GB2219410A

GB2219410A - An exercise machine has means indicative of the work done

Info

Publication number: GB2219410A
Application number: GB8811924A
Authority: GB
Inventors: Andrew Clive Michell; John Burch
Original assignee: R A T
Current assignee: R A T
Priority date: 1988-05-20
Filing date: 1988-05-20
Publication date: 1989-12-06
Anticipated expiration: 2008-05-20
Also published as: AU3575689A; GB2219410B; WO1989011314A3; GB8811924D0; WO1989011314A2

Abstract

A rowing exercise machine is arranged so that each stroke causes rotation of a flywheel and the shaft of an alternator. The resistive forces are primarily provided by the alternator which is driven by a constant but adjustable current. In the intervals between strokes, the deceleration of the flywheel is measured to provide an indication of the resistive forces being generated by the machine. This measurement is used to control the forces and/or to provide an indication of the work carried out by the user.

Description

EXERCISE MACHINES This invention relates to exercise machines, and is particularly but not exclusively concerned with rowing machines.

Exercise machines of this type are well known and widely used. Attempts have been made to provide such machines with a mechanism which responds to the user's activities in a manner which simulates actual rowing.

For example, US Patent 4674741 discloses a machine which is said to simulate the "feel" of actual rowing by electronically controlling a brake to apply a constant torque to oppose the movement of a flywheel which is rotated by the force of the user's activity, the torque being independent of the rotational velocity of the flywheel. However, this arrangement would not provide a true simulation of the "feel" of actual rowing, as is commonly desired.

Another problem with known exercise machines both of the rowing type and of other types is that the response characteristic of the machine, that is the amount of energy required to operate the machine, is not accurately predictable or repeatable. For example, although a machine may be adjustable so that it has different settings corresponding to different amounts of energy required to operate the machine, the amount of work required of the user at a particular setting would vary from machine to machine, and from time to time with the same machine. This means that users cannot set the machine so that a known amount of work is carried out by the user. Nor can they accurately monitor their progress or compare their abilities with each other.

According to a first aspect of the invention there is provided an exercise machine in which the resistance to the work performed by the user is provided at least in part, and preferably substantially entirely, by an electrical machine, such as an alternator or dynamo, in which the exciting field is of a substantially constant magnitude. This, it has been found, provides a response from the machine which exercises the user better, which the user finds more satisfactory, and which in a rowing exercise machine simulates more accurately the response achieved in actual rowing. It is believed that this is a result of the resistive force acting against the userbeing substantially proportional to the speed at which the exercise machine is operated.

The exciting field is preferably provided by one or more windings carrying a substantially constant current. Preferably, the current is adjustable to provide different degrees of resistance.

Alternatively, the exciting field could be produced by permanent magnets, and adjustability could be achieved by providing a variable resistance across the output windings of the electrical machine.

In accordance with another aspect of the invention there is provided an exercise machine having means for sensing the degree of at least part of the resistance presented to the work performed by a user so as to provide a signal indicative thereof for either controlling the resistance or providing an indication to the user in response thereto. In a particularly preferred embodiment of the invention, the machine has an inertial mechanism, preferably a flywheel, which is intermittently driven by the user during operation of the machine, and the means for sensing the degree of resistance is operable to determine the decrease in speed of the mechanism in an interval between times at which it is driven by the user.

The above arrangement thus provides a signal which can be used to compensate for variations in the degree of the resistance, either by altering the resistance or altering an indication thereof. For this purpose, it is not essential that the signal accurately represent the entire resistance. It is desired merely that the sensing of resistance be done in a consistent manner and take into account that part of the resistance affected by the particular mechanical and electrical tolerances of the machine, as these are the factors which tend to vary from time to time and from machine to machine. If desired, a calibration operation could be effected to determine approximately the relationship between the value of the signal and the actual resistance presented by the exercise machine.

It will be appreciated that, even though the degree of resistance presented to the user may vary during the operation of the machine, e.g. in proportion to the speed of operation, it is not essential that these variations be monitored, so long as they are reasonably predictable. However, a signal which more accurately represents the work being carried out by the user could be achieved by taking into account such variations. Thus, for example, by assuming or calculating the form of a relationship between the speed of the flywheel and the degree of resistance presented to the user, and by monitoring the speed of the flywheel as it is driven by the user, it is possible to calculate a value which accurately represents the work being carried out by the user.

