Wearable measuring device, aid system comprising a wearable measuring device, method for determining the muscle hardness of a skeletal muscle

Description

[0001] The present invention relates to a wearable measuring device comprising a measuring unit with at least two measuring units and a holding device for attaching the measuring unit to a part of a person's body. The present invention also relates to an auxiliary system comprising such a measuring device and a wearable exoskeleton. Furthermore, the present invention relates to a method for determining the muscle stiffness of a person's skeletal muscle.

[0002] Wearable exoskeletons can be used to transfer loads on a user, for example when lifting heavy objects, either directly into the ground or at least through selected areas of the user's body. In this way, the user's joints and muscles can be protected.

[0003] To effectively relieve the strain on a user through an exoskeleton, it is necessary to determine the user's support needs. For example, it is known to monitor a user's skeletal muscle and derive the support requirements from this monitoring. Traditionally, wearable measuring devices are used to monitor a skeletal muscle. Such devices comprise a measuring unit for monitoring the skeletal muscle and a holding device for attaching the measuring unit to a body part containing the skeletal muscle. In this regard, for example, publications WO 2018 050 191 A1 and ES 2 335 337 B1 disclose wearable measuring devices in the form of force sensor wristbands. Publications CN 111 150 373 B and KR 101 675 577 B1 disclose wearable measuring devices in the form of gas pressure sensor wristbands.

[0004] However, well-known force sensor wristbands and gas pressure sensor wristbands have the disadvantage that the measurement result is distorted by various effects. For example, the tightness with which the wristbands are applied influences the measurement result. In addition, the measurement result is also affected by bulges in the monitored skeletal muscle, which occur during movement and are accompanied by a change in circumference.

[0005] The invention addresses the problem of improving the monitoring of skeletal muscle in a wearable measuring device.

[0006] This problem is solved according to the invention by an attachable measuring device with the features of claim 1.

[0007] The dependent claims and the description specify advantageous variants and embodiments.

[0008] According to the invention, a wearable measuring device is provided. The measuring device comprises a measuring unit that includes at least two measuring units for monitoring a person's skeletal muscle. The measuring device also includes a holding device for attaching the measuring unit to a body part of the person containing the skeletal muscle. Preferably, the body part is an extremity of the person, in particular an arm or a leg.

[0009] The design now proposes that each measuring unit comprise a force sensor and an associated spring unit, with the spring units each having different spring constants. The measuring units can be attached to the body part in such a way that the spring units can be subjected to force, or tensioned, by a different section of the skeletal muscle, and that the force sensors are designed to detect the tension force of the associated spring unit.

[0010] The invention is based on the premise that a skeletal muscle can be viewed as a grid or array of spring units with the same spring constant. The strength or value of the spring constant of the skeletal muscle varies with the degree of tension in the skeletal muscle. If the measuring units according to the invention are attached to the body part in such a way that the spring units can be tensioned by a different section of the skeletal muscle, then the spring units, together with their respective, associated sections of the skeletal muscle, each form a spring arrangement with a different equivalent spring constant. Because the spring constants of the spring units differ from one another, the equivalent spring constants of the resulting spring arrangements also differ from one another. When the monitored skeletal muscle is tensed, a greater tension force is transmitted to the spring unit with the higher spring constant than to the spring unit with the lower spring constant.Based on the tension forces detected by the force sensors, the muscle stiffness of the skeletal muscle can then be determined or estimated as a spring constant. In the idealized case, where the skeletal muscle exhibits a linear spring characteristic, a calculation of the skeletal muscle's spring constant would be possible. In reality, due to various effects, an estimate is more likely, but one with sufficient accuracy. This approach overcomes the disadvantages previously mentioned in connection with force sensor wristbands and gas pressure sensor wristbands. Consequently, the user's support needs can be derived from the skeletal muscle's spring constant in a user-friendly and reliable manner. Furthermore, determining the skeletal muscle's spring constant is largely independent of influencing factors such as the person using the device or the time or muscle tension at which the device is applied.With the same level of muscle tension, a comparable spring constant can always be determined, regardless of such influencing factors.

