Results for “Torsional Spring”

NASA NTRS1994

Variable stiffness torsion springs

In a torsion spring the spring action is a result of the relationships between the torque applied in twisting the spring, the angle through which the torsion spring twists, and the modulus of elasticity of the spring material in shear. Torsion springs employed industrially have been strips, rods, or bars, generally termed shafts, capabable of being flexed by twisting their axes. They rely on the variations in shearing forces to furnish an internal restoring torque. In the torsion springs herein the restoring torque is external and therefore independent of the shearing modulus of elasticity of the torsion spring shaft. Also provided herein is a variable stiffness torsion spring. This torsion spring can be so adjusted as to have a given spring constant. Such variable stiffness torsion springs are extremely useful in gimballed payloads such as sensors, telescopes, and electronic devices on such platforms as a space shuttle or a space station.

Alhorn, Dean C.↗

NASA NTRS1995

Variable stiffness torsion springs

In a torsion spring the spring action is a result of the relationships between the torque applied in twisting the spring, the angle through which the torsion spring twists, and the modulus of elasticity of the spring material in shear. Torsion springs employed industrially have been strips, rods, or bars, generally termed shafts, capabable of being flexed by twisting their axes. They rely on the variations in shearing forces to furnish an internal restoring torque. In the torsion springs herein the restoring torque is external and therefore independent of the shearing modulus of elasticity of the torsion spring shaft. Also provided herein is a variable stiffness torsion spring. This torsion spring can be so adjusted as to have a given spring constant. Such variable stiffness torsion springs are extremely useful in gimballed payloads such as sensors, telescopes, and electronic devices on such platforms as a space shuttle or a space station.

Alhorn, Dean C.↗

NASA NTRS2012

Planar torsion spring

A torsion spring comprises an inner mounting segment. An outer mounting segment is located concentrically around the inner mounting segment. A plurality of splines extends from the inner mounting segment to the outer mounting segment. At least a portion of each spline extends generally annularly around the inner mounting segment.

Ihrke, Chris A.↗

NASA NTRS2012

Rotary series elastic actuator

A rotary actuator assembly is provided for actuation of an upper arm assembly for a dexterous humanoid robot. The upper arm assembly for the humanoid robot includes a plurality of arm support frames each defining an axis. A plurality of rotary actuator assemblies are each mounted to one of the plurality of arm support frames about the respective axes. Each rotary actuator assembly includes a motor mounted about the respective axis, a gear drive rotatably connected to the motor, and a torsion spring. The torsion spring has a spring input that is rotatably connected to an output of the gear drive and a spring output that is connected to an output for the joint.

Ihrke, Chris A.↗

NASA NTRS2013

Rotary Series Elastic Actuator

A rotary actuator assembly is provided for actuation of an upper arm assembly for a dexterous humanoid robot. The upper arm assembly for the humanoid robot includes a plurality of arm support frames each defining an axis. A plurality of rotary actuator assemblies are each mounted to one of the plurality of arm support frames about the respective axes. Each rotary actuator assembly includes a motor mounted about the respective axis, a gear drive rotatably connected to the motor, and a torsion spring. The torsion spring has a spring input that is rotatably connected to an output of the gear drive and a spring output that is connected to an output for the joint.

Ihrke, Chris A.↗

NASA NTRS2013

Rotary Series Elastic Actuator

A rotary actuator assembly is provided for actuation of an upper arm assembly for a dexterous humanoid robot. The upper arm assembly for the humanoid robot includes a plurality of arm support frames each defining an axis. A plurality of rotary actuator assemblies are each mounted to one of the plurality of arm support frames about the respective axes. Each rotary actuator assembly includes a motor mounted about the respective axis, a gear drive rotatably connected to the motor, and a torsion spring. The torsion spring has a spring input that is rotatably connected to an output of the gear drive and a spring output that is connected to an output for the joint.

Ihrke, Chris A.↗

NASA NTRS1984

A practical adaptive-grid method for complex fluid-flow problems

A practical solution, adaptive-grid method utilizing a tension and torsion spring analogy is proposed for multidimensional fluid flow problems. The tension spring, which connects adjacent grid points to each other, controls grid spacings. The torsion spring, which is attached to each grid node, controls inclinations of coordinate lines and grid skewness. A marching procedure was used that results in a simple tridiagonal system of equations at each coordinate line to determine grid-point distribution. Multidirectional adaptation is achieved by successive applications of one-dimensional adaptation. Examples of applications for axisymmetric afterbody flow fields and two dimensional transonic airfoil flow fields are shown.

