Patent Publication Number: US-2007118237-A1

Title: Autocontrol simulating system and method

Description:
FIELD OF THE INVENTION  
      This invention relates to simulating systems and methods and, more particularly, to a simulating system for an autocontrol system and a simulating method thereof.  
     DESCRIPTION OF RELATED ART  
      Autocontrol systems are widely used in modern electronic industry because autocontrol systems can reduce labor costs and improve control accuracy. In general, the autocontrol system includes a controller, a plant, and a sensor. The controller sends control commands to the plant to control operations of the plant. The sensor retrieves states of the plant and transmits information on the states of the plant to the controller. Based on the information on the states of the plant, the controller modifies the control commands to conform to the states of the plant. The controller has some parameters whose values can be modified to conform to different applications.  
      In a development and/or an improvement of the autocontrol system, parameter values should be adjusted to be optimal so as to make the autocontrol system achieve a maximum performance. During the adjustment, a testing apparatus is connected to the autocontrol system and used to test whether the parameters values for the autocontrol system are optimal. Therefore, the autocontrol system is required to participate in the whole adjustment and testing process. However, it is troublesome to have an entire autocontrol system participate in the whole adjustment and testing process, especially when the autocontrol system is in a large size.  
      Therefore, a simulating system for simulating the autocontrol system is desired.  
     SUMMARY OF THE INVENTION  
      An autocontrol simulating system is used for creating a simulated model that represents an autocontrol system. The autocontrol system includes a controller and a plant. The simulated model includes a simulated controller and a simulated plant corresponding to the controller and the plant respectively. The autocontrol simulating system includes a loading module, a first adjusting module, a calculating module, and a depicting module. The loading module is used for loading parameter values of the controller. The loaded parameter values of the controller are used as parameter values of the simulated controller. The first adjusting module is used for adjusting parameter values of the simulated plant. The calculating module is used for calculating values of characteristic indicators of the simulated plant. The depicting module is used for depicting characteristic curves of the simulated plant based on the values of characteristic indicators.  
      An autocontrol method is provided for creating a simulated model that represents an autocontrol system. The autocontrol system includes a controller and a plant. The simulated model includes a simulated controller and a simulated plant corresponding to the controller and the plant respectively. The autocontrol simulating method includes steps of: loading parameter values of the controller, the parameter values of the controller being used as values of the simulated controller; setting parameter values of the simulated plant; calculating values of characteristic indicators of the simulated plant; and depicting characteristic curves of the simulated plant based on the values of characteristic indicators.  
      A storage medium is recorded with an application program. The application program has a computer executable steps of: setting parameter values of a simulated model having a simulated controller, a simulated sensor and a simulated plant; calculating values for characteristic indicators of the simulated model; and depicting characteristic curves of the simulated model based on the values for characteristic indicators of the simulated model.  
      Other advantages and novel features will become more apparent from the following detailed description of preferred embodiments when taken in conjunction with the accompanying drawings, in which: 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      Many aspects of the autocontrol simulating system and the autocontrol simulating method thereof can be better understood with reference to the following drawings. The components in the drawings are not necessarily to scale, the emphasis instead being placed upon clearly illustrating the principles of the present disc drive. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views.  
       FIG. 1  is a block diagram of an autocontrol system, the autocontrol system including a controller, a sensor, and a plant;  
       FIG. 2  is a block diagram of an autocontrol simulating system, the simulating system creating a simulated model including a simulated controller, a simulated sensor, and a simulated plant;  
       FIG. 3  is flow chart illustrating a simulating procedure of the autocontrol simulating system of  FIG. 1 ;  
       FIG. 4  is a block diagram of a disc drive;  
       FIG. 5  is an exemplary user interface of the autocontrol simulating system of  FIG. 1  used for adjusting parameters of the simulated plant; and  
       FIG. 6  is an exemplary user interface of the autocontrol simulating system of  FIG. 1  used for adjusting parameters of the simulated controller and the simulated sensor. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
      Reference will now be made to the drawings to describe the preferred embodiment of the present autocontrol simulating system and the present simulating method, in detail.  
      Referring to  FIG. 1 , a block diagram of an autocontrol system  10  is illustrated. The autocontrol system  10  includes an operator  102 , a controller  104 , a plant  106 , and a sensor  108 . The controller  104  is used for controlling operations of the plant  106 . The sensor  108  is used for sensing states of the plant  106  and feeding back the states of the plant  106  to the controller  104 .  
      An exemplary working procedure of the autocontrol system  10  is as follows: first, an external input R is inputted to the operator  102 . At the same time, the sensor  108  feeds back a state signal Y representing the states of the plant  106  to the operator  102 . Second, the operator  102  subtracts the state signal Y from the external input R to get an input signal α of the controller  104 . Third, the controller  104  generates a control signal F based on the input signal α of the controller  104 . The control signal F is then sent to the plant  106 . Finally, the plant  106  generates an output signal X based on the control signal F. The output signal X is also outputted to the sensor  108 .  
      Each of the input signal α, the control signal F, the output signal X, and the state signal Y depends on a time parameter t. According to Laplace transformation theorem, signals in the time domain (also called t-domain) can be transformed into a complex frequency domain (also called s-domain). That is, each of the input signal α, the control signal F, the output signal X, and the state signal Y can be transformed to depend on a complex frequency parameter s.  
      According to autocontrol principles, the input signal α(s) of the controller  104  can be defined as follows:
 
