JP4522055B2 - Driving method and driving apparatus for ultrasonic motor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a driving method and a driving apparatus of an ultrasonic motor, and more specifically to fine movement control of a resonant ultrasonic motor.
[0002]
[Prior art]
Conventionally, as shown in FIG. 7, two ultrasonic transducers 101a and 101b, a holding member 102 that holds the ultrasonic transducers 101a and 101b at a predetermined angle (for example, 90 degrees), and a substantially V-shape A head 103 which is in contact with the rotor 105 which is a driven body at the apex portion thereof, and which is connected to the ultrasonic transducers 101a and 101b at its end portion (the V-shaped open side). A resonance-type ultrasonic motor 100 provided is known (see, for example, Patent Document 1).
[0003]
In this ultrasonic motor 100, the ultrasonic transducers 101 a and 101 b are driven at resonance frequencies whose phases are shifted by 90 degrees, whereby elliptical motion occurs at the tip of the head 103. When the elliptically moving head 103 is pressed against the end face of the rotor 105 with a constant force, a thrust force in the tangential direction of the outer periphery of the rotor 105 is applied by the frictional force generated between the head 103 and the rotor 105, so that the rotor 105 rotates. (Hereinafter, this is referred to as “resonance driving”).
[0004]
[Patent Document 1]
JP 2000-152671 A (paragraphs 24 to 29, FIG. 1)
[0005]
[Problems to be solved by the invention]
However, even if the ultrasonic vibrators 101a and 101b are driven by applying an AC voltage having a predetermined frequency in the resonance frequency band to the ultrasonic vibrators 101a and 101b, and then the driving of the ultrasonic vibrators 101a and 101b is stopped. The head 103 moves minutely due to inertia. At this time, since the head 103 applies a thrust to the rotor 105, it is difficult to position the rotor 105 with high accuracy (for example, positioning on the nanometer order).
[0006]
In order to solve this, a minute displacement control by a DC voltage can be considered (hereinafter referred to as “DC drive”). In direct current drive, the stroke is limited and cannot be sent indefinitely. For this reason, when such control is performed, it is necessary that the displacement due to the DC voltage is larger than the positioning accuracy of the high-speed drive due to resonance.
When the distance from the stop position to the target position after high-speed movement by resonance driving is longer than the displacement due to direct current, the target position cannot be reached by direct current driving, and high-precision positioning is not completed.
[0007]
However, when the size of the piezoelectric ceramic portion is reduced, for example, when it is desired to make the motor smaller, the displacement due to the direct current drive is not smaller than the positioning accuracy of the high-speed drive due to the resonance drive, and thus high-accuracy positioning cannot be performed. The problem that occurred.
[0008]
The present invention has been made in view of such circumstances, and an object of the present invention is to provide an ultrasonic motor driving method that enables highly accurate positioning. The present invention also provides an ultrasonic motor driving method that enables high-speed and highly accurate positioning. A further object of the present invention is to provide a driving apparatus used for driving such an ultrasonic motor.
[0009]
[Means for Solving the Problems]
According to the present invention, there are two Langevin type ultrasonic transducers each including a piezoelectric element, a holding member that holds the two ultrasonic transducers at a predetermined angle, and a substantially V-shaped configuration. And a contact member which is in contact with the driven body at the apex portion and connected to the two ultrasonic transducers at the end portion thereof, and a method of driving the ultrasonic motorIn,
When the position sensor detects that the driven body has approached a predetermined distance from the target position, the drive control apparatus stops the operation of the first feedback control apparatus that generates the resonance drive signal, and then the DC voltage signal. Command to start the operation of the second feedback control device for generating
The DC voltage signal is divided into a reverse voltage input to one of the two amplifiers after being subjected to positive / negative inversion processing by a signal inverter, and a forward voltage directly input to the other of the two amplifiers, A forward voltage is applied to the piezoelectric element included in one of the two ultrasonic transducers after being amplified to a certain voltage value, and a reverse voltage is applied to the piezoelectric element included in the other of the two ultrasonic transducers. To drive the ultrasonic motor to position the driven body at a target position,
Changing the DC voltage applied to the piezoelectric element included in one of the two ultrasonic transducers to move the contact member in a small direction by moving the contact member in one direction;
When the driven body still does not reach the target position, the sign of the DC voltage signal applied to the piezoelectric elements included in the two ultrasonic transducers is abruptly reversed.
A method for driving an ultrasonic motor, wherein the speed of the contact member is rapidly changed to slide between the contact portion and a driven body in contact (hereinafter referred to as “sliding drive”). Is provided.
