JPH04308489A - Servo controller - Google Patents

Abstract

PURPOSE:To realize optimal auto-tuning state at all times by estimating new specifications at a parameter identifying section at a time point when physical specifications of mechanical system are modified and then automatically setting new control gains corresponding to respective specifications based on thus estimated values. CONSTITUTION:A feedforward control section 7 receives an output signal S12 from a parameter identifying section 4, a target value S2 of speed signal and a target value S3 of acceleration signal, and outputs a torque command, i.e., a feedforward signal S11. A feedback gain calculating section 8 receives a target characteristic S18 of control system and an output signal S12 from the parameter identifying section 4, and outputs a signal S13 which is fed to a feedback control section 9. A disturbance compensating section 5 also receives the output signal S12 from the parameter identifying section 4 and then performs internal operation to output a disturbance compensation signal S6 which is fed to an adder/subtractor 10 and the parameter identifying section 4.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a servo control device configured so that even if the physical specifications of a mechanical system are changed, constant performance is always maintained by an auto-tuning function.

0002

2. Description of the Related Art Conventional servo control devices have a configuration in which tuning is performed on the premise that the physical specifications of the mechanical system are constant.

0003

[Problem to be Solved by the Invention] In the conventional device configured as described above, when physical specifications are changed, adjustments must be made while measuring the response state again at the site, which requires many adjustments. The drawback was that it required time and effort.

[0004] An object of the present invention is to provide a servo control system having a function of automatically tuning the control gain of each control section to the optimum state at all times according to the above-mentioned specifications even if the physical specifications of the mechanical system are changed. The goal is to provide equipment.

[0005]

[Means for Solving the Problems] In order to solve the above problems and achieve the objects, the following measures have been taken in the present invention.

That is, a feedback control section 9 inputs a target value S2 of the speed signal and an actual value S16 and outputs a feedback signal S14 to the servo device, and inputs the target value S2 of the speed signal and the target value S3 of the acceleration signal. and a feedforward control section 7 that outputs a feedforward signal S11 to the servo device, and a disturbance that inputs an input value S15 of the servo device and an actual measured value S16 of the speed signal and outputs a disturbance compensation signal S6 to the servo device. In a servo control device having a compensator 5, the target value S2 of the speed signal, the target value S3 of the acceleration signal, and the disturbance compensation signal S6 are input, and the moment of inertia J and the viscosity coefficient D of the servo device are input. and outputs the results as parameters to the feedforward control section 7 and the disturbance compensation section 5, and the moment of inertia J and viscosity coefficient D identified by the parameter identification section 4.
The present invention includes a feedback gain calculating section 8 that calculates the gain of the feedback control section 9 based on the above, and outputs the obtained gain to the feedback control section 9.

[0007]

[Action] As a result of taking the above measures, the following effects occur. When the physical specifications of the mechanical system are changed, new specifications are estimated by the parameter identification section 4, and based on the estimated values, the feedforward control section 7, disturbance compensation section 5, and feedback gain calculation section 8 each calculate the new specifications. A new control gain is automatically set according to the specifications. In this way, even if the physical specifications of the mechanical system are changed, an optimal control system can always be maintained.

[0008] Note that the symbols S2 and the like described in the above section of "Solution Means" are abbreviated symbols used to simplify the description. Also in the embodiments described below, abbreviated symbols will be used as appropriate for the same purpose.

Table 1 shown below is a comparison table of informal codes and formal codes.

0010

[Table 1]

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram showing the configuration of a servo control device according to an embodiment of the present invention. Position, velocity, and acceleration commands of a trapezoidal wave velocity pattern are given to the three terminals shown at the left end of FIG. That is, S1 is the target value of the position signal, S2 is the target value of the speed signal, and S3 is the target value of the acceleration signal. 4 is a parameter identification section, which includes the target value S2 of the speed signal and the target value S3 of the acceleration signal.
, and a disturbance compensation signal (disturbance estimated value) S6 which is the output of the disturbance compensator 5 is input. The output signal S12 of the parameter identification section 4 is input to the disturbance compensation section 5, the feedforward control section 7, and the feedback gain calculation section 8.

