Shape memory material actuator and hybrid actuator having the same

Abstract

The shape memory material actuator has a frame, a pair of terminals connected to the frame, a motion mechanism movable relative to the frame, and a length of shape memory material extending between and connected to the pair of terminals. A portion of the length of shape memory material extending between the pair of terminals also extends over a surface of the motion mechanism such that contraction of the length of shape memory material applies a force in compression to the motion mechanism, thereby displacing it. Hybrid actuators can include shape memory material actuators as well as non-back-drivable non-shape memory material actuators coupled to the frame. Hybrid actuators can be used inside robotic manipulators to control joints that flex in response to the movement of floating pulleys through which artificial tendons connected to the hybrid actuators are threaded.

Description

[Technical field]

[0001] Technical Field FIELD OF THE DISCLOSURE

[0001] The present disclosure is directed to shape memory material actuators and hybrid actuators having shape memory material actuators. [Background technology]

[0002] background

[0002] The human hand is an impressive biomechanical device. It can be positioned in any number of different orientations, can carefully approach an object for grasping at various distances and speeds, and, if necessary, can rapidly apply a grasping force to the object well in excess of the force required to initially move the hand in its vicinity. Moreover, it does this while being relatively small and lightweight. As a result, efforts to create robotic manipulators have focused primarily on mimicking the desirable properties of the hand. Summary of the Invention [Means for solving the problem]

[0003] overview

[0003] According to a first aspect, there is provided a shape memory material actuator comprising a frame, a pair of terminals connected to the frame, a motion mechanism movable relative to the frame, and a length of shape memory material extending between and connected to the pair of terminals, wherein a portion of the length of shape memory material extending between the pair of terminals also extends over a surface of the motion mechanism such that contraction of the length of shape memory material applies a force in pressure contact with the motion mechanism and thereby displaces it.

[0004]

[0004] The shape memory material actuator may further include a first group of one or more pulleys at one angular position about the motion mechanism and a second group of one or more pulleys at another angular position about the motion mechanism. Individual portions of the length of shape memory material may be reeved through the first and second groups of pulleys, and the portion of the length of shape memory material applying a force in compression to the motion mechanism may be located between the portions of the length of shape memory material reeved through the first and second groups of pulleys.

[0005]

[0005] Each of the pulleys may be seated on an electrically insulating axle and may have a metallic sheave.

[0006]

[0006] The motion mechanism may have a channel through which the length of shape memory material extends, in which case the surfaces along which the length of shape memory material applies a force in a pressed state comprise the walls of the channel, and a first group of one or more pulleys may have a first block and tackle having opposing sets of pulleys, a second group of one or more pulleys may have a second block and tackle having opposing sets of pulleys, and the channel may be positioned axially along the motion mechanism between the opposing sets of pulleys having the first block and tackle and between the opposing sets of pulleys having the second block and tackle.

[0007]

[0007] Contraction of the length of the shape memory material can cause the motion mechanism to move from an unactuated position to an actuated position, and the shape memory material actuator can further include a spring positioned to urge the motion mechanism from the actuated position back to the unactuated position.

[0008]

[0008] The spring can bias the walls of the channel of the motion mechanism against the frame when the motion mechanism is in a non-actuated position.

[0009]

[0009] The shape memory material may include a shape memory alloy that contracts in response to an electrical signal.

[0010]

[0010] The frame may be electrically insulating.

[0011] The shape memory material actuator may further include a current sensor electrically coupled to the first pair of terminals for measuring the stress experienced by the length of the shape memory material.

[0012]

[0012] The shape memory material actuator may further include an infrared position sensor aligned with the motion mechanism and positioned to emit infrared light toward the motion mechanism. The tip of the motion mechanism may be convex and infrared reflective.

[0013]

[0013] The movement mechanism may have a piston.

[0014]

[0014] According to another aspect, a hybrid actuator is provided having a first shape memory material actuator having a shape memory material actuator of any of the aspects described above or a suitable combination thereof, and a non-back-drivable non-shape memory material actuator connected to a frame.

[0015]

[0015] The non-shape memory material actuator can have a worm gear DC electric motor and an output pulley powered by the worm gear DC electric motor. More generally, and regardless of whether the non-shape memory material actuator has a different type, the self-locking worm gear is one way in which the non-shape memory material actuator can be non-backdrivable.

[0016]

[0016] The frame may have a printed circuit board and a pair of terminals, and the worm gear DC electric motor may be mounted to the printed circuit board.

[0017]

[0017] The hybrid actuator may further comprise one or more further shape memory material actuators. Each of the one or more further shape memory material actuators may comprise a shape memory material actuator of any of the above-mentioned aspects or suitable combinations thereof. The movement mechanisms of the first shape memory material actuator and of the one or more further shape memory material actuators may be fixed together.

[0018]

[0018] According to another aspect, a robotic manipulator is provided comprising an end effector having a robotic joint, the robotic joint having a floating pulley, and movement of the floating pulley causing bending of the robotic joint; a hybrid actuator having a first shape memory material actuator and a non-back-drivable non-shape memory material actuator; and an artificial tendon connected to the first shape memory material actuator and the non-shape memory material actuator, where a portion of the artificial tendon is located between where the artificial tendon is connected to the first shape memory material actuator and where the non-shape memory material actuator is reeved through the floating pulley.

