Abstract:
Sensors, including ultrasonic components, within a robotic system facilitate the overall operation and efficiency of the robotic system through the detection of objects and surfaces, including the levels of liquids, without contacting the objects or surfaces. The sensors are well-suited for use in connection with microfluidic volumes and biological materials.

Description:
TECHNICAL FIELD  
       [0001]     The present invention relates generally to detection systems and methods such as those used in connection with a robotic system to provide detection of objects and surfaces such as liquid levels, without contacting the objects or surfaces.  
       BACKGROUND INFORMATION  
       [0002]     Robotic systems for the manipulation of objects typically require varying degrees of human control. For example, a human operator, using a hardware or software interface to a controller of a robotic system, directs the position of manipulators or other movable elements to perform particular tasks. This requires that the operator be vigilant for changing or unexpected conditions, so as to react accordingly and alter the operation of the system, if necessary.  
         [0003]     As tasks become more complex, it becomes increasingly difficult for an operator to control the robotics under changing conditions. Consequently, sophisticated robotic systems typically employ sensors that provide data to the system controller, and software that interprets the data and performs automatic adjustments to system operation. This generally occurs with little or no operator intervention.  
         [0004]     Robotic systems designed to handle fluid volumes, chemicals, and biological materials typically manipulate fluid-handling apparatus, such as vials, pipettes, tubes, plates, lids, and the like in order to dispense, collect, and monitor samples. One example of such a robotic system is the Microlab® STARlet, which is commercially available from the Hamilton Company of Reno, Nev. That robotic system provides automated liquid handling, typically involving biological materials, using pipettes and other manipulating hardware.  
         [0005]     There is a need in the art for improved robotic systems for the handling of liquids.  
       SUMMARY OF THE INVENTION  
       [0006]     The present invention provides systems and methods comprising independently-movable controllers for monitoring and manipulating objects. In a particular embodiment, the invention provides non-contact sensors that monitor the status and characteristics of surfaces, including liquid surface levels. Methods of the invention allow for the control of characteristics of the surfaces being monitored. For example, sensors according to the invention monitor the level of a liquid in a reservoir, and further communicate information to controllers that interact to control liquid levels and contents in the reservoir. In a preferred embodiment, sensors and controllers of the invention gather data and control downstream manipulation without physically contacting the sample. Robotic systems that incorporate sensors of the invention are able to modify their operation as conditions change.  
         [0007]     In one aspect, the invention features a system comprising two or more independently controllable and movable devices, at least one of which comprises an ultrasonic transmitting and receiving module. The module is used to measure parameters, such as the location of objects, the level of liquids, and surface properties. One or more of the devices can be used to manipulate objects, dispense liquids and perform other functions at the direction of a programmer.  
         [0008]     In certain embodiments, a robotic system uses movable devices to collect and/or dispense a sample volume, and then to monitor the level of the dispensed liquid. In one example, monitoring is accomplished using an ultrasonic sensor that is attached to a movable device so that it can be placed over a dispensed fluid volume. As the dispensed liquid is transferred (i.e., for transport to other hardware for analysis), the sensor monitors fluid level and discontinues transferring the liquid at a predetermined level. In one embodiment, the sensor monitors fluid level to cause a predetermined fill level and/or a dispensing level. In particular, as discussed below, the sensor determines when a fluid reservoir is empty and communicates with control apparatus to terminate fluid dispensing.  
         [0009]     In a preferred embodiment of the invention, ultrasonic sensors are used to monitor and detect a liquid level in a reservoir. In such an embodiment, fluid is dispensed into the reservoir and an ultrasonic probe monitors the dispensed liquid level. The ultrasonic probe may be attached to the dispensing robotics or may be separate. At a predetermined fill level, the sensor terminates the dispensing operation. The same or a different sensor is used to monitor liquid level in the reservoir as liquid is transferred from the reservoir. In one embodiment, the reservoir is a funnel into which reagents are placed for use in chemical and biochemical reactions. In a preferred embodiment, the reservoir comprises beveled edges in order to deflect ultrasonic waves from a detector so as to prevent false level reading.  
         [0010]     Another aspect of the invention comprises using alternative non-contact sensing technologies, such as radar, LIDAR, and vision systems, to provide data to a robotic system.  
