WO1995005141A1

WO1995005141A1 - A wheel device for a wheel chair

Info

Publication number: WO1995005141A1
Application number: PCT/SE1994/000741
Authority: WO
Inventors: Thomas Harald Johannes Andersson; Johan Magnus Carlsson
Original assignee: Andersson Thomas Harald Johann; Johan Magnus Carlsson
Priority date: 1993-08-16
Filing date: 1994-08-15
Publication date: 1995-02-23
Also published as: SE9400869L; SE9400869D0

Abstract

The invention is intended to provide a measuring chair function which will enable the propulsion force applied to a drive ring by the chair user to be measured, and also to provide an electrically operated powerservo on conventional, manually driven wheelchairs. Power or force sensors (2.1) are placed adjacent a respective attachment between drive ring (3) and wheel (4) and function to measure the propulsion force applied on the drive ring by the user. The drive ring is also held by other types of attachment means (2.2) which lack the provision of power or force sensors and which solely provide a force effect in an axial direction and which have the smallest possible effect in the peripheral direction of the drive ring. Each wheel can be substituted for the conventional wheel of a wheelchair and includes quick coupling means to this end. Furthermore, each wheel may be provided with a drive assembly (41) including a motor (64) which can be controlled in response to the measurement signals delivered by the power sensors. A computer unit (56) receives the power signal (55) from each wheel, the wheel speed (57) and also the settings chosen by the user and entered on an instrument panel (8), and calculates useful user information and is effective in controlling the motor in accordance with a variable program, in such instances when the arrangement includes a motor.

Description

A WHEEL DEVICE FOR A WHEEL-CHAIR.

Description

The present invention is concerned with the provision of an electric powerservo on conventional, manually activated wheelchairs, and also with the provision of a wheelchair measuring function on conventional types of wheelchairs in which a drive ring is coupled to each of the chair drive wheels for the purpose of measuring the forward propulsion force applied to the drive ring by the user.

Wheelchairs are either powered manually or electrically. Electrical wheelchairs are needed when the handicapped person is unable to propel a wheelchair manually by himself/herself. There are a large number of people who are bound to a wheelchair and who have control over their arm movements but lack the physical strength to propel a wheelchair manually. All of those belonging to this group are compelled to use electric wheelchairs that are equipped with joystick controls, since no other type of electric wheelchair that can better satisfy the need of such people is available commercially.

The problem (the fault) with such joystick-controlled chairs is that they do not utilize the power resources of the user, resulting, among other things, in passivation or inactivation of the user's arm muscles, and also causing the user to feel more handicapped than he/she actually is.

There are also a number of situations in which it is desirable to obtain a correct and objective assessment of the strength and fitness of a handicapped person and also of the technique used by such a person when propelling a manually-driven wheelchair. This objective assessment is important in enabling important decisions to be made with regard to the type of wheelchair chosen by the handicapped person, the sitting posture, the training program adopted, daily requirements, and so on. Solutions which enable the physical strength of a handicapped user to be measured are known to the art, although these solutions are relatively expensive, particularly since specially constructed power sensors are used or because of the need to use a large number of sensors and to combine the signals delivered by these sensors.

Neither is there available commercially a system which can be installed directly on a wheelchair that is used normally by a handicapped person, by simply exchanging the chair wheels. This latter possibility is extremely important in practice, since wheelchairs are tested individually.

A test result obtained when investigating the propelling force exerted by a wheelchair user is described in an article "Erfassung von Belastungsgrόssen beim

Rollstuhlfahren" by W. Lesser, Messtechnische Breite 20 (1984), Heft 1. Each attachment between drive ring and wheel rim of the tested wheelchair was provided with a respective strip-like strain gauge which were connected in a bridge coupling. A box containing battery-powered evaluating equipment, not described in detail, was mounted on the wheelchair. A separate slip-ring transmission device functioning to transfer the signals from the strain-gauge strips to the evaluating equipment is also described. This device records the obtained signals, which are subsequently processed on external computer equipment. The equipment described in this article is expensive.

U.S. 5,234,006 describes a wheelchair which includes the possibility of applying additional forward propulsion to the drive wheels of a wheelchair, by virtue of power sensors mounted on all attachments between drive ring and wheel. This wheel drive is mounted on the actual wheelchair itself, and thus not on each separate wheel. The additional propulsion force, or booster force, is calculated with the aid of conventional circuits which cannot be adjusted automatically on the basis of the working performance of the handicapped persons themselves. The equipment described is bulky and results in relatively wide wheels. The solution does provide for some manual adjustment possibilities, however.

