Sang-Ho Hyon

Full-Body Compliant Human–Humanoid Interaction: Balancing in the Presence of Unknown External Forces

This paper proposes an effective framework of human-humanoid robot physical interaction. Its key component is a new control technique for full-body balancing in the presence of external forces, which is presented and then validated empirically. We have adopted an integrated system approach to develop humanoid robots. Herein, we describe the importance of replicating human-like capabilities and responses during human-robot interaction in this context. Our balancing controller provides gravity compensation, making the robot passive and thereby facilitating safe physical interactions. The method operates by setting an appropriate ground reaction force and transforming these forces into full-body joint torques. It handles an arbitrary number of force interaction points on the robot. It does not require force measurement at interested contact points. It requires neither inverse kinematics nor inverse dynamics. It can adapt to uneven ground surfaces. It operates as a force control process, and can therefore, accommodate simultaneous control processes using force-, velocity-, or position-based control. Forces are distributed over supporting contact points in an optimal manner. Joint redundancy is resolved by damping injection in the context of passivity. We present various force interaction experiments using our full-sized bipedal humanoid platform, including compliant balance, even when affected by unknown external forces, which demonstrates the effectiveness of the method.

CB : a humanoid research platform for exploring neuroscience

This paper presents a 50-d.o.f. humanoid robot, Computational Brain (CB). CB is a humanoid robot created for exploring the underlying processing of the human brain while dealing with the real world. We place our investigations within real—world contexts, as humans do. In so doing, we focus on utilizing a system that is closer to humans—in sensing, kinematics configuration and performance. We present the real-time network-based architecture for the control of all 50 d.o.f. The controller provides full position/velocity/force sensing and control at 1 kHz, allowing us the flexibility in deriving various forms of control. A dynamic simulator is also presented; the simulator acts as a realistic testbed for our controllers and acts as a common interface to our humanoid robots. A contact model developed to allow better validation of our controllers prior to final testing on the physical robot is also presented. Three aspects of the system are highlighted in this paper: (i) physical power for walking, (ii) full-body compliant control—physical interactions and (iii) perception and control—visual ocular-motor responses.

Physical interaction between human and a bipedal humanoid robot-realization of human-follow walking

This research is aimed at the development of bipedal humanoid robots working in a human living space, with a focus on its physical construction and motion control method. At the first stage, we developed the bipedal humanoid robot WABIAN (Waseda bipedal humanoid), and proposed a control method for dynamic cooperative biped walking. In this paper, we present a follow-walking control method with a switching patterns technique for a bipedal humanoid robot to follow human motion by hand contact. By a combination of both algorithms, the robot is able to perform dynamic stepping and walking forward and backward in a continuous time while someone is pushing or pulling its hand. In this paper, the authors describe the control methods for the realization of physical interaction between a human and a bipedal humanoid robot.

Compliant Terrain Adaptation for Biped Humanoids Without Measuring Ground Surface and Contact Forces

This paper reports the applicability of our passivity-based contact force control framework for biped humanoids. We experimentally demonstrate its adaptation to unknown rough terrain. Adaptation to uneven ground is achieved by optimally distributed antigravitational forces applied to preset contact points in a feedforward manner, even without explicitly measuring the external forces or the terrain shape. Adaptation to unknown inclination is also possible by combining an active balancing controller based on the center-of-mass (CoM) measurements with respect to the inertial frame. Furthermore, we show that a simple impedance controller for supporting the feet or hands allows the robot to adapt to low-friction ground without prior knowledge of the ground friction. This presentation includes supplementary experimental videos that show a full-sized biped humanoid robot balancing on uneven ground or time-varying inclination.

CB: A Humanoid Research Platform for Exploring NeuroScience

This paper presents a 50 degrees of freedom humanoid robot, CB -Computational Brain. CB is a humanoid robot created for exploring the underlying processing of the human brain while dealing with the real world. We place our investigations within real world contexts, as humans do. In so doing, we focus on utilising a system that is closer to humans - in sensing, configuration and performance. The real-time network-based control architecture for the control of all 50 degrees of freedom will be presented. The controller provides full position/velocity/force sensing and control at 1 KHz, allowing us the flexibility in deriving various forms of control schemes. Three aspects of the system are highlighted in this paper: 1) physical power for walking; 2) full-body compliant control - physical interactions; 3) perception and control - visual ocular-motor responses

