Patent Description:
Exercise and physical fitness are steadily gaining in popularity. The growing interest in physical fitness is reflected by the growing number of gyms found in both public and private settings.

Exercise machines are often used for physical exercise, for example weight machines in which stacked weight plates are lifted by the user against the action of gravity. Conventionally, the user has to keep a manual record of the exercises performed on the machines and the outcome of the respective exercise.

Recently, automated monitoring systems have been developed to help a user to track and record progress on exercise machines. One example is disclosed in <CIT>, in which exercise machines are arranged to transmit exercise data and machine identity data for storage at a server, which is arranged to allow the user to access its exercise data, for example to evaluate progress in training. The respective exercise machine is configured to generate the exercise data by use of a sensor arrangement arranged at the stacked weight plates to detect their movement. The sensor arrangement may thereby provide data on the number of repetitions performed and the number of weight plates lifted. Such data may be at least partly obtained from output data of one or more time-of-flight (ToF) sensors, which measure distance in the exercise machine by transmitting a signal and receiving a reflection of the transmitted signa In Document <CIT> the information about the need for maintenance is solely based on the number of hours that the respective machine has been used.

One challenge of automated monitoring systems is to ensure operability of the sensor arrangement in the respective exercise machine over time. Contamination by dirt, dust, oil, sweat and other deposits is likely to occur in exercise settings, which inherently exhibit significant human movement, sweating, etc. ToF sensors are sensitive to contamination and will require cleaning from time to time. The amount of deposits accumulated on the respective exercise machine may depend on its location with the gym, the type of ventilation system, the cleaning procedure, the frequency of cleaning, etc. Typically, all exercise machines in a gym would have to be cleaned at regular intervals irrespective of the actual degree of fouling of the individual exercise machine, requiring a significant work effort.

It is an objective to at least partly overcome one or more limitations of the prior art.

A further objective is to enable predictive maintenance of exercise machines that comprise one or more time-of-flight sensors.

A yet further objective is to provide a technique of detecting a current or upcoming need for cleaning of time-of-flight sensors in exercise machines.

According to the invention, the problem posed is solved by the method of claim <NUM>, the computer-readable medium of claim <NUM> and the apparatus of claim <NUM>.

A first aspect is a method of detecting a need for maintenance of an exercise machine comprising a time-of-flight sensor, the method comprising: obtaining, by the time-of-flight sensor during a measurement period, a plurality of measurement values indicative of measured distance between the time-of-flight sensor and a reflective element in the exercise machine, each of the measurement values corresponding to a respective signal pulse emitted by the time-of-flight sensor, computing one or more evaluation parameters as a function of the plurality of measurement values, and evaluating the one or more evaluation parameters for detection of the need for maintenance.

A second aspect is a computer-readable medium comprising computer instructions which, when executed by a processor, cause the processor to perform the method of the first aspect.

A third aspect is an apparatus configured to detect a need for maintenance of an exercise machine comprising a time-of-flight sensor, the apparatus comprising: an input for receiving a measurement signal from the time-of-flight sensor, and logic configured to: obtain, via the input, a plurality of measurement values indicative of distance between the time-of-flight sensor and a reflective element in the exercise machine, each of the measurement values corresponding to a respective signal pulse emitted by the time-of-flight sensor during a measurement period; compute one or more evaluation parameters as a function of the plurality of measurement values; and evaluate the one or more evaluation parameters for detection of the need for maintenance.

Still other objectives, as well as features, embodiments, aspects and technical effects will appear from the following detailed description, the attached claims and the drawings.

Embodiments will now be described in more detail with reference to the accompanying schematic drawings.

Embodiments will now be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all, embodiments are shown. Indeed, the subject of the present disclosure may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure may satisfy applicable legal requirements.