One object of the present invention is to provide a robust, simple and inexpensive arrangement for measuring the force that is applied to the drive wheels of a wheelchair by the user, wherein it is possible to use the wheelchair as a measuring instrument.

Another object of the invention is to provide an arrangement by means of which the force applied by the user under different driving conditions during the course of wheelchair movement can be noted and recorded.

Another object of the invention is to provide a wheel arrangement which can be readily substituted for the normal wheel assembly of a conventional wheelchair.

Still another object of the invention is to provide a wheel arrangement for an electric wheelchair with which the user's own resources are utilized, and with which the wheelchair solely adds the additional force required to propel the wheelchair forwards in all conceivable situations, i.e. an individually controllable powerservo. The user controls the wheelchair in the same way as when controlling a conventional, manually activated wheelchair and will feel stronger as a result of the additional force delivered by the wheelchair and therewith be able to propel the wheelchair to places which were earlier out of range. Another object of the invention is to provide a wheel arrangement for an electric wheelchair provided with a controllable powerservo which can be changed automatically in accordance with the prevailing, individual requirements of the person seated in the wheelchair.

Still another object of the invention is to enable the user himself/herself to determine the magnitude of the additional force, when so desired. Different users will have different levels of strength and fitness and may wish to develop a certain degree of ability by training.

These objects are fulfilled by means of the measures and features set forth in one or more of the following Claims.

The inventive power measuring arrangement provides the following advantages:

* Two different types of attachments between driving ring and wheel rim enable the use of a number of power sensors, for instance only two such sensors, that are governed by what is required to obtain the necessary calculation basis. Power or force measuring attachments are expensive.

Power measuring devices, measuring electronics, signal transmission means, speed gauges and current-supply slip-rings are mounted on the wheel and can be fitted to different wheelchairs by virtue of quick-couplings.

The wheel is provided with an additional, controllable powerservo and can be readily substituted for a conventional wheel.

* The wheelchair is provided with a computer which is able to present a driving result through the medium of a display unit, such as the force exerted by the person using the wheelchair, the speed at which the wheelchair is propelled, the total power used in propelling the wheelchair, the distance travelled and the time taken to cover said distance, and so on, therewith providing the user of the wheelchair with feedback regarding his/her driving of the wheelchair as the chair is driven. The computer includes memory devices which enable measurement data to be collected and processed to some extent as the wheelchair is propelled by the user.

* The computer fitted to the wheelchair has a capacity sufficient to present the driving result. The calculating capacity of the chair-mounted computer can be increased, however, by transferring stored series of signals from the chair-mounted computer to a stationary, external computer of greater capacity with regard to software and display screen, for instance to a personal computer. The information can be stored so as to enable it to be recovered on later occasions and compared with the results of fresh test runs.

This type of measuring wheelchair, or instrument, has several areas of use. Since the measuring wheelchair provides an objective and correct assessment of the strength of the test person and his/her technique in propelling a wheelchair, it can be used advantageously in conjunction with the rehabilitation of wheelchair-bound people. In this regard, it can be used by therapists and physiotherapists as an instrument for planning a proper training program for each individual, and also to provide a concrete basis for the type of wheelchair that a user may be given in order for the user to utilize his/her own power and individual driving technique to the best extent. The inventive wheelchair can also be used as a stimulant for injured persons, since they are able to see in plain figures the extent of their improvement during rehabili- tation. The measuring function is also of interest to wheelchair athletes.

The invention will now be described in more detail with reference to exemplifying embodiments thereof and also with reference to the accompanying drawings, in which Fig. 1 is an overview from the front of a wheelchair, with one drive wheel sectioned through the wheel axle and shown in position for fitting the wheel to the wheelchair;

Fig. 2A is a side view of a first embodiment of a drive wheel, and shows schematically the attachment of the drive ring to the wheel rim, the positioning of the power sensors and a signal transmission unit;

Fig. 2B is a sectional view of the drive wheel shown in

Fig. 2A, taken on the line A-A in said Figure; Fig. 2C illustrates a slip ring unit having guide tracks for the drive wheel shown in Figs. 3A and 3B; Fig. 3 illustrates an embodiment of an attachment which lacks the provision of a power or force sensor; Fig. 4A is a side view of an attachment which includes a detector and a power sensor, and which shows the attachment secured between a wheel rim and a drive ring;

Fig. 4B illustrates the attachment means in Fig. 4A from beneath; Fig. 4C illustrates the coupling of power sensors on two attachment means according to Figs. 4A and 4B; Fig. 5 illustrates an embodiment of a wheel provided with a drive package or assembly, as seen in the same sectional view as that shown in Fig. 2B; Fig. 6A is a sectional view of one embodiment of an inventive wheel arrangement provided with quick- coupling means and slip-ring transmission means;

Fig. 6B is a sectional view taken on the line B-B in Fig. 6A, in larger scale; Fig. 7A is a schematic overview of the signal flow through the system; Fig. 7B illustrates a microprocessor unit for the system shown in Fig. 7A; and Figs. are diagrams which illustrate different control 8A-8D possibilities relating to wheel-mounted drive assemblies.

