Positioning control device and positioning control method

Abstract

[Problem] To provide a positioning control device and positioning control method with which an operation target can be positioned without using a sensor for detecting the position of the operation target. [Solution] A positioning control device that positions an object by controlling a pneumatic actuator having a first chamber and a second chamber air-tightly separated by a moving member and comprises: a gas supply unit for supplying and discharging gas to the first chamber and the second chamber of the pneumatic actuator; and a control unit for controlling the supply of gas to the first chamber and the second chamber of the pneumatic actuator by the gas supply unit. The control unit controls the amount of movement of the moving member by controlling the supply of gas to the first chamber of the pneumatic actuator while the second chamber of the pneumatic actuator is air-tightly sealed.

Description

Positioning Control Device and Positioning Control Method

[0001] The present invention relates to a positioning control device and a positioning control method. More specifically, it relates to a positioning control device and a positioning control method suitable for controlling a pneumatic actuator that uses pneumatic pressure such as a pneumatic cylinder as a working fluid.

[0002] Various devices are adopted for actuators that drive robots, mechatronic devices, etc. As actuators that utilize fluid pressure, hydraulic cylinders and pneumatic cylinders are generally used. For example, when moving an object (actuated object) actuated by such an actuator to a target position and placing it at that position, that is, when moving the actuated object by a predetermined amount, the actuator is controlled based on the difference (deviation) between the current position and the target position of the actuated object. That is, the current position of the actuated object is measured by a sensor, and the actuator is controlled so that the deviation between the measured position and the target position becomes zero (see, for example, Patent Document 1, Non-Patent Documents 1 and 2).

[0003] Japanese Patent Application Laid-Open No. 7-98002

[0004] Kei-Ren PAI and Ming-Qiang SHTH, nanoaccuracy Position Control of a Pneumatic Cylinder Driven Table, JSME International Journal, Series C, Vol.46, No. 3,1062- 1067, 2003Kaiji Sato, Yusuke Sano, Practical and intuitive controller design method for precision positioning of a pneumatic cylinder actuator stage, Precision Engineering 38 703-710, 2014"Pneumatic Drive Actuator System Using a Potential Mass Flow Sensor of an Actuator", Masao Shimizu, Oil Hydraulics Technology, December 2024 issue

[0005] As mentioned above, when using an actuator to move an object by a predetermined amount or position it in a predetermined location, a sensor is required to detect the position of the object. If the position of the object could be controlled without using a position-detecting sensor, the configuration of the device could be simplified and the cost of the device could be reduced.

[0006] Non-patent document 3 describes a technique that uses a mass flow sensor to move an object by a predetermined amount or position it in a predetermined location using an actuator, without using a position sensor. However, the technique described in Non-patent document 3 makes it difficult to achieve sufficient positioning. In such conventional techniques, positioning requires measuring the temperature of the gas supplied into the actuator cylinder with a temperature sensor and feeding this information back to the control system. Due to factors such as the uniformity of the temperature distribution within the cylinder and the slow temperature transfer rate, it is difficult to obtain the precise positioning accuracy of tens of microns required in factory automation (FA). Furthermore, changes in the gas temperature inside the cylinder in response to changes in ambient temperature also affect the positioning accuracy, posing a similar problem.

[0007] In view of the above circumstances, the present invention aims to provide a positioning control device and a positioning control method that do not require a sensor to detect the position of the object to be worked on and can position the object to be worked on without depending on the temperature supplied into the cylinder.

[0008] <Positioning Control Device> The positioning control device of the first invention is a control device for positioning an object by controlling a pneumatic actuator having a first chamber and a second chamber airtightly separated by a moving member, comprising: a gas supply unit that supplies and discharges gas to the first chamber and the second chamber of the pneumatic actuator; and a control unit that controls the supply of gas to the first chamber and the second chamber of the pneumatic actuator by the gas supply unit, wherein the control unit controls the amount of movement of the moving member by controlling the supply of gas to the first chamber of the pneumatic actuator while the second chamber of the pneumatic actuator is airtightly sealed. The positioning control device of the second invention is characterized in that, in the first invention, the control unit sets a target pressure for the second chamber of the pneumatic actuator based on the ideal gas law, and controls the supply of gas to the first chamber of the pneumatic actuator so that the pressure in the second chamber becomes the target pressure. The positioning control device of the third invention is characterized in that, in the first or second invention, the control unit supplies gas to the second chamber of the pneumatic actuator while the volume of the first chamber of the pneumatic actuator is close to zero, before controlling the amount of movement of the moving member, and then airtightly seals the second chamber of the pneumatic actuator. The positioning control device of the fourth invention is characterized in that, in the third invention, after the previous positioning operation is completed, the control unit replaces the gas in the second chamber of the pneumatic actuator after the volume of the first chamber of the pneumatic actuator is close to zero, and then airtightly seals the second chamber of the pneumatic actuator after the replacement is completed. The positioning control device of the fifth invention is characterized in that, in the first invention, after positioning an object, the control unit controls the supply of gas to the first chamber of the pneumatic actuator so that the differential pressure between the first chamber and the second chamber of the pneumatic actuator becomes constant.The positioning control device of the sixth invention is characterized in that, in the first invention, the control unit has a function to generate a control input for controlling the pneumatic actuator, and the control unit has a first control input generation function that generates a first control input when there is a deviation of the controlled amount from a target value, a second control input generation function that generates a second control input that increases as the deviation of the controlled amount from a target value decreases when there is a time change in the controlled amount, and an output generation function that generates the control input based on the first control input and the second control input. The positioning control device of the seventh invention is characterized in that, in the sixth invention, the first control input generation function has a function to generate a steady-state control input as the first control input, or, when there is a time change in the controlled amount, has a function to generate a control input that combines a fluctuating control input that decreases as the deviation of the controlled amount from a target value decreases and a steady-state control input as the first control input. The control input generation device of the eighth invention is characterized in that, in the first invention, the pneumatic actuator is a pneumatic cylinder, and the first chamber and the second chamber of the pneumatic actuator are a chamber located on the head side of the pneumatic cylinder and a chamber located on the rod side of the pneumatic cylinder, respectively. <Positioning control method> The positioning control method of the ninth invention is a control method for positioning an object by controlling a pneumatic actuator having a first chamber and a second chamber airtightly separated by a moving member, characterized in that the amount of movement of the moving member is controlled by controlling the supply of gas to the first chamber of the pneumatic actuator while the second chamber of the pneumatic actuator is airtightly sealed. The positioning control method of the tenth invention is characterized in that, in the ninth invention, a target pressure of the second chamber of the pneumatic actuator is set based on the ideal gas law, and the supply of gas to the first chamber of the pneumatic actuator is controlled so that the pressure of the second chamber becomes the target pressure.The positioning control method of the 11th invention is characterized in that, in the 9th or 10th invention, before controlling the amount of movement of the moving member, gas is supplied to the second chamber of the pneumatic actuator while the volume of the first chamber of the pneumatic actuator is set to zero, and then the second chamber of the pneumatic actuator is airtightly sealed. The positioning control method of the 12th invention is characterized in that, in the 11th invention, after the previous positioning operation is completed, the volume of the first chamber of the pneumatic actuator is set to zero, the gas in the second chamber of the pneumatic actuator is replaced, and after the replacement is completed, the second chamber of the pneumatic actuator is airtightly sealed. The positioning control method of the 13th invention is characterized in that, in the 9th invention, after positioning an object, the supply of gas to the first chamber of the pneumatic actuator is controlled so that the differential pressure between the first chamber of the pneumatic actuator and the second chamber of the pneumatic actuator remains constant. The positioning control method of the 14th invention is characterized in that, in the 9th invention, a first control input is generated when there is a deviation of the controlled amount from a target value, and when there is a time change in the controlled amount, a second control input is generated which increases as the deviation of the controlled amount from the target value decreases, and the control input is generated based on the first control input and the second control input. The control input generation method of the 15th invention is characterized in that, in the 14th invention, the first control input is a steady-state control input, or when there is a time change in the controlled amount, the first control input is a control input which is a combination of a variable control input which decreases as the deviation of the controlled amount from the target value decreases and a steady-state control input. The control input generation method of the 16th invention is characterized in that, in the 9th invention, the pneumatic actuator is a pneumatic cylinder, and the first chamber and the second chamber of the pneumatic actuator are a chamber located on the head side of the pneumatic cylinder and a chamber located on the rod side of the pneumatic cylinder, respectively.

[0009] <Control Input Generation Device> According to the first to third inventions, an object can be positioned at a predetermined location by controlling a pneumatic actuator without using a position sensor. According to the fourth invention, a decrease in the positioning accuracy of the object can be prevented even if the positioning control is repeated. According to the fifth invention, after positioning the object, the state in which the object is positioned at the predetermined location can be maintained. According to the sixth and seventh inventions, if the generated control input is used to control the pneumatic actuator, the responsiveness of the pneumatic actuator near the target value can be improved, and overshoot with respect to the target value can be suppressed, thereby increasing the accuracy of operating the pneumatic actuator to reach the target value. Moreover, overshoot with respect to the target value can be prevented. According to the eighth invention, an object can be positioned at a predetermined location using a pneumatic cylinder. <Control Input Generation Device> According to the ninth to eleventh inventions, an object can be positioned at a predetermined location by controlling a pneumatic actuator without using a position sensor. According to the twelfth invention, a decrease in the positioning accuracy of the object can be prevented even if the positioning control is repeated. According to the thirteenth invention, after positioning the object, the state in which the object is positioned at the predetermined location can be maintained. According to the 14th and 15th inventions, by using the generated control input to control a pneumatic actuator, the responsiveness of the pneumatic actuator near the target value can be improved, and overshoot of the target value can be suppressed, thereby increasing the accuracy of operating the pneumatic actuator to reach the target value. Moreover, overshoot of the target value can be prevented. According to the 16th invention, an object can be positioned at a predetermined location using a pneumatic cylinder.

