Showing papers on "Torsion spring published in 2017"

Flapping foil power generator performance enhanced with a spring-connected tail

Abstract: The flexibility effects on the performance of a flapping foil power generator are numerically studied by using the immersed boundary-lattice Boltzmann method at a Reynolds number of 1100. The flapping foil system consists of a rigid NACA0015 foil undergoing harmonic pitch and plunge motions and a passively actuated flat plate pinned to the trailing edge of the rigid foil. The flexibility is modeled by a torsional spring model at the conjuncture of the rigid foil and the tail. Here, a parametric study on mass density and natural frequency is conducted under the optimum kinematic condition of the rigid system identified from the literature and numerical simulations made for reduced frequency f* = 0.04–0.24 and pitch amplitude θ0 = 40°–90°. Four typical cases are discussed in detail by considering time histories of hydrodynamic loads and tail deformations under the optimal and non-optimal kinematic conditions. Results show that under the rigid-system optimal kinematic condition, a tail with appropriate mass ...

Design and characterization of a magneto-rheological series elastic actuator for a lower extremity exoskeleton

Abstract: In this paper, an innovative actuator named magneto-rheological series elastic actuator (MRSEA) is designed for the knee joints of a lower extremity exoskeleton CUHK-EXO. MRSEA is designed to reduce the mechanical impedance of the exoskeleton and filter out unwanted collisions. It can also provide large controllable braking torque with low power, and hence improve the system energy efficiency. A description of CUHK-EXO developed to help paraplegic patients regain the mobility to stand up, sit down and walk is firstly introduced, followed by the mechanical design of MRSEA and simulation of the torsion spring pack (TSP) and magneto-rheological (MR) brake of MRSEA. Prototype of MRSEA is fabricated. Preliminary tests are performed to investigate the characteristics of the TSP and MR brake, and walking experiments with a paraplegic patient are performed to evaluate the performance of MRSEA. Experimental results of MRSEA match the modeling and simulation. As compared with the electric motor, the energy efficiency of the innovative MRSEA is improved by 52.8% during a gait cycle.

Development of a Meso-Scale SMA-Based Torsion Actuator for Image-Guided Procedures

Abstract: This paper presents the design, modeling, and control of a meso-scale torsion actuator based on shape memory alloy (SMA) for image-guided surgical procedures. Developing a miniature torsion actuator is challenging, but it opens the possibility of significantly enhancing the robot agility and maneuverability. The proposed torsion actuator is bidirectionally actuated by a pair of antagonistic SMA torsion springs through alternate Joule heating and natural cooling. The torsion actuator is integrated into a surgical robot prototype to demonstrate its working performance in the humid environment under C-Arm CT image guidance.

Design and Fabrication of a 2-Axis Electrothermal MEMS Micro-Scanner for Optical Coherence Tomography

Abstract: This paper introduces an optical 2-axis Micro Electro-Mechanical System (MEMS) micromirror actuated by a pair of electrothermal actuators and a set of passive torsion bars. The actuated element is a dual-reflective circular mirror plate of 1 m m in diameter. This inner mirror plate is connected to a rigid frame via a pair of torsion bars in two diametrically opposite ends located on the rotation axis. A pair of electrothermal bimorphs generates a force onto the perpendicular free ends of the mirror plate in the same angular direction. An array of electrothermal bimorph cantilevers deflects the rigid frame around a working angle of 45 ∘ for side-view scan. The performed scans reach large mechanical angles of 32 ∘ for the frame and 22 ∘ for the in-frame mirror. We denote three resonant main modes, pure flexion of the frame at 205 Hz , a pure torsion of the mirror plate at 1.286 kHz and coupled mode of combined flexion and torsion at 1.588 kHz . The micro device was fabricated through successive stacks of materials onto a silicon-on-insulator wafer and the patterned deposition on the back-side of the dual-reflective mirror is achieved through a dry film photoresist photolithography process.

