This study discusses an airbag system as a landing gear of a spacecraft for a planetary exploration. The inflated airbag has the capability to attenuate impact acceleration at the instant of landing and submergence into regolith that covers a planetary surface. Crash tests in this paper verify the attenuation performance of the airbag and specify an issue.

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The Martian Moons eXploration (MMX) mission to be launched on 2024 by JAXA aims to send a spacecraft towards the Martian moon and to land it on the surface of the Phobos. One of the most critical phase on the mission is the landing phase of the spacecraft since an impact force at the landing may damage the spacecraft. This paper describes a landing dynamics analysis of a Martian moon lander. The analysis exploits a similarity rule to correlate a lander dynamics with a model experiment. Since the gravitational acceleration of the Martian moon is much smaller than that of the earth, the gravity term in the similarity rule is explicitly considered when model experiments are carried out to estimate the impact force. The drop experiment apparatus developed in this work has a 1.8-meter-long linear motion guide placed vertically, and the model of the spacecraft freely falls along with the guide. The velocity of the model can be arbitrarily given by putting the model at an appropriate initial height which satisfies a basic physics of the free-fall equation. A laser displacement sensor measures the vertical displacement of the model, and therefore, an impact acceleration of the model at the landing phase can be estimated as a 2nd-order time derivative of the displacement. An impact force applied to the real spacecraft is then estimated from the impact force of the model experiment based on the similarity rule. The drop test were performed with varied model velocity and model mass. The experimental result clarifies that the impact force and landing velocity has a positive correlation one another.

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A dust accumulated on a solar array panel of a planetary exploration robot is of particular concern since the dust shades the sunlight and decreases the power generated by the solar array panel. Recent studies in the dust removal technique has proposed an electrodynamic screen as an energy efficient devise for such application, however, an open issue is to supply a power for those devices in a simple and cable-less way. One possible solution for this issue is to exploit a kinetic energy harvester as an energy source. The work described in this paper experimentally demonstrate a vibrationbased kinetic energy harvester towards dust removal for a mobile robot. A power generated by the vibration-based kinetic energy harvester inherently decreases as a vibration frequency applied to the harvester being apart from the specific frequency of the harvester. Therefore, a cantilever mechanism is developed to convert a frequency of ambient vibration to the specific frequency of the harvester so that the power generated from the harvester mounted on the cantilever would increase. In this paper, the proof of concept for the cantilever mechanism for the vibration-based kinetic energy harvester is experimentally confirmed in a field test using a mobile robot in rough terrain. In the field test, dynamic characteristics of solar array panels mounted on the robot is also measured. This measurement clearly indicates that the tip of solar array panel is favorable for the harvester to be mounted since the tip excites its vibration and increases enough power for an operation of a dust removal device.

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We have developed a particle-size sorting system using an electrostatic traveling-wave to extract metals such as platinum and indispensable resources contained in small particles of lunar regolith for In-Situ Resource Utilization on the moon. The particles were initially set on the transport substrate inclined for 10-40 °. The substrate is made of polyimide. Then, small particles were transported upward by the electrostatic traveling-wave, and large particles were pulled back to another side of the conveyer by gravitational force. The size-sorting of lunar regolith simulant was experimentally demonstrated when the inclination angle of substrate, the frequency of applied voltage and the pitch between electrodes of substrate were changed. The system could sort particles smaller as the inclination was increased. The optimum frequency was about 10-20 Hz for size sorting in all cases of the inclination ranging 10-40 °. Particles smaller than 23 μm could be sampled when the interelectrode pitch was 1.3 mm, and smaller than 16 μm could be sampled when the interelectrode pitch was 0.8 mm. The system utilizes only the electrostatic force, it doesn’t need gas, liquid, or even mechanical moving parts, and power consumption is small, thus making it suitable for space applications.

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In this study, we proposed a new mobility device using tether under the microgravity named Tether Space Mobility Device (TSMD). TSMD is the mobility device that moves user by winding tether which is attached to the structure in the destination. However, this system has problems that TSMD user moves with rotation because the center of gravity of the user deviates from tensile line of action of tether. Therefore, we focused on winding of tether and proposed the attitude control method of TSMD with controlled winding speed. The effectiveness of winding control was inspected by the experiment. The experiment is performed in the two-dimensional microgravity environment. Winding control is that winding speed becomes slow when the acceleration of the experiment equipment exceeded the acceleration threshold. In addition, winding acceleration set small just after the experiment start. In this paper, we producted an experimental equipment that excludes the arm mechanism installed for attitude control. We examined the effectiveness of this system by experiments simulating microgravity using an experimental equipment that was smaller and lighter than conventional equipment.

