Social Humanoid Robot SARA: Development and Dilemmas Marko Penčić, Member, IEEE, Maja Čavić, Srđan Savić, Member, IEEE, Milan Gnjatović, Member, IEEE, Branislav Borovac, Member, IEEE, and Zhenli Lu, Member, IEEE Abstract—Paper presents the development of a humanoid ro- Basis of the control system represents is a cognitive system bot Sara and dilemmas that have accompanied the development. in which information of different nature are being collected Robot should represent anthropomorphic mobile platform for and which need to be interpreted in different ways. Therefore, the research of social behavior of the robot in the immediate we will not specifically discuss the cognitive system, but only human environment. This implies several significant dilemmas – highlight where it must be included. the need to enable verbal and nonverbal communication, cogni- It is necessary to couple verbal communication and the cog- tive system in all aspects of use, problem of motion and orienta- nitive system, because verbal communication represents the tion of robots in unstructured environment, manipulation and main source of information about the task that human asks ro- handling objects, realization of complex sensor system and the need to enable energy autonomy of the robot. Sara will be able to bot to do. Cognitive aspects are extremely important, because communicate verbally and nonverbally. To express emotion by they ensure the adequacy and logic of the robots operation. One face, the robot will be able to move the eyes and eyelids. To ex- aspect is to understand the speech of a human which is not sub- tend the spectrum of nonverbal communication, the robot will be jected to all the rules of grammar. Other is learning that is based able to shrug when the question is confusing or when the robot on the previous experience – the human assumes that the robot does not know what to answer. In addition, Sara will have two remembers or correctly understands the event that has happened anthropomorphic arms with a total of 14 DOFs, neck with 3 in the past and that will accordingly act in the future. DOFs and lumbar spine with 7 DOFs in order to increase the Nonverbal communication is extremely important and mobility of the upper body without moving the lower. should be realized the same way a human would and can un- derstand – facial expressions and body language. Nonverbal Index Terms—Social humanoid robot; verbal and nonverbal communication; facial expressions; mechanical design. messages are sending clear signals regardless to the meaning of the spoken word, which is why researchers are working intensively on improving the interactive elements of the robot. I. INTRODUCTION However, other ways of nonverbal communication can be explored that are not typical for a human, but that human can Sara is social humanoid robot for direct interaction with understand, such as the different types of luminous messages. people in everyday human environment that is dynamic and For example, a man perfectly understands dog behavior alt- unstructured. This implies several requirements and dilemmas. hough nonverbal communication of the dog – tail wagging, is The most important are: (i) the necessity of verbal communica- not done by humans. tion because it is the most natural form of communication be- A special task is efficient motion and orientation of the robot tween people and is also expected to be the case between hu- in the space. When one says to the robot, for example, "Bring mans and robots, (ii) the need to enable nonverbal communica- my glass from the kitchen!", besides that he needs to know what tion and the ways for its realization, seeing that even 2/3 of the glass is and to which glass the request relates, he needs to communication between humans is based on the nonverbal know how he can arrive to the kitchen from its current location. communication, (iii) cognitive system which implies the inclu- Solving this task has to rely on the cognitive system as well. sion and integration of the different aspects of cognitive func- Manipulation and handling of the objects in the human en- tioning – from recognition of the objects in the living and vironment implies several classes of tasks that are based on working space of the humans to managing in environment in the technical and ergonomic requirements. Thus, opening/ which it operates, (iv) problems of motion and orientation in closing doors is related to the handling of the knob, while space that is not predefined, (v) manipulation and handling of switching on/off the light is performed by pressing the switch objects in the human environment, (vi) the sensor system and with a certain force. To activate the electrical device is neces- (vii) how to provide sufficient energy autonomy of the robot as sary to insert the plug in the socket, where beside to the prop- well as independent energy recharging. All these aspects repre- er mutual orientation it is necessary to produce adequate force