JP3888555B2 - Position control device and position control method - Google Patents

Description

  The present invention relates to a position control device and a position control method, and in particular, compares an output position with a target value of a position, inputs a deviation to a control element, and matches the position of a controlled object with the target value by the control element. The present invention relates to a position control device and a position control method.

  Motion control technology exists as a representative industrial control technology. Motion control technology is an important technology for establishing various operations of composite systems of electricity and machines in the fields of FA equipment, mechatronics, robotics and the like. Such technology includes positioning control.

  For example, in Japanese Patent Laid-Open No. 5-252772, in high-speed positioning control of a servo motor, a compensator having frequency characteristics of disturbance suppression characteristics and noise resistance characteristics is connected in series to the servo motor, and the servo motor is operated at high speed only by position information. A control method for positioning is disclosed, and according to such a configuration, the servo motor can be positioned only by position information without using speed or acceleration information.

  Of such positioning control, the configuration of a positioning control system based on the decomposition acceleration control method will be described with reference to FIG. This control system controls the controlled object 1 by the control element 2. The integrator 3 is connected to the output side of the controlled object 1, and the integrator 4 is further connected to the output side of the integrator 3. Further, a comparator 5 for comparing the output of the integrator 4 and the target position, and a comparator 6 for comparing the output of the integrator 3 and the target value of the speed are provided. The proportional element 7 is connected to the output side of the comparator 6, and the proportional element 7 is connected to the adder 8.

  In such a control system, the acceleration obtained as the output of the controlled object 1 is converted into a speed by an equivalent integrator 3 included in the controlled object 1, and this speed is converted into a position by the integrator 4. The position information is compared with the target position by the comparator 5 and the deviation is input to the control element 2. On the other hand, the speed output of the integrator 3 is compared with the target speed by the comparator 6 and added to the control input of the control object 1 output from the control element 2 by the adder 8 via the proportional element 7. Here, the target value of acceleration is further added by the adder 8. The control object 1 is controlled using the output of the adder 8 as a control input.

Such a decomposition acceleration control method having the configuration shown in FIG. 8 requires the position and speed information of the controlled object 1, and the transfer characteristics of the system are determined by the position deviation gain _Kp and the speed deviation gain _Kv . is there.

  FIG. 9 shows the configuration of another conventional position control apparatus. Here, in addition to the control element 2 for controlling the controlled object 1, the disturbance observer 11 and the output of the disturbance observer 11 are compared with the output position. Comparator 12, a disturbance observer 13 having reverse motion characteristics, an adder 14 for adding the output of the disturbance observer 13 to the control input, and a differentiator 15 for differentiating the output position. Is supplied to the comparator 6.

  In such a configuration, the comparator 5 compares the position that is the output of the controlled object 1 with the target value position, and inputs the deviation to the control element 2. The position which is the output of the control object 1 is differentiated by the differentiator 15 and converted into a speed. This speed is compared with the target speed by the comparator 6 and added to the control input by the adder 8 through the proportional element 7. The adder 8 also adds the acceleration target value to the control input. The control input is input to the disturbance observer 11, and the output of the disturbance observer 11 and the output position of the controlled object 1 are compared by the comparator 12, and the deviation is controlled by the adder 14 through the disturbance observer 13 having an inverse characteristic. Thus, the control object 1 is controlled.

In this control system, regardless of the position deviation gain _Kp and the speed deviation gain _Kv , it is possible to achieve a transmission characteristic that makes the transmission gain of the system very close to 1. However, since the configuration of the acceleration control system is a feedback type, there is a risk of deteriorating noise characteristics and stability. In addition, it is necessary to redesign the position controller in order to perform a closed loop system pole operation. Also, a speed sensor or position differential calculation is required. Although the method using a disturbance observer is shown here, the same applies to the case of configuring an acceleration control system.In this case, the order of the controller is often higher, and the amount of computation is proportional to the order. There are increasing problems.

