Continuum robot stiffening

Abstract

To provide means for improving the stiffness and reaction of a robotic system to external and internal loads that are placed upon the robotic system.SOLUTION: There is provided a rigid link for a flexible robot. The rigid link comprises a rigid link body having a hollow core. The rigid link is provided with at least two arms having proximal and distal ends. The arms are connected to the rigid link body. The arms are deployable between: a closed configuration in which the proximal and distal ends of the arms are positioned proximate to the rigid link body; and an open configuration in which the arms are moved so that the distal ends of the arms are positioned away from the body of the rigid link.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to a means for stiffening a flexible-arm robot, and in particular to a means for stiffening a section of a flexible-arm robot by means of compliant tendrils extending from a core of rigid links. [Background technology]

[0002] Continuum-arm or snake-arm robots are of growing interest in several applications because they can be maneuvered into spaces not easily accessible by other robotic systems or human operators. This is due to the ability to manipulate the body with several degrees of freedom so that end instruments can be precisely and easily positioned. This positioning is controlled by actuators that operate tendons within the robot so that each joint of the arm can be individually controlled within a high degree of positional precision.

[0003] Most robotic arm systems have six or fewer degrees of freedom. However, if a task requires a greater amount of dexterity, the number of degrees of freedom required is increased. This increase in the number of degrees of freedom means that the arm can operate in a confined area, for use, for example, in repairing complex structures or in minimally invasive surgery. Continuum-arm robots are designed along two main lines: first, snake-type robots consisting of multiple rigid link sections connected either by rigid R / U / S (revolute / swivel / ball) joints or by compliant joints. Each section is composed of one or more pieces and is controlled independently of the others by on-board or remote actuation. Second, there are continuum robots consisting of a compliant backbone, whose local and global deformations are controlled by one or more actuators.

[0004] Despite the above functionality, there are problems with current designs of highly compliant robots that result from the number of joints required in the robot arm. As a result of these joints, the robot arm suffers from a lower degree of stiffness when compared to conventional six-degree-of-freedom robots. This reduced stiffness also results in a reduced load capacity, reducing the interaction the arm can have with the environment in which it operates. Current technology aims to overcome this by "freezing" the system by locking actuators or by adding stiffening means to the backbone. While this may work for shorter length robotic arms, when used with longer length robots, the arm behaves like a long cantilever beam, and deflection of the beam causes significant position and navigation problems. This limits the use of such robots to light-duty tasks due to the risk of damaging the robot and / or the object on which it is working. Therefore, there is a need for an improved continuum-arm robot system to overcome these problems. Summary of the Invention [Means for solving the problem]

[0005] According to a first aspect of the present disclosure, there is provided a rigid link for a flexible robot, the rigid link including a rigid link body having a hollow core and provided with at least two arms having proximal and distal ends, the arms being connected to the rigid link body and being deployable between a closed configuration in which the proximal and distal ends of the arms are positioned adjacent to the rigid link body, and an open configuration in which the arms are moved such that the distal ends of the arms are positioned away from the body of the rigid link.

[0006] The arms can be individually controlled. The arms may be individually deployable. The arms can be opened so that they have different distances between the distal ends of the arms and the flexible robot body.

[0007] The proximal end of the arm may be pivotally connected to the body of the rigid link. The arms may be tendrils having elastic properties and may be configured to curve when deployed. The tendrils may be formed from nitinol and may be notched along the length of the tendrils.

[0008] The body of the rigid link may be shaped to house portions of the arms along the length of the arms. The arm may be extensible perpendicular to an axis parallel to the hollow core of the rigid link body. The arms may be formed from a folded origami structure. The arm may be actuated by a motor, tendon, or linear actuator. The arm may be provided with a sensor. The ends of the arms may be compliant so that they do not damage the workspace. The sensors can be used to determine the forces applied between the arm and the workspace in which the flexible robot is operating.

[0009] The flexible robot may be a continuum arm robot. The rigid link may be incorporated into the body of the continuum robot. The rigid links may be positioned around the outer body of the continuum arm robot.

[0010] According to a second aspect of the present disclosure, there is provided a method of operating a flexible-arm robot according to any one of the preceding claims, comprising the steps of: inserting a flexible-arm robot into a cavity in a workpiece until the flexible-arm robot reaches a desired positioning; deploying the arms of the rigid link section from their closed positions to their open positions; performing a desired task using the tip section of the flexible arm robot; retracting the arms of the rigid link section from their open positions to their closed positions; The step of extracting the flexible arm robot A method is provided, comprising:

[0011] After the step of retracting the arms of the rigid link sections, the flexible arm robot may be repositioned and the arms deployed to perform further tasks before the arms are retracted again.