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Recently, small Earth observation satellites have been utilized, and an agile large angle satellite attitude maneuver has been required. Meanwhile, small Earth observation satellites acquire high-resolution data, which results in an increase in the time required for data communication. However, the directly data communication is limited because of the short visibility to ground stations. The situation can be improved by a data relay via GEO-stationary satellites. Owing to these reason, it has become important to ensure that small Earth observation satellites are capable of being maneuvered rapidly and to extend the communication time by using a data relay system. In conventional operation, the antenna motion is carried out after satellite attitude maneuver. But this method has a time delay between the completion of the attitude maneuver and the start of data communication. The purpose of this study is to extend the time of Earth observation and data communication. To achieve the purpose, we propose a simultaneous control method of satellite maneuver and antenna motion. Proposed method solves minimum-time optimization problem restricted by state equation. Firstly, we divide the control input to transfer a minimum-time optimization problem to a nonlinear programming problem. Secondly, we solve the nonlinear programming problem by the sequential quadratic programming. To verify the effectiveness of the proposed method, numerical simulations are carried out under condition of rest-to-rest attitude maneuver mission in this paper. And we confirm that the proposed method could reduce the total settling time of the satellite and antenna.

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Because the analysis of substances from asteroids will contribute to elucidate the origin of the solar system, the establishment of technologies to bring back samples from asteroids to the Earth is indispensable. Ice that exists on asteroids is considered the origin of water on the Earth. This leads to elucidate the origin of life. For the sake of technology establishment, it is necessary to develop a reliable sampling mechanism. A sampling system that utilizes alternative electrostatic force and does not need any mechanical activators was developed. Parallel screen electrodes (wire diameter: 1.2 mm, pitch: 5.0 mm, gap: 5.0 mm) are used to this sampling system. When rectangular two-phase high voltage is applied between the parallel screen electrodes, Coulomb force and dielectrophoresis force act on particles near the electrodes and some agitated particles pass through the openings of the screen electrodes. In this study, the basic properties of the sampling system for ice particles in addition to lunar regolith simulant were investigated. Experiment was carried out and aims to collect 0.1 g particles (with diameters of 1.0 mm or larger) that are minimum amount to give a scientific analysis. As a result, maximum 0.77 g of diameter 1.0 mm or less ice particles were collected by the sampling system. Also, 0.071 g of ice in 1.0-3.0 mm diameter was collected.

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This paper proposes a "tethered sampler" method to be performed in an asteroid exploration mission. In this method, a sampler tethered to a hovering mothership is set to collide with an asteroid. Upon collision, the corer (collector) at the sampler tip is implanted in the asteroid to collect layered samples. Then, the corer is extracted using the tension of the tether. Focusing on the implantation and extraction phases, this research team has conducted experimental analyses on the resistive load during corer extraction, as well as and numerical and experimental analysis on the effect of the angle of attack α (between the corer’s positional and velocity vectors) on the penetration depth. We have also devised measures to counter issues that will arise in the extraction phase. To reduce the resistance load during extraction, a dual-core mechanism was developed and its effectiveness confirmed with a principle model. In addition, to prevent the sample from falling off during extraction, we devised the "Yubihabu" gripping mechanism, which is modeled after a traditional Okinawan toy, Yubihabu. Its basic operational characteristics were also verified. The results of these analyses have yielded numerous findings that will be effective in realizing the "tethered sampler" method.

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The authors have installed a tiny rover payload “MINERVA-II” into Hayabusa2 spacecraft which was launched in 2014. The payload consisted of three rovers installed in two containers. Two of them packed together in one container were the responsibilities of the authors. The other one in the secondary container came from the domestic university members. We developed a new rover deployment mechanism ejected from the containers. The rovers and the cover of the container were released by one action. But the cover headed for different direction of the one from rovers, so as to prevent the combination of them. The deployment mechanism was evaluated under the microgravity environment using a drop tower. This paper describes the deployment mechanism as well as the results of the microgravity experiments.

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For planetary exploration, small robots of just a few kilograms installed in the main spacecraft have a lot of advantages. In order to move on the surface of a “low gravity” object, like the Moon by a small robot, there are several options of locomotion, such as jumping, wheels, and legs. Jumping locomotion has capable of moving a long distance by one action and the number of actuators required for jumping capability is very small. In addition, it can travel a longer distance on a planet or satellite which has a gravity lower than the Earth. For instance, it can jump 6 times longer on the Moon than on the Earth. To realize jumping locomotion for small robots in a low gravity environment, authors proposed a new jumping locomotion method which consists of one jumping mechanism and one wheel for attitude and direction change, as well as they are now studying the mechanism which moves in a space environment (vacuum, high radiation). In this paper, the jumping mechanism is mainly described. The design of the jumping mechanism, test results on granular media are presented.

