Hybrid pneumatic-magnetic isolator-actuator

• US 20040099784A1
• Filed: 11/21/2003
• Published: 05/27/2004
• Est. Priority Date: 02/20/2002
• Status: Active Grant

• Current Assignee: Moog Incorporated
• Original Assignee: CSA Engineering Co.
• Inventors: Kienholz, David A.
• Granted Patent: US 6,942,202 B2
• Time in Patent Office: Days
• US Class Current: 248/550
• CPC Class Codes: F15B 15/088 the motor using combined actuation, e.g. electric and fluid actuation
• CPC Class Codes: F16F 13/002 comprising at least one fluid spring F16F13/005, F16F13/02, F16F13/04 take precedence
• CPC Class Codes: F16F 15/0232 with at least one gas spring F16F15/027 takes precedence
• CPC Class Codes: F16F 15/03 using magnetic or electromagnetic means F16F9/53, F16F15/005 take precedence
• CPC Class Codes: H02K 41/0356 moving along a straight path

Abstract

The invention disclosed is a compact and lightweight hybrid pneumatic-magnetic isolator-actuator capable of large force, substantial stroke and bandwidth actuation with near frictionless operation and vibration isolation with very low break frequency. Pneumatic and magnetic forces are applied to a single carriage comprised primarily of a coaxially arranged air piston and coil. The carriage is driven relative to a frame or housing including an internally mounted cylindrical piston sleeve and magnetic actuator body. A combination of air bearings and air bearing piston construction provide for frictionless motion of the carriage relative to the frame. The pneumatic piston provides the actuation force for both static loads and low frequency dynamic loads. An integrally mounted sensor and control unit determine the pressure error resulting at the pneumatic piston. The control unit utilizes the pressure error to drive a high bandwidth magnetic actuation capability in parallel with the pneumatic actuation capability. An air tank of prescribed volume may be connected to the pneumatic piston for effecting a desired air-spring stiffness upon the isolator-actuator.

Claims

1. A vibration isolation, position actuation device comprising:

a pneumatic actuator,

a pressure servo-valve,

an air pressure supply,

a coil and magnet,

a state variable sensor, and

a control unit

wherein the pressure servo-valve accepts an input command signal and modulates the air pressure supply which is applied to the pneumatic actuator, wherein the state variable sensor measures a state variable of the pneumatic actuator resulting from the applied modulated air pressure supply, wherein the control unit determines the error existing in the measured state variable relative to the command signal, and wherein the control unit modulates electrical current applied to the coil such that a magnetic force is applied to the pneumatic actuator by the magnet in such proportion to negate the measured error in the state variable of the pneumatic actuator.

2. The device of claim 1 further comprising an air tank connected to the pneumatic actuator such that the combined air volume of the pneumatic actuator and air tank provide an air volume yielding a prescribed air-spring stiffness.

3. The device of claim 1 wherein the pneumatic actuator is further comprised of a carriage and a housing wherein the carriage is constrained to move within the housing upon air bearings such that frictionless motion of the carriage is achieved.

4. The device of claim 1 wherein the coil is attached to one of the carriage and housing and the magnet is attached to the other.

5. The device of claim 1 wherein the state variable sensor is a pressure transducer positioned to read the pressure applied to the pneumatic actuator and yield an amplified voltage equal to the force resulting from the pneumatic actuator.

6. The device of claim 1 wherein the control unit compares the amplified voltage from the pressure transducer to the input command signal to determine a force error measurement of the pneumatic actuator such that the control unit is then enabled to apply the force error measurement directly as an input current to the coil.