Passive knee exoskeleton using torsion spring for cycling assistance

Abstract: In this paper, we introduce a concept of passive knee exoskeleton for cycling assistance. Considering a knee moment and a knee angle varying with a pedal crank angle, the knee extension moment can be supported by a torsion spring storing energy from knee flexion in order to release it as the knee is extended. The reduction of knee extension effort is corresponding to the torsion spring stiffness and activation range. Exoskeleton prototypes were developed for the concept validation. A crossing four-bar mechanism was chosen for the knee joint to provide kinematic compatibility covering extreme knee flexion. Constant power cycling experiment was performed on a cycling trainer by a healthy subject wearing the exoskeletons on both legs. With the torsion spring support, the surface electromyography recorded from some major leg muscles shows the decrease of knee extensor muscle activity as the leg is moving around the pedal crank top dead center. Verifying the reduction of leg muscle fatigue over repetitive contractions in multiple subjects is our future plan of study.

Characterizing Torsional Properties of Microwires Using an Automated Torsion Balance

Abstract: In order to characterize the torsional behavior of microwires, an automated torsion tester is established based on the principle of torsion balance. The main challenges in developing a torsion tester at small scales are addressed. An in-situ torsional vibration method for precisely calibrating the torque meter is developed. The torsion tester permits the measurement of torque to nN m, as a function of surface shear strain to a sensitivity of sub-microstrain. Using this technique, we performed (monotonic and/or cyclic) torsion tests on polycrystalline copper and gold wires. It is found that (i) a size effect appears in both the initial yielding and the plastic flow of torsional response; (ii) a reverse plasticity occurs upon unloading in cyclic torsion response; and (iii) the Hall-Petch effect and the strain gradient effect are synergistic. We also performed cyclic torsion tests on human hairs and spider silk which are natural protein fibers with a different morphological structure to metallic wires. It is shown that the single hair exhibits torsional recovery, and that the spider silk displays torsionally superelastic behavior whereby it is able to withstand great shear strain.

Correlating field performance to laboratory dynamic modulus from indirect tension and torsion bar

Abstract: Dynamic modulus has several useful functions in flexible pavements, including stress/strain characterisation, rutting and cracking characterisation, an input into several analytical and numerical models, and a primary input into Pavement ME Design. While the traditional dynamic modulus test is run in the uniaxial configuration, this is not possible for field cores. Therefore, the indirect tension dynamic modulus (IDT |E*|) and torsion bar shear modulus (torsion bar |G*|) have been developed. However, there has been limited research looking at analysing the data from field cores for these two geometries, comparing modulus data from the two geometries, examining in-service ageing of dynamic modulus, and quantifying pavement conditions using dynamic modulus. This research examines 10 field sections in Arkansas, comprising of 4 “good” performing sections, 2 “medium” performing sections, and 4 “poor” performing sections in an attempt to address these four questions. First, this research found that using AASHTO...

When Cavendish meets Feynman: A quantum torsion balance for testing the quantumness of gravity

Abstract: We propose a thought experiment, based on a mechanism that is reminiscent of Cavendish's torsion balance, to investigate the possible quantum nature of the gravitational field generated by the quantum superposition state of a massive system. Our proposal makes use of the dynamics of a ultra-stable optically levitated nanomechanical rotor endowed with a spin to generate a quantum angular superposition that is then tested through standard Ramsey-like scheme. Gravity manifests itself as an effective decoherence mechanism, whose strength is different-and, as we show, appreciable-in the classical and quantum case. By incorporating both the source for decoherence and the mechanism to probe it, the experiment that we propose allows for a much reduced degree of control and dynamical engineering.

A modified pseudo-rigid-body modeling approach for compliant mechanisms with fixed-guided beam flexures

Abstract: . In the present paper, we investigate a modified pseudo-rigid-body (MPRB) modeling approach for compliant mechanisms with fixed-guided beam flexures by considering the nonlinear effects of center-shifting and load-stiffening. In particular, a fixed-guided compliant beam is modeled as a pair of fixed-free compliant beams jointed at the inflection point, where each fixed-free beam flexure is further modeled by a rigid link connected with an extension spring by a torsion spring, based on the beam constraint model (BCM). Meanwhile, the characteristic parameters of the proposed MPRB model are no longer constant values, but affected by the applied general tip load, especially the axial force. The developed MPRB modeling method is then applied to the analysis of three common compliant mechanisms (i.e. compound parallelogram mechanisms, bistable mechanisms and 1-DOF translational mechanisms), which is further verified by the finite element analysis (FEA) results. The proposed MPRB model provides a more accurate method to predict the performance characteristics such as deformation capability, stiffness variation, as well as error motions of complaint mechanisms with fixed-guided beam flexures, and offers a new look into the design and optimization of beam-based compliant mechanisms.

