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A Guide to help FEA Engineers get started with Vehicle Dynamics - Part - 2

This is part two of a two-part series, you can find the first part, which talks about the introduction to vehicle dynamics - here.

In the 21st century, the safety of vehicles has become paramount. According to an article by the National Highway Traffic Safety Administration in the United States, “The average vehicle on the road in 2012 would have an estimated 56% lower fatality risk for its occupants than the average vehicle on the road in the late 1950s.” 

The organization estimates that improvements in vehicle safety have played a part in increasing the number of lives saved annually from 115 in 1960 to 27,621 in 2012, thereby saving more than a cumulative of 600,000 lives over five decades.

Several of the safety improvements have arisen out of top-notch vehicle design. This short article will cover a brief introduction to the various components of vehicle design. 

Additionally, it will help explain the different vehicle dynamics simulations that help produce good vehicle designs and the possible entry-level jobs that are available in vehicle dynamics, simulations, and data acquisition.

Vehicle Design

A holistic vehicle design consists of five aspects: 

  • Suspension Kinematics
  • Suspension Ride and Roll
  • Steering Kinematics
  • Frame Design
  • Tire Modelling

At a fundamental level, all five of these aspects should be considered and optimized to ensure a satisfactory end product.

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1. Suspension Kinematics

Suspension kinematics is a crucial aspect of vehicle design. It helps in maintaining the contact and balance between the vehicle and the ground by balancing the multiple moments and forces when it is in motion, especially in moments such as a steady-state cornering. 

Suspension kinematics ensures that the forces operating on the vehicle body are in sync and do not work against each other, thereby causing increased wear-and-tear to the vehicle components.

2. Suspension Ride And Roll

Ride rates and roll rates are crucial characteristics of vehicle dynamics, which affect the suspension behavior significantly. A vehicle’s roll rate may not modify the full weight transfer in the car. 

However, it changes the speed and weight percentage transferred from axle to axle via the chassis. Usually, higher roll rates lead to higher and quicker weight transfers. 

Ride rates arise from the cumulative effects of wheel rates and help in analysis points such as suspension stiffness and travel requisites for the vehicle dynamics.

3. Steering Kinematics

Steering kinematics helps in ensuring the generation of the appropriate torque from the vehicle center point. Getting the correct slip angle through the steering input and keeping the tire rotations in synch are also crucial functions of the steering kinematics.

4. Frame Design

The frame design also has a pivotal influence on the overall vehicle dynamics as it affects the other parameters as well. For example, frame stiffness is a critical element of frame design, and stiffness usually has a role to play in the efficacy of the suspension mechanisms. A stiff chassis facilitates the use of the suspension and tires for turning maneuvers.

Excess of body flex in the chassis is a symptom of structural frailty in the vehicle design. It forces the frame to bear the ‘slack’ rather than parts such as suspension, which are meant for such purposes. 

In a nutshell, good frame design is an aspect of vehicle dynamics that ensures the long-term viability of the vehicle.

5. Tire Modelling

Tires are important components of the vehicle. They maintain contact with the ground while working in sync with the other aspects such as frame design and the suspension. 

To ensure consistent and robust functioning of tires, OEMs will often carry out tire modeling, a basic element of structural finite element analysis (FEA) in the automotive industry.

Tire modeling enables one to figure out the small but crucial details such as the generation of the slip angle and ratio at different speeds and its effect on the overall vehicle dynamics.

Vehicle Dynamics Simulation

Almost all automotive manufacturers carry out predictive vehicle dynamics simulations at the design stages to ensure the best possible and safest product. Some of the vital vehicle dynamics simulations are as follows:

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1. Static Simulations

Static simulations cover use-cases such as vehicle weight application, tire inflating, and suspension pre-loadings. Static simulations are nonlinear static analysis at a fundamental level. 

They are ultimately used to make decisions on aspects such as suspension design for loads, stresses in frames, and other vehicle parts even before the prototype vehicle is built and tested in the hardware form.

2. Quasi-Static Simulations

Quasi-static simulation models help in determining three-dimensional suspension kinematics and compliance properties. The analytics from such simulations are applied to improve equations that help describe the suspension motions and finally fed into the overall model for the vehicle dynamics.

In layman terms, executing these quasi-static simulations helps ensure that the suspension kinematics of the vehicle function appropriately without any issues.

3. Transient Simulations

Transient simulations, as the name suggests, help in transient analysis of the vehicle. Use cases of a dynamic nature are simulated and tested via transient simulations. For example, turning on a bumpy road, checking whether stability while braking is happening simultaneously with turning, or changing lanes while accelerating.

4. HIL Simulations

Hardware working in sync with simulation software is one of the most important aspects of getting the vehicle dynamics right. Hardware-in-the-loop simulations act as ideal bridges to connect the hardware systems to the relevant simulation models. 

Such solutions are provided by learning data acquisition providers such as Texas Instruments, Sony, etc. Hardware-in-the-loop simulations are one of the vehicle dynamics simulations to assist with efficient vehicle design.

At a more specific level, HIL simulations help developing robustness in the real-time embedded systems of the vehicle, including aspects such as the controller design. Real-time embedded systems have the all-important job of ensuring that the vehicle hardware and software work together for a high-quality and safe product.

Careers in Vehicle Dynamics

The above concepts were just a primer into the world of vehicle dynamics, simulations, and what constitutes good vehicle design. If one is looking at building a career in this field, then there are several entry-level jobs of varying skills and interests available such as Vehicle Dynamics Engineer, Data Acquisition Engineer, or even a Simulation Engineer. 

All these roles require a passion for the automotive sector, attention to detail, and a sharp analytical mind. If you want to learn more about the field of FEA and vehicle dynamics, you can check out Skill-Lync today.



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