DE2640080A1 - DEPENDENCY CONTROL - Google Patents

Description

The invention relates to a dependency control at that the variable parameter is compared with a command signal will] the control particularly concerns the proportional controls.

The disadvantages of the "all or nothing" controller the. only become active when the variable parameter has exceeded the setpoint or command value are known. According to the rate of change of the parameter under consideration, the inertia of the device to be controlled and the hysteresis occur in the device pumping phenomena

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around the setpoint with more or less great importance; these phenomena can cause difficulties in use; resulting from the control

It. there are also the prορortzonal controls that allow it, to completely eliminate these errors and to achieve the setpoint without pumping in a very short period of time »

In the very carefully worked out controls of this type, an input value consists of the derivative of the variable input parameter, which generally requires expensive devices which are difficult to use.

The object of the invention is to provide a dependency control to create that is not much more complicated than an "All or Nothing '% control and the function a proportional control guaranteed.

The subject of the invention is a dependency control with a comparator »whose first input is connected to elements that generate a signal corresponding to a target value: and whose second input is connected to elements that generate a signal corresponding to an actual value * while the output of the comparator is connected to elements for controlling a controlled organ; this control is characterized in that it also comprises elements which, in combination with the signal corresponding to the actual value, feed a signal to the second input of the comparator which is the algebraic sum of the actual value signal and its derivative.

Another object of the invention is a dependency control of the type defined above, which is characterized is that it also contains an oscillator whose

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Output connected to the second input of the! Comparator and is intended to give the signal from the algebraic sum of the actual value signal and its derivation a modulation signal to superimpose, the amplitude and frequency of which are suitable, an area in the puncture field of the dependency control to create in which the response speeds for small deviations from the actual signal compared to the target signal are small while the response speed for errors that exceed the level of the modulation signal remains at a maximum.

Further features of the invention will become apparent from the following description.

The attached drawings are only examples of the invention; show it:

Fig. 1 is a schematic representation of a first embodiment of the control according to the invention ;

FIG. 2 shows a schematic representation of a control variant of FIG. 1; FIG.

FIG. 3 shows a schematic representation of the control circuit according to FIG. 2 in its application the speed control of an automobile;

FIG. K shows a schematic representation of a control analogous to that in FIG. 1, in which, however, an additional improvement is used;

5 shows the response curve of an "all or nothing" control in an open circuit without modulation;

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Pig. 6 shows the response curve of an "all or nothing" control in an open circuit with modulation;

7 shows a schematic representation of a further

Improvement of the control according to the invention; and

8 shows a schematic representation of a further one

Improvement of the control according to the invention.

The circuit shown in Fig. 1 has a controlled member, which is shown as a potentiometer 1 and between a positive voltage source and the ground is connected.

The runner of the potentiometer is connected to an input of a comparator 3 via a resistor 2. Of the the other input of the comparator 3 is connected to the runner of a potentiometer 4, which is intended to be the comparator to supply a signal corresponding to a setpoint value.

The output of the comparator changes its state, depending on whether the signal transmitted through the resistor 2 is larger or smaller than the setpoint signal that it receives from the potentiometer H.

The output of the comparator is connected to a power amplifier 5, which has a control element 6, for example an electric motor, via a relay 7 for switching the supply of the motor 6 on or off.

The motor is connected to the rotor of the potentiometer 1, the position of which is the position at every moment the output shaft of the motor reproduces.

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One such control is an "all or." Nothing "that necessarily has to pump around the setpoint, because the motor is fully fed, in every sense that is set by the potentiometer 4, as far as one is on one side or the other of the setpoint is located.

In order to prevent this pumping, one has according to the invention in the above-mentioned circuit in parallel with the resistor 2 a differential amplifier 8 between the runner of potentiometer 1 and the corresponding input of the! Comparator 3 switched.

The amplifier 8 has its two inputs with the lau- * fer of potentiometer 1, one connected via the in Series connected resistors 9, 10 of the same value R and with a capacitor 11 connected between the junction of resistors 9 and 10 and the ground; and the other input via a resistor 12 of the value 2R.

The resistor 9 and the capacitor 11 form an integral stage for the actual signal.

The operation of the circuit just described results are as follows:

The signal coming from the potentiometer 1 is sent to the comparator directly via the resistor 2 and indirectly via the amplifier 8 and its two input circuits 9, 10, 11 on the one hand and 12 on the other hand.

