Abstract:
A practical intelligent assist device is provided that eliminates the complex use of force sensing weigh cells and vector interpreting software. By simplifying the input to a series of traditional voltage inputs, i.e. 1-4 volt signals, the use of standard available control componentry becomes available. Utilizing a series of such simplified inputs, including a load angle feedback, the processing of the vector math can be accomplished within a programmable logic controller (PLC). Outputs can then be simply generated to control a series of 0-60 Hz digital signals to drive direct drive motors.

Description:
RELATED APPLICATIONS 
   There are no previously filed, nor currently any co-pending applications, anywhere in the world. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to the field of intelligent assist devices (IAD), and in particular, to a practical intelligent assist device (PIAD) that can interact with human operators in a practical, easily maintainable fashion. 
   2. Description of the Related Art 
   In an industrial application such as a manufacturing assembly line or general material handling situation, the payload may be too large for a human operator to move without mechanical assistance or risking injury. Even with lighter loads it may be desirable to provide a human operator with mechanical assistance in order to allow more rapid movement and assembly, avoid strain, fatigue or repetitive motion injuries. Thus, a great deal of industrial assembly and material handling work is done with the help of personnel assist devices. 
   Intelligent Assist Devices (“IADs”) are a class of computer-controlled machines that interact with a human operator to assist in moving a payload. IADs may provide a human operator a variety of types of assistance, including supporting payload weight, helping to overcome friction or other resistive forces, helping to guide and direct the payload motion, or moving the payload without human guidance. The Robotics Industries Association T15 Committee on Safety Standards for Intelligent Assist Devices describes IADs as a single or multiple axis device that employs a hybrid programmable computer-human control system to provide human strength amplification, guiding surfaces, or both. These multifunctional assist devices are designed for material handling, process and assembly tasks that in normal operation involve a human presence in its workspace. Typically, Intelligent Assist Devices (IADs) are force-based control devices that range from single axis payload balancing to multiple degree of freedom articulated manipulators. 
   However, the use of forced-based control in particular, and intuitive directional control in general, can lead to many practical problems on the factory floor. Such systems and devices are complicated, both electronically and control wise. These systems must estimate or predict the control functions of the operator from limited inputs, and these limited inputs are subject to ambiguity, interference, and downright failure. For example, with only one physical input, i.e. force applied to a load cell on the operator control, an IAD will need to gauge and predict the desired direction (in both “x” and “y” planes) and speed, while at the same time taking into account vibration within the facility, structural interferences of the assembly line, safety of the operator (position relative to direction of travel), variations among different individual operators and, possibly, unintentional input by the operator. The typical commercial response to these challenges has been an over technical, over engineered control algorithm that requires complex damping, calibration, and tuning. Further, such solutions require constant re-assessment in a manner that is difficult for the arena in which they are operated. In other words, typical facilities do not have the technical resources or proprietary know-how for maintaining such devices. 
   A need exists to provide a practical intelligent assist device (PIAD) to merge the best of the powered assistance currently available with current IAD&#39;s, but with an easier to program and maintenance characteristics. Consequently, a need has been felt for providing an intelligent assist device that is direct and easy to operate, while at the same time being capable of being programmed, tuned, and maintained without the need of specialty hardware or technical resources that are generally unavailable in most manufacturing settings. 
   SUMMARY OF THE INVENTION 
   It is therefore an object of the present invention to provide an improved intelligent assist device. 
   It is a feature of the present invention to provide an improved intelligent assist device that a man-machine interface that is clearly and ergonomically designed for efficient use of the system and safety of the operator. 
   Briefly described according to one embodiment of the present invention, a practical intelligent assist device is provided that eliminates the complex use of force sensing weigh cells and vector interpreting software. By simplifying the input to a series of traditional voltage inputs, i.e. 1-4 volt control signals, the use of standard available control componentry becomes available. Utilizing a series of such simplified inputs, including a load angle feedback, the processing of the vector math can be accomplished within a programmable logic controller (PLC). Outputs can then be simply generated to control a series of 0-60 Hz digital signals to drive AC variable frequency direct drive gear motors. In this fashion, maintenance, repair, installation, programming, etc. can be done with the resources of the plant level technical resources, with little or no reliance on proprietary hardware and software, or specialized technical consultants. 
