Kazuo Tanaka

This paper presents a guaranteed-cost disturbance observer and controller design to achieve accurate path tracking control for a powered paraglider (PPG) in the presence of unknown rudder trim and wind disturbances. The key contribution of this paper is a theoretical approach that ensures given flight control performance even in the presence of these unknown variables. Due to the complex and highly nonlinear nature of PPG dynamics, our approach utilizes a nonlinear control framework based on Takagi-Sugeno fuzzy models. Although this paper designs a nonlinear controller that compensates the rudder input not only with the trim but also with the wind estimated by the disturbance observer, it successfully derives guaranteed-cost design conditions that allow the separate design of the disturbance observer and the nonlinear controller within this framework. In addition, the influence of observer estimation errors on control performance degradation is discussed in terms of considering the upper bound of given control performance. The effectiveness of the proposed approach is demonstrated through extensive flight simulations using a high-precision PPG simulator, which accurately models the real-world flight dynamics of two rigid bodies with seven degrees of freedom. This validates the practical utility of the guaranteed-cost disturbance observer and controller design in maintaining control performance under unknown rudder trim and wind disturbances.

This article explores the observer-based feedback control problem for a nonlinear hyperbolic partial differential equations (PDEs) system. Initially, the polynomial fuzzy hyperbolic PDEs (PFHPDEs) model is established through the utilization of the fuzzy identification approach, derived from the nonlinear hyperbolic PDEs model. Various types of state estimation and controller design problems for the polynomial fuzzy PDEs system are discussed concerning the state estimation problem. To investigate the relaxed stability problem, Euler’s homogeneous theorem, Lyapunov–Krasovskii functional with polynomial matrices (LKFPM), and the sum-of-squares (SOSs) approach are adopted. The exponential stabilization condition is formulated in terms of the spatial-derivative-SOSs (SD-SOSs). Additionally, a segmental algorithm is developed to find the feasible solution for the SD-SOS condition. Finally, a hyperbolic PDEs system and several numerical examples are provided to illustrate the validity and effectiveness of the proposed results.

Recounts the career and contributions of Michio Sugeno.

This article presents a practical design approach for complex path tracking control of a tailless fixed-wing unmanned aerial vehicle (UAV) with a single pair of elevons, which is considered to be one of the most challenging UAVs to control. The proposed approach provides a well-balanced design that considers both the kinematics and dynamics of the UAV. A sum-of-squares (SOS) design framework is employed to achieve the complex path tracking control of the tailless UAV. By introducing $\cal {S}$ -procedure relaxations, more relaxed SOS conditions are newly derived to design a controller that satisfies three design requirements: 1) a sufficient decay rate of the bank angle error, 2) a real actuator constraint, and 3) a smaller $L_{2}$ gain with respect to the rotational motion dynamics. Instead of finding a unique and fully optimized feedback gain that satisfies the three SOS design requirements, the design approach finds a selectable region of semioptimized feedback gains that satisfy the SOS inequality constraints. The design policy is suitable for practical use as it allows for adjusting feedback gains within the specific selectable region during actual experiments to handle flight performance degradation caused by unmodeled characteristics. Finally, flight experiment results demonstrate the utility of the proposed design approach.

Arrhythmias are conditions characterized by a faster, slower, or irregular heart rhythm. Some of them may be harmless and brief, but others can lead to sudden cardiac arrest. Thus, procedures that safely restore a normal heartbeat are a matter of interest. Laboratory experiments have evidenced that some arrhythmia exhibit nonlinear deterministic behavior, which justifies the need to build mathematical models for heartbeat description. The study of these models may contribute to a better understanding of arrhythmias mechanism and new heartbeat control treatments. This paper addresses a model-based tracking control method for heart rhythm regulation in a cardiac model. Since there is no consensus on the equations describing the heart dynamics, we leverage a nonlinear oscillator that is able to reproduce a variety of electrocardiogram-like waveforms when adjusting a parameter. First of all, the nonlinear system under study is represented as a Takagi-Sugeno fuzzy model. Due to its multiple local linear systems structure, tracking control design conditions for both nominal and uncertain slave systems are formulated as linear matrix inequalities. The simulation examples show that the proposed feedback control framework can restore the heart rhythm dynamics from a non-desirable situation to the normal behavior given by the reference system, which reveals a proof of concept to use tracking control techniques to suppress pathological behaviors.

This paper proposes a method for the movement of a snake robot on crowded pipes or one with large branches. The robot moves along a pipe by grasping it with its entire body instead of wrapping around it, and it adjusts its body shape to the target curve. The proposed robot contains a part that does not contact the pipe, allowing it to move in two directions: along or around the pipe axis. It avoids obstacles by combining these movements while making contact with itself to reduce joint torque and preserve body shape. Experiments demonstrated the efficacy of the proposed robotic snake motion by circumnavigating an obstacle on a pipe in several situations. GRAPHICAL ABSTRACT

This paper presents a descriptor representation-based guaranteed cost design methodology for polynomial fuzzy systems. This methodology applies the descriptor representation for presenting the closed-loop system of the polynomial fuzzy model with a parallel distributed compensation (PDC) based fuzzy controller. By the utility of descriptor representation, the guaranteed cost control (GCC) design analysis can utilize polynomial fuzzy slack matrices for obtaining less conservative results. The proposed GCC design is presented as the sum-of-squares (SOS) conditions. The application of polynomial fuzzy slack matrices leads to the double fuzzy summation issue in the control design. Accordingly, the copositive relaxation works out the problem well and is adopted in the control design analysis. The GCC design minimizes the upper limit of a predesignated cost function. According to the performance function, two simulation examples are provided to demonstrate the validity of the proposed GCC design. In these two examples, the proposed design obtains superior results.

This paper proposes a method for an articulated mobile robot to change its local body shape in a complex environment. By coexisting a heuristic approach which is easy to design a motion in a complex three-dimensional environment and a model-based approach which can utilize the redundancy of the robot, the robot achieves propulsion in a complex environment and the local body shape control simultaneously. A part of the robot's body shape is changed based on a kinematic model, whereas the rest of it is controlled to follow the original shape or maintain its original position based on a heuristic method. As an application of the proposed method, the recovery motion from a stuck state is proposed. The robot is recovered from a stuck state by controlling the part of the robot that is in collision with an obstacle to move it away from the obstacle. The effectiveness of the proposed method is verified by experiments on an actual robot. GRAPHICAL ABSTRACT