The wheelchair shown in Fig. 1 can be fitted with a new drive wheel 1 with the aid of an attachment means 2 placed between a drive ring 3 and a wheel rim 4 as a module, such as to render the invention independent of the type of wheelchair concerned. As shown schematically to the right of the Figure, the wheels can be substituted for the conventional wheels of a wheelchair in accordance with the invention. Signals produced by power or force sensors on part of the attachments on and the sensed wheel speed are transmitted to a calculating unit, preferably in the form of a computer, such as a microcomputer housed in a box 5 together with batteries, etc., and fitted to the chair. The result of the calculations made by the unit 5 can be shown on a display unit 6, which may be fitted to the wheelchair so as to enable the result to be easily seen by the user. The wheels may also be fitted with a drive motor 7 which functions to deliver additional power to the wheels when necessary, in response to a control from the calculating unit. The display unit 6 may be housed in a setting control box 8 provided with knobs or keys 9 and 10, for instance, by means of which the user is able to set that power level for each wheel from which the additional power shall be delivered. The calculating unit may also be provided with software or the like which will allow the user to switch to a control lever 11, or joystick, when desiring to use this type of forward propulsion control means instead of the drive rings.

Figs. 2A-2C illustrate a first embodiment of an inventive wheel which can be substituted for a normal wheel of a conventional wheelchair. In the case of this embodiment, the inventive wheel is provided solely with measuring equipment, i.e. the wheel is intended to function as a measuring instrument.

When a manually activated wheelchair is driven by applying a force to the drive rings 3 with the hands, a propulsion force is generated between the tyres of respective wheels 1 and the surface on which the chair is driven. This propul¬ sion force multiplied by the wheel radius is identical with the torque that the drive ring 3 transmits to the wheel through the attachments 2.1, with regard to the wheel axle 5 in a plane perpendicular to the wheel axle 15. Thus, when measuring the forward propulsion force, it is only necessary to measure the torque between drive ring 3 and wheel.

If all the attachments of the drive ring 3 are effective in transmitting forward propulsion power from the drive ring to the wheel rims, it must be possible to measure the torque that each attachment transmits with regard to the wheel axle 15, and then add these torque values together so as to obtain the desired torque.

This is unnecessary according to the inventive concept, and a force analysis shows that only desired torque can be measured solely with the aid of power sensors mounted at two attachment points between the drive ring 3 and the wheel rim 4. These attachments need not necessarily lie so that their mutually connecting line will intersect the wheel axle 15, even though this is preferred. The two power sensors shall be designed to measure solely the force acting at right angles to the wheel axle 15 and at right angles to the wheel radius, i.e. tangentially to the wheel periphery. The desired torque can then be obtained solely by adding together the measuring results of these power sensors. According to the present invention, this possibility is utilized to reduce the number of power sensors required, preferably down to two. The invention is not limited, however, to only two power sensors.

As indicated in Figs. 2A and 2B, the attachments between the drive ring 3 and the rim 4 are of two different kinds, of which one kind 2.1 functions to hold the drive ring and the wheel rim so that force from the drive ring 3 will be transmitted in all directions and then also tangentially to the wheel rim 4, and where the second type of attachment 2.2 functions to hold the drive ring in relation to the rim so that force from the drive ring will be transmitted to the wheel rim essentially solely in the direction of the wheel axle, i.e. it will not take-up load in the plane perpendicular to the wheel axle 15. This means that all forces acting in the plane extending at right angles to the wheel axle 5 and transmitted from the drive ring attach¬ ments to the wheel are taken-up by the attachments 2.1 provided with power sensors.

To prevent the drive ring from wobbling and feeling limp or flimsy to the user, there will preferably be at least four attachments between the drive ring 3 and the wheel rim 4. It is essential in this regard that the drive ring is maintained parallel with the wheel rim.

Fig. 2B illustrates one embodiment of the attachment 2.2. The attachment is pivotal in all directions with regard to both drive ring 3 and wheel rim 4, through the medium of two pivotal or universal connections 13.

