Evaluating the Efficacy of Parallel Elastic Actuators on High-Speed, Variable Stiffness Running

2020 ◽  
Author(s):  
John V. Nicholson ◽  
Sean Gart ◽  
Jason Pusey ◽  
Jonathan E. Clark
Keyword(s):  
High Speed ◽  
Variable Stiffness

The Double Pendulum Model and Nonlinear Dynamic Characteristics of the Pantograph of High-Speed Train

2013 ◽  
Vol 275-277 ◽  
pp. 767-770
Author(s):  
Hua Li ◽  
Shu Qian Cao
Keyword(s):  
Numerical Simulation ◽  
Dynamic Characteristics ◽  
High Speed ◽  
Lagrange Equation ◽  
Variable Stiffness ◽  
Nonlinear Damping ◽  
Double Pendulum ◽  
High Speed Train ◽  
Pendulum Model ◽  
Damping Torque

In this paper, the double pendulum model of the pantograph was developed, in which a square angular velocity damping torque was used to describe the nonlinear damping torque of the hydraulic vibration damper, and the catenary was described as a variable stiffness spring. Considering the nonlinear factors caused by hydraulic damping and the interaction between the catenary and the pantograph, the motion differential equations based on the double pendulum model were established in Lagrange equation, and then were simplified. The dynamic characteristics were analyzed through numerical simulation. The result of numerical simulation shows that there are quasi-periodic motion and chaos in the system, which are both affected by the pendulum length ratio. The results are helpful to research the dynamic characteristics of the pantograph of high-speed train.

Performing Energy-Efficient Pick-and-Place Motions for High-Speed Robots by using Variable Stiffness Springs

2021 ◽  
pp. 1-12
Author(s):  
Rafael Balderas Hill ◽  
Sebastien Briot ◽  
Abdelhamid Chriette ◽  
Philippe Martinet
Keyword(s):  
High Speed ◽  
Variable Stiffness ◽  
Robot Dynamics ◽  
Suggested Approach ◽  
High Speeds ◽  
Pick And Place ◽  
Operational Phase ◽  
Parallel Configuration ◽  
Braking Phase ◽  
Displacement Phase

Abstract Typically, for pick-and-place robots operating at high speeds, an enormous amount of energy is lost during the robot braking phase. This is due to the fact that, during such operational phase, most of the energy is dissipated as heat on the braking resistances of the motor drivers. In order to increase the energy-efficiency during the high-speed pick-and-place cycles, this paper investigates the use of variable stiffness springs (VSS) in parallel configuration with the motors. These springs store the energy during the braking phase, instead of dissipating it. The energy is then released to actuate the robot in a next displacement phase. This design approach is combined with a motion generator which seeks to optimize trajectories for input torques reduction (and thus of energy consumption), through solving a boundary value problem (BVP) based on the robot dynamics. Experimental results of the suggested approach on a five-bar mechanism show the drastic reduction of input torques, and therefore of energetic losses.

Hybrid modeling and analysis of multidirectional variable stiffness of the linear rolling guideway under combined loads

2020 ◽  
Vol 234 (13) ◽  
pp. 2716-2727
Author(s):  
Lei Yang ◽  
Lei Wang ◽  
Wanhua Zhao
Keyword(s):  
Machine Tool ◽  
High Speed ◽  
Complex Loading ◽  
Variable Stiffness ◽  
Time Varying ◽  
Modeling And Analysis ◽  
Combined Loads ◽  
Machine Tool Structure ◽  
High Feed ◽  
Stiffness Characteristics

In the working process of high-speed multiaxis machine tools, inertial loads due to high feed acceleration and time-varying gravity loads due to changing configuration of multiaxis structure result in time-varying complex loads applied to linear rolling guideway. Existing models cannot efficiently represent the effect of complex loads on multidirectional stiffness variation of linear rolling guideway. In this paper, a hybrid model of multidirectional stiffness of linear rolling guideway and the solving algorithm are proposed. The complex loading conditions of linear rolling guideway in high-speed multiaxis machine tool structure are considered. And contact flexibilities between rolling balls and grooves are modeled with the effect of elastic deformations of runner block and rail. The proposed model can calculate the multidirectional stiffness with high accuracy. Meanwhile the differences between the stiffness characteristics in different directions are represented correctly. The variations of multidirectional stiffness of linear rolling guideway under time-varying combined loads are analyzed. This study provides an effective way to comprehensively evaluate the stiffness characteristics of linear rolling guideway which can contribute to the dynamic analysis and active design of high-speed machine tool structure.

