ABSTRACT
I. Introduction ...................................................................................................................... 328
II. Basics of Active Suspensions .......................................................................................... 328
A. Concepts ................................................................................................................... 328
B. Active and Semi-Active........................................................................................... 328
C. Design Considerations ............................................................................................. 330
III. Tilting Trains.................................................................................................................... 331
A. Concept and Equations ............................................................................................ 331
B. Mechanical Configurations ...................................................................................... 333
C. Control: Strategies and Assessment......................................................................... 334
1. Control Approaches........................................................................................... 334
2. Assessment of Controller Performance ............................................................ 336
D. Summary of Tilting.................................................................................................. 338
IV. Active Secondary Suspensions ........................................................................................ 338
A. Concepts and Requirements..................................................................................... 338
B. Configurations .......................................................................................................... 339
C. Control Strategies..................................................................................................... 339
1. Sky-Hook Damping........................................................................................... 339
2. Softening of Suspension Stiffness..................................................................... 342
3. Low-Bandwidth Controls .................................................................................. 342
4. Modal Control Approach .................................................................................. 343
5. Model-Based Control Approaches.................................................................... 344
6. Actuator Response............................................................................................. 344
7. Semi-Active Control ......................................................................................... 344
D. Examples .................................................................................................................. 345
1. Servo-Hydraulic Active Lateral Suspension..................................................... 345
2. Shinkansen/Sumitomo Active Suspension........................................................ 346
V. Active Primary Suspensions ............................................................................................ 347
A. Concepts and Requirements..................................................................................... 347
B. Configurations .......................................................................................................... 348
C. Control Strategies..................................................................................................... 349
1. Stability Control — Solid-Axle Wheelset ........................................................ 349
2. Stability Control — Independently Rotating Wheelset.................................... 349
3. Steering Control — Solid-Axle Wheelset ........................................................ 350
4. Guidance Control — Independently Rotating Wheelset .................................. 350
5. Integrated Control Design ................................................................................. 351
6. Assessment of Control Performance................................................................. 351
D. Examples .................................................................................................................. 352
VI. Technology....................................................................................................................... 353
A. Sensing and Estimation Techniques ........................................................................ 353
B. Actuators .................................................................................................................. 354
C. Controllers and Fault Tolerance .............................................................................. 355
VII. Long Term Trends ........................................................................................................... 355
Nomenclature................................................................................................................................ 355
References..................................................................................................................................... 356
It is clear from the preceding chapters that the subject of railway vehicle dynamics has developed
principally as a mechanical engineering discipline, but an important technological change is
starting to occur through the use of active suspension concepts. The use of advanced control has
been common for many decades in the power electronic control of traction systems, and it is now
firmly established as the standard technology which has yielded substantial benefits, but its
application to suspensions is much more recent. Although the term “active suspension” is
commonly taken to relate to providing improved ride quality in fact, it is a generic term which
defines the use of actuators, sensors, and electronic controllers to enhance and/or replace the springs
and dampers that are the key constituents of a conventional, purely mechanical, “passive”
suspension; as such it can be applied to any aspect of the vehicle’s dynamic system.