Also, it will be understood that, where possible, any of the advantages, features, functions, devices, and/or operational aspects of any of the embodiments described and/or contemplated herein may be included in any of the other embodiments described and/or contemplated herein, and/or vice versa. In addition, where possible, any terms expressed in the singular form herein are meant to also include the plural form and/or vice versa, unless explicitly stated otherwise. As used herein, "at least one" shall mean "one or more" and these phrases are intended to be interchangeable. Accordingly, the terms "a" and/or "an" shall mean "at least one" or "one or more", even though the phrase "one or more" or "at least one" is also used herein. As used herein, except where the context requires otherwise owing to express language or necessary implication, the word "comprise" or variations such as "comprises" or "comprising" is used in an inclusive sense, that is, to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments. The term "compute", and derivatives thereof, is used in its conventional meaning and may be seen to involve performing a calculation involving one or more mathematical operations to produce a result, for example by use of a computer.

It will furthermore be understood that, although the terms first, second, etc. may be used herein to describe various elements, these elements should not be limited by these terms. For example, a first element could be termed a second element, and, similarly, a second element could be termed a first element, without departing the scope of the present disclosure.

<FIG> is an isometric view of a stacked weight exercise machine <NUM> having a plurality of weights <NUM>. <FIG> depict the arrangement of weights <NUM> in further detail. The exercise machine <NUM> comprises a lifting mechanism <NUM> and an engaging member ("selector pin") <NUM> for selectively engaging a number of stacked weights to the lifting mechanism <NUM>. The lifting mechanism <NUM> may be coupled, in a manner well known to the skilled person, to one or more gripping or pushing members via one or more cables, belts, rods, etc. In the illustrated example, the lifting mechanism <NUM> includes a support member having a rod-shaped portion, configured to pass vertically through corresponding holes in the weights <NUM>. The support member <NUM> may further include a top portion, such as a fixed top weight. A sensor arrangement is associated with the weights <NUM> and comprises a time-of-flight (ToF) sensor <NUM> and a reflective element ("reflector") <NUM>. In the illustrated example, the ToF sensor <NUM> is arranged on top of the stacked weights <NUM> and is thus moving when a user performs an exercise in the machine <NUM>. The reflector <NUM> is located at a fixed position spaced from the top of the weights <NUM>. For example, the reflector <NUM> may be attached to or part of the frame of the machine <NUM>. In a variant, not shown, the positions of the ToF sensor <NUM> and the reflector <NUM> may be reversed.

In exercise machines comprising stacked weights, the user may typically select how many of the weights should be used or engaged in the exercise, by inserting the selector pin <NUM> in one of the weights. During exercise, the user will then lift the selected weights, as exemplified in <FIG>, where the selected portion 11a of the stacked weights is lifted in relation to a remaining portion 11b. The training may be tracked by monitoring how many times the selected weights are lifted (number of repetitions) and, optionally, how many weights are selected to be lifted.

The exercise machine <NUM> has a "rest state", which is attained when the user does not apply force to the machine <NUM>. In the example of <FIG>, the rest state (<FIG>) results in a maximum distance ("rest distance") Dr between the ToF sensor <NUM> and the reflector <NUM>. When not in the rest state, the machine <NUM> is in a loaded state (<FIG>) at which the distance is smaller than the maximum distance Dr. The exercise machine may or may not attain the rest state between repetitions, depending on the training schedule of the specific user.

The sensor arrangement is configured to provide sensor data indicative of a measured distance between the sensor <NUM> and the reflector <NUM>. The sensor data thereby enables determination of the number of repetitions. For example, a repetition may be detected when the measured distance has changed a predetermined amount from the rest distance, which thus corresponds to the selected portion 11a being lifted a given distance, and/or when the measured distance starts to increase after having decreased, which corresponds to the selected portion 11a being lifted from and then returned towards an initial position.

The exercise machine may be connected to an exercise monitoring system which allows the user to access exercise data that quantifies the exercise performed in the exercise machine by the user. The structure and functionality of the exercise monitoring system and the communication of data from the exercise machine goes beyond the scope of the present disclosure. The above-mentioned sensor data may be transmitted, optionally after further processing, from the exercise machine over any suitable wired and/or wireless communication channel, in real time during the exercise or after a completed session. In some embodiments, the user may also be allowed to enter data to the exercise monitoring system via a user interface on the exercise machine or on a handheld or wearable user device connected to the exercise monitoring system.