[0011] Preferably, the spring constant of one spring unit is at least 1.1 times the spring constant of the other spring unit. This configuration of the spring units ensures that the sensor signals from the force sensors differ sufficiently from each other for a particularly precise determination of the spring constant of the skeletal muscle.

[0012] Preferably, the spring units according to the invention each comprise only a single spring element. However, the spring units can also each comprise several spring elements, which are connected, for example, in series or in parallel to one another.

[0013] The force sensors according to the invention are designed to detect a tension force of the associated spring unit, i.e., a tension force of the spring unit of the same measuring unit. Depending on the design of the measuring units, the force sensors can detect the tension force as a tensile force or as a compressive force. Within the scope of the disclosure, the term "force" refers to both force in the narrower sense and surface pressure and gas pressure. Consequently, the force sensors according to the invention can detect the tension force, at least in some embodiments, also as surface pressure or as gas pressure.

[0014] In particular, the measuring device comprises only a single measuring unit, meaning that it can only monitor a single skeletal muscle of the person as intended. However, the measuring device can also include multiple measuring units, each of which can be assigned to a different skeletal muscle of the same body part. This makes it possible to monitor several different skeletal muscles of the same body part simultaneously using the same measuring device. If, for example, the body part is an arm, a measuring device with two measuring units can simultaneously monitor, for instance, both the biceps brachii and the triceps brachii muscles.

[0015] According to the invention, the measuring device comprises an evaluation unit configured to determine the spring constant of the skeletal muscle based on sensor signals from the force sensors. For example, the evaluation unit determines the spring constant according to a lookup table, a characteristic map, a calculation rule, or a computational network. In some alternative embodiments, the measuring device itself is free of an evaluation unit. In such cases, an external evaluation unit can be provided, which is connected to the force sensors via communication technology and configured to determine the spring constant of the skeletal muscle based on the sensor signals from the force sensors.

[0016] Various designs are possible with regard to the construction of the spring units. Preferably, at least one of the spring units comprises a metal spring or an elastomer spring. The use of such springs allows for a cost-effective implementation of the measuring device.

[0017] Regarding the material of the spring units, materials that allow for a linear or at least substantially linear spring characteristic are preferred. The spring units can, for example, be made of a textile material or a metal. The spring constant of the spring units is preferably on the order of the spring constant of the skeletal muscle being monitored.

[0018] Various designs are possible with regard to the shape of the spring units. Preferably, at least one of the spring units is cylindrical, spiral, disc-shaped, beam-shaped, ribbon-shaped, or strand-shaped. Such spring units are readily available at low cost. Furthermore, the compact design allows for the creation of an overall compact measuring device. This results in a high level of user comfort.

[0019] In some preferred embodiments, at least one of the spring units comprises a gas spring. Gas springs have the advantage of exhibiting a spring characteristic with an approximately linear profile. A spring characteristic with a linear or nearly linear profile enables a particularly precise determination of the spring constant of the skeletal muscle.

[0020] Various designs are possible with regard to the type of force sensor. Preferably, at least one of the force sensors comprises at least one force-dependent electrical resistance, at least one force-dependent electrical capacitance, at least one force-dependent electrical inductance, or at least one piezoelectric element. Force sensors with force-dependent electrical resistance are also known as FSR sensors (force sensing resistors) or strain gauge elements. Force-dependent electrical resistances, capacitances, inductances, or piezoelectric elements are characterized by their low profile, so that a particularly compact measuring device can be realized by using force-dependent electrical resistances, capacitances, inductances, or piezoelectric elements.

[0021] In some preferred embodiments, the spring units have a first end section and a second end section, wherein the associated force sensor is operatively connected to the spring unit via the first end section, and wherein the spring unit is operatively connectable or operatively connected to the skeletal muscle via the second end section. With the measuring device arranged as intended, the spring units are thus positioned between the skeletal muscle and the force sensors. This arrangement of the force sensors has the advantage of facilitating communication with the force sensors, in particular communication with the aforementioned evaluation unit.

