Integrating Electromechanical Systems in Commercial Vehicles for Improved Handling, Stability, and Comfort 2014-01-2408
The 2014 SAE Buckendale Lecture will address the past developments and challenges of electromechanical “smart” systems for improving commercial vehicles' functionality. Electromechanical systems combine traditional mechanical devices with electrical components to provide far higher degree of functionality and adaptability for improved vehicle performance. The significant advances in microprocessors and their widespread use in consumer products have promoted their implementation in various classes of vehicles, resulting in “smart” devices that can sense their operating environment and command an appropriate action for improved handling, stability, and comfort.
The chassis and suspension application of electromechanical devices mostly relate to controllable suspensions and vehicle dynamic management systems, such as Electronic Stability Control. Controllable suspensions include an active or semiactive element-most commonly, damper-that enables changing the dynamic characteristics of the suspension in real time, to adapt to the instantaneous driving dynamics of the vehicle. Such suspensions most often use an electromagnetic actuator, mechanically adjustable damper, or magneto-rheological fluid to change the damping force at the suspension with sufficiently high dynamic bandwidth to respond to every bump and each steering maneuver of the driver. Various analytical and experimental studies for automobiles and heavy trucks have shown significant improvements in suspension performance, substantially beyond those achievable with a conventional passive suspension, for both highway driving and off-highway operations.
Active safety systems broadly refer to devices that can improve the rollover dynamics and directional stability of vehicles. Such devices include Roll Stability Control (RSC), Electronic Stability Control (ESC), and Vehicle Dynamics Integrated Management (VDIM) systems, among other trade names that are commonly used. Active safety systems continuously monitor a series of stability indicators and, when needed, reduce the vehicle speed and implement a corrective steering moment (through applying the foundation brakes at selected wheels) to reduce the over turning accelerations in a turn and maintain the directional stability of the vehicle. It has been shown that such systems can significant reduce the likelihood of rollovers and understeer, oversteer, or jackknifing during a steering maneuver, particularly in adverse road conditions or emergency steering maneuvers.
Chapter 1 provides a historical perspective on vehicle handling and stability, along with the application of active safety systems and controllable suspensions for commercial trucks. The concept of controllable suspensions for vehicles, particularly as it relates to magneto-rheological dampers, is introduced in Chapter 2, in addition to the common control methods for semiactive suspensions. The critical design aspects of magneto-rheological dampers along with the results of a simulation study that highlights their benefits in improving vehicle ride, handling, and stability are also introduced in this chapter. Chapter 3 is dedicated to highlighting the benefits of Electronic Stability Control (ESC) and Roll Stability Control (RSC) systems, and their effect on reducing rollovers in heavy trucks. It also includes the physics of tripped and untripped rollovers, the working principle of RSC and ESC systems, the government rulemaking efforts as documented in FMVSS 136, standard used for assessing ESC effectiveness, and the effectiveness of a control algorithm called Direct Yaw Control (DYC).