Rubber Bellows Research Articles

Static and dynamic analysis of a hyperelastic toroidal air-spring structure

The present work proposes a novel toroidal air-spring model consisting of two cylindrical elastomeric membranes unlike conventional convoluted air-spring with one rubber bellow. The membranes are attached with two annular plates at top and bottom in circumferential direction, forming a closed space in between. With internally pressurizing the setup, the inflated bellow in the shape of a toroidal air-spring structure is formed. The static and dynamic analysis of the air-spring model is performed under transverse loading on top plate. The static analysis is carried out by compressing the air-spring to different suspension heights, assuming adiabatic compression of the enclosed air. The conditions for impending wrinkling, its prevention measures by choosing suitable design parameters, and the effect using cord-reinforced membranes are explored. The dynamic study under harmonic forcing is performed using the method of assumed modes coupled with a perturbation technique to solve the Eigenvalue problem of the discretized membrane structure. The radial asymmetric perturbations are included in the formulation to explore the symmetry breaking during dynamic study. The Eigen frequencies of the structure are obtained for different inflation pressures of the air-spring. Interestingly, a frequency veering phenomenon is observed between a few Eigen modes associated with closely spaced natural frequencies, where the possibility of mode swapping exists. The forced vibration analysis around a few Eigen frequencies shows beating like responses. The stiffness of the proposed air-spring is found to be linear under both static and dynamic conditions, which is inline with the stiffness nature of the convectional convoluted air-springs.

Dynamic characteristic analysis and key parameter optimization of throttling orifice type air damping air spring

Abstract The unique hysteretic characteristic of rubber bellows and the nonlinear flow of internal airflow in the system results in the significant nonlinear dynamic characteristic of throttling orifice type air damping air springs (OADASs). To solve the problem of mathematical representation of dynamic characteristic and key parameters optimization of throttling OADAS, this paper comprehensively considers the hysteretic characteristic of rubber bellows under variable pressure, the nonlinear dynamic characteristic model and linear model of throttling OADAS are established based on the concepts of gas thermodynamics and fluid mechanics. The static and dynamic characteristic tests of the throttling OADAS are conducted, to verify the accuracy and effectiveness of the proposed model, and to reveal the influence laws of excitation amplitude, excitation frequency, and throttling orifice diameter on the quantitative characterization indexes. Finally, a complete throttling orifice diameter optimization method is proposed based on the eight-degree-of-freedom model of the entire vehicle. Optimization results illustrate that the RMS values of the vertical acceleration of the body and the vertical acceleration of the driver are decreased by 19.02% and 38.44%, respectively. Overall, the outcomes of this paper can provide the design idea and theoretical basis for air damping matching and active suspension control.

A Flexible, Architected Soft Robotic Actuator for Motorized Extensional Motion

To advance the design space of electrically‐driven soft actuators, a flexible, architected soft robotic actuator is presented for motor‐driven extensional motion. The actuator comprises a 3D printed, cylindrical handed shearing auxetic (HSA) structure and a deformable, internal rubber bellows shaft. The actuator linearly extends upon applying torque from a servo motor; the rubber bellows shaft is stretchable but resistant to torsional deflection, allowing it to transmit torque from the servo motor to the other end of the HSA. The high flexibility of the HSA and rubber bellows shaft enable the actuator to adaptively extend even when bent. The actuator's two components and its performance are mechanically characterized. Actuation strains of 45% elongation and a maximum blocked pushing force of about 8 N are demonstrated. The actuator's capabilities are showcased in two separate demonstrations: a crawling robot and a sensorized artificial muscle that integrates a microfluidic, liquid metal strain sensor. The architected material design approach for a robust, motor‐driven soft actuator provides several unique features—including a compact form factor and ease of use—over other motorized soft robotic actuators based on HSA assemblies or cable tendon mechanisms.

