Servo control device

US 7,449,857 B2
Filed: 07/27/2005
Issued: 11/11/2008
Est. Priority Date: 07/27/2004
Status: Expired due to Fees

First Claim

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1. A servo control device comprising:

a speed controller for performing speed control of a motor;

a position controller for inputting a target command increment value as an increment of the sampling period of a target command and a position output increment value as an increment of the sampling period of the position output of the motor and outputting a speed command to the speed controller; and

a first feed-forward controller for inputting the target command increment value and outputting a first speed feed-forward signal to the speed controller;

whereinthe first feed-forward controller adds a third speed feed-forward signal obtained by multiplying the second-order differentiation of the target command by a control gain to a second speed feed-forward signal V_FF, outputs as a first speed feed-forward signal V_F2the resulting signal to the speed controller and sets the control gain so that the deviation between the target position and the position output of the motor will be zero at a constant acceleration.

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Abstract

An object of the invention is to provide a servo control device capable of making zero the positional deviation the positional deviation at a constant speed as well as the positional deviation at a constant acceleration or at constant acceleration and jerk, thereby providing a high-precision follow-up response.

In order to solve this problem, the servo control device according to the invention includes a position controller (3) for generating a speed command that matches the motor output with a target position, a feed-forward controller (4) for adding a signal obtained by multiplying the differential of a target command by a gain and a signal obtained by multiplying the second-order differentiation of the target command by a gain and generating a speed feed-forward signal, and a speed controller (2) for performing I-P or PI control of the motor (1).

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17 Claims

1. A servo control device comprising:
- a speed controller for performing speed control of a motor;
  
  a position controller for inputting a target command increment value as an increment of the sampling period of a target command and a position output increment value as an increment of the sampling period of the position output of the motor and outputting a speed command to the speed controller; and
  
  a first feed-forward controller for inputting the target command increment value and outputting a first speed feed-forward signal to the speed controller;
  
  whereinthe first feed-forward controller adds a third speed feed-forward signal obtained by multiplying the second-order differentiation of the target command by a control gain to a second speed feed-forward signal V_FF, outputs as a first speed feed-forward signal V_F2the resulting signal to the speed controller and sets the control gain so that the deviation between the target position and the position output of the motor will be zero at a constant acceleration.
- View Dependent Claims (3, 5, 6, 7, 8, 9)
- - 3. The servo control device according to claim 1, whereinthe first feed-forward controller generates a speed feed-forward signal V_F2in accordance with the expression $\begin{matrix} V_{F} \end{matrix}$
    - ⁢
      
      2 = K 2 T ⁢
      
      ⁢
      
      s 2 ⁢
      
      ( 1 - z - 1 ) ⁢
      
      Δ
      
      ⁢
      
      ⁢
      
      r + V F ⁢
      
      ⁢
      
      F [ Formula ⁢
      
      ⁢
      
      1 ] where Δ
      
      r is the target command increment value, Ts a sampling period, K₂a control gain set so that the deviation between the target position and the position output of the motor will be zero, and z^−
      
      1a delay corresponding to one sampling period, and outputs the signal to the speed controller.
  - 5. The servo control device according to claim 1 or 2, whereinthe position controller is a predictive controller for inputting the target command increment value Δ
    - r(i+M) at an M sampling future and the position output increment value Δ
      
      r(i−
      
      K) before K (K≧
      
      0) sampling at the current time i, and outputting a speed command u(i) that minimizes the evaluation function $\begin{matrix} J = \sum_{m = 1}^{M} w_{m} {e^{*} (i + m) + α e (i - K)}^{2} + c {u (i)}^{2} + c_{d} {Δ u (i)}^{2} & [Formula 4] \end{matrix}$ will be minimum, wherein e*(i+m) is a deviation predicted value at an m sampling future time, w_m, α
      
      are coefficients to multiply a deviation by, c and c_dare coefficients to multiply a speed command u(i) and its increment value Δ
      
      u(i).
  - 6. The servo control device according to claim 3 or 4, wherein the position controller has the characteristic of the transfer function $\begin{matrix} u = V_{sum} - f \end{matrix}$
    - ⁢
      
      f ⁢
      
      ⁢
      
      v T ⁢
      
      ⁢
      
      s ⁢
      
      X ⁡
      
      ( z ) + E 1 - z - 1 1 + G ⁡
      
      ( z ) ⁢
      
      Δ
      
      ⁢
      
      ⁢
      
      r - E 1 - z - 1 + P 0 1 + G ⁡
      
      ( z ) ⁢
      
      Δ
      
      ⁢
      
      ⁢
      
      y [ Formula ⁢
      
      ⁢
      
      5 ] where u is the speed command, Δ
      
      y the position output increment value, E a control parameter, ffv a feed-forward gain, and V_sum, G(z), X(z), P₀are respectively
      V_sum=v_sum/{K_gv(1+C_D)}
      G(z)=(g₁*−
      
