Control circuit for an electromechanical actuator

Claim 2

In a control system including an actuator means having an actuator shaft movable between at least first and second positions, shaft positioning means including drive means and hold means for positioning said shaft at any one of a plurality of positions including said first and second positions and positions intermediate said first and second positions, and position sensing means for providing a sense signal indicating the position of said shaft, a control circuit responsive to said sense signal and a command signal indicating a desired position for said shaft for effecting energization of said drive means and said hold means for positioning said shaft, said control circuit comprising first switching means operable when enabled to provide an energizing signal for said drive means, second switching means operable when enabled to provide an energizing signal for said hold means, said first and second switching means being enabled concurrently whenever the difference between said command and sense signals exceeds a first predetermined amount to permit said shaft to be driven from a given position toward said second position, and to be maintained at any one of said discrete positions intermediate said given position and said second position, said second switching means being enabled independently of said first switching means whenever the difference between said command and sense signals exceeds a second predetermined amount to permit said shaft to be moved from a given position toward said first position and to be maintained at any one of the positions intermediate said given position and said first position.

Claim 3

A control circuit as set forth in claim 1 which includes signal comparator means responsive to said command and sense signals for providing a control signal that is proportional to the difference in the amplitudes of said command and sense signals for selectively enabling said first and second switching means as a function at the difference between the command and sense signals.

Claim 4

A control circuit as set forth in claim 2 wherein said position sensing means provides an AC sense signal and wherein said signal comparator means includes means for deriving a DC sense signal from the AC sense signal provided by said positioning means.

Claim 5

In a control system including an actuator means having an actuator shaft movable between at least first and second positions, shaft positioning means including drive means and hold means for positioning said shaft, bias means normally urging said shaft toward said first position, and position sensing means for providing a sense signal indicating the position of the shaft, a control circuit for effecting selective energization of said drive means and said hold means for positioning said shaft, said control circuit comprising first switching means operable when enabled to provide an energizing signal for said drive means, second switching means operable when energized to provide an energizing signal for said hold means, and signal comparator means responsive to said sense signal and a command signal indicative of a desired position for said shaft to enable said first and said second switching means concurrently whenever the difference between said command and sense signals exceeds a first predetermined amount to permit said shaft to be driven to and maintained at said desired position, said signal comparator means thereafter being responsive to a further predetermined difference between said command and sense signals to enable said second switching means independently of said first switching means to permit said shaft to be moved from said desired position toward said first position.

Claim 6

In a control system including an actuator means having an actuator shaft movable between at least first and second positions, shaft positioning means including drive means and hold means for positioning said shaft, bias means normally urging said shaft toward said first position, and position sensing means for providing a sense signal indicating the position of the shaft, a control circuit for effecting selective energization of said drive means and said hold means for positioning said shaft, said control circuit comprising first switching means operable when enabled to provide an energizing signal for said drive means, second switching means operable when energized to provide an energizing signal for said hold means, and signal comparator means responsive to said sense signal and a command signal indicative of a desired position for said shaft to enable said first and said second switching means concurrently whenever the difference between said command and sense signals exceeds a first predetermined amount to permit said shaft to be driven to and maintained at said desired position, said signal comparator means thereafter being responsive to a further predetermined difference between said command and sense signals to enable said second switching means independently of said first switching means to permit said shaft to be moved from said desired position toward said first position.

Claim 7

In a control system including an actuator means having an actuator shaft movable to a plurality of discrete positions, shaft positioning means including drive means and hold means for positioning said shaft at any one of said positions, bias means normally urging said shaft toward a first one of said positions, and position sensing means for providing a sense signal indicating the position of said shaft, a control circuit for providing selective energization of said drive means and said hold means to enable said shaft to be positioned at a desired one of said discrete positions, said control circuit comprising first switching means operable when enabled to provide a signal for energizing said drive means, second switching means operable when enabled to provide a signal for energizing said hold means, and input means responsive to said sense signal and to a command signal indicative of a desired position for said shaft to provide a control signal of an amplitude proportional to the difference between said command and sense signals for said first and second switching means, said first and second switching means including first and second threshold detecting means, respectively, having different preselected turn-on and turn-off thresholds to permit said first and second switching means to be enabled concurrently in response to a control signal of a first amplitude to effect energization of said drive means and said hold means permitting said shaft to be driven from one of said positions toward a second one of said positions and to permit said second switching means to be enabled independently of said first switching means in response to a control signal of a lower amplitude permitting said shaft to be moved toward said first position and to be maintained at any one of the positions intermediate said second and first positions.

