Patent Publication Number: US-2022234205-A1

Title: Method and automated motion system for controlling a component handler

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a U.S. National Phase application under 35 U.S.C. § 371 of International Application No. PCT/EP2020/066731, filed on Jun. 17, 2020, and claims benefit to European Patent Application No. EP 19182653.6, filed on Jun. 26, 2019. The International Application was published in English on Dec. 30, 2020 as WO 2020/260087 A1 under PCT Article 21(2). 
    
    
     FIELD 
     The present invention relates to a method of controlling a component handler of an automated motion system for applying constant and repetitive forces of an optimal value on components, such as electronic components, to be handled. Optimal force control ensures the handling of components at high speed without any damage to the components, and allows performing different processes, such as bonding processes, where precise force control is essential. The invention also relates to an automated motion system adapted to perform the method thereof. 
     BACKGROUND 
     Automated motion systems, for example of the type of turret handlers, comprise a stationary support on which actuators are mounted and a carousel (turret) rotatably mounted relative to the stationary support. Components are loaded on the carousel and indexed at high speed to individual test stations. 
     Handling components at high speed raises proportionally the challenge of handling carefully the components. Turret handlers are equipped with multiple component handlers. Each component handler comprises a vertical actuator and a component holder in the form of a pipet. The pipet comprises a tube slidably mounted through a plain bearing, a compression spring arranged around the tube, and a vacuum pick-up nozzle at a distal end of the tube for components handling. 
     Because of the nature of the components to be handled, such as electronic components, which have become over the years considerably thinner, and which may be made of brittle materials, force control has become extremely important to avoid breaking or even marking the components, or to perform some operations. 
     However, the friction occurring between the plain bearing and the pipet and the spring stiffness under operating conditions may change over time, so that a same force or displacement applied by an actuator to the pipet may result in varying force or displacement of the distal end of the pipet. Regular recalibration using a force sensor is therefore necessary for force control, which is a cumbersome and costly procedure. 
     In robotic systems, servo motor position and torque information, deduced from motor currents, have been used to calculate and control forces at a robot&#39;s end effector. Simpson et al. [“Sensorless Force Estimation for Robots with Friction”, Proc. 2002 Australasian Conference on Robotics and Automation, Auckland, 27-29 Nov. 2002] have proposed a method for estimating forces applied at the end effector of a Selective Compliance Assembly Robot (SCARA robot) using force estimation models based in particular on inertia and coulomb frictions parameters to address the problem of frictions and other torques the motor&#39;s torque must overcome. 
     The estimation models used in the work presented in the above reference are adapted for SCARA robots which differ significantly from automated motions systems for electronic components handling in terms of parameters having an influence on the desired force to be applied on the electronic components. 
     US 2014/0212246 discloses an apparatus for picking and placing or picking and transferring or for picking, placing and pressing semiconductor components to and from a workstation. The apparatus comprises a rotatable turret holding a plurality of pressers. Each of these pressers is a voice coil assembly. The apparatus further comprises a pre-calibrated linear encoder which provides a linear relationship between the pressing force and the current flowing on the voice coil. 
     One disadvantage of using linear encoder stems from the fact that they are usually expensive. 
     SUMMARY 
     In an embodiment, the present disclosure provides a method of controlling a component handler of an automated motion system, for picking up a component from a pick-up position. The method includes acquiring and using calibration data. The component handler includes a calibrated actuator comprising a stationary part, a movable part, one or more coils, a permanent magnet and an actuating member, and a component holder comprising a distal end and an elastic member. The component holder is arranged to be actuated from a resting position to an extended position by the actuating member of the actuator and from the extended position to the resting position by the elastic member. The calibration data is acquired by: bringing the actuating member into contact with an actuable portion of the component holder, moving the component holder in at least one position within the resting and extended position, measuring a required current in the one or more coils to maintain or move the component holder in the at least one position, and determining the calibration data from the current. The calibration data is used to control the actuator for moving the component holder such that the distal end applies a predetermined force on the component in the pick-up position. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Subject matter of the present disclosure will be described in even greater detail below based on the exemplary figures. All features described and/or illustrated herein can be used alone or combined in different combinations. The features and advantages of various embodiments will become apparent by reading the following detailed description with reference to the attached drawings, which illustrate the following: 
         FIG. 1  shows a cross-sectional view of a component handler comprising an actuator and a component holder according to an embodiment of the present invention; 
         FIG. 2  shows a perspective view of a turret test handler comprising a computer for controlling the component handler of  FIG. 1  according to an embodiment of the present invention; 
         FIG. 3  is a graph illustrating an example of a Kt calibration as a function of the position of the actuating member of the actuator; 
         FIG. 4  is a graph derived from calibration data based on a force estimation model; and 
         FIG. 5  is a graph representing the force generated by the gravity compensator of the actuator as a function of the position of the distal end of the actuating member of the actuator. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments of the present invention provide for a number of improvements and advantages including providing: a method of controlling a component handler of an automated motion system capable of applying constant and repetitive forces of an optimal value on a component without any force sensor; an automated motion system with advanced soft-contacting component handlers; an automated motion system which is cost-effective; and/or a computer program for controlling the automated motion system. 
     These improvements and advantages are achieved by a method of controlling a component handler of an automated motion system, for picking up a component from a pick-up position, according to an embodiment of the present invention. The component handler comprises a calibrated actuator and a component holder. The actuator comprises a stationary part, a movable part, one or more coils, a permanent magnet, and an actuating member. The component holder comprises a distal end and an elastic member. The component holder is arranged to be actuated from a resting position to an extended position by the actuating member of the actuator and from the extended position to the resting position by the elastic member. The method comprises: 
     a) acquiring calibration data of the component holder by:
         operating the actuator to move said actuating member into contact with an actuable portion of the component holder,   moving the component holder in at least one position within said resting and extended position, and   measuring the required current in said one or more coils to maintain or move the component holder in said at least one position, and   determining said calibration data from said current,       