[0019]

[0019] The first shape memory material actuator may have any of the shape memory material actuator aspects described above or any suitable combination thereof, and the artificial tendon may be connected to the movement mechanism of the first shape memory material actuator.

[0020]

[0020] The non-shape memory material actuator can have a worm gear DC electric motor and an output pulley powered by the worm gear DC electric motor. At least a portion of the second artificial tendon can be reeved through the output pulley. More generally, and regardless of whether the non-shape memory material actuator has a different type, the self-locking worm gear is one way that the non-shape memory material actuator can be non-backdrivable.

[0021]

[0021] The frame may have a printed circuit board and a pair of terminals, and the worm gear DC electric motor may be mounted to the printed circuit board.

[0022]

[0022] The robot manipulator may further comprise one or more further shape memory material actuators, each of which comprises a shape memory material actuator of any of the above aspects or suitable combinations thereof. The motion mechanisms of the first shape memory material actuator and of the one or more further shape memory material actuators may be fixed together.

[0023]

[0023] The one or more further shape memory material actuators may be secured together using one or more connectors and the first artificial tendon may be attached to the one or more connectors.

[0024]

[0024] The robotic manipulator may further have a controller communicatively coupled to the hybrid actuator and configured to use the non-shape memory material actuator to move the end effector to a first position and to use the first shape memory material actuator to apply a gripping force to an object using the end effector when the end effector is in the first position.

[0025]

[0025] The robotic manipulator may have a robotic hand and may be arranged with a hybrid actuator, and the hybrid actuator may be arranged on the outside of the fingers that form part of the robotic hand.

[0026]

[0026] According to another aspect, there is provided a method of using a robotic manipulator of any of the above aspects or suitable combinations thereof, the method comprising using a non-shape memory material actuator to move an end effector to a grasping position, and using a first shape memory material actuator to apply a grasping force to an object using the end effector when the end effector is in the grasping position.

[0027]

[0027] This summary does not necessarily describe the entire scope of all aspects. Other aspects, features, and advantages will become apparent to those of ordinary skill in the art upon review of the following description of specific embodiments.

[0028] BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The accompanying drawings, which show one or more example embodiments, are as follows: [Brief description of the drawings]

[0029] [Figure 1]

[0029] Figure 1 illustrates a robotic hand with hybrid actuators according to an illustrative embodiment. [Figure 2A]

[0030] 2 illustrates a hybrid actuator and robotic phalanges that form part of the robotic hand of FIG. 1 according to an illustrative embodiment. [Figure 2B]

[0031] 2B depicts a cross-sectional view of the robotic phalange of FIG. 2A taken along line 2B-2B of FIG. 2A. [Diagram 3]

[0032] FIG. 2B depicts a perspective view of the hybrid actuator of FIG. 2A in an unactuated state. [Figure 4]

[0033] FIG. 2B depicts a top view of the hybrid actuator of FIG. 2A in an unactuated state. [Diagram 5]

[0034] FIG. 2B depicts a front view of the hybrid actuator of FIG. 2A in an unactuated state. [Figure 6] FIG. 2B illustrates a rear view of the hybrid actuator of FIG. 2A in an unactuated state. [Figure 7]

[0035] FIG. 2B depicts a right side view of the hybrid actuator of FIG. 2A in an unactuated state. [Figure 8] FIG. 2B illustrates a left side view of the hybrid actuator of FIG. 2A in an unactuated state. [Figure 9]

[0036] FIG. 2B depicts a front view of the hybrid actuator of FIG. 2A in an actuated state. [Figure 10] FIG. 2B illustrates a rear view of the hybrid actuator of FIG. 2A in an actuated state. [Figure 11]

[0037] 2B illustrates a front view of the hybrid actuator of FIG. 2A in an unactuated state, in which the frame of one of the shape memory material actuators that form part of the hybrid actuator has been removed to reveal the interior of the hybrid actuator. [Figure 12]

[0038] 2B illustrates a block diagram of a circuit that constitutes a portion of the hybrid actuator of FIG. 2A. [Figure 13]

[0039] 10 illustrates a method of using a robotic manipulator in conjunction with a hybrid actuator according to another illustrative embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0030] Detailed Description

[0040] Robotic manipulators, such as robotic hands used for prosthetic limbs and robotic end effectors used for production processes such as assembly and sorting, are becoming increasingly prevalent. In part, this is due to developments in artificial intelligence based techniques, for example in the field of computer vision, which allow relatively sophisticated recognition and manipulation of objects by manipulators.

[0031]

[0041] Regardless of the application of a robotic manipulator, generally speaking, to grasp an object, the manipulator's end effector is first positioned in a "grasping position" adjacent the object and then used to apply a grasping force to the object. The characteristics of the force used to move the end effector to the grasping position and the grasping force itself are significantly different. That is, a relatively small amount of force is typically required to move the end effector a relatively large distance in positioning the end effector in the grasping position and prior to grasping. In contrast, the grasping force itself is relatively large and moves the end effector only a small distance, if at all.

