Web transport capstan control system

A web transport system comprising:

• a web storage system positioned to supply and take up a length of web member moving along a web path;
• a single capstan positioned to engage a length of web member in nonslip relationship to control web member motion along the web path;
• a capstan motor coupled to rotationally drive the capstan in accordance with capstan motor rotation;
• and
• a motor energization system coupled to energize the capstan motor, the motor energization system including (1) a tachometer coupled to sense capstan motion and generate a direction signal indicative of the direction of capstan motion and an actual motion signal indicative of actual capstan speed, (2) a reference generator generating a reference motion signal indicative of desired capstan speed, (3) a comparator coupled to compare the reference and actual motion signals and generate a motion error signal having a relative polarity and magnitude indicative of the difference therebetween, (4) a direction control circuit coupled to selectively invert the polarity of the motion error signal in response to operator commands and actual capstan motor motion information, the polarity of the motion error signal being in a first state of inversion selected to command capstan motor energization for acceleration in a first direction when web motion in a first direction is commanded and actual speed is not greater than the reference speed, the first state of inversion also being commanded when actual motion is in the first direction and actual speed is greater than the reference speed or when motion stop is commanded and actual motion is in a second direction opposite the first direction, a second state of inversion opposite the first state being selected when web motion in a second direction is commanded and actual speed is not greater than reference speed, or actual motion is in the second direction and actual speed is greater than a first speed and (5) a motor drive circuit coupled to energize the capstan motor in response to the magnitude and polarity of the motion error signal.

A web transport system comprising:

• a web storage system positioned to supply and take up a length of a web member as the length of web member moves along a web path;
• a capstan positioned along the web path for continuous engagement with a length of web member to control the motion of the length of web member along the web path;
• a direct current motor coupled to rotationally drive the capstan in accordance with rotation of the motor;
• and
• a motor energization system coupled to energize the motor, the motor energization system including a current driver coupled to energize the motor with current of a polarity and magnitude indicated by an applied energization command, the current driver including an amplifier having an output coupled to energize the motor and an inverting input coupled to receive the energization command signal and also including a current feedback circuit coupled to provide a current feedback signal to the negative input that is indicative of actual motor current, the current feedback signal being opposite in polarity and equal in magnitude to the energization command signal when actual motor current equals commanded motor current, a position reference signal indicating a motor reference position which changes at a nonzero rate with respect to time, an actual motor position detector generating an actual position signal indicating actual rotational position of the motor and a comparator coupled to compare the actual position signal and the reference position signal and generate an energization command signal indicative of the difference between actual and reference motor positions, the current driver further including a bipolar voltage limiting circuit which limits the maximum positive and negative voltages that can be applied across the motor.

A web transport system comprising:

• a web storage system positioned to supply and take up a length of a web member as the length of web member moves along a web path;
• a capstan positioned along the web path for continuous engagement with a length of web member to control the motion of the length of web member along the web path;
• a direct current motor coupled to rotationally drive the capstan in accordance with rotation of the motor;
• a motor energization system coupled to energize the motor, the motor energization system including a current driver coupled to energize the motor with current of a polarity and magnitude indicated by an applied energization command, a position reference source generating a position reference signal indicating a motor reference position which changes at a nonzero rate with respect to time, an actual motor position detector generating an actual position signal indicating actual rotational position of the motor and a comparator coupled to compare the actual position signal and the reference position signal and generate an energization command signal indicative of the difference between actual and reference motor positions;
• velocity error detection circuitry coupled to detect and indicate actual motor velocities less than the nonzero time rate of change of position indicated by the position reference signal;
• an acceleration command circuit generating an acceleration command signal commanding a constant motor current of a polarity dependent upon an operator determined direction of motion;
• circuitry generating a second energization command signal in response to the acceleration command signal;
• and
• a switching network responsive to operator commands and the velocity error detection circuitry, the switching network operating to apply a selected one of the energization command signals to the current driver, the energization command signal from the comparator being applied only when a speed indicated by the position reference signal is commanded by an operator and an actual motor velocity less than that indicated by the position reference signal is not indicated.

