Teijin Seiki Co., Ltd.

Toijin Seiki Co., Ltd.

Shigeyuki Takagi

Toshio Kamimura

Wataru Takebayashi

In a stability compensating mechanism of an electro-hydraulic servo system which includes a load-displacement detecting unit for detecting a displacement of a piston of actuator or a displacement of a load connected to the piston, and a control valve for supplying a hadraulic oil to the actuator to drive the load and in which a piston-displacement detection signal of the load-displacement detecting unit is fed as a feedback signal back to a forward circuit and the control valve is operated by a deviation signal between the feedback signal and a command signal, the stability compensating mechanism comprising a valve-displacement detecting unit for detecting a valve displacement of the control valve and outputting a valve-displacement detection signal representative of the valve displacement, and a load-pressure computing unit for computing a load pressure that is acted on the actuator due to the load, on the basis of the piston-displacement detection signal of the load-displacement detecting unit and the valve-displacement detection signal of the valve-displacement detecting unit, and for feeding a load pressure signal representative of the load pressure back to the forward circuit.

Stability compensating mechanism of electro-hydraulic servo system

A stability compensating circuit of a servomechanism wherein the output displacement of an actuator is controlled, comprising: a unit generating a reference input signal corresponding to a target value; a first adder which is provided in a first line between the reference input signal generating unit and the actuator and to which a feedback signal from the actuator is inputted through a second line between the first adder and the actuator; a second adder provided in the first line between the first adder and the actuator; a first compensating circuit provided in the first line between the first and second adders; and a second compensating circuit provided in a third line between the second adder and the actuator, the feedback signal from the actuator being inputted to the second adder through the second compensating circuit.

Stability compensating circuit

A hydraulic vibration buffer for connection between two members with a case coupled with the first member, a piston rod with its top end coupled with a second member, a piston coupled with a base end of the piston rod and housed within the cylinder case so as to divide the cylinder case into first and second chambers, fluid source, a tank, and a control valve disposed in fluid paths connecting the cylinder case, the fluid source, and the tank with one another. The vibration buffer also includes returning-force application device constituted by a swingable link with its one and other ends coupled with the first member and the housing block through which the fluid paths extend, and a pair of springs disposed between a center portion of the swingable link and the spool of the control valve.

Vibration buffer

A hydraulic servo actuator adapted to control a driven member in accordance with an operation of a servo circuit through which servo oil flows comprises a main cylinder and an associated piston, associated piston being reciprocable within the cylinder and the main cylinder divided by the piston into a first chamber and a second chamber which are adapted to be in fluid communication with the servo oil, a damper means provided within the main piston for dampening reciprocating movement of the main piston. A hydraulic servo actuator also includes a throttle means for imparting a predetermined restriction to the servo oil that flows between the second chamber and the damper means along the predetermined passage formed within the cylinder.

Servo actuator

A stability compensating circuit of a servomechanism wherein the output displacement of an actuator is controlled, comprising: a signal source generating a reference input signal corresponding to a target value; a first summing amplifier to which the reference input signal and a signal corresponding to the actual output displacement of the actuator are inputted; a primary amplifier to which an output of the first summing amplifier is inputted and which amplifies the output of the first summing amplifier; a secondary amplifier to which an output of the primary amplifier is inputted and which further amplifies the output; a second summing amplifier to which an output of the amplifier is inputted. The circuit further comprises a first order lag circuit to which the output of the primary amplifier is also inputted and which lags the output of the primary amplifier; and a differential circuit differentiating the signal corresponding to the actual output displacement of the actuator; and a third summing amplifier to which an output of the first order lag circuit and an output of the differential circuit are inputted and which transmits to the second amplifier the difference between the outputs of the first order lag circuit and the differential circuit; the second summing amplifier outputting the error between the output of the secondary amplifier and the difference, to control the output displacement of the actuator.

A servo system having an improved loop stability and response time. A phase shifting circuit is inserted in the feedback loop providing an open loop phase lag characteristic at a resonance frequency of a load system in a range of -270.degree. to -360.degree.. The transfer function of the phase shifting circuit is preferably of the form: ##EQU1## where .tau..sub.3 and .tau..sub.4 represent time constants of the circuit.

Servo system

In a dynamic characteristic compensating device for an electrical hydraulic servo actuator, a differential pressure detecting piston is displaced in proportion to the difference in pressure between two hydraulic operating chambers provided on opposite sides of the main piston in the actuator, and a speed detector converts the displacement of the differential pressure detecting piston into an electrical signal. The electrical signal is fed back to the control signal input circuit side of an electrical hydraulic servo valve, to control the valve in such a manner that differential pressure variations due to disturbances applied to the actuator are canceled out by the feedback signal.

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Gifu, Japan

Shigeyuki Takagi