Control device for astatic system having dead time

Abstract

A control device (1) for controlling a control target comprising an astatic system (2) that has dead time is provided with: a dead time compensation system (5) that compensates for dead time at the control target based on the dynamic characteristics of the control target; and an integration error compensation system (6) that compensates for integration errors originating in the dead time compensation system (5). The integration error compensation system (6) comprises: an ideal response unit (7) in which the dynamic characteristics of the control target while in a state in which interference is not input are used as a model; and a correction unit (8) that is configured to correct a comparative value for the output of the ideal response unit (7) and the output of the control target and subsequently input the result to the control target.

Claims

1. A control device that controls a tire running test apparatus for a tire, said tire running test apparatus including an endless belt looped between a pair of drums and being configured to cause a tire for test to roll on the belt, said tire running test apparatus having dynamic characteristics, the dynamic characteristics having dead time and integration characteristics, the control device comprising: a dead time compensation system that compensates for the dead time at the tire running test apparatus based on an input and an output of the tire running test apparatus; and an integration error compensation system that compensates for an integration error originating in the dead time compensation system based on the input and the output of the tire running test apparatus, wherein the integration error compensation system includes an ideal response unit in which the dynamic characteristics of the tire running test apparatus in a state in which a disturbance is not input to the tire running test apparatus during execution of the dead time compensation system are used as a model, and a correction unit that receives an input comparative value for the output of the ideal response unit and the output of the tire running test apparatus, corrects the input comparative value by multiplying the input comparative value by a predetermined gain, and then inputs the corrected comparative value to the tire running test apparatus, wherein a swing quantity or a swing force of the drum is the input of the tire running test apparatus, and a position of the belt is the output of the tire running test apparatus.

2. A control device that controls a tire running test apparatus for a tire, said tire running test apparatus including an endless belt looped between a pair of drums and being configured to cause a tire for test to roll on the belt, said tire running test apparatus having dynamic characteristics, the dynamic characteristics having dead time and integration characteristics, the control device comprising: a Smith compensation system that compensates for the dead time at the tire running test apparatus based on an input and an output of the tire running apparatus; and an integration error compensation system that compensates for an integration error originating in the Smith compensation system based on the input and the output of the tire running test apparatus, wherein the integration error compensation system includes an ideal response unit in which the dynamic characteristics of the tire running test apparatus in a state in which a disturbance is not input to the tire running test apparatus during execution of the dead time compensation system are used as a model, and a correction unit that receives an input comparative value for the output of the ideal response unit and the output of the tire running test apparatus, corrects the input comparative value by multiplying the input comparative value by a predetermined gain, and then inputs the corrected comparative value to the tire running test apparatus, wherein a swing quantity or a swing force of the drum is the input of the tire running test apparatus, and a position of the belt is the output of the tire running test apparatus.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 is a block diagram showing a control system that executes cascade control for an astatic system having dead time and integration characteristics.

(2) FIG. 2 is an illustration showing the result of control in the control system in FIG. 1.

(3) FIG. 3 is a block diagram showing a control system that executes Smith compensation for an astatic system having dead time and integration characteristics.

(4) FIG. 4 is an illustration showing the result of control in the control system in FIG. 3.

(5) FIG. 5 is a block diagram showing a control system that executes Smith compensation and additionally has high-pass characteristics, for an astatic system having dead time and integration characteristics.

(6) FIG. 6 is an illustration showing the result of control in the control system in FIG. 5.

(7) FIG. 7 is a block diagram of a control system according to a first embodiment.

(8) FIG. 8 is an illustration showing the result of control in the control system according to the first embodiment.

(9) FIG. 9 is a block diagram of a control system according to a second embodiment.

(10) FIG. 10 is an illustration showing an overview of a tire running test apparatus for a tire.

(11) FIG. 11(a) to FIG. 11(e) are illustrations showing various forms of Smith compensation control.

DESCRIPTION OF EMBODIMENTS

(12) Embodiments of a control device for an astatic system having dead time according to the invention are described below with reference to the drawings.

(13) First, before a control device 1 of each embodiment is described, an astatic system 2 having dead time is described first.