It is to be understood that the sensor arrangement may include one or more further sensors (not shown) configured to provide further sensor data, for example sensor data indicative of the selected weights. For example, as disclosed in <CIT> and <CIT>, such a further sensor may be arranged to measure the distance between the selector pin <NUM> and a reference point, which is located such that the measured distance is indicative of the selected weight. The sensor also may be a ToF sensor, and the distance may be measured between the selector pin <NUM> and a reference point on the selected portion 11a above the selector pin <NUM> (for example, on top of the stacked weights) or between the selector pin <NUM> and a stationary reference point beneath the selector pin <NUM>. Alternatively, the user may enter the selected weight manually via the above-mentioned user interface.

Time-of-flight (ToF) is an established technique for distance determination ("range finding" or "ranging") and involves measuring the roundtrip time of a signal provided by a source onto a target, with the distance being given by half the roundtrip time multiplied by the propagation speed of the signal. The signal is typically an electromagnetic signal, for example a light signal in the ultraviolet, visible or infrared wavelength range. The light signal may be generated by a laser or an LED.

There are two main principles for determining the roundtrip time, denoted "direct method" and "indirect method" herein. In the direct method, the signal is emitted in pulses and the roundtrip time is given by the time difference between an outgoing signal pulse and a corresponding incoming (reflected) signal pulse. The direct method may involve timestamping outgoing signal pulses and incoming signal pulses and computing the difference between corresponding timestamps. In a variant, the direct method may involve synchronizing the detection of incoming signal pulses with the generation of outgoing signal pulses (for example, by use of a so-called gate detector), thereby making the detected signal strength of the incoming signal proportional to the distance. The distance may be given by a single pulse but to improve SNR a plurality of single-pulse measurements may be combined to produce a measured distance. In the indirect method, a modulated signal is emitted and the roundtrip time is given by the phase difference between the outgoing signal and the incoming (reflected) signal. The modulated signal may, for example, be sinusoidal. The modulation frequency sets the maximum range of the ToF sensor <NUM>, i.e. the largest distance that may be measured. Any type of phase detector may be used for detecting the phase difference between the signals.

<FIG> shows an example of a ToF module <NUM> in a ToF sensor <NUM> for use in the exercise machine <NUM> of <FIG>. The module <NUM> comprises a source <NUM> for emitting an outgoing signal and a detector <NUM> for detecting an incoming signal, which is generated by reflection of the outgoing signal against the reflector <NUM>. In the illustrated example, the module <NUM> further comprises a reference detector <NUM> which is arranged to provide an electric signal representative of the outgoing signal. The ToF sensor <NUM> further comprises a front panel <NUM> which is arranged to transmit the outgoing and incoming signals while protecting the module <NUM> and its sensitive electrooptical components. As indicated in <FIG>, the provision of the front panel <NUM> introduces an internal signal path between the source <NUM> and the detector <NUM>, in addition to the external signal path from the source <NUM> to the detector <NUM> via the reflector <NUM>. The internal signal path is known as cross-talk and introduces noise in the distance measurement. <FIG> corresponds to <FIG> but illustrates a situation with deposits <NUM> on the front panel <NUM>. The deposits <NUM> will scatter the outgoing signal and result in increased cross-talk, as schematically indicated by grey arrows in <FIG>. Thereby, deposits <NUM> will increase measurement noise and reduce measurement accuracy, ultimately producing totally unreliable distance measurements.

<FIG> schematically depicts an example configuration of a ToF sensor <NUM> for use in an exercise machine <NUM>, for example as depicted in <FIG>. In the illustrated example, a ToF module <NUM> is arranged within a protective housing comprising the front panel <NUM>. The ToF sensor <NUM> further comprises a processing unit <NUM> which is configured to control the operation of the ToF module <NUM> and to process electric signals provided by the sensors <NUM>, <NUM> to determine a measured distance to the reflector <NUM>. The processing unit <NUM> is also configured to output a measurement signal via an output interface <NUM>, which is arranged for wired or wireless data transmission.

