Mechanical Structure Design Research Articles

Design and Control of a Nonlinear Series Elastic Cable Actuator Based on the Hill Muscle Model

The bionic design of muscles is a research hotspot at present. Many researchers have designed bionic elastic actuators based on the Hill muscle model, and most of them include an active contraction element, passive contraction element and series elastic element, but they need more parametric design of mechanical structure and control under the guidance of Hill muscle model. In this research, a nonlinear series elastic cable actuating mechanism is designed in which the parameters of the elastic mechanism are optimized based on the Hill muscle model to fit the nonlinear passive elasticity of a muscle. Through the force–position relationship determined by the Hill muscle model, the output force and position of a nonlinear series elastic cable actuator are controlled to simulate the active contraction performance of a muscle. The experiments show that the proposed design and control method can make the nonlinear cable actuator have good muscle-like output force–displacement characteristics.

Application of the quality function deployment method in the mechanical structure design of subsea power devices

Mechanical structure design is the most important process in the research and development of undersea equipment. Traditional design methods have limitations in obtaining functional demand information, determining the design direction, focusing on technical resources, guaranteeing systematic quality, etc. These limitations often reflect many problems, such as low design efficiency, waste of resources, and weak reliability of the finished products. By integrating the idea of grasping “the beginning” and “the end” into the process of mechanical design, this paper introduced a method called quality function deployment (QFD) and applied it to the mechanical design of subsea power devices to demonstrate and verify a robust design process with a clear direction and focused application of resources. Combined with the example of the mechanical design for the subsea power device, QFD was applied to analyse functional technical elements by establishing the house of quality (HoQ) models. And then, it was achieved a stable deployment and realization of the structural function for the subsea power device. Furthermore, for the key purpose of ensuring adequate structural strength and watertight reliability, this study selected suitable material, designed reasonable structures, and integrated finite element analysis technology to carry out mechanical simulations. Finally, the design of the mechanical structure for the subsea power device was robustly implemented.

Mechanical Design and Research of Wearable Exoskeleton Assisted Robot for Upper Limb Rehabilitation

Based on the biomechanical mechanism of human upper limb, the disadvantages of traditional rehabilitation training and the current status of upper limb rehabilitation robot, a six degree of freedom, flexible adjustment, wearable upper limb rehabilitation exoskeleton design scheme is proposed. Firstly, the mechanics of each joint of the upper limb is analyzed, and the virtual prototype design of the whole mechanical structure of the upper limb rehabilitation wearable exoskeleton is carried out by using CATIA three-dimensional software. The tooth transmission of the forearm and the upper arm single row four point contact ball bearing with internal/external rotation and the shoulder flexible passive adjustment mechanism (viscoelastic damper) are innovatively designed. Then, the joints of the upper limb rehabilitation exoskeleton are analyzed, theoretical analysis and calculation of the driving torque, the selection of the motor and gearbox of each driving joint are carried out. Finally, the whole finite element analysis of the upper limb exoskeleton is carried out. The research and experimental results showed that the design scheme of the upper limb exoskeleton assist structure is highly feasible, which can help the patients with upper limb paralysis and motor dysfunction self-rehabilitation.

Design and synthesis of magnetic porous carbon nanofibers with excellent microwave absorption

The magnetic porous carbon nanofibers (CNFs) are highly desirable due to the excellent reflection loss (RL) and impedance matching in microwave absorption applications. Herein, the porous Ni/NiO/CNFs were fabricated by electrospinning combined with vacuum calcination and etching technology. Porous Ni/NiO/CNFs with different electromagnetic (EM) parameters and impedance matching could be easily obtained by adjusting the calcination temperature. On account of the synergistic loss mechanism composed of magnetic loss and dielectric loss leads to excellent impedance matching, the porous structure caused multiple reflection and scattering of incident electromagnetic waves (EMW), combined with the polarization loss between different components, the as-prepared materials exhibited enhanced EMW absorbing property compared with traditional microwave absorbers (MAs). The resulting porous Ni/NiO/CNFs obtained at 650 °C exhibited the optimal EMW absorption performance with an RL of −47.9 dB at 9.5 GHz and broad effective absorption bandwidth (EAB) of 3.5 GHz with a thickness of 3.0 mm. This work provides a mentality for multi-component loss mechanism and rational structure design of CNFs-based absorbing materials.