[0012] Those skilled in the art will appreciate that, except where mutually exclusive, a feature described in relation to any one of the above-described embodiments may be applied mutatis mutandis to any other embodiment. Furthermore, except where mutually exclusive, any feature described herein may be applied to any embodiment and / or combined with any other feature described herein. Embodiments will now be described, by way of example only, with reference to the figures, in which: [Brief explanation of the drawings]

[0013] [Figure 1a] FIG. 1a shows a prior art example of a cutaway view of a continuum arm robot. [Figure 1b] FIG. 1b is a diagram showing an example of a joint of a continuum arm robot. [Figure 2] 1A-1D illustrate examples of deflection of a continuum arm robot according to the prior art and the present disclosure. [Figure 3] 1A and 1B illustrate rigid link profiles for a continuum arm robotic system according to the present disclosure. [Figure 4]10A-10C illustrate alternative configurations of rigid links for a continuum arm robotic system according to the present disclosure. [Figure 5] Figure 5a shows an example of the tendril arm in its closed configuration, and Figure 5b shows an example of the tendril arm in its open configuration. [Figure 6] 10A-10C illustrate alternative configurations of rigid links for a continuum arm robotic system according to the present disclosure. [Figure 7] FIG. 1 illustrates a flowchart of the operation of a continuum-arm robot according to the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0014] Aspects and embodiments of the present disclosure will now be discussed with reference to the accompanying figures. Further aspects and embodiments will be apparent to those skilled in the art.

[0015] FIG. 1a shows a prior art example of a cutaway view of a continuum arm robot. The prior art continuum arm robot includes a continuum arm robot portion 101 that is permanently integrated and extends from an actuator pack 102. The actuator pack 102 contains multiple independent actuators 103. These actuators are used to adjust tension in tendons that run through the continuum arm 101. The tendons are associated with joints in the arm, each of which is designed to move in response to tightening or loosening of the tendons associated with the joint. This tightening or loosening of the tendons therefore causes the joint to contract or lengthen, which allows the continuum arm to bend. The actuator pack is shown positioned on rails or supports 104 that are positioned near the component to be tested. The actuators are further provided with multiple power and signal cables 105 that are used to power and address the actuators. Individual signals traversing the array of actuators provide joint control so that the continuum arm 101 can be commanded. Not shown in Figure 1 is the need for an operator with a computing device linked to the actuator to control the movement of the continuum arm and to perform the desired task. Because the continuum arm is permanently integrated into the actuator pack, if a different instrument is required, it requires the use of a complete continuum arm robot system including the actuator. The computing device connected to the prior art actuator can be any suitable computing system, such as a laptop computer, featuring the requisite operating software for the robot and a control input, such as a joystick, that allows the continuum arm to be controlled.

[0016] FIG. 1b shows an example of a continuum-arm robot joint. The arm includes multiple joints, requiring at least two cables per joint. For example, a system with three joints, each with four tendons per joint, would require 12 actuators to actuate. Increasing the number of joints requires either an increased number of actuators or a reduced number of tendons per joint. Highlighted joints 106, 107, and 108 are capable of being manipulated to move in three dimensions. The joints are configured such that joints 106 and 108 are capable of bending in the same plane relative to the center of the arm, while the plane in which joint 107 can move is shifted by 90° relative to joints 106 and 108. It is this repeated configuration of alternating joint angles, each resulting in movement in a different orthogonal plane, that allows the arm to be manipulated in three dimensions. Each joint in the arm has a limit to the amount it can bend, which is dictated by the arm's design and the materials used. The bending limit at each joint sets properties such as the minimum bend radius and the torque required to cause a resulting change in the joint. It is the presence of space at the joints that allows the joints to move and the ease of joint movement results in the arm's low stiffness compared to other robotic arms of the same length. This is because the structural behavior of a snake-type robotic manipulator can be likened to a cantilever beam under load, since the system is fixed at one end to a base with an actuation puck, and the remainder of the arm is used to navigate through the environment without any other points of contact. In this situation, any load applied to the snake-type robot's body and / or tip, including the snake-type robot's own weight, imposes a significant deflection from the ideal position. At the end of the arm is positioned an instrument or probe that is designed to perform one or more functions once the continuum arm is in place.The head of a continuum-arm robot is often provided with an optical system to allow an operator to view the head as it is inserted into a component and to control the head as it performs its task. The optical system is also often coupled to a lighting system. Control cables for instruments, power connectors for the lighting system, and optical cables can usually run through the center of the joint in the continuum arm. This has the benefit of protecting the cables from any potential damage.