   Advantage of the present invention are the ability to connect and integrate a number of IAD components selected from those generally available devices that manufacturing facilities are already familiar with in the operation and maintenance, i.e., no complex, proprietary systems, and a computer interface design that allows an technician or system integrator to easily program, operate and monitor the status. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The advantages and features of the present invention will become better understood with reference to the following more detailed description and claims taken in conjunction with the accompanying drawings, in which like elements are identified with like symbols, and in which: 
       FIG. 1  is a perspective view of a Practical Intelligent Assist Device, or PIAD, according to an exemplary embodiment of the present invention; 
       FIG. 2  is a perspective view of an operator control mechanism  30  for use therewith; 
       FIG. 3  is a detailed perspective view of a bridge drive assembly  18  for use therewith; 
       FIG. 4  is a detailed perspective view of a fixture drive assembly  21  for use therewith; 
       FIG. 5  is a vector diagram describing the operation of the column pivot position for use therewith; and 
       FIG. 6  is a perspective view of a cable type Practical Intelligent Assist Device according to an alternate embodiment of the present invention. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Because IADs are intended for close interaction with human operators, unambiguous communication of IAD mode of operation to the human operator is particularly important. The man-machine interface should be clearly and ergonomically designed for efficient use of the system and safety of the operator. Ease and intuitiveness of operation is necessary for achieving high levels of productivity. Because of the close interaction of man and machines, safety of the human operator is most important so that attention should be paid to the design of the operator&#39;s controls such that inadvertent or mistaken changes of mode are minimized. As such, a number of fail-safe systems are known in the art and it is anticipated that they can be easily incorporated within a PIAD. 
   For purposes of an enabling disclosure, an exemplary mode for carrying out the invention is presented in terms of a preferred embodiment, herein depicted within the Figures. 
   DETAILED DESCRIPTION OF THE FIGURES 
   Referring now to  FIGS. 1-5 , a practical intelligent assist device generally noted as  10  is shown having a support  12 , shown herein as an overhead rail support, and a power assisted manual manipulator  14 . The support  12  is anticipated as being movable and variably affixable within the manufacturing environment. For purposes of disclosing the enablement of the present invention, the support  12  is shown as a pair of parallely spaced overhead rails  16  defining a generally horizontal first axis “X”. The power assisted manual manipulator  14  is shown as a carriage supported on the overhead rail and movable along the X-axis by a bridge drive assembly  18  housing a first AC drive motor. The operation of the bridge drive assembly and first motor  18  will be described in greater detail below, but it is anticipated that a number of such motors can be used together to accomplish movement of the carriage  14  along the X-axis. The carriage  14  itself is shown as being formed of a pair of parallely spaced support rails  20  defining a generally horizontal second axis “Y” perpendicular to the first axis “X”. A lift mechanism  22  for moving an end effector  24 , wherein said lift mechanism  22  is supported by carriage support rails  20  and having a main arm extending from said carriage  14  in a third axis “Z” and being rotatable in the plane of the X-Y axes. The carriage  14  is movable along the Y-axis by fixture drive assembly  21  having a second AC drive motor. A vertical lift mechanism  26 , shown herein as a pneumatic lift, provides vertical control of the end effector  24 . It is anticipated that a number of interchangeable end effectors can be utilized, with each being binary coded with a proximity sensor and proximity flag combination that would allow the device  10  to automatically adapt the programming for the controls to conform to the use limits and functionality of the specific end effector. A linkage  29  pivotally attaches the lift mechanism  22  to the carriage  14 , and provides to the system an input that allows the calculation of the directional angle of the end effector  24  relative to the support axes X and Y as will be described in greater detail below. 
   An operator control mechanism  30  for receiving the operator inputs and provide intent commands to the control mechanism is affixed to the lift mechanism  22  in a position fixed relative to the end effector  24 , and in a position that allows the operator to easily see the end effector and to provide guidance and control thereto. Instead of a plurality of force sensors disposed between the operator control mechanism and the lift mechanism as would be provided in the prior art,  FIG. 2  shows in greater detail the more practical operator control mechanisms of the present invention. Operator inputs are anticipated as being provided by a left joystick  40 , a right joystick  42 , and a display touchscreen  44 . In general, the touchscreen  44  is anticipated as being supported in the center of the control mechanism  30 , with a left hand grip  41  and a right hand grip  43  extending laterally outward therefrom. This provides an intuitive ergonomic for gripping, guiding, and controlling the end effector  24 . The operator must grasp both the left hand grip  41  and right hand grip  43  in order to engage a safety interlock (not shown) anticipated as preventing movement of the system unless actual operator contact at both hand grip positions can be confirmed. Once such a safety condition is met, the left joystick  40  and right joystick  41  can be engaged. Although the control functionality of each joystick can be interchangeable, for purposes of disclosure the left joystick  40  controls the vertical motion of the end effector  24 . Placed at a locations on the left hand grip  41  easily manipulated by the operator&#39;s left thumb, by toggling the left joystick  40  up or down a variable current signal generated between 1 volt (full down) to 4 volt (full up) or proportionally there between is generated as an operator vertical intent input. Based upon the value of this signal, a programmable logic controller (PLC)  50  or similar control system of a type readily industrially available and known can determine the operators&#39;s intent on the desired vertical vector for the end effector, i.e., the direction (up or down) as well as rate of rise or decent (speed) is extrapolated from this operator vertical intent input. For example, a 1 volt signal would represent a rapid lowering of the end effector; a 4 volt signal would represent a rapid raising of the end effector.; a 2.5 volt signal would represent no vertical motion; a 3.25 volt signal would represent a (relatively) slow raising of the end effector; and so on. 