Fig. 3 illustrates another embodiment of the attachment which lacks a power sensor. Thus, there is shown an attachment 2.20 which has a modulus of elasticity which is negligible in comparison with the modulus of elasticity of the attachment(s) 2.1 having power sensors. This means that the force transmitted by the attachment(s) 2.20 in the forward drive direction between drive ring 3 and wheel rim 4 is negligible in comparison with the force taken-up by the attachment(s) 2.1 provided with the power sensors. This is achieved when the attachment(s) 2.20 includes or include a rubber bushing 14, for instance.

In the case of the embodiment of the attachments 2.1 provided with power sensors and illustrated in Figs. 4A-4C, the drive ring 3 is fixed to the wheel rim 4 by means of two supports 19 whose mutual connecting line passes through the wheel axle 15 and extends at right angles to the connecting line that extends between two power sensors 18 placed on a detector 17 that extends parallel with the supports 19, as illustrated in Figs. 4A and 4B. The power sensors 18 are mutually connected in a manner to form a measuring bridge, as illustrated in Fig. 4C. The measuring bridge will then produce an output signal ΔU which is a linear function of the torque between drive ring 3 and wheel with regard to the wheel axle 15, it being desired to measure this torque moment.

The detector 17 is a mechanical device which changes its properties, e.g. its shape, when subjected to force, whereas the power sensors 18 have the form of a device which measures the force-dependent changes in the properties of the detector 17. The power sensors may, for instance, have the form of resistive strain gauges 18, piezo-resistive or piezo-electric sensor elements glued to the detector or holder part 17. The detector 17 is journalled on the drive-ring support 25 for movement in the direction of the mutual connecting line, whereby the drive ring 3 is pivotally hinged at 21 through the connecting line. The support 25 is shown to be straight in Fig. 4A, since the illustrated drive ring has generally the same diameter as the wheel rim 4. Other drive ring diameters are possible, of course, in which case the support 25 may be curved. It is also conceivable to attach some type of frame structure to the wheel at its different types of attachment or holder against which the drive ring is secured, or alternatively the different types of holder may be mounted directly onto the wheel hub, which must then be stable.

As illustrated in Fig. 2A, the measuring bridge is connected to a measurement signal amplifier and to a bridge supply circuit 22, which is also connected by a cable 23 to a unit 24 mounted on the wheel hub and provided with means for slip-ring transmission of voltage supply and of measurement signals from the power sensors 18, and which is provided with a speedometer. The circuit 22 will also preferably perform signal processing operations, with conversion of the detected or sensed analog signal ΔU to a pulse signal of different frequency, said frequency being dependent on the magnitude of the signal ΔU.

As shown in Fig. 2B, one part 26 of the unit 24 is provided with slip ring tracks in accordance with Fig. 2C and is placed so as to be co-rotational with the wheel, while another part 27 of said unit is placed so as to be held stationary on the wheelchair. This can be achieved by using the hollow bolt and its polygonal screw head, which is stationary on the majority of wheelchairs, such as to hold the wheel axle 15, with its screw head as an anvil surface or counterpressure surface, and by providing the part 27 with a central opening having a configuration adapted to the configuration of the screw head.

The wheel, drive ring 3, power sensor 2, signal transmission means thus form a replaceable module 1. The module 1 may also include a drive assembly or drive package 41 described below with reference to Fig. 5. This module construction which can be coupled to the wheel of the wheelchair both quickly and simply enables the inventive wheel to be readily fitted to and removed from different wheelchairs. This provides the user with the freedom of choosing to keep his own wheelchair intact or to himself dismantle the wheelchair into easily-handled units, for instance when transporting the wheelchair by car.

As illustrated in Fig. 2C, the slip ring transmission includes three conductive tracks 28, for instance gold- plated copper tracks, which are insulated from one another for transmission of voltage supply to the strain gauges 18 and for transmission of the pulse signals from the circuit 22. Also found in the outer part is a portion which includes alternately conductive parts 29 and non-conductive parts 30, of which the conductive parts are mutually connected for simple measurement of the speed at which the wheelchair moves in accordance with well known methods, wherein the brushes move in a path along the conductive and non-conductive parts.