     b) using said calibration data to control the actuator for moving the component holder such that its distal end applies a predetermined force on the component in the pick-up position. 
     In an embodiment, the step of acquiring calibration data comprises: 
     a1) measuring the required currents in said one or more coils to maintain the component holder in at least two distinct positions within said resting and extended position, 
     a2) determining the force applied on the actuable portion of the component holder by the actuating member at each of the at least two distinct positions according to said required currents and the force constant of the actuator in said at least two distinct positions, and 
     a3) determining calibration data based on the force applied by the actuating member on said actuable portion of the component holder at each of said at least two distinct positions. 
     In an embodiment, the calibrated actuator further comprising one or more bearings mounted around the movable part, and an actuating member bearing through which the actuating member passes, wherein the force applied on the actuable portion of the component holder under step b) is determined by further taking into consideration friction coefficient of said one or more bearings and of the actuating member bearing. 
     In an embodiment, the calibrated actuator further comprises a gravity compensator. The force applied on the actuable portion of the component holder under step b) is determined by further taking into consideration the force generated by the gravity compensator in said at least two distinct positions. 
     In an embodiment, step a) comprises: 
     i) measuring the required currents in said one or more coils to maintain the component holder in multiple distinct positions within said resting and extended position, and 
     ii) moving the component holder at constant speed within said resting and extended position and measuring again the required currents in said one or more coils in said multiple distinct positions when the component holder is moving past each distinct position. 
     In an embodiment, steps i) and ii) are preformed when the component holder is moved downwardly and upwardly. 
     In an embodiment, the component holder comprises a tube connected to vacuum means. The actuator is controlled to move the distal end of the tube at constant speed to a position above a suction surface, whereupon the speed is decreased such that said distal end is at or near a standstill as soon it reaches the suction surface. 
     Another embodiment of the invention provides an automated motion system having a computer comprising a processor and a memory with a computer program stored thereon and for storing calibration data. The computer program comprises instructions to cause, when executed by the processor, the automated motion system to perform the method according to any embodiment of the present invention. 
     In an embodiment, the automated motion system is a turret handler. 
     Another embodiment of the invention relates to a computer-readable medium having stored thereon a computer program comprising instructions to cause the automated motion system to perform the method according to any embodiment of the present invention. 
     Another embodiment of the invention relates to a method of monitoring an automated motion system to detect any actuator that has drifted over time and lost its accuracy. The automated motion system comprises multiple actuators and at least one component holder. Each actuator comprises a stationary part, a movable part, one or more coils, a permanent magnet and an actuating member. The component holder comprises a distal end and an elastic member supported by a mounting base of the automated motion system movable relative to said multiple actuators. The method comprises: 
     a) controlling one of said multiple actuators for moving the component holder such that its distal end applies a predetermined force on a given surface, 
     b) measuring the required current in said one or more coils to apply said predetermined force on the surface, 
     c) moving the mounting base to align the component holder successively with each other actuator of said multiple actuators and repeating step a) and b) for each other actuator, wherein the distal end of the component holder applies a predetermined force on a corresponding given surface, 
     d) comparing said required current between the multiple actuators, and 
     e) determining whether any actuator has drifted over time and lost its accuracy based on any discrepancy in the measured currents for all actuators. 
