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This paper discusses the model identification of a biplane which has superior lift generation capability and the influences of identification errors on trajectory generation using updating final-state control (UFSC). Aerodynamic parameters are identified using a combination of wind tunnel tests and computational fluid dynamics (CFD) analysis. The influences of parameter errors on approach trajectory generation are also investigated using Monte Carlo simulations. The simulations clearly demonstrate the relationship between the parameter errors and the trajectory accuracies. In addition, the acceptable range of parameter errors is investigated.

ABSTRACT: This study discusses robust control problems related to the fall of two-wheel motor vehicles during parking or low-speed driving. The robotic motorcycle includes a new rotary axis that can vary the position of the total center of gravity. Some authors have already reported preliminary control demonstrations using a typical PID controller and simple LQR. Moreover, the mathematical model of a robotic motorcycle derived using multibody dynamics methods and its optimal regulator simulation were developed. However, an experimental investigation of a robust control strategy for practical implementation has not yet been conducted. Therefore, this study proposes a practical method based on applying a sliding mode controller (SMC) to improve robust stability in a real usage environment. Here, we introduce the control system design combining a novel mathematical model, including a minor PID control loop and the SMC, with its hyperplane designed by the frequency-shaped optimal regulator. Finally, its effectiveness is verified by experiments using an actual robotic motorcycle.

Descent deceleration using parachutes is widely used in the aerospace field for scenarios such as weather observation using the descent of high-altitude balloons (radiosondes), re-entry during space sample return, and emergency drone landings. These parachutes are used to protect the aircraft and samples, and to avoid hazards with objects and humans on the ground. However, it is difficult to control the dropping point using parachutes, and there have been concerns regarding accidents caused by insufficient deceleration and adverse environmental effects caused by the disposal of unrecovered objects. To solve these problems, we propose a control method for the aerial recovery of low-speed descent objects using fixed-wing unmanned aerial vehicles (UAVs). Our previous work has shown a flight trajectory generation method that employs updating final-state control (UFSC) to handle variations in the terminal target states until the object is recovered. The frequency-shaped optimal regulator control that enables a return to steady-state flight has also been used after UFSC. However, owing to the characteristics of each control method, the problem of sudden fluctuations in the control input before and after recovery of a descending object remained, and performing aerial recovery using an actual aircraft was predicted to be difficult. In this study, this problem is avoided by switching from UFSC to adaptive nonstationary control (ANC), which has proposed in previous studies. ANC can be applied when the aircraft approaches a descending object, and it can be confirmed that the control input is smooth in a series of trajectory designs until return to steady-state flight.

To deal with the flexibility in the electric aircraft design, this study develops a structural parameter optimization method. The quad tilt-wing aircraft exhibits rotary-wing flight and fixed-wing flight modes by tilting its wings. This study focuses on the domain of attraction, which is a class of state vectors that converge to a static equilibrium point after infinite time. The method indirectly estimates the size of domain of attraction of an aircraft by calculating the radius of a sphere that is encompassed by the domain. In addition, after investigating the relationship between change in structural parameters and the size of the domain of attraction, the structural parameters that maximize the size of the domain are surveyed. The effectiveness of the proposed method is demonstrated for the optimization of the quad tilt-wing aircraft. The quad tilt-wing aircraft exhibits rotary-wing flight and fixed-wing flight modes by tilting its wings. As the characteristics of the dynamics of the quad tilt-wing aircraft demonstrate a significant nonlinear change depending on the tilt angle of the wing, we propose a method to optimize the structural parameters for an easy control of the aircraft. Simulation results show that the optimization scheme identifies the parameters that enable the aircraft to perform agile control to address a disturbance moment. Further, although the same controller is used in the original and optimized aircraft, the optimized aircraft can handle a disturbance in a shorter time when compared with the original aircraft.

