Showing papers on "Torsion spring published in 2022"

A Lower Limb Rehabilitation Assistance Training Robot System Driven by an Innovative Pneumatic Artificial Muscle System.

Abstract: This study aims to develop the application of pneumatic artificial muscle (PAM) for a 2-degrees of freedom (2-DOF) lower limb rehabilitation assistance training robot system. The proposed lower limb robot system can be divided into two axes, such as hip joint and knee joint. Each joint contains a pneumatic proportional valve to control a single-PAM with a torsion spring to simulate joint extension and flexion bionics characteristics and achieve a human-like 2-DOF lower limb robot system design and experimental prototype system. By analyzing the kinematics, the derived kinematics conforms to the lower limb motion pattern of the moving human body. Single PAM is difficult to achieve high accuracy control due to the different characteristics between extension and contraction. In our previous research, dual PAMs have been developed to drive a rotational joint which can achieve better control accuracy, however, cannot be suitable for multiaxial robotic design. The mechanism will become very complex and result in lower response and control accuracy. Thus, in this article the novel concept using single PAM with torsion spring was proposed to drive a joint to achieve two-axial robotic design. It has the advantage of multiaxial mechanism design, but the difficulty in joint control due to motion nonlinearity between contraction and extension. The torsion spring can improve motion nonlinearity between contraction and extension partly. Thus, the joint controller using adaptive self-organizing fuzzy sliding mode controller (ASOFSMC) was developed to solve this problem and achieve the required control performance for the joint angle positioning and gait planning control. Through the novel combination of single PAM, torsion spring, and the ASOFSMC joint controller with novel mechanism design and controller design, the two-axial robot mechanism designs and achieves the required control accuracy. The experimental results show that ASOFSMC can effectively control a 2-DOF lower limb robot system, and can modify fuzzy rules online, and adapt to rapid changes in the external environment and load to improve system control performance. The results prove that the proposed innovative single-PAM with a torsion spring and the control strategy can achieve the performance of 2-DOF lower limb rehabilitation assistance training robot system.

A Three-Dimensional Finite Element Analysis Model of SAW Torque Sensor with Multilayer Structure

Abstract: A three-dimensional finite element analysis model of surface acoustic wave (SAW) torque sensor based on multilayer structure is proposed in this paper. Compared with the traditional saw torque sensor with quartz as piezoelectric substrate, the SAW torque sensor with multilayer structure has the advantages of fast propagation speed and high characteristic frequency. It is a very promising torque sensor, but there is very little related research. In order to successfully develop the sensor, it is essential to understand the propagation characteristics and torque sensing mode of SAW in multilayer structure. Therefore, in this study, we first established a multi-layered finite element analysis model of SAW device based on IDT/128° Y-X lithium niobate/diamond/Si (100). Then, the effects of different film thicknesses on the characteristic frequency, electromechanical coupling coefficient, s parameter, and mechanical quality factor of SAW device without changing the wavelength are analyzed. Then, based on the finite element analysis, a three-dimensional research model of a new SAW torque sensor suitable for small diameter torsion bar (d = 10 mm) is established, and the relationship between saw device deformation and torque under the condition of small torque (±40 Nm) is tested. The shape variable is introduced into the finite element analysis model of multi-layer SAW device. Finally, the relationship between saw torque sensor with multi-layer structure and torque is established by using the deformation relationship, which shows the perfect curve of sensor performance.

Pendulum energy harvester with torsion spring mechanical energy storage regulator

Abstract: This paper presents the integration of a novel mechanical torsion spring regulator into a pendulum energy harvester system. This regulator was designed to provide the same voltage-smoothing benefits of a flywheel without the start-up issues caused by increasing system inertia. In addition, the introduction of the spring between the input and output stages of the device acts as a buffer for any sudden impacts, which not only allows the energy from such events to be fully absorbed and dissipated slowly through the output but significantly reduces the torque stress and torque fluctuation stress on critical components to improve the reliability of the system. Through experimentation and simulation, the transducer was shown to reduce the voltage fluctuation range from 13.85 to 28.16 V to 16.41 to 23.59 V for the pendulum energy harvester at resonance, and comparison of start-up response to that of a device with a flywheel shows a significant improvement in initial acceleration of the output when subjected to excitation. The energy harvester with spring has demonstrated a maximum normalised average power output of 12.09 W/g 2 , a maximum normalised average voltage of 109.96 V/g, and a maximum normalised power density of 7.8 W/g 2 /kg, at a resonant frequency of 1.2 Hz. The effectiveness of the spring mechanism for regulating output voltage and power, improving start-up performance, and reducing stress on critical components has significant implications for the real-world viability of pendulum energy harvesters, with the potential to improve their reliability in often unpredictable environments. • Achieves key benefits of a flywheel, while overcoming the major drawbacks. • Spring reduces variation of output voltage, similar to the effect of a flywheel. • Improved start-up performance of energy harvester. • Significant reduction in torque on critical components e.g. clutches.