[0010] This is a block diagram of the control system 1 having the positioning control device of this embodiment. This is an explanatory diagram of the operation of the pneumatic cylinder 2 controlled by the positioning control device of this embodiment. This is a diagram showing an example of a pressure control system having the positioning control device of this embodiment. This is a diagram showing an example of a force control system having the positioning control device of this embodiment. This is a table showing the relationship between the compensation input Yc, the deviation e, and the velocity v. This is an explanatory diagram of the state change of the compensation input Yc until the object M comes to rest at the target value Lr. This is an explanatory diagram of the flow until the object M comes to rest at the target value Lr. This is a table showing the relationship between the controlled quantity and the parameter. This is a diagram showing an example of the calculation circuit of this embodiment. This is a schematic explanatory diagram of the control board B that generates the control input for the control by the positioning control device of this embodiment. This is a diagram showing an example of an experiment to set constants. This is a schematic explanatory diagram of a conventional positioning control system with a disturbance observer added. (A) is a diagram showing the relationship between the gain K1 and the deviation e, and (B) is a diagram showing the relationship between the gain K2 and the displacement velocity v. This is a schematic explanatory diagram showing an example of a positioning control system. This is a diagram showing the results of Example 1. This is a diagram showing the results of Example 1. This is an explanatory diagram of the device used in Example 2. This is a diagram showing the results of Example 2. This is an explanatory diagram of the apparatus used in Example 3. This is a diagram showing the results of Example 3. This is a diagram showing the results of Example 3. This is a diagram showing the results of Example 3.

[0011] Next, embodiments of the present invention will be described with reference to the drawings. The positioning control device of this embodiment is a device that generates control inputs used for controlling a pneumatic actuator, and is characterized by its simplified device configuration and low manufacturing cost.

[0012] <Actuator> The pneumatic actuator used in the positioning control device of this embodiment is not particularly limited, but examples include pneumatic cylinders and pneumatically operated rotary actuators. In this specification, the moving member refers to the piston in a pneumatic cylinder and the vane in a rotary actuator; displacement velocity refers to the moving speed of the cylinder rod in a pneumatic cylinder and the angular velocity of the rotation axis in a rotary actuator; and displacement acceleration refers to the displacement acceleration of the cylinder rod in a pneumatic cylinder and the angular acceleration of the rotation axis in a rotary actuator.

[0013] <Regarding the machines in which the positioning control device of this embodiment is employed> The machines and devices in which the positioning control device of this embodiment is employed are not particularly limited. For example, robot arms, robot grippers, single-axis transport devices, multi-axis XY tables, pneumatic vibration isolation tables, etc., which are operated by the above-mentioned pneumatic actuators, are examples of machines and devices in which the positioning control device of this embodiment is employed.

[0014] <Positioning Control Device of This Embodiment> Next, the positioning control device of this embodiment will be described. Figure 1 shows a control system 1 that operates an object by controlling a pneumatic cylinder with the positioning control device of this embodiment, and reference numeral 2 indicates the pneumatic cylinder whose operation is controlled by the control unit 10 of the positioning control device of this embodiment. In the control system 1, the object M is fixed to the rod 2r of the pneumatic cylinder 2, and when the rod 2r moves (i.e., when the rod 2r of the pneumatic cylinder 2 extends or retracts), the object M moves together with the rod 2r.

[0015] As shown in Figure 1, the pneumatic cylinder 2 has a cylinder 2a that is airtightly separated into a first chamber h1 and a second chamber h2 by a piston 2p. The first chamber h1 and the second chamber h2 within the cylinder 2a are connected to the pneumatic source 4 via piping 3 and a servo valve 5, respectively. The control unit 10 of the positioning control device of this embodiment (hereinafter sometimes simply referred to as "control unit 10") is electrically connected to the servo valve 5. A valve that can be opened and closed manually may be provided in the piping 3 that connects the second chamber h2 and the pneumatic source 4, so that the supply of air to the second chamber h2 is stopped or the second chamber h2 is closed manually. Alternatively, a control valve such as a two-way valve may be provided in the piping 3 that connects the second chamber h2 and the pneumatic source 4 (for example, the piping 3 that connects the second chamber h2 and the servo valve 5), in addition to the servo valve 5, so that gas is supplied to the second chamber h2 from an air supply means such as a regulator via that control valve. In this case, the gas may be supplied from the air pressure source 4, or the gas may be supplied to the second chamber h2 from an air pressure source provided separately from the air pressure source 4. The piping 3, servo valve 5, air pressure source 4, valve, control valve, regulator, and other air supply means correspond to the gas supply unit as referred to in the claims.

[0016] The control unit 10 controls the operation of the pneumatic cylinder 2 by controlling the operation of the servo valve 5, and has a function to receive information about target values, that is, the position and amount of movement of the object M (or the position in which the object M is kept stationary), from an input means. The control unit 10 is supplied with signals from pressure sensors PG1 and PG2, which measure the pressure in the first chamber h1 and the second chamber h2 of the pneumatic cylinder 2. Therefore, the control unit 10 can detect the force generated by the pneumatic cylinder 2 and its direction based on the differential pressure between the pressure sensors PG1 and PG2.

[0017] Furthermore, the control unit 10 has the function of using the pressure detected by pressure sensors PG1 and PG2 to control the supply of gas from the pneumatic actuator 2 to the first chamber h1 in order to move the object M to the target position based on the standard state equation of the gas in the second chamber h2 (hereinafter simply referred to as the state equation). Specifically, the positioning control device of this embodiment constitutes the pressure control system shown in Figure 3, and the control unit 10 controls the supply of gas from the pneumatic actuator to the first chamber h1 so that the pressure P2 of the gas in the second chamber h2 becomes pressure Pr2, based on the pressure P2 of the second chamber h2 measured by pressure sensor PG2 and the target pressure P2r of the second chamber h2.

[0018] The target pressure P2r in the second chamber h2 is calculated based on the equation of state for a gas sealed within the second chamber h2 under standard conditions. For example, the target pressure P2r can be calculated based on the following equation F1: Equation F1 Pr1・(S・L1) = P2r・(S・L2) Pr1: Initial pressure of the second chamber h2 P2r: Pressure in the second chamber h2 (target pressure) when object M is placed at the target position S: Pressure-receiving area of ​​the rod side surface 2f of the piston 2p L1: Maximum stroke amount L1 of the pneumatic cylinder 2 L2: Distance from the rod side surface 2f of the piston 2p to the inner surface of the rod-side cylinder chamber when object M is placed at the target position

[0019] Given the above configuration, the positioning control device of this embodiment performs position control as follows.

[0020] First, preparations for position control are made. The control unit 10 controls the servo valve 5 to move it to a position where the head side 2f of the piston 2p contacts the inner surface of the first chamber h1 of the pneumatic cylinder 2. In other words, the first chamber h1 of the pneumatic cylinder 2 is opened and air is supplied to the second chamber h2 so that the inner surface of the first chamber h1 and the head side are in contact (see Figure 2(B)). That is, the volume in the first chamber h1 is made to be 0 or close to 0. Next, the control unit 10 controls the servo valve 5 (or operates the valve manually) to close the second chamber h2. That is, air is trapped in the second chamber h2 while the inner surface of the first chamber h1 and the head side are in contact. The pressure P2 in the second chamber h2 in this state becomes the initial pressure Pr1.

[0021] Once the preparations for position control are complete, the control unit 10 starts position control. Specifically, when a target value is input to the control unit 10 from an input means or the like, it controls the pneumatic cylinder 2 as follows. First, when a target position for positioning object M is input, L2, which will be the target position, is calculated based on the known installation state and structure of the pneumatic cylinder 2 (for example, the length of the rod 2r and the size of the piston 2p, etc.) (see Figures 2(A) and (C)). Then, the control unit 10 calculates the target pressure P2r of the second chamber h2 based on L2 and equation F1. Once the target pressure P2r is calculated, the control unit 10 controls the supply of air to the first chamber h1 so that the pressure P2 in the second chamber h1 of the pneumatic cylinder 2 matches the target pressure P2r. In other words, it calculates the flow rate of air to be supplied to the first chamber h1 of the pneumatic cylinder 2 and supplies a signal related to that flow rate to the servo valve 5. Then, the servo valve 5 adjusts the flow rate of air supplied to the first chamber h1 of the pneumatic cylinder 2 to extend the pneumatic cylinder 2.

[0022] The control unit 10 measures the pressure P2 in the second chamber h1 and repeatedly calculates the flow rate of air supplied to the first chamber h1 of the pneumatic cylinder 2, thereby positioning the object M at the target location.

[0023] As described above, with the positioning control device of this embodiment, the object M can be positioned simply by measuring the pressure P2 in the second chamber h2 of the pneumatic cylinder 2, without the need for a position sensor. Moreover, instead of the conventional positioning operation based on absolute pressure values ​​using the ideal gas law, the positioning operation is based on the relative pressure Pr1 / P2r resulting from the relative change from the initial pressure Pr1. As a result, mass flow sensors and temperature sensors required in positioning operations based on absolute pressure values ​​become unnecessary, allowing for a smaller and simpler device configuration and reducing the manufacturing cost of the device. Furthermore, improved position accuracy is also possible. In addition, by performing the above-mentioned preparation for position control as the initial operation of positioning, the initial volume of the second chamber h2 of the pneumatic cylinder 2 can be determined. Then, by controlling with the pressure value measured by the pressure sensor, positioning operation based on relative pressure changes defined as PV = constant becomes possible without measuring mass flow rate or nRT. Moreover, since the second chamber h2 of the pneumatic cylinder 2 is sealed, the target pressure corresponding to the target position is uniquely determined regardless of the magnitude of the load, so positioning of the target position can be achieved regardless of load fluctuations or changes.

