Control method and control arithmetic device for a pneumatic actuator

Abstract

The present application provides a technology capable of performing more stable positioning control. A control operation device performs an operation for compensating a volume change amount of each pressure chamber caused by a position change of a pressure receiving plate in a cylinder chamber with respect to each position command value output to two servo amplifiers, and then outputs the compensated position command value to the two servo amplifiers, respectively, to perform origin positioning of a position of a slider in order to compensate the volume change amount.

Description

[0001] This application claims priority based on Japanese Patent Application No. 2020-202876 filed on December 7, 2020. The entire contents of the Japanese application are incorporated herein by reference. TECHNICAL FIELD

[0002] The present application relates to a control method of a pneumatic actuator and a control arithmetic device. BACKGROUND

[0003] A pneumatic actuator is known, which includes a guide shaft and a slider capable of moving along the guide shaft, a cylinder chamber is formed between the guide shaft and the slider, and a pressure receiving plate that divides the cylinder chamber into two pressure chambers in the moving direction is provided in one of the guide shaft and the slider, and compressed gas is capable of entering and exiting the two divided pressure chambers via a servo valve to drive the slider according to the pressure difference between the two pressure chambers. In the past, a pneumatic actuator has been proposed that is capable of compensating for changes in dynamic characteristics caused by the position of the slider, thereby enabling stable control of the slider within the stroke.

[0004] Patent Literature 1: Japanese Patent Application Publication No. 2002-295404 SUMMARY

[0005] The present application was completed in view of the above circumstances, and one of the exemplary objects of an embodiment of the present application is to provide a technology capable of performing more stable positioning control.

[0006] To solve the above problem, one embodiment of the present application provides a control method of a pneumatic actuator including a guide portion and a slider capable of moving along the guide portion, a cylinder chamber is formed between the guide portion and the slider, and a pressure receiving plate that divides the cylinder chamber into two pressure chambers in the moving direction is provided in one of the guide portion and the slider, and compressed gas is capable of entering and exiting the two divided pressure chambers via a servo valve to drive the slider based on the pressure difference between the two pressure chambers, and the pneumatic actuator is provided with a position sensor for detecting the position of the slider, two servo amplifiers for controlling the two servo valves, respectively, and a control arithmetic device that receives a position detection signal from the position sensor and outputs a position command value to the two servo amplifiers, in the control method of the pneumatic actuator, the control arithmetic device performs an operation for compensating for the volume change amount of each pressure chamber due to a change in the position of the pressure receiving plate in the cylinder chamber with respect to each position command value output to the two servo amplifiers, and then outputs the compensated position command value to the two servo amplifiers, respectively, and the control arithmetic device performs a home positioning of the position of the slider in order to compensate for the volume change amount.

[0007] Another embodiment of the present application provides a control method of a pneumatic actuator including a guide portion and a slider capable of moving along the guide portion, a cylinder chamber being formed between the guide portion and the slider, and a pressure receiving plate being provided in one of the guide portion and the slider to divide the cylinder chamber into two pressure chambers in a moving direction, compressed gas being capable of entering and exiting the two divided pressure chambers via servo valves respectively to drive the slider based on a pressure difference between the two pressure chambers, and the pneumatic actuator being provided with a position sensor for detecting a position of the slider, two servo amplifiers for controlling the two servo valves respectively, and a control arithmetic device receiving a position detection signal from the position sensor and outputting a position command value to the two servo amplifiers, in the control method of the pneumatic actuator, the control arithmetic device switches a gain when each position command value output to the two servo amplifiers is calculated based on the position detection signal from the position sensor before and after a home position positioning of the position of the slider is completed.

[0008] Still another embodiment of the present application provides a control arithmetic device. The device receives a position detection signal from a position sensor and outputs a position command value to two servo amplifiers of a pneumatic actuator including a guide portion and a slider capable of moving along the guide portion, a cylinder chamber being formed between the guide portion and the slider, and a pressure receiving plate being provided in one of the guide portion and the slider to divide the cylinder chamber into two pressure chambers in a moving direction, compressed gas being capable of entering and exiting the two divided pressure chambers via servo valves respectively to drive the slider based on a pressure difference between the two pressure chambers, and the pneumatic actuator being provided with the position sensor for detecting a position of the slider, and the two servo amplifiers for controlling the two servo valves respectively, in the control arithmetic device, after an operation of compensating each pressure chamber volume change amount caused by a position change of the pressure receiving plate in the cylinder chamber is performed with respect to each position command value output to the two servo amplifiers, the compensated position command value is output to the two servo amplifiers respectively, and a home position positioning of the position of the slider is performed in order to compensate the volume change amount.

