JP2004364407A - Method and device for controlling rotational position of multi-degrees of freedom ultrasonic motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and device for controlling rotational position, capable of controlling rotational position in three-degrees of freedom of a multi-degrees of freedom ultrasonic motor with no use of kinetic model. <P>SOLUTION: A rotational position controller α applied to a multi-DOF ultrasonic motor β employs a featuristic configuration that includes a rotational angle measuring sensor 1 for measuring current rotational position of a rotor 5 in rotational movement, a rotational position monitoring part 2 that calculates the amplitude value of an AC voltage applied to piezoelectric elements 4a, 4b, and 4c and outputs it as an amplitude command value so that the rotor 5 is made to reach a pre-set target rotational position from the measurement value of the current rotational position measured with the rotational angle measuring sensor 1, and a high frequency rotational direction switching part 3 that outputs the AC voltage of a plurality of phases having the same amplitude value as the amplitude command value inputted from the rotational position monitoring part 2 and also having a phase difference required for rotating the rotor 5 to the piezoelectric elements 4a, 4b, and 4c. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【００５９】
さらに、高周波回転方向切替部３は、回転角度計測センサ１から入力された現在回転位置の回転角度から予め設定された目標回転位置の目標角度に到達するために、より多くの回転制御を必要とする回転方向に対して、他の回転方向よりも優先的な交流電圧の印加を行うよう構成されてもよく、限られた数の圧電素子４ａ，４ｂ，４ｃを回転速度が要求される方向の回転に有効利用することが可能である。
【００６０】
加えて、高周波回転方向切替部３から圧電素子４ａ，４ｂ，４ｃに交流電圧が印加することで発生する機械的振動によって、多自由度超音波モータβの回転子５の回転駆動が誘起されて、例えば、各圧電素子４ａ，４ｂ，４ｃの固有振動数は、２０ｋＨｚを超えており、各圧電素子４ａ，４ｂ，４ｃを振動させるために、高周波回転方向切替部３から、各圧電素子４ａ，４ｂ，４ｃの固有振動数と同じ値の交流電圧の周波数を印加するよう機能構成されることで、エネルギー効率が高くなる。
【００６１】
（方法例）
続いて、以上のように構成された回転位置制御装置αを用いて、多自由度超音波モータβの回転子５の回転位置の制御を行う場合に適応される多自由度超音波モータの回転位置制御方法の具体例を説明する。
【００６２】
図４は、本発明の多自由度超音波モータの回転位置制御方法を説明するためのシーケンス図である。
【００６３】
同図に示すように、本形態例では、まず、回転角度計測センサ１において、多自由度超音波モータβの回転運動に伴う回転子５の現在回転位置を計測し（ＳＴ１）、次いでこの現在回転位置の計測値を出力された回転位置監視部２において、回転子５を、予め設定された目標回転位置に到達させるべく、固定子４を構成する圧電素子４ａ，４ｂ，４ｃに印加すべき交流電圧の振幅値を計算する（ＳＴ２）。
【００６４】
回転位置監視部２にて計算された振幅値は、振幅指令値として高周波回転方向切替部３に出力されて（ＳＴ３）、続いて、高周波回転方向切替部３において振幅指令値と同じ振幅を持ち、回転子５を回転させるために必要な位相差を持たせた複数相の交流電圧を圧電素子４ａ，４ｂ，４ｃに対して印加する（ＳＴ４）ことにより、回転子５の回転方向の制御を為す。
