Abstract:
Disclosed herein are a system and a method for controlling a speed of a motor. The method for controlling a speed of a motor includes: receiving a signal from a hall sensor of the motor to measure a current speed of the motor; comparing the current speed of the motor measured with a reference speed to calculate errors; outputting a speed control value of the motor based on the calculated errors; limiting the output speed control value to values within a predetermined range; controlling a duty or a phase of current applied to the motor according to the limited values within the predetermined range; and generating a motor driving signal based on the duty control or the phase control and applying the generated motor driving signal to the motor.

Description:
CROSS REFERENCE(S) TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit under 35 U.S.C. Section 119 of Korean Patent Application Serial No. 10-2012-0137869 entitled “System And Method For Controlling Speed Of Motor” filed on Nov. 30, 2012, which is hereby incorporated by reference in its entirety into this application. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Technical Field 
         [0003]    The present invention relates to a system and a method for controlling a speed of a motor, and more particularly, to a system and a method for controlling a speed of a motor capable of maximizing efficiency of a motor by simultaneously controlling a duty value and a phase value in controlling a speed of a motor. 
         [0004]    2. Description of the Related Art 
         [0005]    As a method for controlling a speed of a motor, there are an open loop control method and a closed loop control method. As the open loop control method does not detect a current speed of a motor, the open loop control method may not accurately control the speed of the motor due to a change in surrounding environment. On the other hand, the closed loop control method may maintain a constant speed at all times as the control of the speed adaptively reacts to the surrounding environment. According to the related art, a method for controlling a speed of a motor based on a duty has been used. However, the method may not implement a maximum efficiency according to characteristics of a motor. 
         [0006]      FIG. 1  is a diagram illustrating an example of a system for controlling a speed of a motor based on a closed loop control method according to the related art. 
         [0007]    As illustrated in  FIG. 1 , the system for controlling a speed of a motor according to the related art is configured to include a speed measurement unit  107 , a comparison unit  102 , a speed control unit  103 , a limiting unit  104 , and a PWM generation unit  105 . 
         [0008]    As described above, when the system for controlling a speed of a motor according to the related art intends to control the speed of the motor based on the PWM, the speed of the motor becomes lowest when the duty is 0% and the speed of the motor becomes highest when the duty is 100%. Even though the PWM generation unit  105  applies the PWM of duty 100% to a motor  106 , the speed of the motor may be controlled no longer when the speed of the motor  106  does not reach a reference speed  101 . Generally, there are many cases in which the maximum speed of the motor  106  may be limited at the time of controlling the speed of the motor only with the duty value. That is, as the control results of the speed control unit  103 , the maximum duty is physically 100% even though the duty over 100% comes out, such that the limiting unit  104  limits the duty value within a range of 0 to 100%. Therefore, there is a problem in that the efficiency of the motor may not be maximized. 
       RELATED ART DOCUMENT 
     Patent Document 
       [0000]    
       
         (Patent Document 1) Korean Patent Laid-Open Publication No. 10-2012-0076724 (Laid-Open Publication Date: Jul. 10, 2012) 
         (Patent Document 2) Korean Patent Laid-Open Publication No. 10-2010-0041794 (Laid-Open Publication Date: Apr. 22, 2010) 
       
     
       SUMMARY OF THE INVENTION 
       [0011]    An object of the present invention is to provide a system and a method for controlling a speed of a motor capable of maximizing efficiency of a motor by simultaneously controlling a duty value and a phase value of current applied to a motor in controlling a speed of a motor. 
         [0012]    According to an exemplary embodiment of the present invention, there is provided a system for controlling a speed of a motor, including: a speed measurement unit that receives a signal from a hall sensor mounted in the motor to measure a current speed of the motor; a comparison unit that compares the current speed of the motor measured by the speed measurement unit with a reference speed to calculate errors; a speed control unit that outputs a speed control value of the motor based on the errors calculated by the comparison unit; a limiting unit that limits the speed control value output from the speed control unit to values within a predetermined range; a duty control unit that controls a duty of current applied to the motor according to the values within the predetermined range limited by the limiting unit; a phase control unit that controls a phase of current applied to the motor according to the values within the predetermined range limited by the limiting unit; and a motor driving unit that generates a motor driving signal based on the duty control by the duty control unit and the phase control by the phase control unit and applies the generated motor driving signal to the motor. 
