DD226407B5 - Position controlled electrohydraulic actuating cylinder drive - Google Patents

Description

For this 3 pages drawings

Field of application of the invention

The invention relates to a position-controlled electro-hydraulic actuating cylinder drive with a control cylinder upstream servo valve, which may be without internal feedback, the position control loop subordinate speed control loop and arranged between position controller and speed controller Geschwindigkeitsdifferenzbildner, the control operations computer-aided and sampled run and a subtractor of the position control circuit Soll -Weg increments and actual-displacement increments are supplied and an integrator is connected downstream, using an incremental position-actual-value encoder that outputs an actual path increment in the duty cycle, which maps an actual speed value.

Characteristic of the known technical solutions

At a position-controlled actuating cylinder drive, the requirement is made that it should perform positioning operations quickly, free from overshoot and even at the lowest feed speeds.

In order to achieve this dynamic behavior, it is already known from the journal о + ρ "Ölhydraulik und pneumatik" 1982 No. 8, pages 579-584, to provide a multi-loop control loop structure, but the complexity increases with the number of control loops The computer carries a part of this effort within the scope of the control tasks assigned to it, but it is only used economically if it fulfills other tasks, which requires the control to be keyed and the periods of time reserved for the others to be as long as possible By contrast, the above-mentioned dynamic behavior of the actuating cylinder drive can be achieved the better, the shorter the scanning times for the control are away from each other, which disadvantageously leads to uneconomical utilization of the computer and thus to great expense.

From the journal о + ρ "oil hydraulics and pneumatics" 1982 No.7 page 524, it is also already known to achieve the dynamic behavior described by the fact that in the actuating cylinder drive a servo valve with better dynamics is used.

Such a servo valve is equipped with an internal feedback and more expensive than a conventional simple servo valve.

Object of the invention

The aim of the invention is to achieve the desired dynamic behavior with less effort and to get along with a simple servo valve without internal feedback.

Presentation of the essence of the invention

The cause of the defect indicated in the characteristic of the known technical solutions consists in the insufficient effort optimization according to oppositely influencing influencing factors.

To remedy this cause, the invention has the object, a computer-aided and keyed working control for a position-controlled electro-hydraulic actuating cylinder drive, consisting of a hydraulic, a carriage driving actuating cylinder, which is preceded by a servovalve equipped with or without internal feedback, wherein the carriage with an incremental position-actual-value encoder, which outputs a speed-mapping actual-path increment per duty cycle, is equipped, and the output of the position-actual value encoder with the subtrahend input of a subtractor whose minuenden input to a setpoint generator for the Sollweginkrement the Tastzyklusses and its output is connected via an integrating member forming the positional deviation with the input of a position controller whose output is connected to the Minuendeneingang a speed difference former, the subtrahendeneingang via a product image generator for amplification Speed feedback is also connected to the output of the position-actual value encoder, and the output of the speed difference former is connected via a speed controller to the input of the servo valve, so that can be positioned quickly and free from overshoot at long sampling times and also at smallest feed rates, the movement is continuous. In a first inventive solution, this is achieved in that a first input of an adaptation element with the Minuendeneingang the difference former and the output of the position setpoint value encoder, and a second input of the adaptation element with the Subtrahendeneingang the difference former and with the output of the position actual value encoder

connected, and the output of the adaptation element via a signal source for the gain of the

Velocity feedback is connected to the gain input of the product builder. In this case, the adaptation element is internally from its first input via a first absolute value generator with a first input

a switch and from its second input via a second amount forming with a second input of the

Comparator and connected to a second input of the switch, the output of the comparator with the Control input of the switch is connected and the neutral point of the switch forms the output of the Adaptionsgiteds. The signal source for the gain factor of the speed feedback is internal in a first advantageous embodiment

from its input via a threshold to the control input of a switch, the switch is connected via its first input to a first signal generator for a high value of the gain and its second input to a second signal generator for a low value of the gain and the

Star point of the switch forms the output of the signal source. The signal source for the gain factor of the speed feedback is in a second advantageous embodiment

internally from its input to a first input of a multiplier and the output of the multiplier to the

Subtrahendeneingang a Subtrahiergliedes led, wherein a first signal transmitter fulbaktungsfaktor with a

second input of the multiplier and a second signal generator for a high value of the gain with the

Minuendeneingang the subtractor is connected and the output of the subtractor the output of the signal source

forms.

In a second solution according to the invention this is achieved in that the output of the integrator at a Amount generator and its output via a signal source for the gain factor of the Velocity feedback with

connected to the gain input of the product designer. The further internal design of the signal source for the

Reinforcement factor of the speed feedback takes place in the same advantageous embodiments as in the first

solution according to the invention.