[0024] <Maintaining a fixed position> When an object M is positioned at a predetermined location using the positioning control device of this embodiment, even if the temperature of the gas supplied to the pneumatic cylinder 2 and the ambient temperature (the temperature of the air around the pneumatic cylinder 2) are different, the operation time is shorter in the transient state leading to the target position compared to the case where the positioning state is maintained. Furthermore, since the same operation is repeated in actual use, absolute position accuracy can be ensured by ensuring repeatability and applying corrections. In addition, even if the object M is positioned at a predetermined location using the positioning control device of this embodiment and the temperature of the gas supplied to the pneumatic cylinder 2 and the ambient temperature are different, the positioning state can be maintained at that location for a short period of time. On the other hand, if the positioning state is maintained for a long period of time, the temperature of the air in the first chamber h1 and the second chamber h2 of the pneumatic cylinder 2 will change, and as a result, even if the aforementioned control (i.e., the control to move the object M to the predetermined position and position it) is maintained, the position of the object M may deviate from the target position. Furthermore, even if the period of time is not that long, a similar situation may occur if there is a change in the surrounding environment. Therefore, when the positioning control device of this embodiment is to hold an object M in a predetermined position, it is desirable to control the flow rate of air supplied to the first chamber h1 so that the differential pressure between the pressure P1 in the first chamber h1 and the pressure P2 in the second chamber h2 of the pneumatic cylinder 2 remains constant. In other words, until the object M is placed in the predetermined position, the positioning control device of this embodiment controls the flow rate of air supplied to the first chamber h1 so that the pressure in the second chamber h2 of the pneumatic cylinder 2 becomes the target pressure P2r (positioning control). After the object M is placed in the predetermined position, it is desirable to control the flow rate of air supplied to the first chamber h1 so that the differential pressure between the pressure P1 in the first chamber h1 and the pressure P2 in the second chamber h2 of the pneumatic cylinder 2 remains constant (position holding control).

[0025] <Regarding the Equation of State> The equation of state used by the positioning control device of this embodiment to set the target pressure P2r of the second chamber h2 of the pneumatic actuator 2 is not limited to F1 above, and an equation of state based on adiabatic change can be adopted. Specifically, the target pressure P2r of the second chamber h2 of the pneumatic actuator 2 can be set based on the following equation of state F2. Note that the equation of state used to set the target pressure P2r of the second chamber h2 of the pneumatic actuator 2 is not limited to the following equation. (Equation F2) Pr1(SL2) κ = P2r(SL2) κ κ: Specific heat ratio

[0026] <Control based on the pressure in the first chamber h1 of the pneumatic actuator 2> In the example described above, control was explained using the pressure P2 in the second chamber h2 of the pneumatic actuator 2 as the target pressure. However, control may also be performed using the pressure P1 in the first chamber h1 of the pneumatic actuator 2 as the target pressure. In other words, if there is no frictional force fc, the force P1A1 applied to the head side of the piston 2p and the force P2A2 applied to the rod side of the piston 2p will be equal (P1A1 = P2A2). Therefore, by configuring the control system to compensate for the frictional force fc, it is possible to control the pneumatic actuator 2 based on the force P1A1 applied to the head side of the piston 2p. In other words, it is possible to control the pneumatic actuator 2 based on the pressure P1 in the first chamber h1.

[0027] For example, a control system as shown in Figure 4 can be configured with a pneumatic actuator 2 as the control target. The control system in Figure 4 acts to match the force applied to the head side of the piston 2p by the head-side generated force P1A1, that is, the pressure P1 in the first chamber h1, to its target value P1rA1 in conventional force control using a disturbance observer. In addition, a proposed compensation signal based on the force deviation (P1rA1 - P2A2) is applied to the control input u. Furthermore, a friction force fc estimated by the force deviation (P1A1 = P2A2) is pre-applied to the target value P1rA1. Therefore, by configuring a control system as shown in Figure 4, friction compensation can be performed, making it possible to control the pneumatic actuator 2 based on the force P1A1 applied to the head side 2f of the piston 2p (i.e., the pressure P1 in the first chamber h1).

[0028] <When positioning operations are performed repeatedly> When the positioning control device of this embodiment repeatedly positions the object M, the preparation for position control described above may be performed when the first positioning operation is performed, and the preparation for position control may not be performed for subsequent positioning operations. Alternatively, after performing positioning operations multiple times, the preparation for position control may be performed again. On the other hand, when positioning operations are performed multiple times by the pneumatic actuator 2, the state of the air in the second chamber h2 changes, and even if the same control is performed, the position to be positioned may shift.

[0029] Therefore, when positioning operations are performed repeatedly, it is desirable to prepare for position control and replace the air in the second chamber h2 after each positioning operation is completed. In other words, when the positioning operation is completed, the piston 2p of the pneumatic cylinder 2 returns to the reference position, that is, the position where the side of the head of the piston 2p contacts the inner surface of the first chamber h1 (see Figure 2(B)). When this state is reached, new air is supplied to the second chamber h2 to expel all the air that was sealed in the second chamber h2, and the second chamber h2 is filled only with the newly supplied air. In other words, the air that was sealed in the second chamber h2 is replaced with new air during the positioning operation. Then, when the second chamber h2 is filled only with new air, the second chamber h2 is closed. As a result, the second chamber h2 is filled only with air whose state is known, so a decrease in positioning accuracy in the next positioning operation can be prevented.

[0030] The timing of the air replacement operation in the second chamber h2 is not particularly limited. For example, it may be performed immediately after the piston 2p returns to the reference position, or immediately before starting the next positioning operation. In particular, performing it immediately before starting the next positioning operation allows the positioning operation to be performed without any change in the state of the air in the second chamber h2 after it has been sealed inside the second chamber h2, thus maintaining high positioning accuracy.

[0031] <Regarding the reduction of the effects of temperature changes> In order to prevent a decrease in positioning accuracy or misalignment due to changes in the temperature of the air in the first chamber h1 and the second chamber h2 of the pneumatic cylinder 2, the temperature of the air in the first chamber h1 and the second chamber h2 may be measured and the measurement results may be reflected in the equation of state.

[0032] <Correction by Effective Stroke LV1> In the pneumatic cylinder 2, the first chamber h1 and the second chamber h2 are connected to the pneumatic source 4 via piping 3 and a servo valve 5 (or manual valve). However, the piping 3 between the servo valve 5 and the second chamber h2 is a space DV (dead volume DV) where no change in volume occurs even when the piston 2p moves. Considering the air present in this space DV, the position control performance of the position control device of this embodiment can be improved. For example, if the volume of the space DV between the second chamber h2 and the servo valve 5 is Vd, then Vd is a constant value. Therefore, if we express the uncertain displacement element as ΔL and Vd = SΔL, then equation F1 becomes equation F1-2. Using this equation F1-2, the position control performance of the position control device of this embodiment can be improved. Equation F1-2 Pr1・(S・LV1) = P2r・(S・LV2) LV1: L1 + ΔL LV2: L2 + ΔL Pr1: Initial pressure of the second chamber h2 P2r: Pressure in the second chamber h2 when the object M is placed at the target position (target pressure) S: Pressure-receiving area of ​​the rod side surface 2f of the piston 2p L1: Maximum stroke amount of the pneumatic cylinder 2 L2: Distance from the rod side surface 2f of the piston 2p to the inner surface of the rod-side cylinder chamber when the object M is placed at the target position LV1: Effective stroke The effective stroke LV1 can be determined in advance, for example, by pressing the tip of the rod against a mechanical jig that provides precise displacement and measuring the pressure P2r at that time. Also, as mentioned above, if a control valve that opens and closes the connection between the second chamber h2 and the servo valve 5 is provided in the piping 3 that connects the two, the space from the second chamber h2 to the control valve becomes space DV (dead volume DV).

[0033] <Regarding the generation of control inputs in the control unit 10 of the positioning control device of this embodiment> When an object is moved and positioned using the positioning control device of this embodiment, the control unit 10 of the positioning control device of this embodiment has a function to generate control inputs for controlling pneumatic actuators and the like. Specifically, the control unit 10 of the positioning control device of this embodiment has a main control input generation unit 11 that generates general control inputs for controlling pneumatic actuators, and a compensation control input generation unit 15 that receives general control inputs. The compensation control input generation unit 15 of the control unit 10 of the control input generation device of this embodiment will be described below.

[0034] <Compensation Control Input Generation Unit 15> First, in the case of a pneumatic cylinder 2, the compressibility of the air and the influence of friction between object M and other objects greatly affect the control accuracy (i.e., the difference between the stopping position of object M and the target value Lr). For this reason, in order to improve the control accuracy, the main control input generation unit 11 is generally configured as a control system using a disturbance observer. However, even when a control system using a disturbance observer is used, if the main control input generation unit 11 generates the control input using a general control method, it is difficult to raise the control accuracy above a certain level. This is for the following reasons.

