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Aiming at the problems of complex movement posture, many degrees of freedom and flexible movement of the human body’s lower limbs, a dynamic mathematical model of the squat posture was established, and analyzed the dynamic parameters of the hip joint, knee joint and ankle joint during the squatting posture of the wearable lower extremity exoskeleton robot. Based on the MATLAB simulation software, the motion characteristics of the squat posture are simulated and analyzed, and the results show that: in the process of squatting, the theoretical calculation results are quite different from the simulation results, indicating that the process of squatting is unstable. Therefore, based on the Zero Moment Point (ZMP) theory, a stable polygon of the squat posture is established, the instability rate is defined. From a qualitative and quantitative point of view, the effects of the squat posture and the change of the center of gravity (COG) on the motion stability are analyzed. An experimental platform was built and the experiment was performed to verify the COG and ZMP changes in the squatting posture, which verified the correctness of the theoretical calculation conclusions and the influence of COG changes on ZMP.

Given that mobile soft robots are adaptable to the environment, they are always tethered with slow locomotion speed. Compared with other types of mobile robots, mobile soft robots may be more suitable for rescuing tasks, accompanying elderly people, and being used as a safe toy for children. However, the infinite freedom of soft robots increases the difficulty of precision control. In addition, the large volume and long tube of the conventional soft actuator structure limit the range of motion of current mobile soft robots. In this article, a newly designed innovative untethered-bioinspired quadrupedal robot based on double-chamber pre-charged pneumatic (DCPCP) soft actuators with highly flexible trunk is proposed. Asymmetrical cross-tendons actuated by servo motors are used to drive the DCPCP soft legs so that buckling can be avoided and mimic the gait of quadruped animals with the simplest drive and control strategy. In addition, the proposed design greatly improves energy efficiency and exhibits superior performance of variable stiffness. The bioinspired highly flexible trunk is designed with the supporting spine structure and tendon driven muscle to deform, which can constantly adjust to the contact situation between the foot and the ground to adjust the center of gravity of the soft quadruped robot and increase stability when walking and turning. The proposed soft quadruped robot does not require any air compressors, valves, and hoses. The characteristics of untethered, high-energy efficiency, linear control, and stability make the soft quadruped robot suitable for many applications.

Road security has become with time a topic of concern in our society as per the increasing number of accidents and deaths occurring on the highways. Regulatory experts on road users have constantly been working for ways to solve this problem and thence better the lives of the citizens. This paper is aimed at proposing a mathematical model integrating specific parameters, describing the dynamic lateral behavior of a vehicle’s tire and chassis systems and enabling to state a relationship between road characteristics and vehicle dynamics. To achieve this, we made used of the fundamental theorems of dynamics for the modeling of the vehicle’s suspended and non-suspended masses and load transfers, then we associated this with the Pacejka Tire model to obtain a complete vehicle model. After the particularization of a global model, a simulator was realized named “DYNAUTO SIMULATOR” which iterates the given variables to produce a consistent result. After an experimental research made on the Ndokoti – PK 24 road section we could, thanks to our simulator determine the maximum speed to have at every turn of this road section and also understand the effect of the modification of a vehicle’s center of gravity on its stability. This work will be an important tool which can be recommended to the regulatory board as a major asset in the road construction policy and also in the improvement of road safety measures.

All terrain vehicles (ATV) perform tasks in unstructured environments where the advanced adaptive ability of rigid terrain has become a key factor. In this article, we propose a novel horse inspired all terrain eight-wheeled vehicle with four swing arms for transportation in the mountain battlefield. The mechanism structure and system configuration of the ATV are designed based on the horse leg kinematics analysis. In order to analyze the obstacle surmounting strategy of the ATV, the kinematics model and the center of gravity of the ATV are represented. A model reference adaptive control method is proposed for the hydraulic attitude control system. Then the model for obstacle surmounting is proposed for dynamics performance and geometric kinematics. Additionally, the simulation is executed in Adams to verify the analysis and strategy. Finally, the experiment is demonstrated for climbing a vertical wall, which is a challenging and typical terrain of the mountain battlefield.

With rapid advances in virtual reality (VR) technology, the use of haptics has become important to allow users to feel the physical properties of virtual objects. Current research has focused mainly on either weight variation or changing the center of gravity, which limits the simulation potential and may affect the feeling of immersion. This research explores the design and development of a device that can simulate both weight and center of gravity using low-cost components. Through an iterative design process and continuous testing with users, we arrived at a final prototype, FluidWeight, a device that can be attached to a typical VR handheld controller. FluidWeight uses fluid, which is transported from a central storage to a receptacle attached to the controller. A final experiment shows that users enjoyed using it because it could help increase the sense of realism in VR applications.

The purpose of this research is to develop an omnidirectional low-floor mobility. The mobile platform and the interface have already been developed. The height of the mobile platform is 37 mm from ground to the boarding surface. Omnidirectional movement is realized by using four mecanum wheels. This mobility utilizes sway of the center of gravity of the users. In order to operate this mobility, the users voluntarily tilt their bodies. This body inclination is estimated from the load distribution information of eight load cells installed on the boarding surface of this mobility. This enables forward-backward, lateral, and turning movements. However, the motion of this mobility is oscillatory, because inertia of this mobility causes unintended human body movements, which are input to the interface. In this research, in order to solve this problem, the authors introduce not only an inverted pendulum model but also a human postural control model. In order to change the body inclination voluntarily to operate this mobility, it is indispensable for a human postural control model to be able to follow an arbitrary target inclination angle, not just an upright state. The authors have now achieved forward-backward movement. In this paper, the authors propose a control model for following target inclination angle in lateral direction. First, a control model for maintaining an upright posture is introduced. Next, the authors conduct a body postural maintenance experiment in lateral inclination. A model is identified as a control model for following target inclination angle based on the result of this experiment.

