The purpose of this study is to develop a lightweight and intelligent soft actuator which can be safely attached to the human body. A novel flexible pneumatic cylinder that can be used even if it is deformed by external force had been proposed. The cylinder can realize both pushing and pulling motions even if the cylinder bends. In this paper, a flexible pneumatic cylinder with a built-in flexible linear encoder is proposed and tested. The encoder can detect the cylinder displacement even if the cylinder bends. In the next step, to realize an intelligent flexible cylinder, it is essential to recognize the angle of deflection of the cylinder to estimate the direction of the external force. Therefore, a flexible bending sensor that can measure the directional angle by attaching it to the end of the cylinder is also proposed and tested. The tested bending sensor also consists of four inexpensive photo-reflectors set on the circumferential surface to the cylinder tube every 90 degrees from the center of the tube. By measuring the distance between the photo reflector and the surface of the tube at each point, the bending directional angle of the cylinder can be obtained. A low cost measuring system using a micro-computer incorporating a programmed Up/Down counter to measure the displacement of the cylinder is also developed. As a result, it was confirmed that the measuring accuracy of the bending directional angle was good, less than 0.7 degrees as a standard deviation.

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In this paper, we study consensus problems of continuous-time multiagent systems. A multiagent system forms a communication network where each agent receives information from its neighbors. This information is used to obtain the control inputs necessary for achieving consensus. It is assumed that delays exist in communication networks. Communication delays are time dependent and differ for each communication channel. In addition, it is assumed that communication networks have switching topologies, and feedback gains are time varying. Under these assumptions, we show that a network system consisting of first-order agents is bounded and find a condition under which it achieves consensus. Stability is shown by using the Lyapunov theorem. In addition, we extend the consensus algorithm for first-order systems to an output consensus algorithm for high-order systems.

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It is preferable to refrain from switching the torque in mechanical systems because the abrupt change tends to cause vibration and noise. However, such vibration can be beneficial if it is used to store mechanical energy. Moreover, torque switching operations at higher frequencies are becoming possible because of the recent advances in clutch devices. This paper describes a novel torque conversion mechanism based on torque switching operations. The fundamental principle of the mechanism is the reciprocal translation between the work to and from axles and the rotational energy of a flywheel. Clutches are used to intermittently connect or disconnect the axles with the flywheel; the output torque is controlled by changing the time ratio of the connection. By performing switching operations at a higher frequency, almost continuous torque conversion can be realized. A prototype was created using electrorheological fluid clutches, and it showed the potential for torque conversion. The performance of the prototype was also analyzed by numerical simulation; this showed that the prototype worked in accordance with the principle. Moreover, the potential capability of the principle was investigated using a numerical model and the results suggest that by improving the mechanical design, a considerable improvement in performance is possible.

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To suppress two-dimensional load sway caused by the horizontal boom motion of a rotary crane, both horizontal and vertical boom motions are generally used. However, it would be more energy efficient and safer if a control scheme is developed that only used horizontal boom motion, eliminating the need for any vertical boom motion. In addition, if we can suppress load sway without the need to measure it, reduction in the cost of sensors can be achieved. Furthermore, use of simple velocity trajectory patterns such as a trapezoidal velocity pattern and an S-curve acceleration/deceleration pattern, which are widely used in industrial automation systems, may provide cost-effective implementation of controllers. This study examines the analytical conditions for a simple S-curve trajectory of horizontal boom motion to suppress residual load sway without sensing it. Numerical simulation and experimental results demonstrate the effectiveness of the proposed conditions.

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This paper proposes a yaw rate tracking control method that distributes the driving/ braking force exerted on vehicles at the time of negotiating sharp turns and driving at high speeds. The proposed method employs quadratic programming to distribute the driving/braking force in order to equalize the tire load factor on all wheels and consider the limits of the driving/braking force. The yaw rate tracking performance can be improved even while driving at high speeds and negotiating sharp turns by setting limits for the driving/braking force, differential moment, etc. The effectiveness of our proposed method is proven by a numerical simulation.

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In braking situations, it is known that a motorcycle may become unstable. In this paper, a front-steering assist control is designed to stabilize a motorcycle during braking. The rider-motorcycle system with its pitching motions is linearized around an equilibrium point of quasi-steady state straight running with constant deceleration. From the viewpoints of eigenvalues and frequency responses, the linearized model is analyzed and a reduced-order model is obtained to design the control system by using H_∞ control theory. By carrying out simulations, it is demonstrated that the control system can stabilize a motorcycle during braking when receiving a sudden disturbance from the front wheel, and its applicable scope is discussed for several situations including different maneuvering of a rider.

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In this study, we propose a real-time model predictive control method for leg/wheel mobile robots which simultaneously achieves both obstacle avoidance and wheel allocation at a flexible position. The proposed method generates both obstacle avoidance path and dynamical wheel positions, and controls the heading angle depending on the slope of the predicted path so that the robot can keep a good balance between stability and mobility in narrow and complex spaces like indoor environments. Moreover, we reduce the computational effort of the algorithm by deleting usage of mathematical function in the repetitive numerical computation. Thus the proposed real-time optimization method can be applied to low speed on-board CPUs used in commercially-produced vehicles. We conducted experiments to verify efficacy and feasibility of the real-time implementation of the proposed method. We used a leg/wheel mobile robot which is equipped with two laser range finders to detect obstacles and an embedded CPU whose clock speed is only 80MHz. Experiments indicate that the proposed method achieves improved obstacle avoidance comparing with the previous method in the sense that it generates an avoidance path with balanced allocation of right and left side wheels.

