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The safety performance of cooperative robots is particularly important. This paper aims to study collision detection and response of cooperative robots, which meet the lightweight requirements of cooperative robots and help to ensure the safety of humans and robots.

This paper proposes a collision detection, recognition and response method based on dynamic models. First, this paper identifies the dynamic model of the robot. Second, an external torque observer is established based on the model, and a dynamic threshold collision detection method is designed to reduce the interference of model uncertainty on collision detection. Finally, a collision position and direction estimation method is designed, and a robot collision response strategy is proposed to reduce the harm caused by collisions to humans.

Comparative experiments are conducted on static threshold and dynamic threshold collision detection, and the results showed that the static threshold only detected one collision while the dynamic threshold could detect all collisions. Conducting collision position and direction estimation and collision response experiments, and the results show that this method can determine the location and direction of collision occurrence, and enable the robot to achieve collision separation.

This paper designs a dynamic threshold collision detection method that does not require external sensors. Compared with static threshold collision detection methods, this method can significantly improve the sensitivity of collision detection. This paper also proposes a collision position direction estimation method and collision separation response strategy, which can enable robots to achieve post collision separation and improve the safety of cooperative robots.

The purpose of this paper is to perform the simulation to explore the gap flow field under a hypersonic air flow. Thermal protection systems of hypersonic vehicles generally consist of thermal insulation tiles, and gaps between these tiles probably cause a severe local aerodynamic thermal effect.

The discretizations of convection flux term and temporal term in the governing equation with chemical equilibrium, respectively, take AUSM+-up flux-vector splitting scheme and the implicit lower-upper symmetric Gauss–Seidel method. Based on these, the flow field in a deep gap is simulated by means of the computer codes that the authors have written.

The numerical results show that the heat flux distribution in a gap has a good agreement with experimental results. Importantly, the distribution of heat flux is “U” shaped and the maximum of the heat flux occurs at the windward corner of a gap.

To explore the gap flow field under a hypersonic air flow, which is a chemically reacting, all speed and viscous flow, a novel model with an equivalent ratio of specific heats is presented. The investigation in this paper has a guide for the design of the thermal protection system in hypersonic vehicles.

With the continuous increase of space activities and insight into space exploration, the velocity of near space hypersonic vehicles becomes higher and higher, which leads to the aerothermodynamic phenomenon getting worse around a vehicle; therefore, the exploration of numerical scheme applicability is essential for hypersonic flow simulations.

The implicit finite volume schemes are derived from axisymmetric Navier–Stokes equations for chemical equilibrium flow and programmed in Fortran. Taking the atmosphere at 30 km as an example, the performance of spatial discretization schemes such as AUSMPW and AUSMPW+ are analyzed in a range of Mach numbers from 17 to 32.

The AUSMPW scheme appears pressure jump near the stagnation if the Mach number is over 18, but AUSMPW+ scheme shows better performance in comparison.

This study will help the aerothermodynamic design in near space hypersonic vehicles.

The transpiration has been recognized as one of the most effective thermal protection methods for future hypersonic vehicles. To improve efficiency and safety, it is urgent to optimize the design of the transpiration system for heat and drag reduction. The purpose of this paper is to investigate the effects of transpiration on heat and drag reduction.

A chemical nonequilibrium flow model with the transpiration is established by using Navier–Stokes equations, the shear-stress transport turbulence model, thermodynamic properties and the Gupta chemical kinetics model. The solver programmed for this model is verified by comparing with experimental results in the literature. Effects of air injection on the flow field, the aerodynamic resistance and the surface heat flux are calculated with the hypersonic flow past a blunt body. Furthermore, a modified blocking coefficient formula is proposed.

Numerical results show that the transpiration can reduce the aerodynamic resistance and the surface heat flux observably and increase the shock wave standoff distance slightly. It is also manifested that the modified formula is in better agreement with the wind tunnel test results than the original formula.

The modified formula can expand the application range of the engineering method for the blocking coefficient. This study will be beneficial to carry out the optimal design of the transpiration system.

The purpose of this paper is to explore the characteristics of hypersonic flow past a blunt body.

The implicit finite volume schemes are derived from axisymmetric Navier–Stokes equations by means of AUSM+ and LU-SGS methods, and programmed in FORTRAN. Based on the verified result that a 2D axisymmetric chemical equilibrium flow has a good agreement with the literature, the characteristics of hypersonic flow past a sphere are simulated by using four different models which involve four factors, namely, viscous, inviscid, equilibrium and calorically perfect gas.

Compared with the calorically perfect gas under hypervelocity condition, the shock wave of the equilibrium gas is more close to the blunt body, gas density and pressure become bigger, but gas temperature is lower due to the effect of real gas. Viscous effects are not obvious in the calculations of the equilibrium gas or the calorically perfect gas. In a word, the model of equilibrium gas is more suitable for hypersonic flow and the calculation of viscous flow has a smaller error.

