WO1997020287A2

WO1997020287A2 - Position sensing system

Info

Publication number: WO1997020287A2
Application number: PCT/GB1996/002830
Authority: WO
Inventors: James Peter Tagg; Alistair James Campbell
Original assignee: James Peter Tagg; Alistair James Campbell
Priority date: 1995-11-15
Filing date: 1996-11-15
Publication date: 1997-06-05
Also published as: WO1997020287A3; AU7583196A; GB9523506D0; EP0885428A2

Abstract

The invention provides position-sensing means (10) that comprise two potentiometer areas (12, 14) face to face, each said area (12, 14) having a connection (60, 62, 64, 66) at each of two opposite sides able to be used to apply a potential gradient across the area (12, 14), transmission means (18) to enable transmission to each said area (e.g. 14) of a position-indicating signal (20) derived from the other area (e.g. 12) at a position (24) to be sensed, high impedance amplification means (72) and microprocessor means (98) having four ports (741, 761, 781, 801) connected or able to be connected respectively to the four connections (60, 62, 64, 66) and adapted or programmable to switch between a first condition to apply a said gradient across one said area (e.g. 12) and connect the other said area (e.g. 14) to the high impedance amplification means (72) to produce a signal (92) indicative of the potential at said position (24) and hence indicative of a coordinate of said position (24) and a second condition to apply a said gradient across said other area (e.g. 14) and connect said one area (e.g. 12) to the high impedance amplification means (72) to produce a signal (92) indicative of the potential at said position (24) and hence indicative of another coordinate of said position (24). It also provides sensing means (10) that are adapted to be interrogated to indicate a sensed position (24); and/or that comprise means (98, 130, 132, 134, 136, 138, 150, 152) adapted or programmable to adopt a low power consumption condition between interrogations and possibly to detect whether interrogations have failed to occur and consequentially to adopt an even lower power consumption condition; and/or that comprise an element (34) adapted to be positioned by a thumb where each possible position of the positioning element (34) corresponds to a unique position of the thumb. It also provides a system that comprises a devices (196) to be controlled and a plurality of controllers (194) for the device (196) each comprising position-sensing means as above.

Description

POSITION-SENSING SYSTEM

Background to the Invention

This invention relates to position-sensing and control means.

In order to control the position of e.g. a cursor on a computer screen, various control devices are known, e.g. a mouse, a joystick and a trackerball. These devices commonly suffer from a range of problems, for example: difficulty of use by people who are not computer-literate; movement in two dimensions requiring use of at least two parts of the human body, e.g. two out of finger, wrist, elbow, shoulder; there is difficulty of making the analogy between the source of movement control and the target movement and/or there is low conformity therebetween; feedback to the brain of the correctness of target movement often depends on visual checking with the target due to low proprioception (awareness of position without the need to use other means, e.g. sight) of the human appendage/s in use.

Another class of input means that have been proposed for two-dimensional positional control utilises movement of a finger or stylus as a pressure device over a flat surface. In one proposed type the surface has an X-direction potential gradient and a Y-direction potential gradient, both of which are sensed to determine the position of the pressure point. If the two potential gradients are applied to the same surface, they interfere at the corners and produce non-linear fields at the corners. If the two potential gradients are applied to different surfaces, utilising respective pick-up points, complicated articulation means are required to ensure that the pick up points on the two surfaces correspond precisely at all times. A proposal has been made to have the surfaces face to face, separated by non-conducting pimples and using pressure at a selected position to deform one of the surfaces so as to make contact with the other, the X-potential and the Y-potential being sensed alternately rapidly by suitable circuitry. This first applies the X-potential to one surface and picks up the potential at the selected position by way of the other surface, feeding into a high impedance amplifier so as to reduce the effect of the varying resistance of the said

other surface as the said position changes. The roles of the two surfaces are then interchanged for the Y-potential. This has the disadvantage that the continual pressurising and flexing of one surface causes breakdown thereof. Also, pressing in order to define a position on the opposite side of the member being pressed is inherently inaccurate. The Invention

One aspect of the invention consists in position-sensing means as claimed in claim 1. This has the advantages that the superjacent areas have a common position to be sensed so that no particular articulation is required of the transmitting means in order to ensure that the sensed positions correspond on the two potentiometer areas, and the transmitting means avoid deformation of one of the areas and consequent deterioration as well as inaccuracy of positioning. Also, the use of transmitting means between the two areas avoids constructional difficulties and inaccuracies which can arise from taking a signal from the transmitting means itself. By arranging the position-sensing means so that the transmitting means are positionable at a position to be sensed common to both areas, the aforementioned difficulties of articulation can be avoided.

