Method for controlling the movement of an actuator

Abstract

Method for controlling the movement of an actuator (2) which is connected to an actuator port (5, 6) of an actuator controller (1), wherein the actuator port (5, 6) in the actuator controller (1) is connected to a fluid outlet (48) via a line (47) in which a line valve (18, 21) is arranged, and wherein a flow sensor (29) is assigned to the fluid outlet (48), characterized in that when the line (47) is at least partially opened by the line valve (18, 21) and the actuator moves, a fluid volume flow from the actuator (2) to the fluid outlet (48) is detected by the flow sensor (29) and the line valve (18, 21) is controlled in a flow-dependent manner to influence the actuator movement according to a predefinable movement profile.

Description

[0001] The invention relates to a method for controlling the motion of an actuator. Such a method can be implemented, for example, with an actuator controller for controlling a fluidically operated actuator. For this purpose, the actuator controller comprises a supply line for an inflow of a compressible working fluid from a fluid port to an actuator port and a discharge line for an outflow of the compressible working fluid from the working port to a fluid outlet, wherein the supply line is assigned a supply valve and the discharge valve a discharge valve, each designed to influence a fluid volume flow at the actuator port, as well as a control device for controlling the supply valve and the discharge valve.

[0002] From DE 10 2008 028 189 A1, an electropneumatic valve for controlling pneumatic actuators for operating valves in automation systems is known. The valve has at least one electropneumatic transducer and one pneumatic amplifier, wherein the pneumatic amplifier has at least one valve device for selectively connecting a connection channel to the actuator with an inlet channel or with an outlet channel, which is actuated via the electropneumatic transducer depending on an electrical control signal. It is provided that at least one flow sensor is arranged in the connection channel to the actuator, the output signal of which is fed back to the electrical control signal.

[0003] DE 10 2014 200 469 A1 discloses a valve device for controlling a consumer, in particular a cylinder. The valve device has a pressure port, a tank port, a first working port and a second working port, at least one first controllable valve and a second controllable valve, wherein the valve positions of the first valve and the second valve are independently adjustable in order to selectively connect the pressure port to either the first working port or the second working port, and a volume flow sensor for detecting a volume flow passing through one of the working ports.

[0004] From DE 10 2009 017 879 A1, a fluid power system with a valve assembly for supplying fluid to fluid consumers is known, wherein the valve assembly has several valve modules; the valve modules each comprise a channel body and four 2 / 2-way valves, which are interconnected in a full bridge arrangement and can be switched between a closed position and a released position; and with a control device for individually controlling the 2 / 2-way valves of the valve modules.According to the invention, the first working channel and the second working channel are connected by a connecting channel and a valve means is assigned to the valve module, which can be individually switched between a blocked position and a released position by the control device, in order to influence a free cross-section of the connecting channel in order to temporarily release the communicating connection between the first and the second working channel.

[0005] DE 199 09 713 A1 discloses a control valve device for controlling the movement of at least one hydraulic consumer, wherein the connection of at least one pressure medium connection associated with the consumer to a delivery connection and to a tank connection can be controlled by a relative movement of a control spool of a control valve to a housing, the control spool is movable relative to the housing by means of an actuating device, and wherein the housing has a multi-layered structure of plates bonded together with each other, comprising intermediate plates arranged between two end plates, characterized in that the thickness of the end plates exceeds the thickness of the intermediate plates.wherein the end plates are provided with a fastening device for the actuating device and / or a connection device for the conveying line connected to the conveying connection and / or a connection device for the tank line connected to the container connection and / or a connection device for the pressure medium line connected to the pressure medium connection.