         [0011]     Other aspects and advantages of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, illustrating the principles of the invention by way of example only. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]     The foregoing and other objects, features, and advantages of the present invention, as well as the invention itself, will be more fully understood from the following description of various embodiments, when read together with the accompanying drawings, in which:  
         [0013]      FIG. 1A  is a perspective view depicting a robotic system in accordance with an embodiment of the invention;  
         [0014]      FIGS. 1B, 1C , and  1 D are perspective views depicting a portion of the robotic system in  FIG. 1A  in accordance with an embodiment of the invention;  
         [0015]      FIG. 2A  is a schematic sectional view depicting a funnel that can be used in connection with the operation of the system of  FIG. 1A ;  
         [0016]      FIG. 2B  is a schematic plan view depicting a funnel that can be used in connection with the operation of the system of  FIG. 1A ; and  
         [0017]      FIG. 3  is a flow chart depicting a method for real-time detection of liquid level in accordance with an embodiment of the invention. 
     
    
     DESCRIPTION  
       [0018]     As shown in the drawings for the purposes of illustration, the invention may be embodied in systems and methods for detecting surfaces dynamically without contacting those surfaces. Embodiments of the invention are useful in conjunction with robotic systems.  
         [0019]     In brief overview,  FIG. 1A  is a perspective view of a robotic system  100  in accordance with an embodiment of the invention. In the depicted embodiment, the system  100  is configured to handle fluidic volumes, including chemical and biological materials. The system  100  typically includes two or more movable devices  102 A,  102 B (collectively,  102 ), that are capable of moving in at least two and preferably three directions (i.e., along the x-, y-, and z-axes). Controller  104 A is in communication with the movable device  102 A, and controller  104 B is in communication with the movable device  102 B, to control the movement of each movable device. In an alternative embodiment, a single controller is in communication with all movable devices  102  to control their movements (separately or conjunctively). In either case, an operator uses a computer  105 , typically a personal computer, to programmatically control or set each of the controllers  104 A,  104 B (collectively,  104 ), or movable devices  102 , or both.  
         [0020]     Each of the movable devices  102  moves independently of the other movable devices  102 . In other words, one movable device  102 A can be directed by the controller  104 A to move in a different direction, or at a different rate, or both, compared to a second movable device  102 B. A user typically accomplishes this by programming the controllers  104  with the corresponding commands or software using the computer  105 .  
         [0021]     The system  100  typically includes a rail  106  along which the movable devices  102  move. As shown in  FIG. 1A , movement along the rail  106  corresponds to movement along a y-axis. The system  100  also includes a deck  108  on which samples, reagents  110 , or other objects are placed. In general, each of the movable devices  102  is capable of manipulating items placed on the deck  108 .  
         [0022]     In some embodiments, the movable devices  102  include mating adapters  112 A,  112 B (collectively,  112 ) that link each of the movable devices  102 A,  102 B to functional tips  114 A,  114 B, respectively. The tips  114 A,  114 B (collectively,  114 ) perform particular functions. For example, the tips  114  can include gripping paddles that grasp the samples  110  or other objects placed on the deck  108 . In this configuration, the movable devices  102  are able to manipulate the items on the deck  108 . The tips  114  can also include pipettes that dispense and collect sample volumes for analysis.  
         [0023]     A storage region  116  can be located within the range of movement of the movable devices  102 . The storage region  116  is a repository for, for example, the tips  114 . When one of the movable devices  102  needs a particular tip to perform a particular function, the controller  104  for that particular movable device  102  (i) directs the movable device  102  to travel to the storage region  116 , (ii) locates the needed tip  114 , and (iii) causes the movable device  102  to connect to the needed tip  114  using the mating adapter  112 . After performing the particular function, the controller  104  can direct the movable device  102  to return to the storage region  116 , disconnect the tip  114 , and leave the tip  114  in the storage region  116 . This facilitates use of the particular tip  114  by another of the movable devices  102 .  