Nakahashi, K.↗

NASA NTRS1991

Adaptive Grids For Computations Of Three-Dimensional Flows

Self-adaptive-grid method devised and enhanced for efficient computation of complicated three-dimensional flows. Extension of method developed for two-dimensional flows. Fictitious springs connecting points of computational grid used to determine optimum grid spacing. Each point connected to neighboring points by tension and torsion springs. Stiffnesses of tension springs related to flow-field quantities. Stiffnesses of torsion springs resist departure of grid from orthogonality.

Djomehri, M. Jahed↗

NASA NTRS1991

Ground-based testing of the dynamics of flexible space structures using band mechanisms

A suspension system based on a band mechanism is studied to provide the free-free conditions for ground based validation testing of flexible space structures. The band mechanism consists of a noncircular disk with a convex profile, preloaded by torsional springs at its center of rotation so that static equilibrium of the test structure is maintained at any vertical location; the gravitational force will be directly counteracted during dynamic testing of the space structure. This noncircular disk within the suspension system can be configured to remain unchanged for test articles with the different weights as long as the torsional spring is replaced to maintain the originally designed frequency ratio of W/k sub s. Simulations of test articles which are modeled as lumped parameter as well as continuous parameter systems, are also presented.

Yang, L. F.↗

NASA NTRS1988

An experimental and analytical evaluation of the tapered tension-torsion strap concept

A new free-tip rotor moment controller designed to increase torque output (a restoring moment) was proposed. The controller would be used as a retention device for the freely pitching tip of a helicopter rotor. The new design featured a tapered tension-torsion strap instead of the previously used parellel strap. A tapered strap has a larger separation between the tension wires at the retention end than at the oscillating end; separation is equal at both ends for a parallel strap. A simple dynamic analysis was developed and an experiment performed to evaluate this tapered strap concept. The test results indicated that the torsional spring stiffness of the strap, represented by a torsional pendulum, increased with the amount of taper. The predicted dynamic characteristics of the pendulum also confirmed this observation and correlated reasonably well with the experimental results. It could be concluded from the experimental and analytical results that the tapered strap accomplished increased torque output when compared to the parellel strap.

Louie, Alexander↗

NASA NTRS1990

A solution adaptive grid procedure for an upwind parabolized flow solver

A solution adaptive grid procedure based on an error equi-distribution scheme is developed and applied to a Parabolized Navier-Stokes solver. An improved method for selecting weighting functions is introduced which involves normalizing a combination of flowfield gradients and curvature of a number of dependent variables and then selecting the largest at each point. The scheme re-distributes grid points line-by-line, with grid point motion controlled by forces analogous to tensional and torsional spring forces with the spring constants set equal to the weighting functions. Torsional terms are functions of the grid point positions along neighboring grid lines and provide grid smoothness and stability. A grid-fitting scheme is introduced for external flows in which the number of grid points in the freestream are reduced to a minimum. Results for several problems are presented to demonstrate the improvements obtainable with the solution adaptive grid procedure.

Harvey, Albert D.↗

NASA NTRS1982

Application of an airfoil stall flutter computer prediction program to a three-dimensional wing: Prediction versus experiment

An aerodynamic computer code, capable of predicting unsteady and C sub m values for an airfoil undergoing dynamic stall, is used to predict the amplitudes and frequencies of a wing undergoing torsional stall flutter. The code, developed at United Technologies Research Corporation (UTRC), is an empirical prediction method designed to yield unsteady values of normal force and moment, given the airfoil's static coefficient characteristics and the unsteady aerodynamic values, alpha, A and B. In this experiment, conducted in the PSU 4' x 5' subsonic wind tunnel, the wing's elastic axis, torsional spring constant and initial angle of attack are varied, and the oscillation amplitudes and frequencies of the wing, while undergoing torsional stall flutter, are recorded. These experimental values show only fair comparisons with the predicted responses. Predictions tend to be good at low velocities and rather poor at higher velocities.