[0032]

[0042] Direct current electric motors ("DC motors") can be used as actuators for end effectors. While reasonably sized DC motors can be used to move end effectors over long distances, DC motors suffer from a relatively low power-to-weight ratio. As a result, DC motors are a poor choice for generating gripping forces for end effectors, especially when used as prosthetic limbs, given the large weight and size of DC motors that would be required. In contrast, shape memory alloys ("SMAs"), which are metallic alloys that deform in response to changes in temperature, can also be used as actuators for end effectors. SMAs have a higher power-to-weight ratio than DC motors, and tend to have relatively small (e.g., about 4% to about 8%) recoverable deformations. This makes SMAs more suitable than DC motors for use in generating gripping forces for end effectors.

[0033]

[0043] Given the complementary properties of SMAs and DC motors, attempts have been made in the actuator environment to combine DC motors with SMA actuators, however these attempts have suffered from one or more technical problems such as unacceptably large positional inaccuracies (e.g., deviations of about 5%), orientation of the SMA resulting in large stresses being applied to the SMA and resulting in relatively short SMA operational life and / or reduced SMA performance, the inability to directly monitor the forces generated by the SMA, bulky mechanical designs that do not lend themselves to the miniaturization required to fit actuators within prosthetic hands, and interference between actuation generated by the DC motor versus the SMA.

[0034]

[0044] In at least some embodiments herein, shape memory material ("SMM") actuators and hybrid actuators having SMM actuators are described. SMMs are elastically deformable materials that deform in response to changes in temperature. One example of an SMM is an SMA, but other examples of SMMs are, for example, polymer-based (e.g., they include at least one polymer and may exclude any metallic alloys). SMM actuators generally include a frame, a pair of terminals connected to the frame, a motion mechanism movable relative to the frame, and a length of SMM extending between and connected to the pair of terminals. The length of SMM used in the depicted embodiments is a filament of SMM, and generally speaking, a "filament" can include, for example, a fiber, rope, string, strand, cord, thread, or ribbon. More generally, any suitably shaped length of SMM can be used in an SMM actuator. For example, the length of SMM can include a flat sheet of polymer-based SMM configured to be capacitive or to be a bar of SMM.

[0035]

[0045] A portion of the filament extending between the pair of terminals also extends over the surface of the motion mechanism such that contraction of the filament applies a force to the motion mechanism in a compressed state and thus displaces it. Contraction can be obtained, for example, as a result of application of an electrical signal across the terminals such that the SMM heats up and thus contracts. Various pulleys positioned about the motion mechanism can be used to increase the length of the SMM that the actuator can accommodate in a space-efficient manner, while keeping the stress experienced by the SMM relatively small, thereby increasing the amount of force that the SMM actuator can generate in a space-efficient manner. Multiple SMM actuators can be aligned and connected together to further increase the total output force available from a single device in a space-efficient manner. A hybrid actuator may have one or more SMM actuators and other non-SMM actuators such as DC motors, where 1) the output of the one or more SMM actuators and 2) the output of the non-SMM actuators are connected to first and second artificial tendons, respectively. As a result, a non-SMM actuator and one or more SMM actuators can be used, respectively, to position a robotic manipulator, such as a prosthetic limb, in a grasping position and to apply a grasping force to an object without interfering with each other.

[0036]

[0046] Referring now to FIG. 1, a perspective view of a robotic hand 100 is depicted, which is an example of a robotic manipulator according to an illustrative embodiment. The robotic hand 100 has a palm 102 and five fingers 104, where each finger 104 has a proximal, middle, and distal phalanges. Disposed within the palm 102 is a hybrid actuator 200, such as that depicted in FIG. 2A. In FIG. 2A, the hybrid actuator 200 is shown connected to a robotic joint 204 at the base of one of the middle phalanges 202 of the hand 100 via first and second artificial tendons 206a,b. FIG. 2B shows a cross-section of the robotic joint 204 taken along line 2B-2B in FIG. 2A. The artificial tendons 206a,b can be constructed, for example, from nylon-coated braided steel cable. 2B illustrates three robotic joints 204 depicting the proximal, middle, and distal phalanges of the robotic hand 100, with the floating pulley 208, bolt 210, and mandrel 212 of only the middle phalange labeled for clarity of illustration. A first portion of the first artificial tendon 206a (e.g., a first end of the artificial tendon 206a) is connected to a motion mechanism 314a,b (shown in FIGS. 3, 5, 6, and 9-11) that constitutes a part of the first and second SMM actuators 300a,b, a second portion of the first artificial tendon 206b (e.g., a second end of the artificial tendon 206b) is connected to an output pulley 310 of the hybrid actuator 200, which is powered by a DC motor 1102 (shown in FIG. 11), and a third portion of the artificial tendon 206a between the first and second portions is reeved through the floating pulley 208. Thus, different ends of the artificial tendon 206a can be actuated by the DC motor 1102 and by the SMM actuators 300a,b, respectively. Actuation by one or both of the DC motors 1102 and by the SMM actuators 300a,b translates the entire floating pulley 208 through space, thereby bending the robotic joint 204 and causing it to rotate about the mandrel 212.A tension spring 212 is attached to the second artificial tendon 206b, which is attached to the bolt 210. The tension spring 212 is attached to an attachment point located, for example, in the palm 102, which restores the robotic joint 204 to a straight position in the absence of actuation by the DC motor 1102 and SMM actuators 300a,b.