The solutions according to the invention influence in dependence on the speed modulation of the Servo valve, the actuating cylinder such that in the vicinity of the closed position of the servo valve, a very high gain

consists.

embodiment The invention will be explained in more detail below with reference to an embodiment. Show it

1 shows a block diagram of the position control loop with the electrohydraulic actuating cylinder drive FIG. 2 shows a section from FIG. 1 with a first embodiment of the adaptation element according to the invention FIG. 3 shows a detail from FIG. 1 with a second embodiment of the adaptation element according to the invention a first embodiment of the signal source according to the invention for the gain of

Speed feedback Fig. 5: a second embodiment of the signal source according to the invention for the gain factor of

Velocity feedback. According to FIG. 1, the minuend input of a differential former 2 is connected to a setpoint value transmitter 1. the Difference formers 2 are connected in series with an integrator 3 and a position controller 4. A speed difference former 5 is

connected via its Minuendeneingang the Lageregler4 and the output side to a speed controller 6 out.

An electro-hydraulic drive includes a servo valve 7, a damping throttle 8 and a control cylinder 9. The servo valve. 7

is connected to the speed controller 6 and the actuating cylinder 9 is coupled to the carriage 10 of a machine tool.

From an incremental position-actual value encoder 11, whose displaceable part is fixedly connected to the carriage 10, leads a Connection back to Subtrahendeneingang the difference former 2 and closes the position control loop. The position control loop is subordinated to a speed control loop, wherein a product former 12 with its first input on Position actual value encoder 11 is connected and the output side with the subtrahend input of the speed difference former

5 is connected.

An adaptation element 13 is provided with two inputs. The first input is at the set value encoder 1 and the second input at the Position / actual value encoder 11 connected. A signal source 14 for the gain factor of the speed feedback

connects the output of the adaptation element 13 to the second input of the product former 12.

The adaptation element 13 has, according to FIG. 2, a first absolute value generator 15 at the first input and a second absolute value generator 15 at the first input

second modifier 16 on. A comparator 17 and a first change-over switch 18 are each connected in parallel with their first input parallel absolute value formers 15 and in each case with their second input on the second absolute value generator 16. The

Output of the comparator 17 is connected to the control input of the first switch 18 whose star point the output

of the adaptation member 13 forms

According to Figure 3, the adaptation member 13 is in an alternative embodiment of the difference former 2 and the

Downstream integrator 3 together.

In this case, both the position controller 4 and the signal source 14 for the gain factor of the speed feedback

connected to the integrator 3, since its output forms the output of the adaptation element 13.

The signal source 14 for the gain factor of the speed feedback contains according to Figure 4 on the input side

third absolute value 19. This is a threshold value 20 downstream with adjustable threshold. A second

Switch 21 is provided with its first input to a first signal generator 22 for a high value of the amplification factor

and its second input connected to a second signal generator 23 for a low value of the amplification factor. The neutral point of the second switch 21 forms the output of the signal source 14.

According to FIG. 5, the third absolute value generator 19 in an alternative embodiment of the signal source 14 for the Speed feedback of the first input of a multiplier 24 downstream. The exit

of the multiplier 24 is connected to the subtrahend input of a subtractor 25. The second entrance of the

Multiplier 24 is connected to a third signal generator 26 for an attenuation factor, the Minuendeneingang the subtractor 25 to a fourth signal generator 27 for a high value of the gain factor. The output of the subtracter 25 forms the output of the signal source 14.

The mode of action of the solution according to the invention is as follows:

The position control loop is operated by key. As a result, in each case a speed value corresponds to the setpoint increment output by the setpoint value generator 1 per duty cycle or to the actual displacement increment output by the position / actual value encoder 11 per duty cycle. By touch time, the difference former 2 thus determines a differential speed. The integrator 3 is a summation register, forms the integral of the differential speed and generates an output signal corresponding to the position error. This is at a high speed of movement of the carriage 10 and large when the movement is at rest.

The adaptation member 13 adapts the gain factor of the speed feedback, which is generated by the signal source 14, to the respective movement speed of the actuating cylinder drive.

The adaptation member 13 detects the complex consideration of this movement speed both the actual value and the target value. It outputs a large value at a large actual-value or target-value movement speed, and vice versa.

In its embodiment according to Figure 2, this is done by the fact that the comparator 17 brings the first switch 18 respectively in that position in which the respective larger amount of the input variables, that is, the desired path increment and the actual path increment, in respective duty cycle to the output of the adaptation element 13 passes.

This larger amount is imaged indirectly in the size of the positional error and used according to Figure 3 in a different form.

The gain factor of the speed feedback is generated in the signal source 14. If this has the embodiment according to FIG. 4, then these are two discrete values of the amplification factor. The second switch 21 connects in its rest position the first signal generator 22 for a high value of the gain to the output of the signal source fourteenth

Only when the output signal of the adaptation element 13 reaches a certain size and thereby exceeds the set switching threshold of the threshold value switch 20 does the second changeover switch 21 change from the first signal generator 22 to the second signal generator 23 which outputs a low-value amplification factor.