A web transport system comprising:

• a web storage system positioned to supply and take up a length of a web member as the length of web member moves along a web path;
• a capstan positioned along the web path for continuous engagement with a length of web member to control the motion of the length of web member along the web path;
• a direct current motor coupled to rotationally drive the capstan in accordance with rotation of the motor;
• a motor energization system coupled to energize the motor, the motor energization system including a current driver coupled to energize the motor with current of a polarity and magnitude indicated by an applied energization command, a position reference source generating a position reference signal indicating a motor reference position which changes at a nonzero rate with respect to time, an actual motor position detector generating an actual position signal indicating actual rotational position of the motor and a comparator coupled to compare the actual position signal and the reference position signal and generate an energization command signal indicative of the difference between actual and reference motor positions;
• and
• a limiting circuit coupled to limit the maximum motor energization commanded by the energization command signal to a level at which tape motion will not exceed the capabilities of the web storage system to supply and take up tape under any normal operating conditions.

A web transport system comprising:

• a web storage system positioned to supply and take up a length of a web member as the length of web member moves along a web path;
• a capstan positioned along the web path for continuous engagement with a length of web member to control the motion of the length of web member along the web path;
• a direct current motor coupled to rotationally drive the capstan in accordance with rotation of the motor;
• a motor energization system coupled to energize the motor, the motor energization system including a current driver coupled to energize the motor with current of a polarity and magnitude indicated by an applied energization command, a position reference source generating a position reference signal indicating a motor reference position which changes at a nonzero rate with respect to time, an actual motor position detector generating an actual position signal indicating actual rotational position of the motor and a comparator coupled to compare the actual position signal and the reference position signal and generate an energization command signal indicative of the difference between actual and reference motor positions;
• a web storage system protection circuit coupled to generate a motor energization reduction signal of a magnitude indicative of operational demands placed on the web storage system and of a polarity tending to reduce motor energization;
• an acceleration command circuit generating an acceleration command signal of constant magnitude and of a polarity dependent upon an operator commanded direction of motion, the energization reduction signal and the acceleration command signal being combined to form a second energization command signal;
• and
• switching circuitry coupled to apply a given one but not both of the first mentioned and second energization command signals to the current driver in response to operator commands.

A web transport system comprising;

• a web storage system positioned to supply and take up a length of a web member as the length of web member moves along a web path;
• a capstan positioned along the web path for continuous engagement with a length of web member to control the motion of the length of web member along the web path;
• a direct current motor coupled to rotationally drive the capstan in accordance with rotation of the motor;
• and
• a motor energization system coupled to energize the motor, the motor energization system including a current driver coupled to energize the motor with current of a polarity and magnitude indicated by an applied energization command, a position reference source generating a position reference signal indicating a motor reference position which changes at a nonzero rate with respect to time, an actual motor position detector generating an actual position signal indicating actual rotational position of the motor and a comparator coupled to compare the actual position signal and the reference position signal and generate an energization command signal indicative of the difference between actual and reference motor positions, the comparator including circuitry generating a speed locked signal when actual motor velocity is equal to a time rate of change of position commanded by the reference signal and the comparator further including a gain control circuit coupled to receive the speed locked signal and to increase the D.C. gain of the energization command signal when the speed locked signal is generated relative to the gain of the energization command signal when the speed locked signal is not generated.

A magnetic tape transport system comprising:

• a tape storage system positioned to supply and take up a length of tape as a tape member moves along a tape path under control of a single tape drive capstan;
• a capstan positioned along the tape path for continuous, nonslip engagement with a tape member;
• a direct current capstan motor coupled to drive the capstan in accordance with motor rotation, the motor generating a torque that is approximately linearly proportional to motor current;
• and
• a motor energization system coupled to energize the capstan motor, the motor energization system including a current driver coupled to energize the capstan motor with a current that is linearly proportional to the sum of applied energization commands and further including an energization command system that is responsive to operator commands, the energization command system including (A) a position reference source generating a position reference signal indicating both a commanded rotational position and nonzero rotational velocity for the capstan motor, (B) an actual motor position detector generating an actual position signal indicating both actual position and actual velocity of the capstan motor, (C) a comparator coupled to compare the actual position signal with the reference position signal and (C1) generate a position error signal that varies continuously with the difference between actual and commanded capstan motor positions and (C2) generate a speed locked signal when commanded and actual capstan motor velocities are approximately equal, (D) an acceleration signal generator coupled to generate an acceleration signal of fixed magnitude in response to operator direction commands, (E) an underspeed signal generator coupled to generate an underspeed signal when actual motor velocity is less than the velocity commanded by the reference position signal, (F) and a switching system responsive to operator commands, the speed locked signal and the underspeed signal, and coupled (F1) to apply the position error signal to the current driver as an energization command signal when the speed locked signal is being generated and (F2) to apply the acceleration signal to the current driver as an energization command signal whenever an underspeed signal is generated.

