JP3506157B2 - Motor position control device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a position control device for a driving electric motor such as a robot or NC, and more particularly to a position control device for an electric motor for performing accurate and stable control with respect to a change in conditions of a controlled object. .

[0002]

2. Description of the Related Art Conventionally, in a position control device for an electric motor such as a robot or NC, in order to improve the control performance of a drive system by the electric motor, the target value followability and the disturbance suppression characteristic can be designed independently. A two-degree-of-freedom control system with a conditional feedback structure as shown below has been proposed (Intermediate Textbook, Basic Lecture on Modern Control Theory, JSME 19
January 24, 25, 1991).

In the figure, 51 is a position command generator, 52 is a model controller C _F for determining a target value response, 53 is a feedback controller C ₂ , and 54 is a model controller C _F and an inverse transfer function of the controlled object P. Feedforward controller ( _CF /
P), 55 is a subtractor for subtracting the detection value y of the rotation detector 59 from the output y ₀ of the model controller 52, and 56 is the output U _FB of the feedback controller 53 and the output U _FF of the feedforward controller 54. An adder 57 for controlling the control target P including a torque controller.

The operation of this control system will be described below. The command r of the position command generator 51 is input to the model controller 52, and the model output y ₀ is output. This model output y
_When the deviation between ₀ and the output y of the controlled object 57 is obtained by the subtractor 55 and input to the feedback controller 53, the feedback command U _FB is output. Further, the command r is also input to the feedforward controller 54 including the inverse transfer function of the model controller 52 and the controlled object 57, and the feedforward command U _FF is output.

The addition value of the feedback command U _FB and the feedforward command U _FF is obtained by the adder 56, and the acceleration command is input to the controlled object 57 including the torque controller.

In this figure, when the transfer functions G _yr and G _y0r of r → y and r → y ₀ are calculated,

[0007]

[Equation 1] Can be expressed as

From the above equation, if the controlled object 57 is a nominal value and matches the controlled object model of the feedforward controller 54, the input to the feedback controller 53 becomes 0 at PP ^-1 = 1 and the feedforward command is given. The controlled object 57 is controlled by U _FF . At this time, the transfer function from the command r to the output y, which is the target value response, is determined by the C _F of the feedforward controller 54 regardless of how the feedback controller 53 selects C ₂ .

On the other hand, when the controlled object 57 fluctuates from the nominal value or y ≠ y ₀ due to disturbance or the like,
The feedback characteristic can be designed by C ₂ of the feedback controller 53.

As described above, this control system is capable of adjusting the target value response characteristic and the feedback characteristic independently of each other, and has a conditional feedback effect. Has become.

Further, as an applied form of this conventional example, there is a structure shown in FIG. The display of the symbols in FIG. 6 conforms to that in FIG.
The range surrounded by the chain line of this configuration may be a model controller in a broad sense.

In contrast to this basic control device, for example, when the followability of position control is improved as disclosed in Japanese Patent Laid-Open No. 6-30578, or when the disturbance or the moment of inertia of the load device changes during operation. However, in order to keep the response frequency of the position control constant, improvement methods such as adding a simulated position control circuit and a simulated speed control circuit for the mechanical system have been implemented.

As a control method based on sliding control, there is a control method disclosed in Japanese Patent Laid-Open No. 3-118618. This is to set a sliding mode switching surface composed of a twist angle and a twist angular velocity, which are deviations between the electric motor and the load, and control the electric motor so that the state quantity becomes zero.

[0014]

A conventional two-degree-of-freedom control system inputs a command to a model controller and a feed-forward controller composed of an inverse transfer function of a controlled object in order to improve a target value response characteristic. A forward command is input to the control target.

Here, when the controlled object is correctly identified, the output y can be made to follow the response of the characteristic of the transfer function of the target model controller.

However, in general, it is impossible to accurately identify the controlled object, and, for example, when the inertia of the load fluctuates due to a change in posture like a robot,
There is a problem that the controlled object fluctuates from the nominal value after the identification. As described above, the conventional two-degree-of-freedom control system has a problem that an error occurs with respect to the initially desired response due to the variation of the controlled object.

