Patent Description:
Most vacuum grippers employ vacuum pressures well below <NUM>% of atmospheric pressure, and are referred to herein as high vacuum. A typical source for a high vacuum gripper is a Venturi ejector, which produces high vacuum but low maximum air flow. Because of the low flow, it is essential to get a good seal between a vacuum gripper and an object, and it is also important to minimize the volume to be evacuated.

Suppliers of ejectors and related system components include Vaccon Company, Inc. of Medway, MA, Festo US Corporation of Hauppauge, NY, Schmalz, Inc. of Raleigh, NC and others. In some instances where a good seal is not possible, some systems use high flow devices. Typical high flow devices are air amplifiers and blowers, which produce the desired flows, but cannot produce the high vacuum of a high vacuum source. High flow sources include the side-channel blowers supplied by Elmo Rietschle of Gardner, Denver, Inc. of Quincy, IL, Fuji Electric Corporation of America of Edison, NJ, and Schmalz, Inc. of Raleigh, NC. It is also possible to use air amplifiers as supplied by EDCO USA of Fenton, MO and EXAIR Corporation of Cincinnati, OH. Multistage ejectors are also known to be used to evacuate a large volume more quickly, wherein each stage provides higher levels of flow but lower levels of vacuum. <CIT> discloses a vacuum control system comprising a vacuum source to an end effector, said end effector including a cover that includes an opening.

Despite the variety of vacuum systems, however, there remains a need for an end effector in a robotic system that is able to accommodate a wide variety of applications involving engaging a variety of types of items. There is further a need for an end effector that is able to high flow vacuum using a gripper that is able to handle a wide variety of objects.

In accordance with an embodiment, the invention provides a system for providing vacuum control to an end effector of an articulated arm as defined in the appended claims <NUM>-<NUM>.

In accordance with an embodiment, the invention provides a hybrid high flow / high vacuum gripper that can grip a broader set of objects than grippers based on either high flow or high vacuum alone. Previous designs are usually designed for a particular object. When a good seal between vacuum cup and object is possible, a high vacuum device such as a Venturi ejector is typically employed. When a good seal is not possible because of object surface irregularities or porosity, a high flow device such as a regenerative blower is typically employed. The hybrid gripper of an embodiment of the invention, uses either high vacuum or high flow, selected in real time to provide the most effective grip for the object, object pose, and surrounding context.

In various embodiments, therefore, the invention provides a gripper system that combines multiple sources of vacuum, selecting the source in real time. The invention provides, in an embodiment, a gripper system that switches from a high flow source to a high vacuum source as the pressure drops below the level sustainable by the high flow source, and a gripper system comprising a high flow source with a multistage ejector, so that the non-return valve integrated in the multistage ejector provides a selection mechanism in accordance with further embodiments.

A general approach to a vacuum gripper design, is to characterize the object in question and select the catalog gripper, vacuum source, and other components best suited to the object. Many device suppliers and integrators offer application engineering services to assist in selection of proper components. These options are exercised at system design time however, and result in a system committed to grasp a specific object, or in some instances a few objects.

There are be numerous applications for a gripping system that could handle a broad variety of objects, varying in size, weight, and surface properties. The invention provides an approach to address this need by introducing a mechanism to select between a high flow source and a high vacuum source, depending on the present situation.

<FIG>, for example, shows a system <NUM> in accordance with an embodiment of the present invention in which a high vacuum source <NUM> is provided as well as a high flow source <NUM> and a release source <NUM> that are each coupled to a selection unit <NUM>, that is coupled to an end effector <NUM>. The selection unit <NUM> selects between the high vacuum source <NUM>, high flow source <NUM> and the release source <NUM> for providing any of high vacuum, vacuum with high flow, or a release flow to the end effector. <FIG> therefore shows a general form of the invention, comprising mechanisms for producing high vacuum and high flow, a release source providing either atmospheric pressure via a vent or high pressure (blow off) via a compressor or reservoir, and a mechanism for selecting the source best suited to the present situation.

