[ARTICLE IS WORK IN PROGRESS]
The key difference between semi-active and active suspension is such that:
Fully active suspension: generates and dissipates energy
Semi active suspension: only dissipates energy
Adaptive Damping Systems (ADS) as a part of semi-active suspensions adjust the amount of damping force for different conditions including:
vehicle speed
vehicle cornering attitude (steering angle, steering rate)
vehicle longitudinal accelerations (longitudinal G, braking, throttle)
road morfology (accelerations, frequencies)
Several patented terms and technologies are in wide use in industry:
Magnetic Ride Control - Cadillac
Electronic Air Suspension (EAS) - Range Rover
Active Body Control (ABC) - Mercedes Benz
Active Roll Control - TRW AUtomotive
Dynamic Body Control - Delphi Automotive
Magne Ride - Delphi Automotive
Typically cars that offer ADS have selectable "modes" for the driver to choose from. Audi for example offers a Sport/Comfort button, whereas supercars like McLaren have a Handling mode with selectable Normal/Sport/Track settings.
Typically, damping force can be electronically controlled in two ways:
by varying the opening of the valve orifice that controls oil flow: Continuously Controlled Electronic Suspension (CES)
by making a fluid more or less viscous: Magneto-Rheological dampers (MR)
CES or MR systems are used as OEM parts or aftermarket. For example shown below is a system provided by the german manufacturer KW.
Continuously Controlled Electronic valves are mostly manufactured and sold to other suppliers by Ohlins
Literature:
Gaspar, Szabo - Active Suspension in Integrated Vehicle Control (intechopen.com)
Guglielmino, Sireteanu, Stammers - Semi-Active Suspension Control (Springer ISBN 978-1-84800-231-9; £129 hardback)
Kashem, Nagarajah - Vehicle Suspension Systems and Electromagnetic Dampers (Springer ISBN 978-981-10-5478-5 £129 hardback)
Koch - Adaptive Control of Mechatronic Vehicle Suspension Systems
Liu, Gao, Li - Handbook of Vehicle Suspension Control Systems (IET ISBN 9781849196338)
Mustafizur - Simulation of Preview Controlled Active Suspension for Vehicles (Lambert ISBN 9783659284830 £55 via blackwells.co.uk)
Savaresi - Semi-Active Suspension Control Design For Vehicles
Sun, Gao, Shi - Advanced Control For Vehicle Active Suspension Systems (ISBN 978-3-030-15785-2; £120 hardback)
Yasser - MPC-on-chip in Application to Automotive Active Suspension Systems (Lambert Academic Publishing; Blackwells.co.uk)