CN102483079B - Position measuring device for acquiring the position of at least one actuator of a fluid system without a position sensor - Google Patents

Abstract

A position measuring device for determining the position of at least one actuator (19) of a fluid system (10) without a position sensor arrangement is proposed, wherein at least one fluid control valve (12) for controlling the fluid system (10) is provided. A volume flow and pressure sensor device (17) is connected directly to the inlet line (13) to the fluid system (10)The controller (18) is connected. The controller (18) is provided for controlling the operation of the motor according to the relation (I)Means for calculating the position x of the actuator (19).

Description

Position measuring device for acquiring the position of at least one actuator of a fluid system without a position sensor

technical field

The invention relates to a position measuring device for detecting the position of at least one actuator of a fluid system without a position sensor. Position sensors and travel measuring systems for controlling movements in fluid systems, in particular working cylinders, are known in various variants and are absolutely necessary for process control. Under certain conditions, for example at very high temperatures, the use of position sensors and distance measuring systems is very problematic and expensive. Even in the absence of high temperatures, the temperature sensor and the distance measuring system represent a cost factor which should be kept as low as possible, especially if the requirements for measuring accuracy are not too high.

Background technique

From DE 103 55 250 B4 it is known to arrange a volume flow and pressure sensor arrangement in the supply line to the working cylinder. However, it is not used for the position detection of the piston, but for leak detection by comparing the measured pressure and volume flow values with reference values. In order to detect leaks, end position switches are additionally required.

Contents of the invention

The object of the present invention is to provide a position-measuring device for determining the position of at least one actuator of a fluid system, in which a position sensor or a distance measuring system can be dispensed with.

This object is achieved by a position-measuring device with the features of claim 1 .

In particular, the position-measuring device according to the invention has the advantage that any position-measuring sensor or distance measuring system can be dispensed with and the position(s) can be determined directly by acquiring flow or volume flow and pressure. The sensor system therefore does not have to be arranged along the stroke path of the actuator, but can be arranged in the supply line to the fluid system, ie also outside, wherein the geometrical position is variable. This enables a variable geometric layout of the component with less wiring effort. The costs for position detection can be reduced by replacing the position sensor or the travel system by cheaper volume flow sensors and pressure sensors.

Fluid systems are in particular pneumatic systems which are operated with compressed air.

Advantageous developments and improvements of the position-measuring device specified in claim 1 are possible by means of the measures listed in the subclaims.

It has proven to be particularly advantageous to configure the volume flow and pressure sensor arrangement as a measuring module, in particular as a built-in module or as a built-in module. Such a module can be installed in a simple manner on or in a fluid system or in a variable manner on or in at least one control valve.

If the fluid system has at least one fluid-actuated actuator (Aktor) or it consists of at least one fluid-actuated actuator, the volume flow and pressure sensor arrangement is advantageously arranged at one of the covers of the actuator Or in one, or arranged at its outer side.

If a plurality of control valves form a valve bank, it can expediently be provided with one or with several volume flow and pressure sensor arrangements, in particular in the form of modules.

The volume flow and pressure sensor arrangement can also advantageously be associated with a plurality of fluid-operated actuators as a fluid system. When the controller has means for temporally correlating the acquired measurement signals of the volume flow and pressure sensor arrangement with the correspondingly actuated actuators such that the volume flow and pressure sensor arrangement can be used to acquire the measurements of a plurality of actuators It first proves to be particularly advantageous when implementing the position of the part.

The at least one fluid-operated actuator is, for example, a linear drive, for example a working cylinder, or a rotary drive.

Description of drawings

Exemplary embodiments of the invention are shown in the drawings and explained in more detail in the ensuing description. in:

FIG. 1 shows a schematic view of a working cylinder controlled by a control valve, wherein a volume flow and pressure sensor arrangement is arranged into one of the supply lines to the working cylinder,

Figure 2 shows the arrangement of two modular volume flow and pressure sensor devices at the valve block and

FIG. 3 shows the arrangement of the volume flow and pressure sensor arrangement in the cylinder head of the working cylinder.