In the following text referring lo the claims, before the list of Figures, the references in parentheses to Figures of the drawings are given for ease of reference

in the later description, and are by way of example and not limiting. Said signal may be a d.c. or an a.c. potential. In a preferred embodiment, there are provided means as claimed in claim 2 (e.g. Figures 6 and 7). These means have the advantage of simplicity and may be designed to avoid need for recalibration. They can make use of d.c. potential differences.

Other embodiments can use other kinds of transmission means, e.g. for the signal to be d.c and derived electrostatically (e.g. Figure 11) or, in means as claimed in claim 3, an a.c. signal (e.g. Figure 10). Examples of a.c. potentiometers and bridges are given, for example, in the textbook "Alternating Current Measurements" by B Hague, published by Methuen in London, e.g. for use in cases where there may be d.c. drift.

While the transmission means may lie wholly between the two said areas (e.g.

Figures 6 and 7), they may alternatively be wholly outside the space between the areas

(e.g. Figures 10 and 12), e.g. in an a.c. embodiment as claimed in claim 4 (e.g. Figure

10), or e.g. with the two said areas on opposite faces of a single substrate (which then constitutes the said space between the two said areas) and using the double contact of an embodiment as claimed in claim 2 so that its two contacts make contact with the respective areas at the common position to be sensed with the transmission means lying wholly outside the substrate and embracing the same (e.g. Figure 12). These arrangements may allow a more rigid and simpler construction of the said two areas, e.g. on a single substrate (e.g. Figures 10 and 12) or, in each case, on respective substrates that are bonded together (e.g. Figure 19).

To enable maximum simplicity, and choice in articulation of the transmission means, and to allow the person who operates the position-sensing means to have maximum sensitivity to the position chosen, a positioning element for use by the operator to position the transmission means may be located at the common position

(at least so far as the X- and Y-coordinates are concerned), e.g. in means as claimed in claim 5 (e.g. Figure 6). Again, in embodiments in which the transmission means extend outside (e.g. Figure 20), or are wholly outside (e.g. Figures 10 and 12), the space between the two said areas, the positioning element can back onto the transmission means at said common position, e.g. in the case of an embodiment as claimed in claim 4 (e.g. Figure 10), or back onto at least part of the transmission means, e.g. an external contact (i.e. outside the said space between the two areas) in a suitable embodiment having the features as claimed in claim 2 (e.g. Figures 12 and 20).

Because the human thumb is prehensile and the tip of the thumb has at least two orthogonal degrees of movement (particularly, to and from the wrist and to and from the forefinger), a relatively larger area of the brain is devoted to the thumb than to other muscle motor groups such as the arm. According to a particularly useful embodiment, there are provided means as claimed in ciaim 6 (e.g. Figure 9). This utilises the agility of the thumb in the orthogonal directions to give better control.

While the thumb has been used in prior art position control arrangements such as a trackerball, these have been of the kind in which repeated thumb movements were required to obtain a full length of movement of a target and did not make use of the enhanced proprioception of the thumb due to the relatively larger area of brain devoted to it. In an embodiment as claimed in claim 7 advantage is taken of this property of the brain, ensuring that, for example, each possible position of the positioning element can be reached by a single movement of the thumb from any

other position of the positioning element. In practice, this enables the operator to position the positioning element with little or no visual feedback and more quickly and easily than heretofore. Preferably, the X,Y range of movement of the positioning element is planar, or slightly cylindrical to follow the natural movement of the thumb.

Further to facilitate use of the thumb, there may be provided means as claimed in claim 8 (e.g. Figure 9) or 9 (e.g. Figures 6 and 9).

To make more use of proprioception and to place less reliance on the slower method of visually examining the target, an arrangement may be used having the features of claim 10 (e.g. Figures 6 and 9), whether adapted for positioning by a thumb or fingers. In a practical embodiment, there is provided an embodiment having the features of claim 11 (e.g. Figure 2). Improved accuracy is obtained with an arrangement having the features of claim 12 (e.g. Figure 1 or 3).

By using the additional features of claim 13 (e.g. Figure 2, dashed lines), improved accuracy can be obtained. The output is a pair of signals indicating the X- and Y-coordinates of the

position to be sensed. By using the features of claim 12, not only is a particularly neat embodiment obtained but the possibilities are opened up of producing a wide variety of useful developments, although clearly some of these can be applied to other signal-processing means than a microprocessor. Generally, embodiments can now comprise the features of claim 14. "Condition" in relation to signals means that the quality, accuracy, occurrence or non-occurrence, shape, size or other parameters connected with the signal can be changed, quite apart from the basic switching operations and obtaining of basic signals implicit in the features of claims 11 and 13. In particular, an embodiment having the features of claim 15 in the position-sensing means can produce a much more useful output signal (e.g. Figure 15).

