Torsion Bar Research Articles

Design, Modelling and Control of Novel Series-Elastic Actuators for Industrial Robots

This paper describes data-driven modelling methods and their use for the control of a novel set of series-elastic actuators (SEAs). A set of elastic actuators was developed in order to fulfill the end-user needs for tailored industrial collaborative robot manipulators of different morphologies and payloads. Three different types of elastic actuation were investigated, namely, disc springs, coil springs and torsion bars. The developed algorithms were validated both on single actuators and on a 6-DOF robotic arm composed of such actuators.

Accelerated testing of track vehicle torsion bar

The suspension system of track vehicles is often equipped with torsion bars. The torsion bar is a key element of the vehicle's suspension system. The service life of torsion bars depends primarily on the quality of the material used, the diameter of the torsion bars and the method of attachment and placement. In order to obtain the characteristics of the torsion bar, an experimental test stand was created on which accelerated tests were performed. Furthermore, a virtual model of torsion bar operation was created. The torsion bar was modelled using finite elements (FE part). Dynamic simulation was performed using MSC Adams software. Finally, the values measured in the accelerated tests and the results of simulations were compared. Comparing the values found, it was proved that this difference is not significant. This virtual model can be used to investigate the service life of torsion bars and to predict their service life.

On the Applicability of Thermoforming Characterization and Simulation Approaches to Glass Mat Thermoplastic Composites

Chopped fiber composite materials offer the potential to be used for complex geometries, including local thickness changes, ribs and beads, offering significant potential for functional lightweighting. Depending on the initial mold coverage and flowability of the material, the processing behaves either more like a compression molding or a thermoforming process. The latter is applicable to high initial mold coverages and includes typical thermoforming defects such as local wrinkling. Such defects are not predictable by conventional compression molding simulation approaches usually adopted for this material class. Therefore, thermoforming characterization and simulation approaches and their applicability to glass mat thermoplastic (47 vol.% long glass fiber, Tepex Flowcore) for high initial mold coverages is investigated. Abaqus in combination with several user-subroutines is applied. Valid material characterization results from torsion bar and rheometer bending tests are obtained and applied to an automotive structure in thermoforming simulation. Results indicate that the high stiffness and high viscosity captured by the rheometer bending test at low shear-rates are necessary to reproduce the wrinkling behavior observed in the experimental results. Discrepancy is most likely reducible to thermomechanical effects, and that the modelling approach does not account for thickness deformation due to transverse compression.

Interrelation of rigidness of triangular cross-sections under bar torsion with conformal radii relation

The investigated problems of interrelation of the given geometrical rigidness of bars cross-sections of pure torsion with the geometrical characteristic of cross-sections – the relation of the internal conformal radius to the external conformal radius are covered in the article. Formulas for calculation of values of internal, external conformal radii and their relations for arbitrary, isosceles and rectangular triangles are given and the approximating functions for definition of these geometrical characteristics for triangles of any form are constructed. The graphic analysis of the obtained values shows that all variety of the relations of conformal radii presented graphically depending on one of the triangle corners falls into two subsets. One of them includes all variety of acute triangles, which is limited to isosceles acute triangles and rectangular triangles, and another one is limited with isosceles obtuse triangles and rectangular triangles. The graphic analysis of the whole variety of the known values of the given geometrical rigidness of triangular cross-sections at torsion, presented depending on one corner of a triangle, demonstrates that this geometrical characteristic is functionally connected with the relation of conformal radii; the corresponding approximating functions have linear character.

<b>Tilt Control Mechanism with Rotary Actuator and Anti-roll Bar</b>

This paper describes the development of a bogie equipped with a new type of tilt mechanism capable of providing a tilt of up to 5 degrees which is the same maximum tilt angle as the conventional bolster-type tilt mechanism, though with simpler structure. The tilt mechanism proposed provides the tilting forces to the carbody by adding torsional torque to the torsion bar on the anti-rolling device. The rotary actuator, which is inserted between the torsion bar and the arm in series, generates the torsional torque. The arms and the vertical links transmit the torque to the carbody. A bench test for simulating running on a curve and carbody tilting was conducted. The results demonstrate that it is possible to tilt the carbody with high responsiveness according to the target tilt pattern up to 5 degrees.