         [0013]    The system for controlling a speed of a motor may further include: a control determination unit that determines the duty control or the phase control for controlling the speed of the motor based on the speed control value limited by the limiting unit and the signal from the hall sensor. 
         [0014]    The phase control of current by the phase control unit may be performed by controlling the time when a direction in current starts to change based on the signal from the hall sensor. 
         [0015]    The motor driving unit may include a first circuit unit and a second circuit unit that are connected with each other in parallel, in which the first circuit unit includes a first P channel type MOSFET and a first N channel type MOSFET that are connected with each other in series and the second circuit unit includes a second P channel type MOSFET and a second N channel type MOSFET that are connected with each other in series. 
         [0016]    Diodes may be each mounted between respective source terminals and drain terminals of the first P channel type and N channel type MOSFETs and the second P channel type and N channel type MOSFETs. 
         [0017]    According to another exemplary embodiment of the present invention, there is provided a method for controlling a speed of a motor by a system for controlling a speed of a motor including a speed measuring unit, a comparison unit, a speed control unit, a limiting unit, a duty control unit, a phase control unit, and a motor driving unit, the method including: a) receiving, by the speed measuring unit, a signal from a hall sensor mounted in the motor to measure a current speed of the motor; b) comparing, by a comparison unit, the current speed of the motor measured by the speed measurement unit with a reference speed to calculate errors; c) outputting, by the speed control unit, a speed control value of the motor based on the errors calculated by the comparison unit; d) limiting, by the limiting unit, the speed control value output from the speed control unit to values within a predetermined range; e) controlling, by the duty control unit, a duty of current applied to the motor according to the values within the predetermined range limited by the limiting unit; f) controlling, by the phase control unit, the phase of current applied to the motor according to the values within the predetermined range limited by the limiting unit; and g) generating, by a motor driving unit, a motor driving signal based on the duty control by the duty control unit or the phase control by the phase control unit and applying the generated motor driving signal to the motor. 
         [0018]    The method for controlling a speed of a motor may further include: determining, by a control determination unit, a duty control or a phase control for controlling the speed of the motor based on the speed control value limited by the limiting unit and the signal from the hall sensor, among steps d) to f). 
         [0019]    The phase control of current by the phase control unit in the step f) may be performed by controlling the time when a direction in current starts to change based on the signal from the hall sensor. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0020]      FIG. 1  is a diagram illustrating an example of a system for controlling a speed of a motor based on a closed loop control method according to the related art. 
           [0021]      FIG. 2  is a diagram schematically illustrating a configuration of a system for controlling a speed of a motor according to an exemplary embodiment of the present invention. 
           [0022]      FIG. 3  is a diagram illustrating a configuration of an internal circuit of a motor driving unit of a system for controlling a speed of a motor illustrated in  FIG. 2 . 
           [0023]      FIG. 4  is a flow chart illustrating a process for executing a method for controlling a speed of a motor according to an exemplary embodiment of the present invention. 
           [0024]      FIG. 5  is a diagram illustrating a driving signal pattern of a switch of a driving unit of a single phase BLDC motor using a hall sensor. 
           [0025]      FIGS. 6A and 6B  are diagrams conceptually illustrating an example of a combination of a duty control and a phase control. 
           [0026]      FIG. 7  is a diagram conceptually illustrating that a speed of a motor is controlled by alternately replacing a duty and a phase. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0027]    The terms and words used in the present specification and claims should not be interpreted as being limited to typical meanings or dictionary definitions, but should be interpreted as having meanings and concepts relevant to the technical scope of the present invention based on the rule according to which an inventor can appropriately define the concept of the term to describe most appropriately the best method he or she knows for carrying out the invention. 
         [0028]    Throughout the specification, unless explicitly described otherwise, “comprising” any components will be understood to imply the inclusion of other components but not the exclusion of any other components. In addition, a term “part”, “module”, “unit”, or the like, described in the specification means a unit of processing at least one function or operation and may be implemented by hardware or software or a combination of hardware and software. 
         [0029]    Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. 
         [0030]      FIG. 2  is a diagram schematically illustrating a configuration of a system for controlling a speed of a motor according to an exemplary embodiment of the present invention. 
         [0031]    Referring to  FIG. 2 , a system for controlling a speed of a motor according to the exemplary embodiment of the present invention is configured to include a speed measurement unit  210 , a comparison unit  202 , a speed control unit  203 , a limiting unit  204 , a duty control unit  206 , a phase control unit  207 , and a motor driving unit  208 . 