A unified stiffness model of rolling lobe air spring with nonlinear structural parameters and air pressure dependence of rubber bellows

The structural parameters of the rolling lobe air spring and the mechanical characteristic of rubber bellows are the key factors affecting the stiffness and mechanical characteristic of the rolling lobe air spring. Aiming at the prediction difficulties of structural parameters of the rolling lobe air spring with the composite curved contour piston and the modeling complexity of the hysteretic mechanical characteristic of rubber bellows under variable pressure conditions, the geometrical method is applied to derive the structural parameters models of the rolling lobe air spring with the composite curved contour piston. A new pressure factor is introduced and the Coulomb frictional pressure perturbation model and the fractional derivative Kelvin-Voigt pressure perturbation model are reconstructed to accurately describe the hysteretic mechanical characteristic of rubber bellows under variable pressure conditions. A unified pressure equation is constructed to characterize the evolution of model parameters under variable pressure conditions. Furthermore, a hysteretic mechanical characteristic pressure perturbation model (abbreviated as HMCPP model) of rubber bellows under variable pressure conditions is put forward. Finally, a unified stiffness model of the rolling lobe air spring including prediction models of nonlinear structural parameters and a HMCPP model of rubber bellows is built. Taking a certain type of rolling lobe air spring as the test sample A, the structural parameters tests and static/dynamic characteristic tests of sample A are carried out based on the MTS852.05 test bench, which verified the accuracy of the unified stiffness model of the rolling lobe air spring. The research results provide theoretical support for the mechanical characteristic matching and air pressure precise control of the rolling lobe air spring under variable pressure conditions.

Research on cord-laying angle and mechanical balance of rolling lobe air springs

The inflation of the rubber bellow leads to flexion and deformation during the operational process. The cord, serving as the primary load-bearing element of the rubber bellow in air springs, undergoes continuous changes in angle due to bending, torsion, and internal stress and moment within the bellow. This alteration causes the resultant force on the cord to deviate from its original direction, disrupting the force balance of the bellow and subsequently diminishing its fatigue life. To identify an optimal cord-laying angle that minimizes deviation from the cord's direction under the resulting force during operation, a theoretical model is established for the rubber bellow in rolling lobe air springs. This model is based on thin shell momentless theory and a force analysis of bellow micro-elements. The mapping relationship between the inflated cord angle and the uninflated cord-laying angle is examined. Furthermore, the dynamic variation of the cord angle along the longitudinal direction after the inflation of the rubber bellow is explored in this article. Additionally, a novel indirect measurement method for determining the outer diameter of the bellow is proposed to acquire the cord angle. This method is employed to verify the validity of the optimal cord-laying angle and the finite element model. The results indicate that the optimal setting interval Y for the cord-laying angle of sample A is [45°, 47°]. This finding not only offers theoretical support for the forming process of rubber bellows in rolling lobe air springs and the optimization of bellow characteristics but also introduces a new approach for measuring cord angle variations.

Design of a BP neural network PID controller for an air suspension system by considering the stiffness of rubber bellows

A rubber bellows has certain creep characteristics, and its role has often been ignored in previous air suspension research. To describe the motion state of a vehicle more accurately during driving, this paper uses amplitude correlation and frequency correlation to describe the mechanical characteristics of the rubber bellows in air spring mechanical characteristics research, establishes an air suspension simulation, and explores the role of the rubber bellows in the suspension. In addition, an adaptive neural network controller is designed to simulate and analyze the Body Acceleration (BA), Sprung Mass Displacement (SMD), Unsprung Mass Displacement (UMD) and Dynamic Wheel Load (DWL) of the suspension. Simulation results show that the rubber bellows has a certain impact on suspension SMD and has a great impact on the performance of the active suspension. The root mean square (RMS) can be increased by 4.55 % but little impact is found on other performance indicators. In addition, compared with the conventional PID control strategy, the adaptive neural network control strategy designed in this paper has better control performance, reducing the RMS of BA and SMD by 27.58 % and 16.67 %, respectively, and improving the control effect by about 4.48 % and 4.17 %, respectively compared with PID. Thus, it can better maintain the stability of the car during driving.

Design and performance of a 3D-Printed magnetorheological fluid-based adaptive vibration isolator

Emerging additive manufacturing (or 3D printing) can be advantageous for developing magnetorheological fluid (MRF)-based vibration isolators (MRVIs) because their designs can be easily and efficiently customized and also in-situ fabrication and repairing can be possible. In this study, a simple and compact adaptive MRVI was fabricated by using a 3D printing method. A masked stereolithography (MSLA) 3D printer was used for the fabrication of the rubber bellow and plastic lid parts of the MRVI. The electromagnet was mounted onto the lid, the reservoir was filled with an MRF, and the lid was simply assembled with the reservoir using a 3D-printed large thread without traditionally machined components. Using a material testing machine, the damper forces of the 3D-printed MRVI were measured under a constant velocity loading condition for different magnetic fields. From these tests, the magnetic field-controllable performances of the MRVI such as the MR yield force, the dynamic force range, the dissipated energy, and the secant stiffness were obtained. For the evaluation of the long-term performance reliability of the MRVI due to the MRF sedimentation, its magnetic field-controllable performances were tracked for 156 days with the variable testing intervals. Finally, the feasibility of the 3D-printed MRVI was experimentally confirmed.

