Digital servo control method, digital servo controller, storage device and head position control method

A digital servo control method for receiving an analog observation signal u(t) from a control target, and generating a control signal to servo-control said control target using a following output equation and state equation, comprising the steps of:

• converting said analog observation signal u(t) into a digital signal by an A/D converter at each operation period Ts/N (N is a 2 or higher natural number), and calculating D·ud[k] of the following output equation by a processor;
• calculating the following state equation at each operation period Ts by said processor, and calculating C·x[k+1] of the following output equation based on the result x[k+1] of the calculation of the state equation;
• calculating the control signal yd[k] each time said D·ud[k] and said C·x[k+1] are updated;
• and
• outputting said calculated yd[k] to a D/A converter and outputting said analog control signal y(t).
• Output equation:
• yd[k]=C·x[k]+D·ud[k]State equation:
• x[k+1]=A·x[k]+B·ud[k]
• where ud[k] is an observation signal to be input;
• yd[k] is a control signal to be output;
• x[k] is a state variable;
• A, B, C and D are constant matrixes;
• and k is a parameter to indicate a sampling time.

A digital servo controller which receives an analog observation signal u(t) from a control target and generates a control signal to servo-control said control target using a following output equation and state equation, comprising:

• an analog amplifier for multiplying said analog observation signal u(t) by D;
• an A/D converter for converting said analog observation signal u(t) into a digital observation signal ud[k] at each operation period Ts;
• a processor for receiving said digital observation signal, calculating the following state equation, calculating C·x[k+1] of the following output equation based on the result x[k+1] of the calculation of the state equation, and outputting said calculated value of C·x[k+1] to a D/A converter at a point when Ts/2 has elapsed since u(t) is observed;
• and
• an analog adder for adding said analog observation signal multiplied by D and the output of said D/A converter, and outputting said control signal y(t).
• Output equation:
• yd[k]=C·x[k]+D·ud[k]State equation:
• x[k+1]=A·x[k]+B·ud[k]
• where ud[k] is an observation signal to be input;
• yd[k] is a control signal to be output;
• x[k] is a state variable;
• A, B, C and D are constant matrixes;
• and k is a parameter to indicate a sampling time.

A digital servo controller which receives an analog observation signal u(t) from a control target and generates a control signal to servo-control said control target using a following output equation and state equation, comprising:

• an A/D converter for converting said analog observation signal u(t) into a digital signal at each operation period Ts/N (N is a 2 or higher natural number);
• a processor for calculating D·ud[k] of the following output equation from said digital signal, calculating the following state equation at each operation period Ts, calculating C·x[k+1] of the following output equation based on the result x[k+1] of the calculation of the state equation, and calculating the control signal yd[k] each time said D·ud[k] and said C·x[k+1] are-updated;
• and
• a D/A converter for converting said calculated yd[k] into said analog control signal y(t).
• Output equation:
• yd[k]=C·x[k]+D·ud[k]State equation:
• x[k+1]=A·x[k]+B·ud[k]
• where ud[k] is an observation signal to be input;
• yd[k] is a control signal to be output;
• x[k] is a state variable;
• A, B, C and D are constant matrixes;
• and k is a parameter to indicate a sampling time.

A storage device comprising:

• a head for at least reading a storage medium;
• an actuator for moving said head with respect to said storage medium;
• and
• a digital servo controller for receiving an analog observation signal u(t) from said head and generating a control signal to servo-control said actuator using a following output equation and state equation,
• wherein said digital servo controller comprises:
• an analog amplifier for multiplying said analog observation signal u(t) by D;
• an A/D converter for converting said analog observation signal u(t) into a digital observation signal ud[k] at each operation period Ts;
• a processor for receiving said digital observation signal, calculating the following state equation, calculating C·x[k+1] of the following output equation based on the result x[k+1] of the calculation of the state equation, and outputting said calculated value C·x[k+1] to a D/A converter at a point when Ts/2 has elapsed since u(t) is observed;
• and
• an analog adder for adding said analog observation signal multiplied by D and said output of the D/A converter, and outputting said control signal y(t).
• Output equation:
• yd[k]=C·x[k]+D·ud[k]State equation:
• x[k+1]=A·x[k]+B·ud[k]
• where ud[k] is an observation signal to be input;
• yd[k] is a control signal to be output;
• x[k] is a state variable;
• A, B, C and D are constant matrixes;
• and k is a parameter to indicate a sampling time.