Vibro-Impact Motions of a Three-Degree-of-Freedom Geartrain Subjected to Torque Fluctuations: Model and Experiments

Abstract: In this study, a multi-mesh gear system subjected to torque fluctuations is employed as an example to study vibro-impacts of multi-degree-of-freedom systems having multiple clearances. Such rotational systems are common in various automotive geared drivetrains where external torque fluctuations lead to contact loss at gear mesh interfaces to result in sequences of impacts. The specific configuration considered here is a three-axis, two-gear mesh drivetrain that is commonly used in engine timing gear systems, known for its vibro-impacts resulting in rattling noise. On the theoretical side, a discrete torsion model is developed and solved using a piecewise-linear solution method. Its predictions are compared to measurements from a three-axis geartrain to demonstrate its accuracy. The validated model is exercised at the end to quantify sensitivity of vibro-impact motions and associated nonlinear behavior to key excitation parameters.

Development of a Motor-Direct-Driven Bi-directional Actuation Flapping Wing System Using Extension Spring

Abstract: This paper proposes a direct-driven bi-directional actuation flapping wings system using an extension spring instead of a torsional spring. Then, the proposed flapping-wing system’s mathematical model is derived and analyzed. A prototype is fabricated using a DC motor, an extension spring, pinion gear, spur gear, and a flapping wing. The performance of the proposed wing is measured using an oscilloscope, a load cell, and a high-speed camera. The results demonstrate that the system works well without fatigue failure or the spring’s mechanical deformation. Additionally, it can generate 11.1 g of thrust when 24 Hz driving signal is applied using 12 V PWM, which is sufficient to fly 20 g micro air vehicles using dual flapping-wing systems. The wing flapping system’s energy consumption is 13.95 W, which means that more than a 1-minute flight is possible using a 7.4 V battery with 70 mAh capacity.

Effects of Non-Metallic Inclusions and Mean Stress on Axial and Torsion Very High Cycle Fatigue of SWOSC-V Spring Steel

Abstract: Inclusion-initiated fracture in high-strength spring steel is studied for axial and torsion very high cycle fatigue (VHCF) loading at load ratios of R = −1, 0.1 and 0.35. Ultrasonic S-N tests are performed with SWOSC V steel featuring intentionally increased numbers and sizes of non-metallic inclusions. The fatigue limit for axial and torsion loading is considered the threshold for mode I cracks starting at internal inclusions. The influence of inclusion size and Vickers hardness on cyclic strength is well predicted with Murakami and Endo’s √ area parameter model. In the presence of similarly sized inclusions, stress biaxiality is considered by a ratio of torsion to axial fatigue strength of 0.86. Load ratio sensitivity is accounted for by the factor ((1 − R)/2)α, with α being 0.41 for axial and 0.55 for torsion loading. VHCF properties under torsion loading cannot appropriately be deduced from axial data. In contrast to axial loading, the defect sensitivity for torsion loading increases significantly with superimposed static mean load, and no inclusion-initiated fracture is found at R = −1. Size effects and the stress gradient effective under torsion loading are considered to explain smaller crack initiating inclusions found in torsion ultrasonic fatigue tests.

Torsion pendulum measurement method for time varying moment of inertia

Abstract: A time-varying moment of inertia (MOI) measurement model based on the torsion pendulum method is studied. According to the principle of dynamics, the motion equation of torsion pendulum with single degree of freedom is established by using the second Lagrange equation modeling, which indicates the time-varying MOI can be obtained by the instantaneous undamped natural frequency of torsional pendulum motion and the torsion bar coefficient. Among them, the instantaneous frequency is calculated by the instantaneous angular frequency and envelope signal of angular displacement using Hilbert transform. The torsion bar coefficient is calibrated by the standard weight with known MOI, and has been compensated by temperature. Based on air floating turntable, the torsion pendulum system is built to measure the MOI of fine sand in the funnel, which can minimize the effects of mechanical friction. The relative error of MOI between calculating the result and measuring the value is less than 0.65%, which verifies the effectiveness of the proposed time varying temperature compensation method.