Claim 8

In a control system including an actuator means having an actuator shaft movable to a plurality of discrete positions, shaft positioning means including drive means and hold means for positioning said shaft at any one of said positions, bias means normally urging said shaft toward a first one of said positions, and position sensing means for providing a sense signal indicating the position of said shaft, a control circuit for providing selective energization of said drive means and said hold means to enable said shaft to be positioned at a desired one of said discrete positions, said control circuit comprising first switching means operable when enabled to provide a signal for energizing said drive means, second switching means operable when enabled to provide a signal for energizing said hold means, and input means responsive to said sense signal and to a command signal indicative of a desired position for said shaft to provide a control signal of an amplitude proportional to the difference between said command and sense signals for said first and second switching means, said first and second switching means including first and second threshold detecting means, respectively, having different preselected turn-on and turn-off thresholds to permit said first and second switching means to be enabled concurrently in response to a control signal of a first amplitude to effect energization of said drive means and said hold means permitting said shaft to be driven from one of said positions toward a second one of said positions and to permit said second switching means to be enabled independently of said first switching means in response to a control signal of a lower amplitude permitting said shaft to be moved toward said first position and to be maintained at any one of the positions intermediate said second and first positions.

Claim 9

In a control system including an actuator means having an actuator shaft movable to a plurality of discrete positions and means associated with said actuatoR shaft for providing a sense signal indicating the position of said actuator shaft, drive means operable when energized to drive said actuator shaft from a first one of said positions to a desired position and hold means operable when energized to enable said actuator shaft to be driven to and maintained in a desired position, a control circuit for controlling the operation of said actuator means, said control circuit comprising input means for providing a command signal representing the desired position for said actuator shaft, first switching means for controlling the operation of said drive means, second switching means for controlling the operation of said hold means, said first and second switching means being enabled concurrently whenever the difference in amplitudes of said command and sense signals exceeds a predetermined value to permit said actuator shaft to be driven toward said desired position, the amplitude of said sense signal changing as said actuator shaft is driven toward said desired position to thereby decrease the difference between said command and sense signals, said first switching means being disabled and said second switching means remaining enabled when the difference between said command and sense signals has decreased to a further predetermined value when said shaft is at said desired position whereby said drive means is deenergized and said acutator shaft is maintained at said desired position by said hold means, said second switching means being disabled to deenergize said hold means when said command signal decreases a predetermined amount relative to said sense signal to permit said actuator shaft to move toward said first position.

Claim 10

In a control system including an actuator means having an actuator shaft movable to a plurality of discrete positions and means associated with said actuatoR shaft for providing a sense signal indicating the position of said actuator shaft, drive means operable when energized to drive said actuator shaft from a first one of said positions to a desired position and hold means operable when energized to enable said actuator shaft to be driven to and maintained in a desired position, a control circuit for controlling the operation of said actuator means, said control circuit comprising input means for providing a command signal representing the desired position for said actuator shaft, first switching means for controlling the operation of said drive means, second switching means for controlling the operation of said hold means, said first and second switching means being enabled concurrently whenever the difference in amplitudes of said command and sense signals exceeds a predetermined value to permit said actuator shaft to be driven toward said desired position, the amplitude of said sense signal changing as said actuator shaft is driven toward said desired position to thereby decrease the difference between said command and sense signals, said first switching means being disabled and said second switching means remaining enabled when the difference between said command and sense signals has decreased to a further predetermined value when said shaft is at said desired position whereby said drive means is deenergized and said acutator shaft is maintained at said desired position by said hold means, said second switching means being disabled to deenergize said hold means when said command signal decreases a predetermined amount relative to said sense signal to permit said actuator shaft to move toward said first position.

Claim 11

A control circuit as set forth in claim 6 wherein said first switching means comprises a first threshold detecting means having a preselected turnon threshold and a preselected turnoff threshold, and wherein said second switching means comprises a second threshold detecting means having a preselected turnon threshold and a preselected turnoff threshold, at least the turnoff threshold of said second threshold detecting means being lower than the turnoff threshold of said first threshold detecting means.

Claim 12

A control circuit as set forth in claim 6 wherein said input means includes a signal comparator means responsive to said command and sense signals to provide a control signal that is proportional to the difference in the amplitudes of said command and sense signals for selectively enabling said first and second switching means.