Friction model of elastic-plastic line contact in mixed lubrication regime with non-Newtonian lubricant

The friction characteristics of the lubricated rough surfaces are of great significance for the lubrication design of mechanical structures. To study the behaviour of friction coefficient in the rolling-sliding coexisting line contact rough surfaces under mixed lubrication regime, the Kogut-Etsion elastic-plastic model and the Carreau rheological model are utilized to describe the dry rough contact and the non-Newtonian characteristics of the lubricant film, respectively. A mixed lubrication model for predicting friction coefficient is proposed based on the load-sharing concept at which the normal load is shared by the lubricant film and the asperity component. The effects of normal load, surface roughness and lubricant inlet viscosity on hydrodynamic scaling factor, film thickness parameter and the coefficient of friction were analyzed. The dimensionless predictive expression for the critical sliding velocity is derived by nonlinear regression. The research results provide theoretical guidance for the lubrication design and optimization of mechanical structures.

Mechanical Structure Design and Actuation Characteristics Analysis of the Parallel Driven Variable Stiffness Actuator With Unrestricted Rotation Range of the Output Shaft

Among many types of flexible robot actuators, the variable stiffness actuator (VSA) is an actuator that can adjust the compliance of the actuator output shaft by adjusting the equivalent stiffness of its internal elastic element. Compared with the traditional rigid actuators, the VSAs have inherent flexibility and adjustable stiffness because they contain elastic elements and stiffness adjusting mechanisms. They have advantages in human-robot physical interaction security and task adaptability. The independent controllability of position and stiffness and the ability of stiffness adjustment make the VSAs have research value and application prospects in the fields of rehabilitation training equipment, prosthetics, wearable devices and so on. The mechanical scheme design of the VSA is an open research field. At present, there is no perfect mechanical structure design of any type of VSA. Optimizing and improving the mechanical structure design of the VSA is helpful to improve its actuation characteristics and application value. Due to the limitation of the mechanical structure design, most of the existing VSAs have limited rotation angle range of the output shaft, which limits their application. The purpose of this paper is to design the parallel driven VSA whose rotation angle range of output shaft is not limited. Moreover, inspired by the mechanical structure design ideas of some stiffness adjustment mechanisms with good implementation schemes and elastic elements with good force transmission characteristics, this paper makes some improvement, synthesis and innovation in the mechanical structure design of the VSA, so as to improve the structural compactness design, assembly modular design, mechanical transmission reliability design and actuation characteristics. In this paper, six types of parallel driven VSAs with different mechanical structure design schemes are proposed. Their common point is that the rotation angle range of the output shaft is not limited, and the differences are that they have different implementation schemes of variable stiffness mechanisms and elastic elements. The transmission structure diagrams of the designed VSAs show the working principle and stiffness adjustment principle. The actuation characteristics of the designed VSAs are analyzed and their differences are compared. The detailed mechanical structure design of the VSA is shown. In the designed VSAs, the model of the VSA based on the symmetrical Archimedes spiral cam groove mechanism is printed and assembled to show the feasibility of the implementation of the designed mechanical structure scheme. Finally, a manual adjustment experiment verifies the stiffness adjustment ability of the assembled VSA model, and shows that the rotation angle range of the output shaft of the assembled VSA model is unlimited.