[0035] In the positioning control system shown in Figure 12, the controller (having the same function as the main control input generation unit 11) controls the pneumatic cylinder 2 using a general control method (e.g., PD control). The positioning control system shown in Figure 12 includes a force generation control system, and by applying disturbance observers to each, the effects of parameter fluctuations due to load changes, nonlinearity of the pressure response section, and frictional forces are compensated for. In the disturbance observer in Figure 12, the controlled object P of the generated force is... ｆ and the object of motion control P ｋ Since the effects of variations from the nominal model are also estimated as disturbances, in order to guarantee the stability of the control system, the disturbances are passed through low-pass filters Qk and Qf to estimate disturbance D. ｆｅ , D ｐｅIt is adapted to be input to the target generated force Fr and the control input U. Note that each parameter in FIG. 12 indicates the following. F ｒ : Target generated force U: Control input P ｆ : Control target of generated force P ｋ : Control target of motion P ｆｎ －１ : Inverse nominal model of control target of generated force P ｋｎ －１ : Inverse nominal model of control target of motion Q ｆ : D ｐ : Low-pass filter for estimated value of Q ｋ : D ｆ : Low-pass filter for estimated value of D ｆ : Frictional force and external force D ｐ : Disturbance to pressure response part D ｆｅ : D ｆ : Estimated value of D ｐｅ : D ｐ : Estimated value of

[0036] When the operation of the pneumatic cylinder 2 is controlled by such a positioning control system, even if the object M moves to the target value Lr, it does not stop at the target value Lr but overshoots, and a typical stick-slip phenomenon occurs. This is a phenomenon that occurs because although the generated force F can follow the target generated force Fr, the target generated force Fr does not change even when the deviation shrinks. When the deviation e becomes extremely small, in addition to the weakening of the braking action due to the differential operation of PD control, it is considered that the cause is that the control system is of type 1 and has an integral characteristic, so the response to the variation of the deviation e becomes dull. As a countermeasure to reduce such overshoot, there is a method of increasing the differential gain K ｄ However, in this case, there is a problem that the stability in the transient state is significantly reduced.

[0037] On the other hand, in the control unit 10 of the positioning control device of this embodiment, as shown in Figures 3 and 4, a compensation control input generation unit 15 is provided to generate a compensation input Yc that corrects the main input generated by the main control input generation unit 11, thus configuring a positioning control system. In other words, in the control unit 10 of this embodiment, the compensation input Yc generated by the compensation control input generation unit 15 is added to the main input as a control input, and by inputting a control input including such compensation input Yc, the stick-slip phenomenon of the pneumatic cylinder 2 is suppressed, and the accuracy of positioning control of the object M is improved.

[0038] The compensation control input generation unit 15 that generates the compensation input Yc has, as shown in Figure 1, a first control input generation function 16, a second control input generation function 17, and an output generation function 18, and has the function of generating the compensation input Yc when the target value Lr, the control amount L, and the velocity v are input. Note that when controlling pressure or force instead of position as in this embodiment, the target value Lr and the control amount L become force or pressure, the deviation e becomes the pressure deviation, and the velocity v becomes the derivative of pressure (see Figure 8).

[0039] Specifically, the system has a function to generate a compensation input Yc (Yc = S1 - S2) using a first control input S1 generated by a first control input generation function 16 and a second control input S2 generated by a second control input generation function 17. The first control input S1 is an input that promotes the movement of the pneumatic cylinder 2 toward a target value Lr (an input that causes the pneumatic cylinder 2 to exert an accelerator function), and the second control input S2 is an input that suppresses the movement of the pneumatic cylinder 2 toward a target value Lr (an input that causes the pneumatic cylinder 2 to exert a brake function). By appropriately generating the first control input S1 and the second control input S2, the positioning control accuracy of placing the object M at the target position using the compensation input Yc can be improved to the level of the detection accuracy of the position sensor.

[0040] <First Control Input Generation Function 16> The first control input generation function 16 has the function of generating a first control input S1 when there is a deviation e between the target value Lr and the controlled amount L. Specifically, the first control input generation function 16 has the function of generating a steady-state control input as the first control input S1. For example, the first control input generation function 16 generates the first control input S1 based on the following equation 1. Equation 1 S1 = K １ sgn(e) e: Deviation between target value Lr and controlled variable L K １ = Gain that compensates for the nonlinear friction of the pneumatic cylinder 2 and generates thrust. Note that sgn(e) is a function that outputs 1 when e > 0, -1 when e < 0, and 0 when e = 0.

[0041] <Second Control Input Generation Function 17> The second control input generation function 17 has the function of generating a second control input S2 that increases as the deviation e between the target value Lr and the control quantity L decreases, when there is a time change in the control quantity L. Specifically, the second control input generation function 17 has a predicted step count calculation function 17b that calculates the predicted number of steps N until the control quantity L matches the target value Lr, based on the deviation e between the target value Lr and the control quantity L and the velocity v. The second control input generation function 17 has the function of generating a second control input S2 that increases as this predicted step count N decreases, based on the predicted number of steps N calculated by the predicted step count calculation function 17b.

[0042] For example, the second control input generation function 17 can generate the second control input S2 based on the following equation 2. Note that the displacement velocity v of the pneumatic cylinder 2 is the same as the movement velocity v of the piston in Figure 3. Equation 2 S2 = K2 / N α sgn(v) e: Deviation of the controlled variable from the target value v: Operating speed of the pneumatic cylinder 2 α: Index to adjust the timing at which the suppressing force that inhibits the operation of the pneumatic cylinder 2 begins to act K ２ = A gain that generates a suppression force to reduce overshoot with respect to the target value Lr. Note that sgn(v) is a function that outputs 1 when v > 0, -1 when v < 0, and 0 when v = 0.

[0043] <Third Control Input Generation Function 18> The third control input generation function 18 has the function of generating a compensation input Yc based on the first control input S1 generated by the first control input generation function 16 and the second control input S2 generated by the second control input generation function 17. The third control input generation function 18 corresponds to the output generation function referred to in claim 6 of the claims.

[0044] For example, the compensation control input generation unit 15 can generate a compensation input Yc based on the following equation 3: Equation 3: Yc = K １ ・sgn(e)-K2 / N α sgn(v) e: Deviation between target value Lr and controlled variable L v: Displacement velocity of pneumatic cylinder 2 α: Index to adjust the timing at which the suppressing force that inhibits the operation of pneumatic cylinder 2 begins to act K １ = Gain K that compensates for the nonlinear friction of the pneumatic cylinder 2 and generates thrust. ２ = Gain that generates a suppressive force to reduce overshoot relative to the target value Lr.

[0045] As described above, the third control input generation function 18 generates a compensation input Yc by combining the first control input S1 generated by the first control input generation function 16 and the second control input S2 generated by the second control input generation function 17, thus providing the following advantages.

[0046] First, when the first control input generation function 16 generates the first control input S1 according to the above equation 1, the first control input S1 becomes an on / off control that changes in three stages. Then, if there is a deviation e between the target value Lr and the controlled amount L, the compensation signal Yc will include a steady value with the same sign as the deviation e as the first control input S1, and if the deviation e is 0, the first control input S1 will be 0. Therefore, since the compensation signal Yc, which includes a constant first control input S1 regardless of the magnitude of the deviation e, is added to the main input Ms as the control input, the responsiveness in transient states can be improved. For example, friction generated in the piston of the pneumatic cylinder 2 or in object M can be compensated for near the target value Lr, so the responsiveness near the target value Lr can be improved.

[0047] Furthermore, when the second control input generation function 17 generates the second control input S2 according to the above equation 2, if there is velocity, that is, if the piston of the pneumatic cylinder 2 is moving, the compensation signal Yc will be the second control input S2, which is inversely proportional to the expected number of steps N, subtracted from the first control input S1. If the velocity is 0, the second control input S2 will be 0, so the first control input S1 will become the compensation signal Yc. Therefore, the effect of suppressing (braking) the operation of the pneumatic cylinder 2 near the target value Lr is enhanced, so the occurrence of the stick-slip phenomenon can be suppressed and a highly accurate positioning effect at the target value Lr can be obtained.

[0048] As described above, in the control unit 10 of this embodiment, the compensation input Yc generated by the compensation control input generation unit 15 is added to the main input Ms generated by the main control input generation unit 11 to form a control input. This improves the responsiveness of the pneumatic cylinder 2 in transient states and allows for highly accurate positioning at the target value Lr.

[0049] <State of Compensation Input Yc> The following describes the process until the object M comes to rest at the target value Lr (until the control converges), based on Figures 5 and 6.

[0050] The compensation signal Yc is determined by the difference e between the target value Lr and the controlled variable L, and the sign of the displacement velocity v (displacement velocity v of the pneumatic cylinder 2), as shown in the table in Figure 5. Therefore, when the pneumatic cylinder 2 starts operating from a state where it is not operating (for example, e > 0, v = 0), the compensation signal Yc = K １ As a result, the pneumatic cylinder 2 moves toward the target value Lr (forward movement). As the pneumatic cylinder 2 moves toward the target value Lr and approaches the target value Lr, the deviation e decreases, and eventually the second control input S2 (K2 / N) α Due to the effect of (), the speed of the pneumatic cylinder 2 decreases, and eventually the operation of the pneumatic cylinder 2 stops (v = 0).

[0051] At this time, if the controlled amount L of the pneumatic cylinder 2 matches the target value Lr (e=0), the pneumatic cylinder 2 will remain stationary. On the other hand, if there is a deviation e even when the operation of the pneumatic cylinder 2 has stopped (if it stops before the target value Lr, e>0), the first control input S1(K １ Due to the influence of ), the pneumatic cylinder 2 starts operating and moves toward the target value Lr.

