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Overhead high-voltage transmission line (HVTL) inspection robots are used to inspect the transmission lines and/or maintain the infrastructures of a power transmission grid. One of the most serious problems is that the load on the front wheel is much larger than that on the back one when the robot travels along a sloping earth wire. Thus, ongoing operation of the inspection robot mainly depends on the front wheel motor’s ability. This paper aims to extend continuous operation time of the HVTL inspection robots.

By introducing a traction force model, the authors have established a dynamic model of the robot with slip. The total load is evenly distributed to both wheels. According to the traction force model, the desired wheel slip is calculated to achieve the goal of load balance. A wheel slip controller was designed based on second-order sliding-mode control methodology.

This controller accomplishes the control objective, such that the actual wheel slip tracks the desired wheel slip. A simulation and experiment verify the feasibility of the load balance control system. These results indicate that the loads on both wheels are generally equal.

By balancing the loads on both wheels, the inspection robot can travel along the earth wire longer, improving its efficiency.

A mathematical model is developed for the description of the thermohydraulics of the two‐phase flow phenomenon in a vertical pipe. Using an additional momentum equation for the slip velocity, it is shown that the computation of slip and pressure drop from the model equations is possible without the use of any external correlations. The finite element method is used to solve the governing equations. The predictions for a steam‐water two‐phase flow in vertical upflow with constant wall heat flux agree well with experimental results and with widely used correlations.

Driving safety on a wet road is closely related to the wet skid resistance of tires. The purpose of this paper is to reveal the evolution of wet skid resistance at different water film thicknesses and provide some guidance on the design of a tread pattern with improved traction on rainy roads.

Brake tests are performed in a laboratory with a viscoelastic tribotester at various water film thicknesses. The initial water film thickness is 3 mm, which decreases with an increase in the test number. Brake friction force is dynamically measured at water film thicknesses ranging from 0 mm to 3 mm.

The results show that water film thickness exerts a great influence on the forms of tire motion and slip ratio. The tire is much easier to slide on the road with thick water film and also with a considerably thin water film (about 0-1 mm) during a sharp braking process. The brake traction can be very low under this road condition despite the apparently safe quality of the road.

The authors design and establish a new viscoelastic tribotester which is used to simulate the real braking sliding process and study the tribological properties between tire rubber and road surface. The variation in the wet friction coefficient and slip ratio at different water film thicknesses have a great influence on the design of a tread pattern with improved traction on rainy roads.

This paper aims to examine how using lattice Boltzmann method (LBM) aids the study of the isothermal‐gas flow with slight rarefaction in long microtubes.

A revised axisymmetric lattice Boltzmann model is proposed to simulate the flow in microtubes. The wall boundary condition combining the bounce‐back and specular‐reflection schemes is used to capture the slip velocity on the wall. Appropriate relation between the Knudsen number and relax‐time constant is defined.

The computed‐slip velocity, average velocity and non‐linear pressure distribution along the microtube are in excellent agreement with analytical solution of the weakly compressible Navier‐Stokes equations. The calculated‐friction factors are also consistent with available experimental data. For simulations of slip flow in microtube, LBM is more accurate and efficient than DSMC method.

The laminar flow in circular microtube is assumed to be axisymmetric. The present LBM is only applied to the simulation of slip flows (0.01 < Kn₀<0.1) in microtube.

Lattice‐BGK method is a very useful tool to investigate the micro slip flows.

A revised axisymmetric D2Q9 lattice Boltzmann model is proposed to simulate the slip flow in axisymmetric microtubes.

This study aims to uncover the influencing mechanism of the tilt angles of the cage pocket walls of the high-speed cylindrical roller bearing on the bearing skidding.

A novel cylindrical roller bearing with the beveled cage pockets was proposed. Using the Hertz contact theory and the elastohydrodynamic and hydrodynamic lubrication formulas, the contact models of the bearing were built. Using the multibody kinematics and the Newton–Euler dynamics theory, a dynamics model of the bearing was established. Using the Runge–Kutta integration method, the dynamics simulations and analysis of the bearing were performed.