(14) A representative example of the astatic system 2 having the dead time is a tire running test apparatus for a tire T disclosed in PTL 1 (Japanese Unexamined Patent Application Publication No. 2010-122006). FIG. 10 shows a tire running test apparatus 50 for a tire T.

(15) This tire running test apparatus 50 includes a driving drum 52 coupled with a driving motor 51 and being rotatable in forward and reverse directions, a driven drum 53 provided at a distance with respect to the driving drum 52 so that their axes are parallel to each other, and an endless belt 54 looped between the driving drum 52 and the driven drum 53. The tire T for test is grounded on a road surface (test road surface) formed on a flat surface of the belt 54. The tire running test apparatus 50 is configured to evaluate driving characteristics of the tire T by causing the tire T to be grounded on and roll on the test road surface on the belt 54.

(16) Further, the tire running test apparatus 50 includes a belt meandering prevention apparatus 55. The belt meandering prevention apparatus 55 corrects meandering and positional shift of the belt 54 by swinging the driven drum 53, which is one of the driving drum 52 and the driven drum 53 provided in the tire running test apparatus 50, relative to the driving drum 52.

(17) The belt meandering prevention apparatus 55 includes drum swinging means 56 for swinging the driven drum 53 relative to the driving drum 52 around a swinging axis extending along the up-down direction, and a control unit 57 that controls the drum swinging means 56. The drum swinging means 56 causes the position of the belt 54 to be variable in accordance with a swing parameter, such as its swing quantity θ, swing speed θ′, or swing force. The belt meandering prevention apparatus 55 actually measures the belt position by a sensor 58 or the like, and then controls the belt position by using the integral value of the swing quantity of the drum.

(18) A system represented by this tire running test apparatus 50 has dead time and integration characteristics, and therefore may be conceived as “an astatic system 2 having dead time.”

First Embodiment

(19) FIG. 7 shows a first embodiment of the invention, and shows a control system expressing characteristics of the tire running test apparatus 50, that is, an astatic system 2 having dead time and a control device 1 that controls the astatic system 2, in the form of a block diagram.

(20) The astatic system 2 having dead time (hereinafter, occasionally merely referred to as astatic system 2) is configured of P(s) originating in dynamic characteristics of the tire running test apparatus 50, e.sup.−Ls expressing dead time, and an integrator 1/s. A disturbance d is input to the input side of the integrator 1/s.

(21) At the input part of such an astatic system 2, a first controller 3 (indicated as control 1 in the drawing) and a second controller 4 (indicated as control 2 in the drawing) for controlling the astatic system 2 are provided. The first controller 3 and the second controller 4 may employ P control and I control. A target input value is input to the astatic system 2 through the first controller 3 and the second controller 4. The astatic system 2 is controlled accordingly.

(22) Also, the control device 1 according to this embodiment includes a Smith compensation system 5 (dead time compensation system) for the astatic system 2.

(23) Any of various forms shown in FIG. 11 may be employed as a configuration of the Smith compensation system 5. In this embodiment, a configuration in FIG. 7, in other words, a configuration in FIG. 11(a) is employed. In particular, the input value to the astatic system 2 (the output of the second controller 4) is split and input to P(s) that configures the Smith compensation system 5. The output of P(s) in the Smith compensation system 5 is split into two, and one is directly input to an integrator. The other is input to dead time e.sup.−Ls, and a minus value of the output of e.sup.−Ls is input to the integrator. The output of the integrator of the Smith compensation system 5 is added to the output of the astatic system 2, and then negatively fed back to the input of the first controller 3. The added value of the output of the integrator of the Smith compensation system 5 and the output of the astatic system 2 is differentiated, and then negatively fed back to the input of the second controller 4.

(24) Since the above-described control is cascade control and the feedback value to the first controller 3 is the output of the astatic system 2, it is conceived that the control corresponds to a position control loop in the tire running test apparatus 50 (control loop with swing quantity θ). Since the feedback value to the second controller 4 is the differential value of the output of the astatic system 2, it is conceived that the control corresponds to a speed control loop in the tire running test apparatus 50 (control loop with swing speed θ′).

(25) Further, as shown in FIG. 7, in case of this embodiment, an integration error compensation system 6 (integration error compensation loop) that restricts an integration error generated, for example, when a disturbance d is input to the astatic system 2 is provided.

