Towards Elucidating Control Mechanism underlying Legged Locomotion 

Intelligence through Embodiment

The concept of embodiment [1], in which intelligence emerges through the interaction between brain, body, and environment, is the key to understand extraordinary locomotive ability of animals on the earth and to build robots that can adaptively locomote in the real world.

[1] R. Pfeifer, C. Scheier, Understanding intelligence, (MIT Press, Cambridge, MA, 1999).


A synthetic approach grounded in embodiment, whereby we aim to understand the mechanisms underlying animal locomotion by building a physical robot that can move in the real world [2,3]. This approach has two advantages:

  1. we can test such a robot in environments similar to those encountered by animals without the need to model the environments, thus allowing for sound evaluation of their performance, e.g., in terms of efficiency.
  2. we can design a minimal robot by simplifying its musculoskeletal and neural systems, allowing for extraction of sufficient conditions to explain the underlying mechanism of interest.

[2] B. Webb, Nature 417, 359 (2002).

[3] A. J. Ijspeert, Science 346, 196–203 (2014).

Neuro-robotics: Neuroscience for Robotics, Robotics for Neuroscience

  •  Understanding of human motor performance (adaptation to environments and plasticity of neural and biomechanical systems) from the viewpoint of both “Engineering” and “Neuroscience”.
  • Motor control, Learning mechanism, Sensory perception
  • Robotics technology for neuroscience analysis
  • Neuro-rehabilitation that enables to maximize motor learning effects.



Quadruped robot, oscillex

Versatile gait patterns that depend on the locomotion speed, environmental conditions, and animal species are observed in quadrupeds. Locomotor patterns are generated via the interlimb coordination, which is partially controlled by an intraspinal neural network called the “central pattern generator” (CPG). However, there is currently no clear understanding of the adaptive interlimb coordination mechanism. We hypothesize that the interlimb coordination should rely more on the physical interaction between leg movements through the body rather than the interlimb neural connection. To understand the coordination mechanism, we developed a simple-structured quadruped robot [4, 5, 6] and proposed an unconventional CPG model that consists of four decoupled oscillators with only local force feedback in each leg. Experimental results show that our CPG model allows the robot to exhibit steady gait patterns [4], adaptability to changes in body properties [4], and adaptive gait transition from walking, to trotting [5], to galloping [6]. Our robot mimics locomotor patterns of real quadrupeds following which it can capture the basic mechanism underlying the adaptive interlimb coordination.

[4] D. Owaki et al., J. of Roy Soc Interface, vol. 10, doi: 10.1098/rsif.2012.0669 (2012).

[5] D. Owaki et al., Proc. of IROS2012, pp. 1950-1955 (2012).

[6] D. Owaki and A. Ishiguro, Scientific Reports, 7:277, doi: 10.1038/s41598-017-00348-9, (2017).

Hexapod robot, Mushibot2

Insects exhibit adaptive and versatile locomotion despite their minimal neural computing. Such locomotor patterns are generated via coordination between leg movements, i.e., an interlimb coordination, which is largely controlled in a distributed manner by neural circuits located in thoracic ganglia. However, the mechanism responsible for the interlimb coordination still remains elusive. Understanding this mechanism will help us to elucidate the fundamental control principle of animals’ agile locomotion and to realize robots with legs that are truly adaptive and could not be developed solely by conventional control theories. This study aims at providing a “minimal” model of the interlimb coordination mechanism underlying hexapedal locomotion, in the hope that a single control principle could satisfactorily reproduce various aspects of insect locomotion. To this end, we introduce a novel concept we named “Tegotae,” a Japanese concept describing the extent to which a perceived reaction matches an expectation. By using the Tegotae-based approach, we show that a surprisingly systematic design of local sensory feedback mechanisms essential for the interlimb coordination can be realized. We also use a hexapod robot we developed to show that our mathematical model of the interlimb coordination mechanism satisfactorily reproduces various insects’ gait patterns.