Purpose Excellent obstacle surmounting performance is essential for the robotic vehicles in uneven terrain. However, existing robotic vehicles depend on complex mechanisms or control algorithms to surmount an obstacle. Therefore, this paper aims to propose a new simple configuration of an all-terrain robotic vehicle with eight wheels including four-swing arms. Design/methodology/approach This vehicle is driven by distributed hydraulic motors which provide high mobility. It possesses the ability to change the posture by means of cooperation of the four-swing arms. This ensures that the vehicle can adapt to complex terrain. In this paper, the bionic mechanism, control design and steering method of the vehicle are introduced. Then, the kinematic model of the center of gravity is studied. Afterward, the obstacle surmounting performance based on a static model is analyzed. Finally, the simulation based on ADAMS and the prototype experiment is carried out. Findings The experiment results demonstrate that the robotic vehicle can surmount an obstacle 2.29 times the height of the wheel radius, which verifies the feasibility of this new configuration. Therefore, this vehicle has excellent uneven terrain adaptability. Originality/value This paper proposes a new configuration of an all-terrain robotic vehicle with four-swing arms. With simple mechanism and control algorithms, the vehicle has a high efficiency of surmounting an obstacle. It can surmount a vertical obstacle 2.29 times the height of the wheel radius.

[Purpose] Stand-and-ride personal mobility devices controlled by movements of the user's center of gravity are used for balance training. We aimed to describe the physical activity required to operate this type of mobility device. [Participants and Methods] Eleven healthy males performed the following tasks: 1) moving their center of gravity forward or backward while standing on the floor (control task) and, 2) moving the mobility device forward or backward by moving their center of gravity (experimental task). [Results] We observed that the displacement of the center of gravity and the center of pressure, as well as angular displacements of the hips and knee joints, and maximum muscle activities of the biceps femoris, the medial head of the gastrocnemius and peroneus longus muscles were lesser during the experimental than during the control task. The distance moved by the device was significantly greater than the displacement of the user's center of gravity during the experimental task. [Conclusion] We observed that moving the device forward or backward required lesser physical activity than that required to shift the user's center of gravity forward or backward while standing on the floor. Additionally, we observed that even a small displacement of the user's center of gravity produced a large displacement of the device. We concluded that during balance training, the greater and more easily perceived movement of the mobility device would provide helpful feedback to the user.

A motion-planning method that can adapt to changes in the surrounding environment is proposed and evaluated. Automation of work is progressing in factories and distribution warehouses due to labor shortages. However, utilizing robots for transport operations in a distribution warehouse faces a problem; that is, tasks for setting up a robot, such as adjustment of acceleration for stabilization of the transportation operation, are time consuming. To solve that problem, we developed an "evolvable robot motion-planning method." The aim of this method is to reduce the preparation cost by allowing the robot to automatically learn the optimized acceleration according to the weight and center of gravity of the objects to be transported. It was experimentally demonstrated that the proposed method can learn the optimized acceleration control from time-series data such as sensor information. The proposed method was evaluated in a simulator environment, and the results of the evaluation demonstrate that the learned model reduced the inertial force due to the acceleration of robot motion and shortened the transport time by 35% compared with the conventional method of manual adjustment. The proposed method was also evaluated in a real machine environment, and the evaluation results demonstrate that the method can be applied to a real robot. Since the speed of the robot does not need to be adjusted in the case of the proposed method, the adjustment man-hours can be reduced.

Herein, we propose a real-time stable control gait switching method for the exoskeleton rehabilitation robot. Exoskeleton rehabilitation robots have been extensively developed during the past decade and are able to offer valuable motor ability to paraplegics. However, achieving stable states of the human-exoskeleton system while conserving wearer strength remains challenging. The constant switching of gaits during walking may affect the center of gravity, resulting in imbalance of human–exoskeleton system. In this study, it was determined that forming an equilateral triangle with two crutch-supporting points and a supporting leg has a positive impact on walking stability and ergonomic interaction. First, the gaits planning and stability analysis based on human kinematics model and zero moment point method for the lower limb exoskeleton are demonstrated. Second, a neural interface based on surface electromyography (sEMG), which realizes the intention recognition and muscle fatigue estimation, is constructed. Third, the stability of human–exoskeleton system and ergonomic effects are tested through different gaits with planned and unplanned gait switching strategy on the SIAT lower limb rehabilitation exoskeleton. The intention recognition based on long short-term memory (LSTM) model can achieve an accuracy of nearly 99%. The experimental results verified the feasibility and efficiency of the proposed gait switching method for enhancing stability and ergonomic effects of lower limb rehabilitation exoskeleton.

The final goal of this paper was to realize swordplay (Tankendo) matches between humans and robots. For a mobile trolley robot that cannot suddenly start and stop like a human, we devised a robot system design method that would allow a robot to defend against human attack by moving immediately before a valid attack. In the preliminary experiment, of the control parameters for the mobile trolley robot used, the authors changed the direction of movement and rotational elements to find the best conditions for a robot to avoid taking defensive action until the last possible second to avoid an attack. In this experiment, we calculated the threshold from the movement speed of the center of gravity of the body during striking and thrusting by a human and designed a system to determine the robot defense initiation time.

