GB2028030A - Direct current multiple load control circuit - Google Patents

Abstract

A direct current circuit for controlling two pairs of servo motors (M1, M2; M3, M4) controlling the flight of a flying body consists of two bridge circuits with power amplifiers (T11, T12, T13, T14; T21, T22, T23, T24) in the arms of the bridges, the servo motor pairs (M1, M2; M3, M4) being connected across respective bridge diagonals (C1, D1; C2, D2). The bridge circuits are connected in parallel by their other diagonals (A1, B1; A2, B2) across a direct current source and the central points (P1, P2) between the servo motors are connected to a centre tap on the direct current source. A control unit (KV) issues command signals (UI, UII, UIII, UIV) for the control of the power amplifiers (T11, T12, T13, T14; T21, T22, T23, T24) in accordance with input signals (UN, UR, UG) representative of pitch, roll and yaw. A further input signal (Jmp) representative of current flow into or out of the centre tap (O) on the direct current source is used to ensure that the current into or out of the centre tap (O) is substantially zero so that the weight of the current source may be minimised. <IMAGE>

Description

SPECIFICATION Direct current multiple load control circuit The invention relates to a circuit arrangement for operating a number of electrical loads from one source of direct current. Such a circuit is known in which the direct current source is applied to respectively one bridge diagonal of at least one bridge circuit constructed from current control elements and at least one respective load is arranged in the other bridge diagonal.

Bridge circuits of this kind are used, for example, to operate D.C. motors, in order to make possible the operation thereof for both directions of rotation. The bridge circuit can then be constructed from control elements such as simple switches which either connectthe motor, in accordance with the desired direction of rotation, to the poles of the source of direct current, or disconnect it from said poles. The bridge circuit can, however, also be constructed from control elements in the form of controllable power amplifiers by means of which the motors are not only switched on and off, but which are also operative to control the power consumption (and thus rotational speed) thereof.

For the operation of electrical loads with the aid of such bridge circuits, four control elements are necessary per bridge circuit. When a fairly large number of electrical loads is to be operated the expenditure on control elements thus becomes very great both costwise and weightwise.

An aim of the present invention is therefore to provide a circuit arrangement for operating a number of electrical loads from one source of direct current which employs a minimum number of control elements. Afurther aim is to provide an arrangement which makes it possible to keep the maximum necessary capacity of the source of direct current, and thus the weight of the source, as low as possible.

According to the present invention there is provided a direct current multiple load control circuit comprising a centre-tapped source of direct current, one or a plurality of bridge circuits constructed from electrical current control elements, and a plurality of electrical loads, said current source being connected across one diagonal of the or each bridge circuit, said loads being connected in series pairs in the or each other diagonal of the or each bridge circuit and the centre point of the or each pair of loads being connected to the centre tap of the source of direct current.

By means of such a circuit arrangement the result is achieved that with four control elements two loads can be operated independently of one another. The circuit arrangement in accordance with the invention furthermore makes it possible to arrange the loads, with respect to the current removal direction averaged over a fairly long period of time, in such a way that the source of direct current is uniformly loaded on a time average to both sides of the centre tap. For a time-limited operation of the loads from one battery the capacity of the battery and thus also the weight can be restricted to a minimum; D.C.

generators having a centre tap can be designed accordingly weaker and thus lighter.

The current supply for electrical servo units or motors of a flying body for example represents a temporally limited operation of this kind. The individual servo motors are usually intended to produce in pairs simultaneous control-surface deflections in the same direction or in the opposite directions. In accordance with an advantageous application of the invention, for this purpose respectively two simultaneously operated servo motors are arranged in series in the bridge diagonal of a bridge circuit constructed from current control elements.

Thus, for the operation of four electrical servo motors for a cross tail plane consisting of four separately swingable surfaces, of an aircraft, the servo motors of the respectively opposite surfaces - in other words for example the two side rudders on the one hand and the two elevators on the other hand can be arranged in pairs in the respectively one bridge diagonal of two bridge circuits, in which respect the bridge circuits are connected in parallel via the respectively other bridge diagonal, and the connecting points of the two pairs of servo motors are connected to one another.

In the case of the above-mentioned aircraft, the performance of a roll command represents a particular loading of the course of direct current, since in this case all of the servo motors are operated simultaneously. For a specific kind of aircraft steering, the rolling is of particular importance, so that steering commands for regulating the rolling are particularly frequent. In such cases, the servo motors are switched with respect to their direction of rotation, in such a way that upon the performance of steering commands in at least one steering axis, in other words for example of roll commands, the current consumption of the two bridge circuits from the centre tap of the source of direct current when timeaveraged is of the same magnitude and the current flows are oppositely directed.In the event that other steering commands than the above mentioned roll commands dominate upon the mission of an aircraft or missile the above mentioned optimisation upon the loading of the source of direct current is designed for the correspondingly frequently actuated pairs of servo motors.

Despite the above mentioned optimised connection of the electrical loads the various tolerances particularly in the electrical components being used may result in a non-uniform time averaged loading of the source of direct current. In this event it is advantageous if the central-point current of the direct current source is measurable and is feedable to a command distributor as input variable. The command distributor then varies the current flow in the corresponding electrical current control elements in such a way that the central-point current for specific, frequently-occurring steering commands becomes nil.

