GB2207812A

GB2207812A - Electromagnetic actuators

Info

Publication number: GB2207812A
Application number: GB08718751A
Authority: GB
Inventors: Wladyslaw Wygnanski; Robin Whittaker
Original assignee: OUT BOARD ELECTRONICS Ltd
Current assignee: OUT BOARD ELECTRONICS Ltd
Priority date: 1987-08-07
Filing date: 1987-08-07
Publication date: 1989-02-08
Anticipated expiration: 2007-08-07
Also published as: GB2207812B; GB8813919D0; GB8718751D0

Abstract

The movement of a slider along a track 16 (eg for use in audio or lighting equipment) is controlled by a magnetic coil 18 which is disposed parallel to the track and is connected to a control unit 24 for supplying d.c. current to the coil. The slider comprises a permanent magnet 12, whereby the resultant magnetic interaction with the coil 18 causes the slider to move at a desired speed to any position along the track which may be programmed into a memory of the control unit. A position sensor 14 cooperates with a track 28 to feedback position data to the control unit 24. <IMAGE>

Description

Title: Movement Controlling Apparatus Field of the Invention This invention relates to apparatus for controlling movement of a device along a path, and more particularly to the positioning of a device along a linear path.

Background to the Invention In many applications it is necessary to move a device to a particular position or series of positions. For example, in studios it may be necessary to move one or more sliders for lighting or audio equipment to predetermined positions. This has heretofore been done by complicated electric motors, requiring gearboxes, moving belts and ancillary driving equipment.

Summary of the Invention According to the invention there is provided apparatus for controlling movement of a device along a path, comprising a first magnetic means connected to said device, guide means defining said path along which the device is moveable, second magnetic means disposed along said path and in magnetic contact with said first magnetic means, and control means for supplying electric current to at least one of said magnetic means to cause the device to perform the required movement.

Preferably the first magnetic means is a permanent magnet, and the second magnetic means is an electromagnetic coil connected electrically to said control means.

Due to the magnetic coupling between the permanent magnet and the coil, a magnetic driving force is applied to the device, the direction of which depends on the direction of the electric current flow; therefore the device can be moved in either direction by switching over the polarity of the coil. The magnitude of the driving force, for a given condition, will be proportional to the magnitude of the electric current. The device will therefore stay at a given position, and can also easily be moved manually when the coil is disconnected or the voltage across the coil is zero.

The guide means is preferably a sliding bearing, the device being in the form of a slider moveable along the bearing. Said path of movement may be straight, or curved (e.g. part of a circle or a spiral).

Said control means preferably includes a sensor coupled to the slider which gives a signal in an analog or digital form corresponding to the linear displacement of the slider. Alternatively the velocity or acceleration of the slider may be controlled. By appropriate processing of the signal the control means can accurately control the position (or velocity/acceleration) of the slider.

The slider may be moveable along a position track which is coded by means of a magnetic, optic or other suitable coding system. Alternatively the position track may take the form of a contactless positioning device, e.g. based on ultrasonics.

The first magnetic means may be equipped with a sensor attachment as an integral part of the position detection system, e.g. a mirror or other form of relector, or alternatively a receiver or transmitter may be attached to the magnet.

Consequently, with the ability to control the direction and magnitude of the electric current in the coil from the control means, while monitoring the position, velocity or acceleration (or any combination thereof) of the slider, it is possible to move the slider from one position to another under the influence of interactive magnetic forces. The velocity of movement of the device is dependent on the magnetic field strength and coupling, as well as on the static and dynamic friction of the slide.

An advantage of the invention lies in the fact that the driving force is obtained without any additional mechanical or electrical moving attachment, so that inertia forces are negligible in both the manually and electrically operated slider modes. This compares with the formerly used linearly moving devices which are driven typically by an electric motor with other moving attachments such as a gearbox, a driving belt, pulleys, rolls and other moving parts.

The invention will now be further described, by way of example only, with reference to the single figure of the accompanying drawing, which is a schematic diagram of a moving slider in accordance with the invention.

Description of the Embodiment The single figure shows generally at 10 a moving slider, which is a moveable assembly comprising a permanent magnet 12 and a position sensor 14. The moving slider 10 is slideably mounted on a rectilinear slide or bearing 16.

Positioned in close magnetic proximity to the permanent magnet 12 and disposed parallel to the slide bearing 16 is a coil 18 having a plurality of turns of wire wound on a magnetic core 20.

The ends 22 of the coil 18 are electrically connected to a control unit 24 which incorporates a memory and is capable of delivering sufficient d.c driving power to move the slider 10 and any additional attachments which may be connected to it. The magnitude and direction of such driving current depend on the input data, represented by arrow 26, which is input to the control unit 24 and which may be given in an analog or any coded form. Amongst such input data is a feed back control signal which, in the example illustrated, is derived from a position track 28 with which the position sensor is associated, and which leads to the control unit 24 via a control line 30.

It will be understood that the magnetic coil 20 may instead take the form of a more complex magnetic assembly, e.g. with two or more bars, tubes or discs and with more than one coil fitted; also the slide bearing 16 may be an integral part of the magnetic assembly.

The apparatus according to the invention is capable of adaptation to a whole variety of systems which require a device to be moved to a predetermined programmable position along a track, or which require to be moved at a desired velocity, e.g. to alter the position(s) of other controllers. The control unit 24 has a memory sufficient to store a plurality of different settings or programmed movements, allowing subsequent repetition as required.

Claims

1. Apparatus for controlling movement of a device along a path, comprising a first magnetic means connected to said device, guide means defining said path along which the device is moveable, second magnetic means disposed along said path and in magnetic contact with said first magnetic means, and control means for supplying electric current to at least one of said magnetic means to cause the device to perform the required movement.

2. Apparatus according to claim 1 in which the first magnetic means is a permanent magnet, and the second magnetic means is an electromagnetic coil connected electrically to said control means.

3. Apparatus according to claim 1 or claim 2 in which the guide means is a sliding bearing, said device being in the form of a slider moveable along the bearing.

4. Apparatus according to any one preceding claim in which said path of movement is straight or regularly curved.

5. Apparatus according to claim 3 or claim 4 in which said control means includes a sensor coupled to the slider which gives a signal in an analog or digital form corresponding to a movement parameter of the slider.

6. Apparatus according to claim 5 in which said parameter is the linear displacement of the slider.

7. Apparatus according to claim 5 in which said parameter is the velocity or acceleration of the slider.

8. Apparatus according to any one of claims 3 to 7 in which the slider is moveable along a position track which is coded by means of a magnetic, optic or other equivalent coding system.

9. Apparatus according to any one of claims 3 to 7 in which the slider is moveable along a position track in the form of a contactless positioning device, eg based on ultrasonics.

10. Apparatus according to any one of claims I to 7 or claim 9 in which said first magnetic means is equipped with a sensor attachment as an integral part of a position detection system, eg a mirror or other form of reflector.

11. Apparatus according to claim 10 in which said sensor attachment is a receiver or transmitter attached to the first magnetic means.

12. Apparatus for controlling movement of a device along a path substantially as herein described with reference to and as shown in the accompanying drawing.