[0006] From DE 100 56 157 A1, a control system for an electrohydraulic valve is known, wherein the control system is used to control the operation of a working element by applying operator input control mechanisms which generate operator input signals when applied, wherein the valve is connected to the working element via a hydraulic circuit which has actuating means which are coupled to the working element to control its operation, wherein the control system has: a flow sensor which is positioned in connection with the valve and is suitable for determining an actual valve outlet flow rate of a hydraulic fluid flowing through it, wherein the flow sensor outputs a signal which indicates the actual valve outlet flow rate;a pressure sensor positioned in conjunction with the actuating means and suitable for sensing a load pressure applied to the actuating means, wherein the pressure sensor outputs a signal indicating the load pressure; means for determining the desired valve outlet flow rate in conjunction with the pressure sensor and the operator input control mechanisms for receiving the load pressure signal and the operator input signal and for determining a desired valve outlet flow rate for the valve based thereon, wherein the means for determining the desired valve outlet flow rate outputs a signal indicating the desired valve outlet flow rate;a comparator or comparison device in conjunction with the flow sensor and the means of determining the desired valve outlet flow rate, suitable for receiving signals therefrom, wherein the comparison device is operable to compare the actual valve outlet flow rate with the desired valve outlet flow rate and to generate a comparator or comparison device output signal representing the difference between them; and a control device in conjunction with the comparison device and the valve, suitable for receiving the comparison device output signal and modifying an input flow rate signal to the valve based on the comparison device output signal, so that the desired valve outlet flow rate is achieved from the valve.

[0007] WO 2013 / 115 986 A1 discloses a hydraulic system with a pump that draws fluid from a reservoir and an actuator with a first port and a second port. A metering valve assembly controls the fluid flow through the actuator and comprises an inlet valve positioned between the pump and the first port, and an outlet valve positioned between the second port and the reservoir. A control unit manages the operation of the metering valve assembly. In inlet mode, the control unit manages the fluid flow rate through the actuator by controlling the opening size of the inlet valve. In outlet mode, the control unit manages the fluid flow rate through the actuator by controlling the opening size of the outlet valve.The control unit determines the fluid flow rate through the actuator based on data derived from the exhaust valve in both inlet and outlet modes.

[0008] The object of the invention is to provide a method for controlling the motion of an actuator, with which reliable operation for the motion control is ensured.

[0009] For example, the actuator control mentioned at the beginning can have a flow sensor in a line section between the drain valve and the fluid outlet, which is designed to determine a fluid volume flow in the drain and to provide a flow signal and which is coupled to the control device to enable motion control for an actuator movement depending on the flow signal.

[0010] Due to the placement of the flow sensor in the pipe section between the discharge valve and the fluid outlet, the average pressure of the working fluid flowing through the sensor is lower than if the sensor were located in the supply line, where the pressure for the pressurized working fluid is present. This is because the working fluid has already transferred some of its energy to the connected actuator. Furthermore, at the fluid outlet, the working fluid is discharged either into the environment or into a non-pressurized storage tank, so throttling losses of the working fluid after passing the flow sensor can be considered negligible.Furthermore, the pressure level in the pipe section where the flow sensor is located is reduced by flow losses of the working fluid as it flows out of the actuator and by targeted throttling in the discharge through appropriate control of the discharge valve. Due to this low pressure level for the flow sensor, its design can be simpler than if the flow sensor were located in the supply line, where a higher pressure level prevails. Preferably, the arrangement of the flow sensor according to the invention allows for an advantageous combination of a cost-effective flow sensor design with high measurement accuracy.

[0011] Typical methods for determining flow rate include ultrasonic flow measurement, differential pressure measurement at a predefined orifice plate, or electromechanical flow measurement. For example, the flow sensor provides an electrical flow signal, in particular a variable voltage or current level, which is transmitted to the control unit and bears a predefined ratio to the actual working fluid flow through the flow sensor. Based on the flow signal, the control unit can then determine how the actuator, which might be, for example, a piston in a pneumatic or hydraulic cylinder assembly, is moving.Knowing the movement speed of the actuator, the control device can effect movement control for the actuator depending on the flow signal by influencing the inflow of working fluid into the actuator and / or the outflow of working fluid from the actuator or by other measures such as controlling a braking device for the actuator.

