Engineering Design for Robot Aesthetics

Proceedings of the ASME 2015 International Design Engineering Technical Conferences & Computers and Information in Engineering Conference IDETC/CIE 2015 August 2-5, 2015, Boston, Massachusetts, USA

DETC2015-47218 ENGINEERING DESIGN FOR ROBOT AESTHETICS Wenchang Zhang Tsinghua University Beijing, China

Annan Dai Tsinghua University Beijing, China

Yiming Rong* Tsinghua University, Beijing, China *Also Worcester Polytechnic Institute, Worcester, MA, USA ABSTRACT This paper presents a show case of aesthetic robot design considering technical function constraints and using engineering performance analysis method. First a project goal was determined based on a robot aesthetic analysis. Decision matrices were used to evaluate the aesthetic satisfaction in both component and assembly levels of the design while the scores were assigned subjectively through panel discussion. 3D printing technique was used to get the physical models for rapid verification of the design and to facilitate the design evolution. Examples are given for robot component design as well as the overall evaluation of the robot aesthetics.

the high-end market focusing on the implementation of cutting edge technology, industrial robots demanding on precision and efficiency, the toy market creating joys with robots and selling for profit, and the educational market cultivating students' interest and helping them doing research. The educational market is mainly focused on the youth people and children with a combination of function and attraction requirements. At present, the humanoid robot industry is booming up. Numerous universities, colleges, enterprises and countless entrepreneur makers over the world show great interests in this field of study and participate in different levels. To meet the popular need, the low-cost and attractive robots are the most prospective robots, ahead of which there still remains a big amount of vacancy in market. The first electronic autonomous robot with complex behavior was created in 1948[2]. Over the half-century development since then, technologies used in robot operation and application are very comprehensive and systematic. In today’s robot market, with a variety of robots in high quality, it is hard to differentiate robots only by their functional value, while robot aesthetic design plays a vital role in the market competition. However, there is not a standardized or systematic way to design and evaluate the aesthetic aspect of robots[3]. In this paper, an engineering analysis method is introduced to evaluate the aesthetic design of robot and clarify the advantages it brings. Technical requirements of functions and aesthetic attractiveness are coupled together. How to represent the robot aesthetic requirement and performance in a logic way is the first challenge. Then how to rapidly generate and evaluate the aesthetic robot design with function requirements as constraints in design iteration is also a challenge. In this study, a panel evaluation based scoring system is used to evaluate the product

INTRODUCTION Thanks to the advancement in robotics, robots are now being developed with various functions, playing more and more important roles in different industries and even in our daily life. Robots can be divided roughly into four types according to their applications[1], i.e., 1) highly specialized robots with advanced functions and leading technologies in specific fields, such as space and deep sea exploration as well as intelligent applications in complex operation environments without much constraint of cost; 2) high accuracy, high reliability, and high efficiency robots in industrial applications with advanced functions, large quantity, and low cost; 3) toy robots which focus on children as accompanies that do not need to be complex in function but friendly and highly attractive; and 4) low-cost and attractive robots which are oriented for commercial or educational use, while desired to be easy access and emerging into our daily life. Accordingly, the general robot industry can be divided by four typical market economies, i.e.,

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design, with the goal to enhance customers’ satisfaction. Sketching, CAD modeling, and 3D printing are the techniques used in the study to facilitate the evolution of the design. Within a short project time, an initial robot design is analyzed and improved to demonstrate the effectiveness of combining engineering design and aesthetic evaluation in robot design.

a robot to human person and also to avoid creepy appearance in a vague area of humanoid robotic aesthetics, the child-like and cartoon-featured robot may be a better design choice. Christopher Alexander as an architect, famous for his design patterns theory in architecture, indicated that those design patterns were regarded as design guideline for the building design, which could be used to help architects in generating new building designs [9]. Similar patterns were referred to in the field of human-robot interaction to enhance the sociality of humanoid robots, such as the initial introduction and didactic communication for robots to become good friends with human persons [9]. But such patterns may not be fundamental, because even with the social motions guided by the patterns, robots may also be unsocial with the creepy appearance. Therefore it would be much beneficial to come up with certain measures (criteria) to evaluate the design patterns and to compare different robot aesthetic designs. By looking into the robotic aesthetics, in this study, typical representing measures are defined to include the following,

ROBOT AESTHETICS It is much desirable, particularly in education domain, to make the interesting world of robotics more accessible and sociable for students and robot enthusiasts. Each of these criteria has a twofold meaning: the sociable aspect must be both cute and cool to the consumer, while accessibility requires the hardware to be affordable and the part motion to be software hackable. Cute represents the endearing appearance, behaviors, and emotional effect, while cool can be described based on young and hip/fashion impression. Figure 1 is an example[4].

