Hardware Improvement of Cybernetic Human HRP-4C for Entertainment Use

Kenji KANEKO, Fumio KANEHIRO, Mitsuharu MORISAWA, Tokuo TSUJI,

Kanako MIURA, Shin’ichiro NAKAOKA, Shuuji KAJITA and Kazuhito YOKOI Abstract — Hardware improvement of cybernetic human HRP-4C for entertainment is presented in this paper. We coined the word “Cybernetic Human” to explain a humanoid robot with a realistic head and a realistic figure of a human being. HRP-4C stands for Humanoid Robotics Platform–4 (Cybernetic human). Its joints and dimensions conform to average values of young Japanese females and HRP-4C looks very human-like. We have made HRP-4C present in several events to search for a possibility of use in the entertainment industry. Based on feedback from our experience, we improved its hardware. The new hand, the new foot with active toe joint, and the new eye with camera are introduced.

1. Introduction Up to now, several bipedal humanoid robots [1-17] have been developed. Currently, research on bipedal humanoid robots is one of the most exciting topics. It is no exaggeration to say that the great success of HONDA humanoid robot triggered the world’s research on humanoid robots [1-4]. However, the applications achieved by the current bipedal humanoid robots have been limited. Especially, those of human-size humanoid. New ASIMO (Advanced Step in Innovative MObility) was revealed in 2004 while the first ASIMO made it’s debut in 2000. New ASIMO showed us the capability of running at 6 [km/h] on December 13, 2005 [4]. New ASIMO as well as the first ASIMO is presented in events, gives us a high-tech stage show highlighting ASIMO’s unique capabilities, and goes on TV as an advertisement ambassador. We have developed several HRP series humanoid robots with the collaboration of private companies. HRP-2 was developed in 2002 to show the possibility of working humanoid robots [5, 6]. As a humanoid robotics platform for R&D, about 20 HRP-2’s have been put into use internationally so far. To show the potential for use in the

Fig. 1. Cybernetic human HRP-4C improved with new hands, an active toe joint, and a new eye with camera

so-called 3D jobs (dirty, dangerous and demanding), we developed HRP-3 equipped with dust-proof and drip-proof capabilities as well as precise motion [7]. Although HRP-3 was developed as the succeeding model of HRP-2, the use of HRP-3 is limited and HRP-3 has been also used as a platform of R&D in our institute. Korea Advanced Institute of Science and Technology (KAIST) also developed several humanoid robots. The latest model: HUBO2 (KHR-4) has a capability of running at 3.24 [km/h] [8]. About 8 units have been used as a platform of R&D internationally so far. From this introduction, it is so hard to figure out the practical application of current bipedal humanoid robots. Though they have been used as a platform of R&D, and have played as an advertisement ambassador showing the state of the art of each institute. To overcome this situation, we thought that one practical application for them would be the entertainment industry, such as exhibitions and fashion shows, provided the robots can move very realistically like humans. For this reason, we developed HRP-4C [9] and made HRP-4C to present in several events to search for a possibility of use in the entertainment industry [18]. Based on our experience in demonstrating at various events, we improved the hardware of HRP-4C (see Fig. 1).

Manuscript submitted to 2011 IEEE/RSJ International Conference on Intelligent Robots and Systems. K. Kaneko, F. Kanehiro, M. Morisawa, K. Miura, S. Nakaoka, S. Kajita, and K. Yokoi are with Humanoid Research Group, Intelligent Systems Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Umezono, Tsukuba, Ibaraki 305-8568, Japan (e-mail: {k.kaneko, f-kanehiro, m.morisawa, kanako.miura, s.nakaoka, s.kajita, kazuhito.yokoi } @aist.go.jp). T. Tsuji is with Vision and Manipulation Research Group, Intelligent Systems Research Institute, AIST, 1-1-1 Umezono, Tsukuba, Ibaraki 305-8568, Japan (e-mail: tokuo.tsuji@aist.go.jp).

2011 IEEE/RSJ International Conference onIntelligent Robots and SystemsSeptember 25-30, 2011. San Francisco, CA, USA

978-1-61284-455-8/11/$26.00 ©2011 IEEE 4392

The rest of this paper is organized as follows; after looking back on the design concepts and principal specification of HRP-4C in Section 2, we introduce the overview of the events in which HRP-4C was presented in Section 3. We present the new hand, the new foot with toe joint, and the new eye, which have been improved from the original. We examine these modifications in Sections 4, 5 and 6 respectively.

