Pneumatically actuated and safely compliant skeletal joints for robotic characters

A robot that includes two or more skeletal or rigid links interconnected by a joint. The joint is pneumatically actuated and includes a pneumatic joint actuator that allows the robot's skeletal links to be moved in an expressive manner. The pneumatic actuator includes a pair of opposing air bladders encased within a housing or body of the joint. Each air bladder is positioned on an opposite side of an actuating lever arm, which is rigidly attached to one of the skeletal links and is pivotally mounted on the joint body or housing. Movement of the actuating lever arm causes the attached skeletal link to pivot. To obtain this selective movement, one of the two air bladders is filled with a gas, such as air, while the other is left un-inflated or less inflated, and this forces the lever arm and attached skeletal link to pivot about their mounting point.

BACKGROUND

1. Field of the Description

The present description relates, in general, to robots such as robotic characters for use in the entertainment industry and such as robots for interacting safely with humans in other applications. More particularly, the present description relates to techniques for actuating joints, such as rotational joints, in robots in an effective (e.g., responsive and rapid movements) and safe manner.

2. Relevant Background

With the development of new engineering techniques, miniaturization of electronics, and the increase of computing power, designers are now able to design robots or robotic devices that can perform many intricate tasks including cooperative or interactive tasks with humans. While many have predicted a much more rapid expansion of the use of robots in industry, at home, and in entertainment applications, safety implications have created barriers that designers must address and overcome as most robots have the potential to cause damage to their surroundings including humans that may be nearby.

As one example, a biped humanoid robot is a robot with an appearance based on that of the human body. Humanoid robots have been designed for providing interaction with various environments such as tools and machines that were made for humans and often are adapted for safely and effectively interacting with human beings. In general, humanoid robots have a torso with a head, two arms, and two legs each with some form of foot such that the robot can walk on planar surfaces, climb steps, and so on. Humanoid robots may be formed with many rigid links or skeletal components that are interconnected by joints (such as rotational joints) that are operated or positioned through electronic controls of drive motors that apply a force or torque to each joint to move and position a robot.

In order to interact with human environments, humanoid robots require safe and compliant control of the force-controlled joints. In this regard, a controller is provided for each robot that has to be programmed to determine desired motions and output forces (contact forces) and, in response, to output joint torques to effectively control movement and positioning of the humanoid robot. However, it has often proven difficult to achieve desired results with force-controlled robots because while performing a task in a complex environment the robot may encounter uneven ground or even steps, static and dynamic obstacles, and even humans.

A number of useful techniques have been developed for controlling humanoid robots, but, regardless of the specific control techniques implemented by the robot controller, particular data that may be provided by sensors or be calculated has to be accurate for adequate control to be achieved. As one particular example with regard to kinematic parameters, a robot may include a sensor at each joint that is used to provide input to the controller for identifying or determining joint angles, and these joint angles are kinematic parameters used to further control and/or position the robot through movement of its joints.

These and other examples of robots and robotic applications shows show that robots are often designed to perform specific tasks involving speed and precision. Typically, these robots utilize high performance and/or powerful hydraulic or electric motors to actuate or move the skeletal limbs or rigid links by, for example, moving a joint between two of these limbs or links. In order to make these robots safe around humans, their speed and power are mitigated by the use of sensors and complex control hardware and software. Neither the hydraulic actuator nor the electric motor-based actuator is inherently compliant such that robots with these actuators must rely, therefore, on the control system to make them safe (e.g., compliant when in contact with their surroundings if needed such as when in contact with a human). As a result of these and other design requirements, many of these robots are complex and expensive to design, build, and maintain.

In many settings, robots may have differing design criteria that would not require as precise of movement or may require less force to achieve desired functions. For example, robotic characters in theme park attractions or in many human-interactive settings are not required to perform tasks that include high-precision movements. Instead, these robots or robotic characters simply may need to be expressive or to move in a “life-like” and repeatable manner. In other words, these robots may just need to act such as to wave their hand, move their fingers, turn their heads, and so on, but these actions need to be done in a manner that is deemed safe around humans. Presently, these characters have been implemented using hydraulic or electric actuators that, as discussed above, require complex control systems to operate safely.

Hence, there remains a need for improved methods and devices for allowing a robot to be moved or actuated in a less complex manner but while still meeting or exceeding all safety demands for use with or nearby humans.