[0010]
According to such a driving method of the ultrasonic motor, the driven body can be moved with infinitely high accuracy, so even if the positioning accuracy of high-speed driving by resonance driving is worse than the driving range by DC driving, high accuracy is achieved. Can be positioned.
[0011]
According to this ultrasonic motor driving method, the driven body can be moved to the vicinity of the target position in a short time by resonantly driving the ultrasonic vibrator, and the driven body is moved to the vicinity of the target position. Driving the ultrasonic transducer after reaching it, more precisely, by applying a direct voltage to the piezoelectric element and driving the ultrasonic transducer to produce a static displacement in the ultrasonic transducer, The driven body can be positioned at the target position with high accuracy. At this time, when the stop position after high-speed movement exceeds the driving range by DC driving, or when the position shifts outside the DC driving range due to disturbance or the like, driving combining DC driving and sliding driving according to the present invention By the method, the target position can be approached to within the range of DC driving, and high-precision positioning by DC driving becomes possible.
[0012]
In addition, when the driven body is a rotating body and the rotating body is rotated by a predetermined angle, the rotating body is rotated at high speed to the vicinity of the target angle by first resonantly driving the ultrasonic transducer, and then The rotation angle can be positioned with high accuracy by direct current driving. At this time, when the stop position after high-speed movement exceeds the driving range by DC driving, or when the position shifts outside the DC driving range due to disturbance or the like, driving combining DC driving and sliding driving according to the present invention By the method, the target position can be approached to within the range of DC driving, and high-precision positioning by DC driving becomes possible.
[0013]
In such a driving method of the ultrasonic motor, after the ultrasonic vibrator is DC-driven and the driven body is moved in one direction minutely, by holding a DC voltage applied to the piezoelectric element, Hold the driven body in a fixed position. In this state, when the range of displacement due to DC voltage is exceeded due to disturbance or the like, it can be moved within the range by using this method and returned to the range of displacement due to DC voltage. As a method of sliding the ultrasonic transducer, a method in which the drive voltage is rapidly changed by only one piezoelectric element of the two ultrasonic transducers, and one piezoelectric element of the two ultrasonic transducers are used. There is a method of abruptly displacing with a forward voltage and abruptly displacing the other piezoelectric element with a reverse voltage.
[0014]
According to the present invention, a driving device for driving the ultrasonic motor in this way is provided. That is, two Langevin type ultrasonic transducers provided with a piezoelectric element, a holding member for holding the two ultrasonic transducers at a predetermined angle, and a substantially V-shaped shape, its apex An ultrasonic motor drive device comprising: a contact member that is in contact with a driven body at a portion and connected to the two ultrasonic vibrators at an end portion thereofInA position sensor that detects the position of the driven body, and a resonance driving device that moves the driven body by resonance driving the ultrasonic transducer with an alternating voltage;
The two ultrasonic transducersHasA DC driving device that moves the driven member in contact with the contact member in one direction by driving the piezoelectric element with a DC voltage to move the contact member, and the resonance driving device according to a detection signal of the position sensor Or a drive control device for sending a drive signal for driving the DC drive device;
A first feedback control device that is provided in the resonance drive device, generates an AC voltage for resonance driving the ultrasonic motor by the drive signal from the drive control device, and sends the AC voltage to an amplifier;
A second feedback control device that is provided in the DC drive device, generates a DC voltage for DC driving of the ultrasonic motor by the drive signal from the drive control device, and sends the DC voltage to an amplifier;
A signal inverter provided in the DC drive device for reversing the polarity of the DC voltage;
Two amplifiers,
Comprising
When the position sensor detects that the driven body has approached a predetermined distance from the target position, the drive control device stops the operation of the first feedback control device, and then the second feedback control device. Command to start
The DC voltage is divided into a reverse voltage that is input to one of the two amplifiers after being subjected to positive / negative inversion processing by the signal inverter, and a forward voltage that is directly input to the other of the two amplifiers. A forward voltage is applied to the piezoelectric element included in one of the two ultrasonic transducers after being amplified to a certain voltage value, and reversely applied to the piezoelectric element included in the other of the two ultrasonic transducers. The ultrasonic motor is driven by applying a voltage to position the driven body at a target position,
The position of the driven body isTarget positionIf it is outside the predetermined rangeOr if the DC voltage applied to the piezoelectric element has reached the allowable limit of the piezoelectric element but does not come to the target position,
Moving the driven member in contact with the contact member by displacing the piezoelectric element with a DC voltage and moving the contact member;
The two ultrasonic transducersHasBy suddenly reversing the polarity of the DC voltage applied to the piezoelectric element
The speed of the contact member is changed abruptlyThen, by repeatedly sliding between the contact portion and the driven body in contact with the contact portion, the driven body in contact with the contact member is moved from a designated position to a predetermined range.An ultrasonic motor driving device is provided.
