DE102009006056A1 - Actuating device comprises drive element, control device for controlling the drive element, actuating element driven by the drive element, and sensor device, which determines characteristic value for the movement of the actuating element - Google Patents

Abstract

The actuating device comprises a drive element (2), a control device (4) for controlling the drive element, an actuating element (10) driven by the drive element, first sensor device (6), which determines first characteristic value for the movement of the actuating element and releases characteristic signal derived from the characteristic value at the control device, and second sensor device (8), which determines second characteristic value for the movement of the actuating element and releases second characteristic signal derived from the second characteristic value at the control device. The actuating device comprises a drive element (2), a control device (4) for controlling the drive element, an actuating element (10) driven by the drive element, a first sensor device (6), which determines a first characteristic value for the movement of the actuating element and releases a characteristic signal derived from the characteristic value at the control device, a second sensor device (8), which determines a second characteristic value for the movement of the actuating element and releases a second characteristic signal derived from the second characteristic value at the control device, a logic linking device, which links the signals together derived from the first and second characteristic value and releases a characteristic reference value for logic linking, and a smoothing device, which smoothes the reference value by averaging. The first sensor device is a position sensor and the second sensor device is a force sensor. The sensor devices are arranged on the actuating element. The logic linking device differentiates the second characteristic signal to the first characteristic signal. An independent claim is included for a method for regulating an actuating device.

Description

The The present invention relates to an actuator for operating machines. In such actuators can For example, cylinders for pneumatic or hydraulic drives act, but also to electrically powered Drive devices or drive elements. The invention is However, it is described with reference to electric servo cylinders It should also be noted that the invention also applies to other drive systems. or actuators may apply.

Out the prior art are such actuators known for a long time. It is also known in particular that Such actuators have regulations that for example, depending on a position of a Actuate perform this regulation.

independent Position controls are well known in servo technology. Also, force and torque controls are known. It is in particular known that in electric drives, the current or voltage is regulated, in hydraulic and pneumatic systems, the pressure.

The Actuators are either pneumatic, hydraulic or electrically powered. The regulation of the actuators will correspondingly by pneumatic, hydraulic or electrical switching elements realized. Increasingly, however, a superordinate electrical system is spreading Control technology. In the following, therefore, this technique becomes exemplary further described.

The The heart of an electrical control is the current control loop. It is superordinated to a speed control loop, the also called speed control loop. Again, about it then arranged the position control loop. This position control is over realized a first sensor, directly on the actuator attached and the actual position or position value supplies. The speed value is usually by Differentiation of the position value formed and not by a separate Sensor.

in the State of the art, the actuators not only in position control, but also in speed control operate. On the exact regulation of the actual position is then waived. Likewise can also on the speed control be waived and the actuator only in current control be operated, the current then proportional to an exerted Force or a moment is.

such However, indirect force controls have the disadvantage of being vulnerable are for disturbances. If the Power is generated by an electric motor, then the actual Power is proportional to the engine torque, but this is because the finite number of poles depends on the instantaneous angle of the rotor relative to the stator. The moment is distorted by the so-called cogging torque. In addition, the engine torque is still due to the temperature, the speed, acceleration, friction, slippage and deviations affected. The same applies to linear motors.

A particularly favorable application for an inventive Actuating device results for welding tongs and in particular spot welding guns, in this application the forces exercised within defined Precise control of force limit values. The present invention is on any task for force control or force monitoring Applicable, because of compliances, friction, resistances, variable or unsteady stiffnesses, non-linearities, current fluctuations, Torque deviations or other disturbances the position of an actuator is better and more precisely controlled than its force effect. Furthermore, it should be noted that the present invention Also applicable to pressure controls.

at the above-described application of a servo spot welding gun the force of the pliers should be within certain position values of the Pliers position or the pliers opening monitored and / or readjusted become. The pliers may only or must have certain forces exercise the sheets to be welded. In doing so may but the forces only occur within certain positions because sudden deviations, such as B. false sheet thicknesses, lost or glued electrodes, deformed components or show faulty welds. On the other hand should However, creeping deviations, as z. B. by gradual Wear occurs within certain defined limits be tolerated.

direct Force regulations are purely mechanical only outside the friction of the system possible. As long as a force smaller than the self-friction, the effect remains in the self-friction hang. Only when a force is greater than it can also be effective. The amount The self-friction gives the range of force variation that can create a movement, and within that range is No regulation possible because nothing moves.

