Servo control system for a serial printer print head

Claim 3

The system of claim 1 wherein each of said calculating means comprises: means for calculating a numerical difference count for displacing the print head to the new print position in a forward direction; means for calculating a numerical difference count for displacing the print head to the new print position in a reverse direction; and means for selecting the numerical difference count and corresponding direction which will result in the least distance of travel of the print head in moving to the new character position.

Claim 4

The system of claim 2 further comprising: means for sensing the displacement of the print head, said sensing means attached to said print head and generating a displacement signal; means for generating pulses in response to the displacement signal, said pulse generating means connected to said displacement sensing means; and means for feeding back the pulses to said means for storing the numerical difference count so as to provide an accounting of how many character positions have been traversed by the print head since moving from the previous print position.

Claim 5

The system of claim 3 wherein each of said means for storing the numerical difference count comprises: a downcounter for storing the numerical difference count as it is initially outputed from said means for selecting the numerical difference count, said downcounter being connected to said means for feeding back the pulses so as to be decremented each time a pulse appears at the decrementing input side thereby making the stored numerical difference count equal to the number of character positions on the print head yet to be traversed in moving the print head to the new print position.

Claim 6

The system of claim 4 wherein each of said means for selecting a constant displacement rate corresponding to the stored numerical difference count comprises: A plurality of logic gates each of which generates a binary command indicative of a given constant displacement rate; and means for activating one of said logic gates at any one time in response to each stored numerical difference count within said downcounter.

Claim 7

The system of claim 1 wherein each of said means for displacing the print head comprises: means for generating a step signal having a ramp between each successive step level in response to the various constant displacement rates outputed from said command means; a motor connected to said step signal generating means for moving the print head at a ramp velocity rate dictated by the amplitude of the step signal; means for sensing a rate of displacement of the print head; and means for feeding back the rate of displacement to be summed with the step signal.

Claim 8

The system of claim 6 wherein each of said means for generating a step signal having ramp between each successive step level further comprises: circuit means for generating a step signal having step levels corresponding to the constant displacement rate levels at which the means for displacing the print head is to move; and means for generating ramps between the various constant displacement rates of the step signal having step levels.

Claim 9

The system of claim 7 wherein each of said means for generating ramps between the various constant displacement rates of the step signal having step levels comprises: a differential amplifier one side of which is connected to said circuit means for generating a step signal; a current source circuit connected to the output of said differential amplifier; a circuit for drawing off current connected to the output of said differential amplifier; a capacitance connected to both said current source circuit and to said current drawing circuit so as to either linearly charge or discharge depending on whether the current source circuit or the current drawing circuit are turned on; and a feedback path connected to said capacitance circuit and connected to said differential amplifier so as to feedback the capacitance voltage for summing with the step signal having step levels which appears as the other input to said differential amplifier.

Claim 10

The system of claim 8 wherein each of said means for displacing the print head further comprises: means for feeding back the print head displacement, said means for feeding back the print head displacement being connected to said means for sensing the print head displacement; means for conditionally switching the fed back print head displacement into the input of said motor for moving the print head; means for detecting a portion of the final ramp of the step signal having a ramp between each successive step level as it declines to a zero displacement rate said detection means connected to said differential amplifier; and means for applying the output of said detection means to said conditional switch means so as to switch the feedback of the print head displacement into said motor when the step signal having a ramp between each successive step level has gone to zero.

Claim 13

The system of claim 10 wherein said means for inputing the selected constant displacement rate comprises: means for generating a signal in response to the selected displacement rates; and means for generating ramps between the various step levels of the step signal to thereby form a step signal having a ramp between each successive step level.

Claim 14

The system of claim 11 further containing a second feedback path comprising: means for sensing the displacement rate of the print head; and means for summing the displacement rate with the step signal having a ramp between each successive step level.

Claim 15

The system of claim 12 further containing a third feedback path comprising: means for generating an analog displacement signal, said analog generating means connected to said displacement sensing means; and means for conditionally feeding back the analog displacement signal for input to the means for displacing the print head.

Claim 16

The system of claim 13 wherein said means for conditionally feeding back the analog displacement signal comprises: means for conditionally switching the fedback analog displacement into the input of said means for displacing the print head; means for detecting the final ramp of the step signal having a ramp between each successive step level as it declines to a zero displacement, said detection means connected to said means for generating ramps; and means for applying the output of said detection means to said conditional switch means so as to switch the fedback analog displacement signal into the input of said means for displacing the print head.