Hybrid Robotic Manipulator Using Sensorized Articulated Segment Joints With Soft Inflatable Rubber Bellows

Robotic manipulators have been used inindustry for decades. However, their heavy mass and rigidity make them unsuitable for environments where they may coexist with humans. This has spurred interest in robotic arms with compliance in their joints using methods, such as impedance control. However, inherent compliance is safer, less computationally expensive, and does not require complex sensing solutions. In this article, the design of a sensorized hybrid hard-soft articulated joint using inflatable soft rubber bellows for actuation and simple angular potentiometers for angular position sensing is presented. The joint is hybrid in the sense that it combines rigid motion with soft actuation. This design allows for a simple yet effective solution that combines the precise sensing of rigid manipulators with the compliance of soft ones. Closed-loop control of this joint was implemented and it was capable of following a given trajectory while rejecting disturbances. This design was then extended to a two degrees of freedom (DOFs) joint with the path following capability, and then, integrated with a rigid base joint to form a 6-DOFs hybrid robotic manipulator for use in small retail businesses. This manipulator can handle payloads up to 1 kg over a large work area and was tested for pick-and-place operations.

Determination of basal metabolism and lung function by AOOZ-M apparatus

In 1957, in an article by engineers M.I. Abdrakhmanov and I.A. In 1958, a more advanced design of this kind of apparatus with a closed breathing circuit of the AOOZ-M type was developed (Fig. 1), in which the capacity of the rubber bellows was increased to 10 liters and the entire gas line (with a tank) - up to 60 liters; this makes it possible to conduct studies of basal metabolism both when breathing air and on pure O2 in a large volume.

TROUBLE SHOOTING OF RAW MATERIAL HANDLING IN BAGASSE PULPING

The agitator bearing and shaft bending due to foreign materials is reduced by using stuffing box in the agitator between bearing unit and impeller. The foreign materials in the bagasse wet washing are collected by using SS Pivot Needles/Bars in the wet washing system. The vibrations which cause damage (cracks) in the pump pipe line are reduced by using rubber bellow between the pump and delivery pipeline. The rubber bellow absorbs the vibration and deflections due to vibration which protects the pump and pipeline from damages. Earlier the foreign materials were struck up in the pump impeller. These foreign materials were removed by dismantling the entire pump set up. In the current work, the design of suction line was altered by introducing an inspection dummy. At the end of the suction line, through the new design the foreign materials were moved off from the pump impeller easily by removing the inspection dummy instead of dismantling the entire pump set up. Through the new design, the efficiency of the wet washing plant is increased upto 55%. Further, the downtime of wet washing plant also reduced and availability of equipment is increased.

Analysis model of restoring force of a rubber air spring

Not only has the dynamic stiffness of a rubber air spring been inherited by effects of the compressed air, but it has also been affected by hysteresis behaviors caused by the friction, viscoelasticity of bellow material. Hence, this paper will analyze comprehensively the stiffness model of a commercial rubber air spring. One of the first works is to predict the structure parameters including effective area, volume and their change rate. Then, the restoring force generated by compressed air will be analyzed and built through the theory of thermodynamics. The hysteresis model of the rubber bellow will be obtained based on the Berg’s frictional model connecting in parallel with fractional Kelvin-Voigt model. Next, an experimental apparatus is set up to identify the parameters of this model as well as evaluate the proposed restoring force model of the rubber air spring. The study results show that the analysis model of the rubber air spring matches well the measured data. This work will offer a helpful insight in the design of the vibration isolation system using rubber air springs as elastic elements.