According to the present invention, the positioning accuracy can be increased to the detection limit (resolution limit) of the position detection sensor.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is an explanatory diagram showing a schematic configuration of the ultrasonic motor 10. Although this ultrasonic motor 10 has the same structure as the ultrasonic motor 100 previously shown in FIG. 7, the structure of the ultrasonic motor 10 will be described again in more detail.
[0016]
The ultrasonic motor 10 is in contact with two driven vibrators 15, two ultrasonic vibrators 11 a and 11 b having a Langevin structure, a holding member 12 that holds the ultrasonic vibrators 11 a and 11 b at an angle of 90 degrees. And a head 13 having a substantially V-shape. A pressing mechanism 14 is attached to the holding member 12, and the pressing mechanism 14 presses the head 13 against the driven body 15 with a predetermined force.
[0017]
The ultrasonic transducers 11a and 11b have the same structure. The ultrasonic transducer 11a includes a bolt 21 having both ends threaded, a cap nut 22 having a screw hole that fits into a screw groove of the bolt 21, and two ring-shaped piezoelectric plates through which the bolt 21 can pass. 23a and 23b, and ring-shaped electrode plates 24a to 24c through which the bolts 21 can pass. Similar to the ultrasonic transducer 11a, the ultrasonic transducer 11b includes a bolt 21 ', a cap nut 22', two ring-shaped piezoelectric plates 23a 'and 23b', and ring-shaped electrode plates 24a 'to 24a'. 24c '. Electrodes (not shown) are formed on the front and back surfaces of the piezoelectric plates 23a, 23b, 23a ', and 23b'.
[0018]
The holding member 12 is provided with a hole for allowing the bolt 21 to pass therethrough. The head 13 connects the contact portion 13a in contact with the driven body 15, the connection portions 13b and 13b 'connected to the ultrasonic transducers 11a and 11b, and the contact portion 13a and the connection portions 13b and 13b'. Neck portions 13c and 13c 'are formed, and screw holes are formed in the connecting portions 13b and 13b' to fit into the screw grooves of the bolts 21 and 21 ', respectively. The piezoelectric plates 23a and 23b are fastened with a predetermined force by the connecting portion 13b of the cap nut 22 and the head 13, thereby obtaining the Langevin type ultrasonic transducer 11a. It is also a component of the acoustic wave oscillator 11a. Similarly, the connecting portion 13b ′ is also a constituent element of the ultrasonic transducer 11b.
[0019]
As shown in FIG. 1, the piezoelectric plates 23 a and 23 b are arranged so as to be sandwiched between the electrode plates 24 a to 24 c, and bolts 21 are inserted into the holes of the piezoelectric plates 23 a and 23 b, the electrode plates 24 a to 24 c and the holding member 12. The head 13 and the cap nut 22 are attached to the end portions of the bolts 21, respectively. Accordingly, the piezoelectric plates 23a and 23b are fastened with a predetermined force. Thus, in the ultrasonic motor 10, the head 13 not only gives thrust to the driven body 15, but also plays a role as a member constituting the Langevin type vibrator by tightening the piezoelectric plates 23a and 23b. Of course, a Langevin type vibrator constituted by fastening the piezoelectric bodies 23a and 23b with two nuts is prepared, and one nut is attached to the connecting portion 13b of the head 13 by screwing, bonding with an adhesive, welding or the like. Thus, an ultrasonic motor equivalent to the ultrasonic motor 10 may be configured.
[0020]
For the piezoelectric plates 23a and 23b, piezoelectric ceramics such as PZT are preferably used. The directions of polarization of the piezoelectric plates 23a and 23b are symmetric with respect to the electrode plate 24b sandwiched between the piezoelectric plates 23a and 23b. The electrode plates 24a and 24c are electrically connected to each other. Therefore, when a voltage is applied between the electrode plate 24b and the electrode plate 24c, the piezoelectric plates 23a and 23b are displaced (vibrated) in the same phase. That is, the piezoelectric plates 23a and 23b extend in the thickness direction or contract together.
[0021]
Usually, the bolt 21, the cap nut 22, and the holding member 12 are made of metal, and in this case, the electrode plates 24 a and 24 c are electrically connected to the cap nut 22 through the holding member 12. Therefore, the holding member 12 or the cap nut 22 of the ultrasonic transducer 11a can be used as a ground electrode for driving the piezoelectric bodies 23a and 23b. At this time, the piezoelectric plate 23a ′ included in the ultrasonic transducer 11b is provided. -The earth for driving 23b 'can be taken simultaneously.