A magnetic tape transport system comprising:

• a tape storage system positioned to supply and take up a length of tape as a tape member moves along a tape path under control of a single capstan;
• a single drive capstan positioned along the tape path for continuous, nonslip engagement with a tape member;
• a direct current capstan motor coupled to drive the capstan in accordance with motor rotation;
• a motor energization system coupled to energize the capstan motor, the motor energization system including a motor drive circuit coupled to energize the capstan motor to produce a motor acceleration that is linearly proportional to the sum of applied energization commands and an energization command system that is responsive to operator commands, the energization command system including (A) circuitry for generating (A1) a play command in response to an operator command requiring operation at a first given speed at which recording and reproducing of information on tape occurs, (A2) a spooling command in response to an operator command requiring operation at a second given speed greater than the first given speed, (A3) a shuttle command in response to an operator command to move tape at a speed greater than the second given speed, (A4) a stop command in response to an operator command to stop tape motion, and (A5) a direction command indicating an operator commanded direction of motion;
• (B) an A.C. reference signal generator generating an A.C. reference signal, the reference signal having a given first frequency in response to a play command and a given second frequency greater than the first frequency in response to a spooling command;
• (C) a tachometer coupled to generate an A.C. tachometer signal having transitions between signal levels which have a predetermined relationship to capstan motor rotational position;
• (D) a comparator coupled to respond to the reference signal and the tachometer signal and generate an underspeed signal when the frequency of the tachometer signal is less than the frequency of the reference signal and a position error signal that varies with the phase difference between the reference and tachometer signals when their frequencies are substantially equal;
• (E) an acceleration generator coupled to generate an acceleration signal of fixed magnitude and of a polarity determined in accordance with a required direction of acceleration;
• and (F) a switching network coupled to apply the position error signal to the motor drive circuit as an energization command when the underspeed signal is not being generated and either a play command or a spooling command is being generated and coupled to apply the acceleration signal to the motor drive circuit as an energization command when the underspeed signal is generated or a shuttle command is generated or a stop command is generated while the capstan motor is rotating.

A web transport system comprising:

• a web storage system positioned to supply and take up a length of web member as the length of web member moves along a web path;
• a capstan positioned along the web path to control the motion of the length of web member along the web path;
• a motor coupled to rotationally drive the capstan in accordance with rotation of the motor;
• and
• a motor energization system coupled to energize the motor, the motor energization system including (1) a motor drive amplifier circuit coupled to energize the motor in response to an energization command, (2) a digital tachometer circuit generating digital information signals indicative of actual rate and direction of motion of tape at the capstan, (3) a reference signal generator generating a digital velocity reference signal indicative of a reference rate of tape motion, (4) a phase comparator coupled to compare signals indicative of actual and reference rates of tape motion and generate an underspeed signal when the indicated actual rate of motion is less than the reference rate and an error signal indicative of a difference between an actual and a predetermined phase relationship between the signals indicating actual and reference rates of motion, (5) a switching circuit responsive to the underspeed signal and to operate commands and arranged to couple the error signal to the motor drive amplifier circuit as an energization command signal only when the underspeed signal does not indicate an underspeed condition and operator commands indicate a mode of operation wherein tape velocity is to equal the reference rate of motion, and (6) an acceleration circuit responsive to the underspeed signal and to operator command signals, the acceleration circuit generating a constant acceleration signal and including switching circuitry coupling the constant acceleration signal to the motor drive amplifier circuit as an energization command signal commanding energization to produce a constant rate of web acceleration only when web motion is commanded and the underspeed signal indicates an underspeed condition or a rate of motion greater than the reference rate is commanded or zero web motion is commanded and the web is moving, the motor energization then being of a polarity tending to reduce web speed in the vicinity of the capstan.

A magnetic tape transport system comprising:

• a tape storage system positioned to supply and take up tape moving along a tape path;
• a single capstan positioned to control the motion of tape along the tape path;
• a capstan motor coupled to rotationally drive the capstan;
• and
• a motor energization system coupled to energize the capstan motor, the energization system including (1) an error signal generator coupled to sense actual tape speed, compare actual tape speed with commanded tape speed, generate a motion error signal indicative of the difference between actual tape speed and a commanded tape speed, and generate a speed locked signal when actual tape speed equals commanded tape speed (2) a motor drive amplifier coupled to energize the capstan motor in response to the motion error signal and (3) compensation circuitry coupled to respond to the speed locked signal by increasing the magnitude of low frequency components of capstan motor energization relative to the magnitude of the difference indicated by the error signal whenever the speed locked signal is generated.

