Automotive suspension is a compromise between comfort and control. Suspension systems are comprised of springs and dampers that store and release energy. Spring rates and damping coefficients are adjusted to set the balance between these two opposing criteria. Using conventional means, this compromise is set once and for all in the developmental stage. Whether it is a suspension system for a Cadillac limousine or a Ferrari sports car, some balance between comfort and control is chosen. Active suspension is the name given to an approach that allows this compromise to vary based on driving conditions.
The term “active” suspension indicates that there is some controlled response to incurred conditions. Many active suspensions have an integrated actuator. An actuator is any device that outputs force and movement. The actuators used for active suspensions are very large and require significant power inputs. The goal of the research being conducted at the University of South Carolina is to reduce the power consumption while maintaining comfort and control in active suspension.
Researchers at the University of South Carolina have developed a full body vehicle dynamics model. This model can be configured to represent any four-wheel passenger vehicle. The modeled vehicle’s responses are tested over a range of varying conditions. This current working models demonstrates the behavior of a standard suspension system.
Shown above is a Simulink model of suspension and vehicle dynamics.
Also shown is Nathan Trevett inspecting an accelerometer on USC's racecar test bed.
The computer model is being validated using USC’s legends car. The legends car is equipped with accelerometers and data transmission equipment. This data acquisition system records the vehicle’s dynamic response while driven through a test course. A virtual test course modeled from the actual course is developed, and the virtual legends car is put through the simulation. The empirical data and simulated dynamic response are compared to evaluate the performance of the model.
Work is currently being done to model active suspension systems, both existing and conceptual systems. Using the vehicle dynamics model, evaluations can be made on the quality of each system. The model will be able to show comfort of the passengers, stability of the vehicle, and the power demands on the system. Using this process, new suspension systems will be evaluated to determine their merit before thousands of dollars are invested into prototype development. This modeling capability will both expedite the design process and improve the quality of developed systems. The work being done at the University of South Carolina will bring researchers worldwide one-step closer to seeing high quality active suspensions on low-cost production vehicles.