Patent Description:
An artificial knee joint or a prosthetic limb worn by a person who has lost a leg due to an injury or a disease, in which the rotational resistance of the knee shaft is controlled in accordance with the phase of walking of the wearer, is known. In the Stance phase in which the prosthetic limb is in contact with the ground and is under load, the rotational resistance of the knee shaft is increased to prevent the knee from being bent under load. In the Swing phase in which the prosthetic limb leaves the ground and is swung, the rotational resistance of the knee shaft is decreased to bend the knee and prevent the prosthetic limb from touching the ground. <CIT> discloses an artificial knee joint according to the preamble of claim <NUM>. [Patent literature <NUM>] <CIT>.

We have studied multiple aspects of control of the rotational resistance of a knee shaft for the purpose of further improving the convenience of an artificial knee joint or a prosthetic limb.

The present invention addresses the above-described issue and a purpose thereof is to provide a highly convenient artificial knee joint or prosthetic limb.

This is achieved by an artificial knee joint according to claim <NUM>. Preferred embodiments are laid down in the dependent claims. An artificial knee joint according to an aspect disclosed herein includes: a thigh joint part provided on a side of a thigh part; a lower leg part coupled to the thigh joint part and provided to be rotatable around a knee shaft; a thigh part inclination angle acquisition unit that acquires an inclination angle formed by the thigh part relative to a vertical line passing through the knee shaft; and a rotational resistance control unit that weakens a rotational resistance of the knee shaft in accordance with a transition from a positive inclination angle formed when the thigh part is inclined rearward relative to the vertical line to a negative inclination angle formed when the thigh part is inclined forward relative to the vertical line.

Another aspect disclosed herein also relates to an artificial knee joint. The artificial knee joint is provided with a thigh joint part provided on a side of a thigh part and with a lower leg part coupled to the thigh joint part and provided to be rotatable around a knee shaft, and includes: a forward movement amount sensing unit that senses a forward movement amount of a user wearing the artificial knee joint; and a rotational resistance control unit that strengthens a rotational resistance of the knee shaft when the forward movement amount sensed makes a transition from a state in which the forward movement amount is equal to or larger than a predetermined forward movement amount threshold value to a state in which forward movement amount is smaller than the forward movement amount threshold value.

Another aspect disclosed herein also relates to an artificial knee joint. The artificial knee joint is provided with a thigh joint part provided on a side of a thigh part and with a lower leg part coupled to the thigh joint part and provided to be rotatable around a knee shaft, and includes: a forward movement amount sensing unit that senses a forward movement amount of a user wearing the artificial knee joint; and a rotational resistance control unit that enables controlling a rotational resistance of the knee shaft to be weaker when the forward movement amount sensed is equal to or greater than a predetermined forward movement amount threshold value.

Another aspect disclosed herein also relates to an artificial knee joint. The artificial knee joint is provided with a thigh joint part provided on a side of a thigh part and with a lower leg part coupled to the thigh joint part and provided to be rotatable around a knee shaft, and includes: a rotational resistance control unit that weakens a rotational resistance of the knee shaft in accordance with a transition of a user walking and wearing the artificial knee joint from a Stance phase to a Swing phase; a walk information acquisition unit that acquires walk information indicating a state of walk of the user; and a control timing determination unit that determines a timing according to which the rotational resistance control unit weakens the rotational resistance of the knee shaft, based on the walk information.

Another aspect disclosed herein relates to an adjustment support apparatus for an artificial knee joint. The apparatus is an adjustment support apparatus for an artificial knee joint provided with a thigh joint part provided on a side of a thigh part and with a lower leg part coupled to the thigh joint part and provided to be rotatable around a knee shaft, the adjustment support apparatus including: a walk information acquisition unit that acquires walk information indicating a state of walk of a user walking and wearing the artificial knee joint; and a control timing determination unit that determines a timing according to which a rotational resistance of the knee shaft is weakened in accordance with a transition of the artificial knee joint from a Stance phase to a Swing phase, based on the walk information.

Optional combinations of the aforementioned constituting elements, and implementations of the disclosure in the form of methods, apparatuses, systems, recording mediums, and computer programs may also be practiced as additional modes of the present invention.

Embodiments will now be described by way of examples only, with reference to the accompanying drawings which are meant to be exemplary, not limiting and wherein like elements are numbered alike in several Figures in which:.

The invention will now be described by reference to the preferred embodiments. This does not intend to limit the scope of the present invention, but to exemplify the invention.

<FIG> and <FIG> show a schematic configuration of an artificial knee joint <NUM> and a prosthetic limb <NUM> according to an embodiment of the present invention. The prosthetic limb <NUM> is provided with a plastic socket <NUM> as a thigh part, a thigh joint part <NUM> to which the socket <NUM> is connected, a lower leg part <NUM> coupled to the thigh joint part <NUM> and provided to be rotatable around a knee shaft <NUM>, and a foot part <NUM> coupled to the lower end of the lower leg part <NUM>. The thigh joint part <NUM> to which the socket <NUM> is connected and the lower left part <NUM> bend or stretch the artificial knee joint <NUM> corresponding to the knee joint by relatively rotating around the knee shaft <NUM> provided in the joint between the thigh joint part <NUM> and the lower leg part <NUM> and perpendicular to the plane of <FIG>. Further, the foot part <NUM> is formed by an elastic member, and the relative posture under a small load from the ground (e.g., when the foot part <NUM> does not touch the ground or when the wearer stands upright) is maintained constant by elasticity. Further, the elastic member is elastically deformed under a heavy load from the ground (e.g., when the wearer is walking) to produce a propelling power to kick the ground.

The artificial knee joint <NUM> is provided with the lower leg part <NUM> formed by a high-strength frame, the thigh joint part <NUM> connected to the socket <NUM> as a thigh part and coupled to the lower leg part <NUM> so as to be rotatable around the knee shaft <NUM>, a cylinder <NUM> that restricts or permits the rotational motion around the knee shaft <NUM>, i.e., the bending and stretching motion of the artificial knee joint <NUM>, and a control mechanism <NUM> for driving the cylinder <NUM>. <FIG> shows the artificial knee joint <NUM> in which the thigh joint part <NUM> and the lower leg part <NUM> are joined by a single link and which is rotatable around the single knee shaft <NUM> at a particular position. The present invention is equally applicable to the artificial knee joint <NUM> in which the thigh joint part <NUM> and the lower leg part <NUM> are joined by, for example, two front and rear links, and which is rotatable around the knee shaft <NUM> as a rotational center virtually and instantaneously formed inward of the total of four joints.