2. Design Concepts of HRP-4C Since applications in the entertainment industry such as a fashion model or the master of ceremony are leading candidates for practical application of current bipedal humanoid robots, we set the design concepts of HRP-4C as follows when we developed it.

Design concepts: A) Capability of bipedal walking B) Realistic figure of an average young Japanese

female C) Configuration to imitate human-like motion

With regard to the design concept B), we referred to the anthropometry database of Japanese 1997-1998 [19], in which the average is recorded. The data not recorded in the database [19] is obtained by measuring a commercially available skeleton [20]. In the process of the mechanical design, the principal items were selected from among the database at designing HRP-4C. The selected items were deformed as follows.

Deformation policies: 1) Link length and breadth of HRP-4C are deformed

to be from 90% to 110% of the average dimension of a young Japanese female.

2) Circumference is deformed to less than 110% of the average dimension of a young Japanese female.

But the ankle joint height and foot size of HRP-4C are exceptions of deformation policy 1) in consideration of the effect on putting on shoes. The dimension of hand was also

another exception of deformation policy 1), because of the development delay. The principal specifications of HRP-4C, which was first released to the press on March 16, 2009, are as follows. HRP-4C is 1580 [mm] high and has 8-DOF face, 3-DOF neck, 6-DOF for each arm, 2-DOF for each hand, 3-DOF waist, and 6-DOF for each leg, no toe joints, and 42-DOF in total.

3. Trials of HRP-4C The HRP-4C has presented in several events in search of a possibility of use in the entertainment industry. Fig. 2 shows some examples of events with HRP-4C. HRP-4C was first presented on the stage of a fashion show: the 8th Japan Fashion Week in Tokyo (JFW in Tokyo) which opened on March 23, 2009. The role of HRP-4C was master of ceremonies (MC) in the special stage named “SHINMAI Creator’s Project”. HRP-4C walked (see Fig. 2(a)), bowed and made a speech about one minute long. Then HRP-4C turned and walked off stage. In 2009 YUMI KATSURA Grand Collection in Osaka (July 22, 2009), HRP-4C made the first professional catwalk appearance. HRP-4C wore a wedding dress made by the designer: Ms. Yumi KATSURA who is a leader of wedding dress design, as shown in Fig. 2(b). HRP-4C walked smoothly up and down about 17 [m] each way on the catwalk, which was about 25 [m] long, and 6[m] wide. HRP-4C then struck various poses, and gazed sidelong at the delighted audience with a short speech. HRP-4C acted in a one man show in the Digital Contents Expo 2009 (Oct. 22-25, 2009) as shown in Fig. 2(c). Using the motion editor software [21], we successfully made a 5 minute motion for HRP-4C using a human actress’s motion created by SAM who is a choreographer. HRP-4C didn’t move her legs, but the way she moves her arms, head and facial muscles were sufficiently human-like, and was also able to tell jokes. In the events held in 2009 as shown in Fig. 2, we received several opinions from spectators. One of them

(a) Opening address

SHINMAI Creator’s Project JFW in Tokyo

(March 23, 2009)

(b) Fashion model

2009 YUMI KATSURA Grand Collection in Osaka

(July 22, 2009)

(c) Actress

DIGITAL CONTENT EXPO 2009 (Oct. 22-25, 2009)

Fig. 2. Examples of events with HRP-4C

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Fig. 3. Target specifications of new hand based on average of young Japanese female [19, 22, 23]

(Note: Draw line doesn't show the strict outline of Japanese female hand shape.)

Fig. 4. Principal dimensions of new hand (Note: These values slightly change due to the condition of the elastic cover.)

mentioned that the hand of HRP-4C was out of proportion to its body. Since the dimensions of HRP-4C are set to averages of young Japanese females except for the hand as mentioned above, we decided that this opinion was worth taking into consideration. We then developed the new hand as presented in Section 4. Another opinion from spectators was that the motion of HRP-4C was not natural. Although there were numerous causes, we thought things could be improved by adjusting the joint configuration of HRP-4C to be closer to that of a real human. Therefore, we developed the new foot with toe joint as presented in Section 5. We also felt that the view from the HRP-4C might help us during remote operation from a backyard in the events. Although we were sometimes supplied with images taken by fixed point video cameras set up by event management, almost all camera images were useless because the robot was lost from view. In addition, the view from the robot may be useful to realize robot motion responding to spectators. To achieve this, we implemented the new eye with camera into HRP-4C as presented in Section 6.