sent separate research areas, which, in case of realized unique for the plug to be put in or pulled out of the socket. All this device, need to be integrated and harmonized. require that the robot must have a very sophisticated device for grasping and manipulating objects which performs very Marko Penčić, Maja Čavić, Srđan Savić, Milan Gnjatović and Branislav much like the human hand. This has not been fully realized, Borovac are with the Faculty of Technical Sciences, University of Novi Sad, Trg Dositeja Obradovića 6, 21000 Novi Sad, Serbia (e-mail: {mpencic, although there are several noticeable attempts. A particular scomaja, savics, milangnjatovic, borovac}@uns.ac.rs). problem is grasping and manipulation of the objects, because Zhenli Lu is with the School of Electrical Engineering and Automation, the same object can be taken in different ways depending on Changshu Institute of Technology, Hushan Road 99, 215500 Changshu, Chi- its use. This aspect is also inevitably linked to the cognitive na (e-mail: [email protected]). Proceedings of 4th International Conference on Electrical, Electronics and Computing Engineering, pp. ROI2.5.1-6 IcETRAN 2017, Kladovo, Serbia, June 05-08, ISBN 978-86-7466-692-0 system which presents a set of highly complex requirements. pendently – it is possible to move each eyelid individually or Sensor system represents the basis of human interaction both together, while the lower eyelids are usually immovable. with the environment. Therefore, bearing in mind that the ro- Power transmission and motion from the actuators to the eye- bot will operate in unstructured and dynamic environment, it is balls and eyelids is usually performed by belt mechanisms, lev- necessary that such a system exists in robots as well. Basic er mechanisms and low backlash gear mechanisms that provide sensor that humans use is visual and although researches in this high positioning accuracy and repeatability of movements. area are significant, there are still not good enough results. It is There are two basic groups of robots that can move the head certain that the vision must be coupled with a cognitive system independently from the trunk by activating the cervical spine and that information obtained through vision – pictures, needs i.e. neck. The first group of robots has a neck with 2, 3 or 4 to be interpreted in different ways in order to fulfill different joints whereby each joint have 1 DOF – rigid structures, while tasks. For example, from the image that robot got at the speci- the second group has a biologically inspired neck with a 3-7 fied time, it is necessary, in one case, to extract information joints – viscoelastic structures with 9-19 DOFs. The neck with about a possible path so the robot can get to the desired loca- 2 DOFs – movements about the pitch and yaw axes, is used in tion, while in the second case, it is necessary to see whether the robots Pepper [13], NAO [14], MARKO [15] etc., the neck glass that the robot is searching for, is on the table in front of with 3 DOFs – movements about the yaw, roll and pitch axes, him. In the third case, the robot should recognize where is he is used in robots Affetto [16], EveR-2 [17], HRP-4C [18] etc., currently located and in which direction to go to reach the des- while the neck with 4 DOFs – yaw, roll, upper and lower pitch tination. The sense of hearing also represents a very important movements, can be found in Romeo [19], SAYA [20], Flutis sensory system that should ensure quality reception of the au- Robot WF-4RVI [21] etc. Neck structures of these robots usu- dio signal from the interlocutor in real conditions where ambi- ally consist of the rigid and low backlash mechanisms which ent noise is the basic problem. The sense of touch is also ex- are interconnected – harmonic drive, cable-driven mechanisms, tremely important for contact detection of different parts of the spindle drive, low backlash gears etc. The advantage of these body with the environment as well as for application in the mechanisms is low backlash that provides high positioning realization of the functional requirements. Detection of the accuracy that enables high accuracy and repeatability of intensity and the position of the contact force are also neces- movements, which is essential for motion control. sary for the realization of walking and when grasping of the There are two basic groups of robots which can move the objects with the hand, but a method for interpretation of the trunk independently of the pelvis. The first group has a so- information in these two cases is quite different. called waist/torso joint with 1-3 DOFs – rigid structure, while It is extremely important to integrate all these aspects into a the second group have a trunk which is based on the human single device, because only then one can consider all the com- spine with 3-5 lumbar vertebrae – viscoelastic structure with 9- plexity and interdependence that arises here, therefore it is 15 DOFs.