If the time constant RC of the integration stage 9, H are determined exactly as a function of the dynamic response times of the load, the following results:

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a) If the input phenomenon is invariable or only subject to very slow changes, the amplifier 8 has the same signal on its two inputs and supplies a signal O, so that the comparator 3 only receives the actual signal at its input connected to the potentiometer 1 which is fed to him through the resistor 2;

b) if the entrance phenomenon in one or the other Direction changes, the amplifier 8 receives a signal difference at its inputs during the change. the Time constant RC of the circuit 9, 11 brings a delay in the change of the input signal coming through 9 across from the other entrance. The amplifier 8 then supplies a signal with an amplitude and a direction that corresponds to the Speed and the direction of change of the phenomenon.

If you go to this correction signal the main signal the input of the comparator 3 adds, this switches in the sense of a correction before the controlled element 1 the Actual value has reached, and this all the faster as the signal varies more quickly.

In the vicinity of the setpoint, the command is no longer uniform, but pulsating and therefore carries out a Modulation in the speed of the control motor 6 brings about.

The result makes it possible to reach the setpoint faster with this preload and without pumping to persist in him.

FIG. 2 shows a variant of the control according to FIG. 1. This variant is based on the fact that it is possible

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is borrowed the same way to amplify the signal and to use it Generating the "anticipation" to use, which saves components and facilitates the regulation.

The circuit in Fig. 2 differs from that in Fig. 1 in that it contains an integration circuit, which consists of a resistor 13 and a capacitor 14, which are switched into the reaction circuit of the amplifier 8 are. The connection point of the components 13 and 14 of the RC circuit is at that input of the amplifier connected, which is not connected to the potentiometer 1, through a resistor 15.

Here, as in the previous example, the gain of the amplifier 8 is constant and the output does not change if the actual signal coming from potentiometer 1 does not change.

If the input signal of amplifier 8 changes, the time constant of the circuit 13, 14 modifies the gain of the amplifier during the change and its output signal is increased or decreased by a value, the size and direction of which depends on the speed and the The direction of change of the input variable depends.

In this way, a very effective look-ahead phenomenon is created and the time constant of the RC circuit 13, 14 becomes carefully selected taking into account the system that you want to control.

Today it is possible to control amplifiers for speed, position, temperature etc. with the help of a switching block

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to manufacture starting from amplifiers with integrated Circles is commercially available today, for example as type LM 3900.

Fig. 3 gives a specific embodiment that is to be regarded as an example and in no way restrictive. It is a speed control of an automobile.

The control shown in Fig. 3 is similar to that of Fig. 2. It also has a pulse generator 16 which is coupled to a wheel R of an automobile and to a The input of the amplifier 8 is connected via an integrator 17. At the output of the integrator 17 one receives a Voltage proportional to the speed of the vehicle.

After amplification by the amplifier 8, this voltage is compared with a target voltage that is determined by the Potentiometer 4 comes from, the rotor of which is operated by the driver of the vehicle.

Depending on whether the target signal is greater or less than the speed signal, the comparator delivers Signal that corresponds to a "1" or a "0".

This signal is used to feed the control motor 6 via the power amplifier, which is connected to the control of the gas flap of the vehicle engine is connected.

The motor 6 controlled in this way ensures the opening or closing of the motor inlet in order to obtain the speed set by the potentiometer h

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is _s , namely Qwithout the intervention of the vehicle driver, .. ■ · ..-. ": - · -

A control as just described * is applicable to an automobile with a certain speed to _run: blank without the handlebar must intervene.

Of course, in practice, in which the speed of the vehicle is subject to the wishes of the driver, the control device only intervenes in order to limit the speed to a given value by engaging a movable stop which is designed to control the Limit the travel of the accelerator pedal when this given speed is reached. Such an arrangement is described in particular in FR patent application 7 ^ 21 7 ^ 0, which was filed on 6/21/197. The control of the type described above is a two-state control whose linearity of response is constant, causing uncomfortable feelings under the foot that is pressing the accelerator pedal. --_, - _ ■ ..-..- ■

It has consequently been deemed necessary Take precaution so that the control with relatively low Response speed is possible.

In the embodiment that has now been described one intends to switch the control to two states, such as this is the case with the control of FIG. 1, into a Control: with three states to transform in order to approach the set point via a high approach speed and a low one Response speed to have around this set point. .--, -: -; : ■ - --... ■ -.-_- ■ -... '

The linear controls are generally used

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a device for modulation or for auto-modulation, the signal of which is superimposed on the actual signal to achieve the effect the threshold that occurs around the soil point when the errors or deviations are small.

In such a case the command is maximal for small errors, which is a good linearity of the response results; however, it causes the response speed to decrease in the entire control range.

It is possible to eliminate this drawback by creating a controller that is within its functional area has a zone in which the response speeds for small errors are reduced, while for large errors, exceeding a given level, the response speed is maximum.