SUMMARY

The present invention addresses the above problems by providing a robot or robotic system that includes two or more skeletal or rigid links interconnected by a joint. Significantly, the joint is designed to be pneumatically actuated as it includes a pneumatic joint actuator that allows the robot's skeletal links to be moved in an expressive manner. The pneumatic actuator includes a pair of opposing air bladders (or resilient and gas-tight bladders) encased within a housing or body of the joint. Each air bladder (a first bladder and a second bladder) is positioned on opposite sides of an actuating lever arm, which is rigidly attached to one of the skeletal links and is pivotally mounted on or within the joint body/housing. In this way, movement of the actuating lever arm causes the attached skeletal link to pivot.

To obtain this selective movement, one of the two air bladders is filled with additional amounts of a gas, such as air, while the other is left un-inflated or, more typically, is less inflated (under a lower pressure after the addition of gases to the other bladder as the two bladders may initially be filled to equal pressures). This forces the lever arm and attached skeletal link to pivot about their mounting point (e.g., a pin extending from the joint housing/body). More accurately, the bladders are pressurized to first and second pressures (P1and P2for the first and second air bladders), and movement or positioning of the lever arm and connected link is controlled by making one pressure greater than the other. The greater the pressure differential the greater the amount of rotation or joint actuation, and the quicker the change in pressures the quicker the movement of the lever arm and link about the rotation axis extending through the mounting pin or pivotal mounting element.

Safety is assured or enhanced with this joint actuator in part because the air bladders are formed of a flexible material (e.g., a rubber, a softer plastic, a fabric sheet, or the like that is can contain a gas) that causes the joint and attached links or skeletal structural elements to be naturally compliant. For example, an external force can be applied to the skeletal link that is being positioned by the pneumatic joint actuator, and the external force can cause the skeletal link to stop its rotation/movement or cause it to move to another position. This is achieved, in some cases, by limiting the amount of pressure applied to each bladder to actuate the joint so that the two bladders are compressible under a relatively low external force on the skeletal link or structural element attached to the actuating lever arm. In other cases, a relief valve may be provided in one of the gas supply lines to allow the joint to be compliant once a certain external force is applied that forces some air out of one or both bladders.

The robot or robotic system includes a joint control assembly that is used to selectively supply controlling gas (e.g., air) to each of the bladders to actuate the joint. Controlling gas flow (or air flow) may be directed through tubes running within one of the two skeletal links or structural elements. In another embodiment, a pair of flow channels is provided within the body of the skeletal link or structural element itself so that there is no need for tubing to be run in the robot, and one of the air bladders is fluidically connected at one end of each of the flow channels to receive controlling gas flow (e.g., to gas outlets of the flow channels).

The joint control assembly also includes first and second gas sources that can be selectively operated to provide the pressurized control gas to the first and second air bladder with the gas source connected to the second end of the flow channels (or supply lines/tubes if used), and a controller is included that transmits control signals to the two gas sources to achieve desired joint actuation or robotic movements. The joint control assembly may include a feedback pressure sensor or gauge on or within each flow channel to measure the pressures in the two flow channels. This measured or sensed gas pressure is used, in some embodiments, as an indicator of the amount of fill of each bladder (volume of gas in the bladder) that, in turn, may be calibrated to an amount of rotation of the actuating lever arm and its attached skeletal link. In operation, the controller may process the signals from the feedback pressure sensors to determine whether or not to provide additional control gas flow to either of the two bladders to provide a desired movement of the skeletal link (e.g., to actuate the joint by changing P1, P2, or both bladder pressures concurrently or sequentially to provide desired amounts of inflation or first and second volumes, V1and V2, in the first and second bladders).

More particularly, a robotic joint assembly is provided that is designed to provide expressive movement but yet also to be compliant to enhance its safe use in locations where human interaction is allowed or likely. The assembly includes a first skeletal link with a body extending from a first end to a second end, and the assembly also includes a rotational joint, mounted to the second end of the first skeletal link, which includes a joint housing (or body) with sidewalls defining an interior space and with a pivotal mounting element (e.g., a pin or post, a rotational coupling, or the like) that is supported in or on the joint housing. The assembly further includes a second skeletal link with a body extending from a first end to a second end, and the first end of the body is pivotally coupled to the pivotal mounting element of the joint housing. Significantly, the assembly includes a pneumatic joint actuator with first and second gas bladders positioned within the interior space of the joint housing, and the second skeletal link is pivoted with inflation of at least one of the first and second gas bladders (e.g., inflate one bladder while leaving the other bladder uninflated or less inflated).