According to a development of the above embodiments, they are provided with the features of claim 16 (e.g. Figure 15). This opens up a range of possibilities for further developments. For example, an embodiment having the features of claim 17 is much more useful because it can operate with long life. A neat way of doing this is found in the features of claim 18, more usefully with the features of claim 19 which can improve power economy since the data need not be held for so long. By utilising the features of claim 20, a much improved degree of power economy can be obtained, and this itself can be much improved by the features of claim 21.

The aforementioned features of the claims can clearly be applied to making a substantially improved hand-held controller adapted to control a device to which it is not electrically connected (e.g. Figure 17). The controller and device can then usefully be included in a system to which the foregoing advantages can apply. In particular, the system may comprise a plurality of such controllers for the device with synergistic improvement in the advantages compared with use of a single such controller. For example, the whole system can become better rationalised, for example by means of the features of claim 28.

According to another aspect of the invention, there are provided position- sensing means as claimed in claim 32. These have the advantages mentioned above. According to another aspect of the invention, there are provided position- sensing means having the features of claim 33. A particular advantage of using microprocessor means in this manner is to produce versatile position-sensing means capable of many degrees of control. It also has the advantages mentioned above of an embodiment having the features of claim 11.

According to another aspect of the invention, there are provided position- sensing means as claimed in claim 34. These allow the possibility of a wide variety of applications and many degrees of control.

Yet another aspect of the invention consists in position-sensing means as claimed in claim 35. This and embodiments thereof having the features of claims 35 to 44 have the advantages recited above in relation to claims 16 to 21, 24 to 28 and

a hand-held controller. These features may have wider application, e.g. to sensing means in general or to any means or system allowing, enabling or using two-way communication.

Reference will now be made by way of example to the accompanying drawings in which:-

Figure 1 is a schematic circuit diagram of position-sensing means embodying the invention;

Figure 2 is a schematic circuit diagram corresponding to Figure 1, functionally arranged;

Figure 3 is a practical circuit diagram of an improved form of the Figure 1 embodiment; Figures 4 and 5 are plan views of respective printed circuit boards comprising

the two potentiometer areas of the Figure 1 embodiment;

Figure 6 is a schematic side elevation of part of the Figures 1 and 3 embodiments showing the potentiometer areas and transmission means; Figure 7 is an enlarged detail of Figure 6; Figure 8 is a side elevation and corresponding plan elevation of a contact spring seen in Figure 7;

Figure 9 is a schematic plan view corresponding generally to Figure 6; Figures 10 - 14 are views corresponding to part of Figure 6 showing variations; Figure 15 is a block circuit diagram of a development of the Figures 1 and 3 embodiments;

Figure 16 is a timing diagram illustrating operation of the Figure 15 embodiment; and

Figure 17 is a schematic block diagram illustrating a system comprising a plurality of controllers embodying the invention.

Reference is now made to the drawings. In the various embodiments, references having the same first pair of digits denote members that have a similar function and some of these may not be mentioned herein explicitly, or their function detailed, where this notation makes their function obvious. Position-sensing means 10, Figure 9, comprise two potentiometer areas 12 (the

X-coordinate area), 14 (the Y-coordinate area), Figure 1, superjacent and spaced apart by a space 16, Figure 6, means 10 comprising transmission means 18, Figure 2, positionable to enable transmission to each said area, e.g. 14, Figure 2, of a position- indicating signal 20 derived from the other area, e.g. 12, Figure 2. The transmission means 18 comprise a wiper with a double contact 22, Figure 6, to make electrical contact simultaneously with both of said areas 12, 14 at a position 24 to be sensed. This arrangement is suitable for a d.c. potential applied across each area 12, 14. It is also suitable for an a.c. potential applied thereacross. The position-indicating signal 20 may be derived from such an a.c. signal 26, Figure 2, from the area, e.g. 12, by variant means as illustrated in Figures 10 to 14, also having the features mentioned