On the other hand, in a precision stage, for example, a precision stage used in an exposure apparatus for manufacturing a semiconductor, a step-and-repeat driving method has been mainstream. In the future, it is clear that the system will be replaced with a continuous trajectory drive system to improve productivity. In this case, from the viewpoint of control, the conditions of high response, high speed, and low tracking error must be satisfied at the same time.
JP-A-5-252772

  An object of the present invention is to provide a position control device and a position control method that can simultaneously satisfy the conditions of high responsiveness, high speed, and low tracking error.

  Another object of the present invention is to provide a position control device and an ideal gain of a transfer characteristic with respect to a target value of each state quantity (position, velocity, or acceleration) approaching 1 to improve control performance for a continuous trajectory profile, and It is to provide a position control method.

  Still another object of the present invention is to provide a position control device and a position control method capable of controlling with excellent response characteristics with respect to a continuous trajectory.

  Another object of the present invention is to provide a position control device and a position control method that can be widely applied to the control field having a continuous trajectory as a profile, such as a precision stage, NC machine tool, industrial robot, and autonomous flight control. .

  The above-described problems and other problems of the present invention will be clarified by the technical idea of the present invention and the embodiments thereof described below.

A main invention of the present application is a position control device that compares an output position with a target value of a position, inputs a deviation into a control element, and controls the position of a controlled object to match the target value by the control element.
A state observer, the state observer outputs an estimated value of speed based on an output position, and adds a deviation between the estimated value of speed and a target value of speed to the output of the control element to Enter
In addition, the position control device is configured to add the product of the target value of the speed and the reverse motion characteristic of the controlled object to the output of the control element and input to the controlled object ,
An adder is provided on the output side of the control element, and the adder calculates a deviation between the estimated value of the speed and the target value of the speed, and a product of the target value of the speed and the reverse motion characteristic of the controlled object. The present invention relates to a position control device characterized in that a control input is added to a control input .

  Here, the control target may include a viscosity term in its dynamic characteristics. Further, the control element, the state observer, the means for forming the product of the speed target value and the dynamic characteristic to be controlled, and the adder may be configured by a computer.

A main invention related to a control method is a position control method in which an output position is compared with a target value of a position, a deviation is input to a control element, and the position of a controlled object is controlled by the control element so as to match the target value.
The state observer outputs an estimated value of speed based on the output position, and adds the deviation between the estimated value of speed and the target value of speed to the control input by an adder provided on the output side of the control element. Enter the target,
Moreover the present invention relates to a position control how, characterized by inputting the product of reverse dynamic characteristic of the controlled object to the target value of the speed to the control object is added to the control input by the adder.

  Here, the transfer gain of the entire control system may be set to approximately 1. Further, the product of the target value of the speed and the reverse motion characteristic of the controlled object may be added to the control input as a proper transfer function by a low-pass filter.

  A preferred aspect of the present invention relates to a control system design method for the purpose of improving followability with respect to a continuous trajectory profile, and the proposed control system design method is a conventional decomposition acceleration control method (see FIG. 8). The system is expanded by utilizing the dynamic characteristics of the system. Its features are that it can achieve a transfer characteristic close to the ideal transfer gain 1 with a simple configuration that does not use an acceleration control system. It is not necessary, and allows the configuration of the control system only by position information. Since there is no pole operation by feedback, it can be added to and expanded to the currently used position control. With such a configuration, control with excellent responsiveness to a continuous trajectory is enabled.

A main invention related to a control device is a position control device that compares an output position with a target value of a position, inputs a deviation into a control element, and controls the position of a controlled object to match the target value by the control element. A state observer is provided, and the state observer outputs an estimated value of the speed based on the output position, and adds the deviation between the estimated value of the speed and the target value of the speed to the output of the control element and inputs it to the control target In addition , the position control device adds the product of the target value of speed and the reverse motion characteristic of the controlled object to the output of the control element and inputs it to the controlled object, and has an adder on the output side of the controlled element. The adder adds the deviation between the estimated value of speed and the target value of speed, and the product of the target value of speed and the reverse motion characteristic of the control object to the control object by adding it to the control input . Is.