In some cases, the assembly also includes an actuating lever arm extending outward from the first end of the body of the second skeletal link into the interior space so as to be disposed or positioned between the first and second gas bladders. As a result of this arrangement, movement of the actuating lever arm urges the first end of the body of the second skeletal link to pivot about the pivotal mounting element. Particularly, the selective inflation of the first gas bladder causes the first gas bladder to apply a first actuation force on a first side of the actuating lever arm and inflation of the second gas bladder causes the second gas bladder to apply a second actuation force on a second side opposite the first side, i.e., the first and second actuation forces are opposing forces urging the lever arm to move and the connected second skeletal link to rotate or pivot.

The joint housing may include encasement barriers in the interior space that are configured to define, with the sidewalls or interior surfaces of the housing, first and second encasements in which the first and second gas bladders are placed (e.g., fixed volume spaces in the joint housing). In such cases, the actuating lever arm extends between first and second encasements such that the bladders have to move toward each other through the lever arm when their volumes are increased (i.e., inflated with a pressurized gas such as compressed air or the like). The first and second gas bladders may take the form of an inflatable bag formed from a flexible and compliant material such as a rubber, plastic, or fabric, which allows it to be expanded in volume when inflated but also to readily be compressed to a smaller volume (e.g., when an external force is applied to the second skeletal link it is relatively free to pivot in either direction even with one or both bladders inflated or under pressure).

In some implementations of the assembly, the first skeletal link includes a first flow conduit extending through the body of the first skeletal link that is coupled at one end to an inlet to the first gas bladder, and the first skeletal link includes a second flow conduit extending through the body of the first skeletal link that is coupled at one end to an inlet to the second gas bladder. In this way, the flow channels or conduits of gas used to inflate the gas bladders are provided through passageways in the structural components of the robot itself rather than through additional tubing, and this allows the conduits or channels to be formed integrally with the body of a skeletal link.

The assembly may also include a first control gas supply fluidically linked to the first flow conduit and a second control gas supply fluidically linked to the second flow conduit. Then, the first and second control gas supplies can be independently operable to provide a pressurized gas to the first and second flow conduits to perform the selective inflation of the first and second gas bladders. Further, the assembly may include a joint controller providing control signals to the first and second control gas supplies to perform the selective inflation to move the second skeletal link through a predefined motion profile. In such embodiments, first and second pressure sensors can be provided for sensing pressures in the first and second flow conduits and, in response, providing pressure feedback signals to the joint controller. The joint controller may then process the pressure feedback signals and generate the control signals based on the pressure feedback signal processing.

In some particular implementations, the assembly may also include an additional joint housing pivotally attached to the second end of the body of the second skeletal link. This assembly can include a third gas bladder filled with a fixed volume of a gas. Typically, in the assembly, the third gas bladder extends through or on the body of the second skeletal link with a first end positioned in the interior space of the joint housing and abutting one or more exterior surfaces of the first end of the second skeletal link and with a second end positioned in an interior space of the additional joint housing. The assembly then may further include an additional actuating lever arm extending outward from the second end of the second skeletal link into the interior space of the additional joint housing.

During operation, the first end of the third gas bladder is compressed during pivoting of the second skeletal link on the pivotal mounting element, and, in response, the second end of the third gas bladder is expanded causing the second end of the third gas bladder to apply an additional actuating force, whereby the additional joint housing pivots on the second end of the body of the second skeletal link. In any of these embodiments, the second skeletal link may be pivoted about a longitudinal axis of the body of the second skeletal link with the inflation of at least one of the first and second gas bladders while other implementations may call for the link to rotate about an axis passing through the pivotal mounting element.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Briefly, robotic joints are described that are naturally compliant to enhance safety and are relatively simple to manufacture, maintain, and operate. Each robotic joint includes a pair of opposing gas bladders (e.g., air bladders) within the joint body or housing. The joint housing may be mounted onto a first skeletal link or structural element, and a second skeletal link may be pivotally coupled to the first skeletal link such as at or within the joint housing.

Further, an actuating lever arm is included that extends from or is connected to the second skeletal link (e.g., a cantilevered member extending out from the end of the second skeletal link on a side opposite to the pivotal mounting pin or element), and the actuating lever arm is positioned between the two gas bladders. Actuation of the joint is provided by selectively supplying a gas such as air to one or both of the gas bladders to apply equal or differing actuation forces to opposite sides of the actuating lever arm. For example, one bladder may be fully inflated with a controlling or actuating gas flow selectively provided by a controller from a pair of pressurized gas sources or supplies, and this applies a much greater force upon one side of the actuating lever arm, which causes the lever arm to move within the joint housing and the interconnected second skeletal link to rotate about the pivotal mounting pin or element.