The DE 44 32 573 C2 try this pro to solve and describes a method for controlling the force on a resistance welding clamp or the like. In this method, a numerically controlled electric motor is provided, which is equipped with a screw drive. In this case, before a welding process, the electric motor via a screw drive on the welding electrodes successively two different forces, and the associated rotation angle are recorded. From these values, a spring constant of the power train of the welding machine is determined, and by means of this spring constant, during each phase of the subsequent welding process, a unique relationship is established between any desired force and the corresponding angle of rotation to be performed by the electric motor.

This will be in the DE 44 32 573 C2 describes how the rigidity of the system is determined via two force-position coordinate points and this rigidity is then used for conversion. Thus, in the case of this development, no force control is performed, but a force determination over the way and a spring constant. From the position is closed back to the force and no longer regulated on the force but only on the situation. In the actual process, after determination of the spring constant, no force sensor is any longer involved in the regulation.

The described method according to the DE 44 32 573 C2 has the disadvantage that the stiffness must be determined separately and stored and then not changed, so that it is actually only a force control. A return of the instantaneous force signal does not take place.

To EP 1 508 396 B1 Another method of force control in welding processes is to register position data and compare it with the force data. Via a calibration run or a precalculation, a desired course of the force over the position is determined and a permissible deviation or a permissible tolerance band is defined. During operation, the actual data are then compared with the expected values. Thus, in this approach, no direct control is performed, but only a monitoring, the expected data over several operating cycles can also be adjusted. The patent explicitly emphasizes that the force regulator is connected either before or after the position controller. So there is only one manipulated variable on the position value, but no cascade control. In addition, the force signal is not combined with the position signal and processed to adjust and correct the guide size D, which corresponds to the pliers stiffness. It is assumed that this guideline is constant. In reality, however, the force-displacement behavior is non-linear, especially if the sheets to be welded are not sufficiently close to each other and must first be compressed.

Of the The present invention is therefore based on the object, a scheme for such actuators available to provide, which in comparison to the described prior art works more accurately and in particular, for example, engine-related Deviations and nonlinearities can compensate. Especially should be exercised in a spot welding gun Forces within defined force-position limits dominated become.

This is inventively by an actuator according to claim 1 and a method according to claim 8. advantageous Embodiments and developments are the subject of Dependent claims.

A Actuator according to the invention has a drive element and a control device for control of the drive element. Furthermore, one of the drive element provided driven actuator, wherein the actuating device a first sensor device having a first for a movement of the actuator characteristic Characteristic determined and derived from this characteristic characteristic Output signal to the control device.

According to the invention the actuator a second sensor device on which a second for the movement of the actuating element characteristic characteristic value and one from this characteristic value derived characteristic signal to the control device outputs. The actuating element may be, for example to act an actuating rod, which is another Machine drives. Also, it may be in the actuator to act a servo cylinder, in turn, a welding gun actuated. The actuating element and the drive element can also exist as a unit and are also referred to below as an actuator designated.

Of the Prior art is first through the present invention by extended a superordinate force control. The special The invention is that the force control in addition to linked to the underlying position control loop. From both Signals, the force and the path, a guideline value D is formed, which can then be further processed and for the scheme most advantageous options offers.

Under a characteristic of the movement of the actuator value can at For example, be understood by the force exerted by this force, its speed or its acceleration. The same applies to the second characteristic of the movement of the actuator characteristic. The characteristic signal may be, for example, a position value or a force value.

In order to is proposed in the context of the present invention, which naturally to use the finite stiffness of a system to the resulting actually applied force through a change the deflection, deformation or the position to regulate. about this stiffness relationship is the force dependent on the deflection. So if the position of an actuator can be regulated, it can directly the applied force can be regulated.

at an advantageous embodiment, the actuating device a linking device, which from the first Characteristic derived signal and derived from the second characteristic Signal linked together and one for this Link outputs characteristic guideline. In this The guideline can, for example, be a derivation of the force act according to the situation.

More accurate if the drive element can be an actuator, for example, an electric servo cylinder or any other Element. This actuator already has conditional in the prior art by the task of a control a sensor, for example a position sensor or a force or pressure sensor. For the inventive execution of the combined Regulation is this drive element still with another sensor Mistake. It is possible that a force-actual signal is compared with a force command value and a force correction value is output. In addition, as mentioned, with the force and the position signal determines a benchmark and thus again generates a position correction value. This correction value becomes together with the position setpoint and the position actual value to the drive passed.

Corresponding is at least one sensor device from a group of sensor devices which force sensors, position sensors, acceleration sensors, Speed sensors, temperature sensors, magnetic field sensors, or the like. In particular, the first sensor device a position sensor and the second sensor device, a force sensor.