         [0024]     In some embodiments, the tips  114  include sensors that monitor the environment in or around the system  100 . For example, the tips  114  can include an ultrasonic transmitter and an ultrasonic receiver. In one embodiment, the transmitter and receiver are combined into a single module. In another embodiment, the single module is contained in an ultrasonic transducer. In either case, one or more of the ultrasonic transmitter, ultrasonic receiver, or module is movable, typically when in contact with at least one of the movable devices  102 . For example, one of the movable devices  102  could pick up, or move, or push the ultrasonic device.  
         [0025]     Embodiments using ultrasonic components typically use the components to assess distances and surface conditions. This is accomplished by taking advantage of the piezoelectric effect that ultrasonic transmitters and ultrasonic receivers exhibit. Materials demonstrating the piezoelectric effect (i.e., the generation of electricity in crystals subjected to mechanical stress, and the generation of stress in such crystals when they are subjected to an applied voltage) can be employed as both an ultrasonic transmitter and an ultrasonic receiver (i.e., a single piezoelectric object can serve as transmitter and receiver). Separate transmitter and receiver devices are also contemplated.  
         [0026]     A typical sequence of events comprises the ultrasonic transmitter emitting an ultrasonic signal that encounters an object or obstruction. This generates a return ultrasonic “echo” signal. The ultrasonic receiver senses this echo and converts it to an electrical signal that is subjected to further signal processing. Either the controller  104  or another processor (such as the computer  105 ) can perform this signal processing, typically in conjunction with additional signal conditioning hardware. Software (running on the computer  105 , for example) then analyzes the processed signal to characterize the sensed object or obstruction. This can include an assessment of distance between the ultrasonic devices and the object or obstruction. The system  100  can then choose among several options for proceeding with its tasks, depending on the presence and nature of the sensed object or obstruction.  
         [0027]     In some embodiments, the ultrasonic components can be used to sense the absence of an obstruction. For example, samples  110  would give rise to an echo signal when subjected to a transmitted ultrasonic signal. If the samples  110  were moved, the expected echo signal would not be received, and the system  100  could proceed accordingly (e.g., abort the operation, signal an alarm  120 , check another location for the samples  100 , etc.).  
         [0028]     Because the ultrasonic components can sense surfaces, some embodiments employ them to detect the level of liquid in a container. The ultrasonic components sense the “surface” of the liquid itself by emitting an ultrasonic signal that impinges the surface of the liquid. The ultrasonic receiver senses the echo signal reflected back from the surface of the liquid, and the controller  104  or another processor (such as the computer  105 ) processes this signal. By assessing the characteristics of the echo signal (e.g., the elapsed time between its reception and the earlier ultrasonic transmission), the system  100  gauges the volume of liquid in the samples  110 .  
         [0029]     In some embodiments, the tips  114  include other types of sensors, generally referred to as “perception sensors” because the sensors collect information about their immediate environment. For example, in one embodiment, the tips  114  include a position sensor that allows the movable device  102  to ascertain its location within the system  100 . Of course, other types of position sensors may be used as well. For example, an optical encoder in communication with the movable device  102  can also provide position information. In other embodiments, the perception sensors include a radar transmitter and receiver (i.e., a radar system), or a laser transmitter and receiver (e.g., a LIDAR system, which involves detecting distant objects and determining their position, velocity, or other characteristics by analysis of laser light reflected from their surfaces).  
         [0030]     As described above, changing the tips  114  allows the movable devices  102  to perform different functions, depending on the task as hand. Nevertheless, in some embodiments, one or more movable devices  102  may have fixed functionalities, typically achieved by permanently connecting the movable device  102  to a particular tip  114 . In this configuration, the permanently connected tip  114  may have a design that is different from the removable tips  114  described above and, instead, could be an integral part of the corresponding movable device  102 .  
         [0031]     In some embodiments, the system  100  includes or interacts with a funnel  118 , depicted generally in  FIG. 1A  and more specifically in  FIGS. 2A and 2B . ( FIG. 2B  is a top view of the funnel  118 .) The funnel  118  can be constructed from any suitable material, including a keytone-based polymer such as polyetheretherketone which can be obtained from PLC Corporation under the trademark PEEK®. Sample volumes (e.g., reagents) are dispensed into the funnel  118  through an aperture  202 . In various embodiments, the aperture  202  has a diameter of approximately 0.188 inch to approximately 0.25 inch. The funnel may be located on the deck  108  or anywhere accessible by the movable devices  102 . The funnel  118  is typically connected to additional analysis hardware using piping or tubing for transporting the sample volumes that are introduced into the aperture  202 . The tubing can be connected to a bottom port  203  of the funnel  118 . In one embodiment, the funnel  118  has a length (L) of approximately 0.88 inch and a diameter or width (W) of approximately 0.50 inch. In another embodiment, the funnel  118  has a length (L) of approximately 1.03 inches and a diameter or width (W) of approximately 0.50 inch.  