Cohesive zone analysis of torsional tubular joints with an epoxy adhesive

Nowadays, adhesive bonding gained a lot of presence in the design of mechanical structures in the most varied industries, especially aeronautics and automotive. Such a method of joining has several advantages over more traditional methods such as welding or mechanical joining. These advantages include the weight reduction of the structure and the easiest application of the adhesive. In terms of manufacturing time and cost, this is a versatile method that enables the bonding of different materials, including composites, without damaging the structures to be bonded. Tubular adhesive joints have varying applications, such as in trusses, machine axles, and piping. This work evaluated the torsional performance of a structural adhesive in aluminum tubular joints (AW6082-T651), considering the variation of the main geometric parameters: overlap length (LO), and tube thickness. In order to predict the strength, the Finite Element Method (FEM) was used with the Cohesive Zone Model (CZM), whose analysis was based on the analysis of shear stresses (τxy) and joint strength, measured by the maximum torsional moment (Mm). Previously, validation with experimental data was carried out. The technique was positively validated, and a significant geometry effect on Mm was found.

Mechanical structure design and analysis of the outside needle pipe climbing robot

This study designed a crawling mechanism that can solve the measurement problems of slender and needle pipes by detecting the heating vertical needle pipe, which is greatly applied in the petrochemical and refinery industry. The robot’s walking system uses a single driven wheel to stick on the way, with a scissor-hand structure to adapt to changes in diameter between 50 and 90 mm. This study lists the dynamic analysis equation of the robot, thereby obtaining the optimum range of Angle α between the horizontal line and the center line of the main driving wheel and the main clamping wheel. Moreover, the study uses multi-body dynamics simulation software for dynamics simulation analysis. Results indicate that the crawling system has the advantages of anti-deviation, can adapt to different pipe diameters and has a simple structure.

Numerical Analysis of the Mechanical Responses and Transition Section Design of Pavement Structures in the Entrance and Exit Sections of Highway Tunnel

The entrance and exit sections of a tunnel are subject to different environments, pavements, and traffic conditions, which is quite different from the average highway, and it should be considered differentially, when designing pavement structures. However, there are no clear regulations on it in Chinese specifications. Over the years, a lot of studies were carried on the entrance and exit sections of a tunnel, but there are few ones on the pavement design and its mechanical response characteristics. In this paper, the Huangjiayu tunnel and the Yangkou tunnel in Shandong province were taken as case study engineerings and their pavement structures in the entrance and exit sections are referred to as Str‐1 and Str‐2, respectively. In Str‐1, asphalt pavement was applied inside and outside the tunnel and a transition section was applied. In Str‐2, asphalt pavement was applied outside the tunnel and concrete pavement was applied inside the tunnel when it was built in 2004 and a transition section was not applied. Meanwhile, 7 alternative pavement structures (referred to as Str‐1a∼Str‐1g), in which the lengths of transition sections were different, were proposed, simulated, and analyzed through FE program ANSYS. Through the analysis of maximum shear stresses in asphalt courses and tensile stresses at the bottom of base courses, it was found that setting a transition structure is essential, and it can ensure the continuity of pavements and significantly reduce the sudden change of shear stress of asphalt layer and thus prevent premature pavement distresses. Hence, Str‐1 is more reasonable compared with Str‐2. Besides, it was also found that when the asphalt surface outside the tunnel is designed to be three layers, it is more appropriate to use Str‐1, in which the concrete slab in the transition structure has variable cross section, and the length of the concrete slab is 4.5 m. When the asphalt surface outside the tunnel is designed to be two layers, Str‐1b is more reasonable and the length of the concrete slab is also 4.5 m.

Development, construction and tests of the Mu2e electromagnetic calorimeter mechanical structures