[0052] When moving towards the target value Lr, the second control input S2(K2 / N) α Due to the influence of (v=0), the operation of the pneumatic cylinder 2 stops. In this case, if it stops before reaching the target value Lr (e>0), the state of moving in the forward direction and stopping is repeated until the controlled amount L of the pneumatic cylinder 2 matches the target value Lr.

[0053] On the other hand, if the controlled amount L of the pneumatic cylinder 2 exceeds the target value Lr (e < 0), the first control input S1 (K １ ) and second control input S2 (K2 / N α Both of these function as brakes, quickly stopping the operation of the pneumatic cylinder 2 (v=0). In this case, a deviation e occurs (e<0), so the first control input S1(K １ Due to the influence of the above, the pneumatic cylinder 2 starts operating and moves toward the target value Lr. In other words, it starts moving toward the target value Lr in the opposite direction to the initial direction of movement (reverse movement).

[0054] When the pneumatic cylinder 2 starts operating, the second control input S2 (K2 / N) α Due to the influence of (), the speed of the pneumatic cylinder 2 decreases, and eventually the operation of the pneumatic cylinder 2 stops (v=0). At this time, if the controlled amount L of the pneumatic cylinder 2 matches the target value Lr (e=0), the pneumatic cylinder 2 remains stationary. On the other hand, if it stops before reaching the target value Lr (e<0), the state of moving in the opposite direction and stopping is repeated until the controlled amount L of the pneumatic cylinder 2 matches the target value Lr.

[0055] Furthermore, even in the reverse direction of movement, the controlled amount L of the pneumatic cylinder 2 may become smaller than the target value Lr (e > 0). In this case, similar to the case of overshoot, the first control input S1 (K１ ) and second control input S2 (K2 / N α Both of these function as brakes, quickly stopping the operation of the pneumatic cylinder 2 (v=0). In this case, a deviation e occurs (e>0), so the first control input S1(K １ Due to the influence of ), the pneumatic cylinder 2 starts operating, and the state of moving in the forward direction and stopping is repeated.

[0056] As described above, the pneumatic cylinder 2 can adjust the controlled amount L to match the target value Lr by repeatedly moving toward the target value Lr and stopping due to the compensation input Yc. Moreover, the first control input S1(K) when restarting after stopping １ Since ) is constant, even if the deviation e is small, the pneumatic cylinder 2 can be moved again at high speed from a stopped state. Also, near the target value Lr, the second control input S2 (K2 / N α As the size increases, the occurrence of stick-slip phenomena can be suppressed, and positioning to the target value Lr with high precision can be achieved.

[0057] <About the First Control Input Generation Function 16> The first control input generation function 16 has been described in the case where it generates a steady-state control input as the first control input S1. However, the first control input generation function 16 may also have the function of generating a first control input S1 that combines a steady-state control input with a variable control input that decreases as the deviation e of the controlled quantity L with respect to the target value Lr decreases. For example, in the initial stage of a transient response where the deviation is relatively large, advantages such as improved responsiveness can be obtained by adding a variable control input to the first control input S1.

[0058] <Gain K of the first control input S1> １ and the gain K of the second control input S2 ２ Regarding > Gain K of the first control input S1 １ and the gain K of the second control input S2 ２The gain K of the first control input S1 may be the same regardless of the direction of movement of the pneumatic cylinder 2, but it may also be different depending on the direction of movement of the pneumatic cylinder 2. When the pneumatic cylinder 2 is a single-rod cylinder, the pressure-receiving area of ​​the piston differs on both sides of the piston due to the influence of the rod. Therefore, in the case of a single-rod cylinder, the pushing motion of the piston (movement on the opposite side of the rod) generates more force than the pulling motion of the piston (movement on the rod side). In other words, the pushing motion makes it easier to move the piston than the pulling motion. Therefore, when the pneumatic cylinder 2 is a single-rod cylinder, the gain K of the first control input S1 depends on the direction of movement of the piston as follows. １ and the gain K of the second control input S2 ２ You may change it. K １ = K １ a (e > 0) K １ = K １ b (e < 0) K ２ = K ２ a(v>0) K ２ = K ２ b (v < 0) where K １ a < K １ b, K ２ a < K ２ b

[0059] Furthermore, the pneumatic cylinder 2 is also affected when a force is applied in one direction. Consequently, even when the same amount of movement or speed of movement is achieved, the required force, or in other words, the differential pressure generated between the first chamber h1 and the second chamber h2 of the pneumatic cylinder 2, will differ depending on the direction of piston movement. Therefore, even when an external force is applied to the pneumatic cylinder 2 in the direction of a pushing motion, the gain K of the first control input S1 will be affected in the same way as described above. １ and the gain K of the second control input S2 ２ You may set this. On the other hand, if an external force is applied to the pneumatic cylinder 2 in the direction of pulling, K １ a>K １ b, K ２ a>K ２ The gain K of the first control input S1 is set to b. １ and the gain K of the second control input S2 ２ You may set it to that.

[0060] Furthermore, the gain K of the first control input S1 １ and the gain K of the second control input S2 ２ The gain K of the first control input S1 may be a fixed value (constant), but it may also be made to change according to the actual deviation or displacement velocity. １ By setting it as shown in Equation 2-1, a predetermined input can be generated that promotes movement toward the target value until the deviation e reaches the required positioning accuracy (required deviation). On the other hand, when the absolute value of the deviation e |e| becomes smaller than the required deviation, it can be set to an input that dampens the movement, thereby further improving responsiveness near the target value. Also, the gain K of the second control input S2 ２ Set as shown in Equation 2-2, and when the displacement velocity becomes smaller than the required displacement velocity (required displacement velocity), the gain K ２ Setting this to 0 prevents the second control input S2 from becoming unstable in the extremely low-speed range where the effect of noise becomes significant. Equation 2-1 K １ =Ka |e| > Eth K １ = Ka / (Eth * |e|) When |e| ≤ Eth Ka: Minimum control input that causes displacement Eth: Required positioning accuracy (required deviation) (deviation threshold) |e|: Absolute value of deviation e Equation 2-2 K ２ =Kb |v|>Vth K ２ = 0 |v| ≤ Vth Kb: Minimum control input that causes displacement Vth: Threshold of displacement velocity considering the effect of observation noise |v|: Absolute value of velocity v

[0061] The gain K of the first control input S1 is as shown in Equation 2-1. １ When you set it, gain K １ The relationship between the first control input S1 and the deviation e is as shown in Figure 13(A). Also, the gain K of the second control input S2 is as shown in Equation 2-2. ２ When you set it, gain K ２ The relationship between the second control input S2 and the displacement velocity v is as shown in Figure 13(B).

[0062] In this invention, based on the following technical concept, the compensation input Yc is generated by the first control input S1 and the second control input S2 as described above.

[0063] First, using equations 2-1 and 2-2 described above, the gain K of the first control input S1 １ and the gain K of the second control input S2 ２ When setting and generating the compensation input Yc based on equation 3, the gain K of the first control input S1, which is the first term, １The gain is designed to exceed the maximum static friction force. Therefore, the first control input S1 is designed to be a control input that moves the controlled object so that its displacement does not stop until the deviation reaches a predetermined threshold (until the absolute value of the deviation becomes smaller than the predetermined threshold) under any conditions or environment (it is designed to be a control input that reaches a state where the absolute value of the deviation reaches a predetermined threshold). Even if the displacement of the controlled object seems to stop in the process of reaching a state where the absolute value of the deviation reaches a predetermined threshold, the movement of the controlled object can be continued until the absolute value of the deviation reaches a predetermined threshold by making the second control input S2 of the second term a value close to 0. In other words, when the absolute value of the deviation approaches a predetermined threshold and the controlled object is about to stop, the expected number of steps N becomes large (in other words, the change in displacement ΔL from one sampling time becomes a small value), so the second control input S2 of the second term, which applies a braking force to the movement of the controlled object in the compensation input Yc, becomes a value close to 0. Then, the compensation input Yc is essentially in the state of only the first term, so the controlled object can overcome the friction force and continue to operate. On the other hand, the second control input S2 is designed so that when the deviation falls within a predetermined threshold (the absolute value of the deviation becomes smaller than the predetermined threshold) and reaches the target value (e=0), if the velocity (absolute value of the velocity) at that time exceeds a predetermined threshold, a braking force is generated on the controlled object to stop its movement, and the displacement is stopped there. Furthermore, by designing the first control input S1 and the second control input S2 as described above, when the deviation is within a predetermined threshold (when the absolute value of the deviation is smaller than the predetermined threshold), the function of the first control input S1 in the first term provides the effect of quickly returning the deviation to within the threshold even if it falls outside the predetermined threshold (when the absolute value of the deviation becomes larger than the predetermined threshold). Since the main controller generally has an integrator, as long as the deviation is not zero, a signal is output that integrates the deviation in an attempt to make it zero. As a result, it is usually possible for the deviation to fall outside the predetermined threshold, but the effect of the first control input S1 in the first term above quickly returns the deviation to within the threshold.Furthermore, by designing the first control input S1 and the second control input S2 as described above, even if some external force acts and the speed (absolute value of speed) of the controlled object exceeds a predetermined threshold, and the deviation falls outside the predetermined threshold (the absolute value of the deviation becomes larger than the predetermined threshold), the function of the second control input S2 (described in the second term) allows a large braking force to be applied to the controlled object to prevent the deviation from deviating too far from the threshold. As a result, the effect of the first control input S1 (described in the first term) quickly brings the deviation back within the threshold.