[0037]

[0047] 3-8, which respectively depict perspective, plan, front, and rear views, and right and left side views, of the hybrid actuator 200 shown in FIG. 2A in an unactuated state. FIGS. 9 and 10 respectively depict front and rear views of the hybrid actuator of FIG. 2A in an actuated state. As shown particularly in FIG. 3, the hybrid actuator 200 generally includes adjacent first and second SMM actuators 300a,b, each having a first and second frame 302a,b. FIG. 11 depicts the first frame 302a removed from the hybrid actuator 200 to show the interior of the hybrid actuator 200. A description of the structure of the hybrid actuator 200 will now be provided with reference to FIGS. 3-11.

[0038]

[0048] More specifically, the hybrid actuator 200 has adjacent first and second SMM actuators 300a,b and a non-SMM actuator in the form of a DC motor 1102, which may be of the brushed or brushless type. A DC motor 1102 is used as an example non-SMM actuator in the depicted embodiment, although alternative types of non-SMM actuators are possible in different embodiments. Exemplary alternative types of non-SMM actuators include AC motors, hydraulic systems, gas pressure systems, and solenoid-based systems, and generally speaking, these non-SMM actuators have the ability to provide a large range of motion to cause the robot joint 204 to move to a corresponding extent within the gripping position. In the depicted embodiment, the first and second SMM actuators 300a,b are identical. Focusing now on the first SMM actuator 300a, the first SMM actuator 300a includes a first frame 302a, a first pair of terminals 312a connected to the first frame 302a, a first motion mechanism 314a movable relative to the first frame 302a, and a first filament of shape memory material ("SMM filament") 322a extending between and connected to the pair of terminals 312a. The frame 302a and the pair of terminals 312a are attached to a PCB 304 on the bottom of the hybrid actuator 200. The SMM filament 322a in the depicted embodiment includes an SMA such as Flexinol™, which is a type of Nitinol™ nickel titanium alloy, although other suitable SMAs or SMMs may be used.The portion of the SMM filament 322a that extends between the pair of terminals 312a also extends over the surface of the motion mechanism 314a such that contraction of the SMM filament 322a applies a force to and thereby displaces the motion mechanism 314a in a compressive state, thereby causing the SMM actuator 300a to move in a translational manner to its "actuated state" as shown in Figure 9, and while for purposes of clarity Figure 9 shows the SMM actuator 300a in its "fully actuated state", more generally the actuated state includes any state in which the SMM filament 322a is contracted such that the motion mechanism 314a shifts downward relative to its position as shown in Figure 5, even if the motion mechanism 314a is not shifted as far downward as shown in Figure 9. The SMM filament 322a contracts in response to an electrical signal applied across its terminals 312a, causing an electrical current to flow through the SMM filament 322a, thereby heating it and causing it to contract. In the depicted embodiment, the motion mechanism 314a has a piston that displaces axially downward toward the PCB 304 upon actuation, although in other embodiments (not depicted), actuation of the SMM actuator 300a can result in different types or directions of motion (e.g., rotational motion or non-axial translational motion).

[0039]

[0049] The SMM actuator 300a has a first block and tackle 324a with opposing sets of pulleys at one angular position about the motion mechanism 314a, and a second block and tackle 324b with opposing sets of pulleys at another angular position about the motion mechanism 314a. As depicted, the first and second block and tackles 324a,b are separated by 180 degrees in the depicted embodiment (i.e., the first and second block and tackles 324a,b and the motion mechanism 314a are aligned), although they can have different angular separations in other embodiments. More generally, the blocks and tackles 324a,b are individual examples of first and second groups of one or more pulleys around which the SMM filament 322a is reeved, where the portion of the SMM filament 322a that applies a force in a compressive state to the motion mechanism 314a upon actuation is located between the portions of the SMM filament 322a reeved through the first and second groups of pulleys, respectively.

[0040]

[0050] In the depicted embodiment, each of the pulleys has a sheave fabricated using 7075 aluminum with 1 mm x 3 mm x 1 mm steel micro-bearings to reduce friction during contraction and relaxation of the SMM filament 322a in response to application and removal of an electrical signal across the terminals 312a, respectively. The 7075 aluminum is used due to its hardness, which helps prevent the pulleys from deforming when under pressure from the SMM filament 322a; indeed, the pulleys are designed to withstand stresses in the range of, for example, 1850 psi to 2250 psi (12.76 kPa to 15.51 kPa). Additionally, the aluminum has a small enough thermal mass to prevent the pulleys from storing excess residual heat from the SMM filament 322a, while still allowing them to function as a heat sink during relaxation of the SMM filament 322a. The steel micro-bearings have a lower thermal conductivity than the aluminum sheaves, and also function to insulate the pulley axle 1106.

