Abstract: In a motion effector for use in a virtual reality system, a plant is a target of control and for producing an output signal reflecting the actual movement of a moving part therein and a reference input provider provides a reference input signal which reflects a desired motion of the plant. In addition, a subtractor produces an error signal by subtracting the output signal from the reference input signal. A feedback compensator generates a first control signal by using the error signal and a feed-forward compensator generates a second control signal by using the reference input signal. An adder generates a final control signal by adding the first and the second control signals and provides the final control signal to the plant, wherein the final control signal is used to control the plant.

Abstract: A simulator includes a base plate, a platform, a plurality of actuators, each of the actuators having a hydraulic cylinder, a sensor, a servo valve and a pair of universal joints, and a weight supporting actuator including a pressure sensor and designed to support a specific weight of the platform and the substance thereon. The sensors and the pressure sensor sense the variation of length and weight imposed on each of the hydraulic cylinders, respectively. The servo valve selectively passes a high pressure fluid to an upper and a lower portions of the cylinder and the pair of universal joints have a three degrees of freedom to allow the platform to have six degrees of freedom. A controller controls the servo valve of both actuators to vary the length of each of the hydraulic cylinders thereof, thereby lessening the load imposed on the actuators.