scholarly journals Multi-body Dynamic Modelling and Error Analysis of Planar Flexible Multilink Mechanism Considering Clearance and Thermal-mechanical Coupling Effect of the Crankshaft-bearing Structure

2021 ◽  
Author(s):  
Hongfan Long ◽  
Zhao Han ◽  
Shuyun Jiang ◽  
Enlai Zheng ◽  
Yongnian Zhang ◽  
...  
Keyword(s):  
Dynamic Model ◽  
High Speed ◽  
Coupling Effect ◽  
Dynamic Modelling ◽  
Variable Stiffness ◽  
Position Error ◽  
Mechanical Coupling ◽  
Spindle Bearing ◽  
Bearing Structure ◽  
Bearing System

Abstract In order to study the dynamic position accuracy of bottom dead point (BDP) for multilink high-speed precision presses (MHSPPs), it’s essential to develop a dynamic model of planar multilink mechanism with clearance and spindle-bearing structure. Traditional models always neglect the effect of thermal characteristics of spindle-bearing structure, which reduces the prediction accuracy of dynamic model for multilink transmission mechanisms. To overcome the shortcomings of the previous models, a thermal network model (TNM) of the crankshaft-bearing system is established firstly considering the effects of thermal contact resistance and variable stiffness of bearing concerning the temperature rise. Then, dynamic model of the crankshaft-bearing system is built through the finite element method, which includes rigid disk, Timoshenko beam and quasi-statics model of ACBB. On this basis, an improved dynamic model of planar flexible multilink mechanism with clearance considering the thermal-mechanical coupling effect of the crankshaft-bearing structure is developed and the corresponding dynamic error dimension chain between slider and crankshaft is constructed in this work. Compared to the simulation from traditional models, the simulated slider’s BPD position error from the improved model agrees better with experimental data, which verifies the correctness of the proposed model. It’s demonstrated that the punching force and thermally induced variable stiffness of bearing lead to a significant increase of slider’s BDP position error, which reduces the machining precision of MHSPP. Furthermore, the influence of crankshaft speed, contact angle of bearing and clearance size on the slider’s BDP position error is also investigated.

scholarly journals Increasing Energy Efficiency of High-Speed Parallel Robots by Using Variable Stiffness Springs and Optimal Motion Generation

2018 ◽  
Author(s):  
Rafael Balderas Hill ◽  
Sébastien Briot ◽  
Abdelhamid Chriette ◽  
Philippe Martinet
Keyword(s):  
Energy Efficiency ◽  
Energy Consumption ◽  
High Speed ◽  
Variable Stiffness ◽  
Parallel Robots ◽  
Motion Generation ◽  
Suggested Approach ◽  
Pick And Place ◽  
Lightweight Structure ◽  
Parallel Configuration

The classical approach to decrease the energy consumption of high-speed robots is by lowering the moving elements mass in order to have a lightweight structure. Even if this allows reducing the energy consumed, the lightweight architecture affects the robot stiffness, worsening the accuracy of the mechanism. Recently, variable stiffness actuators (VSAs) have been used in order to reduce the energy consumption of high-speed pick-and-place robots. The idea is to smartly tune online the stiffness of VSA springs so that the robot is put in near a resonance mode, thus considerably decreasing the energy consumption during fast pseudo-periodic pick-and-place motions. However, the serial configuration of springs and motors in the VSA leads to uncontrolled robot deflections at high-speeds and, thus, to a poor positioning accuracy of its end-effector. In order to avoid these drawbacks and to increase the energy efficiency while ensuring the accuracy, this paper proposes the use of parallel arrangement of variable stiffness springs (VSS) and motors, combined with an energy-based optimal trajectory planner. The VSS are used as energy storage for carrying out the reduction of the energy consumption and their parallel configuration with the motors ensure the load balancing at high-speed without losing the accuracy of the robot. Simulations of the suggested approach on a five-bar mechanism are performed and show the increase on energy efficiency.

Modeling and Simulation of Nonlinear Combination Disc-Spring Vibration Isolator for High-Speed Press

2011 ◽  
Vol 211-212 ◽  
pp. 40-47 ◽  
Author(s):  
En Lai Zheng ◽  
Fang Jia ◽  
Zhi Sheng Zhang ◽  
Jin Fei Shi
Keyword(s):  
High Speed ◽  
Damping Ratio ◽  
Variable Stiffness ◽  
Harmonic Excitation ◽  
Adaptive Performance ◽  
Vibration Isolator ◽  
Different Types ◽  
Solid Foundation ◽  
The Mathematical Model ◽  
Disc Spring

