JP3216840B2 - Ultrasonic motor control method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of applying a frequency voltage to a piezoelectric body to vibrate the piezoelectric body, generating a progressive vibration wave in an elastic body disposed on the piezoelectric body, and contacting the elastic body. The present invention relates to a so-called ultrasonic motor that drives a moving body provided by the traveling vibration wave, and particularly to a control method thereof.

[0002]

2. Description of the Related Art Conventionally, as a speed control method of an ultrasonic motor, a method of changing a frequency of a frequency voltage is known. On the other hand, the rotational speed and frequency of the ultrasonic motor fluctuate without being uniquely determined due to the characteristic difference of the motor itself to be controlled or the characteristic change due to the magnitude of the load as shown in FIG. For this reason, a target rotation speed cannot be stably obtained, and there is a disadvantage that stable slow start control and slow stop control cannot be performed.

[0003]

As such a solution, there is known a method of learning each time the characteristic of the motor is controlled and reflecting the result in the next control. If the load is significantly different, the target speed cannot be obtained. It is also known to feed back speed information at the time of control and adjust the frequency based on the information.However, in this method, the control result can be understood only by giving a frequency, so that a smooth slow start control or a slow stop control can be performed. Can not do. Accordingly, an object of the present invention is to enable smooth slow start control and slow stop control to be stably executed.

[0004]

According to a first aspect of the present invention, a frequency voltage is applied to a piezoelectric body to vibrate the piezoelectric body, and a progressive vibration is applied to an elastic body disposed on the piezoelectric body. A speed detecting means for generating information about a rotation speed of an ultrasonic motor for driving a moving body provided in contact with the elastic body by the traveling vibration wave, and changing a frequency of the frequency voltage. A frequency adjusting means for causing the motor to operate by changing the frequency by the frequency adjusting means, and detecting the rotation speed information and frequency information from the start to the specified number of rotations and detecting the information. The learning stored in the memory is executed in advance,
Thereafter, the motor is started by giving a frequency stored in the memory indicating a sufficiently lower speed than the target rotation speed in actual operation, and thereafter, the rotation speed information and the frequency information when the motor actually starts operating are provided. , A second step of obtaining the frequency change rate corresponding to the rotational speed information obtained in the first step by referring to the previously stored information, and a second step of obtaining the frequency change rate corresponding to the rotational speed information obtained in the first step. The third step of updating the drive frequency of the motor from the frequency change rate and a difference obtained by subtracting the current rotation speed from the target rotation speed is repeatedly executed.

In the second invention, a frequency voltage is applied to the piezoelectric body to vibrate the piezoelectric body, and a traveling vibration wave is generated in the elastic body disposed on the piezoelectric body, and the piezoelectric body is provided in contact with the elastic body. An ultrasonic motor that drives the moving body by the traveling vibration wave, a speed detecting unit that detects information about a rotational speed of the ultrasonic motor, a frequency adjusting unit that changes a frequency of the frequency voltage, and a memory; The motor is operated by changing the frequency by the adjusting means, learning is performed in advance to detect rotation speed information and frequency information from the start thereof to the specified number of rotations and store the information in the memory, Then, when the motor is to be slow-started, the motor is started by giving the frequency stored in the memory indicating a sufficiently lower speed than the target rotation speed, and then the motor actually starts operating. A first step of detecting the rotation speed information and the frequency information at the time of the rotation, and a second step of obtaining the frequency change rate corresponding to the rotation speed information obtained in the first step by referring to information stored in advance. And this second
Repeating the third step of updating the motor driving frequency using the frequency change rate obtained in the step and the acceleration speed obtained by dividing the difference obtained by subtracting the current rotation speed from the target rotation speed by the time required for slow start. It is characterized by performing.

