Linear-acting controllable pneumatic actuator and motion control apparatus including a field responsive medium and control method therefor

A motion control apparatus, comprising:

• (a) a pneumatically controlled actuator including a housing with a gas cavity formed therein, a first piston slidably disposed in the gas cavity, the first piston subdividing the gas cavity into first and a second gas chambers, and an output member coupled to the first piston, the output member being movable in response to movement of the first piston, the first piston being movable along an axial axis of the housing as a result of a differential pressure between the first and second chambers;
• (b) a controllable brake for controlling the motion of the output member, the brake being coupled to the pneumatically controlled actuator, the brake including a medium containing cavity subdivided into a first and second chambers, a second piston rigidly interconnected with, and longitudinally aligned with, the first piston and moveable in the medium containing cavity along said axial axis, a passageway interconnecting the first and the second chambers, a field responsive medium contained in the chambers and passageway, a field generator for producing a field to change the rheology of the field responsive medium in the passageway upon exposure to the field causing a braking force to be applied to the output member to control motion thereof;
• and
• (c) a pneumatic supply system including a pressure source for providing a supply of pressurized gas to the gas cavity.