[0022]
When the piezoelectric plates 23a and 23b of the ultrasonic transducer 11a are expanded and contracted, and at the same time, the piezoelectric plates 23a 'and 23b' of the ultrasonic transducer 11b are expanded and contracted, the neck portions 13c and 13c 'of the head 13 are moved. As a result, the displacements of the ultrasonic transducers 11a and 11b are synthesized at the contact portion 13a, and thereby the contact portion 13a is displaced.
[0023]
For the head 13, a material having excellent wear resistance, for example, a metal material such as stainless steel or cemented carbide, or a ceramic such as alumina, silicon nitride, or silicon carbide is used. If the head 13 is made of metal, it is easy to form a screw groove for connecting the bolt 13 to the head 13. Even if the head 13 is made of metal, since the head 13 is electrically connected to the electrode plate 24a, if either the holding member 12 or the cap nuts 22 and 22 'of the ultrasonic transducers 11a and 11b are grounded, the head 13 Are also grounded. It is also preferable that the head 13 is made of a metal material, and the surface of the contact portion 13a is coated with silicon nitride or the like. Alternatively, the head 13 may be made of a metal material, and a ceramic member may be disposed on the contact portion 13 a so that the ceramic member substantially contacts the driven body 15.
[0024]
As the pressing mechanism 14, for example, an air cylinder, a hydraulic cylinder, a spring coil, or the like is used.
[0025]
When the ultrasonic motor 10 having such a structure is driven to resonate, the ultrasonic vibrator 11a and the ultrasonic vibrator 11b are driven with an AC voltage whose phase is shifted by 90 degrees. For example, as shown in FIG. 1, V = V is applied to the electrode plate 24b of the ultrasonic transducer 11a.₀sin (2πft) (V₀A zero-peak voltage, f; frequency, t; time), and at the same time, V = V is applied to the electrode plate 24b 'of the ultrasonic transducer 11b.₀An AC voltage of cos (2πft) is applied. As a result, the ultrasonic transducers 11a and 11b expand and contract, and a counterclockwise elliptical motion as shown in FIG. 1 occurs in the contact portion 13a, and the driven member 15 moves in the + X direction.
[0026]
Conversely, V = V is applied to the ultrasonic transducer 11a.₀cos (2πft) is applied, and V = V is applied to the ultrasonic transducer 11b.₀When an alternating voltage of sin (2πft) is applied, clockwise elliptical motion is generated, so that the driven body 15 can be moved in the −X direction. Further, V = V is applied to the ultrasonic transducer 11a.₀sin (2πft) is applied, and V = −V is applied to the ultrasonic transducer 11b.₀When an alternating voltage of cos (2πft) is applied, a clockwise elliptical motion is generated, so that the driven body 15 can be moved in the −X direction.
[0027]
The positioning accuracy of the driven body 15 when the ultrasonic motor 10 is driven to resonate in this way is that the contact portion 13a moves minutely due to inertia even when the voltage for driving the ultrasonic transducers 11a and 11b is turned off. The order of tens to hundreds of nanometers is the limit. Therefore, in order to position the driven body 15 with higher accuracy, the ultrasonic motor 10 is driven by a DC voltage.
[0028]
FIG. 2 is an explanatory diagram showing an example of a mode in which the ultrasonic motor 10 is DC driven. As shown in FIG. 2, when a forward voltage (when the polarization direction and the electric field direction are the same) is applied to the piezoelectric plates 23a and 23b of the ultrasonic transducer 11a, the piezoelectric plates 23a and 23b are moved in the thickness direction by the piezoelectric longitudinal effect. The contact portion 13a tends to be displaced in the direction of arrow A. At this time, the contact portion 13a applies a thrust force to the driven body 15 in the + X direction, and the driven body 15 moves in the + X direction in contact with the contact portion 13a.
[0029]
As shown in FIG. 2, a forward voltage is applied to the piezoelectric plates 23a and 23b of the ultrasonic transducer 11a, and at the same time, a reverse voltage (polarization direction and electric field) is applied to the piezoelectric plates 23a 'and 23b' of the ultrasonic transducer 11b. Is applied), the piezoelectric plates 23a 'and 23b' are contracted, and the displacement of the contact portion 13a is increased. That is, the movement range of the driven body 15 can be widened. The drive control range of the contact portion 13a by the direct current drive of the ultrasonic transducers 11a and 11b, that is, the displacement amount of the contact portion 13a is the contact portion 13a when the ultrasonic transducers 11a and 11b are driven to resonate. The positioning accuracy length is preferably longer than the positioning accuracy length, but it is also conceivable that the drive control range is smaller than the positioning accuracy length depending on the size of the motor.