         [0032]    The speed measurement unit  210  receives a signal from a hall sensor  209   s  mounted in a motor  209  to measure a current speed of the motor  209 . 
         [0033]    The comparison unit  202  compares the current speed of the motor  209  measured by the speed measurement unit  210  with the reference speed to calculate errors. 
         [0034]    The speed control unit  203  outputs a speed control value of the motor  209  based on the errors calculated by the comparison unit  202 . 
         [0035]    The limiting unit  204  limits the speed control value output by the speed control unit  203  to values within a predetermined range. 
         [0036]    The duty control unit  206  controls a duty of current applied to the motor  209  according to the values within the predetermined range that are limited by the limiting unit  204 . 
         [0037]    The phase control unit  207  controls a phase of current applied to the motor  209  according to the values within a predetermined range that are limited by the limiting unit  204 . 
         [0038]    The motor driving unit  208  generates a motor driving signal based on a duty control by the duty control unit  206  and a phase control by the phase control unit  207  and applies the generated motor driving signal to the motor  209 . 
         [0039]    Here, the system for controlling a speed of a motor may further include a control determining unit  205  that determines the duty control or the phase control for controlling the speed of the motor  209  based on the speed control value limited by the limiting unit  204  and the signal from the hall sensor  209   s.    
         [0040]    Further, the phase control of current by the phase control unit  207  may be performed by controlling the time when a direction of current starts to change based on the signal from the hall sensor  209   s.    
         [0041]    In addition, the motor driving unit  208  includes a first circuit unit  208   a  and a second circuit unit  208   b  that are connected with each other in parallel. In this configuration, the first circuit unit  208   a  includes a first P channel type MOSFET Q1 and a first N channel type MOSFET Q2 that are connected with each other in series and the second circuit unit  208   b  includes a second P channel type MOSFET Q3 and a second N channel type MOSFET Q4 that are connected with each other in series. 
         [0042]    Preferably, diodes are each disposed between respective source terminals and drain terminals of the first P channel type and N channel type MOSFETs Q1 and Q2 and the second P channel type and N channel type MOSFETs Q3 and Q4. 
         [0043]    Hereinafter, the method for controlling a speed of a motor by the system for controlling a speed of a motor according to the exemplary embodiment of the present invention having the foregoing configuration will be described. 
         [0044]      FIG. 4  is a flow chart illustrating a process of executing a method for controlling a speed of a motor according to an exemplary embodiment of the present invention. 
         [0045]    Referring to  FIG. 4 , the method for controlling a speed of a motor according to the exemplary embodiment of the present invention is the method for controlling a speed of a motor by the system for controlling a speed of a motor including the speed measurement unit  210 , the comparison unit  202 , the speed control unit  203 , the limiting unit  204 , the duty control unit  206 , the phase control unit  207 , and the motor driving unit  208  as described above. According to the method for controlling a speed of a motor according to the exemplary embodiment of the present invention, the speed measurement unit  210  first receives the signal from the hall sensor  209   s  that is mounted in the motor  209  so as to measure the current speed of the motor  209  (S 401 ). 
         [0046]    Next, the comparison unit  202  compares the current speed of the motor  209  measured by the speed measurement unit  210  with the preset reference speed  201  to calculate errors (S 402 ). 
         [0047]    Next, the speed control unit  203  outputs the speed control value of the motor based on the errors calculated by the comparison unit  202  (S 403 ). 
         [0048]    Further, the limiting unit  204  limits the speed control value output from the speed control unit  203  to the values within the predetermined range (S 404 ). 
         [0049]    Next, the duty control unit  206  controls the duty of current applied to the motor  209  according to the values within the predetermined range that are limited by the limiting unit  204  (S 405 ). 
         [0050]    Further, the phase control unit  207  controls the phase of current applied to the motor according to the values within a predetermined range that are limited by the limiting unit  204  (S 406 ). In this case, the phase control of current by the phase control unit  207  may include controlling the time when the direction of current starts to change based on the signal from the hall sensor  209   s.    
         [0051]    Further, preferably, the method for controlling a speed of a motor may further include determining the duty control or the phase control for the control determining unit  205  to control the speed of the motor  209  based on the speed control value limited by the limiting unit  204  and the signal from the hall sensor  209   s , among S 404  to S 406 . 
         [0052]    By doing so, when the duty control by the duty control unit  206  or the phase control by the phase control unit  207  are completed, the motor driving unit  208  generates the motor driving signal based on the duty control or the phase control and applies the generated motor driving signal to the motor  209  (S 407 ). By performing the processes, the method for controlling a speed of a motor according to the exemplary embodiment of the present invention is completed. 