α( s )= R ( s )− Y ( s )  (1)
 
 wherein R(s) represents the external input signal, and Y(s) represents the state signal fed back to the operator  102  by the sensor  108  concurrently. 
 
      It is presumed that the sensor  108  includes a transfer function H(s). The state signal Y(s) can be defined as follows:
 
 Y ( s )= H ( s )* X ( s )  (2)
 
 wherein H(s) represents the transfer function of the sensor  108 , and X(s) represents the output signal of the plant  106 . 
 
      It is presumed that the controller  104  includes a transfer function C(s). The control signal F(s) can be defined as follows:
 
 F ( s )= C ( s )*α( s )  (3)
 
 wherein C(s) represents the transfer function of the controller  104 , and α(s) represents the input signal of the controller  104 . 
 
      It is presumed that the plant  106  includes a transfer function G(s). The output signal X(s) can be defined as follows:
 
 X ( s )= G ( s )* F ( s )  (4)
 
 wherein G(s) represents the transfer function of the plant  106 , and F(s) represents an output signal of the controller  104 . 
 
      Based on the above-mentioned conditions (1), (2), (3) and (4), X(s) and R(s) can be represented by following expressions (5) and (6):
 
 X ( s )= G ( s )* F ( s )= G ( s )* C ( s )*α( s )  (5)
 
 R ( s )=α( s )+ Y ( s )=α( s )+ H ( s )* X ( s )=α( s )+ H ( s )* G ( s )* C ( s )*α( s )  (6)
 
      It is presumed that the autocontrol system  10  has a transfer function T(s). The transfer function T(s) of the autocontrol system  10  can be defined as follows:  
                     T   ⁡     (   s   )       =       X   ⁡     (   s   )       /     R   ⁡     (   s   )                     =       (       G   ⁡     (   s   )       *     C   ⁡     (   s   )       *     α   ⁡     (   s   )         )     /     (       α   ⁡     (   s   )       +       H   ⁡     (   s   )       *     G   ⁡     (   s   )       *     C   ⁡     (   s   )       *     α   ⁡     (   s   )           )                   =       (       G   ⁡     (   s   )       *     C   ⁡     (   s   )         )     /     (     1   +       H   ⁡     (   s   )       *     G   ⁡     (   s   )       *     C   ⁡     (   s   )           )                     (   7   )             
 
      Generally, the plant  106  can be regarded as a second order system and the transfer function G(s) of the plant  106  can be represented by the following expression:
 
 G ( s )= K /( Ts 2 +s+K )  (8)
 
 wherein s represents an variable parameter of the equation (8), K represents a invariable flexibility parameter of the plant 106, T represents an invariable time parameter of the plant  106 . 
 