It is also conceivable that the positioning position exceeds the drive control range due to disturbance or the like.
[0030]
In such a case, if the voltage applied to the piezoelectric plates 23a, 23b, 23a ', 23b' is suddenly changed, and the moving speed of 13a is suddenly changed, the driven body 15 cannot follow, only 13a moves, The DC drive can be performed again toward the target position.
[0031]
In this way, positioning by DC driving can be continued without using resonance driving even when the DC driving range is exceeded, so even when a motor whose DC driving range is below the positioning accuracy during resonance driving is used, Positioning accuracy is ensured.
[0032]
FIG. 6 shows that the ultrasonic motor 10 is driven by applying a forward voltage to the piezoelectric plates 23a and 23b of the ultrasonic transducer 11a and a reverse voltage to the piezoelectric plates 23a 'and 23b' of the ultrasonic transducer 11b in a sawtooth shape. FIG. 5 is a graph showing the applied voltage at that time. From FIG. 6, it was confirmed that the movement in one direction was about 1 μm / sec due to continuous DC driving and sliding driving.
[0033]
Next, a method for driving the ultrasonic motor 10 by combining resonance driving, DC driving, and sliding driving will be described. FIG. 3 is an explanatory diagram showing the driving device 50 of the ultrasonic motor 10. The driving device 50 includes a position sensor 31 that detects the position of the driven body 15, a resonance driving device 32 that drives the ultrasonic motor 10 to resonate, a DC driving device 33 that drives the ultrasonic motor 10 by DC, and a position sensor 31. And a drive control device (CPU) 34 for sending a drive command signal to the resonance drive device 32 or the DC drive device 33 according to the detection signal. The resonance driving device 32 and the DC driving device 33 share the amplifiers 35a and 35b. Further, the resonance driving device 32 has a first feedback control device 36 and a phase control device 37, and the DC driving device 33 has a second feedback. A control device 38 and a signal inverter 39 are included.
[0034]
As the position sensor 31, a non-contact optical sensor system using a laser is preferably used. For example, marking (not shown) for indicating the position of the driven body 15 is provided on the driven body 15, and the position sensor 31 detects the position of the driven body 15 from the reflected light pattern.
[0035]
When the first feedback control device 36 receives a command signal for resonantly driving the ultrasonic motor 10 from the drive control device (CPU) 34, the first feedback control device 36 generates a resonant drive signal for resonantly driving the ultrasonic motor 10, and amplifies it. Send to 35a and 35b. The first feedback control device 36 receives the detection signal of the position sensor 31 and adjusts the moving speed of the driven body 15. Therefore, the first feedback control device 36 can appropriately change the waveform of the resonance drive signal (for example, change the zero-peak voltage value).
[0036]
A resonance drive signal having the same waveform is output from the first feedback control device 36 to the amplifiers 35a and 35b. Therefore, the phase of the resonance drive signal sent to one amplifier, that is, the amplifier 35a, is shifted by 90 degrees by the phase controller 37 before being input to the amplifier 35a. For example, the resonance drive signal output from the first feedback control device 36 is V = V.₀In the case of sin (2πft), the amplifier 35b has this V = V₀A resonance drive signal of sin (2πft) is input, but the amplifier 35a is phase-controlled by the phase control device 37 V = V₀cos (2πft) or V = −V₀A resonance driving signal of cos (2πft) is input.
[0037]
The resonance drive signal output from the first feedback control device 36 is V = V₀It may be cos (2πft). In this case, V = V from the phase control device 37.₀sin (2πft) or V = −V₀A resonance drive signal of sin (2πft) is output.
[0038]
When receiving a command signal for direct drive of the ultrasonic motor 10 from the drive control unit (CPU) 34, the second feedback control device 38 generates a direct current voltage signal for direct drive of the ultrasonic motor 10 and amplifies it. Send to 35a and 35b. The second feedback control device 38 can receive a signal from the position sensor 31 and appropriately adjust the voltage value of the DC voltage signal and send it to the amplifiers 35a and 35b.