A storage device comprising:

• a head for at least reading a storage medium;
• an actuator for moving said head with respect to said storage medium;
• and
• is a digital servo controller for receiving an analog observation signal u(t) from said head and generating a control signal to servo-control said actuator using a following output equation and state equation,
• wherein said digital servo controller comprises:
• an A/D converter for converting said analog observation signal u(t) into a digital signal at each operation period Ts/N (N is a 2 or higher natural number);
• a processor for calculating D·ud[k] of the following output equation from said digital signal, calculating the following state equation at each operation period Ts, calculating C·x[k+1] of the following output equation based on the result x[k+1] of the calculation of the state equation and calculating the control signal yd[k] each time said D·ud[k] and said C·x[k+1] are updated;
• and
• a D/A converter for converting said calculated yd[k] into said analog control signal y(t).
• Output equation:
• yd[k]=C·x[k]+D·ud[k]State equation:
• x[k+1]=A·x[k]+B·ud[k]
• where ud[k] is an observation signal to be input;
• yd[k] is a control signal to be output;
• x[k] is a state variable;
• A, B, C and D are constant matrixes;
• and k is a parameter to indicate a sampling time.

A head position control method for receiving an analog observation signal u(t) from a head and generating a control signal to servo-control an actuator for moving the head using a following output equation and state equation, comprising the steps of:

• multiplying said analog observation signal u(t) by D using an analog amplifier;
• converting said analog observation signal u(t) into a digital observation signal ud[k] by an A/D converter at each operation period Ts, calculating said state equation by a processor, and calculating C·x[k+1] of said output equation based on the result x[k+1] of the calculation of the state equation;
• outputting said calculated value of C·x[k+1] to a D/A converter at a point when Ts/2 has elapsed since u(t) is observed;
• and
• adding said analog observation signal multiplied by D and the output of said D/A converter, and outputting said control signal y(t).
• Output equation:
• yd[k]=C·x[k]+D·ud[k]State equation:
• x[k+1]=A·x[k]+B·ud[k]
• where ud[k] is an observation signal to be input;
• yd[k] is a control signal to be output;
• x[k] is a state variable;
• A, B, C and D are constant matrixes;
• and k is a parameter to indicate a sampling time.

A head position control method for receiving an analog observation signal u(t) from a head and generating a control signal to servo-control an actuator for moving the head using a following output equation and state equation, comprising the steps of:

• converting said analog observation signal u(t) into a digital signal by an A/D converter at each operation period Ts/N (N is a 2 or higher natural number), and calculating D·ud[k] of the following output equation by a processor;
• calculating the following state equation at each operation period Ts by said processor, and calculating C·x[k+1] of the following output equation based on the result x[k+1] of the calculation of the state equation;
• calculating the control signal yd[k] each time said D·ud[k] and said C·x[k+1] are updated;
• and
• outputting said calculated yd[k] to a D/A converter and outputting said analog control signal y(t).
• Output equation:
• yd[k]=C·x[k]+D·ud[k]State equation:
• x[k+1]=A·x[k]+B·ud[k]
• where ud[k] is an observation signal to be input;
• yd[k] is a control signal to be output;
• x[k] is a state variable;
• A, B, C and D are constant matrixes;
• and k is a parameter to indicate a sampling time.

A digital servo control method comprising the steps of:

• converting an analog observation signal from a control target into a digital observation signal by an A/D converter at each operation period Ts, calculating terms other than the term α0 of a following transfer equation by a processor, and outputting the result to a D/A converter;
• multiplying said analog observation signal by α0;
• and
• adding said analog observation signal multiplied by α0 and the output of said D/A converter and outputting a control signal y(z).
• 9 y ⁡ ( z ) u ⁡ ( z ) = α 0 · z ^ n + α 1 · z ^ ( n - 1 ) + ⋯ + α n - 2 · z ^ 1 + α n - 1 z ^ m + β 1 · z ^ ( m - 1 ) + ⋯ + β m - 2 · z ^ 1 + β m - 1 ( 3 )
• (where y(z) is a control signal to be output to the amplifier 6, u(z) is an observation signal to be input from the A/D converter, αi and βi are constants, n and m are arbitrary integers, and z is a discrete time operator.)

