Knee joint, prosthetic leg, method for controlling knee joint, and control program for knee joint

Abstract

To provide a knee joint or a prosthetic leg that can be set to a bicycle mode at the right timing.SOLUTION: A knee joint 20 comprises: a thigh connection, a leg part, an angle acquisition unit 110, a rotational resistance control unit 100 an a setting unit 140. A socket corresponding to the user's thigh part is connected to the thigh connection. The leg part is connected to the thigh connection to be rotatable around a knee axis. The angle acquisition unit 110 acquires at least one of the thigh angle which is an inclination angle of the axis of the socket relative to a vertical line and the knee angle which is an angle formed by the axis of the socket and the axis of the leg part around the knee axis. The rotational resistance control unit 100 controls the rotational resistance of the knee axis on the basis of the angle acquired by the angle acquisition unit 110. The setting unit 140 sets the operational mode of the rotational resistance control unit 100 to a bicycle mode when at least one of the thigh angle and the knee angle meets a prescribed condition.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present invention relates to a knee joint, a prosthetic leg, a method for controlling a knee joint, and a program for controlling a knee joint. [Background technology]

[0002] 2. Description of the Related Art A known knee joint or prosthetic leg attached to the lower limb of a person who has lost a leg due to injury or illness controls the rotational resistance of the knee axis according to the walking phase of the user (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Special Publication No. 2013-510605 Summary of the Invention [Problem to be solved by the invention]

[0004] In a knee joint or prosthetic leg, it is preferable to control the rotational resistance of the knee axis differently when riding a bicycle than when walking. However, the technology described in Patent Document 1 could not automatically set the bicycle mode.

[0005] In view of the above problems, an object of the present invention is to provide a knee joint and prosthetic leg that can be set to bicycle mode at an appropriate time. [Means for solving the problem]

[0006] In order to solve the above problems, a knee joint of one aspect of the present invention comprises a thigh connection part to which a socket corresponding to the thigh of a user is connected, a lower leg part connected to the thigh connection part so as to be rotatable around a knee axis, an angle acquisition part that acquires at least one of a thigh angle, which is the inclination angle that the axis of the socket makes with respect to a vertical line, and a knee angle, which is the angle between the axis of the socket and the axis of the lower leg part about the knee axis, a rotational resistance control part that controls the rotational resistance of the knee axis on the basis of the angle acquired by the angle acquisition part, and a setting part that sets the operation mode of the rotational resistance control part to a bicycle mode when at least one of the thigh angle and the knee angle satisfies a predetermined condition.

[0007] A prosthetic leg of one embodiment of the present invention comprises a socket corresponding to a user's thigh, a thigh connection portion to which the socket is connected, a lower leg portion connected to the thigh connection portion so as to be rotatable around a knee axis, an angle acquisition unit that acquires at least one of a thigh angle, which is the inclination angle that the axis of the socket makes with respect to a vertical line, and a knee angle, which is the angle that the axis of the socket and the axis of the lower leg portion make around the knee axis, a rotational resistance control unit that controls the rotational resistance of the knee axis based on the angle acquired by the angle acquisition unit, and a setting unit that sets the operating mode of the rotational resistance control unit to bicycle mode when at least one of the thigh angle and the knee angle satisfies a predetermined condition.

[0008] A control method for a knee joint according to one aspect of the present invention is a control method for a knee joint comprising a thigh connection part to which a socket corresponding to a user's thigh is connected, and a lower leg part connected to the thigh connection part so as to be rotatable around a knee axis, the control method including the steps of: acquiring at least one of a thigh angle, which is an inclination angle that the axis of the socket makes with respect to a vertical line, and a knee angle, which is an angle that the axis of the socket and the axis of the lower leg part make around the knee axis; controlling rotational resistance of the knee axis based on the acquired angle; and setting an operation mode for the step of controlling rotational resistance of the knee axis to a bicycle mode when at least one of the thigh angle and the knee angle satisfies a predetermined condition.

[0009] A control program for a knee joint according to one embodiment of the present invention is a control program for a knee joint comprising a thigh connection part to which a socket corresponding to the thigh of a user is connected, and a lower leg part connected to the thigh connection part so as to be rotatable around a knee axis, the control program causing a computer to execute the following steps: acquiring at least one of a thigh angle, which is an angle of inclination that the axis of the socket makes with respect to a vertical line, and a knee angle, which is an angle between the axis of the socket and the axis of the lower leg part around the knee axis; controlling rotational resistance of the knee axis based on the acquired angle; and setting the operation mode of the step of controlling rotational resistance of the knee axis to a bicycle mode when at least one of the thigh angle and the knee angle satisfies a predetermined condition.

[0010] In addition, any combination of the above, or mutual substitution of the components or expressions of the present invention among methods, devices, programs, temporary or non-temporary storage media recording programs, systems, etc., are also valid aspects of the present invention. Effect of the Invention

[0011] According to the present invention, it is possible to provide a knee joint and prosthetic leg that can be set to bicycle mode at an appropriate time. [Brief description of the drawings]

[0012] [Figure 1] 1 is a diagram showing a schematic configuration of a knee joint and a prosthetic leg according to a first embodiment. FIG. [Diagram 2] 1 is a diagram showing a schematic configuration of a knee joint and a prosthetic leg according to a first embodiment. FIG. [Diagram 3] FIG. 2 is a schematic diagram showing the relationship between the angles when a user of the prosthetic leg in FIG. 1 is riding a bicycle. [Figure 4] FIG. 3 is a schematic diagram showing the cylinder and control mechanism of FIG. 2. [Diagram 5] Fig. 5(a) is a diagram showing the flow of oil during bending motion of the knee joint of Fig. 1. Fig. 5(b) is a diagram showing the flow of oil during extension motion of the knee joint of Fig. 1. [Figure 6]It is a diagram schematically showing the functional blocks of the knee joint of FIG. 1. [Figure 7] It is a diagram showing an example of the time change of the thigh angle θ from when the user of the prosthetic leg of FIG. 1 gets on a bicycle from a walking state, then gets off the bicycle and transitions back to the walking state. [Figure 8] It is a diagram showing an example of the relationship between the thigh angle θ and the knee angle θ during the period when the user of the prosthetic leg of FIG. 1 is riding a bicycle. [Figure 9] It is a diagram schematically showing the circumference along which the pedal of the bicycle rotates during the period when the user of the prosthetic leg of FIG. 1 is riding a bicycle. [Figure 10] It is a flowchart showing an example of the processing by the control unit of the knee joint of FIG. 1. [Figure 11] It is a diagram schematically showing the functional blocks of the knee joint and the bicycle according to the second embodiment. [Figure 12] It is a diagram schematically showing the functional blocks of the system according to the third embodiment. [Figure 13] It is a diagram showing an example of the relationship between the usage state of the knee joint determined by the control unit of FIG. 12 and the basis for the determination. [Figure 14] It is a diagram showing an example of the content of power control and rotational resistance control corresponding to each usage state of the knee joint of FIG. 12 that has been determined.

Embodiments for Carrying Out the Invention

[0013] Among the embodiments disclosed in this specification, those composed of a plurality of objects may integrate the plurality of objects, and conversely, those composed of one object can be divided into a plurality of objects. Whether integrated or not, it should be configured so as to achieve the object of the invention.

[0014] Among the embodiments disclosed in this specification, those in which multiple functions are provided in a distributed manner may have some or all of the multiple functions integrated together, and conversely, those in which multiple functions are provided in a distributed manner may have some or all of the multiple functions integrated together. Regardless of whether the functions are integrated or distributed, it is sufficient that the configuration is such that the object of the invention can be achieved.

[0015] In addition, separate components that have something in common are distinguished by adding "first," "second," etc. to the beginning of their names, and these are omitted when referring to them collectively. In addition, terms including ordinal numbers such as first and second are used to describe various components, but these terms are used only for the purpose of distinguishing one component from other components, and do not limit the components.

[0016] A knee joint according to one aspect of the present disclosure comprises a thigh connection part to which a socket corresponding to the thigh of a user is connected, a lower leg part connected to the thigh connection part so as to be rotatable about a knee axis, an angle acquisition part that acquires at least one of a thigh angle which is an inclination angle that the axis of the socket makes with respect to a vertical line and a knee angle which is an angle between the axis of the socket and the axis of the lower leg part about the knee axis, a rotational resistance control part that controls the rotational resistance of the knee axis based on the angle acquired by the angle acquisition part, and a setting part that sets the operation mode of the rotational resistance control part to a bicycle mode when at least one of the thigh angle and the knee angle satisfies a predetermined condition. With this configuration, the bicycle mode can be set at an appropriate time based on the characteristics of the operation of the knee joint.

