17-07-2012, 04:27 PM
Some Issues in Humanoid Robot Design
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Introduction
Even though the market size is still small at this moment, applied fields of robots
are gradually spreading from the manufacturing industry to the others in recent
years. One can now easily expect that applications of robots will expand into the
first and the third industrial fields as one of the important components to support
our society in the 21st century. There also raises strong anticipations in Japan that
robots for the personal use will coexist with humans and provide supports such as
the assistance for the housework, care of the aged and the physically handicapped,
since Japan is the fastest aging society in the world.
Consequently, humanoid robots and/or animaloid robots have been treated as
subjects of robotics researches in Japan such as a research tool for human/animal
science, an entertainment/mental-commit robot or an assistant/agent for humans in
the human living environment.
Over the last couple of years, some manufactures started to develop prototypes or
even to sell mass production robots for the purposes mentioned above, such as the
SONY’s pet robot AIBO and the small size humanoid robot QRIO, the TMSUK’s
tele-humanoid robot TMSUK04 and the TMSUK-SANYO's home utility robot
ROBORIOR, the HONDA’s humanoid robot ASIMO, the TOYOTA’s partner
humanoid robots, the NEC’s information agent robot PaPeRo, etc. Most of those
robots have some lifelikeness in their appearances and behaviors. Moreover,
AIST, METI of Japan launched some national projects, such as Humanoid
Research Project (HRP) in 1998 and the New Generation Robot Project in 2004 to
develop humanoid robots and service robots, to accelerate the market growth of
personal and service robots in the near future.
Bipedal Humanoid RobotWABIAN-2
In retrospect, many researchers have studied the control and mechanism of biped
robots in recent years (Sakagami et al. 2002), (Nishiwaki et al. 2000), (Nishiwaki et al. 2002), (Löffler et al. 2003). These humanoid robots assimilated dynamic and
stable walks. However, there are a few studies on human-like upper body. The
Japanese National Institute of Advanced Industrial Science and Technology with
cooperation of Kawada Industries, Inc., have developed HRP-2 and HRP-2P,
which have 2-DOF trunk system and implement falling down motion in a positive
way and rising from a lying position (Kaneko et al. 2002), (Fujiwara et al. 2003).
This robot effectively bent its trunk in the experiments. The humanoid research
group of Waseda University has also been studying biped humanoid robots since
1966. Research on the WABIAN (WAseda BIpedal humANoid) series had set
walking with 3-DOF trunk motion and walking with 3-axis ZMP (Zero Moment
Point) compensation using the trunk (Lim H et al. 1999), (Lim H et al. 2002).
In advance of this study, we already have developed a new biped walking robot
named WABIAN-2/LL (WAseda BIpedal humANoid-2 Lower Limb). Moreover,
we have developed an algorithm that enables the robot to stretch its knees in
steady walking avoiding singularity by using waist motion, and carried out stretch
walking experiment by using this robot (Ogura Y et al. 2004), (Ogura Y et al.
2004). WABIAN-2/LL without upper limb originally developed as a lower limb
system for a humanoid type robot WABIAN-2(WAseda BIpedal humANoid-2). In
this chapter, we propose this new humanoid robot WABIAN-2 which has two 7-
DOF legs, a 2-DOF waist, a 2-DOF trunk, and two 7-DOF arms. In the
development of the robot, new design principle for a robot which can be used as a
walking assist machine for a handicapped or elderlies is set as the first goal of this
study.
Design Concept
Human motion
Human body mechanism basically comprises bones as rigid links, cartilage that
lines the joints, muscles and tendons that actuate each part of the body. It is
impossible to replace all of this muscular-skeletal system by current mechanical
components.
Therefore, we determined that the primary goal of the mechanical design is to
develop a robot that can imitate equivalent human motion.
Klopsteg et al. have proposed the result of the gate analysis of humans (Klopsteg
et al. 1963). Figure 3 shows the pelvis and the knee motion plotted in the steady
walking phase. The data is based on experimental results of 8 people walking
motion who do not have physical or mental handicaps. In the result, human’s
pelvis motion in steady walking is observed in frontal plane (defined as roll
motion in this study) and horizontal plane (defined as yaw motion). Waist motion
in side plane (defined as pitch motion) is seldom observed. According to this a
humanoid robot which can perform walks similar to human should be able to
move its hips in the roll and yaw axes. These hip movements have to be
independent in its trunk position.
Mechanisms
Overview
The whole mechanical design was done by using a 3D CAD software, SolidWorks
2003. The frameworks of WABIAN-2 are mainly made of duralumin in order to
realize antithetical concepts; light weight, high stiffness and wide movable range.
Each actuator system of joint consists of a DC motor, a Harmonic drive gear, a lug
belt and two pulleys. This double speed reduction mechanism allows high
reduction ratio, and also a joint axis to be set apart from a motor axis. Therefore,
we could design a human-like joint mechanism without a big projection. In this
paper, we mainly focus on the development of the waist, trunk and arms.
Specifications of each joint such as maximum torque and rotating speed are
designed based on results of software simulations. Those results were computed
by using Newton-Euler’s Method and estimated mass distribution. The several
types of the simulations were carried out for the determination of the joint
specification. The details are described as follow.
Conclusions and FutureWork
This paper describes how we designed the two humanoid robots WABIAN-2 and
WE-4RII. WABIAN-2 has 7-DOF legs, a 2-DOF waist, a 2-DOF trunk, and 7-
DOF arms. In the development of the robot, new design principle for a robot
which can use walking assist machine is proposed. In the near future, we shall
propose a hardware simulator system capable of being applied to the evaluation of
welfare machines or robots. In order to demonstrate the validity of the proposal,
we are presently preparing an experiment in which a biped humanoid robot uses a
walking assist machine. The measurements of the current or force/torque sensors
will present a quantitative clarification of the manner in which the machine assists
humanoid walking. We also designed the 9-DOFs Emotion Expression Humanoid
Arms as well as the 6-DOFs RCH-1s, and integrated them into the Emotion
Expression Humanoid Robot WE-4R. We also have developed an emotion
expression control method for WE-4RII and that was presented in IROS 2004. In
the future, we shall increase the emotional expression patterns and robot
behaviors. And, we also shall introduce the behavior model which autonomously
determines and outputs the most suitable behavior or emotional patterns according
to the situation which is one of the essential functionalities of an intelligent robot
to interact with humans.