Muffoletto, A. J.↗

NASA NTRS1966

Bellows joint absorbs torsional deflections in duct system

Long, thin-walled bellows compressed into a short length absorbs the same amount of torsional deflection as the same tube in full length condition and saves in cost, complexity and space. This bellows has lower torsional spring rate to absorb the bulk of the duct assembly tortional deflections, leaving the other bellows free to absorb axial and angular deflections.

Daniels, C. M.↗

NASA NTRS1973

Model support roll balance and roll coupling

The design concepts of two specialized wind tunnel model support mechanisms are described. The forced oscillation roll balance mechanism was designed to meet the specific requirement to measure aerodynamic forces and moments to permit determination of the damping-in-roll parameters of winged configurations. A variable speed motor is used to oscillate the model by means of an offset crank. The oscillating motion is resisted by a torsion spring to provide a restoring torque and is attached to the section forward of the strain-gage balance. This spring action allows the model to be oscillated at a frequency for velocity resonance, whereby the mechanical spring and any aerodynamic spring balance. This spring action allows the model to be oscillated at a frequency for velocity resonance, whereby the mechanical spring and any aerodynamic spring balance out the model inertia. The only torque then required to oscillate the model at that particular frequency is equal to that due to aerodynamic damping. The second mechanism, a roll coupling for remotely rotating a model, was designed to invert or roll a model about its longitudinal axis when mounted for testing.

Sharpes, R. E.↗

NASA NTRS1975

Flutter analysis of two parallel elastically coupled flat plates

Flutter of two parallel elastically coupled flat plates was investigated analytically. A closed-form solution including both aerodynamic and structural damping is presented for flutter of flat orthotropic plates coupled by an elastic medium. Both plates are simply supported along the side edges but are supported by deflectional, rotational, and torsional springs of arbitrary stiffness at the leading and trailing edges. Two-dimensional quasi-steady aerodynamics was utilized in the solution. Since the large number of variables present in the problem precludes extensive parametric studies, results are presented to indicate the basic flutter characteristics of coupled two-plate systems and to assess the validity of previously published modal solutions for similar problems.

Shore, C. P.↗

NASA NTRS1985

Development of the space shuttle body flap actuation subsystem

Development of the Body Flap Actuation Subsystem for Space Shuttles included alterations from the original design to mechanical stops, planet gears, control valves, and solenoid valves. The mechanical stops were redesigned to absorb stall load and rotating inertia of the hydraulic motors instead of only stall load. The institution of a quill shaft (torsion spring) was a successful solution. The planet gears in the geared rotary actuators developed cracks during testing. This failure was alleviated via modification to the gears. A motor pressurization - brake release timing technique was developed thru analysis and testing. This resulted in a control valve configuration which would not permit freewheeling of the body flap surface. Finally, several solenoid valve configurations were tested to obtain the desired performance. Conceptual redesigns and modifications were weighted against each other to optimize a solution. Tradeoffs were usually made between life, performance, failure tolerance, and reliability versus weight, envelope, and maintainability.

Boggs, C. R.↗

NASA NTRS1985

A three-dimensional adaptive grid method

A three-dimensional solution-adaptive-grid scheme is described which is suitable for complex fluid flows. This method, using tension and torsion spring analogies, was previously developed and successfully applied for two-dimensional flows. In the present work, a collection of three-dimensional flow fields are used to demonstrate the feasibility and versatility of this concept to include an added dimension. Flow fields considered include: (1) supersonic flow past an aerodynamic afterbody with a propulsive jet at incidence to the free stream, (2) supersonic flow past a blunt fin mounted on a solid wall, and (3) supersonic flow over a bump. In addition to generating three-dimensional solution-adapted grids, the method can also be used effectively as an initial grid generator. The utility of the method lies in: (1) optimum distribution of discrete grid points, (2) improvement of accuracy, (3) improved computational efficiency, (4) minimization of data base sizes, and (5) simplified three-dimensional grid generation.

Nakahashi, K.↗

NASA NTRS1986

Synchronously Deployable Truss Structures

Structure lightweight, readily deployed, and has reliable joints. New truss concept, designated as "pac truss," developed. Features easy deployment without need for complex mechanisms. Structures of this type deployed in free flight by controlled release of stored energy in torsional springs at selected hinges located throughout structure. Double-folding technique used in beam model applicable to flat planar trusses, allowing structures of large expanse to fold into compact packages and be deployed for space-platform applications.

Rhodes, M. D.↗