The “muon-to-electron conversion” (Mu2e) experiment at Fermilab will search for the charged lepton flavour violating neutrino-less coherent conversion of a muon into an electron in the field of an aluminum nucleus. The observation of this process would be the unambiguous evidence of the existence of physics beyond the standard model. Mu2e detectors comprise a straw-tracker, an electromagnetic calorimeter and an external veto for cosmic rays. In particular, the calorimeter provides excellent electron identification, a fast calorimetric online trigger, and complementary information to aid pattern recognition and track reconstruction. The detector has been designed as a state-of-the-art crystal calorimeter and employs 1348 pure Cesium Iodide (CsI) crystals readout by UV-extended silicon photosensors and fast front-end and digitization electronics. A design consisting of two identical annular matrices (named “disks”) positioned at the relative distance of 70 cm downstream the aluminum target along the muon beamline satisfies the Mu2e physics requirements. The hostile Mu2e operational conditions, in terms of radiation levels (total expected ionizing dose of 12 krad and a neutron fluence of 5 × 1010 n/cm2 @ 1 MeVeq (Si)/y), magnetic field intensity (1 T) and vacuum level (10−4 Torr) have posed tight constraints on scintillating materials, sensors, electronics and on the design of the detector mechanical structures and material choice. The support structure of each 674 crystal matrix is composed of an aluminum hollow ring and parts made of open-cell vacuum-compatible carbon fiber. The photosensors and front-end electronics for the readout of each crystal are inserted in a machined copper holder and make a unique mechanical unit. The resulting 674 mechanical units are supported by a machined plate of vacuum-compatible plastic material. The plate also integrates the cooling system made of a network of copper lines flowing a low temperature radiation-hard fluid and placed in thermal contact with the copper holders to constitute a low resistance thermal bridge. The data acquisition electronics are hosted in aluminum custom crates positioned on the external lateral surface of the disks. The crates also integrate the electronics cooling system as lines running in parallel to the front-end system. In this paper we report on the calorimeter mechanical structure design, the mechanical and thermal simulations that have determined the design technological choices, and the status of component production, quality assurance tests and plans for assembly at Fermilab.

Design and Characterization of a Flexible Self-Inflating Mechanical Structure

Abstract Inflatable structures are commonly used in a variety of engineering applications such as robotics, space structures, medical devices, and automotive safety devices. However, inflation in these systems often requires a non-flexible external pressurized fluid source. Integration of the pressurized fluid source and the flexible construct sacrifices some of the main advantages of the soft structures such as overall flexibility of the system, weight, and cost of fabrication. In this paper, we introduce a novel design for self-inflating structure with embedded pressurizing module. The design is based on integrating a flexible dome with a cylinder. The pressure inside the cylinder is controlled by subjecting dome to a cyclic compression, causing air exchange between the dome and the cylinder. The performance of this design is fully validated through finite element simulations using fluid structure interactions as well as experimental investigations. The results show that a higher pressure is achieved by having smaller dome height. In addition to controlling internal pressure of the cylinder, the design can be used to control the stiffness of the flexible structure such as soft robotics through pressurization. An application of this conceptual device such as pressurizing a tire is presented. This device is integrated within a tire and tire rotation as well as load on the tire have been shown to pressurize the tire. The final pressure and time to achieve maximum pressure depend on the load to the axel of the tire and tire rotational speed, respectively.

Determination of Physical and Mechanical Properties of Sugarcane Single-Bud Billets

HighlightsCoefficients of restitution between billet and steel decreased with an increase in drop height and moisture content.Coefficients of restitution between billets increased with an increase in moisture content.Static friction coefficient between billet and steel, and between billets decreased with an increase in contact area.Rolling friction coefficient between billet and steel increased with an increase in angle and interval.Rolling fiction coefficient among billets first increased and then decreased with an increase in angle.Abstract. Determining the physical and mechanical properties of sugarcane single-bud billets is a critical step in the mechanical structure design of a sugarcane planter. In this study, samples of the Tai Tang F66 cultivar sugarcane billets were analyzed. The moisture content of the samples of billets ranged from 63.78% to 77.72%, and their average density was 244.67 kg/m3. The coefficient of restitution (CoR) of the samples was determined by a drop test wherein samples were dropped onto a steel plate from different heights. The static friction coefficient (SFC) of four types of samples was determined by the inclined plate method at two orientations. In addition, the rolling friction coefficient (RFC) was determined at three plate inclination angles and sample displacement. The experiment results showed that with increasing drop height and moisture content, the billet-steel CoR decreased from 0.625 to 0.458, while the billet-billet CoR increased from 0.603 to 0.698. With an increase in contact area, the billet-steel SFC decreased from 0.515 to 0.377 and the billet-billet SFC decreased from 0.498 to 0.323. With increasing angle and sample displacement, the billet-steel RFC increased from 0.0315 to 0.2175 and the billet-billet RFC increased from 0.0203 to 0.1007. These parameters can help to build a more accurate simulation model of a single-bud billet particle for the discrete element analysis of a sugarcane single-bud billet planter mechanical structure. Keywords: Coefficient of restitution, Rolling friction coefficient, Single-bud billet, Static friction coefficient.

