GB2090026A - Position control using electromagnetic clutch - Google Patents

Abstract

Device for positioning and attitude-stabilizing an inert mass e.g. a tank gun slewable on a movable base in at least one axis has oppositely rotatable driving parts supported on either the base or the mass, and the driven parts on the other of the base or mass are friction coupled to the driving parts under the control of one or more controllable electromagnetic clutches. The magnetic field strength in an airgap 3 between stator 1 and rotor 4 is measured by a plate 7 and compared with a desired torque value. The resultant signal is amplified and used to determine the current supplied to coils 2, thereby regulating the magnetic field. <IMAGE>

Description

SPECIFICATION Device for positioning and attitude-stabilizing a slewable inert mass supported on one base The invention concerns a device for positioning and attitude-stabilizing a slewable inert mass such as a tank gun supported on a base such as a vehicle hull for rotation about at least one axis, the device having two oppositely rotatable driving parts which are arranged to be pressed, under the control of one or two control devices, into frictional contact with cooperating driven parts, the driving parts being supported on the mass and the driven parts on the base or vice versa. Such a device is referred to herein as being of the kind specified.

A device of the kind specified is described in British patent application no. 06545/73. In that case the control device includes a valve arrangement which, depending on the desired slewing direction of the directional or tracking torque to be produced, acts upon at least one of two pistons with a hydraulic pressure medium so that the selected piston presses a friction pad against one of two rotating discs, or both pistons each press one friction pad against both rotating discs with differing contact pressure. Herewith, a control torque is transmitted from the rotatable disc supported on a base such as a mobile vehicle hull to a mass such as a gun, in order to enable its accurate aiming and tracking also during a mobile state of the base. Owing to the fact that the inert mass in the normal state is connected, i.e.

"balanced", with the base only through its bearing arrangement which can be low-friction configured, the inertia of the inert mass is completely used for stabilization so that the inert mass, whose fulcrum is located substantialf in the centre of gravity, in the case of a motion of the base continues to remain in a fixed position as long as a directioning or tracking torque is not exerted on the inert mass in the manner described above by pressure of the friction pad against the disc.

The control device must, on one hand, show quite low response time and, on the other hand, make it possible for the entire torque required for aiming or tracking of the inert mass to be transmitted independently from the rotational speed of the disc, i.e. without nonlinearity. These requirements are satisifed by the control device according to the application No. 06545/73, an adjusting device being inserted there as actuator in an automatic control circuit with an automatic controller of the first order (proportional plus rate action controller). The control device is a hydraulically operating device which is expensive in both manufacture and maintenance, has a large space requirement and requires an expensive ducting of hydraulic fluid between parts rotating relative to each other. In addition, a hydraulic fluid source is not available for all typical applications.

The invention has as its main object to provide a device of the kind specified in which the above mentioned disadvantages maybe reduced or avoided. More particularly, the invention should enable well-tested, problem-free commercially available components to be used for the control device whereby the control simplified in this manner would nevertheless still satisfy the above mentioned requirements, especially with respect to the minimum response time and the good control properties.

In order to solve this object, according to the invention in a device of the kind specified, the or each control device comprises at least one controllable electromagnetic clutch or brake in which the magnetic field is controlled by hyperexcitation of the exciting coil through feedback and amplification of the measured magnetic field strength.

Electromagnetic clutches or brakes having a current control are known (control engineers handbook "Clutches and Brakes", Chapt. 14.3, 14.20, J.G. Truxal (Editor) McGraw Hill, 1958).

Electrical energy is available and easy to supply in practically all typical applications. Space requirement, maintenance cost and price of electromagnetic clutches or brakes are low.

Electromagnetic clutches or brakes are commercially available components. However, the time lag between a modification of the voltage applied to the exciting coil and the subsequently produced torque is nevertheless quite large. In order, however, to achieve the required short response times, the controllability of the electromagnetic clutches or brakes which are moreover commercially available is envisaged according to the invention.

Control of the magnetic field of the or each electromagnetic clutch is advantageous in that the required short response time is achieved and in that the non-ideal magnetic characteristics of the clutch or brake are taken into account.

By the control of the magnetic field of the electromagnetic clutch or brake it is made possible for the above indicated time lag or dead and response times to be able to be kept to minimum orders of magnitude as with the control device according to British patent application No.