In the third aspect, a frequency voltage is applied to the piezoelectric body to vibrate the piezoelectric body, and a progressive vibration wave is generated in the elastic body disposed on the piezoelectric body, and the piezoelectric body is provided in contact with the elastic body. An ultrasonic motor that drives the moving body by the traveling vibration wave, a speed detecting unit that detects information about a rotational speed of the ultrasonic motor, a frequency adjusting unit that changes a frequency of the frequency voltage, and a memory; The motor is operated by changing the frequency by the adjusting means, learning is performed in advance to detect rotation speed information and frequency information from the start to the specified number of rotations and store the information in the memory, When a predetermined command is given to stop this from the state where it is rotated, the rotational speed information at that time is detected and the corresponding frequency change rate in the memory is obtained. Step 1 and slow down the frequency change rate and the current rotational speed obtained in the first step.
The second step of updating the drive frequency of the motor using the deceleration speed divided by the time required for the stop is repeatedly executed.

[0007]

The change rate of the rotational frequency and the excitation or drive frequency (rotational speed / frequency) stored under an arbitrary temperature or load condition is considered to be substantially constant regardless of the characteristic change when a short period is assumed. By sequentially correcting (updating) the excitation or driving frequency using the change rate (rotation speed / frequency), stable slow start control and slow stop control can be executed. The correction principle is as follows. (1) The motor is started at a frequency (f0) obtained from stored information indicating a speed sufficiently lower than the set target speed. (2) An actual motor rotation speed (N) obtained as a result of starting at f0 is detected by a speed detection circuit.

(3) The difference ΔN between the set target rotation speed (Nf) and the actual rotation speed is calculated. ΔN = (Nf−N) (4) On the other hand, the rotation speed at the rotation speed N and the gradient B of the excitation or drive frequency in the stored motor characteristics are obtained. B = δf / δn (δ indicates a change in a minute section) (5) The frequency Δf to be changed is Δf = B × ΔN. The above is the principle of the present invention. Here, the case where the slow start control is performed is as follows.

(A) The acceleration speed α is calculated from the slow start time Δt and the target rotation speed Nf by the following equation. α = (Nf−N) / Δt (b) At the rotation speed N in the stored motor characteristics,
The rotation speed and the gradient B of the excitation or drive frequency are obtained. B = δf / δn (δ indicates a change in a minute section) (c) The frequency Δf to be changed is Δf = α × B. By repeating the above, slow start control can be realized. In addition, the slow stop control can be similarly performed assuming that the target rotation speed Nf is Nf = 0.

[0010]

FIG. 1 is a flowchart showing an embodiment of the present invention, FIG. 2 is a block diagram of a control device to which the present invention is applied, and FIG. 3 is a waveform diagram for explaining the operation of FIG. First,
FIG. 2 will be described. In the figure, 1 is an ultrasonic motor, 2A and 2B are drive transformers, 3A to 3D are driver FETs, 4 is a phase shift circuit, 5 is a speed detector, 6
Is a variable oscillation circuit, 7 is a processing circuit (CPU), 8, 9, 1
0 is a setting device, and 11 is an instruction input circuit. That is, the variable oscillation circuit 6 changes the oscillation frequency to be output according to the code signal set from the CPU 7, and the phase shift circuit 4 generates four signals having phases different from each other by 90 degrees from the output of the variable oscillation circuit 6. .

That is, as shown in FIG. 3, the phase shift circuit 4 outputs a1, a2, b1,
A signal whose phase is shifted by 90 degrees as shown by b2 is generated. The signals a1 and a2 generate currents of opposite phases to the transformer 2A via the FETs 3A and 3B, so that the secondary current of the transformer 2A becomes a sinusoidal drive signal as shown by a signal a0. Become. On the other hand, signal b
1 and b2 are similarly connected to the transformer 2B and the FETs 3C and 3B.
D generates a current of opposite phase, whereby the secondary current of the transformer 2B becomes cosine as shown by the signal b0.
Drive signal. The speed of the ultrasonic motor 1 is detected by the speed detector 5.