Claim 13

A control circuit as set forth in claim 8 wherein said first threshold detecting means comprises first Schmitt trigger means enabled whenever the amplitude of said control signal exceeds a first predetermined value and disabled when the amplitude of the control signal decreases to a second predetermined value, and wherein said second threshold detecting means comprises second Schmitt trigger means enabled at least whenever the amplitude of said control signal exceeds said first value and disabled when the amplitude of said control signal decreases to a third predetermined value which is less than said second predetermined value.

Claim 14

In a control system including a hydraulic actuator having an actuator shaft movable to a plurality of discrete positions, pump means operable when energized to pump hydraulic fluid into an expandable chamber of said hydraulic actuator via an inlet port to move the actuator shaft against the force of a restoring spring from a given position to a desired position, dump valve means operable when energized to close an outlet port of said expandable chamber to maintain the hydraulic fluid in said expandable chamber and thereby enable said actuator shaft to be driven to and maintained at said second position, and means associated with said actuator shaft for producing a sense signal which varies as a function of displacemnt of said actuator shaft to indicate the position of said actuator shaft, a control circuit comprising first sWitching means for controlling the operation of said pump means, second switching means for controlling the operation of said dump valve means, and signal comparator means responsive to said sense signal and a command signal indicative of the desired position for said shaft for enabling said first and second switching means, said signal comparator means being responsive to a first predetermined difference between the command and sense signals to enable said first and second switching means to effect energization of said pump means and said dump valve means to permit said actuator shaft to be moved to said desired position, said signal comparator means being responsive to the difference between the sense signal and the command signal when the shaft reaches the desired position to disable said first switching means while maintaining said second switching means enabled such that said pump means is deenergized and said dump valve means remains energized causing said actuator shaft to be maintained at said desired position, and said signal comparator means being responsive to a further difference between the command signal and the sense signal to disable said second switching means such that said dump valve means is deenergized, opening said outlet port permitting the hydraulic fluid to flow out of the expandable chamber to thereby permit said actuator shaft to be moved toward said first position under the force of the restoring spring.

Claim 15

In a control system including a hydraulic actuator having an actuator shaft movable to a plurality of discrete positions, pump means operable when energized to pump hydraulic fluid into an expandable chamber of said hydraulic actuator via an inlet port to move the actuator shaft against the force of a restoring spring from a given position to a desired position, dump valve means operable when energized to close an outlet port of said expandable chamber to maintain the hydraulic fluid in said expandable chamber and thereby enable said actuator shaft to be driven to and maintained at said second position, and means associated with said actuator shaft for producing a sense signal which varies as a function of displacemnt of said actuator shaft to indicate the position of said actuator shaft, a control circuit comprising first sWitching means for controlling the operation of said pump means, second switching means for controlling the operation of said dump valve means, and signal comparator means responsive to said sense signal and a command signal indicative of the desired position for said shaft for enabling said first and second switching means, said signal comparator means being responsive to a first predetermined difference between the command and sense signals to enable said first and second switching means to effect energization of said pump means and said dump valve means to permit said actuator shaft to be moved to said desired position, said signal comparator means being responsive to the difference between the sense signal and the command signal when the shaft reaches the desired position to disable said first switching means while maintaining said second switching means enabled such that said pump means is deenergized and said dump valve means remains energized causing said actuator shaft to be maintained at said desired position, and said signal comparator means being responsive to a further difference between the command signal and the sense signal to disable said second switching means such that said dump valve means is deenergized, opening said outlet port permitting the hydraulic fluid to flow out of the expandable chamber to thereby permit said actuator shaft to be moved toward said first position under the force of the restoring spring.

Claim 16

A control circuit as set forth in claim 10 wherein said signal comparator means comprises differential amplifier means having a first input connected to receive said command signal and a second input connected to receive said sense signal, said differential amplifier means being operable to provide a control signal representing the difference between said command and sense signals for enabling said first and second switching means.

Claim 17

A control circuit as set forth in claim 10 wherein said first switching means comprises a first Schmitt trigger circuit having a first preselected turnon threshold and a first preselected turnoff threshold and wherein said second switching means comprises a second Schmitt trigger circuit having a second preselected turnon threshold and a second preselected turnoff threshold, at least said second turnoff threshold being lower than said first turnoff threshold to enable said second Schmitt trigger circuit to remain enabled to energize said dump valve means when said first Schmitt trigger circuit becomes disabled.