How can you predict vehicle stability and control with computer simulations?

1 Vehicle dynamics

Vehicle dynamics is the study of how a vehicle moves and reacts to external forces, such as gravity, aerodynamics, friction, and steering. It involves modeling the vehicle as a system of interconnected components, such as tires, suspension, chassis, brakes, and steering, and applying the laws of physics and mathematics to describe their behavior. By using computer simulations, engineers can analyze how the vehicle responds to various inputs, such as speed, acceleration, braking, cornering, and road surface. They can also evaluate the effects of different design parameters, such as weight distribution, center of gravity, wheelbase, track width, and tire characteristics, on the vehicle's stability and control.

2 Stability analysis

Stability analysis is the process of determining whether a vehicle can maintain its intended path and orientation, or if it will deviate or lose control due to external disturbances or driver errors. One of the most common ways to assess stability is by using the linearized bicycle model, which simplifies the vehicle as a two-wheeled system with a single mass and two degrees of freedom: lateral displacement and yaw angle. By applying small perturbations to the system, engineers can calculate the natural frequencies and damping ratios of the vehicle's modes of motion, such as roll, pitch, yaw, and weave. These values indicate how quickly and effectively the vehicle can return to equilibrium after being disturbed. A stable vehicle has positive damping ratios, while an unstable vehicle has negative or zero damping ratios.

3 Control design

Control design is the process of designing and implementing systems that can improve the vehicle's stability and performance by adjusting its parameters or applying corrective actions. For example, a control system can modify the steering angle, brake pressure, or engine torque to counteract unwanted motions or enhance desired ones. One of the most common types of control systems is the electronic stability control (ESC), which monitors the vehicle's speed, yaw rate, and lateral acceleration, and compares them with the driver's intended direction. If the system detects a mismatch, it can apply selective braking or throttle reduction to prevent skidding, spinning, or rollover. Another example is the adaptive cruise control (ACC), which adjusts the vehicle's speed and distance to the preceding vehicle by using sensors and actuators.

4 Simulation tools

Simulation tools are software applications that can create realistic and interactive models of vehicles and their environments, and run various tests and scenarios to evaluate their stability and control. Popular simulation tools for automotive design include CarSim, a commercial software that can simulate the dynamic behavior of passenger vehicles, light trucks, and motorcycles; MATLAB/Simulink, a programming environment and graphical tool for numerical computations, data analysis, and system modeling; and OpenModelica, an open-source software that supports various libraries and interfaces for vehicle dynamics, control systems, and multi-domain modeling. All of these tools provide powerful capabilities for designing automotive systems.

5 Simulation benefits

Computer simulations can offer a number of advantages to automotive engineers and designers compared to physical testing and experimentation. Cost reduction is one of the main benefits, as simulations can reduce the need for expensive prototypes, test rigs, and test tracks. Simulations are also more time-efficient, allowing for rapid iterations and modifications of the design. Additionally, simulations can avoid potential hazards and damages to the vehicle, the test drivers, and the environment. Finally, they can generate large amounts of data and information that can be used for analysis, validation, and optimization of the design.

6 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?