[0009] Yet another embodiment of the present application provides a control arithmetic device. The device receives a position detection signal from a position sensor and outputs a position command value to two servo amplifiers of a pneumatic actuator including a guide and a slider capable of moving along the guide, a cylinder chamber being formed between the guide and the slider, and a pressure receiving plate being provided in one of the guide and the slider to divide the cylinder chamber into two pressure chambers in a moving direction, compressed gas being able to enter and exit the two divided pressure chambers via servo valves to drive the slider based on a pressure difference between the two pressure chambers, and the pneumatic actuator having: the position sensor for detecting the position of the slider; and the two servo amplifiers for controlling the two servo valves, respectively, in which the control arithmetic device switches a gain when calculating the respective position command values to be output to the two servo amplifiers based on the position detection signal from the position sensor before and after the origin positioning of the position of the slider is completed.

[0010] In addition, any combination of the above-described components or an embodiment obtained by mutually replacing the components or expressions of the present application between a method, a device, a system, and the like is also effective as an embodiment of the present application.

[0011] According to one embodiment of the present application, more stable positioning control can be performed. BRIEF DESCRIPTION OF DRAWINGS

[0012] Figure 1 is a cross-sectional view of a pneumatic actuator related to the embodiment.

[0013] In the drawing: 13 - slider, 14 - guide shaft, 16 - cylinder space, 16A - pressure chamber, 16B - pressure chamber, 17 - pressure receiving plate, 22A, 22B - servo valve, 15 - position sensor, 21A, 21B - servo amplifier, 20 - control arithmetic device. DETAILED DESCRIPTION

[0014] Hereinafter, in each drawing, the same symbols are attached to the same or equivalent components and parts, and repeated explanation is appropriately omitted. Also, in each drawing, the size of the components is appropriately enlarged or reduced for the convenience of understanding. Also, in each drawing, a part of the components which is not important for the explanation of the embodiment is omitted.

[0015] Figure 1 is a cross-sectional view of a pneumatic actuator 1 related to the embodiment. The pneumatic actuator 1 includes a guide shaft 14 whose both end portions are fixed by a support body and extends along a single axis direction, and a slider 13 capable of moving along the guide shaft 14. The slider 13 is a cylindrical body capable of surrounding the periphery of the guide shaft 14. A cylinder space 16 is formed between the guide shaft 14 and the slider 13. In this example, the central portion of the guide shaft 14 is formed thin, thereby forming the cylinder space 16 between the slider 13 and the guide shaft 14.

[0016] A pressure receiving plate (partition wall) 17 is fixed to the inner wall of the slider 13. The pressure receiving plate 17 is movable along the guide shaft 14 together with the slider 13. Alternatively, the pressure receiving plate 17 can be fixed to the guide shaft 14. In the axial direction, the cylinder space 16 is divided into a pressure chamber 16A and a pressure chamber 16B by the pressure receiving plate 17.

[0017] The slider 13 and the guide shaft 14 form a static pressure gas bearing. Specifically, by jetting compressed gas (e.g., air) from an air cushion provided on the inner side of the slider 13 or the outer side of the guide shaft 14, the slider 13 is floated from the guide shaft 14, and the slider 13 is movable relative to the guide shaft 14 in a non-contact manner. Thus, there is no sliding resistance when moving.

[0018] The position sensor 15 detects information about the position of the slider 13 and outputs the information about the position in an electric signal. The position detection signal from the position sensor 15 is input to the control arithmetic device 20.

[0019] The control arithmetic device 20 performs a control arithmetic based on the input position information and outputs a position command signal to the servo amplifiers 21A, 21B. At this time, the command values to the servo amplifiers 21A, 21B use values having the same absolute value but opposite signs.

[0020] The servo amplifiers 21A, 21B control the valve stem positions of the servo valves 22A, 22B based on the command values, respectively.

