Hitoshi Arisumi

Dynamic Lifting Motion of Humanoid Robots

This paper describes a motion generation method for dynamic lifting by a humanoid robot. The proposed technique suggests the possibility of taking advantage of the whole body motion in order to facilitate the lifting movement. In particular, the idea is to perform a preliminary motion in order to generate a momentum which is instantaneously transferred to the object as an impulsive force. This allows the humanoid to lift up an object that could not be lifted up only by continuous force. However an impulsive force may make the humanoid unstable. Then, we propose to set the center of percussion (CoPn) of the whole system at the center of the support polygon of the humanoid when it lifts up the object. We also propose a design method of a preliminary motion of the humanoid that generates a sufficient momentum to lift up an object without any slip, tumble and hop of the whole system. The effectiveness of the proposed method is confirmed by simulation and experiment.

Whole-body motion of a humanoid robot for passing through a door - opening a door by impulsive force -

There are many kinds of large, heavy objects, or objects with geometrical constraints in our daily life, but non-fixed robots such as humanoid robots are still not able to manipulate them sufficiently well. In this paper we focus on a swing door as a heavy object with geometrical constraints, and present a method for the humanoid robots to open it by using impulsive forces. We first discuss on momentum transfer from the robot to the door. Then we propose a method of generating a whole body motion to impact on the door. We analyze the dynamic model of the door, and we confirm the validity of our method through simulation. At last, we realize a motion of the robot opening a swing door quickly by the method in experiment with the HRP-2 robot hardware.

Dynamic lifting by whole body motion of humanoid robots

A motion control method of lifting a heavy object up to a higher position with humanoid robots is developed. The key issue of lifting motion is how to reduce the load on humanoid arms in which low-power actuators are implemented. The use of singular postures of arms is well-known to avoid actuator saturation of the arms. By combining two different kinds of humanoid motions such as accelerating an object upward and sliding the body into under the object, we propose a method that enables to transit one singular posture of arms to another while lifting the object. Simulation results show the effectiveness of the proposed method for reducing the load on the arms. We realize a motion of lifting a heavy object dynamically with the humanoid robot HRP-2 through experiment.

Casting Manipulation—Midair Control of a Gripper by Impulsive Force

We have developed a casting manipulator that includes a flexible light string in the link mechanism to enlarge the workspace of the manipulator. In the casting manipulation, an end-effector is launched to its target by releasing the string connected to it, and its trajectory is controlled by the tension of the string. In this paper, we present the midair control of the end-effector. As a simple way, we propose the braking technique to apply impulsive force to the end-effector by braking the movement of the string. Examining dynamic characteristics of the string when an impulsive force applies to it, we show that the midair motion of the end-effector can be controlled by the braking technique. Then, we apply the braking technique to the multiple braking control of the trajectory. We confirm the effectiveness of the proposed method through simulations and experiments using casting manipulator hardware.

Mobility of Humanoid Robots: Stepping over Large Obstacles Dynamically

Humanoid robots are getting increasing attention in the robotics community, not only for the scientific challenge of the complex multibody system issues and mechatronic designs, but also due to their high mobility and versatility. Humanoid robots have the potential to navigate through complex environments such as the standard living surrounding of humans. This is mainly due to the bipedal legged nature of the robotic system, which allows higher mobility than its wheeled counterpart. One of the advantages is that it can negotiate obstacles by stepping over them, which is the topic of the work presented in this paper. The main focus of this research is to investigate stepping over large obstacles. Previous work has reported on algorithms using quasi-static balancing, which resulted in somehow unnatural slow motions. This work however focuses on stepping over larger obstacles in a fluent dynamic motion, using stability criteria on zero moment point instead of center of gravity. All the work is formulated in function of the elaborate HRP-2 humanoid research platform. In this paper a preliminary 2D study on stepping over leg trajectories and their dynamic implications on the overall stability are investigated. The paper discusses the implementation of the stepping over procedure in the overall dynamic motion generator, the implications on the kinematics and dynamics and finally the actual stepping over foot trajectory planner

Dynamic simulator for humanoids using constraint-based method with static friction

A dynamic simulator using constraint-based method is proposed. It is the extension of the formalism previously introduced by Ruspini and Khatib by including static and dynamic friction without friction cone discretization. The main contribution of the paper is in efficiently combining the operational space formulation of the multi-body dynamics in the contact space and solving for contact forces, including friction, using an iterative Gauss-Seidel approach. Comparing to existing work in this domain, we illustrate our method with scenarios involving humanoid in manipulation tasks while contacting with the environment; an experiment validates our results. Technical details that allow an efficient implementation and problems with future orientation to improve the simulator are also discussed. This work is aiming to be a potential module of the next OpenHRP simulator generation.

Swing motion control of casting manipulation

We begin by describing the process of casting manipulation and discussing the swing motion phase. We propose a method of generating the desired swing motion by keeping the string taut from the initial state when the links are hung. We investigate a method for choosing feedback gain using an off-line simulation chart. The method is evaluated by numerical experiments and shown to be effective. We constructed a two-link casting manipulator and conducted an experiment in swing motion control. The experimental results show that the proposed method of swing motion control was effective.

Posture control of casting manipulation

We develop a casting manipulator which includes a flexible string in the link mechanism to enlarge the work space of the manipulator. During casting manipulation the gripper is thrown to the target by releasing the string at a suitable time after generating enough motion by swinging. In this paper we deal with the posture control of the gripper after the throwing motion. First, we point out the problems of planning for throwing the gripper while considering its posture when catching. Then we propose a method of applying an impulsive force to the gripper in the air through the string by restricting the motion of the string. Investigating the characteristics of the string through experiments, we confirm the effectiveness of the impulsive force. This method was evaluated by comparing the results of numerical simulations with those of our experiments using the experimental casting manipulator hardware.

Casting manipulation (braking control for catching motion)

We have been developing a casting manipulator which includes flexible string in the link mechanism to enlarge the work space of the manipulator. In the casting manipulation, a gripper is thrown to its target by releasing the string at a suitable time after generating enough motion of the gripper by swinging. In the paper we deal with the midair motion control of the gripper after throwing it for catching a target. First, we point out the necessity of controlling the gripper in midair after throwing it. Then we propose the utilization of an impulsive force applied to the gripper in the air by restricting and releasing the motion of the string. Investigating the impulsive force generation through experiments, we proposed the plural braking control of the gripper and confirmed the effectiveness of the method by simulation results.

Swing motion control of casting manipulation (experiment of swing motion control)

We have been developing a casting manipulator which includes a flexible string in the link mechanism in order to enlarge the work space of the manipulator. Like the casting motion of fly fishing, the necessary motion of the gripper, which is attached at the end of the string, is generated by swinging a rigid link The gripper is thrown to the target by releasing the string at the suitable time. In this paper we deal with the basic swing motion control of the casting manipulator. We describe a method of oscillating the casting manipulator by considering it as a two-degrees-of-freedom nonholonomic system By planning a time-periodic reference for the second joint while controlling the first joint, the desired swing motion of the system can be generated. The method was evaluated by comparing the results of numerical simulation and those of experiments using the casting manipulator hardware.