The setting unit 8 has a slow start time Δ
t, a speed target value Nf is set in the setter 9, a slow stop time Δt 'is set in the setter 10, and an instruction input circuit 11 is given an instruction to start and stop the motor. FIG. 4 is a flowchart showing a motor characteristic storing operation (learning operation), and FIG. 5 is an explanatory diagram for explaining a specific example thereof. This operation is performed when the CPU 7 shown in FIG. 2 automatically determines whether or not there is stored information when the motor is started, and when there is no stored information, or when the control device is shipped as shown in FIG. . That is, in step S1, the motor is driven at a sufficiently high initial frequency f0. Next, it is determined in step S2 whether the motor actually operates based on the frequency f0. If the motor does not operate, the initial frequency f0 is changed to f0−δf in step S3.
Waiting for the operation while updating sequentially.

When the motor actually operates, in step S4, the speed and frequency of the motor at that time are stored in a predetermined memory. In the specific example of FIG. 5, the frequency at this time is 49.5 KHz, and the rotation speed is 10. next,
After the operation starts, the motor speed at that time is sequentially stored while decreasing the frequency by δf (steps S5 and S5).
6). Then, if you reach a certain point, step S
At 7, the motor drive is stopped. FIG. 5 (a) shows the above result, which is as shown in the table (b). Further, the rate of change (inclination) xn between the rotational frequency and the excitation frequency in each rotational speed section is expressed as xn. Calculation is performed from the relationship as shown in the following equation (1), and this is stored as shown in (c).

[0014] However, the meaning of each symbol is as follows. xn: rate of change of excitation frequency from rotation speed Nn to (n-1) Nn: rotation speed at time n N (n-1): rotation speed at time (n-1) fn: excitation indicating rotation speed Nn Frequency f (n-1): excitation frequency indicating rotation speed N (n-1) n: sample number (0 to 4)

Here, a case where the motor characteristics during actual operation are different from the characteristics stored as described above (characteristics at the time of learning) as shown in FIG. 6 will be described with reference to FIG. FIG.
A indicates a motor characteristic during learning, and B indicates a motor characteristic during actual operation. First, the CPU of FIG.
7 receives a start instruction input via the start instruction input circuit 11 and sets a target speed value (target speed) Nf to the setting unit 9.
(See steps S1 and S2). next,
In step S3, the CPU 7 starts motor driving at the excitation (drive) frequency f0 at the time when the motor actually starts moving, obtained by the learning operation as shown in FIG. 4 or FIG.
In the example of FIG. 5, the frequency is 49.5 KHz. The rotation speed at this time is detected by the speed detector 5 in FIG. 2, and in the example of FIG. 6, this is 28 rotations.

Next, the CPU 7 refers to the inclination value xn in the rotation speed section where the current operation speed (28 rotations) is located, and corrects the excitation frequency f by the following relational expression. f = f + slope × (Nf−N) (2) In the specific example, the corrected frequency f is as follows: f = 49.5 + (− 160) × (70−28) = 42.78 KHz The actual rotation speed at this time is 105
Because of the rotation, the next correction becomes f = 42.78 + (− 35) × (70−105) = 44.00 KHz in the same manner as described above.

Since the actual rotational speed corresponding to f = 44.00 KHz is 85 from the characteristic shown in FIG. 6, the next correction is similarly performed as follows: f = 44.00 + (− 35) × (70−85) = 44.52 KHz. The actual rotation speed at this time is 75 rotations based on the characteristic of FIG. 6, and the next correction is f = 44.52 + (− 35) × (70−75) = 44.69 KHz.

Since the actual rotational speed corresponding to f = 44.69 KHz is 73 from the characteristic shown in FIG. 6, the next correction is similarly performed as follows: f = 44.69 + (− 35) × (70−73) = 44.79 KHz. The actual rotation speed at this time is 71 rotations from the characteristic in FIG. The above operation is executed in steps S4 to S8 in FIG. Thus, the target 70 rotations can be quickly reached. When a stop command is given in step S5 during the operation, the motor drive is turned off in step S9, and a series of operations is ended.

By doing so, even if the motor characteristics fluctuate due to load fluctuation or the like after the target rotational speed is reached,
Since correction is performed in the same manner as described above, stable tracking control can be performed. Here, an example has been described in which the control converges after the target rotation speed is once exceeded, but the target rotation speed can be exceeded by using a percentage of the inclination value stored in advance as a parameter. Needless to say, the control can be converged without any change.