Claim 17

In a serial printer wherein a print head is caused to move axially and rotationally in positioning a given character on its surface for impact printing, a system for controlling the movement of the print head in the axial direction and for controlling the movement of the print head in the rotational direction comprising: means for calculating initial minimum distance to be traveled in moving the print head in the respective axial and rotational direction so as to position a particular character on its surface; means for commanding a series of different constant displacement rates for moving the print head in the axial direction in response to the calculated initial minimum distance to be traveled in moving the print head in the axial direction, said axial command means comprising: means for selecting an initial constant axial displacement rate corresponding to the initial minimum distance to go in the axial direction, said selecting means including a plurality of different constant axial displacement rates each of which corresponds to a range of travel distances for input to go in the axial direction of movement; an axial servo drive for positioning the particular character on the print head surface in the axial direction in response to the commanded constant displacement rates as outputted from said axial command means, the displacement rate of the print head in the calculated direction occurring at a first commanded axial displacement rate corresponding to the initial minimum distance to be traveled in the axial direction and at subsequently commanded different axial displacement rates corresponding to the distance yet to be traveled iN the axial direction; means for commanding a series of different constant displacement rates for moving the print head in the rotational direction in response to the calculated minimum distance to be traveled in moving the print head in the rotational direction, said rotational command means comprising: means for selecting an initial constant rotational displacement rate corresponding to the initial minimum distance to go in the rotational direction, said rotational means including a plurality of different constant rotational displacement rates each of which corresponds to a range of travel distances for input to the rotational servo drive in response to the calculated mimimum distance to go in the rotational direction of movement; and a rotational servo drive for positioning the particular character on the print head surface in the rotational direction in response to the commanded constant displacement rates as outputted from said rotational command means, the displacement rate of the print head in the calculated direction occurring at a first commanded rotational displacement rate corresponding to the initial minimum distance to be traveled in the rotational direction and at subsequently commanded different rotational displacement rates corresponding to the distance yet to be traveled in the rotational direction.

Claim 18

In a serial printer wherein a print head is caused to move axially and rotationally in positioning a given character on its surface for impact printing, a system for controlling the movement of the print head in the axial direction and for controlling the movement of the print head in the rotational direction comprising: means for calculating initial minimum distance to be traveled in moving the print head in the respective axial and rotational direction so as to position a particular character on its surface; means for commanding a series of different constant displacement rates for moving the print head in the axial direction in response to the calculated initial minimum distance to be traveled in moving the print head in the axial direction, said axial command means comprising: means for selecting an initial constant axial displacement rate corresponding to the initial minimum distance to go in the axial direction, said selecting means including a plurality of different constant axial displacement rates each of which corresponds to a range of travel distances for input to go in the axial direction of movement; an axial servo drive for positioning the particular character on the print head surface in the axial direction in response to the commanded constant displacement rates as outputted from said axial command means, the displacement rate of the print head in the calculated direction occurring at a first commanded axial displacement rate corresponding to the initial minimum distance to be traveled in the axial direction and at subsequently commanded different axial displacement rates corresponding to the distance yet to be traveled iN the axial direction; means for commanding a series of different constant displacement rates for moving the print head in the rotational direction in response to the calculated minimum distance to be traveled in moving the print head in the rotational direction, said rotational command means comprising: means for selecting an initial constant rotational displacement rate corresponding to the initial minimum distance to go in the rotational direction, said rotational means including a plurality of different constant rotational displacement rates each of which corresponds to a range of travel distances for input to the rotational servo drive in response to the calculated mimimum distance to go in the rotational direction of movement; and a rotational servo drive for positioning the particular character on the print head surface in the rotational direction in response to the commanded constant displacement rates as outputted from said rotational command means, the displacement rate of the print head in the calculated direction occurring at a first commanded rotational displacement rate corresponding to the initial minimum distance to be traveled in the rotational direction and at subsequently commanded different rotational displacement rates corresponding to the distance yet to be traveled in the rotational direction.

Claim 19

The system of claim 15 wherein said calculating means comprises two independently functioning calculating means each of which comprises: means for retaining a positional description of the previous character printed; means for calculating a distance to be traveled in positioning the new character to be printed from a first approach direction; means for calculating a distance to be traveled in positioning the new character to be printed from a second approach direction; and means for selecting the lesser of the two distances to be traveled and the corresponding approach direction.

Claim 20

The system of claim 16 further comprising: means for sensing the axial and rotational displacements of the print head as it moves to position a particular character on its surface; means for separately feeding back the axial and rotational displacements to the respective axial and rotational selection means; said axial and rotational selection means each comprising means for retaining a representation of the respective axial and rotational distances yet to be traveled in positioning the character on the print head surface and means for updating the representation of the distance yet to be traveled within said retaining means in response to the respectively fed back displacement from said means for separately feeding back the axial and rotational displacements.

Claim 21

The system of claim 17 further comprising; means for generating a step signal in response to the selected constant displacement rates; and means for generating ramps between the various step levels of the step signal to thereby from a step signal having a ramp between each successive step level.