       FIG. 1  illustrates an exemplary embodiment of a component handler  10  for an automated motion system such as for example a turret handler  100  as shown in  FIG. 2 . The structural and functional parts of the component handler  10  will first be described with reference to  FIG. 1  as to understand the different parameters which need to be taken into consideration for calibration in order to provide a component handler  10  capable of applying constant and repetitive force of a desired value on electronic components. 
     The component handler  10  comprises a vertical actuator  20  and a component holder  40 . The actuator  20  comprises a stationary housing  22  and a movable part  28  slidably mounted inside the stationary housing  22  along an axial direction. An upper and a lower portion  24   a ,  24   b  of a coil are mounted around the movable part  28  and are fixed to a cylindrical yoke  37 , made of magnetic material, which is bonded against the inner walls of the stationary housing  22 . 
     The movable part  28  comprises upper and lower cylindrical guiding parts  38   a ,  38   b , made for example of stainless steel, and arranged on both sides of a permanent magnet  30 . The upper and lower cylindrical guiding parts  38   a ,  38   b  are slidably mounted against a first and a second bearing  26   a ,  26   b , which are fixed respectively to the upper and lower parts of the stationary housing  22  of the actuator  20 . Upper and lower ferromagnetic rings  39   a ,  39   b  are mounted against two opposite sides of the permanent magnet  30  and between the magnet  30  and the upper and lower cylindrical guiding parts  38   a ,  38   b  respectively. 
     The lower cylindrical guiding part  38   b  comprises a bore receiving a proximal end  32   a  of an actuating member  32  which may be for example in form of a rod. The lower part  34   b  of the stationary housing  22  comprises an actuating member bearing  25  through which the actuating member  32  passes. The upper part  34   c  of the stationary housing  22  is made of non-magnetic material. An upper magnetic part  36 , which may be for example in the form of a magnetic pin, is connected to the non-magnetic upper part  34  such that the central axis of the magnetic pin  36  coincides with the central axis of the movable part. The magnetic pin  36  is magnetically isolated from the magnet yoke  37  since the non-magnetic upper part  34  separates the magnetic pin  36  and the magnet yoke  37  from each other. 
     The upper portion  24   a  of the coil is wound in a first direction while the lower portion  24   b  of the coil is wound in a second direction, opposite the first direction. The coil therefore defines a single-phase actuator which, however, is disposed such that the magnetic field generated by the lower portion  24   a  has a direction which is opposite to the direction of the magnetic field generated by the upper portion  24   a  of the coil. 
     The movable part  28  of the vertical actuator  20  as described above remains in a position of stable equilibrium, upon absence of a current supply, which corresponds to a high or upper position of the movable part  28 . This position depends on the resultant of forces applied over the entire functional range of the actuator, such that in response to the absence of a current supply, the movable part is able to reach the position of stable equilibrium from any position of the functional range provided. An upward resultant force is produced by the arrangement of the magnetic pin  36 , and the upper ferromagnetic ring  39   a  of the movable part  28 , which act together as a gravity compensator. 
     Still referring to  FIG. 1 , the component holder  40  of the component handler  10  is configured to be mounted on a mounting base  112  of a carrousel  110  of the automated motion system as described subsequently. The component holder  40  comprise a tube  42  passing through a bearing  114  mounted on the mounting base  112 , and an actuable part  44  configured to be actuated downwardly by the distal end  32   b  of the actuating member  23  of the actuator  20 . The tube  42  is connected to vacuum means for lifting off electronic components by suction. 
     An elastic member, which is preferably in the form of a compression spring  46 , is arranged around the tube  42 . The opposite ends of the compression spring  46  rest respectively against the mounting base  112  and the lower portion of the actuable part  44  of the component holder. The distal end  43  of the tube  42  is configured to be brought in a predetermined axial position to come into contact with an electronic component with an optimal force without risking damaging such component. 
