Advanced Robotics, 2013 http://dx.doi.org/10.1080/01691864.2012.754079

SHORT PAPER Development of open platform humanoid DARwIn-OP Inyong Ha*, Yusuke Tamura and Hajime Asama

Department of Precision Engineering, The University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-8656, Japan (Received 24 January 2012; accepted 27 March 2012)

To develop an appropriate research platform, this paper presents the design method for a humanoid which has a net- work-based modular structure and a standard PC architecture. Based on the proposed method, we developed DARwIn- OP which meets the requirements for an open humanoid platform. DARwIn-OP has an expandable system structure, high performance, simple maintenance, familiar development environment and affordable prices. Not only hardware but also software aspects of open humanoid platform are discussed in this paper. Keywords: open platform; humanoid; DARwIn-OP

1. Introduction lution from E series [3]. Then, they opened the first ver- A is a robot that has a general structure sion of ASIMO which walked stably at 1.6 km/h to the of the human body, such as two legs, two arms, a torso, public in 2000 [4]. A new ASIMO was introduced in and a head. Although, some shapes of a humanoid robot 2005 and it could run and walk up and down stairs. Sup- may not be exactly the same as that of a human, a ported by the Ministry of Economics, Commerce and humanoid robot has a basic similar appearance and func- Industry, Japan, the HRP-2 was developed by National tions of a human. For its human-like features described Institute of Advanced Industrial Science and Technology above, a humanoid robot has a potential to conduct tasks and Kawada Industries, Inc. from 1998 to 2002 [5]. The fi in human environments. Furthermore, a humanoid robot HRP-2 was the rst humanoid robot which a research may even use tools designed for a human without modi- institute and a company were involved in. They also fication. The development purpose of a humanoid robot developed the HRP-3 in 2007 [6] and the HRP-4 [7] and is to make a robot that thinks and acts like a human. At the HRP-4C in 2009. Different from previous humanoid the end, the humanoid robot will do work on behalf of a , the HRP-4C is a female humanoid robot which fi human, and a human can concentrate on more productive has realistic head, and a gure based on averages from activities. The other significant development purpose is the Japanese body dimension database. to understand mental and physical fundamentals of a On the other hand, small-size humanoid robots also human. So, many researchers from different fields adopt have been developed. Although small-size humanoid humanoid robots for their research platform for its syn- robots are hard to be applied to a work for a human

Downloaded by [University of Tokyo] at 15:54 06 February 2013 thetic characteristics. because of their limited size and performance, they can Recently, many kinds of full-size humanoid robots be appropriate research platforms for their manageability have been developed extensively during the past several and affordability. Not only for research platforms but decades. The first complete humanoid robot was the also for the entertainment, small-size humanoid robots WABOT-1 which was created by Kato from Waseda have competitive features. Boosted by these merits, Sony University, Japan in 1973 [1]. The WABOT-1 had a introduced the biped entertainment robot SDR-3X [8] in walking control, a manipulating control, a vision and a 2000, and through the consisting development of SDR conversation system. After that, in 1984, Sugano et al. series, they showed the SDR-4X II [9] named as QRIO developed the WABOT-2 known as the first personal in 2003. The QRIO had a voice and a face recognition fi robot and showed the performance of playing piano [2]. system, could run 23 cm/s and was known as the rst Inspired by these academic research activities on human- running biped robot. Meanwhile, for the research plat- oid robots, companies and research institutes also under- form, released the HOAP series, the HOAP-1 in took the development of humanoid robots. From 1993 to 2001, the HOAP-2 in 2003, and the HOAP-3 in 2005 1997, Honda created the humanoid robot P1–P3, an evo- [10]. By adopting a standard personal computer as the

*Corresponding author. Email: [email protected]

Ó 2013 Taylor & Francis and The Robotics Society of Japan 2 I. Ha et al.

have no choice but to develop a robot because most humanoid robots in the current market do not satisfy requirements for research platform. For an appropriate research platform, a humanoid robot must be constructed considering expandable, modifiable system structure, high performance, simple maintenance, familiar develop- ment environment, and affordable prices. Therefore, in this paper, we suggest the design method for humanoid platform which has a network- based modular structure and a standard PC architecture to meet above mentioned requirements, and develop the- small-size humanoid robot named as DARwIn-OP shown in Figure 1. A preliminary version of this article was delivered at the SICE Annual Conference in Tokyo, 2011.