[0017] As an example, the setting unit sets the bicycle mode on the condition that at least one of the thigh angle is greater than a first set threshold and the knee angle is greater than a second set threshold. In this case, the bicycle mode can be set based on the characteristics of the knee joint movement when the knee joint user rides a bicycle, thereby reducing the risk that the bicycle mode is set during other movement states such as walking.

[0018] As one example, the setting unit sets the bicycle mode under at least one of the conditions that the thigh angle exceeds the first set threshold and the sign of the thigh angular velocity, which is the angular velocity of the thigh angle, repeatedly reverses between positive and negative, and that the knee angle exceeds the second set threshold and the sign of the knee angular velocity, which is the angular velocity of the knee angle, repeatedly reverses between positive and negative. In this case, the bicycle mode is set after the user of the knee joint rotates the bicycle pedal one or more times, thereby further reducing the risk that the bicycle mode is set during another operating state.

[0019] As an example, while the bicycle mode is set, the setting unit cancels the bicycle mode under at least one of the conditions that the thigh angle is equal to or less than a first release threshold and that the knee angle is equal to or less than a second release threshold. In this case, since the bicycle mode is canceled when it is estimated that the user of the knee joint has dismounted from the bicycle, it is possible to reduce the risk of the user of the knee joint bending and falling when dismounting from the bicycle and putting their foot on the ground.

[0020] As one example, while the bicycle mode is set, the setting unit cancels the bicycle mode on the condition that the angle deviates from a predetermined elliptical orbit in an orthogonal coordinate system having the thigh angle as one coordinate axis and the knee angle as the other coordinate axis. In this case, the bicycle mode is continued or canceled based on the specific knee joint movement when a knee joint user rides a bicycle, so that it is possible to more reliably determine whether a knee joint user is riding a bicycle.

[0021] As an example, the angle acquisition unit acquires at least two angles from the thigh angle, the knee angle, and the lower leg angle, which is an inclination angle of the axis of the lower leg with respect to a vertical line, and the setting unit cancels the bicycle mode on the condition that the bicycle mode deviates from a predetermined elliptical orbit in an orthogonal coordinate system having any two angles from the thigh angle, the knee angle, and the lower leg angle as coordinate axes. In this case, the bicycle mode is continued or canceled based on the specific knee joint movement when a knee joint user rides a bicycle, so it can be more reliably determined whether or not a knee joint user is riding a bicycle.

[0022] As one example, the setting unit sets the bicycle mode on the condition that a predetermined elliptical orbit is traced in an orthogonal coordinate system having the thigh angle as one coordinate axis and the knee angle as the other coordinate axis. In this case, the bicycle mode can be set based on a specific knee joint movement when a knee joint user rides a bicycle.

[0023] As an example, the angle acquisition unit acquires at least two angles from the thigh angle, the knee angle, and the lower leg angle, which is an inclination angle of the axis of the lower leg with respect to a vertical line, and the setting unit sets the bicycle mode on the condition that a predetermined elliptical orbit is traced in an orthogonal coordinate system having any two angles from the thigh angle, the knee angle, and the lower leg angle as coordinate axes. In this case, the bicycle mode can be set based on the specific knee joint movement when a knee joint user rides a bicycle.

[0024] As an example, the rotational resistance control unit reduces the rotational resistance of the knee axis when the bicycle mode is set, which can reduce heat generation and power consumption of the knee joint when the bicycle mode is set.

[0025] As an example, when the bicycle mode is set, the rotational resistance control unit increases the rotational resistance of the knee axis when at least one of the thigh angle being within a first angle range and the knee angle being within a second angle range is satisfied. In this case, a user of the knee joint can strongly step on the pedals of the bicycle to generate propulsive force for the bicycle.

[0026] Hereinafter, the present disclosure will be described based on preferred embodiments with reference to the drawings. In the embodiments and modified examples, the same or equivalent components and members are given the same reference numerals, and duplicated descriptions are omitted as appropriate. In addition, the dimensions of the members in each drawing are enlarged or reduced as appropriate for ease of understanding. In addition, some of the members that are not important for explaining the embodiments are omitted in each drawing.

[0027] [First embodiment] Hereinafter, the first embodiment will be described with reference to the drawings. FIG. 1 and FIG. 2 show a schematic configuration of a knee joint 20 and a prosthetic leg 10 according to the first embodiment. The prosthetic leg 10 includes a plastic socket 11 corresponding to the user's thigh, a thigh connection part 22 to which the socket 11 is connected, a lower leg part 21 connected to the thigh connection part 22 so as to be rotatable around a knee axis 23, and a foot part 12 connected to the lower end of the lower leg part 21. In this specification, the "front-rear direction" refers to the front-rear direction from the viewpoint of the user of the prosthetic leg 10, the front being the right side of FIG. 1, and the rear being the left side of FIG. 1. Similarly, in this specification, the "left-right direction" refers to the left-right direction from the viewpoint of the user of the prosthetic leg 10, the left being the back side of the paper in FIG. 1, and the right being the front side of the paper in FIG. 1.

[0028] The thigh connection part 22 and the crus part 21 rotate relatively around a knee axis 23 that is provided at their connection and is perpendicular to the plane of the paper in Fig. 1, thereby bending and straightening the knee joint 20, which corresponds to the knee joint. The foot part 12 is formed of an elastic member, and the relative position is kept constant by elasticity when the load from the ground is small, such as when not touching the ground or standing upright. When the load from the ground is large, such as when walking, the elastic member elastically deforms to generate a propulsive force that pushes off the ground.

[0029] The knee joint 20 comprises a lower leg part 21 formed by a high-strength frame, a thigh connection part 22 connected to a socket 11 corresponding to the user's thigh and rotatably connected to the lower leg part 21 around a knee axis 23, a cylinder 30 that limits or allows the rotational movement around the knee axis 23, i.e., the bending and straightening movement of the knee joint 20, and a control mechanism 40 that drives the cylinder 30. Note that Fig. 1 shows the knee joint 20 in which the thigh connection part 22 and the lower leg part 21 are connected by a single link and are rotatable around the single knee axis 23 located at a specific position. The knee joint 20 may be such that the thigh connection part 22 and the lower leg part 21 are connected by, for example, two links, one in the front and one in the back, and be rotatable around the knee axis 23 as a rotation center that is formed virtually and instantaneously inside a total of four connection points.

[0030] The amount of extension and contraction of the cylinder 30 and the knee angle, which is the rotation angle of the knee joint 20 around the knee axis 23, correspond approximately one-to-one. A knee angle sensor 60 that detects the knee angle of the knee joint 20 by measuring the amount of extension and contraction of the cylinder 30 is provided near the cylinder 30 and the thigh connection part 22. The knee angle detected by the knee angle sensor 60 is used by the control part 50. The knee angle sensor 60 can be configured with any sensor that can measure the amount of extension and contraction of the cylinder 30, but can be configured with, for example, a Hall element that can detect the position of a magnet embedded in the piston rod 34 that moves with the extension and contraction of the cylinder 30. The knee angle is the angle formed around the knee axis 23 by the axis of the socket 11 corresponding to the user's thigh and the axis of the lower leg part 21. For example, as shown in FIG. 1, when the user of the prosthetic leg 10 stands upright and the axis of the socket 11 and the axis of the lower leg part 21 are on a straight line, the knee angle is 0 degrees. In addition, when the user of the prosthetic leg 10 sits down and the axis of the socket 11 is changed to a horizontal direction while the axis of the lower leg 21 remains vertical in FIG. 1, the knee angle becomes 90 degrees.

[0031] The inertial sensor 75 provided on the lower leg 21 detects the posture and movement of the lower leg 21 by measuring the speed (angular velocity) and / or acceleration (angular acceleration) in the translational and / or rotational directions of the three axes governing the movement of the lower leg 21. As described later, among the postures of the lower leg 21 detected by the inertial sensor 75, the lower leg angle, which is the inclination angle of the axis of the lower leg 21 with respect to the vertical line, is used for controlling the knee joint 20 of this embodiment. Note that the lower leg angle and the thigh angle described later can be detected in two directions, the front-rear direction and the left-right direction, and can each be used for controlling the knee joint 20, but hereinafter, they refer to the inclination angle in the front-rear direction unless otherwise specified. The inertial sensor 75 can be installed at any location on the lower leg 21, but for example, it is mounted together with the control unit 50 on a control board installed on the outer periphery of the cylinder 30.

