Position feedback control system for a numerically controlled machine tool

Claim 2

A feedback position control system controlling the displacement of at least one movable member of a numerical control apparatus and further having transducer means, responsive to excitation signals, operatively connected to each movable member for generating an output signal having a cyclically recurring phase relationship with respect to the excitation signals that is correlatable with the displacement of the at least one movable member, the feedback position control system comprising: command means for generating a command signal indicative of the desired position of the at least one movable member; feedback means for generating a feedback signal indicative of the motion of said at least one member comprising: phase detecting means for determining the phase of said output signal relative to a determinable reference irrespective of the d.c. bias level of the output signal; conversion means for converting said determined phase into a first signal indicative of the motion of said at least one movable member during a particular cycle of said output signal; and wherein said system further includes comparator means for comparing said command signal and said feedback signal and for generating an error signal for driving said at least one member to the desired position.

Claim 3

The system as recited in claim 1 wherein said feedback means further includes: direction of motion sensing means for generating an accumulative signal indicative of the number of completed cycles of said first signal; combining means for combining said first signal and said accumulative signal to generate said feedback position signal.

Claim 4

The system as recited in claim 2 further including signal shaping means for conditioning and shaping said output signal prior to input to said phase detecting means.

Claim 5

The system as recited in claim 3 wherein said signal shaping means is a zero crossing detector responsive to the zero voltage crossings of said output signal.

Claim 6

A feedback position control system controlling the displacement of at least one movable member of a numerical control apparatus and further having transducer means, responsive to excitation signals, operatively connected to each movable member for generating an output signal having a cyclically recurring phase relationship with respect to the excitation signals that is correlatable with the displacement of the at least one movable member, the feedback position control system comprising: command means for generating a command signal indicative of the desired position of the at least one movable member; feedback means for generating a feedback signal indicative of the motion of said at least one member comprising: phase detecting means for determining the phase of said output signal relative to a determinable reference irrespective of the d.c. bias level of the output signal including: reference counter means for generating a recurring real time count having a predetermined period; phase means responsive to the output signal of said transducer means for determining the phase relationship between said output signal relative to the transducer excitation signals; first zero crossing means responsive to zero crossings of said output signal in a determinable direction for generating an indicator signal indicative of the first of said zero crossings in said determinable direction occurring during a predetermined interval of the excitation signals; second zero crossing means responsive to said output signal for generating a second signal upon the occurrence of the next zero crossing of said output signal; first means responsive to said indicator signal for storing a first count having the value of the count within said reference counter means at the occurrence of said indicator signal; second means responsive to said second signal for generating a summed count by adding to said stored first count the value of the count within said reference counter means at the occurrence of said second signal; and dividing means for dividing said summed count by a determinable factor to generate a number indicative of the phase relationship between a predetermined point with the excitation signals and the first maximum of the output signal occurring after said indicator signal; conversion means for converting said determined phase during a particular cycle of said output signal into a first signal indicative of the motion of said at least one movable member; and wherein said system further includes: comparator means for comparing said command signal and said feedback signal and for generating an error signal for driving said at least one member to the desired position.

Claim 7

A feedback position control system controlling the displacement of at least one movable member of a numerical control apparatus and further having transducer means, responsive to excitation signals, operatively connected to each movable member for generating an output signal having a cyclically recurring phase relationship with respect to the excitation signals that is correlatable with the displacement of the at least one movable member, the feedback position control system comprising: command means for generating a command signal indicative of the desired position of the at least one movable member; feedback means for generating a feedback signal indicative of the motion of said at least one member comprising: phase detecting means for determining the phase of said output signal relative to a determinable reference irrespective of the d.c. bias level of the output signal including: reference counter means for generating a recurring real time count having a predetermined period; phase means responsive to the output signal of said transducer means for determining the phase relationship between said output signal relative to the transducer excitation signals; first zero crossing means responsive to zero crossings of said output signal in a determinable direction for generating an indicator signal indicative of the first of said zero crossings in said determinable direction occurring during a predetermined interval of the excitation signals; second zero crossing means responsive to said output signal for generating a second signal upon the occurrence of the next zero crossing of said output signal; first means responsive to said indicator signal for storing a first count having the value of the count within said reference counter means at the occurrence of said indicator signal; second means responsive to said second signal for generating a summed count by adding to said stored first count the value of the count within said reference counter means at the occurrence of said second signal; and dividing means for dividing said summed count by a determinable factor to generate a number indicative of the phase relationship between a predetermined point with the excitation signals and the first maximum of the output signal occurring after said indicator signal; conversion means for converting said determined phase during a particular cycle of said output signal into a first signal indicative of the motion of said at least one movable member; and wherein said system further includes: comparator means for comparing said command signal and said feedback signal and for generating an error signal for driving said at least one member to the desired position.