[0021] Compressed gas (e.g., air) adjusted to an appropriate pressure by a regulator not shown is supplied to the servo valves 22A, 22B, and the flow rate passing through varies depending on the valve stem positions in the servo valves 22A, 22B. The gas passing through the servo valves 22A, 22B is supplied to the two pressure chambers 16A, 16B provided in the slider 13. As a result, a pressure difference is generated in the pressure chambers 16A, 16B, and the pressure difference acts on the pressure receiving plate 17 mounted on the inner wall of the slider 13, moving the slider 13.

[0022] Such a pneumatic actuator is compact in structure and capable of controlling a large output, and thus is expected to be used as an actuator for positioning between two points. However, when performing continuous positioning, such a pneumatic actuator is difficult to control stably due to nonlinear characteristics such as changes in dynamic characteristics caused by the position of the pressure receiving plate, and it is difficult to take a long effective stroke with respect to the mechanical stroke of the slider. This is because, if the position of the pressure receiving plate in the cylinder chamber changes, the pressure of the pressure chamber also changes, which affects stable control.

[0023] Therefore, a method of compensating for a change in dynamic characteristics caused by the position of the slider 13 and stably controlling the slider 13 within a stroke in the pneumatic actuator 1 that uses two servo valves 22A, 22B to drive the slider 13 using gas pressure will be described.

[0024] The main symbols shown below are pressure P, volume V, temperature θ, gas constant R, and pressure receiving area A of the pressure receiving plate 17, the subscript 1 indicates a state quantity on the pressure chamber 16A side, and the subscript 2 indicates a state quantity on the pressure chamber 16B side. Also, in the various formulas shown below, a symbol with a • (dot) added above the symbol indicates a first-order time derivative, for example, a symbol with a dot added above the symbol x is called x dot, and a symbol with two • (dots) added above the symbol indicates a second-order time derivative, for example, a symbol with two dots added above the symbol x is called x double dot. On the other hand, a symbol with a - (overline) added above the symbol indicates a state quantity when the pressure chambers 16A, 16B are in an equilibrium state, for example, a symbol with an overline added above the symbol P is called P overline.

[0025] As described above, the pneumatic actuator 1 of the present embodiment is an actuator that uses two servo valves 22A, 22B, two servo amplifiers 21A, 21B, and a control arithmetic device 20 to control the compressed gas flow rate supplied to the pressure chambers 16A, 16B and drives the slider 13 by the pressure difference between the pressure chambers 16A, 16B.

[0026] If the state change of the gas in the pressure chamber is assumed to be an adiabatic change (adiabatic coefficient k), the state change is represented by the following formula (1).

[0027] [Formula 1]

[0028]

[0029] Here, G1 indicates the mass flow rate of the gas supplied from the servo valve 22A.

[0030] The state equation of formula (1) is nonlinear, and therefore, if the volume of the pressure chamber changes, the characteristics also change.

[0031] If the state in which the slider 13 is stopped with the pressure receiving plate 17 positioned near the center of the slider 13 (pressure P overline, volume V overline, temperature θ overline) is taken as a reference state and linearized, it becomes the following formula (2).

[0032] [Formula 2]

[0033]

[0034] At this time, the temperature change is very small, and is represented as θ1 = θ overline. In formula (2), the center of the slider is taken as the reference state, and the volume is set to V overline = constant, so there is no change in characteristics.

[0035] The input Gl of the formula (1) is made G1' to make the following formula (3), and the input of the following formula (4) is considered.

[0036] [Formula 3]

[0037]

[0038] [Formula 4]

[0039]

[0040] If the formula (4) is substituted into the formula (3), the nonlinear equation of the formula (1) becomes a linear equation equal to the formula (2).

[0041] The formula (linearization of the through flow of the servo valve 22A) obtained by linearizing the through flow of the servo valve 22A (the servo valve 22A is set to the intake state, and the servo valve 22B is set to the exhaust state) is represented by the following formula (5).

[0042] [Formula 5]

[0043]

[0044] where K f , δ are coefficients determined by the shape of the servo valve and the supply pressure, K se is the gain between the opening of the servo valve and the command to the servo amplifier, and ul is the position command value to the servo amplifier 21A.

[0045] If a new input to the servo amplifier 21A is set to ul' in the formula (5) and the following formula (6) is obtained from the formula (4) and the formula (5),

[0046] [Formula 6]

[0047]

[0048] The compensation (formula of the mass flow) of the formula (4) can be converted into a formula of the command value to the servo amplifier 21A. In this formula, the command from the control arithmetic device 20 to the servo amplifier 21A is output as the input, and therefore the arithmetic of the formula (6) is performed by the control arithmetic device 20, and a new input ul' is output to the servo amplifier 21A.