The Fig, 'ü shows a circuit which is in all respects the same as that of FIG. 1, but which also contains an oscillator 18 which is connected to the positive input of the comparator via a resistor 19 which is connected to the resistor which the positive input of the comparator connects to the potentiometer 1, together forms a summation stage. The oscillator 18 is advantageously a generator for triangular or sinusoidal signals of small amplitude and a high frequency relative to the response frequency of the controlled device.

The operation of the just described control will be explained to 6 with reference to FIGS. H. It is initially assumed that the actual signal changes very slowly; the amplifier 8 supplies a signal O, so that the comparator 13 at its corresponding input

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only receives the actual signal that it receives via the resistor is fed; However, the output signal of the oscillator via the resistor 19 is superimposed on this actual signal.

If the distance between the nominal value and the actual value is smaller than the amplitude of the oscillator signal, there is it every time the signal of the oscillator 18 the desired signal exceeds, a triggering of the command for correction, so that the motor 6 acts on the potentiometer, to return the actual signal to a value that is smaller than the target signal.

But since the frequency of the oscillator signal of the oscillator 18 is greater than the response frequency of the motor 6, the change in the actual signal is not ended as soon as a the setpoint signal value is exceeded again.

This is the response speed of the control for small differences between the target and the actual signal low, as shown in FIG. 6, on which one recognizes a line 20 with a slight inclination in the right segment, which shows the Change in the response speed of the motor 6 as a function of the deviation amount for small values of the deviation reproduces.

This route segment 20 is on one side and the other by two sections 21 with a steep incline extended, which show the response speed for deviations that are significantly greater than the actual value relative to is the setpoint.

For significant deviations, the speed is not determined by the presence of the signal from the oscillator 18, which the actual signal is superimposed, changed so that the

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Control in the related Pig. I described Way works.

In the example of the invention just described, it is assumed that this is an "all or nothing" control is used as illustrated in FIG.

However, the improvement of the invention can just as well be applied to the embodiments according to FIGS. 2 and 3 use.

The circuit shown in FIG. 7 is a partial representation of the control according to FIG. 4, which _{contains a storage circuit 22 for the target value between the target signal U 1} and the corresponding input of the comparator 3.

In certain types of application, such as holding a setpoint value recorded "on the fly" or a setpoint value through Remote transmission, for example by radio-electrical means, it may be necessary to store the setpoint electronically and to retain this information until new information is acquired. The circuit 22 allows to ensure this function.

This circuit has a capacitor 23 for storing the setpoint value U ₁ , which is connected to the source for the setpoint value via a switch 24 which is actuated by a relay 25, the supply of which is ensured by regularly occurring signals. The capacitor is connected to the grid electrode of a field effect transistor 26,

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whose source electrode (source) to a positive voltage, and whose drain electrode is connected to ground via a resistor 27. The drain is also connected to the input of the! Comparator 3, which controls the Absorbs setpoint *

The remainder of the circuit is that of FIG. 4 analogue. The parts of this circuit that are attached to the other Input of the! Comparator 3 and connected to the output are represented by rectangles 27 and 28.

When a regular pulse causes the relay 25 to be actuated, the switch 2k closes and the instantaneous setpoint value U. is fed to the storage capacitor 23.

At the terminals of the resistor 27, the transistor supplies a voltage which is essentially equal to U ₁ , with a low impedance. The voltage U ₁ at the terminals of the capacitor does not change significantly over time if the capacitor 23 and the transistor 26 are selected in a suitable manner and this as long as the supply of the device is not interrupted. The control can therefore work with a stabilized setpoint due to the action of the storage circuit 22 «

With certain applications it may be necessary to free the system from the control setpoint and then quickly resume that setpoint.

The circuit of Figure 8 enables this function to be performed.

This circuit is also in accordance with the controller

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4 combined, but only the comparator 3 is shown.

The additional circuit has a contact 30 between the positive terminal of the setpoint potentiometer 4 and the negative input of the comparator 3 is connected.

The contact 30 is mechanically connected to the output shaft of the motor 6 of the controller (Fig. 4). For example, he can can be controlled by the reaction of the sheath of the control cable, not shown, of the potentiometer 1. the clamp of contact 30, which is opposite to the positive voltage, is connected to the negative input of the comparator via the series circuit a diode 31 and a resistor 32 connected, while the junction between the diode 31 and the contact 30 also to the ground via a capacitor 33 and a resistor 34 connected in parallel therewith is.