[0041]

[0051] Because the SMM filament 322a is electrically conductive, it is desirable to prevent any two points along the length of the SMM filament 322a from being electrically shorted together when an electrical signal is applied across the terminals 312a due to current being conducted by anything other than the SMM filament 322a itself. Given that the SMM filament 322a and the aluminum sheaves of the pulley are electrically conductive, to prevent electrical shorting when the SMM actuator 300a is in an actuated state, the pulley is seated on an electrically insulating axle 1106, and more particularly, in the depicted embodiment, the axle 1106 is a fiberglass rod. Additionally, the frame 302a itself is fabricated from an electrically insulating material, such as a glass composite resin; for example, the frame 302a may be 3D printed from Rigid 10k™ resin and heat cured to promote greater strength and operating temperature.

[0042]

[0052] The motion mechanism 314a has a first hollow rod 320a extending between and projecting from opposite sides of the motion mechanism 314a, more specifically, the rod 320a projects from and extends through the sides of the motion mechanism 314a facing the first and second blocks and tackles 324a,b, respectively, thereby defining a channel through which the SMM filament 322a passes and acting as a channel wall. The rod 320a, and therefore the channel, is positioned axially along the motion mechanism 314a between the opposing sets of pulleys having the first block and tackle 324a and between the opposing sets of pulleys having the second block and tackle 324b. The motion mechanism 314a also extends through a coil spring 318a biased against the frame 302a and a first lip 326a on the motion mechanism 314a. When the SMM actuator 300a is in a fully actuated state, as shown in Figures 9 and 10, the retracted SMM filament 322a applies a force against the lip 326a against the bottom portion of the frame 302a. When the SMM actuator 300a is in an unactuated state, the spring 318a biases the lip 326a until the rod 320a contacts the top portion of the frame 302a. As a result, the spring 318a assists in the transition of the motion mechanism 314a from an actuated position to an unactuated position, and further maintains the motion mechanism 314a in the unactuated position until an electrical signal is applied to the terminal 312a. The spring 318a also assists in keeping the SMM filament 322a in a stressed state when in an unactuated state to prevent the SMM filament 322a from slipping off the pulley.

[0043]

[0053] In the depicted embodiment, the motion mechanism 314a is located between the two blocks and tackles 324a,b, although different configurations are possible in different embodiments (not depicted). The motion mechanism 314a may be adjacent to one edge of the frame 302a, for example, and the blocks and tackles 324a,b may be disposed adjacent to each other and between the motion mechanism 314a and the other edge of the frame 302b. As another example, the first block and tackle 324a may be in one plane, the second block and tackle 324b may be in a different second plane, and the motion mechanism 314a may be positioned between these two planes, as opposed to the blocks and tackles 324a,b and the motion mechanism 314a being located on the same plane.

[0044]

[0054] The rod 320a may be made of any suitable material, such as metal (e.g., brass or aluminum) or ceramic. And while the spring 318a in the depicted embodiment is a coil spring through which and along which the motion mechanism 314a extends, in different embodiments (not depicted), the spring 318a may have a different configuration. For example, the spring 318a in different embodiments may include a coil spring or a leaf spring that is not located on the motion mechanism 314a.

[0045]

[0055] The second SMM actuator 300b, in the depicted embodiment, is identical in structure to the first SMM actuator 300a. The first frame 302a, first pair of terminals 312a, first motion mechanism 314a, first spring 318a, first rod 320a, first SMM filament 322a, first and second block and tackle 324a,b, and first lip 326a of the first SMM actuator 300a are respectively similar to the second frame 302b, second pair of terminals 312b, second motion mechanism 314b, second spring 318b, second rod 320b, second SMM filament 322b, third and fourth block and tackle 324c,d, and second lip 326b of the second SMM actuator 300b. Although the first and second SMM actuators 300a,b are identical in the depicted embodiment, in a different embodiment (not depicted) they need not be identical. For example, the two actuators 300a,b could have different numbers of pulleys, different types and / or lengths of SMMs, and / or different SMM orientations.

[0046]

[0056] A connector in the form of a bolt 316 connects the first and second motion mechanisms 314a,b together. The bolt 316 extends perpendicular to the motion mechanisms 314a,b in the depicted embodiment. As shown in FIG. 4, the top of each of the first and second frames 302a,b has slots that collectively form an aperture 402 that allows the first artificial tendon 206a to be connected to the bolt 316. The total force acting on the first artificial tendon 206a due to the bolt 316 connecting the motion mechanisms 314a,b together is the sum of the forces generated by each of the SMM actuators 300a,b. Additionally, the use of pulleys in the SMM actuators 300a,b in the depicted embodiment allows the length of the SMM filaments 322a,b to be increased in a space efficient manner relative to an embodiment lacking pulleys. Thus, the pulley and bolt 316 both contribute to increasing the amount of force that the SMM actuators 300a,b can collectively generate and apply to the artificial tendon relative to known conventional systems.

[0047]

[0057] 11 specifically, a non-SMM actuator is adjacent to the SMM actuators 300a,b. In the depicted embodiment, the non-SMM actuator comprises a DC motor 1102 mechanically coupled to an output pulley 310 by a worm gear 1104, thereby allowing the DC motor 1102 to power the output pulley 310 (the DC motor 1102 and worm gear 1104 are collectively a "worm gear DC motor"). Although the depicted embodiment shows the DC motor 1102 as the non-SMM actuator, in a different embodiment (not depicted), the non-SMM actuator could instead comprise a different type of actuator, as discussed above. Due to the worm gear, the worm gear DC motor is self-locking and, as a result, non-back-drivable, such that pressure applied to the worm gear through the artificial tendons 206a, such as when the SMM actuators 300a,b are being used to apply a gripping force, will not move the worm gear 1104 or DC motor 1102 and inadvertently change the position of the joint 204. Although a worm gear is used to make the DC motor 1102 non-back-drivable, different embodiments can use different mechanisms such as a ratchet, including different embodiments that use types of non-SMM actuators other than the DC motor 1102, such as the AC motors mentioned above, hydraulic systems, gas pressure systems, or solenoid-based systems.