  Therefore, according to such a position control device, an acceleration control system is not required, the configuration can be simplified, and a transfer characteristic with an ideal transfer gain of approximately 1 can be achieved. Further, the configuration of the control system is made possible by only the position information without requiring a speed sensor or position approximate differentiation. In addition, since there is no pole operation by feedback, it can be added / extended to the control system currently used. Therefore, such a control device enables control with excellent response characteristics with respect to a continuous trajectory.

  The present invention will be described below with reference to embodiments shown in the drawings. FIG. 1 shows a system configuration of a position control apparatus according to the present embodiment. This position control apparatus controls the position of a control target 30 by a control element 31. An integrator 32 is connected to the output side of the controlled object 30. A comparator 33 is provided for comparing the output of the integrator 32 and the target value. The system further includes a state observer 35, and the output of the state observer 35 is compared with a target speed value in a comparator 36. The proportional element 37 is connected to the output side of the comparator 36, and the output side of the proportional element 37 is connected to the adder 38. The adder 38 adds the output of the proportional element 37 to the output of the control element 31. The adder 38 also adds the output of the multiplier 39.

  Such a system performs the following operations. The output of the controlled object 30 is converted into position information by the integrator 32, and this position information, that is, the output position is compared with the target position by the comparator 33. The output of the comparator 33 is supplied to the control element 31, and the control target 30 is controlled by the control element 31.

  Here, the state observer 35 calculates an estimated value of the speed based on the output position information obtained as the output of the integrator 32 and the control input. The calculated estimated value of the speed is compared with the target value of the speed in the comparator 36, and this target value is added to the control input that is the output of the controlled object 31 by the adder 38 through the proportional element 37. Further, the multiplier 39 obtains a value obtained by multiplying the target speed value by the reverse motion characteristic of the control system, and the adder 38 adds the output of the multiplier 39 to the control input. Therefore, the control input is obtained by adding the above two values to the output of the control element 31, and the added value is input to the control object 30 as the control input to perform position control.

In such a continuous trajectory tracking control system, P (s) in FIG. 1 indicates the dynamic characteristic of the controlled object 30, and C (s) is the transfer characteristic of the position controller 31. S represents a Laplace operator. The difference from the conventional acceleration control system (see FIG. 8) is that the acceleration command acc ^ref in FIG. 8 is input, and instead of configuring the acceleration control system, P (s) is added to the speed command vel ^ref. The reverse motion characteristic P ⁻¹ (s) is multiplied and input. Here, F (s) is a low-pass filter for making P ⁻¹ (s) a proper transfer function. This feedforward term makes it possible to achieve a transfer characteristic very close to the transfer gain 1 without configuring an acceleration control system. At the same time, since there is no pole operation by acceleration feedback control, the present invention can be applied to a currently used position control system. In addition, since the state observer 35 is configured using the dynamic characteristics, the speed can be estimated, so that an approximate differential calculation of the speed sensor and the position becomes unnecessary.

  In such a control system, parts other than the control object 30 and the integrator 32 are achieved by a computer. FIG. 2 shows a flow chart that allows such a computer to operate the system shown in FIG. In the flowchart shown in FIG. 2, the central routine shows the operation of the control element 31 forming the framework of the control system. On the other hand, the routine on the left shows the operation of adding the output calculated by the multiplier 39 to the adder 38. Further, the routine on the right side shows an operation in which the speed estimated value by the state observer 35 is compared by the comparator 36 and added to the control input by the adder 38 through the proportional element 37.

  A major feature of this control system is that a transfer characteristic very close to the transfer gain 1 can be achieved as described above. The fact that the transmission gain is 1 is as shown in the following proof.

In the control method shown in FIG. 1 and FIG. 2, in order to set the transfer characteristic for the command of each state quantity of position, velocity, and acceleration to the ideal gain 1, not the acceleration control system but the reverse characteristic P ^{−1 of the} controlled object. (S) is used for the feedforward unit. Therefore, viscosity compensation can be easily performed by including a viscosity term in the dynamic characteristics of the controlled object 30. In addition, while having a simple control system configuration, it is possible to achieve control performance equal to or higher than that of the prior art. Moreover, since the pole of the control system is not changed, there is an advantage that the stability is excellent.