The controlling or actuating gas flow may be provided through flow channels in the body of the first skeletal link or structural element, with a connector or connection fitting provided at each end of the flow channels (e.g., to avoid running tubing within the robotic links). The gas bladders may be formed of a soft and flexible material such as a rubber, a plastic, or a fabric that can contain a gas. Hence, the pneumatic joint actuator can be compliant to applied external forces to enhance safe operations of a robot with such a pneumatic joint actuator as the flexible material can readily be deformed and the bladders compressed. Gas relief valves may be provided in the gas supply lines to allow such compression by allowing an externally applied force to push gas out of the bladders (e.g., to maintain gas pressures in the bladders below a predefined maximum value).

FIG. 1illustrates a functional block diagram of a portion of a robot or robotic system100with a pneumatically actuated joint130(or a joint with a pneumatic joint actuator). The robot or robotic system100includes a first skeletal link (or structural element)120that is coupled with a second skeletal link (or structural element)110via the pneumatically actuated joint130. To this end, the joint130includes a joint body122affixed to an end of the first skeletal link120(or to an end of the linear or other-shaped body of the link120). The joint130includes a pivotal mounting element132such as a pin or post extending output from a surface of the joint body122, and, at one end, the second skeletal link110is pivotally coupled to the pivotal mounting element132to allow it to rotate or pivot as shown with arrow134about a pivot axis133extending through the pivotal mounting element132. In this way, the joint130is designed to pivotally couple the two skeletal links110,120. As shown, the mounting element132is a circular shaped post or pin and the end of the skeletal link110or its body includes a circular-shaped passageway or bore for receiving the element132, but this arrangement may be reversed or another pivotal mounting arrangement may be used to allow the skeletal link to pivot134about the axis133on joint body122.

To provide pneumatic actuation or a pneumatic actuator, the joint130includes first and second gas bladders140,144, and the bladders140,144are contained within the joint body122such as within an interior space defined by sidewalls of the joint body122. The gas bladders140,144are formed of a flexible material such as a rubber, and each bladder140,144has an at-rest or uninflated size that allows it to be inserted into first and second encasements124,126within the joint body122. The encasements124,126may be defined by sidewalls or interior surfaces of the joint body122. When the bladders140,144are filled with gas, they expand first to fill the space or volume of the encasements124,126. Secondly, though, an opening is provided between the two encasements124,126, and the bladders140,144will then expand or extend into the volume or space of the adjacent or neighboring encasement124,126.

The pneumatic joint actuator may be thought of as including the two gas bladders140,144and the encasements124,126of the joint body122as well as the pivotal mounting element132. Further, the actuator may be thought of as including an actuating lever arm136that extends from and is rigidly attached to the second skeletal link110(e.g., from the end of the link's body that is also coupled to the pivotal mounting element132). The actuation lever arm136is positioned in the joint body122to extend between the two spaces or interior volumes of the bladder encasements124,126.

As a result of this positioning, the first bladder140applies a first force, F1, as shown with line141upon a first side of the lever arm136while the second bladder144concurrently applies a second force, F2, as shown with line145upon a second side of the lever arm136, which is opposite the first side of the lever arm136. Hence, the two bladder-provided forces, F1and F2, are opposing actuation forces urging the lever arm136to move in different directions within the joint body122and to cause the interconnected skeletal link110to rotate134in different directions.

When the two forces, F1and F2, are equal, the lever arm136and link110may be at a first or central position, and, when the forces F1and F2differ from each other, rotation134will occur about axis133. Each bladder140,144will have a volume, V1and V2, and an internal or gas pressure, P1and P2, during operation of the robotic system100, and these parameters can be varied to achieve a desired actuation of the joint130including rotation134of the skeletal link110in either a clockwise or counterclockwise direction about axis133or selective positioning of the link110at a particular location or angular offset.

The robotic assembly100further includes a joint control assembly150to set and change the pressures, P1and P2, and the volumes, V1and V2, of the bladders140,144of the pneumatic joint actuator of joint130to control movement134of the link110relative to its connection to the link120. The control assembly150includes a joint controller160that includes a processor or CPU162that operates to manage the memory166(e.g., store and retrieve data in digital form) and to run one or more control programs (in non-transitory computer readable medium).