Claim 22

In a printer, the method of moving a print head to a new print position from a previous print position comprising the steps of: calculating the initial positional difference for the print head moving in a forward direction; calculating the initial positional difference for the print head moving in a reverse direction; selecting the calculated initial positional difference and calculated direction wherein the print head has the least distance to move to a new print position; selecting an initial constant displacement rate corresponding to the least distance to move to the new print position from a number of possible different constant displacement rates each of which corresponds to a range of positional differences, said selection being made according to the calculated initial positional difference; moving the print head at the selected initial displacement rate in the selected, calculated direction; measuring the distance of travel as the print head moves towards the new print position; decrementing the positional difference representing the current distance yet to be traveled by the print head according to the measured distance of travel; selecting a constant displacement rate at which the print head is to be moved from a number of possible different constant displacement rates each of which corresponds to a range of positional differences, said selection being made according to the decremented positional difference; moving the print head at the selected rate only in the selected, calculated direction; and repeating said steps of measuring, decrementing, selecting and moving at the selected rate until the new print position is reached.

Claim 23

In a printer, the method of moving a print head to a new print position from a previous print position comprising the steps of: calculating the initial positional difference for the print head moving in a forward direction; calculating the initial positional difference for the print head moving in a reverse direction; selecting the calculated initial positional difference and calculated direction wherein the print head has the least distance to move to a new print position; selecting an initial constant displacement rate corresponding to the least distance to move to the new print position from a number of possible different constant displacement rates each of which corresponds to a range of positional differences, said selection being made according to the calculated initial positional difference; moving the print head at the selected initial displacement rate in the selected, calculated direction; measuring the distance of travel as the print head moves towards the new print position; decrementing the positional difference representing the current distance yet to be traveled by the print head according to the measured distance of travel; selecting a constant displacement rate at which the print head is to be moved from a number of possible different constant displacement rates each of which corresponds to a range of positional differences, said selection being made according to the decremented positional difference; moving the print head at the selected rate only in the selected, calculated direction; and repeating said steps of measuring, decrementing, selecting and moving at the selected rate until the new print position is reached.

Claim 24

The method of claim 19 wherein said step of adjusting the displacement rate comprises the steps of: selecting a constant displacement rate corresponding to the decremented positional difference; and forming a multi-level signal in which each successively selected constant displacement rate is lower than the previous displacement rate.

Claim 25

The method of claim 20 wherein said step of forming a multi-level signal comprises the steps of: generating a step signal indicative of the various selected displacement rates at which the print head is to be moved; and generating ramps between the various steps of the step signal.

Claim 26

The method of claim 21 further comprising the steps of: detecting the final ramp as it hits a zero displacement rate; generating a detection signal; measuring the distance of travel remaining to finally position the print head; and moving the print head the remaining measured distance in response to the measured distance of travel when the detection signal occurs.

Claim 27

In a serial printer wherein a print head is caused to move axially and rotationally in positioning a given character on its print head surface for impact printing, a method of controlling the axial and rotational movements of the print head comprising the steps of: calculating minimum distances to be traveled in moving the print head in the respective axial and rotational directions so as to position a particular character on its surface; commanding initial axial and rotational constant displacement rates at which the print head is to initially move; moving the print head at the initially commmanded constant axial and rotational displacement rates; sensing the axial and rotational displacements of the print head as it moves to position a particular character on its surface; separately feeding back the sensed axial and rotational displacements; calculating axial and rotational distances yet to be traveled from the feedback of the axial and rotational displacements of the moving print head; selecting constant displacement rates from among a group of constant displacement rates wherein each displacement rate corresponds to a range of distances yet to be traveled for each direction of movement; generating a series of downwardly stepped constant displacement rates for each respective direction of movement in response to said selected constant displacement rates corresponding to a range of distances yet to be traveled; and moving the print head at each of the downwardly stepped constant displacement rates in each direction of movement.

Claim 28

In a serial printer wherein a print head is caused to move axially and rotationally in positioning a given character on its print head surface for impact printing, a method of controlling the axial and rotational movements of the print head comprising the steps of: calculating minimum distances to be traveled in moving the print head in the respective axial and rotational directions so as to position a particular character on its surface; commanding initial axial and rotational constant displacement rates at which the print head is to initially move; moving the print head at the initially commmanded constant axial and rotational displacement rates; sensing the axial and rotational displacements of the print head as it moves to position a particular character on its surface; separately feeding back the sensed axial and rotational displacements; calculating axial and rotational distances yet to be traveled from the feedback of the axial and rotational displacements of the moving print head; selecting constant displacement rates from among a group of constant displacement rates wherein each displacement rate corresponds to a range of distances yet to be traveled for each direction of movement; generating a series of downwardly stepped constant displacement rates for each respective direction of movement in response to said selected constant displacement rates corresponding to a range of distances yet to be traveled; and moving the print head at each of the downwardly stepped constant displacement rates in each direction of movement.

Claim 29

The method of claim 23 wherein said step of generating a series of downwardly stepped constant displacement rates for each respective direction of movement comprises the step of: generating a step signal in response to the selected displacement rates; and generating ramps between the various step levels of the step signal to thereby form a step signal having a ramp between each successive step level.

Claim 30

The method of claim 24 further comprising the steps of: detecting the final ramp as it hits a zero displacement rate; generating a detection signal; measuring the distance of travel remaining to finally Position the print head; and moving the print head the remaining measured distance in response to the measured distance of travel when the detection signal occurs.