Method and apparatus for seat detection and soft seating in a piezoelectric device actuated valve system

A valve, comprising:

• an actuator comprised of a piezoelectric device comprising one or more prestressed electroactive benders;
• a member operatively connected to the actuator;
• a contact surface, wherein the member is operable to move relative to the contact surface and to contact the contact surface;
• and
• a control system operatively connected to the actuator for controlling the velocity of the member relative to the contact surface.

An apparatus for determining position of a valve member relative to a valve contact surface, wherein the member is operatively connected to an actuator, comprising:

• an actuator control circuit operatively connected to the actuator and operable to apply a control signal to the actuator, the control signal controlling movement of the member relative to the contact surface, and operable to receive an output from the actuator;
• and
• a seat detection circuit operatively connected to the actuator control circuit and operable to determine contact of the member with the contact surface from the output;
• wherein the actuator is a piezoelectric device.

An apparatus for controlling velocity of a valve member relative to a valve contact surface, wherein the member is operatively connected to an actuator, comprising:

• an actuator control circuit operatively connected to the actuator and operable to apply a control signal to the actuator, the control signal controlling movement of the member relative to the contact surface, and operable to receive an output from the actuator;
• a seat detection circuit operatively connected to the actuator control circuit and operable to determine contact of the member with the contact surface from the output;
• and
• a velocity control circuit operatively coupled to the actuator control circuit and seat detection circuit and operable to provide an input to the actuator control circuit for controlling velocity of the member;
• wherein the actuator is a piezoelectric device.

A method of determining position of a valve member relative to a valve contact surface, wherein the member is operatively connected to an actuator comprised of a prestressed electroactive bender, comprising:

• applying a control signal to the actuator to cause the member to move relative to the contact surface;
• determining an output of the actuator;
• and
• determining contact of the member with the contact surface from the output.

A method of controlling velocity of a valve member relative to a valve contact surface, wherein the member is operatively connected to an actuator comprised of a prestressed electroactive bender, comprising:

• storing an output of the actuator in a prior actuation cycle;
• determining an output of the actuator in a current actuation cycle;
• and
• modifying the velocity of the member as a function of the stored and current outputs.