The simulation results show that the effects of the tilt angles of the front and rear walls of the pocket on the bearing skidding are remarkable. Under a 5° tilt angle of the front wall of the pocket and a 10° tilt angle of the rear wall, the bearing skidding can be effectively decreased in the rotational speed range of 10,000-70,000 r/min.

In this paper, a novel cylindrical roller bearing with the beveled cage pockets was proposed; a dynamics model of the bearing was established; the influence mechanism of the tilt angles of the front and rear walls of the pocket on the bearing skidding was investigated, which can provide fundamental theory basis for optimizing the pocket.

The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-01-2020-0035/

This paper is concerned with the peristaltic transport of an incompressible non-Newtonian fluid in a porous elastic tube. The impacts of slip and heat transfer on the Herschel-Bulkley fluid are considered. The impacts of relevant parameters on flow rate and temperature are examined graphically. The examination incorporates Newtonian, Power-law and Bingham plastic fluids. The paper aims to discuss these issues.

The administering equations are solved utilizing long wavelength and low Reynolds number approximations, and exact solutions are acquired for velocity, temperature, flux and stream functions.

It is seen that the flow rate in a Newtonian fluid is high when contrasted with the Herschel-Bulkley model, and the inlet elastic radius and outlet elastic radius have opposite effects on the flow rate.

The analysis carried out in this paper is about the peristaltic transport of an incompressible non-Newtonian fluid in a porous elastic tube. The impact of slip and heat transfer on a Herschel-Bulkley fluid is taken into account. The impacts of relevant parameters on the flow rate and temperature are examined graphically. The examination incorporates Newtonian, Power-law and Bingham plastic fluids.

In Fig. 29 are plotted the data obtained during a dynamometer calibration of the DB‐601A engine. The family of curves on the left hand side of the figure gives the sea level power characteristics for various r.p.m. in the operating range, plotted against absolute manifold pressure in inches of mercury. From these curves it will be noted that the automatic boost control takes charge to restrict the manifold pressure to a limiting value of 39 in. of mercury absolute at engine speeds above 1,900 r.p.m. Below 1,900 r.p.m. the full throttle manifold pressure is less than the boost limit established by the automatic regulator. The normal rating of the engine at 2,400 r.p.m. is thus established at 995 horsepower. For take‐off the automatic regulator is overruled by the pilot's throttle for a time interval of one minute established by an automatic clock mechanism, to produce an excess boost in the manifold which, at an engine speed of 2,500 r.p.m., gives the take‐off rating of 1,150 horse‐power at 43·2 in. of mercury absolute manifold pressure. The take‐off power at 2,500 r.p.m. versus absolute manifold pressure characteristics are shown at the upper left hand portion of Fig. 29. The sea level power ratings are somewhat flexible since it is possible to adjust the oil How into the fluid coupling of the supercharger and, by changing the slip, vary the effective impeller ratio. Thus it may be desirable for bomber installations involving take‐off with heavy loads to increase the effective impeller ratio for the maximum boost possible with the quality of fuel available.

The purpose of this paper is to design a multi-sensory anthropomorphic prosthetic hand and a grasping controller that can detect the slip and automatically adjust the grasping force to prevent the slip.

To improve the dexterity, sensing, controllability and practicability of a prosthetic hand, a modular and multi-sensory prosthetic hand was presented. In addition, a slip prevention control based on the tactile feedback was proposed to improve the grasp stability. The proposed controller identifies slippages through detecting the high-frequency vibration signal at the sliding surface in real time and the discrete wavelet transform (DWT) was used to extract the eigenvalues to identify slippages. Once the slip is detected, a direct-feedback method of adjusting the grasp force related with the sliding times was used to prevent it. Furthermore, the stiffness of different objects was estimated and used to improve the grasp force control. The performances of the stiffness estimation, slip detection and slip control are experimentally evaluated.

