Closed loop electrohydraulic actuator control circuit

A hydraulic control system for controlling expansion and contraction of a cylinder wherein said cylinder comprises an extension chamber and a contraction chamber and said hydraulic control system comprises:

• a first servovalve comprising a first pressure supply port and a first pressure discharge port and adapted to selectively communicate said expansion chamber with said first pressure supply port and with said first pressure discharge port;
• a second servovalve comprising a second pressure supply port and a second pressure discharge port and adapted to selectively communicate said contraction chamber with said second pressure supply port and with said 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 and said four way servovalve is adapted to selectively communicate said expansion chamber with said third pressure supply port and said third pressure discharge port and to selectively communicate said contraction chamber with said fourth pressure supply port and with said fourth pressure discharge port;
• a feedback device capable of measuring at least one property of said cylinder and providing a signal proportional to said property;
• a controller capable of receiving said signal and comparing said property to a desired property to determine a difference and activating at least one of said first servovalve, said second servovalve or said four way servovalve to decrease said difference
• wherein said controller activates said first servovalve, said second servovalve and said four way servovalve to expand said cylinder in accordance with the following process:
• when said difference is above a first predetermined value said first pressure supply port supplies hydraulic fluid to said expansion chamber;
• when said difference is below said first predetermined value and above a second predetermined threshold said third pressure supply port supplies hydraulic fluid to said expansion chamber;
• when said difference is below said second predetermined threshold said third pressure supply port supplies hydraulic fluid to said expansion chamber and said first pressure discharge port discharges hydraulic fluid.

A hydraulic control system for controlling expansion and contraction of a cylinder wherein said cylinder comprises an extension chamber and a contraction chamber and said hydraulic control system comprises:

• a first servovalve comprising a first pressure supply port and a first pressure discharge port and adapted to selectively communicate said expansion chamber with said first pressure supply port and with said first pressure discharge port;
• a second servovalve comprising a second pressure supply port and a second pressure discharge port and adapted to selectively communicate said contraction chamber with said second pressure supply port and with said 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 and said four way servovalve is adapted to selectively communicate said expansion chamber with said third pressure supply port and said third pressure discharge port and to selectively communicate said contraction chamber with said fourth pressure supply port and with said fourth pressure discharge port;
• a feedback device capable of measuring at least one property of said cylinder and providing a signal proportional to said property;
• a controller capable of receiving said signal and comparing said property to a desired property to determine a difference and activating at least one of said first servovalve, said second servovalve or said four way servovalve to decrease said difference wherein said controller activates said first servovalve, said second servovalve and said four way servovalve to contract said cylinder in accordance with the following process:
• when said difference is above a first predetermined value said second pressure supply port supplies hydraulic fluid to said contraction chamber;
• when said difference is below said first predetermined value and above a second predetermined threshold said fourth pressure supply port supplies hydraulic fluid to said contraction chamber;
• when said difference is below said second predetermined threshold said fourth pressure supply port supplies hydraulic fluid to said contraction chamber and said second pressure discharge port discharges hydraulic fluid.

A hydraulic control system for controlling expansion and contraction of a cylinder wherein said cylinder comprises an extension chamber and a contraction chamber and said hydraulic control system comprises:

• a first servovalve comprising a first pressure supply port and a first pressure discharge port and adapted to selectively communicate said expansion chamber with said first pressure supply port and with said first pressure discharge port;
• a second servovalve comprising a second pressure supply port and a second pressure discharge port and adapted to selectively communicate said contraction chamber with said second pressure supply port and with said 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 and said four way servovalve is adapted to selectively communicate said expansion chamber with said third pressure supply port and said third pressure discharge port and to selectively communicate said contraction chamber with said fourth pressure supply port with said fourth pressure discharge port;
• a feedback device capable of measuring a property of said cylinder and providing a signal proportional to said property;
• a controller capable of receiving said signal and comparing said property to a desired property to determine a difference and activating at least one of said first servovalve, said second servovalve or said four way servovalve to decrease said difference and wherein said controller selects between the following sequences:
• a) said first pressure supply port supplies hydraulic fluid to said expansion chamber and said second pressure discharge port allows hydraulic fluid to exit said contraction chamber;
• b) said second pressure supply port supplies hydraulic fluid to said contraction chamber ans said first pressure discharge port allows hydraulic fluid to exit said contraction chamber;
• c) said third pressure supply port supplies hydraulic fluid to said expansion chamber and said second pressure discharge port allows hydraulic fluid to exit said contraction chamber;
• d) said fourth pressure supply port supplies hydraulic fluid to said contraction chamber and said first pressure discharge port allows hydraulic fluid to exit said contraction chamber;
• e) said first pressure supply port and said third pressure supply port supply hydraulic fluid to said expansion chamber and said second pressure discharge port allows hydraulic fluid to exit said contraction chamber;
• f) said second pressure supply port and said fourth pressure supply port supply hydraulic fluid to said contraction chamber and said first pressure discharge port allows hydraulic fluid to exit said expansion chamber;
• g) said third pressure supply port supplies a first amount of hydraulic fluid to said expansion chamber and said first pressure discharge port allows a second amount of hydraulic fluid to exit said expansion chamber and said second pressure discharge port allows a third amount of hydraulic fluid to exit said contraction chamber wherein said first amount is more than said second amount and said third amount equals the difference between said first amount and said second amount;
• and
• h) said fourth pressure supply port supplies a fourth amount of hydraulic fluid to said contraction chamber and said second pressure discharge port allows a fifth amount of hydraulic fluid to exit said contraction chamber and said first pressure discharge port allows a sixth amount of hydraulic fluid to exit said expansion chamber wherein said fourth amount is more than said fifth amount and said sixth amount equals the difference between said fourth amount and said fifth amount.

A system for controlling hydraulic fluid between a first chamber and a second chamber wherein said system comprises:

• a first three way servovalve comprising a first pressure supply port and a first pressure discharge port and adapted to selectively communicate said first chamber with said first pressure supply port and with said first pressure discharge port;
• a second three way servovalve comprising a second pressure supply port and a second pressure discharge port and adapted to selectively communicate said second chamber with said second pressure supply port and with said 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 and said four way servovalve is adapted to selectively communicate said first chamber with said third pressure supply port and said third pressure discharge port and to selectively communicate said second chamber with said fourth pressure supply port and with said fourth pressure discharge port;
• a feedback device capable of measuring at least one property of said first chamber and providing a signal proportional to said property;
• a controller capable of receiving said signal and comparing said property to a desired property to determine a difference and activating at least one of said first servovalve, said second servovalve or said four way servovalve to decrease said difference.

A hydraulic control system for hydraulic fluid between a first chamber and a second chamber and said hydraulic control system comprises:

• a first servovalve comprising a first pressure supply port and a first pressure discharge port and adapted to selectively communicate said first chamber with said first pressure supply port and with said first pressure discharge port;
• a second servovalve comprising a second pressure supply port and a second pressure discharge port and adapted to selectively communicate said second chamber with said second pressure supply port and with said 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 and said four way servovalve is adapted to selectively communicate said first chamber with said third pressure supply port and said third pressure discharge port and to selectively communicate said second chamber with said fourth pressure supply port with said fourth pressure discharge port;
• a feedback device capable of measuring a property of said cylinder and providing a signal proportional to said property;
• a controller capable of receiving said signal and comparing said property to a desired property to determine a difference and activating at least one of said first servovalve, said second servovalve or said four way servovalve to decrease said difference and wherein said controller selects between the following sequences:
• a) said first pressure supply port supplies hydraulic fluid to said first chamber and said second pressure discharge port allows hydraulic fluid to exit said second chamber;
• b) said second pressure supply port supplies hydraulic fluid to said second chamber and said first pressure discharge port allows hydraulic fluid to exit said second chamber;
• c) said third pressure supply port supplies hydraulic fluid to said first chamber and said second pressure discharge port allows hydraulic fluid to exit said second chamber;
• d) said fourth pressure supply port supplies hydraulic fluid to said second chamber and said first pressure discharge port allows hydraulic fluid to exit said second chamber;
• e) said first pressure supply port and said third pressure supply port supply hydraulic fluid to said first chamber and said second pressure discharge port allows hydraulic fluid to exit said second chamber;
• f) said second pressure supply port and said fourth pressure supply port supply hydraulic fluid to said second chamber and said first pressure discharge port allows hydraulic fluid to exit said first chamber;
• g) said third pressure supply port supplies a first amount of hydraulic fluid to said first chamber and said first pressure discharge port allows a second amount of hydraulic fluid to exit said first chamber and said second pressure discharge port allows a third amount of hydraulic fluid to exit said second chamber wherein said first amount is more than said second amount and said third amount equals the difference between said first amount and said second amount;
• and
• h) said fourth pressure supply port supplies a fourth amount of hydraulic fluid to said second chamber and said second pressure discharge port allows a fifth amount of hydraulic fluid to exit said second chamber and said first pressure discharge port allows a sixth amount of hydraulic fluid to exit said first chamber wherein said fourth amount is more than said fifth amount and said sixth amount equals the difference between said fourth amount and said fifth amount.

A method for controlling hydraulic fluid between a first chamber and a second chamber wherein said hydraulic control system comprises:

• a first servovalve comprising a first pressure supply port and a first pressure discharge port and adapted to selectively communicate said first chamber with said first pressure supply port and with said first pressure discharge port;
• a second servovalve comprising a second pressure supply port and a second pressure discharge port and adapted to selectively communicate said second chamber with said second pressure supply port and with said 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 and said four way servovalve is adapted to selectively communicate said first chamber with said third pressure supply port and said third pressure discharge port and to selectively communicate said second chamber with said fourth pressure supply port with said fourth pressure discharge port;
• a feedback device capable of measuring a property of said cylinder and providing a signal proportional to said property;
• a controller capable of receiving said signal and comparing said property to a desired property to determine a difference and activating at least one of said first servovalve, said second servovalve or said four way servovalve to decrease said difference and wherein said method comprises:
• causing said first pressure supply port to supply hydraulic fluid to said first chamber and said second pressure discharge port allows hydraulic fluid to exit said second chamber;
• causing said second pressure supply port to supply hydraulic fluid to said second chamber and said first pressure discharge port allows hydraulic fluid to exit said second chamber;
• causing said third pressure supply port to supply hydraulic fluid to said first chamber and said second pressure discharge port allows hydraulic fluid to exit said second chamber;
• causing said fourth pressure supply port to supply hydraulic fluid to said second chamber and said first pressure discharge port allows hydraulic fluid to exit said second chamber;
• causing said first pressure supply port and said third pressure supply port to supply hydraulic fluid to said first chamber and said second pressure discharge port allows hydraulic fluid to exit said second chamber;
• causing said second pressure supply port and said fourth pressure supply port to supply hydraulic fluid to said second chamber and said first pressure discharge port allows hydraulic fluid to exit said first chamber;
• causing said third pressure supply port to supply a first amount of hydraulic fluid to said first chamber and said first pressure discharge port allows a second amount of hydraulic fluid to exit said first chamber and said second pressure discharge port allows a third amount of hydraulic fluid to exit said second chamber wherein said first amount is more than said second amount and said third amount equals the difference between said first amount and said second amount;
• and
• causing said fourth pressure supply port to supply a fourth amount of hydraulic fluid to said second chamber and said second pressure discharge port allows a fifth amount of hydraulic fluid to exit said second chamber and said first pressure discharge port allows a sixth amount of hydraulic fluid to exit said first chamber wherein said fourth amount is more than said fifth amount and said sixth amount equals the difference between said fourth amount and said fifth amount.