By way of example, if the resistance is provided by an alternator or dynamo driven by a constant current, in accordance with the first aspect of the invention mentioned above, and if it is assumed that the degree of resistance presented to the user varies in proportion to the speed of the flywheel, then by measuring the deceleration of the flywheel over a particular speed range in the interval between the time at which it is driven by the user, it is possible to predict the resistance presented at other flywheel speeds. Consequently, by monitoring the speed of the flywheel when it is driven by the user it is possible to calculate the work being carried out at any given instant, and by integrating this value over one cycle of operation, the total amount of work carried out during that cycle can be calculated.Thus, in a preferred embodiment, it is this signal that is used for controlling the degree of resistance or providing an indication to the user of the work being carried out.

The resistance may be provided by any electrically-operated braking means, such as an electro-mechanical or electro-magnetic brake, but is preferably provided by an alternator or dynamo. The signal derived from the sensing means may be used to control the braking means so as to determine the degree of braking so that the detected resistance matches a predetermined value. In this way, it can be ensured that different machines, and the same machine at different times, can give substantially predictable and repeatable responses.

It may be desired in some circumstances for the degree of resistance to be controllably altered as the user operates the machine, e.g. throughout the user's stroke if the machine is a rowing machine. For example, in an arrangement in which an alternator or dynamo provides the resistance and, at any given time, is driven at a substantially constant current, a control circuit of the machine may be arranged to alter the level of that current in a predetermined manner (preferably as a function of speed) during the stroke.

Preferably, the machine has different settings, so that the sensed resistance can be controlled to match a plurality of different desired values.

In addition or as an alternative to this control technique, the signal indicative of the degree of resistance may be used to provide a substantially accurate indication of the amount of work being expended by the user. This could be in the form of a simple indication dependent upon the current sensed resistance, or the signal can be processed, e.g. by integration over the course of a cycle of operation as mentioned above. Alternatively or additionally, processing can be carried out so that the indication represents the total amount of work expended during the course of a work session.

An arrangement embodying the invention will now be described by way of example with reference to the accompanying drawings, in which: Figure 1 is a schematic perspective view of an exercise machine in accordance with the invention; Figure 2 is a plan view to illustrate the function of the mechanical parts of the apparatus; Figure 3 is a side elevation of the parts shown in Figure 2; and Figure 4 is a schematic block diagram of a control circuit of the machine.

Referring to Figures 1 to 3, the rowing machine 2 has a seat 4 mounted for movement along a frame 6, and arms 8 which can be drawn rearwardly by a user on the seat 4 with his feet on rests 10. The arms are attached to a rope 12 which extends around pulleys 14 and 16 to a reel 18 mounted on a chassis 20 supported beneath the frame 6. As will be explained, the reel 18 is spring-biased so that after the rope 12 has been unwound from the reel 18 as the user draws back the arms, the reel tends to wind up the rope and therefore draw the arms 8 back to their original position. The user operates the machine in the usual way, expending energy in order to draw back the arms against the resistive force provided by a mechanism described below, and then permitting the arms to be drawn back to their original position.

One feature of the present embodiment is the use of the rope 12, as distinct from the chains and cables conventionally used. This is wound uniformly over the reel 18, and enables a smoother operation of the machine. However, other elongate members, such as chains or cables, could alternatively be used.

The reel 18 has a shaft 22 coupled via a belt 24 to a pulley 26 on the end of a cylinder 28 carrying a helical spring 30. In Figure 2, part of the spring 30 is omitted to reveal the cylinder 28. As the rope 12 is unwound from the reel 18, the belt 24 causes the pulley 26 to rotate, thus winding up and tensioning the helical spring 30, which is attached at one end to the chassis 20 of the machine and at the other end to the pulley 26. Thus, when the user permits the arms 8 to be retracted, this is achieved by the spring 28 rewinding the reel 18 via the belt 24. The spring force is very small, and is negligible in comparison with the resistive force applied against the user when he pulls the arms rearwardly.

This resistive force is provided by an alternator 31 mounted on the chassis 20 and having a rotor (32 in Figure 4) mounted on a shaft 33 coupled to the takeup reel 18 via a belt 34, which extends around a relatively small diameter pulley 36 on the alternator shaft 33 and a large-diameter pulley 38 on the shaft 22 of the reel. The alternator shaft 33 also carries a flywheel 42.

Thus, as the arms 8 are pulled back by the user, the flywheel 42 and alternator rotor are caused to rotate very rapidly due to the gearing-up effect of the pulleys 36 and 38. This means that the flywheel may be lighter than would otherwise be required. A conventional one-way clutch (not shown) allows the flywheel and rotor to continue to rotate as the spring 30 rewinds the rope 12 at the end of the stroke.

