Patent Grant
6965188
This application claims benefit of Japanese Application NO. 2003-104486 filed in Japan on Apr. 8, 2003, the contents of which are incorporated by this reference.
1. Field of the Invention
The present invention relates to ultrasonic-actuator driving apparatuses and ultrasonic-actuator driving methods. More particularly, the present invention relates to an ultrasonic-actuator driving apparatus and an ultrasonic-actuator driving method in which applying frequency signals to an ultrasonic transducer in an ultrasonic actuator friction-drives a driven body that is in contact with the ultrasonic transducer.
2. Description of the Related Art
Ultrasonic motors (also referred to as ultrasonic actuators) have drawn attention in recent years as new motors which can be used in place of electromagnetic motors. The ultrasonic actuators have the following advantages, compared with known electromagnetic motors.
A driving apparatus ordinarily drives each of the ultrasonic actuators having the above advantages.
Known arts involving such a driving apparatus for an ultrasonic actuator include a controlling apparatus for a vibration actuator disclosed in U.S. Pat. No. 6,031,316.
The controlling apparatus for a vibration actuator (also referred to as an ultrasonic actuator) disclosed in the above publication evaluates a real moving state of a driven body (moving body) for driving the ultrasonic actuator in order to overcome the problem in that the position control of the ultrasonic actuator is unstable.
In other words, the controlling apparatus for an ultrasonic actuator has a moving-state detecting unit for outputting signals corresponding to the absolute motion of the driven body with respect to the ultrasonic actuator. The signals output from the moving-state detecting unit are sampled at a timing being synchronized with a multiple-fold frequency of the vibration frequency of the ultrasonic actuator to evaluate the moving state based on a value in accordance with the average value of the sampled signals.
Specifically, as shown in
An ultrasonic-actuator driving apparatus of the present invention includes an ultrasonic actuator having a transducer and a driven body that is in contact with the transducer, the transducer to which a frequency signal is applied friction-driving the driven body; an original-signal outputting unit for outputting an original signal on which the frequency of the frequency signal depends; a waveform averaging unit for averaging the original signals during a predetermined period to calculate average-waveform data; a position detecting unit for detecting an absolute position of the driven body with respect to the transducer; a position averaging unit for averaging the absolute positions during a predetermined period to calculate average-position data; a control-signal calculating unit that generates a control signal for controlling the frequency of the original signal based on the average-waveform data and the average-position data and supplies the generated control signal to the original-signal outputting unit; and a driving unit for generating the frequency signal based on the original signal and applying the generated frequency signal to the transducer.
These objects and advantages of the present invention will become further apparent from the following detailed explanation.
Embodiments of the present invention will be described below with reference to the drawings.
First Embodiment
(Structure)
Referring to
Specifically, the ultrasonic actuator in which the driven body 2, which is in contact with the transducer 1, is friction-driven is provided in the ultrasonic-actuator driving apparatus. The transducer 1 in the ultrasonic actuator is electrically connected to the driving unit 3, which applies frequency voltage to the transducer 1.
The driving unit 3 is electrically connected to the original-signal outputting unit 4, which supplies pulse signals, on which the frequency voltage depends, to the driving unit 3.
The original-signal outputting unit 4 is electrically connected to the waveform averaging unit 5 and the control-signal calculating unit 8. The driven body 2 is electrically connected to the position detecting unit 6 for detecting positions.
The position detecting unit 6 is electrically connected to the position averaging unit 7. The control-signal calculating unit 8 is electrically connected to the waveform averaging unit 5, the position averaging unit 7, and the original-signal outputting unit 4.
(Operation)
In the ultrasonic-actuator driving apparatus having the structure described above, the driving unit 3 receives an original signal from the original-signal outputting unit 4 to generate a rectangular-wave signal having a frequency of 50 KHz to 400 KHz, which is a resonant frequency of the transducer 1 in the ultrasonic-actuator, and a voltage of 4 V to 30 V, and supplies the generated rectangular-wave signal to the transducer 1.
According to the first embodiment, the rectangular-wave signal generated in the driving unit 3 optimally had, for example, a resonant frequency of 83 KHz and a driving voltage of 4.4 V. The application of such a rectangular-wave signal to the transducer 1 by the driving unit 3 friction-drives the driven body 2, which is in contact with the transducer 1.