[0064] <About the Predicted Step Count Calculation Function 17b> The method by which the Predicted Step Count Calculation Function 17b of the Second Control Input Generation Function 17 calculates the predicted step count N is not particularly limited. For example, the predicted step count N may be the time required for the controlled variable L to match the target value Lr, based on the sampling period Δt (for example, the period during which the position sensor detects the controlled variable L) used to detect the deviation e between the target value Lr and the controlled variable L. In other words, as shown in Figure 1, the Second Control Input Generation Function 17 may be provided with a destination time calculation function 17a that calculates the time (destination time Ta) from the current value to the target position, and the value obtained by dividing the destination time Ta calculated by this destination time calculation function 17a by the sampling period Δt (i.e., N = Ta / Δt) may be used as the predicted step count N. If the Predicted Step Count Calculation Function 17b calculates the predicted step count N in this way, the advantage of making the calculation of the predicted step count N easier can be obtained. Note that N = Ta / Δt may also be calculated by the following equation 5. Note that v・Δt is the same as the amount of displacement ΔL per sampling period (in other words, the change in displacement from one sampling time before). Equation 5 N(e,v) = e / ΔL = e / (v・Δt) e: deviation between target value Lr and controlled amount L v: displacement velocity of pneumatic cylinder 2 ΔL: change in displacement from one sampling time before

[0065] Alternatively, N in Equation 5 may be determined by the following Equation 5-1. Equation 5-1 N(Lr, L) = (Lr(k) - L(k)) / (L(k) - L(k-1)) Lr(k): Target position L(k): Current position L(k-1): Current position one step ago Note that the target position and current position are values ​​obtained from the equation of state based on the pressure in the second chamber.

[0066] Furthermore, the predicted step count calculation function 17b may also have a function to set the predicted step count N to the threshold X if the predicted step count N is smaller than a predetermined threshold X. For example, if the threshold X is set to 1, the predicted step count calculation function 17b may also have a function to set the predicted step count N to 1 if the predicted step count N becomes smaller than 1.

[0067] The reasons for providing such a function are as follows: For example, if the second control input S2 has a gain (K2 / N) as described above. α If the system has a second control input S2, and the velocity v is too large relative to the deviation e between the target value Lr and the controlled variable L, the second control input S2 may become extremely large and diverge to infinity, potentially causing the control system to malfunction. Therefore, in order to limit the value of the second control input S2 and prevent the control system from malfunctioning, it is desirable to set the threshold X to the minimum value of the expected number of steps N.

[0068] In the above example, the case where the second control input S2 is generated by Equation 2 was explained, but the method by which the predicted step count calculation function 17b generates the second control input S2, that is, the equation for generating the second control input S2 (second control input generation equation), is not limited to Equation 2. It is sufficient to generate the second control input S2 such that it increases as the predicted step count N decreases. In other words, it is sufficient to generate the second control input S2 so that the operation of the actuator can be appropriately converged by the compensation input Yc generated based on the first control input S1 and the second control input S2. That is, it is sufficient to adopt a second control input generation equation that generates a second control input S2 that can bring the convergence of the actuator's operation to a desired state.

[0069] <Regarding the calculation method of arrival time Ta> In the second control input generation function 17, the method by which the arrival time calculation function 17a calculates the arrival time Ta, which is the time required for the controlled variable L to match the target value Lr, is not particularly limited. For example, in the following equation 4, assuming a and v are known values, the arrival time Ta can be calculated using, for example, Newton's method. Equation 4 (1 / 2)・a・Ta ２ +v・Ta - e = 0 a: Displacement acceleration of pneumatic cylinder 2 v: Displacement velocity of pneumatic cylinder 2 Ta: Arrival time (Arrival time - Current time) e: Deviation (Target position - Current position) Note that the target position and current position are values ​​obtained from the equation of state based on the pressure in the second chamber.

[0070] <Regarding the Third Control Input Generation Function 18> In the above example, the case in which the third control input generation function 18 generates a compensation input Yc based on equation 3 was explained, but the equation (compensation input generation equation) used by the third control input generation function 18 to generate the compensation input Yc is not particularly limited. A compensation input generation equation can be adopted that can generate a compensation input Yc that can appropriately converge the operation of the actuator based on the first control input S1 and the second control input S2. In other words, a compensation input generation equation can be adopted that can generate a compensation input Yc that can bring the convergence of the actuator's operation to a desired state based on the first control input S1 and the second control input S2.

[0071] <Calculation Circuit> The control unit 10 of the positioning control device in this embodiment may be configured as a calculation circuit. That is, a calculation circuit having an input terminal into which the target value and the current value are input as input signals, and an output terminal that outputs a signal equivalent to the control input generated by the control input generation device of this embodiment as an output signal may be manufactured, and this calculation circuit may be used as the control unit 10 of the positioning control device in this embodiment.

[0072] In other words, when a target value and a controlled variable are input as input signals, a circuit can be formed that includes a first control input generation unit that generates a first control input when there is a deviation of the controlled variable from the target value, a second control input generation unit that generates a second control input that increases as the deviation of the controlled variable from the target value decreases when there is a time change in the controlled variable, and an output generation unit that generates and outputs a control input based on the first control input and the second control input, and can be provided as the control unit 10 of the positioning control device of this embodiment. For example, a circuit with the configuration shown in Figure 9 can be used to configure the control unit 10 of the positioning control device of this embodiment having the above functions.

[0073] <Control Board> The control unit 10 of the positioning control device in this embodiment may be configured as a control board. That is, a control board may be manufactured that has input terminals into which the target value and the current value are input as input signals, and output terminals that output a signal equivalent to the control input generated by the control input generation device of this embodiment as an output signal, and this control board may be used as the control unit 10 of the positioning control device in this embodiment.

[0074] For example, the control board B shown in Figure 10(A) is equipped with an input terminal IT to which a target value and a control variable (a signal from a pressure sensor in Figure 10(A)) are input. Based on the input target value and control variable, a main controller MC generates a control input (main control input) equivalent to that of a general control device, and a compensator CM has the same function as the compensation control input generation unit 15 described above (i.e., it has the function of generating a compensation control input). The control board B is equipped with an output generation unit D3, which is an addition circuit that generates a control input by combining (adding) the main control input and the compensation control input, and an output terminal OT that outputs the control input generated by the output generation unit D3 to the outside. By providing such a control board B, the control input generation method of this embodiment can be introduced into the control of existing equipment by replacing the existing control device (control board) with the control board B.

[0075] In Figure 10(A), the main control input generated by the main controller MC is first output from the output terminal OT and then input to the input terminal and supplied to the power generation unit D3. However, the main control input generated by the main controller MC may be configured to be directly input to the output generation unit D3 without being output from the output terminal OT. In the configuration of Figure 10(A), it is also possible to supply only the main control input output from the output terminal OT, that is, without combining it with the compensation control input, as the control input to the controlled object, thereby increasing the degree of freedom in controlling the controlled object.

[0076] Furthermore, when introducing the control unit 10 of the positioning control device of this embodiment to the positioning control of existing equipment, the control board B may be configured to generate a control input including a compensation input by utilizing the control input output by the existing control device EM, that is, an external control input. For example, as shown in Figure 10(B), the control board B is provided with an input terminal IT for inputting target values ​​and control quantities, as well as an input terminal IT for inputting the control input output by the existing equipment's control device EM. The output generation unit D3 may then use the control input received from this input terminal IT as the main control input to generate the control input. By providing such a control board B, the control according to the positioning control device method of this embodiment can be introduced to the existing control device EM simply by connecting the control board B to the existing control device EM.

[0077] <Control Input Generation Program> In the example described above, the control method of the positioning control device of this embodiment was introduced by making the control unit 10 of the positioning control device of this embodiment a control board. However, it is also possible to introduce the control method of the control input generation method of this embodiment by using a program that implements the control input generation method of this embodiment.

[0078] In other words, it is possible to introduce control by the positioning control method of this embodiment to the controlled object by installing a program that implements the positioning control method of this embodiment on the actuator to be controlled or on the control equipment (computer, etc.) of the machine or device employing such actuator, or by providing the program via an internet connection. When installing the program on the control equipment, the program may be provided and installed via an internet connection, or the program may be stored on a storage medium readable by the control equipment and the program may be installed from that storage medium.

[0079] For example, when a target value and a controlled variable are input as input signals, a program (the control input generation program of this embodiment) is installed in the control equipment of an existing machine or device. This program performs the following functions: a first control input generation function that generates a first control input when there is a deviation of the controlled variable from the target value; a second control input generation function that generates a second control input that increases as the deviation of the controlled variable from the target value decreases when there is a time change in the controlled variable; and an output generation function that generates and outputs a control input based on the first and second control inputs. By adding the compensation input generated by the control input generation program of this embodiment to the control input (main control input) generated by the control equipment of the existing machine or device, it becomes possible to implement control using the control input generation method of this embodiment in the existing machine or device.

[0080] Furthermore, the control input generation program of this embodiment may have a function to generate a control input corresponding to the main control input. In other words, the control input generation program of this embodiment may have a function to generate the main control input, a function to generate a compensation input, and a function to generate a control input based on the main control input and the compensation input. In this case, by installing the control input generation program of this embodiment in place of the existing control program in the control equipment of an existing machine or device, it becomes possible to introduce control by the control input generation method of this embodiment to the control equipment of the existing machine or device.

[0081] As a storage medium storing the control input generation program of the present embodiment, for example, a floppy (registered trademark) disk, a hard disk, an optical disk, a magneto-optical disk, a CD (Compact Disk)-ROM, a magnetic tape, a non-volatile memory card, or a ROM can be used. Also, not limited to those that execute processing with only the program itself, those that operate on an OS (Operating System) and execute processing in cooperation with other software or the functions of an expansion board are also included in the scope of each embodiment.