The invention will be explained in more detail with reference to an exemplified embodiment shown in the accompanying drawing. The exemplified embodiment relates to a circuit arrangement for operating a number of electrical steering servo motors for a cross tail unit consisting of four separately swingable surfaces, of a flying body. The current supply to four servo motors M1 to M4 is provided from a battery with centre tap (0) although a D.C. generator with centre tap could of course alternatively be used.

Let M1 and M2 be the steering servo motor for the side control, and Ma and M4 those for the height control. The pairs of servo motors Mt and M2 or M3 and M4 are respectively arranged in the bridge diagonal C, D1 orC2 D2 of two bridge circuits. Each bridge has four power amplifiers T,1 to T14 ore21 to T24 respectively. The power amplifiers can be for example of the kind shown in the 3rd edition of"Halbleiterschaltungstechnik" by Tietze & Schenk at page 374. The power amplifiers are controlled at the points I to IV by direction and magnitude of the control voltages emanating from a command distributor KV. Thus, for example, the power consumption and the direction of rotation of M1 is determined by the power amplifiers T11 and T12.The connection of the two bridge circuits to the battery is produced by connecting the points A1 and A2 to the positive pole, B1 and B2 to the negative pole, and P1 and P2 to the centre tap 0. The steering servo motors M1 to M4 are so connected with respect to their direction of rotation, that for example upon the performance of a roll command with right-hand rotation about the roll axis the central-point currents Jrr in both bridge circuits are of the same magnitude, but oppositety directed, so that the overall current removal from the centre tap of the battery is nil. In the event of a roll command with left-hand rotation about the roll axis, the central-point currents Jre flow in the direction shown in broken lines.

Since the steering servo motors M1 and M2 or M3 and M4 respectively are at all times simultaneously operated and side and height steering commands during a flying body mission are to some extent statistically distributed, the battery is largely uniformly loaded to both sides of the centre tap, so that the capacity thereof, i.e. the weight thereof, can be restricted to a minimum.

Since, as mentioned previously, by tolerances or assymmetries, more especially in the electrical components, nevertheless a one-sided loading of the source of direct current might occur, the centralpoint current Jmp is measured by way of a measuring resistor RM and supplied to the command distributor. In addition to the current signal Jmp, the command distributor receives pitching, rolling and yawing signals UN, UR and UG from corresponding regulators N, R and G. From these four input parameters and command distributor calculates the output parameters U to Uiv, which are used to control the power amplifiers T11 to T14 and T21 toT24.

The control voltages U1 to Uiv for performing a steering command are generally calculated from the following set of equations: U, = UN + UNi U1 = UN U11 = UG + URa Uiv = UGUR4.

The following conditions apply to the performance of a roll command: Urn + UR2 + UR3 + UR4 = UR (1).

Since, in the case of a roll command, no pitching moment should occur, a second equation must also be satisfied: UR1 = URZ (2) Since, furthermore, no yawing moment should occur, a third equation must be satisfied as follows: UR3 = U (3) Afourth defining equation arises from the face that the sum of the central-point currents of both bridge circuits, in other words the overall centralpoint current Jmp should become nil.

From these four defining equations the four control voltages U1 to U,v can be unequivocally calculated, so that the intended steering command is carried out with simultaneous loading of the battery.

Claims (7)

1. A direct current multiple load control circuit comprising a centre-tapped source of direct current, one or a plurality of bridge circuits constructed from electrical current control elements, and a plurality of electrical loads, said current source being connected across one diagonal of the or each bridge circuit, said loads being connected in series pairs in the or each other diagonal of the or each bridge circuit and the centre point of the or each pair of loads being connected to the centre tap of the source of direct current.

2. A circuit as claimed in claim 1 wherein the electrical loads are servo motors for a flying body operative to produce in pairs simultaneous controlsurface deflections in the same or opposite directions, each pair of simultaneously operated servo motors being disposed in series in a respective bridge diagonal of a respective one of said bridge circuits.

3. A circuit as claimed in claim 2 in which two pairs of servo motors are provided to control a cross tail plane of a flying body, the tail plane consisting of four separately swingable surfaces, each pair of servo motors being associated with two respective opposite surfaces of the tail plane and each pair of motors being disposed in a respective one of two bridge circuits which are connected in parallel by way of the respectively other bridge diagonals of the bridge circuits, the connection points between each pair of servo motors being connected to one another

4.A circuit arrangement as claimed in claim 3, in which the servo motors are connected with respect to their directions of rotation, in such a way that upon the performance of steering commands about at least one steering axis the time average current consumptions of the two bridge circuits from the centre tap of the source of direct current are of the same magnitude but opposite direction.

5. A circuit arrangement as claimed in claim 4, further comprising a control unit operative to provide command signals to said current control elements, and means for measuring current flow from the centre tap of the current source and feeding a signal representative of said current flow to an input of said control unit.

6. A circuit arrangement as claimed in any preceding claim wherein said current control elements are power amplifiers.

7. A circuit arrangement substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.