This paper studies the remote evaluation system of tennis batting action standard based on acceleration sensor, which aims to help improve the standard degree and technical level of tennis batting action. The system includes a data acquisition module to collect original signal data of tennis batting action by the acceleration sensor signal acquisition device in the bracelet and upload to the personal computer (PC) for storage, data preprocessing module to smooth original signal data and extract the key time and frequency domain features as the evaluation basis, and remote evaluation module to assess tennis batting action standard. We applied our system to five tennis trainees from the experimental university, and the results show that the batting action standard level of student c and student e is lower. Student c is weak mainly in the best position of the hitting point and the timing of the lead shot, while student e mainly shows poor performance in the timing of movement and the stability of the overall center of gravity. Compared with the proposed system or device, our system has a short real-time delay under the concurrent use of different types of users indicating stable and high real-time evaluation performance. More importantly, our system strictly protects the user’s privacy when uploading the user’s data remotely. In short, the evaluation results obtained by our system can be used as a scientific basis to improve the tennis batting action standard.

An imaginary point where the total mass is concentrated is known as the center of gravity (CG) of an object. The center of gravity has an important role in satellite launch vehicles for its smooth journey to space. The measurement of CG should be accurate for launch vehicle to keep its intended trajectory. This paper explains a novel method to get high accuracy in the measurement of CG in real time using customized software. The paper also explains the calibration method of load cells for getting better accuracy while measurement. Three-point and four-point methods are tested for different-shaped launch vehicle sub-assemblies. The exact CG point will help the launch vehicle to eject the satellites very accurately. Multiple position measurement has been conducted to find out the repeatability of measurements. The method finds out the error in horizontal leveling and load cell reading by using the measured values in real time.

A correct reproduction of a motorcycle rider’s movements during driving is a crucial and the most influential aspect of the entire motorcycle–rider system. The rider performs significant variations in terms of body configuration on the vehicle in order to optimize the management of the motorcycle in all the possible dynamic conditions, comprising cornering and braking phases. The aim of the work is to focus on the development of a technique to estimate the body configurations of a high-performance driver in completely different situations, starting from the publicly available videos, collecting them by means of image acquisition methods, and employing machine learning and deep learning techniques. The technique allows us to determine the calculation of the center of gravity (CoG) of the driver’s body in the video acquired and therefore the CoG of the entire driver–vehicle system, correlating it to commonly available vehicle dynamics data, so that the force distribution can be properly determined. As an additional feature, a specific function correlating the relative displacement of the driver’s CoG towards the vehicle body and the vehicle roll angle has been determined starting from the data acquired and processed with the machine and the deep learning techniques.

The moment of inertia is an important factor affecting the comfort of the helmet. However, the shape of the helmet has irregular characteristics, so the moment of inertia (MI) is difficult to measure. Therefore, this paper develops a device that accurately measures the MI of the helmet. The device uses the weighing method and the torsion method combined with the lever theory to measure the MI of the irregular helmet. Visual C++ is used as the development environment to create visualization software, which can display and print data. The device can accurately measure the center of gravity and moment of inertia of the helmet without damaging the helmet. It is a new method of measuring MI, and It is simple and reliable.

In this paper, an easy-to-use two-wheeled self-balancing vehicle was implemented by using an Arduino control board, inertial measurement unit, and six load sensors. The two-wheeled balance vehicle designed in this paper is based on the inertial sensor to detect the inclination of vehicle, and a load sensor is added to detect the driver's posture of standing on the two-wheeled balance vehicle. In order to improve the situation that the motor output is not as expected due to the ankle angle change causing the vehicle to misjudge the center of gravity angle, the load sensors were not only to detect the left and right changes of center of human’s gravity, but also used to detect the front and rear changes of center of gravity to correct the angle difference of the center of human’s gravity and the center of the vehicle. In addition, the load sensors were also used to estimate the height of the center of human’s gravity, so that people with different heights and weights can have a similar riding experience.

Powered two-wheeler (PTW) riders and passengers are among the group of vulnerable road users (VRU). This group uses the road transportation system together with other better-protected users such as passenger cars and truck drivers. The main vulnerability of PTW rider lies in their unequal position during the crash, due to the inability of application of the crashworthiness concept during the PTW vehicle design. This inequality could be somehow mitigated by the design of personal protective equipment (PPE). Mostly the design of the PPE’s is led by the standards which often are obsolete and takes into account only simple drop-tests (ECE 22.05). Those tests did not take into account complicated kinematics of the motorcycle accidents and biomechanics of the human body (the assessment is based only on the linear acceleration of the headform center of gravity). The authors propose a virtual approach for the PTW rider injury risk assessment, which coupled with the pre-impact conditions, could be used for the new PPE protection standards preparation. In this paper, authors want to present a numerical study on the most common PTW impact scenarios, which are described in ISO 13232. The simulations of the accidents were conducted in the VPS numerical environment (PAM-Crash explicit solver). Accidents participants, namely opposite vehicle (OV) modeled by finite element method (FEM) approach, powered two-wheeler (PTW) modeled by multibody system (MBS) approach, PTW driver represented by hybrid FE-MBS human body model Virthuman and a helmet (modeled by FE approach) were coupled to represent the 7 most common accident scenarios. The helmet is the only PPE enforced by the law, but not in all territories (Afghanistan, Dominica, Guyana, Mexico, Libya, Senegal, USA). Due to the complexity of the OV FE model, there was a necessity of model simplification and revalidation, which also was done in this work. The results of the simulations were examined with special emphasis on realistic representation of real accident kinematics. In each configuration, an injury risk assessment was done on the PTW rider model. The assessment was done based on injury criterion used by the NCAP, UNE 135900 and the LNL criterion. The paper shows that the virtual approach using the Virthuman human body model could be used for the simulation of PTW accidents. The results of this paper could be used for future PPE design.