A digital servo control method for receiving an analog observation signal from a control target and generating a control signal to servo-control said control target using a following transfer equation, comprising the steps of:

• converting said analog observation signal into a digital signal by an A/D converter at each operation period Ts/N (N is a 2 or higher natural number), and calculating a term α0 of the following transfer equation by a processor;
• calculating terms other than the term α0 of the following transfer equation at each operation period Ts by said processor;
• and
• adding the calculating result of the term α0 and the calculation result of terms other than said term α0 at period Ts/N, outputting the result to a D/A converter, and outputting an analog control signal y(z).
• 10 y ⁡ ( z ) u ⁡ ( z ) = α 0 · z ^ n + α ⁢ ⁢ 1 · z ^ ( n - 1 ) + ⋯ + α n - 2 · z ^ 1 + α n - 1 z ^ m + β 1 · z ^ ( m - 1 ) + ⋯ + β m - 2 · z ^ 1 + β m - 1 ( 3 )
• (where y(z) is a control signal to be output to the amplifier 6, u(z) is an observation signal to be input from the A/D converter, αi and βi are constants, n and m are arbitrary integers, and z is a discrete time operator.)

A digital servo controller, comprising:

• an A/D converter for converting an analog observation signal from a control target into a digital observation signal;
• a processor for receiving said digital observation signal and calculating terms other than a term α0 of a following transfer equation;
• a D/A converter for converting said calculation result into an analog signal;
• an analog amplifier for multiplying said analog observation signal by α0;
• and
• an addition circuit for adding said analog observation signal multiplied by α0 and the output of said D/A converter, and outputting a control signal y(z).
• 11 y ⁡ ( z ) u ⁡ ( z ) = α 0 · z ⋀ ⁢ ⁢ n + α 1 · z ⋀ ⁡ ( n - 1 ) + … + α n - 2 · z ⁢ ⋀ ⁢ 1 + α n - 1 z ⋀ ⁢ ⁢ m + β 1 · z ⋀ ⁡ ( m - 1 ) + … + β m - 2 · z ⋀ ⁢ ⁢ 1 + β m - 1 ( 3 )
• (where y(z) is a control signal to be output to the amplifier, u(z) is an observation signal to be input from the A/D converter, αi and βi are constants, n and m are arbitrary integers, and z is a discrete time operator.)

A digital servo controller for receiving an analog observation signal from a control target and generating a control signal to servo-control said control target using a following transfer equation, comprising:

• an A/D converter for converting said analog observation signal into a digital observation signal at each operation period Ts/N (N is a 2 or higher natural number);
• a processor for receiving said digital observation signal, calculating the term α0 of following transfer equation at a period Ts/N, calculating terms other than the term α0 of the following transfer equation at each operation period Ts, and adding the calculation result of the term α0 and the calculation result of said terms other than α0 at period Ts/N;
• and
• a D/A converter for converting said addition result into an analog signal, and outputting an analog control signal y(z).
• 12 y ⁡ ( z ) u ⁡ ( z ) = α 0 · z ⋀ ⁢ ⁢ n + α 1 · z ⋀ ⁡ ( n - 1 ) + … + α n - 2 · z ⁢ ⋀ ⁢ 1 + α n - 1 z ⋀ ⁢ ⁢ m + β 1 · z ⋀ ⁡ ( m - 1 ) + … + β m - 2 · z ⋀ ⁢ ⁢ 1 + β m - 1 ( 3 )
• (where y(z) is a control signal to be output to the amplifier, u(z) is an observation signal to be input from the A/D converter, αi and βi are constants, n and m are arbitrary integers, and z is a discrete time operator.)