratuwa Moratuwa, Sri Lanka Abstract- A vast range of human-friendly interactive robotic heads is being developed by researchers. However these robot heads require improvements in construction and behavior to achieve more human-like performance. Therefore this paper proposes a design of a robotic head with human-like movements. The details of the kinematic analysis, particulars on mechanical design of the neck, the electrical and control system of the robotic neck are discussed. The design parameters have been identified by analyzing the bio-mechanical information related to basic head movements of the humans. This paper includes a way to imitate human neck movements of flexion and lateral flexion. Design of this robotic neck platform is done in such a way that it can be used as a platform for facilitating further developments in integrating more additive features to a robotic neck, which are to be incorporated as per needed by any developer. Keywords—robot neck mechanism; human biomechanics; robot kinematics; mechanical design I. INTRODUCTION Developing robots which can interact with humans with a close resemblance to human to human interactions has been an area of major interest for quite some time [1-7]. Through excessive research and analysis, many robotic heads have been developed around the world, each of which possesses human like interactive features to some degree [8-10]. Despite the developments in features associated with robot heads, human- like performance of developed robot necks still remains a challenge. In early stages of robot head development, robotic designers mainly focused on modelling the human neck as a joint with three degrees of freedom. This eventually resulted in artificial movements when compared with human head. Other than to that, the stability of head was compromised when making all three movements using rotational movement actuators. Control mechanism mainly took the form of controlling three separate motors associated with three rotational movements. Therefore the controlling of overall movement was a simultaneous movement of three rotations. Fig.1 shows a common arrangement found among robot head developers when it comes to neck design. Fig.1. Modeling human neck with three motors [8]. This paper suggests a way of developing a robot neck with minimal control effort. That is to use two linear actuators or a built linear actuating mechanism which uses screws and stepper motors to overcome the complexity, stability and most importantly the closeness of neck movements to that of a human. Following sections of this paper will discuss in detail regarding biomechanics of a human head, mapping of the modelled movement space with that of a natural head, suggested solution, control mechanism and evaluation of the design. II. BIOMECHANICS OF HUMAN NECK The human neck consists of seven vertebrae and it is a complex mechanical system from a kinematic point of view. The vertebrae are capable of providing flexion/extension movements, lateral flexion movement and rotational movement. Human cervical vertebrate system has been studied to identify and gather information on the natural neck motions in order to design a mechanism that is capable of appropriately reproducing movements in the neck of attentive robot head [8]. Table I indicates the extent to which, each part of the vertebrate in a human neck are utilized for different motions [11]. Here C0 is the skull and C1….C7 are the disks of cervical vertebrae. The configuration of cervical vertebrae is shown in Fig.2 [12]. Table II provides statistical data on the ranges of motion of human neck [13]. This work was funded by the University of Moratuwa