In this study, we designed a dynamic output feedback control for a walking assistance training robot. The proposed system addresses the problems of shifts in the center of gravity and vibration associated with time-varying arm of force in omniwheel to improve the accuracy of the trajectory tracking of the walking assistance training robot. The dynamic output feedback controller was developed by constructing a velocity observer on a stochastic dynamic model of the walking assistance training robot via integration with a Lyapunov function. An analysis of the time-varying arm of force in omniwheel revealed that it increased the accuracy of the walking assistance training robot dynamic model. Thus, an adaptive law was designed such that the vibration caused by the time-varying arm of force in omniwheel was eliminated. The mean absolute practical stability in the position and velocity tracking errors was verified based on Young’s inequality and stochastic stability theory. The simulation results show that the walking assistance training robot with the shifts in the center of gravity was able to track a designed trajectory and that the application of the adaptive law effectively eliminates the vibrations caused by the time-varying arm of force in omniwheel.

In this research, a miniaturized humanoid robot is constructed to ride and pedal a bicycle of comparable size. The design of the controller for the robot to balance and steer the bicycle using the ...

Advances in low-cost wearable head impact sensor technology provide potential benefits regarding sports safety for both consumers and researchers. However, previous laboratory evaluations are not directly comparable and do not incorporate test conditions representative of unhelmeted impacts. This study addresses those limitations. The xPatch by X2 Biosystems and the SIM-G by Triax Technologies were placed on a National Operating Committee on Standards for Athletic Equipment (NOCSAE) headform with a Hybrid III neck which underwent impact tests using a pendulum. Impact conditions included helmeted, padded impactor to bare head, and rigid impactor to bare head to represent long- and short-duration impacts seen in helmeted and unhelmeted sports. The wearable sensors were evaluated on their kinematic accuracy by comparing results to reference sensors located at the headform center of gravity. Statistical tests for equivalence were performed on the slope of the linear regression between wearable sensors and reference. The xPatch gave equivalent measurements to the reference in select longer-duration impacts, whereas the SIM-G had large variance leading to no equivalence. For the short-duration impacts, both wearable sensors underpredicted the reference. This error can be improved with increases in sampling rate from 1 to 1.5 kHz. Follow-up evaluations should be performed on the field to identify error in vivo.

Anthropomorphic testing devices (ATDs) used in vehicle crash testing are the industry standard for occupant safety research, but they are expensive and complex equipment. The purpose of this research was to develop and build a simplified dummy and sled for a low-impact frontal crash. The design of the simplified ATD was inspired by the commercially available crash test dummy ECE-R16 model. The dummy was designed such that it matched weight and center of gravity of an adult passenger. A pendulum was created for imposing an impact force to the sled accommodating the dummy. This simplified ATD was used to measure acceleration based injury criteria. The experimental results were compared with a Finite Element (FE) simulation of the Hybrid III dummy in a 2002 Ford Explorer. The simplified physical experiment results followed a similar trend as the FE Hybrid III simulation results.

A novel approach to onboard in-flight weight and balance estimation systems is presented. Data from an Airbus A320 fleet from an airline were used to assess the feasibility of the approach. Simple flight mechanics in combination with statistics allowed for the identification of weight and center of gravity position using cruise angle of attack, Mach number and elevator deflection values. The good agreement between the theoretical model and the obtained values for the lift curve slope as a function of Mach as well as the standard error of the estimate for center of gravity position and cruise flying weight indicate that the method is sound. The major implication of this work is that the development of onboard and in-flight weight and balance systems can be significantly simpler than previous literature suggested. The impact of this paper could be immediate for airlines since all the tools required to implement the system as described are readily available. This could have an effect in operating costs, safety and environment.

This study presents a resolved viscoelasticity control (RVC) method to handle multiple viscoelasticity in a humanoid system. A previous study proposed an RVC by explicitly considering structure-variability and demonstrated biped walking motions on an uneven terrain and a slope. In this study, the RVC is extended to multiple viscoelasticity, namely viscoelasticity on multiple feature points and multiple values in single viscoelasticity. The resolved multiple viscoelasticity control can improve both tracking performance and stability. The results indicate that resolving center of gravity (COG) and swing foot viscoelasticity improves the walking performance and that switching multiple values of the COG viscoelasticity improves the balancing performance. The proposed method is validated by using forward dynamics simulations.

This paper proposes a dual lifting and its cooperative control system with two different kinds of floating cranes. The Mega-erection and Giga-erection in the ship building are used to handle heavier and wider blocks and modules as ships and off-shore platforms are enlarged. However, there is no equipment to handle such Tera-blocks. In order to overcome the limit on performance of existing floating cranes, the dual lifting is proposed in this research. In the dual lifting, two floating cranes are well-coordinated to add up the lift capabilities of both cranes without any loss such that virtually a single crane is lifting, maneuvering and unloading. Two main constraints for the dual lifting are as follows: First, two barges of floating cranes should be constrained as a rigid body not to cause a relative motion between two barges and main hooks of the two cranes should be controlled as main hooks of a single crane. In order words, it is necessary to develop the cooperative control of two floating cranes in order to sustain a center of gravity of the module and minimize the tilting angle during the lifting and unloading by the two floating cranes. Two floating cranes are handled as a master-slave system. The master crane is able to gather information about all working conditions and make a decision to control the individual hook speed, which communicates the slave crane by TCP/IP. The developed control system has been embedded in the real floating crane systems and the dual lifting has been demonstrated five times at SHI shipyard in 2015. The moving angles of the lifting module are analyzed and verified to be suitable for hoisting control. It is verified that the dual lifting can be applied for many heavier and wider blocks and modules to shorten the construction time of ships and off-shore platforms.

