1. An apparatus for controlling a power converter in which an output voltage is controlled by pulse-width-modulation control, the apparatus comprising:
a voltage-vector control unit that determines, based on a voltage instruction value for the power converter, voltage vectors, including zero-voltage vectors, output from the power converter in a control cycle of the pulse-width-modulation control and durations of outputting of the voltage vectors;
a voltage-vector adjusting unit that adjusts the durations of outputting of the voltage vectors so that,
if total of the durations of outputting of the zero-voltage vectors in the control cycle is longer than a predetermined time that is longer than zero, the voltage-vector adjusting unit adjusts durations of outputting of the zero voltage vectors to a fixed time or longer, and,
if the total is shorter than the predetermined time, the voltage vector adjusting unit adjusts the durations of outputting of the zero voltage vectors to zero; and
a firing-pulse generating unit that generates a signal for turning on and off semiconductor switching elements included in the power converter, based on the durations of outputting of the voltage vectors, as adjusted by the voltage-vector adjusting unit.
2. The apparatus according to claim 1, wherein the voltage-vector adjusting unit adjusts the durations of outputting of the zero voltage vectors to the fixed time or longer without changing relative ratio between durations of outputting of non-zero voltage vectors, excluding the zero-voltage vectors.
3. The apparatus according to claim 1, wherein, the voltage-vector adjusting unit adjusts durations of outputting of non-zero voltage vectors, excluding the zero-voltage vectors, to another fixed time or longer, or to zero, if the voltage-vector adjusting unit adjusts the durations of outputting of the zero voltage vectors to zero.
4. An apparatus for controlling a power converter in which an output voltage is controlled by pulse-width-modulation control, the apparatus comprising:
a voltage-vector control unit that determines, based on a voltage instruction value for the power converter, voltage vectors, including zero-voltage vectors, output from the power converter in a plurality of control cycles of the pulse-width-modulation control and durations of outputting of the voltage vectors;
a voltage-vector adjusting unit that adjusts the durations of outputting of the voltage vectors so that, if total of the durations of outputting of the zero-voltage vectors in the control cycles is shorter than a predetermined time, the voltage-vector adjusting unit adjusts durations of outputting of middle zero voltage vectors, between two adjacent control cycles, to zero, and distributes the durations of outputting of the middle zero-voltage vectors to duration of outputting of end zero-voltage vectors at ends of the two adjacent control cycles; and
a firing-pulse generating unit that generates a signal for turning on and off semiconductor switching elements included in the power converter, based on the durations of outputting of the voltage vectors, as adjusted by the voltage-vector adjusting unit.
5. An apparatus for controlling a power converter in which an output voltage is controlled by pulse-width-modulation control, the apparatus comprising:
a voltage-vector control unit that determines, based on a voltage instruction value for the power converter, voltage vectors, including zero-voltage vectors, output from the power converter in a plurality of control cycles of the pulse-width-modulation control and durations of outputting of the voltage vectors;
a voltage-vector adjusting unit that adjusts the durations of outputting of the voltage vectors so that, if total of the durations of outputting of the zero-voltage vectors in the control cycles is shorter than a predetermined time, the voltage-vector adjusting unit groups durations of outputting identical voltage vectors in the control cycles into one; and
a firing-pulse generating unit that generates a signal for turning on and off semiconductor switching elements included in the power converter, based on the durations of outputting of the voltage vectors, as adjusted by the voltage-vector adjusting unit.
6. An apparatus for controlling a power converter in which an output voltage is controlled by pulse-width-modulation control, the apparatus comprising:
a voltage-vector control unit that determines, based on a voltage instruction value for the power converter, voltage vectors, including zero-voltage vectors, output from the power converter in a control cycle of the pulse-width-modulation control and durations of outputting of the voltage vectors;
a voltage-vector adjusting unit that adjusts the durations of outputting of the voltage vectors so that, if total of durations of outputting the zero-voltage vectors is shorter than a predetermined value, upon receiving voltage vectors used for an adjustment in a previous control cycle, the voltage-vector adjusting unit, based on whether a voltage vector lastly output in the previous control cycle is a zero-voltage vector, adjusts a first duration of outpuffing one of the zero-voltage vectors in a current control cycle to zero and distributes an amount of the first duration to a second duration of outputting another of the zero-voltage vectors; and
a firing-pulse generating unit that generates a signal for turning on and off semiconductor switching elements included in the power converter, based on the durations of outputting of the voltage vectors, as adjusted by the voltage-vector adjusting unit.