Fluid-structure interaction of a rolling restrained body of revolution at high angles of attack

Abstract: The current work investigates numerically rolling instabilities of a free-to-roll slender rigid-body of revolution placed in a wind tunnel at a high angle of attack. The resistance to the roll moment is represented by a linear torsion spring and equivalent linear damping representing friction in the bearings of a simulated wind tunnel model. The body is subjected to a three-dimensional, compressible, laminar flow. The full Navier-Stokes equations are solved using the second-order implicit finite difference Beam-Warming scheme, adapted to a curvilinear coordinate system, whereas the coupled structural second order equation of motion for roll is solved by a fourth-order Runge-Kutta method. The body consists of a 3.5-diameter tangent ogive forebody with a 7.0-diameter long cylindrical afterbody extending aft of the nose-body junction to x/D = 10.5. We describe in detail the investigation of three angles of attack 20°, 40°, and 65°, at a Reynolds number of 30 000 (based on body diameter) and a Mach number of ...

Capture spin elimination mechanism suitable for spin space fragments

Abstract: The invention provides a capture spin elimination mechanism suitable for spin space fragments. The capture spin elimination mechanism comprises a rotating part and a fixed part. Multiple finger mechanisms with underactuation mechanism forms are arranged on a shell at the front end of the rotating part, each finger mechanism is provided with multiple rotating joints, each joint is provided with a torsion spring, each finger is dragged by one rope to form an underactuation mechanism, bending actions can be completed, and adaptive capacity is achieved for contact shapes. The torsion spring of each joint resists traction force of the corresponding rope, and unbending power is provided for the fingers. All the fingers are arranged pairwise in an intersecting mode, and objects of different sizes can be held when the fingers close up. The ropes of all the fingers are fixed to a sliding block, and linkage can be achieved. The sliding block is located in the rotating part, can do translational motion relative to the rotating part along the rotating axis, but cannot rotate relative to the rotating part. The sliding block is driven by a lead screw-nut mechanism, and the sliding block is connected with a nut through a rotating pair.

Dynamics of a mass–spring–beam with 0:1:1 internal resonance using the analytical and continuation method

Abstract: The nonlinear harmonic response of an autoparametric system comprised of a linear oscillator with a vertically attached flexural beam is investigated and the capability of the beam as a vibration absorber is assessed. A weak torsional spring is used for constraining the rotation of the beam giving rise to an almost non-flexural rotational mode with a low frequency. The system parameters are also tuned to enforce the zero-to-one-to-one internal resonance condition. The Lagrange’s formulation accompanied by the assumed-mode method is used to derive the discretized equations based on the order three nonlinear Euler–Bernoulli beam theory. An analytical solution is developed based on the method of multiple scales where the generalized coordinate corresponding to the non-flexural rotational mode is approximated by higher order perturbation expansion than the other coordinates, due to much larger contribution of the non-flexural rotation to the response. Comprehensive response and bifurcation analysis are performed using analytical and direct numerical solutions. The results are obtained for vertically-aligned and also initially inclined beams and various interesting behaviors are recognized for different non-dimensional system parameters. Different types of bifurcations such as the Pitch-fork, Hopf, Period-doubling and symmetry breaking bifurcations are observed in the solution of slow-flow equations and some of them are found to be beneficial for vibration absorption in a limited range of excitation amplitudes and frequencies.