  Next, an embodiment in which the above-described continuous trajectory tracking position control is used for controlling a precision stage for semiconductor manufacturing will be described. As shown in FIG. 4, the control device includes a stage 42 and is supported by a pair of linear guides 43 so as to be movable in the length direction thereof. The stage 42 is moved along the linear guide 43 by a non-resonant ultrasonic motor 44. The non-resonant type ultrasonic motor 44 is controlled by a controller 45 incorporating a computer that performs the above-described continuous trajectory tracking position control.

  The controller 45 receives the output of the linear encoder 47 that reads position information from the output of the linear scale 46 and the output of the limit sensor 48. Further, the controller 45 is connected to the operation personal computer 49.

  The non-resonant type ultrasonic motor 44 includes driving legs 51 and 52. These drive legs 51 and 52 are each provided with an expansion / contraction deformation part 53 and a shear deformation part 54 as shown in FIG. The expansion / contraction deformation part 53 is polarized in the expansion / contraction direction, that is, the length direction, while the shear deformation part 54 is polarized in the lateral direction.

  Here, when a voltage is applied to the expansion / contraction deforming portion 53 of the driving leg 51, the driving leg 51 expands, and the tip side portion of the driving leg 51 comes into contact with the stage 42. In this state, the shear deformation portion 54 is subjected to shear deformation, so that the distal end portion of the drive leg 51 applies a driving force to the stage 42 in the feed direction. At this time, since the expansion / contraction deformation portion 53 of the driving leg 52 on the opposite side is contracted, the tip end portion of the driving leg 52 is separated from the stage 42. The shear deformation portion 54 of the drive leg 52 having the tip portion separated from the stage 42 in this way is shearing in the opposite direction in preparation for the next drive.

  Such an operation is alternately and sequentially repeated by the two drive legs 51 and 52, whereby the stage 42 is moved in the length direction of the linear guide 43 indicated by an arrow. The position is read by a linear encoder 47 that contacts the linear scale 46 and input to the controller 45.

  Actually, the results applied to a precision stage with a 100 mm stroke are shown. As design conditions of the control system, the position control bandwidth is 100 Hz, the speed control bandwidth is 400 Hz, the F (s) bandwidth is 400 Hz, the state estimation observer bandwidth is 1000 Hz, and the sampling time is 0.1 ms.

  FIG. 5 shows a stage position 42 and a tracking error with respect to a lamp position command having an inclination of 5 mm / sec. FIG. 5 shows the proposed method (proposed) and the conventional method (conventional 1), and further improves the conventional method (using a PI controller for the position controller, disturbance and speed using estimated values from the state observer: conventional 2). Results are shown simultaneously. In the conventional method, since the position controller has only the proportional term, the steady-state deviation is large. However, in the proposed method, it can be confirmed that the steady-state deviation is small and the responsiveness is improved.

FIG. 6 shows the position and tracking error with respect to the sine wave position command (± 1 mm _pp , 1 Hz). It can be confirmed that the tracking error can be reduced by the proposed method. FIG. 7 shows the frequency distribution of the tracking error for the proposed method and the conventional improved system. Here, the number of data is 10,000 and the sensor resolution is 0.1 μm. It is confirmed that both the frequency within the sensor resolution and the standard deviation are improved by the proposed method.

As described above, the present embodiment is an expansion of the decomposition speed control method used for improving the followability to the continuous trajectory by using the dynamic characteristics of the system. The feature is (1) the reverse dynamic characteristic P ^{− of the} system. ^{By using 1} (s) for feedforward, a transfer gain of 1 can be theoretically achieved with a simple configuration that does not use an acceleration control system. (2) A speed sensor and position approximate differentiation are not required, and a control system can be configured only by position information. (3) Since there is no pole operation by feedback, it can be added / extended to the currently used position control system. This makes it possible to construct a control system with excellent response characteristics for a continuous trajectory.