Detailed ways

In the embodiment shown schematically in FIG. 1 , a fluid working cylinder 10 as an example of a fluid system is controlled by a pressure source 11 with a pressure P via a valve assembly 12 , in which case a 5-position, 3-way valve or two separate valves, which lead into the two supply lines 13 , 14 to the two chambers of the fluid cylinder 10 . Throttle check valves 15 , 16 are connected into the two supply lines 13 , 14 , which are expedient but not absolutely necessary. In addition, a volume flow and pressure sensor device 17 designed as a measuring module is connected to one of the two supply lines 13, via which the volume flow and pressure sensor device 17 measures the The returned volume flow Q _N and the corresponding pressure p.

The measured values Q _N and p of the volume flow and pressure sensor device 17 are fed to a controller 18 , which can be designed as an external control center or as a separately associated control device. This transmission can take place via a cable or also wirelessly. In this controller 18, from the measured values Q _N and p according to the relation

$\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; \&Integral;</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; A</span>}}<span\; class="notranslate">\; \&CenterDot;</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; Q</span>}}_{\mathrm{<span\; class="notranslate">\; N</span>}}{\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; p</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; -</span>\frac{{\mathrm{<span\; class="notranslate">\; Q</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}}}{{\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; p</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&CenterDot;</span>\mathrm{<span\; class="notranslate">\; dt</span>}$

The corresponding position x of the piston of the cylinder 10 serving as actuator 19 is calculated. Here, A is the pressure impactable area of the actuator 19, that is, the piston of the working cylinder 10, and Q _k is the compression flow rate, which is according to the relation

Q _K ＝V·dp/dt

Proportional to actuator volume and pressure change, where V is the volume, which consists of dead volume (i.e. volume of lines, hoses, etc.) and stroke-dependent cylinder volume. K _p1 and K _p2 are pressure-dependent correction factors for the volume flow Q _N and the compression flow Q _k . These correction factors take into account the current pressure and temperature effects/heating effects, which are taken into account together with polytropic factors. This coefficient is automatically determined by the translational speed of the cylinder, the pressure change and the magnitude of the pressure. The calculated position value x results from the integral of the piston velocity, so that it is also obtained in a simple manner by discarding the integral.

The volume flow and pressure sensor device 17 can be used both for the supply of pressure medium via the associated supply line 13 and for the discharge of the pressure medium. The two correction factors are expediently taken into account as positive values if the measurement takes place during a fluid feed. The two correction factors are expediently taken into account as negative values when measuring during fluid discharge.

The volume flow and pressure sensor device 17 can also be connected to the other ( 14 ) of the two feed lines. Likewise, there is the possibility of simultaneously connecting the respective volume flow and pressure sensor systems to all supply lines 13 , 14 , which are then expediently connected to one and the same controller 18 .

The determined position value x can be displayed and/or stored or recorded in the display device and/or the recording device 20 .

When determining the position according to the method described above or according to the relationship explained above, the measurement begins with the control signal for the valve assembly 12 via which the volume flow is initiated. By subjecting the pressure model and the volume flow model to plausibility control, the method can also be made more reliable and simpler for pure end position determination. For example, the measured values for pressure and volume flow are equal to zero at the start of the process. When the actuator 9 leaves the end position, the pressure and the volume flow reach their maximum values. When the opposite end position is reached by the actuator 9, the final value is determined for the pressure, while the volume flow becomes zero.

Additional diagnostics can also be carried out using the volume flow and pressure sensor arrangement 17 , for example by measuring the pressure rise time and detecting the switch-on time via the pressure sensor.