For example, the processor162runs actuator software module(s)164to control operations of the robotic joint130(or its pneumatic joint actuator) including outputting control signals182,184. The control signals182,184are used to selectively operate a first control gas supply152and a second control gas supply153. The control signals182,184may be provided by a motion profile168retrieved from memory166(e.g., a listing of differing pressures, P1and P2, to be provided for predefined time periods to achieve a desired motion134of the link110about the pivotal mounting element132in joint body130). The positions achieved by differing pressures P1and P2in bladders140,144may be defined as calibrated positions169, which may be defined by test runs of the system100in which different pressures, P1and P2, are applied and achieved movements134or positions of the link110are documented (e.g., mapping of joint or link positions to bladder pressures such as with a visual sensing system). Such calibration data169may be used to manually provide movements of the link110by an operator of the joint controller and/or may be used to generate the motion profiles168and their pressure values.

The control assembly150uses the first control gas supply152to provide gas (e.g., air) flow156through a flow channel154in or on the link120to the first gas bladder140to set the bladder pressure, P1, and to modify the bladder volume, V1. Similarly, the control assembly uses the second control gas supply153to provide gas flow157through a flow channel155to the second gas bladder144to set the bladder pressure, P1, and to adjust the bladder volume, V2. The flow channels154,155may be tubes in or on a body of the link or structural element120. In other cases, though, the channels154,155are provided as integral conduits or passageways formed in the body of the link120, e.g., the body of the link120may be formed such as with 3D printing, molding, machining, or the like to include the flow channels154,155extending between two ends of the link's body. Connectors or connection elements are provided at opposite ends of the channels154,155to allow fluidic or leak-tight connection with the bladders140,144and with outlet tubing or components of the pressurized gas supplies152,153.

The control assembly150is shown to include a pair of feedback pressure sensors170,174that are linked to the flow channels154,155to obtain measurements as shown at171,175of the bladder pressures, P1and P2. The pressure sensors170,174are communicatively linked (wired or wireless) to the joint controller160to provide feedback signals172,176, which can be processed by the controller160or its software164to determine whether or not to transmit control signals182,184to increase or decrease gas flow156,157to achieve desired bladder pressures, P1and P2, (as may be defined in motion profiles168) and associated movements134of the skeletal link110.

With the pneumatically actuated joint130and its operation understood, it may now be useful to provide specific examples of implementations of pneumatic joint actuators that may be used within nearly any robot with two joined links for which expressive and compliant motion is desired.FIGS. 2A and 2Billustrate a robotic joint assembly200in two operating states or with its pneumatic actuator in two operating states to move a link210to two differing positions. As shown, the assembly200includes a link or structural element210with a body extending from a first end212(outboard or cantilevered end) to a second end214(inboard or pivotally coupled end). The assembly200further includes a second link or structural element250with outer sidewalls252,254upon which is mounted (or, in some cases, integrally provided) a joint body or housing230.

The link or structural element210is pivotally coupled (e.g., the joint provided in assembly200is a rotational joint) to the link or structural element250within the joint body or housing230. To this end, the joint body230includes a pivotal mounting element218, such as a post or pin, extending from an interior surface232of the joint housing230, and the link210is coupled at end214to the mounting element218such that it is free to move, as shown with arrows219, relative to the stationary mounting element218, e.g., to have mating or bearing surfaces slide relative to each other. Opposite sidewalls of the joint housing230, e.g., the one providing surface232and the one removed to provide the view shown inFIG. 2A, may be used to retain the link end214on the post/mounting element218.

An actuating lever arm220is provided in the assembly200that extends from the link end214. The lever arm220may be a linear member with a width that matches or is some amount less than the width of an interior bladder-receiving space in the joint housing230defined by opposite sidewalls234,236so that the lever arm220is spaced apart from the surfaces of the joint housing. The lever arm220further may have a length that is 30 to 50 percent or more (e.g., 75 to 90 percent or more) of the depth of this interior bladder-receiving space in the joint housing, and, significantly, the lever arm220is positioned to generally divide the interior bladder-receiving space into two equal spaces or volumes in which first and second gas bladders240,242are positioned. Stated differently, the lever arm220is positioned so that it extends between the opposing bladders240,242within the joint housing230.