      C_D)z^−
      
      1/(1+C_D)
      X(z)=(1+g₁*·
      
      z^−
      
      1(1+C_D)
      P₀=(−
      
      1−
      
      g₁*+T_sv_sum)/{K_gvT_s(1+C_D)} and g₁*, v_sum, C_Dare controller parameters and K_gva constant gain from a speed command to a speed feedback.
  - 7. The servo control device according to claim 6, whereinthe speed controller is an I-P controller,the speed feed-forward signal in the feed-forward controller is given from a feed-forward gain ffv by
    V_FF=ffv/Ts·
    - Δ
      
      r, andK₂as a control gain is given by
      K₂=T_i·
      
      (1−
      
      ffv)+T_s{C_D(1−
      
      ffv)−
      
      g₁*}/(1+g₁*)+D·
      
      T_i/(J·
      
      K_v)where D is a viscous friction coefficient, Jmotor inertia, T_ia speed loop integration time in the speed controller, and K_va speed loop gain in the speed controller.
  - 8. The servo control device according to claim 6, whereinthe speed controller is a PI controller,the second speed feed-forward signal V_FFin the first feed-forward controller is given from the feed-forward gain ffv by
    V_FF=ffv/Ts·
    - Δ
      
      r, andK₂as a control gain is given by
      K₂=T_s{C_D(1−
      
      ffv)−
      
      g₁*}/(1+g₁*)+D·
      
      T_i/(J·
      
      K_v)where D is a viscous friction coefficient, Jmotor inertia, T_ia speed loop integration time in the speed controller, and K_va speed loop gain in the speed controller.
  - 9. The servo control device according to claim 3 or 4, whereinthe position controller is a proportional controller,the speed controller is a PI controller or an I-P controller, andthe speed feed-forward signal V_FFin the feed-forward controller is given from the feed-forward gain ffv by
    V_FF=ffv/Ts·
    - Δ
      
      r andK₂and ffv as parameters are given by
      K₂=D·
      
      T_i/(J·
      
      K_v)
      ffv=1where D is a viscous friction coefficient, Jmotor inertia, T_ia speed loop integration time in the speed controller, and K_va speed loop gain in the speed controller.

2. A servo control device comprising:
- a speed controller for performing speed control of a motor;
  
  a position controller for inputting a target command increment value as an increment of the sampling period of a target command and a position output increment value as an increment of the sampling period of the position output of the motor and outputting a speed command to the speed controller; and
  
  a first feed-forward controller for inputting the target command increment value and outputting a first speed feed-forward signal to the speed controller;
  
  whereinthe first feed-forward controller adds a third speed feed-forward signal obtained by multiplying the second-order differentiation of the target command by a control gain to a second speed feed-forward signal V_FF, outputs as a first speed feed-forward signal V_F2the resulting signal to the speed controller and sets the control gain so that the deviation between the target position and the position output of the motor will be zero at a constant acceleration and, when the target command increment value Δ
  
  r is equal to or below a preset threshold at deceleration, makes zero or multiplies the output of the third feed-forward signal by a present gain and outputs the resulting signal.
- View Dependent Claims (4)
- - 4. The servo control device according to claim 2, whereinthe first feed-forward controller generates a speed feed-forward signal V_F2in accordance with the expression $\begin{matrix} V_{F} \end{matrix}$
    - ⁢
      
      2 = K 2 T ⁢
      
      ⁢
      
      s 2 ⁢
      
      ( 1 - z - 1 ) ⁢
      
      Δ
      
      ⁢
      
      ⁢
      
      r + V F ⁢
      
      ⁢
      
      F [ Formula ⁢
      
      ⁢
      
      2 ] where Δ
      
      r is the target command increment value, Ts a sampling period, K₂a control gain set so that the deviation between the target position and the position output of the motor will be zero, and z^−
      
      1a delay corresponding to one sampling period and, only when the target command increment value Δ
      
      r is equal to or below a preset threshold at deceleration, generates a speed feed-forward signal V_F2in accordance with the expression $\begin{matrix} V_{F 2} = V_{F F} or V_{F 2} = \frac{K_{2} K_{3}}{T s^{2}} (1 - z^{- 1}) Δ r + V_{F F} & [Formula 3] \end{matrix}$ where K₃is a gain, and outputs the signal to the speed controller.