As used herein, a "distance" is not restricted to units of length but could be given in any other unit that is equivalent to a unit of length. For example, a distance measured by a ToF sensor <NUM> may, instead of a unit of length, be given by the above-mentioned roundtrip time, half the roundtrip time, or any other quantity derived from the roundtrip time.

<FIG> is a flow chart of a detection method <NUM> in accordance with a first main embodiment. The method <NUM> may be performed by the ToF sensor <NUM> (cf. processing unit <NUM> in <FIG>), by a separate monitoring device (<NUM> in <FIG>) based on the measurement signal from the ToF sensor <NUM>, or by a combination thereof. The detection method <NUM> aims at detecting a need for cleaning the ToF sensor <NUM>, specifically its front panel <NUM>. Intuitively, the measured signal strength at the sensor <NUM> might be believed to represent fouling of the ToF sensor <NUM>. However, it has been found that such fouling (cf. deposits <NUM> in <FIG>) generally does not result in a significant reduction in signal strength at the detector <NUM>, but rather causes a redistribution of signal from the external signal path to the internal signal path of the ToF sensor <NUM>. The first main embodiment is instead based on the surprising finding that the measured distance by the ToF sensor <NUM>, for a fixed actual distance, will decrease with increasing fouling of the front panel <NUM>. Thus, by evaluating the measured distance over time, a need for cleaning may be inferred in advance of a situation in which the measurement signal from the ToF sensor <NUM> misrepresents the training performed in the exercise machine. It is presently believed that the first main embodiment is particularly useful for predictive maintenance of ToF sensors <NUM> that operate by the indirect method.

The method <NUM> comprises a step <NUM> of obtaining, at a current time, a measurement signal of the ToF sensor <NUM> at a predetermined operating condition of the exercise machine <NUM>. The current time is thus any time point when the exercise is in the predetermined operating condition. In the predetermined operating condition, the exercise machine <NUM> attains a fixed actual distance between the ToF sensor <NUM> and the reflector <NUM>. The actual distance is thus a physical distance in the exercise machine and is effectively constant over time. In one embodiment, the predetermined operating condition involves the weight stack <NUM> being immobile, for example when the machine <NUM> is in its rest state, or substantially in its rest state. In the illustrated example of <FIG>, the rest state corresponds to a maximum distance between the ToF sensor <NUM> and the reflector <NUM>. In other implementations, the rest state may correspond to a minimum distance, for example if distance is measured between the selector pin <NUM> and a reference point below the selector pin <NUM>.

In one example, step <NUM> may be performed at a time point when the machine <NUM> is known to be in its rest position, for example during closing hours of a gym. In another example, if the user is required to check in to the above-mentioned exercise monitoring system before starting the training session at the exercise machine and check out after completing the training session, step <NUM> may be performed between check-ins. In a further example, step <NUM> may be performed responsive to a signal indicative of the predefined operating condition. Such a signal may be provided by a motion sensor attached to or included in the ToF sensor <NUM>, the weight stack <NUM>, the selector pin <NUM> or the lifting mechanism <NUM>. The motion sensor, exemplified as <NUM> in <FIG>, may include an accelerometer, a vibration sensor, etc. The signal may alternatively be provided by a switch on the machine or in a machine management system, which may be actuated by an operator (for example, a gym manager) to trigger step <NUM> at one or more exercise machines.

In step <NUM>, a measured distance is determined based on the measurement signal. The measured distance is thus a perceived distance between the ToF sensor <NUM> and the reflector <NUM> at the predetermined operating condition.