[0032] From the knee angle acquired by the knee angle sensor 60 and the lower leg angle acquired by the inertial sensor 75, the thigh angle, which is the inclination angle of the axis of the socket 11 corresponding to the user's thigh with respect to the vertical line, can be calculated. That is, since the lower leg angle is the inclination of the lower leg 21 from the vertical line and the knee angle is the inclination of the axis of the socket 11 from the axis of the lower leg 21, the thigh angle, which is the inclination of the axis of the socket 11 from the vertical line, can be calculated by adding up the two. Note that the thigh angle may be directly measured by providing an inertial sensor in the socket 11 or the thigh connection part 22. In this case, the lower leg angle can be calculated based on the measured knee angle and thigh angle. Similarly, even if the knee angle sensor 60 is not provided, the knee angle can be calculated by measuring the thigh angle and lower leg angle. That is, the thigh angle, lower leg angle, and knee angle are in such a relationship that if information on two of these angles is obtained, information on the other angle can also be obtained.

[0033] FIG. 3 is a schematic diagram showing the relationship between the angles when a user of the prosthesis 10 is riding a bicycle. The thigh angle θ1 is the inclination angle of the axis of the socket 11 with respect to the vertical line VA. The thigh angle θ1 is positive when the axis of the socket 11 is inclined forward with respect to the vertical line VA, and negative when it is inclined backward. In the example shown in FIG. 3, the axis of the socket 11 is inclined forward with respect to the vertical line VA, so the thigh angle θ1 takes a positive value. The lower leg angle θ2 is the inclination angle of the axis of the lower leg 21 with respect to the vertical line VA. The lower leg angle θ2 is positive when the axis of the lower leg 21 is inclined forward with respect to the vertical line VA, and negative when it is inclined backward. In the example shown in FIG. 3, the axis of the lower leg 21 is inclined backward with respect to the vertical line VA, so the lower leg angle θ2 takes a negative value. The knee angle θ3 is the angle between the axis of the socket 11 and the axis of the lower leg 21 around the knee axis 23. The knee angle θ3 is positive when the axis of the lower leg 21 is inclined backward with respect to the axis of the socket 11, and negative when it is inclined forward. In the example shown in FIG. 3, the axis of the lower leg 21 is inclined backward with respect to the axis of the socket 11, and the knee angle θ3 is a positive value. As shown in FIG. 3, the absolute value of the knee angle θ3 is the sum of the absolute value of the thigh angle θ1 and the absolute value of the lower leg angle θ2. As described above, the thigh angle θ1 and the knee angle θ3 are positive values, and the lower leg angle θ2 is a negative value, so the thigh angle θ1, the lower leg angle θ2, and the knee angle θ3 satisfy the relational expression "θ1=θ2+θ3".

[0034] Returning to Figures 1 and 2, as a sensor other than the knee angle sensor 60 and the inertial sensor 75, a load sensor 70 that detects the load acting between the lower leg 21 and the foot 12 may be provided at the lower end of the lower leg 21. The load sensor may be provided at the thigh connecting part 22 or at the knee part between the thigh connecting part 22 and the lower leg 21. Also, a temperature sensor 80 that measures the temperature of the oil in the cylinder 30 may be attached to the outer wall or inner wall of the cylinder 30. The measurement information of each of these sensors is used by the control unit 50.

[0035] A vibrator 85 may be provided on the thigh connection part 22 or the lower leg part 21. The vibrator 85 notifies or alerts the user wearing the prosthetic leg 10 by vibration, and is controlled by the control part 50.

[0036] The control unit 50 controls the control mechanism 40 based on measurement information from various sensors, such as the knee angle sensor 60, load sensor 70, inertia sensor 75, and temperature sensor 80, to control the resistance to the extension and contraction movement of the cylinder 30, i.e., the rotational resistance of the knee axis 23 during the bending movement of the knee joint 20. A battery 55 that supplies power to each component of the knee joint 20 is connected to the control unit 50. Note that although the control mechanism 40, control unit 50, and battery 55 are shown outside the knee joint 20 in Figure 2, they may be provided inside the lower leg 21 as components of the knee joint 20.

[0037] The cylinder 30 is a hydraulic cylinder that uses oil as a working fluid to generate resistance and thereby limits or allows the bending or extension movement of the knee joint 20. The cylinder 30 is supported by an upper support point 31 provided near the knee axis 23 that rotatably connects the thigh connection part 22 and the lower leg part 21, and a lower support point 32 connected to a part of the lower leg part 21, and can be extended and contracted between the two support points. In a contraction process in which the cylinder length is reduced, a bending movement is performed in which the lower leg part 21 rotates clockwise in FIG. 1 around the knee axis 23 relative to the thigh connection part 22. In an extension process in which the cylinder length is increased, an extension movement is performed in which the lower leg part 21 rotates counterclockwise in FIG. 1 around the knee axis 23 relative to the thigh connection part 22. Here, the cylinder length refers to the length between the upper support point 31 and the lower support point 32 of the cylinder 30.

[0038] Next, the cylinder 30 and the control mechanism 40 will be described with reference to Fig. 4. The cylinder 30 has a cylinder tube 33, a piston rod 34 that is inserted from one end side (the right end side in Fig. 4) of the cylinder tube 33 and is movable along the longitudinal direction of the cylinder tube 33 (the left-right direction in Fig. 4), and a piston 35 that is fixed to the piston rod 34 inside the cylinder tube 33 and is slidable in the longitudinal direction along the inner wall of the cylinder tube 33. The inside of the cylinder tube 33 is divided by the piston 35 into a first cavity 36 at one end side (the right end side in Fig. 4) and a second cavity 37 at the other end side (the left end side in Fig. 4). The first cavity 36 and the second cavity 37 are filled with oil, which is a working fluid.

[0039] The control mechanism 40 is a hydraulic drive mechanism that hydraulically drives the cylinder 30 to extend and retract. The control mechanism 40 has an extension-side hydraulic circuit 41 and a flexion-side hydraulic circuit 42, each of which is connected to the cylinder 30. The extension-side hydraulic circuit 41 and the flexion-side hydraulic circuit 42 each communicate with the first cavity 36 at one end and with the second cavity 37 at the other end. The extension-side hydraulic circuit 41 has an extension-side valve 43 and an extension-side check valve 44, which serve as valves that can open and close the flow path of oil that generates rotational resistance of the knee axis 23. By opening the extension-side valve 43, oil can flow through the extension-side hydraulic circuit 41, but the extension-side check valve 44 acts to allow the oil to flow only in the direction from the first cavity 36 to the second cavity 37, and not in the reverse direction.

[0040] The bending side hydraulic circuit 42 has a bending side valve 45 and a bending side check valve 46 as valves that can open and close the flow path of oil that generates rotational resistance of the knee axis 23. By opening the bending side valve 45, oil can flow through the bending side hydraulic circuit 42, but due to the action of the bending side check valve 46, the oil flows only in the direction from the second cavity 37 to the first cavity 36, and does not flow in the opposite direction. The opening degree of the extension side valve 43 and the bending side valve 45 is individually controlled by the control unit 50. The opening degree of each valve can be any value between fully open (maximum opening degree) and fully closed (minimum opening degree). When each valve is fully closed, the flow of oil is blocked and the hydraulic resistance is maximum. In addition, as the opening degree of each valve increases toward full opening, the cross-sectional area through which oil can flow within each valve increases, and the hydraulic resistance decreases.

[0041] FIG. 5(a) shows the flow of oil during bending of the knee joint 20. Bending is a contraction process in which the cylinder length becomes smaller, and the piston rod 34 contracts to the left in FIG. 5, and the piston 35 moves to the retraction side. The oil pushed out from the second cavity 37 by the movement of the piston 35 cannot flow through the extension-side hydraulic circuit 41 having the extension-side check valve 44, so it flows through the bending-side hydraulic circuit 42 and flows into the first cavity 36. At this time, if the opening of the bending-side valve 45 is reduced, it is possible to make it difficult for oil to flow through the bending-side hydraulic circuit 42, thereby limiting the bending motion of the knee joint 20. In this way, the control unit 50 controls the opening of the bending-side valve 45 to control the rotational resistance of the knee shaft 23 during bending of the knee joint 20.

