Sho Sakaino

Multi-DOF Micro-Macro Bilateral Controller Using Oblique Coordinate Control

In this study, we show that tasks can be realized by appropriate coordinate transformation. This approach, oblique coordinate control, decouples tasks. Even though a system is large, they can be designed by a combination of small tasks. Therefore, tasks can be regarded as reusable components. In this study, micro-macro bilateral control is achieved as a complicated task. Small objects can be manipulated as large objects in micro-macro bilateral control. However, ideal micro-macro bilateral controllers are usually derived only for single-degree-of-freedom (DOF) systems. Then, we propose a micro-macro bilateral controller for multi-DOF on the basis of oblique coordinate control. To obtain multi-DOF bilateral control, we first derive control goals as kinematic relations. This study also considers the case where scaling gains of position and force are selected in a different manner. The goals of micro-macro bilateral control are then controlled by oblique coordinate control. The validity of the proposed method is experimentally verified.

Walking Trajectory Planning on Stairs Using Virtual Slope for Biped Robots

In this paper, a “virtual slope method” for walking trajectory planning on stairs for biped robots is proposed. In conventional methods for walking on stairs, there are two problems about the zero-moment point (ZMP). One is a ZMP equation problem, and the other is a ZMP definition problem in a double-support phase. First, a ZMP equation on stairs is different from that on flat ground. Therefore, the same trajectory generation as flat ground cannot be implemented. This problem is defined as a “ZMP equation problem.” Second, the ZMP cannot be defined in the double-support phase on stairs because contact points of the feet do not constitute a plane. The ZMP can be defined only on the plane. This problem is defined as a “ZMP definition problem.” These two problems are solved concurrently by the virtual slope method. It is the method that regards the stairs as a virtual slope. In walking trajectory planning on a slope of the constant gradient, the two problems about the ZMP do not exist. Additionally, a trajectory planning procedure based on the virtual slope method is explained. The validity of the proposed method is confirmed by some simulations and experiments.

Real-Time Walking Trajectory Generation Method With Three-Mass Models at Constant Body Height for Three-Dimensional Biped Robots

In this paper, a real-time walking trajectory generation method with three-mass models at constant body height for 3-D biped robots is extended for a diagonal walking. By realization of the diagonal walking, the availability is improved. The modeling of this method is more precise than that of conventional real-time walking trajectory generation methods. In this method, the zero-moment point equation of a body is derived, and an analytic solution of a body trajectory at a constant body height in a single support phase is obtained. Because the analytic solution is used, real-time trajectory generation can be realized. In addition, this method has advantages of the body trajectory at the constant body height. The validities are confirmed from simulations of the 2-D walking and an experiment of the 3-D diagonal walking.

Precise Position/Force Hybrid Control With Modal Mass Decoupling and Bilateral Communication Between Different Structures

In this study, we achieve haptic communication between different structures. In haptic communication, tactile sensation is transmitted to a remote place by cooperating robots. Conventional haptic communication is implemented under the assumption that the masses of the actuators are equal. We have found that haptic communication system is a kind of position/force hybrid control system and that it is not necessary to follow that assumption. In addition, exact modeling of haptic communication system and decoupling of tasks are essential for highly precise haptic communication. First, we describe the kinetic and dynamic behaviors of haptic communication system for cardiac surgery. The deterioration of haptic performance is shown to depend on an interference term, due to off-diagonal parameters in the modal mass matrix. Second, we propose a novel hybrid controller for the decoupling of the responses, and we analyze its performance, stability, and robustness. Simulations and experiments toward cardiac surgery are shown, and the effectiveness of the proposed method is verified.

Development of a physical therapy robot for rehabilitation databases

With increasing demands for rehabilitation, the need for physical therapy robots is also increasing. This paper proposes the construction of a rehabilitation database inspired with medical cloud technologies. We discuss the possibility of establishing a new validation methodology by generating a database based on the data collected using rehabilitation equipment. In this research, data was obtained by rehabilitation equipment and statistical processing was applied to the data to investigate an example of a validation method. The experimental results suggest that improvement of tracking property of subjects is much larger than improvement of maneuverability.

Motion reproduction system with haptic information for different environment location

A motion reproduction system with haptic information for different environment location is proposed in this paper. In recent years, save and reproduction of human motion have been researched. Using a motion save system, position and force of the human motion are able to be saved as haptic information. In the conventional reproduction method, the reproduction of the human motion is not applicable when the environment location is different. Therefore, the motion reproduction system for the different environment location is proposed. In order not to be dependent on the environment location, two reproduction principles are defined and velocity data is used in the proposed method. Thus, advanced motion reproduction in various situations is realized with the haptic information by the motion save system and the proposed motion reproduction system. Validity of the proposed method was confirmed by experiments.

Parameter design for ZMP disturbance observer of biped robot

In this paper, a parameter design for ZMP (Zero-Moment Point) disturbance observer of biped robots is proposed. ZMP disturbance observer is used for the walking stabilization of biped robots. A decision method of six parameters is based on the stability and the performance. Relation between the parameters and the performance is shown. Gains of the position compensation and the acceleration compensation are decided. Additionally cutoff frequencies of filters are decided. Characteristics of ZMP disturbance observer are shown. The validity of the proposed parameter design was confirmed by the simulations and the experiments.

Oblique coordinate control for advanced motion control - Applied to micro-macro bilateral control -

A controller for oblique coordinates is proposed in this paper. In an oblique coordinate, certain vector is expressed by two forms. One is a covariant vector, the other is contravariant vector. Usually, position is described by a contravariant vector, and force is given by a covariant vector. In order to realize hybrid control in a oblique coordinate, position and force should be unified into same vectors. These vectors are synthesized by a metric tensor, and a novel hybrid controller for oblique coordinate is obtained. The dynamic properties are given by “task mass matrix”. By this method, whatever tasks given by position and force would be decoupled. Micro-macro bilateral is considered as an example of the oblique coordinate control. It was confirmed by some simulations and an experiment.

A Novel Motion Equation for General Task Description and Analysis of Mobile-Hapto

In this paper, mobile-hapto is analyzed, which is a remote control system that enables the realization of two tasks: velocity control of a mobile robot and force transmission between a handle robot and a mobile robot. To date, there have been no analyses of mobile-hapto because of the fact that the dynamics of mobile-hapto is difficult to derive without the motion equation proposed in our previous study. This motion equation, in turn, allowed for the proposal of a stable mobile-hapto controller. In this paper, the proposed mobile-hapto controller is analytically compared to a conventional mobile-hapto controller. The results show that decoupled tasks can be obtained only in the proposed method. We also show the robustness of the proposed method. To confirm the validity of the proposed method, the proposed controller is experimentally compared to the conventional controller. This is the foremost study on the analysis and experimental comparison of mobile-hapto. Consequently, the usefulness of the proposed motion equation is shown.

Real-time walking trajectory generation method at constant body height in single support phase for three-dimensional biped robot

In this paper, a real-time walking trajectory generation method at constant body height in a single support phase for three-dimensional biped robots is proposed. An analytic solution of a body trajectory was obtained from a ZMP (Zero-Moment Point) equation of a body and a swing leg trajectory. Real-time body trajectory is generated based on an analytic solution. This body trajectory is applied, the biped robot walks stably without up and down of the body height. Additionally, the modeling of the proposed method is more precisely than that of the conventional methods. The validity of the proposed method was confirmed by some simulations and an experiment.