Bistability, i.e., the existence of just two stable equilibria, is known to play an important role in biological systems, e.g., cellular differentiation and apoptosis. In this paper, we consider the bistability but as a structural property of a class of network systems, that is, the bistability under the assumption that the information on the network structure is available but the information on the components is not available. First, we introduce Boolean networks as a model of biological network systems and give the notion of structural bistability. We next focus on the systems with a flower-shaped network structure and present a necessary and sufficient condition based on three characteristics of the network topology. Finally, the result is extended to the Boolean networks with a chain-shaped network structure.

We propose a new device for controlling traffic in intersection, named linear traffic light. The linear traffic light detects vehicles entering the intersection and shows personalized traffic signal to them by linearly aligned traffic lights. The main features of the traffic control system based on the linear traffic light are its simplicity and reliability. In contrast to the other newly developed traffic control systems, the systems with the linear traffic light are implementable only with highly reliable and mature technologies. And, the system does not depend on neither vehicle-to-vehicle communication nor self-localization, which is relatively difficult and whose reliability is crucial in other newly developed traffic control strategies. In this paper, the design of linear traffic light and a traffic control strategy for a simple intersection are shown. Also, the implementability and effectiveness of the linear traffic light are verified through an experiment with prototype miniature traffic control system.

Chemotaxis is the biological phenomenon in which organisms move to a more favorable location in an environment with a chemical attractant or repellent. Since chemotaxis is a typical example of the environmental response of organisms, it is a fundamental topic in biology and related fields. We discuss the performance of the internal controllers that generate chemotaxis. We first propose performance indices to evaluate the controllers. Based on these indices, we evaluate the performance of two controller models of Escherichia coli and Paramecium caudatum. As a result, it is disclosed that the E. coli-type controller achieves chemotaxis quickly but roughly, whereas the P. caudatum-type controller achieves it slowly but precisely. This result will be a biological contribution from a control theoretic point of view.

In this paper, we propose a new example of non-holonomic mobile robot, which we call the surface walker. This robot is composed of a hemisphere-shaped shell and a 2-d.o.f. mass-control device (pendulum) inside it, and undergoes the rolling contact constraint between the hemispherical surface of the robot and the ground. Unlike a lot of non-holonomic robots which have ever been researched, the drift term exists in the system of the hemisphere robot. First, we show basic concepts which the hemisphere robot has, and construct the kinetic model of this robot. Then we realize the locomotion control of the robot by periodically oscillating the internal pendulum and show its effectiveness by control experiments.

This paper proposes a new type of output coupling mechanisms using the harmonic drive. The mechanism uses the input surplus power through distributing it to the other outputs, which enables us to use the input power more effectively. The proposing mechanism has ability of speed reduction and non-backlash anew. We can keep the increase of torque loss and inertia to a minimum because we can put together output coupling mechanisms and reduction gears. We express in this paper about a compositional principle of this mechanism and experimental results. And we show the effectiveness of this mechanism.

The paper presents a new control method which achieves autonomous obstacle avoidance for manipulators with rate constraints. More precisely, in order to achieve the autonomous obstacle avoidance, we exploit the freedom of the coordinate transformation for feedback linearization of nonlinear control systems. At the same time, we cope with the rate constraints by adopting the state-dependent time scale transformation. Furthermore, we apply this method to an actual two-link robot manipulator, and evaluate its effectiveness by experiment, which is the most important part of the paper.

This paper proposes a new type of iterative learning control algorithm for manipulators, which seeks the desired input in an appropriate finite dimensional input subspace. The method achieves perfect tracking for uncertain manipulators without using time derivative of tracking error signals in the learning law. The convergence condition of the learning process is derived, and the effectiveness of the proposed method is evaluated by experiments using a two-link direct drive arm.

In this paper, a new adaptive robust control scheme for manipulators is proposed that overcomes the drawbacks of conventional adaptive robust control methods. The proposed controller has a simple structure by exploiting the special structure of the manipulator dynamics, and achieves the specified tracking precision without any a priori information on uncertainty. Furthermore, the feedback gain of the proposed method is almost necessary and minimum for the specified precision. To verify the advantages of the method, experimental results are shown for the trajectory control of a 2-DOF direct-drive arm.>

Deals with robust control of robot manipulators in the case where joint torque sensors are available. First, the authors derive a dynamic equation of the manipulator with joint torque sensors that explicitly expresses the total nonlinear multivariable structure. This dynamic equation makes it possible to construct the control system of the manipulator with joint torque sensors using the same method as in the conventional case without the sensors. Second, based on this dynamic equation, they propose a robust trajectory control scheme which achieves the specified tracking accuracy in the presence of the modeling errors including the modeling errors of actuator systems. In the proposed method, the joint torque sensor information is fully exploited to compensate the uncertainty of link and load parameters. Furthermore, an illustrative simulation result is given to show the effectiveness of the proposed control method.>

An approach to designing controllers for dynamic hybrid position/force control of robot manipulators is presented, and preliminary experimental results are given. Dynamic hybrid control is an extension of an approach proposed by M.H. Raibert and J.J. Craig (1981) to the case where the full manipulator dynamics is taken into consideration and the end-effector constraint is explicitly given by the constraint hypersurfaces. This design method consists of two steps. The first step is the linearization of the manipulator dynamics by nonlinear state feedback. Formulation of the constraint by the constraint hypersurfaces plays an essential role in establishing the linearizing law. The second step is the design of position and force controllers for the linearized model using the concept of two-degrees-of-freedom servocontroller. The merit of this servocontroller is that it can take account of both the command response and the robustness of the controllers to modeling errors and disturbances. Preliminary experiments using a SCARA robot show the validity of the approach.>

An approach to designing controllers for dynamic hybrid position/force control of robot maniulators is presented and preliminary experimental results are given. Dynamic hybrid control is an extension of the hybrid control approach proposed by Raibert and Craig to the case where the full manipulator dynamics is taken into consideration. This design method consists of two steps. The first step is the linearization of the manipulator dynamics by nonlinear state feedback. The second step is the design of position and force controllers for the linearized model which takes account of both the command response and the robustness of the controllers to modeling errors and disturbances. Preliminary experiments using a SCARA robot show the validity of the approach.