robotics Article HBS-1: A Modular Child-Size 3D Printed Humanoid Lianjun Wu, Miles Larkin, Akshay Potnuru and Yonas Tadesse * Received: 6 November 2015; Accepted: 4 January 2016; Published: 13 January 2016 Academic Editor: Huosheng Hu Humanoid, Biorobotics and Smart Systems Laboratory (HBS Lab), Department of Mechanical Engineering, The University of Texas at Dallas, Richardson TX 75080, USA; [email protected] (L.W.); [email protected] (M.L.); [email protected] (A.P.) * Correspondence: [email protected]; Tel.: +1-972-883-4556; Fax: +1-972-883-4659 Abstract: An affordable, highly articulated, child-size humanoid robot could potentially be used for various purposes, widening the design space of humanoids for further study. Several findings indicated that normal children and children with autism interact well with humanoids. This paper presents a child-sized humanoid robot (HBS-1) intended primarily for children’s education and rehabilitation. The design approach is based on the design for manufacturing (DFM) and the design for assembly (DFA) philosophies to realize the robot fully using additive manufacturing. Most parts of the robot are fabricated with acrylonitrile butadiene styrene (ABS) using rapid prototyping technology. Servomotors and shape memory alloy actuators are used as actuating mechanisms. The mechanical design, analysis and characterization of the robot are presented in both theoretical and experimental frameworks. Keywords: humanoid; mechanical design; actuators; manufacturing; 3D printing 1. Introduction Humanoid robots have great potential for use in our daily life by accompanying or working together with people. Growing interest in humanoid robots has spurred a substantial increase in their development over the past decade. Researchers have shown several prototypes in the literature focusing on various aspects. This paper primarily focuses on the design of a child-size humanoid robot named HBS-1. The overall form factor is an important parameter in the design of humanoids. As shown in Figure1, a small humanoid robot that matches children 3–10 years old could be used for several application areas. These include teaching, training and therapeutic treatment for children with autism spectral disorder (ASD). The majority of children in this age range enjoy interacting with humanoids. The new idea presented in this paper is the design method of a humanoid, which is based on a combination of design for assembly (DFA) and design for manufacturing (DFM) for the full realization of humanoids in additive manufacturing. This paper tries to answer the fundamental question, such as how to design humanoid robots or what is the best approach to designing humanoids. The design requirements of the robot include: (1) being able to 3D print in an affordable 3D printer that can be housed in academic institutes; (2) being proportional to the actual size of a child in the age range of 6–12 years old; (3) being able to handle common objects of a load of 0.1kg in the hand; (4) having a sufficient degree of freedom in the upper body to manipulate objects; (5) using the design for assembly (DFA) and design for manufacturing (DFM) approaches; (6) being low cost in material; and (7) and serving as a platform to study artificial muscles. It is extremely important to review the existing humanoid robots in various categories and to describe their DOF, characteristics and cost to give a wider perspective to readers or researchers in the area. The existing humanoids can be categorized into three: humanoids with wheeled locomotion, humanoids with legged locomotion and humanlike robots [1]. Robotics 2016, 5, 1; doi:10.3390/robotics5010001 www.mdpi.com/journal/robotics Robotics 2016, 5, 1 2 of 28 Robotics 2016, 5, 1 2 of 28 FigureFigure 1. HBS 1. HBS-1-1 compared compared to humans to humans ( the (theschematic schematic drawing drawing is redrawn is redrawn following following the scale the from scale Andrew from LoomisAndrew [2]). Loomis [2]). 1.1.1.1 Humanoids. Humanoids with with Legged Legged Motion Motion HumanoidsHumanoids with with legged legged motion motion are are simply simply humanoid humanoid robotsrobots thatthat havehave legslegs andand cancan walk.walk. 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It is 190with cm astronauts (613”) tall, in costs space about [5]. It $2.5is 190 million cm (6 [5′3]″ and) tall, has costs 42 DOF.about HRP-4C $2.5 million [6] is [5] designed and has to 42 work DOF. in HRP human-4C environments,[6] is designed usesto work tools in likehuman a human environments, to manipulate uses objectstools like and a human is able to manipulate speak and sing object ass anand entertainment is able to speak robot. and Itsing has as 42an DOF, entertainment is the size robot. of a 14-year-old It has 42 DOF, adolescent, is the size with of 158a 14 cm-year in-old height, adolescent and costs, with about 158 $200,000cm in height, [7]. Mahruand costs and Ahraabout [ 8$200,000] were developed [7]. Mahru to operateand Ahra as network-based[8] were developed machines to operate that can as walk network at a speed-based ofmachines 0.9 km/h that (0.56 can mph), walk talkat a speed and recognize of 0.9 km/h gestures. (0.56 mph), They talk can and both recognize understand gestures. speech They and can learn both fromunderstand their own speech experience. and Theylearn arefrom 150 their cm tall, own the experience. average 13-year-old They are boy, 150 with cm a 35tall, DOF, the and average cost around13-year $236,000-old boy, [9 with]. Pino a 35 [10 DOF] is developed, and cost around by ZMP $23 Inc.6,000 to accelerate[9]. Pino [10] the is research developed and by development ZMP Inc. to ofaccelerate humanoids the by research providing and technical development information of humanoids to the general by providing public. Ittechnical has a height information of 70 cm, to the the averagegeneral nine-month-old public. It has a baby,height 26 of DOF, 70 cm, and the costs average around nine $30,000-month [11-old]. Sony’s baby, 26 QRIO DOF, [12 and] is designedcosts around to perform$30,000 voice[11]. Sony’s and face QRIO recognition; [12] is designed it can remember to perform people’s voice and faces, face as wellrecognition; as express it can its likesremember and dislikes.people’s The faces costs, as ofwell QRIO as express have been its likes compared and dislikes. to the price The ofcosts a luxury of QRIO car have [13]. been It has compared 38 DOF and to the is 58price cm tall,of a about luxury the car size [13] of. aIt four-month-oldhas 38 DOF and baby. is 58 Toyota’s cm tall, Partnerabout the Robots size of [14 a] four are being-month developed-old baby. withToyota’s human Partner characteristics, Robots [14] which are being include developed being agile, with friendlyhuman characteristics, and intelligent which enough include to operate being devicesagile, friendly for personal and assistanceintelligent and enough care for to theoperate elderly. devices They arefor 83personal cm tall, assistance resembling and a 1–6-year-old care for the child.elderly. Kotaro They [ 15are] has83 cm a human-like tall, resembling skeletal a 1– structure6-year-old and child. a flexible Kotaro spine [15] has that a acts human very-like similar skeletal to humanstructure muscles. and a Kotaro flexible is 133spine cm that tall, acts approximately very similar the to size human of a nine-year-old muscles. Kotaro child, is with 133 91cm DOF. tall, approximately the size of a nine-year-old child, with 91 DOF. Poppy is a humanoid, which is also Robotics 2016, 5, 1 3 of 28 Poppy is a humanoid, which is also mostly 3D printed, like the humanoid presented in this paper. It is 84 cm tall, weighs 3 kg, has 25 motors and an LCD screen, and it costs around $11,000 [16,17]. 1.2. Humanlike Robots Humanlike robots are designed to mimic the appearance and behavior of humans realistically [1], such as facial movements (facial expressions). The robots may be legged, as in Albert HUBO [18] and HRP-4C [6], or stationary, as in SAYA [1] and Repliee Q2 [19]. Several examples are given in this section.