In this manner, inflation of the bladders240,242with a control gas flow causes the bladders240,242to apply opposing actuation forces, F1and F2, onto opposite sides228,226, respectively, of the lever arm220. Since the lever arm220is rigidly attached (or integrally formed with) the end214of the link210, movement of the lever arm220due to application of forces, F1and F2, causes the link210to pivot or rotate219about the mounting element218. The interior space or encasements of the joint housing230used to receive the bladders240,242may be defined by the opposite sidewalls234,236and also be end stops238,239extending between the sidewalls234,236proximate to the mounting element218. The end stops238,239may be used to limit the expansion of the bladders240,242(e.g., to define a maximum volume of the bladders240,242by furthering the encasing of the bladders240,242by sidewalls234,236), and the end stops238,239may also be used to limit rotation of the link210by limiting rotation or angular movement of the lever arm220within the joint housing230. This limited rotation may be useful to define a range of movement for link210such as over a 90 to 120 degree range (e.g., plus or minus 45 to 60 degrees from the position shown inFIG. 2Aas measured along a linear axis of the link210). Such a movement limitation may be seen inFIG. 2Bwith end stop239contacting the lever arm220to limit further rotation219of the link210.

The bladders240,242are, as discussed above, formed of a flexible material with a sidewall and an opening241,243(e.g., each bladder240,242is an inflatable bag) to receive a gas that inflates the bladders240,242. The bladders240,242may be formed similar to a conventional balloon to be inflated into a spherical shape or be shaped differently such as with a rectangular at rest shape as shown inFIG. 2A. The open ends or inlets241,243of the bladders240,242are fluidically coupled with outlets261,263of flow channels or gas conduits260,262in the structural element or link260.

The flow channels260,262are defined by outer sidewalls252,254and interior or dividing wall256. As shown, the flow channels260,262extend the length of the body of the link or structural element250, with inlets or connectors266,267provided at an end of the link250to allow the flow channels260,262to be coupled with supply tubes or lines (not shown) from pressurized gas supplies. In this manner, gas (e.g., air) flow or pneumatic control can be provided to the bladders240,242(or a pneumatic joint actuator) through integral and/or internal airflow channels260,262in a structural component of the robot, e.g., through the body of the skeletal link rather than with additional tubing/lines that can make the robot more complex to manufacture, implement, and/or maintain.

As shown inFIG. 2A, the bladders240,242are inflated to matching volumes (i.e., V1=V2) such as by applying equal pressures (i.e., P1=P2) to each bladder240,242with control gas flow through flow channels260,262. Such an operating state of the pneumatically actuated joint of the assembly200may be useful for placing the link210in a desired positioned such as with link210extending straight outward from joint housing230or with its longitudinal axis aligned with or parallel to a longitudinal axis of link250. Changing the pressure of either bladder240or242will cause there to be a pressure differential (P1<P2or P1>P2) between the two bladders240and242(or a differing actuation force, F1does not equal F2, being applied to sidewalls226,228of the lever arm220), and this will cause the lever arm220and interconnected link210to rotate or pivot219about pin or mounting element218.

An exemplary secondary operating state of the assembly200is shown inFIG. 2Bwhere the pressure, P1, of the bladder240is caused by a controller (not shown) to be greater than the pressure, P2, of the bladder242. This causes a greater force, F1, to be applied to the arm220by the bladder240than the force, F2, applied to the arm220by the bladder242, which causes the bladder240to expand in volume, V1(and bladder242to shrink in volume, V2). As a result, the lever arm220is moved within the housing230and the link210is pivoted or rotated219about the pivotal mounting element218.

The controller can achieve the state shown inFIG. 2Bfrom the state shown inFIG. 2Aby increasing gas flow to the bladder240to increase its pressure, P1, while holding the flow and pressure, P2, constant in the bladder242. Alternatively, the pressure, P2, of the bladder242may be reduced while holding the pressure, P1, of the bladder240constant or as shown inFIG. 2A, or a combination of these may be used (e.g., inflate bladder240while also actively or passively allowing bladder242to be deflated). As shown, the bladder240expands toward the bladder242because it is encased (at least partially) in all other directions such that it can only move toward the other or opposing bladder242via the lever arm220. The bladders240,242are shown to contact substantially all or the full length of the opposite sides226,228of the lever arm220(from the end222mated with end214of link210to the tip224). In other embodiments, though, the bladders240,242may only contact a portion of the lever arm to apply the actuation forces, F1and F2, such as at a contact point or contact area distal to the pivotal mounting element218.