Design and Experiment on Rotary Cutting Test Bench for Sweet Potato Vine

In order to study the cutting mechanism of sweet potato vine, provide technical support and theoretical basis for the development of sweet potato vine harvesting machinery and improve the resource utilization rate of sweet potato vine, a cutting test bench for sweet potato vine was designed. The test bench consists of two parts: Mechanical part and measurement-control part. In this study, the requirements for the mechanical structure design of the test bench are first put forward and then the structure and hardware of the measurement control system are described. Using this platform, the cutting experiment of sweet potato vine was carried out and the effects of cutter roller speed, conveying speed and feeding amount on cutting torque, cutting power and cutting force were deeply discussed. The test shows that the sweet potato cutting test bench not only realizes the visualization of the test process, but also has the characteristics of small measurement error, stable operation and simple operation. Through experiments, when the cutter roller speed is 1266 r·min-1, the conveying speed is 0.54 m·s-1 and the feeding amount is 1.0 kg, the sweet potato vine cutter has excellent working performance such as high processing efficiency and low energy consumption. The platform can provide reliable scientific basis for cutter design and power selection of sweet potato vine harvesting machinery.

Semisolid-lubricant-based ball-bearing triboelectric nanogenerator for current amplification, enhanced mechanical lifespan, and thermal stabilization

Triboelectric nanogenerators (TENGs) represent a promising tool for harvesting mechanical energy and can generate electrical output through the surface charge of materials. However, because this conversion is based on contact electrification, frictional contact inevitably occurs between materials, and the high surface charge considerably limits the electrical output of TENGs. To effectively decrease the frictional wear of triboelectric materials, commercial lubricants can be applied while ensuring a suitable mechanical structure design. In this study, we demonstrated a ball-bearing-type TENG with a commercial semisolid lubricant, which could overcome the mechanical and electrical limitations of conventional TENGs. The application of a nonpolar semisolid lubricant on the surface of triboelectric materials could effectively suppress air breakdown and enhance the mechanical lifespan of the device by reducing friction. Owing to the reduced wear and enhanced thermal stability, the ball-bearing-type TENG could generate a consistent electrical output for over 55 h of continuous operation.

Reducing Anthropomorphic Hand Degrees of Actuation with Grasp-Function-Dependent and Joint-Element-Sparse Hand Synergies

In this paper, a set of grasp-function-dependent and joint-element-sparse hand synergies was proposed. First, hand synergies were extracted from five basic categories of movements by principal component analysis (PCA). Then, varimax rotation was applied on these synergies, so each sparse synergy only represented a limited number of joints. Next, according to the contribution to these sparse synergies, finger joints were clustered into different joint modules. Finally, integrating the joint modules in different categories of hand movements, the minimum number of actuators and joint synergic modules for anthropomorphic hands were determined. The results showed that using 5 groups of joint modules and 7–9 actuators we can achieve the best performance of grasp function and motion flexibility. Furthermore, through the reasonable design of adaptive and hyperextension functional joint modules, anthropomorphic hands can better meet the requirements of different tasks like power grasping and precision pinching. Comparing with traditional finger-based actuation strategy, the joint coupling scheme achieved better anthropomorphic performance and larger workspace. These above findings will benefit the development of mechanical structure design and control method of anthropomorphic hands.

