Design Parameter Sensitivity for a Mountain Bike Rear Shock

2006 ◽  
Author(s):  
Robin C. Redfield
Keyword(s):  
High Speed ◽  
Current Trend ◽  
Graph Model ◽  
Bond Graph ◽  
Design Parameters ◽  
Mountain Biking ◽  
Mountain Bike ◽  
Suspension Systems ◽  
Experimental Response ◽  
And Performance

As the sport of mountain biking matures, equipment continually evolves to afford better biking performance, enjoyment, and safety. In the arena of suspension systems, mountain bikes have moved from rigid suspensions with large, knobby tires to front fork suspensions, and finally full suspensions. Suspensions have gone from elastomeric compliance to air and coil springs with adjustable travel. Damping has progressed from fixed to adjustable rebound, compression, and lockout. The current trend is to add force or frequency dependent damping to minimize response of a suspension from pedal input. A bond graph model of a mountain bike rear shock is developed incorporating adjustable rebound and low-speed compression, high-speed compression, and rider controlled, compression damping initiation. An air shock with a nitrogen charge is modeled with velocity across the shock as input. The dynamic equations that come from the bond graph are simulated to predict key forces, pressures, and flow-rates. Experimental response (forces, displacements, and velocities) of the modeled shock is acquired subject to periodic velocity inputs. The experimental response is used to tune the design parameters of the model and for validation. A sensitivity analysis is then undertaken to determine how significant key design parameters are to the performance of the shock. Once validated, the model is used to better understand the physics and performance of the mountain bike shock and to relate performance to the requirements of expert mountain bikers.

Research and Development of Minitype Twin-Bladed Air Turbine

2009 ◽  
Author(s):  
Shih-Chun Wang ◽  
Kuang-Yuh Huang
Keyword(s):  
High Speed ◽  
Turbine Blades ◽  
Design Parameters ◽  
Operational Parameters ◽  
Micro Fabrication ◽  
Air Turbine ◽  
Speed Performance ◽  
Operational Energy ◽  
And Performance

In order to improve the machining efficiency of ultra-precision and micro fabrication technology, a high speed spindle is essential for the minitype tools widely applied in systems such as PCB drilling machines, micro fabrication machines, dental handpieces, etc. To realize the high speed performance, the air driven turbine is verified to be more feasible than the electromagnetic actuator. Furthermore, the operational efficiency and quality of the high speed spindle are significantly influenced by the turbine blades and the bearings respectively. Through detailed configurational studies and performance analyses on diverse minitype turbine blades, we have derived the efficiency- and quality-influential parameters. And based on optimization results, we have developed a novel type of twin bladed air turbine (TB-air turbine), which consists of two parallel blades with an angular offset. The offseted twin blades can efficiently and smoothly transform pneumatic energy into rotational energy. Therefore, steady driving force and less dynamic unbalance are able to be easily achieved for reducing nervous disturbances such as vibration, noise, and wear. By applying finite element analytical method, the operational performances and quality of the new developed twin bladed air turbine such as rotational speed, torque, vibration and noise were analyzed for comprehending influences of the design parameters and the operational parameters. While the inlet angle, the blade shape and its geometric parameters are the dominant design parameters; the inlet pressure and mass flow rate, and the outlet pressure are the main operational parameters. Through the turbine blades, the pneumatic energy will be transformed into operational energy in form of the flow field and the pressure distribution and the energy loss in form of turbulence. Also by integrating knowledge of production technology, a neat design of the turbine blades suitable for automatic manufacturing process is developed. And furthermore, through an elaborate layout of the flow guiding, a minimum rotational runout can be effectively achieved without any complicate and costly dynamic balancing process. Consequently, it has significantly depressed the stream noise and raised the operation lifetime of bearings. According to our experimental verification, the vibration and the stream noise of our TB-air turbines are 60% and 50% lower than traditional counterparts respectively. Our developed minitype spindle with novel TB-air turbine can efficiently realize high speed rotation with high torque, less vibration and less noise.