     It is therefore important that the component handler  10  is capable of applying constant repetitive force of a desired value on the components. Constant repetitive force is however difficult to achieve as the automated motion system  100  as shown in  FIG. 2  comprises multiple component handlers  10  and the desired value of the force to be applied on electronic components are dependent upon several parameters of the component handler  10  which may vary significantly from one component handler to another, and over time. It is therefore provided thereafter a method of controlling a component handler of an automated motion system, for applying in a repetitive manner a constant predetermined force on a component in a pick-up position. 
     The automated system of  FIG. 2  comprises a stationary actuator support  120  and a carousel  110  rotatably mounted relative to the stationary actuator support  120 . The automated motion system  100  comprises multiple component handlers  10 . Each component handler  10  is configured to load components, such as resistors, diode, capacitor, simple ICs or wafer dies, to different stations, for example bonding station, test station, visual inspection station and/or laser marking station. Each actuator  20  and the corresponding component holder  40  of each component handler  10  are mounted respectively on the stationary actuator support  120  and the carousel  110 . 
     The automated motion system  100  with the actuators  20  of the component handlers  10  is provided by the manufacturer of the system while the component holders  40  may be provided by users of the system. The actuators  20  are calibrated in the course of quality control stages of the automated motion system. 
     In order to achieve constant repetitive force of a desired value on electronic components, a number of parameters must be taken into account both at the actuator level and at the component holder level. At the actuator level, at least the following parameters must be taken into consideration: the force constant (K t ) variation of the motor, the force of friction F f  of the first and second bearings  26   a ,  26   b  and of the actuating member bearing  25 , and the force F g  generated by the gravity compensator. 
     In a variant, the first and second bearings and the actuating member bearing may advantageously be replaced by spring blades which have the advantage that their stiffness and (very low) friction change very little with temperature and time. The force versus position curve of the spring blades must however be measured for every actuator to determine the spring constant of the spring blades. 
     At the component holder level, at least the following parameters must be taken into consideration: the force constant (K) of the spring  46 , and the frictions of the bearing  114 . 
     The actuator  20  offers a typical ±10 to ±20% force constant (Kt) variation by design. The impact on the force applied to the component for a given level of current is varying accordingly. Therefore, the determination of the constant Kt of each actuator requires a calibration. This can be performed during production using a force sensor. The change in force due to temperature (around 0.11% per Kelvin for NdB rare-earth magnets) can also be taken into account if needed. The actuator calibration data may be stored either in a memory on the actuator itself or in a computer that controls the system. As will be described later, the actuator may be recalibrated after production, based on measurements with calibrated component holders. 
       FIG. 3  illustrates an example of a Kt calibration as a function of the position of the actuating member of the actuator on the assumption that the force generated by the frictions of the bearings is known and constant. 
     Since the actuator is calibrated, it can be used for determining the calibration data of a component holder  40  mounted onto that actuator. More specifically, the force to be applied by the actuator to move or maintain the distal end of the component holder  40  to/at a given position depends on the known, calibrated parameters of the actuator, and on the unknown parameters of the component holder; since the parameters of the actuator are known, the force applied by the actuator to reach or maintain a given position can be used for determining the calibration data of the component holder. 
     The component holder calibration data may be acquired through a process comprising different displacements of the component holder, in one or two senses. For example, the actuator  20  may be controlled to bring the component holder to different positions x i  and populate a Table 1 as shown below. 
     
