Device for controlling rotational speed of motor

• US 5,130,626 A
• Filed: 11/29/1990
• Issued: 07/14/1992
• Est. Priority Date: 11/30/1989
• Status: Expired due to Fees

• Current Assignee: Mita Industrial Co., Ltd. (Kyocera Corporation)
• Original Assignee: Mita Industrial Co., Ltd. (Kyocera Corporation)
• Inventors: Harada Hiroyuki, Kajitani, Tetsuji
• Primary Examiner(s): Shoop, Jr., William M.
• Assistant Examiner(s): Cabeca, John W.
• Application Number:
  US07/619,617
• Time in Patent Office: 593 Days
• Field of Search: 318/560, 318/599, 318/603, 318/606, 318/608, 318/809, 318/811, 388/811, 388/812, 388/813, 388/820, 388/912
• US Class Current: 318/608
• CPC Class Codes: H02P 7/293 using phase control H02P7/295 takes precedence

Abstract

A device for controlling the rotational speed of a motor carries out feedback control by a speed difference control signal and a phase difference control signal. A first time period from a reference time point to a time when a newest detection pulse is outputted is calculated every time a predetermined number of detection pulses are counted by detection pulse counters. A second time period from the reference time point to the time when a command pulse, which is assigned an ordinal number equal to the ordinal number of the newest detection pulse and which thereby corresponds to the newest detection pulse, is calculated on the basis of the total number of pulses counted by the detection pulse counters in the time period from the reference time point to the time when the newest detection pulse is outputted, and the period of the command pulse. The phase difference between the newest detection pulse and the command pulse corresponding thereto is calculated on the basis of the first time period and the second time period and the period of the command pulse. A phase difference control signal proportional to the phase difference calculated is thus determined.

Claims

1. A device for controlling the rotational speed of a motor which carries out feedback control of the motor on the basis of a speed difference control value based on the difference between a command speed and rotational speed and a phase difference control value based on the phase difference between a command pulse and a detection pulse, comprising:

detection pulse output means for outputting a detection pulse proportional to the rotational speed of the motor;

command pulse output means for outputting a command pulse proportional to the command speed;

reference time point setting means for setting a reference time point;

detection pulse counting means for counting a number of detection pulses outputted;

period measuring means for measuring the period of the command pulse;

first time period calculating means for calculating a time period from the reference time point to the time when a newest detection pulse is outputted every time a predetermined number of detection pulses are counted by the detection pulse counting means;

second time period calculating means for calculating a time period from the reference time point to the time when a command pulse, which is assigned an ordinal number equal to the ordinal number of the newest detection pulse, and which corresponds to the newest detection pulse is outputted on the basis of the total number of pulses counted by the detection pulse counting means in the time period from the reference time point to the time when the newest detection pulse is outputted, and the period of the command pulse measured by the period measuring means;

phase difference calculating means for calculating the phase difference between the newest detection pulse and the command pulse corresponding thereto on the basis of the time period calculated by the first time period calculating means and the time period calculated by the second time period calculating means and the period of the command pulse; and

phase difference control value output means for outputting a phase difference control value proportional to the phase difference when the phase difference calculated by the phase difference calculating means is within a predetermined range and continuing to output a control value in a critical state when the phase difference is outside the range.

2. A device for controlling the rotational speed of a motor which carries out feedback control of the motor on the basis of a speed difference control value based on the difference between a command speed and rotational speed and a phase difference control value based on the phase difference between a command pulse and a detection pulse, comprising:

detection pulse output means for outputting a detection pulse proportional to the rotational speed of the motor;

command pulse output means for outputting a command pulse proportional to the command speed;

reference time point setting means for setting a reference time point;

detection pulse counting means for counting a number of detection pulses outputted;

period measuring means for measuring the period of the command pulse;

first time period calculating means for calculating a time period from the reference time point to the time when a newest detection pulse is outputted every time a predetermined number of detection pulses are counted by the detection pulse counting means;