[0082] <Regarding the control amount> In the above example, the case where the control amount by the control unit 10 of the positioning control device of the present embodiment is the pressure of the air cylinder 2 or the force generated by the air cylinder 2 has been described. The control amount controlled by the control input or compensation input generated by the control unit 10 of the positioning control device of the present embodiment is not limited to the pressure of the air cylinder 2 or the force generated by the air cylinder 2 described above. For example, if it is set as the following formula 6 and each parameter corresponds to the table in FIG. 8, it is possible to generate and control a compensation input Yc (or a control input) for the displacement speed of the pneumatic cylinder 2 and the force generated in the pneumatic cylinder 2 in the same manner as the position control. Formula 6 Yc = K １ ·sgn(e) - K2 / N α ·sgn(v) N = e / (v·Δt) = (x ｒ (k) - x(k)) / (x(k) - x(k - 1)) xr(k): target value x(k): current value x(k - 1): current value one step before

[0083] Also, N in formula 6 may be obtained by the following formula 6-1. Formula 6-1 N(xr, x) = (xr(k) - x(k)) / (x(k) - x(k - 1)) xr(k): target value x(k): current value x(k - 1): current value one step before

[0084] <Regarding Constant Estimation> As mentioned above, the formula used by the compensation control input generation unit 15 to generate the compensation input Yc requires the setting of various constants such as gains. These constants are usually determined through trial and error. In other words, the control input generation device 1 of this embodiment is used to operate the controlled object (equipment operated by an air cylinder, etc.) while changing the constants, and the operating status is checked. The constants are then changed to achieve an appropriate operating state, and the final constants to be adopted are set.

[0085] For example, if the compensation input is generated by equation 3 described above, the gain K １ The controlled object is operated by a compensation input generated by setting constants such as K2 and the exponent α, and the result of that operation is evaluated to ultimately set the combination of constants that yields an appropriate evaluation as the final constant.

[0086] However, while it may be possible to find suitable constants relatively quickly when setting them in this way, it is more common for a very large number of experiments to be conducted before the desired operating accuracy can be achieved.

[0087] Therefore, by creating an estimation device that can estimate constants using machine learning models, it becomes possible to estimate appropriate constants based on the constants used in the experiment and their operating results, even with a small number of experiments.

[0088] For example, an evaluation function is set to evaluate the operation results when a controlled object is activated. Training data is collected that associates a constant set when the controlled object is activated, the result of evaluating the operation of the controlled object using the evaluation function based on the set constant (evaluation result), and the evaluation of the experimental results. Then, by training a machine learning model, which is an estimation device, with the training data, evaluation results can be obtained simply by inputting the constant into the estimation device, without having to conduct experiments using the controlled object.

[0089] The machine learning model used in the estimation device is not particularly limited, but support vector machines (SVM), neural networks (NN), random forests (RF), etc., can be used.

[0090] The evaluation function used to assess the operational accuracy described above can be appropriately chosen depending on the object being controlled and the amount of control it provides. For example, when the target is the position control of a pneumatic cylinder, the operational accuracy can be evaluated using the following equation 7 as the evaluation function (see Figure 11). In this case, the smaller the evaluation score S1, the more appropriately the position control is performed (the target trajectory R and the actual behavior A match). Equation 7 S1 = w1・OR + w2・PA S1: Evaluation score OR: Ratio of overshoot amount OS to target displacement amount DA (OS / DA) PA: Position accuracy polarity ACC > E: 1 ACC ≤ E: 0 w1, w2: Weights The position accuracy polarity PA is defined as follows: When the actual behavior A is in a stable state, if the difference ACC between the target displacement amount DA and the actual displacement amount RA in the stable state falls within a predetermined value E, then PA is 0; if it is greater than E, then PA is 1.

[0091] Furthermore, when an operating command (target trajectory R) as shown in Figure 11 is implemented, the following equation 8 can also be used as the evaluation function. With this evaluation function as well, the smaller the evaluation score S2, the more appropriately the position control is performed (the target trajectory R and the actual behavior A match). Equation 8 S2 = w3・OS + w4・ACC + w5・TM S1: Evaluation score OS: Overshoot amount relative to the target movement amount DA ACC: Difference between the target movement amount DA and the actual movement amount RA when the system is in a stable state TM: Time from the start of control until movement stabilizes w3, w4, w5: Weights

[0092] <Regarding the target control system> By employing the control input generation device 1 of this embodiment described above, the positioning control accuracy for placing object M at the target position can be improved to the detection accuracy of the position sensor. On the other hand, if there are changes in the external environment that affect the movement of object M, the positioning control accuracy may decrease during the response to the changes in the external environment (transient response). However, if the control input generation device 1 of this embodiment constitutes a type 2 control system with a disturbance observer and feedforward control is implemented to cancel its dynamics, the tracking accuracy to the target trajectory during transient response can be improved.

[0093] The method for designing the control input generation device 1 of this embodiment to constitute a type 2 control system having a disturbance observer is not particularly limited. For example, in the position control system shown in Figure 14, Gf(s) / (1-Q(s)・Gf(s)) (where Gf(s) is the transfer function of the force control system) is 1 / s ２ By designing the control system to independently include (1 / s is an integrator), the control input generation device 1 of this embodiment can be made into a type 2 control system with a disturbance observer.

[0094] As described above, when the control unit 10 of the positioning control device in this embodiment is designed to be a type 2 control system with a disturbance observer, even when changes in the external environment affecting the movement of object M occur, it is possible to suppress the decrease in tracking accuracy to the target trajectory during transient response caused by changes in the external environment. In other words, when controlling the movement of object M, even if changes in the external environment such as load fluctuations occur along the way, it is possible to maintain stable movement of object M.

[0095] The effectiveness of positioning control was confirmed using the position control method of the present invention.

[0096] The pneumatic cylinder used in the experimental setup was a general-purpose double-acting pneumatic cylinder (manufactured by SMC, model CDJ2E16-150Z-B, with an inner diameter of 16 mm and a rod length of 150 mm).

[0097] The double-acting pneumatic cylinder was driven by a flow-controlled servo valve (Festo, MPYE-5-M5-010-B) and a manual valve. Specifically, the pressure in the head chamber and rod chamber of the pneumatic cylinder was measured by a pressure sensor (Nidek Components, PA-500-103G), and the amount of air supplied to the head chamber was adjusted by the servo valve based on these measurements. The supply and closure of air to the rod chamber was controlled by a manual valve. The air supply pressure to the servo valve was 0.4 MPa.

[0098] To confirm the positioning effect of the position control method of the present invention, the displacement of the rod of a double-acting pneumatic cylinder was measured using a linear encoder (Magnescale BL50H, resolution 6.1 pm).

[0099] The control system that generates the control signals supplied to the servo valve is a Type 1 control system with a disturbance observer as shown in Figure 4. It is built on a PC using RTAI, a real-time extension of the Linux® kernel. Pressure data acquisition and voltage application to the servo valve by the control system are performed via SPI communication between various IC chips and a Raspberry Pi 4B. Pressure data is acquired by A / D conversion of the signal supplied from the pressure sensor, and voltage application to the servo valve by the control system is performed by D / A conversion of the control signals generated by the control system. Displacement data from the linear encoder of the control system is acquired via UART communication.

[0100] The control system's sampling period is 2ms, and socket communication between the Raspberry Pi 4B and the PC is performed via UDP. Since the process from A / D conversion request to obtaining the converted value takes approximately 0.5ms, real-time tasks can be executed with sufficient efficiency.

[0101] <Example 1> In Example 1, in order to confirm the positioning control by the position control method of the present invention, a double-acting pneumatic cylinder was controlled to move the tip of the rod from the initial state (see Figure 2(B)) to a predetermined position and stop at that position. In Example 1, the target value Pr1A1 was input in steps, and the pressure P2 in the rod side chamber and the position of the rod tip were confirmed in relation to the input. In Example 1, the experiment was repeated 10 times. The pressure P2 in the rod side chamber in the initial state was set to 150 kPa, and the target value of the pressure P1 in the head side chamber was set to 200 kPa.

[0102] The results are shown in Figures 15 and 16. As shown in Figure 15(A), in 10 experiments, the rod reached the target position in approximately 0.4 seconds each time, and the movement of the rod was controlled to maintain that position thereafter. Furthermore, as shown in Figure 15(B), in the 10 experiments, there was only an error of about 0.04 mm in the position of the rod tip 4 seconds after the start of movement, and it was confirmed that the repeatability of the positioning accuracy was 32 μm. In other words, it was confirmed that the position control method of the present invention can appropriately position the tip of the rod. Figure 16 shows the box plot of the position of the rod tip from 2 to 4 seconds after the start of movement, and the average value of the standard deviation was 5 μm. From these results, it was confirmed that if the position control method of the present invention is used to position the tip of the rod, the variation is very small and the position can be maintained stably.

[0103] In this experiment, the air in the rod-side chamber was not replaced when returning to the initial state. Therefore, we believe that positioning accuracy could be further improved if the air in the rod-side chamber were replaced when returning to the initial state.

[0104] <Example 2> In Example 2, the robustness of the positioning method of the present invention was confirmed. Example 2 was carried out using the apparatus shown in Figure 17. In this apparatus, a table supported by a frame was provided, and this table was lifted by a pneumatic cylinder. Specifically, the table was positioned so that it could move along the vertical direction guided by the frame, but could not move below a predetermined height. The pneumatic cylinder was then positioned to contact the table from below. In other words, the pneumatic cylinder was positioned so that its axial direction was parallel to the vertical direction, and so that the cylinder could extend and retract along the vertical direction. Then, when the pneumatic cylinder extended, the table could be lifted by the pneumatic cylinder. A plate was provided at the tip of the rod of the pneumatic cylinder to stably support the table.

