Abstract:
A test device comprises a base and a first fixture coupled to the base. The first fixture holds a first portion of an electronic device mounted in the test device. The test device includes a second fixture rotatably coupled to the base and a lever coupled to the second fixture. The second fixture holds a second portion of the electronic device mounted in the test device. The test device also includes an actuator that forcibly moves the lever to rotate the second fixture and apply a torsion stress on the electronic device mounted in the test device. The test device may be used to test the functionality of electronic devices, such as small form-factor disc drives, while under torsion stresses.

Description:
TECHNICAL FIELD 
     The invention relates to torsion testing of electronic devices. 
     BACKGROUND 
     Many portable consumer devices, such as notebook computers, cell phones, digital music players, personal digital assistants (PDAs) and the like may include a small form factor disc drive for data storage. For example, one currently available small form factor disc drive with a five gigabyte (Gb) capacity has a profile smaller than a credit card with a thickness of less than a quarter inch. 
     Small form factor disc drives are more susceptible to external shocks and other forces than the larger disc drives commonly designed for use in desktop computers. Portable electronic devices tend to experience significant shocks and forces through normal everyday use. For example, a user may accidentally drop a portable electronic device or a user may place a portable electronic device in a back pants pocket and sit on it. If a disc drive inside the portable electronic device breaks as a result of such external shocks and forces, the portable electronic device itself will likely be unusable. For these and other reasons, small form factor disc drives should be robust enough to withstand the external shocks and forces associated with portable electronic devices. 
     SUMMARY 
     In general, the invention is directed to techniques for torsion testing of electronic devices. Torsion testing of an electronic device includes twisting an exterior housing of the electronic device, e.g., twisting under a defined torque or a defined angular displacement and testing the functionality of the electronic device during and/or after twisting. Embodiments of the invention include testing processes and machines for using the processes. 
     In one embodiment, the invention is directed to a test device comprising a base and a first fixture coupled to the base. The first fixture holds a first portion of an electronic device mounted in the test device. The test device includes a second fixture rotatably coupled to the base and a lever coupled to the second fixture. The second fixture holds a second portion of the electronic device mounted in the test device. The test device also includes an actuator that forcibly moves the lever to rotate the second fixture and apply a torsion stress on the electronic device mounted in the test device. 
     In another embodiment, the invention is directed to a method comprising incrementally twisting an electronic device according to a plurality of increments. A strain on the electronic device caused by the incremental twisting changes for each of the plurality of increments. The method further comprises testing the electronic device at least some of the plurality of increments to determine functionality of the electronic device during the at least some of the plurality of increments. 
     In another embodiment, the invention is directed to a method comprising a means for applying a torsion stress to a disc drive, a means for measuring the torsion stress applied to the disc drive and a means for determining the functionality of the disc drive while the torsion stress is applied to the disk disc drive. 
     The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is an illustration of a torsion testing device that provides torsion testing according to defined angular displacements. 
         FIG. 2  is an illustration of a torsion testing device that provides torsion testing according to defined angular displacements and/or defined torques. 
         FIG. 3  is a flowchart illustrating techniques for torsion testing an electronic device using incremental angular displacements. 
         FIG. 4  is a flowchart illustrating techniques for torsion testing an electronic device using incremental torque adjustments. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  is an illustration of torsion testing device  100 , which allows torsion testing according to defined angular displacements of electronic device  120 . Torsion testing device  100  includes clamp  103  that fixedly couples electronic device  120  to base  102 . Torsion testing device  100  also includes clamp  104  that rotatably couples the opposite end of electronic device  120  to base  102 . Electronic device  120  is supported only by clamps  103  and  104 . 
     Clamp  104  is coupled to shaft  106 . Shaft  106  is supported by rotary bearings  116 A and  116 B to rotatably couple clamp  104  to base  102 . Shaft  106  also connects clamp  104  to lever  108 . Lever  108  includes two screw holes  109 A and  109 B (screw holes  109 ) through which screws  110 A and  110 B (screws  110 ) pass through. Screws  110  are actuators that can be extended to press on base  102  to apply a torsion stress to electronic device. E.g., if screw  110 A is extended to press on base  102 , lever  108 , shaft  106  and clamp  104  rotate clockwise (from the viewpoint shown in  FIG. 1 ). The interaction of screws  110  on lever  108  and shaft  106  allows high precision at high loads, which is necessary for accurate testing of electronic device  120 . The rotation of lever  108 , shaft  106  and clamp  104  is limited to a fixed line defined by bearings  116 , which hold shaft  106 . Only one of screws  110  is used at a time to apply a torsion stress on electronic device  120 . 