Fig. 5 illustrates another embodiment of exchangeable wheelchair wheels, this embodiment including a drive assembly 41 which, as shown in Fig. 7A, includes a motor 64, brake means 65, transmission means 66 and a measuring sensor (not shown) which indicates the speed of the motor and its direction of rotation. The speed of the motor 64 is controlled by a microcomputer unit 56, described in more detail below, either directly or through the medium of a motor control circuit. The brake 65 can be applied and disengaged electrically and will guarantee that the wheelchair will not move away from a stationary position in an uncontrolled fashion. The measuring sensor may be a tachometer, regenerator or Hall effect sensor. Thus, in the case of this embodiment, there is controlled a drive assembly 41 which is mounted on each wheel and which includes a motor which is controlled on the basis of the signals produced by respective power sensors 18. The wheel may be provided with a quick-coupling, so as to enable the wheel to be readily substituted for a conventional wheel of a wheelchair. However, in this case, it is necessary to provide the wheelchair with an anvil means or counterpressure means, in order to make the change possible. It must be possible to secure the axle in a rotationally free manner, and arrangements to this end are well known to the skilled person and will not therefore be shown and described in detail; see for instance German Patent Specification No. DE-41272577. The signals produced by the power sensors may be transmitted with the aid of a slip ring contact also in the case of this embodiment, although in the illustrated case the pulses obtained from the circuit 22 (see Fig. 2A) are shown to be coupled to an IR light-emitting diode 121 which transmits the pulses in the form of IR light which is received by an IR phototransistor 122 fitted to the wheelchair S. The pulse signals received by the IR phototransistor 122 are converted to signals which can be read into the microcomputer unit 56. In the case of this embodiment, the circuit 22 includes a battery for powering the power sensors.

Figs. 6A and 6B illustrate in detail another embodiment of the slip ring transmission system and the quick-coupling unit used in accordance with the invention. Naturally, this type of transmission can be used with both types of wheel, i.e. with or without the drive assembly. However, as mentioned above, it is necessary in the case of wheels that are equipped with a drive assembly to provide a separate arrangement which will ensure that the wheel axle is stationary in relation to the wheelchair. A chair-holding unit 42 (not described in detail) having a stationary bolt 43, for instance a hollow bolt, provided with a polygonal head 44 is provided for accommodating the wheel axle of the wheelchair drive wheel. Each wheel 45 is provided with a hollow axle 46 which is connected to the wheel through the medium of ball bearings. The axle 46 is held in place by balls 48 or the like which are moved outwardly of the inner end of the rod by the end of said rod and which rest against the inner end of the bolt 43. The axle is under a spring bias which serves to hold an inner part of larger diameter than the remainder of the axle pressed against the balls.

The spring bias is obtained with the aid of a rod 49 inserted in the hollow space of the axle 46 and having in the illustrated case a spring arrangement 50 mounted at the inner end of the rod so as to press the rod outwards. The outer end of the rod 49 protrudes slightly outwards. This slightly protruding end of the rod is pressed inwards when fitting and removing the wheel, therewith enabling the balls 48 to move inwards while passing the wheel axle through the bolt 43, and then return to their outward position when the pressure on the outer end of the rod is removed.

In this case, the slip ring arrangement is placed in circumferentially extending and mutually parallel tracks 41 on the outer surface, or mantle surface, of a ring 52 fitted firmly to the wheel hub. A bearing 53, such as a ball bearing or roller bearing, is mounted in the ring 52. The inner part of the bearing has a polygonal cavity whose shape corresponds to the polygonal shape of the bolt head 44, which is fitted into the cavity when fitting the wheel 45 to the wheelchair, so that this inner part will be stationary with the wheelchair. A unit 54 which includes slip contacts 54' is also attached to the inner part of the bearing 53. Although the conductors leading from the slip contacts to the box 5 have not been shown, it will be understood that these conductors can be connected to the slip ring contacts by means of a multi-pole contact. As will also be understood, a drive assembly 41 having a freewheel or release capacity of the kind similar to that shown in Fig. 5 may be provided for rotating the wheel 45 in relation to the axle 46, which is stationary in relation to the wheelchair. Arrangements for achieving this are well known to the art and will not therefore be described here. For instance, the wheel axle can be clamped in the vicinity of the bolt 43.

As illustrated in Fig. 7A, the torque signal 55 obtained, i.e. the converted measurement signal ΔU, is transmitted from each of the drive wheels 1 to the wheelchair and is there delivered to a microcomputer unit 56 housed in the box 5 (Fig. 1). In addition to this signal, the microcomputer unit 56 also receives information 57 relating to the speed of each drive wheel 1 and information 58 relating to the settings made on the instrument panel 8. The microcomputer unit 56 performs the selected function on the basis of these signals as input data.

When choosing to use the wheelchair in its measuring capacity, the microcomputer unit 56 will store at least the measurement signals 55, 57 in its memory.

The memory can then be read and the memory contents trans¬ ferred by the microcomputer unit 56 to a conventional personal computer 59 for further processing, through the medium of a multi-pole contact device 60.