In this case, the waveform averaging unit 5 averages the outputs from the original-signal outputting unit 4, and supplies the averaged result to the control-signal calculating unit 8. The position averaging unit 7 averages signals detected in the position detecting unit 6 for detecting the absolute position of the driven body 2, and supplies the averaged result to the control-signal calculating unit 8.
Thereafter, the control-signal calculating unit 8 determines the current state based on the averaged results supplied from the waveform averaging unit 5 and the position averaging unit 7 to generate a correction signal for stable positioning and driving, and sequentially feeds back the generated correction signal to the original-signal outputting unit 4.
Although the rectangular-wave signal is applied to the transducer 1 in the first embodiment, the signal applied to the transducer 1 is not limited to the rectangular-wave signal and may be a sinusoidal signal or a sawtooth signal.
(Advantages)
As described above, according to the first embodiment, the ultrasonic-actuator driving apparatus is structured such that the control-signal calculating unit 8 determines the current state based on the averaged results supplied from the waveform averaging unit 5 and the position averaging unit 7 to generate the correction signal for stable positioning and driving and sequentially feeds back the generated correction signal to the original-signal outputting unit 4. Hence, even when a movement state or a velocity is varied, that is, even when the movement state is varied because of the variation in temperature, humidity, and/or load or a resonant frequency is accidentally varied, it is possible to achieve high-precision and stable positioning.
In addition, a sharp change in response characteristics relating to waveform data, which possibly occurs when the movement state or the resonant frequency is varied, or relating to position data can advantageously be moderated.
Furthermore, it is possible to control a starting position of deceleration of the driven body 2 in accordance with a sharp change in response characteristics, which possibly occurs when the movement state is varied because of the variation in temperature, humidity, and/or load or the resonant frequency is varied, and to control the frequency of the original signal in accordance with the controlled starting position of deceleration.
Second Embodiment
(Structure)
The ultrasonic-actuator driving apparatus of the second embodiment differs from the ultrasonic-actuator driving apparatus of the first embodiment in that the waveform averaging unit 5, the position averaging unit 7, and the control-signal calculating unit 8 are each divided into units and that the ultrasonic-actuator driving apparatus further includes a stopping-range setting unit 9, in order to achieve drive control for higher-precision and stable positioning.
Referring to
The position averaging unit 7 includes an average-position-data calculator 7a and a position-data storage 7b.
The control-signal calculating unit 8 includes a deceleration-starting-position calculator 8a and a control-signal generator 8b.
Specifically, in the waveform averaging unit 5, the waveform-information detector 5a is electrically connected to the original-signal outputting unit 4 and the waveform-data storage 5b. The average-waveform-data calculator 5c is electrically connected to the waveform-data storage 5b and the deceleration-starting-position calculator 8a.
The waveform-information detector 5a samples original rectangular-wave signals supplied from the original-signal outputting unit 4 during a predetermined sampling period to acquire waveform information output during the sampling period, and supplies the waveform information to the waveform-data storage 5b.
The waveform-data storage 5b stores pieces of the waveform information acquired in the sampling by the waveform-information detector 5a one by one.
The average-waveform-data calculator 5c averages the waveform data stored in the waveform-data storage 5b, and supplies the averaged result to the deceleration-starting-position calculator 8a in the control-signal calculating unit 8.
Meanwhile, in the position averaging unit 7, the position-data storage 7b is electrically connected to the position detecting unit 6 and the average-position-data calculator 7a.
The position-data storage 7b receives moving distance sampled during a predetermined sampling period in the position detecting unit 6, and stores the moving distance, in the same way as in the waveform-data storage 5b.
The average-position-data calculator 7a averages the position data stored in the position-data storage 7b, and supplies the averaged result to the deceleration-starting-position calculator 8a in the control-signal calculating unit 8.
In the control-signal calculating unit 8, the deceleration-starting-position calculator 8a is electrically connected to the average-waveform-data calculator 5c, the average-position-data calculator 7a, and the control-signal generator 8b.
The deceleration-starting-position calculator 8a calculates a starting position of deceleration of the driven body 2 by using the averaged results, that is, average-position data and average-waveform data, and supplies the calculated position to the control-signal generator 8b.