To solve these problems, an improvement method for controlling the above-mentioned simulated position and simulated speed has been proposed. However, although the followability can be improved, if the rigidity of the torque transmission mechanism is low, the load side becomes oscillating. There is also a problem that the output of the electric motor deviates from the output of the mechanical system simulation circuit due to the fluctuation of the controlled object.

Further, in the control by the sliding mode control described above, since the dynamics on the load side is not taken into consideration, the vibration of the load cannot be completely suppressed. Further, when the electric motor is positioned, if the twist angle is not zero due to the influence of gravity disturbance on the load side, there is a problem that chattering occurs due to switching of the sliding mode control.

It is an object of the present invention to provide a position control device for an electric motor, in which the state quantities of the electric motor and the load follow the reference output of the model controller even if the controlled object fluctuates, and which enables accurate and stable control. It is in.

[0020]

In order to solve the above problems, in a position control device for a motor of the present invention, a position command generator for outputting a target position command of a motor for driving a load and a model feed for inputting the command. A model controller that outputs a forward command signal and a model state value command signal of the electric motor, a rotation detector that detects rotational position information of the electric motor, an acceleration command to the electric motor, and rotation of the electric motor detected by the rotation detector. The deviation between the observer that estimates the state quantity of the motor and the load from the position information, the model state quantity output from the model controller, and the rotation position information detected by the rotation detector and the estimated state quantity estimated by the observer is calculated. A feedback controller that inputs and outputs a feedback command, a model feedforward command output from the model controller, and a feedback A regulator that adds the feedback command output from the buck controller and outputs it to the torque controller as an acceleration command to the electric motor, and a torque controller that supplies the electric power of the required condition to the electric motor by the acceleration command of the adjuster. In the equipped motor position control device, the model controller outputs the command of the state value of the model of the load, the observer estimates the state quantity of the motor and the load, and a plurality of preselected sliding surfaces for the sliding mode control are selected. The sliding mode compensation amount calculated by the positive / negative of the value calculated from the plurality of state values using the reference state value surface consisting of the state values of the model state amount output from the model controller and the rotation detector. Sliding so that the deviation between the rotational position information detected by and the estimated state quantity estimated by the observer converges to zero. Having a sliding mode controller for adding over de compensation amount in the feedback controller.

The sliding mode control switching surface is displayed on the basis of deviations between model load positions and load positions, deviations between model load speeds and load speeds, deviations between model torsion angles and torsion angles,
Alternatively, the deviation between the model torsion angular velocity and the torsion angular velocity may be used, the deviation between the model electric motor position and the electric motor position, the deviation between the model electric motor speed and the electric motor speed, and the deviation between the model torsion angle and the torsion angle may be used.

The sliding mode control switching surface may also be used as a deviation between model electric motor positions and electric motor positions, a deviation between model electric motor speeds and electric motor speeds, a deviation between model torsion angles and torsion angles, and a deviation between model torsion angular velocities and torsion angular velocities. Good.

[0023]

The model controller outputs a command for the state value of the load model, the observer estimates the state amount of the load, and a reference state value consisting of a plurality of state values selected in advance as a switching surface for sliding mode control. The sliding mode compensation amount calculated by the positive or negative of the value calculated from the plurality of state values using the surface is obtained, the model state amount output from the model controller, and the rotational position information detected by the rotation detector and It has a sliding mode controller that adds the sliding mode compensation amount to the feedback controller so that the deviation from the estimated state amount estimated by the observer converges to zero.

Therefore, even when the rigidity of the transmission mechanism between the electric motor and the load is low, the output of the load can be made to follow the target response. Even if the state value of the load to be controlled fluctuates from the nominal value, the deviation of the state value is constrained by the reference state value plane that contains the preset target value, and the deviation value decreases every time the reference plane is crossed. The coefficient is switched to, and the deviation value 0 converges to the deviation value 0 asymptotically and stably with the passage of time without being affected by the fluctuation of the parameter of the controlled object, and the state quantity of the controlled object follows the target state quantity of the model. It becomes possible.