In steps <NUM>-<NUM>, the measured distance is evaluated for detection of a need for maintenance of the exercise machine <NUM>. In the illustrated example, step <NUM> obtains a reference distance <NUM>, step <NUM> checks the measured distance with respect to the reference distance, for example by comparing the distances, and step <NUM> decides if there is a need for maintenance based on the outcome of step <NUM>. If no need for maintenance is detected by step <NUM>, the method <NUM> may return to perform step <NUM> at a subsequent time point (i.e., at a new "current time"). When a need for maintenance is detected by step <NUM>, the method may proceed to step <NUM>, which generates an output signal to indicate a need for maintenance. The need for maintenance of this specific machine may, for example, be signaled locally by an audible and/or visual indication on a feedback unit (not shown) on the exercise machine, or may be signaled centrally to a provider, for example a manager of a gym that hosts the machine, by an email, an alert in a machine management system, etc..

In the example of <FIG>, if the predetermined operating condition is the rest state of the machine <NUM>, the reference distance is or represents the distance Dr in <FIG>.

In one embodiment of the detection method <NUM>, step <NUM> retrieves the reference distance from a memory. The reference distance in the memory may be predefined for the exercise machine, for example given by a nominal value or be set by calibration in production of the machine.

Alternatively, the reference distance in the memory may have been determined by the method <NUM> by receiving the measurement signal generated by the ToF sensor <NUM> at an earlier time ("reference time") when the exercise machine <NUM> is in the predefined operating condition (corresponding to step <NUM>) and by determining the reference distance as a function of the measurement signal (corresponding to step <NUM>). The reference distance may thus be given by the measured distance at the reference time, assuming that the ToF sensor <NUM> is substantially clean at the reference time. In one example, the reference time may be set to directly follow upon a cleaning of the ToF sensor <NUM>. Thus, the method <NUM> may determine the reference distance whenever an operator signals, by any suitable means, that cleaning has been completed. It is conceivable that the reference time extends over a time period and that the reference distance is given as an aggregated value (average, median, etc.) of a plurality of measured distances determined during this time period. An example is illustrated in <FIG>. Grey dots represent values of measured distance <NUM> as a function of time in the exercise machine of <FIG>. The reference distance, Dr, is computed based on a plurality of measured distances within a time period, Δt, at the reference time. <FIG> also illustrates a measured distance, Dc, determined for a current time, tc. For example, if the difference between Dr and Dc exceeds a predefined threshold, steps <NUM>-<NUM> of method <NUM> may detect a need for maintenance. The threshold may be set to allow for preventive maintenance. Steps <NUM>-<NUM> may require plural differences to exceed the threshold before detecting the need for maintenance.

It should be noted that the evaluation in steps <NUM>-<NUM>, instead of or in addition to being made in relation to a reference distance, may detect the need for maintenance based on a trend analysis of the progression of measured distances <NUM>, e.g. by statistical analysis of the measured distances up to the current time, by analysis of the derivate of a curve fitted to the measured values up to the current time, by extrapolation of the measured values up to the current time, etc..

In an alternative implementation of the method <NUM>, exemplified in <FIG>, step <NUM> obtains the reference distance at the current time, tc, but with a different range setting of the ToF sensor <NUM> compared to the range setting used in step <NUM>. The range setting defines the largest distance (maximum range) that the ToF sensor <NUM> is capable of measuring. Most commercially available ToF sensors <NUM> provide the option of changing the range setting. It has been found that the sensitivity to fouling, with respect to measured distance, differs between range settings. In the example of <FIG>, grey dots represent values of measured distance <NUM> as a function of time with a first range setting of the ToF sensor <NUM>, and the curve <NUM> schematically depicts measured distance with a second range setting of the ToF sensor <NUM>. In this example, the second range setting has a larger maximum range than the first range setting. Step <NUM> may comprise receiving the measurement signal generated by the ToF sensor <NUM> when set in the second range setting and at the predefined operating condition of the exercise machine <NUM> (corresponding to step <NUM>) and determining the reference distance as a function of the measurement signal (corresponding to step <NUM>). Steps <NUM>-<NUM> may be performed as shown in <FIG>, by step <NUM> checking the measured distance with respect to the reference distance, for example by comparing the distances, and by step <NUM> deciding if there is a need for maintenance based on the outcome of step <NUM>. For example, if the difference between Dr and Dc exceeds a predefined threshold, steps <NUM>-<NUM> of method <NUM> may detect a need for maintenance. The threshold may be set to allow for preventive maintenance. Steps <NUM>-<NUM> may require plural differences to exceed the threshold before detecting the need for maintenance.