[0022] In some preferred embodiments, the spring units have a first end section and a second end section, wherein the associated force sensor is operatively connected to the spring unit via the first end section, and wherein the spring unit is operatively connectable to or operatively connected to the skeletal muscle via the force sensor. Thus, with the measuring device arranged as intended, the force sensors are positioned between the skeletal muscle and the spring units. Even with such an arrangement of the spring units, the spring units can be tensioned by the skeletal muscle.

[0023] In some preferred embodiments, the measuring device comprises at least three measuring units. Increasing the number of measuring units can improve the robustness and / or precision with regard to determining the spring constant of the skeletal muscle. In particular, the spring units of the measuring units each have a different spring constant. Alternatively, the spring units of at least two measuring units have the same spring constant. At least one of the measuring units is therefore redundant and can, for example, be used to validate the sensor signals of the other measuring units.

[0024] In some preferred embodiments, the holding device comprises a retaining strap, a retaining cuff, or a retaining bandage. Such holding devices enable secure and precise attachment of the measuring device to the body part. Furthermore, such holding devices offer a high level of user comfort.

[0025] In some preferred embodiments, the holding device comprises a particularly rigid support structure, with the measuring units arranged on the support structure. Arranging the measuring units on the common support structure facilitates the intended attachment of the measuring units to the body part. The support structure is particularly preferably detachably attached to the holding strap, retaining cuff, or retaining bandage.

[0026] In some preferred embodiments, the spring units extend radially to the body part when the measuring device is arranged as intended. With this orientation, the spring units are subjected to a tension force acting longitudinally along the spring units by the skeletal muscle. In particular, in this embodiment, the measuring units are arranged side by side on the aforementioned support structure, with the spring units extending away from the support structure in the same direction.

[0027] In some preferred embodiments, the spring units extend along the skeletal muscle in the circumferential direction of the body part when the measuring device is arranged as intended. The two ends of the same spring unit are preferably arranged one behind the other in the circumferential direction. This configuration of the measuring device also enables a sufficiently precise determination or estimation of the spring constant of the skeletal muscle. Preferably, the spring units are arranged such that, when the measuring device is arranged as intended, they are axially offset from one another with respect to the longitudinal center axis of the body part. To detect the tension force of the spring units, the force sensors can each be operatively connected to one end of the associated spring unit. In this embodiment, the spring units are particularly preferably designed as elastic textile bands.

[0028] The problem to be solved is also solved by an auxiliary system with the features of claim 13. The auxiliary system comprises a wearable exoskeleton with at least one controllable actuator. Furthermore, the auxiliary system comprises a measuring device configured as described above. The auxiliary system also comprises a control unit configured to control the actuator of the exoskeleton based on information provided by the measuring device. This information includes, in particular, a spring constant of a skeletal muscle to which the measuring device is assigned, determined or estimated by the measuring device.

[0029] Regarding the advantages achievable with the auxiliary system, reference is made to the relevant explanations concerning the measuring device. The features described in connection with the measuring device can serve as a basis for further developing the auxiliary system.

[0030] It should be noted that the measuring device is not limited to use in an assistive device system with an exoskeleton. For example, it can also be used as part of a digital ergonomics assessment tool or in training to track changes in muscle fitness.

[0031] The problem to be solved is also solved by a method with the features of claim 14, which serves to determine the muscle stiffness of a person's skeletal muscle. It is provided that at least two spring units, which differ from each other in their spring constant, are attached to a body part of the person containing the skeletal muscle in such a way that the spring units can be tensioned by a different section of the skeletal muscle, that the tension forces of the spring units are continuously recorded, and that a spring constant of the skeletal muscle is determined as a function of the recorded tension forces.

[0032] Preferably, the method is carried out using an attachable measuring device designed as described above.

[0033] Regarding the advantages achievable with this method, reference is made to the relevant explanations concerning the measuring device. The features described in connection with the measuring device can serve to further develop the method.