         [0053]    Hereinafter, the method for controlling a speed of a motor according to the exemplary embodiment of the present invention as described above will be described in more detail. 
         [0054]      FIG. 5  is a diagram illustrating a driving signal pattern of a switch of a driving unit of a single phase BLDC motor using a hall sensor. 
         [0055]    As illustrated in  FIG. 5 , signals POUT1, POUT2, NOUT1, and NOUT2 are changed based on the instant that the output HALL OUTPUT of the hall sensor is changed. The (commutation) phase control performed by the method of the present invention controls the time starting to commutate from high to low or from low to high based on the signal from the hall sensor. Generally, since the time delay is generated until the position signal is detected and the communication starts is generated and the change in current increases later as inductance of the motor even when voltage is changed, the speed of the motor may be fast when the commutation is performed (that is, when the ‘high’ or ‘low’ value of the pulse input signal is changed) before the signal from the hall signal is output. 
         [0056]    Therefore, the method for controlling a speed of a motor according to the exemplary embodiment of the present invention is to maximize efficiency by simultaneously controlling the duty value and the phase value in controlling the speed of the motor. 
         [0057]    In the related art, the limiting unit limits the duty value to 0 to 100%. According to the exemplary embodiment of the present invention, the upper limit of the limiting unit  204  may be set to be 100 or more in consideration of the control value of the phase control. 
         [0058]      FIGS. 6A and 6B  are diagrams conceptually illustrating an example of a combination of the duty control and the phase control. 
         [0059]      FIG. 6A  illustrates the case in which the duty is set to be 0 to 100 and the phase is set to be 0 to 100.  FIG. 6B  illustrates the case in which the limit range of the limiting unit  204  is set to be 0 to 200 and the duty value and the phase are combined. The combination method may set a preset value as a reference. 
         [0060]      FIG. 7  is a diagram conceptually illustrating that the speed of the motor is controlled by alternately replacing a duty and a phase. 
         [0061]    As illustrated in  FIG. 7 , the speed of the motor is first controlled only by using the duty value. Next, when the duty or the speed reaches the specific instant, the duty value is changed to the phase value and the speed is controlled. In this case, after the duty value and the initial value of the phase are appropriately set according to the characteristics of the motor, the speed of the motor is controlled as illustrated in  FIG. 7 . 
         [0062]    Meanwhile, when the duty control and the phase control are performed according to the method of the present invention, the control may be performed by placing priority on any one of them. For example, when the priority is placed on the duty control, the duty is first adjusted to adjust the phase by 1 step when the motor reaches the maximum speed. Further, the duty is adjusted again. When the motor reaches the maximum speed, the phase is again adjusted  1  step.  FIG. 7  is a diagram illustrating the control method as described above. When the phase value is adjusted using the duty value after the motor reaches the maximum speed (RPM), the motor may be faster. 
         [0063]    As another example, when the priority is placed on the phase control, the phase is first adjusted, and then the duty value is adjusted when the speed of the motor reaches the reference speed or the maximum speed. In this case, when the speed of the motor is adjusted by first controlling the phase, the method for performing fine adjustment using the duty value is used if the speed of the motor does not reach the reference speed. 
         [0064]    As described above, the method for controlling a speed of a motor according to the exemplary embodiments of the present invention can maximize the efficiency of the motor by simultaneously controlling the duty value and the phase value of current applied to the motor based on the duty value and the phase value used as the feedback value controlling the speed of the motor. 
         [0065]    Further, the duty value and the phase value are also fed back to search the optimized phase value independent of the deviations in position of the rotor that are present at each sample of the signal from the hall sensor. 
         [0066]    As set forth above, according to the exemplary embodiments of the present invention, it is possible to maximize the efficiency of the motor by simultaneously controlling the duty value and the phase value of current applied to the motor based on the duty value and the phase value that are used as the feedback value controlling the speed of the motor. 
         [0067]    As described above, the present invention will be described with reference to the exemplary embodiments, but is not limited thereto. It can be apparent to those skilled in the art that the exemplary embodiments of present invention can be variously changed and applied within the scope of the present invention without departing from the technical idea of the present invention. Therefore, the protection scope of the present invention must be construed by the appended claims and it should be construed that all spirits within a scope equivalent thereto are included in the appended claims of the present invention.