[0048]

[0058] Figure 12 illustrates a block diagram 1200 of a circuit having a portion of the hybrid actuator of Figure 2A. The block diagram 1200 shows a controller 1202, which may comprise, for example, an STM32™ microprocessor. The controller 1202 is communicatively coupled to first and second infrared ("IR") position sensors 1204a,b used to monitor the position of each of the first and second SMM filaments 322a,b, an encoder 306 used to monitor the position of the DC motor 1102, which returns a digital signal representative of the position of the DC motor 1102 (i.e., the amount that the output shaft of the DC motor 1102 has rotated), a programming probe 1206 used to program the controller 1202, a motor driver 1208 for driving the DC motor 1102 and more specifically for controlling the direction and speed of the DC motor 1102, and a power field effect transistor ("FET") 1210 for applying electrical signals to first and second pairs of terminals 312a,b to operate the first and second actuators 300a,b, respectively. The encoder 306 includes a cylindrical rotating magnet and a pair of Hall effect sensors that respond to the position of the magnet by outputting respective "Hall-1" and "Hall-2" signals in block diagram 1200. The "Force 1" and "Force 2" signals in block diagram 1200 represent signals representative of the current flowing through the first and second SMM filaments 322a,b, as measured through first and second shunt resistors, respectively, thereby allowing a direct measurement of the force being experienced by the first and second SMM filaments 322a,b.

[0049]

[0059] The controller 1202, IR position sensors 1204a,b, programming probe 1206, motor driver 1208, power FETs 1210, and encoder 302 are all mounted on PCB 304. Block diagram 1200 also shows a master board 1212 that receives USB serial and power inputs via a flexible printed cable connector 1214 and outputs power, clock, and various other signals to the controller 1202. The master board 1212 is located in a suitable location outside the palm 102 of the robotic hand 100, such as in a compartment (not depicted) connected to the base of the hand 100.

[0050]

[0060] As shown in FIG. 11 with respect to the first SMM actuator 300a, the first IR position sensor 1204a is aligned with the longitudinal axis of the piston with the first motion mechanism 314a. The IR position sensor 1204a outputs IR light and receives a reflection of the emitted IR light from the tip of the first motion mechanism 314a, and then determines the distance from the sensor 1204a to the tip of the motion mechanism 314a from the transit time of the reflected IR signal. To facilitate proper reflection of the IR light, the tip of the motion mechanism 314a is convex, and in the depicted embodiment, hemispherical. In addition, the tip of the motion mechanism 314a and the portion of the frame 302a exposed to the IR light are IR reflective (e.g., painted white) so that the IR position sensor 1204a can measure a sufficiently strong reflected IR signal. In another embodiment (not depicted), the frame 302a may not be located close enough to the tip of the motion mechanism 314a to ensure that it is IR reflective.

[0051]

[0061] 2A, the first artificial tendon 206a is connected on one end to the bolt 316, passes through the aperture 402, is reeved through the floating pulley 208, and has an opposite end connected to the output pulley 310. Thus, the hybrid actuator 200 can actuate the robot joint 204, and more generally any suitable end effector, by using different types of forces output by the DC motor 1102 and the SMM actuators 300a,b to apply pressure to the end of the artificial tendon 206a reeved through the floating pulley 208. This causes the entire floating pulley 208 (i.e., sheaves and axle) to move through space, thereby bending the finger 104. As a result, threading the artificial tendon 206a through the floating pulley 208 results in less precision error and greater grip strength of the pulley than would result from SMM filament 322a being directly connected to the axle of floating pulley 208. For purposes of clarity, and as discussed above, actuation of SMM actuators 300a,b includes actuation resulting from contraction of SMM filaments 322a,b that only partially shifts motion mechanisms 314a,b such that hollow rods 320a,b are not biased against the bottom portions of frames 302a,b.

[0052]

[0062] 13 illustrates a flow chart of a method 1300 of using a robotic manipulator that may be implemented using, for example, the hybrid actuator 200. The controller 1202 first uses a non-SMM actuator, such as a worm gear DC motor, to move an end effector, such as a robotic hand 100, to a gripping position, in block 1302. Then, when the end effector is in the gripping position, the controller 1202 uses at least a first SMM actuator 300a to apply a gripping force to an object using the end effector, in block 1304. The method 1300 may be expressed as computer program code stored in a memory that constitutes a part of the controller 1202 and executable by a processor that constitutes a part of the controller 1202, such that when the controller 1202 executes the computer program code, the hybrid actuator 200 performs the method 1300. The computer program code may implement, for example, an overdamped proportional-integral-derivative ("PID") controller to control the end effector.