[0039]
The same DC voltage signal is output from the second feedback control device 38 to the amplifiers 35a and 35b. For this reason, the DC voltage signal sent to the amplifier 35a is inverted by the signal inverter 39 before being input to the amplifier 35a. Thereby, for example, when a forward voltage is applied to the piezoelectric plates 23a and 23b of the ultrasonic transducer 11a, a reverse voltage can be applied to the piezoelectric plates 23a 'and 23b' of the ultrasonic transducer 11b.
[0040]
FIG. 4 shows a control range when the driven body 15 is moved from the state where the point K of the driven body 15 is located at the position S1 to the state located at the target position S2, using the driving device 50. 4A is an explanatory diagram, FIG. 4A is an overall view thereof, and FIG. 4B is an enlarged view centering on a dotted frame in FIG. 4A.
[0041]
In the initial state, the position sensor 31 sends a detection signal indicating that the point K is at the position S1 (the driven body 15 is at the position indicated by the two-dot chain line) to the drive control device (CPU) 34. The driven body 15 is marked so that the position sensor 31 can detect that the K point is at the target position S2 or the like when the driven body 15 moves. From this state, for example, an operator inputs a signal for instructing to move the point K to the target position S2 to the drive control device (CPU) 34. The drive control device (CPU) 34 determines from the position detection signal received from the position sensor 31 whether to drive the resonance drive device 32 or the DC drive device 33.
[0042]
Assuming that the movable distance of the driven body 15 by direct current driving of the ultrasonic motor 10 is L, the range in which positioning by the direct current driving device 33 is possible is as shown in FIG. It is between position S5 and position S6 which are separated by a distance. Here, it is assumed that the position S1 is out of the positions S5 to S6. Therefore, the drive control device (CPU) 34 sends an operation command signal to the resonance drive device 32, and the resonance drive device 32 starts driving the driven body 15.
[0043]
The ultrasonic motor 10 does not have driving accuracy for positioning the driven body 15 so that the K point is always located at the target position S2. Therefore, the driven body 15 is moved so that the point K enters between the positions S5 and S6 (preferably between the positions S3 and S4). Note that “the K point is located at the target position S2” refers to a state in which it is determined that the K point is at the target position S2 as a result of the position detection of the driven body 15 by the position sensor 31. For example, when a laser length measuring device is used, the range is ± 0.7 nm or less.
[0044]
Specifically, the first feedback control device 36 included in the resonance driving device 32 is configured to output a resonance driving signal (for example, V = V₀sin (2πft)) is generated and sent to the amplifiers 35a and 35b. As described above, the amplifier 35a has a resonance drive signal (V = V) whose phase is shifted by 90 degrees by the phase controller 37.₀cos (2πft)) is input. The amplifiers 35a and 35b perform voltage amplification of the inputted resonance driving signal, and the voltage amplified signals are inputted to the ultrasonic transducers 11a and 11b, respectively. As a result, the ultrasonic motor 10 is driven to resonate, and the driven body 15 starts to move.
[0045]
In order to move the driven body 15 at a high speed from the target position S2 to the position S7 that is a predetermined distance away, the zero-peak voltage value and the frequency of the resonance drive signal output from the first feedback control device 36 are determined. The amplification factor of the resonance drive signal in the amplifiers 35a and 35b is controlled so that the speed is constant.
[0046]
The position of the driven body 15 is detected by a position sensor 31, and the detection signal is sent to a drive control device (CPU) 34 and a first feedback control device 36. The drive control device (CPU) 34 notifies the resonance drive device 32 until it receives a detection signal from the position sensor 31 that the point K has entered between the positions S5 and S6 (more preferably between the positions S3 and S4). Send an operation command signal. On the other hand, when the first feedback control device 36 receives a detection signal from the position sensor 31 that the point K exceeds the position S7 and enters the target position S2, the first feedback control device 36 decelerates the moving speed of the driven body 15. Thus, the K point is easily inserted between the positions S5 and S6.
[0047]
As a method of reducing the moving speed of the driven body 15, a method of reducing the zero-peak voltage value of the resonance drive signal or changing the frequency at and near the resonance frequency can be mentioned. Here, “resonance frequency and its vicinity” refers to a frequency at which the ultrasonic motor 10 is substantially resonantly driven. The first feedback control device 36 reduces the moving speed of the driven body 15 and then outputs the resonance drive signal until receiving a detection signal from the position sensor 31 that the point K is between the positions S5 and S6. It outputs to amplifier 35a * 35b.