(26) The integration error compensation system 6 has an ideal response unit 7 (response characteristics of ideal control) having control response characteristics from the input to the output in an ideal state without a disturbance or an integration error during execution of the Smith compensation. In the integration error compensation system 6, the input value to the first controller 3 is split and input to the ideal response unit 7. On the other hand, the output from the astatic system 2 is fed back to the integration error compensation system 6, and the difference (comparative value) between the output of the astatic system 2 and the output of the ideal response unit 7 is calculated. This comparative value is input to a correction unit 8 included in the integration error compensation system 6. The output of the correction unit 8 is added to the input of the second controller 4. The correction unit 8 multiplies the input value by a predetermined gain (gain may be equal to 1), and outputs the result. Alternatively, a configuration that returns the output of the correction unit 8 to the first controller 3 may be employed, or a configuration that returns the output of the correction unit 8 to the output value of the second controller 4 may be employed.

(27) In this case, the characteristics of the ideal response unit 7 are given by Expression (1).

(28) $\begin{array}{cc}\left[\mathrm{Math}.1\right]& \\ G\left(s\right)=\frac{C1\left(s\right).Math.C2\left(s\right).Math.P\left(s\right)}{C1\left(s\right).Math.C2\left(s\right).Math.P\left(s\right)+\left\{1+C2\left(s\right).Math.P\left(s\right)\right\}.Math.s}.Math.e^{\mathrm{Ls}}& \left(1\right)\end{array}$

(29) Herein, P(s) indicates dynamic characteristics after the integration characteristics and the dead time of the control target are removed, C1(s) indicates dynamic characteristics of the first controller 3, and C2(s) indicates dynamic characteristics of the second controller 4.

(30) FIG. 8 shows the control result when the control device (embodiment) of this embodiment that adds the output of the correction unit 8 to the input of the second controller 4 is used. The control condition is the same as that in FIG. 6.

(31) As shown in FIG. 8, with the control device of this embodiment, it is found that the overshoot in the response initial phase disappears as compared with the control method of the Smith compensation system 5 (with the high-pass filter). Accordingly, step response with high response can be provided. In addition, with the control device of this embodiment, it is found that the influence of the integration error when the disturbance d being the problem is applied, that is, the offset error D.sub.off as shown in FIG. 4 is eliminated early, and becomes substantially zero in a short time.

(32) As described above, with the control device 1 according to the first embodiment, by providing the dead time compensation system 5 with the Smith compensation, high response by gain-up can be attained. At this time, the offset error due to the integration error generated at the Smith compensation system 5 is restricted by additionally providing the integration error compensation system 6. Hence, the influence of the disturbance or the like can become restricted as soon as possible. The integration error compensation system 6 executes control in accordance with the difference between the output with the ideal control response characteristics at the Smith compensation and the actual output. Accordingly, generation of the offset error due to the disturbance can be restricted without providing the high-pass filter or the like at the downstream side of the Smith compensation.

Second Embodiment

(33) FIG. 9 shows a second embodiment of the invention.

(34) A control device 1′ of the second embodiment shown in FIG. 9 is similar to the control device 1 of the first embodiment in that the control target is “an astatic system having dead time.” Also, the Smith compensation system 5 is similarly provided for the astatic system 2. Further, the integration error compensation system 6 that restricts the integration error generated, for example, when the disturbance d is input to the astatic system 2 is similarly provided. The integration error compensation system 6 similarly includes the ideal response unit 7 and the correction unit 8.

(35) However, the control device 1′ of the second embodiment shown in FIG. 9 is significantly different from the control device 1 of the first embodiment in that the control device 1′ includes only a single controller.

(36) In particular, in the control device 1′ of the second embodiment, the input to the astatic system 2 is made through a controller 9. The output of the astatic system 2 is added to the output of the Smith compensation system 5, and then is negatively fed back to the input of the controller 9. That is, the control system of the second embodiment is a non-cascade system, and the feedback value to the controller 9 is the output of the astatic system 2. Hence, for example, the control system corresponds to a control system that controls a motor.