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In many countries in which the phenomenon of population aging is being experienced, motor function recovery activities have aroused much interest. In this paper, a sit-to-stand rehabilitation robot utilizing a double-rope system was developed, and the performance of the robot was evaluated by analyzing the dynamic parameters of human lower limbs. For the robot control program, an impedance control method with a training game was developed to increase the effectiveness and frequency of rehabilitation activities, and a calculation method was developed for evaluating the joint moments of hip, knee, and ankle. Test experiments were designed, and four subjects were requested to stand up from a chair with assistance from the rehabilitation robot. In the experiments, body segment rotational angles, trunk movement trajectories, rope tensile forces, ground reaction forces (GRF) and centers of pressure (COP) were measured by sensors, and the moments of ankle, knee and hip joint were real-time calculated using the sensor-measured data. The experiment results showed that the sit-to-stand rehabilitation robot with impedance control method could maintain the comfortable training postures of users, decrease the moments of limb joints, and enhance training effectiveness. Furthermore, the game control method could encourage collaboration between the brain and limbs, and allow for an increase in the frequency and intensity of rehabilitation activities.

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Many studies have been conducted to investigate the change in human response under various experimental conditions. Usually, these experiments were conducted using many subjects and the inter-subject variation was evaluated. However, the intra-subject variation in human response is also necessary for understanding the change in an individual's physical response to whole-body vibration (WBV). The aim of this study is to investigate the intra-subject variation in biodynamic responses (both apparent mass and seat-to-head transmissibility) of a seated human exposed to vertical whole-body vibration over time. In the experiments, nine male subjects were exposed to vertical random vibration (0.2-0.3 m/s² in r.m.s.) in the 0-30Hz frequency range. The measurement variation was also evaluated, wherein the measurements were repeated five times without any change to form the “baseline” for each subject, and the intra-subject variations were evaluated by comparing their responses with these “baseline.” The intra-subject variation was examined from two different viewpoints: variation “within a day” and that “over several days.” To determine the intra-subject variation “within a day”, the five measurements were obtained at two-hour intervals on the same day. In the intra-subject variation “over several days”, the five measurements were obtained again, but at the same time of the day on five consecutive days. The results show that the intra-subject variations (both “within a day” and “over several days”) in biodynamic responses are larger than the “baseline.” However, when the variation “within a day” in biodynamic responses is compared to that “over several days,” no common trend is observed among subjects. Although the magnitude of intra-subject variation in biodynamic responses depends on each subject, both variations “within a day” and that “over several days” have a similar range of variation.

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A simple nonlinear system that generates synchronization is developed to clarify the mechanism behind the phenomenon. The present system consists of two nonlinear self-excited oscillators subjected to Coulomb friction, resulting in the generation of stick-slip motion. These oscillators are directly coupled in series by a coil spring and a dashpot. The synchronization generated in this system is studied both analytically and experimentally. The validity of the model and the numerical method based on the shooting method are verified by comparing the numerical and experimental results. As a result, it is found that two types of synchronized solutions exist in this system, and the vibratory patterns of the synchronized solutions are closely related to the undamped free vibration characteristics of the model without Coulomb friction. In addition, differences between the occurrence mechanisms of the synchronized solutions are analytically confirmed by examining the energy transmission between the two oscillators through the coupling element. It is also proved that unstable regions caused by internal resonance exist in the solution branch, in which the two oscillators vibrate nearly in phase.

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This paper presents a response evaluator which evaluates the response of the system and decides the control input to the system. It is applied to a base isolated structure with a semi-active oil damper whose damping coefficient has large or small values. Absolute acceleration of a top story and displacement of an isolated layer are the input signals of the response evaluator, and switching parameter for the damping coefficient is the output signal of the response evaluator. The response evaluator consists of a layered neural network, and a genetic algorithm is used to adjust the neural network parameters which decide the performance of the response evaluator. A computer simulation is carried out using several kinds of earthquake motions, and absolute acceleration and displacement of each story which are trade off relations of each other are reduced to the intermediate value of the response in case where constant damping coefficients are large or small. From the result of simulations, the effectiveness of the response evaluator is verified.

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Japan's progressing aging society increasingly needs evaluation of equipment used for human assistance. Earlier studies have evaluated the use of wheelchairs. However, the manner in which the equipment moderates the generated consumption energy of helpers has not been described sufficiently. This study performs mechanical evaluation of a helper's walking using a wheelchair on a slope. We use the Musculoskeletal Model to estimate the joint moment and energy consumption. Results obtained with 14 volunteers who assisted these wheelchair experiments were considered for cases in which the energy consumption of the wheelchair increased by 13% from that of a normal gait when moving up an incline. This evaluation method is useful for developing practical assistance equipment.

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