[0042] FIG. 5(b) shows the flow of oil during the extension operation of the knee joint 20. Extension is an extension process in which the cylinder length increases, and the piston rod 34 extends to the right in FIG. 5, and the piston 35 moves to the extrusion side. The oil pushed out from the first cavity 36 by the movement of the piston 35 cannot flow through the bending side hydraulic circuit 42 having the bending side check valve 46, so it flows through the extension side hydraulic circuit 41 and flows into the second cavity 37. At this time, if the opening of the extension side valve 43 is reduced, the oil can be made less likely to flow through the extension side hydraulic circuit 41, so the extension operation of the knee joint 20 can be limited. In this way, the control unit 50 controls the opening of the extension side valve 43 to control the rotation resistance of the knee axis 23 during the extension operation of the knee joint 20. The control function of the control unit 50 shown in FIGS. 5(a) and 5(b) corresponds to the rotation resistance control unit 100 described later.

[0043] Returning to FIG. 2, the various sensors provided in the prosthetic leg 10 will be described in more detail.

[0044] The knee angle sensor 60 measures the extension / retraction position of the piston rod 34. For example, the position of a magnet attached to the piston rod 34 is measured by a magnetic sensor provided inside the cylinder tube 33. Since there is an approximately one-to-one correspondence between the extension / retraction position of the piston rod 34 and the knee angle of the knee joint 20 or the rotation angle of the knee axis 23, the knee angle sensor 60 can convert the detected extension / retraction position of the piston rod 34 into the knee angle of the knee joint 20. The calculation for converting the extension / retraction position of the piston rod 34 into the knee angle of the knee joint 20 may be performed by the control unit 50. In this case, the knee angle sensor 60 measures the extension / retraction position of the piston rod 34 and provides it to the control unit 50.

[0045] The temperature sensor 80 measures the temperature of the cylinder 30 or the temperature of the oil in the cylinder 30 and, for example, detects that the cylinder 30 has become hot due to heat generation caused by hydraulic resistance, and transitions to a high temperature mode in which the operation of the knee joint 20 is restricted. In addition, the hydraulic resistance changes in response to temperature changes due to the physical properties of the oil, but the control unit 50 can realize the desired hydraulic resistance by controlling the control mechanism 40 in response to the temperature measured by the temperature sensor 80. Specifically, a control data set for the control mechanism 40 to realize each value of hydraulic resistance is created for each temperature and stored in the control unit 50. The control unit 50 selects the control data set corresponding to the temperature measured by the temperature sensor 80 and uses it for control.

[0046] 6 shows a schematic diagram of functional blocks of the knee joint 20. The control unit 50 of the knee joint 20 includes an angle acquisition unit 110, an angular velocity acquisition unit 120, a determination unit 130, a setting unit 140, and a rotational resistance control unit 100.

[0047] Each functional block shown in each figure including Fig. 6 can be realized in hardware by electronic elements and mechanical parts such as a computer CPU, and in software by a computer program, but here, functional blocks realized by the cooperation of these are depicted. Therefore, it will be understood by those skilled in the art that these functional blocks can be realized in various forms by combining hardware and software.

[0048] First, an overview of the processing of the control unit 50 in the present embodiment will be described. The angle acquisition unit 110 acquires at least one of the thigh angle θ1 and the knee angle θ3. The rotational resistance control unit 100 controls the extension side valve 43 and the flexion side valve 45 based on the angle acquired by the angle acquisition unit 110, thereby controlling the rotational resistance of the knee axis 23. The determination unit 130 determines whether at least one of the thigh angle θ1 and the knee angle θ3 satisfies a predetermined setting condition. This setting condition is a condition for determining that the user of the prosthetic leg 10 is riding a bicycle. When the determination unit 130 determines that the setting condition is satisfied, the setting unit 140 causes the operation mode of the rotational resistance control unit 100 to be set to the bicycle mode. When the setting unit 140 causes the bicycle mode to be set, the rotational resistance control unit 100 controls the extension side valve 43 and the flexion side valve 45 to, for example, decrease the rotational resistance of the knee axis 23. In this way, since the knee joint 20 sets the bicycle mode based on at least one of the thigh angle θ1 and the knee angle θ3, the bicycle mode can be set at an appropriate timing without requiring an operation by the user of the prosthetic leg 10.

[0049] Also, during the setting of the bicycle mode, the determination unit 130 determines whether at least one of the thigh angle θ1 and the knee angle θ3 satisfies a predetermined release condition. This release condition is a condition for determining that the user of the prosthetic leg 10 has dismounted from the bicycle. When the determination unit 130 determines that the release condition is satisfied, the setting unit 140 releases the bicycle mode. When the setting unit 140 releases the bicycle mode, the rotational resistance control unit 100 controls the extension side valve 43 and the flexion side valve 45 to cancel the decrease in the rotational resistance of the knee axis 23. In this way, since the knee joint 20 releases the bicycle mode based on at least one of the thigh angle θ1 and the knee angle θ3, the bicycle mode can be released at an appropriate timing without requiring an operation by the user of the prosthetic leg 10.

[0050] The processing of the control unit 50 in this embodiment will be described in detail. The angle acquisition unit 110 includes a thigh angle acquisition unit 112, a lower leg angle acquisition unit 114, and a knee angle acquisition unit 116. The lower leg angle acquisition unit 114 acquires the lower leg angle θ2 detected by the inertial sensor 75 constantly or at predetermined time intervals. The knee angle acquisition unit 116 acquires the knee angle θ3 detected by the knee angle sensor 60 constantly or at predetermined time intervals.

[0051] The thigh angle acquisition unit 112 acquires the thigh angle θ1 constantly or at a predetermined time interval. As described above, the thigh angle θ1, the lower leg angle θ2, and the knee angle θ3 satisfy the relational expression "θ1=θ2+θ3". Therefore, the thigh angle acquisition unit 112 can calculate the thigh angle θ1 based on the lower leg angle θ2 acquired by the lower leg angle acquisition unit 114 and the knee angle θ3 acquired by the knee angle acquisition unit 116.

[0052] The angular velocity acquisition unit 120 includes a thigh angular velocity acquisition unit 122 and a knee angular velocity acquisition unit 124. The thigh angular velocity acquisition unit 122 acquires a thigh angular velocity that is the angular velocity of the thigh angle θ1. Specifically, the thigh angular velocity acquisition unit 122 calculates the thigh angular velocity by time-differentiating the thigh angle θ1 acquired by the thigh angle acquisition unit 112. The knee angular velocity acquisition unit 124 acquires a knee angular velocity that is the angular velocity of the knee angle θ3. Specifically, the knee angular velocity acquisition unit 124 calculates the knee angular velocity by time-differentiating the knee angle θ3. Note that, when the inertial sensor 75 can directly measure the lower leg angular velocity that is the angular velocity of the lower leg angle θ2, the thigh angular velocity acquisition unit 122 may calculate the thigh angular velocity based on the lower leg angular velocity acquired by the inertial sensor 75 and the knee angular velocity acquired by the knee angular velocity acquisition unit 124.

[0053] The determination unit 130 includes a set condition determination unit 132 and a release condition determination unit 134. The set condition determination unit 132 determines whether at least one of the thigh angle θ1 and the knee angle θ3 satisfies the set condition of the bicycle mode. Specifically, the set condition determination unit 132 determines, as the set condition, at least one of whether the thigh angle θ1 exceeds a first set threshold value and whether the knee angle θ3 exceeds a second set threshold value. That is, the set condition determination unit 132 may determine, as the set condition, whether the thigh angle θ1 exceeds a first set threshold value or whether the knee angle θ3 exceeds a second set threshold value or whether both of these conditions are satisfied. The first set threshold value is 0° or more. As shown in FIG. 3, when the user of the prosthesis 10 is riding a bicycle, the thigh angle θ1 is always 0° or more, so by setting the first set threshold value to 0° or more, the set condition determination unit 132 can determine that the user of the prosthesis 10 is riding a bicycle.

[0054] In detail, the set condition determination unit 132 may perform the following process. When the thigh angular velocity transitions from negative to positive, that is, when the thigh angle θ1 changes from decreasing to increasing, the set condition determination unit 132 acquires the minimum value of the thigh angle θ1. When the acquired minimum value of the thigh angle θ1 exceeds the first set threshold, the set condition determination unit 132 sets a first flag. When the first flag is set, the set condition determination unit 132 may determine that the set condition is satisfied. The first set threshold has a lower limit of 0° as described above, but the upper limit may be, for example, 30°, and may be any value within the range of 0° to 30°. The first set threshold may be a value that can determine that the user of the prosthetic leg 10 is not walking but is riding a bicycle, depending on the physique of the user of the prosthetic leg 10, the shape and size of the bicycle, and the like. This also applies to other thresholds described later.