above. The transmission means 18 may simply be a conductor or may be more complex, e.g. to condition the signal carried by the transmission means (e.g. to reduce noise, or jitter on digital-analogue conversion) or even to respond to an input signal to produce an output signal, e.g. on being triggered or controlled by the input signal. In the Figure 10 embodiment, potentiometer areas 121 (X), 141 (Y) are formed on opposite sides of a common insulating substrate 28 and have on the outer face of one area 121 a layer 30 of wear-resistant material, e.g. PTFE, transparent to magnetic fields, itself surmounted by a small mass 32 of mu-metal that is elongate and lying at approximately 45° to the X- and Y-axes, itself surmounted by a thumb button 341 and having the effect of transmitting a proportion of the a.c. signal from each of the areas 121, 141 to the other in turn. Alternatively, mass 32 may be a low resistance, short-circuited coil, e.g. of material that is superconducting at working (room) temperature. In the Figure 11 embodiment, potentiometer areas 122, 142 are separated by dielectric (insulating) layers 281, 282 from a capacitor plate 321 serving to transmit a proportion of the a.c. signal from one to the other of areas 122, 142. The mass 32 and conductive capacitor plate 321 serve as the transmission means in these two embodiments. The mass 32 and thumb button 341 mounted thereto (and both on a mounting 361 similar to the mounting means 36, Figure 6) are at that face 38 of one of said areas 121 remote from the other said area 141. In the Figure 12 embodiment, the potentiometer areas 123, 143 are on the opposite faces of a common insulating substrate 283 with a double contact 221 making electrical contact simultaneously with the outer faces 381, 382 of the areas 123, 143, in contrast to the transmission means 18 comprising double contact 22, Figure 6, which are mounted to a positioning element 34 by mounting means 36 such that the transmission means 18 (comprising double contact 22) and the positioning element 34 are at opposite faces 383, 384 of one of said areas 12 at the same position 24. The potentiometer areas 125, 126,

Figure 13, are manufactured on respective substrates 285, 286 which are then bonded together. By having the double contact 222, Figure 14, rest on the upper sides of the potentiometer areas 127, 128, there can be less wear on the latter since the former need not be urged against the latter (and can even be biased upwardly, off the latter, to break the transmission) except while the thumb button 342 is pressed. This transmission break can be utilised to control the position-sensing means, e.g. to save power by switching it off if it is not being used, e.g. after 2 seconds' non-use.

The position-sensing means 10 are adapted for the positioning element 34 to be positioned by a thumb by virtue of the shaping of the chassis 42, Figure 9, thereof, so that when this is held naturally in the hand the thumb will be correctly located for this purpose. The positioning element 34 carries a plastics bearing shim 44, Figure 6, e.g. of PTFE for low friction, by which it bears on a bearing plate 46 which in turn has mounted thereto clearly defined and readily propriocepted tactile boundaries 48, e.g. the edges 481 of a window (in which element 34 moves) in the chassis 42, Figure

9. The circumference of the shim 44 will encounter boundaries 481 and hence define a usable resistive potentiometer area 124. It is clear from Figure 9 that each possible position of the position element 34 corresponds to a unique position of the thumb and a single movement of the thumb will be able to reach every possible position of the positioning element 34 from every other such position.

As will be seen from Figures 6 and 9, for positioning of the element 34, the latter is mounted to mounting means 36, the size and arrangement of which are adapted to conform to movements of a human thumb. The usable area 124 is preferably 5 centimetres (2 inches) from side to side as seen in Figure 9 by 3.5

centimetres (1.5 inches), though these dimensions can usefully vary down to 50% or up to 120% of these values, or possibly more. The double contact 22 is mounted to a plastic actuator arm 50 riveted to a metal actuator arm 52 to which is mounted the positioning element 34 in the form of a thumb button having a depression in its upper surface to receive the tip of the thumb, such that element 34 and double contact 22 are all located at the common position 24 in relation to the X,Y plane. The plastics actuator arm 50 has a groove 54 which coacts with a sliding bearing post 56 to provide a slide-pivot means for the positioning element 18 to follow the degrees of freedom of movements of a human thumb.

The double contact 24 is a contact spring, preferably of stainless steel, and has the shape seen in more detail in Figures 7 and 8. It clips onto the end of arm 50. The exact shape of chassis 42 will depend upon ergonomics, e.g. the thumb- positioning requirements mentioned above.

Turning now to the electrical aspects and referring to Figure 2, each area 12, 14 has a connection 60, 62 and 64, 66, respectively, at each of two opposite sides of the area. These connections are able to be used lo apply a potential gradient across each area 12, 14. As will be clearer from Figures 4 and 5, the gradient across each area can be made linear and uniform, since the connections 60, 62, 64, 66 are substantially non-resistive compared with the areas 12, 14. The two gradients across the respective areas 12, 14 are arranged to be mutually orthogonal, so that when one area 12 is laid over the other 14 (so that they are superjacent) the two potentials at a common position 24, where the transmission means 18 is located, will serve as X- and Y-coordinates of that position. The position-sensing means 10 comprise signal- processing means 70, which in turn comprise high impedance amplification means 72 and have four ports 74, 76, 78, 80 connected (or able to be connected) to the four said connections 60, 62, 64, 66 respectively. The signal-processing means 70 are adapted or programmable to switch between a first condition shown in Figure 2 and a second condition in which the switches 82, 84, 86 are switched to their other pole. The first condition serves to apply a said gradient across one said area 12 (X) by connecting connection 60 to line 88 at +5 volts and connection 62 to line 90 at 0 volts and to connect the other said area 14 (Y) by its connection 64 to the high impedance amplification means 72. The transmission means 18 picks up the potential at the position 24 on area 12 and transmits this as a position-indicating signal 20 to area 14, the resistance of which can be ignored due to the high impedance of amplification means 72, thereby producing an output signal 92 indicative of the potential at the position 24 on area 12 and hence indicative of the X-coordinate of position 24. In the second condition, with switches 82, 84, 86 reversed, signal 92 is indicative of Ihe Y- coordinate of position 24 in relation to area 14. Amplification means 72 are provided by an operational amplifier connected as a voltage follower. The switches 82, 84, 86 can be provided by a standard electronically-controlled switching chip 94, Figure 1,