       
         
           
               
               
               
               
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                 Direction 
                 Position x 
                 Speed [mm/s] 
                 Force 
                 Speed [mm/s] 
                 Force 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
            
               
                 Down 
                 0 
                 0 
                 6.23 
                 20 
                 8.04 
               
               
                 Down 
                 1 
                 0 
                 7.20 
                 20 
                 9.00 
               
               
                 Down 
                 2 
                 0 
                 8.03 
                 20 
                 9.92 
               
               
                 Down 
                 3 
                 0 
                 9.53 
                 20 
                 10.57 
               
               
                 Down 
                 4 
                 0 
                 10.56 
                 20 
                 12.07 
               
               
                 Down 
                 5 
                 0 
                 11.45 
                 20 
                 12.65 
               
               
                 Down 
                 6 
                 0 
                 11.82 
                 20 
                 13.33 
               
               
                 Down 
                 7 
                 0 
                 13.62 
                 20 
                 14.56 
               
               
                 Down 
                 8 
                 0 
                 14.15 
                 20 
                 15.73 
               
               
                 Down 
                 9 
                 0 
                 15.34 
                 20 
                 16.99 
               
               
                 Down 
                 10 
                 0 
                 15.83 
                 20 
                 17.98 
               
               
                 Up 
                 10 
                 0 
                 14.13 
                 20 
                 12.40 
               
               
                 Up 
                 9 
                 0 
                 13.73 
                 20 
                 12.31 
               
               
                 Up 
                 8 
                 0 
                 12.48 
                 20 
                 11.16 
               
               
                 Up 
                 7 
                 0 
                 11.48 
                 20 
                 9.89 
               
               
                 Up 
                 6 
                 0 
                 9.89 
                 20 
                 8.58 
               
               
                 Up 
                 5 
                 0 
                 9.58 
                 20 
                 7.50 
               
               
                 Up 
                 4 
                 0 
                 7.80 
                 20 
                 7.13 
               
               
                 Up 
                 3 
                 0 
                 6.86 
                 20 
                 5.65 
               
               
                 Up 
                 2 
                 0 
                 6.26 
                 20 
                 5.31 
               
               
                 Up 
                 1 
                 0 
                 5.05 
                 20 
                 3.71 
               
               
                 Up 
                 0 
                 0 
                 4.08 
                 20 
                 2.89 
               
               
                   
               
            
           
         
       
     
     The actuator  20  of  FIG. 1  is first controlled to move the distal end  32   b  of the actuating member  32  into contact with the actuable portion  44  of the component holder  40  in an initial position x corresponding to position 0 mm in the above table. The required current (Loll) in the upper and lower portion  24   a ,  24   b  of the coil of the actuator  20  to maintain the distal end of the actuating member in this position is measured. The actuator  20  is then controlled to move the component holder  40  in several position within a resting position and an extended position. To that end, the distal end  32   b  of the actuating member  32  is moved downwardly in several positions within its entire stroke, for example in ten distinct positions with an interval of 1 mm from each other, and the required currents I coil  in the coil of the actuator to maintain or bring the distal end  32   b  of the actuating member  32  in each of these positions x i  are measured and used to determine the force applied by the actuator at each position. 
     The actuator  20  is then controlled to move upwardly the distal end  32   b  of the actuating member  32  in the same distinct positions and the required currents in the coil of the actuator  20  to maintain or bring the distal end  32   b  of the actuating member  32  in each of these positions are measured again. 
     The actuator is then controlled to move the distal end of the actuating member downwardly and upwardly at constant speed, for example at 20 mm/s, and the currents in the coil are measured while the distal end of the actuating member passes each of the same distinct positions at constant speed. 
     For each position x, the force generated by the actuator is obtained by the equation: 
         F   em   =K   t   ·I   coil   i)
 