[0017] Figure 2 shows an example of the problem of the effects of loading on a compliant robotic device. In this example, a continuum-arm robot extends into a desired workspace. A compliant robot typically consists of a manipulable tip made up of several movable links, each with a joint between them, and a flexible connector that carries the cables required by the tip and the instrument at its end. The flexible connector serves as a carrier to deliver these cables and the compliant tip to a desired location in the workspace, which may be several meters in distance from the actuators used to control the tip section and the instrument. The structural behavior of a snake-type robotic manipulator can be likened to that of a cantilever beam under load, because the system is anchored at one end to a base with an actuation pack, power supply, and / or control unit and is intended to navigate through an environment without any other points of contact. Figure 2 shows an idealized example of operation. In this example, the robot has an ideal, straight configuration 201, and any loads, including the snake's own weight, applied to the body and / or tip of the snake robot impose significant deflection and deviation 202 from the ideal position 201. In this disclosure, the addition of auxiliary mechanisms 204 is used to add one or more points of contact 205 with the workspace environment, such as the walls of a cavity. The use of these contact points can reduce the deflection of the continuum-arm robot because the effect of the additional points of contact acts to reduce the length of the cantilever beam. Thus, the system achieves a more balanced configuration 203 that is closer to the ideal configuration 201. This therefore allows for more accurate positioning of the continuum-arm robot and end effector, which produces a more reliable working configuration. Furthermore, the points of contact can support loads on the tip through reaction forces at those points, thus enabling the robot to perform more invasive interventional and repair techniques.This incidental point of contact therefore serves to increase the utility of the robot by increasing the number of tasks that can be performed using such a continuum arm robot.

[0018] FIG. 3 shows an example of a section of a compliant robot according to the present disclosure. The figure shows an example of an additional module that can be added onto a continuum robot to increase its strength. The reinforcement feature consists of a rigid link 301 with a hollow core 302 so that the rigid link 301 can be fitted around the body of an existing compliant robot to reinforce the robot. This rigid linkage is shown to have a pair of arms 303 that can be actuated from a "closed" configuration 304, in which the arms are held along the body of the rigid link, to an "open" configuration 305, in which the arms are moved an appropriate distance from the rigid link. The arms can be controlled as a unit. Alternatively, the arms can be controlled individually, allowing them to be individually deployable. Movement of the arms from the closed configuration to the open configuration allows the reinforcement feature to create points of contact with the workspace environment. The arms can open to any suitable angle. As such, the arms can be controlled to extend varying distances from the compliant robot's body. If the arms are individually deployable, it may be the case that one of the arms remains closed and the other opens, or alternatively, the arms open to different angles to better fit the workspace, depending on the task environment. The arms may be connected to rigid links through the use of joints 306, which may both be rigid rotational or equivalent joints, or compliant joints. Movement of the arms may be driven by cable actuation of the joints or any other suitable mechanism that will be apparent to those skilled in the art. For example, this may be through the use of electronic actuators or through the use of materials that can transition between one configuration and another, such as shape memory alloys. The arms may have sensors on them to aid in positioning. The sensors may be pressure sensors. The pressure sensors may provide feedback to a control mechanism to prevent the arms from opening further once a predetermined force is exerted.While this reinforcing feature is shown as an add-on addition to a continuum-arm robot, it is also possible to add this reinforcing feature into the body of a compliant robot, which could be in the passive section and / or at the junction between the passive section and the active compliant section. This has the advantage that the body and arms of the rigid link can be made to have the same diameter as the active and passive compliant sections, thus minimizing the chance of issues with snagging or creating gaps in the robot when inserting or removing it from the work area. However, if the system is an add-on unit such as that shown in FIG. 3, the exterior surface of the reinforcing feature can be shaped so that the reinforcing feature has a smooth diameter transition with the existing robot, thereby minimizing the chance of snagging or creating gaps. The ends or arms can even be compliant so that, in their open state, they do not damage the surface of the workspace. The arms on the rigid link can even be of different lengths and / or thicknesses. There may even be multiple rigid link sections positioned along the length of the robot. In such cases, the arms may be used to open one side of the arm to provide scaffolding for the robot, i.e., to lift the robot off the workspace surface. If more than one rigid link is used, the arms may be of different lengths and / or thicknesses for each of the arms.

