1. A data storage device comprising:
a head actuated over a disk;
a spindle motor configured to rotate the disk; and
control circuitry configured to:
sample a speed of the spindle motor at a sampling rate;
generate an error signal based on a difference between the sampled speed and a target speed;
generate a sliding mode control signal for controlling a speed of the spindle motor based on the error signal; and
when the error signal exceeds a threshold, increase the sampling rate.
2. The data storage device as recited in claim 1, wherein the control circuitry is further configured to:
sample the speed of the spindle motor based on a back electromotive force (BEMF) voltage generated by the spindle motor;
when the error signal is less than the threshold, sample the speed once per revolution of the disk; and
when the error signal exceeds the threshold, sample the speed at least twice per revolution of the disk.
3. The data storage device as recited in claim 2, wherein:
the BEMF voltage crosses a threshold at least twice per revolution of the disk; and
the control circuitry is further configured to sample the speed based on a duration between the BEMF voltage crossings.
4. The data storage device as recited in claim 1, wherein the disk comprises a plurality of servo sectors and the control circuitry is further configured to sample the speed of the spindle motor based on the servo sectors.
5. The data storage device as recited in claim 4, wherein the control circuitry is further configured to sample the speed based on a duration between the servo sectors.
6. A method of operating data storage device, the method comprising:
sampling a speed of a spindle motor at a sampling rate;
generating an error signal based on a difference between the sampled speed and a target speed;
generating a sliding mode control signal for controlling a speed of the spindle motor based on the error signal; and
when the error signal exceeds a threshold, increasing the sampling rate.
7. The method as recited in claim 6, further comprising:
sampling the speed of the spindle motor based on a BEMF voltage generated by the spindle motor;
when the error signal is less than the threshold, sampling the speed once per revolution of the disk; and
when the error signal exceeds the threshold, sampling the speed at least twice per revolution of the disk.
8. The method as recited in claim 7, wherein:
the BEMF voltage crosses a threshold at least twice per revolution of the disk; and
the method further comprises sampling the speed based on a duration between the BEMF voltage crossings.
9. The method as recited in claim 6, wherein the disk comprises a plurality of servo sectors and the method further comprises sampling the speed of the spindle motor based on the servo sectors.
10. The method as recited in claim 9, further comprising sampling the speed based on a duration between the servo sectors.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. An empty bag supplying apparatus in a continuous conveying type bag-filling packaging machine wherein said empty bag supplying apparatus receives empty bags that are positioned in a vertical attitude with mouths of said bags facing upward and transfers said bags to respective gripper pairs of said continuous conveying type bag-filling packaging machine, said gripper pairs being moved continuously at a constant speed and at a uniform spacing and gripping both side edges of said bags by means of gripping sections thereof and conveying said bags in a vertically suspended fashion; and wherein:
said empty bag supplying apparatus is comprised of:
downward-facing bag holding members which open and close at a specified timing so as to hold upper portions of said bags when closed,
a reciprocating movement mechanism which causes said bag holding members to perform a reciprocating motion along an arc-shaped path on a horizontal plane and which causes said bags held by said bag holding members to be set substantially parallel to a direction of movement of said gripper pairs at all times, and
a bag transfer region that is established at an intermediate point on said arc-shaped path, said arc-shaped path substantially overlapping a movement path of said gripping sections of said gripper pairs within said bag transfer region, and a speed of said reciprocating motion of said bag holding members in a direction of movement of said gripper pairs being set to be substantially equal to a moving speed of said gripper pairs at least within said bag transfer region.
2. The empty bag supplying apparatus in a continuous conveying type bag-filling packaging machine according to claim 1, wherein
a plurality of said bag holding members are provided on a common supporting member which performs a reciprocating motion along an arc-shaped path and which performs a translational motion during said reciprocating motion, and
said bag holding members are disposed along a direction of movement at equal spacing as said gripper pairs.
3. The empty bag supplying apparatus in a continuous conveying type bag-filling packaging machine according to claim 2, wherein a mechanism that causes said supporting member to perform said reciprocating motion comprises:
two pivot shafts disposed with a specified distance in between, and
respective swing shafts which are kept positioned at equal distances and in a same direction with respect to said respective pivot shafts, said swing shafts swinging about said respective pivot shafts as said pivot shafts are rotated; wherein
said supporting member performs said translational motion as a result of being connected to said swing shafts.
4. A product-filled bag extraction apparatus in a continuous conveying type bag-filling packaging machine wherein said product-filled bag extraction apparatus receives product-filled bags, upon which packaging treatment has been completed, from respective gripper pairs of said bag-filling packaging machine and then discharges said product-filled bags to an outside of an movement path of said gripper pairs, said gripper pairs being moved continuously at a constant speed and at a uniform spacing and gripping both side edges of said bags by means of gripping sections thereof and conveying said bags in a vertically suspended fashion; and wherein:
said product-filled bag extraction apparatus is comprised of:
downward-facing bag holding members which open and close at a specified timing so as to hold upper portions of said bags when closed,
a reciprocating movement mechanism which causes said bag holding members to perform a reciprocating motion along an arc-shaped path on a horizontal plane and which causes said bags held by said bag holding members to be set substantially parallel to a direction of movement of said gripper pairs at all times, and
a bag receiving region that is established at an intermediate point on said arc-shaped path, said arc-shaped path substantially overlapping a movement path of said gripping sections of said gripper pairs within said bag receiving region, and a speed of said reciprocating motion of said bag holding members in a direction of movement of said gripper pairs being set to be substantially equal to a moving speed of said gripper pairs at least within said bag receiving region.
5. The product-filled bag extraction apparatus in a continuous conveying type bag-filling packaging machine according to claim 4, wherein
a plurality of said bag holding members are provided on a common supporting member which performs a reciprocating motion along an arc-shaped path and which performs a translational motion during said reciprocating motion, and
said bag holding members are disposed along a direction of movement at equal spacing as said gripper pairs.
6. The product-filled bag extraction apparatus in a continuous conveying type bag-filling packaging machine according to claim 5, wherein a mechanism that causes said supporting member to perform said reciprocating motion comprises:
two pivot shafts disposed with a specified distance in between, and
respective swing shafts which are kept positioned at equal distances and in a same direction with respect to said respective pivot shafts, said swing shafts swinging about said respective pivot shafts as said pivot shafts are rotated; wherein
said supporting member performs said translational motion as a result of being connected to said swing shafts.