[0055] The condition for the setting condition determination unit 132 to set the first flag may further include the following conditions. For example, the condition may be that the minimum value of the thigh angle θ1 is less than a predetermined threshold. This threshold may be, for example, 60° or more and 70° or less. This allows, for example, a state in which the user of the prosthesis 10 is sitting on a chair or the like to be excluded from the determination conditions. For example, the condition may be that the knee angle θ3 is greater than a predetermined threshold. This threshold may be, for example, 30° or more and 50° or less. This threshold is based on the fact that when the user of the prosthesis 10 rides and drives a bicycle, it is normal for the knee not to be fully extended. For example, the condition may be that the knee angular velocity is positive when the thigh angular velocity is positive. This is based on the fact that when the user of the prosthesis 10 rides and drives a bicycle, when the thigh angle θ1 increases by lifting the thigh, the knee joint 20 corresponding to the knee joint is bent and the knee angle θ3 increases. The set condition determination unit 132 may determine that the condition for setting the above-mentioned first flag is met when the thigh angle θ1 is greater than the minimum value of the thigh angle θ1 by a predetermined value, for example, 10° or more. This makes it possible to stably determine the condition for setting the first flag.

[0056] The set condition determination unit 132 may determine, as a set condition for the bicycle mode, at least one of whether the thigh angle θ1 exceeds a first set threshold and the sign of the thigh angular velocity repeatedly reverses between positive and negative, and whether the knee angle θ3 exceeds a second set threshold and the sign of the knee angular velocity repeatedly reverses between positive and negative. That is, the set condition determination unit 132 may determine, as a set condition, whether the thigh angle θ1 exceeds a first set threshold and the sign of the thigh angular velocity repeatedly reverses between positive and negative. The set condition determination unit 132 may also determine, as a set condition, whether the knee angle θ3 exceeds a second set threshold and the sign of the knee angular velocity repeatedly reverses between positive and negative. The set condition determination unit 132 may set the set condition to be satisfied for both of these conditions.

[0057] In detail, the setting condition determination unit 132 may perform the following process. The setting condition determination unit 132 may not determine that the setting condition of the bicycle mode is satisfied even if the above-mentioned first flag is set, and may determine that the setting condition is satisfied only when the second flag and the third flag described below are also set. When the thigh angular velocity becomes negative with the first flag set, the setting condition determination unit 132 erases the minimum value of the thigh angle θ1 and sets the second flag. When the above-mentioned condition for setting the first flag is satisfied with the first flag and the second flag set, the setting condition determination unit 132 sets the third flag. However, when at least one of the following is satisfied before setting the third flag: the thigh angle θ1 is equal to or less than the first setting threshold and the knee angle θ3 is equal to or less than the second setting threshold, the setting condition determination unit 132 determines that the user of the prosthetic leg 10 has dismounted from the bicycle and releases all flags. When all of the first to third flags are set, the setting condition determination unit 132 determines that the setting condition is satisfied. That is, the set condition determination unit 132 determines that the set condition is satisfied when the thigh angle θ1 exceeds the first set threshold value and the sign of the thigh angular velocity repeatedly inverts positive and negative once. In this case, the set condition corresponds to the user of the prosthesis 10 performing the action of pedaling the bicycle one revolution or more.

[0058] In the above-mentioned setting condition, the repeated positive / negative inversion of the signs of the thigh angular velocity and the knee angular velocity is not limited to one positive / negative inversion, but may be multiple positive / negative inversions. By setting multiple positive / negative inversions as the setting condition, the bicycle mode is not set unless the user of the prosthesis 10 rotates the pedals multiple times, but it is possible to more reliably detect that the user is riding a bicycle.

[0059] The release condition determination unit 134 determines whether or not at least one of the thigh angle θ1 and the knee angle θ3 satisfies the release condition of the bicycle mode while the bicycle mode is set. The release condition is a condition for detecting that the user of the prosthesis 10 has dismounted from the bicycle. Specifically, the release condition determination unit 134 determines, as the release condition, at least one of whether or not the thigh angle θ1 is equal to or less than the first release threshold and whether or not the knee angle θ3 is equal to or less than the second release threshold. That is, while the bicycle mode is set, the release condition determination unit 134 may determine, as the release condition, whether or not the thigh angle θ1 is equal to or less than the first release threshold, or whether or not the knee angle θ3 is equal to or less than the second release threshold, or may determine whether or not both of these conditions are satisfied. The first release threshold may be the same as the first set threshold or may be smaller than the first set threshold. The second release threshold may be the same as the second set threshold or may be smaller than the second set threshold.

[0060] FIG. 7 is a diagram showing an example of the change over time in the thigh angle θ1 from when the user of the prosthesis 10 gets on a bicycle from a walking state, gets off the bicycle, and then transitions to a walking state again. In FIG. 7, the vertical axis indicates the thigh angle θ1, and the horizontal axis indicates time. FIG. 7 shows an example in which the first set threshold and the first release threshold are the same value. At the beginning of the time axis shown in FIG. 7, the thigh angle θ1 repeats increasing and decreasing, but at the timing when the thigh angle θ1 changes from decreasing to increasing, the thigh angle θ1 is smaller than the first set threshold, so the set condition determination unit 132 does not set the first flag. After that, at the timing when the minimum value when the thigh angle θ1 changes from decreasing to increasing exceeds the first set threshold, the set condition determination unit 132 sets the first flag. After that, when the thigh angle θ1 changes to decreasing, the set condition determination unit 132 sets the second flag. If the thigh angle θ1 then changes from decreasing to increasing again without becoming equal to or less than the first set threshold, the set condition determination unit 132 sets a third flag and determines that the set condition is met. After that, the thigh angle θ1 repeatedly increases and decreases while the bicycle mode is set, but the bicycle mode setting continues while the thigh angle θ1 is above the release threshold. After that, when the thigh angle θ1 becomes equal to or less than the first release threshold while the bicycle mode is set, the release condition determination unit 134 determines that the release condition is met.

[0061] The release condition determination unit 134 may set the bicycle mode release condition to be deviation from a predetermined elliptical orbit in an orthogonal coordinate system with the thigh angle θ1 as one coordinate axis and the knee angle θ3 as the other coordinate axis. FIG. 8 is a diagram showing an example of the relationship between the thigh angle θ1 and the knee angle θ3 during the period when the user of the prosthesis 10 is riding a bicycle. In FIG. 8, the vertical axis indicates the thigh angle θ1, and the horizontal axis indicates the knee angle θ3. The hatched area in FIG. 8 indicates the range of values ​​that the thigh angle θ1 and the knee angle θ3 take during the period when the user of the prosthesis 10 is riding a bicycle. As shown in FIG. 8, during the period when the user of the prosthesis 10 is riding a bicycle, the prosthesis 10 continues to rotate around the pedal while repeating approximately the same movement, so that the thigh angle θ1 and the knee angle θ3 follow a predetermined elliptical orbit. Therefore, the release condition determination unit 134 can determine that the user of the prosthesis 10 has finished riding a bicycle by setting the condition of deviation from the elliptical orbit area shown by hatching in FIG. 8 as the release condition. In this case, the determination can be made more quickly than when the release condition is determined by a single threshold value. Note that the shape and size of the ellipse may vary depending on the physique of the user of the prosthetic leg 10, the shape and size of the bicycle, and the like.

[0062] The release condition determination unit 134 may determine whether or not the angle deviates from a predetermined elliptical orbit in an orthogonal coordinate system formed by the thigh angle θ1 and the knee angle θ3 by the following process. If the coordinate of the knee angle θ3 at a certain point in time is Xi and the coordinate of the thigh angle θ1 at a certain point in time is Yi, the elliptical orbit can be expressed by the following formula (1). Xi 2 +AXiYi+BYi 2 +CXi+DYi+E=0 (1)

[0063] Here, for formula (1), the least squares method is used to find coefficients A to E so that the sum of the squares of the left-hand side at multiple points in time is minimized, thereby making it possible to calculate the equation of the elliptical orbit. Σ(Xi 2 +AXiYi+BYi 2 +CXi+DYi+E) 2 =0 (2) By partially differentiating the above equation (2) with respect to the coefficients A to E and multiplying both sides of the matrix equation by the inverse matrix, the following equation (3) is obtained.