A novel design of torsion spring-connected non-linear stiffness actuator based on cam mechanism

Abstract: The non-linear stiffness actuator (NSA) is a kind of compliant joint with variable stiffness that is necessary for human-machine collaboration and has received extensive research attention. This academic work presents the principle of a torsion spring-connected non-linear stiffness actuator (TSNSA), a NSA suitable for implementing revolute motions, which contrasts with existing NSAs that often have bulky mechanisms and are affected by a limited range of movement. It has a split sleeve, disc springs and cam mechanisms (CMs) that when correctly configured, can passively and actively adjust stiffness, where the speed of stiffness regulation can be effectively improved. The mathematical model of a split sleeve inserted into a torsion spring is designed to analyze the behavior of mechanical components. Further, a detailed CM profile has been designed to obtain the desired non-linear stiffness. Its theoretical analysis includes numerical simulations with results that are consistent with the desired deflection-torque profile.

Optimal design of rear-seat restraint system based on new safety seat during frontal collisions

Abstract: Owing to the narrow rear-row space of compact cars, the head of a rear-seat occupant can easily hit against the headrest or the seatback of the front seat in frontal collisions, thereby causing injuries to the occupant. A prototype design of a new safety seat is proposed to increase the safety of rear-seat occupants. The aim of this study is to investigate the protective effects of the new safety seat and further optimise the rear-seat restraint system in 100% and 40% overlapped frontal collisions. First, a simulation model of the restraint system is developed and validated. Second, the effects of the original seat and the new safety seats with different torsional stiffness of the torsion spring on the injuries to a female rear-seat occupant are compared. Finally, the design parameters of the rear-seat restraint system are optimised globally to minimise injuries to the female rear-seat occupant. Compared with the original seat case, the head injury criterion HIC15 and thorax 3 ms resultant acceleration T3MS of the female rear-seat occupant in the new safety seat case reduce, whereas the neck injury criterion Nij increases. When the torsional stiffness of the torsion spring decreases gradually, HIC15 and T3MS decrease. The optimum torsional stiffness of the torsion spring determined via analysis is 10 N m/°. The optimal combination of the design parameters of the rear-seat restraint system is obtained. After optimisation, for the 100% overlapped collision, HIC15 and T3MS decrease by 40.20% and 5.75%, respectively, Nij decreases by 35.94% and the peak left and right femur forces (FL and FR, respectively) decrease by 9.65% and 12.26%, respectively. For the 40% overlapped collision, HIC15 and T3MS reduce by 39.92% and 11.64%, respectively, and Nij, FL and FR decrease by 8.89%, 7.50% and 6.09%, respectively.

Stable Torsion Torque Control Based on Friction-Backlash Analogy for Two-Inertia Systems with Backlash

Abstract: Torsion torque control (TTC) has been studied in applications ranging from industrial robots to electric vehicles. However, its performance is severely compromised when there is joint backlash, causing limit cycles and inducing unstable behavior. This study proposes a stable TTC scheme for two-inertia systems with joint backlash based on an analogy between static friction and backlash phenomena. First, a transformation of the joint torsion dynamics into a first-order system is applied, and a proportional torsion torque controller is proposed. Then, an analogy between the transformed joint torsion dynamics with backlash and one-mass systems with static friction is established. Based on this analogy, a combination of a switched disturbance observer and an impact torque suppression controller is proposed, ensuring rapid control over backlash and stable reengagement with reduced gear collision impact. The effectiveness of the proposed method is verified through simulation and experimental results.

Lateral Dynamic Simulation of a Bus under Variable Conditions of Camber and Curvature Radius

Abstract: The objective of this paper is to describe a model for the simulation of the lateral dynamics of a vehicle, specifically buses, under variable trajectory conditions, such as camber and radius of curvature; in addition, a variable speed is added as a simulation parameter. The objective of this study is the prevention of vehicle rollover and sideslip. An 8 degrees of freedom model was developed, considering a front and a rear section of the bus with its respective suspension system, and both sections have been connected by a torsion spring that emulates the torsional stiffness of the vehicle chassis. A Panhard bar is also added at the rear as an additional element to the suspension and the behavior of the bus when it is added is analyzed. This model also allows the evaluation of the force on each suspension component, which allows for future controllability of the active suspension components. The results show the dynamic behavior of the vehicle, and some indicators are introduced to show the possible sideslip or rollover. As a conclusion, the influence of the road parameters on the dynamic behavior of the bus and the effect of the Panhard bar on the dynamic behavior of the bus can be pointed out.