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When the rover travel to the destination in uneven terrain, it is necessary to travel safely so as not to make the rover unable to run. In order to travel safely on the uneven terrain, suspension mechanisms and traction control of the motor methods that improve running performance have been studied. Suspension mechanism requires link and actuator. If the rover has many links, its size and weight of the mechanism will become large. Reducing the link and increasing the number of actuators complicates the control. Suspension with few links and actuators is suitable for mounting suspension mechanism on small rovers. In this paper, we propose a suspension mechanism that can control the center of gravity. This suspension has two links and use driving motor as actuators. We produce the testbed using the suspension and propose a center-of-gravity position control for getting out from the wheel stack and getting over steps. We experiment with testbed and verify the effectiveness of the suspension mechanism on uneven terrain.

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This paper investigates a hybrid type UAV of which configuration is fixed wing with multi-rotor enabled vertical take-off and landing. In the previous our work for multi-rotor UAV, a trirotor geometry with four rotors was built and experimented flight in the laboratory. VTOL type UAV enables the flight without take-off and landing spaces. So, there many researches for VTOL type UAVs, but the effective configuration of wing and electric propulsion unit is not discovered. We propose a tailless wing configuration combined with the trirotor geometry for VTOL UAV. The Tailless wing airplane has advantage of low friction force, simple structure and lighter than the normal airplane with same wing area. In the previous research a tailless wing is built with a hole for the front part of trirotor mechanism. Then the experimental tailless wing model carried out stable flight in the test field. Wind tunnel is used to measure the tailless wing with/without a hole. This paper discusses the aerodynamics of proposed fixed wing platform of VTOL UAV.

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This paper proposes an extended SSM for autonomous vehicle with the front wheel steering mechanism moving in the real world environment. In previous paper the extended SSM was applied to Smart Dump 9 and AR Chair for following the preset way points on the map. These papers are shown only the schematic idea of this method but the precise performance of the generated trajectory is not shown. This paper derives the geometrical relation between steering angle and way points in the three dimensional map. Simulation and Experimental data are compared with each other. Finally, experimental data in the Tsukuba challenge 2016 demonstrates the advantage of extended SSM and the developed control system.

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Due to the high development of artificial intelligence technology, robotic technology and automatization of household chores or building maintenance, our living quality has been dramatically improved. It is expected that introduction of cleaning robots to indoor is more rapidly proceed than ever by this trend. An automatic cleaning robot that runs around indoors and performs cleaning, is representative as service robots. Hence we would like to introduce this paper to present the first step of intention to approach of modifcations and improvements of current cleaning robot, by applying the Reinforcement Learning algorithm to cleaning robot, making the robot to learn how to map situations to actions, so as to maximize a numerical signal (reward). Applying model-base to cleaning robot of certain area that needs to be vaccumed, the robot will achieve self-guided of planning path, to search and vacuum desired space of dirts automatically.

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This paper presents an intelligent expert control system to improve accuracy of positioning for 3/6 axes arm robot. It was possible to decrease also the control deviation within the small range by a semi-closed-loop control of the angle of the servo that used a cheap arm robot with cheap potentiometers by extending to the whole area of the targeted value in the positioning control, and the average decrease rate of control deviation was 36.7%.

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To reduce the collision shock and risk of injury to an infant in an in-car crib (or a child safety bed) during a vehicle crash, it is necessary to limit the force acting on the crib below a certain allowable value. To realize this objective, we propose a semi-active in-car crib system with the joint application of regular and inverted pendulum mechanisms. The crib is supported by an arm similar to a pendulum, and the pendulum system itself is supported by an arm similar to an inverted pendulum. In addition, the arm acting as a regular pendulum is joined with the arm acting as an inverted pendulum through a linking mechanism, and the friction torque of the joint connecting the base and the latter arm is controlled using a brake mechanism, which enables the proposed in-car crib to gradually increase the deceleration of the crib and maintain it at around the target value. This system not only reduces the impulsive force but also transfers the force to the infant’s back using a spin control system, i.e., the impulse force is made to act perpendicularly on the crib. The spin control system was developed in our previous work. The present work focuses on the acceleration control system. A semi-active control law with acceleration feedback is introduced using a dynamic equation for the jerking of the crib. In addition, the effectiveness of the system is demonstrated by control experiment using the scale model, and some of results are reported.

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Recently, more researchers have focused on nursing-care assistant robot and placed their hope on it to solve the shortage problem of the caregivers in hospital or nursing home. In this paper, in order to maintain the stable posture of two-link object regarded as a care receiver by non-prehensile two-cooperative-arm robot, a method to obtain stable region for robot arm motion is proposed. In details, firstly a mathematical model of the two-link object is built. By assuming the actual nursing care site, in this research, the model is considered as static problem. Secondly, considering the static friction and normal force occurred at the contact point between the link and the arm of the robot, and the stability conditions of twolink are created. When frictional force occurs between the caregiver and the care receiver, it gives pain to the care receiver, so the static frictional force is considered to be nearly zero and the distance from joint position to contact point of link and arm was kept considering the mental condition of the care receiver. According to the above stability condition, simulation is done to obtain the stable region which is related to the angles of two links for robot arm motion by using Matlab. Finally, an experiment is done to demonstrate the effectiveness of the proposed method.

