Variable speed drive

A variable speed drive apparatus, comprising:

• a mechanically-adjustable variable speed drive, having an input shaft and an output shaft drivingly coupled thereto, and an actuable member operatively associated with said shafts for mechanically adjusting the drive ratio therebetween;
• power input means for rotatably driving said variable speed drive input shaft at a substantially constant speed;
• actuator control means for ocntrollably adjusting the position of said variable speed drive actuable member so as to mechanically adjust the output speed of said output shaft thereof relative the substantially constant speed of said input shaft thereof;
• tachometer feedback means for sensing the rotational speed of said variable speed drive output shaft and providing a tachometer signal corresponding to same;
• speed setting means for providing a speed signal corresponding to a user-defined desired speed for said variable speed drive output shaft;
• digital controller means, responsive to said tachometer signal and said speed signal, for driving said actuator control means so as to maintain said variable speed drive output shaft at said desired speed thereof;
• wherein
• said digital controller means further includes automatic dead band means for adapting to changes in the relationship between said tachometer and speed signals by adjusting automatically the width of a response dead band used by said controller means in driving said actuator control means, whereby excessive hunting of said controller means is adaptively prevented;
• and further wherein
• said controller means further includes manually-selectable dead band means for adjusting said width of said response dead band, subject to automatic adjustment thereof by said automatic dead band means;
• and
• said automatic dead band means functions to incrementally increase said width of said response dead band from the setting thereof established by said maually-selectable dead band, responsive to the occurrence of said actuator control means being driven in reverse actuations by asid controller means a given number of times within a predetermined period of time, with subsequent incremental decreases from such increased dead band widths as the number of such actuation reverses decreases below said given number in said predetermined period of time.

A variable speed drive apparatus, comprising:

• a mechanically-adjustable variable speed drive, having an input shaft and an output shaft drivingly coupled thereto, and an actuable member operatively associated with said shafts for mechanically adjusting the drive ratio therebetween;
• power input means for rotatably driving said variable speed drive input shaft at a substantially constant speed;
• actuator control means for controllably adjusting the position of said variable speed drive actuable member so as to mechanically adjust the output speed of said output shaft thereof relative the substantially constant speed of said input shaft thereof;
• tachometer feedback means for sensing the rotational speed of said variable speed drive output shaft and providing a tachometer signal corresponding to same;
• speed setting means for providing a speed signal corresponding to a user-defined desired speed for said variable speed drive output shaft;
• digital controller means, responsive to said tachometer signal and said speed signal, for driving said actuator control means so as to maintain said variable speed drive output shaft at said desired speed thereof;
• and
• display means, driven by said digital controller means, for displaying rotational speed information concerning said variable speed drive output shaft;
• wherein
• said digital controller means in a normal mode drives said display means to display output shaft actual rotational speed information as derived from said tachometer signal, and said digital controller means further includes a user-actuable preset means for operating said controller means in a preset mode to inhibit driving of said actuator control means and to cause said display means to display desired speed settings for said output shaft as determined by said speed setting means, whereupon return to said normal mode from said preset mode said controller means drives said actuator control means so as to attain the most recently displayed desired speed setting;
• said apparatus further comprising
• limit setting means for providing a threshold signal corresponding to a user-defined limit for a selected load characteristic of a device or process adapted to be driven by said variable speed drive output shaft;
• and wherein said digital controller means further includes
• limit means, responsive to said threshold signal and a load characteristic signal form such device or process being driven by said output shaft corresponding to said selected load characteristic, for driving said actuator control means to limit the rotation speed of said output shaft whenever said threshold signal is exceeded by such load characteristic signal;
• adjustable dead band means for permitting a user to manually select the width of a response dead band in which said controller means will not respond to differences between said tachometer signal and said speed signal to drive said actuator control means;
• automatic dead band means, operative whenever the smallest response dead band width is selected and responsive to predetermined characteristics of said driving of said actuator control means by said digital controller means, for automatically increasing and subsequently decreasing said selected response dead band width so as to prevent excessive hunting of said controller means;
• feedback loss protection means, responsive to loss of said tachometer signal by said controller means, for operating said controller means in a fail-safe mode to drive said actuator control means so as to establish a predetermined minimum speed for said variable speed output shaft;
• and
• message function means for driving said display means to indicate respective user-indentifiable indications whenever said controller means is operating in said fail-safe mode thereof, and whenever said limit means is driving said actuator control means.