Structural Optimization for Stiffness and Stochastic Fatigue Life Improvement of a Sport Utility Vehicle Chassis

To further improve the structural dynamic performance of the Land-Wind X-6 chassis, structural optimization was performed: An X-shape cross member with high stiffness is added to the chassis, in addition, the cross member connecting the two torsion bar attachments is also strengthened. Extensive Finite Element Analysis (FEA) demonstrates that the inadequate torsion stiffness has been greatly increased by 102.6% after optimization, and the adequate bending stiffness has also been slightly improved by 3.8%, in addition, the level of local stresses on the chassis has been considerably declined; After optimization, the fatigue life coefficient when the vehicle is running on A-class concrete road at a speed of 110 km/h has been improved by about 40.36%, and that when the vehicle is running on D-class macadam road at a speed of 60 km/h has been improved by about 33.43%. Followed industrial implementation, field test result and product feedback information verify that the structural optimization performed in this study is effective and significant.

Dynamic high pressure torsion: A novel technique for dynamic severe plastic deformation

Abstract Severe plastic deformation (SPD) processing of polycrystalline metals is often used to obtain ultra-fine grained and nano-crystalline microstructures. Increasing the strain rate during the SPD process is known to have a favorable effect on both grain fragmentation and mechanical properties, mainly through its effect on dislocation densities and twinning. However, dynamic SPD is barely explored, mainly because of the lack of suitable experimental techniques. In the present paper, a novel dynamic high pressure torsion facility is presented which imposes a dynamic, torsional deformation to a sample subjected to high hydrostatic pressure. The setup combines basic features of both split Hopkinson torsion bar (SHTB) and static high pressure torsion (HPT) devices. Torsional speeds up to 30,000 rpm can be reached, giving rise to strain rates in the sample up to 10,000/s. The first series of tests have been performed on commercially pure aluminum. The effect of DHPT processing on the mechanical properties and microstructure is evaluated by hardness and electron back-scatter diffraction measurements, respectively. The properties and microstructural features are compared with those obtained in conventional, statically deformed HPT samples.

Study regarding the influence of the flexible lamella on the elastic characteristic for a suspension with longitudinal torsion bars

A main component of the car suspension is the stabiliser bar, that has the role to reduce the roll oscillations, and it is constructively materializes, within the conventional suspension, via a transversal torsion bar connected direct and indirect between the wheels of the axle. There are constructive solutions of suspensions with torsion bar as elastic element, longitudinal disposed, and that replaces the conventional stabiliser bar with a flexible lamella connected between the ends of the longitudinal torsion bars. So, the flexible lamella has two functions: reduces the roll oscillations and works as an additional elastic element of the suspension. Via this second function it is improved the elastic characteristic aspect of the suspension with positive consequences on the comfort and safety. The paper aims to highlight this influence by the experimental determination of the elastic characteristic of the suspension with and without lamella and the comparing of the two elastic characteristics. It is carried out and a complex theoretical model of the suspension with longitudinal torsion bars and flexible lamella, validated via the experimental research, that allows the optimization of such a suspension.

Torsional vibration analysis of torsion bar spring for off road vehicle driver seat

Torsional bar is used in driver seat for off road vehicle is important for driver comfort. Generally, Torsional bar is designed to absorb both shock and impact load. The proposed work is a special kind of torsion bar for absorbing vibration on the driver seat. A stepped bar with control arm used a mechanism and that bar could be made by two different stiffness to absorb loads transmitted to driver seat. We have analyses the shearing stress distribution, deflection, stiffness and dimensions for proposed stepped bar by using ANSYS and compared the results with numerical result.

Modeling of stress and strain states induced by torsion of straight rods with elliptical cross sections

Torsion of bars of various cross-section is of great practical utility in engineering, structural design and mechanical work. It is applied in machine construction, steel bridge or railway construction. Many publications can be found in literature that present the stress-strain analysis in the case of straight rods with constant profiles subjected to torsion. Most of these works were however directed to the case of rods with simple connected domains as cross sections. The present work uses a semi-inverse method which permits to determine general equations for stress-strain analysis in the case of rods having a multiple connected domain as cross section, subjected to torsion. For the present study, the general equations were customized for two particular cases that of an elliptical cross section and that of an elliptical ring.The determined analytical equations were implemented to a specific situation by aid of Mathcad software. This permitted to graphically represent the distribution of torsion stresses and cross-section deflection.

Computation of a torsion spring stabilizer bar rigidity and fatigue resistance

The stabilizing bar is the suspension element that reduces the sliding of the car by stopping any kind of uneven vertical movement between the wheels to which it is connected. The stabilizer bar is a piece designed to increase stability during curves, in the case of sharp turns or maneuvers, and to enhance vehicle maneuverability. In general, sports cars are equipped with such stabilizing bars both on the front and rear. In this paper we present research on the experimental determination of the characteristic and rigidity of the torsion bar springs used in suspensions of motor vehicles. The determination of the torsion bar spring characteristic is done by two methods: analytical and experimental. The results obtained by the two methods are similar. In the second part of the paper there is discussed a test bench used for the experimental determination of fatigue resistance of the torsion bar spring. Also, angular deformations of torsion bar with resistive strain gauge transducers are monitored during fatigue applications. The results of the fatigue application are also studied by numerical simulation in the ANSYS FEA program.

