Motor controller and motor control method

Abstract

A motor controller of the present invention comprises units which obtain information indicative of a motor speed (ω) and information indicative of motor torque (T), an air flow calculation section which calculates an air flow (Q) of a fan based on the motor speed (ω) and the motor torque (T); and a speed command generation section which generates a speed command (ω*) of a motor such that the air flow (Q) coincides with the predetermined air flow command (Q*).

1 . A motor controller for controlling a motor which drives a fan for supplying air to a desired location through an air flow passage, the motor controller comprising:
 an air flow calculator configured to obtain speed information indicative of a motor speed at which the motor is running and torque information indicative of a motor torque which the motor is outputting and calculate an air flow of the fan from the motor speed and the motor torque; and
 a speed command generator configured to generate a speed command given to rotate the motor at a target motor speed so that the air flow coincides with a predetermined air flow command, wherein the speed command generator is configured to compare the calculated air flow and the predetermined air flow command and subject to a comparison result between the calculated air flow and the predetermined air flow command, use a ratio of the predetermined air flow command with respect to the air flow to derive the speed command. 
   
     
     
         2 . The motor controller according to  claim 1 , wherein the speed command generator is further configured to use a difference between the calculated air flow and the predetermined air flow command to derive the speed command when the difference between the calculated air flow and the predetermined air flow command falls within a predetermined range. 
     
     
         3 . The motor controller according to  claim 1 ,
 wherein the speed command generator is further configured to:
 receive the predetermined air flow command which directs a target air flow; 
 compare the predetermined air flow command and the calculated air flow; and 
 upon a determination that a difference between the predetermined air flow command and the calculated air flow falls outside a first predetermined range, multiply the ratio between the predetermined air flow command and the calculated air flow by a target motor speed of previous update to derive the speed command which directs the motor to rotate at the target motor speed. 
   
     
     
         4 . The motor controller according to  claim 1 , further comprising a motor driving controller configured to generate a signal used for controlling a driving voltage to the motor in such a way that the motor speed will track the target motor speed. 
     
     
         5 . The motor controller according to  claim 1 , wherein the speed command generator is configured to integrate a difference between the predetermined air flow command and the calculated air flow to derive the target motor speed when the difference between the predetermined air flow command and the calculated air flow falls within a predetermined range. 
     
     
         6 . The motor controller according to  claim 1 , wherein the speed command generator is configured to multiply, by a gain, a difference between the predetermined air flow command and the calculated air flow and add the motor speed to a result of multiplication to derive the target motor speed, when the difference between the predetermined air flow command and the calculated air flow falls within a predetermined range. 
     
     
         7 . The motor controller according to  claim 1 , wherein the speed command generator is configured to correct the speed command in such a way that a difference between the speed command and the motor speed will fall within a predetermined speed range, when the difference between the speed command and the motor speed falls outside the predetermined speed range. 
     
     
         8 . The motor controller according to  claim 1 , wherein the speed command generator is configured to update the target motor speed at intervals, the speed command generator being configured to replace the speed command, when a difference between the motor torque and a motor torque obtained previously falls within a predetermined torque range. 
     
     
         9 . The motor controller according to  claim 1 , wherein the speed command generator is configured to store a minimum motor speed and a maximum motor speed and further configured to adjust the target motor speed to fall within a range between the minimum and the maximum motor speeds. 
     
     
         10 . The motor controller according to  claim 1 , wherein the air flow calculator is configured to divide the motor torque with a square of the motor speed and multiply the motor speed with the result of division. 
     
     
         11 . The motor controller according to  claim 1 , further comprising a first detector configured to detect the motor speed and output the speed information. 
     
     
         12 . The motor controller according to  claim 1 , further comprising a second detector configured to detect a current flowing through the motor and output the torque information. 
     
     
         13 . A motor control system comprising:
 a motor;   the motor controller according to  claim 1 ; and   a motor driving controller configured to drive the motor based on a speed command provided by the motor controller,   wherein the motor driving controller is disposed outside the motor controller.   
     
     
         14 . A motor control system comprising:
 a motor;   the motor controller according to  claim 1 ; and   a motor driving controller configured to drive the motor based on a speed command provided by the motor controller,   wherein the motor driving controller is disposed inside the motor controller.   
     
     
         15 . A method of controlling a motor which drives a fan for supplying air to a desired location through an air flow passage, the method comprising:
 obtaining speed information indicative of a motor speed at which the motor is running and torque information indicative of motor torque which the motor is outputting;   generating a speed command given to rotate the motor at a target motor speed so that the air flow coincides with a predetermined air flow command, wherein generating a speed command comprises comparing the air flow and the predetermined air flow command and, subject to a result of comparison between the air flow and the predetermined air flow command, use a ratio of the predetermined air flow command with respect to the air flow to generate the speed command; and   controlling the motor with the generated speed command in such a way that the fan will output a target air flow.