[0012] It is advantageous if the control device for implementing motion control is designed to actuate the drain valve and / or the supply valve depending on the flow signal. The motion control for the actuator movement can, in particular, be a speed control, which is carried out by the control device depending on the determined flow signal in the drain. To influence the actuator's movement for the purpose of motion control, it can be provided to affect the working fluid flowing out of the actuator by appropriately actuating the drain valve. Such motion control can be implemented for both single-acting and double-acting actuators, especially for fluidic working cylinders.In a single-acting actuator, a variable-sized working chamber is filled with a suitable quantity of working fluid, depending on the desired position of the actuator. Such an actuator can be subjected to an internal or external load, for example, an external weight force or the force of a return spring. A motion control system using the actuator control according to the invention can be provided, for example, for a retraction movement of the actuator, during which the working chamber of the actuator is reduced in size due to the externally applied weight force or the action of the return spring. In this process, the working fluid contained in the actuator flows into the drain after passing through the actuator connection and escapes from the fluidic system at the fluid outlet after passing through the drain valve and the flow sensor.In this operating mode, the position of the drain valve can be influenced based on the flow signal from the flow sensor, in order to achieve a predefined movement profile for the actuator. In addition to or as an alternative to controlling the drain valve, an external braking device can also be controlled to regulate the movement based on the flow signal.

[0013] In a double-acting actuator having two variable-size working chambers separated by a movable piston, it may be possible, for example, to provide each of the working chambers with its own actuator control, wherein the actuator control connected to the shrinking working chamber of the double-acting actuator during movement of the actuator performs the flow measurement in the discharge and, based on the determined flow signal, controls the movement of the actuator, optionally exchanging information with the other actuator control responsible for supplying the pressurized working fluid to the expanding working chamber.

[0014] It is advantageous if the inlet valve and / or the outlet valve are designed as a proportional valve, particularly for electrical actuation by the control unit, and / or as a combined valve assembly, particularly as a 3 / 3-way valve. With a proportional valve, the control unit can effect a predefinable throttling effect on the working fluid flowing through the respective valve by specifying a signal level. Preferably, electrical actuation of the inlet valve and / or the outlet valve by the control unit is provided. Alternatively, the inlet valve and the outlet valve can be designed as a combined valve assembly in the form of a spool valve, particularly as a 3 / 3-way valve.

[0015] Preferably, a pressure sensor is associated with the supply line, which is coupled to the control unit and is designed to provide a pressure-dependent supply pressure signal to the control unit. Using the supply pressure signal provided by the pressure sensor in the supply line to the control unit, improved motion control for the actuator movement can be achieved, for example, when the supply pressure for the working fluid in the supply line changes. Considering the supply pressure signal is particularly effective when the control of the discharge valve is solely dependent on the flow rate signal, since in this case, pressure fluctuations in the supply line can lead to a time lag in the response to the flow rate due to the actuator's inertia, which makes balanced motion control more difficult.Accordingly, it is advantageous to have up-to-date information on possible pressure fluctuations for the supply pressure of the working fluid in the supply line at an early stage, in order to be able to take this into account for the motion control.

[0016] It is advantageous to have a pressure sensor assigned to the actuator connection, which is coupled to the control unit and designed to provide a pressure-dependent working pressure signal to the control unit. With the aid of the pressure sensor at the actuator connection, when the actuator control is assigned to a single-acting actuator, a pressure signal can be processed in the control unit in addition to the flow signal during the discharge of working fluid from the actuator, thus enabling more precise motion control. In the case of a double-acting actuator, a pressure sensor can be assigned to the working chamber that is supplied with working fluid during the actuator's movement, as well as, additionally or alternatively, to the working chamber that experiences an outflow of working fluid during the actuator's movement.By evaluating the pressure signal from at least one pressure sensor, an improvement in the control of the actuator movement can also be achieved, especially when using gaseous working fluids, where the compressibility of the working fluid has a significant influence on the movement behavior of the actuator.

[0017] It is advantageous to have two actuator connections, each with an inlet line and inlet valve, and an outlet line with an outlet valve. The outlet lines terminate in a common fluid outlet, and the flow sensor is located at this outlet. Such an actuator control system allows for simple motion control of a double-acting actuator. Each actuator connection is assigned to a corresponding working chamber of the double-acting actuator. Due to the actuator's mechanical design, when working fluid is supplied to one working chamber, it is simultaneously discharged from the other. The outgoing working fluid always passes through one of the outlet lines and its associated outlet valve before exiting the common fluid outlet and the flow sensor located at the outlet.Accordingly, the use of such an actuator control system results in a particularly simple design for a double-acting actuator, since it is not necessary to assign a separate flow sensor to each discharge valve. Furthermore, such an actuator control system allows for a particularly advantageous coordinated supply of working fluid to one of the actuator's working chambers and a discharge of working fluid from the other working chamber of the actuator using a single control unit.