2. System overview Figure 1. Open platform humanoid robot DARwIn-OP. DARwIn-OP has a network-based modular structure and a standard PC architecture, as shown in Figure 2. All main controller, the HOAP-3 showed the promise for the devices, such as actuators, sensors, LEDs, buttons, and general research platform. external I/Os, are connected to the sub-controller by a Based on these humanoids, various challenging serial bus network which fully supports DYNAMIXEL robotics researches on motion planning, walking, manip- protocol [11]. Each device has a memory-mapped opera- ulating, communication, vision processing, and artificial tion structure with designated ID. intelligence have been carried out and remarkable results For the main controller, we adopted the Intel’s also have been shown. From the overall point of view, it ATOM Z530 CPU, normally used for netbooks. The is no exaggeration to say that a humanoid is the most main controller communicates with the sub-controller by adequate platform for robotics research. USB. The sub-controller works as a gateway to access Although marvelous humanoid robots already exist, devices, as shown in Figure 3. Therefore, all devices are many researchers are still making their efforts and spend- encapsulated as an USB device, which means that the ing time to build new platforms. Of course, for some development environment is just like a standard PC. researchers, it can be an essential work to build a robot in itself because their design scheme is one of the most 3. Hardware structure important research areas. But, for the others, it can be a 3.1. Mechanics burden to make a new robot, and furthermore, it also can be a major disincentive for research. Even those Figure 4 illustrates overall mechanical design scheme of researchers who do not need to make a robot platform DARwIn-OP. A basic configuration of DARwIn-OP has Downloaded by [University of Tokyo] at 15:54 06 February 2013

Figure 2. Modularized component of DARwIn-OP based on PC architecture. Advanced Robotics 3

Figure 3. System block diagram. Downloaded by [University of Tokyo] at 15:54 06 February 2013

Figure 4. Mechanical design of DARwIn-OP.

20° of freedom. The center of mass is located at the cen- ing and proper distribution of inertia during gait, ter of its pelvis. Its location is optimal for proper balanc- especially at the extremities. The modular network-based 4 I. Ha et al.

Figure 5. Different types of grippers for DARwIn-OP.

Downloaded by [University of Tokyo] at 15:54 06 February 2013 Figure 6. Developed MX-28 actuator for DARwIn-OP.

nature of the robot can help the researcher modify any optional gripper types for DARwIn-OP, as shown in extremities by isolating the desired limb from the rest of Figure 5. the body with virtually no overall performance compro- mise of DARwIn-OP. 3.2. Actuators The frames for DARwIn-OP were designed for robot sturdiness and durability. Hollowness of the frames We designed a new improved MX-28 actuator for allows the robot to maintain a fairly low overall weight. DARwIn-OP, as shown in Figure 6, which has a higher The hollow frames were also designed with the assump- resolution, faster communication speed, and a more tion that the user will include additional sensors to the sophisticated controller compared to the previous RX-28 robot. The frames were designed to accommodate such [12]. The previous RX-28 featured a conventional poten- additional sensors and their respective wiring. The hol- tiometer for position control. Over time, the contact low design maintains the scope of a network-based mod- required to give proper position measurement eventually ular structure and facilitates periodic robot maintenance. wears the potentiometer out. The MX-28 implements an Various optional frames for connecting actuators and absolute contactless magnetic potentiometer; its contact- other devices were also designed. Such frames are for less aspect of the encoder virtually eliminates any limited Advanced Robotics 5

Figure 7. Device information of DARwIn-OP.