The control-signal generator 8b controls the frequency of the original signal output from the original-signal outputting unit 4, based on the result calculated by the deceleration-starting-position calculator 8a.
The stopping-range setting unit 9 is electrically connected to the original-signal outputting unit 4. The stopping-range setting unit 9 sets a stopping range of the driven body 2, and supplies a stop signal to the original-signal outputting unit 4, when the absolute position of the driven body 2 is within the stopping range, to cause the original-signal outputting unit 4 to stop outputting the original signal.
Other structures are the same as in the first embodiment.
(Operation)
When the ultrasonic-actuator driving apparatus in
The waveform-data storage 5b stores pieces of the waveform information acquired during a sampling period of 30 milliseconds by the waveform-information detector 5a one by one. The number of pieces of the stored waveform information is 2 to 100. Thirty pieces of the waveform information was stored in the second embodiment.
Thereafter, the average-waveform-data calculator 5c averages the waveform data stored in the waveform-data storage 5b, and supplies the averaged result to the deceleration-starting-position calculator 8a.
The position detecting unit 6 supplies a moving distance sampled during a sampling period of, for example, 30 milliseconds to the position-data storage 7b.
And then, the position-data storage 7b stores 2 to 100 pieces of the position information, in the same way as in the waveform-data storage 5b. Thirty pieces of the position data sampled in the position detecting unit 6 was stored in the second embodiment.
After that, the average-position-data calculator 7a averages the position data stored in the position-data storage 7b, and supplies the averaged result to the deceleration-starting-position calculator 8a.
Thereafter, in the control-signal calculating unit 8, the deceleration-starting-position calculator 8a calculates a starting position of deceleration of the driven body 2 by using the average-position data and the average-waveform data based on the amount of movement per one pulse during the sampling or the like, and supplies the calculated position to the control-signal generator 8b.
And then, the control-signal generator 8b controls the frequency of the original signal output from the original-signal outputting unit 4, based on the result calculated by the deceleration-starting-position calculator 8a. The stopping-range setting unit 9 sets a stopping range of the driven body 2, and supplies a stop signal to the original-signal outputting unit 4, when the absolute position of the driven body 2 is within the stopping range, to cause the original-signal outputting unit 4 to stop outputting the original signal.
Other operations are the same as in the first embodiment.
Although the number of pieces of the waveform data and position data stored in the waveform-data storage 5b and the position-data storage 7b, respectively, was set to 30 in the second embodiment, it is not limited to this figure and may be varied in accordance with the ultrasonic-actuator. Also, although the sampling period was set to 30 milliseconds in the second embodiment, it is not limited to this figure and may be varied in accordance with the ultrasonic actuator.
(Advantages)
Accordingly, the ultrasonic-actuator driving apparatus of the second embodiment has the advantage of being capable of performing high-precision positioning with respect to a target stopping position by setting the range of the target stopping position to an integral multiple of resolution in the position detecting unit 6 in the positive and negative directions, in addition to the same advantages as in the first embodiment. It is further possible to stably drive the ultrasonic actuator.
Third Embodiment
(Structure)
The ultrasonic-actuator driving apparatus of the third embodiment is characterized in that the driving unit 3 is divided into a frequency-divider 3a, a phase-pulse generator 3b, and an amplifier 3c, and is characterized by including a stopping-position determining unit 10, a stopping unit 11, a driving-direction setting unit 12, and a position instructing unit 13, in addition to the components in the second embodiment, in order to achieve drive control for further higher-precision and stable positioning.
Referring to
The frequency-divider 3a is electrically connected to the phase-pulse generator 3b and the original-signal outputting unit 4. The amplifier 3c is electrically connected to the phase-pulse generator 3b and the transducer 1.
The frequency-divider 3a divides the frequency of an original signal supplied from the original-signal outputting unit 4, and supplies the frequency-divided signal to the phase-pulse generator 3b. The phase-pulse generator 3b generates a phase-pulse signal from the supplied frequency-divided signal, and supplies the generated phase-pulse signal to the amplifier 3c. The amplifier 3c amplifies the supplied phase-pulse signal at a predetermined amplification factor, and supplies the amplified signal to the transducer 1 as a driving signal.