It was found from the experiment of stiffness estimation that the accuracy rate of identification of the hard metal bottle could reach to 90%, while the accuracy rate of identification of the plastic bottles could reach to 80%. There was a small misjudgment rate in the identification of hard and soft plastic bottles. The stiffness of soft plastic bottles, hard plastic bottles and metal bottles were 0.64 N/mm, 1.36 N/mm and 32.55 N/mm, respectively. The results of slip detection and control show that the proposed prosthetic hand with a slip prevention controller can fast and effectively detect and prevent the slip for different disturbances, which has a certain application prospect.

Due to the small size, low weight, high integration and modularity, the prosthetic hand is easily applied to upper-limb amputees. Meanwhile, the method of the slip prevention control can be used for upper-limb amputees to complete more tasks stably in daily lives.

A multi-sensory anthropomorphic prosthetic hand is designed, and a method of stable grasps control based on slip detection by a tactile sensor on the fingertip is proposed. The method combines the stiffness estimation of the object and the real-time slip detection based on DWT with the design of the proportion differentiation robust controller based on a disturbance observer and the force controller to achieve slip prevention and stable grasps. It is verified effectively by the experiments and is easy to be applied to commercial prostheses.

Internal gearings are commonly used in transmissions due to their advantages like high-power density. To ensure high efficiency, load-carrying capacity and good noise behavior, a profound knowledge of the local gear mesh is essential. The tooth contact of internal gears relates to a convex and concave surface that form a conformal contact. This is in contrast to external gears, where two convex surfaces form a contraformal contact. This paper aims at a better understanding of conformal contacts under elastohydrodynamic lubrication (EHL) to improve the design of internal gearings.

An existing numerical EHL model is used for studying the characteristic properties of a hard conformal EHL line contact. A hard contraformal EHL line contact is studied as reference. Non-Newtonian fluid behavior and thermal effects are considered. By taking into account the local contact conformity and kinematics, the effects and relevance of the curvature of the lubricant gap and micro-slip are analyzed. In a parameter study, scale effects of the contact radii on film thickness, temperature rise and friction are examined.

The curvature of the lubricant gap and effects of micro-slip are small in hard conformal EHL line contacts. For high micro-slip, it can be neglected. Hence, the modeling of conformal contacts using an equivalent geometry of the contact problem is reasonable. The parameter study shows beneficial tribological aspects of the conformal contact compared to the contraformal contact. Higher film thickness and lower fluid coefficient of friction are observed for conformal contacts, which can be attributed to lower pressures for the case of the same external normal force, or to a higher contact temperature rise for the case of equivalent contact pressure.

Despite its widespread existence, the local geometry and kinematics in hard conformal EHL line contacts like in internal gearings have been rarely studied. The findings help for a better understanding of local contact characteristics and its relevance. The quantified scale effects help to improve the efficiency and load-carrying capacity of machine elements with hard conformal EHL contacts, like internal gearings.

The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-12-2022-0366/

The purpose of this paper is to investigate the distribution and surface characteristic of transfer film of polyamide composites filled with ZnOw during traction rolling.

In this paper, the traction rolling tribological behavior of polyamide composites filled with ZnOw was studied with a twin-disc traction rolling tester. The topography of transfer film was observed with a three dimensional profiler. Meantime the thickness of transfer film was measured. The chemistry elements of transfer film were analyzed with EDS and XRD.

The results indicated that transfer film of composites patchily covered on the surface of counter disc, the amount of which increased with increasing cycles. The coverage and thickness of pure PA film increased against rolling cycles. However, the thickness of 15 wt.% ZnOw/PA film remained at 6 μm as the coverage rose against rolling cycles. Fe element was found in pure PA transfer film, which existed in Fe0 and FeO for chemical reaction between Fe and atmospheric oxygen. Transfer film of 15 wt.% ZnOw/PA composites included a little Zn and Fe element. Fe element existed as Fe0. Zn element existed as ZnO.

This paper presented the distribution and surface characteristic of transfer film during traction rolling.