operation angle of the actuator. Another feature of the tion and balancing are mounted in the upper body. A MX-28, not featured on the previous RX-28, is the USB-based camera and a total of three microphones are Downloaded by [University of Tokyo] at 15:54 06 February 2013 increased 12-bit resolution for more precise position con- located in the head. Optional sensors are Force Sensing trol all over 360° without any gaps or stops. Registers (FSR) modules, in which four FSR’s are placed The MX-28 supports PID controller for position and in each foot, for ground reaction force measurements. speed control. The user can adjust not only position and Additional sensors also can be attached via external I/O speed profile but as well as PID gain parameter in real at the user’s discretion. time. One of the purposes of the accessibility of PID DARwIn-OP makes full use of the provided three- controls of the MX-28 is to minimize or control actuator axis accelerometer and gyroscope for balancing and pos- harmonic resonance-related aspects. As a result, from a ture estimation without compromising walking perfor- holistic standpoint, PID controls provide DARwIn-OP mance. In conjunction of proper implementation of with the highest performance for a humanoid of its type. closed-loop feedback control based on ‘immediate per- formance history,’ DARwIn-OP may be able to increase performance, such as faster walking or quicker recovery 3.3. Sensors time after falling. DARwIn-OP has pluralities of sensors, as illustrated in There is an USB-based camera for image processing Figure 7, which maintains the scope of a network-based placed inside the head. Unlike many other humanoids, modular structure. Basic sensors are a three-axis gyro- the basic configuration of DARwIn-OP only requires a scope and a three-axis accelerometer for posture estima- single camera. The camera is a high-definition camera 6 I. Ha et al.

Figure 8. Software framework class diagram for DARwIn-OP. Downloaded by [University of Tokyo] at 15:54 06 February 2013

Figure 9. Software framework pipeline for DARwIn-OP. Advanced Robotics 7

Figure 10. Application software for DARwIn-OP. Downloaded by [University of Tokyo] at 15:54 06 February 2013

Figure 11. Dynamics simulation environment for DARwIn-OP.

that interfaces with the robot via the USB standard. The camera power source, therefore, keeping the scope of the high-definition aspect of the camera provides much architecture simple. detailed information. Another result of implementing a The microphone allows DARwIn-OP to receive voice high-definition camera is that a single camera device can commands. A simple API can be installed in DARwIn- help maintain a fairly robot simple configuration, there- OP for voice recognition followed by any programmed fore, eliminating the need for a dedicated camera actua- sequential behavior from the voice command. Two addi- tor. The flexibility of the USB standard allows tional microphones are also placed inside the head as implementation of any desired type of camera or well for the purposes of sound localization. Audio sig- multiple cameras for ‘stereo’ vision. Last but not least, nals given by each microphone may be differentiated the USB-based camera eliminates the need of a dedicated from each other by simple differential margin; where the 8 I. Ha et al.

Figure 12. Movie captures of walking test of DARwIn-OP.

Table 1. Overall specification of developed DARwIn-OP. Additional FSR are implemented on each foot for more accurate ground reaction force. These sensors inter- Category Description Data face with DARwIn-OP with the same communication Dimension Height 0.455 m and power line shared by the actuators, while maintain- Weight 2.8 kg ing the daisy chain configuration. This common line DOF Head 2 DOF eliminates the need to add a dedicated line for the FSR’s Arm 2 Â 3 DOF Â helping keep architecture simple. Placing four sensors Leg 2 6 DOF fi Main controller CPU Intel atom Z530 @ per foot allows for more precise information the speci c 1.6 GHz amount of force in a specific area of the foot at a specific RAM DDR2 1 GB pose of DARwIn-OP during its walk. A closed-loop Disk Flash disk 4 GB feedback control augmented with data from the FSR can Network Ethernet/WiFi allow the researcher to refine DARwIn-OP’s gait. Such USB port 2 Â USB2.0 Sub controller CPU ARM 32-bit cortex-M3 data can also be implemented to improve gait during Downloaded by [University of Tokyo] at 15:54 06 February 2013 Frequency 72 MHz unexpected changes on walking surface. Flash memory 512 KB SRAM 64 KB Actuator RX- Holding torque 24 kgfÁcm @ 12 V 3.4. Display and Interfaces 28 M Speed 45 RPM @ No Load Position sensor Magnetic potentiometer DARwIn-OP comes equipped with full-color range RGB Resolution 0.072° LED’s in the eyes and forehead. The researcher can pro- Command Serial 3 MBPS gram specific colors of each LED. The colors can help Interface or alert the researcher visually in real time with the sta- Sensor Gyroscope 3-axis tus of DARwIn-OP. There are also status LEDs and but- Accelerometer 3-axis Pressure-meter 2 Â 4 FSR tons in the back panel. For purposes of direct development environment, DARwIn-OP is also equipped with external ports such robot can accurately localize the sound source by said as HDMI, USB, flash memory port, and Ethernet port. differential margin. The additional microphones, in con- These external ports facilitate interfacing, communica- junction with the voice recognition microphone, can also tions, data storage, and software implementation with the be tools for improving sound localization for a more robot due to the standardized nature of said external accurate source detection. ports in their PC implementation. The external ports Advanced Robotics 9