e.g. that known under the trade designation "4053", under the control of a selecting signal 96 to select between the first and second conditions. In practice, chip 94 has six ports, two pairs of which are strapped together to produce the functions of switches 82 and 84 as seen in Figure 2. The connections of the "4053" chip 94 as seen in Figure 1, will be clear to one skilled in the art by reference to the usual trade lettering used in Figure 1. All of the functions of the signal-processing means 70, Figure 1, together with the further functions of providing signal 96 and utilising and/or processing signal 92 can be combined in a microprocessor 98, Figure 3, e.g. the programmable integrated circuit microprocessor made by Arizona Micro Systems and known under their trade name "PIC".

The signal-processing means 70 are adapted or programmable to connect the high impedance amplification means 72 to preferably each said connection 60, 62 or 64, 66 of the said area 12 or 14 connected thereto to produce a signal 92 more accurately indicative of the potential at said position 24. For this purpose, two switches 110 and 112 are inserted in the lines leading to ports 76, 80 so as to feed thereto the signal from connection 60 alternately to 62 and 66 alternately to 64, when these connections are serving for pick up of a signal. For example, in the said first condition illustrated in Figure 2, the previous Y-coordinate signal from area 14 will be stored and used to prorate the difference between the signals picked up alternately from connections 64 and 66 when the X-coordinate signal from area 12 is being derived. This can be done in the microprocessor 98.

The signal-processing means 70 in the microprocessor 98 are further adapted or programmable to condition signals processed by said means 70, usually to improve the condition or quality of the signal, e.g to reduce noise or, in analogue to digital conversion, to reduce jitter.

Further, microprocessor 98 may be adapted or programmable to determine if a signal 20 to be sensed is absent and/or if it appears to indicate a speed of variation, or other parameter related to the sensed position 24, being outside a predetermined acceptable range. In these cases, microprocessor 98 can consequentially create or change an output signal 114 indicative of said position 24. For example, if a signal

20 is absent at a time when it should be present, a like signal 20 may be created having the value of the last produced corresponding signal 20.

There have thus been provided, in a preferred embodiment, position-sensing means 10 that comprise two potentiometer areas 12, 14 face to face, each said area

12, 14 having a connection 60, 62, 64, 66 at each of two opposite sides able to be used to apply a potential gradient across the area 12, 14, transmission means 18 to enable pick-up from each said area 12, 14 to the other, (in fact transmission to each said area, e.g. 14, of a position-indicating signal 20 derived from the other area, e.g. 12, at a position 24 to be sensed,) high impedance amplification means 72 and microprocessor means 98 having four ports 741, 761, 781, 801 connected or able to be connected respectively to the four connections 60, 62, 64, 66 and adapted or programmable to switch between a first condition to apply a said gradient across one said area, e.g. 12, and connect the other said area, e.g. 14, to the high impedance amplification means 72 to produce a signal 92 indicative of the potential at said position 24 and hence indicative of a coordinate of said position 24 and a second condition to apply a said gradient across said other area, e.g. 14, and connect said one area, e.g. 12, to the high impedance amplification means 72 to produce a signal 92 indicative of the potential at said position 24 and hence indicative of another coordinate of said position 24.

The position-sensing means 106, Figure 15, have all the above-mentioned features and in addition are adapted to be interrogated to indicate a sensed position 24.

For this purpose, a polling signal 118 is applied through interface circuitry 130 to microprocessor 98 to ask for the latest stored values of the signals indicating the X- and Y-coordinates, in response to which suitable signals 114 are transmitted.

Position-sensing means 106 are adapted or programmable to adopt a low power consumption condition between interrogations, in this embodiment being adapted to measure time between regular interrogations and adopt said low power consumption condition after an interrogation until just prior to the next interrogation. To give the nearest to a true reading, the position 52 is sensed just prior to the next interrogation.

