Patent Description:
Such vacuum grippers exist in many configurations in the prior art. Generally, such devices use compressed air to generate a vacuum by use of a Venturi pump. The vacuum is then presented at the object to be acquired through any one of a variety of interfaces.

One type of interface is a single large open port, which maximizes the suction pressure from the vacuum and is thus well equipped to acquire heavy objects or those packaged in loose plastic. This configuration is commonly referred to as a bag type gripper.

Another type of interface is an array of smaller ports, each of which may have integrated flow control (due to their small hole size) designed to close or reduce them if they are not making contact with the object to be acquired. By closing unsealed ports, the suction pressure at ports that have successfully mated with the object to be acquired should be maximized. This approach provides flexibility in object acquisition since not all ports need to mate with an object in order to successfully acquire it. This flow control is generally accomplished by means of metering (or making the ports small enough that the resulting leakage from an unsealed port is immaterial).

In other vacuum gripper systems, integrated check valves may be used in port chambers that contact the environment. Typically, such devices include seals around the vacuum ports at the surface that meets the object to be acquired. This approach, while being more mechanically complicated, has the advantage of stronger overall suction force, since unsealed ports truly close at the opening, rather than just restricting leakage flow. For single large ports, a large suction cup or foam ring is used. For the array of ports configuration, an array of suction cups or a foam pad with holes for each of the individual ports are commonly used.

In some vacuum gripper systems, a set of actuated valves is provided for the air flowing through the gripper; a valve on the compressed air input allows for shutting the vacuum on and off, allowing the gripper to drop an object. This approach, however, is slow due to time constants of air pressure equalization within the gripper body. The speed of release is dramatically increased by adding a second controlled valve to the exhaust port of the vacuum generator; by closing this valve, compressed air is diverted through the gripper body and out the vacuum ports, effectively blowing the acquired object off of the gripper surface quickly.

The vacuum grippers in the prior art are generally designed for a specific object or material in a predetermined orientation. The specific gripper style and configuration is chosen to optimize for a particular acquisition problem (for instance, palletizing and de-palletizing a particular size/type of cardboard cartons). Such grippers are not at all well suited to a wide array of objects in non-predetermined orientations.

Further, in such vacuum gripper systems, software systems and algorithms are provided that are developed around the concept of maximizing speed and efficiency of abort/retry cycles for robotic manipulators acquiring objects. These algorithms have been focused in some applications on heavily instrumented multiple-finger mechanical grasping manipulators. The algorithms use the data from joint angles and motor power to determine how well an object is grasped and immediately retry if the grasp is not good enough.

In many such vacuum gripper systems, abort/retry techniques with vacuum grippers are unsophisticated. These techniques generally consist of applying vacuum, lifting the gripper, and looking at coarse flow rate or weight sensors to determine whether an object has been acquired; if it has not, the gripper is placed back on the object and acquisition is re-attempted. This is due largely to two reasons: <NUM>) most currently deployed vacuum gripping systems are customized so heavily for the material being acquired that acquisition failures are rare, resulting in no real need for rapid abort and retry cycles, and <NUM>) no vacuum grippers exist with the type of sophisticated instrumentation present in, for instance, a multi-fingered grasping type end effector. The result is that existing abort/retry algorithms cannot obtain from a vacuum gripper the information they need to be able to operate.

There remains a need, therefore, for an improved vacuum gripper for use in an articulated arm that provides improved performance in acquiring a wide variety of known and unknown objects.

<CIT> appears to disclose 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.

<CIT> discloses a vacuum control system comprising a vacuum source to an end effector, said end effector including a cover that includes an opening.

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

In accordance with a further embodiment, the invention provides a method of engaging and moving a load presented by an object at an end effector in a high flow vacuum system, as defined by the appended claims <NUM>-<NUM>.

In accordance with various embodiments, the invention provides a new instrumented hybrid-modality vacuum gripper system that has three main features as follows. First, the system provides hybrid modality. The gripping surface is a unique design that incorporates the advantages of both the single large port configuration and the array of controlled ports configuration of vacuum gripper, resulting in a single device that is more effective than either previously existing configuration. Second, the system provides unique instrumentation. The gripper is mounted to the end effector using a load cell array, such that controlling software has precise knowledge of weights and torques being applied to the gripper by the acquired object. Each individual vacuum port in the gripping surface is also instrumented such that controlling software has precise knowledge of how well each individual port is gripping the object that is being acquired. Third, the novel software and algorithms provide that presented sensor data may be used to maximize the efficiency of abort/retry cycles using this instrumented gripper. The general approach of hybrid modality, instrumentation, and algorithms applied to vacuum grippers is illustrated, in part, by the following examples.

The instrumented gripper assembly in accordance with an embodiment is shown in <FIG>. The gripper assembly <NUM> includes a vacuum generation head <NUM>, a plenum block <NUM>, a check valve plate <NUM>, a screen plate <NUM> and sealing foam <NUM> having gripping surfaces <NUM>. The sealing foam includes two sets of apertures, one set that is generally centrally located with respect to the other set as further shown in <FIG>.

The vacuum generation and control is provided by moving compressed air through a control valve to a Venturi pump, which creates a vacuum for the gripper to distribute to the gripping surface. A second valve on the output of the Venturi pump allows one to blow-off acquired objects, as described above.

The plenum block is provided below the Venturi pump, and the plenum block distributes the generated vacuum to each of the individual ports in series by means of a channels that are machined into the block. This approach minimizes the vacuum pressure required to check any individual port's control valve.

With further reference to <FIG>, the check valve plate consists of a number of chambers, each having a straight opening <NUM> at the bottom and a chamfered opening <NUM> at the top. A single such chamber (supply conduit) <NUM> is shown in detail in <FIG>, together with a supply conduit plug (ball) <NUM> and the opening to the vacuum plenum block <NUM>, and a pressure sensor <NUM>. The pressure sensor <NUM> is responsive to the pressure within the chamber <NUM> and provides a signal to a printed circuit board <NUM> in the check valve plate <NUM>. The screen plate <NUM> includes a plurality of screen openings in communication with chamber <NUM>. Each of the openings <NUM> and chambers <NUM> align with and are associated with a unique aperture in the sealing foam gripper <NUM>, and each check valve assembly (including the chamber <NUM>, opening <NUM>, conduit plug <NUM> and pressure sensor <NUM>) functions independent of the other check valve assemblies.

The top opening <NUM> mates to the plenum, thus providing a vacuum to the check valve chamber <NUM>. The bottom opening <NUM> delivers the vacuum through the screen plate <NUM> to the bottom surface of the gripper <NUM>, and thence to the object being acquired. The plug <NUM> in each check valve chamber is a plastic ball, of such a size and weight that if the bottom opening is open to atmosphere (i.e., not making contact with an object to be acquired) and a vacuum is applied to the top opening, the plastic ball <NUM> will be pulled by the vacuum up to the top opening, where it will seat firmly against the chamfer there and effectively seal that particular check valve port. By using these types of ports, it is ensured that any ports that are not actually making contact with an object to be acquired are sealed and not bleeding off vacuum pressure.

The screen plate <NUM> mounts to the bottom of the check valve plate <NUM>. It consists of a thin metal piece with openings that mate to each check valve. These openings are of such a size and shape (trefoil shape is used here) as to allow the ball <NUM> to sit on the opening without falling out, and without sealing the lower opening <NUM>. In this way, when the port is not making contact with an object to be acquired, air will flow through this opening, lifting the ball to the top of the chamber and sealing off that particular port. When the port is making contact with an object, the vacuum will be present in the chamber <NUM> and will hold the object against the surface <NUM> of the gripper <NUM>.

Of significance in this design is the incorporated printed circuit board <NUM>. The check valve plate is split into two pieces, top and bottom as shown in <FIG>, and the printed circuit board <NUM> is sandwiched between these two halves. On the printed circuit board <NUM> is mounted an array of MEMS barometers, each of which is provided as a pressure sensor <NUM> for a port (again, a single port is shown in <FIG>). These sensors (MEMS barometers) are placed such that they are able to detect the air pressure in the bottom of the valve chamber near the gripper surface. Other openings <NUM> in the gripper <NUM> are associated with other valve assemblies (including other chambers, openings, conduit plugs and pressure sensors).

When a vacuum is applied to the gripper, ports that are contacting the object being acquired will remain unchecked, meaning that the sensors in those ports will read vacuum pressure (<< <NUM> atmosphere). Any ports that are not contacting the object will check, meaning the pressure in the bottom of the chamber will be equivalent to atmospheric pressure. By reading all of the sensors, the software system will know exactly which ports are checked and which are making solid contact (and thus providing gripping force) to the object being acquired. Even once an object has been acquired, if it starts to "peel off" of the gripper, or falls off completely, the sensor readings will change accordingly, allowing the software system to know this in real time.

The gripper is circular at the gripping surface, as shown in <FIG>. This shape and symmetry provide another degree of freedom to the software control system. Again, the gripping surface <NUM> consists of an array of ports, each of which has an integrated check valve and pressure sensor as described above. Further, the gripping surface is comprised of two sections, a radially inner section <NUM> and a radially outer section <NUM>. The sections are separated by a foam ring <NUM>, which encloses the central grouping of apertures <NUM> and extends beyond the rest of the gripping surface. The second piece of foam fits around the outside of the first foam ring and extends to the outer edge of the gripper surface. It contains individual apertures <NUM> for each vacuum port.

The effect of this arrangement is a hybrid modality gripper combining the benefits of the single-large-port (or "bag") configuration and the array-of-controlled-ports configuration. The ports <NUM> in the middle (as shown in <FIG>) are all commonly open to each other within the foam ring, so that they can achieve the suction strength of a single large port while still being controlled with check valves. The foam ring is smaller and extends further than the rest of the gripping surface; this essentially acts as a secondary smaller gripper, allowing this device to access and acquire smaller object surfaces where the larger gripper could not otherwise fit. For larger items, simply pushing the entire device down to compress the foam ring will present the entire gripping surface to the object, allowing for compliant lifting of large objects with non-uniform surfaces.

<FIG> show the portion of the check valve plate that provides that multiple ports in the gripper may be commonly in communication with a single vacuum source. In particular, the central portion of the check valve plate includes a chamber <NUM> having straight openings <NUM> at the bottom and a chamfered opening <NUM> at the top. A single such chamber (supply conduit) <NUM> is shown in detail in <FIG>, together with a supply conduit plug (ball) <NUM> and the opening to the vacuum plenum block <NUM>, and a pressure sensor <NUM>. Again, the pressure sensor <NUM> is responsive to the pressure within the chamber <NUM> and provides a signal to the printed circuit board <NUM> in the check valve plate <NUM>. The screen plate <NUM> includes screen openings aligned with chamber <NUM>. Each of the openings <NUM> are in communication with the chamber <NUM>.

The top opening <NUM> mates to the plenum, thus providing a vacuum to the check valve chamber <NUM>. The bottom openings <NUM> deliver the vacuum through the screen plate <NUM> to the bottom surface of the gripper <NUM> in the inner area <NUM> as a common group of apertures, and thence to the object being acquired. Again, the plug <NUM> in the check valve chamber is a plastic ball, of such a size and weight that if the bottom opening is open to atmosphere (i.e., not making contact with an object to be acquired) and a vacuum is applied to the top opening, the plastic ball <NUM> will be pulled by the vacuum up to the top opening, where it will seat firmly against the chamfer there and effectively seal that particular check valve port as shown in <FIG>. By using these types of ports, it is ensured that any ports that are not actually making contact with an object to be acquired are sealed and not bleeding off vacuum pressure. When the port is not making contact with an object to be acquired, air will flow through this opening, lifting the ball to the top of the chamber and sealing off that particular port. When the port is making contact with an object, the ball <NUM> will drop (as shown in <FIG>) and the vacuum will be present in the chamber <NUM> and will hold the object against the surface of the gripper <NUM> in the inner area <NUM>.

This hybrid modality allows for successful acquisition of a much broader spectrum of objects than either prior type of vacuum gripper by itself. Heavy objects in plastic bags (e.g., a bag of oranges) typically cannot be acquired by standard port-array type vacuum grippers, but only by single large port type grippers; the central port grouping on the novel gripper presented here can acquire these objects. Another example is a bottle of shampoo standing upright; a typical single large port type gripper will be too large to seal to the top of the cap, and thus will not acquire the object. The novel gripper here can use a single port from the outer ring to seal to the shampoo cap; all other ports, including the central group, will check, allowing this device to successfully acquire the object. In other embodiments, different vacuum pressures may be applied to the inner set of apertures as compared to the outer set of apertures in a variety of ways, including for example, restricting air flow in the outer set of apertures.

This combination of power and flexibility is unique and powerful. By combining the benefits of multiple configurations, the result is greatly reduced or eliminated need for tool changing, along with the associated cost and time.

In accordance with certain embodiments, the invention further provides a system for providing high flow vacuum control to an end effector of an articulated arm. In accordance with various embodiments, the invention provides a dynamic high flow gripping system, and may optionally include a mechanism to select between the high flow source and a high vacuum source, depending on the application. High flow vacuum systems of the invention may therefore optionally be used with high vacuum sources.

The system, for example, may include a first vacuum source for providing a first vacuum pressure with a first maximum air flow rate (to for example, the inner area <NUM>), and a second vacuum source for providing a second vacuum pressure with a second maximum air flow rate (to for example, the outer area <NUM>). In certain embodiments, 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 reverse also possible in other applications. 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. The high flow source may be used together with a high vacuum source, or as a single source.

<FIG>, for example, shows a system <NUM> for use with an end effector in accordance with an embodiment of the present invention in which an optional 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 particular, <FIG> shows a system <NUM> 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 <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 in some examples, and no more than about <NUM>,<NUM> Pascals below atmospheric in other examples. 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).

In accordance with the present invention therefore, end effectors of the invention include a central region of a gripper surface that provides high flow gripping. The surface at the central region of the gripper includes a specialized opening cover for use with a high flow vacuum gripper. In particular and as shown in <FIG> (articulated arm facing side) and 10B (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, which are not in accordance with invention, 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.

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.

<FIG> shows an end effector gripper <NUM> having such a cover <NUM> used in connection with a gripper surface having an outer section <NUM> as discussed above, and an inner section <NUM> providing high flow through the cover <NUM>. The cover may also be flush with the circular wall <NUM> as shown.

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 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 may include 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.

The invention therefore provides a system 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 flow rate to the end effector, and the end effector includes a cover including an air flow resistant material on a proximal side of the cover and a compliant material on a distal side of the cover for contacting objects to be grasped. 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. The opening may be generally star shaped or asterisk shaped. The cover may be formed of a compliant material and include compliant foam on a distal side of the cover that engages an object to be grasped, and the cover may include an air flow resistant material on a proximal side of the cover. The vacuum pressure may be no more than about <NUM>,<NUM> Pascals or <NUM>,<NUM> Pascals below atmospheric, and the air flow rate may be at least about <NUM> cubic feet per minute.

Covers with openings in accordance with 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 sized 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 asterisks 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.

The gripper assembly may be mounted to the end of a wide variety of <NUM>- or <NUM>-axis robotic arms. The mounting assembly <NUM> incorporates load cells, as shown in <FIG>. There are four load cells <NUM>, placed between the mounting bracket <NUM> at the end of the robotic arm and the top surface of the gripper body <NUM>. One of these load cells is placed at each corner of the gripper body, allowing the SW system to precisely know the distribution of weight of an acquired object and the resulting forces and torques that the object is placing on the gripper. These sensors will also detect if an object has fallen off of the gripper during acquisition or movement; the Software system will integrate this data with the data provided by the array of pressure sensors in the check valve block to provide input to the algorithms that are maximizing abort/retry efficiency and speed.

The system therefore, does not require the use of sophisticated software algorithms that use probabilistic and predictive processes to maximize speed and efficiency of acquisition / failure / abort / retry cycles with multi-fingered hand-type grasping end effectors. These algorithms rely on precise data about joint angles and motor speeds / currents / torques as well as image data from 2D or 3D camera systems to know whether or not an acquisition has been successful and plan a retry if necessary. Because vacuum grippers have previously lacked any type of similarly sophisticated sensing, and because previous applications have been limited and highly controlled, these algorithms have not been applied previously to vacuum gripping situations.

The novel gripper described here provides such data using inexpensive sensors (load cells and MEMS barometers). When the gripper is placed on an object and the vacuum is enabled, the software control system will immediately have a map of which ports are providing suction to the object and which are checked closed. With a priori knowledge of the object (from 2D/3D imaging and database matching, for instance), the SW will be able to calculate a success percentage for object acquisition.

If the percentage is below a threshold, the control system can shut off vacuum and reposition the gripper to try again quickly without having to actually attempt and fail at acquisition first. This will greatly enhance retry speed.

If the percentage is above some threshold, the control system can raise the gripper. At this point, the data from the load cell array will begin to tell the control system whether or not the object weight is being lifted, and at what position and torque. As the object is being moved, the load cell and port pressure data will also warn the control system if the acquisition is failing and the object is going to fall, allowing the control system to take appropriate action.

This data will provide the software control system a real time picture of where, how, and how well an object is acquired, from before the gripper has even been moved all the way through object delivery and release. This data can be used by a software control system as input for efficient abort / retry algorithms previously only used by more sophisticated manipulators.

The instrumented hybrid-modality vacuum gripper presented here therefore, combines the benefits of prior vacuum gripper configurations into a single device, at the same time integrating sensors that provide the kind of detailed acquisition data needed to enable advanced abort/retry efficiency software algorithms previously reserved for more sophisticated multi-finger type grippers. The result is a single inexpensive end effector that can be used to rapidly and efficiently acquire and move a very broad spectrum of object types, sizes, weights, and packaging types, in a variety of orientations.

Claim 1:
A system for providing high flow vacuum control to an end effector of an articulated arm, said system comprising: a high flow vacuum source that provides an opening at a distal end of the end effector with an area of high flow vacuum at the end effector such that an object is engageable at the opening for movement by the articulated arm while permitting substantial flow of air through the opening, wherein the opening is provided by a cover (<NUM>, <NUM>, <NUM>, <NUM>), said cover (<NUM>, <NUM>, <NUM>, <NUM>) including a compliant outwardly facing material, and wherein the opening of the cover (<NUM>, <NUM>, <NUM>, <NUM>) includes a plurality of openings (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>), said plurality of openings (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>) providing more air flow at the central region of the cover than at the peripheral region of the cover (<NUM>, <NUM>, <NUM>, <NUM>).