[0049] For the pressure chamber 16B, it is assumed that the servo valve 22B becomes the exhaust side, and therefore the through flow formula of the servo valve 22B is represented by the following formula (7).

[0050] [Formula 7]

[0051]

[0052] If a formula corresponding to formula (6) is derived in the same manner for the side of the pressure chamber 16B, it becomes the following formula (8).

[0053] [Formula 8]

[0054]

[0055] By adding the compensation of formula (6) and formula (8) in the control operation by the control operation device 20, the change in the dynamic characteristics caused by the change in the position of the slider 13 (i.e., the position of the pressure receiving plate 17 in the slider 13) is eliminated, resulting in the dynamic characteristics being consistent with the characteristics when the pressure receiving plate 17 is located at the center of the slider 13 regardless of the position of the pressure receiving plate 17 in the slider 13.

[0056] The operation of the control operation device 20 will be described below.

[0057] (1) The position of the slider 13 is detected by the position sensor 15 to obtain an electric signal indicating the position information. The position detection signal from the position sensor 15 is input to the control operation device 20. The following operations (2) to (6) are performed in the control operation device 20.

[0058] (2) The slider position x input from the position sensor 15 is differentiated to calculate the velocity xdot, and further differentiated to calculate the acceleration xddot.

[0059] (3) The position command value u is calculated using the slider target position X ref and the slider position x, the velocity xdot, and the acceleration xddot, and according to the following formula (9).

[0060] [Formula 9]

[0061]

[0062] where K p , K v , and K a are proportionally, velocity, and acceleration gains, respectively, which are appropriately designed.

[0063] (4) The position command values ul, u2 to the servo amplifiers 21A, 21B are calculated in the following manner.

[0064] ul = u

[0065] u2 = -u

[0066] (5) The new position command value ul' to the servo amplifier 21A is calculated using formula (6) as the following formula (10).

[0067] [Formula 10]

[0068]

[0069] Here, the pressure P1 of the formula (6) is set as the equilibrium pressure Ptopline at the time when the slider stops (measured in advance), and the temperature θ1 is set as the equilibrium temperature θtopline = atmospheric temperature θ a . And, the position command value u2' to the servo amplifier 21B is calculated using the formula (8), as the following formula (11).

[0070] [Formula 11]

[0071]

[0072] Here, the pressure P2 of the formula (8) is set as the equilibrium pressure Ptopline at the time when the slider stops, and the temperature θ2 is set as the equilibrium temperature θtopline = atmospheric temperature θ a .

[0073] In addition, in the formula (10) and the formula (11), the servo valve 22A is set as the supply side, and the servo valve 22B is set as the exhaust side.

[0074] In the case where the supply side is opposite to the exhaust side, the following formula (12) and the formula (13) are used.

[0075] [Formula 12]

[0076]

[0077] [Formula 13]

[0078]

[0079] In addition, regarding V1, V2, since the cross-sectional area in the slider 13 is constant in the axial direction and is known, it can be calculated from the position of the slider 13.

[0080] (6) The position command value u1' is output to the servo amplifier 21A, and the position command value u2' is output to the servo amplifier 21B.

[0081] (7) The servo amplifiers 21A, 21B control the valve rod positions of the servo valves 22A, 22B, respectively, according to the position command values. The gas supplied to the servo valves 22A, 22B is adjusted to an appropriate pressure, and the flow rate of the compressed gas passing through varies according to the valve rod positions of the servo valves 22A, 22B.

[0082] (8) The gas passing through the servo valves 22A, 22B is supplied to the two pressure chambers 16A, 16B in the slider 13. And, the pressure difference of the pressure chambers 16A, 16B acts on the slider 13 to drive the slider 13.

[0083] (9) Repeating (1) to (8) to control the position of the slider 13 at the target position X ref .