In accordance with certain embodiments, therefore, the invention provides a system for providing dynamic vacuum control to an end effector of an articulated arm. The system includes a first vacuum source for providing a first vacuum pressure with a first maximum air flow rate; and a second vacuum source for providing a second vacuum pressure with a second maximum air flow rate, wherein the second vacuum pressure is higher than the first vacuum pressure and wherein the second maximum air flow rate is greater than the first maximum air flow rate. The flow rates are characterized as maximum air flow rates because, when an object is engaged at an end effector, the flow rate may drop significantly.

In other embodiments, the invention provides a method for providing a vacuum at an end effector on an articulated arm. The method includes the steps of providing a first vacuum at the end effector at a first vacuum pressure with a first maximum air flow rate, and changing the vacuum at the end effector to a second vacuum with a second vacuum pressure and a second maximum air flow rate.

The selection mechanism may include a set of pneumatic valves driven by an estimated task state, based for example, in part, on sensor input information. The selection mechanism may also select a vent or blow-off source to release a part. In certain cases, the selection mechanism may be based in part on a non-return valve (see <FIG>), in other cases, a non-return valve integrated in a multistage ejector, with an additional valve to select a vent or blow-off source in order to release a part (see <FIG>).

In particular, <FIG> shows a system in accordance with an embodiment of the invention that includes a compressor <NUM> that is coupled to an ejector <NUM> to provide a high vacuum source that is coupled to a solenoid valve <NUM>. A blower <NUM> is also coupled to the solenoid valve <NUM> via a non-return valve <NUM>, and the blower <NUM> provides a vacuum source with a high maximum flow rate. A vent or blow-off source is also provided to the solenoid valve <NUM>, the output of which is provided to an end effector <NUM>. The system therefore, provides the ejector <NUM> as the high vacuum source, the regenerative blower <NUM> as the high flow source, the non-return valve <NUM> as a passive selection mechanism, and the solenoid valve <NUM> connecting the effector to the release source, either vent or blow-off.

The vacuum pressure provided by the ejector <NUM> may be, for example, at least about about <NUM>,<NUM> Pascals below atmospheric and the vacuum pressure provided by the blower <NUM> may be only no more than about <NUM>,<NUM> Pascals below atmospheric, and no more than about <NUM>,<NUM> Pascals below atmospheric in further embodiments. The vacuum pressure provided by the blower <NUM> is therefore higher than the vacuum pressure provided by the ejector <NUM>. The maximum air flow rate of the ejector may be, for example, no more than about <NUM> cubic feet per minute (e.g., <NUM> - <NUM> cubic feet per minute), and the maximum air flow rate of the blower may be, for example at least about <NUM> cubic feet per minute (e.g., <NUM> - <NUM> cubic feet per minute).

<FIG>, for example, shows another embodiment of the invention that includes a multi-stage ejector <NUM>, a compressor <NUM> and a blower <NUM>. The multi-stage ejector <NUM> provides a dynamic vacuum pressure to a solenoid valve <NUM> that may switch between providing an end effector <NUM> with either the dynamic vacuum pressure and a vent or blow-off positive air pressure source. The system uses the non-return valve of a multi-stage ejector as the selection mechanism. In particular, the multi-stage ejector includes a series of apertures of increasing size (e.g., left to right as illustrated in <FIG>). At first, the largest aperture is dominant, evacuating air quickly until the air pressure drops, then the next size aperture become dominant until air pressure drops further, and finally the smallest size aperture becomes dominant. The system of <FIG>, however, includes check valves on the larger aperture paths as well as the blower <NUM> to keep the air flow path from defeating the high vacuum, smallest aperture, in the event of a good seal.