Next, the operation in the case of having the slow start function will be described with reference to FIG. That is, when the CPU 7 of FIG. 2 receives a start instruction input via the start instruction input circuit 11, a speed target value (target speed) Nf
Is read via the setting device 9, and the time Δt until the target speed Nf set in the setting device 8 is reached is read (steps S1 to S3). Next, driving of the motor is started at the frequency f0 stored in advance, and the rotation speed N at the time when the motor actually starts operating is input (steps S4 and S5).

Here, in step S6, the CPU 7 in FIG. 2 calculates the acceleration speed α as shown by the following equation (3).
Is calculated. α = (Nf−N) / Δt (3) Next, after waiting for a predetermined time to elapse in step S7, the CPU detects the rotation speed at that time in step S8, and corresponds to the rotation speed at that time. The inclination xn is calculated in step S
9, the excitation or drive frequency f is corrected or updated according to the following equation (step S1).
0). f = f + α × slope (xn)

Next, the slow start operation when the motor characteristics during actual operation and the motor characteristics during learning are as shown in FIG. 8 will be specifically described. At this time, for example, Nf =
It is assumed that 70 rotations, Δt = 10 ms, f0 = 49.5 KHz, and correction is performed every 1 ms. In this case,
Since the actual rotation speed is 25 rotations by the initial frequency f0, the acceleration speed α is α = (Nf−N) / Δt = (70−25) /10=4.5, and the correction frequency after 1 ms is f = 49.5 + 4.5 × (−160) = 48.8 KHz, and the rotation speed at that time is 27. Hereinafter, FIG.
FIG. 9 is a graph showing the change over time of the rotational speed in FIG.
(A) Also, as shown in the table, the result is as shown in (b), and it can be seen that the target rotation speed can be reached in the target time of 10 ms.

FIG. 10 shows the operation at the time of slow stop.
That is, if there is no input from the start instruction input circuit 11 during the motor operation, the CPU reads the slow stop time Δt ′ via the setting unit 10 assuming that the stop instruction has been input (steps S1 and S2).
In step S3, the rotation speed N of the motor at that time is read. Then, in step S4, the CPU calculates a deceleration speed β per unit time as shown in the following equation from these values. β = (0−N) / Δt ′ (4)

Next, in step S5, the actual rotational speed of the motor is detected, and the excitation or drive frequency f is corrected as follows using the rate of change (inclination) of the frequency corresponding to the rotational speed range ( Steps S6 and S7). f = f + β × inclination (xn) In other words, this relational expression can be said to correspond to the case where the target speed in the relational expression at the time of slow start is 0, and by using such a relation, the motor is set for the set time Δt. 'It is possible to stop smoothly inside.

In the above description, the rotation speed of the motor is controlled by controlling the excitation or drive voltage. However, the same control as described above can be performed by controlling the phase of the excitation or drive voltage.

[0026]

According to the present invention, since the characteristics of the ultrasonic motor, particularly the gradient (speed / frequency), are substantially constant regardless of the characteristic fluctuation, the gradient is learned under an arbitrary temperature or load condition, and this is learned. Since the operation of updating the drive frequency or the drive frequency is repeated as necessary, there is an advantage that smooth and stable start / stop control can be performed irrespective of characteristic fluctuation.

[Brief description of the drawings]

FIG. 1 is a flowchart showing an embodiment of the present invention.

FIG. 2 is a configuration diagram showing a control device to which the present invention is applied.

FIG. 3 is a waveform chart for explaining the operation of FIG. 2;

FIG. 4 is a flowchart illustrating a learning operation.

FIG. 5 is an explanatory diagram for specifically explaining a relationship between a driving frequency and a rotation speed in FIG. 4;

FIG. 6 is a graph for explaining an example in which motor characteristics during actual operation and motor characteristics during learning do not match.

FIG. 7 is a flowchart illustrating a slow start control operation according to the present invention.

FIG. 8 is a graph for explaining a slow start control operation when the motor characteristics during actual operation and the motor characteristics during learning do not match.