from the standard PC also maintain scope of the open 5. Conclusion architecture nature of DARwIn-OP. In this paper, we suggested the design method for humanoid which has a network-based modular structure 4. Software architecture and a standard PC architecture to meet the requirements 4.1. Software framework for an open humanoid platform. We surveyed the requirements for the humanoid robot research platform The software aspect of DARwIn-OP has been built with and defined considerable matters for the development of a hierarchical framework considering modularity and the robot. Also, we explained the software aspect of the independency. The framework consists of device com- DARwIn-OP and proposed the hierarchical framework munication module, motion module, walking module, which has modularity and independency for the human- sensing module, behavior module, vision module, and oid robot research platform. DARwIn-OP’s key features diagnostics module, as shown in Figures 8 and 9. The are illustrated in Table 1. framework has been developed with C++ programming All resources of DARwIn-OP including source codes, language where the code is operating system indepen- circuit diagrams, mechanical CAD files, and parts infor- dent. The operating system independent aspect of the mation are open to the public. We hope that DARwIn- framework is essential so that the code can be ported to OP will contribute to robotics research. any existing or future computer operating system. The user may simply write a behavioral code for Notes on contributors DARwIn-OP without the need to develop a separate Inyong Ha received his BS and MS in framework set. In such case, software simulator is the electronic engineering from Korea most practical method of writing the program and testing University, Republic of Korea, and his PhD said program for DArwIn-OP, given that such simulator in precision mechanical engineering from makes use of the provided framework. Due to the open- the University of Tokyo, Japan, in 1998, source nature of DARwIn-OP, the user is encouraged to 2000, and 2012, respectively. Since 1999, share the developed program with other users. However, he has been with the Research Center of the users may not be limited to open-DARwIn-SDK. ROBOTIS Co., Ltd, and he is now the There is currently another independently developed CTO and the vice president of the software that does not implement open-DARwIn-SDK. ROBOTIS. His research interests include humanoid robot, service robot, automatic control, and artificial intelligence. There are some examples where software has been developed at ‘levels.’ For instance, low-level program- ming can take care of the robot’s sub-routines, such as Yusuke Tamura received his PhD degree camera refresh times or read the actuator’s position. The in Engineering from the University of high-level programming can take care of the more Tokyo, Japan in 2008. From 2006 to 2008, he was a research fellow of the Japan abstract aspects of the robots. The different levels are Society for the Promotion of Science. He practical so that recompiling of the entire code is unnec- worked as a project researcher in Research essary on simple changes in subroutine behaviors or into Artifacts, Center for Engineering parameters. (RACE) and Graduate School of Engineering, the University of Tokyo, from Downloaded by [University of Tokyo] at 15:54 06 February 2013 2008 to 2009 and from 2009 to 2012, respectively. He is 4.2. Application tools currently an associate professor in Faculty of Science and We also designed application tools such as action editor, Engineering, Chuo University, Japan. firmware updater, device monitor, walking tuner, and off- set tuner based on software framework above, as shown Hajime Asama received his BMS, and Dr in Figure 10. We also prepared dynamics simulation Eng in Engineering from the University of environment by Webots [13] which is well known as a Tokyo, in 1982, 1984, and 1989, development environment for modeling, programming, respectively. He was a research associate, and dynamics simulating, as shown in Figure 11. research scientist, and senior research Physical properties of DARwIn-OP are used in Webots scientist in RIKEN (The Institute of for model data. We also ported software framework for Physical and Chemical Research, Japan) the simulation. from 1986 to 2002. He became a professor of RACE (Research into Artifacts, Center We also built demonstration program with framework for Engineering), the University of Tokyo in 2002 and a open-DARwIn-SDK for evaluating the performance of professor of School of Engineering, the University of Tokyo in DARwIn-OP. Simple walking algorithm based on gait 2009. He received JSME (Japan Society of Mechanical pattern generator and walk stabilizer are implemented on Engineers) Robotics and Mechatronics Division Academic the robot, as shown in Figure 12. 10 I. Ha et al.