The feedforward control section 7 inputs the output signal S12 of the parameter identification section 4, the target value S2 of the speed signal, and the target value S3 of the acceleration signal, and outputs the feedforward signal S11 as a torque command. Output.

The feedback gain calculation section 8 receives the target characteristic S18 of the control system and the output signal S12 of the parameter identification section 4, and outputs an output signal S13. This output signal S13 is input to the feedback control section 9.

The disturbance compensation section 5 also receives the output signal S12 of the parameter identification section 4, performs internal calculations shown in FIG. 2, which will be described later, and outputs a disturbance compensation signal S6. This disturbance compensation signal S6 is input to the adder/subtractor 10 and the parameter identification section 4.

The feedback control section 9 reads the output signal S13 of the feedback gain calculation section 8 as a gain, and executes an internal calculation shown in FIG. 9, which will be described later. The output signal S14 of the feedback control section 9 is transmitted to the adder/subtractor 1.
0 as an addition input. The adder/subtractor 10 receives the output S of the feedforward control section 7 in addition to the above signal S14.
11 is also input, and an output signal S15 is output. This output signal S15 is supplied as a torque input to the positioning machine 19 to be controlled.

[0016] When the parameter identification section 4 outputs the output signal S12 indicating a new parameter, each control section changes its own gain based on this.
Auto tuning works.

Next, detailed contents of each control section will be explained. The disturbance compensation section 5, parameter identification section 4, feedforward control section 7, feedback gain calculation section 8, and feedback control section 9 will be explained in this order.

[About the disturbance compensator 5] The role of the disturbance compensator 5 is to estimate an unknown torque disturbance acting on the servo system and feed it back to cancel the torque disturbance. For this purpose, a disturbance observer is used. A disturbance observer is obtained using the following procedure.

The equation of motion of the rigid system is (1) in [Equation 1]
Expressed by the formula. (1) In the equation, J is the moment of inertia, ω is the angular velocity, D is the viscosity coefficient, U is the generated torque, and d is the disturbance torque.

[0020] An observer that estimates only the disturbance torque d uses the equation (1), where the time constant required for estimation is T0.
2) It is expressed by the Laplace transform formula shown in Eq.

[0021] Here, in order to accurately determine the disturbance, J=
Must be J0. In this way, the disturbance compensator 5 has a function of inputting the angular velocity ω and the generated torque U and outputting an estimated disturbance (d with a ridge).

FIG. 2 is a block diagram showing the configuration of the disturbance compensator 5. As shown in FIG.

“About the parameter identification unit 4” (1)
Disturbances in the equation include those where a constant load weight is applied, such as the Z-axis of a machining center, and those where the direction of force changes depending on the direction of speed, such as Coulomb friction. The disturbance d is
It becomes as shown in equation (3) of [Math. 1].

FIG. 3 is a block diagram showing the configuration of the positioning machine 19 to be controlled. As shown in the figure, in the positioning machine 19, there is a steady disturbance S19 and a Coulomb friction 3.
7 works.

When the disturbance in equation (3) is estimated by an observer, it becomes equation (4) in [Equation 1]. Therefore, (1
) Solved equation for U and substituted into equation (4),
Further, by substituting equation (3), equation (5) in [Math. 1] is obtained.

[0026] Here, J-J0 = ΔJ, D-D0 = Δ
When D, equation (5) becomes equation (6) in [Math. 1]. According to formula (6), if there are errors ΔJ and ΔD,
It can be seen that the influence of parameter errors appears on the estimated disturbance value. Using this, even if the parameters of the mechanical system change, the changes ΔJ and ΔD are calculated, and J0 ← J0 + ΔJ
,D0 ←D0 +ΔD, the parameter is also
becomes a true value (parameter identification).

