You didn't say how much you could spend on this project...
Actually what you are referring to is a custom hydraulic suspension system, consisting of several specialized air pumps and special heavy duty air shocks.
For vehicles of course, the system operates on a 12V system, so substantial power is required to operate the pumps. Several car batteries are required to produce and sustain the necessary power for extended use. The pumps, hoses, batteries and ancillary hardware take up a lot of real estate, so large early-model Chevy and GM "road boats" are the preferred project vehicles for this task. The setup is relatively expensive as well. Look at an issue of "lowrider" magazine on a newsstand, and plenty of shops carry this stuff.
A basic "lowrider" setup consists of a single pump, which can raise or lower each shock simultaneusly. A four-pump setup therefore allows individual control of each shock, allowing tricks like making the vehicle, "dance" or "hop".
The project you are working on sounds a little dangerous, in both weight and frequency. The "lowrider" equipment is pretty powerful stuff...it's not a "Bill Nye, Science Guy" kitchen-table-kind-of thing.
How about a 6 foot lever with a fulcrum at 3 feet, attached to an eccentric pulley connection on a household appliance electric motor? Much safer...
2009 ML350 (84K) - Family vehicle
2001 CLK430 Cabriolet (71K) - Wife's car
2005 BMW 645CI (124K) - My daily driver
2012 Mustang V6 (60K) - Daughter's car