Achievement Award in 2001, RSJ (Robotics Society of Japan) [5] Kaneko K, et al. Humanoid robot HRP-2. Proceeding of Best paper Award, JSME Robotics, and Mechatronics Award in the IEEE International Conference on Robotics and Auto- 2009. He is the vice president of Robotics Society of Japan mation; New Orleans; 2004. p. 1083–1090. since 2011. He was an AdCom member of IEEE Robotics and [6] Kaneko K, et al. Humanoid robot HRP-3. Proceed- Automation Society from 2007 to 2009, an editor of Journal of ing of the IEEERSJ International Conference on International Journal of Intelligent Service Robotics, Journal of Intelligent Robots and Systems; Pasadena; 2008. p. Field Robotics, and Journal of Robotics and Autonomous 2471–2478. Systems. He played the director of the Mobiligence – (Emergence of adaptive motor function through the body, [7] Kaneko K, et al. Humanoid robot HRP-4 humanoid brain, and environment) program in the MEXT Grant-in-Aid robotics platform with lightweight and slim body. for Scientific Research on Priority Areas from 2005 to 2009. Proceeding of the IEEERSJ International Conference on He is a fellow of JSME since 2004 and RSJ since 2008. His Intelligent Robots and Systems; San Francisco; 2011. main research interests are distributed autonomous robotic p. 4400–4407. systems, ambient intelligence, service engineering, [8] Kuroki Y. A small biped entertainment robot. Proceeding Mobiligence, and service robotics. of the International Symposium on Micromechatronics and Human Science; Kawasaki; 2001. p. 3–4. References [9] Ishida T. A small biped entertainment robot SDR-4X II. Proceeding of the IEEE International Conference on [1] Kato I. Development of WABOT 1. Biomechanics Robotics and Automation; Taipei; 2003. p. 297–302. – 1973;173 214. [10] Fusitsu Laboratories. The history of the robot of Fusitsu [2] Sugano S, Kato I. WABOT-2: autonomous robot with Laboratory [cited 2011 May 28]. Available from: http://jp. fi dexterous nger-arm coordination control in keyboard fujitsu.com/group/labs/techinfo/techguide/list/robotics_p11. performance. Proceeding of the IEEE International html Conference on Robotics and Automation; Raleigh; 1987. [11] ROBOTIS Co., Ltd. ROBOTIS: overview of communica- – p. 90 97. tion [cited 2011 Jun 12]. Available from: http://support. [3] Hirai K, et al. The development of Honda humanoid robotis.com/en/product/dynamixel/dxl_communication. robot. Proceeding of the IEEE International Conference htm. – on Robotics and Automation; Leuven; 1998. p. 1321 [12] ROBOTIS Co., Ltd. ROBOTIS: robot actuator dynamixel 1326. RX-28 [cited 2011 July 13]. Available from: http://sup- [4] Hirose M, Haikawa Y. Development of humanoid robot port.robotis.com/en/product/dynamixel/rx_series/rx-28.htm ASIMO. Proceeding of the IEEERSJ International Confer- [13] Cyberbotics Ltd. Webots: robot simulator – overwiew ence on Intelligent Robots and Systems; Hawaii; 2001. p. [cited 2011 June 19]. Available from: http://www.cyber- – 1 6. botics.com/overview Downloaded by [University of Tokyo] at 15:54 06 February 2013