Welcome to our 2nd Special Issue on Humanoid Robots. In this issue you will find some important articles in this exciting field. We believe that this field overlaps significantly with the intended scope of our Applied Bionics and Biomechanics.
First, the article Optimal Limb Length Ratio of Quadruped Robot Minimizing Joint torque on Slopes, by Tadayoshi Aoyama, Kosuke Sekiyama, Yasuhisa Hasegawa, and Toshio Fukuda, aims to determine an optimal structure for a quadruped robot, which will allow the robot's joint torque sum to be minimised. The authors perform a numerical simulation that analyses the joint torques for various limb lengths and slope angles in order to determine the optimal structure of a robot walking on a slope. Their investigation determines that the optimal ratio of rear leg length (RRL) can be derived by the use of a simulation designed to determine the physical structure of a quadruped robot. The analysis suggests that joint torque will increase as the slope angle becomes steeper if the rear legs of the robot are shorter than its forelegs, and that joint torque will decrease as the slope angle declines if the robot's forelegs are shorter than its rear legs. The article also presents experimental results that validate the simulation analysis.
Next, Construction of Gait Adaptation Model in Human Splitbelt Treadmill Walking, by Yuji Otoda, Hiroshi Kimura, and Kunikatsu Takase, proposes a simple control model (to construct the gait adaptation model of human splitbelt treadmill walking) and makes a newly developed 2D biped robot walk on the splitbelt treadmill. This paper combines the conventional limit-cycle based control consisting of joint PD-control, cyclic motion trajectory planning, and a stepping reflex with a newly proposed adjustment of P-gain at hip joint of the stance leg. The experimental data demonstrates the success of the proposed gait adaptation model in human splitbelt treadmill walking, and confirms the validity of the authors' hypotheses and the proposed model using the biped robot. Afterwards, AAU-BOT1: a Platform for Studying Dynamic, Life-like Walking, by Mads S⊘lver Svendsena, Jan Helbo, Michael Rygaard Hansen, Dejan B. Popovic, Jakob Stoustrup, and Mikkel Melters Pedersen, describes the development of the humanoid robot AAU-BOT1, to investigate humanlike walking and in this context, to test prosthetic limbs. The AAU-BOT1 [with 19 degrees of freedom (DoF), 17 actuated and 2 un-actuated as passive toe joints] is designed based on modularity, making it possible to replace, e.g. the lower leg to test trans-femoral or trans-tibial prosthesis or orthosis. Recorded motion data from a human male test person, along with approximated inertial and mass properties, are used to determine necessary joint torques in human walking as design parameters for the robot. In order to reduce the robot construction costs, off-the-shelf hardware is utilised and three groups of masters students carry out the development and instrumentation. The result is a low-cost humanoid robot fully assembled and equipped with sensors ready to take its first steps.
The Rh-1 Full-Size Humanoid Robot: Design, Walking Pattern Generation and Control, by M. Arbulu, D. Kaynov, L. Cabas, and C. Balaguer, presents an overview of the humanoid robot Rh-1. The robot mechanical design includes the development of some specifications in order to construct a platform which is capable of stable biped walking. The construction of the humanoid robot also includes the design of hardware and software architectures relaying on standardised solutions frequently used in the automation industry and on commercially available hardware components. Thus, the proposed architectures provide scalability, modularity, and application of standardised interfaces and bring the design of the complex control system of the humanoid robot out of a closed laboratory to industry. The three dimensional linear inverted pendulum model (3D-LIPM) and the cart-table models are used in order to achieve natural and dynamic biped walking. Additionally, a control architecture for dynamic humanoid robot walking is proposed that allows to make online modifications of the motion patterns in order to adjust it to a continuously changing environment. Also, some experimental results concerning biped locomotion of the Rh-1 humanoid robot are presented and discussed.
In a subsequent article, Forward Models Applied in Visual Servoing for a Reaching Task in the iCub Humanoid Robot, by Daniel F. Tello Gamarra, Lord Kenneth Pinpin, Cecilia Laschi and Paolo Dario, details the application of a forward model to improve a reaching task. The reaching task is accomplished by a humanoid robot with 53 d.o.f. and a stereo-vision system. The article explores via simulations a new way of constructing and utilising a forward model that encodes eye-hand relationships. A forward model is constructed using the data obtained from only a single reaching attempt. ANFIS neural networks are used to construct the forward model which is updated online with new information that comes from each reaching attempt. Based on the obtained forward model, an initial image Jacobian is estimated and is used with a visual servoing controller. Simulation results demonstrate that errors are lower when the initial image Jacobian is derived from the forward model.
Binaural Active Audition for Humanoid Robots to Localise Speech Over The Entire Azimuth Range, by Hyun-Don Kim, Kazunori Komatani, Tetsuya Ogata, and Hiroshi G. Okuno, applies motion theory to robot audition to improve inadequate performance. First a sound source localisation system is designed and integrated with cross-power spectrum phase (CSP) analysis and an EM algorithm. The CSP of sound signals obtained with only two microphones is used to localise the sound source without having to measure impulse response data whereas the EM algorithm helps the system to cope with several moving sound sources and reduce localisation errors. Also proposed is a way of constructing a database for moving sounds to evaluate binaural sound source localisation. The evaluated sound localisation method using artificial moving sounds confirmed that it could effectively localise moving sounds slower than 1.125 rad/s. Thus, solving the problem of distinguishing whether sounds are coming from the front or rear by rotating and/or tipping the robot's head equipped with only two microphones. The system is applied to a humanoid robot (SIG2), and its ability to localize sounds over the entire azimuth range is confirmed.
Finally, KASPAR – A Minimally Expressive Humanoid Robot for Human–Robot Interaction Research, by Kerstin Dautenhahn, Chrystopher L. Nehaniv, Michael L. Walters, Ben Robins, Hatice Kose-Bagci, N. Assif Mirza, and Mike Blow, provides a comprehensive introduction to the design of the minimally expressive robot KASPAR, which is particularly suitable for human–robot interaction studies. A low-cost design with off-the-shelf components is used in a novel design inspired from a multi-disciplinary viewpoint, including comics design and Japanese Noh theatre. The design rationale of the robot and its technical features are described in detail. Three research studies using KASPAR extensively are presented. These studies differ in the way as to how the robot is being operated and its role in social interaction scenarios. Each is introduced briefly and examples of the results are provided. Reflections on the specific design features of KASPAR that are important in these studies and lessons learnt from these studies concerning the design of humanoid robots for social interaction are also discussed. An assessment of the robot in terms of utility of the design for human–robot interaction experiments concludes the article.
I would like to mention that Applied Bionics and Biomechanics will be publishing in the near future another (our 3rd) special issue on Biologically Inspired Robots and Mechanisms. That special issue will again contain significant contributions in the field. I would like also to bring to your attention that we will also be publishing in the near future other Special Issues on related topics such as: Robot Assisted Surgery; Assistive and Rehabilitation Robotics; Human-Robot Interface/Interaction; and Personal Care Robotics.
We warmly welcome past, present, and new authors to the regular and special issues of our journal that is truly international in scope with published manuscripts from all over the world. I hope that our regular issues, this second special issue on humanoid robots, and the upcoming special issues, will continue to be of great interest, use, and benefit to you.