Meanwhile, the position detecting unit 6, which is, for example, a linear scale, is electrically connected to the driven body 2, the position-data storage 7b, the stopping-position determining unit 10, and the driving-direction setting unit 12.
The position instructing unit 13 is electrically connected to the stopping-range setting unit 9 and the driving-direction setting unit 12. The stopping-position determining unit 10 is electrically connected to the position detecting unit 6, the stopping-range setting unit 9, and the stopping unit 11.
The original-signal outputting unit 4 is electrically connected to the stopping unit 11, the driving-direction setting unit 12, the waveform-information detector 5a, the control-signal generator 8b, and the frequency-divider 3a.
The position instructing unit 13, for example, a keyboard, which is an externally-attached input device of a computer, is a unit for inputting instruction information for instructing a target position (referred to as target-position data), and supplies the target-position data to the stopping-range setting unit 9 and the driving-direction setting unit 12.
The stopping-range setting unit 9 sets a predetermined range for the supplied target-position data as a target stopping-position range, and supplies the set stopping-position range data to the stopping-position determining unit 10.
The stopping-position determining unit 10 determines a stopping position based on the position data supplied from the position detecting unit 6 and the stopping-position range data supplied from the stopping-range setting unit 9, and supplies the determined result, that is, a stop determination signal, to the stopping unit 11.
The stopping unit 11 limits the output from the original-signal outputting unit 4 based on the supplied stop determination signal.
The driving-direction setting unit 12 decides a driving direction based on the position data supplied from the position detecting unit 6 and the target-position data supplied from the position instructing unit 13, and supplies a driving-direction signal indicating the driving direction to the original-signal outputting unit 4.
Other structures are the same as in the first and second embodiments.
(Operation)
Next, an ultrasonic-actuator driving method, according to the third embodiment of the present invention, using the ultrasonic-actuator driving apparatus will now be described in detail with reference to
The ultrasonic-actuator driving apparatus shown in
A controlling unit (not shown) for performing various controls of the overall ultrasonic-actuator driving apparatus in
And then, the controlling unit sets a dead band within a range of ±0.1 μm for the read target position to set a target stopping-position range, and proceeds to Step S31.
In Step S31, the controlling unit causes the stopping-range setting unit 9 to acquire the current position of the ultrasonic actuator from a signal detected by the position detecting unit 6 (linear scale).
After the current position is acquired, in Step S32, the controlling unit causes the driving-direction setting unit 12 to set a driving direction based on the deviation of the current position from the target position.
After the driving direction is decided, in Step S33, the controlling unit causes the original-signal outputting unit 4 and the driving unit 3 to perform acceleration drive at a predetermined acceleration constant based on the decided driving direction. In this case, when the acceleration drive reaches a maximum speed that can be arbitrarily set in a range from 1,000 pps (pulse per second) to 15,000 pps, the controlling unit causes the original-signal outputting unit 4 and the driving unit 3 to perform constant-speed drive at the maximum speed. According to the third embodiment, the maximum speed was set to 3,000 pps.
After the acceleration drive is performed in Step S33, the controlling unit proceeds to Step S34 shown in
In this case, the sampling period was set to 30 milliseconds here in the third embodiment. In the step of storing the position data in Step S35, since there is no previous sampled value for the first stored position data, the deviation of the first stored position data from zero is determined for storage.
And then, in Step S36, the controlling unit causes the average-position-data calculator 7a to average the stored position data based on the number of pieces of the position data. In Step S35 in the third embodiment, the position data is stored in 30 arrays. In other words, since one piece of the position data exists in the first averaging operation, the averaging cannot be performed, thus supplying the position data without being averaged to the deceleration-starting-position calculator 8a in the control-signal calculating unit 8. In the subsequent sampling, as described above, the controlling unit determines the deviation of the new position data sampled in Step S34 from the position data stored in the position-data storage 7b in Step S35, and stores the position data to the position-data storage 7b in Step S35.
Hence, in Step S35, new data takes priority over old data and two pieces of the position data are stored in the position-data storage 7b.
In Step S36, the controlling unit causes the average-position-data calculator 7a to average the two pieces of the position data and to supply the averaged result to the deceleration-starting-position calculator 8a. As described above, the controlling unit repeats the above steps to determine average-position data.