For further economy, position-sensing means 106 are adapted or programmable to detect whether interrogations have failed to occur and consequentially to adopt an even lower power consumption condition, for example if the interrogating device has been switched off. For this purpose, means 106 are adapted to time a relatively long interval in said even lower power consumption condition compared with the time between regular interrogations and then return to an interrogable condition for a period longer than, preferably just longer than, the time between two regular interrogations and if an interrogation should not occur in that period then return to said even lower power consumption condition. For these purposes, microprocessor 98 is provided with

a high frequency clock 132, a low frequency clock 134, and a watchdog timer 136 and controls the power supply 138 to areas 12, 14 and a power supply 150 to interface circuitry 130. It is convenient, for better power control, in this embodiment for conditioning circuitry 152 to be interposed between areas 12, 14 and microprocessor

98.

Assuming that polling (interrogations 190) occurs on a regular basis, and referring to Figure 16, the microprocessor is activated at time 154, at time 156 it senses and decodes a coded polling signal that indicates that a request for data is active, scans its store of sensed signals and returns the required data while simultaneously counting the time until the next polling request at time 158, this counted time being taken as the regular polling period 170. Having responded to this new request at time 158, the microprocessor 98 turns off power to external circuitry and enters a low-power counting mode until time 172 which is just before the next request is expected at time 174. The microprocessor 98 may take one reading of an X-coordinate signal and one reading of a Y-coordinate signal between times 172 and 174 and store these until polled at time 174, though more usually it will take several readings and average them. If no polling request is decoded when expected, e.g. at time 176, the microprocessor 98 remains "awake" until a valid request is detected at time 178 and then starts the whole process again, as described from time 156, which includes measuring the new polling period 171 in case this has changed. The vertical arrows, e.g. 190, in the upper row of Figure 16 represent poll requests while the "pulses", e.g. 192, in the lower row represent times of power being switched on, i.e. the microprocessor 98 being "awake".

There may also be other polling requests occurring for other units, each comprising a position-sensing means 106, at different time relationships from those indicated in Figure 16, e.g. being phased differently to be interspersed therewith or being at different polling rates. Each unit will synchronise with its own polling request code sequence as sensed and decoded by its processor, in the same manner as just described.

Control of the power can be achieved by switching off or reducing the power consumption of what may be called the sensor areas 12, 14 and of the conditioning circuitry 152 and interface circuitry 130 and also switching over from clock unit 132 to clock unit 134. Clock unit 132 provides normal speed running. Clock unit 134 provides "sleep" speed running and "deep sleep" (the aforesaid "even lower power consumption condition") speed running of microprocessor 98. When the latter is run at a lower frequency, the power consumption is decreased dramatically. Example values can be, say, 4MHz for normal operation and lOOKHz for "sleep" mode, typically giving a power reduction in the microprocessor by a factor of 40: "deep sleep" running can be at 2Hz - 0.5Hz. The watchdog timer 136 can also be used to ensure that the microprocessor does not "put itself to sleep" for unduly long periods; it does this by setting a default maximum time before the timer 136 restarts the microprocessor 98 if timer 136 has not meanwhile been "reloaded" (reset) by the latter.

The embodiment of Figure 9 may be a hand-held controller 194 adapted to control another device 196, Figure 17, and comprises a self-contained power supply 198 and the position-sensing means 10. The host device 196 to be controlled by the controller 194 may interface with the controller 194 by wire, radio, infra-red or any other data link method. As indicated in Figure 17, the controller 194 is adapted to control the device 196, being a device to which it is not electrically connected. There may be a plurality of the controllers 194 (e.g. for operation by respective players of a video game appearing on a VDU screen of device 196 to control respective objects or pointers on the screen), each having its own recognition code for selective polling by the device 196. The device and controller/s together form a control system 202. Figure 16 can be considered as a timing diagram of a controller (e.g. a hand¬ held remote control unit) that allows control of power therein by "flywheel" operation in low power mode between requests for data from the controlled (host) device. The following points should be noted:

1. If there is only one controller per control system, the poll may be simple

(i.e. without any identification information). 2. In a control system with multiple controllers, the poll (interrogation) signals can be encoded so that each controller can identify which poll signal is relevant to itself. Preferably, the controlled device is able to set each of the controllers to respond to a different interrogation signal, e.g. by supplying to them in turn a specially coded pseudo-poll signal that is detected as such by the poll signal sensor and controls the microprocessor to reset its poll signal recognition code to one included in the specially coded signal, which is different for each controller.

3. These differently encoded polling signals may have the same cycle time as each other, in which case the controllers are polled in turn, or if different cycle lengths are used then each controller may be polled (sampled) at different rates. 4. The control system will function most effectively when the cycle time of each controller is fixed, and no poll signals arc omitted.

5. The controller (or at least its sensor areas and conditioning circuitry, which consume most power) does not have to be reactivated until a valid poll signal is achieved, but the best performance will be achieved if the controller data are prepared in a short period prior to the poll signal being sensed so that the data may be returned immediately.