      The expression (8) can be transformed to another expression:
 
 G ( s )=ω n   2 /( 2 +2 *s*ω   n *ξ+ω n   2 )  (9)
 
 wherein ω n  represents an undamped oscillation frequency of the second order system and satisfies: ω n =(K/T 1/2 , ξ represents a damping ratio of the second order system and satisfies: ξ=1/(2*(K*T 1/2 ). The parameters K, T, ω n , and ξ are adjustable constant parameters. 
 
      Each of the transfer function C of the controller  104  and the transfer function H of the sensor  108  can be presumed as a linear compound function of three functions F 1 (s), F 2 (s), and F 3 (s). The three functions F 1 (s), F 2 (s), and F 3 (s) satisfy the following equations:
 
 F   1 ( s )= a   p   (10)
 
 F   2 ( s )= c   1 /(a 1   *s+b   1 )  (11)
 
 F   3 ( s )= a   D   *s+b   D   (12)
 
 wherein a p , C 1 , a 1 , b 1 , a D , and b D  are adjustable constant parameters. 
 
      According to the expressions (7), (9), (10), (11), and (12), the transfer function T(s) of the autocontrol system  10  can be determined by the adjustable constant parameters K, T, ω n , ξ, a p , c 1 , a 1 , b 1 , a D , and b D , and variable parameter s. In order to make the autocontrol system  10  run in a best mode, each adjustable constant parameter should be given an optimal value. After every adjustment, a test should be done to determine whether the adjusted values are optimal.  
      In order to perform the tests, bode diagrams are used as evaluation indicators. Such bode diagrams include an amplitude-phase characteristic curve which reflects relationships between gain ratios M(ω) and frequencies of the autocontrol system  10 , and a phase characteristic curve which reflects relationships between phase differences φ(ω) and frequencies of the autocontrol system  10 . It is presumed that s satisfies an equation: s=j*ω, wherein j is an invariable coefficient, ω is a variable parameter that represents a frequency of the autocontrol system  10 . Therefore, the transfer function T(s) of the autocontrol system  10  can be represented by T(j*ω). The gain ratio M(ω) between the input signal R and the output signal X of the autocontrol system  10  satisfies: M(ω)=/T(j*ω)/. The phase difference φ(ω) of the autocontrol system  10  satisfies: φ(ω)=&lt;T(j*ω). Therefore, each of the adjustable constant parameters K, T, ω n , φ, a p , c 1 , a 1 , b 1 , a D , b D , and j has an affect on the amplitude-phase characteristic curve and the phase characteristic curve. Each of the adjustable constant parameters K, T, ω n , φ, a p , c 1 , a 1 , b 1 , a D , b D , and j should be give an optimal value to ensure the amplitude-phase characteristic curve and the phase characteristic curve in a predetermined form.  
      However, the adjustable constant parameters may depend on each other, thus making a design task of selecting an optimal value to each adjustable constant parameter more complicated and tedious.  
      In order to make the complicated and tedious tasks easier, an autocontrol simulating system  20  is used to create a simulated model to represent behavior characteristics of the autocontrol system  10 . The simulated model includes a simulated controller corresponding to the controller  104 , a simulated plant corresponding to the plant  106 , and a simulated sensor corresponding to the sensor  108 .  
      Referring to  FIG. 2 , a block diagram of the autocontrol simulating system  20  is illustrated. The autocontrol simulating system  20  includes a loading module  202 , a calculating module  204 , a first adjusting module  206 , a second adjusting module  208 , an output module  210 , a depicting module  212 , and a display interface  214 . The loading module  202  is used for receiving a group of parameter values. The received parameter values include parameter values of the simulated controller and the simulated sensor. The received values can be obtained from an input terminal (not shown), or be read from a storing module (not shown) for storing given values of parameters.  
      The calculating module  204  is used for calculating depicting data of the simulated plant and the simulated model based on each group of parameter values.  
      The first adjusting module  206  is used for setting and adjusting the parameter values of the simulated plant, so as to make an amplitude-phase characteristic curve and a phase characteristic curve for the simulated plant substantially the same as those for the plant  106 .  
      The second adjusting module  208  is used for adjusting the parameter values of the simulated controller and the simulated sensor to be “satisfied”. The output module  210  is used for outputting “satisfied” parameter values of the simulated controller and the simulated sensor.  