[0064]

number

[0065] The release condition determination unit 134 can find the coefficients A to E by solving the above formula (3). The release condition determination unit 134 constantly calculates the right side of formula (1) using the found coefficients A to E. Here, the right side of formula (1) is 0 when the elliptical orbit follows a single ellipse, but since the elliptical orbit does not necessarily follow a single ellipse in reality, it varies around 0. Therefore, if the absolute value of the right side of formula (2) is equal to or less than a predetermined threshold, the release condition determination unit 134 can determine that the elliptical orbit is being followed and the release condition is not satisfied, and if the absolute value exceeds the predetermined threshold, the release condition determination unit 134 can determine that the elliptical orbit has been deviated from and the release condition is satisfied.

[0066] The release condition determination unit 134 may determine whether or not the knee angle θ3 deviates from a predetermined elliptical orbit in an orthogonal coordinate system formed by the thigh angle θ1 and the knee angle θ3 by the following process. The release condition determination unit 134 determines whether or not the knee angle θ3 deviates from a predetermined elliptical orbit in an orthogonal coordinate system formed by the thigh angle θ1 and the knee angle θ3 during the period when the user of the prosthesis 10 is riding the bicycle by using the variance σ 1 2 and the variance of thigh angle θ1 σ 2 2 and the covariance σ of the knee angle θ3 and the thigh angle θ1 12 If the vector consisting of the knee angle θ3 and the thigh angle θ1 is expressed as a vector x, and the vector consisting of the average value of the knee angle θ3 and the average value of the thigh angle θ1 is expressed as a vector μ, the Mahalanobis distance d can be obtained from the following equation (4).

[0067]

number

[0068] The release condition determination unit 134 constantly calculates the Mahalanobis distance d. When the Mahalanobis distance d exceeds a predetermined threshold, the release condition determination unit 134 determines that the release condition is satisfied as the elliptical orbit has deviated. The release condition determination unit 134 preferably calculates the Mahalanobis distance d because the calculation load is smaller than when calculating the equation of the elliptical orbit described above. However, the Mahalanobis distance d can be calculated even when the user of the prosthesis 10 is not riding a bicycle, for example, walking normally. Therefore, if data during normal walking is used for the calculation, the Mahalanobis distance d may not exceed the predetermined threshold even if the user of the prosthesis 10 gets off the bicycle. Therefore, it is preferable that the release condition determination unit 134 calculates the Mahalanobis distance d while the bicycle mode is set as described above. In addition, if the user of the prosthesis 10 stops riding a bicycle while riding a bicycle, the average value of the data may be biased. Therefore, for example, the release condition determination unit 134 may be configured to determine that driving is interrupted if the movement speed of the prosthetic leg 10 is equal to or lower than a predetermined threshold value, and not to acquire the thigh angle θ1 and the knee angle θ3 for that period.

[0069] The determination of whether or not the angle deviates from a predetermined elliptical orbit in an orthogonal coordinate system formed by the thigh angle θ1 and the knee angle θ3 may be used in determining the setting condition by the set condition determination unit 132. That is, the set condition determination unit 132 may set the bicycle mode on the condition that the angle follows a predetermined elliptical orbit in an orthogonal coordinate system having the thigh angle θ1 as one coordinate axis and the knee angle θ3 as the other coordinate axis.

[0070] In the above example, a predetermined elliptical orbit in an orthogonal coordinate system with the thigh angle θ1 as one coordinate axis and the knee angle θ3 as the other coordinate axis has been described as the elliptical orbit used by the determination unit 130 for the determination. However, the present invention is not limited to this, and the elliptical orbit used by the determination unit 130 for the determination may be a predetermined elliptical orbit in an orthogonal coordinate system with any two angles of the thigh angle θ1, the knee angle θ3, and the lower leg angle θ2 as the coordinate axes.

[0071] The release condition determination unit 134 may determine the release condition based on information other than the angle obtained by the angle acquisition unit 110 and the angular velocity obtained by the angular velocity acquisition unit 120. For example, the release condition determination unit 134 may determine the release condition based on information from the load sensor 70 that detects the load acting between the above-mentioned lower leg 21 and the foot 12, assuming that the user of the prosthetic leg 10 gets off the bicycle and places the foot on the ground.

[0072] Returning to FIG. 6, the setting unit 140 sets and cancels the bicycle mode based on the determination result of the determination unit 130. In detail, when the setting condition determination unit 132 determines that the setting condition of the bicycle mode is satisfied, the setting unit 140 sets the bicycle mode. When the cancel condition determination unit 134 determines that the cancel condition of the bicycle mode is satisfied, the setting unit 140 cancels the bicycle mode. The setting unit 140 may be capable of setting and canceling an operation mode of the rotational resistance control unit 100 other than the bicycle mode, such as a normal walking mode. The setting unit 140 sets the operation mode of the rotational resistance control unit 100 to the set operation mode by transmitting a signal or the like to the rotational resistance control unit 100.

[0073] The rotational resistance control unit 100 controls the rotational resistance of the knee axis 23 during the extension and bending of the knee joint 20 by controlling the opening degree of each of the extension side valve 43 and the bending side valve 45 based on the operation mode set by the setting unit 140. When the bicycle mode is set, the rotational resistance control unit 100 may reduce the rotational resistance of the knee axis 23 during the extension and bending of the knee joint 20. The reduction in the rotational resistance of the knee axis 23 here means reducing it at least more than the rotational resistance in the normal walking mode. If the rotational resistance of the knee axis 23 is the same as that in the walking mode even during the period when the user of the prosthesis 10 is riding a bicycle, the cylinder 30 may generate heat due to the yielding resistance. In addition, when the user of the prosthesis 10 rides a bicycle, even if the rotational resistance of the knee axis 23 is reduced, the knee joint 20 repeats bending and stretching in accordance with the reciprocating movement of the user's thigh, so the user can ride the bicycle. In this way, the rotational resistance control unit 100 reduces the rotational resistance of the knee axis 23 of the knee joint 20 when the bicycle mode is set, so that heat generation and power consumption of the knee joint 20 can be reduced.

[0074] Furthermore, when the bicycle mode is released, the rotational resistance control unit 100 may stop reducing the rotational resistance of the knee axis 23, i.e., increase the rotational resistance. In this way, the rotational resistance control unit 100 increases the rotational resistance when the bicycle mode is released, which can reduce the risk of bending the knee when, for example, the user of the prosthesis 10 gets off the bicycle and puts his / her foot on the ground.

[0075] As shown in FIG. 6, the control unit 50 may further include a pedal position estimation unit 150. FIG. 9 is a diagram showing a circumference 154 around which the pedal 152 of the bicycle rotates while the user of the prosthetic leg 10 is riding the bicycle. For the sake of explanation, FIG. 9 shows a circumference 154 with an enlarged radius without changing the center position, compared to the circumference that the pedal 152 actually follows when the pedal 152 rotates. The region of the circumference 154 around which the pedal 152 rotates, where the user of the prosthetic leg 10 should press the pedal 152 relatively hard to generate propulsive force on the bicycle via the pedal 152, is set as the pressing range 156. As described above, when the bicycle mode is set, the rotational resistance control unit 100 may reduce the rotational resistance of the knee axis 23 of the knee joint 20, but when the pedal 152 is located in the pressing range 156, it is better to increase the rotational resistance of the knee axis 23 so that the user of the prosthetic leg 10 can press the pedal 152 hard.

[0076] From this viewpoint, the pedal position estimation unit 150 may determine whether or not at least one of the following conditions is satisfied during the bicycle mode setting: the thigh angle θ1 is within a first angle range and the knee angle θ3 is within a second angle range. The first angle range is an angle range in which the pedal 152 is estimated to be located in the depression range 156 if the thigh angle θ1 is within this range. Similarly, the second angle range is an angle range in which the pedal 152 is estimated to be located in the depression range 156 if the knee angle θ3 is within this range. Then, when the pedal position estimation unit 150 determines that at least one of the following conditions is satisfied: the thigh angle is within the first angle range and the knee angle is within the second angle range, the rotational resistance control unit 100 may increase the rotational resistance of the knee axis 23. In other words, when at least one of the following conditions is satisfied: the thigh angle is outside the first angle range and the knee angle is outside the second angle range, the rotational resistance control unit 100 may decrease the rotational resistance of the knee axis 23. As a result, the rotational resistance control unit 100 increases the rotational resistance of the knee axis 23 when it is estimated that the pedal 152 is located in the depression range 156, allowing the user of the prosthesis 10 to press down hard on the pedal 152 to generate propulsive force for the bicycle.

[0077] 10 is a flowchart showing an example of processing by the control unit 50 of the knee joint 20. The angle acquisition unit 110 acquires a thigh angle θ1, a lower leg angle θ2, and a knee angle θ3 (S10). In addition, the angular velocity acquisition unit 120 acquires a thigh angular velocity and a knee angular velocity.