This paper proposes an experience-based lecture style that offers dual-scale experiments in combination. Lectures for vibration engineering were designed based on the proposed style and offered to undergraduate students. In the proposed style, experiments on free vibration on a seismic building for second-year students and advanced vibration control using an effective device for fourth-year students are examined in combination. The lecture style trials were repeated twice, once each in 2015 and 2016, with about two hundred second-year students; the students felt the free vibration of the five-story building which had a 6,100 ton weight inside and witnessed the mechanism of the base-isolated layer. To follow the demonstration steps, we developed an experimental device. The experimental device is composed of a vibration component corresponding to a building, and a motor cart with a handle corresponding to the ground. These are connected via a linear actuator that can exert one-dimensional force on the vibration component as a function of the input voltage. In the lectures conducted in 2017 and 2018, the students oscillate the cart and observe the motion of the vibration component. In addition, the virtual reality cameras for offering students a visually rich experience attracted students' interest. The questionnaire results showed that almost all of the students valued the lectures as useful. Since most of the students answered that the combination of the large-scale demonstration and scale-down experiment was useful, the proposed lecture style achieved the expected overall goals.

Introduction: Krüppel-like factor 4 (KLF4) is considered one of the Yamanaka factors, and recently, we and others have shown that KLF4 is one of the transcription factors essential for reprogramming non-human corneal epithelial cells (HCECs) into HCECs. Since epithelial to mesenchymal transition (EMT) suppression is vital for homeostasis of HCECs via regulation of transcription factors, in this study, we aimed to investigate whether KLF4 prevents EMT in HCECs and to elucidate the underlying mechanism within the canonical TGF-β signalling pathway, which is involved in corneal epithelial wound healing. Methods: HCECs were collected from cadaver donors and cultivated. We generated KLF4-knockdown (KD) HCECs using siRNA transfection and analysed morphology, gene or protein expression, and endogenous TGF-β secretion. KLF4 was overexpressed using lentiviral KLF4 expression vectors and underwent protein expression analyses after TGF-β2 treatment. Results: KLF4-KD HCECs showed a fibroblastic morphology, downregulation of the epithelial markers, keratin 12 and keratin 14, and upregulation of the mesenchymal markers, fibronectin 1, vimentin, N-cadherin, and SLUG. Although E-cadherin expression remained unchanged in KLF4-KD HCECs, immunocytochemical analysis showed that E-cadherin–positive adherens junctions decreased in KLF4-KD HCECs as well as the decreased total protein levels of E-cadherin analysed by immunoblotting. Moreover, within the TGF-β canonical signalling pathway, TGF-β2 secretion by HCECs increased up to 5 folds, and several TGF-β–associated markers (TGFB1, TGFB2, TGFBR1, and TGFBR2) were significantly upregulated up to 6 folds in the KLF4-KD HCECs. SMAD2/3, the main signal transduction molecules of the TGF-β signalling pathway, were found to be localised in the nucleus of KLF4-KD HCECs. When KLF4 was overexpressed, cultivated HCECs showed upregulation of epithelial markers, keratin 14 and E-cadherin, indicating the contributory role of KLF4 in the homeostasis of human corneal epithelium in vivo. In addition, KLF4 overexpression in HCECs resulted in decreased SMAD2 phosphorylation and altered nuclear localisation of SMAD2/3, even after TGF-β2 treatment. Conclusions: These results show that KLF4 prevents EMT in HCECs and suggest a novel role of KLF4 as an endogenous TGF-β2 suppressor in the human corneal epithelium, thus highlighting the potential of KLF4 to prevent EMT and subsequent corneal fibrotic scar formation by attenuating TGF-β signalling. Keywords: KLF4, EMT, Corneal epithelium, TGF-β signalling pathway, SMAD2, SMAD3

The heat-inactivated, enteric-colonizing Lactobacillus gasseri CP2305 (CP2305) ameliorates psychological stress-related symptoms. In this study, we examined effects of CP2305 on top athletes experiencing physical and mental stresses. Forty-nine male university Ekiden (long distance relay race) runners daily took the CP2305-containing beverage for 12 weeks during training for and competing in All-Japan university championships. The CP2305 intake significantly facilitated recovery from fatigue and relieved anxiety and depressive mood, compared with placebo intake. The CP2305 intake significantly prevented the training-induced reduction of hemoglobin and facilitated exercise-induced increase in serum growth hormone levels. The CP2305 intake significantly increased the alpha- and beta-diversities of fecal microbiota, and the compositions of Bifidobacterium and Faecalibacterium. Gene expression profiling of peripheral blood leukocytes indicated that CP2305 prevented the stress-induced changes in the expression of genes related to mitochondrial functions. Our results suggest that daily intake of paraprobiotic CP2305 may be beneficial to athletes facing stressful situations.