The flywheel 42 is provided with notches 44 in its periphery. An optical sensor arrangement 46 (e.g.

comprising an LED 48 and a phototransistor 50 as indicated in Figure 4) is mounted such that as the flywheel 42 rotates the notches 44 pass the sensor 46 in succession. The sensor arrangement thus provides pulses at a rate dependent upon the flywheel speed.

Referring to Figure 4, the alternator 31 is of the type in which the rotor 32 provides the exciting field in response to direct current supplied through slip-rings (not shown). The stator 52 forms the armature, the output of which is dissipated through a resistor 54. In the present embodiment the rotor is driven with a constant current. The interaction between the rotor and stator fields provides the main resistance to the pulling of the arms.

The circuit shown schematically in Figure 4 operates as follows. The sensor arrangement 46 is coupled to a frequency to voltage converter 56 which provides a signal at a level dependent upon flywheel speed. This signal is delivered to a first comparator 58 which provides an output when the flywheel speed decreases below a first threshold level represented by reference voltage Tl, and a second comparator 60 which provides a signal when the flywheel speed decreases below a second, lower level represented by T2. These signals are delivered to a timer 62, whereby the first signal initiates the operation of the timer and the second signal halts that operation. The timer thus provides an output indicating the length of time for the flywheel speed to decrease between the two threshold levels, and hence inversely proportional to the deceleration of the flywheel.This in turn will be dependent upon the inherent mechanical and electrical tolerances of the machine, in addition to the resistive force generated by the alternator.

A summing circuit 64 sums the signal representing the deceleration and a reference potential, and the resulting signal is used to control a constant current generator 66 so as to determine the level of current supplied to the alternator rotor 32.

The reference voltage is an accurately-controlled voltage related to the desired level of resistive force presented to the user. The circuit arrangement described above ensures that if the actual measured resistance as indicated by the deceleration signal departs from the desired level, the current supplied to the alternator will be adjusted to compensate.

Switch means 68 are provided for selecting different reference voltages R1,R2,R3 and R4 and thereby enabling the machine to operate at different settings corresponding to different work requirements.

Preferably, the current for the rotor 32 is derived from a battery 70 which is charged by the output of the alternator during use of the machine.

The battery 70 may also supply the current for the rest of the control circuitry. Preferably, a switch 72 is provided for disconnecting the battery 70 from the rotor 32 until the speed of the flywheel as indicated by the output from converter 56 exceeds a predetermined value represented by threshold T3, as detected by a comparator 74. In this way, it can be ensured that no current is supplied to the rotor, and thus very little power is consumed by the machine, until the user starts to operate the machine and the flywheel speed reaches a preselected, low value.

It will be appreciated that the circuit described above is merely an example of many different ways in which similar functions could be accomplished. For example, the various circuit components could be replaced by completely digital or completely analogue circuits, or by a microprocessor programmed to perform the corresponding functions.

If desired, the signal indicative of deceleration could be used to operate an indicator so that the user is provided with an indication of his current output. Clearly, the smaller the output from the timer, the greater the deceleration, which represents larger resistive forces and hence a greater amount of work required to operate the machine.

Processing means, such as an integrator, may be provided so that the indication represents the total amount of work during, e.g., the current session.

In the above arrangements, the constant current applied to the alternator results in the resistive force throughout the stroke altering substantially in proportion to the speed of rotation of the flywheel.

As indicated above, this produces better response characteristics. If desired, the response characteristics can be controlled throughout the stroke by altering the constant current value according to a stored, and possible alterable, program. The timing of the alteration could be responsive to the speed sensor, processed if desired to indicate what stage of the stroke has been reached.

Preferably, the circuit is arranged so that the flywheel speed monitoring occurs in between every stroke, i.e. every time the flywheel speed decreases from the first threshold value to the second.

However, this is not essential, especially if the signal indicative of resistive forces is intended merely to provide an indication of work done, rather than to control the alternator. One alternative would be for the measuring operation to be carried out only when commanded by the user, for which purpose a switch may be provided. ' Thus, the user could operate the switch at any time during a session, to check on the degree of resistance currently being provided. The control circuit could use one or a few measurements made in this way, combined with a signal indicative of the number of strokes performed by the user or the number of flywheel rotations, to generate a signal indicative of the total amount of work carried out during the current session. This modification may be particularly useful in machines other than rowing machines.For example, the invention could be applied to an exercise bicycle in which the pedals are normally driven continuously. Periodically, the user may temporarily stop pedalling, so that during a "freewheeling" interval the control circuit can operate to measure the resistive forces.