In the embodiment according to FIG. 5, instead of two discrete amplification factors, a single amplification factor which can be set to any desired size is effective. The basic value of this amplification factor is supplied by the fourth signal generator 27. Its arbitrarily reducible size is formed by means of the third signal generator 26, which generates an adjustable attenuation factor and makes the same via the multiplier 24 in the subtractor 25 effective.

The amplification factor output by the signal source 14 has a magnitude inversely proportional to the output signal of the adaptation element 13. For example, the lower the positional error, the greater the gain factor of the speed feedback. The functional complex of the adapter 13 and the signal source 14 works equally when it is assumed that instead of the positional error of the movement speed. The condition for realizing an increased speed feedback gain is met at low default and actual values for the movement speed of the carriage 10, where it causes a high degree of movement continuity. It is thus fulfilled in or near the target position and prevents overshoot there.

The length of the tactile time can be extended by the introduced circuit changes in the position control loop. This results in a duty cycle free time shares that can be used in a computer-aided execution of the position control loop from the computer for other tasks, so that at the same time an economical use of the computer is secured.

Claims (5)

claims: 1. Position-controlled electrohydraulic actuating cylinder drive, consisting of a hydraulic, a carriage driving actuator cylinder, which is preceded by a servovalve equipped with or without internal feedback, wherein the carriage in a computer-aided and keyed working arrangement with an incremental position-actual-value encoder, the one per cycle outputs a velocity-mapping actual-displacement increment is equipped, and the output of the position-actual value encoder with the subtrahend input of a subtractor whose minuenden input to a setpoint value encoder for the desired value increment of the Tastzyklusses and whose output is connected via an integrating member forming the position deviation with the input of a position controller whose output is connected to the Minuendeneingang a speed difference former whose Subtrahendeneingang via a product image generator for gain control of the speed feedback ebe.nfalls on Au the position of the position difference sensor is connected via a speed controller to the input of the servo valve, characterized in that a first input of an adaptation element (13) with the Minuendeneingang the difference former (2) and the output of the position setpoint value encoder (1), and a second input of the adaptation element (13) to the Subtrahendeneingang the difference former (2) and to the output of the position-actual value encoder (11) is connected, and the output of the adaptation element (13) is connected to the gain input of the product former (12) via a speed feedback gain signal source (14). 2. Position controlled electrohydraulic actuating cylinder drive, consisting of a hydraulic, a carriage driving actuating cylinder, which is preceded by a servovalve equipped with or without internal feedback, wherein the carriage in a computer-aided and keyed working arrangement with an incremental position-actual value encoder, the is equipped with a velocity-depicting actual-displacement increment per cycle, and the output of the position-actual-value encoder with the subtrahend input of a subtractor whose minuenden input to a setpoint value encoder for the desired path increment of Tastzyklusses and whose output is connected via an integrating member forming the position deviation with the input of a position controller whose output is connected to the Minuendeneingang a speed difference former whose subtrahenden input via a product generator for gain control of the speed feedback also at the output ng the position-actual value encoder is connected, and the output of the speed difference former is connected via a speed controller to the input of the servo valve, characterized in that the output of the integrator (3) to an absolute value generator (19) and its output via a Signal source (14) for the gain factor of the speed feedback to the gain input of the product former (12) is connected. 3. Position-controlled electro-hydraulic actuating cylinder drive according to claim 1, characterized in that the first input of the adaptation member (13) via a first absolute value generator (15) with a first input of a comparator (17) and with a first input of a changeover switch (18) is connected and the second input of the adaptation element (13) is connected via a second absolute value generator (16) to a second input of the comparator (17) and to a second input of the changeover switch (18) and the output of the comparator (17) to the control input of the changeover switch (17). 18) is connected and the neutral point of the changeover switch (18) forms the output of the adaptation element (33). 4. Position-controlled electro-hydraulic actuating cylinder drive according to claim 1 or 2, characterized in that the input of the signal source (14) for the amplification factor of the speed feedback via a threshold value switch (20) on the control input of a changeover switch (21) is guided, the changeover switch (21) via its first input is connected to a first signal generator (22) for a high value of the amplification factor and via its second input to a second signal generator (23) for a low value of the amplification factor and the star point of the changeover switch (21) the output of the signal source (14 ). 5. Position-controlled electrohydraulic actuating cylinder drive according to claim 1 or 2, characterized in that the input of the signal source (14) for the gain of the speed feedback to a first input of a multiplier (24) and the output of the multiplier (24) to the subtrahend input of a subtractor ( 25), a first signal generator (26) for a attenuation factor is connected to a second input of the multiplier (24) and a second signal generator (27) for a high value of the amplification factor is connected to the minuend input of the subtracter (25) and the output of Subtractor (25) forms the output of the signal source (14).