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Magnetic bearings can support rotating shafts without any contact and have been used in special conditions such as in cryogenic, vacuum, and clean environments. In this paper, consequent-pole type 5-DOF self-bearing motor is proposed. By using this motor structure, the rotor radial and tilt position control is easily possible because the forces and torques don’t depend on the rotational angle of the rotor. The three-dimensional magnetic field analysis using the finite element method is carried out. Based on these analysis results, the experimental setup was made and the motor performances are confirmed. Though the further improvement of the motor efficiency is necessary, the consequent-pole type 5-DOF self-bearing motor satisfies the target motor torque and shows the feasibility as an artificial heart pump.

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This paper proposes a novel structure of an axial gap self-bearing motor. The axial gap self-bearing motor controls both axial force and motor torque by using the similar structure of a disc motor, then the structure and control system can be simplified. In this paper, for further simplifying the structure, the number of the stator coil is reduced to four for one side stator for a 4-pole disc rotor. One side stator produces only 4-pole magnetic flux, then the whole of the stator coils can be connected in series and driven by the single amplifier. Two stators are required to produce continuous motor torque and the bidirectional axial force, then the drive system can be composed of eight concentrated coils and two power amplifiers. To obtain continuous motor torque, the permanent magnets are attached to the rotor to have 45 degrees phase difference between two sides of the disc. In this paper, the axial force and motor torque of the proposed structure are analyzed theoretically, and the control method of the axial force and motor torque are derived. Experimental results show that the proposed motor can control the axial position and the rotation speed simultaneously.

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Amagnetic levitation system using wireless power transfer has been proposed. It consists of a wireless power transfer mechanism and a Lorentz force levitation system. In this paper, a prototype and the control method of the levitation system has been considered and conduct a non-contact levitation using PID control.

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In this study, we proposed a hybrid stator comprising a superconductor and a ring-shaped permanent magnet and measured the oscillation characteristics of a magnet levitating above various hybrid stators. By adding a ring magnet, the vertical magnetic attractive force and stiffness were increased compared with those of a simple superconducting stator. The oscillation frequency of the hybrid stator is higher than that of the simple superconducting stator. The proposed hybrid stator exhibits better oscillation characteristics than a simple superconducting one. An improvement in the stability of the levitating magnet is realized by the hybrid stator using a superconductor and a ring-shaped magnet.

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This paper proposes non-contact control of supporting of an elastic long shaft by using active magnetic bearing (AMB) system. We aimed to develop a magnetic bearing system that takes dynamic of the elastic body into consideration An experimental system supporting the shaft with two AMBs is built and control experiments are carried out. As a first trial simple Proportional-Derivative (PD) feedback controllers are applied and levitation of the shaft is succeeded, While the 1st elastic mode of the shaft is appeared but undamped.

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Parallel magnetic suspension that controls multiple floators or multi-degree-of-freedom motions with a single power amplifier has already been realized. In this system, all of the suspended points move simultaneously even when a disturbance acts on one of the suspended points solely because all electromagnet’s coils are connected. This paper studies the moving direction of each suspended point with respect to a step disturbance in double parallel magnetic suspension system. The analytical study shows that the response direction is determined by the system parameter that relates the response speed of each subsystem. In the slower subsystem, the suspended point moves in the same direction as the applied force while in the faster subsystem, the suspended point moves in the opposite direction. In other words, the slower subsystem has positive stiffness while the faster system has negative stiffness. To confirm this prediction, step responses are measured in the experimental apparatus.

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In the development of complex systems such as automated driving systems (ADS), Model-Based systems engineering approaches through the use of a system model are useful to manage system complexity. At the current practice of system developments, there is a high possibility that the system requirements, behavior, and even more system constraints will not be reflected if analytical models are built without system models. Therefore, it is difficult to maintain traceability with requirements as development progresses. In this paper, building analytical models for ADS based on the system models are presented. First, system models of ADS are built. In particular, the behavior of ADS is described in terms of functional flow and state using the function based on the safety requirement relating to driving authority delegation of ADS. Then, system parameters and constraints are identified from the behavior of ADS when constructing analytical models relating to driving authority delegation of ADS, and reflect them in the system models. Finally, analytical models are built based on the system model describing the constraints, and system level analysis are performed on driving authority delegation of ADS using analysis models. Analytical models based on the system models allow system engineers to essentially analyze behaviors and constraints reflecting requirements on the system.