Multi-objective optimization design of anti-rolling torsion bar based on modified NSGA-III algorithm

PurposeHow to get a lighter and stronger anti-rolling torsion bar has become a barrier for the development of high-speed railway vehicles. The purpose of this paper is to realize the multi-objective optimization of an anti-rolling torsion bar with a Modified Non-dominated Sorting Genetic Algorithm III (MNSGA-III), which aims to obtain a better design scheme of an anti-rolling torsion bar device.Design/methodology/approachFirst, the Non-dominated Sorting Genetic Algorithm III (NSGA-III) uses a simulated binary crossover (SBX) operator and a polynomial mutation operator, while the MNSGA-III algorithm proposed in this paper introduces an arithmetic crossover and an adaptive mutation operator to change the crossover and mutate operator in NSGA-III. Second, two algorithms are tested by ZDT3, ZDT4 functions. Both algorithms set the same population size and evolutionary generation, and then compare the results of NSGA-III and MNSGA-III. Finally, MNSGA-III is applied to the multi-objective model of an anti-rolling torsion bar which is established by taking the mass and stiffness of the torsion bar as the optimization object. After that, it obtains the Pareto solution set by solving the multi-objective model with MNSGA-III. The only optimal solution selected from the Pareto solution set is compared with the traditional design scheme of an anti-rolling torsion bar.FindingsThe MNSGA-III converges faster than NSGA-III. Besides, MNSGA-III has better diversity of Pareto solutions than NSGA-III and is closer to the ideal Pareto frontier. Comparing with the results before the optimization, it shows that the volume of the anti-rolling torsion bar reduces by 1.6 percent and the stiffness increases by 3.3 percent. The optimized data verifies the effectiveness of this method proposed in this paper.Originality/valueThe simulated binary crossover operator and polynomial mutation operator of NSGA-III are changed into an arithmetic crossover operator and an adaptive mutation operator, respectively, which improves the optimization performance of the algorithm.

Fault Tolerant Control of EPS System with Sensor Fault

Taking into account the sensors faults, modeling of electric power steering (EPS) behavior improves steering reliability. Such task becomes difficult considering the nonlinearity of EPS systems. Therefore, in order to ensure the good behavior stability of the EPS, it is important to validate such established models on a real system. Hence, a fault tolerant control (FTC) design is herein proposed by considering an occurring fault at the torsion bar. A Luenberger observer is used to estimate the torque sensor fault. The FTC is performed to compensate this sensor fault by using the inverse bond graph (BG) modeling. Our simulations reveal the importance of proposed control strategy to improve the EPS system performance but also to reduce the system complexity.

Determination of length to diameter ratio of the bars in torsional Split Hopkinson bar

Split Hopkinson bar is a well-known device for mechanical characterization of materials under dynamic loading. The device can be compressive, tensile, and torsional or shear. The effect of dimensions of SHB in particular the length to diameter ratio, L/D, of the bars has been the subject of some investigations over the past several decades. However, no work has so far been performed on the forgoing ratio in torsional Split Hopkinson bar (TSHB). In this work, the length to diameter ratio of the input or output bar, L/D, is studied by numerical simulation, theory through Lagrange diagram of the TSHB and experiment. It has been found that for L/D>80, the incident, reflected and transmitted wavelengths obtained from simulations and Lagrange diagram are the same. This value of L/D is quite consistent with that usually recommended for compressive and tensile versions of SHB. The numerical model of TSHB is validated by Lagrange diagram and experiment.

Two-dimensional MEMS Fe-based metallic glass micromirror driven by an electromagnetic actuator

A 2D MEMS Fe-based metallic glass micromirror driven by an electromagnetic actuator is studied and proposed. Fe-based metallic glass is an amorphous metal that has excellent mechanical and magnetic properties. In this paper, Fe-based metallic glass is used as magnetic actuation material and torsion bar structure material. The Fe-based metallic glass thin film deposited on a micromirror surface is used as magnetic material that can be magnetically polarized by permanent magnets. Besides, the micromirror consists of two pairs of metallic glass torsion bars to achieve 2D scanning. The excellent mechanical properties of metallic glass were used for increasing the strength and reliability of the micromirror. The fabricated 2D micromirror can be actuated by an electromagnetic solenoid in dual resonant modes. The result shows that the scanning angle of the outer slow axis is 11° at 800 Hz and that of the inner fast axis is 90° at 5249 Hz.