     

Gendered vs. Neutral Skeletal vs. Covered Action Figure vs. Doll Social Polished Humanoid Movement

and distributed in face, arms, torso, and legs, as shown in Figure 2. Figure 1. An example of children attractive robot A humanoid robot may strengthen the interaction between human and robots. There still remains a question about how close the humanoid robots should look like human. A famous theory about the aesthetics of humanoid robots is called the uncanny valley which tells us that the familiarity of a robot to human may change along with the similarity of a robot to human. In the relation curve, there exists a valley right before the 100% human likeness, which means that a robot close to human in appearance may look like a corpse or zombie [5]. But in the meantime, another essay indicates that if an object resembles a person too closely, a mismatch may be expected between perceptions of “object” and “person”, which may cause disorientation and result in what is also called “uncanny”[6]. From artistic aspect of robot design, one challenge is to determine the design criteria, from experience/feeling type of personal preference to a systematic way which can be justified. For an interactive robot, it does not need to imitate exactly the same human motions and gestures. Good social interaction with human plays a more important role than the accuracy in applications in order to attract customers. With some tolerance in the range of motions, the robot can perform better and provide its owner with psychological enrichment [7]. Besides, aesthetic interactions of robot like an innocent play make it look sociable, even if it expresses any negative emotion or fails to imitate human actions perfectly [8]. To enhance the sociality of

Gendered -Neutral

SkeletalCovered

Action Figure -Doll

Social

Polished

Humanoid Movement

Body Part Face Arms Torso Legs

Figure 2. Robot aesthetic measures GENERAL ROBOT-DESIGN PROCEDURE The typical engineering approach to design a robot is using quantized criteria building a robot like any other machines to reach specific measurable objectives. For instance, Atlas by Boston Dynamics is a high-mobility humanoid robot designed to negotiate outdoor, rough terrain[10]. The functions may include the capability of walking bipedally leaving the upper limbs free to lift, carry, and manipulate the environment. In extremely challenging terrain, Atlas is strong and coordinated enough to climb using hands and feet, to pick its way through

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humanoid robot, where the result shows that people can easily understand the facial expressions, gestures and actions of humanoid robots. But in the meantime, the human people tend to be more severe in evaluating humanoid robots than machinelike robots. Many factors should be carefully considered, including the noise generated by actuators, the size and weight. The technical specifications of the humanoid robot to be designed include 24 degrees of freedom, with NiMH Battery, 24 5v Servos, & a Raspberry Pi Controller, as shown in Figure 3.a and an initial design was conducted as shown in Figure 3.b, with consideration but without quantitative evaluation of the aesthetics. Additionally, the servo design could not be changed to allow for smaller robot dimensions, because these servos had already been specialized to provide force feedback which will lend the robot a new layer of accessibility.

congested spaces. The appearance of Atlas doesn't look like a human, it's more like a combination of mechanical components. On the other side, the artistic approach which doesn't have a compact and systematic methodology as the engineering approach but pays a lot effort into the aesthetic improvement. The typical example would be the movie props robot. It doesn't need to actually have the ability to do what it needs to do in a movie story. It just needs to look that way. Those two approaches may lead to different results. When one only uses the engineering approach, focused mostly on the functions, the robot may result as a high performance machine with remarkable capability, while on the other hand, an roughly designed appearance possibly make it hard to interact with. Similarly when one only uses the artistic approach, focused mostly on the appearance and human interactions, the robot may result as an elegant shape but probably won't satisfy the work requirements. From the early theoretical model[11] to explain biped locomotion to the state-of-art robots like PETMAN, HRP-2 or successful commercial robots like Nao, the development of humanoid robot was mainly focused on the technical perspective. A lot of research has been done on the robot kinematics, fascinating mechanism, flexible operational capabilities, error robustness and other technical challenges. However there is not a general procedure and methodology to design the aesthetic aspect of robots with enjoyable appearance and actions; low cost, easy to tweak and comfortable to play with. Researchers have yet to plumb the depths of the "nontechnical" issue, as many customers desire. These performance should also be measured for comparison in design stage. For instance, how comfortable does a person feel when he or she approaches one robot, or what kind of first impression does one robot present? The purpose of this study is to explore a systematic way to design a robot which possesses a nicelooking appearance and user-friendly social interactions, while with adequate capabilities as a condition. The typical robot design procedure can be summarized like other mechanical design as [12],  Need identification to determine the design specifications;  Brainstorming and conceptual design;  Detail design and performance analysis;  Prototyping and testing; and  Finalization of the design. Certainly many steps of evaluation/feedback may be involved in the design process. Similarly these steps could be applied to the aesthetic design of robots.

