JP2000323325A - Circuit for actuator control - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a circuit controlling an actuator whose cost is low and reliability is high by using very simple design. SOLUTION: This circuit is provided with a power source 1 which mainly supplies a DC voltage supplying power to an actuator 7, and a first control path which has series connection of first current control elements 4, 5 for controlling supply of power to the actuator and a first free wheel element 6 and has an output terminal wherein the series connection is connected with a terminal of the power source. The actuator has a first terminal 8 connected with a first node between the first current control elements and the first free wheel element, and a second terminal 10 connected with the first free wheel element and a first terminal of the power source.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a circuit for controlling an actuator.

[0002]

BACKGROUND OF THE INVENTION Actuators, particularly those of the single wire type with permanent magnets, are particularly suitable for actuating mechanical actuators by means of electric current.
The advantage lies in a particularly clear and preferably substantially linear characteristic between the currents applied to the actuators and the torques or forces generated by them. In particular, this feature does not show any hysteresis.

From US Pat. No. 5,347,419 is known a drive circuit for a solenoid, preferably used in an electric relay, which, as described in that patent, has an initial drive for a predetermined period of time. The solenoid is driven by the drive current, and then driven with a lower sustain current.

[0004] To maintain the magnitude of the drive and sustain currents, the switching device pulses the current applied to the solenoid between upper and lower limits. The pulses are collected, resulting in a nearly constant current due to the solenoid's inductance. The processor determines the magnitude of the current in the solenoid. The signal representing the magnitude of the desired current is compared with the signal representing the current in the solenoid, and the signal representing the difference between these currents is used to control the switching device. The voltage developed between the resistors connected in series to the solenoid is applied to a differential amplifier. The amplifier has an output connected to a peak detector that minimizes the rate of decay of current in the solenoid, and a signal representative of the measured solenoid current is obtained from the peak detector. The power consumption by the solenoid drive circuit is low, and the drive circuit is of a short-circuit prevention type. The output signal of the peak detector is monitored by a processor for fault detection and counting.

The operation of actuators where the problem of maintaining different currents for initiation and maintenance does not play a significant role is not discussed in this document.

US Pat. No. 5,414,792 discloses a semiconductor control circuit for an electric motor that cooperates with a semiconductor throttle control device and a vehicle sensor circuit. This electrical circuit includes the following elements: Hall effect position sensor for throttle controller, throttle position signal amplifier circuit, vehicle reverse condition circuit, vehicle operation inhibition circuit, pulse width modulation circuit, reversing function. A MOSFET driver circuit, a plurality of power MOSFET circuits, a low voltage circuit, and a current supply circuit connected to an external DC motor. These circuit elements convert a mechanical throttle position into a voltage level signal that can be converted into a pulse signal by a pulse width modulation circuit. This pulse signal drives a switch bank of MOSFET semiconductor switches to control the current that flows through the DC motor. This circuit separates the DC power supply from the power consuming elements of the circuit, and the operating parameters of the vehicle,
For example, forward or backward movement and ON / OFF operation are sent from the vehicle to the power control circuit.

As described above, in the circuit disclosed in US Pat. No. 5,414,792, the supply of power to the DC motor of the electric drive vehicle is controlled by the electronic control and power supply device depending on the driver's intention. This driver's intention is taken from the throttle position with the help of a Hall sensor. This technical teaching does not consider the operation of the actuator.

It is an object of the present invention to provide a simple circuit for controlling an actuator.

[0009]

According to the present invention, this object is achieved by the following actuator control circuit,
The circuit comprises a voltage source mainly for supplying a DC voltage for supplying power to the actuator, a first current control element for controlling power supply to the actuator, and a first freewheel element connected in series, wherein the voltage source is A first terminal connected to a first node between the first current control element and a first freewheel element, the first terminal including an output terminal connected to the first current control element and a first freewheel element. And a second terminal connected to a first terminal of the voltage source, wherein the first terminal of the voltage source is connected to a first freewheel element.

The construction of this circuit according to the invention is very simple, preferably consisting of a semiconductor switch such as a field effect transistor, and having only one current control element. The freewheeling element, which preferably takes the form of a polarity-placed diode with respect to the voltage source, need not be separately controlled. Such a simple circuit allows the use of a simple control circuit for the current control element with respect to the current required in the control path. In particular, in such a circuit, only a voltage of a given polarity should be applied to the actuator. This simple design guarantees high reliability in operation. Furthermore, power consumption is minimal. This saves energy and keeps the thermal load of the circuit low.

In another embodiment of the present invention, the circuit includes a second current control element for controlling the supply of power to the actuator; It has a series configuration with a freewheel element having an output terminal connected to the terminal of the voltage source. A second terminal of the actuator is connected to a second node between the second current control element and the second freewheel element, and is connected to a second terminal of the voltage source via a second current control circuit. , The second node is further connected via a second freewheeling circuit to a second terminal of the voltage source.