This study developed an online observable augmented reality dynamics experimental system that can be used in the current COVID-19 pandemic, where face-to-face experiments are difficult to conduct. The developed system enables the broadcast of mass point and rigid body measurements using an online depth camera, and remote observation using mobile devices. The mass point measurement enables students to quantitatively analyze results by utilizing 2D projected trajectories. Students can view the virtual trajectories by modifying the gravity or restitution coefficient, which is not possible in real experiments. The complex motion of the rigid body can be shown separately as the motion of the center of gravity and the moment of inertia with respect to the center of gravity. © 2021 IOP Publishing Ltd.

The purpose of this study was to develop a textile component system that could be added to a compression garment to achieve body posture that more closely resembles an ideal balanced posture. The approach of this study was to find a middle ground of posture correctors and compression garments by combining structural support elements with garment compression to achieve effective posture modification as well as comfort. To achieve this goal, a Posture Modification System using Soft materials structures (PMSS) was developed by experimenting with textile elastic bands to mimic the structure and placement of anatomical postural features (muscles and spinal column) of a woman’s back torso. For prototype development, a bodysuit type shapewear garment was used to incorporate the PMSS and a wear test with female participants was conducted. To assess posture changes through body angles, participants were 3D scanned and questionnaires were administered to determine wearer acceptability. Body angle assessment indicated that wearing the prototype positively affected posture changes including more balanced shoulders, more aligned lateral center of gravity, and straighter spine. As assessed with a questionnaire, the prototype achieved higher wearer acceptability in terms of posture, body shape, and fit compared to the shapewear without the PMSS. This study shows the potential of developing the soft structural posture modification system for use beyond the lingerie category. Furthermore, more aligned postures exhibited by participants wearing the PMSS enhanced garment while carrying loads indicate potential in developing soft-structured posture support garments for load-bearing situations in industrial and military settings.

Hitherto unaddressed issue of six degree-of-freedom transient dynamics during asymmetric ejection of stores with finite velocity, onboard a combat aircraft, is addressed and modeled from the first principle. Further, the effect of asymmetric center-of-gravity shift, post ejection of the store, on some complex high angle-of-attack maneuvers such as cobra and Herbst is also investigated. It is shown that the performance of the maneuvers drastically deteriorates when carried out with controller designed for the pre-ejection symmetric c . g . based dynamics. In order to improve the deteriorated performance, two new control schemes based on the standard sliding mode technique are proposed. The first sliding control is designed based on a simple ad-hoc model for the asymmetric dynamics, whereas the states are propagated using the exact model developed. It is shown that using this scheme the lost maneuver performance can be reasonably recovered. The second control scheme is formulated using an accurate asymmetric dynamics. This proposed control scheme almost completely recovers the original maneuver performance.

In this paper, the fuzzy control strategy for a hexapod robot walking on an incline is proposed. In order to maintain the vertical projection of the center of gravity (COG) remaining in the support pattern, the robot’s posture is adjusted by a fuzzy controller depending on the slope of incline. At first, Denavit–Hartenberg convention is applied to calculate the positions of motors and end points of legs. When the robot is walking on an incline, a rotation matrix, which can be acquired by an inertial measurement unit settled on the center of robot’s body, is required to obtain the vertical projection of COG. Then, the fuzzy controller is designed to adjust the angles of motors for supporting legs such that the vertical projection of COG approaches the COG of support polygon. Finally, several experiments are implemented by a hexapod robot to demonstrate the effectiveness of the proposed fuzzy control strategy.

Achilles tendon vibration generates proprioceptive information that is incongruent with the actual body position; it alters the perception of body orientation leading to a vibration-induced postural response. When a person is standing freely, vibration of the Achilles tendon shifts the internal representation of the verticality backward thus the vibration-induced postural response realigned the whole body orientation with the shifted subjective vertical. Because utricular otoliths information participates in the creation of the internal representation of the verticality, changing the natural orientation of the head-neck system during Achilles tendon vibration could alter the internal representation of the earth vertical to a greater extent. Consequently, it was hypothesized that compared to neutral head-neck orientation, alteration in the head-neck orientation should impair balance control immediately after Achilles tendon vibration onset or offset (i.e., sensory transition) as accurate perception of the earth vertical is required. Results revealed that balance control impairment was observed only immediately following Achilles tendon vibration offset; both groups with the head-neck either extended or flexed showed larger body sway (i.e., larger root mean square scalar distance between the center of pressure and center of gravity) compared to the group with the neutral head-neck orientation. The fact that balance control was uninfluenced by head-neck orientation immediately following vibration onset suggests the error signal needs to accumulate to a certain threshold before the internal representation of the earth vertical becomes incorrect.

When a floater such as a ship or an offshore structure is damaged in the sea, it is necessary to determine whether the floater will sink in water or not. If the floater will sink, the time to sink should be estimated to make an emergency plan. In addition, causes of the flooding should be investigated carefully. For this purpose, a method for performing intermediate flooding and sinking simulation of the damaged floater in time domain is proposed in this study. Overall process of the proposed method consists of several steps. In the first step, data of the damaged floater such as hull form and compartments are prepared. In the second step, physical characteristics of the floater such as the increased weight considering incoming water, the center of gravity, the changed buoyancy, and the center of buoyancy are calculated at every time step. In the third step, the quasi-static equilibrium position of the floater is calculated. The second and third steps are repeated until the floater reaches to sink or to be in equilibrium. As a result, the final condition of the floater can be determined. To check the feasibility of the proposed method, it is applied to a simple box problem. Finally, it is applied to intermediate flooding simulation of a barge-type damaged floater. Two cases having damaged holes of different locations are selected. As a result, it was confirmed that the floater can be in equilibrium or sink according to the damaged position. The time to be in equilibrium or the time to sink was estimated. Highlights Flooding and sinking procedures of a damaged floater is defined. A method for intermediate flooding and sinking simulation of the damaged floater in time domain is proposed. Theoretical background for the simulation is established. We perform the intermediate flooding and sinking simulation. The time to be equilibrium or the time to sink is estimated from the simulation.