The amount of extension/contraction of the cylinder <NUM> and the knee angle, which is a rotational angle around the knee shaft <NUM> are substantially in one-to-one correspondence. A knee angle sensor <NUM> as a knee angle acquisition unit for measuring the amount of extension/contraction of the cylinder <NUM> to detect the knee angle of the artificial knee joint <NUM> is provided in the vicinity of the cylinder <NUM> and the thigh joint part <NUM>. The knee angle detected by the knee angle sensor <NUM> is used by a control unit <NUM>. The knee angle sensor <NUM> may be formed by an arbitrary sensor capable of measuring the amount of extension/contraction of the cylinder <NUM>. For example, the knee angle sensor <NUM> may be formed by a Hall device capable of sensing the position of a magnet embedded in a piston rod <NUM> that moves in association with the extension/contraction of the cylinder <NUM>. The knee angle is an angle formed by the axis of the socket <NUM> as the thigh part and the axis of the lower leg part <NUM>. As shown in <FIG>, for example, the knee angle formed when the user of the prosthetic limb <NUM> is standing upright and the axis of the socket <NUM> and the axis of the lower leg part <NUM> are aligned is <NUM> degrees. Further, the knee angle, formed when the user of the prosthetic limb <NUM> is seated, the axis of the lower leg part <NUM> remains aligned in the vertical direction of <FIG>, and the axis of the socket <NUM> changes to the horizontal direction, is <NUM> degrees.

An inertial sensor <NUM> provided in the lower leg part <NUM> senses the posture and motion of the lower leg part <NUM> by measuring the speed (angular speed) and/or acceleration (angular acceleration) in the translational direction and/or rotational direction of the three axes defining the motion of the lower leg part <NUM>. As described later, the shin angle, which defines the posture of the lower leg part <NUM> sensed by the inertial sensor <NUM> and which is a inclination angle formed by the axis of the lower leg part <NUM> relative to the vertical line passing through the knee shaft <NUM>, is used to control the artificial knee joint <NUM> according to the embodiment. The shin angle and the thigh angle, which is described later, can be sensed in two directions including the longitudinal direction and the transversal direction and can be used to control the artificial knee joint <NUM>. Hereinafter, the terms shin angle and thigh angle shall refer to an inclination angle in the longitudinal direction unless otherwise specified. The inertial sensor <NUM> capable of sensing the shin angle forms a lower leg part inclination angle acquisition unit of the present invention. The inertial sensor <NUM> can be provide at an arbitrary position of the lower leg part <NUM>. For example, the inertial sensor <NUM> is implemented on a control board provided in the outer circumference of the cylinder <NUM> along with the control unit <NUM>.

The thigh angle, which is an inclination angle formed by the axis of the socket <NUM> as the thigh part relative to the vertical line passing through the knee shaft <NUM>, can be computed from the knee angle acquired by the knee angle sensor <NUM> and the shin angle acquired by the inertial sensor <NUM>. In other words, the shin angle is the inclination of the lower leg part <NUM> from the vertical line passing through the knee shaft <NUM>, and the knee angle is the inclination of the axis of the socket <NUM> from the axis of the lower leg part <NUM>. By totaling the two, therefore, the thigh angle, which is the inclination of the axis of the socket <NUM> from the vertical line passing through the knee shaft <NUM>, can be computed. Therefore, the knee angle sensor <NUM> and the inertial sensor <NUM> form a thigh part inclination angle acquisition unit of the present invention for acquiring the thigh angle. Alternatively, an inertial sensor may be provided in the socket <NUM> or the thigh joint part <NUM> to measure the thigh angle directly. In this case, the shin angle can be computed based on the knee angle and the thigh angle measured. Similarly, even if the knee angle sensor <NUM> is not provided, the knee angle can be computed by measuring the thigh angle and the shin angle.

<FIG> schematically shows a transition of the knee angle θ, the thigh angle Ψ, and the shin angle Φ in accordance with the phase of walking (A)-(B) of the wearer of the prosthetic limb <NUM>. The phase of walking (A) is the Initial Contact (IC) phase in which the prosthetic limb touches the ground. The phase of walking (B) is the Loading Response (LR) phase in which the weight of the wearer is supported by the prosthetic limb <NUM> touching the ground. The phase of walking (C) is the Mid Stance (MSt) to Terminal Stance (Tst) phase during which the gravitational center of the wearer moves ahead of the prosthetic limb <NUM> while the prosthetic limb <NUM> is supporting the weight. The phase of walking (D) is the Pre-Swing (PSw) phase in which the prosthetic limb <NUM> starts kicking the ground to make a transition to the subsequent Swing phase. The phases of walking (E), (F), and (G) are the Initial Swing (ISw), Mid Swing (MSw), and Terminal Swing (TSw) phases, respectively, in which the prosthetic limb <NUM> having left the ground is swung from back to front.

The thigh angle Ψ is defined to be negative (illustrated as -Ψ) when the socket <NUM> is inclined forward around the knee shaft <NUM> with reference to the vertical line passing through the knee shaft <NUM> and is defined to be positive (illustrated as +Ψ) when the socket <NUM> is inclined rearward. The shin angle Φ is defined to be positive (illustrated as +Φ) when the lower leg part <NUM> is inclined forward around the knee shaft <NUM> with reference to the vertical line passing through the knee shaft <NUM> and is defined to be negative (illustrated as -Φ) when the lower leg part <NUM> is inclined rearward. The knee angle θ is defined to be positive (illustrated as +θ) when the lower leg part <NUM> is inclined rearward around the knee shaft with reference to the axis of the socket <NUM>. The knee angle θ, the thigh angle Ψ, and the shin angle Φ defined as described above always meet the relational expression "θ+Φ=Ψ".

As illustrated, the knee angle θ is substantially zero/the thigh angle Ψ is positive/the shin angle Φ is positive in the Initial Contact phase (A), the knee angle θ is substantially zero/the thigh angle Ψ is positive/the shin angle Φ is positive in the Loading Response phase (B), the knee angle θ is substantially zero/the thigh angle Ψ is negative/the shin angle Φ is negative in the Mid Stance/Terminal Stance phase (C), the knee angle θ is positive/the thigh angle Ψ is negative/the shin angle Φ is negative in the Pre-Swing phase (D), the knee angle θ is positive/the thigh angle Ψ is positive/the shin angle Φ is negative in the Initial Swing phase (E), the knee angle θ is positive/the thigh angle Ψ is positive/the shin angle Φ is negative in the Mid Swing phase (F), and the knee angle θ is positive/the thigh angle Ψ is positive/the shin angle Φ is positive in the Terminal Swing phase (G).

To focus on the knee angle θ, the knee angle θ increases and decreases monotonically such that the knee angle θ is substantially zero in the Stance phases (A)-(C) in which the prosthetic limb <NUM> in contact the ground supports the weight of the wearer, the knee angle θ maintains a value from substantially zero to positive in the Pre-Swing phase (D) between the Stance phases (A)-(C) and the Swing phases (E)-(G), and has a maximum value in the Mid-Swing phase (F) of the Swing phases (E)-(G), in which the prosthetic limb <NUM> leaves the ground and swung.

Control of the knee angle θ like this, i.e., bend control of the artificial knee joint <NUM>, is performed by the control unit <NUM> via the control mechanism <NUM> and the cylinder <NUM>. In other words, the knee angle θ is maintained to be substantially zero in the Stance phases (A)-(C) by increasing the hydraulic resistance of the cylinder <NUM> and restricting the rotation around the knee shaft <NUM> to prevent the artificial knee joint <NUM> from being bent by the weight of the wearer. In the Pre-Swing phase (D), the hydraulic resistance of the cylinder <NUM> is reduced to permit the rotation around the knee shaft <NUM> so as to make it possible for the artificial knee joint <NUM> to start bending in preparation for the subsequent Swing phases (E)-(G), which ensures that the knee angle θ has a positive value. In the Swing phases (E)-(G), the hydraulic resistance of the cylinder <NUM> is maintained to be low to allow the artificial knee joint <NUM> to be bent easily so that the prosthetic limb <NUM> swung away from the ground does not contact the ground. Details of bend control of the artificial knee joint <NUM> will be described later.

A description of the prosthetic limb <NUM> will be continued by referring back to <FIG> and <FIG>. A load sensor <NUM> for detecting the load exerted between the lower leg part <NUM> and the foot part <NUM> may be provided at the lower end of the lower leg part <NUM>, as a sensor other than the knee angle sensor <NUM> and the inertial sensor <NUM>. Since it is possible to recognize the phase of walking of the wearer of the prosthetic limb <NUM> based on the magnitude and direction of the load detected by the load sensor <NUM>, the load sensor <NUM> may be used for bend control of the artificial knee joint <NUM> in addition to the knee angle sensor <NUM> and the inertial sensor <NUM>. The load sensor may be provided in the thigh joint part <NUM> or in the knee part between the thigh joint part <NUM> and the lower leg part <NUM>. Meanwhile, as described later, bend control of the artificial knee joint <NUM> can be performed by using the knee angle sensor <NUM> and the inertial sensor <NUM> only so that the load sensor <NUM> may be omitted to configure the artificial knee joint <NUM> inexpensively. Further, a temperature sensor <NUM> for measuring the temperature of the oil in the cylinder <NUM> is attached to the outer wall or the inner wall of the cylinder <NUM>. The measurement information of these sensors is used in the control unit <NUM>.

A vibrator <NUM> is provided in the thigh joint part <NUM> or the lower leg part <NUM>. The vibrator <NUM> notifies or alerts the user wearing the prosthetic limb <NUM> by vibration and is controlled by the control unit <NUM>.

The control unit <NUM> controls the control mechanism <NUM> based on the measurement information of various sensor such as the knee angle sensor <NUM>, the load sensor <NUM>, the inertial sensor <NUM>, and the temperature sensor <NUM> to control the resistance to the extension/contraction motion of the cylinder <NUM>, i.e., the rotational resistance of the knee shaft <NUM> during the bending motion of the artificial knee joint <NUM>. A battery <NUM> for supplying power to the parts of the artificial knee joint <NUM> is connected to the control unit <NUM>. <FIG> shows the control mechanism <NUM>, the control unit <NUM>, and the battery <NUM> outside the artificial knee joint <NUM> but in practice are provided inside the lower leg part <NUM> as components constituting the artificial knee joint <NUM>.

The cylinder <NUM> is a hydraulic cylinder that restricts or permits the bending or stretching motion of the artificial knee joint <NUM> by producing a drag by using oil as a working fluid. The cylinder <NUM> is supported by an upper support point <NUM> provided in the vicinity of the knee shaft <NUM> that rotatably couples the socket <NUM> and the lower leg part <NUM> and by a lower support point <NUM> coupled to a part of the lower leg part <NUM> and can extend or contract between the support points. In the compression step in which the cylinder length is reduced, a bending motion in which the artificial knee joint <NUM> is rotated counterclockwise of <FIG> around the knee shaft <NUM> is performed. In the expansion step in which the cylinder length is enlarged, a stretching motion in which the artificial knee joint <NUM> is rotated clockwise of <FIG> around the knee shaft <NUM> is performed. The cylinder length refers to a length between the upper support point <NUM> and the lower support point <NUM> of the cylinder <NUM>.

A description will now be given of the cylinder <NUM> and the control mechanism <NUM> with reference to <FIG>. The cylinder <NUM> is provided with a cylinder tube <NUM>, a piston rod <NUM> inserted from the side of one end (the right end side of <FIG>) of the cylinder tube <NUM> and movable along the longitudinal direction (the transversal direction of <FIG>) of the cylinder tube <NUM>, and a piston <NUM> secured to the piston rod <NUM> in the cylinder tube <NUM> and slidable in the longitudinal direction along the inner wall of the cylinder tube <NUM>. The piston <NUM> partitions the interior of the cylinder tube <NUM> into a first cavity <NUM> on the side of the one end (the right end side of <FIG>) and a second cavity <NUM> on the side of the other end (the left end side of <FIG>). The first cavity <NUM> and the second cavity <NUM> are filled with oil as a working fluid.

The control mechanism <NUM> is a hydraulic driving mechanism for driving the cylinder into expansion or compression by a hydraulic pressure. The control mechanism <NUM> is provided with an stretching side hydraulic circuit <NUM> and a bending side hydraulic circuit <NUM> respectively connected to the cylinder <NUM>. The stretching side hydraulic circuit <NUM> and the bending side hydraulic circuit <NUM> respectively communicate with the first cavity at one and communicate with the second cavity <NUM> at the other end. The stretching side hydraulic circuit <NUM> is provided with a stretching side valve <NUM> as a valve capable of opening or closing the fluid path of the oil for producing the rotational resistance of the knee shaft <NUM> and with a stretching side check valve <NUM>. Opening the stretching side valve <NUM> allows the oil to be distributed in the stretching side hydraulic circuit <NUM>. The action of the stretching side check valve <NUM> causes the oil to flow only in the direction from the first cavity <NUM> to the second cavity <NUM> and not to flow in the opposite direction.

The bending side hydraulic circuit <NUM> is provided with a bending side valve <NUM> as a valve capable of opening or closing the fluid path of the oil for producing the rotational resistance of the knee shaft <NUM> and with a bending side check valve <NUM>. Opening the bending side valve <NUM> allows the oil to be distributed in the bending side hydraulic circuit <NUM>. The action of the bending side check valve <NUM> causes the oil to flow only in the direction from the second cavity <NUM> to the first cavity <NUM> and not to flow in the opposite direction. The positions of the stretching side valve <NUM> and the bending side valve <NUM> are individually controlled by the control unit <NUM>. The position of each valve can have an arbitrary value between fully open (the most open position) and fully closed (the least open position). When the valve is fully closed, the flow of the oil is interrupted so that the hydraulic pressure is maximized. The more open the valve toward full open, the larger the cross section through which the oil can be distributed in the valve and the smaller the hydraulic resistance.

<FIG> shows the flow of the oil in the bending motion of the artificial knee joint <NUM>. Bending is a compression step in which the cylinder length is decreased. The piston rod <NUM> recedes leftward in <FIG>, and the piston <NUM> moves toward the intake side. The oil extruded from the second cavity <NUM> by the movement of piston <NUM> cannot be distributed in the stretching side hydraulic circuit <NUM> provided with the stretching side check valve <NUM> and so flows into the first cavity <NUM> via the bending side hydraulic circuit <NUM>. Controlling the bending side valve <NUM> to be less open in this process makes it difficult for the oil to flow in the bending side hydraulic circuit <NUM> and so can restrict the bending motion of the artificial knee joint <NUM>. Thus, the control unit <NUM> constitutes the rotational resistance control unit of the present invention for controlling the rotational resistance of the knee shaft <NUM> during the bending motion of the artificial knee joint <NUM>, by controlling the position of the bending side valve <NUM>.

<FIG> shows the flow of the oil in the stretching motion of the artificial knee joint <NUM>. Stretching is an expansion step in which the cylinder length is increased. The piston rod <NUM> advances rightward in <FIG>, and the piston <NUM> moves toward the extrusion side. The oil extruded from the first cavity <NUM> by the movement of piston <NUM> cannot be distributed in the bending side hydraulic circuit <NUM> provided with the bending side check valve <NUM> and so flows into the second cavity <NUM> via the stretching side hydraulic circuit <NUM>. Controlling the stretching side valve <NUM> to be less open in this process makes it difficult for the oil to flow in the stretching side hydraulic circuit <NUM> and so can restrict the stretching motion of the artificial knee joint <NUM>. Thus, the control unit <NUM> constitutes the rotational resistance control unit of the present invention for controlling the rotational resistance of the knee shaft <NUM> during the stretching motion of the artificial knee joint <NUM>, by controlling the position of the stretching side valve <NUM>.

Reference is made back to <FIG>, and the sensors provided in the prosthetic limb <NUM> will be described further.

The knee angle sensor <NUM> measures the position of the piston rod <NUM> extended or contracted. For example, the position of a magnet attached to the piston rod <NUM> is measured by a magnetic sensor provided in the cylinder tube <NUM>. The position of the piston rod <NUM> extended or contracted and the knee angle of the artificial knee joint <NUM> or the rotational angle of the knee shaft <NUM> are in one-to-one correspondence. Therefore, the knee angle sensor <NUM> can convert the detected position of the piston rod <NUM> extended or contracted into the knee angle of the artificial knee joint <NUM>. The computation to convert the position of the piston rod <NUM> extended or contracted into the knee angle of the artificial knee joint <NUM> may be performed in the control unit <NUM>. The knee angle sensor <NUM> in this case measures the position of the piston rod <NUM> extended or contracted and provides the measurement to the control unit <NUM>.

The inertial sensor <NUM> senses the posture and motion of the lower leg part <NUM> based on the measured speed and/or acceleration of the respective axes. For example, the phase of walking of the wearer of the prosthetic limb <NUM> can be recognized from the variation in the speed/acceleration measured by the inertial sensor <NUM>, and the position of the lower leg part <NUM> during waling can be tracked by integrating measurement values of the inertial sensor <NUM>. Therefore, the step length, which is an amount of displacement per step, and the walking speed per step can be determined. The computation to determine the position by integrating measurement values of the inertial sensor <NUM>, etc. is performed by the control unit <NUM>.

The load sensor <NUM> is comprised of, for example, a strain sensor and is provided in the ankle part between the lower leg part <NUM> and the foot part <NUM>. The load exerted on the ankle part produces a strain in the object that constitutes the strain sensor so that the load can be measured by detecting the strain. By providing a load sensor like this in the thigh joint part <NUM>, the load exerted on the knee joint can also be measured. The computation to convert the strain detected by the strain into the load may be performed by the control unit <NUM>. The load sensor <NUM> in this case provides the detected strain to the control unit <NUM>. Further, the control unit <NUM> can recognize the phase of walking of the wearer of the prosthetic limb <NUM> from the variation in the magnitude and direction of the load measured by the load sensor <NUM> and so can determine the step length and the walking speed by computation. Also, information on the moment exerted on the artificial knee joint <NUM> can be obtained from the position, magnitude, direction of the load measured by the load sensor <NUM>.

The temperature sensor <NUM> measures the temperature of the cylinder <NUM> or the temperature of the oil in the cylinder <NUM>. For example, the temperature sensor <NUM> initiates a transition to a high-temperature mode in which the action of the artificial knee joint <NUM> is restricted upon detecting that the cylinder <NUM> reaches a high temperature due to the head from the hydraulic resistance. Further, depending on the physical property of the oil, the hydraulic resistance varies in accordance with the temperature variation. Therefore, the control unit <NUM> can realize a desired hydraulic resistance by controlling the control mechanism <NUM> in accordance with the temperature measured by the temperature sensor <NUM>. More specifically, control data set for the control mechanism <NUM> to realize the respective values of hydraulic resistance is created for each temperature and stored in the control unit <NUM>. The control unit <NUM> selects the control data set corresponding to the temperature measured by the temperature sensor <NUM> and uses the data for control.

<FIG> schematically shows functional blocks that provide bend control of the artificial knee joint <NUM>. The figure shows only those constituting elements of the prosthetic limb <NUM> related to bend control of the artificial knee joint <NUM>. Further, the illustrated constituting elements are provided in the artificial knee joint <NUM> except for the socket <NUM>. The constituting elements that provide information processing such as a rotational resistance control unit <NUM> are implemented in the control unit <NUM>.

An inclination angle acquisition unit <NUM> is provided with a thigh angle computation unit <NUM> that acquires the thigh angle Ψ, which is an inclination angle formed by the socket <NUM> as the thigh part relative to the vertical line passing through the knee shaft <NUM>, constantly or at a predetermined time interval and with the inertial sensor <NUM> as a shin angle sensor that acquires the shin angle Φ, which is an inclination angle formed by the lower leg part <NUM> relative to the vertical line passing through the knee shaft <NUM>, constantly or at a predetermined time interval. As described above, the knee angle θ, the thigh angle Ψ, and the shin angle Φ meet the relational expression "θ+Φ=Ψ" so that the thigh angle computation unit <NUM> can compute the thigh angle Ψ=θ+Φ based on the knee angle θ measured by the knee angle sensor <NUM> and the shin angle Φ measured by the inertial sensor <NUM>.

An angular speed acquisition unit <NUM> is provided with a thigh angular speed acquisition unit <NUM> (a thigh part inclination angular speed acquisition unit) that acquires the angular speed of the thigh angle Ψ and a shin angular speed acquisition unit <NUM> that acquires the angular speed of the shin angle Φ. More specifically, the thigh angular speed acquisition unit <NUM> determines the thigh angular speed by differentiating the thigh angle Ψ computed by the thigh angle computation unit <NUM> with respect to time, and the shin angular speed acquisition unit <NUM> determines the shin angular speed by differentiating the shin angle Φ measured by the inertial sensor <NUM> with respect to time. When the inertial sensor <NUM> as a shin angle sensor can measure the shin angular speed directly, the inertial sensor <NUM> itself constitutes the shin angular speed acquisition unit <NUM>. Alternatively, the thigh angular speed may be computed based on the shin angular speed acquired by the shin angular speed acquisition unit <NUM> and the knee angular speed determined by differentiating the knee angle θ measured by the knee angle sensor <NUM> with respect to time.

The rotational resistance control unit <NUM> controls the rotational resistance (hereinafter, bend resistance) of the knee shaft <NUM> during the bending motion of the artificial knee joint <NUM>, by controlling the position of the bending side valve <NUM>. The rotational resistance control unit <NUM> is provided with, as constituting elements for acquiring various information used for control of bend resistance, a delay time acquisition unit <NUM>, a walking mode sensing unit <NUM>, a load line acquisition unit <NUM>, and a forward movement amount sensing unit <NUM>. The rotational resistance control unit <NUM> need not be provided with all of these functional units but may be provided with at least one of the function units.

The delay time acquisition unit <NUM> acquires a delay time that elapses until the result of control of the bending side valve <NUM> by the rotational resistance control unit <NUM> is reflected in the actual bend resistance. The delay time is primarily determined by the control period of the rotational resistance control unit <NUM> and by the driving period during which the motor is driven to open or close the bending side valve <NUM> to a desired position. Given, for example, that the control period of the rotational resistance control unit <NUM> is <NUM> and the driving period of the motor is <NUM>, a delay time of about <NUM> in total is produced. As described later, the bend resistance is controlled in the embodiment by allowing for the delay time as well.

The walking mode sensing unit <NUM> senses the walking mode of the user wearing the prosthetic limb <NUM> based on the posture and motion of the respective parts of the prosthetic limb <NUM> that can be sensed by the knee angle sensor <NUM>, the inertial sensor <NUM>, the thigh angle computation unit <NUM>, the angular speed acquisition unit <NUM>, etc. For example, the walking mode sensing unit <NUM> can sense that the wearer of the prosthetic limb <NUM> is walking forward ordinarily as shown in <FIG> and can sense the phases of walking (A)-(G) during the walk. The walking mode acquisition unit <NUM> can also sense a particular walking mode different from the ordinary walking mode of <FIG>. For example, the walking mode acquisition unit <NUM> can sense an abnormal walk mode such as backward walking and a forward, backward, leftward, rightward, or upward jump.

The load line acquisition unit <NUM> acquires a load line L indicating the direction of load exerted on the lower leg part <NUM>. <FIG> shows load lines L in the phases of walking, equally shown in <FIG>, as arrows or vectors. The length of the load line L represents the magnitude of load. The phases of walking (A)-(G) of <FIG> correspond to the phases of walking (A)-(G) of <FIG>, but the Mid Stance/Terminal Stance phase shown as one phase of walking (C) in <FIG> is divided into two phase of walking, i.e., the Mid Stance MSt phase (C1) and the Terminal Stance Tst phase (C2), in <FIG>.

To focus on the relationship between the load line L and the knee shaft <NUM> in the phases of walking (C1)-(D), the knee shaft <NUM> (the virtual and instantaneous rotational center in the artificial knee joint <NUM> in which the thigh joint part <NUM> and the lower leg part <NUM> are joined by a plurality of links) is slightly behind the load line L in the Mid Stance phase (C1). The knee shaft <NUM> is on the load line L in the Terminal Stance phase (C2), and the knee shaft <NUM> is in front of the load line L in the Pre-Swing phase (D). Thus, the knee shaft <NUM> makes a transition from a point behind the load line L to a point in front of the load line L, in association with the transition between the phases of walking (C1)-(D). Like the walking mode described above, the load line L is determined based on the posture and motion of the respective parts of the prosthetic limb <NUM> that can be sensed by the inertial sensor <NUM>, the thigh angle computation unit <NUM>, the angular speed acquisition unit <NUM>, etc. Further, the load line L can be measured directly by the sensor <NUM> when the load sensor <NUM> is provided in the artificial knee joint <NUM>.

The forward movement amount sensing unit <NUM> senses the amount of forward movement of the user wearing the artificial knee joint <NUM>. As shown in the Terminal Stance phase (C2) and the Pre-Swing phase (D) of <FIG>, the component Lx of the load line in the horizontal direction or the direction of travel is the forward movement amount, which represents an advancing force from the load that contributes to the advancement of the wearer of the prosthetic limb <NUM>. It is sufficient if the variation or increase/decrease of the forward movement amount is known for control of bend resistance by the rotational resistance control unit <NUM>. It is not necessary to sense the forward movement amount or the advancing force strictly. Therefore, it is sufficient for the forward movement amount sensing unit <NUM> to acquire data correlated to the forward movement amount.

Data indicative of the forward movement amount is exemplified by the thigh angular speed acquired by the thigh angular speed acquisition unit <NUM>. In association with the occurrence of a forward movement amount in the Terminal Stance phase (C2) and the Pre-Swing phase (D) of <FIG>, the thigh angular speed has a negative value in the Mid Stance/Terminal Stance phase (C) and the Pre-Swing phase (D) of <FIG>. Therefore, a negative thigh angle speed suggests a forward movement amount.

Data indicative of the forward movement amount can also be obtained from a ground contact sensing unit <NUM> or a length acquisition unit <NUM>. The ground contact sensing unit <NUM> senses the contact of the artificial knee joint <NUM> with the ground. The length acquisition unit <NUM> acquires the length of the artificial knee joint <NUM> from the thigh joint part <NUM> to the lower end of the lower leg part <NUM>. In the Terminal Stance phase (C2) and the Pre-Swing phase (D) in which a forward movement amount occurs, the leg wearing the artificial knee joint <NUM> is in contact with the ground, and the line connecting the toe and the waist W is inclined forward. It can therefore be said that a forward movement amount is present when the angle α of forward inclination of the waist W has increased relative to the vertical line when the ground contact sensing unit <NUM> senses that the artificial knee joint <NUM> is in contact with the ground.

When the artificial knee joint <NUM> is provided with the load sensor <NUM> as a load sensing unit, the ground contact sensing unit <NUM> can directly sense that the artificial knee joint <NUM> is in contact with the ground by referring to the load measured by the load sensor <NUM>. However, it might not be possible to distinguish between an ordinary walk and a backward walk merely by the load vertically above sensed by the load sensor <NUM>. In this case, the two modes of walking can be distinguished according to the thigh angle Ψ computed by using the inertial sensor <NUM>. Specifically, in an ordinary walk as shown in <FIG>, the thigh angle Ψ maintains a large positive value in the phases of walking (G) through (A), in which the prosthetic limb <NUM> is in contact with the ground, but, in a backward walk, the thigh angle Ψ makes a transition from a positive value to a negative value in the phases of walking (E) through (D), in which the prosthetic limb <NUM> is in contact with the ground. Therefore, the two modes of walking can be distinguished. It is ensured that control to weaken the rotational resistance of the knee shaft <NUM> is not performed when a backward walk is detected.

When the artificial knee joint <NUM> is not provided with the load sensor <NUM>, on the other hand, the ground contact sensing circuit <NUM> can sense whether the foot part <NUM> is in contact with the ground according to the posture of the respective parts of the prosthetic limb <NUM> (the foot part <NUM>, the lower leg part <NUM>, the knee shaft <NUM>, the thigh joint part <NUM>, the socket <NUM>, etc.) that can be sensed by referring to the measurement data of the inertial sensor <NUM> and the knee angle sensor <NUM> that function as a load sensing unit and according to geometrical computation based on the length of the artificial knee joint <NUM> acquired by the length acquisition unit <NUM>. Further, the angle α of forward inclination α of the waist W can be approximately computed from the shin angle Φ, the knee angle θ, the thigh angle Ψ, the length of the artificial knee joint <NUM> acquired by the length acquisition unit <NUM>, etc. When the inertial sensor <NUM>, which has not detected a load, detects an abrupt acceleration vertical above, it can be assumed that the foot part <NUM> moving downward hits the ground and comes to a stop, which permits a determination that the artificial knee joint <NUM> was not in contact with the ground previously. In this case, it is determined that the user walks backward when the thigh angle Ψ makes a transition from a positive value to a negative value, and control of the rotational resistance of the knee shaft <NUM> to be weaker is prohibited. Alternatively, the rotational resistance of the knee shaft <NUM> is controlled to be stronger if it has already been weakened.

A description will now be given of specific bend control of the artificial knee joint <NUM> by the rotational resistance control unit <NUM>. As described above with reference to <FIG>, the rotational resistance control unit <NUM> maintains the knee angle θ to be substantially zero in the Stance phases (A)-(C), by controlling the bending side valve <NUM> to be less open to strength the bend resistance and restricting the rotation around the knee shaft <NUM>, in order to prevent the artificial knee joint <NUM> from being bent under the weight of the wearer. In the Pre-Swing phase (D), the rotational resistance control unit <NUM> controls the bending side valve <NUM> to be more open to weaken the bend resistance gradually and permit the rotation around the knee shaft <NUM> so as to make it possible for the artificial knee joint <NUM> to start bending in preparation for the subsequent Swing phases (E)-(G), which ensures that the knee angle θ has a positive value. In the Swing phases (E)-(G), the rotational resistance control unit <NUM> maintains the bending side valve <NUM> to be highly open and maintains a state in which the bend resistance is weak and the artificial knee joint <NUM> is easily bent so as to prevent the prosthetic limb <NUM> swung away from the ground does not contact the ground.

For the purpose of realizing a smooth walk of the wearer of the prosthetic limb <NUM>, it is particularly important to cause the bending side valve <NUM> to make a transition from a less open state to a more open state and to cause the bend resistance to make a transition from a strong state to a weak state in the Mid Stance/Terminal Stance phase (C) or the Pre-Swing phase (D). If the bend resistance is weakened too early, an irregular action of the wearer of the prosthetic limb <NUM> such as an abrupt stop increases the likelihood of "knee instability" in which the artificial knee joint <NUM> that has made a transition to a state of weak bend resistance is bent unintentionally. If the bend resistance is weakened too late, on the other hand, the bend resistance remains strong even in the Initial Swing phase (E) to prohibit the artificial knee joint <NUM> from being bent so that the likelihood that the prosthetic limb <NUM> swung away in an stretched state contacts the ground is increased.

The embodiment addresses this by determining the timing of weakening the bend resistance in the Mid Stance/Terminal Stance phase (C) or the Pre-Swing phase (D) according to various criteria listed below. Each of the criteria contributes to resolution of the above issue alone, but the timing of weakening the bend resistance can be optimized by combining these criteria as appropriate.

According to the first criterion, the rotational resistance control unit <NUM> weakens the bend resistance of the knee shaft <NUM> in accordance with a transition of the thigh angle Ψ computed by the thigh angle computation unit <NUM> from positive to negative. As shown in <FIG>, the thigh angle Ψ makes a transition from positive to negative from the Loading Resistance phase (B) to the Mid Stance/Terminal Stance phase (C). Therefore, the artificial knee joint <NUM> in which the bend resistance is weakened in association with this can make a smooth transition to the Swing phases (D)-(G). The point of time when the rotational resistance control unit <NUM> starts controlling the bend resistance of the knee shaft <NUM> to be weaker, i.e., the point of time when the rotational resistance control unit <NUM> starts controlling the bending side valve <NUM> to be more open, may be a point of time when the thigh angle Ψ decreasing from positive to negative reaches <NUM> degrees, a point of time when the thigh angle Ψ falls below a negative threshold value, a point of time when the thigh angle Ψ starts to decrease, after a predetermined period of time elapses since the thigh angle Ψ starts to decrease, a point of time when the amount of decrease since the thigh angle Ψ starts to decrease is equal to greater than a predetermined amount, or a point of time when the decrease rate acquired by the thigh angular speed acquisition unit <NUM> is equal to or greater than a predetermined value.

The rotational resistance control unit <NUM> determines a point of time to start controlling the bend resistance of the knee shaft <NUM> to be weaker by also allowing for the delay time acquired by the delay time acquisition unit <NUM>. In other words, when the angular speed of the thigh angle Ψ acquired by the thigh angular speed acquisition unit <NUM> is negative, the rotational resistance control unit <NUM> starts controlling the rotational resistance of the knee shaft <NUM> to be weaker while the thigh angle Ψ is larger than a threshold value to prevent the thigh angle Ψ from falling below the threshold value during the delay time acquired by the delay time acquisition unit <NUM>. As described above, given, for example, the control period of the rotational resistance control unit <NUM> is <NUM> and the driving period of the motor for opening or closing the bending side valve <NUM> is <NUM>, a delay time of <NUM> is produced at a maximum. Given that the thigh angle Ψ is +<NUM> degrees and the thigh angular speed is -<NUM> degrees/ms, the likelihood that the thigh angle Ψ becomes <NUM> degrees or negative during the delay time of <NUM> (<NUM> degrees/ms×<NUM>=<NUM> degrees) is high. Thus, even when the thigh angle Ψ is positive (+<NUM> degrees), the rotational resistance control unit <NUM> starts controlling the bend resistance to be weaker in advance when recognizing the likelihood that the thigh angle Ψ becomes <NUM> degrees or negative during the delay time, by referring to the negative thigh angular speed (-<NUM> degrees/ms) and the delay time (<NUM>).

According to the second criterion in isolation not part of the invention, the rotational resistance control unit <NUM> weakens the bend resistance of the knee shaft <NUM> before the knee shaft <NUM> makes a transition from a point behind the load line L acquired by the load line acquisition unit <NUM> to a point in front. As shown in <FIG>, the knee shaft <NUM> makes a transition from a point behind of the load line L to a point in front of the load line L from the Mid Stance phase (C1) to the Pre-Swing phase (D). Therefore, the artificial knee joint <NUM> in which the bend resistance is weakened in association with this can make a smooth transition to the Pre-Swing phase (D) and the Swing phases (E)-(G). When the knee shaft <NUM> is behind the load line L (e.g., the Mid Stance phase (C1)), the knee shaft <NUM> is not bent regardless of the magnitude of the load. When the knee shaft <NUM> is in front of the load line L (e.g., the Pre-Swing phase (D)), on the other hand, the knee shaft <NUM> is bent provided that the load is greater than the bend resistance. Thus, the bend resistance is weakened, according to the second criterion, before the knee shaft <NUM> makes a transition from a point behind the load line L to a point in front so that the artificial knee joint <NUM> can be bent smoothly when the knee shaft <NUM> reaches a point in front of the load line L.

The point of time when the rotational resistance control unit <NUM> starts controlling the bend resistance of the knee shaft <NUM> to be weaker, i.e., the point of time when the rotational resistance control unit <NUM> starts controlling the bending side valve <NUM> to be more open, may be immediately before the knee shaft <NUM> moving from back to front reaches a point aligned to the load line L, a point of time when the knee shaft <NUM> starts a forward relative movement with respect to the load line L in the phases of walking (C1)-(D), after a predetermined period of time elapses since the knee shaft <NUM> starts a forward relative movement with respect to the load line L, a point of time when the amount of relative movement since the knee shaft <NUM> started a forward relative movement with respect to the load line L is equal to or greater than a predetermined amount, or a point of time when the forward relative speed of the knee shaft <NUM> with respect to the load line L is equal to or greater than a predetermined value. In consideration of the likelihood that the wearer of the prosthetic limb <NUM> loses balance suddenly, it is desired that control is started immediately before the knee shaft <NUM> reaches a point in front of the load line L. As in the case of the first criterion, the rotational resistance control unit <NUM> may determine a point of time to start controlling the bend resistance of the knee shaft <NUM> to be weaker by also allowing for the delay time acquired by the delay time acquisition unit <NUM>.

According to the third criterion, the rotational resistance control unit <NUM> weakens the bend resistance of the knee shaft <NUM> when the first or second criterion is met, and when the angular speed of the thigh angle Ψ and/or the shin angle Φ acquired by the angular speed acquisition unit <NUM> remains negative for a predetermined period of time continuously. As shown in <FIG>, the thigh angle Ψ and the shin angle Φ decrease and has a negative angular speed from the Loading Response phase (B) to the Pre-Swing phase (D9).

When the thigh angle Ψ and/or the shin angle Φ has a negative angular speed for a predetermined period of time continuously as described above, the likelihood of an ordinary forward walk as shown in <FIG> is high so that the rotational resistance control unit <NUM> is permitted to weaken the bend resistance of the knee shaft <NUM>. Conversely, when the thigh angle Ψ or the shin angle Φ does not have a negative angular speed for a predetermined period of time continuously, it is likely that the wearer is walking in an abnormal manner (e.g., walking backward, jumping, etc.) different from the ordinary walking mode of <FIG>, so that the wearer might fall due to knee instability if the bend resistance of the knee shaft <NUM> is weakened. Therefore, the rotational resistance control unit <NUM> secures the safety of the wearer of the prosthetic limb <NUM> by controlling the bending side valve <NUM> to be less open to strengthen the bend resistance.

According to the fourth criterion, the rotational resistance control unit <NUM> weakens the bend resistance of the knee shaft <NUM> when the first or second criterion is met and when the thigh angle Ψ and/or the shin angle Φ acquired by the inclination angle acquisition unit <NUM> at a predetermined time interval has decreased a predetermined number of times consecutively. The fourth criterion, which requires "the thigh angle Ψ and/or the shin angle Φ has decreased a predetermined number of times consecutively" is equivalent to the third criterion, which requires " the angular speed of the thigh angle Ψ and/or the shin angle Φ remains negative for a predetermined period of time continuously".

According to the fifth criterion in isolation not part of the invention, the rotational resistance control unit <NUM> weakens the bend resistance of the knee shaft <NUM> when the knee angle θ measured by the knee angle sensor <NUM> is equal to or smaller than a predetermined value. As shown in <FIG>, the knee angle θ is substantially zero in the Mid Stance/Terminal Stance phase (C), in which the bend resistance should be weakened in an ordinary walk on a level ground. When the knee angle θ is equal to or smaller than a predetermined value at a point of time to weaken the bend resistance, the likelihood of an ordinary walk on a level ground is high so that the rotational resistance control unit <NUM> is permitted to weaken the bend resistance of the knee shaft <NUM>.

Conversely, when the knee angle θ is larger than the predetermined value at a point of time to weaken the bend resistance, it is likely that the wearer is walking on a sloping road, etc., bending the artificial knee joint <NUM>. If the bend resistance of the knee shaft <NUM> is weakened, the wearer might fall due to knee instability. Therefore, the rotational resistance control unit <NUM> secures the safety of the wearer of the prosthetic limb <NUM> by controlling the bending side valve <NUM> to be less open to strengthen the bend resistance. The fifth criterion may require, in addition to or in place of the requirement that the knee angle θ is equal or smaller than a predetermined value, that the angular speed of the knee angle θ is equal to or smaller than a predetermined value. During an ordinary walk on a level ground, the angular speed of the knee angle θ is substantially zero in the Stance phases (A)-(C). During a walk on a sloping road, etc. on the other hand, the knee angle θ varies in the Stance phases (A)-(C) and has an angular speed larger than the predetermined value. Therefore, the modes of walking can be distinguished effectively.

According to the sixth criterion in isolation not part of the invention, the rotational resistance control unit <NUM> does not control the bend resistance of the knee shaft <NUM> to be weaker even if any of the above criteria are met, provided that the walking mode sensed by the walking mode sensing unit <NUM> is a particular walking mode. More specifically, when an abnormal walking mode (e.g., backward walk, jump, etc.) different from the ordinary walking mode of <FIG> and <FIG> is sensed, the wearer might fall due to knee instability if the bend resistance of the knee shaft <NUM> is weakened. Therefore, the rotational resistance control unit <NUM> secures the safety of the wearer of the prosthetic limb <NUM> by controlling the bending side valve <NUM> to be less open to strengthen the bend resistance.

According to the seventh criterion in isolation not part of the invention, the rotational resistance control unit <NUM> strengthen the bend resistance of the knee shaft <NUM> even if any of the above criteria for weakening the bend resistance is met, provided that the forward movement amount sensed by the forward movement amount sensing unit <NUM> makes a transition from a state in which the forward movement amount sensed by the forward movement amount sensing unit <NUM> is equal to or larger than a predetermined forward movement amount threshold value to a state in which forward movement amount is smaller than the forward movement amount threshold value. When the wearer of the prosthetic limb <NUM> loses speed abruptly in the Terminal Stance phase (C2) of <FIG> so that the advancing force Lx is lost, for example, only the load in the vertical direction remains so that the load line L moves behind the knee shaft <NUM>. If the bend resistance of the knee shaft <NUM> remains weakened in this state, the vertical load might cause instability of the artificial knee joint <NUM>, which might lead to a fall of the wearer. Thus, the rotational resistance control unit <NUM> secures the safety of the wearer of the prosthetic limb <NUM> by controlling the bending side valve <NUM> to be less open to strengthen the bend resistance.

The forward movement amount threshold value can be set as desired. It is preferable that the forward movement amount threshold value be set based on data for the forward movement amount in a past round of walk of the user wearing the artificial knee joint <NUM>. More specifically, the forward movement amount Lx or data indicative thereof that occurs in the Terminal Stance phase (C2) or the Pre-Swing phase (D) of <FIG> is measured in multiple rounds of walk under different conditions. The forward movement amount threshold value is set to an arbitrary value smaller than the measured amounts with significance. The bend resistance of the knee shaft <NUM> may be strengthened when the amount of decrease (loss) of the forward movement amount sensed by the forward movement amount sensing unit <NUM> exceeds a predetermined amount of decrease threshold value, or when the decrease rate (speed of loss) of the forward movement amount sensed by the forward movement amount sensing unit <NUM> exceeds a predetermined decrease rate threshold value.

According to the eighth criterion, control by the rotational resistance control unit <NUM> to weaken the bend resistance of the knee shaft <NUM> is enabled according to the above criteria, provided that the forward movement amount sensed by the forward movement amount sensing unit <NUM> is equal to or greater than a predetermined forward movement amount threshold value. In other words, when the forward movement amount Lx of a predetermined amount or greater is sensed, the likelihood of an ordinary forward walk as shown in <FIG> is high so that the rotational resistance control unit <NUM> is permitted to weaken the bend resistance of the knee shaft <NUM>.

According to the ninth criterion in isolation not part of the invention, control by the rotational resistance control unit <NUM> to weaken the bend resistance is enabled provided that a state, in which the forward movement amount sensed by the forward movement amount sensing unit <NUM> is equal to or greater than a forward movement amount threshold value, continues for a predetermined period of time. The spirit of the ninth criterion is the same as that of the eighth criterion. Requiring that a state in which the forward movement amount Lx equal to or greater than a predetermined amount continues to be sensed for a predetermined period of time makes it more certain that the wearer is walking forward ordinarily.