For example, with reference to <FIG>, if a good seal is formed between an end effector <NUM> (which may for example, be a tubular or conical shaped bellows) and an object <NUM> on an articulated arm <NUM>, then the vacuum pressure provided by the smaller aperture in the multi-stage ejector <NUM> remains dominant because the non-return valves in the multi-stage ejector <NUM> prevent air flow backwards through the blower <NUM>. This will provide that the grasp of object <NUM> will be maintained by the lower pressure vacuum with a lower maximum air flow rate.

With reference to <FIG>, if a good seal is not formed between an end effector <NUM> and an irregularly shaped object <NUM> on an articulated arm <NUM>, then the blower <NUM> will dominate maintaining a high flow, maintaining a grasp of object <NUM> with a higher maximum air flow rate.

With reference to <FIG>, in accordance with a further embodiment, the system may include an articulated arm <NUM> to which is attached an end effector <NUM>, again, which may be a tubular or conical shaped bellows. The end effector <NUM> also includes a sensor <NUM> that includes an attachment band <NUM> on the bellows, as well as a bracket <NUM> attached to magnetic field sensor <NUM>, and a magnet <NUM> is mounted on the articulated arm <NUM>. As the bellows moves in any of three directions (e.g., toward and away from the articulated arm as shown diagrammatically at A, in directions transverse to the direction A as shown at B, and directions partially transverse to the direction A as shown at C. The magnetic field sensor <NUM> may communicate (e.g., wirelessly) with a controller <NUM>, which may also communicate with a flow monitor <NUM> to determine whether a high flow grasp of an object is sufficient for continued grasp and transport as discussed further below. In certain embodiment, for example, the system may return the object if the air flow is insufficient to carry the load, or may increase the air flow to safely maintain the load.

<FIG> show the process steps of a system in accordance with an embodiment of the present invention, wherein the process begins (step <NUM>) by applying a high flow / low vacuum source to an end effector (step <NUM>). The end effector is then applied to an object to be moved (step <NUM>). Generally, the system begins and continues lifting the object until the end of the lifting routine (step <NUM>), begins and continues moving the object until the end of the moving routine (step <NUM>), then applies a positive air pressure force to urge the object from the end effector (step <NUM>) and then ends (step <NUM>). If the air flow at the end effector at any points falls too low, then the system may automatically switch to a high vacuum / low flow source as discussed above. In certain embodiments, sensor(s) may be employed to either confirm that such a switch is need and / or has been made. In further embodiments, the sensor output(s) may drive a mechanical switch to change vacuum sources.

For example, <FIG> also shows that once the end effector is applied to an object (step <NUM>), a subroutine is a called (at A to B) that first reads the one or more sensors (step <NUM>). If any of the one or more sensor output(s) is outside of a threshold (step <NUM>), then the system may confirm that the system has switched to a high vacuum / low flow source (step <NUM>). As noted above, in certain embodiments, the sensor output(s) may drive a mechanical switch the changes the vacuum at the end effector to be a high vacuum / low flow source (step <NUM>). Then system then returns to the step from which it was called. During execution of the beginning and continuing lifting until end (step <NUM>), the system continuously calls the subroutine (A to B) until the object is fully lifted. The system then moves to the step of beginning and continuing moving the object until end (step <NUM>), and during execution of this action, the system continuously calls the subroutine (A to B) until the object is fully moved.

The system may therefore, automatically switch between high flow / low vacuum and low flow / high vacuum sources. In certain embodiments, the system may employ sensors to monitor and confirm that such switching is needed and is performed. As noted, the system may also effect the switching responsive to the one or more sensor output(s).

During low vacuum / high flow use, a specialized end effector may be used that provides improved grasping of long narrow objects. Certain grippers that are designed for high flow use to acquire and hold an object generally require large apertures in order to obtain an air flow rate that is high enough to be useful for object acquisition. One drawback of some such grippers in certain applications, is that the object to be acquired may be small, not so small that each of its dimensions is smaller than the high flow opening, but small enough that certain of an object's dimensions is smaller than the opening. For example, long narrow objects such as pens, pencils etc., do not occlude enough of the high flow opening to generate sufficient negative forces to hold the object securely.