     Pointer  112  is connected to shaft  106  and serves to indicate the angular position of shaft  106  relative to base  102  on protractor  114 . Lever  108 , shaft  106  and clamp  104  are significantly stiffer than electronic device  120 , such that substantially all the relative motion of lever  108  compared to base  102  is experienced by electronic device  120 . The relative change in the position of pointer  112  relative to protractor  114  from a neutral position serves as a measurement of the torsion stress on electronic device  120 . Using this measurement, electronic device  120  can be twisted to incrementally increase the torsion stress on electronic device  120 . For example, shaft  106  may be rotated a total of four degrees in increments of one degree. The functionality of electronic device  120  may be tested at each increment. 
     As shown in  FIG. 1 , torsion testing device  100  includes test module  130 , which tests the functionality of electronic device  120 . Test module  130  is electronically connected to electronic device  120  via cable  105 . For example, if electronic device  120  is a disc drive, cable  105  may be an IDE, ATA, SCSI, USB or other interface cable. In different embodiments, test module  130  may communicate with electronic device through other means, such as wireless communication. To test the functionality of electronic device  120 , test module  130  may instruct electronic device  120  to perform read and/or write operations. For example, test module  130  may instruct electronic device  120  to perform a random write operation. Test module  130  may repeat testing of electronic device  120  at a plurality of angular displacement increments as indicated by pointer  112  on protractor  114 . Test module  130  may repeat testing of electronic device  120  automatically or when instructed by a user. For example, a user may manually adjust the angular displacement of shaft  106   
     In other embodiments, test module  130  may not be required, e.g., the functionality of electronic device  120  may readily determinable without using test module  130 . For example, electronic device  120  may be able to perform self-diagnostics. As another example, a user may attempt to operate electronic device  120  to determine its functionality, e.g., if electronic device  120  is a cell phone, a user may attempt to make a phone call to determine if electronic device  120  is functional. Exemplary techniques for using torsion testing device  100  are described in further detail with respect to  FIG. 3 . 
       FIG. 2  is an illustration of torsion testing device  200  providing torsion testing of electronic device  220  according to defined angular displacements and/or defined torques. Torsion testing device  200  is similar to torsion testing device  100  of  FIG. 1  with the addition of measurement assembly  240 , which is mounted directly on base  202 . For example, measurement assembly  240  may be an add-on component for torsion testing device  100  to produce torsion testing device  200 . For purposes of brevity, portions of torsion testing device  200  that are the same or similar to torsion testing device  100  are not described in extensive detail. 
     Electronic device  220  is mounted to torsion testing device  200  with two clamps. The first clamp fixedly couples electronic device  220  to base  202 . The second clamp is connected to shaft  206  and rotatably couples the opposite end of electronic device  220  to base  202 . Shaft  206  is supported by rotary bearings to rotatably couple shaft  206  to base  202 . Lever  208  is also connected to shaft  206 . Lever  208  includes two screw holes through which screws  210  pass through. Screws  210  can be extended to press on base  202  and rotate lever  208  a fixed line defined by the rotary bearings that couple shaft  206  to base  202 . Screws  210  serve as actuators to forcibly move lever  208  to apply a torsion stress on electronic device  220 . 
     Pointer  212  is connected to shaft  206  and serves to indicate the angular position of shaft  206  relative to base  202  on protractor  214 . The relative change in the position of pointer  212  relative to protractor  214  from a neutral position serves as a measurement of the torsion stress on electronic device  220 . Using this measurement, electronic device  220  can be twisted to incrementally increase the torsion stress on electronic device  220 . The functionality of electronic device  220  may be tested at each increment. 
     Measurement assembly  240  is fixed to base  202  as part of torsion testing device  200 . For example, measurement assembly  240  may be secured to base  202  using screws, clamps or by other means. Measurement assembly  240  includes two measurement instruments useful in determining the stress and strain applied to electronic device  220  by torsion testing device  200 : linear displacement gauge  250  and load cell  241 . Measurement assembly  240  interacts with shaft  206  via level arm  248 , which is fixedly attached to shaft  206 . Level arm  248  is sufficiently stiff such that all motion of shaft  206  is transferred directly to level arm  248  and vice-versa. 
     Linear displacement gauge  250  measures the distance that level arm  248  moves, which allows a calculation of the strain of electronic device  220 . The angle of rotation of shaft  206 , a measurement of the torsion stress on electronic device  220  can be calculated using Equation 1: 
     