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This paper presents a driving simulation environment for automated driving systems (ADS) to be used in future design and testing efforts. As the human driver and ADS either wrestle or assign away control to each other, the interaction that this creates becomes a significant design challenge. A Model-Based Systems Engineering (MBSE) approach is utilized in this paper to define the ADS’s concept through to its behavior, forming a base for design and testing plans. Additionally, some software is selected to perform the custom design of the human-machine interface, the driving environment, and also the vehicle simulation model. In the future, this work can be expanded upon through testing combinatorial selections and designs of visual, audio and tactile channels of communication.

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To avoid rework in the automobile engine calibration and verification process, engine test bench is expected to improve precision of standard test for in fuel consumption. In this paper, the control system that switches conventional feedback control to feedforward control is proposed to the acceleration change phase of in order to satisfy the required following precision to the reference vehicle speed. Feedforward control input is calculated as the driving force of the automobile by giving final-state control on the controlled object model based on the equivalent inertial mass and running resistance. It is seen from comparison with experimental results on engine test bench that highly precise fuel consumption test can be realized.

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Durability tests of two water hydraulic cylinders with different surface roughness are made. The piston diameter, rod diameter and stroke of the test cylinders are 50 mm, 28 mm, and 250 mm, respectively. Each test cylinder is operated at a velocity of 0.25 m/s under a supply pressure of about 10.5 MPa by an electro-oil hydraulic servo cylinder which is placed in alignment with the test cylinder. The variations of friction characteristic, low speed performance, leakage characteristic of each test cylinder with operating distance are measured until 300 km operation. Friction force decreases at first with increasing operating distance and then becomes an almost constant value. No negative resistance characteristic is observed at low velocities. Both test cylinders can move very smoothly at velocities lower than 0.1 mm/s without stick-slip irrespective of the magnitude of surface roughness. Leakage flow rate tends to increase with increasing operating distance and surface roughness.

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Micro robot has a lot of attention in the field of rescue robot, inspection robot, medical robot because of its mobility in narrow spaces. In particular, many robotic researchers focus on a “biomimetic” micro robot, which can mimic natural creatures as it has functional locomotion systems. Electro-conjugate fluid (ECF) is a kind of functional fluid, which produces a jet flow when subjected to a high DC voltage. In this paper, a novel micro suction pad actuator having a flexible rubber film and a sucker driven by the ECF jet flow is proposed and developed. The actuator mechanism imitates an adhesive mechanism of octopus sucker. A prototype model with 25.5 mm long, 10 mm wide and 5 g weight was fabricated to confirm the adhesive mechanism. ECF flow generator for pressure source was also fabricated and integrated in the micro suction pad actuator. Displacement of the rubber film mounted on the top of micro suction pad actuator was measured by a laser sensor. The rubber film extended until 1.2 mm at the applied pressure of 2.45 kPa. Mathematical model was proposed to calculate the adhesive force of the micro suction pad actuator. The adhesive force of 0.79 N at the applied voltage of 8.0 kV was estimated by the mathematical model.

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Terrestrial gastropods, such as snails, are able to crawl by generating traveling waves under the ventral foot. Although the speed of the animal is slow, they are able to adapt to any surface with continuous contact point by using their soft single ventral foot. These characteristics are difficult to realize by conventional rigid robots, such as wheeled, legged, and crawler. If those movement characteristics can be artificially achieved, many application can be realized. For example, research robot for confined space purposes, or a mobile device capable of transporting fragile objects without damaging the environment. In this paper, we propose a method to create various waveforms for our proposed actuator called “Wavy-sheet”. Wavy-sheet is a pneumatic sheet actuator that can generate traveling waves inspired by gastropod’s locomotion. Several rubber tubes are passed through the sleeve which determines the waveform of the actuator. By arranging the inner rubber tubes, various waveforms can be designed that has different characteristics such as amplitude, velocity, and stiffness. First, we derived a combination of waveforms. The result showed that there are mainly three kinds of waveforms that are actuated by three input. Next, amplitude and velocity had been analyzed. Finally, two prototypes of the actuators had been fabricated and characteristics were measured by some experiments. The results showed that each wave has different characteristics and it is effective to select the waveform depending on the application.

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This paper describes a human-friendly flexible manipulator capable of sliding under a human body without friction and helping the person turn over in bed. It aims to prevent pressure ulcers in bedridden patients by changing contact points. The proposed manipulator, termed “Slip-in Manipulator,” is composed of two soft chambers and an electric motor. It can slip in between the bed and human body by drawing out the inner chamber using pneumatic pressure. It can also perform bending motion by pressurizing the other chamber. In this paper, we first illustrate the design concept. The characterization of slip-in and bending motions are described. Next, we introduce the control system and control method of the manipulator. Finally, the experimental results of the developed prototype are shown, which suggest that the manipulator works well by proposed control method, the slip-in motion can slide under the human body and the bending motion is effective in assisting turning over.