  Since such a control device can greatly improve the followability to the continuous trajectory, not only the precision stage control shown as an example, but also NC machine tools, industrial robots, autonomous flight control, etc. It can be widely applied to almost all control fields using a trajectory as a profile. Further, it is most suitable for additional introduction into the control device of such equipment.

  While the present invention has been described with reference to the illustrated embodiments and examples, the present invention is not limited to the above-described embodiments and examples, and various modifications are possible within the scope of the technical idea of the invention included in the present application. Is possible.

  The present invention can be applied to a position control device having a profile of a continuous locus in a precision stage, NC machine tool, industrial robot, autonomous flight control, and the like.

It is a block diagram which shows the structure of the system of a position control apparatus. It is a flowchart for implement | achieving operation | movement of the system by computer. It is a block diagram of the positioning device of a stage. It is a principal part front view which shows operation | movement of a non-resonance type | mold ultrasonic motor. It is a graph which shows the comparison of the position of a stage with respect to a lamp position command, and a tracking error. It is a graph which shows the comparison of the position and tracking error with respect to a sine wave position command. It is a graph which shows the comparison of the frequency distribution with respect to a tracking error. It is a block diagram which shows the system configuration | structure of the conventional decomposition acceleration control method. It is a block diagram which shows the system configuration | structure of the acceleration control system by the conventional disturbance observer.

Explanation of symbols

1 ... Control target, 2 ... Control element, 3 ... Integrator, 4 ... Integrator, 5 ... Comparator, 6 ... Comparator, 7 ... Proportional element, 8 ... Adder, 11 ... ... Disturbance observer, 12 ... Comparator, 13 ... Disturbance observer, 14 ... Adder, 15 ... Differentiator, 30 ... Control target, 31 ... Control element, 32 ... Integrator, 33 ... Comparison 35 ... State observer, 36 ... Comparator, 37 ... Proportional element, 38 ... Adder, 39 ... Multiplier, 42 ... Stage, 43 ... Linear guide, 44 ... Non-resonant type Sonic motor, 45 ... Controller, 46 ... Linear scale, 47 ... Linear encoder, 48 ... Limit sensor, 49 ... Operating PC, 51, 52 ... Drive leg, 53 ... Stretching deformation part, 54 ... …… Shear deformation part

Claims (6)

In a position control device that compares an output position with a target value of a position, inputs a deviation into a control element, and controls the position of a controlled object to match the target value by the control element.
A state observer, the state observer outputs an estimated value of speed based on an output position, and adds a deviation between the estimated value of speed and a target value of speed to the output of the control element to Enter
In addition, the position control device is configured to add the product of the target value of the speed and the reverse motion characteristic of the controlled object to the output of the control element and input to the controlled object ,
An adder is provided on the output side of the control element, and the adder calculates a deviation between the estimated value of the speed and the target value of the speed, and a product of the target value of the speed and the reverse motion characteristic of the controlled object. A position control device characterized in that the control input is added to the control input .   The position control device according to claim 1, wherein the controlled object includes a viscosity term in its dynamic characteristics. A control element, a state observer, and means for forming the product of the target value and the dynamic characteristic of the controlled object speed, according to claim 1 or claim 2 and wherein the adder is characterized in that it is composed of a computer Position control device. In a position control method for comparing an output position with a target value of a position, inputting a deviation into a control element, and controlling the position of a controlled object to match the target value by the control element,
The state observer outputs an estimated value of speed based on the output position, and adds the deviation between the estimated value of speed and the target value of speed to the control input by an adder provided on the output side of the control element. Enter the target,
Moreover position control how, characterized by input to the control target the product of the inverse dynamics of the target value and the control target speed is added to the control input by the adder. 5. The position control method according to claim 4 , wherein a transfer gain of the entire control system is set to approximately 1. 5. The position control method according to claim 4 , wherein the product of the target value of speed and the reverse motion characteristic of the controlled object is added to the control input as a proper transfer function by a low-pass filter.

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