Closed loop electrohydraulic actuator control circuit

A hydraulic control system for controlling expansion and contraction of a cylinder. The cylinder comprises an extension chamber and a contraction chamber. The hydraulic control system comprises a first servovalve comprising a first pressure supply port and a first pressure discharge port and adapted to selectively communicate the expansion chamber with the first pressure supply port and with the first pressure discharge port. A second servovalve, comprising a second pressure supply port and a second pressure discharge port, is adapted to selectively communicate the contraction chamber with the second pressure supply port and with the second pressure discharge port. A four way servovalve, comprising a third pressure supply port, a third pressure discharge port, a fourth pressure supply port and a fourth pressure discharge port, is adapted to selectively communicate the expansion chamber with the third pressure supply port and the third pressure discharge port and to selectively communicate the contraction chamber with the fourth pressure supply port and with the fourth pressure discharge port. A feedback device is provided which is capable of measuring at least one property of the cylinder and providing a signal proportional to the property. A controller is provided which is capable of receiving the signal and comparing the property to a desired property to determine a difference and activating at least one of the first servovalve, the second servovalve or the four way servovalve to decrease the difference.