[0019] FIG. 4 shows an alternative embodiment for a rigid link according to the present disclosure. In this example, there are multiple arms surrounding the rigid link. These arms can be individually controlled. Alternatively, the arms can be controlled together or coupled together so as to be controlled. As in the example shown in FIG. 3, the rigid link has a hollow core so that it can be fitted around the outside of an existing robot or used as a component of a new compliant robot as a new joint or link within the compliant robot's structure. In either case, one or more of the rigid links can be provided at suitable points along the length of the robot to allow the robot to support itself. If using two or more support structures in a compliant robot, each of the links can be independently addressed so that each can be separately activated and deactivated. Similarly, in any of the examples, the arms can even be individually activated so that they can be individually deployed and retracted. In this way, the deployment of the arms can be configured to suit the workpiece cavity in which the system is working. FIG. 4 shows the presence of multiple arms attached to a snake-shaped segment or section. In this illustration, a rigid link 401 has a hollow core 402 and is designed to embed several arms. In this case, the arms are shown as compliant tendrils rather than rigid arms, as might also be used. FIG. 4 shows these tendrils both in a "closed" configuration 403 along the section and in an "open" configuration 404. The rigid links are constructed so that the tendrils, when in the retracted state, reside within recesses on the rigid links so that they do not significantly increase the diameter of the compliant robot, thereby reducing the chance of snagging or snagging the rigid links during insertion or removal of the robot.

[0020] FIGS. 5a and 5b show examples of tendril arms used in the example device shown in FIG. 4 in their closed and open configurations, respectively. The tendrils form a compliant mechanism whose shape can be controlled by the user. This provides an advantage over rigid arms, which may not be fully activated to act as support and therefore do not provide such strong support. The compliant tendril mechanism 501 in this example is implemented by placing notches 502 in the side of a tube with elastic behavior. An example of such a rod can be created using Nitinol. The notches allow the rod to be deformed in shape, causing the tendrils to curve (503). The curve in the tendrils can be induced by stretching a tendon or equivalent mechanism through the tendrils. This mechanism allows the shape of the tendrils to be controlled by modifying their curvature, as shown in the configurations shown in FIGS. 5a and 5b. The tendrils can all be the same size. Alternatively, the tendrils may be of different lengths and / or thicknesses.

[0021] FIG. 6 shows another example according to the present disclosure. In this example, the arms are constructed from expandable scaffolding. The scaffolding can be retracted (602) into the body of the robot 601. When the robot is in position, the operator actuates one or more arms to deploy and to the extent that they are deployed (603) so that they can contact the walls of the workspace 604. Once the task has been completed, the arms are retracted back into the body. In both deployments, the arm's scaffolding expands either through the use of actuator cables or through the use of electronic systems such as electronic actuators. As discussed, deployment involves expanding the joints in the scaffolding so that it occupies a larger volume and can therefore engage the walls of the cavity into which the robot is inserted. As with the other examples above, sensors can be used to determine the degree of unfolding of the folding structure. Additionally, soft compliant pads may be used on the distal end to prevent damage to the workspace. The folding mechanism may be an origami mechanism, such as the example in Figure 6. In such a case, the mechanism can fold into the robot body, as in configuration 602, and unfold and extend to be in contact with the environment, as in configuration 603.

[0022] Although the above has been described in terms of a continuum arm robot, the principles are applicable to any suitable flexible robot, e.g., a compliant, boroscope, continuum arm. For example, an arm may be used to hold the head in position during a boroscope process, or to keep the body of a flexible robot away from the side of the enclosure in which it is operating.

[0023] FIG. 7 shows a flowchart of the operation of a compliant / flexible arm robot according to the present disclosure. In a first step 701, the robot is inserted into the workpiece cavity. This insertion can be through any suitable doorway or hole in the workspace. In a second step 702, once the flexible arm robot is in position, one or more arms can be extended by the operator so that the arms touch the walls of the cavity, such that the flexible arm robot is supported by the robot's arms. In a third step 703, the robot performs the desired task required. In a fourth step 704, once the task is completed, the robot's arms are retracted. In a fifth step 705, the robot is removed from the workpiece cavity.