   Similarly, the right joystick  42  controls the horizontal motion of the end effector  24 . Placed at a locations on the right hand grip  43  easily manipulated by the operator&#39;s right thumb, by toggling the right joystick  42  left or right, front or back, a pair of variable current signal generated between 1 volt (full left) to 4 volt (full right) or proportionally there between is generated as an operator horizontal intent input. Based upon the value of this signal, a programmable logic controller (PLC)  50  can determine the operators&#39;s intent on the desired horizontal vector for the end effector, i.e., the direction (left, right, forward, backward) as well as rate of movement (speed) in the desired direction is extrapolated from this operator horizontal intent input. For example, a 1 volt signal would represent movement of the entire carriage  14  rapidly to the left; a 4 volt signal would represent a rapid movement to the right; a 2.5 volt signal would represent no horizontal movement; a 3.25 volt signal would represent a (relatively) slow movement to the right; and so on. 
   While lateral intent can be inferred from such an operator horizontal intent input, the actually direction that the operator desires the carriage  14  to travel will be relative to the current position of the carriage  14  or end effector  24  within the X-Y plane. In order to determine this relative motion, and thus the intent of the operator, a column angle feedback from the linkage  29  provides a column pivot position. This is anticipated as being provide by a resolver based rotary encoder, such as provided by an AMCI Duracoder™ or functional equal. Such an encoder provides a control signal, herein a 0-10VDC control in put that is a proportional function to the rotary position of the linkage  29 . The column angle feedback, along with the joystick feedback, determines the final trajectory of movement. The joystick  42  feeds back two analog 1-4 volt signals to the processor  50 . One signal is the X-plane control signal, the other is the Y-plane control signal. These X and Y coordinates are translated into a joystick vector that describes the angle and magnitude of motion being commanded by the operator. The rotating column  29  has a single feedback device into the processor that is translated into a column feedback angle position. This column angle position then offsets the joystick vector angle to form a final trajectory relative to the bridge position or the X-Y plane of the system. This vector is then decoded into two vectors: one in the X plane; and, one in the Y plane. The sum of these two vectors equals the final trajectory vector. The X and Y vector magnitude are then outputted to the various AC direct drive gear motors (for the bridge drive assembly  18  and fixture drive assembly  21 ) to determine final drive speeds. 
   This results in an intuitive form of motion: if the operator pushes the joystick  42  forward, the PIAD  10  travels forward relative to the position of the column  14 . Another advantage that can be extrapolated from this simple programmability and intuitive functionality is the ability for remote operator synchronization, in which the device  10  is tracked stationary relative to a moving assembly line. By tracking to follow the line speed, the joystick functionality can be programmed to have consistent relative functionality, independent of line speed. 
   Referring now to  FIG. 3 , the bridge drive assembly  18  is shown in greater detail, in which and first motor  18   a  is supported to a first trolley housing  51 . The trolley housing  51  is fabricated to be adaptable to a number of existing overhead rail systems that are currently in use. The motor  18   a  drives a bridge drive roller  52  that rides upon the overhead rails  16 , and the housing  51  connects to the carriage  14  such that as the first motor  18   a  drives the drive roller  52 , the carriage  14  will move about the rails  16  along a generally horizontal first axis “X”. The motor  18   a  is anticipated as being an AC direct drive gear motor, such that the speed of the motor will be directly proportional to a 4-20 mA control signal output from the controller  50 . Relative “position” of the carriage  14  about the X plane is determined by at least one analog laser sensor  54 , mounted rigidly to the trolley housing  51  and aimed at a fixed target (not shown) positioned at a reference location along the rail  16 . 
   Referring now to  FIG. 4 , the fixture drive assembly  21  is shown in greater detail, in which a second motor  21   a  is supported to a second trolley housing  61 . The trolley housing  61  is fabricated to be adaptable to a number of existing overhead rail systems that are currently in use. The gear motor  21   a  drives a fixture drive roller  62  that rides under the support rails  20  of the carriage  14 , and has a pneumatic cylinder to apply an upward engagement force. The housing  61  connects to the lift mechanism  22  is such that as the second motor  21   a  drives the drive roller  62 , the lift mechanism  22  will move about the rails  20  along a generally horizontal second axis “Y”. The motor  21   a  is anticipated as being an AC direct drive gear motor, such that the speed of the motor will be directly proportional to a 0-10 VDC control signal output from the controller  50 . Relative “position” of the lift mechanism  22  along the carriage  14  about the Y plane is determined by at least one analog laser sensor  64 , mounted rigidly to the trolley housing  61  and aimed at a fixed target (not shown) positioned at a reference location along the rail  20 . It is anticipated that the use of such position sensing can allow the operator to program “null zones” or “travel limits” along the overall work area, or to program pre-determined automatic travel paths. However, it is also anticipated that such analog linear target detection can be used to reduce the travel speed of the bridge drive assembly  18  as it approaches the travel limit of the overhead rails  16 , or the speed of the lift mechanism  22  along as is approaches the travel limits of the carriages rails  20 , or both. 
   Finally, various other control of the lift mechanism  22  or end effector  24  can be accomplished through the display touchscreen  44 , as well as other informational reporting or display. Functions such as clamping or unclamping of the end effector, release or locking of the entire carriage or lift mechanism, or other various alarms can be controlled from or displayed on this user input means. It is anticipated that in a manufacturing environment that will find the most use from an intelligent assist device will require various functionality, programmability, and adaptability in a manner that is direct and easy to operate, while at the same time being capable of being programmed, tuned, and maintained without the need of specialty hardware or technical resources that are generally unavailable in most manufacturing settings. The use of such a joystick-handgrip-touchscreen combination is intended to meet this goal without resorting to a complex, difficult to tune force-based control device that range from single axis payload balancing to multiple degree of freedom articulated manipulators. 
   OPERATION OF THE PREFERRED EMBODIMENT 
   In operation, the present invention disclosed herein provides for a more natural and intuitive control of the motion of a payload. The system and method are implemented on an overhead rail system of known type. In such use, the operator would merely guide and direct the end effector by providing directional input to the joystick  40 ,  42 . Because the left-right control signal is calculated relative to the actual angular position of the lift column  22 , such a control signal will always be interpreted relative to the position that the operator is facing, i.e. toward the load or end effector. 
   It should be understood, however, that the present embodiments are not limited to the exemplary embodiments disclosed herein, but that they may also be implemented in systems that utilize other kinds of material handling systems including gantry cranes, jib cranes, monorails, articulated systems, and so forth. Therefore, details regarding the overhead rail system including the types of material handling hardware are provided as an example, and are not necessary to the invention unless otherwise specified as such. 
   The foregoing descriptions of specific embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teaching. Once such example is shown in  FIG. 6 , in which a cable-type practical intelligent assist device generally noted utilizing a similar support  12  as with the previously described embodiment in which an overhead rail support is movable and variably affixable within the manufacturing environment. 
   In this embodiment, a pneumatic hoist  60  drives a cable support  68 . The end effector  24  is supported at it&#39;s center of gravity through axis “CG-CG”, with the operator control mechanism  30  for receiving the operator inputs and provide intent commands to the pneumatic hoist  60  as well as the various “X” axis and “Y” axis controls as previously described. It is envisioned that the “Z” axis lift control of the cable  68  via the pneumatic hoist  60  can be accomplished by a conventional analog regular for converting conventional 0-10 VDC control signals in to an adjustable and controllable pneumatic pressure. Based upon the value of this signal, the analog regulator  64  can determine the operators&#39;s intended vector based upon the desired operator intent input. Additional features, such an an electronic compass  66 , can provide additional directional feedback for calculation in the control signal. 
   The above embodiments were chosen and described in order to best explain the principles of the invention and its practical application, to thereby enable others skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the Claims appended hereto and their equivalents. Therefore, the scope of the invention is to be limited only by the following claims.