       
         
           
             
               
                 
                   
                     
                       tan 
                       
                         - 
                         1 
                       
                     
                     ⁡ 
                     
                       ( 
                       
                         
                           level_arm 
                           ⁢ 
                           _length 
                         
                         linear_displacement 
                       
                       ) 
                     
                   
                   = 
                   
                     angle_of 
                     ⁢ 
                     _rotation 
                   
                 
               
               
                 
                   ( 
                   
                     Equation 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     1 
                   
                   ) 
                 
               
             
           
         
       
     
     Linear displacement gauge  250  is perpendicular to level arm  248  when torsion testing device  200  holds electronic device  220  in a neutral (unstressed) position. This allows the change in angle of rotation of electronic device  220  to be calculated using an inverse tangent function as demonstrated by Equation 1. Linear displacement gage  250  may provide a much more accurate measurement of the stress on electronic device  220  than pointer  212  and protractor  214 . For example, if level arm  248  is 30 centimeters long, a change in measurement of 1 millimeter at linear displacement gauge  250  is equivalent to approximately 0.01 degrees of rotation of shaft  206 . This degree of precision is likely not possible with only pointer  212  and protractor  214 . 
     Measurement assembly  240  also includes screw  242 , which provides an alternative to screws  210  as a means for applying a torsion stress to shaft  206 . It should be noted that linear displacement gauge  250  may be used to measure the angle of rotation of shaft  206  caused by any of screws  210  or screw  242 . 
     Load cell  241  measures the force applied to bar  245  by screw  242 . Bar  245 , as part of measurement assembly  240 , is separate from level arm  248 , but directly transfers loads from screw  242  to level arm  248  at interface  246 . Bar  245  may be fixedly attached to bar  246  such that screw  242  may be extended or retracted to apply a torsion stress to electronic device  220  either clockwise or counterclockwise respectively. The force measured at load cell  241  may be converted to a torque applied on electronic device  200  according to Equation 2:
 
cos(angle_of_rotation)*load*load_radius=torque  (Equation 2)
 
     For angles of rotation near zero, Equation 2 can be approximated with Equation 3:
 
load*load_radius=torque  (Equation 3)
 