Measuring and adjusting the distance between the center of mass and optical center of a free-falling body in an absolute gravimeter

Abstract: In an absolute gravimeter based on optical interferometry, the rotation of a falling body leads to inaccurate gravity measurement. By arranging the center of mass (COM) of the falling body together with its optical center (OC), the rotation error can be minimized rapidly. An optical measurement system with a two-stage pendulum structure is proposed to measure the distance between the COM and the OC of the falling body. The displacement of the OC is measured by an orthogonal interferometer while the falling body twists around the torsion wire, and the rotation angle of the falling body is measured synchronously by a photoelectric autocollimator. It is proved that a twist of the falling body by 2.4 degrees leads to a significant offset of about 0.2 nm along the direction of the laser beam. This results in a limit error of the measurement of the distance between the OC and the COM less than 1 μm. Thus, the rotation error in absolute gravity measurement is reduced to 0.07 μGal.

Design and performance of a nano-Newton torsion balance.

Abstract: Here, we present a novel torsion balance with a torsional spring that can reach a resolution in the nano-Newton range while allowing for a total experimental weight of 2 kg. The balance uses an off-the-shelf electromagnetic actuator, which was calibrated. The oscillation of the balance is damped using an adaptable eddy-current brake to fine-tune the damping factor. Experiments and electronics are controlled and powered through four coaxial liquid contacts. The balance is shown to be highly linear between 0.01 and 300 μN. After an automated post-processing, the noise of a measurement was 1.0 nN, and an applied force of 10 nN had a calculated error of 11.9%.

Design of Hybrid Fully-Actuated and Self-Adaptive Mechanism for Anthropomorphic Robotic Finger

Abstract: Prior research on robotic hands predominantly focuses either on high degree of freedom of fully-actuated fingers to replicate a real human hand or on creative designs of under-actuated fingers to make a self-adaptive motion. However, in most cases, fully-actuated fingers encounter difficulty in grasping unstructured objects while under-actuated fingers experience problems in performing precise grasping motions. To deal with any possible scenarios, this study presents a novel design of an anthropomorphic robotic finger that combines both advantages – fully-actuated and self-adaptive grasping (aka FASA) modes – at once. Actuated by tendons, the FASA finger can grasp objects adaptively and achieve accurate angle positioning with the same mechanical design which is introduced in this paper. Based on the kinetostatic analysis, the guideline for the selection of torsion spring is proposed to fulfill the functions of the FASA finger and attain the optimal design of torsional stiffness which manifests itself in a series of tests on different configurations of torsion spring. Likewise, the kinematic analysis for the fully-actuated mode is given as the proof that two joints can move independently by controlling two motors. Ultimately, experimental results again reflect the capability of the FASA finger to perform not only independent precision angle motion but also self-adaptive grasping motion without any change in mechanical structure.

Platform Design and Preliminary Test Result of an Insect-like Flapping MAV with Direct Motor-Driven Resonant Wings Utilizing Extension Springs

Abstract: In this paper, we propose a platform for an insect-like flapping winged micro aerial vehicle with a resonant wing-driving system using extension springs (FMAVRES). The resonant wing-driving system is constructed using an extension spring instead of the conventional helical or torsion spring. The extension spring can be mounted more easily, compared with a torsion spring. Furthermore, the proposed resonant driving system has better endurance compared with systems with torsion springs. Using a prototype FMAVRES, it was found that torques generated for roll, pitch, and yaw control are linear to control input signals. Considering transient responses, each torque response as an actuator is modelled as a simple first-order system. Roll, pitch, and yaw control commands affect each other. They should be compensated in a closed loop controller design. Total weight of the prototype FMAVRES is 17.92 g while the lift force of it is 21.3 gf with 80% throttle input. Thus, it is expected that the new platform of FMAVRES could be used effectively to develop simple and robust flapping MAVs.

10.1119/10.0006965.1

Abstract: 10.1119/10.0006965.1The dynamics of a swinging payload suspended from a stationary crane, an unwanted phenomenon on a construction site, can be described as a simple pendulum. However, an experienced crane operator can deliver a swinging payload and have it stop dead on target in a finite amount of time by carefully modulating the speed of the trolley. Generally, a series of precisely timed stop and go movements of the trolley are implemented to damp out the kinetic energy of the simple harmonic oscillator. Here, this mysterious crane operator's trick will be revealed and ultimately generalized to capture the case where the load is initially swinging. Finally, this modus operandi is applied to a torsion balance used to measure G, the universal gravitational constant responsible for the swinging of the crane's payload in the first place.

