Apparatus and method compensating recurring false speed errors in DC motor and disk drive adopting same
View Patent ↗Provided are an apparatus and method of controlling a motor by compensating for recurring false speed errors generated in a direct current (DC) motor. The apparatus includes a learning control unit adapted to calculate recurring false speed errors related to a mechanical tolerance associated with the motor in each one of a plurality of controlling sections associated with a single rotation of the motor, and generate a corresponding reference speed for each controlling section, and a motor control unit adapted to control the rotational speed of the motor in relation to a speed error defined by a difference between the reference speed for each controlling section and an actual measured speed of the motor for each controlling section.
1. A motor control apparatus compensating recurring false speed errors in a direct current (DC) motor, comprising:
a learning control unit configured to calculate an average value for an actual measured motor speed in each of a plurality of controlling sections associated with a single rotation of the motor, calculate an average value of control input signals driving the motor in each of the controlling sections, calculate an estimated motor speed in each of the controlling sections according to the average value of the control input signals, and generate a reference speed in each of the controlling sections by subtracting the estimated motor speed in each of the controlling sections from the average value of the actual measured motor speed; and
a motor control unit adapted to control the rotational speed of the motor in relation to a speed error defined by a difference between the reference speed for each controlling section and an actual measured speed of the motor for each controlling section.
2. The apparatus of claim 1 , wherein the learning control unit comprises; a plant modeling tool configured to generate the reference speed in each of the controlling sections.
3. The apparatus of claim 2 , wherein the actual measured speed of the motor is calculated using a phase signal generated in relation to a back electromotive force of the motor.
4. The apparatus of claim 2 , wherein the learning control unit further comprises:
a first average calculator configured to calculate the average value of the actual measured motor speed in each of the controlling section in which a recurring false speed error is generated in relation to an initial reference speed;
a second average calculator configured to calculate the average value of control input signals driving the motor in each of the controlling sections in which a recurring false speed error is generated in relation to the initial reference speed;
wherein the plant modeling tool is further configured to calculate the estimated motor speed in each of the controlling section according to the average value of the control input signals;
a subtractor configured to calculate the false speed error in each controlling section by subtracting the estimated motor speed in each of the controlling sections from the average value of the actual measured motor speed; and
a reference speed adjustor configured to adjust the reference speed in each of the controlling sections to decrease the false speed error.
5. The apparatus of claim 4 , wherein the plurality of controlling sections is N, N being an integer greater than 1, and the number of controlling sections having a recurring false speed error is N.
6. The apparatus of claim 4 , wherein the reference speed adjustor is further configured to adjust the reference speed of each controlling section using a look-up table in which corrected reference speed information corresponding to false speed errors in each of the controlling sections is defined.
7. The apparatus of claim 6 , wherein the motor includes a brushless DC motor.
8. A method controlling operation of a direct current (DC) motor, the motor having a mechanical tolerance generating recurring false speed errors, the method comprising:
determining operation of the motor at a constant speed;
controlling the speed of the motor in accordance with an initial reference speed;
calculating an average value for an actual measured motor speed in each of a plurality of controlling sections associated with a single rotation of the motor;
calculating an average value of control input signals driving the motor in each of the controlling sections;
calculating an estimated motor speed in each of the controlling sections according to the average value of the control input signals;
generating a reference speed in each of the controlling sections by subtracting the estimated motor speed in each of the controlling sections from the average value of the actual measured motor speed; and
changing the reference speed from the initial reference speed for each controlling section to decrease the corresponding false speed error of each controlling section.
9. The method of claim 8 , wherein calculating the estimated motor speed in each of the controlling sections according to the average value of the control input signals comprises
estimating the motor speed in relation to the average value of the control input signals using a plant modeling tool.
10. The method of claim 9 , wherein the plurality of controlling sections is N, N being an integer greater than 1, and the number of controlling sections having a recurring false speed error is N.
11. The method of claim 8 , wherein the changing of the reference speed from the initial speed for each of the controlling sections comprises using a look-up table in which corrected reference speed information corresponding to false speed errors is defined.