Analysis of a Unibody Stub Axle-Hub Design for an ATV

This paper aims to design and model a unibody hub and stub axle Wheel assembly to withstand rough terrain conditions while adhering to design optimization objectives of weight, costs, and manufacturability. For any ground vehicle, its dynamics and control behaviour are majorly governed by the design of its wheel assembly since it experiences all the major loads an ATV faces. We aimed to design and fabricate a unibody hub and stub axle that is lightweight and more durable in comparison to the present form of design in which the hub and stub axle is manufactured and assembled separately. The advantages of this unibody design are lesser components, easy replacement, and easy manufacturing. This report also considers the simulation of this unibody using FEM through Ansys, considering all the loads acting on the unibody. Also, the cost and strength comparison of different materials is done for the selection of the best material. Design is done in such a way to consider all the parameters such as performance, reliability, manufacturability, serviceability, weight, and cost. The model achieves a significant reduction in unsprung mass, improving the dynamic performance of the ATV, without requiring a change in suspension geometry. We also analyze the improvement in vehicle performance in shifting from the classic independent stub through hub design to this integrated unibody design.

Geometry optimization of a planar double wishbone suspension based on whole-range nonlinear dynamic model

Dynamic analysis is an essential task in the geometry design of suspension systems. Whereas the dynamic simulation based on numerical software like Adams is quite slowly and the existing analytical models of the nonlinear suspension geometry are mostly based on small displacement hypothesis, this paper aims to propose a whole-range dynamic model with high computational efficiency for planar double wishbone suspensions and further achieve the fast optimal design of suspension geometry. Selection of the new generalized coordinate and explicit solutions of the basic four-bar mechanism dramatically reduce the complexity of suspension geometry representation and provide analytical solutions for all of the time varying dimensions. By this means, the running speed and computational accuracy of the new model are guaranteed simultaneously. Furthermore, an original Matlab/Simulink implementation is given to maintain the geometric nonlinearity in the solving process of dynamic differential equations. After verifying its accuracy with an ADAMS prototype, the presented whole-range model is used in the vast-parameter optimization of suspension geometry. Since both kinematic and dynamic performances are evaluated in the objective function, the optimization is qualified to give a comprehensive suggestion to the design of suspension geometry.

A detailed study on design, fabrication, analysis, and testing of the anti-roll bar system for formula student cars

This study explains a coherent flow for designing, manufacturing, analyzing, and testing a tunable anti-roll bar system for a formula student racecar. The design process starts with the analytical calculation for roll stiffness using constraining parameters such as CG (Center of Gravity) height, total mass, and weight distribution in conjunction with suspension geometry. Then, the material selection for the design i.e. Aluminum 7075 T6 is made based on parameters such as density and modulus of rigidity. A MATLAB program is used to iterate deflection vs load for different stiffness and shaft diameter values. This is then checked with kinematic deflection values in Solidworks geometry. To validate with the material deflection, finite element analysis is performed on ANSYS workbench. Manufacturing accuracy for the job is checked using both static analysis in lab settings and using sensors on vehicles during on-track testing. The error percentage is found to be 4% between the target stiffness and the one obtained from static testing. Parameters such as moment arm length, shaft diameter and length, and deflection were determined and validated. This paper shows the importance of an anti-roll bar device to tune the roll stiffness of the car without interfering with the ride stiffness.

Computational Modeling of Combat Helmet Performance Analysis Integrating Blunt and Blast Loadings

Combat helmets have gone through many changes, from shells made of metal to advanced composites using Kevlar and Dyneema, along with introduction of pad suspensions to provide comfort and protection. Helmets have been designed to perform against ballistic and blunt impact threats. But, in today’s warfare, combat helmets are expected to protect against all three threats, blunt, ballistic impacts and blast effects to minimize traumatic brain injury (TBI) and provide a better thermal comfort. We are developing a helmet system analysis methodology integrating the effect of multiple threats, i.e., blast and blunt impacts, to achieve an optimal helmet system design, by utilizing multi-physics computational tools. We used a validated human head model to represent the warfighter’s head. The helmet composite shell was represented by an orthotropic elasto-plastic material model. A strain rate dependent model was employed for pad suspension material. Available dynamic loading data was used to calibrate the material parameters. Multiple helmet system configurations subjected to blast and blunt loadings were considered to quantify their influence on brain biomechanical response. Parametric studies were carried out to assess energy absorption for different suspension geometry and material morphology for different loadings. The resulting brain responses were used with published injury criteria to characterize the helmet system performance through a single metric for each threat type. Approaches to combine single-threat metrics to allow aggregating performance against multiple threats were discussed.

Design of Upper A Arm of Double Wishbone Suspension System

Every All-Terrain vehicle right now uses independent suspension system which consists of double wishbones connected to all the tires. As All-Terrain vehicles generally operated on different road conditions it is an absolute necessity to have a robust design of wish bones. A good deformation rate and good FOS determines how good a design. In this study we have designed three types of upper wishbones in Solid Works whose suspension geometry based on wheel base, track width, roll center and pith center of the vehicle is validated in LOTUS software and the following graphs of camber, castor, toe, kingpin inclination are obtained. Linear static structural analysis is performed on all the three types designed in Ansys software and total deformation rate, equivalent stresses generated and FOS is calculated and the based on the results the best design is used for the vehicle. The design provided greater suspension travel, reducing the un-sprung mass of the vehicle, maximizing the performance of the suspension system of the vehicle and better handling of vehicle while cornering. The design is used in SAE BAJA 2020 competition Conducted in Chitkara University Punjab.

On the Influence of Suspension Geometry on Steering Feedback

Feedback through the steering wheel is known as the most important source of information to the driver. The so-called steering feeling, composed of self-aligning actions coming from tyres and suspension geometry all the way through mechanical linkages to the driver’s hands, provides vital communication for intuitive driving, and it is therefore utterly important for safety and for a pleasant driving experience as well. Subtle forces and vibrations, due to the interaction between the tyre contact patch and the road surface texture, also play a role, provided they are not heavily filtered or cancelled by the power steering system. Human perception is guided by experience in order to establish correlations between steering feedback and vehicle motion in terms of straight-line stability, cornering speed, tyre adhesion and available friction, vehicle balance, and so on. A front-wheel drive car is potentially a critical vehicle from this point of view, especially when the powertrain can deliver large torque figures, and even more so if a limited-slip differential (LSD) or a similar active device is present in order to improve traction capabilities. Any difference between the two wheels in terms of tractive force can result into the so-called torque steer issue, that is to say, a “pulling” sensation on the steering wheel or a shifting of the vehicle from the desired trajectory. This paper analyses the torque steer phenomenon on an all-wheel-drive, full electric sportscar where a significant portion of the torque is transferred to the front axle. The effects of suspension kinematics and the load variation at tyre contact patch level are taken into account. For evaluating the impact of steering feedback, the VI-grade® simulation software is adopted and a test campaign on the professional driving simulator available at the University of Brescia has been carried out in order to understand the impact of steering feedback on driver perception and performance.