Microwave antenna and dielectric property change frequency compensation system in electrohydraulic servo with piston position control
US4757745A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Feb 26, 1987 |
| Grant date | Jul 19, 1988 |
| Priority date | — |
| Expiry date | Feb 26, 2007 |
Classification
- Technology area (CPC F)Mechanical Engineering; Lighting; Heating
- CPC primaryF15B15/28
- WIPO fieldMechanical elements
- WIPO sectorMechanical engineering
Abstract
An electrohydraulic servo system which includes an actuator having a cylinder and a piston variably positioned therewithin, a servo valve responsive to valve control signals for coupling the actuator to a source of hydraulic fluid, and control electronics responsive to piston position for generating the valve control signals. A variable frequency rf generator is coupled through associated directional couplers to a pair of antennas which are positioned within the actuator cylinder and physically spaced from each other in the direction of piston motion by an odd multiple of quarter-wavelengths at a nominal generator output frequency. A phase detector receives the reflected signal outputs from the directional couplers, and provides an output through an integrator to the frequency control output of the generator to automatically compensate frequency of the rf energy radiated into the cylinder and thereby maintain electrical quarter-wavelength spacing between the antennas against variations in dielectric properties of the hydraulic fluid due to changes in fluid temperature, etc. A second phase detector is coupled to the generator and one antenna to generate a piston position signal.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.