7. An apparatus for controlling a power converter in which an output voltage is controlled by pulse-width-modulation control, the apparatus comprising:
a voltage-vector control unit that determines, based on a voltage instruction value for the power converter, voltage vectors, including zero-voltage vectors, output from the power converter in a control cycle of the pulse-width-modulation control and durations of outputting of the voltage vectors;
a voltage-vector adjusting unit that adjusts the durations of outputting of the voltage vectors so that, upon receiving voltage vectors used for an adjustment in a previous control cycle, if a total of a third duration of outpuffing of a zero-voltage vector lastly adjusted in the previous control cycle and a fourth duration of outputting of a zero-voltage vector firstly received from the voltage-vector control unit in a current control cycle is shorter than a predetermined time, the voltage vector adjusting unit adjusts the fourth duration to a fifth duration which is obtained by subtracting the fourth duration from the predetermined time;
a delay unit that delays the voltage vectors output from the voltage-vector adjusting unit by one control cycle, and outputs the voltage vectors to the voltage-vector adjusting unit; and
a firing-pulse generating unit that generate a signal for turning on and off semiconductor switching elements included in the power converter, based on the durations of outputting of the voltage vectors, as adjusted by the voltage-vector adjusting unit.
8. An apparatus for controlling a power converter in which an output voltage is controlled by pulse-width-modulation control, the apparatus comprising:
a voltage-vector control unit that determines, based on a voltage instruction value for the power converter, voltage vectors, including zero-voltage vectors, output from the power converter in a control cycle of the pulse-width-modulation control and durations of outputting of the voltage vectors;
a voltage-vector adjusting unit that
adjusts the durations of outputting of the voltage vectors by calculating an error generated by an adjustment of the durations of outputting of the voltage vectors and by correcting the durations of outputting of the voltage vectors in a current control cycle with the error calculated in a previous control cycle, and
adjusts total of durations of the zero-voltage vectors to a fixed time or longer, if the total is longer than a predetermined time, and adjusts the total to zero, if the total is shorter than the predetermined time;
a delay unit that delays the voltage vectors output from the voltage-vector adjusting unit by one control cycle, and outputs the voltage vectors to the voltage-vector adjusting unit; and
a firing-pulse generating unit that generates a signal for turning on and off semiconductor switching elements included in the power converter, based on the durations of outputting of the voltage vectors, as adjusted by the voltage-vector adjusting unit.
9. An apparatus for controlling a power converter in which an output voltage is controlled by pulse-width-modulation control, the apparatus comprising:
a voltage-vector control unit that determines, based on a voltage instruction value for the power converter, voltage vectors, including zero-voltage vectors, output from the power converter in a control cycle of the pulse-width-modulation control and durations of outputting of the voltage vectors;
a voltage-vector adjusting unit that adjusts the durations of outputting of the voltage vectors by changing durations of outpuffing of the zero-voltage vectors to zero and replacing a first voltage vector firstly output in a current cycle with a last voltage vector lastly output in a previous control cycle, if the last voltage vector is different from the first voltage vector; and
a firing-pulse generating unit that generates a signal for turning on and off semiconductor switching elements included in the power converter, based on the durations of outputting of the voltage vectors, as adjusted by the voltage-vector adjusting unit.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
What is claimed is:
1. Apparatus for sweeping and collecting ball-like objects on a substantially horizontal surface, comprising, in combination:
frame means substantially perpendicular to said surface and having a generally concave shape for sweeping and collecting said objects, and
flexible means partially enclosing said concave shape for allowing entry and impeding exit of said objects.
2. The apparatus according to claim 1, where said flexible means comprises a strap connected with said frame means and disposed at an acute angle with respect to said surface.
3. The apparatus according to claim 1, where said ball-like objects have a substantially uniform nominal diameter and said frame means is spaced from said substantially horizontal surface by an amount greater than zero and less than one-half said nominal diameter.
4. The apparatus according to claim 1, where said frame means contacts said rolling objects at a height above said substantially horizontal surface less than one-half said nominal diameter.
5. The apparatus according to claim 3, where said flexible means comprises a strap connected with said frame means.
6. The apparatus according to claim 5, where said strap has a width substantially equal to said nominal diameter.
7. The apparatus according to claim 2, where said acute angle is between about 25 degrees and about 65 degrees.
8. The apparatus according to claim 3, further including roller means attached to said frame means for spacing said frame means from said horizontal surface.
9. The apparatus according to claim 8, further including handle means detachably connected with said frame means for propelling said apparatus.
10. The apparatus according to claim 1, where said flexible means is held in tension by said frame means.