second time period calculating means for calculating a time period from the reference time point to the time when a command pulse, which is assigned an ordinal number equal to the ordinal number of the newest detection pulse, and which corresponds the newest detection pulse is outputted on the basis of the total number of pulses counted by the detection pulse counting means from the reference time point to the time when the newest detection pulse is outputted and the period of the command pulse measured by the period measuring means;

first phase difference calculating means for calculating the phase difference between the newest detection pulse and the command pulse corresponding thereto on the basis of the time period calculated by the first time period calculating means, the time period calculated by the second time period calculating means and the period of the command pulse;

state discriminating means for discriminating among a first state where the phase difference calculated by the first phase difference calculating means is within one period of the command pulse, a second state where the newest detection pulse lags the corresponding command pulse by a phase difference of a predetermined time period or more which is larger than one period of the command pulse, and a third state where the newest detection pulse leads the corresponding command pulse by a phase difference of a predetermined time period or more which is larger than one period of the command pulse;

first phase difference control value output means responsive to the discrimination of the first state by the state discriminating means for outputting a phase difference control value on the basis of the value of the phase difference calculated by the first phase difference calculating means;

third time period calculating means responsive to the discrimination of the second state by the state discriminating means for calculating a time period from the reference time point to the time when a command pulse preceding the command pulse corresponding to the newest detection pulse is outputted on the basis of the number obtained by subtracting one from the total number of pulses counted by the detection pulse counting means in the time period from the reference time point to the time when the newest detection pulse is outputted and the period of the command pulse measured by the period measuring means;

fourth time period calculating means responsive to the discrimination of the third state by the state discriminating means for calculating a time period from the reference time point to the time when a command pulse subsequent to the command pulse corresponding to the newest detection pulse is outputted on the basis of the number obtained by adding to 1 the total number of pulses counted by the detection pulse counting means in the time period from the reference time point to the time when the newest detection pulse is outputted and the period of the command pulse measured by the period measuring means;

second phase difference calculating means responsive to the calculation of the time period by the third time period calculating means for calculating the phase difference between the newest detection pulse and the command pulse preceding the command pulse corresponding to the newest detection pulse on the basis of the time period calculated by the third time period calculating means, the time period calculated by the first time period calculating means and the period of the command pulse;

second phase difference control value output means for outputting a phase difference control value on the basis of the value of the phase difference calculated by the second phase difference calculating means;

third phase difference calculating means responsive to the calculation of the time period by the fourth time period calculating means for calculating the phase difference between the newest detection pulse and the command pulse subsequent to the command pulse corresponding to the newest detection pulse on the basis of the time period calculated by the fourth time period calculating means, the time period calculated by the first time period calculating means and the period of the command pulse; and

third phase difference control value output means for outputting a phase difference control value on the basis of the value of the phase difference calculated by the third phase difference calculating means.

3. A method of calculating the phase difference between a speed command pulse and a speed detection pulse which is required to carry out feedback control of a motor, comprising the steps of:

preparing detection pulse output means for outputting a detection pulse proportional to the rotational speed of the motor, command pulse output means for outputting a command pulse proportional to a command speed, reference time point setting means for setting a reference time point, detection pulse counting means for counting a number of detection pulses outputted, and period measuring means for measuring the period of the command pulse;

calculating a first time period from the reference time point to the time when a newest detection pulse is outputted every time a predetermined number of detection pulses are counted by the detection pulse counting means;

calculating a second time period from the reference time point to the time when a command pulse, which is assigned an ordinal number equal to the ordinal number of the newest detection pulse, and which corresponds to the newest detection pulse is outputted on the basis of the total number of pulses counted by the detection pulse counting means in the time period from the reference time point to the time when the newest detection pulse is outputted, and the period of the command pulse measured by the period measuring means; and

calculating the phase difference between the newest detection pulse and the command pulse corresponding thereto on the basis of the first time period and the second time period calculated and the period of the command pulse.