According to this embodiment, the circuit for controlling the actuator according to the present invention is such that each of the control paths arranged in parallel with the voltage source forms a bridge arm of the current control element, and connects another bridge arm of the freewheel element. The asymmetric bridge circuit is extended. A full bridge thus comprises only two controlled current control elements, which is also simpler as compared to a symmetrical full bridge with four current control elements. In this way, an asymmetric bridge makes it possible to use a simplified control circuit for the control of the current control element. This results in a small number of components and therefore high reliability. The power consumption is reduced compared to the full bridge described above, so that in this case energy is saved and the thermal load is reduced. The reduced thermal load produces, on the one hand, high circuit reliability and, on the other hand, allows for further savings to be achieved on heat sink components. As described below, an asymmetric bridge is referred to as a unipolar circuit as compared to a simple embodiment having only one control path, allows for improved dynamic behavior, and has a symmetrical configuration with four current control elements. A higher control rate can be obtained as compared with a full bridge.

In an embodiment of the invention having two control paths, both current control elements in these two control paths are preferably used simultaneously to drive the actuator. In the conducting state, current flows simultaneously from the current source through the two current control elements to the actuator. When the current control element is interrupted, the current flowing in the actuator flows only through the freewheel element.

Still another circuit according to the present invention includes a control circuit for controlling one or more current control elements according to a command signal. Preferably, the value of the force or torque applied by the actuator is transmitted to the control circuit by this command signal. The control circuit derives one or two signals for controlling the current control element from the command signal. In a particular embodiment of the invention, this is affected by a pulse width signal whose modulation depth is defined by the command signal.

The circuit according to the invention is advantageously used in a control system for driving a control by an internal combustion engine. Such controls in internal combustion engines include, in particular, throttle valves or fuel control valves. Preferably, such a control system has a combination of an actuator and a reset device that reacts thereto. Such a reset device is preferably of a fail-safe or passive design. For this purpose, the reset force can be generated by mechanical or in particular by magnetic means. The actuator is controlled by the circuit according to the invention.

In addition, the circuit according to the invention is also suitable for implementing other control means within or outside the automotive engineering field.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In a control system of the type described below, an actuator is used to generate a force or torque in one direction, the one direction being "open" (o).
pening). Conversely, a reset device provides a reverse force or reverse torque, which direction is commonly referred to as "closing". The actuator must drive the control element to a predetermined position with high accuracy against the force and torque of the reset device. This position must be maintained exactly in the case of any kind of disturbing force. This is achieved by the circuit according to the invention for controlling such an actuator. Embodiments of the invention, given by way of example, are shown in the drawings and are described in more detail below. Similar elements in each figure are given the same reference numerals.

In the simplified circuit diagram of FIG. 1A, reference numeral 1 indicates a power supply basically supplying a DC voltage U0. The first control path is connected to the terminals 2 and 3 of the power supply 1 and has a serial configuration of a first current control element and a first freewheel element 6. The first control element has a parallel connection of a first switching element 4 and a first protection diode 5. The diode is reversely polarized with respect to the DC voltage U0. Actuator 7 is the first
Connected to a first node internally connected to a current control element 4,5 and a node 9 connected to a first freewheel element 6 in a first control path 4,5,6. Terminal 8. Second terminal 10 of actuator 7
Is connected to a second terminal 3 of the power supply 1, which connection is made by a direct electrical connection in the embodiment shown in FIG.

FIG. 1A shows an actuator 7 as an equivalent circuit in which an ohmic resistor Ra, an inductance La and a voltage source are arranged in series. Inductance L
a and the ohmic resistance Ra constitute the internal impedance of the actuator. The voltage source represents the voltage Ui caused by the actuator 7. During operation, the voltage Ua of the actuator appears between the terminals 8 and 10 of the actuator 7,
The actuator current Ia flows.

FIG. 1B shows a current path for the actuator current when the first switching element 4 is conducting, that is, when the first current control elements 4 and 5 are switched on. The DC voltage U0 is supplied from the power source 1 to the terminals 8 and 10 of the actuator 7 through the first switching element 4 and the current Ia
Is applied. When the switching element 4 is assumed to be ideal, a DC voltage U0 from the power supply 1 appears at both ends of the actuator, ie at the terminals 8, 10, which means that the actuator voltage UA is related to the DC voltage U0. I do.

When the first switching element 4 is turned off so as to start from the state shown in FIG. 1B, the actuator current Ia only attenuates gradually according to the inductance La. Since the first switch element 4 is open or non-conductive, the current Ia between the terminals 8, 10 flows through the first freewheel element 6, ie the diode which constitutes this element. When this element is assumed to be ideal, the actuator voltage Ua is equal to the first
Is zero in this situation as long as the freewheel element 6 is conductive. Thus, the decay time of the actuator current is determined only by the elements of the actuator 7, namely the inductance La and the ohmic resistance Ra
And voltage Ui.