Especially at least one sensor device is preferred, and particularly both sensor devices are arranged on the actuating element and thus directly measure a parameter of this Actuating element.

The described force-position control can be the rigidity or even the Monitor or compensate for the inherent friction of a system. The force generating engine torque or the pressure of a fluid is tracked depending on the position signal. To this In this way, navigation on the force-displacement level is possible. More precisely, the actual course of the force-distance coordinates with a Target course compared. According to the invention So a multi-dimensional regulation, which also still by more Sensors, linking devices and detection units can be extended. It is particularly irrelevant where exactly which sensors are mounted spatially or structurally, decisive is the logical use.

With This force control can be driven very gently on a hard stop become. The position setpoint does not have to match the position of the stop cover, he may even lie before the plot. In this case is the force-actual value is smaller than the desired force desired value, so that this position setpoint continues in the control loop for so long until the stop is touched and a force reaction he follows.

Also it would be possible to differentiate the force signal according to the position signal, d. H. of the second characteristic Signal after the first characteristic signal also a piercing process to detect and regulate, in which case said Benchmark becomes negative. This negative value results from corresponding negative differences of the forces.

Prefers the linkage differentiates the second characteristic Signal after the first characteristic signal, d. H. especially the force signal after the position signal. It would be too possible instead of or in addition to this differentiation of the force signal after the position signal to use the inverse of this signal to possible limit value problems in a subsequent forecasting module to avoid.

at A further advantageous embodiment is a smoothing device provided, which the above-mentioned guide values, in particular even by averaging. It is possible to further improve the properties of force control by: the said benchmark over an averaging smoothed or via a statistical evaluation is prepared for a forward-looking prognosis. More detailed knowledge The system also allows other measures, such as Security functions or the monitoring of error possibilities.

The The present invention is further directed to a method of controlling an actuating device, in particular an actuating device of the type described above. It drives a drive element the actuator is an actuator and the drive element is controlled by a control device. In this case, a first sensor device determines a first for the Movement of the actuator characteristic characteristic and gives a characteristic derived from this characteristic Signal to the control device off. Derived from this Signal can be both the signal itself and by a value determined from this, for example by derivation or differentiation or other mathematical operations, resulting Value.

According to the invention the actuator a second sensor device or even further sensor devices, which have a second characteristic of the movement of the actuator Characteristic determines (or even further) and one from these characteristic values derived characteristic benchmark to the Regulierungsseinrichtung weiterergibt and in particular the drive element on the basis of which multidimensional control is provided.

there it is, as mentioned, not required to be immediate the said signals can be used, it can also off signals derived from these signals are used, such as those above mentioned differentiations, averaging and the like.

at A preferred method is based on the first characteristic Signal and the second characteristic signal is a benchmark formed and the drive element also based on the benchmark regulated. This benchmark may be as mentioned above, for example, a derivative of the Force value according to the position value act.

at Another preferred method is the drive element as well controlled on the basis of position setpoint values and / or force setpoint values. These For example, force command values and target position values by a user or by a parent Machine control can be specified. Preferred is based on of the guide value and a force difference value, a position correction value determined. This position correction value in turn serves to control of the drive element. In this case, this position correction value, for example by multiplying the guideline value with the force difference value be determined.

at Another preferred method is the position correction value together with a position setpoint and a position actual value to the Control device output for controlling the drive element.

at Another preferred method will be occurring deviations between setpoints and actual values only with a certain sign authorized.

Because of the functional relationship between position and force arises in reality often a deviation between nominal and actual value. However, it may require further signal conditioning above-mentioned guide value or the correction values be done so that a control deviation only in a desired Direction on the force-displacement level results.

at Another preferred method is at least one correction value limited. More precisely, it is possible to or monitoring member the force-position actual values, an additive position correction value or also a force correction value or a processed position setpoint to limit or monitor before the drive to unwanted or to exclude oversized movements or to monitor possible errors.

Further advantages and embodiments will become apparent from the attached drawing:
Showing:

1 a block diagram-like representation of an actuating device according to the invention.

1 shows an actuating device according to the invention 1 , This actuator has a drive element 2 on. In addition, there is a control device 4 provided which a position control of a drive element 2 performs. In particular, speeds V and currents I of the drive element can be regulated. This drive element 2 is in communication with an actuator and forms with this an actuator. At the in 1 In the embodiment shown, this actuator is an electro-servo cylinder. Furthermore, this actuator has two sensor devices 6 . 8th more precisely a position sensor 6 and a force sensor 8th on which _is respectively appropriate force and position values F and X _is determined and output. The position value X _is thereby both at a subtraction point 24 issued as well as to a linkage point 14 ,

Also, the force value F _is to this linking device 14 output. This linking device 14 determines a guideline value D, which is a derivative of the force value according to the position value. Furthermore, the force value F _is also at a subtraction point 18 is output, where it _is compared with an input force setpoint F _soll and a difference value .DELTA.F is output accordingly.