Experimental investigations for the guidance of a medium-caliber projectile by using a single impulse thruster located at the center of gravity are presented. Free-flight tests were performed on a proving ground for modified 40 mm Bofors projectiles equipped with a complete pyrotechnic impulse-thruster chain, including a 3 N·s impulse thruster, a high safety electropyrotechnic detonator, and a safety and arming device that was designed especially to reach the required specifications in terms of response time and safety. Modified projectiles were launched with a 40 mm rifled gun. The functioning of the impulse thrusters during the flight and the projectile behavior were observed by means of radar and a high-speed video tracking system. Dispersion of the shells was precisely observed on a target located at the end of the trajectory. The results have shown that projectiles are clearly diverted from their normal ballistic trajectory with a reproducible deflection angle.

Current VR/AR systems are unable to reproduce the physical sensation of fluid vessels, due to the shifting nature of fluid motion. To this end, we introduce SWISH, an ungrounded mixed-reality interface, capable of affording the users a realistic haptic sensation of fluid behaviors in vessels. The chief mechanism behind SWISH is in the use of virtual reality tracking and motor actuation to actively relocate the center of gravity of a handheld vessel, emulating the moving center of gravity of a handheld vessel that contains fluid. In addition to solving challenges related to reliable and efficient motor actuation, our SWISH designs place an emphasis on reproducibility, scalability, and availability to the maker culture. Our virtual-to-physical coupling uses Nvidia Flex's Unity integration for virtual fluid dynamics with a 3D printed augmented vessel containing a motorized mechanical actuation system. To evaluate the effectiveness and perceptual efficacy of SWISH, we conduct a user study with 24 participants, 7 vessel actions, and 2 virtual fluid viscosities in a virtual reality environment. In all cases, the users on average reported that the SWISH bucket generates accurate tactile sensations for the fluid behavior. This opens the potential for multi-modal interactions with programmable fluids in virtual environments for chemistry education, worker training, and immersive entertainment.

In the case of large-scale accident or disaster such as earthquake, search/rescue robots are required to gather information and save lives in dangerous areas for humans. In our previous studies, the Legged Air Vehicle was designed and built for search operations at a disaster site. It is equipped with four legs and a tandem rotor, and is designed to be operated in various environments by combining flight and walking. In flight, the attitude is controlled by moving the center of gravity by turning the legs in order to reduce the number of actuators. In this paper, a new algorithm of the movement of the center of gravity is suggested, and the attitude controller is redesigned accordingly. Also, the attitude control is installed on the robot and its control performance is validated by flight experiments.

Exerting large force is one of the difficult problems for a humanoid robot. In particular, the task which needs large force with a tool or the task whose reference force is unknown such as digging are more difficult. The task of digging was realized in the previous research, but with that method the robot cannot exert large force even though force is not enough for digging because the decision method of reference shovel force is only changing the direction of the current shovel force, and modification of the robot's CoG (center of gravity) is only used for balancing. In this paper, we proposed methods to determine the reference shovel force which is necessary enough to realize the task of digging, and generate feasible posture which exerts the reference shovel force within joint torque limits. To verify the methods, we conducted experiments of the task of digging using a life-size humanoid robot JAXON. JAXON succeeded digging with some soil from soft to hard.

With the increasing in the number of elderly people and the deterioration of their leg muscles, wheelchairs have become an important mean of transportation. In the market, most wheelchairs that can climb stairs use a crawler-type or double planetary gears' wheel. But the crawler has the disadvantages of being bulky and has big friction on the ground and double planetary gears' wheel will cause big shake while climbing stairs. Rocker-bogie is also a mechanism can step over high obstacles but cannot climb stairs. To climb stairs smoothly and safely, we designed a wheelchair that based on the three mechanisms with advantages of all of them. With linkage mechanisms, the wheelchair can also adjust the location of the center of gravity (COG) of the user for safer climbing. Additionally, the linkage mechanism can also assist the user to stand up, which is more helpful for the user of the wheelchair. It is composed of four-linkage and parallelogram mechanisms. To assist the user to stand up with the normal posture of a healthy elderly, three parameters were taken into account in the design of chair part: trajectory of COG, the change of the upper body angle and the trajectory of the hip joint of the user while standing up. From the simulation results, the torque of the knee and ankle joint of the user being assisted to stand up decreased much. From theoretical calculations and experiments of the scaled models, different new mechanisms were compared and the one that was able to climb stairs most smoothly and stably was chosen. The effectiveness of the new mechanism was confirmed.

The objective of this study was to develop a mouthpiece sensor with improved head kinematic measurement for use in non-helmeted and helmeted sports through laboratory validation and pilot field deployment in female youth soccer. For laboratory validation, data from the mouthpiece sensor was compared to standard sensors mounted in a headform at the center of gravity as the headform was struck with a swinging pendulum. Linear regression between peak kinematics measured from the mouthpiece and headform showed strong correlation, with r2 values of 0.95 (slope = 1.02) for linear acceleration, 1.00 (slope = 1.00) for angular velocity, and 0.97 (slope = 0.96) for angular acceleration. In field deployment, mouthpiece data were collected from four female youth soccer players and time-synchronized with film. Film-verified events (n = 915) were observed over 9 practices and 5 games, and 632 were matched to a corresponding mouthpiece event. This resulted in an overall sensitivity of 69.2% and a positive predictive value of 80.3%. This validation and pilot field deployment data demonstrates that the mouthpiece provides highly accurate measurement of on-field head impact data that can be used to further study the effects of impact exposure in both helmeted and non-helmeted sports.