FIGS. 3 and 4illustrate in more detail a prototype of the robotic link assembly200with a perspective view and an enlarged view of the pneumatically actuated joint with an outer cover or sidewall of the joint housing230removed to expose one of the bladders240. As shown, the joint assembly200can be actuated by selectively providing a control gas flow via a first supply line310coupled to connector267and a second supply line312coupled to connector266of the flow channels in link or structural element250. Pressure gauges or sensors311,313may be included in the supply lines310,312to provide a controller with feedback readings of the pressures in the lines310,312and, in turn, in the opposing bladders encased or contained within joint housing230. When the pressures measured with gauges311,313are allowed (by a controller) to differ from each other, the link or structural element210of the robotic joint assembly200will be caused to rotate or pivot about the pivotal mounting element or pin218, which in this prototype extends through the joint housing230, as one of the bladders is filled with a greater volume of gas (e.g., expands to a greater volume such that V1does not equal V2).

FIG. 4shows that one implementation or prototype of the joint actuator may utilize rectangular-shaped (when at rest or under an actuation pressure matching atmospheric pressure) gas bladders as shown with bladder240. When uninflated or at rest, the bladder240is shown to generally fill the interior space or void within the joint housing230(between the link250and the link end214(which encapsulates and mates pivotally with mounting element/pin218) and to abut the opposite sidewalls of the joint housing230. When the housing230is reassembled with the removed sidewall attached, the bladder240is encased such that it has only one path or direction to expand (or substantially one path as it may expand some amount linearly along the axis of the housing230toward the link210and/or expand to until all or most of its surfaces abut the inner surfaces of the encasing sidewalls of the joint housing230) and that is toward the opposing bladder through the actuating lever arm affixed to link end214.

The use of pneumatically actuated joints (or pneumatic actuators in robotic joints) may readily be expanded from use in a joint to provide rotation about a single pivot or rotation axis to provide double or dual joint movements (i.e., movement or pivoting about two pivot or rotation axes that may or may not be parallel to each other). For example,FIGS. 5A and 5Billustrate a dual movement joint assembly500of the present description. The assembly500includes components shown in the robotic joint assembly200ofFIGS. 2A and 2B, with repeated components being numbered similarly in both sets of figures. Specifically, the assembly includes the skeletal link250with a body having sidewalls252,254,256defining internal and integral flow conduits or channels260,262to provide control gas flow independently and selectively to a pair of opposing gas bladders240,242in a joint housing230. The selective inflation or pressurization of the gas bladders240,242is used to apply actuating and opposing forces, F1and F2, on sides226,228of the actuating lever arm220within the joint housing230.

The skeletal link210of assembly200, however, is replaced in assembly500with the skeletal link510, which includes a linear structural element514that is pivotally coupled at a first end518to the pivotal mounting member218of the joint housing230. Thus, the linear structural element514will be caused to pivot as shown with arrows519about the axis of member218with movement of the lever arm220by opposing bladders240,242similar to link210in assembly200. In contrast, though, the skeletal link510has an interior space or void515that is used to contain and support a third gas bladder530.

The third gas bladder530has a first end532inserted into the void or interior space of the joint housing230adjacent and, typically, abutting one or more surfaces of the end515of the linear structural element. This positioning is selected such that, as shown inFIG. 5B, when the lever arm220is moved in one of the two rotation directions (actuated by one of the two bladders240,242when F1>F2(or vice versa)) as shown with arrow519, the link514applies a third actuation force, F3, onto the third gas bladder in end532as the link514.

The third gas bladder530is an enclosed or sealed bladder or bag without a gas inlet or outlet such that it can be filled with a fixed amount or volume, V3, of a gas (or liquid is some embodiments)534. Hence, when the end532is compressed by actuation force, F3, the gas (or liquid)534is forced to moved out of the end532into other portions that are caused to expand inFIG. 5Bwith bladder end536expanding to apply a forth actuation force, F4, to provide dual motion or dual actuation within the joint assembly500.

The assembly500includes a second joint housing or body530that is attached to the linear structural element514at end516(opposite the end518pivotally coupled to mounting element or member218). The end516is pivotally coupled to the second joint housing530within an interior space or void as defined by sidewalls or interior surfaces513of the housing530via pivotal mounting element or post520. Actuating lever arm517is rigidly affixed to the end516. Hence, when the end536of the bladder530is expanded by movement of the contained gas/fluid534as shown inFIG. 5B, the bladder end536applies an actuation force, F4, against the lever arm517and encasing portions of the joint housing530, which causes the housing530to pivot as can be seen inFIG. 5Bwith end512rotating512about the pivot axis passing through mounting element or post520. When the end536later shrinks (e.g., when F2is equal to or greater than F1), the housing530will pivot521in the opposite direction about the mounting element520. In this manner, dual actuation or movement is achieved in robotic joint assembly500with only one directly controlled or actuated joint (in housing or body230with opposing bladders240,242providing a part of the pneumatic joint actuator).

