A proportional braking system for use with a movable surface which is movable relative to a housing, the proportional braking system comprising: a variable displacement brake (151, 152) which is configured for displacement toward or away from braking engagement with the movable surface (120, 121, 130, 131) in proportion to an input command; and a brake driver which is receptive of data reflective of movements of the movable surface relative to the housing and which issues the input command to the variable displacement brake in accordance with the data; and characterised in that the variable displacement brake (151, 152) comprises: a first body comprising brake plates; a second body comprising thrust plates, the second body being disposed such that the thrust plates are interleaved with the brake plates and being rotatable and movable with respect to the first body; an elastic element that urges the second body to move toward the first body such that the thrust plates are urged toward braking engagements with the brake plates to inhibit rotations of the second body with respect to the first body; a coil at a first side of the brake plates, which, when energized, generates a flux moment on the second body in opposition to the urging of the elastic element; and a booster coil at a second side of the brake plates, which, when energized, generates a second flux moment on the second body in support of the urging of the elastic element. a variable displacement brake (151, 152) which is configured for displacement toward or away from braking engagement with the movable surface (120, 121, 130, 131) in proportion to an input command; and a brake driver which is receptive of data reflective of movements of the movable surface relative to the housing and which issues the input command to the variable displacement brake in accordance with the data; and characterised in that the variable displacement brake (151, 152) comprises: a first body comprising brake plates; a second body comprising thrust plates, the second body being disposed such that the thrust plates are interleaved with the brake plates and being rotatable and movable with respect to the first body; an elastic element that urges the second body to move toward the first body such that the thrust plates are urged toward braking engagements with the brake plates to inhibit rotations of the second body with respect to the first body; a coil at a first side of the brake plates, which, when energized, generates a flux moment on the second body in opposition to the urging of the elastic element; and a booster coil at a second side of the brake plates, which, when energized, generates a second flux moment on the second body in support of the urging of the elastic element. a first body comprising brake plates; a second body comprising thrust plates, the second body being disposed such that the thrust plates are interleaved with the brake plates and being rotatable and movable with respect to the first body; an elastic element that urges the second body to move toward the first body such that the thrust plates are urged toward braking engagements with the brake plates to inhibit rotations of the second body with respect to the first body; a coil at a first side of the brake plates, which, when energized, generates a flux moment on the second body in opposition to the urging of the elastic element; and a booster coil at a second side of the brake plates, which, when energized, generates a second flux moment on the second body in support of the urging of the elastic element.