         [0032]     As shown in  FIG. 2A , the funnel  118  typically has an interior chamber  204  that receives the sample volumes. The interior chamber  204  defines an inner aperture  205  through which the sample volumes pass when traveling to the bottom port  203 . In some embodiments, at least a part of the interior chamber  204  has a conical cross section characterized by an opening angle A. In some embodiments, the opening angle is approximately thirty degrees. In other embodiments, the opening angle is approximately 10 to approximately 25 degrees, preferably about 20 to approximately 21.5 degrees. In any case, this configuration facilitates the visual and ultrasonic inspection of liquid level in the funnel  118 . For example, as the level of liquid is reduced in the interior chamber  204 , the taper of the walls of the chamber  204  (due to the conical cross section) causes the diameter of the top surface of the liquid to become smaller. This reduction in the diameter is observable to the naked eye. In contrast, if the walls of the chamber  204  were not tapered (e.g., if the chamber  204  did not have a conical cross section), it would be more difficult to observe changes in the level of the liquid from a viewpoint above the funnel  118 , in part because the diameter of the top surface of the liquid would not change according to the liquid level.  
         [0033]     In embodiments in which the funnel  118  and an ultrasonic transducer are used together, the system  100  provides a method  300  for monitoring of liquid levels, as depicted in  FIG. 3 . This arrangement typically includes having a controller  104  command at least one of the movable devices  102  configured as a pipette to (i) move to the samples  110  (STEP  302 ), (ii) collect a sample volume (STEP  304 ), (iii) move to the funnel  118  (STEP  306 ), (iv) dispense the contents of the pipette into the funnel  118  (STEP  308 ), and (v) move away from the funnel  118  (STEP  310 ). In some embodiments, the controller  104  would then instruct the movable device  102  to disconnect from the pipette and connect to the ultrasonic transducer. In other embodiments, a different movable device  102  would connect to the ultrasonic transducer. In yet other embodiments, the ultrasonic transducer is an integral part of another movable device  102 . In any case, the controller  104  commands the movable device  102  having the ultrasonic transducer to move to a position over the funnel  118  (STEP  312 ). The controller  104  then activates the ultrasonic transducer (STEP  314 ), which emits an ultrasonic signal  206  shown in  FIG. 2A . In an alternative embodiment, the ultrasonic transducer is active at all times and thus constantly or periodically emitting the signal  206  without the need for the controller  104  to activate specifically the transducer at a particular point in time as indicated by STEP  314 . Whether the transducer is active at all times or just activated at a certain time, the resulting ultrasonic echo signal is received by the active transducer, and this return signal then can be processed by the controller  104 , computer  105 , or some other computer or processing equipment to allow the level of liquid in the funnel  118  to be determined.  
         [0034]     In an alternative embodiment, a transducer transport  122  is disposed adjacent to the funnel  118 . As shown in  FIG. 1B , the transducer transport  122  includes an ultrasonic transducer  124 , and is spring loaded or otherwise biased such that it remains adjacent to the funnel  118 . The movable device  102  configured as a pipette includes a bumper  126  that may be attached to the mating adapter  112  as shown in  FIG. 1B , or anywhere else on the movable device  102  or tip  114 , such that the bumper  126  contacts the transducer transport  122  as the movable device  102  approaches the transducer transport  122 . In this configuration, the bumper  126  pushes the transducer transport  122  so the latter moves away from the movable device  102  and the funnel  118  thereby giving the pipette unobstructed access to the funnel  118 . The pipette then dispenses its contents into the funnel  118 . Once this is completed, the movable device  102  moves away from the funnel  118  and the transducer transport  122  returns to a position adjacent to the funnel  118 , as shown in  FIG. 1D . Movement of the transducer transport  122  may be rotational, as shown in  FIGS. 1C and 1D , or translational (not depicted). At this point, the ultrasonic transducer  124  can be activated to emit the ultrasonic signal  206  or, in an alternative embodiment, the ultrasonic transducer  124  is active at all times and thus constantly or periodically emitting the signal  206  without the need to be activated specifically at a particular point in time.  