[0053]

[0063] Thus, the hybrid actuator 200 as depicted in the figures and described above allows for independent application of forces by the DC motor 1102 and the SMM filaments 322 a, b, has reduced position error when a gripping force is applied to the robot joint 204 as shown in FIG. 2B in relation to at least some alternative hybrid actuators, provides real-time position feedback using the encoders 306 and IR position sensors 1204 a, b, helps maintain the stress on the SMM filaments 322 a, b in an acceptable state by using pulleys to orient the SMM filaments 322 a, b in a preferred manner and by monitoring the stress on the SMM filaments 322 a, b using current sensing, and achieves this in a space efficient manner by using pulleys and a stacked design that allows the forces generated by multiple SMM actuators 300 a, b to be combined. Various other embodiments (not shown) of the hybrid actuator 200 may illustrate only a subset of these features (e.g., it may allow for independent application of forces by non-SMM and SMM actuators, and may result in reduced position error when used in conjunction with the floating pulley 208 of FIG. 2B, in the absence of pulley and current / position sensing).

[0054]

[0064] The embodiments have been described above with reference to flow, sequence, and block diagrams of methods, apparatuses, systems, and computer program products. In this regard, the depicted flow, sequence, and block diagrams illustrate the architecture, functionality, and operation of implementations of various embodiments. For example, each block and sequence diagram of the flow and block diagrams may represent a module, segment, or portion of code, which may have one or more executable instructions for implementing one or more actions specified. In some alternative embodiments, one or more actions described in the block or operation may occur in a different order than described in the diagram. For example, two blocks or operations shown in a sequential manner may be executed substantially simultaneously in some embodiments depending on the functions involved, or the blocks or operations may often be executed in the reverse order. Although some specific examples of the above-mentioned subject matter are described above, the described examples are not necessarily the only examples. Each block and sequence diagram operation of the flow and block diagrams, and combinations of those blocks and operations, can be implemented by a system based on special purpose hardware that performs the specified functions or acts, or by a combination of special purpose hardware and computer instructions.

[0055]

[0065] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting. Thus, the singular forms "a," "an," and "the" as used herein should be construed to include the plural forms as well, unless the context clearly indicates otherwise. It should be further understood that the terms "comprises" and "comprising," as used herein, specify the presence of one or more stated features, integers, steps, operations, elements, and components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and groups. Directional terms such as "top," "bottom," "upwards," "downwards," "vertically," and "laterally" are used in the following description only to provide a relative reference and are not intended to imply any limitations on the manner in which any item must be positioned in use or attached in an assembly or with respect to an environment. In addition, as used herein, the term "connect" and variations thereof such as "connected," "connects," and "connecting" are intended to include indirect and direct connections unless otherwise indicated. For example, if a first device is connected to a second device, the coupling may be through a direct connection or may be through an indirect connection via other devices and connections. Similarly, when a first device is communicatively connected to a second device, the communication may be through a direct connection or may be through an indirect connection via other devices and connections.The term "and / or" as used herein in the context of a list means any one or more of the items from that list. For example, "A, B, and / or C" means "any one or more of A, B, and C."

[0056]

[0066] The controller 1202 used in the above-described embodiments may comprise, for example, a processor unit (processor, microprocessor, or programmable logic controller) communicatively coupled to a non-transitory computer-readable medium having stored thereon program code for execution by a processing unit, a microcontroller (having both a processing unit and a non-transitory computer-readable medium), a field programmable gate array (FPGA), a system-on-chip (SoC), an application-specific integrated circuit (ASIC), or an artificial intelligence accelerator. Examples of computer-readable media are non-transitory and include disk-based media such as CD-ROMs and DVDs, magnetic media such as hard drives and other forms of magnetic disk storage, semiconductor-based media such as flash media, random access memory (including DRAM and SRAM), and read-only memory.

[0057]

[0067] It is contemplated that any portion of any aspect or embodiment described herein can be implemented or combined with any portion of any other aspect or embodiment described herein.

[0058]

[0068] In interpreting the claims, it should be understood that the use of a computing device, such as a processor, to implement the embodiments described herein is essential at least if the presence or use of that computing device is affirmatively recited in the claims.

[0059]

[0069] One or more exemplary embodiments have been described for purposes of illustration only. This description has been presented for purposes of illustration and description, and is not intended to be exhaustive or limited to the disclosed form. It will be apparent to one skilled in the art that certain modifications and variations can be made without departing from the scope of the claims.

Claims

1. (a) a frame; (b) a pair of terminals connected to the frame; and (c) a motion mechanism movable relative to the frame; (c) a length of shape memory material extending between and connected to the pair of terminals, a portion of the length of shape memory material extending between the pair of terminals also extending over a surface of the motion mechanism such that contraction of the length of shape memory material applies a force in compression to the motion mechanism, thereby displacing it; and A shape memory material actuator comprising:

2. (a) a first group of one or more pulleys at an angular position about the motion mechanism; (b) a second group of one or more pulleys at another angular position about the motion mechanism, wherein individual portions of the length of the shape memory material are reeved through the first and second groups of pulleys, and the portions of the length of the shape memory material that apply a force in compression to the motion mechanism are located between the portions of the length of the shape memory material reeved through the first and second groups of pulleys; and The shape memory material actuator of claim 1 further comprising:

3. 3. The shape memory material actuator of claim 2, wherein each of said pulleys is seated on an electrically insulating axle and has a metallic sheave.