A refined stiffness model of rolling lobe air spring with structural parameters and the stiffness characteristics of rubber bellows

An accurate model of rolling lobe air spring (RLAS) is the key to achieve the design, matching and optimization of air suspension. A refined stiffness model of RLAS with structural parameters and the stiffness characteristics of rubber bellows is developed in this paper. Prediction models of structural parameters, including effective area and its change rate, effective volume and its change rate, are obtained by geometrical and mechanical analysis. A nonlinear hysteresis model of rubber bellows is also proposed, which is composed of a fractional Kelvin-Voigt model and a smooth friction model in parallel. The structural parameters were identified by the experiments, including static stiffness and dynamic stiffness tests using the MTS370. The conclusions suggest that amplitude dependency and frequency dependency of RLAS can be completely characterized by the refined stiffness model. The refined stiffness model provides theoretical support for mechanical property match of RLAS.

Study on dynamic characteristics of underwater pressure compensator considering nonlinearity

Abstract. The external pressure is the biggest problem faced by underwater hydraulic systems. The strength and sealing ability of the structure are facing enormous challenges. For this problem, the common solution is to use pressure compensation technology. The pressure of the seawater is transmitted to the inside of the hydraulic system through a pressure compensator, which equalizes the return pressure of the hydraulic system and the seawater pressure. The structure of the compensation system, the volume and dynamic characteristics of the compensator, and the compensation failure caused by hydraulic oil leakage will all affect the normal operation of the underwater equipment. Therefore, it is necessary to study the pressure compensation system. This paper analyzes the pressure characteristics of the rubber-bellows type compensator. The dynamic characteristic equation of the pressure is established. Due to the strong nonlinear nature of rubber, the finite element method is used to simulate the deformation process of the rubber-bellows type pressure compensator. The relationship between the volume variation and the spring displacement of the rubber-bellows type pressure compensator is calculated by FE simulation. The relationship is brought into the theoretical equation result to obtain the pressure characteristics of the compensator. Through the control variable method, the influence of damping, total mass, effective area and spring stiffness on the internal pressure of the compensator is obtained. According to the analysis result, the damping ratio should be appropriately increased to reduce the overshoot of pressure fluctuations in the design. Since the damping is difficult to control, the total mass of the end cap, the guide post, the rubber bellows and the spring can be minimized. It also reduces the quality of the equipment. The spring stiffness and effective area have a significant influence on the steady-state pressure. A softer spring should be used and the effective area should be increased as much as possible to reduce the final steady-state pressure.

Suction pad unit using a bellows pneumatic actuator as a support mechanism for an end effector of depalletizing robots

This paper describes a vacuum suction-type end effector for depalletizing robots in distribution centers. The developed end effector has multiple suction pad units to which a bellows pneumatic actuator is applied as the support mechanism. Load-bearing capacity is improved due to a high-strength wire provided inside the bellows, and the contraction force is improved due to ring members placed inside of the ridges of the rubber bellows. The developed end effector is attached to the arm of a linear motion-type depalletizing robot, and its real-world performance is verified. Verification results confirm that the suction pad units tolerate cardboard box inclination and differences in box height by a simple lowering motion of the arm, and multiple cardboard boxes can be simultaneously unloaded. Moreover, as compared with conventional end effectors, the developed end effector achieves large expansion and contraction in a thin structure. The developed end effector is expected to broaden applications for depalletizing robots.

Analytical approach for the design of convoluted air suspension and experimental validation

An improved analytical design to investigate the static stiffness of a convoluted air spring is developed and presented in this article. An air spring provides improved ride comfort by achieving variable volume at various strokes of the suspension. An analytical relation is derived to calculate the volume and the rate of change in the volume of the convoluted bellow with respect to various suspension heights. This expression is used in the equation to calculate the variable stiffness of the bellow. The obtained analytical characteristics are validated with a detailed experiment to test the static vertical stiffness of the air spring. The convoluted air bellow is tested in an Avery spring-testing apparatus for various loads. The bellow is modeled in the ABAQUS environment to perform finite element analysis (FEA) to understand and visualize the deflection of the bellow at various elevated internal pressures and external loads. The proposed air spring model is a fiber-reinforced rubber bellow enclosed between two metal plates. The Mooney–Rivlin material model was used to model the hyperelastic rubber material for FEA. From the results, it is observed that the experimental and analytical results match with a minor error of 7.54%. The derived relations and validations would provide design guidance at the developmental stage of air bellows. These expressions would also play a major role in designing an effective active air suspension system by accurately calculating the required stiffness at various loads.