[0025]

Embodiments of the present invention will now be described with reference to the drawings.

FIG. 1 is a basic configuration block diagram of a two-degree-of-freedom control system to which the model of the present invention is applied.

The position control device for an electric motor according to the embodiment of the present invention includes a position command generator 100, a model controller 200, a feedback controller 300, an observer 400, a sliding mode controller 500, a regulator 600 and a torque controller 700. , The rotation detector 850, and the electric motor 80
The load 950 is drive-controlled via 0 and the speed reducer 900. The torque controller 700 is composed of a torque control circuit having a transfer function shown and a power converter.

In the transfer function in the figure, Kt is a torque constant, J
m is the moment of inertia of the motor, J _L is the moment of inertia of the load, N is the reduction ratio, Kc is the reduction gear spring constant, and θ is the state value.
_m is the motor position and θ _L is the arm position.

FIG. 2 is a block diagram showing the detailed structure of the model controller 200. In the figure, the model controller 200
Are the position controller model 201 and the speed controller model 20.
2, feedforward command generator 203, torque controller model 204, electric motor model 205, speed reducer model 2
06, load model 207, gains 208, 209, differentiator 210, subtractor 211, adder / subtractors 212, 213 and adder 214, and position command generator 100
Input terminal 221 connected to the feedback controller 30
Output terminals 223, 224, 225, 226 connected to 0
And an output terminal 222 connected to the regulator 600.

FIG. 3 shows a sliding mode controller 500.
3 is a block diagram showing a detailed configuration of FIG. In the figure, a sliding mode controller 500 includes a positive / negative determination mechanism 501 for sliding mode control S, a gain switching mechanism 502 for Tcomp1 to 6 and a differentiator 503, and input terminals 521 and 522 connected to the model controller 200.
523 and 524, input terminals 525 and 526 connected to the observer 400, an input terminal 527 connected to the rotation detector 850, and an output terminal 528 connected to the feedback controller 300.

FIG. 4 is a block diagram showing a detailed structure of the feedback controller 300. In the figure, a feedback controller 300 includes a position controller 301 and a speed controller 3
02, differentiator 303, gains 304 and 305, subtractor 3
11, 314, 315, adder / subtractor 312 and adder 3
13, 316, 317, and the model controller 2
Input terminals 321, 322, 323, 32 connected to 00
5, input terminals 324, 32 connected to the observer 400
6, input terminal 327 connected to sliding mode controller 500, input terminal 32 connected to rotation detector 850
8 and the output terminal 329 connected to the regulator 600.

The observer 400 inputs the command of the regulator 600 and the information of the rotation detector 850, estimates the state of the load 950, the twist angle and the twist angular velocity between the electric motor 800 and the load 950, and determines the feedback controller 300 and the sliding mode. The estimated value is output to the controller 500.
The adjuster 600 adds the command from the feedback controller and the feedforward command from the model controller to obtain an acceleration command as an observer 400 and a torque controller 700.
The torque controller 700 supplies the electric power necessary for acceleration to the electric motor 800 based on the acceleration command from the regulator,
The electric motor 800 drives the load 950 via the speed reducer 900.

A rotation detector 850 for measuring the rotation angle of the motor shaft is connected to the electric motor 800, and the detected rotational position information is output to the feedback controller 300 and the observer 400.

The position controller model 201, the speed controller model 202, and the feedforward command generator 20 shown in FIG.
3, torque controller model 204, electric motor model 205,
The speed reducer model 206 and the load model 207 are pseudo models of the control system and the controlled object (here, the robot dynamics). The position command Xref is input from the position command generator 100 to the terminal 221 of the model controller 201, and the feedforward command U in consideration of the robot dynamics.
_FF is calculated and output from the terminal 222 to the regulator 600 to perform feedforward compensation on the acceleration term of the electric motor. Further, from the model controller 200, the reference model motor position θ _Mm , model motor speed

[0035]

[Outer 1] , Model twist angle θ _MS , model twist angular velocity

[0036]

[Outside 2] Is calculated and output from the terminals 223 to 226 to the feedback controller 300. (Hereinafter, each element which is the output of the model controller is represented by adding a'model 'M in front of the word). At this time, the target value response characteristic is determined by the model controller 20.
It is determined by the parameter of 0.