     where the force constant Kt of the actuator for each position x is known and calibrated as shown in  FIG. 3 . The force applied by the distal end of the actuating member on the actuable part  44  of the component holder  40  is obtained by the equation: 
         F   act   =−F   em   −F   b   +F   g   ii)
 
     where F b  is the friction forces of the first and second bearings  26   a ,  26   b  and the actuating member bearing  25  of the actuator  20  of  FIG. 1 , which are known, or the recoiling force depending on the spring constant of the spring blades that depends on position if all the bearings of the actuator are replaced by spring blades, and F g  is the force generated by the gravity compensator of the actuator which has been measured for each distinct position with an interval of 1 mm from each other as shown in  FIG. 5 . Equations i) and ii) have been used to populate the above table. 
       FIG. 4  shows a graph representing the above calibration data. Four parameters of the component holder  10  may be determined using a non-linear least-squares fitting algorithm, whereby:
         the slope of the linear regression provides the spring constant K,   the initial force F 0  is found at position 0 in the intersection of the linear regression with the Y-axis, and   the dry and viscous friction coefficients F c  and F v  are obtained by the vertical offset between the average of the linear regression of the force F act  in multiple distinct positions calculated during both downward and upward movements of the actuating member when the distal end of the actuating member is at a standstill in each distinct position (linear regression intersecting the Y-axis) and the linear regression of the force F act  in multiple distinct positions when the actuating is moving at constant speed.       

     Using the calibration data of the component holder  40 , the four parameters F 0 , F c , F v  and K can be calculated for each component handler  10  of the automated motion system. 
     In order to apply on electronic components a force F of an optimal value by the distal end  43  of the tube  42  for an operation performed at a standstill, for example a bonding process requiring 1N of vertical force, the automated motion system  100  as shown in  FIG. 2  comprises a computer  102  having a processor  104  and a memory  106  storing a computer program comprising instructions which, when the program is executed by the processor  104 , cause the computer to carry out following operations: 
     calculating the friction force F f  or recoiling force of the component holder using the equation: F f =F c    
     calculating the force that must be applied by the distal end of the actuating member  32  of the actuator on the actuable part  44  of the component holder  40  using the following equation: 
     
       
      
       F 
       act 
       =F+F 
       0 
       +K·x+F 
       f  
      
     
     where x is the distance between the initial position 0 and the new position of the distal end of the actuating member, 
     add to this force F act  the bearing force and substract the gravity compensator force F g  to calculate the generated force by the actuator using the equation: 
     
       
      