4. New Hand 4-1. Design Concept We resized the human-size hand to further match HRP-4C. Since the joints and dimensions of HRP-4C are set to average values of young Japanese females except for the previous hands and the budget for improvements was limited, we set the design concepts of the new hand as follows.

Design concepts of new hand: D) Keep design concept of previous hand E) Reduce backlash F) Realize the average size of a young Japanese female

The design concepts kept from the previous hand were as

follows.

D1) Lighter hand D2) Capability of creating dance performance motion

It is ideal for entertainment use to imitate human-like hand motion as close as possible. A multi-DOF fingered hand is necessary to achieve this. However, there were too many hurdles to realize this during the initial development of the previous hand. In the present situation, we have kept the basic design. So based on design concept D), the new hand as well as the previous hand has 2-DOF. and two servomotors are located inside of the hand. Towards design concept E), planetary gears are used in the new hand for the final reduction gear. Although miter gears and bevel gears were adopted inside of the previous hand, they are not used in the new hand. To realize design concept F), we referred to the anthropometry database of Japanese [19, 22, 23]. Although there are several measured items concerning human hands in the database, the principal dimensions were selected from the database for designing the new hand. Fig. 3 shows the selected dimensions and the average for young Japanese females. 4-2. Mechanism and Examinations Based on the design concepts D), E) and F), the new hand was developed. During the mechanical design stage, the link length and thickness of the new hand were deformed to be from 90% to 110% of the average dimension of a young Japanese female. Fig. 4 shows the new developed hand and its principal dimensions. As shown in Figs. 3 and 4, the dimensions of the new hand are almost that of a young Japanese female. Fig. 5 shows an illustration of the new hand mechanism. Fig. 5(a) shows the exterior of the new hand which has a

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(a) New Hand

(b) Abducted posture of thumb

(c) Adducted posture of thumb

(d) Extended posture of 4 fingers

(e) Flexed posture of 4 fingers

Fig. 5. Illustration of new hand mechanism

Fig. 6. Previous hand [left] and new hand [right]

Fig. 7. Japanese female hand [left] and new hand of HRP-4C

which is overlaid with its mechanism [right] (Note: Left picture doesn't show the strict size of Japanese female standard.)

thumb and 4 fingers. The new hand, without its palm plate, is shown in Figs. 5(b) and 5(c). These figures tell us that the 1st servomotor with the 1st planetary gear (see servomotor #1 and planetary gear #1 in Figs. 5(b) and 5(c)) enables abduction and adduction of the thumb. The new hand, without its palm plate and thumb mechanism, is shown in Figs. 5(d) and 5(e). As shown in these figures, the 2nd servomotor and the 2nd planetary gear (see servomotor #2 and planetary gear #2 in Figs. 5(d) and 5(e)) are also located inside the new hand. Pulleys and timing belt are also located between them. The output torque of the 2nd planetary gear is transmitted to proximal links of 4 fingers (index, middle, ring, and little fingers), which are locked together, via a parallel crank mechanism as shown in Fig. 5(d). Since each distal link and each middle link are linked with proximal

links, 4 fingers work together during extension and flexion when driven by the 2nd servomotor. The previous hand and the new hand are shown side by side in Fig. 6. The left side of Fig. 7 shows a real Japanese female hand. Her hand length from crease is 170.0[mm], while the average for young Japanese females is 167.8 [mm]. The right side of Fig. 7 shows the new hand on which is overlaid the mechanism. Fig. 6 shows how small the new hand is compared to the previous one. Fig. 7 shows that a human-size hand with a realistic skin was developed. However, there are cases where some spectators still feel the new hand attached to HRP-4C is still out of proportion to its body. Since there might be numerous causes including a psychological issue, we will carefully consider the solution to overcome this issue in the future.

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5. New Foot with Toe Joint 5-1. Design Concept The new foot with an active toe joint was developed for realizing human-like walking motion. Up to now, several bipedal humanoid robots with toe joint have been developed. WABIAN-2R (WAseda BIpedal humANoid- No.2 Refined) developed by Waseda University has a passive toe joint. Bipedal walk with heel-contact and toe-off motion was realized using foot with a passive toe joint [10]. However, we think that the passive toe joint may restrict relative motion between toe and ankle parts. H6 developed by the University of Tokyo has an active toe joint [11]. Using the active toe joint, bipedal and full-body motion was enhanced. However, it can catch something such as a lost article on the floor or carpet fiber between the "U" shaped toe sole plate and heel sole plate. After careful consideration, the design concepts of new foot with toe joint were decided as follows.