Modulation of simple sinusoidal patterns by a coupled oscillator model for biped walking

We show that a humanoid robot can step and walk using simple sinusoidal desired joint trajectories with their phase adjusted by a coupled oscillator model. We use the center of pressure location and velocity to detect the phase of the lateral robot dynamics. This phase information is used to modulate the desired joint trajectories. We applied the proposed control approach to our newly developed human sized humanoid robot and a small size humanoid robot developed by Sony, enabling them to generate successful stepping and walking patterns

Symmetric Walking Control: Invariance and Global Stability

This paper first presents a novel control strategy for periodic motion control based on a Hamiltonian system. According to the strategy, hybrid symmetric orbits (ideal walking gaits) are explored using reversal symmetry of the Hamiltonian system. Then, an invariance controller, a Symmetric Walking Controller, is derived systematically to distribute the symmetric orbits densely throughout the entire phase space. Finally, a new robust walking speed controller is formulated based on the passivity of the controlled system. Consequently, solutions starting from any point globally converge to a stable limit cycle having a desired energy level. The controller has strong passivity and robustness, thereby rendering it capable of using external disturbances as energy for walking propulsion. It requires no model parameters and can be implemented in a very small program size. Furthermore, it is applicable to any biped robot without major modification. In this report, the effectiveness of this controller is proved mathematically, validated numerically, and confirmed experimentally.

Energy-preserving control of a passive one-legged running robot

Fast and energy-efficient control is an increasingly important and attractive area of research in legged locomotion. In this paper, we present a new simple controller for a planar one-legged passive running robot having a springy leg and a compliant hip joint. The most distinctive advantage of the controller over previously proposed ones is it does not require any pre-planned trajectories nor target dynamics. Instead, it utilizes exact non-linear dynamics. Our results are summarized as follows. First, we propose an energy-preserving control strategy for energy-efficient and autonomous gait generation. This strategy is successfully implemented as a new touchdown controller at the flight phase. Simulation results show that the robot can hop from a wide set of initial conditions. Moreover, the running gaits generated are found to be quasi-periodic orbits, which can be seen in Hamiltonian systems. Since the controlled running gaits exist for every admissible energy level, they have some robustness against disturbances. Next, it is shown that an adaptive control of the touchdown angle, which is similar to a delayed feedback controller for a chaotic system, can asymptotically stabilize these quasi-periodic gaits to the periodic ones of the desired period, with some limitations. In particular, for one-periodic gait, by using some additional adaptive controllers, the robot eventually hops without any control inputs. Since our energy-preserving strategy is clear and implementation of the controller is straightforward, we believe it can be easily applied to a wide class of legged mechanisms.

Passivity-Based Full-Body Force Control for Humanoids and Application to Dynamic Balancing and Locomotion

This paper proposes a passivity-based hierarchical full-body motion controller for force-controllable multi-DOF humanoid robots. The task-space forces are treated in a uniform manner for a variety of position/force tracking and force/moment compensation. The contact force closure is optimally solved and transformed directly into the joint torques in real-time without any joint trajectory planning. With this framework, we introduce gravity compensation at the lowest layer of the controller that makes the closed-loop system passive with respect to additional inputs as well as external forces. Furthermore, we propose two upper-layers: one layer controls the ground reaction forces, which enables the robot keep the dynamic balance. The other layer is the another passification control, which constructs an invariant manifold that prevents the robot from falling during walking. Four realistic dynamic simulations: balanced squatting, reaching, externally driven, or speed-controlled walking with disturbances demonstrate the effectiveness of the proposed methods

Disturbance Rejection for Biped Humanoids

This paper proposes a simple passivity-based disturbance rejection scheme for force-controllable biped humanoids. The disturbance rejection by force control is useful not only for self-balance, but also for stable and safety physical interaction between human and humanoid robots. The core technique is passivity-based contact force control with gravity-compensation. This makes it easy to control the contact forces in a satisfactory dynamic range without canceling all non-linear terms. The disturbance rejection is located at the higher layer above the contact force controller. It is composed of three sub-controllers; 1) a balancing controller; 2) a stepping controller; and 3) the trigger. Numerical simulations and experiments evaluate the effectiveness of the proposed controller. Although the method is incomplete in the sense that the self-collision between the limbs is ignored, a preliminary experimental result on a real humanoid platform demonstrates that the proposed method can actually make the robot recover the balance under large unknown external perturbations.