[0078] If the bicycle mode is not set (N in S12), the determination unit 130 determines whether the setting conditions for the bicycle mode are met (S14). If the determination unit 130 determines that the setting conditions are met (Y in S14), the setting unit 140 sets the bicycle mode (S16) and ends the process. On the other hand, if the determination unit 130 determines that the setting conditions are not met (N in S14), the process ends.

[0079] If bicycle mode is set (Y in S12), the determination unit 130 determines whether or not the bicycle mode cancellation conditions are met (S18). If the determination unit 130 determines that the cancellation conditions are met (Y in S18), the setting unit 140 cancels the bicycle mode (S20) and ends the process. On the other hand, if the determination unit 130 determines that the cancellation conditions are not met (N in S18), the process ends. The control unit 50 constantly executes the process of the flowchart in FIG.

[0080] [Second embodiment] Next, a second embodiment will be described. In the drawings and description of the second embodiment, the same or equivalent components and members as those of the first embodiment are denoted by the same reference numerals. Explanations that overlap with the first embodiment will be omitted as appropriate, and the description will focus on the configurations that differ from the first embodiment.

[0081] FIG. 11 is a schematic diagram showing the functional blocks of a knee joint 20A and a bicycle 200 according to the second embodiment. The knee joint 20A and the bicycle 200 are connected to each other so that they can communicate with each other, and as a whole constitute a knee joint system. The communication between the knee joint 20A and the bicycle 200 is short-range wireless communication, such as BLE (Bluetooth (registered trademark) Low Energy). The knee joint 20A differs from the knee joint 20 in that it further comprises a communication unit 90 in addition to the configuration of the knee joint 20 of the first embodiment. The bicycle 200 has each configuration that a normal bicycle has in addition to the configuration shown in FIG. 11, but a description thereof will be omitted.

[0082] Bicycle 200 includes a pedal position sensor 210, a pedal load sensor 220, a control unit 230, and a communication unit 240. Pedal position sensor 210 is a sensor for acquiring position information of the pedal of bicycle 200. Pedal position sensor 210 includes, for example, a rotary encoder, and acquires position information on the circumference on which the pedal rotates. Pedal load sensor 220 is a sensor for acquiring information on the load applied to the pedal of bicycle 200. Pedal load sensor 220 includes, for example, a strain gauge.

[0083] The control unit 230 acquires pedal position information from the pedal position sensor 210 and pedal load information from the pedal load sensor 220. Specifically, the control unit 230 calculates pedal position information based on data received from the pedal position sensor 210. The control unit 230 also calculates pedal load information based on data received from the pedal load sensor 220. The communication unit 240 transmits the pedal position information and load information acquired by the control unit 230 to the knee joint 20A. The communication unit 90 of the knee joint 20A receives the pedal position information and load information from the bicycle 200 and sends it to the control unit 50.

[0084] The determination unit 130 of the control unit 50 may determine whether or not the setting condition of the bicycle mode is satisfied based on the pedal load information, or may determine whether or not the release condition of the bicycle mode is satisfied. Specifically, the setting condition determination unit 132 may determine that the user of the prosthesis 10 is not pedaling and that the setting condition of the bicycle mode is satisfied if the pedal load is equal to or greater than a predetermined threshold. Also, the release condition determination unit 134 may determine that the user of the prosthesis 10 is not pedaling and that the release condition of the bicycle mode is satisfied if the pedal load is less than a predetermined threshold.

[0085] The determination unit 130 may determine whether the setting condition of the bicycle mode is satisfied or not, or may determine whether the release condition of the bicycle mode is satisfied or not, based on the communication strength with the bicycle 200 in addition to the pedal load information. Specifically, the setting condition determination unit 132 may determine that the user of the prosthesis 10 is not pedaling and that the setting condition of the bicycle mode is satisfied if the pedal load is equal to or greater than a predetermined threshold and the wireless strength is equal to or greater than a predetermined threshold. Also, the release condition determination unit 134 may determine that the user of the prosthesis 10 is not pedaling and that the release condition of the bicycle mode is satisfied if the pedal load is less than a predetermined threshold and the wireless strength is less than a predetermined threshold.

[0086] The rotational resistance control unit 100 of the control unit 50 may control the rotational resistance of the knee axis 23 based on pedal position information. Specifically, the rotational resistance control unit 100 may increase the rotational resistance of the knee axis 23 when the pedal position is in the depression range 156 shown in Fig. 9. In this way, the rotational resistance control unit 100 increases the rotational resistance of the knee axis 23 when the pedal is located in the depression range 156, allowing the user of the prosthesis 10 to step on the pedal hard to generate propulsive force for the bicycle.

[0087] The pedal position sensor 210 of this embodiment may be configured to output a signal when the pedal reaches one or more specific positions on the circumference along which the pedal rotates. The control unit 230 or the control unit 50 can estimate the rotational speed of the pedal from the frequency with which the signal is received and determine whether or not the pedal is located in the depression range 156. Furthermore, at least a part of the processing executed by the control unit 50 of the knee joint 20 described above may be executed by the control unit 230 of the bicycle 200.

[0088] [Third embodiment] Next, a third embodiment will be described. In the drawings and description of the third embodiment, the same or equivalent components and members as those of the first and second embodiments are denoted by the same reference numerals. Explanations that overlap with the first and second embodiments will be omitted as appropriate, and the description will focus on the configurations that differ from the first and second embodiments.

[0089] FIG. 12 is a schematic diagram showing a functional block of a system 302 according to the third embodiment. The system 302 includes a knee joint 20B and a mobile terminal 300. The mobile terminal 300 is a terminal device carried by a user of the prosthetic leg 10, and is located at approximately the same position as the knee joint 20B included in the prosthetic leg 10. The knee joint 20B and the mobile terminal 300 are connected to each other so that they can communicate with each other. The communication between the knee joint 20B and the mobile terminal 300 is short-range wireless communication such as BLE. The mobile terminal 300 may be connected to an external server via a network so that they can communicate with each other. The knee joint 20B may have a configuration similar to that of the knee joint 20A of the second embodiment.

[0090] The mobile terminal 300 includes an air pressure sensor 310, a positioning sensor 320, a control unit 330, and a communication unit 340. The air pressure sensor 310 measures atmospheric pressure. The positioning sensor 320 acquires position information, for example, by a global positioning system (GPS). The control unit 330 acquires atmospheric pressure information from the air pressure sensor 310 and position information from the positioning sensor 320. The control unit 330 calculates the altitude at which the mobile terminal 300 is located based on the acquired atmospheric pressure information. The control unit 330 calculates the moving speed of the mobile terminal 300 based on the acquired position information. The communication unit 340 transmits various pieces of information acquired and calculated by the control unit 330 to the knee joint 20B. The communication unit 340 also receives angle information from the knee joint 20B and sends it to the control unit 330. In this embodiment, the angle information is any one or more of the thigh angle θ1, the lower leg angle θ2, the knee angle θ3, the thigh angular velocity, the lower leg angular velocity, and the knee angular velocity.

[0091] The control unit 330 determines the use state of the knee joint 20 based on at least any of the angle information, altitude information, position information, and movement speed information of the knee joint 20. The use state of the knee joint 20 is information that indicates the environment in which the knee joint 20 is being used, and includes information such as whether or not the user is walking, whether or not the user is on an elevator such as an escalator or elevator, or whether or not the user is on a vehicle. The determination of the use state of the knee joint 20 may be performed by the control unit 50 of the knee joint 20.

[0092] FIG. 13 is a diagram showing an example of the relationship between the use state of the knee joint 20 determined by the control unit 330 and the basis for the determination. The control unit 330 can estimate whether the state is walking, standing, or sitting, based on the angle information, by a known method. As shown in FIG. 13, for example, when the control unit 330 estimates the state as a walking state from the angle information and the moving speed is less than a threshold value estimated as the speed of a bus, for example, less than 20 km / h, the control unit 330 determines that the use state is a normal walking state. For example, when the control unit 330 estimates the state as a standing state from the angle information and the altitude is rising or descending and the moving speed is less than a threshold value, the control unit 330 determines that the state is standing on an escalator. For example, when the control unit 330 estimates the state as a standing state from the angle information and the moving speed is equal to or greater than a threshold value, the control unit 330 determines that the state is standing on a vehicle such as a train or a bus. For example, the control unit 330 estimates a seated state from the angle information, and when the moving speed is equal to or greater than a threshold, determines that the user is seated in a vehicle such as a car, train, bus, or airplane.