Design concepts of new foot: G) No deviation from the appearance of previous foot H) Active joint I) Prevent the danger of sandwiching anything between toe sole plate and heel sole plate

To keep the appearance of HRP-4C, the design concept G) was adopted. When we designed the previous foot without a toe joint, its foot size was designed as a foot with shoes on. There were several reasons why the deformation policy 1) was not applied to the design of the previous foot. One of reasons was that the final appearance was decided by the covers put on the foot mechanism. So, we kept the deformation policy 1) for the previous foot cover design. Another reason was that it is easier to make a stable walk by using a bigger foot. Therefore, we designed the previous foot to be as large as possible keeping its sole outline inside sole cover outline. The third reason was that we needed a 6-axes Force/Torque sensor on the foot to stabilize the humanoid

using our controller [24, 25]. We also needed the mechanism for absorbing the landing impact. Although these didn't allow us to realize the narrow heel on the previous foot, we saw to it that the size of the previous foot was close to be the average of young Japanese females according to the anthropometry database of Japanese [19]. Fig. 8 shows the principal dimensions we considered from among the database and its average of young Japanese females. Since these hurdles are not cleared yet, we designed the new foot with the active joint in consideration of the effect on putting on shoes in accordance with the previous foot. The design concept H) is indispensable both to imitate humanlike toe motion and to make arbitrary toe motion. For safe operation, the design concept I) is required. 5-2. Mechanism and Examinations Based on the design concepts G), H) and I), the new foot with a toe joint was developed. As mentioned in Section 5-1, the new foot with the active joint is designed in consideration of the effect on putting on shoes together with the previous foot. Fig. 9 shows the sole size of the new foot with the newly developed toe joint. The sole size of the new foot is 245 [mm] long and 105 [mm] wide. This is almost the same dimensions as the previous one. Figs. 8 and 9 show us that the size of the new foot is a bit larger than the average young Japanese female. The foot cover of the new foot is almost the same as that of previous foot (Length: 270 [mm] × Width: 121 [mm]) [9], though this can change slightly depending on the condition of the elastic cover. It is designed in the image of a foot wearing a shoe like the previous foot. Fig. 10 shows the mechanism of the new foot with the active toe joint. This figure shows that the new foot is connected to a shin link through 2-DOF ankle joint. The rotational axis of toe joint is illustrated by using a dot-dash line in Fig. 10. As shown in Fig. 10, four bar linkage mechanism is adopted between the toe sole plate and the

Fig. 8. Average of sole size of young Japanese female [19] (Note: Draw line doesn't show the strict outline of Japanese female sole shape.)

Fig. 9. Sole size of HRP-4C

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Fig. 10. Toe joint mechanism

(a) Tiptoe lifted up

(b) Toe joint angle = 0 [deg.]

(Note: Red line doesn't show the strict outline of Japanese female foot shape.)

(c) Tiptoe lifted down

Fig. 11. Examples of toe joint posture

Fig. 12. Walking motion using the active toe joint (walking speed: 1.8 [km/h], step length: 400 [mm], step cycle: 0.8 [sec/step]

heel sole plate to drive the active toe joint. A servomotor and a harmonic drive gear are integrated in the heel sole plate in accordance with design concepts G) and H). To transmit the output torque of the servomotor to the input shaft of the harmonic drive gear, pulleys and timing belt are utilized. The rotational axis of the active driven joint of the four bar linkage mechanism is connected with the output shaft axis of harmonic drive gear (see Fig. 11(c)). One rotational axis of 3 passive free joints of four bar linkage mechanism is consistent with the toe joint axis (see Fig. 11(c)). By using this mechanism, the motion around the toe pitch axis is achieved by driving the servomotor. Fig. 11 shows examples of toe joint posture. In Figs. 11(a) and 11(c), the toes are shown lifted up and down respectively. Fig. 11(b) shows that the toe sole plate and the heel sole plate are in the same plane. In Fig. 11(b), an imitated outline of human foot shape is also illustrated by using a red line. Although it doesn't show the strict outline of

young Japanese female standard, it is illustrated to show that component parts realizing the toe joint mechanism are carefully placed to imitate human foot shape. As shown in Fig. 11, the four bar linkage mechanism enables the height of the toe joint to be close to floor level. It also means that the relative displacement between both sole plates (see surface A illustrated in Fig. 11(a)) is not much, even if the toe joint rotates on its axis. Namely, this mechanism prevents the danger of sandwiching anything between the toe sole plate and the heel sole plate. Fig. 12 shows a sequence of snap shots of walking motion using the active toe joints. This walking motion is generated by our new walking pattern generator [25], which is in progress and is improved from our previous ones [26, 27]. The walking speed is 1.8 [km/h] (step length: 400 [mm/step], step cycle: 0.8 [sec/step]). Looking at Fig. 12, we think the walking motion of HRP-4C mimics human walking motion more closely by using the toe joints.