[0084] As is clear from the above description, in the double-acting pneumatic actuator of the present embodiment in which the flow rate of the compressed gas supplied to the two pressure chambers is controlled by the two servo valves to thereby perform position control of the slider, in order to perform stable positioning control with a long effective stroke, positioning control in which compensation of changes in dynamic characteristics caused by changes in the position of the slider is applied in the control method is performed. More specifically, in the present embodiment, compensation of changes in dynamic characteristics caused by changes in the position of the slider 13 and the pressure plate 17 (nonlinearity compensation of changes in dynamic characteristics) is performed by performing an operation to compensate for the amount of change in pressure and the amount of change in volume of each pressure chamber caused by changes in the position of the slider 13 and the pressure plate 17.

[0085] Next, in the above equation (6) and equation (8), the state change of the gas is derived as an adiabatic change, but even if the adiabatic coefficient k is replaced with the polytropic index n, the same equation can be obtained, and thus the above technical idea can also be applied to other state changes (isothermal change, etc.). Hereinafter, this case will be described.

[0086] If the state change of the gas is assumed to be a polytropic change, the state equation of the pressure chamber is represented by the following equation (14),

[0087] [Equation 14]

[0088]

[0089] The state equation of the linearized model is represented by the following equation (15).

[0090] [Equation 15]

[0091]

[0092] where n is the polytropic index.

[0093] Based on the pressure change caused by the servo valve flow rate determined for the linearized model equation (15), the volume V, the pressure P, and the temperature Θ change, and thus a difference occurs between the linearized model and the actual state. To make the flow rate value determined by the linearized model the same as the pressure response based on the nonlinear model equation (14), it can be set to the following equation (16) and equation (17).

[0094] [Equation 16]

[0095]

[0096] [Equation 17]

[0097]

[0098] Here, only the effect due to the volume change is compensated for. If the pressure, temperature change is ignored, then P1=P2=Ptop line, θ1=θ2=θ a Thus, it becomes the following equation (18), equation (19).

[0099] [Equation 18]

[0100]

[0101] [Equation 19]

[0102]

[0103] Here, G1, G2 are represented by the following equation (20), equation (21), respectively.

[0104] [Equation 20]

[0105]

[0106] [Equation 21]

[0107]

[0108] where S e1 , S e2 are the effective cross-sectional areas of the flow paths through the servo valves 22A, 22B, if expressed in terms of effective cross-sectional areas, it becomes the following equation (22), equation (23),

[0109] [Equation 22]

[0110]

[0111] [Equation 23]

[0112]

[0113] Furthermore, according to the following equation and expressed in terms of the position command value (voltage), it becomes the following equation (24), equation (25).

[0114] S e1 = K seu1

[0115] S e2 = K seu2

[0116] [Equation 24]

[0117]

[0118] [Equation 25]

[0119]

[0120] In the operation (5) based on the above-mentioned control operation device 20, equations (24) and (25) can be used to replace equations (10) and (11).

[0121] Thus, similar to when the state change of a gas is adiabatic, positioning control can be performed with compensation applied for the dynamic characteristic changes caused by the change in slider position.

[0122] However, to compensate for the volume change caused by the positional changes of slider 13 and pressure plate 17, it is necessary to calculate the position command value that compensates for the volume change. In this calculation, it is clear from equations (10) to (14), (24), and (25) that the volumes V1 and V2 of pressure chambers 16A and 16B are required. As mentioned above, the cross-sectional area inside slider 13 is constant and known in the axial direction, so the volumes V1 and V2 can be calculated based on the position of slider 13. The position of slider 13 can be detected by position sensor 15.

[0123] To determine the position of slider 13 based on the position detection signal from position sensor 15, "origin positioning" needs to be performed after the control calculation device 20 is powered on. Origin positioning is the process by which the control calculation device 20 recognizes the origin O determined by the user as the origin. Therefore, in order to compensate for the volume change caused by the change in the position of pressure plate 17, origin positioning needs to be performed after the power is turned on.

[0124] First, the case where the position sensor 15 is an absolute position sensor will be explained. In this case, origin positioning is a process in which the control processing unit 20 reads the origin information stored in a predetermined memory into the main memory. The origin information is the position information corresponding to the origin O, and it is the position information represented by the position detection signal output by the absolute position sensor 15 when the slider 13 is located at the origin O. The origin information can be determined and pre-stored in the memory when the absolute position sensor 15 is set.

[0125] Next, the case where the position sensor 15 is an incremental position sensor will be explained. In this case, the origin positioning can be, for example, the process of initializing the sensor count value when the slider 13 is located at the origin O, or the process of determining the count value when the slider 13 is located at the origin O.