4. (a) the motion mechanism has a channel through which a length of the shape memory material extends, the surface along which the length of the shape memory material applies a force in compression comprises a wall of the channel; and (b) the first group of one or more pulleys has a first block and tackle with opposing sets of pulleys, the second group of one or more pulleys has a second block and tackle with opposing sets of pulleys, and the channel is positioned axially along the motion mechanism between the opposing sets of pulleys having the first block and tackle and between the opposing sets of pulleys having the second block and tackle.

4. A shape memory material actuator according to claim 2 or 3.

5. 5. A shape memory material actuator as described in any one of claims 1 to 4, wherein the contraction of the length of the shape memory material causes the motion mechanism to move from an unactuated position to an actuated position, and further comprising a spring positioned to urge the motion mechanism back from the actuated position to the unactuated position.

6. 6. The shape memory material actuator of claim 5, wherein the spring biases the wall of the channel of the motion mechanism against the frame when the motion mechanism is in the unactuated position.

7. 7. A shape memory material actuator according to claim 1, wherein the shape memory material comprises a shape memory alloy that contracts in response to an electrical signal.

8. The shape memory material actuator of claim 7 , wherein the frame is electrically insulating.

9. 9. A shape memory material actuator as claimed in any preceding claim, further comprising a current sensor electrically coupled to the first pair of terminals for measuring a stress experienced by a length of the shape memory material.

10. 10. A shape memory material actuator as claimed in any one of claims 1 to 9, further comprising an infrared position sensor aligned with the motion mechanism and positioned to emit infrared light towards the motion mechanism, the tip of the motion mechanism being convex and infrared reflective.

11. 11. The shape memory material of claim 1, wherein the movement mechanism comprises a piston.

12. (a) a first shape memory material actuator comprising the shape memory material actuator of any one of claims 1 to 11; (b) a non-back-drivable, non-shape memory material actuator connected to the frame; and A hybrid actuator comprising:

13. The non-shape memory material actuator comprises: (a) a worm gear DC electric motor; (b) an output pulley powered by said worm gear DC electric motor; and The hybrid actuator of claim 12 comprising:

14. (a) the frame has a printed circuit board; and (b) the pair of terminals and the worm gear DC electric motor are mounted on the printed circuit board; A hybrid actuator according to claim 13.

15. further comprising one or more additional shape memory material actuators; Each of the one or more further shape memory material actuators comprises a shape memory material actuator according to any one of claims 1 to 8, and 15. A hybrid actuator according to any one of claims 12 to 14, wherein the movement mechanisms of the first shape memory material actuator and of the one or more further shape memory material actuators are fixed together.

16. (a) an end effector having a robotic joint, the robotic joint having a floating pulley, and movement of the floating pulley causing bending of the robotic joint; (b) a hybrid actuator having (i) a first shape memory material actuator; and (ii) a non-back-drivable, non-shape memory material actuator; (c) an artificial tendon connected to the first shape memory material actuator and the non-shape memory material actuator, a portion of the artificial tendon being located between where the artificial tendon is connected to the first shape memory material actuator and where the non-shape memory material actuator is reeved through the floating pulley; A robot manipulator comprising:

17. The first shape memory material actuator comprises a shape memory material actuator according to any one of claims 1 to 11, and 17. The robotic manipulator of claim 16, wherein the artificial tendon is connected to the motion mechanism of the first shape memory material actuator.

18. The non-shape memory material actuator comprises: (a) a worm gear DC electric motor; (b) an output pulley powered by said worm gear DC electric motor; and having 18. The robotic manipulator of claim 17, wherein at least a portion of the second artificial tendon is reeved through the output pulley.

19. (a) the frame has a printed circuit board; and (b) the pair of terminals and the worm gear DC electric motor are mounted to the print path substrate; 20. The robotic manipulator of claim 18.

20. further comprising one or more further shape memory material actuators; Each of the one or more further shape memory material actuators comprises a shape memory material actuator according to any one of claims 1 to 11, and 20. A robotic manipulator according to any one of claims 17 to 19, wherein the movement mechanisms of the first shape memory material actuator and of the one or more further shape memory material actuators are fixed together.

21. the one or more further shape memory material actuators are secured using one or more connectors; and 21. The robotic manipulator of claim 20, wherein the first artificial tendon is attached to the one or more connectors.

22. communicatively coupled to the hybrid actuator; and (a) using the non-shape memory material actuator to move the end effector to a first position; and (b) using the first shape memory material actuator to apply a gripping force to an object using the end effector when the end effector is in the first position; 22. A robot manipulator according to any one of claims 16 to 21, further comprising a controller configured to:

23. the robotic manipulator has a robotic hand; and 23. The robot manipulator of claim 16, wherein the hybrid actuators are positioned outside fingers that form part of the robotic hand.

24. 24. A method of using the robot manipulator of any one of claims 16 to 23, comprising the steps of: (a) using the non-shape memory material actuator to move the end effector to a gripping position; (b) using the first shape memory material actuator to apply a gripping force to an object using the end effector when the end effector is in the gripping position; A method comprising:

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