Although <FIG> shows an example where the measured distance and the reference distance are determined at exactly the same time point, this is not necessary. Generally, the measured distance and the reference distance may be obtained a different time points as long as the changes in measured distance and reference distance are small between these time points.

It may also be noted that more than two range settings may be used in step <NUM>, and that step <NUM> may involve evaluating a measured distance (for a first range setting) in relation to two or more reference distances (for a corresponding number of second range settings).

The embodiment exemplified in <FIG> obviates the need to determine and store a reference distance representative of a substantially clean ToF sensor and thereby simplifies deployment of the method <NUM>. Further, it is currently believed that the embodiment exemplified in <FIG> may result in an increased sensitivity to fouling. For example, as indicated at tc in <FIG>, fouling may be detected even when the measured distance at the first range setting is substantially unaffected by fouling.

It should also be noted that the embodiments exemplified with reference to <FIG> and <FIG> may be combined, for example by the evaluation in steps <NUM>-<NUM> evaluating a measured distance determined for a first range setting in relation to both a first reference distance representative of a substantially clean ToF sensor (for example, determined for Δt in <FIG>) and a second reference distance determined for a second range setting.

<FIG> is a flow chart of a detection method <NUM> in accordance with a second main embodiment. The method <NUM> may be performed by the ToF sensor <NUM> (cf. processing unit <NUM> in <FIG>), by a separate monitoring device (<NUM> in <FIG>) based on the measurement signal from the ToF sensor <NUM>, or by a combination thereof. The detection method <NUM> has the same objective as the detection method <NUM> but is based on a different type of measurement data and a different evaluation thereof. The method <NUM> operates on ToF values ("measurement values") internally computed by the ToF sensor <NUM> for individual signal pulses emitted during a distance measurement period of the ToF sensor <NUM>. The distance measurement period results in a single value of the measured distance, which is thus determined as a function of the ToF values. The individual ToF values may be represented as roundtrip time, distance, etc. It has been found that the distribution of the ToF values, obtained during the distance measurement period, changes with increasing fouling of the ToF sensor <NUM>. As used herein, a "distribution" represents the frequency of different ToF values. It is presently believed that the second main embodiment is useful for predictive maintenance of ToF sensors <NUM> that are configured to emit signal pulses, i.e. at least ToF sensors that operate by the direct method.

The method <NUM> comprises a step <NUM> of obtaining, by the ToF sensor <NUM> during a distance measurement period, a plurality of ToF values indicative of measured distance between the ToF sensor <NUM> and the reflector <NUM>, each of the ToF values corresponding to a respective signal pulse emitted by the ToF sensor <NUM>. In step <NUM>, evaluation parameter data is computed as a function of the plurality of ToF values. The evaluation parameter data may comprise one or more evaluation parameters. In steps <NUM>-<NUM>, the evaluation parameter data is analyzed for detection of a need for maintenance. If step <NUM> does not detect a need for maintenance, the method <NUM> may return to perform step <NUM> for a distance measurement period at a subsequent time point. When a need for maintenance is detected by step <NUM>, the method may proceed to step <NUM>, which may be identical to step <NUM> of method <NUM>.

An example of the change in distribution of ToF values is illustrated in <FIG>, which are schematic histograms of ToF values. In the respective histogram, the entire range of ToF values is divided into a series of non-overlapping intervals (also known as bins). The vertical axis represents the number ("count") of ToF values that fall within the respective bin. <FIG> exemplifies the distribution for a clean ToF sensor <NUM>, where the ToF values form a peak with count Cp. The location of the peak in ToF value corresponds to the measured distance between the ToF sensor <NUM> and the reflector <NUM>. <FIG> exemplifies the distribution for a ToF sensor <NUM> with some fouling on the front panel <NUM>. As seen, the magnitude of the peak (count Cp) has decreased and the number of small ToF values has increased. This is due to the redistribution from the external signal path to the internal signal path as represented in <FIG>.

