Controlling activation of devices

An apparatus for operating a device in a wellbore, comprising:

• at least a first and at least a second actuator activable by an input energy;
• and
• at least an operator member adapted to be moved in incremental steps by the first actuator and latched in its current position by the second actuator,
• wherein the first actuator is responsive to variation of the input energy between on and off states by activating and deactivating, and the second actuator is responsive to the variation of the input energy by remaining activated.

An apparatus for operating a device in a wellbore, comprising:

• at least a first and at least a second actuator activable by an input energy;
• and
• at least an operator member adapted to be moved in incremental steps by the first actuator and latched in its current position by the second actuator,
• wherein at least one of the first and second actuators includes a solenoid actuator.

An apparatus for operating a device in a wellbore, comprising:

• at least a first and at least a second actuator activable by an input energy;
• and
• at least an operator member adapted to be moved in incremental steps by the first actuator and latched in its current position by the second actuator,
• wherein at least one of the first and second actuators includes an actuator having an element expandable and contractable by the input energy,
• wherein the element includes a piezoelectric material.

An apparatus for operating a device in a wellbore, comprising:

• at least a first and at least a second actuator activable by an input energy;
• and
• at least an operator member adapted to be moved in incremental steps by the first actuator and latched in its current position by the second actuator,
• wherein at least one of the first and second actuators includes an actuator having an element expandable and contractable by the input energy,
• wherein the element includes a heat-expandable material.

An actuator system comprising:

• an operating actuator capable of being activated and deactivated;
• a holding actuator that is maintained in an activated state;
• and
• a member engageable by the operating and holding actuators, the operating actuator adapted to move the member in incremental steps and the holding actuator adapted to maintain a current position of the member.

A string for use in a wellbore, comprising:

• a downhole device;
• and
• an actuator assembly operably coupled to the downhole device, the actuator assembly including:
• a first electrically activable actuator;
• a second electrically activable actuator;
• and
• an operator member adapted to be moved by the first electrically activable actuator and maintained in position by the second electrically activable actuator,
• the first electrically activable actuator responsive to an input energy by cycling on and off, and
• the second electrically activable actuator responsive to the input energy by being maintained activated.

A method of operating a device having an operator member, comprising:

• providing an operating actuator and a holding actuator;
• alternately activating and deactivating the operating actuator to move the operator member in predetermined incremental steps;
• and
• maintaining the holding actuator activated to maintain a current position of the operator member.

An actuator apparatus for operating a device, comprising:

• at least first and second actuators activable by input energy,
• the first actuator responsive to the input energy by cycling between energized and de-energized positions,
• the second actuator responsive to the input energy by remaining in an energized position;
• and
• at least one operating member adapted to be moved incrementally by the first actuator cycling between energized and de-energized positions, the operating member adapted to be held in its current position by the second actuator after each incremental movement.