[0018] The object of the invention is achieved according to the invention by a method for controlling the motion of an actuator, as specified in claim 1. The actuator is connected to an actuator port of an actuator controller, in particular the actuator controller described above, and the actuator port is connected via a line in which a drain valve is arranged to a fluid outlet, the fluid outlet being associated with a flow sensor. According to the invention, when the line is at least partially opened by the drain valve and the actuator moves, the flow sensor detects the fluid volume flow from the actuator to the fluid outlet and controls the drain valve in a flow-dependent manner to influence the actuator motion according to a predefinable motion profile.A flow signal is required for actuator motion control, which presupposes a flow of working fluid through the flow sensor. Such a flow rate may not be reliably determined at the start of actuator movement. In this case, the system can be configured to initially open the drain valve in a predefined manner, particularly only partially, to allow actuator movement and the resulting working fluid flow rate. Once the flow sensor provides a stable flow signal, the actuator motion can then be controlled based on the flow sensor's signal, thus regulating the actuator's movement according to the predefined motion profile.

[0019] In a further development of the method, the motion profile includes an approach movement from an end position or intermediate position, and / or a travel movement, and / or a braking movement to an end position or intermediate position for the actuator. For example, the actuator is a double-acting fluidic cylinder in which a working piston with an associated piston rod is movably mounted between a first end position and a second end position. Using the method according to the invention, an approach movement for the working piston from one of the end positions or an intermediate position between the end positions can be provided. Additionally or alternatively, the motion profile can include a travel movement between the end positions, or between an end position and an intermediate position, or between an intermediate position and an end position.Furthermore, the motion profile can include a braking movement to an end position or intermediate position. The motion profile can optionally focus on considering the acceleration of the actuator, achieving predefined target speeds for the actuator, or a combination thereof.

[0020] In an advantageous further development of the method, it is provided that, during the flow-dependent control of the discharge valve assigned to a first actuator port, a flow-dependent control of a supply valve arranged in a supply line to a second actuator port is also performed. The supply valve is controlled based on a sensor signal level from the flow sensor assigned to the fluid outlet of the first actuator port. The combined control of the supply valve for the second actuator port and the discharge valve for the first actuator port enables particularly sensitive motion control of the actuator movement.It is advantageous if both the discharge valve and the supply valve are controlled by the same control device in order to ensure particularly advantageous coordination of the two control processes for carrying out the motion control.

[0021] In an advantageous further development of the method, it is provided that a supply pressure signal from a pressure sensor arranged in the supply line, in particular between the fluid connection and the supply valve or the supply valve and the actuator connection, is used to control the supply valve. This pressure sensor is coupled to the control device. Including the supply pressure signal from the pressure sensor is particularly important because the working fluid is compressible, especially gaseous, and therefore, due to its compressibility, there is no proportionality between the inflow of working fluid into a first working chamber of the actuator and the outflow of working fluid from a second working chamber of the actuator.Accordingly, the pressure signal can be used to predict the movement behavior of the actuator, in order to ensure the desired movement control for the actuator movement according to the predefined movement profile.

[0022] An advantageous embodiment of the invention is shown in the drawing. The drawing shows: Fig. 1 an actuator control for controlling a double-acting fluidically operated actuator.

[0023] One in the Fig. The actuator control 1 shown is intended for controlling a fluidically operated actuator 2, which is not part of the actuator control 1 and is accordingly shown in dashed lines, as are a silencer 3 and a fluid source 4. Fig.Figure 1 shows an example of the actuator control 1, which comprises a first actuator connection 5 and a second actuator connection 6. These are connected, for example, to a first working chamber 7 and a second working chamber 8 of the actuator 2 via fluid lines 9 and 10, respectively. The working chambers 7 and 8 in the actuator 2 are formed in an actuator housing 15 and are separated from each other by a sliding working piston 11, the size of which can be varied. A piston rod 12 is associated with the working piston 11. This piston rod extends through the actuator housing 15 and is designed to transmit motion to a machine element (not shown). By pressurizing the first working chamber 7 and / or the second working chamber 8, a force can be applied to the working piston 11, which is movably and sealingly mounted in the actuator housing 15.According to a force balance for the working piston 11, which depends on the pressure conditions for working fluid in the working chambers 7 and 8 and on the effective surfaces of the working piston 11, a resultant force on the working piston 11 arises, which may lead to a movement of the working piston 11 and the associated piston rod 12 along a path of movement 16.