As an alternative to the above arrangement, the signal from the timer 62 which indicates deceleration (and hence resistance at a particular speed range) could be processed with the output generated by voltage converter 56 (which represents flywheel speed) while the flywheel is being driven by the user. The resultant signal is thus an indication of work being carried out at any given instant by the user which takes into account variations in the resistance of the machine at different speeds of the flywheel.

In this alternative arrangement, it is assumed that the resistance presented by the machine is substantially proportional to the speed of the flywheel, and the resistances at particular speeds during acceleration (when the flywheel is being driven by the user) bear a constant relationship to the resistances during deceleration (in the interval between the times at which the flywheel is driven).

It is thus sufficient to measure the resistance, i.e.

the deceleration of the flywheel, at a single point in the cycle of operation. However, this arrangement is not essential. It is possible to take into account more complex relationships between speed and resistance by measuring the deceleration at two or more speeds. This may also be done if more than one variable is used to control resistance. In such cases, for more accurate results, it may be desirable for the deceleration to be measured at speeds in excess of those normally encountered during operation by the user. For this purpose, a motor may be provided for driving the flywheel at such speeds. This is preferably done only when the user gives the machine a command to enter a calibration mode.

There is no need for the signal representing the resistive forces to monitor variations occurring during use, and indeed it is not even essential for it to represent the major resistive force produced by the alternator so long as the latter is reasonably predictable. In the latter case the alternator could be switched off between strokes. The signal should however represent any forces which tend to vary from machine to machine or from time to time, so that such variations can be compensated for.

Various modifications can be made to the above arrangements. For example, the alternator could be of the type which has a rotating armature, or could be replaced by a dynamo. Instead of having a separate sensor arrangement 46, ripples in the signal applied to the alternator, or the frequency of the output therefrom, could be monitored to detect rotor speed.

Claims

1. An exercise machine having means for sensing the degree of at least part of the resistance presented to the work performed by a user, so as to provide a signal indicative thereof for either controlling the resistance or providing an indication to the user in response thereto.

2. An exercise machine as claimed in claim 1, having an inertial mechanism which is driven by the user during operation of the machine, the sensing means being able to determine an alteration in the speed of the mechanism in an interval between times at which it is driven by the user.

3. An exercise machine as claimed in claim 2, wherein the inertial mechanism is driven in a cyclical manner and said interval occurs between successive cycles.

4. An exercise machine as claimed in claim 2 or 3, wherein the inertial mechanism is a flywheel.

5. An exercise machine as claimed in claim 4, wherein the operation of the machine is arranged to withdraw an elongate member from a takeup reel, the machine including a gear arrangement between the takeup reel and the flywheel so that such withdrawal causes rotation of the flywheel, the gear arrangement being such as to cause the flywheel to rotate with a velocity greater than that of the takeup reel.

6. A machine as claimed in any one of claims 2 to 5, including means for processing a signal representing the speed alteration in said interval with a signal representing speed of operation of the machine to generate the signal indicative of resistance.

7. An exercise machine as claimed in any preceding claim, including means for altering the resistance presented to the user so as to make the sensed resistance correspond to a predetermined level.

8. An exercise machine as claimed in claim 7, wherein the predetermined level is alterable.

9. An exercise machine as claimed in any preceding claim, having an indicator for providing a display of work carried out on the machine in response to the signal indicative of resistance.

10. An exercise machine as claimed in claim 9, wherein the indication means is arranged to indicate the cumulative amount of worked carried out over a period.

11. An exercise machine as claimed in any preceding claim, including an electrical machine which generates at least a substantial part of the resistance by virtue of the interaction between an exciting field and a field induced in windings during relative movement between the windings and the exciting field.

12. An exercise machine as claimed in claim 11, wherein the exciting field is of a substantially constant magnitude.

13. An exercise machine as claimed in claim 12, wherein the field is generated by one or more windings carrying a substantially constant current.

14. An exercise machine as claimed in claim 13, having means operable to control the resistance by varying said constant current.

15. An exercise machine as claimed in any preceding claim, including control means for varying the resistance in a predetermined, controlled fashion during operation of the machine.

16. An exercise machine in which the resistance to the work performed by the user is provided at least in part by an electrical machine in which the exciting field is of a substantially constant magnitude.

17. An exercise machine as claimed in claim 16, wherein the field is produced by one or more windings carrying a substantially constant current.

18. An exercise machine as claimed in any preceding claim, in the form of a rowing machine.

19. An exercise machine substantially as herein described with reference to the accompanying drawings.