       F 
       em 
       =F 
       act 
       +F 
       b 
       −F 
       g  
      
     
     calculating the required current using the equation: I coil =F em /K t  where K t  is the force constant of the actuator when the distal end of the actuating member is at position x, and 
     moving the distal end of the actuating member of the actuator in position x and adjusting the current I coil  to apply on the component the optimal force F by the distal end  43  of the tube  42  of the component holder  10 . 
     It should be noted that it is also possible to interpolate between data points in order to determine directly the current I coil  to be applied to the actuator in order to bring the distal end of the component holder  40  at an intermediate position between two positions x 1 , x 2 ; the current required to reach or maintain those intermediate positions can thus be determined without computing the four parameters F 0 , F c , F v  and K. 
     For processes performed during a vertical movement of the component handler, the equation under step i) must be replaced by the equation F f =F c +F v  in order to take into account the viscous friction coefficient. 
     The computer program for carrying out the above operation contains instructions to control the actuator  20  to move the distal end  43  of the tube  42  at constant speed to a position above a suction surface, whereupon the speed is decreased to ensure that the force applied by the distal end  43  on the component does not exceed a predetermined force as soon it reaches the suction surface. An automated motion system with advanced soft-contacting component handlers is therefore obtained. 
     In another embodiment, there is provided a monitoring method of an automated motion system, for example of the type of a turret test handler, to identify whether any actuator has drifted over time and lost its accuracy using a component handler  40  as a reference standard. 
     The turret handler  100  as shown in  FIG. 2  comprises multiple actuators  20 . Calibrated actuators tend to drift over time and should therefore be recalibrated on a regular basis. Monitoring the actuators regularly to detect as soon as possible inaccurate actuator is essential in order to avoid a drift in the force applied on components in their pick-up position by the component handlers. 
     The method consists in placing a component holder  40  in the mounting base  112  of the carousel  110  of the turret handler  100  such that it is aligned with one of multiple actuators  20  connected to the mounting part  122  of the stationary actuator support  120 . The actuator  20  is then controlled to move the component holder  40  such that its distal end  43  applies a predetermined force on a surface disposed in a given position. 
     The required current I coil  in the coils  24   a ,  24   b  of the actuator  20  to apply the predetermined force on the surface is then measured. The carousel  110  of the turret handler  100  is then rotated to align the component holder  40  successively with each other actuator  20  and required current in the coils  24   a ,  24   b  of the actuator  20  to apply the predetermined force on a corresponding surface in a corresponding given position is measured again for each actuator. Each corresponding surface aligned with each actuator to be tested are positioned together at the same height. 
     The current measured for each actuator is then compared with the other actuators and any actuator that has drifted over time and lost its accuracy is identified, if any, based on possible discrepancies between the measured currents. 
     Although the method of controlling a component handler of an automated motion system as described above is disclosed with an actuator designed such that the permanent magnet is movable relative to a stationary housing comprising coils, the method may also be applied to any linear actuator comprising a stationary cylindrical permanent magnet and a coil movably mounted inside the cylindrical permanent magnet. 
     While subject matter of the present disclosure has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive. Any statement made herein characterizing the invention is also to be considered illustrative or exemplary and not restrictive as the invention is defined by the claims. It will be understood that changes and modifications may be made, by those of ordinary skill in the art, within the scope of the following claims, which may include any combination of features from different embodiments described above. 
     The terms used in the claims should be construed to have the broadest reasonable interpretation consistent with the foregoing description. For example, the use of the article “a” or “the” in introducing an element should not be interpreted as being exclusive of a plurality of elements. Likewise, the recitation of “or” should be interpreted as being inclusive, such that the recitation of “A or B” is not exclusive of “A and B,” unless it is clear from the context or the foregoing description that only one of A and B is intended. Further, the recitation of “at least one of A, B and C” should be interpreted as one or more of a group of elements consisting of A, B and C, and should not be interpreted as requiring at least one of each of the listed elements A, B and C, regardless of whether A, B and C are related as categories or otherwise. Moreover, the recitation of “A, B and/or C” or “at least one of A, B or C” should be interpreted as including any singular entity from the listed elements, e.g., A, any subset from the listed elements, e.g., A and B, or the entire list of elements A, B and C. 
     REFERENCE LIST 
     
         
         Automated motion system  100   
         Computer  102   
         Processor  104   
         Memory  106   
         Carousel  110   
         Mounting base  112   
         Bearing  114   
         Stationary actuator support  120   
         Mounting part  122   
         Component handler  10   
         Actuator  20   
         Stationary housing  22   
         Coil 
         First and second portions  24   a ,  24   b    
         Movable part guiding members 
         First and second bearings  26   a ,  26   b    
         Actuator lower part  34   b    
         Actuating member bearing  25   
         Movable part  28   
         Permanent magnet  30   
         Actuating member  32   
         Proximal end  32   a    
         Proximal end  32   b    
         Rod 
         Gravity compensator 
         Actuator upper part  34   a    
         Upper magnetic part  36   
         Metal pin 
         Cylindrical yoke  37   
         Cylindrical guiding parts  38   a ,  38   b    
         Upper and lower magnetic rings  39   a ,  39   b    
         Component holder  40   
         Tube  42   
         Distal end  43   
         Actuable part  44   
         Elastic member  46   
         Compression spring