FIG. 2 shows a valve assembly 21 designed as a valve block as a fluid system, which consists of a plurality of plate valves 22 or other valves arranged next to each other. Two of the plate valves 22 are correspondingly equipped with a volume flow and pressure sensor device 17 which is assembled as an assembly module to the corresponding plate valve 22 . In principle, each of the plate valves 22 can also be provided with its own volumetric flow and pressure sensor arrangement 17 , wherein, in addition to assembly, an embedded installation is also possible. The evaluation of the model of the control signal at the controller 18 or another control device (also for example an internal control device of a valve island) can reduce sensor costs. These control signals already exist in the valve bank. Since all valves are rarely switched on at the same time, depending on the current switching state, the measurement signals of the volume flow and pressure sensor device 17 are associated with the correspondingly activated valves or plate valves 22 with corresponding actuators. For this purpose, it is also possible to provide only a single volume flow and pressure sensor device 17 for all valves or plate valves 22 , which is arranged in a common fluid supply line. Corresponding evaluation electronics (Auswerteelektronik) with switching matrix (Schaltmatrix) can also be integrated in the valve block. Depending on the application, the volume flow and the number of pressure sensor devices 17 may vary. If only the end positions are of interest, only the volume flow measurement signal can also be evaluated for rough conclusions about the end positions, wherein then no pressure acquisition or a pressure sensor contained in the module is necessary.

FIG. 3 shows an enlarged partial area of fluid-operated cylinder 10 with its piston as actuator 19 . The cylinder 10 has a cylinder casing 23 which is closed at the end region shown by a cover 24 . The volume flow and pressure sensor arrangement 17 is integrated as a built-in module in a cover 24 , which is designed in particular as a cylinder head. As an alternative thereto, it can also be assembled as a module on the outside on the cover 24 or on the outside on the cylinder jacket 23 . In the embodiment, a fluid-operated cylinder is shown as a fluid system. However, the invention can also be applied to other actuators as fluid systems, wherein the fluid system can have several actuators or working cylinders.

As already implemented, the object of the present invention is to obtain indirect position in the fluid system or actuator (eg drive, cylinder, etc.) by using volumetric flow and pressure sensor means. The advantages here are reduced susceptibility to interference, reduced commissioning and wiring costs, and lower maintenance costs.

The cylinder 10 shown has a piston rod, but can also be designed without a piston rod. Instead of the illustrated working cylinder 10 , other fluid-actuated actuators can also be present, for example rotary drives, cracker cylinders, manual actuation devices or clamping devices.

Claims (10)

1. A position measuring device for acquiring the position of at least one actuator (19) of a fluid system (10) without a position sensor arrangement, with a controller and with at least one device for controlling the A fluid control valve (12; 22) of a fluid system (10) and a volumetric flow and pressure sensor device (17) connected to an input line (13) leading to said fluid system (10), which directly connected with the controller (18), wherein the controller (18) has a function according to the relation to calculate the position x of the actuator (19), where A is the area of the pressure impact of the actuator (19), Q _N is the measured volume flow, K _p1 and K _p2 are pressure dependent and Q _K is the compression flow which depends on the effective total volume V and on the time derivative of the measured pressure p. 2. Position measuring device according to claim 1, characterized by a compression flow according to _Qk =V·dp/dt. 3. The position measuring device according to claim 1 or 2, characterized in that the volume flow and pressure sensor device (17) is connected to at least one of the control valves (12, 22) and the fluid system ( 10) Between. 4. The position-measuring device as claimed in claim 1 or 2, characterized in that the volume flow and pressure sensor arrangement (17) is designed as a measuring module. 5. The position measuring device according to claim 1 or 2, characterized in that the volume flow and pressure sensor device (17) is mounted at least one of the control valves (12, 22). 6. The position measuring device according to claim 5, characterized in that a plurality of control valves (22) form a valve block (21) which is provided with at least one volume flow and pressure sensor arrangement (17). 7. The position measuring device according to claim 1 or 2, characterized in that the volume flow and pressure sensor arrangement (17) is associated with a plurality of actuators. 8. The position-measuring device according to claim 7, characterized in that the controller (18) has a function for combining the acquired measurement signals of the volume flow and pressure sensor device (17) with the correspondingly manipulated The devices of the fluidic system are correlated in time. 9 . The position-measuring device according to claim 4 , characterized in that the volume flow and pressure sensor device ( 17 ) is designed as an assembly module or as a built-in module. 10 . 10. The position measuring device according to claim 5, characterized in that the volume flow and pressure sensor device (17) is installed in at least one of the control valves (12, 22).