The method for determining ΔJ and ΔD will be described below.

The servo system is servo-driven in a trapezoidal wave velocity pattern. At this time, a disturbance expressed by equation (3) acts on the servo system.

FIG. 4 is an explanatory diagram of equation (6), and is a diagram showing each state quantity obtained in a trapezoidal wave pattern up to disturbance estimation. Commands for position, velocity, and acceleration are sent to S1, S2, and S3.
shall be. At this time, in the servo drive, it is assumed that the conditions that S1 and θ are approximately equal, S2 and ω are approximately equal, and S3 and S33 (dotted ω) are approximately equal are satisfied. It is also assumed that the transient characteristics of each state can be ignored. Let the sizes of time intervals A to F be TA to TF. If the average of the estimated values in each section is dA to dF, then equations (7) to (12) of [Equation 1] are obtained.

[0030]

[Math. 1] Here, dA to dF are each expressed by (13) of [Math. 1]
Calculate by formula. From the above, ΔJ and ΔD can be found using equation (14) of [Math. 2].

As described above, the parameter identification section has a function of inputting an angular velocity command, an angular acceleration command (or angular velocity, angular acceleration), and a disturbance estimated value, and outputting parameter estimated values J0 and D0.

FIGS. 5 and 6 are diagrams showing the processing flow of the parameter identification section 4. As shown in FIGS. 5 and 6, input is performed in step 27, and calculations A to F are selected in step 28 according to the elapsed time. After completing the calculation for identification, it is checked in step 29 whether or not the end time has been reached. If the end time has not been reached, the process returns to step 27. If it has been reached, the parameter error calculation is performed in step 30, and the parameters are changed in step 31. Correct and finish. This output value is the output signal S12 shown in FIG.

“About the feedforward control unit 7”
In the feedforward control section 7, the target value (
Speed command) S2, target value of acceleration signal (acceleration command) S
3. Parameter identification unit output (parameter estimated value) S12
Input the feedforward signal (torque command) S1
1 and the target value (speed command) S2 of the speed signal shown in equation (15) of [Math. 2] are output. Thereby, when the parameter estimates are updated, the feedforward control section is also adjusted accordingly.

FIG. 7 is a block diagram showing the configuration of the feedforward control section 7. As shown in FIG. As shown in FIG. 7, the output signal S12 of the parameter identification section 4 is directly preset as a feedforward gain. The calculation is performed using the above equation (15), and an output signal S11 is output.

[0035]

[Formula 2] "About the feedback gain calculation section 8" The feedback gain is calculated based on the parameter estimate value which is the parameter identification section output signal S12. Let the target characteristics of the control system be as shown in equation (16) of [Math. 2]. Here, ωc represents a control band, and ξ represents damping. ω
In order to keep c and ξ constant regardless of parameter changes, position control gain Kp and speed control gain K
Change v based on J0 and D0.

FIG. 8 is a diagram showing only the feedback control system of an existing servo device for comparison. The target characteristics of this control system are as shown in equation (17) of [Math. 2]. From this equation (17) and the above equation (16),
Solve for Kp and Kv, and further J and D as J0 and D0
, each gain corresponding to the parameter change value is calculated using equations (18) and (19) in [Equation 2].

The feedback gain calculation unit 8 calculates the target characteristics ξc, ωc of the control system and the parameter estimated value J0.
, D0 are input, and position and speed control gains Kp and Kv are output.

"About the feedback control unit 9" FIG. 9
1 is a block diagram showing the configuration of a feedback control section 9. FIG. As shown in the figure, the configuration includes a position and velocity feedback system. The calculation is performed using equation (20) of [Math. 2]. θ is a feedback position signal. The feedback control unit 9 controls target values S1 and S2 of position and speed signals.
, position and speed feedback signals θ and ω, and position and speed control gains Kp and Kv, and outputs a feedback signal S14 (correction command UFB).

