Control mode switching system for a servomechanism

Claim 2

A control mode switching system for a hydraulic servomehcanism controllable by load control mode or stroke control mode command signals and having means to provide load or stroke feedback signals, and in which an error signal representing the difference between a command signal and a corresponding mode feedback signal is normally used to control the operation of the servomechanism, the system comprising means for changing from a present feedback signal to a new feedback signal of a different control mode, means responsive to actuation of said means for changing for maintaining the value of said error signal substantially constant for a time period subsequent to the operation of said means for changing, means for controlling the servomechanism in accordance with the value of the maintained error signal, said new feedback signal and a corresponding command signal providing a new error signal, means for comparing the maintained error signal and the new error signal, and means responsive to the means for comparing for changing the value of said new command signal during said time period until the new error signal changes in the direction of said maintained error signal to reduce the difference therebetween.

Claim 3

In combination with the control mode switching system set forth in claim 1, a computer, means for feeding information into said computer corresponding to the value of the new feedback signal, the computer subtracting the signal corresponding to the new feedback signal from the command signal to produce a new command signal with the consequence that said new error signal is provided in accordance with the difference between the value of the new command signal and the value of said new feedback signal, said means for comparing comprising a comparator for determining the difference between the new error signal and the maintained error signal, the comparator controlling the computer so as to change the new command signal in a direction to equalize the new error signal with the maintained error signal.

Claim 4

The combination of claim 2 in which said means for maintaining the value of said error signal substantially constant includes a track and store amplifier and a switch connected to said amplifier for causing said amplifier to track the error signal rEpresenting the difference between the value of said command signal and the value of said feedback signal, and means connected to the computer for causing said switch to be closed when said error signal is to be tracked and to be opened when said error signal is to be stored.

Claim 5

The combination of claim 3 in which said last-mentioned means includes a differential amplifier having a pair of input terminals, one of said input terminals being connected to the computer and the other of said input terminals being connected to a fixed potential, and said switch constituting a field effect transistor having its gate connected to said output terminal and its source and drain in circuit with said amplifier to forward said error signal to said amplifier when said transistor is conductive.

Claim 6

In combination with a servomechanism including a normally closed control loop having a summing junction provided with a first input terminal to which a command signal is applied and a second input terminal to which a feedback signal from the servomechanism is applied, said summing junction having an output terminal for providing an error signal representative of any difference between the values of the command and feedback signals applied to said first and second terminals, a track and store amplifier having an input and an output, a switch means selectively connecting the output of said summing junction to the input of said track and store amplifier, a signal comparing means having a pair of inputs and an output, the output of said track and store amplifier being connected to normally control the value of the error signal, and also being connected to one input of the signal comparing means, a control mode switching system for said servomechanism comprising means changing to a different command signal because of change in control mode, means associated with the amplifier for storing a signal corresponding to the value of said error signal, said switch being responsive to the change of control mode to cause said track and store amplifier to deliver the stored signal for controlling the servomechanism in accordance with the stored signal for a period of time, and means connected to the output of said comparing means for adjusting the value of said different command signal during said period of time to provide an error signal having a value approximating that of the stored signal, said switch means returning said amplifier to track mode to track said error signal after said period of time.

Claim 7

In combination with a servomechanism including a normally closed control loop having a summing junction provided with a first input terminal to which a command signal is applied and a second input terminal to which a feedback signal from the servomechanism is applied, said summing junction having an output terminal for providing an error signal representative of any difference between the values of the command and feedback signals applied to said first and second terminals, a track and store amplifier having an input and an output, a switch means selectively connecting the output of said summing junction to the input of said track and store amplifier, a signal comparing means having a pair of inputs and an output, the output of said track and store amplifier being connected to normally control the value of the error signal, and also being connected to one input of the signal comparing means, a control mode switching system for said servomechanism comprising means changing to a different command signal because of change in control mode, means associated with the amplifier for storing a signal corresponding to the value of said error signal, said switch being responsive to the change of control mode to cause said track and store amplifier to deliver the stored signal for controlling the servomechanism in accordance with the stored signal for a period of time, and means connected to the output of said comparing means for adjusting the value of said different command signal during said period of time to provide an error signal having a value approximating that of the stored signal, said switch means returning said amplifier to track mode to track said error signal after said period of time.

Claim 8

The combination of claim 5 including a computer, said control mode switching system comprising a slew line connected between said comparing means and said computer for causing the computer to slew said different command signal so that said error signal at the output terminal of said summing junction is substantially equal to said stored signal.

Claim 9

The combination of Claim 6 in which said computer is a digital computer, and further including a digital-to-analog converter connected between said computer and the first input terminal of said summing junction.

Claim 10

The combination of Claim 7 further including an analog-to-digital converter for converting the value of the feedback signal to a digital signal for entry into the computer so that said computer can subtract the value of the feedback signal delivered to it from the then existing digital command signal to produce the new command signal.

Claim 11

In combination, a servomechanism including a valve amplifier for supplying fluid to said servo-mechanism and a feedback line carrying a signal representative of a measured condition of an actuator element contained in said servo-mechanism, a digital computer, an analog-to-digital converter connected between said feedback line and said computer, a summing junction having first and second input terminals and an output terminal, said feedback line being connected to said second input terminal, a digital-to-analog converter connected between said computer and said first input terminal to apply a command signal to said fiRst input terminal, whereby an error signal representative of the difference between the value of the command signal and the value of the feedback signal appears at the output terminal of said summing junction, a track and store amplifier connected to said output terminal, means controlled by the computer for causing said track and store amplifier to either track the error signal appearing at said output terminal or to cause said amplifier to store the signal appearing at said output terminal, the output of said track and store amplifier being connected to said valve amplifier for delivering either the tracked or stored signal to said valve amplifier, a comparator having first and second input terminals and an output terminal, the first input terminal of said comparator being connected to the output terminal of said summing junction and the second input terminal of said comparator being connected to said track and store amplifier, a digital signal line connected between the output terminal of said comparator and said digital computer for controlling the computer to adjust the command signal delivered to said digital-to-analog converter so as to change the error signal at the output terminal of said summing junction so that it corresponds in value to that of the error signal stored by said track and store amplifier.