Figure 2: Skeleton model of robot’s 24 DOF The physical design had to retain hardware accessibility. This means that the robot should be low-cost and easy for the user to modify, accomplished by minimizing the number of parts and designing all parts to be injection moldable by simplestraight-pull equipment and easy to assemble[13]. Solutions like building connections to be parallel to the part removal were employed to make the robot more manufacturable. Ultimately, this project involves devising solutions while working towards a more accessible and social robot. Since there is not a systematic and easy way of designing robot aesthetics found from literature, a new method was proposed to guide our design and evaluate different iterations of design, which finally led to the new robot within a short time, in our case only 7 weeks. Steps of this method to design robot are listed below:  Problem definition. After given specific market orientations of desired robot, surveys and/or research were carried out to find out what characteristics or attributes are needed and also what target customers want to see in the robot;  Goal. The goal is a target measure to show basic appearance and functions of the robot, which was determined through an analysis on the on-line survey;  Objectives. Objectives are a subset and more specific definition of the goal to define a limited scope of development. The objectives should be concrete, measurable, and achievable;

TECHNICAL CONSTRAINTS IN AESTHETICS DESIGN Our goal is to design a small-scale robot which aims to be accepted by people in all ages. The appearance should be human-robot interactive, or in other words, social. Sociality is a characteristics to describe an object by human’s tendency to stay or play with. A study was carried out to test the sociality of

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









Methods. A decision matrix is applied to determine the design concepts in both overall and component levels, which was accomplished through brainstorming discussion and sketching process. Subjective scores were given through panel discussion; Tasks. To accomplish the design in a highly organized process, tasks were decided to conduct component design with engineering considerations by generating CAD models and to determine the aesthetic performance of the design through evaluation scoring; Criterion selection. Designing an aesthetic robot is different from realizing dynamic functions of the robot. Because aesthetics evaluation is often subjective and hard to quantify, which actually goes beyond the engineering field. Thus a list of criteria is required to assess the design. To regulate the impact of subjective preference, each iteration of design should be evaluated in scores. With a design matrix structure, the design group can tell what are not yet satisfied and what have already met the goal, which can help to drive the design to become a logic design; Implementation. This step usually takes the longest time in the process of actually designing the robot, evaluating the design and then redesigning the robot. Several iterations are expected to reach the final design. Rapid prototyping (i.e., 3D printing) of the components and assemblies were utilized for quick feedback on performance and feasibility verification; and Conclusion. It is to finalize the design and demonstrate the result.

parts as much as possible without restricting movement capabilities. While customers wanted a humanoid robot, it was imperative that the new design should avoid the uncanny valley, especially in the face and hands – the two parts of a humanoid robot (and humans, too) that are key to social interaction. By using the design matrix and the six robot aesthetics measures, the original design of the humanoid robot is evaluated and scored as shown in Table 1. The scores for each category ranged from 0 to 4, which is such chosen so that when a design contributes the most to a category, it would result in a score of 4, while if fails to contribute, it results in a score of 0. After a group discussion particularly on the survey results, a target robot aesthetic design score was determined as the goal as shown in Table 2. It is important to note that the goal score was not the same as the ideal score. It has been constrained by accounting for the limitations of servo location, orientation, and sizes, as well as the degrees of freedom, the number of parts, and the manufacturing cost. Conversely, the goal score did take these considerations into account, so the group prioritized reaching the goal score rather than the ideal score. Table 1: Analysis of original design (ArcBotics’ prototype) Body Part