Range hood's decoration cover mounting structure

Abstract: The utility model provides a range hood's decoration cover mounting structure, includes the fan frame and decorates the cover, decorates the relative fan housings of cover ability and reciprocates, the lateral wall limiting plate outside with being located the decoration cover of decorating the cover offsets its characterized in that: be equipped with the torsional spring installing support on fan frame double -phase is to the lateral wall, installs torsional spring and torsion regulating part on the torsional spring installing support, the first application of force end of torsional spring with decorate the cover correspond the inside wall counterbalance, the torsion regulating part can be held in the second application of force of torsional spring by direct action to and then the packing force of covering the inside wall is decorated to the first application of force terminal pair of ability adjusting button spring. The utility model has the advantages of: this range hood decoration cover mounting structure passes through the effort that adjusting button power regulating part was held to the torsional spring second application of force, just can decorate the packing force of covering by the first application of force terminal pair of adjusting button spring for decorating the cover and can adjusting to wantonly high and not landing, it is very convenient, nimble to adjust, and installation cost is lower, in addition, can also adapt to the decoration cover of installing different weight.

Propulsion via flexible flapping in granular media

Abstract: Biological locomotion in nature is often achieved by the interaction between a flexible body and its surrounding medium. The interaction of a flexible body with granular media is less understood compared with viscous fluids partially due to its complex rheological properties. In this work, we explore the effect of flexibility on granular propulsion by considering a simple mechanical model in which a rigid rod is connected to a torsional spring that is under a displacement actuation using a granular resistive force theory. Through a combined numerical and asymptotic investigation, we characterize the propulsive dynamics of such a flexible flapper in relation to the actuation amplitude and spring stiffness, and we compare these dynamics with those observed in a viscous fluid. In addition, we demonstrate that the maximum possible propulsive force can be obtained in the steady propulsion limit with a finite spring stiffness and large actuation amplitude. These results may apply to the development of synthetic locomotive systems that exploit flexibility to move through complex terrestrial media.

Composite loading device for robot joint reducer performance test

Abstract: The invention relates to the field of simulation loading test class, particularly relates to a simulation loading device for robot joint reducer performance test, and provides a composite loading device for the robot joint reducer performance test The composite loading device comprises a workbench base, a tested reducer module, a loading torsion bar module, a torque loading module, a loading lever module, leading screw loading modules and a hoisting bracket module The loading shaft of the tested reducer module is connected with the elastic torsion bar of the loading torsion bar module The elastic torsion bar is connected with the output flange of the torque loading module The loading shaft is installed in the loading lever of the loading lever module The two sides of the cantilever of the loading lever are provided with two sets of leading screw loading modules The loading lever module is installed in the hoisting bracket module Loading of toque, bending moment, axial force, torque and bending moment composite load and torque and axial force composite load of the reducer can be realized so that the loading performance is table, use is convenient and performing of the working performance test of the reducer is facilitated

Double-layer plane torsional spring for smoothening joint

Abstract: The invention discloses a double-layer plane torsional spring for smoothening a joint. An existing plane torsional spring is small in maximum external force torque. A first plane torsional spring body and a second plane torsional spring body both comprise an inner ring, an outer ring and an elastomer unit; each elastomer unit is provided with n arc-shaped sections; the adjacent arc-shaped sections are connected through connecting sections; each first boss is fixedly connected with the arc-shaped section at one end of one corresponding elastomer unit; m cantilever beams are arranged in each inner ring, and each cantilever beam is connected with the arc-shaped section at the other end of one corresponding elastomer unit. A middle gasket is arranged between the opposite ends of the outer ring of the first plane torsional spring body and the outer ring of the second torsional spring body; a spline shaft is connected with a spline hole of the first plane torsional spring body and a spline hole of the second plane torsional spring body; an outer ring mounting hole of the first plane torsional spring body, a gasket mounting hole in the corresponding position of the middle gasket and an outer ring mounting hole in the corresponding position of the second plane torsional spring body are connected through an output shaft at the corresponding position of an output part. The maximum external force torque of the plane torsional spring is increased.

Aluminum pipe is body clamping structure for drying -machine

Abstract: The utility model discloses an aluminum pipe is body clamping structure for drying -machine, including the drying -machine main part, supporting seat and movable rod, the equal fixed mounting in drying -machine main part both ends has the supporting seat, the upper end of supporting seat is articulated each other with the movable rod, the lower extreme of slip bracing piece is equipped with the connecting rod, the lower extreme of connecting rod is equipped with the connecting block, the spread groove, spring and fixed dog, form a buffer structure, the second presss from both sides tight piece to be connected with the movable rod through reset spring, form a buffer structure, two buffer structure's setting, the aluminum pipe clamping process or the during operation of drying have been guaranteed, clamping device can not lead to the fact the damage to the body, thereby influence the precision or the work of aluminum pipe, be equipped with the pressure spring on the supporting seat, L type slide bar and movable block, the pressure spring can make L type slide bar spacing with the movable rod, the movable block can be with the lapse of L type slide bar, make the tight piece of second clamp on the movable rod grasp the aluminum pipe under the effect of torsional spring, it is easier to make clamping process, simply.