In these comparisons, the situation shown in FIG. 1 (b) occurs when the actuator current Ia turns on again and starts again from the no-current state. The rise time of the actuator current Ia is determined not only by the inductance La, the ohmic resistance Ra and the voltage Ui, but also by the DC voltage U0 of the power supply 1. As a result, the actuator current Ia and the force and torque generated by the actuator 7 rise with a very small time constant, but decrease with a relatively large time constant during the operation of the circuit shown in FIG. This is illustrated as a solid line of time for Ia1 in the actuator in the actuator versus time diagram of FIG. In this figure, the actuator current Ia is plotted on the Y axis, whereas the time T is plotted on the X axis.

Thus, only one switching element 4
In this particular simple circuit with the actuator voltage Ua is always positive (or zero). As a result, the actuator current Ia is always greater than or equal to zero.
This fixed polarity of the actuator voltage Ua and the actuator current Ia limits the control rate of the actuator 7, as shown in FIG. 3 by the curve Ia1. In particular, as soon as it is turned off, a high rate of change of the actuator current is obtained, in which a negative actuator voltage is applied. Such a negative actuator voltage Ua can be obtained by a bridge circuit having four switching elements. Opposing switching elements on two diagonals of the bridge circuit are turned on or off. This concerns the configuration of the inverter for driving the AC motor from a direct voltage source. However, such a circuit with four switching elements is very complicated and thus also requires a complicated control circuit.

FIG. 2 (a) shows a circuit that is considerably simplified as compared to a full bridge, but does not sufficiently exhibit the desirable characteristics of this circuit. Therefore, the circuit shown in FIG. 1A additionally includes a second control path including a series arrangement of the second current control element and the second freewheel element 13. Similarly, for the first current control element, the second
A second current control element is configured by the parallel arrangement of the switching element 11 and the second protection diode 12. Second
Switching element 11 can be similarly controlled to supply power to the actuator. Preferably, the two switching elements 4,11 of the two current control elements 4,5 and 11,12 are simultaneously controlled, i.e. simultaneously in either the conducting state or the blocking state. The first terminal 8 of the actuator 7 is again connected to a first node between the first current control elements 4, 5 and the first freewheel element 6.
Conversely, in the embodiment shown in FIG. 2A, the second terminal 10 of the actuator 7 is connected to the second control path 11,1.
2, 13 connected to the second terminal of the power supply 1, the second terminal 10 being connected to the second current control elements 11, 12
And a second node 14 that connects to a second freewheeling element 13 in a second control path. The second control paths 11, 12, 13 are connected to the terminals 2, 3 of the power supply 1 in parallel with the first control paths 4, 5, 6, respectively.

The operation of the circuit shown in FIG.
(B) and FIG. 2 (c). FIG. 2B shows a state where the switching elements 4 and 11 are operating. The DC voltage U0 is equal to the power supply 1 of the actuator current Ia.
From the first terminal 2 of the actuator 7 to the first terminal 8 of the actuator 7 via the first switching element 4, and from the second terminal of the actuator 7 to the second terminal 3 of the power supply 1
Via the switching element 11. Assuming that the switching elements 4 and 11 are ideal, the actuator voltage Ua corresponds to the DC voltage U0 of the power supply 1.

In order to turn off the actuator current Ia, the two switching elements 4, 11 are turned off simultaneously. Again, the actuator current Ia does not stop suddenly as a result of the inductance La, but the freewheel element 6,
Continue flowing through 13. In contrast to the unipolar circuit shown in FIG. 1, the actuator current Ia in the asymmetric bridge shown in FIG.
Is not short-circuited through the freewheel element 6, but is supplied in the opposite direction from the power supply 1 through the two freewheel elements 6, 13. In this operating state, this results in the actuator voltage Ua being related to the negative value of the DC voltage U0 of the power supply 1. As a result of this actuator voltage Ua, it acts as a reverse voltage and the actuator current Ia decays at a substantially faster rate than in the circuit shown in FIG. As shown in FIG. 2B, the comparison regarding the operating conditions is based on the fact that when the switching elements 4 and 11 change from the cutoff state to the conduction state, the actuator current Ia
Is at least related to the delay of the actuator current Ia after the switching elements 4 and 11 are cut off. Thus, the delay of the actuator current Ia in the asymmetric bridge shown in FIG. 2 proceeds substantially faster than in the unipolar circuit shown in FIG.