Closing of the contact 30, for example caused by an excessive force exerted by the control motor 6, allows the capacitor 33 to be fed from the positive voltage source. The capacitor currently holds a setpoint fixed, which is greater than the value supplied by the potentiometer 4, but without this latter value to change. The action of such a setpoint on the comparator 3 then triggers the control on the part of the motor an effect that seeks to suppress any exertion of force on the connecting means with the potentiometer 1 (Fig. 4).

The contact 30 then opens again, and after a certain time constant RC in the circuit 33, 34 has elapsed During this period, the control takes its normal function

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again until contact 30 closes again.

The circuit which has just been described has the advantage of being with automatic reset or cancellation is working.

In the example shown, the contact 30 is connected to the negative input of the comparator 3, it is but just as well possible to connect it to the positive terminal of the comparator, in which case the other terminal to must be connected to the ground. A nominal value is then obtained which is lower than that given by the potentiometer 4 Setpoint is, so that when contact 30 is closed, the direction of the effect on the controller is reversed.

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Claims (11)

Expectations 1. Dependency control with a comparator whose first input is connected to elements that generate a signal accordingly generate a nominal value, and whose second input is connected to elements that generate a signal accordingly generate an actual value, while the output of the comparator is connected to elements for controlling a controlled organ is, characterized in that the controller also has elements (8, 9, 10, 11, 12; 8, 13, 14, 15) which is connected to the second input of the comparator (3) in combination with the signal corresponding to the actual value, apply a signal that is the algebraic sum of the actual value signal and its derivative is. 2. Controller according to claim 1, characterized in that the elements which the second input of the comparator (3) a Apply a signal which is the algebraic sum of the signal corresponding to the actual value and its derivative, to a differential amplifier (8) include, from which an input to the output of the elements (1) for generating the target signal via a Integrator circuit is connected, which consists of a first resistor (9) and a capacitor (11) and in which the connection point corresponding to these two components with the input of the amplifier (8) via a second resistor (10) is connected, while the other input of this amplifier is connected to the elements for generating the actual signal is connected by a resistor (12), and the output of the amplifier (8) to the second input of the comparator (3) is connected, which is also directly connected to the output of the elements (1) that generate the actual signal. 7098 11/0800 3. Control according to claim I _3, characterized in that the elements for feeding the second inlet of the comparator (3) with a signal which corresponds to the algebraic sum of the actual signal and its derivative contain an amplifier (8), one input of which is directly connected to the output of the mentioned elements (1) for generating the actual signal, furthermore an integration stage, which consists of a resistor (13) and a capacitor (I ¹ I), and is switched into the counter-reaction circuit of the amplifier, and, finally, "which connects a resistor (15), this RC circuit with a different inlet of said amplifier; 4. Control according to any one of claims 1 to 3 »thereby characterized in that it also contains an oscillator (18) whose output is connected to the second input of the comparator (3) is connected and is used to generate the signal from the algebraic sum of the signal corresponding to the actual value and to superimpose a modulation signal on its derivative, whose amplitude and frequency are suitable in which Functional area of the control to create a zone in which the response speed for small deviations of the The actual signal is small in relation to the target signal, while this speed remains at a maximum for deviations which the Exceed the level of the modulation signal. 5. Control according to claim 4, characterized in that the oscillator (18) at the second input of the comparator (3) is connected via a summing resistor - (19). 6. Control according to any one of claims 4 and 5> characterized in that the oscillator (18) is a generator of 7 09811/0800 rectangular or sinusoidal signals. 7. Control according to any one of claims 1 to 3 » characterized in that it also has a storage circuit (22) for the setpoint value, which is in front of the corresponding input of the comparator (3). 8. Control according to claim 7, characterized in that the storage circuit has a storage capacitor (23) which is connected to the elements for generating the setpoint a switch (24) is connected, which is controlled by a relay (25) from a source of trigger signals for the storage process is fed, the capacitor being connected to the input of the comparator (3) via a field effect transistor (26) which is connected to a resistor (27) is charged. 9. Control according to any one of claims 1 to 3 »characterized in that it also comprises a circuit which momentarily separates it from the setpoint of the controller and has means to then get this setpoint again. 10. Control according to claim 9 »characterized in that the circuit for releasing the setpoint contains a contact (30) which is connected to one of the inputs of the comparator (3) is and is operated by the motor (6 in Pig. I) of the control, and a delay circuit (33, 34) to to allow the setpoint to be reintroduced after a given time interval after the contact (30) has opened. 11. Control according to claim 10, characterized in that the contact (30) with the input of the comparator (3) via 709811/0800 a diode (31) and a resistor connected in series with it (32) is connected and that the delay circuit, which consists of a capacitor (33) and a resistor (3 * 0, is connected between the connection between the diode (31) and the contact (30) and the ground. 7098 11/0800 Blank page