Vibration control of very large and lightweight structures mounted on a four-legged platform

Abstract: Large lightweight slender links mounted on mobile robots enlarge their workspace. This work presents one of these robots that has been endowed with 4 legs to improve its static stability—which is put at risk by the large link—and help in the positioning of the link. The efficiency of this system depends on its accuracy in positioning and orientating the end-effector placed at the tip of the link, which is compromised by vibrations that appear in the link during the movement and permanent deflections caused by gravity. A relatively simple control scheme that combines a feedback control of the pose of the mobile platform with a feedforward term that orientates the link is proposed. It uses three legs as actuators; and feeds back measurements of the extensions of the three legs and the orientation of the platform given by an inertial sensor placed in the upper part of the mobile platform. Based on the flatness property of a simplified dynamic model of the link, its dynamics can be easily inverted, being used to implement the proposed feedforward term. Since such feedforward term is used, extra sensors to measure the deflection of the link are not needed, and since the legs are used to move the link, extra actuators mounted on the link are neither needed. All this allows us to reduce the weight and the volume of the payload carried by the mobile platform. Results obtained through a finite elements software and experimentation of the real prototype show the good performance attained with the proposed control strategy.

Design of a Foldable Robot Arm for a Hybrid Robot Manipulator

Abstract: This paper presents the design of a foldable robot arm(FRA) actuated by wires and springs for a hybrid robot manipulator. The arm can be folded actively and extended passively. Folding movement is done actively by pulling wires by a motor and extending is done passively by torsional springs. Selection of torsion springs for each joint is analyzed. Arm pulling mechanism is designed by winding wires. A gear mechanism is designed for one motor to wind all of three cables simultaneously. Actual position control performance is demonstrated by empirical studies to show the feasibility.

Effects of the angle between the spring arm on spring characteristics on the single coiled torsion spring using Ti-Ni shape memory alloy wire.

Abstract: We have been investigated one-coil torsion springs using shape memory alloy (SMA) wire for application to welfare equipment (for example, lower limb orthoses), because one-coil torsion springs using SMA wire have small size and large displacement. It is known that the spring properties of a torsion spring depend on the shape of the spring, and design calculation method for springs made of normal metals have already been established. However, SMA has different characteristics from normal metals, and it is difficult to apply conventional design calculation methods. Therefore, we fabricated several SMA torsion springs with different the angle between the spring arm and investigated the effects of shape of the spring on the spring characteristics of SMA torsion springs by spring characteristic tests and fatigue tests. The experimental results show that increasing the angle between the spring arm improves the fatigue life of the SMA torsion springs but the spring generating force decreased. On the other hand, the functional degradation characteristics are independent of the angle between the spring arms.

Kalker’s coefficient c11 and its influence on the damping and the retuning of a mechanical drive torsion system of a railway vehicle

Abstract: Within the research of electromagnetically excited torsion oscillations in the mechanical part of traction drive systems of modern railway vehicles, which has been realized at the Faculty of mechanical engineering at the CTU in Prague, there are two separate simulation models in use. The basic calculation model, which is utilized to gain basic characteristics of the torsion system as natural frequencies and natural modes of oscillations. And the complex simulation model, which simulates a drive of the vehicle. This contribution is focused on the basic calculation model, which has been built in MATLAB. This model in its first version did not apply the contact between wheels and rails. It was necessary to find out, if this simplification is relevant with respect to subsequent simulations within the complex simulation model and its results. Therefore, the contact interaction as a traction force in longitudinal direction in the wheel-rail contact was realized via the Kalker’s linear theory. This article deals with the comparison between models with and without the implementation of the wheel-rail contact and its influence on the damping within the torsion system and retuning of the torsion system.

Additive Manufacturing of Compliant Mechanisms for Deployable Aerospace Structures

Abstract: In the past 10 years, complex deployable structures have become common on CubeSats and large-scale spacecraft. As new missions are pursued, there is an increased need for more mass and volume efficient deployments. Over the same period, metal additive manufacturing (AM) has enabled new forms of spaceflight hardware. However, AM of compliant mechanisms has not been fully leveraged for deployable aerospace structures. The Surface Water Ocean Topography and NASA-ISRO Synthetic Aperture Radar mission missions launching in 2022 both utilize large deployable masts. Each mast deployment is driven by numerous spring and damper mechanisms. Because of volume constraints, the spring mechanisms designed utilize high aspect ratio rectangular cross section torsion springs that represent the state of the art of manufacturing. This extreme spring design resulted in manufacturing difficulties and hardware failures during ground mechanism testing. Upon re-examining the mechanism design, AM enables torque performance, mass, and complexity improvements. AM allows for torsion spring cross sections not otherwise possible with traditional spring manufacturing methods. Prototype springs of various cross sections were printed in maraging steel and tested. Results confirmed design analysis, and doubling of the spring constant was achieved when compared to the traditional springs. The use of AM also allows springs to be built monolithically with surrounding structure. Design, manufacturing, and test findings will be discussed along with future implications for deployable aerospace structures.