[0048]
When the point K enters between the positions S5 and S6, the drive control device (CPU) 34 stops the operation of the first feedback control device 36, and then commands the second feedback control device 38 to start operation. In driving the driven body 15 by the DC drive device 33, the second feedback control device 38 sends a DC voltage signal to the amplifiers 35 a and 35 b while receiving the detection signal from the position sensor 31. As described above, the DC voltage signal sent to the amplifier 35a is subjected to positive / negative inversion processing by the signal inverter 39 before being input to the amplifier 35a. In the amplifiers 35a and 35b, the DC voltage signal is amplified to a certain voltage value and applied to the piezoelectric plates 23a and 23b of the ultrasonic transducer 11a and the piezoelectric plates 23a 'and 23b' of the ultrasonic transducer 11b. Thereby, the contact part 13a is moved minutely, and the point K is positioned at the target position S2 up to the detection accuracy limit of the position sensor 31.
[0049]
Here, when the K point exceeds the range of S5 and S6, or the voltage applied to the piezoelectric plates 23a and 23b of the ultrasonic transducer 11a and the piezoelectric plates 23a 'and 23b' of the ultrasonic transducer 11b is the element. If the S2 position is not reached even though the allowable limit is reached, the polarity of the DC signal voltage is reversed. In this way, the sliding drive is caused to shift the K point, and the DC driving is resumed.
[0050]
Even when the positioning of the driven body 15 is completed, the K point is always at the target position S2 on the piezoelectric plates 23a and 23b of the ultrasonic transducer 11a and the piezoelectric plates 23a 'and 23b' of the ultrasonic transducer 11b. In addition, the second feedback control device 38 receives the detection signal from the position sensor 31 and applies it to the piezoelectric plates 23a and 23b of the ultrasonic transducer 11a and the piezoelectric plates 23a 'and 23b' of the ultrasonic transducer 11b. The voltage value of the DC voltage signal is changed as appropriate. In a state where the driven body 15 is at the target position S2, for example, if predetermined processing is performed on a workpiece (not shown) attached to the driven body 15, the K point is set to another position as described above. The point is moved by the same method as the method of moving the point from the position S1 to the target position S2.
[0051]
As mentioned above, although embodiment of this invention has been described, this invention is not limited to such a form. For example, in the above description, the form in which the driven body 15 is linearly moved has been described. However, if the ultrasonic motor 10 is driven by pressing the contact portion 13a of the head 13 against the outer peripheral end surface of the rotatable rotor, The rotation angle of the rotor can be controlled with high accuracy. The number of piezoelectric plates included in the ultrasonic transducers 11a and 11b may be one or three or more.
[0052]
【The invention's effect】
As described above, according to the present invention, the driven body can be moved to the vicinity of the target position in a short time by resonantly driving the piezoelectric element and causing the contact member (head) to generate an elliptical motion. Since the driven member can be moved minutely by applying force to the driven member without causing inertia in the contact member, the driven member can be positioned with higher accuracy than in the prior art.
[Brief description of the drawings]
FIG. 1 is a plan view (upper side) and a cross-sectional view (lower side) showing a schematic configuration of an ultrasonic motor to which a driving method of the present invention is applied.
FIG. 2 is an explanatory diagram showing an example of a mode in which an ultrasonic motor is DC-driven.
FIG. 3 is an explanatory diagram showing a schematic configuration of an ultrasonic motor driving device.
FIG. 4 is an explanatory diagram showing a control range when a driven body is moved to a predetermined position.
FIG. 5 is an explanatory diagram showing an example of an applied voltage when the driving method of the present invention is applied.
FIG. 6 is an explanatory diagram showing an example of a sliding drive according to the present invention.
FIG. 7 is an explanatory diagram showing an example of a conventional ultrasonic motor.
