Controller for downhole tool

1. A controller for operating a downhole tool, comprising:

a tubular body;

a balance chamber;

a control chamber;

a seat disposed in the body for receiving first and second pump-down plugs, at least a portion of one of the seat and the plugs being radially displaceable to pass through or allow passage of the other of the seat and the plugs at a first threshold pressure differential;

a toggle linked to the seat to alternate between a locked position and an unlocked position in response to seating of the plugs comprising

a switch mandrel having a pair of seal shoulders and a bypass groove formed between the shoulders; and

a valve housing disposed between the chambers having a passage segment in fluid communication with each chamber,

a control mandrel having a piston shoulder disposed in the control chamber and used for engaging a piston of the downhole tool and the control mandrel linked to the toggle:

to be longitudinally movable between a first position and a second position when the toggle is unlocked, and

to be prevented from movement from the first position to the second position when the toggle is locked.

2. The controller of claim 1 , wherein:

one of the seal shoulders is disposed between the passage segments in the locked position, and

the bypass groove is disposed between the passage segments in the unlocked position.

3. The controller of claim 2 , wherein:

the switch mandrel has one of a cam profile and a follower and a keyed profile, and

the toggle further comprises an index sleeve having the other of the cam profile and a follower and a keyed profile matable or abuttable with the keyed profile of the switch mandrel.

4. The controller of claim 1 , wherein the toggle comprises:

a switch mandrel having one of a cam profile and a follower, and

an index sleeve having the other of the cam profile and a follower and a keyed profile.

5. The controller of claim 1 ,

further comprising a return spring biasing the control mandrel toward the piston,

wherein the control mandrel is also linked to the seat to augment a force applied by the return spring with the first pressure differential.

6. The controller of claim 5 , wherein

the linkage between the control mandrel and the seat is hydraulic.

7. A bottom hole assembly, comprising:

the controller of claim 1 ; and

the downhole tool connected to the controller and comprising:

a second tubular body having a bore therethrough, a pocket formed through a wall thereof, and an extension profile and a retraction profile formed in a surface of the pocket;

an arm:

pivotally connected to the piston and torsionally connected to the second tubular body;

disposed in the pocket in a retracted position;

having an extension profile and a retraction profile;

movable to an extended position where an outer surface of the arm extends outward past an outer surface of the second tubular body; and

the piston:

disposed in the second body bore;

having a bore therethrough;

operable to extend the arm by longitudinally moving the arm in a first direction to disengage the retraction profiles and engage the extension profiles; and

operable to retract the arm by longitudinally moving the arm in a second direction to disengage the extension profiles and engage the retraction profiles.