[0126] Specifically, for example, one side (e.g., Figure 1 The right-hand side of the slider is taken as the origin O. The control and calculation device 20 can move the slider 13 toward the right-hand side of the slider and initialize the count value as the origin when the slider 13 reaches the right-hand side of the slider.

[0127] And, for example, the control computing device 20 can move the slider 13 toward one side movable end and, after the slider 13 has reached the one side movable end, move the slider 13 toward the other side movable end and initialize the count value as the origin positioning when the slider 13 has moved to a position a prescribed distance from the one side movable end, taking the position a prescribed distance from the one side movable end as the origin O.

[0128] And, for example, a slider detection sensor (not shown) that detects the slider 13 when the slider 13 is at the origin O can also be provided, and the control computing device 20 can move the slider 13 and initialize the count value as the origin positioning when the slider detection sensor detects the slider 13. At this time, for example, as a pre-process for the origin positioning, the slider 13 can be moved to the one side movable end, and in the origin positioning the slider 13 can be moved from the one side movable end toward the other side movable end.

[0129] When the slider 13 is moved for the origin positioning, the position of the slider 13 is not known, so the volumes V1, V2 are not known, and thus positioning control with compensation of the dynamic characteristic variation is not possible. Therefore, the control computing device 20 does not perform the above-described operation (5) in the origin positioning, and outputs the position command value u1 (= u) to the servo amplifier 21A and the position command value u2 (= -u) to the servo amplifier 21B in place of the position command value u1' and the position command value u2' in the operation (6). That is, positioning control with compensation of the dynamic characteristic variation is not performed in the origin positioning.

[0130] Here, in the formula (9) for calculating the position command value u, the proportional gain K p , the velocity gain K v , and the acceleration gain K a are gains designed on the premise that positioning control with compensation of the dynamic characteristic variation caused by a change in the position of the slider is performed. In the above-described origin positioning in which compensation of the dynamic characteristic variation is not performed, if the gains designed on the premise that compensation of the dynamic characteristic variation is performed are used, the slider 13 can perform an unexpected action such as oscillation. Therefore, more preferably, until the origin positioning is completed, in the formula (9), the proportional gain K p , the velocity gain K v , and the acceleration gain K a can be replaced with the proportional gain K p0 (< K p ), the velocity gain K v0 (< K v ), and the acceleration gain K a0 (< K a ). For example, the proportional gain K p0 , the velocity gain Kv0 , acceleration gain K a0 may be determined, for example, according to the user's insight, and may be, for example, a proportional gain K p , velocity gain K v , acceleration gain K a of 1 / 2, 1 / 5, 1 / 10, or 1 / 100. In this case, the likelihood of the slider 13 performing an unintended action during the origin positioning can be reduced.

[0131] After the origin positioning is completed, positioning control with compensation applied to the dynamic characteristic change is performed. Also, in this case, the proportional gain K p , velocity gain K v , acceleration gain K a is used in the equation (9) for calculating the position command value u. That is, the gain is switched from the gain for the origin positioning to the gain designed on the premise of performing positioning control with compensation applied to the dynamic characteristic change.

[0132] In addition, when switching from a state in which no compensation is applied to a state in which compensation is applied, in order to avoid the slider 13 performing an unintended action such as oscillation, the switching can be performed after the slider 13 is moved to the neutral point N at which the volumes VI, V2 of the pressure chambers 16A, 16B are equal. As for the neutral point N, if the distance from the origin O is determined in advance, it can be determined based on the origin O. Of course, the origin O can also be set so that the neutral point N becomes the origin.

[0133] According to the present embodiment described above, since the origin positioning for the position of the slider is performed, the position of the slider 13 and the volumes VI, V2 of the respective pressure chambers 16A, 16B can be calculated, and thus the position command value of the volume change amount for which the dynamic characteristic change caused by the position of the slider 13 is compensated can be calculated.

[0134] Also, according to the present embodiment, the gain at the time of calculating the position command value is switched between the gain for the origin positioning and the gain designed on the premise of performing positioning control with compensation applied to the dynamic characteristic change caused by the position change of the slider before and after the origin positioning is completed. Thus, in the origin positioning, by reducing the gain, the likelihood of the slider 13 performing an unintended action can be reduced, and in the positioning control with compensation applied to the dynamic characteristic change, by increasing the gain, the controllability can be improved.

