Motor speed control system

• US 5,093,892 A
• Filed: 09/22/1989
• Issued: 03/03/1992
• Est. Priority Date: 09/22/1988
• Status: Expired due to Fees

• Current Assignee: Janome Sewing Machine Company Limited (Janome Corp.)
• Original Assignee: Janome Sewing Machine Company Limited (Janome Corp.)
• Inventors: Orii, Akira
• Primary Examiner(s): Shoop, Jr., William M.
• Assistant Examiner(s): MARTIN, DAVID S
• Application Number:
  US07/411,322
• Time in Patent Office: 893 Days
• Field of Search: 388/809-815, 388/800-802, 388/904, 388/907.5, 364/550, 364/551.01, 364/551.02, 364/552-554, 364/570, 364/571.02, 364/571.04, 364/571.07
• US Class Current: 388/815
• CPC Class Codes: D05B 69/18 electric , e.g. foot pedals
• CPC Class Codes: H02P 7/2805 whereby the speed is regulated by measuring the motor speed and comparing it with a given physical value
• CPC Class Codes: Y10S 388/904 Stored velocity profile
• CPC Class Codes: Y10S 706/90 Fuzzy logic

Abstract

There is disclosed a motor speed control system particularly applicable to control sewing machine operation, including an evaluator to compare a preset speed of revolution value and an actual speed of revolution value to output one signal representing a deviation between the two speeds and the other representing a rate of increase or decrease of the actual speed of revolution within a predetermined short interval. In response to these parameter signals, one of the stored fuzzy rules is selectively applied to output an appropriate control signal to change electric power supplied to a motor as needed to adjust the speed of revolution toward the preset revolution with quick responsivity and smooth transition.

Claims

1. Motor speed control system comprising evaluating means for comparison of signals representative of the actual speed of revolution of a motor to a reference speed of revolution and for generating of a first parameter representing a deviation between the actual speed ore volution and the reference speed of revolution and for generating a second parameter representing a rate of change in thea ctual speed of revolution, means for storing one of a set of prescribed fuzzy rules which are applicable under specified ranges of the first and second parameters and which correlate various possible values of the respective parameters with various values of control command output, and means responding to the rspective ranges detected for selecting and applying one of said fuzzy rules and in rseponse to the values of first and second parameters to output a control command to the motor for changing the motor speed of revolution, each fuzzy rule comprising a combination of a first membership function correlated with the first parameter, a second membership function correlated with the second parameter, a third membership function providing values of control command for each membership value and a basis for selecting which of the the first and second membership functions shall determine the third, each of the memberhsip functions being appropriate to the motor being controlled, such that a specific value of control command is determined from the control command membership function to correspond with a value of membership values obtained from one of the first and second membership functions and determined by the selected fuzzy rule.

2. The motor speed control system according to claim 1 wherein said control command output has a specific value determined in correspondence with a memberhsip value of either the first and second membership functions of the selected fuzzy rules.

3. Speed control system for controlling speed of revolution of an upper drive shaft driven by a motor in a sewing machine, comprising speed setting means for setting a speed of revolution of the upper drive shaft to a reference value as desired by a sewing machine operator, sensor means for detecting an actual revolution of the upper drive, evaluating means for substantially continuously comparing the actual speed of revolution with respect to the reference speed of revolution to output a first parameter representing the difference between these two speeds of revolution and a second parameter representing a time rate of change in the actual speed of revolution within a predetermined interval, memory means for storing a plurality of prescribed fuzzy rules for various predetermined ranges of first and second parameters, each comprising a first membership function for determining a first membershi value corresponding to each specific detected value of the first parameter, a second membership function for determining a second membership value corresponding to each specific value of the second parameter and a third membership function for determining a control command value for each specific selected membership value, and rule selecting means for selecting one of the prescribed fuzzy rules among those stored in said memory means in response to the first and second parameters input thereto and fuzzy theory applying means for applying said selected fuzzy rule so that results of fuzzy theory application will provide output to the motor of a control command having a specific value determined in the third membership function depending upon the selected on of teh first and second memberhsip values of the selected fuzzy rule, thereby changing the motor revolution and the actual revolution of the upper drive shaft.

4. The speed control system according to claim 3 wherein a specific value of the control command is determined in correspondence with the greater membership value of the first and second parameters.

5. The speed control system according to claim 3 wherein the control command is a signal commanding that electric power supplied to the motor be increased or decreased.

6. The speed control system according to claim 3 which further comprises reduction operation means for reducing the value of the control command when the reference speed of revolution is changed, said reduction operation being made inoperative when the second parameter is reduced below a predetermined value or after a predetermined period of time.

7. The speed control system according to claim 3 wherein the first and second memberhsip functions of the fuzzy rules stored in said memory means are varied with voltage supplied to the motor, and in addition to the first and second parameters a value corresponding to the voltage is also input to said rules selecting means to vary the membership functions in a predetermined manner in accordance with the fuzzy rules.