06545/73 and accordingly maintaining the advantage of minimum response time. The device according to the invention can nevertheless be simpler, cheaper, smaller and lighter than the earlier device owing to the use of commercially available electromagnetic clutch or brake.

An electromagnetic clutch without slip ring is preferably used. The primary side of the one or each electromagnetic clutch can be driven by means of its own drive motor and especially by means of an electric motor. An electric motor is to be preferred to any other drive such as a hydraulic drive or a combustion engine if combustibility is to be avoided. The drive of the primary side of the one or each electromagnetic clutch can nevertheless also be drawn from the traction drive of the self-propelled base such as the hull of a tank.

Especially in this case, a switching on and off of the drive of the primary side of a switchable clutch is advisable. The rotatable driving parts are connected in this case then only with one drive if this is required for stabilizing for an aiming or tracking movement. This saves drive energy. In the sense of such a saving, the drive for the primary side of the one or each electromagnetic clutch or brake can include a flywheel storage unit.

The device of the invention enables a positioning and attitude stabilization about at least one axis. A stabilization about two or more axes can be accomplished by an appropriate arrangement on the two axes, or more devices constructed claimed. Alternatively, however, two axes can also be sufficient for stabilization, by way of example, when in all only one device as claimed is specified and this device takes effect through a branch gearing with two outputs on the two axes as described in German Patent Application P 27 1 6 720.0 (Pietzsch et alii), filed on 15 April 1977.

In one advantageous configuration of the invention, the secondary side of the or each electromagnetic clutch acts through a driven gear output on a gear fastened to the inert mass, and the gear-tooth system of the driven gear output in the drive direction is stressed against the geartooth system of the driven-gear output in order to remove any backlash of teeth. This tension contributes to a further decrease in the dead or response times because the gear-tooth systems are always engaged in the drive direction and time does not have to be spent for turning the drive gear until the backlash of teeth is overcome. Aside from this, this stress enables shock loads of the teeth surfaces and remaining drive components to be avoided when starting. The stress can be produced by always maintaining slight torques for both rotational directions in the electromagnetic clutches.Herewith, it is additionally achieved that inaccuracies in the zero point of the input currenttorque characteristic can be compensated for to a certain extent.

For application of a restoring torque, instead of only for one direction of rotation, the electromagnetic clutches or brakes can be activated for the two directions of rotation whereby then the differential torque is controlled.

Herewith, more output is indeed transformed into useless heat although the input current-torque characteristic with this operating mode can, however, be linearized.

The invention may be carried into practice in various ways, but certain specific embodiments thereof will now be described with reference to the accompanying schematic drawings showing forms of construction. In the drawings: Figure 1 is a cross section through a slipringless-contrnlied electromagnetic clutch used as a control device; Figure 2 is a block diagram for the field variation of an electromagnetic clutch e.g. of Figure 1; Figure 3 is a cross section through an embodiment with one electromagnetic clutch for each direction of rotation; Figure 4 is a cross section through another embodiment with two groups of electromagnetic clutches for torque increase always connected together; Figure 5 is a cross section taken on the line V-V in Figure 4, and Figure 6 is an application diagram.

Figure 1 shows a slipringless electromagnetic clutch as it is used in connection with a drive as a control device for applying a directional torque or tracking torque to a slewable gun (not shown) supported on a vehicle hull. The electromagnetic clutch has as customary a stator 1 with a current coil 2. The stator 1 is separated from rotor 4 and core disc 5 by an air gap 3. A friction facing 6 is accommodated in rotor 4. If the current coil 2 is excited, a magnetic field is generated under whose influence the core disc 5 is pressed against friction facing 6. Herewith, in the case of an excited current coil 2, the core disc 5 is locked in by the, for example, continuously driven rotor 4. The transmitted torque which can be absorbed by the core disc is proportional to the maqnetic field generated in the electromagnetic coil.The field strength of the magnetic field is measured in air gap 3 by means of a field plate 7 which delivers an electrical voltage proportional to the field strength.

The magnetic field strength of the magnetic field excited by the current coil is controlled for the purpose of shortening the relatively high dead or response time with electromagnetic clutches of the type described. In this regard, an internal automatic control system is specified according to Figure 2.