[Explanation of symbols]
10; Ultrasonic motor
11a, 11b; ultrasonic transducer
12: Holding member
13; Head
13a; contact part
13b; connecting part
13c; neck part
14: Pressing mechanism
15; driven body
21 ・ 21 '; Bolt
22.22 '; cap nut
23a, 23b, 23a ', 23b'; Piezoelectric plate
24a-24c; 24a'-24c '; electrode plate
31; Position sensor
32; Resonant drive device
33; DC drive
34; Drive control device (CPU)
35a, 35b; amplifier
36; first feedback control device
37; Phase control device
38; second feedback control device
39; Signal inverter
100; ultrasonic motor
101a, 101b; ultrasonic transducer
102; holding member
103; head
105; rotor

Claims (3)

Two Langevin type ultrasonic transducers provided with piezoelectric elements, a holding member for holding the two ultrasonic transducers at a predetermined angle, and a substantially V-shaped shape, In a driving method of an ultrasonic motor comprising: a contact member that is in contact with a driven body and is connected to the two ultrasonic vibrators at an end thereof;
When the position sensor detects that the driven body has approached a predetermined distance from the target position, the drive control apparatus stops the operation of the first feedback control apparatus that generates the resonance drive signal, and then the DC voltage signal. Command to start the operation of the second feedback control device for generating
The DC voltage signal is divided into a reverse voltage input to one of the two amplifiers after being subjected to positive / negative inversion processing by a signal inverter, and a forward voltage directly input to the other of the two amplifiers, A forward voltage is applied to the piezoelectric element included in one of the two ultrasonic transducers after being amplified to a certain voltage value, and a reverse voltage is applied to the piezoelectric element included in the other of the two ultrasonic transducers. To drive the ultrasonic motor to position the driven body at a target position,
Changing the DC voltage applied to the piezoelectric element included in one of the two ultrasonic transducers to move the contact member in a small direction by moving the contact member in one direction;
When the driven body still does not reach the target position, the speed of the contact member is rapidly increased by reversing the sign of the DC voltage signal applied to the piezoelectric elements included in the two ultrasonic transducers. The method for driving an ultrasonic motor is characterized by sliding between the contact portion and a driven body in contact with the contact portion. Two Langevin type ultrasonic transducers provided with piezoelectric elements, a holding member for holding the two ultrasonic transducers at a predetermined angle, and a substantially V-shaped shape, A method of driving an ultrasonic motor comprising: a contact member that is in contact with a driven body and is connected to the two ultrasonic vibrators at an end thereof;
Detecting that the driven body has approached a predetermined distance from the target position;
The piezoelectric element included in one of the two ultrasonic transducers is displaced with a forward voltage, and the piezoelectric element included in the other is displaced with a reverse voltage, so that the contact member is moved and contacted with the contact member. Move the drive in one direction ,
If the driven body still does not reach the target position,
The direct forward voltage applied to the piezoelectric element included in one of the two ultrasonic vibrators and the positive / negative of the reverse voltage applied to the piezoelectric element included in the other ultrasonic vibrator are rapidly reversed. A method of driving an ultrasonic motor, wherein the speed of the contact member is rapidly changed to slide between the contact portion and a driven body in contact therewith. Two Langevin type ultrasonic transducers provided with piezoelectric elements, a holding member for holding the two ultrasonic transducers at a predetermined angle, and a substantially V-shaped shape, contact with the driven body, the driving device of the ultrasonic motor and a contact member connected to the two ultrasonic transducers at its ends, a position sensor for detecting a position of the driven body, A resonance driving device for moving the driven body by resonance driving the ultrasonic vibrator with an alternating voltage;
A DC driving device that moves the driven body in contact with the contact member in one direction by driving the piezoelectric element included in the two ultrasonic transducers with a DC voltage to move the contact member; A drive control device for sending a drive signal for driving the resonance drive device or the DC drive device according to a detection signal of a position sensor;
A first feedback control device that is provided in the resonance drive device, generates an AC voltage for resonance driving the ultrasonic motor by the drive signal from the drive control device, and sends the AC voltage to an amplifier;
A second feedback control device that is provided in the DC drive device, generates a DC voltage for DC driving of the ultrasonic motor by the drive signal from the drive control device, and sends the DC voltage to an amplifier;
A signal inverter provided in the DC drive device for reversing the polarity of the DC voltage;
Two amplifiers,
Comprising
When the position sensor detects that the driven body has approached a predetermined distance from the target position, the drive control device stops the operation of the first feedback control device, and then the second feedback control device. Command to start
The DC voltage is divided into a reverse voltage that is input to one of the two amplifiers after being subjected to positive / negative inversion processing by the signal inverter, and a forward voltage that is directly input to the other of the two amplifiers. A forward voltage is applied to the piezoelectric element included in one of the two ultrasonic transducers after being amplified to a certain voltage value, and reversely applied to the piezoelectric element included in the other of the two ultrasonic transducers. The ultrasonic motor is driven by applying a voltage to position the driven body at a target position,
When the position of the driven body is outside the predetermined range from the target position , or when the DC voltage applied to the piezoelectric element has reached the allowable limit of the piezoelectric element but does not reach the target position ,
Moving the driven member in contact with the contact member by displacing the piezoelectric element with a DC voltage and moving the contact member;
A driven body in contact with the contact portion by rapidly changing the speed of the contact member by abruptly reversing the sign of the DC voltage applied to the piezoelectric elements included in the two ultrasonic transducers ; An ultrasonic motor driving device characterized in that the driven body in contact with the contact member is moved within a predetermined range from the instructed position by repeating sliding between the two .

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