[0093] The control unit 50 may execute at least one of the power control of the knee joint 20 and the control of the rotational resistance of the knee axis 23 according to the determined use state of the knee joint 20. FIG. 14 is a diagram showing an example of the contents of the power control and the rotational resistance control corresponding to each determined use state of the knee joint 20. For example, when it is determined that the user is walking, the knee joint 20 is in a state of constantly operating, so the control unit 50 turns on the sensing function and executes the rotational resistance control as usual. For example, when it is determined that the user is standing on an escalator, the control unit 50 sets the return time to a short time while turning off the sensing function, because the knee joint 20 has temporarily stopped operating. When it is determined that the user is riding on an ascending escalator, the control unit 50 controls the rotational resistance so that the user does not fall backward, and when it is determined that the user is riding on a descending escalator, the control unit 50 controls the rotational resistance so that the user does not fall forward. For example, when it is determined that the user is standing on a vehicle, the knee joint 20 stops moving for a longer period of time than when the user is on an escalator, so the control unit 50 turns off the sensing function and sets the return time to be longer. In addition, the control unit 50 performs rotational resistance control so that the user does not fall over due to the shaking of the vehicle. For example, when it is determined that the user is sitting on a vehicle, the knee joint 20 is likely not to be used for a long period of time, so the sensing function is turned off, the return time is set to be longer, and the rotational resistance control is reduced. It is also possible to turn off the rotational resistance control by lengthening the sensing interval in accordance with the control cycle, without turning off the sensing function. In this case, the transition from a state other than the walking state to the walking state can be grasped early, and the rotational resistance control can be quickly returned to the normal state.

[0094] In this way, the system 302 of this embodiment determines the usage state of the knee joint 20 and performs power control and rotational resistance control according to the determined usage state, thereby reducing the power consumption of the knee joint 20. This can lead to weight reduction of the knee joint 20 by miniaturizing the battery 55, and improved freedom of housing design by saving space. At least one of the air pressure sensor 310 and the positioning sensor 320 of this embodiment may be provided in the knee joint 20B.

[0095] Above, examples of the embodiments of the present invention have been described in detail. The above-mentioned embodiments merely show specific examples of implementing the present invention. The contents of the embodiments do not limit the technical scope of the present invention, and many design changes such as changing, adding, and deleting components are possible within the scope of the invention as defined in the claims. In the above-mentioned embodiments, the contents for which such design changes are possible are described with the notation "of the embodiment" or "in the embodiment", but design changes may also be permitted for contents without such notation.

[0096] Any combination of the above-described embodiments and modifications is also useful as an embodiment of the present invention. A new embodiment resulting from the combination has the combined effects of the respective embodiments and modifications.

[0097] Among the embodiments disclosed in this specification, those in which multiple functions are provided in a distributed manner may have some or all of the multiple functions integrated together, and conversely, those in which multiple functions are provided in a distributed manner may have some or all of the multiple functions integrated together. Regardless of whether the functions are integrated or distributed, it is sufficient that the configuration is such that the object of the invention can be achieved. [Explanation of symbols]

[0098] θ1...thigh angle, θ2...lower leg angle, θ3...knee angle, 10...prosthesis, 11...socket, 20...knee joint, 21...lower leg portion, 22...thigh connection portion, 23...knee axis, 50...control portion, 100...rotational resistance control portion, 110...angle acquisition portion, 140...setting portion.

Claims

1. A thigh connection portion to which a socket corresponding to the thigh of a user is connected; A lower leg portion connected to the thigh connection portion so as to be rotatable around a knee axis; An angle acquisition unit that acquires at least one of a thigh angle, which is an inclination angle of the axis of the socket with respect to a vertical line, and a knee angle, which is an angle between the axis of the socket and the axis of the lower leg around the knee axis; A rotational resistance control unit that controls the rotational resistance of the knee axis based on the angle acquired by the angle acquisition unit; a setting unit that sets the operation mode of the rotational resistance control unit to a bicycle mode when at least one of the thigh angle and the knee angle satisfies a predetermined condition; A knee joint comprising:

2. the setting unit sets the bicycle mode under at least one of a condition that the thigh angle is greater than a first set threshold and a condition that the knee angle is greater than a second set threshold. The knee joint of claim 1.

3. The setting unit is The thigh angle is greater than the first set threshold value, and the sign of the thigh angular velocity, which is the angular velocity of the thigh angle, repeatedly inverts between positive and negative; and the knee angle is greater than the second set threshold, and the sign of the knee angular velocity, which is the angular velocity of the knee angle, repeatedly inverts between positive and negative; and setting the bicycle mode under at least one of the conditions.

3. The knee joint of claim 2.

4. the setting unit cancels the bicycle mode under at least one of a condition that the thigh angle is equal to or less than a first release threshold and a condition that the knee angle is equal to or less than a second release threshold while the bicycle mode is set. A knee joint according to claim 2 or 3.

5. the setting unit, while the bicycle mode is set, cancels the bicycle mode on the condition that the motion deviates from a predetermined elliptical orbit in an orthogonal coordinate system having the thigh angle as one coordinate axis and the knee angle as the other coordinate axis. A knee joint according to claim 2 or 3.

6. the angle acquisition unit acquires at least two angles from the thigh angle, the knee angle, and a lower leg angle which is an inclination angle that an axis of the lower leg makes with respect to a vertical line; the setting unit cancels the bicycle mode on a condition that the angle deviates from a predetermined elliptical orbit in an orthogonal coordinate system having coordinate axes of any two angles of the thigh angle, the knee angle, and the lower leg angle while the bicycle mode is set. A knee joint according to claim 2 or 3.

7. the setting unit sets the bicycle mode on the condition that a predetermined elliptical orbit is traced in an orthogonal coordinate system having the thigh angle as one coordinate axis and the knee angle as the other coordinate axis. The knee joint of claim 1.

8. the angle acquisition unit acquires at least two angles from the thigh angle, the knee angle, and a lower leg angle which is an inclination angle that an axis of the lower leg makes with respect to a vertical line; the setting unit sets the bicycle mode on the condition that a predetermined elliptical orbit is traced in an orthogonal coordinate system having coordinate axes of any two angles of the thigh angle, the knee angle, and the lower leg angle. The knee joint of claim 1.

9. The rotational resistance control unit reduces the rotational resistance of the knee axis while the bicycle mode is set. The knee joint of claim 1.

10. the rotational resistance control unit increases the rotational resistance of the knee axis when at least one of the thigh angle being within a first angle range and the knee angle being within a second angle range is satisfied during the bicycle mode. The knee joint of claim 1.

11. A socket corresponding to the user's thigh; a thigh connection portion to which the socket is connected; A lower leg portion connected to the thigh connection portion so as to be rotatable around a knee axis; An angle acquisition unit that acquires at least one of a thigh angle, which is an inclination angle of the axis of the socket with respect to a vertical line, and a knee angle, which is an angle between the axis of the socket and the axis of the lower leg around the knee axis; A rotational resistance control unit that controls the rotational resistance of the knee axis based on the angle acquired by the angle acquisition unit; a setting unit that sets the operation mode of the rotational resistance control unit to a bicycle mode when at least one of the thigh angle and the knee angle satisfies a predetermined condition; A prosthetic leg equipped with

12. A method for controlling a knee joint including a thigh connection part to which a socket corresponding to a user's thigh is connected, and a lower leg part rotatably connected to the thigh connection part around a knee axis, comprising: acquiring at least one of a thigh angle, which is an inclination angle of the axis of the socket with respect to a vertical line, and a knee angle, which is an angle between the axis of the socket and the axis of the lower leg around the knee axis; Controlling the rotational resistance of the knee axis based on the acquired angle; a step of setting an operation mode of the step of controlling rotation resistance of the knee axis to a bicycle mode when at least one of the thigh angle and the knee angle satisfies a predetermined condition; Includes control methods.

13. A control program for a knee joint including a thigh connection part to which a socket corresponding to a user's thigh is connected, and a lower leg part rotatably connected to the thigh connection part around a knee axis, acquiring at least one of a thigh angle, which is an inclination angle of the axis of the socket with respect to a vertical line, and a knee angle, which is an angle between the axis of the socket and the axis of the lower leg around the knee axis; Controlling the rotational resistance of the knee axis based on the acquired angle; a step of setting an operation mode of the step of controlling rotation resistance of the knee axis to a bicycle mode when at least one of the thigh angle and the knee angle satisfies a predetermined condition; A control program for causing a computer to execute the above.

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