      The depicting module  212  is used for depicting an amplitude-phase characteristic curve and a phase characteristic curve based on the depicting data. The amplitude-phase characteristic curve and the phase characteristic curve are used to test whether a corresponding group of parameter values are “satisfied”. The display interface  214  is used for timely displaying the amplitude-phase characteristic curve and the phase characteristic curve for the corresponding group of parameter values.  
      Referring to  FIG. 3 , a simulating procedure of the autocontrol simulating system  20  is illustrated. Firstly, in step  302 , the loading module  202  receives parameter values of the controller  104  and the sensor  108 . The received parameter values of the controller  104  and the sensor  108  are used as parameter values of the simulated controller and the simulated sensor, respectively.  
      Secondly, in step  304 , the first adjusting module  206  receives parameter values of the simulated plant from an input terminal. The received parameter values of the controller  104  and the sensor  108 , and the parameter values of the simulated plant are then transferred to the calculating module  204 .  
      Thirdly, in step  306 , the calculating module  204  calculates depicting data of the simulated plant based on the received parameter values of the controller  104 , the sensor  108 , and the simulated plant.  
      Based on the depicting data, the depicting module  212  depicts an amplitude-phase characteristic curve and a phase characteristic curve of the simulated plant to be displayed on the display interface  214  (step  308 ).  
      Then, in step  310 , a conclusion is made as to whether the amplitude-phase characteristic curve and the phase characteristic curve of the simulated plant are conformable to those of the plant  106 . In this embodiment, the amplitude-phase characteristic curve and the phase characteristic curve of the plant  106  are previously stored in the autocontrol simulating system  20 . The amplitude-phase characteristic curve and the phase characteristic curve of the plant  106  are based on the received parameter values of the controller  104  and the sensor  108 .  
      If the amplitude-phase characteristic curve and the phase characteristic curve of the simulated plant are not conformable to those of the plant  106 , the procedure proceeds to step  312  where the parameter values of the simulated plant are re-adjusted while the parameter values of the simulated controller and the simulated sensor are kept unchanged. After re-adjustment in step  310 , the procedure goes back to step  306 .  
      If the amplitude-phase characteristic curve and the phase characteristic curve of the simulated plant are conformable to those of the plant  106 , the simulated plant is proved “satisfied” to serve as a representation of the plant  106 . The procedure proceeds to step  314  where another conclusion is made as to whether the parameter values of the simulated controller and the simulated sensor are “satisfied”.  
      If the parameter values of the simulated controller and the simulated sensor are not “satisfied”, the procedure proceeds to step  316  where the parameter values of the simulated controller and the simulated sensor are adjusted. Then, in step  318 , the calculating module  204  calculates depicting data of the simulated model based on the adjusted parameter values of the simulated controller and the simulated sensor. Based on the depicting data of the simulated model corresponding to the adjusted values, the depicting module  212  depicts an amplitude-phase characteristic curve and a phase characteristic curve of the simulated model to be displayed on the display interface  314  (step  320 ). After that, the procedure goes back to step  314 .  
      If the parameter values of the simulated controller and the simulated sensor are optimal, the procedure proceeds to step  322  where the parameter values of the simulated controller and the simulated sensor are outputted to the autocontrol system  10 .  