In accordance with an embodiment therefore, the invention provides a specialized cover for use with a high flow vacuum gripper. In particular and as shown in <FIG> (articulated arm facing side) and 8B (object facing side), such a cover <NUM> may include a proximal back side <NUM> that does not permit air to flow through the material, and distal front side <NUM> for engaging objects that is formed of a foam material. Slit openings <NUM> in form of a star or asterisk shape are provided through the material in this example. During use, elongated objects may be received along opposing slit openings and held by the foam material.

<FIG>, for example, shows an elongated object <NUM> being held against the foam material <NUM> of a cover <NUM> that is coupled to the end effector <NUM>. While the elongated object <NUM> covers some of the opening provided by the slits <NUM>, other portions <NUM> of the opening provided by the slits <NUM> are remain open. The pattern cut into the material allows for enough area to still obtain a relatively high flow, while providing a number or positions (or orientations) for a long, thin object to block (and thus be held by) a sufficiently high percentage of the air flow.

The compliant foam on the surface <NUM> contacts the object to be acquired, giving the gripper some compliance while also acting to seal the aperture around the object as the foam is compressed and the high flow vacuum is applied. The aperture cover therefore allows a high flow gripper to effectively pick up long narrow objects with an easy to attach cover that may be held in a tool changer and added or removed from the gripper autonomously during real-time operation
In accordance with various embodiments, the cover <NUM> may be applied to the end effector by a human worker into a friction fitting on the end of the end effector, or in certain embodiments, the cover may be provided in a bank of available end effector attachments that the articulated arm may be programmed to engage as needed, and disengage when finished, e.g., using forced positive air pressure and /or a grasping device that secures the end effector attachment for release from the articulated arm.

A system is therefore provided in an embodiment, for providing vacuum control to an end effector of an articulated arm, where the system includes a vacuum source for providing a vacuum pressure at a high flow rate to the end effector, and the end effector includes a cover that includes an opening that varies significantly in radius from a center of the cover. The opening includes finger openings that extend radially from the center of the opening. The opening may be generally star shaped or asterisk shaped. The cover may include compliant foam on a distal side of the cover that engages an object to be grasped, and an air flow resistant material on a proximal side of the cover. The vacuum pressure may be no more than about <NUM>,<NUM> Pascals below atmospheric, and the air flow rate may be at least about <NUM> cubic feet per minute.

Covers with other types of openings not belonging to the present invention are shown in <FIG>, for example, shows a cover <NUM> that includes slit openings <NUM>. <FIG> shows a cover <NUM> that includes different sixed square openings <NUM>, <NUM>. Cover <NUM> shown in <FIG> includes small circular openings <NUM>, and cover <NUM> shown in <FIG> includes differently shaped openings <NUM> and <NUM>. In each of the covers <NUM>, <NUM>, <NUM>, <NUM> and <NUM>, a compliant foam surface may face the object to be acquired, and more area of the cover is provided to be open closer to the center of the cover with respect to the outer periphery of each cover. For example, in the cover <NUM>, the center of the asterisk shape is most open. In the cover <NUM>, the larger slits are provided in the center. In the cover <NUM>, the larger square openings are provided in the center. In the cover <NUM>, the greater concentration of the circular openings is provided in the center, and in the cover <NUM>, the lager shape <NUM> is provided in the center.

Systems in accordance with certain embodiments of the invention are able to monitor flow within the end effector as well as the weight and balance of an object being grasped. <FIG> show an object <NUM> being lifted from a surface <NUM> by the end effector <NUM> that includes the load detection device of <FIG>. The high flow / low vacuum source is initially applied. Upon engaging the object <NUM>, the system notes the position of the detection device and the level of flow (F<NUM>) within the end effector as well as the vacuum pressure (P<NUM>) and load (W<NUM>) as shown in <FIG>. Once the object <NUM> is lifted (<FIG>), the system notes the change in the amount of flow (ΔF<NUM>). In this example, the load provided by the object <NUM> is relatively light (ΔW<NUM>), and a small variation (ΔF<NUM>) in flow may (when considering the load and aperture size) may be accepted, permitting the source to remain high flow / low vacuum. <FIG>, however, show the end effector lifting a heavy object with a more flat surface.