An Analysis of Rigid Sidewall Surface Effect Craft for High-Speed Personnel Transportation

1970 ◽  
Vol 7 (01) ◽  
pp. 55-68
Author(s):  
Eugene R. Miller
Keyword(s):  
High Speed ◽  
Surface Effect ◽  
Transportation Cost ◽  
Total Power ◽  
Design Parameters ◽  
Economic Criterion ◽  
Calm Water ◽  
And Performance ◽  
Commercial Applications ◽  
Sidewall Surface

A number of commercial applications have been proposed for rigid sidewall surface effect craft. The transport of crews to offshore operations is an application which is well-suited to the immediate use of moderately sized craft of this type. Because the crews are paid while they are in transit, high speeds are required to minimize the total transportation costs. The characteristics and performance of rigid sidewall surface effect craft suitable for crew transport operations are developed. The major design parameters studied include pay-load, total power, and machinery type. Performance estimates are made for operations in both calm water and waves. An economic model is developed to simulate crewboat operations. Cost estimates are based on current technology and price levels. The total unit transportation cost is used as the economic criterion in the determination of the relative merit of various craft. For the purpose of comparison the characteristics and costs of planing hull crewboats for the same mission are developed. It is concluded that rigid sidewall surface effect craft have the potential of being economically superior to planing boats for crew transport operations.

Challenges in Controlling Active Suspensions for High-Speed Off-Road Vehicles

2000 ◽  
Author(s):  
Keyanoush Efatpenah ◽  
Joseph H. Beno ◽  
Steven P. Nichols ◽  
Raul G. Longoria
Keyword(s):  
High Frequency ◽  
High Speed ◽  
Graph Model ◽  
Field Tests ◽  
Active Suspension ◽  
Bond Graph ◽  
Ride Quality ◽  
Road Vehicles ◽  
High Attenuation ◽  
Challenge Control

Abstract The literature includes several useful control approaches for active suspension of off-road vehicles. Some of these approaches rely on preview (look-ahead) of the terrain, while others require knowledge of certain variables that have proven difficult to measure reliably for off-road applications. Sky-hook damping is a widely accepted active suspension control law. Experimental and analytical research with active suspension systems for on- and off-road vehicles have successfully demonstrated substantial improvement in ride quality. The paper begins with a short discussion of a bond graph model of an off-road vehicle equipped with an electromechanical active suspension. The bond graph model facilitated the development of a SIMULINK model used for simulation. Comparison of simulation and experimental results has validated the model, especially for high-frequency terrain inputs. The paper examines how specific examples of off-road conditions challenge control algorithm development. Simulations demonstrate that sky-hook damping (without modification) with gains selected for very high attenuation of high-frequency terrain disturbances do not perform well in response to large displacement, low-frequency inputs and cause suspension bottoming out. By modifying the basic control laws and selecting appropriate controller gains, excellent ride performance was achieved in recent field tests under general terrain conditions.

scholarly journals Multi-objective constrained Bayesian optimization for structural design

2020 ◽  
Author(s):  
Alexandre Mathern ◽  
Olof Skogby Steinholtz ◽  
Anders Sjöberg ◽  
Magnus Önnheim ◽  
Kristine Ek ◽  
...  
Keyword(s):  
Structural Design ◽  
Current Trend ◽  
Bayesian Optimization ◽  
Design Parameters ◽  
Multi Objective Optimization ◽  
Structural Concrete ◽  
Design Problems ◽  
Multi Objective ◽  
Trade Offs ◽  
And Performance

Abstract The planning and design of buildings and civil engineering concrete structures constitutes a complex problem subject to constraints, for instance, limit state constraints from design codes, evaluated by expensive computations such as finite element (FE) simulations. Traditionally, the focus has been on minimizing costs exclusively, while the current trend calls for good trade-offs of multiple criteria such as sustainability, buildability, and performance, which can typically be computed cheaply from the design parameters. Multi-objective methods can provide more relevant design strategies to find such trade-offs. However, the potential of multi-objective optimization methods remains unexploited in structural concrete design practice, as the expensiveness of structural design problems severely limits the scope of applicable algorithms. Bayesian optimization has emerged as an efficient approach to optimizing expensive functions, but it has not been, to the best of our knowledge, applied to constrained multi-objective optimization of structural concrete design problems. In this work, we develop a Bayesian optimization framework explicitly exploiting the features inherent to structural design problems, that is, expensive constraints and cheap objectives. The framework is evaluated on a generic case of structural design of a reinforced concrete (RC) beam, taking into account sustainability, buildability, and performance objectives, and is benchmarked against the well-known Non-dominated Sorting Genetic Algorithm II (NSGA-II) and a random search procedure. The results show that the Bayesian algorithm performs considerably better in terms of rate-of-improvement, final solution quality, and variance across repeated runs, which suggests it is well-suited for multi-objective constrained optimization problems in structural design.