On the other hand, in the feedback control system of FIG. 4, Kp is a position gain, Kv is a velocity gain, K1 is a torsion angle feedback gain, and K2 is a torsion angular velocity feedback gain.

The position gain k is calculated based on the deviation between the model motor position θ _Mm and the motor position θ _m , which is the output of the model controller 200.
Multiply p to make a speed command, and add this model to the model motor speed.

[0039]

[Outside 3] And motor speed

[0040]

[Outside 4] The value obtained by adding the deviation between and is multiplied by the velocity gain kv to obtain an acceleration command. This acceleration command includes the model twist angle θ _MS and the twist angle estimated by the observer 400.

[0041]

[Outside 5] The value obtained by multiplying the deviation between and by the feedback gain K1,
Model twist angular velocity

[0042]

[Outside 6] And angular velocity estimated by observer 400

[0043]

[Outside 7] The value obtained by multiplying the deviation between and by the feedback gain K2 is added, and the compensation value Tcomp output from the sliding mode controller 500 is added and output from the terminal 329 to the adjuster 600.

In the regulator 600, the feedback controller 3
00 to the acceleration command output from the model controller 200
Is added to the feedforward command U _FF to output the final motor acceleration command Uref to the torque control circuit of the torque controller 700.

At this time, in the model controller 200, if there is no modeling error of the robot dynamics to be controlled and there is no disturbance, this control system is controlled only by the feedforward command U _FF , and the target value response is the model controller. It corresponds to the state quantity of the model determined by the parameter of. However, if there is a parameter error or disturbance, the state quantity of the controlled object causes a tracking error with respect to the state quantity of the model controller. On the other hand, the response to the disturbance can be determined by the gain of the feedback controller that multiplies the deviation of the state quantity between the model controller 200 and the controlled object. As described above, this control system is a two-degree-of-freedom control system in which the target value response characteristic and the disturbance suppression characteristic can be independently designed.

However, in the control of the robot, the moment of inertia J _L of the load and the spring constant K of the speed reducer depend on the posture of the robot.
Since c fluctuates, there is a problem that the state quantity of the actual machine deviates from the state quantity of the target model only with the control system with the above two degrees of freedom. To cope with this, the following sliding mode control is performed. A sliding mode controller 500 is provided.

Regarding the theoretical aspect of sliding mode control, for example, the theory of nonlinear control that can be used 3, sliding mode control (Hidemoto Hidenori, JSCE, 1
It is publicly known, for example, Vol.

The sliding mode switching surface is connected to the model load position θ _ML and the load position θ _L which are the outputs of the model controller.
Deviation from and model load speed

[0049]

[Outside 8] And load speed

[0050]

[Outside 9] And the deviation between the model twist angle θ _MS and the twist angle θ _S , and the model twist angular velocity

[0051]

[Outside 10] And twist angular velocity

[0052]

[Outside 11] It is defined by the deviation from. According to the above definition, the sliding mode phase plane is expressed by the following equation.

[0053]

[Equation 2] C and D are positive constants.

By using the phase surface of the equation (1),
Since the load position, speed, twist angle, and twist angular velocity follow the output of the model, accurate and stable control can be performed even with changes in the controlled object. Note that the load position θ _L and the load speed

[0055]

[Outside 12] , Twist angle θ _S , twist angular velocity

[0056]

[Outside 13] Is calculated using the estimated value by the observer 400 (not shown).

If no disturbance is applied to the speed reducer or the load side, the twist angle θ _S , the motor position θ m, the load position θ _L , and the reduction ratio N have the following relationships.

[0058]

[Equation 3] Assuming that the state quantity estimated by the observer as shown in FIG. 3 is the twist angle and the twist angular velocity, the equation (1) can be transformed as follows from the equation (2) and its differential value.

