A system for assisting a user in moving a device relative to a structure comprises a magnetorheological (MR) fluid actuator unit including at least one torque source and at least one MR fluid clutch apparatus having an input coupled to the at least one torque source to receive torque from the at least one torque source, the MR fluid clutch apparatus controllable to transmit a variable amount of assistance force via an output thereof. An interface is configured for coupling the output of the at least one MR fluid clutch apparatus to the device or surrounding structure. At least one sensor provides information about a movement of the device. A processor unit for controlling the at least one MR fluid clutch apparatus in exerting the variable amount of assistance force as a function of said information, wherein the system is configured for one of the MR fluid actuator unit and the interface to be coupled to the structure, and for the other of the MR fluid actuator unit and the interface to be coupled to the device for the assistance force from the MR fluid actuator unit to assist in moving the device.