It is realized that are various evaluation parameters that may be computed in step <NUM> to represent the change in distribution illustrated in <FIG>. In one non-limiting example, step <NUM> determines an aggregated count of the ToF values that are indicative of distances within a predefined subset of the total measurement range of the ToF sensor <NUM>. The predefined subset corresponds to a distance interval and is selected to include at least a portion of the ToF values originating from the internal signal path. Thus, the predefined subset is suitably located at a lower end of the total measurement range of the ToF sensor <NUM> and thus corresponds to small distances. In <FIG>, the distance interval is designated by ΔD, and the bins that fall within ΔD are marked as black. While steps <NUM>-<NUM> may detect a need for maintenance solely based on the aggregated count of ToF values within ΔD, the specificity of detection may be improved by also including the peak value, Cp, in the analysis by step <NUM>, for example by evaluating the aggregated count in relation to the peak value. In one non-limiting example, the degree of fouling of the ToF sensor may be assessed based on the ratio or difference between the peak value and the aggregated count. In other embodiments, step <NUM> may comprise evaluating all or part of the distribution of ToF values in relation to a reference distribution. For example, the reference distribution may be given by the distribution for a clean ToF sensor (<FIG>), and an evaluation parameter may be computed to represent a difference between a current distribution and the reference distribution.

As understood from <FIG>, in some embodiments, the detection method <NUM> is performed such that the measured distance is spaced from the distance interval, ΔD. This may be inherent to the exercise machine, if configured such that the smallest distance that may be attained between the ToF sensor <NUM> and the reflector <NUM> exceeds the distances in the distance interval, ΔD. Otherwise, step <NUM> may be selectively performed at a time point when the distance between the ToF sensor <NUM> and the reflector <NUM> is known to lie outside the distance interval, ΔD. For example, step <NUM> may be performed at a predetermined operating condition of the machine <NUM>, for example in its rest state, by analogy with the first main embodiment.

The detection methods exemplified hereinabove may be implemented by a monitoring device <NUM> which is physically separated from the ToF sensor <NUM>, e.g. as shown in <FIG>. Although not shown, the monitoring device <NUM> may be connected to receive measurement signals from ToF sensors in a plurality of exercise machines in one or more locations. The respective measurement signal may be communicated to the monitoring device by wire and/or wirelessly, and optionally over one or more networks of any type. <FIG> illustrate different types of data that may be included in the measurement signal from the ToF sensor <NUM>, in addition to a unique identifier of the exercise machine <NUM> and/or the ToF sensor <NUM>. In <FIG>, the monitoring device <NUM> may implement the method <NUM>. The measurement signal contains the measured distance, Dc, at a respective time (cf. step <NUM>). The measured distance at the respective time is thus computed internally of the ToF sensor <NUM>. In <FIG>, the monitoring device <NUM> may implement the method <NUM>. The measurement signal contains the measured distance, Dc, at a first range setting of the ToF sensor <NUM> and the reference distance, Dr, at a second range setting of the ToF sensor <NUM> (cf. steps <NUM>, <NUM>). In <FIG>, the monitoring device <NUM> may implement either of the methods <NUM>, <NUM>. The measurement signal contains an ensemble of ToF values, [Dc], which are computed by the ToF sensor <NUM> for individual signal pulses during the above-mentioned distance measurement period. When implementing the method <NUM>, the monitoring device <NUM> may determine the measured distance, Dc, as a function of the ensemble of ToF values, by any suitable aggregation algorithm, thereby completing step <NUM>. When implementing the method <NUM>, the monitoring device <NUM> may compute the evaluation parameter data based on the ensemble of ToF values, in accordance with step <NUM>. In <FIG>, the monitoring device <NUM> may implement the method <NUM>. The measurement signal contains evaluation parameter data. The computation of the evaluation parameter data in step <NUM> is thus at least partly performed by the ToF sensor <NUM>.