10. A servo control device that makes control so as to match the output of a motor having viscous friction with a target command, the device comprising:
- a speed controller for performing speed control of the motor;
  
  a position controller for inputting a target command increment value as an increment of the sampling period of the target command and a position output increment value as an increment of the sampling period of the position output of the motor and outputting a speed command to the speed controller; and
  
  a feed-forward controller for inputting the target command increment value and outputting a speed feed-forward signal to the speed controller;
  
  whereinthe feed-forward controller adds a third speed feed-forward signal obtained by multiplying the second-order differentiation of the target command by a control gain to a second speed feed-forward signal V_FF, and outputs as a speed feed-forward signal V_F2the resulting signal, andthe gain ffv and the gain K₂are set so that the deviation between the target command and the position output of the motor will be zero at a constant acceleration and at a constant jerk.
- View Dependent Claims (12, 14, 15, 16, 17)
- - 12. The servo control device according to claim 10, whereinthe feed-forward controller is a feed-forward controller that generates the speed feed-forward signal V_F2in accordance with $\begin{matrix} V_{F} \end{matrix}$
    - ⁢
      
      2 = K 2 T ⁢
      
      ⁢
      
      s 2 ⁢
      
      ( 1 - z - 1 ) ⁢
      
      Δ
      
      ⁢
      
      ⁢
      
      r + V F ⁢
      
      ⁢
      
      F [ Formula ⁢
      
      ⁢
      
      6 ] where Δ
      
      r is the target command increment value, Ts a sampling period, K₂a control gain, and z^−
      
      1a delay corresponding to one sampling period.
  - 14. The servo control device according to claim 10 or 11, whereinthe position controller is a predictive controller for inputting the target command increment value Δ
    - r(i+M) at an M sampling future and the position output increment value Δ
      
      r(i−
      
      K) before K (K≧
      
      0) sampling at the current time I, and outputting a speed command u(i) that minimizes the evaluation function $\begin{matrix} J = \sum_{m = 1}^{M} w_{m} {e^{*} (i + m) + α e (i - K)}^{2} + c {u (i)}^{2} + c_{d} {Δ u (i)}^{2} & [Formula 9] \end{matrix}$ will be minimum, wherein e*(i+m) is a deviation predicted value at an m sampling future time, w_m, α
      
      are coefficients to multiply a deviation by, c and c_dare coefficients to multiply a speed command u(i) and its increment value Δ
      
      u(i).
  - 15. The servo control device according to claim 10 or 11, whereinthe position controller has a transfer function characteristic that $\begin{matrix} u = V_{sum} - \frac{ffv}{T} \end{matrix}$
    - ⁢
      
      s ⁢
      
      X ⁡
      
      ( z ) + E 1 - z - 1 1 + G ⁡
      
      ( z ) ⁢
      
      Δ
      
      ⁢
      
      ⁢
      
      r - E 1 - z - 1 + P 0 1 + G ⁡
      
      ( z ) ⁢
      
      Δ
      
      ⁢
      
      ⁢
      
      y [ Formula ⁢
      
      ⁢
      
      10 ] where u is the speed command, Δ
      
      y the position output increment value, E a control parameter, ffv a feed-forward gain, and V_sum, G(z), X(z), P₀are respectively $\begin{matrix} V_{sum} = \frac{v_{sum}}{K g v (1 + C_{D})} G (z) = \frac{(g_{1}^{*} - C_{D}) z^{- 1}}{1 + C_{D}} X (z) = \frac{1 + g_{1}^{*} \cdot z^{- 1}}{1 + C_{D}} P_{0} = \frac{- 1 - g_{1}^{*} + T s \cdot v_{sum}}{K g v \cdot T s (1 + C_{D})} & [Formula 11] \end{matrix}$ where g₁*, v_sum, C_Dare control parameters, K_gvis a constant gain from a speed command to a speed feedback.
  - 16. The servo control device according to claim 15, whereinthe speed controller is an I-P controller, andthe feed-forward signal V_FFin the feed-forward controller is given from a feed-forward gain ffv by V_FF=ffv/Ts·
    - Δ
      