According to this embodiment described above, the following effects are achieved. Even if the parameters are changed, the parameter identification unit 4 estimates the amount of change, corrects the original parameters, and outputs the estimated values J0 and D0. The feedback gain calculating section 5, the feedback gain calculating section 8, and the feedback control section 9 set the optimum control gain corresponding to the corrected value. Therefore, even if parameters are changed, the system can always be tuned to the optimum state.

FIG. 10 is a simulation diagram showing the above effect. As shown in the figure, when the parameters are changed at time t0, the deviation becomes large in the period before auto-tuning. However, in the period after auto-tuning is started at time t1, the deviation becomes significantly smaller.

Note that the present invention is not limited to this embodiment. For example, in the above embodiment, the present invention is applied to a rotating system, but it is also applicable to a linear system as shown in (21) to (24) of [Equation 2]. Note that x is position, M is mass, D is viscous resistance, d is disturbance, Fc is Coulomb friction,
u is force. It goes without saying that various other modifications can be made without departing from the gist of the present invention.

[0042]

[Effects of the Invention] According to the present invention, even if the physical specifications of a mechanical system are changed, the parameters are corrected in accordance with the change in the parameter identification section and corrected values are output. In the control section, an optimal control gain corresponding to the above correction value is set. In this way, it is possible to provide a servo device having a function of automatically tuning the control gain of each control section to the optimum state at all times according to the above-mentioned specifications.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of a servo control device according to an embodiment of the present invention.

FIG. 2 is a block diagram showing the configuration of a disturbance compensator according to the same embodiment.

FIG. 3 is a block diagram showing the configuration of a positioning machine according to the same embodiment.

FIG. 4 is a diagram showing each state quantity obtained in a trapezoidal wave pattern up to disturbance estimation according to the same embodiment.

FIG. 5 is a diagram showing a part of the processing flow of the parameter identification unit according to the same embodiment.

FIG. 6 is a diagram showing another part of the processing flow of the parameter identification unit according to the same embodiment.

FIG. 7 is a block diagram showing the configuration of a feedforward control section according to the same embodiment.

FIG. 8 is a diagram showing only a feedback control system of a general servo device.

FIG. 9 is a block diagram showing the configuration of a feedback control section according to the same embodiment.

FIG. 10 is a diagram showing the effects of the same embodiment.

[Explanation of symbols]

S1...Target value of position signal (position command), S2...Target value of speed signal (speed command), S3...Target value of acceleration signal (acceleration command), S6...Disturbance compensation signal (disturbance estimated value) S11
...feedforward signal (torque command), S12...parameter identification unit output signal (estimated value), S13...feedback gain calculation unit output signal, S14...feedback signal (correction command), S15...adder/subtractor output signal (torque signal) , S16...actual value of speed signal, S17...feedback position signal, S18...target characteristic of control system, S19
...Steady disturbance.

Claims (1)

[Claims] 1. A feedback control unit that inputs a target value and a measured value of a speed signal and outputs a feedback signal to a servo device; and a feedback control unit that inputs a target value of the speed signal and a target value of an acceleration signal and outputs a feedback signal to the servo device. In the servo control device, the servo control device includes a feedforward control section that outputs a feedforward signal, and a disturbance compensator that inputs an input value of the servo device and an actual measured value of a speed signal and outputs a disturbance compensation signal to the servo device. The target value of the speed signal, the target value of the acceleration signal, and the disturbance compensation signal are input, the moment of inertia and viscosity coefficient of the servo device are identified, and the results are sent as parameters to the feedforward control section and the disturbance compensation section. and a feedback gain calculation that calculates the gain of the feedback control section based on the moment of inertia and viscosity coefficient identified by this parameter identification section, and outputs the obtained gain to the feedback control section. Department and
A servo control device comprising: