High torque active mechanism for orthotic and/or prosthetic devices

Abstract

A high torque active mechanism for an orthotic and/or prosthetic joint using a primary brake which can be provide by magnetorheological (MR) rotational damper incorporating and an additional friction brake mechanism driven by the braking force generated by the MR damper. This combination of MR damper and friction brake mechanism allows an increase in torque density while keeping the same level of motion control offered by the MR damper alone. The increased torque density achieved by this high torque active mechanism allows to minimize the size of the actuating system, i.e. its diameter and/or breath, while maximizing its braking torque capability. In this regard, the friction brake mechanism is advantageously positioned around the MR damper, such that the dimension of the package is minimized.

Claims

1. A torque sensor for an orthotic or prosthetic device comprising a joint portion thereof for providing flexion and extension movement of the device, an actuator providing a controllable force during at least one of the flexion and extension movements, and a frictional band member configured to generate a frictional force during flexion and/or extension movements, said torque sensor comprising: a deformable portion mounted to the joint portion; and a sensor in operational communication with said deformable portion to measure a deformation of said deformable portion, wherein when a braking torque is provided by the actuator the frictional band member provides an additional braking torque which is transmitted to said deformable portion causing deformation thereof, and said sensor measures the deformation of said deformable portion thereby allowing for determining the torque.

2. A torque sensor according to claim 1, wherein said deformable portion comprises a deformable strip and a deformable frame, the deformable strip mounted within the deformable frame.

3. A torque sensor for an orthotic or prosthetic device according to claim 1, wherein the torque sensor comprises a strain-sensor.

4. A prosthetic or orthtotic device comprising: at least one device portion; a joint portion for providing for said at least one device portion to pivot between flexion and extension movements relative to another adjacent device portion or an adjacent limb segment of the user, the joint portion further comprising an actuator providing a controllable force during at least one of the flexion and extension movements; a frictional band member configured to generate a frictional force on the joint portion during flexion and/or extension movements provided by the joint portion; and a torque sensor comprising a deformable portion mounted to said joint portion, and a sensor portion in operational communication with said deformable portion to measure a deformation of said deformable portion, wherein when a braking torque is provided by the actuator said frictional band member provides an additional braking torque which is transmitted to said deformable portion causing deformation thereof, and said sensor measures the deformation of said deformable portion thereby allowing for determining the torque.

5. A prosthetic or orthotic device according to claim 4, further comprising at least one support for mounting the device portion to the joint portion.

6. A prosthetic or orthotic device according to claim 5, wherein the torque sensor is positioned on the at least one support.

7. A prosthetic or orthotic device according to claim 5, further comprising at least one support for mounting the another adjacent device portion or an adjacent limb segment of the user to the joint portion.

8. A prosthetic or orthotic device according to claim 4, wherein said deformable portion comprises a deformable strip and a deformable frame, the deformable strip mounted within the deformable frame.

9. A prosthetic or orthotic device according to claim 4, further comprising a pressure pad adjacent the frictional band member and configured to reversibly cause the frictional band member to be pushed onto the joint portion such that the frictional band member generates the frictional force when pushed by the pressure pad.

10. A prosthetic or orthotic device according to claim 9, wherein the pressure pad comprises a lever.

11. A prosthetic or orthotic device according to claim 4, wherein the joint portion comprises a drum, and the frictional band member is configured to generate the frictional force by contacting the drum.

12. A prosthetic or orthotic device according to claim 4, wherein the joint portion further comprises an actuator configured to controllably exert a rotational force on the at least one device portion.

13. A prosthetic or orthotic device according to claim 12, wherein the actuator comprises a MR damper.

14. A prosthetic or orthotic device according to claim 12, wherein the actuator comprises a mechanical actuator.

15. A prosthetic or orthotic device according to claim 12, wherein the actuator comprises an electric actuator.

16. A prosthetic or orthotic device according to claim 12, wherein the actuator comprises a pneumatic actuator.

17. A prosthetic or orthotic device according to claim 12, wherein the actuator comprises a hydraulic actuator.

18. A prosthetic or orthotic device according to claim 4, wherein the torque sensor comprises a strain-sensor.

19. A prosthetic or orthotic device according to claim 4, wherein the joint portion comprises a knee joint.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Illustrative embodiments of the invention will be described by way of non-limiting examples only with reference to the accompanying drawings, in which like reference numerals indicate like elements throughout and in which:

(2) FIG. 1 is a perspective view of an actuated orthotic device in accordance with an illustrative embodiment of the present invention;

(3) FIG. 2 is a perspective view of a high torque active mechanism according to the illustrative embodiment of the present invention;

(4) FIG. 3 is an exploded perspective view of the high torque active mechanism of FIG. 2;

(5) FIG. 4 is a cross-sectional view of a magnetorheological (MR) rotational damper of the high torque active mechanism of FIG. 2 in accordance with an illustrative embodiment thereof;

(6) FIG. 5 is an exploded perspective view of the magnetorheological (MR) rotational damper of FIG. 4 in accordance with an illustrative embodiment thereof;

(7) FIG. 6 is a lateral side view of the friction band brake mechanism of the high torque active mechanism of FIG. 2 in accordance with an illustrative embodiment thereof;

(8) FIG. 7 is a lateral side view of the flexure mechanism of the friction band brake mechanism of FIG. 6 in accordance with an illustrative embodiment thereof;

(9) FIG. 8 is a lateral side view of the of the flexure mechanism of FIG. 7 in a deformed position;

(10) FIG. 9 is a lateral side view of the frictional braking mechanism of the friction band brake mechanism of FIG. 6 in accordance with an illustrative embodiment thereof;

(11) FIG. 10 is a lateral side view of the torque sensor of the high torque active mechanism of FIG. 2 in a accordance with an illustrative embodiment thereof; and

(12) FIG. 11 is a lateral side view of the torque sensor of the high torque active mechanism of FIG. 10 in a deformed position.

DESCRIPTION OF THE ILLUSTRATIVE EMBODIMENTS

(13) Generally stated, the present invention provides an orthotic/prosthetic device comprising at least one device portion (an orthotic portion or a prosthetic portion), a joint portion for providing for the at least one device portion to pivot between flexion and extension movements relative to another adjacent device portion or an adjacent limb segment of the user. A primary brake is in operational communication with the joint portion for generating a braking force thereon during flexion and/or extension movements. An additional frictional brake is in operational communication with both the primary brake and the joint portion. During flexion the primary brake causes the additional frictional brake to generate an additional frictional braking force on the joint portion.

(14) Generally stated, a non-limitative illustrative embodiment of the present invention provides high torque active mechanism for an orthotic and/or prosthetic joint using a magnetorheological (MR) rotational damper incorporating a friction brake mechanism driven by the braking force generated by the MR damper. This combination of MR damper and friction brake mechanism allows an increase in torque density while keeping the same level of motion control offered by the MR damper alone.

(15) The increased torque density achieved by this high torque active mechanism allows to minimize the size of the actuating system, i.e. its diameter and/or breath, while maximizing its braking torque capability. In this regard, the friction brake mechanism is advantageously positioned around the MR damper, such that the dimension of the package is minimized.

(16) In the context of the forgoing description, “actuator” is used to describe a mechanical device for creating or controlling mechanical motion and as such the high torque active mechanism of the invention comprises an actuator or an actuation/actuator mechanism.

(17) Referring to FIG. 1, there is shown a perspective view of the high torque active mechanism 10 applied to an actuated orthotic device 12.

(18) The actuated orthotic device 12 generally comprises proximal (upper) 14 and distal (lower) 16 device portions. The device portions 14, 16, as depicted, can include structural portions or shells and other components required for the control of the actuation mechanism such as, for example, a processing module 18, power management module 20, a power source 22, for example removable battery packs, integrated to the proximal orthotic shell 14 and a sensor module 24 integrated to the distal orthotic shell 16, feeding inertial data to the processing module 18.

(19) The high torque active mechanism 10 may be mounted on the actuated orthotic device 12 on the lateral side of the user's knee K and is operationally connected between the proximolateral structural support 26 and the distolateral structural support 28 which form part of the proximal 14 and distal 16 portions respectively. A conventional hinge 30 may be used on the medial side, if required, to connect the proximal 14 and distal 16 portions or structural shells.

(20) Referring to FIG. 2, the high torque active mechanism 10 includes a joint portion 32′ in the form of a joint assembly 32 connecting the proximolateral 26 and the distolateral 28 structural supports. A magnetorheological (MR) rotational damper 34 is mounted to the joint assembly 32 and commands the braking torque provided by the high torque active mechanism 10. A rotational sensor 36 located on the MR damper 34 and measures the relative angle between the proximolateral 26 and the distolateral 28 structural supports. A torque sensor 38 is mounted on the proximolateral structural support 26 and the joint assembly 32 and measures the torque provided by the joint assembly 32. An additional frictional brake, namely braking mechanism 40 is mounted to the distolateral structural support 28 and the joint assembly 32 and is controlled by a primary brake, namely in this example, the braking torque provided by the MR damper 34 to augment the total braking capacity of the high torque active mechanism 10.

(21) The joint assembly 32 includes an extension assist spring 42 to help the proximolateral 26 and the distolateral 28 structural supports get back in the extended position as well a rotational locking mechanism 44 which may be activated and deactivated by the user to manually block the high torque active mechanism 10, and consequently the actuated orthotic device 12, at a given angle. The rotational locking mechanism 44 may be, for example, a pin that may be inserted or removed to lock and unlock the rotor from the stator (both of which will be detailed further below).

(22) Referring now to FIG. 3, there is shown an exploded view of the complete joint assembly 32. As shown, the MR damper module 34 is surrounded by a frictional member in the form of a friction band brake mechanism 46 (also see FIG. 6) which is part of the additional frictional brake 40. Each side plate 48a and 48b (also see FIG. 5) of the MR Damper module is respectively attached to bearing covers 50a and 50b. The needle bearings sets 52a and 52b ensure radial positioning of the MR Damper rotor assembly (which as will be further discussed herein and as shown in FIG. 5 comprises cover plates 48a, 48b, rotor body 82, electromagnetic core 80, inductive coil 78, inner splines 81, and rotor blades 74) into the stator body 54, while trust washers 56a and 56b ensure axial positioning. The upper or proximolateral structural support 26 is permanently attached onto the stator body 54 via a rotating member in the form of a band brake drum 58. The lower or distolateral structural support 28 is attached to the bearing covers 50a and 50b through the brake pad levers 60a and 60b respectively. The friction band brake mechanism 46 comprises a frictional band 63. The fixed end 62 of the band 63 is secured to the bearing covers 50a and 50b with a retaining pin 64 through holes 67b. A locking pin 66 also allows to block the rotational movement between the upper or proximolateral structural support 26 and the bearing covers 50a and 50b when inserted in the holes 67a of covers 50a and 50b and of protuberance 59 of the band brake drum 58. A resilient flexible bumper 65 is mounted to the retaining pin 64.

(23) MR Damper

(24) Referring to FIGS. 4 and 5, the controllable dissipative braking torque in the MR damper 34 is obtained by applying a magnetic field 68 through the magnetorheological fluid 70 occupying interstices between the stator blade array 72 and rotor blade array 74. The fluid 70 is sealed from the outside by rotational dynamic seals 76 (see FIG. 5). The magnetic field 68 can be dynamically controlled by regulating the current circulating in the inductive coil 78 winded around the electromagnetic core 80 within the inner spline 81. In the absence of a magnetic field 68, the magnetorheological fluid 70 viscosity is very low and the rotor body 82 is free to rotate inside the stator body 84. When the magnetic field increases, the fluid's ferromagnetic particles align with the magnetic field and created shear resistance between stator blades 72 and rotor blades 74, offering a breaking torque against applied moment through the knee joint.

(25) As previously mentioned, for this invention, the MR damper 34 provides only a portion of the braking torque of the device: the friction brake provides the remaining braking torque. The main advantage of combining both braking technologies over a device comprised of only an MR damper is the greater torque density obtained without compromising the controllability. This results in a smaller package for a given braking torque capacity.

(26) A non-limiting example of a MR damper 34 that may be used is described in U.S. Pat. No. 6,764,520 issues to Deffenbaugh et al. on Jul. 20, 2004 and incorporated herein by reference in its entirety. Of course, as the skilled artisan will readily understand a variety of MR dampers can be used and contemplated within the scope of the present invention.

(27) Friction Band Brake Mechanism

(28) With reference to FIG. 6, the friction band brake mechanism 46 in accordance with an embodiment of the present invention will now be described.

(29) Typically, a friction brake mechanism is complex to control and difficult to drive—as the contact forces required for the friction components are important relative to the size of the package. In the present invention, the friction band brake mechanism 46 is indirectly piloted by torque generated by the MR damper 34, which is easily and continuously controllable by regulating the current in the inductive coil.

(30) In order to provide a compact package, the band-brake type braking system benefits of the substantially cylindrical configuration of the outer diameter of MR damper 34. The friction band brake mechanism 46 is piloted as follows: as the MR damper 34 provides a braking torque, this torque is transmitted to the brake pad lever, generally denoted 60, which basically transforms the torque into a pressure on the pressure pad 86 through a pressure pad engaging portion, namely a leveling system 88. The leveling system 88 is free to rotate around the leveling axis 90 and ensures that the pressure on the pressure pad 86 remains mostly even on its entire surface. The pressure pad 86 transmits the pressure to the free extremity 91, defining a downward flap, of the band 63. The other extremity 62 of the band 63 and the brake pad levers 60a and 60b (see FIG. 3) are connected to the lower or distolateral structural support 28 through the bearing covers 50a and 50b. More specifically, the fixed end 62 is mounted to the bearing covers 50a and 50b, via the retaining pin 64 which engages the respective holes 67b of the covers 50a and 50b. Furthermore, the covers 50a and 50b are also attached to the pad levers 60a and 60b which in turn are mounted to the lower or distolateral structural support 28.

(31) In general, as the band brake drum 58 is also part of the upper structural support 26 as well as being part of the joint portion 32′, the rotation of the upper structural support 26 creates a relative motion between the band 63 and the drum 58. If the rotation of the upper structural support occurs in the clockwise direction (R1 as viewed in FIG. 6 or FIG. 2) during flexion of the joint K, and if the MR damper 34 provides resistive torque, the free extremity 91 of the band 63 will be pulled in the R1 direction, activating this way the whole band brake mechanism 46 and creating an additional braking torque. A more detailed operation will be described further below.

(32) The braking torque provided by the band brake mechanism 46 will be directly proportional to the torque of the MR Damper 34. The band brake mechanism 46 therefore acts as a torque multiplier for the MR Damper 34. The torque multiplication factor typically stands between 120% and 150%

(33) It should be noted that the band brake mechanism 46 will not provide braking torque if the upper structural support 26 pivots or rotates in the counterclockwise or R2 direction, during extension of the joint K, because in this case the braking pad 86 as well as the free extremity 91 of the band brake 63 will be pulled away from the drum 58. In this case, only the MR Damper module 34 will provide braking torque.

(34) The torque multiplication factor provided by the band brake mechanism 46 can be computed with the following information: the tension applied on the free extremity 91 of the band brake 63; the coefficient of friction of the band brake 63 surface with the drum 58; and the contact angle of the band brake 63.

(35) The torque is computed using the following formulas:
M=(T.sub.1−T.sub.2).Math.R  (1)
And
T.sub.1=T.sub.2.Math.e.sup.μθ  (2)

(36) In this implementation of the band brake mechanism 46, the tension (F.sub.2) applied on the free extremity 91 of the band 63 is a reaction to the pressure applied on the free extremity 91 of the band brake 63 by the pressure pad 86. This pressure creates a friction force (F.sub.1) that is computed with the force (F.sub.pad) exerted by the pressure pad 86 and the coefficient of friction (μ) of the band brake 63 on the drum 58.
T.sub.2=μ.Math.F.sub.pad  (3)

(37) The force exerted on the pressure pad 86 depends on the geometry of the brake pad lever 60a and 60b and on the total torque exerted by the actuator 10 the relative to the knee joint K. The force can be computed with the following formula:

(38) $\begin{array}{cc}{F}_{\mathrm{pad}}=\frac{T_{\mathrm{total}}}{L_{\mathrm{lever}}}& \left(4\right)\end{array}$

(39) Where

(40) T.sub.total=Total torque of the actuator

(41) L.sub.lever=Effective lever of the brake pad lever (60a or 60b, but can generally be denoted as 60 in FIGS. 6 to 9)

(42) Brake Pad Lever

(43) With reference to FIGS. 7, 8 and 9, the brake pad lever 60 will be discussed in further detail.

(44) In the present illustrative embodiment, the brake pad lever 60 is a flexure mechanism that provides a virtual pivot point 92. Another embodiment could include a standard rotational axis, such as a bearing. The virtual pivot point 92 provides to move the pivot point further away from the actuator mechanism 10, allowing extending the Effective Lever (L.sub.lever), therefore reducing the pressure applied by the pressure pad 86.

(45) The effective pivot point 92 of the flexure mechanism 60 is theoretically located at the intersection 92 of the lines A and B respectively created by the extension of the two flexures A′ and B′, as shown in the FIG. 7.

(46) FIG. 8 shows deformed shape, which has been exaggerated here for descriptive purposes only, of the flexure mechanism 60 obtained by Finite Elements Analysis. This is valid for small deformations only, but in this application, the displacement will be very small considering that the gap between the pressure pad 86 and the band brake 63 is very small—in the order of 0.25 mm. It should be noted that at the lever length L.sub.lever remains basically the same than in FIG. 7.

(47) With reference to FIG. 9, the brake pad lever 60 is that it is pushed away from the drum by a biasing member 94 in the form of a spring. Biasing spring 94 is mounted between a shoulder formed by the covers, generally denoted here by reference 50 and the shoulder 61 of the lever 60. The spring 94 ensures that the pressure pad 86 does not apply pressure on the band brake 63 when it is not desirable. In fact, one of the design criteria for the actuator 10 of the present invention is to maintain a high ratio between the maximum torque provided and the drag torque when the actuator 10 freely rotates. For that reason, it is desirable to ensure that the pressure pad 86 does not apply a pressure on the band brake 63 when the MR damper 34 is not activated. In fact, this situation normally happens when the joint K is in free swing (when the leg flexes and extends as the foot is not in contact with the ground). The spring 94 therefore provides the required force to maintain the pressure pad 86 away from the band brake 63 and drum 58 when the MR damper 34 is deactivated and while the joint K is moving in free swing (typically, the spring 94 provides the required force to oppose the drag torque of the MR Damper 34 at a maximum rotational speed of 360 deg/s).

(48) A screw (not shown) coaxial to the spring 94 maintains the spring 94 pre-compressed to the desired force and maintains the brake pad lever 60 at the desired distance from the drum 58. It is important to so minimize the total gap between the pressure pad 86 and the drum 58, such that the user will not feel a step in the braking resistance when the band brake 56 engages. The aforementioned screw is also utilized to adjust this gap as the friction material wears.

(49) Torque Sensor

(50) The torque provided by the hybrid actuator 10 is directly measured using a torque sensing module 38 as displayed in FIG. 10. The torque sensor 38 comprises a deformable strip 96 inserted into a deformable frame 98. The braking torque of the actuator 10 is transmitted through the deformable frame 98 and causes the frame 98 to deform slightly. FIG. 11 shows an exaggerated deformation of the torque sensor 38: The deformable strip 96 is affected by the shape change of the frame 98 and deforms also in a generally S-shaped curve. Strain gages (not shown) are placed on the deformable strip 96 allow measuring the deformation and it is possible to compute the torque based on the measured deformation.

(51) Of course, as the skilled artisan will readily comprehend other implementations for measuring the torque are possible, such as measuring the tension of the band 63 through strain gages or through the measured deformation of a spring on which the band 63 would be attached to give but two examples.

(52) For clarity purposes only, it should be noted that the additional frictional brake, which was exemplified in the form of a frictional braking mechanism 40, also provides a frictional braking assembly comprising both the frictional band brake mechanism 46 (having band 63) and a brake pad assembly which includes the band brake lever 60 as well as the pressure pad 86.

(53) Operation of the High Torque Mechanism 10

(54) In operation, during rotation of the drum 58 (along with the upper structure 26), in the clockwise direction R1 (flexion of joint K) about the stator body 54 via the bearing 52a and 52b and between the fixed covers 50a and 50b. As the drum 58 rotates, the MR damper 34, when activated, will begin to resist and progressively break the rotational movement thereof. As the user goes beyond the foregoing resistive force or breaking force, this additional force (for moving drum 58 along with structure 26 in the R1 direction) deforms the break pad lever 60 (as represented in FIG. 8). As the lever 60 deforms, it is brought closer to the drum 58, thereby pushing the breaking pad 86 onto the band 63 and thereby pushing the band 63 onto the drum 58. Thereby, causing the band 63 to rotate or to be trained along with the drum 58 in the R1 direction as it is lead by the free end 91. Since the fixed end 62 of the band is anchored in position as described above, the trained band 63 is progressively strained or stretched as the free end 91 progressive moves in the R1 direction, this tension frictionally breaks the rotating movement of the drum 58.

(55) When rotating the drum 58 in the counterclockwise direction (R2 in FIGS. 2 and 6), the lever 60 returns to its normal or non-deformed shape (see FIG. 7) moving away from the drum 58. Thereby, releasing the breaking pad 86 from being pushed onto the band 63, hence releasing the straining force on the band 63 and as such releasing the frictional force on the drum 58. The drum 58 continues to rotate in the R2 direction until its protuberance 59 engages the in resilient flexible bumper 65 that is fixedly mounted to retaining pin 66. Retaining pin 66 and bumper 65 therefore act as a stopper, the resilient and flexible bumper 65 provides for a cushioned stop.

(56) It should be noted that although not illustrated, the high torque active mechanism can be applied to an actuated prosthetic device in accordance with the present invention.

(57) It is to be understood that the invention is not limited in its application to the details of construction and parts illustrated in the accompanying drawings and described hereinabove. The invention is capable of other embodiments and of being practiced in various ways. It is also to be understood that the phraseology or terminology used herein is for the purpose of description and not limitation. Hence, although the present invention has been described by way of particular embodiments and examples thereof, it should be noted that it will be apparent to persons skilled in the art that modifications may be applied to the present particular embodiment without departing from the scope of the present invention.