A transformable wheel designed in this study is proposed to meet the increasingly complex travel requirements of people because it is urgent to provide a smooth and barrier-free travel scheme in complex and changeable urban land. The transformable wheel, with 10 pivoting-head parts, allows vehicles with the wheels to surmount low-height obstacles that deliberately complicates the terrain such as blind roads, small steps, bumps and door sills, and to achieve low-consumption travel. In this study, we demonstrate that the transformable wheels improve its performance by nearly 30% under the road conditions of low-height obstacles and is especially suitable for carts and suitcases passing through low-height obstacles such as blind lanes and low stairs.

The robust stabilization of the attitude of quadrotors with respect to disturbance torques is a fundamental and crucial control problem in many unmanned aerial vehicle (UAV) applications. For this problem, a control Lyapunov function (CLF)-based robust adaptive control was previously proposed by the authors, and its effectiveness was confirmed through numerical simulations. In this article, we tackle the experimental verification of this controller. We first construct a quadrotor testbed equipped with the self-developed flight controller. Then, we implement the proposed robust adaptive controller and perform flight experiments. According to the results of comparative experiments using a PID-type controller and a non-robust controller, we demonstrate the effectiveness of the proposed controller.

In many unmanned aerial vehicle (UAV) applications, achieving stable flight despite actuator failures is crucial. Among the many existing fault-tolerant control (FTC) methods, adaptive control is a practical approach. In this article, we present experimental verification of a backstepping-based adaptive fault-tolerant controller previously proposed by the authors. As the first step of the experimental verification, we focus on the attitude-loop control of the quadrotor. We construct a quadrotor testbed integrating a self-developed flight controller. After parameter identification, we implement the adaptive fault-tolerant controller on the quadrotor. Finally, real-time experiments on attitude stabilization following actuator faults are conducted. As a result, we confirmed that the controller can be implemented and can stabilize the attitude even in the presence of multi-actuator faults.

Trajectory tracking control of input-constrained systems is an essential problem in many control applications, including robotics. In this paper, we propose a constrained tracking controller for input affine nonlinear systems with convex input constraints based on tracking control Lyapunov functions (TCLFs). To deal with general convex input constraints, we first solve a convex optimization problem that minimizes the time derivative of TCLFs subject to convex input constraints; we refer to its optimal solution as minimizing input. Then, the proposed trajectory tracking is constructed by using the minimizing input and an appropriate scaling function. We prove that the proposed controller locally achieves trajectory tracking and satisfies the given convex input constraints. Finally, we demonstrate the effectiveness of the proposed controller by numerical simulations of a wheeled mobile robot.

Diseases associated with the Eustachian tube include Eustachian tube stenosis, Eustachian tube opening, and otitis media with effusion. The Eustachian tube insufflation method is used both for examining and treating Eustachian tubes and is clinically performed on patients with Eustachian tube diseases. However, the Eustachian tube insufflation sounds that are produced by this method are only auscultated by the doctor. Therefore, there is a disadvantage that the sound is not saved as data, and diagnosis is based on the auditory judgment of doctors, leading to weak objectivity. The purpose of this study is to improve the objectivity of diagnosis by developing a system that quantitatively evaluates the severity of the Eustachian tube insufflation sounds. We collected Eustachian tube insufflation sounds from patients with the Eustachian tube disease. The acoustic characteristics of the collected data were analyzed in order to quantify the difference in the Eustachian tube insufflation sound, depending on the degree of the Eustachian tube disease. In addition, spectrum analysis was performed using the maximum entropy method (MEM), and the abnormal sound was extracted from the cross-correlation function with the template of the abnormal sound. The change of the frequency spectrum with time was expressed. As a result, the time taken to open the Eustachian tube was recorded and an index indicating the severity of normal and stenotic sounds was proposed.