[0034] The invention is described in more detail below with reference to the figures, whereby identical or functionally equivalent elements are, if necessary, only designated once with reference numerals. The description serves as an example and is not to be understood as limiting. The figures show Figure 1 shows a sectional view of a body part with a measuring device attached to it, Figure 2 shows another sectional view of a body part with a measuring device attached to it, Figure 3 shows a sectional view of a body part with a measuring device attached to it according to a further embodiment, and Figure 4 shows an auxiliary system comprising a wearable exoskeleton and a wearable measuring device.

[0035] In theFigure 1 and 2 Figure 1 shows a body part 10 of a person with a wearable measuring device 12 attached to the body part 10. In this case, the body part 10 is an arm 10 of the person.

[0036] This shows Figure 1 a cross-section of body part 10, in which the cutting plane is oriented perpendicular to the longitudinal extent of body part 10. Figure 2 shows a longitudinal section of body part 10, in which the sectioning plane is aligned parallel to body part 10. It should be noted that the Figure 1 and 2 These are merely schematic representations, so that the Figure 1 and 2 In particular, no size relationships can be discerned.

[0037] The measuring device 12 comprises a measuring unit 14, which includes two measuring units 16 and 18 for monitoring a skeletal muscle 20 of the person. Figure 2 Is the measuring device 14 opposite the Figure 1Displayed rotated by 90° so that it also appears in Figure 2 Both measurement units 16 and 18 are visible. In the following, measurement unit 16 will be referred to as the first measurement unit 16 and measurement unit 18 as the second measurement unit 18.

[0038] In the illustrated embodiment, the skeletal muscle 20 is the biceps brachii muscle of the arm 10. However, the measuring device 12 can also be used to monitor a different skeletal muscle. Furthermore, the measuring device 12 can also have an additional measuring device to simultaneously monitor several skeletal muscles of the same body part, e.g., the biceps brachii and the triceps brachii muscles.

[0039] The first measuring unit 16 comprises a force sensor 22 and a spring unit 24 associated with the force sensor 22. The second measuring unit 18 also comprises a force sensor 23 and a spring unit 25 associated with the force sensor 23. The lengths of the spring units 24 and 25 are known. The spring constants of the spring units 24 and 25 differ from each other. In this case, the spring constant of the spring unit 24 is greater than the spring constant of the spring unit 25. Preferably, the spring constants of the spring units 24 and 25 differ from each other by a factor of at least 1.1. One of the spring constants is then at least 10% greater than the other.

[0040] In the illustrated embodiment, the spring units 24 and 25 each comprise a helical spring. Such a configuration of the spring units 24 and 25 is preferred. In other embodiments, however, the spring units 24 and 25 can also comprise disc springs, gas springs, beam springs, or elastomer springs. Furthermore, the spring units 24 and 25 can also comprise more than a single spring element. In particular, the spring units 24 and 25 each comprise several spring elements, which are connected, for example, in series or in parallel with one another. In such a configuration, the spring constant of the spring units 24 and 25 refers to the equivalent spring constant and not the spring constant of a single spring element.

[0041] The force sensors 22 and 23 are designed to detect a clamping force of the associated spring unit 24 and 25, respectively. In this case, the force sensors 22 and 23 each comprise a force-dependent electrical resistance.

[0042] The measuring device 12 also includes a holding device 26 for attaching the measuring device 14 to the body part 10. In the present embodiment, the holding device 26 comprises a deformable retaining band 28. Figure 2 The retaining strap 28 lies outside the cutting plane and is therefore not visible.

[0043] In addition to the retaining strap 28, the holding device 26 comprises a rigid support structure 30, which in this case is plate-shaped. The measuring units 16 and 18 are arranged side by side on the support structure 30 and extend away from the support structure 30 in the same direction. In this case, the force sensors 22 and 23 are directly connected to the support structure 30.

[0044] The measuring device 14 is attached to the body part 10 by means of the holding device 26 such that the spring units 24 and 25 can be tensioned by different sections of the skeletal muscle 20. When the skeletal muscle 20 is tensed, the sections of the skeletal muscle 20 consequently exert tension forces on the spring units 24 and 25.

