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US 4,066,946 AGranted
Servo systems
AssigneeSmiths Industries Limited
InventorsJohn W. D. Jones, Keith R. Oakey
Life of this patent
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AssigneeSmiths Industries Limited
InventorsJohn W. D. Jones, Keith R. Oakey
Estimating the term…
A counter-pointer display of aircraft altitude is driven by a servo in accordance with a digital representation of height provided at regular intervals by an air-data computer. The content of a first register is updated regularly with the height representation, and the difference between this and the content of a second register is entered into a third register. The content of the second register is updated rapidly from a shaft encoder that is coupled to be driven together with the counter-pointer display by a stepping motor, and the content of the third register is updated in synchronism with the updating of the first register to staticize the error between the input height-representation and the output representation provided by the counter-pointer display. The stepping motor is supplied with pulses at a rate dependent on the magnitude of the staticized error value via a pulse-rate divider, the pulse-rate divider being supplied with a regular pulse train via a gate device that is operable to block passage of pulses of the pulse train to the divider. The proportion of pulses passed by the gate device and the magnitude of the voltage energization of the motor are both regulated in accordance with the magnitude of error value staticized by the third register.
In a servo system in which drive means provides output drive in accordance with error between the output of the servo and an input demand that is updated in value intermittently, the improvement for minimizing output-velocity fluctuation of the system in response to high-rates of change of the input-demand value, wherein the system includes means to staticize the said error in the intervals between successive updatings of the input demand, said staticizing means updating the staticized value of said error only in accordance with updating of the said input-demand value, and wherein said drive means is coupled to said staticizing means to respond to the error-values staticized in respect of successive updatings of said input demand, said drive means responding to each such staticized error-value to drive the said output in accordance with the staticized error-value at a substantially constant rate throughout until the next updating of said error value.
A servo system for providing output drive in accordance with an input positional-demand that changes intermittently, comprising a first register, means for updating the digital content of the first register in accordance with the input demand, an output member drivable to have a displacement in accordance with said positional-demand, motor means coupled to said output member for driving said output member, means coupled to said output member to provide a signal representation of the output displacement of said output member, a second register, means for periodically updating the content of said second register in accordance with difference between said signal representation and the digital content of said first register, the updated content of the said second register having a value in accordance with said difference to represent the magnitude of positional error of the said output member, and further means for deriving a command signal in accordance with the updated content of said second register, said command signal having a substantially constant value in accordance with the said magnitude of positional error throughout the interval to the next successive updating of the said second register, said motor means being responsive to said command signal to drive said output member at a substantially constant velocity in accordance with the said magnitude of positional error so that the output member is driven at substantially constant velocity between successive updatings to thereby minimize velocity fluctuation of the output member in response to high-rate change of the input demand.
An instrument for providing an output representation of a value that is dependent on the value of an input variable and adapted to minimize velocity fluctuation of said output representation in response to high-rate of change of the value of the input variable, said instrument comprising means responsive to the input variable to provide a digital representation in accordance with the value thereof, a first register, means to update the content of said first register in accordance with the said digital representation, means drivable to provide said output representation, means coupled to said drivable means for providing a digital representation of the value of the output representation provided thereby, a second register, means operative only following each updating of said first register to update the digital content of said second register in accordance with any difference between the said digital representation of the output value and the content of said first register, the content of said second register being updated in accordance with said difference to represent the extent of errors in said output representation as related to the input value of said variable, and drive means responsive to the updated content of said second register for driving said drivable means in accordance therewith, said drive means driving said drivable means at a substantially constant velocity in accordance with said represented error throughout the period between successive updatings of said second register.
Dependencies are inferred from the claim text.