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The pneumatic positioning system has advantages such as explosion-proof, operable even at power failure, simple structure, easier maintenance and low price. Therefore, applications in a large field are expected. In this study, we propose a model of pneumatic positioning system with mechanical feedback with the aim of realizing inexpensive advanced control system incorporating highly reliable controller and simple mechanism. Then, by conducting simulation and comparing it with experimental results, we verify the effectiveness of the characteristic analysis by simulation using the proposed model. First, a model of the pneumatic positioning system is built with the equation of motion of the constituent elements, and parameters are identified with reference to the experimental apparatus. Next, a simulation model is created and simulation is performed. Then, step response experiments are carried out using a pneumatic positioning system incorporating a cylinder. Finally, by comparing experimental results and simulations, we verify the effectiveness of the characteristic analysis by simulation using the proposed model. In this paper, step response experiments were carried out using two different stroke length of cylinders, and the results of the step response experiments and the simulations were compared. As a result, both transient characteristics are nearly identical. Therefore, it is proved that the proposed model of pneumatic positioning system is effective for analysis of transient characteristics of a system incorporating various cylinders. And we got the prospect that the characteristics of the pneumatic positioning system analyzed by simulation using the proposed model can be used for developing new applications.

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In an oil-hydraulic system, since a positive displacement pump is generally employed, pressure pulsation is generated, which causes oscillation, noise and so on. In general, an accumulator is interposed to suppress it. However, when using an accumulator, regular maintenance is necessary to maintain its performance. Therefore, it seems to be necessary to develop an oil-hydraulic component to reduce pressure pulsation with simple structure and without regular maintenance. In this study, a component to reduce pressure pulsation in oil-hydraulic system is proposed. This component consists of a pipe-shaped metal body and a silicone rubber tube. The silicone rubber tube is inserted into the body. The side of the body has 4 holes, and the surface of the silicone rubber in the metal body is exposed to the atmosphere through these holes. When the pressure is increased, the part of the silicone rubber expands and prevent the increase of the pressure. Then, the energy is stored as elastic energy in the silicone rubber. The elastic energy is transferred back to the oil when the pressure is decreased. This energy transfer prevents the decrease in the pressure. These processes are assumed to be effective for preventing the pressure pulsation. The component is fabricated and some experiments carry out to make clear the validity of the mechanism and the basic characteristics of this component. Based on the experimental results, it becomes clear that the fluctuation range of the pressure pulsation becomes one-tenth by the use of the proposed component.

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This paper deals with a vibration control system using propellers for crane load. Vibration suppression of crane load suspended by hoisting rope is an important issue to speed-up crane operation. In this study, a novel vibration control system using propeller thrust as control forces is presented. The pitch of the propeller can be varied so that the attack angle of the propeller blade possesses negative or positive. Changing the attack angle, the direction of thrust can be altered smoothly. Based on previous conceptual design, life-size experimental device was researched and developed. Its performance is investigated through control experiments.

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Although hydraulic systems have high-power and quick responsibility because its oil has high rigidity, when air bubbles are mixed into oil, they reduce the oil rigidity and change the dynamic characteristics; thus, air bubbles generally should be removed from hydraulic oil. In this study, however, we consider that the reduction of oil rigidity advantageously can works for absorbing impact, and propose to positively utilize the air compressibility for hydraulic actuator. The purpose of this study is to develop a new hydraulic actuator using the compressibility of air effectively. This paper proposes the structure of new hydraulic cylinder. This cylinder has two pistons, and mixed fluid chamber between the two pistons. In the mixed fluid chamber, the hydraulic oil containing air bubbles can be filled. The rigidity of the actuator can be adjusted by changing the amount of air bubbles in oil. To accurately adjust the rigidity of the hydraulic oil in the mixed fluid chamber, it is needed to understand the relationship between the air bubble content and the effective bulk modulus of the hydraulic oil. To clarify the relationship, we propose a mathematical model that expresses the relationship between pressure and effective bulk modulus of oil contains air bubbles. This paper also evaluates the validity of the mathematical model of the effective bulk modulus experimentally. The experiments are conducted by changing pressure in chamber filled with oil containing air bubbles. We confirm that the effective bulk modulus calculated using the mathematical model agrees well with the experimental results. Moreover, the displacement and pressure response of the new cylinder is analyzed by numerical simulation. The results show that air in the cylinder valid for increasing the performance of the impact absorption.

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Energy efficiency is low with the control of the hydraulic system using the pressure loss of throttle valves widely used in current construction machinery but if energy regeneration by PWM control switching high pressure source and low pressure source high speed is used, improvement in efficiency can be expected. We proposed response analysis method considering elasticity of oil, influence of cylinder and load on hydraulic system, and improvement method in efficiency for PWM control using anti-resonance. First, we show the possibilities of reducing in efficiency for PWM control due to the influence system resonance with harmonic of switching frequency in straight pipe. Next, we show piping shape that 2 ^nd and 3 ^rd harmonics of the switching frequency of the valve also become anti-resonance and the possibilities of improvement in efficiency for PWM control.