6. If no poll signal is detected within a given time after an "activate" button on the controller is pressed, then the controller can be arranged to switch off or enter a permanent "sleep" or "deep sleep" mode until a new "activate" command is effected. (In a video game context, this might be called a "player active" button on the controller and might activate the controlled device to start the polling process.)

7. A "deactivate" (or "player out") button on the controller can be arranged to remove this from the polling control system by causing a complete power down until the next "activate" command is issued.

8. The polling period to each controller may be changed, and the latter will in most cases automatically adjust - for both shorter and longer polling periods. If the host controlled device detects a problem with one or more of the controllers then a special reset poll can be sent to cause an "activate" sequence in one or all of the controllers.

Pre-processing (conditioning) and jitter reduction:

1. Because of the nature of analogue to digital conversion, there will always

be a tendency for a 1-bit jitter in the reading from an analogue signal that is converted. This can manifest itself if the system is used as a pointing control system by the rapid jitter of the displayed pointer on the screen in either or both of the X and Y directions, which would be irritating to the user. Pre-processing (e.g. at conditioning circuitry 152, as described above) of the data from successive conversions can filter out these effects by analysing the average of the positions read over a period of time. 2. Additionally, erroneous readings due to a "bad" reading (interference, dust, vibration etc.) that cause an unexpectedly large jump in position can be filtered out by similar techniques. 3. Power reduction control can also be usefully applied in these situations so that the interface (infra-red, radio) transmitter need not be activated until a valid reading is to be communicated to the host.

The invention may be applied, for example, to moving a pointer over a list on a VDU screen of an interactive system, e.g. for teleshopping, or to moving a selected object around a computer screen, and other buttons on the controller may similarly be effective by the polling to select, change and/or effectuate the object (e.g. cause it to

"execute", if it is a listed computer programme).

In the drawings, narrow shading represents conductive material, wide shading insulating (or dielectric) material, and dotted shading wear-resistant material, e.g.

PTFE.

It will be apparent to one skilled in the art, that features of the different embodiments disclosed herein may be omitted, selected, combined or exchanged and the invention is considered to extend to any new and inventive combination thus formed.

Claims

1. Position-sensing means comprising two potentiometer areas superjacent and spaced apart, characterised in that they comprise transmission means positionable to enable transmission to each said area of a position-indicating signal derived from the other area.

2. Means as claimed in claim 1, characterised in that the transmission means comprise a double contact to make electrical contact simultaneously with both of said areas at a position to be sensed.

3. Means as claimed in claim 1 or 2, characterised in that the transmission means are positionable to enable transmission to each said area of a position-indicating signal as aforesaid derived from an a.c. signal from the olher area.

4. Means as claimed in claim 3, characterised in that the transmission means are at that face of one of said areas remote from the other said area.

5. Means as claimed in any one of claims 1 to 3, characterised in that the transmission means are mounted to a positioning element therefor by mounting means such that the transmission means and the positioning element are at opposite faces of

one of said areas at substantially the same position.

6. Means as claimed in any one of claims 1 to 5, characterised in that they comprise a positioning element for the transmission means and are adapted for the positioning element to be positioned by a thumb.

7. Means as claimed in claim 6, characterised in that each possible position of the positioning element corresponds to a unique position of the thumb.

8. Means as claimed in claim 6 or 7, characterised in that the positioning element, for positioning thereof, is mounted to mounting means, the size and arrangement of

which are adapted to conform to movements of a human thumb.

9. Means as claimed in any one of claims 5 to 8, characterised in that the positioning element, for positioning thereof, is mounted to slide-pivot means.

10. Means as claimed in any one of claims 5 to 9, characterised in that clear tactile boundaries are provided to the possible positions of the positioning element.

11. Means as claimed in any one of claims 1 to 10, characterised in that each said area has a connection at each of two opposite sides able to be used to apply a potential gradient across the area, and the position-sensing means comprise signal- processing means comprising high impedance amplification means and having four ports connected or able to be connected to the four said connections respectively and adapted or programmable to switch between a first condition to apply a said gradient across one said area and connect the other said area to the high impedance amplification means to produce a signal indicative of the potential at the position of the transmission means and hence indicative of a coordinate of said position and a second condition to apply a said gradient across said other area and connect said one area to the high impedance amplification means to produce a signal indicative of potential at said position and hence indicative of another coordinate of said position.

12. Means as claimed in claim 11, characterised in that a microprocessor comprises said signal-processing means.

13. Means as claimed in claim 11 or 12, characterised in that said signal- processing means are adapted or programmable to connect the high impedance amplification means to each said connection of the said area connected thereto to produce a signal more accurately indicative of the potential at said position.

14. Means as claimed in any one of claims 11 to 13, characterised in that said signal-processing means are adapted or programmable to condition signals they process.

