Ryuichi Kohzawa

CONTROLLED SYNCHRONIZATION OF TWO 1-DOF COUPLED OSCILLATORS

Two 1-DOF pendulums coupled with a weak spring are considered. This system is a coupled Controlled Hamiltonian Systems that has been studied widely in these days. The control objective is to make pendulums swing synchronously with small input. To this end, Speed Gradient Energy method proposed by Fradkov is adopted to design the controller. Although experimental results showed that the method succeeded in achieving the objective, the mechanism of synchronization was not clear. In this study, the contracted dynamics of the whole system is analyzed and properties of the system are investigated. Through the investigation, a criteria to define the feedback gain of the controller is revealed. Computer simulation and experimental results showed the validity of the method.

Audio servo for robotic systems with pinnae

Sound localization is one of important abilities for robots which utilize auditory information. Binaural information such as interaural time difference (ITD) or interaural intensity difference(IID) is effective for horizontal sound localization. In order to extend this ability to vertical sound localization, spectral cues were utilized in this paper instead of increasing number of microphones. Spectral cues were the information about the vertical position of the sound source on frequency domain. Since spectral cues strongly depended on the shape of pinnae, artificial pinnae for auditory robots were designed based on diffraction-reflection model. A method to detect spectral cues was also developed. By utilizing them, a controller which made the robot orient to the sound source was proposed. Results of an experiment showed the validity of the proposed method.

Spectral Cues for Robust Sound Localization with Pinnae

An important ability in auditory robots is the localization of sound source. In this paper, a robust method to localize the vertical direction of the sound source with two microphones and pinnae is proposed. In order to achieve vertical sound source localization, the method of detecting spectral cues, the relationship between spectral cues and source direction are studied. In addition, this paper considers sound source separation in order to recognize and isolate spectral cues only from the sound source in order to make the method robust to extraneous noise. Furthermore the authors designed an audio servo with the proposed spectral cues and implemented the method in an actual robot. The experimental results confirmed the effectiveness of the method

Flight path control of small unmanned air vehicle

In this paper, a path following control system for a small and light unmanned air vehicle (UAV), called Kiteplane, was proposed. The aircraft contains a large delta-shaped main wing and exhibits stable flying dynamics. Because of this feature, a simple proportional integral differential control method could be implemented since attitude control to stabilize the motion was not needed. Devices installed on board the aircraft were developed for the autopilot system and the proposed control method was implemented. Results of numerical simulations and experiments showed the effectiveness of the approach. This paper also provides an algorithm for using the aircraft to estimate wind direction based on Kiteplane dynamics under the wind effect. A numerical estimation method was proposed and it was implemented on the autopilot system. The experimental results also supported the proposed wind estimating method.

Multivariable adaptive model output following control system based on backstepping strategy and its application to parallel inverted pendulums

In this paper, we propose a design method of an output feedback-based adaptive model output following control system based on backstepping strategy for MIMO plants. It is shown that the proposed adaptive control system has robustness with regard to output-dependent disturbances. Further, the proposed adaptive control method is applied to the parallel inverted pendulums with output-dependent disturbances and the effectiveness of the control system is confirmed through experiments.

Dual-rate Robust Adaptive Control of a Cart-crane System

In this paper, the application of the adaptive output feedback control based on ASPR conditions to a cart-crane system is considered. The multirate sampling and lifting technique and dual-rate control is adopted in order to apply the ASPR based adaptive control scheme. Further, for the obtained dual-rate discrete-time system, a robust adaptive output feedback control which can solve the causality problem is proposed and the boundedness of all the signals in the resulting closed loop control system is analyzed

Control of a flexible arm with input dead zone by a passivity based adaptive output feedback

In this paper, we deal with a tip position control problem of a flexible arm with dead zone for the control input torque. A design method of a passivity based adaptive output feedback control for nonlinear nonminmum-phase flexible arm systems will be presented. To realize an adaptive output feedback control for nonminimum-phase control systems, we introduce a parallel feedforward compensator (PFC) so as to satisfy the OFEP (Output Feedback Exponentially Passive) conditions and design an adaptive feedforward input with a structure of neural networks in order to remove undesired vibration and the steady-state bias error from the PFC output and input dead zone. The effectiveness of the proposed method is examined through experiments for a flexible arm with dead zone.

Sound Localization of Elevation using Pinnae for Auditory Robots

Humans perceive sound lags and differences in loudness between their two ears to ascertain the location of sounds in terms of azimuth, elevation and interval, etc. Humans and animals can determine the direction of sounds using only two ears, by making use of interaural time difference (ITD), interaural phase difference (IPD), interaural intensity difference (IID), etc. Robots can also use sound localization to detect changes in the environment around them; consequently, various sound localization methods for robots have been investigated. Since many animals have two ears, two ears seem to be the minimum requirement for determining sound localization. While most robot’s sound localization systems are based on microphone arrays that consist of three or more microphones, several researchers have attempted achieving binaural sound localization in robots. Nakashima (Nakashima and Mukai, 2004) developed a system that consisted of two microphones with pinnae and a camera that was only utilized in learning. By adopting a neural network that estimated the control command, he proposed a method utilizing sound signals for guiding the robot in the direction of a sound. Takanishi (Takanishi et al., 1993) achieved continuous direction localization of a sound source in the horizontal plane. They used the interaural sound pressure difference and the ONSET time difference as parameters and proposed a method for achieving two-step direction localization in a humanoid head using these parameters. Kumon (Kumon et al., 2003) approached the problem using an adaptive audio servo system based on IID as the control method for orientating the robots in the direction of the sound source in the horizontal plane by using two microphones. This chapter describes the use of an audio servo of elevation for achieving sound localization using spectral cues caused by pinnae. Here, the term “audio servo” denotes a method for simultaneously localizing sound sources and controlling the robot’s configuration, in contrast with conventional methods that are based on the “listen-and-move” principal. The audio servo is characterized by a feedback system that steers the robot toward the direction of the sound by combining dynamic motion of the robot with auditory ability. In order to achieve this, this chapter proposes a method for detecting instantaneous spectral cues, when these cues are not very accurate. Furthermore, controllers that compensate for the inaccuracy of the measured signalare also considered. In addition, this