When a control program for wheels that are provided with an additional drive assembly 41, including a motor, is selected, the microcomputer unit 56 will calculate the additional force that shall be added to the force exerted by the user and then control the drive assembly 41 with the signal 43 individually for each of the wheels. Control signals for the display unit 6 on the instrument panel are delivered through the cable or line 67.

In order for the aforesaid inventive arrangement to be realized, there is required a unit which is able to process the incoming signals quickly. A conventional computer unit can be used to this end. However, it is convenient to use a microprocessor 70 with associated circuits and programs, this processor then becoming a microcomputer unit 56. This unit is able to receive measurement signals and to save the signals and to deliver its own output signals to external units. Communication between the various units, the man- machine communication, and all calculations and data processing operations are carried out by the microprocessor.

Precisely what is expected of the microcomputer unit 56 is determined by the program which accompanies the unit. There is nothing to prevent the microcomputer unit 56 having several programs. This will enable selection of a particular program desired at that time. Conceivable programs, for instance, are programs with which the chair can be used as a measuring instrument, and different control programs.

The control programs include different motor control strategies. The reason why different control programs are desirable is because different users will have different capacities for driving a wheelchair which includes a powerservo effect. This enables the user to find the control program which suits his/her strength, technique and fitness. The user is also able to change the parameters of each program, thereby enabling the motor to be finely adjusted to personal requirements. Examples of such parameters are time delays and the magnitude of the effect of the powerservo.

Figs. 8A-8D illustrate a number of different control strategies. Fig. 8A illustrates the application of an additional force when the torque measured from the drive ring exceeds a given level, which can be set by the user of the wheelchair. The additional force thereafter increases linearly with the torque measured. Instead of illustrating a linearly increasing force addition, Fig. 8B shows a force addition, or force booster, which varies exponentially between the set level beneath which no force booster is produced, and a level of maximum force on the drive rings. This control strategy produces approximately the same force on the drive ring irrespective of the resistance offered by the surface along which the wheelchair moves. The time diagram shown in Fig. 8C illustrates the performance of a control strategy intended to provide linear amplification with integration of the force in those instances when the wheelchair does not begin to roll forwards. This control strategy can be applied when negotiating obstacles, such as raised thresholds, pits or depressions in the floor, etc. After a first time lapse between τ- and τ₂ with linear amplification of the measured drive torque and failure to detect wheel speed, the additionally applied drive torque is increased until a wheel speed is detected at time point τ₃. The additionally applied torque is then lowered to the torque value that prevailed during the first time period. When the detected torque on the drive ring has fallen to zero at time point τ₄, the applied drive is reduced to a lower value, which is maintained until the wheel speed has decreased to zero, i.e. the wheel is stationary. Fig. 8D illustrates a control strategy in which a mean value is formed with the intention of reducing the effect of vibrations in those instances when the wheelchair is used by spastics. The torque measured at a given instance and shown in the upper diagram is divided into a time window with time T. A mean value of the drive torques within respective windows is formed and results in the measured torques illustrated in the lower diagram, which is used to calculate the additional force required on a drive wheel, for instance in accordance with the principle shown in Fig. 8A.

The measuring chair program and the control program can be combined and operated in parallel, therewith enabling the wheelchair to be driven with a powerservo effect while, at the same time, measuring the torque applied and the movement of the wheelchair.

The man-machine communication is effected conveniently via the instrument panel 8 with its units 6, 9, 10, 11 which are readily accessible to the user-and in which information is exchanged between user and microcomputer unit 56. The user is able to request a desired program through the instrument panel 8, for instance by pressing a key or button 62, so as to change between the various program parameters. Thus, the user is able to obtain information relating to program and parameter selection, applied torque, chair speed, his/her own work development, battery resources, distance travelled, etc., all of which is presented on the display unit 6.

The input signals 58 from the user and carrying the settings commanded by the user, the torque signals 55 and the signals 57 relating to wheel movement are the basis on which the microcomputer unit 56 operates. The work performed by the microcomputer unit 56 can be divided into several units. For instance, several microprocessors having mutually different functions can be used. For example, the motor may be controlled by individual units which include a microprocessor or some other motor control circuit means.

Fig. 7B illustrates an exemplifying embodiment of one microcomputer which includes a microprocessor 17 that is connected to different interfaces for the infeed and outfeed of data, such as a motor control unit 71, a unit 72 for communication with an external personal computer, a unit 73 for processing the incoming measurement signals 55 and 57, and a unit 74 for communicating with the instrument panel. The microcomputer 70 is also connected to a fixed, but preferably re-programmable memory 75 containing software, and also to a read/write memory 76 for temporary data storage.