[0024] The actuator control 1 is shown as an exemplary unit, whereby the components of the actuator control 1 described in more detail below can be implemented in both discrete and combined construction.

[0025] The actuator control 1 comprises a control unit 17, several valves 18, 19, 20, 21 and control units 22, 23, 24 and 25 assigned to the valves 18 to 21, as well as several sensors 28, 29 and 30.

[0026] The control unit 17 can, for example, be designed as a microcontroller or microprocessor and is electrically connected to the control units 22 to 25 or the sensors 28, 29 and 30 via control lines 31, 32, 33, 34 and sensor lines 35, 36, 37. Furthermore, the control unit 17 is assigned, by way of example, a communication line 40, which is intended for a communication link with a higher-level control system, in particular a programmable logic controller or other actuator control systems, and which is intended, by way of example, for data exchange according to a predefined communication protocol, in particular a bus communication protocol.

[0027] Valves 18 to 21 are exemplary 2 / 2-way valves with piezoelectric actuation and can be operated as proportional valves. Due to the piezoelectric actuation, the operation of valves 18 to 21 requires a high-voltage signal, which is provided by the respective control unit 22 to 25 via the associated control line 41 to 44. Thus, each of the valves 18 to 21 can be freely set between a closed position and an open position depending on a control signal provided by the control unit 17 to the respective control unit 22 to 25.

[0028] As an example, it is provided that valves 19 and 20 are each connected on their inlet side to a supply line 45 in a fluidically communicating connection, the supply line 45 beginning at a supply port 46 to which the fluid source 4 can be connected. Furthermore, a fluidically communicating connection is provided between the supply line 45 and the sensor 28, which is designed as a pressure sensor. This sensor converts the pressure level prevailing in the supply line 45 into an electrical supply pressure signal, which is provided to the control unit 17 via the sensor line 35. Accordingly, the supply pressure supplied by the fluid source 4 to the supply line 45 and to the downstream valves 19 and 20 can be determined using the sensor 28. Furthermore, valves 19 and 20 are each connected on their outlet side to one of the actuator ports 5 and 4, respectively.6 connected, so that when the respective valve 19, 20 is opened, a fluidically communicating connection between the supply line 45 and the respective actuator connection 5 or 6 can be released to allow a supply of working fluid into the corresponding working chamber 7, 8.

[0029] Valves 18 and 21 are each connected on the inlet side to the respective actuator connection 5 and 6, respectively, and are further connected on the outlet side to a line 47 that passes through the sensor 29, which is designed as a flow sensor, and opens at a fluid outlet 48. Valves 18 and 21 thus enable fluid to flow out of the respective working chambers 7 and 8 of the actuator 2.

[0030] For a movement of the working piston 11 along the movement path 16, the following procedure can be provided as an example: depending on the desired direction of movement for the actuator 2, pressurized working fluid is supplied to the respective working chamber 7, 8 of the actuator 2 at the actuator connection 5 or at the actuator connection 6 by the respective valve 19 or 20 releasing a fluidically communicating connection between the supply line 45 and the respective actuator connection 5 or 6.