[0059]

[Equation 4] In equation (3), the switching surface S is the deviation between the model motor position θ _Mm and the motor position θ _m , the model motor speed.

[0060]

[Outside 14] And motor speed

[0061]

[Outside 15] And the model twist angle θ _MS and the twist angle θ _S , the following describes the phase surface according to the third claim.

The existence condition of the sliding mode is, as is clear from the above-mentioned literature,

[0063]

[Equation 5] Therefore, the condition for the existence of the global sliding mode is

[0064]

[Equation 6] Becomes Differentiating equation (3),

[0065]

[Equation 7] From equation (3),

[0066]

[Equation 8] From Figure 1,

[0067]

[Equation 9] Becomes As shown in FIG. 1, since the shaft torsion torque acts on the electric motor side, the acceleration command Uref to the electric motor is

[0068]

[Equation 10] However, since U _FF is the feedforward command and Tcomp is the sliding mode control input (compensation amount), equation (6) can be expressed as follows from equations (7), (8), and (9).

[0069]

[Equation 11] Therefore,

[0070]

[Outside 16] Is as follows.

[0071]

[Equation 12] Here, in order to normally design C <kv, the first equation (11)
The term is always negative. Therefore, in order for equation (5) to hold,

[0072]

[Equation 13] Therefore, the sliding mode input Tcomp is switched so that the expression (12) is satisfied depending on whether S is positive or negative.

[0073] First, <For 0, (θ _Mm -θ _m) for _{(θ Mm -θ m)> S} 0 when ^{-C 2 + kv (C-kp} )> Tcomp1 (θ Mm -θ m) ≦ 0 When −C ² + kv (C−kp) <Tcomp1 (θ _MS −θ _S ) (θ _MS −θ _S )> 0 N (DC) (kv-C) -k1> Tcomp2 (θ _MS −θ _S ) ≤ 0 N (DC) (kv-C) -k1 <Tcomp2

[0074]

[Equation 14]

[0075]

[Equation 15] For U _FF for -1 <Tcomp5 θ _S when -1> Tcomp5 U _FF ≦ 0 when U _FF> 0

[0076]

[Equation 16] Therefore, the sliding mode control is established if the conditions (1) to (4) are satisfied.

When S> 0, the positive and negative values of the above variables are exchanged. Sliding mode control input Tco
mp,

[0078]

[Equation 17] As a result, the acceleration command to the electric motor may be added and output.

As described above, according to the present invention, the state quantities of the motor, the load and the mutual relations are restricted by the sliding mode switching surface. Therefore, even if the parameter to be controlled fluctuates, the motor position and the load position are the norms of the model controller. Follow the output,
Accurate and stable control is possible.

Even when the switching surface of claim 4 is used, if the switching gain is set so as to satisfy the sliding mode existence condition, the motor position and the load position can follow the reference output of the model controller. Becomes

In this embodiment, an estimated value is used as the state quantity used for the sliding mode switching surface, but a value actually measured using a detector may be used.

Although the speed control of the electric motor has been described as the proportional control, the sliding mode control can be performed even in the case of the proportional and integral control.

Although the DC motor is used as the electric motor, the induction mode or the synchronous motor can be used for the sliding mode control by using the well-known vector control and can be controlled with high speed response.

[0084]

As described above, according to the present invention, the position controller for the electric motor has the sliding mode controller, and the model state quantity output from the model controller and the detected state quantity or observer are used. Since sliding mode control is performed with the deviation from the estimated state quantity as the switching surface, even if the rigidity of the transmission mechanism between the motor and the load is low, the output of the load can follow the target response. it can. Furthermore, even if the parameter to be controlled fluctuates from the nominal value, the state quantities of the electric motor and load follow the reference output of the model controller, and accurate and stable control is possible.

[Brief description of drawings]

FIG. 1 is a basic configuration block diagram of a two-degree-of-freedom control system to which a model of the present invention is applied.

FIG. 2 is a block diagram showing a detailed configuration of a model controller.

FIG. 3 is a block diagram showing a detailed configuration of a sliding mode controller.

FIG. 4 is a block diagram showing a detailed configuration of a feedback controller.