[7] D. Owaki et al., Front. Neurorobot., vol.11:29, doi: 10.3389/fnbot.2017.00029 (2017)

Biped robot, oscilloid

Despite the appealing concept of “central pattern generator” (CPG)-based control for bipedal walking, there is currently no systematic methodology for designing a CPG controller. To tackle this problem, we employ a unique approach: We attempt to design local controllers in the CPG model for bipedal walking based on the viewpoint of “TEGOTAE”, which is a Japanese concept describing how well a perceived reaction matches an expectation. To this end, we introduce a TEGOTAE function that quantitatively measures TEGOTAE. Using this function, we can design decentralized controllers in a systematic manner. We designed a two-dimensional bipedal walking model using TEGOTAE functions and constructed simulations using the model to verify the validity of the proposed design scheme. We found that our model can stably walk on flat terrain.

[8] D. Owaki et al., Living Machines 2016, pp. 472-479 (2016).

Hexapod robot, Mushibot3, to be more “Resilient”

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Intra-leg Coordination 

[12] 宮澤 咲紀子ほか,脚の役割分担を自発的に生成可能な6脚歩行の脚内協調制御則, 第18回計測自動制御学会 (SICE) システムインテグレーション部門講演会 (SI2017), 3D4-05 (2017) 

Leg Amputation

[13] 宮澤 咲紀子ほか,脚の切断状況に応じた歩行運動を生成可能な6脚ロボットの自律分散制御則 , 第30 回自律分散システム・シンポジウム, 127-131 (2018)

[14] 大脇大,脚を切られても歩きつづける昆虫とロボット昆虫と自然vol. 54, pp. 31-34 (2019)  


Sensory Modality Transforming Prosthetics: Auditory Foot

Auditory Foot

Rehabilitation aims for long-term improvements in motor dysfunction through short-term trainings during daily interventions. “Kinesthesia”, i.e. a sense of movement of a body part, plays a crucial role in long-term motor learning as well as in short-term motor control, suggesting that utilizing this kinesthetic feedback is essential for the rehabilitation. Thus, rehabilitation for patients with sensory impairments including kinesthesia should be difficult to improve impaired motor functions.

For rehabilitation of sensory impairments, we proposed a novel biofeedback prosthesis [9] that transforms weak or deficient kinesthetic feedback into an alternative sensory modality. The aim of this study was to verify the short- and long-term effects of this prosthesis in patients with sensory impairments. We applied our prosthesis, called Auditory Foot, which transforms multipoint cutaneous plantar sensations into auditory feedback signals, for walking rehabilitation in a stroke patient with hemiplegia [10].

[9] D. Owaki et al., in Proc. of MHS2015, pp. 229-230, 2015.

[10] D. Owaki et al, Neural Plasticity, doi: 10.1155/2016/6809879, 2016.

Ankle Foot Orthosis with Stiffness Change Using Spring-cam Mechanism

Ankle Foot Orthosis with Stiffness Change

Decreased gait speed is one of challenges for patients with hemiparesis is to be overcome during walking rehabilitation. Joint stiffness, i.e. resistance of the corresponding joint, which is defined as the ratio of its moment variation to its joint angle variation, is an essential factor to increase gait speed on walking in patients. Here, we propose an unconventional Ankle Foot Orthosis (AFO) that enables to change the joint stiffness in response to ankle flexion using spring-cam mechanism. In this study [11], we verified the effect of developed orthosis on walking in one healthy subject. We confirmed the synergetic effect on inter-joint coordination, where increased ankle joint stiffness indirectly decreased both knee and hip joint stiffness, suggesting effectiveness for walking rehabilitation in patients

[11] 大脇大ほか,Proceedings of the 2017 JSME Conference on Robotics and Mechatronics, 2P1-P11, Fukushima, Japan (2017). 


Adaptation after “Leg Amputation”

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“Motion Hacking”

Collaborative Researches with Prof. Dr. Volker Durr and Josef Schmitz at Bielefeld University 

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