This paper discusses that the unsteady aerodynamic forces caused by vehicle motion in road input have a large influence on the vehicle behaviors. In the present coupling analysis, unsteady aerodynamic forces were obtained by using the response functions for vehicle motion derived in our previous study. By attaching a protrusion on the roof which only measures about 3% of the vehicle height, pitch and heave motions are affected significantly by the change of unsteady aerodynamic effects. Due to the coupling of the unsteady aerodynamic forces and vehicle suspension responses, the vehicle behavior depends on the road input frequency. The pitch motion is enhanced in low-frequency road input (1.6 Hz). Meanwhile, the heave motion is suppressed over 1.2 Hz. Such vehicle behaviors were verified in actual running tests, and were consistent to the subjective evaluation of the drivers feeling. Comparing the unsteady aerodynamic coefficients to the equivalent vehicle specification factors, the aerodynamic inertia caused by pitch motion contributes to 39% of the rear vehicle mass inertia effect in pitch motion. This aerodynamic effect is important in designing suspension specifications of vehicles. These results show that the vehicle stability can be affected even by small detail in vehicle shape due to the unsteady aerodynamic forces.

In most motion control problems, precise settling in terminal time of control is a crucial specification. Totani and Nishimura, thus proposed the final-state control (FSC) technique which satisfies the required final-state conditions precisely. Then, the authors proposed a real-time updating version of FSC (updating final-state control: UFSC) by taking the application to time-varying final-state conditions into account. However, huge control inputs often occur at the final control time to suppress the error between the final-state conditions and real state variables, making it challenging to apply UFSC to practical problems. This paper proposes three improved control methods taking the input constraints at the final control time into account to improve feasibility. These are (i) frequency-shaping method (FSM), (ii) time-varying weighting method (TVWM), and (iii) input freezing method (IFM). The effectiveness of the methods has been discussed by comparing the numerical simulation results of a case study. The case study is a mid-air retrieval problem of low-speed-descent objects using fixed-wing unmanned aerial vehicles, which is also discussed in the authors’ prior study. The feasibility of the trajectory generated by the UFSC is also confirmed via experimental demonstration. As a result, this paper concludes the IFM based UFSC is the most realistic method for the control problem.

In this study, unsteady aerodynamic forces induced by forced pitch and heave motions are measured and formulated to the unsteady aerodynamic coefficients by utilizing the 1/4-scale nearly actual vehicle model with wheels and wheel-houses and a system without unnecessary stings exposed to the flow. The unsteady aerodynamic lift forces are measured as input forces at front and rear axles in vehicle suspensions for each, and are expressed as the aerodynamic inerter, aerodynamic damping and aerodynamic spring coefficients which are equivalent in vehicle suspension property. These studies are conducted with less than 1.4 × 106 of Reynolds number and with less than 0.2 of non-dimensional frequency. From the results, it is observed the effect of front aerodynamic forces in proportion to motion acceleration which works as an inerter can be ignored in both of pitch and heave motion, but the effect of rear aerodynamic forces as an inerter must be considered in both motion, and the first-order lag must be considered additionally about the rear only in heave motion. Furthermore, the large difference of unsteady aerodynamic characteristics is obtained while comparing in different vehicle body shapes which are without and with a protrusion on the roof. Especially, the difference of unsteady aerodynamic forces of rear in pitch motion is much large. In the case without the protrusion, the aerodynamic inerter which restrains pitch motion is occurred. On the other hand, in the case with the protrusion, the effect of aerodynamic inerter decreases and other aerodynamic forces promotes pitch motion in opposite. The phenomenon of this difference is closely related to the behavior of flow velocities at near surface around the model. From the above, it is confirmed that the large difference of unsteady aerodynamic forces induced by motions occurs in the detail difference of body shapes at a nearly actual vehicle model, and can be expressed quantitatively as the difference of aerodynamic response.