The reference number 16 refers to a determination unit which, for example, determines an average value or a forecast value on the basis of the reference value D. In this case, this can determine the forecast value and the actual position values _is X and the force values _F are used.

The correction value ΔF is linked to the reference value D, more precisely via a proportional element 26 multiplied by this and in this way a position correction value ΔX is generated. This position correction value .DELTA.X is at a summation point with the position setpoint X _soll 22 is added and together with the actual position value X _is at the subtraction point mentioned above 24 output. At this subtraction point, the difference between the two values is formed and sent to the drive control 4 for controlling the drive element 2 forwarded.

All Features disclosed in the application documents are considered to be essential to the invention as far as they are individually or in combination the prior art are new.

1

actuator

2

driving element

4

control device

6

position sensor

8th

force sensor

10

actuator

14

linking device

16

determining unit

18

subtraction

22

summing

24

subtraction

26

proportional element

D

benchmark

F

force

F _is

force value

F _should

Force command

I

amperage

V

speed

X

location

X _is

position value

X _should

Position setpoint

ΔF, ΔX

difference value the power

.DELTA.X

difference value the situation

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - DE 4432573 C2 [0011, 0012, 0013]
• - EP 1508396 B1 [0014]

Claims (12)

Actuating device ( 1 ) with a drive element ( 2 ), a control device ( 4 ) for controlling the drive element ( 2 ) and with one of the drive element ( 2 ) driven actuator ( 10 ), wherein the actuating device ( 1 ) a first sensor device ( 6 ), which has a first for a movement of the actuating element ( 10 ) characteristic characteristic value and derived from this characteristic characteristic signal to the control device ( 4 ), characterized in that the actuating device ( 1 ) a second sensor device ( 8th ) having a second for the movement of the actuating element ( 10 ) characteristic characteristic value and derived from this characteristic second characteristic signal to the control device ( 4 ). Actuating device ( 1 ) according to claim 1, characterized in that the actuating device ( 1 ) a linking device ( 14 ), which combines the signal (X _actual ) derived from the first characteristic value and the signal (F _actual ) derived from the second characteristic value and outputs a characteristic value (D) characteristic of this combination. Actuating device ( 1 ) according to at least one of the preceding claims, characterized in that the first sensor device ( 6 ) a position sensor and the second sensor device ( 8th ) is a force sensor. Actuating device ( 1 ) according to at least one of the preceding claims, characterized in that at least one sensor device ( 6 . 8th ) on the actuating element ( 10 ) is arranged. Actuating device ( 1 ) according to at least one of the preceding claims 2-5, characterized in that the linking means the second characteristic signal (F _actual ) after the first characteristic signal (x _actual ) differentiated. Actuating device ( 1 ) according to at least one of the preceding claims 1-6, characterized in that a smoothing device ( 18 ) is provided, which smoothes the guide values (D), in particular by averaging. Method for controlling an actuating device ( 1 ), wherein a drive element ( 2 ) of the actuating device is an actuating element ( 10 ) drives and the drive element of a control device ( 4 ) and wherein a first sensor device ( 6 ) a first for a movement of the actuating element ( 10 ) characteristic characteristic value and derived from this characteristic characteristic signal to the control device ( 4 ), characterized in that the actuating device ( 1 ) a second sensor device ( 8th ) having a second for the movement of the actuating element ( 1 ) characteristic characteristic value and derived from these characteristic characteristic guide variable (D) to the control device ( 4 ) and the drive element ( 2 ) is regulated on the basis thereof. A method according to claim 7, characterized in that on the basis of the first characteristic signal (X _actual ) and the second characteristic signal (F _actual ), a directional variable (D) is formed and the drive element ( 2 ) is regulated on the basis of this guide value (D). Method according to at least one of the preceding claims 7-8, characterized in that the drive element is regulated on the basis of position setpoint values (X _setpoint ) and / or of force setpoint values (F _setpoint ). Method according to one of the preceding claims 7-9, characterized in that based on the guide size (D) and a force difference value (.DELTA.F), a position correction value (ΔX) is determined. Method according to at least one of the preceding Claims 7-10, characterized in that occurring Control deviations between setpoints and actual values only after certain Criteria are allowed. Method according to at least one of the preceding Claims 7-11, characterized in that at least a correction value is limited.