Hybrid-model-based stiffness analysis of a three-revolute-prismatic-spherical parallel kinematic machine

2016 ◽  
Vol 231 (14) ◽  
pp. 2561-2576 ◽  
Author(s):  
Jun Zhang ◽  
Yan Q Zhao ◽  
Hai W Luo
Keyword(s):  
High Speed ◽  
Experimental Tests ◽  
Design Parameters ◽  
Parallel Kinematic Machine ◽  
Modeling Methodology ◽  
Parallel Kinematic ◽  
Stiffness Characteristics ◽  
And Performance ◽  
High Dynamics ◽  
Spring Constants

A three-revolute-prismatic-spherical parallel kinematic machine is proposed as an alternative solution for high-speed machining tool due to its high rigidity and high dynamics. Considering the parallel kinematic machine module as a typical compliant parallel mechanism, whose three limb assemblages have bending, extending and torsional deflections, this article proposes a hybrid modeling methodology to establish an analytical stiffness model for the three-revolute-prismatic-spherical device. The developed analytical model is further used to evaluate the stiffness mapping of the three-revolute-prismatic-spherical module over a given work plane which is then validated by experimental tests. The simulations and experiments indicate that the present hybrid methodology can predict the three-revolute-prismatic-spherical parallel kinematic machine’s stiffness in a quick and accurate manner. The solution for eigenvalue problem of the stiffness matrix leads to the stiffness characteristics of the parallel module including eigenstiffnesses and the corresponding eigenscrews as well as the equivalent screw spring constants. Based on the eigenscrew decomposition, the parallel kinematic machine is physically interpreted as a rigid platform suspending by six screw springs. The minimum, maximum and average of the screw spring constants are chosen as indices to assess the three-revolute-prismatic-spherical parallel kinematic machine’s stiffness performance. The distributions of the proposed indices throughout the workspace reveal a strong dependency on the mechanism’s configurations. At the final stage, the effects of some design parameters on system stiffness characteristics are investigated with the purpose of providing useful information for the conceptual design and performance improvement of the parallel kinematic machine.

Planar, Large Excursion Bond Graph Model for Full Suspension Mountain Biking

2005 ◽  
Author(s):  
Robin C. Redfield
Keyword(s):  
Initial Conditions ◽  
Contact Point ◽  
Graph Model ◽  
Bond Graph ◽  
Mountain Bike ◽  
Dynamic Interactions ◽  
Dynamics And Control ◽  
Ground Profile ◽  
And Control ◽  
Main Frame

A bond graph model of a fully suspended mountain bike and non-seated rider is created to develop predictions for the performance of mountain bikes during large excursion maneuvers such as drops, jumps, crashes, and rough terrain riding. The model assumes planar dynamics, a single pivot full suspension bicycle, and a rigid-body rider suspended from the bicycle. The main frame, front fork, rear triangle, two wheels, and rider are modeled as separate bodies interconnected at the main pivot, telescoping fork, pedals, handlebars, and axles. Suspensions are between the main frame and front fork, main frame and rear triangle, handlebars and rider (arms) and pedals and rider (legs). An algorithm is used to allow tracking of a virtual tire-ground contact point for events that separate the wheels from the ground. Significant excursions of motion are allowed to model major slope changes, separations from the ground, and large rotational events (endos). The bond graph approach allows kinematics to drive the significant dynamic interactions with the effort (force and torque) relationships being derived for “free”. Simulations of a ground profile with a rise followed by a steep drop are performed for various initial conditions to qualitatively validate the predictions of the model. Rider strategies for negotiating the drop are examined in the process. Overarching goals of the research are to examine and understand the dynamics and control of interactions between a cyclist and mountain bike. Specific, longer term, goals are to understand the improvement in performance afforded by an experienced rider, to hypothesize human control algorithms that allow riders to perform maneuvers well and safely, to predict structural bike and body forces from these maneuvers, and to quantify performance differences between hard-tail and various full suspension bicycles.

Loading and Design Parameter Uncertainty in the Dynamics and Performance of High-Speed-Parallel-Helical-Stage of a Wind Turbine Gearbox1

2014 ◽  
Vol 136 (9) ◽  
Author(s):  
Fisseha M. Alemayehu ◽  
Stephen Ekwaro-Osire
Keyword(s):  
Wind Turbine ◽  
Design Parameter ◽  
High Speed ◽  
Design Parameters ◽  
Parameter Uncertainties ◽  
Component Reliability ◽  
Input Shaft ◽  
Multibody Dynamic ◽  
Input Variables ◽  
And Performance