Surface A

Toe pitch axis

Servomotor

Harmonic drive gear

Four bar linkage mechanism

Pulleys and Timing Belt

Toe sole plate Heel sole plate

Toe pitch axis (Axis of passive free joint #1)

..

Output shaft axis of harmonic drive gear(Axis of active driven joint)

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6. New Eye with Camera 6-1. Design Concept We developed the new eye with camera towards both providing visual information for operators and realization of motion in response to spectators. The design concepts of the new eye with camera were decided as follows.

Design concepts of new eye: J) No deviation from image of previous eye K) Capability of providing visible information for

operators

It is obvious that the design concept J) is necessary to keep the image of the previous face. Since a face seems to be changed easily by something new such as makeup and color contact lenses, we carefully considered where we can place a camera inside of HRP-4C. Although we tried to place the camera on the forehead as a mole, its image was quite different from the previous face. As a result, we decided to place the camera inside of HRP-4C’s eye. As explained in Section 3, the design concept K) is proposed through experience. 6-2. Realization and Examinations To satisfy the design concepts J) and K), we integrated a tiny camera inside the artificial eye. Fig.13 shows the artificial eye and the tiny camera. The tiny camera is a

CMOS camera. Its resolution is 1280 × 1024, and the horizontal angle of view is 43 [deg.], and is connected a computer with USB. To integrate this tiny camera inside of the artificial eye, we first bored a hole that matches the camera in the artificial eye. Next, we ground the bored surface carefully so that we could get a clear image from the tiny camera through these surfaces. The new eye with camera is installed in the left eye of HRP-4C, while the right eye of HRP-4 has no camera. Looking at Fig. 14, it is clear that the new eye with camera doesn't deviate from the image of the previous eye . Fig. 15 is a picture captured by the camera installed inside of left eye of HRP-4C. Although it is slightly dim, it is enough for operators to control by. We also carried out experiments on color recognition using the new eye with camera. In the color recognition process, predefined colors in the image were extracted and the maximum connected area of the colors was acquired by using a labeling algorithm [28]. In the experiments, the color recognition results were transmitted from HRP-4C to the outside monitor though wireless LAN (IEEE802.11g) reducing its quality so that we could check the color recognition process in real-time. Fig. 16 shows experimental results projected on the outside monitor. Since the quality of the color recognition results was reduced for transmitting to the outside monitor, Fig. 16 is dimmer than Fig. 15. A blue circle shown in Fig. 16 indicates recognition results. As shown in Fig. 16, the new eye with camera can be used for color recognition.

Fig. 13. Artificial eye [left] and tiny camera [right]

Fig. 14. New eye with camera installed to left eye

Fig. 15. View from new eye with camera

Fig. 16. Experimental results on tracking a pink ball (Note: The picture quality is reduced to transmit from HRP-4C.)

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7. Conclusions This paper presented the hardware improvements of HRP-4C for entertainment use. The new hand was redesigned to realize a human-size hand with realistic skin and the average figure of a young Japanese female. The foot with active toe joint was realized by the mechanism using a four bar linkage mechanism, a servo motor, and a harmonic drive gear. This mechanism keeps the appearance of human foot with shoe, but also brings the possibility of human-like locomotion. The new eye with camera provides visible and useful image for operation and color recognition without deviation from human appearance. Future work includes making use of this improved hardware. The realization of human-like locomotion and motion responding to spectators are also future work. The realization of a cybernetic human with both lifelike form and performance for entertainment-related venues, is the future design challenge.

Acknowledgments The new foot with toe joint was partly developed as part of the User Centered Robot Open Architecture (UCROA), one of the projects under the AIST Industrial Transformation Research Initiative (“AIST Initiative”), a 3-year industry-academia joint project implemented by National Institute of Advanced Industrial Science and Technology (AIST) since fiscal 2006. The others were carried out in fundamental research project of AIST. The authors would like to express sincere thanks to them for their financial support.

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