This study discusses the verification of the control system for realizing autonomous standing up from the parking mode of a novel motorcycle with a self-stabilizing mechanism, named “MOTOROiD,” and ensuring its stability on low-speed driving. MOTOROiD has a novel rotary axis that can vary the position of the total center of gravity, referred to as the active mass center control system (AMCES). In the previous study, the authors derived a mathematical model using Lagrange’s equation of motion, designed a control system for standing up from the parking mode, and ensured the motorcycle’s stability by using a two-degree-of-freedom control system based on the established model. However, the robustness of the proposed system was not fully verified. The previous study only verified the robustness of the mass variation with a numerical simulation example. Therefore, this study demonstrates the effectiveness of the proposed control system using several numerical simulations with variations in the system parameters. The simulation conditions are set by considering the characteristics of MOTOROiD in realistic situations related to a parked motorcycle. We consider three cases: (i) MOTOROiD is parked on a sloped ground, (ii) the angle of inclination at parking mode is not as assumed, and (iii) MOTOROiD is influenced by Coulomb friction. We set the simulation parameters based on these cases. Consequently, we confirm that MOTOROiD can stand up autonomously under all these conditions, thereby demonstrating the practicality of the proposed control system.

Corneal endothelial cells (CECs) are essential for maintaining the clarity of the cornea. Because CECs have limited proliferative ability, interest is growing in their potentially therapeutic regeneration from pluripotent stem cells. However, the molecular mechanisms of human CEC differentiation remain largely unknown. To determine the key regulators of CEC characteristics, here we generated a comprehensive promoter-level expression profile of human CECs, using cap analysis of gene expression (CAGE) with a single molecule sequencer. Integration with the FANTOM5 promoter-level expression atlas, which includes transcriptome profiles of various human tissues and cells, enabled us to identify 45 promoters at 28 gene loci that are specifically expressed in CECs. We further discovered that the expression of transcription factor POU class 6 homeobox 2 (POU6F2) is restricted to CECs, and upregulated during human CEC differentiation, suggesting that POU6F2 is pivotal to terminal differentiation of CECs. These CEC-specific promoters would be useful for the assessment of fully differentiated CECs derived from pluripotent stem cells. These findings promote the development of corneal regenerative medicine.

In this paper, we proposed a momentum exchange impact damper using a solenoidal coil and a capacitor to suppress impact vibration. Noise and vibration generated by forging machines and press machines have been a serious problem. In order to reduce impact vibration, the momentum exchange impact damper has been studied by many researchers. The basic principle of this damper is based on the momentum transfer during the collisions of three rigid bodies. This impact damper is the most effective when the mass of the damper is equal to the mass of the bed of the forging machine. However, the mass of the damper is usually smaller than the mass of the bed for practical use. In this study, this problem was solved by using a solenoidal coil and a capacitor. The electrical charge stored in the capacitor flows through the solenoidal coil when the impact damper passes through the solenoidal coil using a switch. The electromagnetic force is generated by the electrical current, and the electromagnetic force absorbs the kinetic energy of the host structure. The effectiveness of the proposed method was verified through simulations and experiments.

Recently, proceeding of the aging society has encouraged research and development of power assist systems. The authors' research group studies on the assist system control using an assist cart as a rollator. The merit of the proposed system is the aging people walk by themselves using the cart as the assisting tool and it helps anti-aging. Most serious problems of the proposed system are the avoidance of fallings and collisions without losing operability. To solve the problem, this paper proposes the remote control system taking operators' safety and operability into account. The remote control has a possibility of the establishment of the cost-effective multiple target control systems by reducing the requirement for each control target system. However, because of the limitation of communication data capabilities, the controller cannot grasp the state of the controlled object completely. To grasp the state and keep the safety, the authors apply an evaluator in the remote control system. It detects the effect of the uncertainty and keeps the controlled object safe. In addition, as an interface for the users to avoid the collisions, this paper applies the stiffness control. Introducing the virtual spring into the control system, the proposed system prevents the controlled object to collide the obstacle, without losing operability. Based on an application example for the one-dimensional assist rollator collision avoidance, this paper reveals the practicality of the proposed system by conducting experiments and the simulations. The result shows the proposed way is one of the effective ways for applying a remote control system to the assist system problem.