[0045] A skeletal muscle can be viewed as a grid or array of spring units with the same spring constant. This is in Figure 2The springs inside the skeletal muscle 20 are indicated by dashed lines. The spring constant of the skeletal muscle 20 varies with the degree of tension of the skeletal muscle. When arranged as intended, the spring units 24 and 25, together with the section of the skeletal muscle 20 through which they can be tensioned, each form a spring arrangement 29 or 31, respectively, with a different equivalent spring constant. As mentioned previously, the spring units 24 and 25 differ from each other with respect to their spring constants. This results in the spring arrangements 29 and 31 also differing with respect to their equivalent spring constants. Because the spring constants of the spring units 24 and 25 differ, the spring units 24 and 25 are subjected to different tension forces when the skeletal muscle 20 is contracted.Specifically, spring unit 24, with the higher spring constant, is subjected to a greater clamping force than spring unit 25, with the lower spring constant. Accordingly, the clamping forces detected by force sensors 22 and 23 also differ in magnitude.

[0046] The measuring device 12 also includes an evaluation unit 32, which is integrated into the supporting structure 30. The evaluation unit 32 is designed to determine a spring constant of the skeletal muscle 20 as a function of sensor signals from the force sensors 22 and 23. The spring constant of the skeletal muscle 20 describes its stiffness. For example, the evaluation unit 32 determines the spring constant of the skeletal muscle 20 according to a lookup table, a characteristic map, a calculation rule, or a computational network.

[0047] The spring units 24 and 25 each have a first end section and a second end section. The end sections are axial sections of the spring units 24 and 25. In the embodiment shown in the figures, the spring units 24 and 25 are operatively connected to the force sensors 22 and 23, respectively, via their first end sections. The free second end sections connect the spring units 24 and 25 to the skeletal muscle 20.

[0048] As from Figure 1 As can be seen, the spring units 24 and 25 extend radially to the body part 10. Given this orientation of the spring units 24 and 25, the skeletal muscle 20 exerts tension forces on the spring units 24 and 25, acting along their longitudinal axis. These tension forces compress the spring units 24 and 25.

[0049] At the in Figure 1In the illustrated embodiment, the spring units 24 and 25 are in direct contact with the user's skin. Alternatively, the measuring device 12 can also be worn over clothing, thus increasing user comfort.

[0050] Figure 3 Figure 12 shows a wearable measuring device according to a further embodiment. In the case of the Figure 3 In the illustrated measuring device 12, the spring units 24, 25 extend circumferentially along the skeletal muscle 20 of the body part 10. It should be noted that in Figure 3 Only measuring unit 16 is visible. The other measuring unit 18 is axially offset from measuring unit 16 with respect to the longitudinal center axis of body part 10 and is therefore located outside the image plane. The spring unit 24 is in Figure 3In simplified terms, it is represented as a coil spring. However, the spring unit 24 could also be, for example, a textile elastic band. When the monitored skeletal muscle 20 is tensed, the spring units 24, 25 are subjected to a radially outward acting tension force and are thereby stretched. This stretched state of the spring unit 24 is in Figure 3 Indicated by dashed lines.

[0051] Figure 4 Figure 34 shows a schematic representation of an auxiliary system 34. The auxiliary system 34 includes, by way of example, the one described above and in [reference to be added]. Figure 1 The illustrated wearable measuring device 12. Furthermore, the auxiliary system 34 includes a wearable exoskeleton 36, which is in Figure 3 This is merely a simplified representation. The exoskeleton 36 comprises a controllable actuator 38, which is integrated in this case into a joint 40 of the exoskeleton 36.

[0052] Furthermore, a control device, not shown in the figures, is present. The control device is designed to actuate the actuator 38 based on information provided by the measuring device 12. In particular, the control device is also integrated into the joint 40. However, the control device can also be implemented externally with respect to the exoskeleton 36. Specifically, the control device actuates the actuator 38 based on the spring constant of the skeletal muscle 20 determined by the evaluation unit 32. With such actuation of the actuator 38, the exoskeleton 36 can support the function of the skeletal muscle 20, thereby protecting the user's joint and muscle system.