It will be observed that the problem of transmitting signals from a rotating wheel to the wheelchair can be solved in ways other than that described with reference to slip ring transmission, for instance by cordless transmission with the aid of IR light or radio signals. One example of signal transmission is to transmit the amplified measurement signal in the form of a pulse train having a frequency which is linearly dependent on ΔU.

The microcomputer 56, the instrument panel 8 and the drive assembly 41 are powered electrically by batteries placed in the box 5 on the wheelchair. The means for measuring torque and transmitting signals may be powered by the wheelchair batteries, as illustrated with the slip ring unit shown in Fig. 2C, or by a separate battery, or by means of some other electric current source mounted on the wheel, for instance in the unit 22.

As seen on the part of the user, the inventive powerservo effect for manual wheelchairs will be experienced as a "conventional" manual wheelchair, but with the difference that the user will feel stronger in the arms.

The powerservo function will satisfy the whole of the human spectrum found in the ranges of those who can almost manage a manual wheelchair and those which are able to control their arms but are unable to propel a manual wheelchair.

The measuring chair function afforded by the present invention provides a correct and an objective measuring instrument which can be used to map the strength, fitness and technique of a wheelchair user when driving the wheelchair.

These functions can be used either together or individually to great advantage in the rehabilitation of wheelchair- bound persons.

It will be understood that many modifications are possible within the scope of the invention as defined in the following Claims.

Claims

1. A wheel arrangement for wheelchairs comprising means for measuring the force applied to a drive ring (3) by a user of the wheelchair, wherein the drive ring is connected to a wheelchair drive wheel (4) through the medium of attachments (2.1, 2.2), characterized in that the attachments comprise at least two different types of attachment, of which the first type of attachment (2.1) includes power or force sensors (18) and provides a holding effect in all directions, and of which the second type of attachment (2.2) provides a holding effect essentially solely in the direction of the wheel axle.

2. A wheel arrangement according to Claim 1, characterized in that the first type of attachment (2.1) are two in number.

3. A wheel arrangement according to Claim 1 or Claim 2, characterized in that the drive ring (3), the drive wheel (4) including the attachments (2.1, 2.2) form part of a wheel assembly which can be substituted for a wheel of a conventional wheelchair; and in that said assembly includes electronic means (22) and signal transmission means (24; 51, 54) for transmitting signals to a computer unit (5; 56), which may be mounted on the wheelchair.

4. A wheel arrangement according to any one of the preceding Claims, characterized in that the drive wheel (4) is provided with a drive assembly or drive package (41) which includes a wheel drive motor (64) which can be controlled on the basis of the signals received from the power sensors.

5. A wheel arrangement according to Claim 3 or Claim 4, characterized in that the computer unit (36) is programmed for calculating continuously the force applied on each wheel and with information that can be used by the user, this information being dependent on the force used, for instance a force/time diagram, and presents selected data to the user on a display unit (6).

6. A wheel arrangement according to any one of Claims 3- 5, characterized by means for measuring the speed of each wheel of the wheelchair and transmitting the measured values to the computer unit (36); in that the computer unit is adapted to calculate useful user information which includes information concerning the force applied and the wheel speed of the wheelchair, for instance force, speed, total work developed, power, the distance travelled, time taken to cover said distance, etc.; and in that one or more of the calculated pieces of information are presented selectively on a user display unit (6) during propulsion of the wheelchair.

7. A wheel arrangement according to Claim 4 and any one of Claims 3, 5, 6, characterized in that there is connected to the computer unit (56) an instrument panel (8) which includes setting means (9, 10) through which a desired force can be changed from the force at which the computer unit (56) controls the drive assembly (41) and therewith impart an additional driving force to the drive wheels.

8. A wheel arrangement according to Claim 4 and according to any one of Claims 3, 5-7, characterized in that there is connected to the computer unit an instrument panel (8) which includes setting means (62) by means of which a change can be made between different programs in the computer unit (56) and/or different program parameters.

9. A wheel arrangement according to any one of the preceding Claims, characterized in that the arrangement includes a slip ring transmission means (51-54) which is mounted adjacent the wheel hub for transmitting the power supply to and signals from the power sensors (18), and which further includes a first part (51) which is firmly mounted ad acent the hub (45) and a second part having a cavity which is intended to be fitted over a unit (44) firmly seated on the wheelchair, said unit (44) having the form, for instance, of a centrally positioned unit having a polygonal outwardly turned periphery and positioned adjacent a wheel axle accommodating opening; and in that the wheel has an extended wheel axle (46) which includes a coupling means (48, 50) which can be fitted into said opening so as to hold the wheel in an axially direction, such that the second part will^be located around the unit (44) having said polygonal periphery.