Gender Neutral

Head

4

Arms

Action Figure -Doll

Soci al

Polish ed

4

3

4

3

2

20

1

1

1

1

1

3

8

Torso

2

4

2

3

3

2

16

Legs

1

0

1

0

2

3

7

Total

Aesthetic goal. Since the goal is to create a cute, cool, sociable and affordable robots, defining cute and cool is important to start the project. In the first step, an online survey was conducted by ArcBotics[14]. Besides the background information about the participants, the survey asked what physical characteristics were desired in a commercial humanoid robot. The survey results are summarized below:  Background information of the survey attendees, o Gender (male: female) o Education: Mostly bachelor’s degree or higher o Income range: large amount of disposable income o Interest (greatest frequency to least): Maker/hacker, tech enthusiast, tech professional  Desired physical characteristics in a humanoid robot o Gender (greatest frequency to least): Neutral, Male, Female o Enclosure (greatest frequency to least): Skeleton with exterior shell, skeleton, fully enclosed o Style: Edgy, Social, and Polished. They were considered almost equally important, while edgy was most popular with a slight margin Based on the survey analysis, it was determined that the best design would be gender-neutral, while enclosing internal

SkeletalCovered

Humanoid Movement

Total

51

Sketch Design. After determining the general design guideline, a series of designs were sketched, both for individual parts and for the robot as a whole. Preliminary sketches were used to explore ideas for the robot’s appearance as well as to brainstorm features that users would find useful or endearing. A sketch then was created that combined the features and aesthetic principles evident in numerous preliminary sketches. Figure 3 shows some examples of our sketches. Certainly the robot aesthetic design is constrained by and coupled with the technical function design. Since the robot required 24 DOF, the servo quantity was fixed at 24. Servo locations and orientations were considered for each joint. Due to the non-trivial size of the servo’s plastic casing, designing joints with multiple degrees of freedom, especially the hips and shoulders, presented significant challenges. The 3-DOF hip was realized by placing two servos together with perpendicular axes (one for the hip extension/flexion and the other for the adduction/abduction). The third servo (for hip internal/external rotation) was placed inside the torso. It rotates an assembly with the first and second servos, which were held together inside a cage, and a clip attached to the first servo. Thus, a ball joint was approximated by a serial chain consisting of three revolute joints[15]. Similarly, the shoulder joint (another 3-

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DOF ball joint) was also approximated by a 3R serial chain. In the case of the shoulder, the servo responsible for internal/external rotation was placed in the upper arm rather than inside the torso, to make room for other internal components in the torso.

Engineering consideration. After selecting components, several engineering factors had to be considered prior to the detail design of the components. Firstly, when sketching each component, a compromise between the amount of plastic covering a joint and that joint’s range of motion (ROM) is necessary. Such compromises occurred at all joints but to varying extents. For example, the hip required greater ROM in all three DOF than the ankle. Therefore the hip would have less plastic around it than the ankle did. The mathematical justification for the inverse relationship between a joint’s amount of covering and its ROM is presented in reference[16]. This problem led to a modification of the scoring system. Ultimately, ROM was prioritized over joint covering. As a result, the goal scores for certain parts were almost but not quite achievable, because an improvement of one point in “Humanoid Movement” could easily lead to a loss of multiple points in other categories, such as “Skeleton-Covered,” “Social,” and “Polished.” To deal with this possibility, a modification of two points away from the goal score was made for each part and 5 points away from the goal score for the entire robot. Secondly, the robot plastic exoskeleton could withstand the own motions of the robot. Based on the material properties of the plastic used (ABS plastic) and conservative approximations (i.e. overestimation) of the robot’s mass, it was determined that even under extreme conditions (such as the robot hitting its arm against a wall or table), the servos would not generate large angular acceleration to break any plastic parts. This conclusion is also justified in reference[16]. A third factor was to ensure the parts from drastically shortening the battery life. Two methods were used to determine power consumed by the robot when walking. The first method used a model based on conservation-of-energy, whereas the second method used a model based on a swinging pendulum with the pivot located at the hip (detail analysis can be found in reference[16]) where half of the robot’s mass was considered to be located at the foot (the free end of the pendulum). The energy loss due to friction were accounted in both models, as well as inefficiencies in the servo controller board. From these two models, it was concluded that, based on the mass of the robot (especially its limbs), if the robot walked at a pace of 1 meter per minute, its battery would last 3 hours.