FIG. 5 is a basic configuration block diagram of a two-degree-of-freedom control system in a conventional example.

FIG. 6 is a basic configuration block diagram of a two-degree-of-freedom control system in a second conventional example.

[Explanation of symbols]

51, 61 Position command generator 52, 62 Model controller 53, 63 Feedback controller 54, 64 Feed forward controller 55, 65 Subtractor 56, 66 Adder 57, 67 Control object 100 Position command generator 200 Model controller 201 position controller model 202 speed controller model 203 feedforward command generator 204 torque controller model 205 electric motor model 206 reducer model 207 load model 208, 209 gain 210 differentiator 211 subtractor 212, 213 adder / subtractor 214 adder 221 Input terminal 222, 223, 224, 225, 226 Output terminal 300 Feedback controller 301 Position controller 302 Speed controller 303 Differentiator 304, 305 Gain 311, 314, 315 Subtractor 312 Adder Subtractor 313, 316, 317 Adder Calculator 321,322,323,325,326,327,3
28 Input terminal 329 Output terminal 400 Observer 500 Sliding mode controller 501 Positive / negative determination mechanism 502 of sliding mode controller S Gain switching mechanism 503 of Tcomp1 to 6 Differentiators 521, 522, 523, 524, 525, 526, 5
27 Input Terminal 528 Output Terminal 600 Regulator 700 Torque Controller 800 Electric Motor 850 Rotation Detector 900 Reducer 950 Load

Continuation of front page (51) Int.Cl. ⁷ Identification code FI G05B 13/04 G05B 13/04 (56) References JP-A-5-216504 (JP, A) JP-A-3-110606 (JP, A) JP-A-6-95708 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G05D 3/00-3/20 G05B 11/00-13/04

Claims (4)

(57) [Claims] 1. A position command generator that outputs a target position command of a motor that drives a load, and a model controller that inputs the command and outputs a model feedforward command signal and a model state value command signal of the motor. A rotation detector that detects rotation position information of the electric motor; and an acceleration command to the electric motor and rotation position information of the electric motor detected by the rotation detector to estimate state quantities of the electric motor and the load. Feedback control for outputting a feedback command by inputting a deviation between an observer, a model state quantity output from the model controller, rotational position information detected by the rotation detector, and an estimated state quantity estimated by the observer Controller, model feedforward command output from the model controller, and output from the feedback controller. A motor having a regulator that adds the generated feedback command and outputs it to the torque controller as an acceleration command to the motor; In the position control device, the model controller outputs a command of the state value of the load model, the observer estimates the state quantities of the electric motor and the load, and is preselected as a switching surface for sliding mode control. A sliding mode compensation amount calculated by the positive and negative of the value calculated from the plurality of state values using a reference state value surface consisting of a plurality of state values, the model state amount output from the model controller, The deviation between the rotational position information detected by the rotation detector and the estimated state quantity estimated by the observer converges to zero. Sea urchin, the position control unit for an electric motor, characterized in that it comprises a sliding mode controller for adding the sliding mode compensation amount to the feedback controller. 2. The position control device for an electric motor according to claim 1, wherein the sliding mode control switching surface includes a deviation between a model load position and a load position, a deviation between a model load speed and a load speed, and a model torsion angle. The position control device for an electric motor according to claim 1, wherein the deviation from the twist angle and the deviation between the model twist angular velocity and the twist angular velocity are used. 3. The position control device for an electric motor according to claim 1, wherein a switching surface of the sliding mode control includes a deviation between a model electric motor position and an electric motor position, a deviation between a model electric motor speed and an electric motor speed, and a model torsion angle and a torsion angle. 2. The position control device for an electric motor according to claim 1, wherein 4. The position control device for an electric motor according to claim 1, wherein the sliding mode control switching surface is provided with a deviation between a model electric motor position and an electric motor position, a deviation between a model electric motor speed and an electric motor speed, a model torsion angle and a torsion angle. And the model torsional angular velocity and the deviation between the torsional angular velocity and the deviation between the model torsional angular velocity and the model torsional angular velocity.