Further, if the number of pieces of the position data is larger than or equal to 30, the controlling unit discards the position data that has been first stored in the position-data storage 7b in Step S35 from the 30 arrays, and stores the latest position data in the position-data storage 7b. In this state, the average-position-data calculator 7a averages the 30 pieces of the position data based on the number of pieces of the position data in Step S36.
Similarly to the case of the position data, after the acceleration drive is performed in Step S33, the controlling unit calculates average-waveform data of the original signal in Steps S37 to S39, concurrently with the Steps S34 to S36. Namely, the controlling unit causes the waveform-information detector 5a to acquire waveform information of the original signal in Step S37.
In Step S38, the controlling unit stores the acquired waveform data in the waveform-data storage 5b.
In Step S39, the controlling unit causes the average-waveform-data calculator 5c to average the waveform data based on the number of pieces of the waveform data stored in the waveform-data storage 5b in Step S38, and supplies the averaged result (the average number of pulses) to the deceleration-starting-position calculator 8a.
In Step S38 in the third embodiment, 30 arrays in which the waveform data is stored are provided, as in the step of storing the position data (Step S35). The process performed when 30 or more pieces of the waveform data have been supplied is the same as in the Step S35.
Specifically, the average-position data P averaged in Step S36 and the average-waveform data W averaged in Step S39 are supplied to the deceleration-starting-position calculator 8a at intervals of 30 milliseconds.
And then, in Step S40, the controlling unit causes the deceleration-starting-position calculator 8a to calculate a starting position of deceleration based on the following equation (Formula 1), where P denotes the average-position data, W denotes the average-waveform data, Sa denotes a sampling rate, Ve denotes a speed set as a reference speed, and d denotes a division ratio of the frequency-divider 3a.
Deceleration starting position=(1/Ve)×Sa×d×P×(W/P) [Formula 1]
Thereafter, in Step S41, the controlling unit compares the starting position of deceleration SP calculated in Step S40 with the current position RP1 acquired in Step S34 to determine whether a relationship of SP≦RP1 is established.
In this case, if the controlling unit determines that the relationship is not established, the process returns back to Step S34 and Step S37. In the meantime, if the controlling unit determines that the relationship is established, in Step S42, the controlling unit causes the original-signal outputting unit 4 and the driving unit 3 to perform deceleration drive at a predetermined deceleration constant. In this case, when the deceleration drive reaches a minimum speed that can be arbitrarily set in a range from 10 pps to 1,000 pps, the controlling unit causes the original-signal outputting unit 4 and the driving unit 3 to perform constant-speed drive at the minimum speed. According to the third embodiment, the minimum speed was set to 20 pps.
After the deceleration drive is performed, in Step S43, the controlling unit acquires the current position RP2. In the determination step in Step S44, the controlling unit causes the stopping-position determining unit 10 to determine whether the current position RP2 is within the target stopping-position range set in Step S30. If the controlling unit determines that the current position RP2 is within the target stopping-position range, in Step S45, the controlling unit causes the stopping unit 11 to stop outputting the original signal from the original-signal outputting unit 4. If the controlling unit determines that the current position RP2 is not within the target stopping-position range, the process returns back to Step S43 and repeats the process until the current position RP2 enters the target stopping-position range in Step S44.
Although the dead band is set within a range of ±0.1 μm from the target position in the third embodiment, the dead band is not limited to this figure. The dead band may be within a range from 0.1 μm to 10 μm in accordance with the ultrasonic actuator.
(Advantages)
Accordingly, the ultrasonic-actuator driving apparatus of the third embodiment has the advantages of being capable of stopping the ultrasonic actuator within the target stopping-position range with a high degree of precision, in addition to the advantages as in the first and second embodiments.
Fourth Embodiment
(Structure)
The ultrasonic-actuator driving apparatus of the fourth embodiment is characterized by including an interrupting unit 14, which is electrically connected between the deceleration-starting-position calculator 8a and the stopping unit 11, in addition to the components in the third embodiment, as shown in
Other structures are approximately the same as in the third embodiment.