A variable speed drive apparatus, comprising:

• a mechanically-adjustable variable speed drive, having an input shaft and an output shaft drivingly coupled thereto, and an actuable member operatively associated with said shafts for mechanically adjusting the drive ratio therebetween;
• power input means for rotatably driving said variable speed drive input shaft at a substantially constant speed;
• actuator control means for controllably adjusting the position of said variable speed drive actuable member so as to mechanically adjust the output speed of said output shaft thereof relative the substantially constant speed of said input shaft thereof;
• tachometer feedback means for sensing the rotational speed of said variable speed drive output shaft and providing a tachometer signal corresponding to same;
• speed setting means for providing a speed signal corresponding to a user-defined desired speed for said variable speed drive output shaft;
• digital controller means, responsive to said tachometer signal and said speed signal, for driving relay means for selectively and alternately determining the rotational direction operation of said actuator control means so as to maintain said variable speed drive output shaft at said desired speed thereof;
• display means, driven by said controller means, for displaying output shaft speed information and messages from said controller means;
• and
• limit setting means for providing a threshold signal corresponding to a user-defined limit for a selected load characteristic of a device or process adapted to be driven by said variable speed device output shaft;
• and wherein
• said digital controller apparatus further includes
• limit means, responsive to said threshold signal and further adapted to be responsive to a load characteristic signal from such device or process being driven by said output shaft, for driving said actuator control means to limit the rotational speed of said output shaft whenever said threshold signal is exceeded by such load characteristic signal,
• automatic dead band means for automatically adjusting to differences between said tachometer and speed signals by making adjustment to the width of a response dead band used by said controller means in driving said actuator control means, so as to adaptively prevent excessive hunting of said controller means said adjustment being responsive to operation of said relay means,
• feedback loss protection means, responsive to loss of said tachometer signal by said controller means, for operating said controller means in a fail-safe mode to drive said actuator control means to establish a predetermined minimum speed for said output shaft, and
• preset means for operating said controller means in a preset mode to prevent driving of said actuator control means and displaying of actual output shaft speed information while causing display of newly set desired speed information designated with said speed setting means, whereupon exit of said preset mode said controller means drives said actuator control means in accordance with such newly set desired speed.

A controller apparatus for controlling a variable speed drive apparatus, including a mechanically-adjustable variable speed drive, having an input shaft and an output shaft drivingly coupled thereto, and an actuable member operatively associated with such shafts for mechanically adjusting the drive ratio therebetween;

• power input means for rotatably driving the variable speed drive input shaft at a substantially constant speed;
• actuator control means for controllably adjusting the position of the variable speed drive actuable member so as to mechanically adjust the output speed of the output shaft thereof relative the substantially constant speed of the input shaft thereof;
• tachometer feedback means for sensing the actual rotational speed of the variable speed drive output shaft and providing a tachometer speed signal corresponding to same;
• and display means, adapted to be driven for displaying rotational speed information concerning the variable speed drive output shaft, said controller apparatus comprising:
• command speed setting means for providing a commanded speed signal corresponding to a user-determined desired speed for the variable speed drive output shaft;
• digital controller means, selectively operative in one of a normal mode and a preset mode, and adapted to be responsive to the tachometer speed signal and said commanded speed signal, for producing in said normal mode thereof drive command signals based on differences between such tachometer speed signal and said commanded speed signal, said drive command signals adapted for driving the actuator control mens so as to adjust the output speed of the variable speed drive output shaft into conformance with said desired speed thereof;
• relay means responsive to said digital controller means for selectively and alternately determining rotational direction operation of said actuator control means so as to adjust said output shaft output speed as desired;
• automatic dead band means for inhibiting driving of said actuator control means when the relationship between said tachometer speed signal and said commanded speed signal is within a predetermined dead band, said predetermined dead band being adaptively changed responsive to operation of said relay means so as to automatically prevent excessive hunting of said digital controller means;
• and
• preset means for selectively placing said digital controller means in said preset mode thereof, during which said controller means is inhibited from producing said drive command signals, but instead is adapted for driving said display means to display desired speed information as determined by a user with said command speed setting means, whereupon return to said normal mode said controller means resumes producing said drive command signals responsive to said desired speed, whereby said preset mode of operation permits a user to accurately and rapidly preset a desired output shaft speed before actually commanding the variable speed drive in accordance with such desired speed.