The data transfer between the ToF sensor <NUM> and the monitoring device <NUM> may be performed by a push or pull mechanism, or a combination thereof. In one example, the ToF sensor <NUM> is configured to repeatedly transmit the measurement signal to the monitoring device <NUM>, for example every hour, and the monitoring device <NUM> selects the appropriate measurement signal to analyze. For example, the monitoring device <NUM> may select a measurement signal containing data obtained during closing hours of a gym to ensure that the respective exercise machine is in its rest state. In another example, the monitoring device <NUM> may be configured to actively request the measurement signal from the respective ToF sensor <NUM> at a selected time.

In an alternative to the embodiments in <FIG>, the monitoring device <NUM> may be arranged on the exercise machine <NUM> or be integrated with the ToF sensor <NUM>.

<FIG> is a block diagram of an exemplifying structure of the monitoring device <NUM>. Generally, the monitoring device <NUM> may be configured to perform any of the methods described herein, or part thereof, by a combination of software and hardware circuitry, or exclusively by specific hardware circuitry. In <FIG>, the monitoring device <NUM> comprises a control circuit <NUM> responsible for the overall operation of the monitoring device <NUM>. As shown, the control circuit <NUM> may include a processing device or processor <NUM>, which may be or include a central processing unit (CPU), graphics processing unit (GPU), microcontroller, microprocessor, ASIC, FPGA, or any other specific or general processing device. The processor <NUM> may execute instructions <NUM> stored in a separate memory, such as memory <NUM>, and/or in an internal memory (not shown) of the control circuit <NUM>, in order to control the operation of the monitoring device <NUM>. The instructions <NUM> when executed by the processor <NUM> may cause the monitoring device <NUM> to perform any of the methods described herein, or part thereof. The instructions <NUM> may be supplied to the monitoring device <NUM> on a computer-readable medium <NUM>, which may be a tangible (non-transitory) product (for example magnetic medium, optical disk, read-only memory, flash memory, etc.) or a propagating signal. As indicated in <FIG>, the memory <NUM> may also store data <NUM> for use by the processor <NUM>, for example one or more reference distances, one or more reference distributions, etc. The memory <NUM> may comprise one or more of a buffer, a flash memory, a hard drive, a removable media, a volatile memory, a non-volatile memory, a random access memory (RAM), or another suitable data storage device. In an exemplary arrangement, the memory <NUM> includes a non-volatile memory for long term data storage and a volatile memory that functions as system memory for the control circuit <NUM>. The memory <NUM> may exchange data with the control circuit <NUM> over a data bus. Accompanying control lines and an address bus between the memory <NUM> and the control circuit <NUM> also may be present. The memory <NUM> is considered a non-transitory computer readable medium. The monitoring device <NUM> may further include an input <NUM>, which may include any conventional communication interface for wired or wireless communication. The input <NUM> is arranged to receive measurement signal(s) from one or more ToF sensors <NUM>.

While the subject of the present disclosure has been described in connection with what is presently considered to be the most practical embodiments, it is to be understood that the subject of the present disclosure is not to be limited to the disclosed embodiments, but on the contrary, is intended to cover various modifications included within the scope of the appended claims.

Further, while operations are depicted in the drawings in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results.

Claim 1:
A method of detecting a need for maintenance of an exercise machine (<NUM>) comprising a time-of-flight sensor (<NUM>), the method comprising:
obtaining (<NUM>), by the time-of-flight sensor (<NUM>) during a measurement period, a plurality of measurement values indicative of measured distance between the time-of-flight sensor (<NUM>) and a reflective element (<NUM>) in the exercise machine (<NUM>), each of the measurement values corresponding to a respective signal pulse emitted by the time-of-flight sensor (<NUM>);
computing (<NUM>) one or more evaluation parameters (EPD) as a function of the plurality of measurement values; and
evaluating (<NUM>, <NUM>) the one or more evaluation parameters (EPD) for detection of the need for maintenance.