With its variable stiffness, capability to provide friction damping by itself, and space-based adaptive performance, the disc spring, by replacing the cylindrical helical spring extensively, has found wide application in fields like aerospace, metallurgy, architecture, machinery and so on. For the nonlinear combination disc-spring vibration isolator, the mathematical model is established in this study on the basis of classical disc spring theories. The simulation results of the combination vibration isolator under simple harmonic excitation and the effects of damping ratio and different types of load on the vibration isolator are explored in depth, the findings of which help to lay a solid foundation for parameterization and serialization of the nonlinear combination disc-spring vibration isolator.

scholarly journals Developing a Strategy to Improve Handling Behaviors of a Medium-Size Electric Bus Using Active Anti-Roll Bar

Symmetry ◽  
2020 ◽  
Vol 12 (8) ◽  
pp. 1334
Author(s):  
Hsiu-Ying Hwang ◽  
Tian-Syung Lan ◽  
Jia-Shiun Chen
Keyword(s):  
Automobile Industry ◽  
Control Strategy ◽  
High Speed ◽  
Variable Stiffness ◽  
Vehicle Body ◽  
Medium Size ◽  
Handling Characteristics ◽  
Electric Bus ◽  
Body Dynamic ◽  
Input Test

Electric vehicles are a major trend in research and development in the automobile industry. A vehicle’s handling ability is changed when the structure of the power system is altered, which is more obvious in medium-sized buses with higher load and a longer body whose body stiffness is relatively less stiff. In this context, flexible multi-body dynamic modeling, instead of rigid body modeling, is used to reflect the stiffness effects of the vehicle body and chassis systems. A control strategy is developed with an active variable stiffness anti-roll bar to improve vehicle handling characteristics by using the flexible body dynamic simulation with consideration of the step and single sinusoidal steering input tests. Through simulation, it was learned that the proposed control strategy could reduce the time of stabilization by 54.08% and suppress undesired handling behaviors in the step steering input test. Moreover, at high speed, the original unsteady condition became stabilized with little sacrifice in yaw velocity. In the single sinusoidal steering input test, the time of stabilization could be reduced by 8.43% and with 14.6% less yaw angle changes in the improved design. The overall handling was improved.

Microfabrication research at the National Submicron Facility

1983 ◽  
Vol 41 ◽  
pp. 86-89
Author(s):  
E.D. Wolf
Keyword(s):  
Integrated Circuits ◽  
Particle Physics ◽  
High Speed ◽  
New Technology ◽  
High Energy ◽  
High Energy Particle ◽  
New Science ◽  
Wide Range ◽  
Intermediate Domain ◽  
Circuit Function

Most microelectronics devices and circuits operate faster, consume less power, execute more functions and cost less per circuit function when the feature-sizes internal to the devices and circuits are made smaller. This is part of the stimulus for the Very High-Speed Integrated Circuits (VHSIC) program. There is also a need for smaller, more sensitive sensors in a wide range of disciplines that includes electrochemistry, neurophysiology and ultra-high pressure solid state research. There is often fundamental new science (and sometimes new technology) to be revealed (and used) when a basic parameter such as size is extended to new dimensions, as is evident at the two extremes of smallness and largeness, high energy particle physics and cosmology, respectively. However, there is also a very important intermediate domain of size that spans from the diameter of a small cluster of atoms up to near one micrometer which may also have just as profound effects on society as “big” physics.

Vacuum System to Minimize the Specimen Contamination of High-Performance EM

1977 ◽  
Vol 35 ◽  
pp. 68-69
Author(s):  
N. Yoshimura ◽  
K. Shirota ◽  
T. Etoh
Keyword(s):  
Electron Microscope ◽  
High Speed ◽  
High Performance ◽  
High Vacuum ◽  
Vacuum System ◽  
Pump System ◽  
Pumping System ◽  
Diffusion Pump ◽  
Almost All ◽  
Cascade Type

One of the most important requirements for a high-performance EM, especially an analytical EM using a fine beam probe, is to prevent specimen contamination by providing a clean high vacuum in the vicinity of the specimen. However, in almost all commercial EMs, the pressure in the vicinity of the specimen under observation is usually more than ten times higher than the pressure measured at the punping line. The EM column inevitably requires the use of greased Viton O-rings for fine movement, and specimens and films need to be exchanged frequently and several attachments may also be exchanged. For these reasons, a high speed pumping system, as well as a clean vacuum system, is now required. A newly developed electron microscope, the JEM-100CX features clean high vacuum in the vicinity of the specimen, realized by the use of a CASCADE type diffusion pump system which has been essentially improved over its predeces- sorD employed on the JEM-100C.

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