Table 2: Goal score rubric for the overall robot design Body Part

Gendered -Neutral

SkeletalCovered

Action Figure -Doll

Social

Polished

Humanoid Movement

Total

Head

4

4

3

4

4

4

23

Arms

3

4

3

2

4

2

18

Torso

4

4

2

4

4

3

21

Legs

3

4

4

4

4

4

23

Total

85

Figure 3. Examples of conceptual design by sketching Generation of a robot component list. Desirable features were selected after sketches of each body part. The features were compiled and analyzed. Characteristics including aesthetics, functionality, and feasibility were considered and discussed, and a list of potential components was created. The feature list included: a face mask, a battery screen and power button, directional noise detection, a backpack, LED pointers and emotional indicators, a watch-like item, etc. These components were chosen because of their likeness to increase the score of the robot based on the criteria. Considering this list, only a few features were implemented in the final sketch of the robot because including all of the components would make the design too cluttered and the robot may not look cohesive and polished. For example, the face mask was included because it provided the area for LEDs to be placed, which would determine how emotive the robot could be. Having a backpack to house the Raspberry Pi computer essentially saved a lot of room within the torso of the robot as well as being an aesthetically pleasing accessory. This meant that the body could be much thinner and have more room to house servos. The battery screen, LED pointers, and wrist items were not included because they were not contributing to the evaluation score. Although the components may be needed on a robot, these could be added on in the detail design stage without much consideration for aesthetics.

Detail design and CAD Modeling. Component design includes many cycles of evolution. The design evolution of the robot hand best illustrates the design process used throughout the project. As indicated in Table 3, the locations of the robot 24 DOF entailed the absence of a wrist joint; i.e. the hand and forearm would move as one unit, actuated by a servo placed at the elbow joint. Another servo placed in the hand would control grasp. In the initial sketching phase, two categories of hand actuation were considered. Designs in the first category used a servo to open and close the hand, much like the claw on a crab or a lobster. Designs in the second category used various mechanisms, such as four-bar-linkages, rack-and-pinion

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looked more like human hand and retained the movement capabilities of the first design, it increased the robot’s part count, which would result in a significant cost increase when the molds for all the parts were machined. The primary goal of the third hand design was to reduce the part count. This was achieved by revising the arrangement of the “fingers.” This rearrangement changed the direction of the simple-straight-pull injection molding process, and as a result, the hand could now split into two halves rather than three parts, returning the hand’s overall part count to four. The hand was also made smaller, and the apparent length of the fingers was reduced. These modification improved the appearance of the hand by making it more like human hand and by making it more proportional to the rest of the body. In general, function and aesthetics designs are coupled together. In parts where aesthetics were prioritized, improvements generally occurred first in function, i.e. ROM, while aesthetic improvements took longer to realize. Conversely, in parts where function was prioritized, aesthetic improvements generally preceded functional improvements. Table 4 shows another example of calf design iteration. To attain humanoid movements, every part of the robot should support the humanoid movements physically. The requirements for the robot calf design includes, 1) to avoid the knee from bending over, there should be a knee cover; 2) to allow the calf to bend back to a large degree, and the back cover of the calf should be low; 3) to allow the feet to have more flexibility, the bottom of calf should be a little angular rather than round so that the calf won’t block the rotation of the servo in the ankle; and 4) to have different degrees of upward rotation and downward rotation for the feet, the length of the front cover and the back cover should be different.

gearings, and worm drives to achieve more complex grasping motions. Table 3. Hand & thumb evolution. Iteration Original

Goal

Gende r

Skelet al

Acti on

Soc ial

Polish ed

Movem ent

To tal

4

1

1

0

1

2

9

3

2

2

1

1

2

11

4

3

3

3

3

2

18

4

3

4

4

3

2

20

4

3

4

4

4

2

21

Two aesthetic categories were also considered. Designs in the first aesthetic category consisted of an upper half and a lower half, dubbed a thumb. Designs in the second category consisted of a palm and multiple separated fingers. Upon considering the manufacturing cost and assembly difficulty associated with individual fingers, all designs in the second aesthetic category were dismissed in favor of the first aesthetic category. Designs in the second actuation category were also rejected in favor of a hand that could be opened and closed simply by one servo, thereby simplifying both the assembly process and the relationship between the hand’s joint space and actuator space. Following these initial considerations, the first sketch of the hand was designed. This design prioritized functions over appearance. The first goal of the design was to locate and orient the servos that actuated the forearm and the elbow. The second goal of the design was to create a thumb that would enable a basic pincher grip and could be enclosed by the upper part of the hand. To achieve these two goals of the first design, the thumb servo was mounted in the upper hand, with the horn attached to the thumb. The design consisted of four parts: two halves of the thumb and two halves of the hand. Subsequent designs varied in servo orientation and placement, as well as aesthetics. Once the method of hand actuation was determined, these variations were minor. The most salient feature of the second iteration were the “fingers” on the upper hand, which simply served to make the hand appear more human. While improving the hand’s appearance, this change introduced other problems. In order to make the hand to remain injection moldable via a simple-straight-pull process, the distal portion of the upper hand (the “fingers”) became one part, and the sides of the hand close to the elbow became two separate parts. Thus, while the second hand design