Development of a lower extremity wearable exoskeleton with double compact elastic module: preliminary experiments

Abstract: . In this paper, a double compact elastic module is designed and implemented in the lower extremity exoskeleton. The double compact elastic module is composed of two parts, i.e., physical human robot interaction (pHRI) measurement and the elastic actuation system (EAS), which are called proximal elastic module (PEM) and distal elastic module (DEM) respectively. The PEM is used as the pHRI information collection device while the DEM is used as the compliance device. A novel compact parallelogram-like structure based torsional spring is designed and developed. An iterative finite element analysis (FEA) based optimization process was conducted to find the optimal parameters in the search space. In the PEM, the designed torsional spring has an outer circle with a diameter of 60 mm and an inner hole with a diameter of 12 mm, while in the DEM, the torsional spring has the outer circle with a diameter of 80 mm and the inner circle with a diameter of 16 mm. The torsional spring in the PEM has a thickness of 5 mm and a weight of 60 g, while that in the DEM has a thickness of 10 mm and a weight of 80 g. The double compact elastic module prototype is embedded in the mechanical joint directly. Calibration experiments were conducted on those two elastic modules to obtain the linear torque versus angle characteristic. The calibration experimental results show that this torsional spring in the PEM has a stiffness of 60.2 Nm rad−1, which is capable of withstanding a maximum torque of 4 Nm, while that in the DEM has a stiffness of 80.2 Nm rad−1, which is capable of withstanding a maximum torque of 30 Nm. The experimental results and the simulation data show that the maximum resultant errors are 6 % for the PEM and 4 % for the DEM respectively. In this paper, an assumed regression algorithm is used to learn the human motion intent (HMI) based on the pHRI collection. The HMI is defined as the angular position of the human limb joint. A closed-loop position control strategy is utilized to drive the robotic exoskeleton system to follow the human limb's movement. To verify the developed system, experiments are performed on healthy human subjects and experimental results show that this novel robotic exoskeleton can help human users walk, which can be extended and applied in the assistive wearable exoskeletons.

A flat torsional spring with corrugated flexible units for series elastic actuators

Abstract: With the fast development in physical Human-Robot Interaction (pHRI), researchers have been focusing on compliant joints to ensure the safety of humanity Series Elastic Actuator (SEA), basically consisting of a motor in series to a spring connected to the load, is an effective solution of compliant joints In this paper, a novel flat torsional spring with corrugated flexible units for SEA is proposed to meet the requirement for the elbow joints of humanoid robots Then a series of tests are performed in Ansys Workbench 150 Under 30 N-m torque, the torsional angel is 0105 rad The torsional stiffness is 2885 N· m/rad Compared to the simulation results of other existing flat torsional springs, the proposed structure has a lower torsional stiffness, which provides workers a better protection What's more, it has a higher radial stiffness and a higher axial stiffness, which decreases the vibration and increases the control accuracy

The Parameters Optimizing Design of Double Suspension Arm Torsion Bar in the Electric Sight-Seeing Car by Random Vibration Analyzing Method

Abstract: This study is about the impact of the performance and the sensitivity analysis for parameters of the torsion bar suspension in the electric sight-seeing car, which the authors’ laboratory designed and which is used in the authors’ university. The suspension stiffness was calculated by using the virtual work principle, the vector algebra, and tensor of finite rotation methods and was verified by the ADAMS software. Based on the random vibration analysis method, the paper analyzed the dynamic tire load (DTL), suspension working space (SWS), and comfort performance parameters. For the purpose of decreasing the displacement of the suspension and limiting the frequency of impacting the stop block, the paper examined the three parameters and optimized the basic parameters of the torsion bar. The results show that the method achieves a great effect and contributes an accurate value for the general layout design.