Horizontal moving body settling control mechanism which is mainly realized by momentum exchange, can be expected to save time of article transportation. Momentum exchange impact damper (MEID) is one of the mechanisms in order to solve shock response control problems. This paper proposes a novel hybrid mechanism consisting of passive MEID (PMEID) deceleration and active MEID (AMEID) rebound suppression for realizing rebound reduction of horizontal moving body colliding with a wall. In this method, all of the dampers are not released to the outside of the horizontal moving body but captured by soft springs to assume the actual usage condition. For the same reasons, the function to reduce the rebound and to extend the time in the state of zero rebound velocity is especially focused. The effectiveness of the proposed method is discussed by simulations and experiments. Simulations are conducted with both ideal and experimental conditions. Compared with the system with AMEID or PMEID only, the proposed hybrid MEID combines the advantages of each system and can realize settling control efficiently without releasing dampers out of the horizontal moving body. Ideal simulation results show that it is possible to reduce the rebound and the acceleration of moving body at the time of the collision, and reduce the active control input, simultaneously. These two advantages of the proposed method are also shown by the simulations with experimental conditions and the experimental results.

In many linear quadratic (LQ) optimal regulator problems, the tuning of design parameters such as weighting coefficients in the criterion function depends on trial-and-error simulations. In this note, an LQ optimal regulator is used to prevent tumbling from power-assisted carts. The cart has two actuators: a DC servomotor that drives the cart, where power assistance is realized by impedance control of the motor; and a linear motor actuator to prevent the conveyed objects from tumbling. This note mainly discusses a systematic LQ optimal regulator design method for the latter actuator. The relationships between the feedback gain tuning of the tumble prevention actuator and controlled object responses were examined by simulation. Actual feedback gains were then determined by gain scheduling of the gains obtained a priori based on the relationships, control specifications and constraints. The effectiveness of the design method was verified by simulation examples.

Lunar/planetary spacecraft should be able to land softly and conduct thorough explorations. Conventional landing methods suffer from various problems such as high rebound, the impossibility of reuse, and necessity of air. Therefore, a novel landing method that solves these problems is required for landing in severe environments. Toward this end, the authors have applied Momentum Exchange Impact Damper (MEID). MEID realizes landing by exchanging the momentum of the spacecraft with damper masses. However, flying damper masses may collide with and damage the spacecraft. Furthermore, they may pollute the lunar/planetary surface. Therefore, in this paper, the authors propose a Non-Flying-Type MEID (NFMEID) mechanism without flying damper masses. Unlike conventional landing methods and MEIDs, the NFMEID (i) reduces a spacecraft's rebound, (ii) can be reused, (iii) can be used in vacuum, and (iv) can protect a spacecraft and the surface pollution from launched masses. Furthermore, the NFMEID may extend the usefulness of MEID because it is considered effective for the shock response control of not only spacecraft but also general mechanical structures. This paper explains the NFMEID mechanism and evaluates its landing performance through some simulations. This study shows that the NFMEID is a promising landing method for further lunar/planetary exploration missions.

In the industrial world, not only autonomous machinery as industrial robots but also man-machine cooperative systems as power-assist systems have attracted special interest recently. Kondo, et al. proposed the scheme of Man-Machine Collaborated Systems (MMCSs) and its application to some assembling work. In MMCSs, efficient mode switching from human-oriented task to machine-oriented task is important. However, its issue has not been fully addressed yet. This study discusses a mode switching control method for MMCSs. Especially, we treat the switching from a power-assist mode (PAM) to an automatic positioning mode (APM) for a simple robotic system. To obtain a smooth switching, this study utilizes a two-degree-of-freedom control system structure which consists of an on-line impedance control simulator and an LQI servo controller. Some smooth reference generation for APM is also introduced. No input saturation and stopping appear at the switching in this method. The effectiveness of the method is verified experimentally.