The nominal signal proportional to a desired control torque of the electromagnetic clutch is fed at 8 into the automatic control system and delivered to a differential amplifier 9 where the nominal signal is compared with an actual signal recovered by the measurement using field plate 7 and introduced at 10 into the differential amplifier. The signal difference 11 is amplified in a voltage amplifier 12 with whose output voltage 1 3 the current coil 2 of the electromagnetic coupling is controlled. The stator current 1 5 building up against the inductivity of the electromagnetic clutch generates a magnetic field 1 6 which encompasses the iron components and the air gap 3 of the electromagnetic clutch 1 to 6.

The magnetic field increased in this way is again measured by means of field plate 7 which returns the actual signal through 10 to the differential amplifier 9. The core disc 5 and rotor 4 of the clutch generate a torque proportional to the controlled magnetic field 1 6 after a response time in the order to magnitude of milliseconds which is very short owing to the control and whereby this torque is delivered by core disc 5, at 20. In the case of the described embodiment, rotor 4 is continuously driven by a drive not shown; e.g. an electric motor.

The established construction according to Figure 3 comprises two electromagnetic clutches with stators 1,1' with therein arranged current coils 2,2', rotors 4,4' which are separated from the stators by air gaps 3,3' in the inactivated state of the clutch. The stators accommodate rotors 4,4', ring-shaped friction facings 6,6' and therewith the core discs 5,5' working together in friction contact in the coupled state.

The rotors 4,4' are driven in opposite directions through a bevel drive gear box by a common hydraulic motor 21. The pinion 22 of the bevel drive gear box is connected torque-rigid with the hydraulic motor 21 and is supported in a housing component 26 firmly bolted with a housing ring 25. The pinion 22 acts on two-axle drive bevel wheels 23,23' which are firmly connected with the respective rotors 4,4'. The axle drive bevel wheels 23,23' are supported in housing ring 25 on ball bearings 24,24'.

The two stators 1,1' are firmly connected by means of a crossbar 28 of the housing ring whereas the core discs 5,5' are arranged on the coaxial output shafts 27, 27' and are torque-rigid although axially shiftable. The output shaft 27' travels through therewith the hollow-formed output shaft 27. The two output shafts 27,27' support drive gears 29,29' adjacent to one another. On the basis of the descirbed arrangement with the bevel drive gear box 22,23,23', the output shafts 27,27' necessarily turn in opposite directions when optionally one of the electromagnetic clutches 1 to 6 or 1' to 6' is activated.In this way, optionally controlled directional or tracking torques can be made available to the drive gears 29,29' in either direction of rotation and there delivered to a toothed wheel rim not shown and which is connected with the inert mass such as a gun likewise not shown which is slewable on a base such as a vehicle hull. The housing 25 is firmly connected with the abovementioned base.

It is understood that the electromagnetic clutches 1 to 6 or 1' to 6' always have an internal automatic control system in accordance with Figure 2 including field plates 7,7' (Figure 1) for measuring the magnetic field.

The hydraulic motor 21 -instead of which an electric motor can also be prescribed -- drives the rotors 4,4' steadily through the axle drive bevel wheels 23,23'. If the electromagnetic clutch is activated by exciting one of the current coils 2,2', it follows that a torque proportional to the magnetic field strength is immediately available at one of the drive gears 29,29'.

In order herewith also to have no delay in overcoming tooth backlash between the driven gear outputs 29 or 29' and the therewith coworking toothed wheel rim, the gears 29 are always stressed in the drive direction with the gear tooth system of the toothed wheel rim (not shown) so that the teeth surfaces of the gear 29 on the driving side always are applied to the teeth surfaces of the toothed wheel rim and likewise the teeth surfaces of the driven gear output 29' on the teeth surfaces of the toothed wheel rim lying in the opposite direction. The tension takes place preferentially in that slight torques are always maintained in the two clutches. Accordingly, both clutches are kept engaged with minimal contact pressure.It is also possible to act simultaneously on the two clutches 1 to 6 and 1' to 6' with differential actuation (with a greater different contact pressure) on the two clutches and utilize the differential torque which is controlled in this case for stabilizing or positioning. This indeed leads to an increased power requirement but nevertheless enables a compensation for nonlinearities in the rotational speed torque characteristic. With the solution according to Figures 4 and 5, two groups of electromagnetic clutches are always provided. Both groups are driven by a common electrical motor 40. The drive pinion 41 of the electric motor 40 drives through an intermediate gear wheel 42 a first input shaft 43 which drives through gears 44,45 the primary rotors 4 of the first group of electromagnetic clutches.The gear 45 simultaneously meshes with a gear 46 of a second input shaft 47 which drives through gears 48,49 the rotors 4' of the second group of electromagnetic clutches.