In the ultrasonic-actuator driving method of the fourth embodiment, the control processing routine in the third embodiment (refer to
(Operation)
The ultrasonic-actuator driving method of the fourth embodiment will now be described in detail with reference to
Although the ultrasonic-actuator driving method of the fourth embodiment is approximately the same as in the control processing routine in
Specifically, in Step S50, after the step of calculating the starting position of deceleration in Step S40, the controlling unit counts the number of times of calculating the starting position of deceleration with a counter (not shown) in the controlling unit. In Step S51, the controlling unit determines whether the value counted in Step S50 is larger than or equal to any value from 20 to 70. If the controlling unit determines that the counted value is larger than or equal to, for example, 50, which were set in the fourth embodiment, the controlling unit forcedly exits the positioning control routine and outputs an interruption control signal to the interrupting unit 14. Then, the controlling unit causes the interrupting unit 14 to supply an interrupting signal to the stopping unit 11 for performing the stopping step in Step S45 shown in
Other operations are the same as in the third embodiment.
(Advantages)
Accordingly, the ultrasonic-actuator driving apparatus of the fourth embodiment has, in addition to the advantages as in the third embodiment, the advantage of preventing thermal destruction or thermal damage of the ultrasonic actuator caused by malfunction of the ultrasonic actuator itself, which possibly occurs when the movement state is varied because of the variation in temperature, humidity, and/or load or the resonant frequency is varied. It is also possible to save electric power.
Fifth Embodiment
(Structure)
The ultrasonic-actuator driving apparatus of the fifth embodiment is characterized by including a stopping-interrupting unit 15, which is electrically connected between the stopping-position determining unit 10 and the stopping unit 11, in addition to the components in the third embodiment, as shown in
Other structures are approximately the same as in the third embodiment.
In the ultrasonic-actuator driving method of the fifth embodiment, the stop processing routine in the third embodiment (refer to
(Operation)
The ultrasonic-actuator driving method of the fifth embodiment will now be described in detail with reference to
Although the ultrasonic-actuator driving method of the fifth embodiment is approximately the same as in the stop processing routine in
Specifically, in Step S60, after the step of acquiring the current position in Step S43, the controlling unit counts the number of times of acquiring the current position with a counter (not shown) in the controlling unit. In Step S61, the controlling unit determines whether the value counted in Step S60 is larger than or equal to any value from 20 to 50. If the controlling unit determines that the counted value is larger than or equal to, for example, 30, which were set in the fifth embodiment, the controlling unit forcedly exits the positioning control routine and causes the stopping-interrupting unit 15 to supply a stopping-interrupting signal to the stopping unit 11 for performing the stopping step in Step S45 shown in
Other operations are the same as in the third embodiment.
(Advantages)
Accordingly, the ultrasonic-actuator driving apparatus of the fifth embodiment reliably achieves the same advantages as in the fourth embodiment.
Sixth Embodiment
(Structure)
The ultrasonic-actuator driving apparatus of the sixth embodiment is characterized by combining the fourth embodiment with the fifth embodiment. Referring to
An ultrasonic-actuator driving method of the sixth embodiment includes the control processing routine of the fourth embodiment (refer to
(Operation)
The ultrasonic-actuator driving method of the sixth embodiment will now be described in detail with reference to
Referring to
Referring to
According to the sixth embodiment, if the controlling unit determines in Step S51 and/or S61 that the value counted in Step S50 and/or S60 is larger than or equal to the set value, the controlling unit forcedly exits the positioning control routine, and performs the stopping step in Step S45 in
Other operations are the same as in the third embodiment.
(Advantages)
Accordingly, the ultrasonic-actuator driving apparatus of the sixth embodiment further reliably achieves the same advantages as in the fourth embodiment.
The present invention is not limited to the first to sixth embodiments. Combination or applications of the first to sixth embodiments can also be applied to the present invention within the scope of the present invention.
The present invention may be applied to an executive program for causing a computer to execute the ultrasonic-actuator driving method of the present invention. In addition, storing the executive program in a storage medium and reading out the executive program from the storage medium to execute the executive program by a computer that controls the ultrasonic-actuator driving apparatus may execute the ultrasonic-actuator driving method of the present invention.
In this invention, it is apparent that various modifications different in a wide range can be made on this basis of this invention without departing from the sprit and scope of the invention. This invention is not restricted by any specific embodiment except being limited by the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2003-104486 | Apr 2003 | JP | national |
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| Number | Date | Country | |
|---|---|---|---|
| 20040201308 A1 | Oct 2004 | US |