Design and development of a capacitance‐based wireless pressure transmitter

A novel, cost- effective and efficient wireless pressure measurement system is modeled for transmission of the signal in harsh environment. The sensing part involves rubber bellows with a capacitive sensor made of copper plates. For remote transmission, monitoring and controlling the mechanical displacement of the bellows is converted into dc output voltage using differentiator and precision half wave rectifier. A linearization circuit is also designed, which linearized the output voltage with a value of percentage deviation from linearity of ±1.8%. For further FSK mode of transmission, the obtained linearized voltage is converted into 1 to 5 volt with a signal conditioning circuit. The transmitted output voltage is recovered using FSK demodulator circuit, LPF and a Decision circuit at receiving end. The full scale percentage error of the measurement system lies within 5% which is in an acceptable range. The proposed method is an economic and efficient transmission technique in hazardous areas where wired transmission is not feasible. The mathematical equations explaining the functioning of the proposed transmitter have been derived. The operation of the proposed pressure transmitter has been experimentally tested. The design approach, mathematical analysis and experimental results of the proposed model are reported in this paper.

Friction and wear characteristics of alloy steel 18CrNiMo7-6 sliding on 42CrMo4

This paper studies the friction and wear behavior of 18CrNiMo7-6 alloy steel sliding on 42CrMo4 via cylinder-on-plate tests. The specimen cylinders are carburized for a hardness of 60 HRC and the plates are quenched and tempered for two hardness classes HRC 52 and HRC 46. On the test rig the specimens were lubricated with grease Gleitmo® 100 S in a specially installed rubber bellows. The friction coefficients and wear intensities of 18CrNiMo7-6 then are tested with improved normal load from 150 N to 900 N on the contact surface. The testing results show that both friction coefficient and wear coefficient decrease rapidly within 1×106 load cycles. Wear mechanism shows that there is obvious adhesive, abrasive and oxidation wear forms after 3×106 load cycles, among which the adhesive and oxidation wear forms were always not focused on in the researches till now. After 9×106 load cycles the wear on the specimens is stable.

Improvement of dynamic characteristics of manipulator driven by a gas-liquid phase-change actuator using an antagonistic drive

The goal of this research is to improve the dynamic characteristics of a manipulator composed of pneumatic artificial rubber muscles driven by gas-liquid phase change. Pneumatic actuators, such as pneumatic artificial rubber muscle (PARM) or rubber bellows, have been widely used in many industrial and research fields. They have merits of being compact and lightweight. However, the large size of the compressor driving the actuator is a problem. To overcome this, the authors researched soft actuators driven by the gas-liquid phase change (GLPC) of fluorocarbon. Fluorocarbon (C5F11NO) is a substance with a relatively low boiling point (50 °C) and a low heat of evaporation (104.65 kJ/kg). The heat of evaporation of water is 2260 kJ/kg. This paper presents the overview of an actuator driven by GLPC. Then, fabrication of a manipulator using the GLPC driven PARM, and details of experiments conducted to determine manipulator characteristics are given. To improve the dynamic characteristics of the manipulator, a force control method using the antagonistic drive of two PARMs is proposed, and experiments are conducted to validate the effectiveness of the proposed method.

Evaluation of air spring textile reinforcement by means of resolving the cord structure in FE analyses

AbstractTextile reinforcement is, among many other applications, widely used in rubber bellows of air springs. The objective of this study is to compare the effect of two different cord set‐ups on local rubber matrix strains and stresses by means of FE analyses. For that purpose, a methodology for taking both the geometry of the cord and the filament structure of its yarns into account is employed. With this, a global FE model comprising a cyclic symmetric section of the bellows, and a submodel are analyzed. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)

A Compliant Telescopic Limb with Anisotropic Stiffness

Soft limbs with anisotropic stiffness are common in nature and enable animals to solve a variety of tasks, including locomotion and manipulation. This mixture of hardness and softness enables animals to efficiently control the unpredictable contact forces that occur while performing such tasks. A challenge for soft robotics is to create artificial limbs that mimic natural mixtures of hardness and softness for use as a building block for soft, adaptable robots. This article presents the design of a novel pneumatic limb module with adjustable length and anisotropic stiffness. The artificial limb is designed with a rigid telescopic endoskeleton inside a rubber bellow, which we show is able to resist buckling, while remaining externally soft. Finally, we present the design of a hexapod walker based on the limb units.