[0105] Furthermore, in Example 2, as shown in Figure 18, when a control signal (Reference, target value) for controlling the operation of the pneumatic cylinder was input, the position control status of the pneumatic cylinder was confirmed in two cases: when a compensator employing a control input generation method designed to make the control system a Type 1 control system with a disturbance observer was applied (Conventional, device 1), and when a compensator employing a control input generation method designed to make the control system a Type 2 control system with a disturbance observer was applied (Improved, device 2). Both device 1 and device 2 implemented feedforward (FF) control.

[0106] The results are shown in Figure 18. As shown in Figure 18, it can be confirmed that even with device 1, although there is a slight delay in reaching the target value during load changes, the fluctuations generally follow the target value. On the other hand, with device 2, the delay from the target value is very small, and it can be confirmed that the fluctuations are almost equivalent to the target value.

[0107] From the above results, it was confirmed that by adopting the positioning method of the present invention, the operation of the pneumatic cylinder can be controlled to show good tracking performance with respect to the target value, even when there are load fluctuations. In particular, it was confirmed that by designing the control system to be a type 2 control system with a disturbance observer, the operation of the pneumatic cylinder can be controlled to move in a manner that closely matches the target value, even when there are load fluctuations.

[0108] <Example 3> In Example 3, the pressure-following performance of the positioning method of the present invention was confirmed. In the experiment, similar to Example 1, the pressure-following performance was confirmed when the pressure P2 in the rod-side chamber in the initial state was set to 150 kPa and the target value of the pressure P1 in the head-side chamber was set to 200 kPa. In Example 3, the same apparatus and conditions as in Example 1 were used, except that a KEYENCE AP-43 pressure sensor was used to measure the pressure in both cylinder chambers.

[0109] The results are shown in Figure 20. Figure 20(A) shows the results when compensation control is not implemented, and Figure 20(B) shows the results when compensation control is implemented, that is, when the position control method of the present invention is adopted.

[0110] As shown in Figure 20, when compensation control is not implemented, it can be confirmed that the pressure P1 in the head chamber and the position of the rod tip are fluctuating around the target value. On the other hand, when compensation control is implemented (when the position control method of the present invention is implemented), it can be confirmed that the pressure P1 in the head chamber and the position of the rod tip are able to follow the target value without any vibration. The characteristic of following the target value without vibration is an important performance characteristic because it is directly related to steady-state position control performance, and it can be confirmed that this characteristic of following the target value without vibration can be achieved by adopting the position control method of the present invention.

[0111] Furthermore, when the above test was performed five times, the variation in displacement of the rod tip, i.e., the positioning error relative to the target position, was confirmed. The results are shown in Figure 21. Figure 21(B) is an enlarged view of the graph in Figure 21(A) in the displacement direction, that is, an enlarged view of the vicinity of the target position of the rod tip. As shown in Figure 21, it can be confirmed that the positioning error was approximately 150 μm after 5 seconds from the start of control, and approximately 100 μm after 10 seconds. The measurement resolution of the pressure sensor is considered to be a factor in the positioning error, so it is thought that the positioning error can be reduced further if the measurement resolution of the pressure sensor is improved.

[0112] Furthermore, Figure 22 shows the step response results when the target position was alternately set to 10 mm and 50 mm. Figure 22(A) shows the experimental results without considering the dead volume between the rod side chamber and the manual valve (hereinafter simply referred to as "dead volume"), that is, the stroke was set to 150 mm, which is the catalog value of the double-acting pneumatic cylinder used, while Figure 22(B) shows the results when the effective stroke considering the dead volume was used. In the preliminary experiment, the effective stroke length was 161.4 mm. Comparing Figure 22(A) and Figure 22(B), it can be seen that the positioning accuracy has improved in Figure 22(B). Also, Figure 22(C) is a magnified view of the vicinity of the target position at the tip of the rod, and it can be seen that the positioning error can be reduced to ±100 μm. As mentioned above, it is thought that the positioning error can be further reduced if the measurement resolution of the pressure sensor is improved.

[0113] The positioning control device of the present invention is suitable as a device for positioning an object by controlling the operation of an actuator that is operated by pneumatic pressure.

[0114] 1 Control system 2 Pneumatic cylinder 3 Piping 4 Pneumatic source 5 Servo valve 10 Control device 11 Main control input generation unit 15 Compensation control input generation unit 16 First control input generation function 17 Second control input generation function 17a Arrival time calculation function 17a 17b Predicted number of steps calculation function 18 Output generation function S1 First control input S2 Second control input Yc Compensation input L Control amount Lr Target value e Deviation

Claims

1. A control device for positioning an object by controlling a pneumatic actuator having a first chamber and a second chamber airtightly separated by a moving member, comprising: a gas supply unit for supplying and discharging gas to the first chamber and the second chamber of the pneumatic actuator; and a control unit for controlling the supply of gas to the first chamber and the second chamber of the pneumatic actuator by the gas supply unit, wherein the control unit controls the amount of movement of the moving member by controlling the supply of gas to the first chamber of the pneumatic actuator while the second chamber of the pneumatic actuator is airtightly sealed.

2. The positioning control device according to claim 1, characterized in that the control unit sets a target pressure for the second chamber of the pneumatic actuator based on the ideal gas law, and controls the supply of gas to the first chamber of the pneumatic actuator so that the pressure in the second chamber becomes the target pressure.

3. The positioning control device according to claim 1 or 2, characterized in that, before controlling the amount of movement of the moving member, the control unit supplies gas to the second chamber of the pneumatic actuator with the volume of the first chamber of the pneumatic actuator set to zero, and then airtightly seals the second chamber of the pneumatic actuator.

4. The positioning control device according to claim 3, characterized in that, after the previous positioning operation is completed, the control unit reduces the volume of the first chamber of the pneumatic actuator to a state close to zero, then replaces the gas in the second chamber of the pneumatic actuator, and after the replacement is completed, seals the second chamber of the pneumatic actuator airtight.

5. The positioning control device according to claim 1, characterized in that, after positioning an object, the control unit controls the supply of gas to the first chamber of the pneumatic actuator so that the differential pressure between the first chamber of the pneumatic actuator and the second chamber of the pneumatic actuator becomes constant.

6. The positioning control device according to claim 1, wherein the control unit has a function to generate a control input for controlling the pneumatic actuator, and the control unit has a first control input generation function that generates a first control input when there is a deviation of the controlled amount from a target value, a second control input generation function that generates a second control input that increases as the deviation of the controlled amount from a target value decreases when there is a time change in the controlled amount, and an output generation function that generates the control input based on the first control input and the second control input.

7. The positioning control device according to claim 6, characterized in that the first control input generation function has a function to generate a steady-state control input as the first control input, or, when there is a time change in the control variable, has a function to generate a control input as the first control input that combines a variable control input which decreases as the deviation of the control variable from the target value decreases and a steady-state control input.

8. The positioning control device according to claim 1, characterized in that the pneumatic actuator is a pneumatic cylinder, and the first chamber and the second chamber of the pneumatic actuator are a chamber located on the head side of the pneumatic cylinder and a chamber located on the rod side of the pneumatic cylinder, respectively.

9. A control method for positioning an object by controlling a pneumatic actuator having a first chamber and a second chamber airtightly separated by a moving member, characterized in that the amount of movement of the moving member is controlled by controlling the supply of gas to the first chamber of the pneumatic actuator while the second chamber of the pneumatic actuator is airtightly sealed.

10. The positioning control method according to claim 9, characterized in that a target pressure is set for the second chamber of the pneumatic actuator based on the ideal gas law, and the supply of gas to the first chamber of the pneumatic actuator is controlled so that the pressure in the second chamber becomes the target pressure.

11. The positioning control method according to claim 9 or 10, characterized in that, before controlling the amount of movement of the moving member, gas is supplied to the second chamber of the pneumatic actuator with the volume of the first chamber of the pneumatic actuator set to zero, and then the second chamber of the pneumatic actuator is airtightly sealed.

12. The positioning control method according to claim 11, characterized in that, after the previous positioning operation is completed, the volume of the first chamber of the pneumatic actuator is reduced to a state close to zero, the gas in the second chamber of the pneumatic actuator is replaced, and after the replacement is completed, the second chamber of the pneumatic actuator is airtightly sealed.

13. The positioning control method according to claim 9, characterized in that, after positioning an object, the supply of gas to the first chamber of the pneumatic actuator is controlled so that the differential pressure between the first chamber of the pneumatic actuator and the second chamber of the pneumatic actuator remains constant.

14. The positioning control method according to claim 9, characterized in that a first control input is generated when there is a deviation of the controlled variable from a target value, a second control input is generated when there is a time change in the controlled variable, and the second control input is generated when the deviation of the controlled variable from a target value becomes smaller, and the control input is generated based on the first control input and the second control input.

15. The positioning control method according to claim 14, characterized in that the first control input is a steady-state control input, or, in the case where there is a time change in the controlled variable, the first control input is a control input that is a combination of a fluctuating control input that decreases as the deviation of the controlled variable from the target value decreases and a steady-state control input.

16. The positioning control method according to claim 9, characterized in that the pneumatic actuator is a pneumatic cylinder, and the first chamber and the second chamber of the pneumatic actuator are a chamber located on the head side of the pneumatic cylinder and a chamber located on the rod side of the pneumatic cylinder, respectively.

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