FIG. 9 is an explanatory diagram for specifically explaining a relationship between a driving frequency and a rotation speed in FIG. 8;

FIG. 10 is a flowchart illustrating a slow stop control operation according to the present invention.

FIG. 11 is a graph for explaining an example of a characteristic change of an ultrasonic motor due to a load.

[Explanation of symbols]

1. Ultrasonic motor, 2A, 2B ... Drive transformer,
3A to 3D: driver FET, 4: phase shift circuit, 5:
Speed detector, 6: Variable oscillation circuit, 7: Processing circuit (CP
U), 8, 9, 10: setting device, 11: instruction input circuit.

──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Hiroyuki Kurusu 3-105 Sugaya, Ageo-shi, Saitama Fukuk Co., Ltd. (56) References JP-A-4-251581 (JP, A) JP-A-4-161076 ( JP, A) JP-A-4-217883 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H02N 2/00

Claims (3)

(57) [Claims] 1. A frequency voltage is applied to a piezoelectric body to vibrate the same, a progressive vibration wave is generated in an elastic body disposed on the piezoelectric body, and a moving body provided in contact with the elastic body is For an ultrasonic motor driven by a progressive vibration wave, a speed detecting means for detecting information about the rotational speed of the ultrasonic motor, a frequency adjusting means for changing a frequency of the frequency voltage, and a memory are provided, and the frequency adjusting means Is changed, the motor is operated, rotation speed information and frequency information from the start thereof to the specified number of rotations are detected, and learning for storing the information in the memory is performed in advance. The motor is started by giving a frequency stored in the memory indicating a sufficiently lower speed than the target rotation speed in actual operation, and thereafter, the rotation speed information and the frequency information when the motor actually starts operating. A first step of detecting, a second step of obtaining a frequency change rate corresponding to the rotational speed information obtained in the first step by referring to the previously stored information, and a frequency obtained in the second step. A third step of updating the drive frequency of the motor from the rate of change and a difference obtained by subtracting the current rotation speed from the target rotation speed. 2. A frequency voltage is applied to a piezoelectric body to vibrate the piezoelectric body, a progressive vibration wave is generated in an elastic body arranged on the piezoelectric body, and the moving body provided in contact with the elastic body is For an ultrasonic motor driven by a progressive vibration wave, a speed detecting means for detecting information about the rotational speed of the ultrasonic motor, a frequency adjusting means for changing a frequency of the frequency voltage, and a memory are provided, and the frequency adjusting means Is changed, the motor is operated, rotation speed information and frequency information from the start thereof to the specified number of rotations are detected, and learning for storing the information in the memory is performed in advance. To slow start
A first step of starting by applying a frequency stored in the memory indicating a sufficiently lower speed than the target rotation speed, and then detecting rotation speed information and frequency information when the motor actually starts operating; A second step in which the frequency change rate corresponding to the rotation speed information obtained in the first step is obtained by referring to information stored in advance, and the frequency change rate obtained in the second step and the target rotation speed are used. A third step of updating the drive frequency of the motor using an acceleration speed obtained by dividing a difference obtained by subtracting the current rotation speed by a time required for slow start, and a method for controlling the ultrasonic motor. . 3. A piezoelectric body is applied with a frequency voltage to vibrate the piezoelectric body, generating a progressive vibration wave in an elastic body disposed on the piezoelectric body, and moving the moving body provided in contact with the elastic body. For an ultrasonic motor driven by a progressive vibration wave, a speed detecting means for detecting information about the rotational speed of the ultrasonic motor, a frequency adjusting means for changing a frequency of the frequency voltage, and a memory are provided, and the frequency adjusting means Was changed, the motor was operated, rotation speed information and frequency information from the start to the specified number of rotations were detected, and learning to store the information in the memory was performed in advance, and the motor was rotated. From a state, when a predetermined command is given to stop this, a first step of detecting rotation speed information at that time and obtaining a corresponding frequency change rate in the memory; Slow stop the first asked at step frequency change rate and the current rotational speed
And a second step of updating the drive frequency of the motor using the deceleration speed divided by the time required for the ultrasonic motor.