This paper presents a control strategy for mini helicopters having four rotors. Based on the back-stepping method together with sliding mode control theories, a nonlinear robust controller is designed to stabilize the hovering helicopter in the presence of model uncertainty with respect to the actuators. The sliding mode controller, which is a part of the whole controller, contributes to achieve the robust properties. The existence of sliding mode is guaranteed by taking account of the model uncertainty. Numerical simulation illustrates the robustness of the proposed controller against not only the model uncertainty but also torque disturbances such as a gust of wind.

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Control Lyapunov functions (CLF's), CLF based controller designs and a disturbance attenuation attract much attention in nonlinear control theory. However, there does exist few researches which considers both the input constraint and the disturbance attenuation problems. For input constrained systems, we cannot stabilize under unbounded disturbances in general. Then, we consider bounded disturbances, and consider a local asymptotically stabilizable robust control Lyapunov function (AS-RCLF) instead of ISS-CLF or RCLF. In this paper, we clarify the condition for a local AS-RCLF and when a proper function becomes a local AS-RCLF. Moreover, we propose a stabilizing controller for input and disturbances constrained nonlinear systems using AS-RCLF which becomes continuous if a local ISS-RCLF has a ISS-CLF small control property.

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According to the internal model principle, the integral compensator is generally necessary for the servo system such as DC Motor tracking control. However this integral compensator becomes one of the causes of the overshoot or stick slip. To overcome this problem, we applied Backstepping that does not require the integral compensator for tracking control. Consequently in case of the friction force of the system was small, the desired performance was gotten. However in case of the friction force was large, the chattering problem occurred, because the high gain input was required to track. So we added the friction compensation to the input based on Backstepping. Then we could get the desired performance that is superior to the LQI.

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This paper presents a modeling technique and analysis based on nonlinear control theory for kinematic systems subject affine constraints. Affine constraints are more general constraints as linear constraints that many researchers have been studied. We have already modeled and investigated kinematic systems subject affine constraints in, however, we introduce a new analysis method for the systems in this paper. We first define affine constraints and affine/non-affine variables, and explain a condition for nonholonomicity of affine constraints. Next, nonholonomic kinematic systems with affine constraints (NKSAC) are derived from affine constriants and control inputs. We then analyze the NKSAC from the view point of nonlinear control theory. Especially, we focus on the most basic issues of nonlinear contro systems, local accessibility, small-time local controllability and local asymptotic stabilizability. By using the analysis method we propose in this paper, we can derive simpler conditions for the NKSAC in comparison with. Finally, some physical examples are illustrated in order to confirm our results.

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This paper deals with a positioning control of a ball-screw driven system. The objective is to control the motion specified by a trapezoidal velocity profile and to achieve the highly accurate positioning, using multi-segment sliding mode control method. The multi-segment switching functions are designed to satisfy the state trajectories corresponding to the trapezoidal velocity profile. The proposed control method is applied to the system driven by an AC servomotor to verify its control performances. The experimental results show that the proposed technique is applicable to the acceleration and deceleration motion even in the range of 2gm/s^2 (g is the gravitational acceleration) and effectively suppresses a position error as well as an overshoot in comparison with the conventional PID control techniques.

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This paper deals with an experimental study of the propulsion performance of the underwater propulsion mechanism by a self-excited flapping wing. The wing of underwater propulsion mechanism is supported elasticity in heaving direction by two elastic plates, is input driving torque in pitching direction by controlling the motor. When the wing is controlled with feedback by quantity of vibration of two elastic plates, self-excited vibration is occurred. The characteristics of the propulsion force and the side force are examined experimentally with changing drive frequency, angle amplitude of the motor, and speed that water flows. In the experiment, propulsion force and side force are examined in speed of a moving fluid 10[cm/s] in water tank. The flow of water around the wing is visualized and the structure of the vortex street is clarified. As a result, it is found that the system tends to be self-excited when the feedback gain is large and lengths of two elastic plates are 130[mm]. It is shown that the wing occurs flapping vibration combined heaving vibration and pitching vibration by self-excited drive method. It is also found that the propulsion performance of the underwater propulsion mechanism becomes high when the jet-flow occurs around the wing.

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This paper presents a new design method of sliding mode controller with short reaching time by using the time-varying switching hyperplane. Sliding mode control is well known for its robustness to disturbance and uncertainties on the matching condition. When the reaching time is shortened, the controlled system becomes more robust, because it is only ensured on the sliding mode. The proposed method has two different points from the conventional methods. One is, that the state can arrive on the switching hyperplane to realize the desired dynamics under the low influence of the initial state. The other is, that the information of initial state is not necessarily given when the controller is designed. In order to realize such a controller, we use an optimal time-varying switching hyperplane. The weightings in criterion function are changed with time from approximate value of 0 to the appropriate value, since the value of initial switching function is minimal enough to shorten the reaching time. In this paper, the design method of non-stationary sliding mode controlled system is given, and its performance is verified through the numerical calculation for positioning control of second-order system.

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This paper verifies a new mass measurement system that uses a variable stiffness mechanism. The system consists of an actuator and the variable stiffness mechanism that controlls an active length of the blade spring for adjustment of the stiffness. A sample is attached at the tip of the blade spring, and the actuator swings the variable stiffness mechanism periodically. Then mass of a sample is estimated with the period of the swing and the length of the blade spring when the system satisfying the anti-resonance condition.

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