The Pull Test is a common practice to assess the postural instability of patients with Parkinson Disease. Postural instability is a serious issue for elderly and people with neurological disease, which can cause falls. The implementation of the Pull Test consists in observing the user response after providing a tug to the patients’ shoulders, in order to displace the center of gravity from its neutral position. The validity of the test can be compromised by a nonstandard backward tug provided to the patient. The solution proposed in this paper consists of a low cost multisensor system allowing an objective estimation of the input solicitation. Moreover, the system provides supplementary information on the user postural instability, by means of a set of features extracted from the user stabilogram, which are useful to assess the user response. A wide set of experiments have been performed to assess the system capability to provide a rough classification between stable and unstable behaviors. Results obtained demonstrate the validity of the approach proposed.

Recently, VR technology has advanced rapidly, and many Head Mounted Displays (HMD) are sold by companies all over the world. In order to have good experiences in VR environment, comfortability of wearing HMD is essential. However, few studies investigated the feelings of fatigue on commercially available HMDs. In this research, we focused on the effects of weight and balance of HMD on physical load. We performed experiment with 188 participants using shooting game played under different weights and balances. After playing the game, the participants were asked to answer a questionnaire to assess the level of physical loads that they perceived. As the results, we clarified that the weight of HMD affects the feelings of fatigue, and its degree varies depending on the position of the center of gravity. The results suggest the joint torque at the neck can be an indicator of the physical load of HMD. Our results will be highly suggestive for designing new HMD.

Recently, the number of alpine ski junior players in Japan has drastically decreased. The causes include a decrease in ski areas and instructors, along with difficulty of early childhood alpine ski guidance. The alpine ski competition is not simply a glide on a slope. It requires understanding of ski deflection and skier posture mechanics. Therefore, a passive ski robot without an actuator was developed for junior racers of the alpine ski competition to facilitate understanding of the turn mechanism. Using this robot can elucidate factors affecting ski turns, such as the position of the center of gravity (COG) and the ski shape. Furthermore, a mechanism for changing the COG height, the edge angle and the ski deflection is added to the passive turn type ski robot. The developed ski robot can freely control the turn by changing those parameters during sliding.

In this paper, an enhanced attitude determination algorithm is proposed to decrease the estimation error by including an additive state variable for the lever arm. Attitude determination generally is carried out by measurements from an IMU (inertial measurement unit), which is typically located at the center of gravity of the vehicle. The IMU lever arm, which spans the distance between the IMU and the center of gravity, causes extra acceleration in the accelerometer and increases the error in attitude estimates. However, if the extra accelerations caused by the lever arm can be removed from the measurements of accelerometers, the increased attitude error caused by the IMU lever arm can be prevented. Because an IMU lever arm is fixed in a vehicle after installation, it can be considered as an additive element of the state vector in Kalman filter for attitude determination. The proposed algorithm is composed of a quaternion-based Kalman filter and includes an estimation of the IMU lever arm. In addition, in order to determine components of lever arm, the gross measure of modal observability is investigated for the system. An evaluation of the proposed algorithm is carried out by simulations with a noise model based on an actual IMU. Evaluations through simulations show that the proposed algorithm improves the performance with regard to errors.

Purpose This paper aims to study the short take-off characteristics and longitudinal controllability of FanWing. As a new structural plane, it has achieved great success at the air shows, but the existing literature is mostly on feasibility and prototype study while little on short take-off performance analysis and controllability. Thus, the paper will do some research on those two aspects. Design/methodology/approach This paper focuses on a certain type of a 3.5 kg FanWing and builds the longitudinal model based on its structure characteristics and operation principle. Its take-off process is simulated and the longitudinal control law is designed. Findings The short take-off performance and the large load characteristic are verified. To attain a better short take-off performance, several factors that influence the take-off distance are researched, and the optimal no-load take-off distance 5 m is obtained when the elevator deflection angle is −30°, the center of gravity is 0.42 m and the cross-flow fan rotation speed is 2500 r/min. The longitudinal controllability is verified through simulation. And without variable cross-flow fan rotation speed control, the longitudinal control of FanWing is the same to that of the conventional aircraft. Practical implications The presented efforts provide markers for designing the fan wing aircraft that would have better performances. And the control of FanWing is similar to that of a conventional airplane. Originality/value It is proved that FanWing can offer a better take-off performance through reasonable configuration. The paper also offers a useful reference on the control of FanWing.

IF=2.377; International audience; The rollover status of a vehicle indicated by the lateral load transfer (LTR) as the vehicle traverses over various driving scenarios is critical in the implementation of antirollover control procedures. The determination of LTR is often carried out by the measurements of the roll angle, the lateral acceleration, vertically acting suspension forces, etc. In all these measurements, sensor faults may occur, which lead to a faulty computation of the rollover status, raising a false alarm. In this work, a scheme based on a robust higher order sliding-mode observer is proposed to estimate the states of a nonlinear two-wheel vehicular system affected by road disturbances, uncertainties in the height of the vehicle's center of gravity, and possible multiple sensor faults. Applying the proposed approach, the unknown inputs and sensor faults are reconstructed. To perform the estimations, adaptive sliding-mode-based observers that do not require the knowledge of the bounds of the uncertainties and unknown inputs are designed. Consequently, the true rollover status of the vehicle is determined, in spite of the presence of sensor faults. The validity of the proposed scheme has been assessed on the vehicle simulation software CarSim as the vehicle undergoes a double lane change maneuver.