<FIG> show an object <NUM> being lifted from a surface <NUM> by the end effector <NUM> that includes the load detection device of <FIG>. The high flow / low vacuum source is initially applied. Upon engaging the object <NUM>, the system notes the position of the detection device and the level of flow (F<NUM> ) within the end effector as well as the vacuum pressure (P<NUM>) and load (W<NUM>) as shown in <FIG>. Once the object <NUM> is lifted (<FIG>), the system notes the change in the amount of flow (ΔF<NUM>). As noted above, in this example, the object <NUM> is heavy (ΔW<NUM>), presenting a higher load. The system will evaluate the load in combination with the flow (F<NUM>) and pressure (P<NUM>) as well as the change in flow (ΔF<NUM>) and change in pressure (ΔP<NUM>) to assess the grasp of the object. The system may automatically switch to the high vacuum, low flow vacuum source as discussed above.

The system may also detect whether a load is not sufficiently balanced. <FIG> show an object <NUM> being lifted from a surface <NUM> by the end effector <NUM> that includes the load detection device of <FIG>. The high flow / low vacuum source is initially applied. Upon engaging the object <NUM>, the system notes the position of the detection device and the level of flow (F<NUM> ) within the end effector as well as the vacuum pressure (P<NUM>) and load (W3) as shown in <FIG>. Once the object <NUM> is lifted (<FIG>), the system notes the change in the amount of flow (ΔF<NUM>). In this example, the object <NUM> presents a non-balanced load (ΔW<NUM>). The system will evaluate the load in combination with the flow (F<NUM>) and pressure (P<NUM>) as well as the change in flow (ΔF<NUM>) and change in pressure (ΔP<NUM>) to assess the grasp of the object. The system may automatically switch to the high vacuum, low flow vacuum source as discussed above. In each of the examples of <FIG>, any of vacuum pressure sensors, flow sensors, weight and balance detections may be employed to monitor the status of the end effector and the load, and the switching may occur automatically, or by analysis of the above values.

In accordance with certain embodiments, the system may switch between a high vacuum, low flow source and a low vacuum high flow source depending on input from the sensor <NUM>. For example, if an object is engaged such that the bellows is substantially moved in either directions B or C, then the system may elect to maintain the high vacuum, low flow source, or may elect to return the object without moving the object.

In accordance with an embodiment, therefore, the system provides vacuum control to an end effector of an articulated arm, where the system includes a vacuum source for providing a vacuum pressure at a flow rate to the end effector, and the end effector includes a cover that includes an opening that varies significantly in radius from a center of the cover. The opening includes finger openings that extend radially from the center of the opening. The opening may be generally star shaped or asterisk shaped. The cover may include compliant foam on a distal side of the cover that engages an object to be grasped, and an air flow resistant material on a proximal side of the cover. The vacuum pressure may be no more than about <NUM>,<NUM> Pascals below atmospheric, and the air flow rate may be at least about <NUM> cubic feet per minute to provide a high flow / low vacuum source. The cover may include an opening that varies significantly in radius from a center of the cover, and the opening may include finger openings that extend radially from the center of the opening, and for example, may be generally star shaped or asterisk shaped.

Claim 1:
A system for providing vacuum control to an end effector of an articulated arm, said system comprising
a vacuum source for providing a vacuum pressure at a maximum air flow rate to the end effector,
said end effector including a cover (<NUM>) that includes an opening having a plurality of slit openings (<NUM>, <NUM>) that extend radially from the center of the opening.