[0031] For the following considerations, it is assumed that the piston rod 12 will extend. Accordingly, the working chamber 7 is supplied with pressurized working fluid, so that the resulting movement of the working piston 11 reduces the size of the working chamber 8 and consequently the fluid is discharged from the working chamber 8 via the actuator connection 6. To pressurize the working chamber 7, the valve 19, also referred to as the supply valve, is moved from the closed position shown to an open position (not shown). This establishes a fluidic connection between the fluid source 4, the supply line 45, and the actuator connection 5, allowing pressurized fluid to flow into the working chamber 7.Due to the force applied to the working piston 11, it is displaced towards the working chamber 8, thereby reducing its volume. Furthermore, the working fluid contained in the working chamber 8 is conveyed via the fluid line 10, the actuator connection 6, the valve 21 (also referred to as the drain valve), and the line 47 to the sensor 29, which is designed as a flow sensor, and then to the fluid outlet 48. After passing through the silencer 3, the fluid can then flow into the environment or a storage container. Depending on the volume flow rate of the working fluid through the sensor 29, the sensor 29 provides an electrical flow signal to the control unit 17 via the sensor line 36.In the control device 17, the actual volume flow rate of the working fluid towards the fluid outlet is then calculated depending on a signal level of the provided flow signal, and based on this calculation, the acceleration and / or velocity of the working piston 11 and the associated piston rod 12 is determined. Preferably, a motion profile, in particular an acceleration profile or a velocity profile, for the movement of the working piston 11 is stored in the control device 17, which can be compared with the actual acceleration and / or velocity of the working piston as determined from the flow signal.In case of deviations between the stored motion profile and the determined motion profile, the control device 17 can optionally throttle the working fluid flowing out of the working chamber 8 by means of the valve 21 and / or throttle the working fluid supplied to the working chamber 7 by appropriately controlling the valve 19.

[0032] Improved adaptation of the actual movement profile for the working piston 11 to a stored movement profile can be achieved by processing at least one pressure signal from the sensors 28 and 30, which are designed as pressure sensors. Sensor 28 determines the supply pressure in the supply line 45 and provides a measurement result as an electrical signal to the control unit 17. Sensor 30, also designed as a pressure sensor, determines a working pressure at the actuator connection 6 and provides a measurement result as an electrical working pressure signal to the control unit 17. The use of at least one pressure sensor 28 and / or 30 is particularly advantageous when the working fluid is a compressible fluid, especially a gas, preferably compressed air, since incorporating the supply pressure and / or the working pressure enables improved movement control.In an embodiment of the actuator control not shown, a working pressure sensor is also assigned to the second actuator connection, which is connected to the control device.

[0033] For the retraction movement of the piston rod 12 and the coupled working piston 11, the valves 20 and 18 are controlled in the reverse order compared to the previous description, so that pressurized fluid can be supplied to the working chamber 8 at the actuator port 6, while working fluid from the working chamber 7 can flow via the actuator port 5 through the valve 18 to the drain 47 and, after passing through the sensor 29, to the fluid outlet 48. During this movement as well, the flow signal from the flow sensor can be used to control the movement of the actuator 2.

Claims

[1] Method for controlling the motion of an actuator (2) which is connected to an actuator port (5, 6) of an actuator controller (1), wherein the actuator port (5, 6) in the actuator controller (1) is connected to a fluid outlet (48) via a line (47) in which a line valve (18, 21) is arranged, and wherein a flow sensor (29) is associated with the fluid outlet (48), characterized by , that when the discharge (47) is at least partially released by the discharge valve (18, 21) and the actuator is moved, a fluid volume flow from the actuator (2) to the fluid outlet (48) is detected by the flow sensor (29) and the discharge valve (18, 21) is controlled in a flow-dependent manner to influence the actuator movement depending on a predefinable movement profile. [2] Method according to claim 1, characterized by, that the motion profile includes an approach movement from an end position or intermediate position and / or a travel movement and / or a braking movement to an end position or intermediate position for the actuator (2). [3] Method according to claim 1 or 2, characterized by , that during the flow-dependent control of the discharge valve (18, 21) which is assigned to a first actuator connection (5, 6), a flow-dependent control of a supply valve (19, 20) which is arranged in a supply line (45) to a second actuator connection (5, 6) is carried out, wherein the supply valve (19, 20) is controlled depending on a sensor signal level of the flow sensor (29) which is assigned to the fluid outlet (48) of the first actuator connection (5, 6). [4] Method according to claim 3, characterized by, that for the control of the supply valve (19, 20) a supply pressure signal of a pressure sensor (28) arranged in the supply line (45), in particular between the fluid connection (46) and the supply valve (19, 20) or the supply valve (19, 20) and the actuator connection (5, 6), is taken into account, which is coupled to the control device (17).

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