Owing to the aging of societies, the research and development of power-assist systems that increase human-operational forces have become popular. However, a power-assist system is a typical human-machine system. Therefore, the design and use of such a system should take into account the safety of both the operator and the conveyed objects. Some of the authors have already studied on power-assist systems, using an assist-control system design consisting of an impedance controller, a disturbance-accommodating optimal controller, a disturbance observer, and a reaction-force controller. However, unintentional input forces acting on a power-assist system may cause reckless motion and severe accidents in actual use. Therefore, we discuss the use of a robust control method to prevent this abrupt motion by substituting a frequency-shaped disturbance-accommodating optimal controller (FSDAOC) for the original optimal controller. The FSDAOC enables us to eliminate high-frequency-range motion by its frequency-shaping characteristic. The objective of this study is to assess the effectiveness of the FSDAOC-based method in enabling a power-assist cart to cope with the unexpected input forces caused by crossing a step without its load tumbling. We verified the effectiveness experimentally and found that our method had a tumble-prevention rate of 80%, which was an improvement over the 23% of the previous method.

The safe and precise landing control method of planetary exploration spacecraft is indispensable to achieve its missions. However, the landing methods used in previous missions have some problems such as high complexity. To improve them, the authors' have focused on the momentum exchange principles and adopted momentum exchange impact dampers (MEIDs) that absorb the controlled object's momentum to extra masses close to the object. This extra mass is called damper mass. Some kinds of MEIDs have been introduced; for example, this paper shows Upper-MEID (U-MEID) that launches the damper mass upward, Lower-MEID (L-MEID) that drops the damper mass downward, and Generalized-MEID (G-MEID) consisting of U-MEID and L-MEID. The authors' previous paper shows the effectiveness of G-MEID. The purpose of this paper is to introduce its improved version called G-MEID-A (G-MEID-Advanced). G-MEID-A can realize downsizing of the damper mass and more effective momentum exchange by tuning of momentum exchange timing. Simulation investigation verifies that the G-MEID-A has some advantages against the rebound reduction of the spacecraft and robustness against some variable conditions.

When the human operator manually conveys a flexible part, vibration may occur in the flexible part. If the vibration occurs, the conveyance efficiency is reduced. To solve this problem, this paper proposes a semi-active operation assist handle, which is referred to an assist-handle, for manual conveyance of a flexible part. The assist-handle can be easily attached to a general hand cart. A human operates the hand cart through the assist-handle. The assist-handle consists of a handle, a variable damper, a mechanical spring and its controller. In order to suppress the vibration of the flexible part, the operating force is shaped by changing the viscous damping coefficient of the variable damper. The viscous damping coefficient of the variable damper is changed by the proposed controller. The controlled model is represented as a bilinear system, in which the inputs are the human force applied to the hand cart and the viscous damping coefficient of the variable damper, and the output is the relative position between the handle and the hand cart. The semi-active operation assist control is designed by using the bilinear optimal control theory. The effectiveness of the proposed assist handle is verified by simulations. From the comparative studies, the vibration suppression effect is seen in the proposed method. Moreover, the vibration suppression mechanism is considered. The proposed controller changes the viscous damping coefficient of the variable damper, by which the hand cart decelerates like step-shape. Then the anti-phase vibration generates in the flexible part and suppresses the vibration.

The corneal endothelium is a monolayer of hexagonal corneal endothelial cells (CECs) on the inner surface of the cornea. CECs are critical in maintaining corneal transparency through their barrier and pump functions. CECs in vivo have a limited capacity in proliferation, and loss of a significant number of CECs results in corneal edema called bullous keratopathy which can lead to severe visual loss. Corneal transplantation is the most effective method to treat corneal endothelial dysfunction, where it suffers from donor shortage. Therefore, regeneration of CECs from other cell types attracts increasing interests, and specific markers of CECs are crucial to identify actual CECs. However, the currently used markers are far from satisfactory because of their non-specific expression in other cell types. Here, we explored molecular markers to discriminate CECs from other cell types in the human body by integrating the published RNA-seq data of CECs and the FANTOM5 atlas representing diverse range of cell types based on expression patterns. We identified five genes, CLRN1, MRGPRX3, HTR1D, GRIP1 and ZP4 as novel markers of CECs, and the specificities of these genes were successfully confirmed by independent experiments at both the RNA and protein levels. Notably none of them have been documented in the context of CEC function. These markers could be useful for the purification of actual CECs, and also available for the evaluation of the products derived from other cell types. Our results demonstrate an effective approach to identify molecular markers for CECs and open the door for the regeneration of CECs in vitro.