Home Robot Control System Based on Internet of Things and Fuzzy Control

The rapid development of intelligent control technology has improved the functions of service robots oriented to the home environment, and the functional requirements of family members for service robots have also been upgraded from simply liberating hands and reducing housework to emotional communication and intelligent escort. Based on the Internet of Things and fuzzy control technology, this paper builds a home robot control system and gives a brief overview around the mechanical structure design of the home service robot, mainly focusing on the core control system and global path planning methods. Moreover, this paper adopts the control system structure that combines the upper computer and the bottom motion controller and combines it with simple and practical system software, so the system stability is high. Finally, this paper verifies the performance of the system constructed in this paper through experimental research. The research results show that the system constructed in this paper has certain practical effects.

Hopping Robot: Current Status and Future Perspectives

Background: Search and rescue in high-risk situations and searches in unknown environments pose certain threats to human physical life. The development of mobile robots with exploratory capabilities that can be adapted to complex sites, with high mobility and high obstacle-crossing capabilities, is therefore a research trend. Existing wheeled and tracked mobile robots have excellent locomotion, but they are less adaptable and less efficient when faced with complex terrain or outer space environments. Therefore, how to increase the obstacle-crossing ability and improve the movement efficiency of mobile robots has become a research hotspot in the field of mobile robotics. Objective: To introduce the classification, characteristics and development of existing hopping robots. Methods: The various products and patents of hopping robots are summarized, and the structural features, differences and applications of typical hopping robots are introduced. Results: By analyzing a variety of hopping robots, the typical characteristics and the current problems of hopping robots are analyzed, the development trend of hopping robots is prospected, the current research status of hopping robots are discussed and the future prospects are carried out. Conclusion: Hopping robots can be divided into mechanical energy drive, combustion energy drive and new energy drive according to the driving method. Depending on the drive energy used, jumping robots can achieve a jump height 0.5-30 times higher than their own size, and combined with a specific mechanical structure design, they have the characteristics of high explosive, high mobility, and can solve interstellar exploration, terrain exploration and rescue problems. Compared to mechanical energy drives, combustion chemistry is two orders of magnitude more energy intensive than even the highest performing batteries. The use of recycled renewable energy solves the energy self-loading problem of chemical combustion drives and is more environmentally friendly than the two previous types of new energy drives. Therefore, such products should be invented and patented in the future.

Design of Intelligent Fermentation Mixer Based on PLC

Aiming at different types of organic fermentation environments, an intelligent fermentation mixer that can be controlled and monitored at multiple points is designed. The system is mainly composed of PLC, inverter, servo motor, touch screen, temperature and humidity detection module, STM32 acquisition module, HMI, cloud server and other units. After completing the electrical design, software design and mechanical structure design of the system, the whole system was debugged. The results showed that the system was operating normally and its functions basically met the original design requirements. The system adjusted the feedback network and algorithm to improve the organic fermentation environment. The control has better stability.

Physical Application of Mechanical Parts and Components Simulate in Receivable Auxiliary Multifunction Mechanical Hand and Claw

Based on the analysis of current office work status and office robots, this paper proposes a design scheme of intelligent mechanical gripper which can transfer data and move objects independently to assist daily office work. It is proposed to design mechanical structure, including mechanism motion design and part structure design, and to use Autodesk Inventor to design and simulate mechanical parts and components. Dimensional and strength checks are carried out on key components, and stress analysis is simulated by using stress analysis module included in Autodesk Inventor. Finally, the mechanical structure design scheme and control system design scheme for the mechanical gripper are proposed. The overall design mainly centers on the functions expected to be completed, and innovates different organizations in combination to achieve the intended objective.

Research on the Trajectory Planning and Control Technology of Industrial Robots Guided by Computer Visualization

With the popularization of computers, the development of all walks of life has become more rapid. This article mainly analyzes the mechanical structure design of the Cartesian coordinate robot system, it also studies the motion control.