15. Means as claimed in any one of claims 1 to 14, characterised in that they are adapted or programmable to determine if a signal to be sensed is absent and/or if it appears to indicate a speed of variation, or other parameter related to the sensed position, being outside an acceptable range and consequentially to create or change an output signal indicative of said position.

16. Means as claimed in any one of claims 1 to 15, characterised in that they are adapted to be interrogated to indicate a sensed position.

17. Means as claimed in claim 16, characterised in that they are adapted or programmable to adopt a low power consumption condition between interrogations.

18. Means as claimed in claim 17, characterised in that they are adapted or programmable to measure time between regular interrogations and adopt said low power consumption condition after an interrogation until just prior to the next interrogation.

19. Means as claimed in claim 17 or 18, characterised in that they are adapted or programmable to sense position just prior to an interrogation.

20. Means as claimed in any one of claims 17 to 19, characterised in that they are adapted or programmable to detect whether interrogations have failed to occur and consequentially to adopt an even lower power consumption condition.

21. Means as claimed in claim 20, characterised in that they are adapted or programmable to time a relatively long interval in said even lower power consumption

condition compared with the time between regular interrogations and then return to an interrogable condition for a period longer than the time between two regular interrogations and if an interrogation should not occur in that period then return to said even lower power consumption condition.

22. Position-sensing means, substantially according to any example hereinbefore described.

23. Position-sensing means substantially according to any example hereinbefore described with reference to and illustrated in the accompanying drawings.

24. A hand-held controller adapted to control another device, characterised in that it comprises a self-contained power supply and position-sensing means as claimed in any one of claims 1 to 23.

25. A hand-held controller adapted to control a device to which it is not electrically connected, characterised in that it comprises position-sensing means as claimed in any one of claims 1 to 24.

26. A system comprising a device to be controlled and a controller for the device, characterised in that the controller is as claimed in claim 24 or 25.

27. A system comprising a device to be controlled, characterised in that it comprises a plurality of controllers for the device each as claimed in claim 24 or 25.

28. A system as claimed in claim 27, characterised in that the controlled device is able to set each of the controllers to respond to a different interrogation signal.

29. A system substantially according to any example hereinbefore described.

30. A system substantially according to any example hereinbefore described with reference to and illustrated in the accompanying drawings.

31. A device to be controlled, characterised in that it is suitable to be the said controlled device of a system as claimed in any one of claims 26 to 28.

32. Position-sensing means comprising an element adapted to be positioned by a thumb, characterised in that each possible position of the positioning element corresponds to a unique position of the thumb.

33. Position-sensing means comprising two potentiometer areas face to face, each said area having a connection at each of two opposite sides able to be used to apply a potential gradient across the area, and means to effect pickup from each area to the other, characterised in that they comprise microprocessor means having four ports connected or able to be connected respectively to the four connections and adapted or programmable to switch between a first condition to apply a said gradient across one said area and connect the other said area to high impedance amplification means to produce a signal indicative of the potential at said position and hence indicative of a coordinate of said position and a second condition to apply a said gradient across said other area and connect said one area to high impedance amplification means to produce a signal indicative of potential at said position and hence indicative of another coordinate of said position.

34. Position-sensing means, characterised in that they are adapted to be interrogated to indicate a sensed position.

35. Position-sensing means, characterised in that they are adapted to be interrogated to indicate a sensed position and are adapted or programmable to adopt a low power consumption condition between interrogations.

36. Means as claimed in claim 35, characterised in that they are adapted or programmable to measure time between regular interrogations and adopt said low power consumption condition after an interrogation until just prior to the next interrogation.

37. Means as claimed in claim 35 or 36, characterised in that they are adapted or programmable to sense position just prior to an interrogation.

38. Means as claimed in any one of claims 35 to 37, characterised in that they are adapted or programmable to detect whether interrogations have failed to occur and consequentially to adopt an even lower power consumption condition.

39. Means as claimed in claim 38, characterised in that they are adapted or programmable to time a relatively long interval in said even lower power consumption condition compared with the time between regular interrogations and then return to an interrogable condition for a period longer than the time between two regular interrogations and if an interrogation should not occur in that period then return to said even lower power consumption condition.

40. A hand-held controller adapted to control another device, characterised in that it comprises a self-contained power supply and position-sensing means as claimed in any one of claims 35 to 39.

41. A hand-held controller adapted to control a device to which it is not electrically connected, characterised in that it comprises position-sensing means as claimed in any one of claims 35 to 40.

42. A system comprising a device to be controlled and a controller for the device, characterised in that the controller is as claimed in claim 40 or 41.

43. A system comprising a device to be controlled, characterised in that it comprises a plurality of controllers for the device each as claimed in claim 40 or 41.

44. A system as claimed in claim 43, characterised in that the controlled device is able to set each of the controllers to respond to a different interrogation signal.

[End]