     Because of the mechanical advantage provided by lever arm  248 , relatively small loads applied by screw  242  can produce large torques on shaft  206 . For example, if the load radius is 40 centimeters, a load of 10 kilograms-force produces 3.93 Newton-meters of torque on electronic device  220 . This mechanical advantage allows load cell  241  to have a relatively small maximum force measurement capacity. 
     As shown in  FIG. 2 , torsion testing device  200  includes test module  230 , which is electronically connected to electronic device  220  via cable  205 . Test module  230  is operable to test the functionality of electronic device  220 . For example, if electronic device  220  is a disc drive, test module  230  may instruct electronic device  220  to perform read and/or write operations. As another example, if electronic device  220  is an electronic device capable of external communications, e.g., a PDA, test module  230  may simply request a response from electronic device  220  to test the functionality of electronic device  220 . Test module  230  may repeat testing of electronic device  220  at a plurality of angular displacement increments as indicated by pointer  212  on protractor  214  or by linear displacement gauge  250 . In other embodiments, test module  230  may repeat testing of electronic device  220  at a plurality of torque increments as indicated by load cell  241 . 
     In other embodiments, test module  230  may not be required, e.g., the functionality of electronic device  220  may readily determinable without using test module  230 . Exemplary techniques for using test device  200  are described in further detail with respect to  FIG. 4 . 
       FIG. 3  is a flowchart illustrating techniques for torsion testing an electronic device using incremental angular displacements. For clarity, the techniques shown in  FIG. 3  are described with respect to torsion testing device  100  of  FIG. 1 . 
     First, electronic device  120  is mounted in torsion testing device  100  ( 302 ). Mounting the disc drive in torsion testing device  100  requires securing clamps  103  and  104  and connecting cable  105 . 
     Next, test module  130  tests the functionality of electronic device  120 . For example, if electronic device  120  is a disc drive, test module  130  instructs the disc drive to perform a random write operation ( 304 ). The random write operation verifies the functionality of the disc drive in an unloaded state. After verifying that electronic device  120  is functional, a user adjusts the twist angle of the disc drive using one of screws  110  ( 306 ). For example, the user may increase the twist angle 0.5 degrees as indicated by pointer  112  on protractor  114 . After adjusting the twist angle, the user checks to see if electronic device  120  is functional ( 308 ). For example, test module  130  retests the functionality of electronic device  120 . For example, if electronic device  120  is a disc drive, test module  130  may again instruct the disc drive to perform a random write operation. 
     If electronic device  120  is not functional the testing of electronic device  120  stops. However, if electronic device  120  is still functional, the user again adjusts the twist angle ( 306 ). For example, the user may increase the twist angle another 0.5 degrees as indicated by pointer  112  on protractor  114 . After adjusting the twist angle for a second time, the user again checks the functionality of electronic device  120  ( 308 ). This process is repeated until electronic device  120  fails. In other embodiments, a user may stop testing after adjusting the twist angle according to a predetermined set of defined angular displacements. While testing of electronic device  120  is generally described as testing whether the drive is function or non-functional, qualitative testing may also be performed. As one example, if electronic device  120  is a disc drive, a bit-error rate test may be performed. 
       FIG. 4  is a flowchart illustrating techniques for torsion testing an electronic device using incremental torque adjustments. For clarity, the techniques shown in  FIG. 4  are described with respect to torsion testing device  200  of  FIG. 2 . 
     First, electronic device  220  is mounted in torsion testing device  200 . For the description of  FIG. 4 , electronic device  220  is described as disc drive ( 402 ). However, other electronic devices may also be tested in accordance with the techniques shown in  FIG. 4 . Mounting the disc drive in torsion testing device  200  requires securing two clamps and connecting cable  205 . 
     Next, test module  230  instructs the disc drive to perform a random write operation ( 404 ). The random write operation verifies the functionality of the disc drive in an unloaded state. After verifying that the disc drive is functional, a user adjusts the torque of the disc drive using screw  242  ( 406 ). For example, the user may increase the torque 1 Newton-meter as indicated by load cell  241 . After adjusting the torque, the user checks to see if the disc drive is functional ( 408 ). For example, test module  230  may again instruct the disc drive to perform a random write operation. 
     If the disc drive is not functional the testing of the disc drive stops. However, if the disc drive is still functional, again adjusts the torque ( 406 ). For example, the user may increase the torque another 1 Newton-meter as indicated by load cell  241 . After adjusting the torque for a second time, the user again checks the functionality of the disc drive ( 408 ). This process is repeated until the disc drive fails. In other embodiments, a user may stop testing after adjusting the torque according to a predetermined set of defined torques. While testing of the disc drive is generally described as testing whether the drive is function or non-functional, qualitative testing may also be performed. As one example, a bit-error rate test or other qualitative test may be performed. 
     Various embodiments of the invention have been described. For example, embodiments have been generally described with respect to torsion testing that requires manual user operation. However, embodiments of the invention also include automated torsion testing. These and other embodiments are within the scope of the following claims.