FIG. 3 is an illustrative graph in the form of a dashed curve Ia2. The current waveform as a function of time T allows for a faster control process to be realized. Furthermore, only a positive actuator current Ia is possible, as in the circuit shown in FIG. This is because, after the actuator current Ia shown in FIG.
3 is cut off and the actuator 7
This is because there is no current until the switching elements 4 and 11 are turned on again. Curve Ia in FIG.
At least a high rate of the relationship between the build-up rate and the decay rate of the actuator current Ia, as shown as 2, reduces the non-linearity in the control of the actuator 7, which results in different build-up times. This causes a delay time, a rate of the actuator current, and a force or torque of the actuator 7.

FIG. 4 shows a control system for driving a control member in an internal combustion engine, such as in a motor vehicle. The command means 15 transmits a command signal to the control circuit 17 via the connection 16. The control circuit 17 controls the actuator current Ia and the torque and force generated by the actuator 7 according to the command signal. For this purpose, the control circuit controls the current control element in the circuit block 18 of FIG. 4, which element is implemented as shown in FIG. 1 or 2. The actuator 7 operates the control member 19. The control member 19 is, as shown in FIG. 4, a throttle valve of an internal combustion engine of an automobile.

More advantageously, the control circuit 17 is, for example, of FIG.
As shown in FIG. 2, a pulse width modulation control signal controls a current control element that controls an associated switching element having a pulse width that varies with a desired average value for the actuator current Ia in the circuit block 18 or, for example, FIG. The current control element is controlled as shown in FIG.

The pulse width or modulation depth of the pulse width modulated control signal for the switching element is given by the command signal. This preferably produces an actuator current Ia that is proportional to the value of the command signal.

FIG. 4 further shows a reset device 20 used in combination with the control member 19 and symbolically represented as a lever with a spring. In fact, other similarly operating reset devices can be used. In particular, a wear-free reset device is desired, in which a permanent magnet generates a reset force on the control member 19 and is coupled to the actuator 7 to form a structure, which is very simple, robust and reliable. There is a compact configuration. The reset device 20 resets the control member 19 to a non-critical position to obtain a fail-safe control system in the event that the actuator 7 or one of the elements controlling this actuator is defective. For this purpose, the throttle valve should be moved to a closed or near closed position. The reset device 20 always opposes the torque or force generated by the actuator 7 on the control member 19. In such a control system, the actuator 7 should apply force or torque in only one direction, such as the opening direction of the control member, and the driving direction for closing is always obtained by the reset device 20.
This makes it possible to simplify the actuator, by which the circuit according to the invention is controlled. Furthermore, a separate reset device provides the necessary fail-safe characteristics, especially in the automotive field of use.

[0032]

As described above, according to the circuit of the present invention, since it has only one current control element, it is very simple, and high reliability and low power consumption can be realized. it can.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a short-pole type first embodiment of the present invention.

FIG. 2 is a circuit diagram showing a second embodiment of the present invention in the form of an asymmetric bridge.

FIG. 3 shows the current and the generated force or torque in the actuator shown in FIGS. 1 and 2;

FIG. 4 schematically shows a control system including a circuit according to the invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Power supply 2, 3 terminal 4, 11 Switching element 5, 12 Protection diode 6, 13 Freewheel element 7 Actuator 8, 10 terminal 15 Command means 17 Control circuit 18 Circuit block 19 Control member

 ──────────────────────────────────────────────────続 き Continuation of the front page (71) Applicant 590000248 Groenewoodseweg 1, 5621 BA Eindhoven, The Netherlands (72) Inventor Jürgen, Halfmann

Claims (6)

[Claims] 1. A circuit for controlling an actuator, comprising:
The circuit includes a power supply that mainly supplies a DC voltage that supplies power to the actuator, and a series connection of a first current control element and a first freewheel element that controls supply of power to the actuator. A first control path having an output terminal connected to a terminal of the power supply, wherein the actuator has a first control path between the first current control element and the first freewheel element. A first terminal connected to the first node of the power supply, and a second terminal of the power supply connected to the first terminal of the power supply, to which the first freewheeling element is connected. 2. The circuit according to claim 1, comprising a series connection of a second current control element for controlling the supply of power to said actuator and a second freewheel element. A series connection is connected to an output terminal connected to the terminal of the power supply, and to a second node between the second current control element and the second freewheeling element, the power supply being connected via the second control element. And a second terminal of the actuator connected to the first terminal of the actuator, wherein the second node is further connected to a second terminal of a power supply via the second freewheel element. Circuit to do. 3. The circuit according to claim 2, wherein the two current control elements are controlled simultaneously to drive an actuator. 4. The circuit according to claim 1, wherein said control circuit controls one or a plurality of current control elements in response to a command signal. 5. The circuit according to claim 4, wherein the one or more current control elements are controlled by pulse width modulation whose modulation depth is defined by a command signal. 6. A control system for driving a control member in an internal combustion engine having the circuit according to claim 1.