      The autocontrol system  10  can be used in many applications, such as in a disc drive, a television, an air-conditioner, and a car. For simplicity of the description, a disc drive  40  is used as an example for illustration. Referring also to  FIG. 4 , the disc drive  40  includes an optical pick-up head  402 , a stepping motor  404 , a spindle motor  406 , an amplifier  410 , a signal processor  412 , and a power driver  414 . The spindle motor  406  spins to bring a disc  408  to spin. The stepping motor  404  spins to drive the optical pick-up head  402  to move so that the optical pick-up head  402  seeks a predetermined track of the disc  108 . The optical pick-up head  402  receives a reflected light from the disc  408  and retrieves optical signals from the reflected light and then transforms the optical signals into electrical signals to be sent to the amplifier  410 . The amplifier  410  amplifies the electrical signals to be sent to the signal processor  412 . The signal processor  412  extracts tracking error signals and/or focusing error signals from the electrical signals and then generates servo control signals based on the tracking error signals and/or focusing error signals to be sent to the power driver  414 . Based on the servo control signals, the power driver  414  outputs corresponding driving voltages to control the stepping motor  404  and the spindle motor  406  to spin, so as to drive the disc  408  to spin and the optical pick-up head to move in a desired pattern.  
      In the disc drive  40 , the signal processor  412  and the power driver  414  cooperates with the optical pick-up head  402 , the amplifier  410 , the stepping motor  404  and the spindle motor  406  to function as the autocontrol system  10 . The signal processor  412  cooperates with the power driver  414  to function as the controller  104 . The optical pick-up head  402  functions as the sensor  108 . The amplifier  410  functions as the operator  102 . The stepping motor  404  and the spindle motor  406  function as the plant  106 .  
      In order to simulate the autocontrol system  10  of the disc drive  40 , the autocontrol simulating system  20  creates a simulated model representing the autocontrol system  10  of the disc drive  40 . The simulated model includes a simulated plant corresponding to the stepping motor  404  and the spindle motor  406 , a simulated controller corresponding to the signal processor  412  and the power driver  414 .  
      Referring to  FIG. 3  again, in step  310 , the characteristic curves for the stepping motor  404  and the spindle motor  406  are obtained by measuring and input and an output of the spindle motor  406  and the stepping motor  404 .  
      Referring to  FIG. 5 , an exemplary user interface  50  of the autocontrol simulating system  20  used for adjusting parameters of the simulated plant corresponding to the stepping motor  404  and the spindle motor  406  is illustrated. The user interface  50  includes a first adjusting area  502  for adjusting the parameter values of the simulated plant, and a first display area  504  for displaying an amplitude-phase characteristic curve and a phase characteristic curve of the simulated plant. After a user selects a group of parameter values of the simulated plant, a corresponding amplitude-phase characteristic curve and a corresponding phase characteristic curve of the simulated plant are displayed in the first display area  504  in an instant manner.  
      Referring to  FIG. 6 , an exemplary user interface  60  of the autocontrol simulating system  20  used for adjusting parameters of the simulated controller corresponding to the signal processor  412  and the power driver  414  is illustrated. The user interface  60  includes a second adjusting area  602  for adjusting the parameter values of the simulated controller, and a second display area  604  for displaying an amplitude-phase characteristic curve and a phase characteristic curve of the simulated model. After a user selects a group of parameter values of the simulated controller, a corresponding amplitude-phase characteristic curve and a corresponding phase characteristic curve of the simulated model are displayed in the second display area  604  in an instant manner. In the second display area  604 , curves in dashed lines corresponds to parameter values of the simulated controller before adjustment, whist curves in continuous lines corresponds to parameter values of the simulated controller after adjustment. By comparing the curves in the dashed lines and in the continuous lines, effects of each parameter on the curves will be visible.  
      The embodiments described herein are merely illustrative of the principles of the present invention. Other arrangements and advantages may be devised by those skilled in the art without departing from the spirit and scope of the present invention. Accordingly, the present invention should be deemed not to be limited to the above detailed description, but rather by the spirit and scope of the claims that follow, and their equivalents.