In operation, wind turbine gearboxes (WTGs) are subjected to variable torsional and nontorsional loads. In addition, the manufacturing and assembly process of these devices results in uncertainty in the design parameters of the system. WTGs are reported to fail in their early life of operation within 3–7 years as opposed to the expected 20 years of operation. Their downtime and maintenance process is the most costly of the failures of any subassembly of wind turbines (WTs). The objective of this work is to perform a probabilistic multibody dynamic analysis (PMBDA) of the high-speed-parallel-helical-stage (HSPHS) of a WTG that considers the uncertainties of generator-side torque-loading and input-shaft speed as well as assembly and design parameter uncertainties. Component reliability (Rc) or probability of failure (Pf) and probabilistic sensitivities of all the input variables toward five performance functions have been measured and conclusions have been drawn. As opposed to the traditional deterministic approach, PMBDA has demonstrated a new aspect of design and installation of WTGs. In addition to revealing Rc or system reliability or underperformance through Pf, the method will also help designers to critically consider certain variables through the probabilistic sensitivity results.

Bond graph model of a PEM fuel cell stack

2008 ◽  
Vol 1 (06) ◽  
pp. 329-334
Author(s):  
S. Rabih ◽  
C. Turpin ◽  
S. Astier
Keyword(s):  
Fuel Cell ◽  
Graph Model ◽  
Pem Fuel Cell ◽  
Bond Graph ◽  
Fuel Cell Stack

scholarly journals Spatially Resolved Experimental Modal Analysis on High-Speed Composite Rotors Using a Non-Contact, Non-Rotating Sensor

Sensors ◽  
2021 ◽  
Vol 21 (14) ◽  
pp. 4705
Author(s):  
Julian Lich ◽  
Tino Wollmann ◽  
Angelos Filippatos ◽  
Maik Gude ◽  
Juergen Czarske ◽  
...  
Keyword(s):  
High Speed ◽  
Natural Frequencies ◽  
Mode Shapes ◽  
Fiber Reinforced ◽  
Structural Dynamic ◽  
Spatially Resolved ◽  
Glass Fiber Reinforced ◽  
Vibration Responses ◽  
And Performance

Due to their lightweight properties, fiber-reinforced composites are well suited for large and fast rotating structures, such as fan blades in turbomachines. To investigate rotor safety and performance, in situ measurements of the structural dynamic behaviour must be performed during rotating conditions. An approach to measuring spatially resolved vibration responses of a rotating structure with a non-contact, non-rotating sensor is investigated here. The resulting spectra can be assigned to specific locations on the structure and have similar properties to the spectra measured with co-rotating sensors, such as strain gauges. The sampling frequency is increased by performing consecutive measurements with a constant excitation function and varying time delays. The method allows for a paradigm shift to unambiguous identification of natural frequencies and mode shapes with arbitrary rotor shapes and excitation functions without the need for co-rotating sensors. Deflection measurements on a glass fiber-reinforced polymer disk were performed with a diffraction grating-based sensor system at 40 measurement points with an uncertainty below 15 μrad and a commercial triangulation sensor at 200 measurement points at surface speeds up to 300 m/s. A rotation-induced increase of two natural frequencies was measured, and their mode shapes were derived at the corresponding rotational speeds. A strain gauge was used for validation.

Aerodynamic and aeroacoustic performance investigations on modified H-rotor Darrieus wind turbine

2021 ◽  
pp. 0309524X2110039
Author(s):  
Amgad Dessoky ◽  
Thorsten Lutz ◽  
Ewald Krämer
Keyword(s):  
Wind Turbine ◽  
High Speed ◽  
Cfd Simulation ◽  
Vertical Axis ◽  
3D Models ◽  
Power Coefficient ◽  
Design Parameters ◽  
Second Phase ◽  
Vertical Axis Wind Turbine ◽  
Guide Vanes

The present paper investigates the aerodynamic and aeroacoustic characteristics of the H-rotor Darrieus vertical axis wind turbine (VAWT) combined with very promising energy conversion and steering technology; a fixed guide-vanes. The main scope of the current work is to enhance the aerodynamic performance and assess the noise production accomplished with such enhancement. The studies are carried out in two phases; the first phase is a parametric 2D CFD simulation employing the unsteady Reynolds-averaged Navier-Stokes (URANS) approach to optimize the design parameters of the guide-vanes. The second phase is a 3D CFD simulation of the full turbine using a higher-order numerical scheme and a hybrid RANS/LES (DDES) method. The guide-vanes show a superior power augmentation, about 42% increase in the power coefficient at λ = 2.75, with a slightly noisy operation and completely change the signal directivity. A remarkable difference in power coefficient is observed between 2D and 3D models at the high-speed ratios stems from the 3D effect. As a result, a 3D simulation of the capped Darrieus turbine is carried out, and then a noise assessment of such configuration is assessed. The results show a 20% increase in power coefficient by using the cap, without significant change in the noise signal.

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