Motor speed control systems

Abstract

A motor speed control system includes a pulse outputting device capable of outputting a pulse each time a motor rotates, a pulse interval determining device capable of determining a pulse interval between the pulses outputted, and a comparative value calculating device capable of obtaining a comparative value as the product of a first value and a second value. The first value can correspond to the pulse interval determined, and the second value can correspond to a set rotational speed of the motor. The system can further include a set value calculating device capable of obtaining a set value as the product of the second value and a third value and a controller capable of controlling a supply of power to the motor such that a difference between the set value and the comparative value decreases.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing a representative motor speed control system according to the present invention;

FIG. 2 is a schematic diagram of a controller;

FIG. 3 is an explanatory view illustrating the principle of operation of a pulse interval determining device;

FIG. 4(A) is a schematic circuit diagram of a motor drive circuit;

FIG. 4(B) is an explanatory view illustrating a gate pulse adjuster;

FIG. 5 is a schematic perspective view of an encoder;

FIG. 6(A) is a schematic block diagram of a known motor speed control system;

FIG. 6(B) is a schematic view illustrating how a pulse interval is determined by the known system; and

FIG. 7 is a block diagram of another known control system.

Claims

1. A motor speed control system comprising: a pulse outputting device capable of outputting a pulse each time a motor rotates;a pulse interval determining device capable of determining a pulse interval between the pulses outputted from the pulse outputting device;a comparative value calculating device capable of obtaining a comparative value as the product of a first value and a second value, the first value corresponding to the pulse interval determined by the pulse interval determining device, and the second value corresponding to a set rotational speed of the motor;a set value calculating device capable of obtaining a set value as the product of a third value and the second value, the third value corresponding to the pulse interval obtained when the motor rotates at the set rotational speed; anda controller controlling a supply of power to the motor such that a difference between the set value and the comparative value decreases.

2. The motor speed control system as in claim 1, further comprising an operation device that is operable to continuously change the second value.

3. The motor speed control system as in claim 1, wherein the controller includes an amplifier, a control gate and a motor driver.

4. The motor speed control system as in claim 3, wherein the amplifier creates a first output by enhancing the signal produced by the difference between the set value and the comparative value.

5. The motor speed control system as in claim 4, wherein the control gate restricts the first output from the amplifier, and further generates and sends a second output to the motor driver.

6. The motor speed control system as in claim 5, wherein the first value is an integer C representing the actual rotational speed N, the second value is a digital value Nsc representing the set rotational speed Ns, and the comparative value calculating device calculates a comparative value D by: D=Nsc*C.

7. The motor control system as in claim 6, wherein the third value is an integer number representing the set rotational speed Ns, and the set value calculating device calculates a set value as the constant value K by: K=Nsc*Cs.

8. A motor speed control system comprising: a controller operable to increase or decrease a power supply to a motor, wherein the controller increases the supply of power when a difference in E is a negative value, the difference in E calculated by: E=K(1−Ns/N)wherein K is a constant value, Ns is a set rotational speed, and N is an actual rotational speed, further wherein the controller decreases the supply of power when the difference in E is a positive value.

9. The motor sp control system as in claim 8, father comprising a comparative value calculating device for calculating a comparative value D by: D=Nsc*C wherein Nsc is a digital value representing set rotational speed Ns, and C is an integer number representing the actual rotational speed N,

10. The motor speed control system as in claim 9, further comprising a set value calculating device for calculating a set value as the constant value K by: K=Nsc*Cs wherein Cs is an integer number representing the set rotational speed Ns, further wherein the difference in E is calculated by: E=K−D=Nsc*Cs−Nsc*C.

11. The motor sp control system as in claim 10, further comprising a pulse interval outputting device for outputting pulses at an interval corresponding to the rotational speed of the motor, wherein the comparative value calculating device comprises a counter operable to count the number of pulses per unit time for obtaining a number of pulses as the integer number C.

12. The motor control system as in claim 11, wherein C=(1/N)/t and Cs=(1/Ns)/t, t being an oscillating period of the counter, because Nsc=K/Cs, the difference E is calculated by: E=K−(K/Cs)*C=K−(K*Ns*t*(1/N*t))=K−K*(Ns/N)=K(1−Ns/N).

13. The motor speed control system as in claim 8, wherein the controller includes an amplifier, a control gate and a motor driver.

14. The motor speed control system as in claim 13, wherein the amplifier cream a first output by enhancing the signal produced by the difference E.

15. The motor speed control system as in claim 14, wherein the control gate restricts the first output from the amplifier, and further generates and sends a second output to the motor driver.