The bus is a vehicle for transport the passenger to the destination safely. The bus manufacturing is produced directly from the company and the bus has been modifying from the bus garage. The Bus modify into popular use in the domestic because it is cheaper. The modified bus is also a safety issue because these vehicles to the tilted test 30 degrees most of the test is not passed. The center of gravity is influenced to the stability of the bus. Which the Company or modify bus garage can not know the position of the center of gravity in advance. When the bus is used to build a center of gravity located in improper placement. Hence, the test does not pass 30 degrees tilt.Which required costs to adjustment and test again. This paper was intended to study the variables that affect the center of gravity of the bus include engine placement, adjustment pressure into air suspension before build bus body, bending chassis, characterized by mounting to the chassis frame. Studies using instruments find the center of gravity of the bus used computer simulation center of gravity nearby real bus. The variable adjustment in order to design a bus with the appropriate center of gravity. Research has found that different variables adjustment engine placement characterized by mounting to the chassis frame have an affect to bending chassis relate to the center of gravity change, Therefore, the variables to be optimized, it is possible to design a bus safety.

In cases of falls, the key issue for forensic scientists is to determine the manner of death. They must distinguish between accidental falls, suicidal falls, falls including blows and falls caused by a blow. Several strategies have been proposed in the literature to help explain injury patterns. Here, we report an original case of a man who died after jumping from a car moving at high speed. A mathematical and modeling approach was developed to reconstruct the trajectory of the body in order to understand the injury pattern and apparent discrepancy between the high speed of the car from which the victim jumped and the topography of the bone fractures, which were limited to the skull. To define the initial values of the model's parameters, a technical vehicle evaluation and several test jumps at low speed were carried out. We studied in greater detail the trajectory of three characteristic points corresponding to the dummy's center of gravity, head and right foot. Calculations were made with and without the air friction effect to show its influence. Finally, we were successful in modeling the initial trajectory of the body and the variation of its head energy over time, which were consistent with the injuries observed.

As navigation algorithms using Kalman filters, fuzzy or adaptive algorithms, interacting multiple model (IMM) algorithms and other possible solutions combining data from several sensors, have been progressively used in the last decade, there has been little advance in developing a robust and accurate device available for car manufacturers. The most solutions fail in long-term reliability and/or use too generalized linearization models. This is why in this paper we have examined some high dynamic manoeuvres which are usually a part of automotive tests. Some major issues during these manoeuvres were identified and a modified Kalman filter solution is presented. The problem of positioning of an inertial device within a vehicle is addressed and a transformation of measured data to the centre of gravity (COG) or rotation point (RP) of the vehicle is introduced. We also propose a few methods to identify the start and the stop of a brake test and show distance difference between conventional and modified Kalman algorithm during driving in circles. Finally, a direct and indirect lever-arm correction is introduced and real road tests are made to present an improvement in outputs using one-device sensor setup.

Current curve speed warning systems take into account mostly vehicle and road factors but not driver behavior. The systems aim at detecting sideslips of small cars on curves without consideration of rollovers for vehicles with an elevated center of gravity. In this study, a curve speed model that considers human, vehicle, and road factors is built to prevent not only sideslips but also rollover accidents for vehicles with an elevated center of gravity. In addition, a risk prediction model is presented to judge accident risk levels and determine levels of warning. Finally, the effectiveness of the presented system is validated with one skilled driver who carries out one test through a simulator under different curve scenarios. To verify the system, data from simulator tests were collected for offline checking of the system. The data were used to calculate safe speeds by using the curve speed model and to determine the levels of risk based on the risk prediction model. The results show that the system is highly compatible with the skilled driver in terms of warning accuracy and timing. Specifically, the correct alarm rate (i.e., the driver brakes and the system’s alarm goes off) of the system is 83.57% and the error alarm rate (i.e., the driver does not brake but the system’s alarm goes off) is 9.79%. Moreover, more than 80% of the time the difference between the system warning time and the operating time of the skilled driver is less than 2 s.

In December of 2014, the United States Congress funded a fundamental shift in the recruiting policy of the US Navy Submarine Force to include the integration of women. As a result, design modifications became necessary, especially those that facilitate integration without inflating costs. Current cost levels associated with new submarine design(s) are maintained through the use of legacy components and systems. Additionally, many of the systems aboard are computer controlled, necessitating man-machine interfaces. As common practice, military activities that involve man-machine interfaces have always focused on the dexterity of the hands, often neglecting the role of movement in the task; therefore, there is a need to understand upper-extremity kinematics issues associated with man-machine interfaces. Joint kinematics of the right upper extremity of 10 subjects was measured using an optoelectronic motion capture system. Center of gravity displacements were measured using a force plate during touchscreen movement tasks paced by six different movement frequencies from a metronome (0, 1.0, 1.3, 1.7, 2.0, and 2.7 Hz). Results showed no significant difference in touch accuracy, task completion time, shoulder and elbow angular displacements, and shoulder and elbow flexion/extension velocity; however, a significant difference (0.002; p ≤ 0.05) in shoulder adduction/abduction velocity was observed. In arranging systems and components in submarine and surface vessel environments, consideration in not only providing a means of adjustability (e.g., height, proximity, and orientation) but in the dimensions of the systems and components themselves must also be considered based on the required operation.