Table 4. Design evolution of robot calf

Many other factors should be considered in the design of the robot. Among them the shape is one of the most important ones. First the gender of the robot should be neutral so that the outlook of the robot should be more like a kid, which leads to a relatively short calf. Then to design the robot a little skeletal, the back of the knee, and the front and the back of the ankle should not be fully covered so that we can see part of the servo inside. On the demure/stylized and social sides, the robots should be humanlike and attract people’s attention to interact with them. Therefore the robot should be polished for looking easy to get along with and less aggressive. Finally to guarantee a good part manufacturability, every part should be designed

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in CAD models and printed again for redundancy and further analysis. Having a physical model made it easy to locate ways to make the parts more manufacturable. For example, placing screw holes in a CAD assembly relies on locating sites that do not interfere with the motion, but using a physical model demonstrated the parts on the assembly that need a screw for structural support. Once every part was fabricated by using 3D printing, they were assembled into the design. It was evaluated by scoring and potential problems were identified, and then the design was modified as necessary, such that the scores of the newest design could approach the goal scores. The improvements in each iteration were conducted in both part and assembly levels. 3D printing was limited by its susceptibility to misprinting and inaccuracy. There may be many factors that contribute to faulty prints, e.g., the difference in ambient, needle, and plate temperature, wrong settings and wrong preferences, gears clogging, etc. Inaccuracies in a 3D printed part were greater than in injection molded parts because in the highest resolution print each layer is 0.15 mm thick, which was often significant, especially when ensuring parts either fit snugly or rotate freely.

with easy straight-pull features, adding ribbing beside the unstable part, and thickening some structure to avoid fragile. In the first iteration, problems were found for too-long size compared to the thigh, off-centered, limited room for ankle rotation, limited angle of knee rotation, and machine-liked appearance. In the second iteration, improvements were made particularly on the coordination with thigh design, and then in the third iteration on the coordination with the ankle design. The CAD models of the four design iterations are shown in Figure 4. Coordination with thigh design

(a) 1st iteration

(b) 2nd iteration

(c) 3rd iteration

Coordination with ankle design

Evaluation of the final design. To evaluate all designs, a scoring rubric was used to evaluate the CAD models and physical models. Upon completion of each iteration of the sketch-CAD-3D print process, the robot was evaluated against the goal in Table 2. The evaluation result is listed in Table 5. Figure 6 shows the CAD models of the design iterations.

(d) 4th iteration

Figure 4. Design iterations of robot calf design 3D printing. Having a physical model in addition to a 3D virtual model is advantageous because it allows for physical manipulation of the part. It also illuminates many faults that are not easily seen in CAD models, i.e. structural flaws or inexact dimensions. A CAD assembly can report the global interference of parts, in the assumption of that the parts manufactured are identical to the parts modeled. Given a physical model, the difference can be evaluated between a theoretical CAD model and its tangible counterpart. This allows for a comparison of the interference calculated in Creo and the actual interference of the physical part. Figure 5 shows the assemblies of the robot with 3D printed parts.

Body Part

Gend ered

Skel etal

Acti on

Soci al

Pol ish

Move ment

Total

Face

4

4

3

4

4

4

23

Arms

3

4

3

2

4

2

18

Torso

4

4

2

4

4

3

21

Legs

3

4

4

4

4

4

23 85

Total

Table 5: Analysis of final design As stated in the introduction, the goal of this project was to design a cool, social and accessible humanoid robot. A quantification of the goal was included in Table 2. The goal score of the improved robot design was set as 85, and as mentioned when taken account of the technical and nontechnical constraints, the final solution was achieved as 81, in comparison to the original score of 51 (as listed in Table 1). The final design did not correspond perfectly with the originally proposed design due to some design constraints identified along the way. For example, one DOF was removed from the head (the original proposal called for 25 DOF instead of 24) to maintain covering and manufacturability of the head piece. As design study showed, certain regions such as the face, hands,