10. A wheel arrangement for a wheelchair, comprising a wheel having a drive ring attached to the wheel with the aid of a plurality of attachment means that include power or force sensors which function to measure the propulsion force acting between the drive ring and the wheel, characterized in that the arrangement includes a slip ring transmission means (51-54) placed adjacent the wheel hub and operative in transmitting power supply to and signals from the power sensors (18), and further including a first part (51) which is secured firmly to the hub (45) and a second part which has a cavity which is intended to be fitted onto a unit (44) which is firmly seated on the wheelchair, for instance a centrally placed unit having a polygonal outwardly facing periphery and positioned adjacent an opening for accommodating a wheel axle; and in that the wheel has an extended wheel axle (46) which includes a coupling means (48, 50) for attachment in said opening so as to hold the wheel in an axially direction such that the said second part is located around the unit (44) having said polygonal periphery.

11. A wheel arrangement according to Claim 10, characterized in that the second part of the slip ring transmission means (51-54) can be connected to a computer unit (5; 56), which can be firmly mounted on the wheelchair and which calculates continuously data obtained from the wheel as the wheelchair is driven, and which optionally presents these calculations on a user display unit (6).

12. A wheel arrangement according to Claim 10 or Claim 11, characterized in that the wheel (4) includes a drive assembly (41) comprising a wheel drive motor (64) which can be controlled on the basis of the measured signals from the power sensors, wherein control signals from the computer unit to the motor are transmitted from the wheelchair, preferably via the wheel axle.

13. A wheel arrangement according to any one of Claims 10-

12, characterized in that means are provided adjacent the slip ring transmission means for measuring the speed of each wheel of the wheelchair and transmitting the measured value to the computer unit (56); and in that the computer unit is programmed to calculate useful user information, including information relating to the force applied and to wheel speed, such as the speed at which the wheelchair moves, total developed work, power, the distance travelled and the time taken to cover said distance, and to present this information on a user display unit (6) as the wheelchair is driven.

14. A wheel arrangement according to any one of Claims 10-

13, characterized in that the arrangement includes at least two different types of attachment, of which the first type of attachment (2.1) includes a power or force sensor (18) and provides a holding effect in all directions; and in that the second type of attachment (2.2) provides a holding effect essentially solely in the direction of the wheel axle.

15. A wheel arrangement for a wheelchair comprising a wheel having a drive ring attached to the wheel and including a plurality of attachments provided with power or force sensors which are adapted to measure the forward propulsion force between the drive ring and the wheel, characterized in that the arrangement includes a drive assembly (41) which, in turn, includes a motor (64) which can be controlled on the basis of the signals delivered by the power or force sensors (18) such as to effect forward propulsion of the wheel when necessary.

16. A wheel arrangement according to Claim 15, characterized by a quick coupling (44, 53, 48, 50) which is adapted to means mounted on the wheelchair so as to enable the wheel arrangement to replace a conventional wheel.

17. A wheel arrangement according to Claim 15 or Claim 16, characterized in that the arrangement includes slip ring transmission means (51-54) mounted adjacent the wheel hub and functions to transmit power to and signals from the power sensors (18) and the drive assembly (41), said transmission means including a first part (51) which is mounted firmly adjacent the hub (45) and a second part having a cavity which is intended to fit over a unit (44) firmly mounted on the wheelchair, for instance a centrally placed unit having a polygonal, outwardly turned periphery and positioned adjacent wheel axle accommodating opening.

18. A wheel arrangement according to any one of Claims 15- 17, characterized in that the wheel is provided with electronics (22) and a signal transmission unit (24; 51, 54) for transmitting signals from the power or force sensors to a computer unit (5; 56) which can be mounted on the wheelchair and which functions to calculate the control of the drive assembly on the basis of the signals delivered by the power sensors.

19. A wheel arrangement according to any one of Claims 15- 18, characterized by means for measuring the speed of each wheel of the wheelchair and transmitting the measured values to the computer unit (56); and further characterized in that the computer unit is programmed to calculate useful user information, including information relating to the force applied and the wheel speed, such as wheelchair speed, total work developed, power, distance travelled, the time taken to cover said distance, etc., and to optionally present said information selectively on a user display unit (6) as the wheelchair is driven.

20. A wheel arrangement according to any one of Claims 15-

19, characterized in that the arrangement includes at least two different types of attachment means, of which the first type of attachment (2.1) includes power or force sensors (18) and provides a holding effect in all directions, and of which the second type of attachment (2.2) provides a holding effect essentially only in the direction of the wheel axle.