Pneumatic joint actuation may be used to rotate a link or structural element about its pivotal mounting point as shown inFIGS. 2A to 5B. In other cases, though, pneumatic actuators for joints may be designed to cause the actuated link to rotate about its longitudinal axis, which may be useful in some robotic system designs. For example,FIG. 6illustrates another robotic link assembly600that may utilize pneumatic actuation of a joint between two links. Particularly, the assembly600includes a joint housing or body610for housing the pneumatic joint actuator along with a first link or structural component630and a second link620or structural component620.

As shown, the joint housing610is supported upon the first link630, which may be a plate or have one or more arms/Linear linkages extending outward (into the page and not shown inFIG. 6). The second link620is pivotally mounted to the first link630via coupling or bearing632, and, as shown, the link620has a body622(e.g., a linear member with a circular cross sectional shape or the like) extending from a first end626affixed to the pivotal mounting member or coupling632to a second end624. When the pivotal member632(which may be considered an end of the link620) rotates the body622rotates as shown with arrow648about the rotation axis (which may coincide with the linear axis of the body622).

Further, the housing610includes a sidewall612that defines an inner space or void618in which the pivotal mounting member or coupling632may be housed. Further, the housing610includes a pair of encasement walls or barriers614,616spaced apart from each other and extending from the sidewall612toward the center of the void/space618so as to define a separate encasement or receiving space619for a pair of opposing gas bladders640,644. The bladders640,644may be selective inflated or pressurized via a pair of control gas flow lines or conduits (not shown inFIG. 6) but located beneath or on an opposite side of the first link630.

The assembly600further includes an actuating lever arm634attached at a first end636to the pivotal mounting member or coupling632and left unattached at a second end637(which is also spaced apart from the sidewall612to allow free movement of the lever arm634). The lever arm634extends between the two gas bladders640,644. Actuation, as discussed above, is achieved by independently and selectively supplying a control gas flow to the bladders640,644so that bladders640,644inflate to fill the void619or at least contact the encasement walls or barriers614,616and opposite side of the lever arm634.

The bladder640or644that is inflated to a greater volume (has a greater gas pressure) will apply a greater actuation force upon the lever arm634causing the lever arm634to move646a distance toward the other bladder640or644, thereby compressing this compliant component. The encasement wall spacing can be used to define or limit the magnitude of the angular rotation of the link620such as clockwise or counterclockwise rotation648through a range of plus or minus 60 degrees (or a rotation angle of 120 degrees), with a rotation angle or angular movement range of about 60 degrees (or plus or minus 30 degrees being shown inFIG. 6.

The movement646of the lever arm634is translated to the pivotal mounting member or coupling632, which causes it to rotate about its center axis and move relative to the first link630. Concurrently, rotation of the coupling632causes the rigidly affixed or connected second link620to rotate643about the rotation axis (or longitudinal axis of the elongated body622of the link620). To implement the assembly600, a cover or retaining plate (not shown) may be positioned over the space or void of the joint housing618to encapsulate and retain the coupling632and bladders640,644(again, defining the encasing space for the bladders640,644along with barriers614,616thus causing the bladders to expand toward each other so as to apply actuation forces onto opposite sides of the lever arm634). The link body622would extend through this housing cover or retaining plate.

For example, the above description discusses playing back stored motion profiles such that a controller may provide control signals to apply differing pressures to the opposing bladders to cause desired joint movements over time. In other cases, though, the pressurizing of the two opposing bladders may be performed based on live input from a human performer (e.g., a controller may process input from a performer to generate control signals to achieve joint movement).

In one prototype of a skeletal joint, each bladder was pressurized to substantially equal pressures such as a pressure in the range of 1 to 15 psi (e.g., P1=P2, which may be in this starting pressure range such as by setting the start pressures at 8 to 12 psi or the like with one test using 10 psi). Then, to get movement of the joint, one of the bladders had its pressure varied to cause movement (plus or minus some predefined amount), with one test applying a pressure that was either 5 psi greater or 5 psi less than the other bladder to apply opposing forces that caused useful movement of the joint.