         [0035]     In a different embodiment (not depicted), the transducer transport  122  and the ultrasonic transducer  124  may be fixed (i.e., not movable) above the funnel  118 , but oriented such that the movable device  102  may have unobstructed access to the funnel  118 . This may be achieved, for example, by mounting the transducer transport  122  above the space where the movable device  102  travels but sufficiently close to the funnel  118  to perform an ultrasonic measurement of the liquid level therein. The ultrasonic transducer  124  can emit the ultrasonic signal  206  after the pipette dispenses its contents into the funnel  118  or, in an alternative embodiment, the ultrasonic transducer  124  is active at all times and thus constantly or periodically emitting the signal  206  without the need to be activated specifically at a particular point in time.  
         [0036]     After the liquid is dispensed into the funnel  118 , the liquid is drawn down and transported to additional analysis hardware. In one embodiment (not depicted), the controller  104  activates a valve that permits the liquid in the funnel  118  to be drawn down by gravity. In another embodiment, the controller  104  activates a vacuum (STEP  316 ) that draws down the liquid (STEP  318 ). As the liquid is drawn down, the ultrasonic transducer senses the increasing distance between the components and the surface of the liquid (STEP  320 ). The controller  104 , computer  105 , or some other computer or processing equipment interprets this and, before the liquid level falls below a prescribed (e.g., minimum acceptable) level, deactivates the vacuum (STEP  322 ) (or closes the valve), deactivates the ultrasonic transducer (STEP  324 ), and may also move the ultrasonic transducer to a position away from the funnel  118  (STEP  326 ). In an alternative embodiment in which the ultrasonic transducer is active at all times and thus constantly or periodically emitting an ultrasonic excitation signal and also receiving any return ultrasonic echo signals without the need to be activated specifically at a particular point in time, the deactivation STEP  324  is unnecessary. In any event, by combining the detection of the liquid level with the control of the valve or vacuum, the system  100  is able to adjust the liquid level as needed.  
         [0037]     When the ultrasonic signal  206  impinges on the funnel  118 , the echo signal typically includes reflections from other nearby objects. These spurious reflections are unrelated to the liquid level and compromise the accuracy of the liquid level determination. One source of the spurious reflections is the upper edge  208  of the funnel  118 . Edges that are perpendicular to the impinging ultrasonic signal  206  typically give rise to strong reflections (e.g., reflections that travel back to the ultrasonic components along the initial axis of propagation). In some embodiments, the edge  208  is designed to deflect the ultrasonic signal  206  so a reflection from the edge  208  will be minimized or, ideally, not travel back to the ultrasonic components. This can be accomplished by beveling the edge  208 , typically at an angle of at least fifteen degrees. Beveling at other angles is possible and also can result in reducing or eliminating reflections due to the upper edge  208  of the funnel  118 . For example, a beveling of greater than fifteen degrees (e.g., thirty or forty degrees) may reduce unwanted reflection more than a beveling of about fifteen degrees.  
         [0038]     Note that in  FIGS. 1A through 3  the enumerated items are shown as individual elements. In actual implementations of the invention, however, they may be inseparable components of other electronic devices such as a digital computer. Thus, actions described above may be implemented in software that may be embodied in an article of manufacture that includes a program storage medium. The program storage medium includes data signals embodied in one or more of a carrier wave, a computer disk (magnetic, or optical (e.g., CD or DVD), or both), non-volatile memory, tape, a system memory, and a computer hard drive.  
         [0039]     From the foregoing, it will be appreciated that systems and methods according to the invention afford a simple and effective way to monitor surfaces, including liquid levels.  
         [0040]     One skilled in the art will realize the invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The foregoing embodiments are therefore to be considered in all respects illustrative rather than limiting of the invention described herein.