The Torsion Bars System Reliability Analysis with Failure Mode in Crawler Vehicle

The traditional reliability analysis of mechanical systems was not considered the correlation between components, which leads to inaccurate analysis. In this paper, Copula function was applied to reliability analysis of the track vehicle torsion bar system, and a system reliability model which failure mode of a track vehicle torsion bar correlated was established. The relationship between trip and system reliability was obtained, and the superiority of Gumbel Copula system reliability model in analyzing the reliability of mechanical system was verified, which provided a new idea for reliability analysis and reliability sensitivity analysis of mechanical system.

On the Development of Material Constitutive Model for 45CrNiMoVA Ultra-High-Strength Steel

For the implementation of simulations for large plastic deformation processes such as cutting and impact, the development of the constitutive models for describing accurately the dynamic plasticity and damage behaviors of materials plays a crucial role in the improvement of simulation accuracy. This paper focuses on the dynamic behaviors of 45CrNiMoVA ultra-high-strength torsion bar steel. According to investigation of the Split-Hopkinson pressure bar (SHPB) and Split-Hopkinson tensile bar (SHTB) tests at different strain rate and different temperatures, 45CrNiMoVA ultra-high-strength steel is characterized by strain hardening, strain-rate hardening and thermal softening effects. Based on the analysis on the mechanism of the experimental results and the limitation of classic Johnson-Cook (J-C) constitutive model, a modified J-C model by considering the phase transition at high temperature is established. The multi-objective optimization fitting method was used for fitting model parameters. Compared with the classic J-C constitutive model, the fitting accuracy of the modified J-C model significantly improved. In addition, finite element simulations for SHPB and SHTB based on the modified J-C model are conducted. The SHPB stress-strain curves and the fracture morphology of SHTB samples from simulations are in good agreement with those from tests.

Influence of thermal history on the intermediate and low-temperature reversible aging properties of asphalt binders

This paper aims to investigate the influence of thermal history on the intermediate and low-temperature characterisation of asphalt binders. First, various asphalt binder intermediate and low-temperature characterisation methods and the significance of thermal history on asphalt characterisation were reviewed. Second, regular Superpave performance grading (PG) test, extended bending beam rheometer (Ex-BBR) test, double edge-notched tension (DENT) test and torsion bar low-temperature frequency sweep test were performed on selected asphalt samples with different treated thermal history. In addition, black space diagrams were also drawn to show the phase separation properties of varying asphalt binder formulations. The results showed that grade loss of wax-based warm mix asphalt almost kept constant when a small amount of microcrystalline wax (1% by mass of binder) was added. However, grade loss increased obviously with adding more microcrystalline wax (higher than 2%). Prolonged isothermal conditioning had a different degree of influence on the small-strain rheological and large-strain damage properties of asphalt binder. Applying slower loading frequency in dynamic shear rheometer (DSR) caused more obvious decrease in phase angle due to prolonged conditioning time.

FEM Simulation of Electric Car Chassis Design with Torsional Bar Technology

A design of electrical vehicle chasis is presented, specifically a FEM simulation is employed to simulate the different kind of load and reaction on vehicle frame. The main goal in this research is to develop an electric car with torsion bar, where the frame will have a self-suspension system. The frame design will be made as original equipment. This research will focus on how an electric car chassis withstand certain load with a defined boundary condition, where the analysis is conducted using Finite element Method using ANSYS software. The main analysis is the Von-Misses Stress, the safety factor, bending, torsion shear stress and vibration.

Modeling of an active torsion bar automotive suspension for ride comfort and energy analysis in standard road profiles

Chassis technology is evolving towards active suspension, in which actuators can provide forces to each wheel individually. This overcomes the traditional trade-off between comfort and handling, at the expense of increased complexity and electric consumption. To reduce power demand, regenerative solutions capable of harvesting a certain amount of energy otherwise dissipated in vehicle suspensions and to enhance vehicle dynamics for improving ride comfort and road safety at the same time have been researched. In this paper, an active suspension based on a torsion bar is modeled and analyzed under the excitation from standardized road profiles according to the ISO 8608 norm. A skyhook controller was implemented in a quarter-car model for assessment of the ride comfort, power consumption and harvesting potential of a DC motor according to the four-quadrant operation, working as a generator. From simulations, results show that for a velocity of 50 km/h it is possible to harvest 50-60 W from a vehicle driving in a class C road with ride comfort trade-off. This constitutes around 25% of the power consumption of the active suspension system.