[0135] The present application has been described above according to the embodiments. The embodiments are merely examples, and those skilled in the art will understand that various modifications can be made to the combination of the respective constituent elements and the respective processing steps, and such modified examples are also within the scope of the present application.

Claims

1. A control method for a pneumatic actuator, the pneumatic actuator comprising a guide portion and a slider movable along the guide portion, a cylinder chamber formed between the guide portion and the slider, and a pressure plate provided on one of the guide portion and the slider to divide the cylinder chamber into two pressure chambers in a moving direction, the compressed gas being able to enter and exit the two pressure chambers via servo valves to drive the slider based on the pressure difference between the two pressure chambers, and the pneumatic actuator comprising: a position sensor for detecting the position of the slider; two servo amplifiers for controlling the two servo valves respectively; and a control calculation unit for receiving position detection signals from the position sensor and outputting position command values ​​to the two servo amplifiers, the control method for the pneumatic actuator being characterized in that... The control calculation device calculates the volume change of each pressure chamber caused by the position change of the pressure plate in the cylinder chamber for each position command value output to the two servo amplifiers, and then outputs the compensated position command values ​​to the two servo amplifiers respectively. The control calculation device performs origin positioning for the slider's position in order to compensate for the volume change. The control and calculation device switches between calculating the gain of each position command value output to the two servo amplifiers based on the position detection signal from the position sensor before and after the origin positioning is completed.

2. A control method for a pneumatic actuator, the pneumatic actuator comprising a guide portion and a slider movable along the guide portion, a cylinder chamber formed between the guide portion and the slider, and a pressure plate provided on one of the guide portion and the slider to divide the cylinder chamber into two pressure chambers in a moving direction, the compressed gas being able to enter and exit the two pressure chambers via servo valves to drive the slider based on the pressure difference between the two pressure chambers, and the pneumatic actuator comprising: a position sensor for detecting the position of the slider; two servo amplifiers for controlling the two servo valves respectively; and a control calculation unit for receiving position detection signals from the position sensor and outputting position command values ​​to the two servo amplifiers, the control method for the pneumatic actuator being characterized in that... The control and calculation device switches between calculating the gain of each position command value output to the two servo amplifiers based on the position detection signal from the position sensor before and after the origin positioning of the slider is completed.

3. A control and calculation device that receives a position detection signal from a position sensor and outputs position command values ​​to two servo amplifiers of a pneumatic actuator, the pneumatic actuator including a guide section and a slider movable along the guide section, a cylinder chamber formed between the guide section and the slider, and a pressure plate provided on one of the guide section and the slider to divide the cylinder chamber into two pressure chambers in the direction of movement, the pressure chambers being divided into two pressure chambers by means of two pressure chambers via servo valves, the slider being driven based on the pressure difference between the two pressure chambers, and the pneumatic actuator comprising: the position sensor for detecting the position of the slider; and the two servo amplifiers for controlling the two servo valves respectively, the control and calculation device being characterized in that... After calculating the volume change of each pressure chamber caused by the position change of the pressure plate in the cylinder chamber, the position command values ​​output to the two servo amplifiers are compensated for, and then the compensated position command values ​​are output to the two servo amplifiers respectively. Origin positioning is performed for the position of the slider to compensate for the volume change. The control and calculation device switches between calculating the gain of each position command value output to the two servo amplifiers based on the position detection signal from the position sensor before and after the origin positioning is completed.

4. A control and calculation device that receives a position detection signal from a position sensor and outputs position command values ​​to two servo amplifiers of a pneumatic actuator, the pneumatic actuator including a guide section and a slider movable along the guide section, a cylinder chamber formed between the guide section and the slider, and a pressure plate provided on one of the guide section and the slider to divide the cylinder chamber into two pressure chambers in the direction of movement, the pressure chambers being divided into two pressure chambers by means of two pressure chambers via servo valves, the slider being driven based on the pressure difference between the two pressure chambers, and the pneumatic actuator comprising: the position sensor for detecting the position of the slider; and the two servo amplifiers for controlling the two servo valves respectively, the control and calculation device being characterized in that... The gain is calculated based on the position detection signal from the position sensor before and after the origin positioning of the slider is completed, and then switched to calculate the position command values ​​output to the two servo amplifiers.

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