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Energy efficiency is low with the control of the hydraulic system using the pressure loss of throttle valves widely used in current construction machinery but if energy regeneration by PWM control switching high and low pressure source at high speed is used, improvement in efficiency can be expected. We proposed response analysis method considering nonlinear pressure loss of valve, elasticity of oil, influence of cylinder and load on hydraulic system using PWM control. First, we showed response analysis method with one degree of freedom system model neglecting elasticity of fluid, and showed a method to handle valve nonlinear pressure loss approximately. Next, we proposed a response analysis method using modal analysis based on the theoretical solution and Fourier series expansion, and showed how the load and fluid elasticity influences the response using the proposed method.

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The purpose of this study is to develop a walking training system for elderly people. This system consists of three components: a wearable walking assist device, a high-performance shoes, and an active walker. In this study, a wearable walking assist device to support them is developed. Their walking speed and step can be improved by supporting a flexing action of hip joint. The device is required to have a lightweight, simple structure, and portability. Therefore a pneumatic rubber artificial muscle which has a lightweight and high power-weight ratio is used as an actuator. Further, CO2 gas cartridge tank is used to realize a portability instead of air compressor as air pressure source. In the experiment, myogenic potential is measured when subject wearing the wearable walking assist device walks on a treadmill. The number subject is five students (healthy adult males). From some experimental results with respect to both walking speed and step, similar waveforms are obtained. When the assist function is on state, the average maximum value of myogenic potential decreases as compared with turned off state. In other words, it became clear that this device can perform similar walking even with small muscular strength. Therefore, it can be said that the wearable walking assist device has a walking assistance function. In the future, we will actually experiment with the elderly people, and improve with the opinions of them. In this paper, descriptions on the development of high-value-added walking training system, the structure of the wearable walking assist device, and experimental results and their evaluation are described.

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In this study, we quantitatively evaluate the reduction of the burden obtained by pneumatic load supporting arms that make use of the advantages of pneumatic robot and redundant arm robot. The robot was produced to support a weight of 35kg, which is half of the assumed weight of workers. It moves only up and down and support workers at various hip heights. Furthermore, myopotentials of thighs and calves of a human wearing the robot were measured. Myopotentials at relaxation, at wearing robot, at not wearing robot, and at maximum muscle strength were measured. Next, the magnitude of the muscle tone was calculated by the value of myopotential at maximum muscle strength. As a result of the evaluation, it was proved that a significant burden reduction effect can be demonstrated in 4 subjects.

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We are developing a hand type multi joint manipulator, which adopts a compact pneumatic cylinder as an actuator. The final goal of this research is to recognize the stiffness of the object and to hold the object with in order to recognize the rigidity of an object, it is necessary to apply a force to the object and measure the displacement and the change in force. However, in order to measure the change in force, it is necessary to install a force sensor in the manipulator, but it is costly. Therefore, by measuring the pressure difference inside the cylinder chamber and calculating the external force from the differential pressure, the force is measured without mounting the force sensor. However, as with the force sensor, the installation of the pressure sensor requires a cost. Hence, in this paper, the pressure observer is designed from the input voltage of the Electro-pneumatic regulator and the position information obtained from the displacement sensor, and the pressure in the cylinder chamber is estimated. Then, an external force was calculated from the estimated pressure, and it was verified whether the estimated external force could be used as a force sensor.

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Previously, we developed the air servo stage available ultra-precise positioning where seals are removed from the pneumatic actuator to reduce the effects of friction force, and the slider of the actuator is mounted with air bearings. The air servo stage available is required not only positioning accuracy but tracking performance for trajectory. However tracking performance in accelerating is not sufficient and considerable tracking error occurs. One of the reasons is calculation delay of the controller using a micro-computer. In this paper, we design the servo valve controller as a discrete time system and apply the calculation delay compensator (CDC). As a result, the dynamic frequency of the servo valve increases twice and tracking error decreases because the loop gain of position controller can be higher.

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Along with the increasing number of disasters caused by large earthquakes in Japan, there is a desire that structures such as tall buildings and viaducts are strong and safe against earthquakes to be confirmed. In addition, from the findings obtained from the damage, earthquakes with new characteristics such as long-period earthquakes attracted attention, reexamination of seismic designs so far become important, and it becomes necessary to clarify the destruction process of structures and the seismic resistance in vibration tests. This paper introduces a methodology to compensate a reaction force of hydraulic shaking tables for earthquake resistance testing facility. The motion of a shaking table is affected by a reaction force caused by a specimen on the table in the seismic testing. The controller is designed by using DMM (Dual Model Matching) based on the characteristic transfer function. We adjust the feedforward controller and the feedback controller to reduce the influence of the reaction force. In addition we propose the control method to compensate the characteristic change of the specimen by using reaction force. The effectiveness of the proposed method is confirmed by using a single-axis hydraulic shaking table, and verified by installing a mechanism for changing the natural frequency of the specimen under excitation.