The electromagnetic clutches of both groups are built in principle as described on the basis of Figures 1 and 3, such that they are not again further described here. It may be noted that the core discs 5 of the first group of electromagnetic clutches are torsion-resistant although axially shiftable (for example, through splines) and worked together with a first hollow output shaft 50 which carried a driven pinion 51 whereas the core discs 5' of the second group of electromagnetic clutches, torsion-resistant although axially shiftable, work together with a second output shaft 52 carries a driven pinion 53 and passes through the first output shaft 51.

The stators 1,1 ' witch corresponding current coils 2,2' are connected with fixed housing components namely the stator located farthest left in Figure 4 and having a housing cover 54 and all remaining stators 1 or 1' with an essentially cylindrical housing body 55.

The electromagnetic clutches of each group are accordingly arranged in parallel circuit and accordingly cause a torque increase in a construction mode which is economical in space whereby each group of electromagnetic clutches acts on one of the two oppositely driven output shafts 50,52.

Figure 6 shows an application diagram. In this case, for the sake of simplicity in portrayal, the two electromagnetic clutches 1 to 6 or 1' to 6' instead of understandably also being specified in accordance with Figure 4 the groups of electromagnetic clutches were not arranged in the construction mode economical of space in accordance with Figures 3 or 4 and 5 but parallel to one another.

In the diagram, a common drive motor 60 drives through a quick-acting clutch 58 and a flywheel storage unit 59 and a driven pinion 61 drives two gears 62,63 in opposite directions. The drive motor 60 is, for example, the traction motor of a tank. The gears 62 and 63 can be connected with driven gear outputs 64,65 which mesh with one gear 66 through electromagnetic clutches 1 to 6 or 1' to 6'. This gear 66 is fixed and coaxial with the trunnion 67 of a gun 68. This gun 68 is supported and slewable in the low friction bearing 69 on the hull of a tank characterized by reference designation 70 or of another vehicle. The stators 1 or 1' as well as the drive motor 60 are also supported on the hull 70. In the nonactuated state of clutches 1 to 6 or 1' to 6' the gun 68 is supported on the hull 70 only by the low friction bearings and will persist in remaining in the same position owing to their inertia independent from motions of hull 70. If a directional or tracking movement is to be transmitted to the gun, it follows that the appropriate electromagnetic clutch is activated and thereby connects the primary rotor 4 or 4' with the corresponding driven gear output 64,65 through a controlled friction contact. In this way, a directional torque can be quite quickly, simply and accurately applied to gun 68.

Claims (11)

1. A device of the kind specified for positioning and attitude-stabilizing a slewable inert mass supported on a base, in which the control device comprises at least one electromagnetic clutch or brake in which the magnetic field is controlled by hyperexcitation of the exciting coil through feedback and amplification of the measured magnetic field strength.

2. A device according to Claim 1 in which the or each control device has a number of electromagnetic clutches in a parallel arrangement.

3. A device according to Claim 2, in which the primaries of the electromagnetic clutches of the or each control device are driven by a common drive and the secondaries each act on a common drive.

4. A device according to Claim 1, in which the primary of the or each electromagnetic clutch or brake can be driven by means of a drive motor, for example an electric motor.

5. A device according to Claim 1, in which the drive of the primary of the one or each electromagnetic clutch or brake is derived from the traction drive of the self propelled base.

6. A device according to one of Claims 4 or 5, in which the drive is connected with the primary of the or each electromagnetic clutch through a switchable clutch.

7. A device according to Claim 6, in which the drive of the primary of the or each electromagnetic clutch comprises a flywheel storage unit.

8. A device according to any one of Claims 1 to 7, in which the secondary of the or each electromagnetic clutch is coupled with the inert mass through a gear transmission.

9. A device according to Claim 8, in which the gear transmission has no play.

10. A device according to Claim 8 or 9, in which the secondary of the or each electromagnetic clutch acts through a drive gear tooth system on a gear tooth system attached to the inert mass, and the output gear tooth system in the drive direction is stressed against the gear tooth system of the mass in order to remove any backlash of the teeth.

11. A device for positioning and attitude stabilizing a slewable inert mass supported on a base, substantially as specifically described herein with reference to Figures 1 and 2, or to Figure 3, or to Figures 4 and 5, or to Figures 4 and 6 of the accompanying drawings.