Claim 12

In combination, a servomechanism including a valve amplifier for supplying fluid to said servo-mechanism and a feedback line carrying a signal representative of a measured condition of an actuator element contained in said servo-mechanism, a digital computer, an analog-to-digital converter connected between said feedback line and said computer, a summing junction having first and second input terminals and an output terminal, said feedback line being connected to said second input terminal, a digital-to-analog converter connected between said computer and said first input terminal to apply a command signal to said fiRst input terminal, whereby an error signal representative of the difference between the value of the command signal and the value of the feedback signal appears at the output terminal of said summing junction, a track and store amplifier connected to said output terminal, means controlled by the computer for causing said track and store amplifier to either track the error signal appearing at said output terminal or to cause said amplifier to store the signal appearing at said output terminal, the output of said track and store amplifier being connected to said valve amplifier for delivering either the tracked or stored signal to said valve amplifier, a comparator having first and second input terminals and an output terminal, the first input terminal of said comparator being connected to the output terminal of said summing junction and the second input terminal of said comparator being connected to said track and store amplifier, a digital signal line connected between the output terminal of said comparator and said digital computer for controlling the computer to adjust the command signal delivered to said digital-to-analog converter so as to change the error signal at the output terminal of said summing junction so that it corresponds in value to that of the error signal stored by said track and store amplifier.

Claim 13

The combination set forth in claim 9 in which said means for controlling the track and store amplifier includes a differential amplifier having a first input terminal, a second input terminal and an output terminal, and a field effect transistor having its gate connected to the output terminal of said differential amplifier, the source of said field effect transistor being connected to the output terminal of said summing junction and the drain of said field effect transistor being connected to said track and store amplifier, the first input terminal of said differential amplifier being connected to said computer and the second input terminal of said differential amplifier being connected to a fixed potential.

Claim 14

In combination with a servomechanism, a digital computer having an input and an output, said computer supplying via its output various primary command signals representing the desired positions of a member actuated by said servomechanism, means providing a feedback signal representing the actual position of said member, summing means having a first input terminal connected to the output of said computer and a second input terminal connected to the feedback means and an output terminal for providing an error signal representing any difference between whatever command signal is applied to the first input terminal of said summing means and the feedback signal applied to the second input terminal thereof so as to provide an error signal at its said output terminal for controlling the position of said member, switch means for connecting said feedback means to the input of said computer to cause said computer to change the value of an existing primary command signal to a secondary command signal having a value approximating the difference between the value of said primary command signal and the value of said feedback signal, means for tracking and storing said error signal prior to the change from said primary command signal to said secondary command signal, means connected between said computer and said tracking and storing means for causing said tracking and storing means to store the error signal prior to said command signal change, comparator means having a first input terminal and a second input terminal and an output terminal, the first input terminal of said comparator means being connected to the output terminal of said summing means and the second input terminal of said comparator means being connected to said tracking and storing means, and means connected to the output terminal of said comparator means for causing the computer to increase or decrease the value of said secondary command signal so that it causes the resulting error signal appEaring at the output terminal of said summing means to equal substantially the value of the stored error signal.

Claim 15

In combination with a servomechanism, a digital computer having an input and an output, said computer supplying via its output various primary command signals representing the desired positions of a member actuated by said servomechanism, means providing a feedback signal representing the actual position of said member, summing means having a first input terminal connected to the output of said computer and a second input terminal connected to the feedback means and an output terminal for providing an error signal representing any difference between whatever command signal is applied to the first input terminal of said summing means and the feedback signal applied to the second input terminal thereof so as to provide an error signal at its said output terminal for controlling the position of said member, switch means for connecting said feedback means to the input of said computer to cause said computer to change the value of an existing primary command signal to a secondary command signal having a value approximating the difference between the value of said primary command signal and the value of said feedback signal, means for tracking and storing said error signal prior to the change from said primary command signal to said secondary command signal, means connected between said computer and said tracking and storing means for causing said tracking and storing means to store the error signal prior to said command signal change, comparator means having a first input terminal and a second input terminal and an output terminal, the first input terminal of said comparator means being connected to the output terminal of said summing means and the second input terminal of said comparator means being connected to said tracking and storing means, and means connected to the output terminal of said comparator means for causing the computer to increase or decrease the value of said secondary command signal so that it causes the resulting error signal appEaring at the output terminal of said summing means to equal substantially the value of the stored error signal.

Claim 16

The combination set forth in claim 11 in which said computer supplies a second primary command signal indicative of a different desired position of said controlled member so that the value of the secondary command signal applied to the first input terminal of said summing means is changed incrementally to the value of the second primary command signal.

Claim 17

The combination set forth in claim 12 in which said computer is a digital computer and in which said feedback signal is an analog signal, the combination further including an analog-to-digital converter connected between said switch means and the input of said computer, and a digital-to-analog converter connected between the output of said computer and the first input terminal of said summing means, said summing means being an analog device.