(37) In the integration error compensation system 6 of the second embodiment, the input value to the controller 9 is split and input to the ideal response unit 7. On the other hand, the output from the astatic system 2 is fed back to the integration error compensation system 6, and the difference (comparative value) between the output of the astatic system 2 and the output of the ideal response unit 7 is calculated. This comparative value is input to the correction unit 8 (gain may be equal to 1) included in the integration error compensation system 6. The output of the correction unit 8 is added to the output of the controller 9.

(38) In this case, the characteristics of the ideal response unit 7 are given by Expression (2).

(39) $\begin{array}{cc}\left[\mathrm{Math}.2\right]& \\ G\left(s\right)=\frac{C\left(s\right).Math.P\left(s\right)}{C\left(s\right).Math.P\left(s\right)+s}.Math.e^{\mathrm{Ls}}& \left(2\right)\end{array}$

(40) Herein, P(s) indicates dynamic characteristics after the integrator and the dead time of the control target are removed, and C(s) indicates dynamic characteristics of the controller 9.

(41) Even with the control device 1′ of the second embodiment, high response by gain-up can be attained for the astatic system 2 having the dead time while restricting the offset error originating in the integration error.

Modifications

(42) The specific configuration of the Smith compensation system 5 described in the first embodiment and the second embodiment is not limited to the described single configuration.

(43) FIG. 11 shows various configurations of the Smith compensation system 5 (Smith compensation loop). In the above-described first embodiment and second embodiment, the configuration in FIG. 11(a) is employed for the Smith compensation system 5. However, any of configurations in FIG. 11(b) to FIG. 11(e) may be employed.

(44) For example, FIG. 11(b) shows a configuration in which the order of the dynamic characteristics P(s), the dead time e.sup.−Ls, and the integrator 1/s is changed, so that a signal is transmitted from the input side in order of the integrator 1/s, the dynamic characteristics P(s), and then the dead time e.sup.−Ls.

(45) FIG. 11(c) and FIG. 11(e) each show a configuration in which the configuration in FIG. 11(a) is changed to parallel arrangement. In particular, in FIG. 11(c), two lines of transmission paths for a signal are provided. The dynamic characteristics P(s), the dead time e.sup.−Ls, and the integrator 1/s are arranged in one line, and a transmitted signal being a minus value is added to the output side (that is, subtraction is performed). Also, the dynamic characteristics P(s) and the integrator 1/s are arranged in the other line. A transmitted signal being a plus value is added to the output side. FIG. 11(e) is different from FIG. 11(c) only for the order of addition and subtraction to the output side.

(46) FIG. 11(d) has a configuration in which the dynamic characteristics P(s) are arranged in parallel as compared with the configuration in FIG. 11(a). In particular, in FIG. 11(d), the input signal is split, the dynamic characteristics P(s) and the dead time e.sup.−Ls are arranged in one line, and the dynamic characteristics P(s) and the integrator 1/s are arranged in the other line. The output of the dead time e.sup.−Ls in the one line is set at a minus value at the input side of the integrator 1/s of the other line and is combined (that is, subtraction is performed), and the output of the integrator 1/s becomes the output of the Smith compensation system 5.

(47) Even if the Smith compensation system 5 of any of FIG. 11(a) to FIG. 11(e) described above is used, the effects and advantages attained by the invention can be provided.

(48) It is to be noted that the embodiments disclosed this time are merely examples for all points and are not limited thereto. In particular, in the embodiments disclosed this time, matters that are not explicitly disclosed, for example, driving conditions, operating conditions, various parameters, dimensions of components, weights, volumes, and so forth, may employ values that are within ranges generally employed by those skilled in the art and that can be easily conceived by those skilled in the art.

(49) For example, the control technology of the invention is not limited to the tire running test apparatus 50 for the tire T, and may be applied to any system as long as the system is expressed by the astatic system 2 having the dead time.

(50) This application is based on Japanese Patent Application (Japanese Patent Application No. 2012-229924) filed Oct. 17, 2012, which is hereby incorporated by reference herein.

REFERENCE SIGNS LIST

(51) 1, 1′ control device 2 astatic system 3 first controller 4 second controller 5 Smith compensation system (dead time compensation system) 6 integration error compensation system 7 ideal response unit 8 correction unit 9 controller 50 tire running test apparatus 51 driving motor 52 driving drum 53 driven drum 54 belt 55 belt meandering prevention apparatus 56 drum swinging means 57 control unit 58 sensor T tire