[0024] The mechanisms described above for immobilization and control of in-situ robotics can be distributed either uniformly or non-uniformly around the central axis of the snake-shaped body. As discussed, the mechanisms can either be incorporated into the body during the assembly phase or retrofitted as a later addition to the system. The use of a uniform distribution can produce improved balancing of general and / or unknown external loads and, therefore, can be more effective when the environment is known to have axisymmetric properties (e.g., a robot for interventional procedures in cylindrical tubular organs). On the other hand, a non-uniform distribution can be used to improve performance in situations where the load is characterized by a preferred direction (e.g., balancing the reaction force on the snake tip generated by an end-effector instrument with a known push direction). Therefore, the choice of design will depend on the desired use and / or the environment into which the robot will be inserted to perform a task. As discussed above, the means of actuation for any of the examples may include any type of motor, actuator, or device capable of generating linear or rotational displacement within a confined space. This type of drive may be selected from, for example, any of the following: pneumatics, hydraulics, linear / rotary motors, electromagnets, piezoelectrics, shape memory alloys, etc.

[0025] The primary application of this disclosure is to improve the stiffness and reaction of robotic systems to external and internal loads imposed on the robotic system. However, the use of this disclosure is not limited to immobilization, as the foldable assistive mechanisms can also be used to improve motor control or to generate motion (e.g., crawling) by themselves.

[0026] This invention describes a mechanism that can be attached to existing snake robotic or flexible-arm robotic platforms or within new robotic structures to provide additional rigidity. Such a rigidifying mechanism is key in scenarios where repair tools (such as grinding balls) can create significant reaction forces at the tip, allowing the robot to sustain a larger load. Use of this mechanism means that the robot utilizes itself against the surrounding environment to lock itself in place during the process. Alternatively, the arm can be used to constrain the robot to limit its movement within a predetermined axis of motion, which can therefore provide a means to overcome reactionary forces resulting from the mechanical task being performed by the head. An example of this is that the robot can be inserted into an inspection hole in a gas turbine engine combustion chamber section and utilize itself against combustion tiles so that machining processes can be performed with tools connected to the tip section. The device's arm may be subsequently retracted to allow the device to be repositioned, or may be retracted after the operation is completed.

[0027] It will be understood that the present invention is not limited to the embodiments described above, and that various modifications and improvements can be made without departing from the concepts described herein. Except where mutually exclusive, any of the features may be used separately or in combination with any other feature, and the present disclosure extends to and includes all combinations and subcombinations of one or more features described herein. [Explanation of symbols]

[0028] 101 Continuum arm robot part, continuum arm 102 Actuator Pack 103 Actuator 104 Rails or supports 105 Power and Signal Cables 106 joints 107 Joints 108 joints 201 Ideal linear configuration, ideal position, ideal configuration 202 Deflection and Deviation 203 A more balanced composition 204 Auxiliary mechanism 205 Points of Contact 301 Rigid Link 302 hollow core 303 Arm 304 "Closed" Configuration 305 "Open" Configuration 306 Joints 401 Rigid Link 402 hollow core 403 "Closed" Configuration 404 "open" configuration 501 Compliant Tendril Mechanism 502 Notch 503 Curved 601 Robot 602 Evacuation, Configuration 603 Deployment and Configuration 604 workspace 701 First Step 702 Second Step 703 Third Step 704 Fourth Step 705 Fifth Step

Claims

1. A rigid link for a flexible robot, comprising: a rigid link body having a hollow core; at least two arms having proximal and distal ends connected to the rigid link body; the arms being deployable between a closed configuration in which the proximal and distal ends of the arms are positioned close to the rigid link body, and an open configuration in which the arms are moved so that the distal ends of the arms are positioned away from the rigid link body; the arms are tendrils having elastic properties and can be configured to curve when deployed.

2. The rigid link of claim 1 , wherein the proximal end of the arm is pivotally connected to the rigid link body.

3. The rigid link of claim 1 , wherein the rigid link body is shaped to accommodate portions of the arm along the length of the arm.

4. The rigid link of claim 1 , wherein the arm is actuated by a motor, tendon, or linear actuator.

5. The rigid link of claim 1 , wherein the flexible robot is a continuum-arm robot.

6. The rigid link of claim 1 , wherein the arms are individually controllable.

7. A method of operating a flexible-arm robot having a rigid link according to any one of claims 1 to 6, comprising the steps of: inserting the flexible arm robot into a cavity in a workpiece until the flexible arm robot reaches a desired positioning; deploying the arms of the section of the rigid link from a closed position to an open position; using the tip section of the flexible arm robot to perform a desired task; retracting the arms of the section of rigid link from the open arms position to the closed arms position; extracting the flexible arm robot; A method comprising:

8. 8. The method of claim 7, wherein after the step of retracting the arm of the section of rigid link, the flexible arm robot is repositioned and the arm is deployed to perform a further task before the arm is retracted again.

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