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This paper presents a variable structure observer for a robotic mini-motorcycle. In general, important forces such as self-aligning torque and side force acting on a motorcycle highly depend on the properties of tires. However, it is not easy to obtain the parameter values to show the properties, and thus there is much uncertainty in the mathematical model for observer design. In this paper, therefore, a model including the parameter uncertainty is introduced, and a robust observer is designed from a view point of the so called matching condition with respect to the uncertainty. It is shown that the proposed controller achieves robust performance in the presence of the perturbation.

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This paper presents a control strategy for a wheeled mobile robot with variable pitch blades which make it highly mobile over irregular terrain. In our previous work, a mathematical model with respect to pitching motion of the robot necessary to climb a stair was developed, and a servo controller for the pitching motion was proposed under the assumption that the reference slip of the wheel to be followed was known in advance. In this paper, an extremum seeking method by applying sliding mode is employed to obtain the desirable reference slip. Simulation results show the effectiveness of the proposed controller.

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This paper provides experimental verification of pose regulation for a fully-actuated hexrotor. Since a hexrotor has 6 inputs, 6 degrees of freedom of translational and rotational motion can be controlled independently. The previous research presents a switching control law combining exact linearization and first order approximation approaches. The Exact linearization method enables to control 6 degrees of freedom independently, and the first order approximation method is advantageous to translational motion. The contribution of this work is to develop a hexrotor prototype and provide experimental verification of the switching control. First, a model of the fully-actuated hexrotor is described. Then, the configuration of the control system and the control methods are shown. In addition, the experimental system of the hexrotor prototype and the observation system is described. Finally, translational flight experiments are conducted to evaluate the result.

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This paper is concerned with a practical synchronization problem in networks of nonidentical or perturbed nonlinear systems with transmission delay couplings. In particular, we focus on delay independent practical synchronization in particular networks, whose either the synchronization error dynamics are described by ordinary differential equations without delay terms, or the network structures are undirected rings. In such network systems, we show practical synchronization emerges for any coupling strength larger than a threshold value, irrespective of the time-delay length. Numerical examples illustrate the validity of obtained results.

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This paper considers pose control of a two-wheeled system on constrained fields. State constraints such as constrained fields are inevitable problems in real systems. For the state constraint problems, methods for designing control laws by using mapping pairs of coordinate transformation and input transformation have been proposed in previous research. However, since this control law generates excessive inputs, they cannot be realized when installed in experimental machines. Therefore, this paper applies the methods to a two-wheeled system and further proposes a control law that takes constrained input into consideration. In addition, this paper carries out experiments and shows the effectiveness of the proposed control law.

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Recently, many nonlinear control design methods have been developed to handle the nonlinearities of the systems to achieve better control performance than linear ones. In this paper, we consider a nonlinear optimal control design method based on stable manifold theory⁽¹⁾ . In nonlinear optimal control problem, we have to solve a partial differential equation called Hamilton-Jacobi equation (HJE). However, in general, it is difficult to solve the HJE analytically. In order to obtain its solution, Sakamoto et al proposed the stable manifold method to solve the HJE iteratively with high accuracy, and then based on the approximated solution, a nonlinear optimal controller is constructed. In this research, we consider a two degree of freedom acrobot. This is an underactuated system with strong nonlinearities, therefore it is often used to evaluate the control performance of nonlinear controller design methods. The control objective is to swing up and stabilize the acrobot around an equilibrium position using a single controller. In the acrobot system, there are four equilibrium points corresponding to different postures of the links. We consider six swing-up motion patterns starting from different initial conditions. For each motion, a nonlinear optimal controller is designed via stable manifold method. The simulation results confirm the effectiveness of the designed controllers.

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[in Japanese]

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When installing a subsea structure like subsea pump, booster, separator etc., the suspended structure and the installation vessel constitute a kind of pendulum system. The installation vessel’s motion becomes an exciting force to the suspended structure. The amplitude of horizontal oscillatory motion of the structure depends on not only the vessel’s motion but also the crane cable speed which means descending speed of the structure. Unlike in the case of offshore oil/gas development, the project cost is strictly limited in the case of scientific research like ocean environment monitoring. So we need to develop a more inexpensive installation method. One possible solution to make the installation cost reduced is applying active control system to the structure to suppress its oscillatory motion using thruster. In this paper, I introduce an experimental system for investigation of active control installation method including floating LBL, an underwater structure model with thrusters.

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