<FIG> is a functional block diagram of an adjustment support apparatus <NUM> for the artificial knee joint <NUM>. The elements corresponding to those of <FIG> are denoted by the same symbols, and a description thereof is omitted. The adjustment support apparatus <NUM> is provided with a walk information acquisition unit <NUM>, a control timing determination unit <NUM>, and an output unit <NUM> and is implemented in the control unit <NUM> of the artificial knee joint <NUM>.

The walk information acquisition unit <NUM> acquires walk information indicating a state of walk of the user of the artificial knee joint <NUM>. Walk information is exemplified by data itself acquired by the knee angle sensor <NUM>, the inertial sensor <NUM>, the thigh angle computation unit <NUM>, the angular speed acquisition unit <NUM>, etc., the posture and motion (speed and acceleration) of the respective parts of the prosthetic limb <NUM> that can be sensed from the data, the walking mode sensed based on the above items (see the description of the walking mode sensing unit <NUM> of <FIG>), the load line (see the description of the load line acquisition unit <NUM> of <FIG>), and the forward movement amount (see the description of the forward movement amount sensing unit <NUM> of <FIG>). These items of walk information may be acquired in a test walk done by the user wearing the artificial knee joint <NUM> for adjustment of the artificial knee joint <NUM> or may be acquired in an ordinary walk of the user wearing the artificial knee joint <NUM> after the adjustment.

The control timing determination unit <NUM> determines the timing according to which the rotational resistance control unit <NUM> weakens the bend resistance of the knee shaft <NUM>, based on the walk information acquired by the walk information acquisition unit <NUM>. More specifically, the control timing determination unit <NUM> determines the timing to weaken the bend resistance according to the first to ninth criteria described with reference to <FIG>. For example, the control timing determination unit <NUM> may, in accordance with the first criterion, determine the point of time when the thigh angle Ψ computed by the thigh angle computation unit <NUM> makes a transition from positive to negative as the point of time when the rotational resistance control unit <NUM> weakens the bend resistance of the knee shaft <NUM>. Alternatively, the control timing determination unit <NUM> may determine the point of time when the thigh angle Ψ decreasing from positive to negative reaches a threshold value set by an adjustment personnel such as a prosthetist as the point of time when the rotational resistance control unit <NUM> weakens the bend resistance of the knee shaft <NUM>. The threshold value can be set as desired by the adjustment personnel but is preferably set between -<NUM> degrees and -<NUM> degrees. The threshold value may be <NUM> degrees. It is preferable to define a negative thigh angle Ψ that cannot be formed when the wearer is standing upright ordinarily as the threshold value, because knee instability may occur contrary to the intension of the wearer of the artificial knee joint <NUM> when the wearer is standing upright with the thigh angle of <NUM> degrees. Even when the prosthetist has set -<NUM> degrees, the bend resistance of the knee shaft <NUM> may be weakened at +<NUM> degree in consideration of a control delay of <NUM> in the case of the thigh angular speed of -<NUM> deg/ms.

Alternatively, the control timing determination unit <NUM> may determine the point of time when the absolute value of the negative angular speed of the thigh angle Ψ acquired by the thigh angular speed acquisition unit <NUM> exceeds a predetermined value as the point of time when the rotational resistance control unit <NUM> weakens the bend resistance of the knee shaft <NUM>. Alternatively, the control timing determination unit <NUM> may determine the point of time when the acceleration of the wearer of the knee shaft <NUM> in the direction of travel exceeds a predetermined acceleration threshold value as the point of time when the rotational resistance control unit <NUM> weakens the bend resistance of the knee shaft <NUM>. Alternatively, the control timing determination unit <NUM> may, in accordance with the second criterion, determine the point of time when the knee shaft <NUM> makes a transition from a point behind the load line to a point in front as the point of time when the rotational resistance control unit <NUM> weakens the bend resistance of the knee shaft <NUM>. Alternatively, the control timing determination unit <NUM> may, in accordance with the eighth criterion, determine the point of time when the forward movement amount exceeds the forward movement amount threshold value as the point of time when the rotational resistance control unit <NUM> weakens the bend resistance of the knee shaft <NUM>.

The control timing determination unit <NUM> may determine the point of time when the rotational resistance control unit <NUM> weakens the bend resistance of the knee shaft <NUM> based on a reference point of time set by the adjustment personnel of the artificial knee joint <NUM> and acquired by a reference timing acquisition unit <NUM>. More specifically, the control timing determination unit <NUM> compares the walk information recorded when the reference timing was set by the adjustment personnel such as a prosthetist with the current walk information acquired by the walk information acquisition unit <NUM> in real time, adds the variation determined by the discrepancy to the reference point of time, and defines the result as the point of time to weaken the bend resistance.

The output unit <NUM> outputs the timing determined by the control timing determination unit <NUM> outside. The adjustment personnel such as a prosthetist can adjust the artificial knee joint <NUM> efficiently for each user, while referring to the timing output in accordance with the actual walk information on the user wearing the artificial knee joint <NUM>.

Described above is an explanation of the present invention based on an embodiment. The embodiment is intended to be illustrative only and it will be understood by those skilled in the art that various modifications to constituting elements and processes could be developed and that such modifications are also within the scope of the present invention.

The functional configuration of the apparatuses described in the embodiment can be realized by hardware resources or software resources or a cooperation of hardware resources and software resources Processors, ROMs, RAMs, and other LSIs can be used as hardware resources. Programs such as operating systems and applications can be used as software resources.

In those the embodiments disclosed in this specification in which a plurality of functions are distributed, some or all of the plurality of functions may be aggregated. Conversely, an aggregation of a plurality of functions may be distributed in part of in the entirety. Regardless of whether functions are aggregated or distributed, the functions may be configured to achieve the purpose of the invention.

Claim 1:
An artificial knee joint (<NUM>) comprising:
a thigh joint part (<NUM>) provided on a side of a thigh part;
a lower leg part (<NUM>) coupled to the thigh joint part (<NUM>) and provided to be rotatable around a knee shaft (<NUM>);
a thigh part inclination angle acquisition unit that acquires an inclination angle formed by the thigh part relative to a vertical line passing through the knee shaft (<NUM>);
a rotational resistance control unit (<NUM>) that weakens a rotational resistance of the knee shaft (<NUM>) in accordance with a transition from a positive inclination angle formed when the thigh part is inclined rearward relative to the vertical line to a negative inclination angle formed when the thigh part is inclined forward relative to the vertical line, characterized by further comprising:
a thigh part inclination angular speed acquisition unit that acquires an angular speed of the inclination angle of the thigh part; and
a delay time acquisition unit (<NUM>) that acquires a delay time that elapses until a result of control by the rotational resistance control unit (<NUM>) is reflected in the rotational resistance, wherein
when the angular speed of the thigh part is negative, the rotational resistance control unit (<NUM>) starts controlling the rotational resistance of the knee shaft (<NUM>) to be weaker while the inclination angle of the thigh part is larger than a predetermined threshold value so as to prevent the inclination angle of the thigh part from falling below the threshold value during the delay time.