      r, that the feed-forward gain ffv is given by $\begin{matrix} f f v = \frac{D \cdot T {i (1 + g 1^{*})}^{2} (T i - 2 T s)}{J \cdot K v {T {i^{2} (1 + g 1^{*})}^{2} + C_{D} \cdot T i \cdot T s (1 + g 1^{*}) + C_{D} \cdot T s^{2} (C_{D} - g 1^{*})}} + \frac{(J {{(1 + g 1^{*})}^{2} K v \cdot T i^{2} + K v \cdot T {s^{2} (C_{D} - g 1^{*})}^{2} - T i (1 + g 1^{*}) (1 + g 1^{*} - C_{D} \cdot K v \cdot T s + g 1^{*} \cdot K v \cdot T s)})}{J \cdot K v {T {i^{2} (1 + g 1^{*})}^{2} + C_{D} \cdot T i \cdot T s (1 + g 1^{*}) + C_{D} \cdot T s^{2} (C_{D} - g 1^{*})}} & [Formula 12] \end{matrix}$ where D is a viscous friction coefficient, Jmotor inertia, T_ia speed loop integration time in the speed controller, and K_va speed loop gain in the speed controller, and K₂as a control gain is given by $\begin{matrix} K_{2} = T i (1 - f f v) + \frac{T s}{1 + g_{1}^{*}} {C_{D} (1 - f f v) - g_{1}^{*}} + \frac{D \cdot T i}{J \cdot K v} & [Formula 13] \end{matrix}$
  - 17. The servo control device according to claim 15, whereinthe speed controller is a PI controller,the speed feed-forward signal V_FFin the feed-forward controller is given from a feed-forward gain ffv by V_FF=ffv/Ts·
    - Δ
      
      r,the feed-forward gain ffv is given by $\begin{matrix} f f v = \frac{\begin{matrix} D \cdot T {i (1 + g 1^{*})}^{2} (T i - 2 T s) - \\ J {{(1 + g 1^{*})}^{2} T i - K v \cdot T {s^{2} (C_{D} - g 1^{*})}^{2}} \end{matrix}}{J \cdot K v \cdot T s^{2} \cdot C_{D} (C_{D} - g 1^{*})} & [Formula 14] \end{matrix}$ where D is a viscous friction coefficient, Jmotor inertia, T_ia speed loop integration time in the speed controller, and K_va speed loop gain in the speed controller, and K₂as a control gain is given by $\begin{matrix} K_{2} = \frac{T s}{1 + g_{1}^{*}} {C_{D} (1 - f f v) - g_{1}^{*}} + \frac{D \cdot T i}{J \cdot K v} . & [Formula 15] \end{matrix}$

11. A servo control device that makes control so as to match the output of a motor having viscous friction with a target command, the device comprising:
- a speed controller for performing speed control of the motor;
  
  a position controller for inputting a target command increment value as an increment of the sampling period of the target command and a position output increment value as an increment of the sampling period of the position output of the motor and outputting a speed command to the speed controller; and
  
  a feed-forward controller for inputting the target command increment value and outputting a speed feed-forward signal to the speed controller;
  
  whereinthe feed-forward controller adds a third speed feed-forward signal obtained by multiplying the second-order differentiation of the target command by a control gain to a second speed feed-forward signal V_FFand outputs as a speed feed-forward signal V_F2the resulting signal,the gain ffv and the gain K₂are set so that the deviation between the target command and the position output of the motor will be zero at a constant acceleration and at a constant jerk, andwhen the target command increment value Δ
  
  r is equal to or below a preset threshold at deceleration, the feed-forward controller makes zero the gain K₂or sets a gain obtained by multiplying the gain K₂by a preset gain K₃.
- View Dependent Claims (13)
- - 13. The servo control device according to claim 11, whereinthe feed-forward controller is a feed-forward controller that generates the speed feed-forward signal V_F2in accordance with $\begin{matrix} V_{F} \end{matrix}$
    - ⁢
      
      2 = K 2 T ⁢
      
      ⁢
      
      s 2 ⁢
      
      ( 1 - z - 1 ) ⁢
      
      Δ
      
      ⁢
      
      ⁢
      
      r + V F ⁢
      
      ⁢
      
      F [ Formula ⁢
      
      ⁢
      
      7 ] where Δ
      
      r is the target command increment value, Ts a sampling period, K₂a control gain, and z^−
      
      1a delay corresponding to one sampling period, and when the target command increment value is equal to or below a preset threshold at deceleration, generates a speed feed-forward signal V_F2in accordance with the expression $\begin{matrix} V_{F 2} = V_{F F} or V_{F 2} = \frac{K_{2} K_{3}}{T s^{2}} (1 - z^{- 1}) Δ r + V_{F F} & [Formula 8] \end{matrix}$ where K₃is a gain.

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Current Assignee
Kabushiki Kaisha Yaskawa Denki
Original Assignee
Kabushiki Kaisha Yaskawa Denki
Inventors
Nakamura, Hiroshi, Ohta, Seitaro
Primary Examiner(s)
Ro; Bentsu
Assistant Examiner(s)
DINH, THAI T

Application Number

US11/658,742
Publication Number

US 20080036413A1
Time in Patent Office

1,203 Days
Field of Search

318/560, 318/567, 318/568.22, 318609-610, 318/628, 318/632
US Class Current

318/560
CPC Class Codes

G05B 11/42 for obtaining a characteris...

G05B 13/048 using a predictor

Servo control device

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Servo control device

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