Claim 8

The system as recited in claim 5 wherein said reference counter means produces a series of reference pulses having a predetermined relationship relative to the zero crossings of the excitation signals.

Claim 9

The system as recited in claim 6 wherein said predetermined relationship of said reference counter means includes maintaining the period of said reference counter means equal to twice the period of the transducer excitation signals.

Claim 10

The system as recited in claim 7 wherein said comparator means includes means for normalizing said phase relative to the time of the first maximum value of said reference signal occurring after said first signal to generate said position feedback signal.

Claim 13

The method as recited in claim 9 including the additional step of adding to the parameter defined in step f a count corresponding to a determinable amount of phase shift to translate the phase shift of said output signal relative to a determinable point within the waveform of the transducer excitation reference signals.

Claim 14

A feedback position control system for controlling the displacement of at least one movable member of a numerical control apparatus and further having transducer means, responsive to excitation signals, operatively connected to each movable member for generating an output signal having a cyclically recurring phase relationship with respect to the excitations signals that is correlatable with the displacement of the at least one movable member, the feedback position control system comprising: command means for generating a command signal indicative of the desired position of the at least one movable member; feedback means for generating a feedback signal indicative of the motion of said at least one member comprising: phase detecting means for determining the phase of said output signal relative to a determinable reference irrespective of the d.c. bias level of the output signal, including: reference counter means for generating a recurring real time signal having a determinable period; wherein said recurring real time signal is a recurring digital count; reference means responsive to said real time signal for generating a periodically repeating first reference signal to excite said transducer means; quadrature means responsive to said real time signal for generating a periodically repeating second reference signal, to further excite said transducer means, that is shifted in phase from and has the same frequency as said first reference signal; first means responsive to said output signal for sampling the count within said reference counter means and for storing a first number corresponding to said count upon the occurrence of a first zero crossing of said output signal in a determinable direction; second means responsive to the next zero crossing of said output signal for sampling the count within said reference counter means and for storing a second number corresponding to the count within said reference means at said next zero crossing; third means for generating a third number that is equal to the sum of said first and said second number and for dividing said third number by a factor; conversion means for converting said determined phase into a first signal indicative of the motion of said at least one movable member during a particular cycle of said output signal; and wherein said system further includes: comparator means for comparing said command signal and said feedback signal and for generating an error signal for driving said at least one member to the desired position.

Claim 15

A feedback position control system for controlling the displacement of at least one movable member of a numerical control apparatus and further having transducer means, responsive to excitation signals, operatively connected to each movable member for generating an output signal having a cyclically recurring phase relationship with respect to the excitations signals that is correlatable with the displacement of the at least one movable member, the feedback position control system comprising: command means for generating a command signal indicative of the desired position of the at least one movable member; feedback means for generating a feedback signal indicative of the motion of said at least one member comprising: phase detecting means for determining the phase of said output signal relative to a determinable reference irrespective of the d.c. bias level of the output signal, including: reference counter means for generating a recurring real time signal having a determinable period; wherein said recurring real time signal is a recurring digital count; reference means responsive to said real time signal for generating a periodically repeating first reference signal to excite said transducer means; quadrature means responsive to said real time signal for generating a periodically repeating second reference signal, to further excite said transducer means, that is shifted in phase from and has the same frequency as said first reference signal; first means responsive to said output signal for sampling the count within said reference counter means and for storing a first number corresponding to said count upon the occurrence of a first zero crossing of said output signal in a determinable direction; second means responsive to the next zero crossing of said output signal for sampling the count within said reference counter means and for storing a second number corresponding to the count within said reference means at said next zero crossing; third means for generating a third number that is equal to the sum of said first and said second number and for dividing said third number by a factor; conversion means for converting said determined phase into a first signal indicative of the motion of said at least one movable member during a particular cycle of said output signal; and wherein said system further includes: comparator means for comparing said command signal and said feedback signal and for generating an error signal for driving said at least one member to the desired position.

Claim 16

The system as recited in claim 5 wherein said feedback means further includes: direction of motion sensing means for generating an accumulative signal indicative of the number of completed cycles of said first signal; combining means for combining said first signal and said accumulative signal to generate said feedback position signal.

Claim 17

The system as recited in claim 11 wherein said feedback means further includes: direction of motion sensing means for generating an accumulative signal indicative of the number of completed cycles of said first signal; combining means for combining said first signal and said accumulative signal to generate said feedback position signal.

Claim 18

The system as recited in claim 13 further including signal shaping means for conditioning and shaping said output signal prior to input to said phase detecting means.

Claim 19

The system as recited in claim 14 wherein said signal shaping means is a zero crossing detector responsive to the zero voltage crossings of said output signal.