The computer codes are developed to simulate the characteristics of hypersonic flows, and this study will be helpful for the design of the thermal protection system in hypersonic vehicles.

Relevant analyses are presented on the base of the compressible vortex method for simulating the development of two or three co-rotating vortices with different characteristic Mach numbers. The paper aims to discuss this issue.

In addition to having vorticity and dilatation properties, the vortex particles also carry density, enthalpy, and entropy. Taking co-rotating vortices in two-dimensional unsteady compressible flow for an example, truncation of unbounded domains via a nonreflecting boundary condition was considered in order to make the method computationally efficient.

For two identical vortices, the effect of the vortex Mach number on merging process is not evident; if two vortices have the same circulation rather than different radiuses, the vorticity and dilatation fields of the vortex under a vortex Mach number will be absorbed by the vortex under a higher vortex Mach number. For three vortices, if the original arrangement of the vortices is changed, the evolvement of the vorticity and dilatation fields is different.

The paper reveals new mechanism of the three co-rotating vortices by a feasible compressible vortex method.

The purpose of this paper is to perform the stimulation in order to examine the effects on the heat transfer coefficient and the flowfield properties at the vicinity of the gap due to variations in the width-to-depth ratio.

The governing equations were discreted by using the finite volume method, and based on pressure-velocity coupled algorithm, the heat transfer coefficients outside and inside the gaps, defined by the width-to-depth ratio of 1, 2/3, 1/2, 1/3 and 1/4, were obtained by the Fluent software.

The number of vortex inside the gap depends on the width-to-depth ratio, and the maximum value of the heat transfer coefficient emerges on the downstream surface.

The study gives a feasible method to simulate the flowfield and the heat transfer inside the gap, which will help the design of the thermal protection system for reentry vehicles.

The effective heat capacity is a key index to estimate the thermal protection performance of charring ablative materials in reentry vehicles subjected to aerodynamic heat loads. The purpose of this paper is to investigate the effects of gradient density on the effective heat capacity.

Based on the Fourier law and the pyrolysis interface model, the authors establish the governing equations for the transient heat conduction with variable density, and then simulate one-dimensional transient thermal behavior of a homogeneous and three types of non-homogeneous charring ablative material in reentry capsules by using the implicit numerical method.

The moving rate of pyrolysis interface and the surface temperature of charring ablative material depend on not only the surface heating history, but also the gradient density. And the gradient density can improve the insulation performance of charring materials, e.g. the effective heat capacity in the bilinear design is larger than that in the homogeneous design under a given heat flux condition.

This study will help the design of the thermal protection system in reentry vehicles.

This paper aims to propose a soft actuator that combines a sponge-based actuating structure and a layer-jamming-based stiffness-improving structure in a cavity.

The proposed soft actuator consists of film-constrained sponge units (FCSUs) and jamming layers. The FCSUs in the proposed soft actuator bend under vacuum pressure, causing bending deformation of the entire actuator. The jamming layers are strongly coupled through friction under vacuum pressure, increasing the stiffness of the entire actuator. The performance of the proposed soft actuator was examined by measuring its stiffness, bending deformation and response performance. A four-finger soft robotic gripper was proposed based on the proposed soft actuator.

Through experiments, it was shown that the proposed soft actuator exhibited acceptable bending deformation, stiffness and response. Moreover, the proposed four-finger soft gripper could effectively grasp objects in daily life.

In this study, the authors proposed a novel bending actuator (with a volume of approximately 43.2 cm³) based on FCSUs and jamming layers. To the best of the authors’ knowledge, this is the first study to combine a sponge-based actuating structure and a layer-jamming structure in a cavity to achieve simultaneous change in actuation and stiffness. The soft actuator exhibited good bending deformation and high stiffness simultaneously under vacuum pressure. Consequently, it could be used effectively to fabricate soft grippers.

The study aims to explore the diverse meanings and sources of frustration among Israeli principals working in special education settings. The study poses two questions: 1. What are the perceived expressions of frustration among principals working in the context of special education? 2. What are the perceived sources of frustration among principals working in special education settings?

A total of 17 semi-structured interviews were conducted with principals working in special education schools for complex disabilities to investigate perceived expressions and sources of frustration.

The study identified four themes through data analysis: helplessness regarding the children, helplessness regarding bureaucratic aspects, frustration from conflicts and disappointment and frustration from feeling alone.

Despite the extensive acknowledgment of emotions and feelings in the context of educational leadership, the experience of work frustration among special education school principals has not been explicitly investigated. This research provides empirical insights into the nuanced experiences of frustration among special education principals, offering both empirical and practical implications for understanding and addressing this critical aspect of their work.