A magnetic tape transport system comprising:

• a tape storage system disposed to supply and take up tape moving along a tape path having a transducer head positioned therealong;
• a single capstan disposed to control the motion of tape along the tape path;
• a capstan motor coupled to rotationally drive the capstan;
• and
• a motor energization system coupled to energize the capstan motor, the energization system including (1) a motor drive amplifier coupled to energize the capstan motor in response to a motor energization command, (2) a comparator circuit coupled to sense actual tape speed, compare actual tape speed with a commanded tape speed, generate a motion error signal indicating the difference between actual and commanded tape speed, generate a speed locked signal when actual tape speed equals a commanded tape speed, and generate an underspeed signal when actual tape speed is less than a commanded tape speed, (3) a constant acceleration circuit generating a constant acceleration signal commanding the motor drive amplifier to energize the capstan motor for constant acceleration, (4) an amplifier circuit coupled to receive the motion error signal as an input and to generate an amplified motion error signal as an output, the amplifier circuit including compensation circuitry responsive to the speed locked signal for increasing the amplification and increasing the low frequency response of the amplified motion error signal relative to the motion error signal, and (5) a switching circuit connected to selectively couple a motion energization command to the motor drive amplifier, the motor energization command being the amplified motion error signal in response to the speed locked signal and the constant acceleration signal in response to the underspeed signal.

A tape transport comprising:

• a tape storage system positioned to supply and take up a length of tape as the length of tape moves along a tape path;
• a capstan positioned along the tape path for continuous engagement with the length of tape to control bidirectional motion of the tape along the tape path;
• a bidirectional motor coupled to rotationally drive the capstan in accordance with rotation of the motor;
• and
• a motor energization system coupled to energize the motor to control bidirectional motion of the length of tape along the tape path, the motor energization system being responsive to operator commands and being operable to drive the motor at a first, closely regulated speed in response to an operator command to move tape at a nominal record or reproduce speed, to drive the motor at a second speed greater than the first speed by at least a factor of 5 in response to an operator command requiring tape motion at a high speed, to stop the motor in response to an operator command requiring zero tape speed and to permit the capstan motor to rotate freely in response to operator manipulation and without opposing the rotation in response to an operator command enabling manual control over capstan rotation by an operator while the tape storage system continues to supply or take up take moving along the tape path.

A web transport system comprising:

• a web storage system positioned to supply and take up a length of web member as the web member moves along a web path, the web storage system including first and second direct current reel motors coupled to drive first and second web member storage reels respectively, a first web loop buffer mechanism positioned between one end of the web path and a first reel of web member and a second web loop buffer mechanism positioned between an end of the web path opposite the one end and a second reel of web member;
• a single drive capstan positioned along the web path for constant engagement with a web member to control bidirectional motion of a length of web member along the web path;
• a summing system coupled to sense voltage across the first and second reel motors and sense the length of web loop stored by the first and second web loop buffer mechanisms, the summing system generating storage system status information indicative of the sum of the first and second reel motor voltages and web loop lengths for the first and second web loop buffer mechanisms;
• a capstan motor energization system coupled to electrically energize the capstan motor in response to motor command signals and the storage system status information, the energization system being operable in at least one mode to decrease the magnitude of capstan motor energization in accordance with the storage system status information, there being no step function changes in the capstan motor energization during an acceleration interval due to the storage system status information.

A magnetic tape transport for playing and recording audio information comprising:

• means for supplying tape to a tape path as required by tape motion along the path, the supplying means including means for providing a first buffer loop of tape;
• means for taking up tape from the tape path as required by tape motion along the path, the taking up means including means for providing a second buffer loop of tape;
• a single drive capstan positioned for continuous engagement with a tape to control tape motion along the tape path, the capstan having a cylindrical tape engaging circumference with a diameter of at least 1.5 inch;
• a D.C. capstan motor coupled directly to the drive capstan;
• a motor drive amplifier coupled to energize the capstan motor in response to a motor energization command signal;
• a first servo control system including means for generating an actual speed signal indicative of the capstan motor rotational speed and means for comparing the actual speed signal with a reference signal indicating a speed and generating a first motor energization command signal indicative of a difference between the actual speed and reference speed signals;
• a second servo control system coupled to generate a second energization command signal commanding a controlled rate of acceleration of the capstan motor throughout an acceleration interval;
• and
• a switching circuit coupled to respond to actual capstan motor rotational speed to couple the second but not the first energization command signal to the motor drive amplifier for acceleration toward a speed indicated by the reference signal and to couple the first but not the second energization command signal to the motor drive amplifier when actual capstan motor speed equals the speed indicated by the reference signal.