Claims

1. Wearable measuring apparatus (12), comprising a measuring device (14) which has at least two measuring units (16, 18) for monitoring a skeletal muscle (20) of a person, comprising a holding device (26) for attaching the measuring device (14) to a body part (10) of the person, which body part has the skeletal muscle (20), and comprising an evaluation unit (32), characterized in that the measuring units (16, 18) each comprise a force sensor (22, 23) and an associated spring unit (24, 25), the spring units (24, 25) differing from each other in their spring constant, in that the measuring units (16, 18) can be attached to the body part (10) in such a way that the spring units (24, 25) can be tensioned by a portion of the skeletal muscle which is different in each case (20), in that each force sensor (22, 23) is designed to detect a tension force of the correspondingly associated spring unit (24, 25), and in that the evaluation unit (32) is designed to determine a spring constant of the skeletal muscle (20) depending on sensor signals from the force sensors (22, 23).

2. Measuring apparatus (12) according to claim 1, characterized in that at least one of the spring units (24, 25) comprises a metal spring or an elastomer spring.

3. Measuring apparatus (12) according to any of the preceding claims, characterized in that at least one of the spring units (24, 25) is cylindrical, helical, planar, bar-shaped, band-shaped or strand-shaped.

4. Measuring apparatus (12) according to any of the preceding claims, characterized in that at least one of the spring units (24, 25) comprises a gas spring.

5. Measuring apparatus (12) according to any of the preceding claims, characterized in that at least one of the force sensors (22, 23) comprises at least one force-dependent electrical resistor, at least one force-dependent electrical capacitor, at least one force-dependent electrical inductor, or at least one piezoelectric element.

6. Measuring apparatus (12) according to any of the preceding claims, characterized in that the spring units (24, 25) have a first end portion and a second end portion, the associated force sensor (22, 23) being operatively connected to the spring unit (24, 25) via the first end portion, and the spring unit (24, 25) being operatively connectable or operatively connected to the skeletal muscle (20) via the second end portion.

7. Measuring apparatus (12) according to any of claims 1 to 5, characterized in that the spring units (24, 25) have a first end portion and a second end portion, the associated force sensor (22, 23) being operatively connected to the spring unit (24, 25) via the first end portion, and the spring unit (24, 25) being operatively connectable or operatively connected to the skeletal muscle (20) via the force sensor (22, 23).

8. Measuring apparatus (12) according to any of the preceding claims, characterized in that the measuring device (14) comprises at least three measuring units.

9. Measuring apparatus (12) according to any of the preceding claims, characterized in that the holding device (26) comprises a holding strap (28), a holding cuff or a holding bandage.

10. Measuring apparatus (12) according to any of the preceding claims, characterized in that the holding device (26) comprises a support structure (30), in particular a rigid support structure, the measuring units (16, 18) being arranged on the support structure (30).

11. Measuring apparatus (12) according to any of the preceding claims, characterized in that the spring units (24, 25) extend radially relative to the body part (10) when the measuring apparatus (12) is arranged as intended.

12. Measuring apparatus (12) according to any of claims 1 to 10, characterized in that the spring units (24, 25) extend along the skeletal muscle (20) in the circumferential direction of the body part (10) when the measuring apparatus (12) is arranged as intended.

13. Assistance system (34), comprising a wearable exoskeleton (36) having at least one controllable actuator (38), at least one wearable measuring apparatus (12) according to any of claims 1 to 12, and a control device, which is designed to control the actuator (38) depending on information that can be provided by the measuring apparatus (12).

14. Method for determining a muscle hardness of a skeletal muscle (20) of a person, in particular by means of a measuring apparatus (12) according to any of claims 1 to 12, wherein at least two spring units (24, 25), which differ from each other in their spring constant, are attached to a body part (10) of the person, which body part has the skeletal muscle (20), in such a way that the spring units (24, 25) can be tensioned by a portion of the skeletal muscle (20) which is different in each case, wherein tension forces of the spring units (24, 25) are detected, and wherein, depending on the detected tensioning forces, a spring constant of the skeletal muscle (20) is determined as muscle hardness.