Figure 5. Assemblies of the robot with 3D printed parts. A 3D printer is capable of swift production of a CAD model through a process of additive manufacturing. Within about an hour, the part becomes tangible. The convenience of 3D printing and the low cost of ABS plastics made it an effective and affordable addition to the design process. In each iteration, a physical 3D model of each part was printed and assembled for analysis of the ROM per subassembly, aesthetics, and cohesiveness. After each evaluation, corrections were made

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REFERENCES 1. R Greenlee, 1995. History of the World since 1901, Penguin Publishers 2. Tim Hindle, The Economist: Management Ideas & Gurus Disruptive Technology/Innovation, May 2009 3. N. Koyama, M. Yamashita, M. Nakajima, “Research on User Involvement in Automobile Design Development”, Human Interface and the Management of Information, IKAS, Springer International Publishing, 2014, pp. 184-192. 4. J. Khanduja, “Great Project by Aldeberan to Build Humanoid Robot NAO for Autistic Kids”, Quality Assurance and Project Management, IKAS, Springer International Publishing, May 28, 2014. 5. M. Mori, K. F. MacDorman and N. Kageki, "The uncanny valley", Robotics & Automation Magazine, IEEE 19.2, pp. 98-100, 2012. 6. D. Hanson, “Expanding the aesthetic possibilities for humanoid robots”, IEEE-RAS international conference on humanoid robots, 2005. 7. T. Shibata, “An overview of human interactive robots for psychological enrichment”, Proceedings of the IEEE, 2004, 92(11), pp. 1749-1758. 8. J-J Lee, et al. "Aesthetic imitative interaction between child and robot with emotional expression." RO-MAN, 2013 IEEE. IEEE, 2013. 9. P. H. Kahn, N. G. Freier, T. Kanda, et al, “Design patterns for sociality in human-robot interaction”, Proc. 3rd ACM/IEEE int. conf. on Human robot interaction, 2008, pp. 97-104. 10. Atlas - The Agile Anthropomorphic Robot, www.bostondynamics.com/robot_Atlas.html. 11. M. Vukobratović and B. Borovac. "Zero-moment point— thirty five years of its life." International Journal of Humanoid Robotics 1.01, 2004, pp, 157-173. 12. R. L. Norton, Machine Design: an Integrated Approach, 5 th ed., Pearson/Prentice Hall, 2013 13. Dominick V. Rosato, Donald V. Rosato, and Marlene G. Rosato, eds. Injection molding handbook. springer, 2000. 14. ArcBotics, “Aesthetic Robot Survey”, Internal Report at ArcBotics, 2014 15. J. J. Craig, Introduction to robotics: mechanics and control, Pearson/Prentice Hall, Upper Saddle River, NJ, USA, 2005. 16. A. Hippen, D. Lynch, B. Yao, W. Zhang, A. Dai, "Arcbotics — Humanoid Robot Design", Senior Project Report, Tsinghua University, Beijing, China, October 16, 2014

and feet were making a heightened impact on consumer impression of the robot. Therefore the aesthetics of these regions were prioritized while the quality of movement was prioritized at other regions, especially the hips, knees, and ankles. Figure 7 shows the comparison of the final design to the original one. More details can be found in reference [16].

Figure 6. The robot design iterations

Figure 7. Comparison of original (ArcBotics’ prototype) and the final design SUMMARY This paper focuses on the aesthetic aspect of the robot design, although it is coupled with the technical function requirement and engineering constraints. Unlike most of the aesthetic design processes, an engineering design procedure was introduced to the process. First the aesthetic goal was clearly defined with survey and data analysis. Then it was explored to use quantitative evaluation criteria to facilitate the design evolution. Although the evaluation scores used in the design matrices were subjective through panel discussion, the decision process was a reasoning process and justifiable. From the comprehensive design process of the improvement to the initial design, it can be seen that most of the engineering design methodologies applied to the robot aesthetics design, such as the incorporation with technical constraints and trade-offs. The process and final result show the effectiveness of the engineering design method applied to aesthetic design of robots. Hopefully it is also valid and beneficial in other applications. ACKNOWLEDGMENTS This project was conducted with project partners and coadviser from University of Notre Dame, Dan Lynch, Ben Yao, Alex Hippen, and Bill Goodwine, under a project exchange program between Tsinghua University and University of Notre Dame. The project is sponsored by Joe Schlesinger and ArcBotics, which is much appreciated. Finally the support from Tsinghua and Notre Dame as well as Worcester Polytechnic Institute is also much acknowledgeable.

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