【００６５】
ここで、回転角度計測センサ１による現在回転位置の計測（ＳＴ１）は、例えば、予め設定された周期で回転子５の現在回転位置を計測（ＳＴ１´）して、計測された現在回転位置が目標回転位置に到達したかどうか確認して、到達した場合には処理を終了する一方、到達していない場合は、再度計測された現在回転位置を回転位置監視部２に出力する等の処理を繰り返す（ＳＴ５）ようにしても構わない。
【００６６】
また、振幅値の計算（ＳＴ２）は、回転角度計測センサ１から入力された現在回転位置から予め設定された目標回転位置までの到達に必要な回転角を、例えば、圧電素子４ａ，４ｂ，４ｃの励振される図２に示した座標軸の各軸をそれぞれ軸回転するピッチ方向、ロール方向及びヨー方向の回転方向の成分に分解して、これら回転方向の成分別に計算する。
【００６７】
加えて、振幅値の計算（ＳＴ２）は、回転子５の回転駆動に対して、予め目標回転角速度が設定された場合に、現在回転位置の計測を継続的に行う（ＳＴ１，ＳＴ１´，・・・）回転角度計測センサからの出力を継続的に監視して、現在回転位置の測定値から得られる回転角速度と計算された振幅値とを比較して、次に印加する交流電圧の振幅値を目標回転速度に達するように計算するようにしてもよい。
【００６８】
次に、図５は、本実施形態例における交流電圧の印加を説明するフロー図である。同図は、図４に示した交流電圧の印加（ＳＴ４）を詳細に説明するためのものである。
【００６９】
同図に示すとおり、高周波回転方向切替部３により行われる交流電圧の印加（ＳＴ４）は、まず、図４に示した回転位置監視部２からの振幅指令値の出力（ＳＴ３）により、ピッチ方向、ロール方向、ヨー方向の各成分方向の振幅指令値を受信する。
【００７０】
振幅指令値の受信（ＳＴ３）に引続き、本形態例では、受信した振幅指令値のそれぞれ対応する、互いに直交して異なる仮想三次元座標３軸方向の制御として、例えば、ピッチ方向回転制御（ＳＴ４ａ）、ロール方向回転制御（ＳＴ４ｂ）、ヨー方向回転制御（ＳＴ４ｃ）を行うものであり、それぞれの実施順は適宜設定されて構わず、これら仮想三次元座標３軸方向の回転制御（ＳＴ４ａ，ＳＴ４ｂ，ＳＴ４ｃ）は、それぞれが回転子５の回転加速所要時間よりも短い周期の高周波で切り替える。
【００７１】
また、ピッチ方向回転制御（ＳＴ４ａ）は、ピッチ方向たわみ振動発生用圧電素子４ａと上下方向伸縮振動発生用圧電素子４ｂとに交流電圧を印加するものであり、同様にして、ロール方向回転制御（ＳＴ４ｂ）は、上下方向伸縮振動発生用圧電素子４ｂとロール方向たわみ振動発生用圧電素子４ｃに、ヨー方向回転制御（ＳＴ４ｃ）は、ロール方向たわみ振動発生用圧電素子４ｃとピッチ方向たわみ振動発生用圧電素子４ａとにそれぞれ交流電圧を印加するものである。
【００７２】
このとき、それぞれ２つの圧電素子（４ａと４ｂ，４ｂと４ｃ，４ｃと４ａ）に印加する交流電圧は、９０度の位相差を持たせたものであり、印加する２つの圧電素子（４ａと４ｂ，４ｂと４ｃ，４ｃと４ａ）、位相及び振幅指令値を高速に切り替えることで、回転子５を目標回転位置に到達するまで行う。
【００７３】
なお、同図においては、まず、ピッチ方向回転制御（ＳＴ４ａ）、次いで、ロール方向回転制御（ＳＴ４ｂ）、引続き、ヨー方向回転制御（ＳＴ４ｃ）を順次行うことを示したが、高周波回転方向切替部３により圧電素子４ａ，４ｂ，４ｃに対して交流電圧の印加（ＳＴ４）が行われるときに、現在回転位置の計測（ＳＴ１´）で得た計測値を高周波回転方向切替部３に出力することで、交流電圧の印加（ＳＴ５）は、計測された現在回転位置の回転角度から目標回転位置の目標角度に到達するために、より多くの回転制御が必要な回転方向について、他の回転方向よりも優先的な制御を行うことができる。
【００７４】
即ち、ピッチ方向回転制御（ＳＴ４ａ）、ロール方向回転制御（ＳＴ４ｂ）、ヨー方向回転制御（ＳＴ４ｃ）の順番は優先される順であって構わず、また、予め設定された順であっても構わず、全ての方向の回転制御が終了したときには、ＳＴ４の処理を終了して、再度、振幅指令値の受信（ＳＴ３）を持つ。
【００７５】
なお、本実施例の回転制御（ＳＴ４ａ，ＳＴ４ｂ，ＳＴ４ｃ）は、それぞれのその切替を一定時間ごとに行い、回転制御（ＳＴ４ａ，ＳＴ４ｂ，ＳＴ４ｃ）方向の切替時間は、適用される多自由度超音波モータβの加速特性を考慮して決定される。
【００７６】
例えば、多自由度超音波モータβの各圧電素子４ａ，４ｂ，４ｃに一定振幅の交流電圧を印加し始めてから、回転子５の回転速度が一定の速度に安定するまでの時間が１０数ミリ秒である場合には、高周波回転方向切替部３における回転方向の切替時間は５ミリ秒よりも小さな値が好ましい。
【００７７】
続いて、図６は、本実施形態例を適用される回転子頭頂点の回転駆動における回転軌跡を示す図である。
【００７８】
同図に示すように、例えば、その回転軸を軸Ａとする回転駆動を誘起される場合に、球状の回転子５の頭頂点５ａは、以上のような回転制御により、ロール方向、ピッチ方向及びヨー方向の回転駆動を誘起される固定子４の上端面において、ロール方向、ピッチ方向及びヨー方向の仮想三次元座標３軸のそれぞれ軸回転方向の例えば、同図の一点鎖線矢印で示すような微小回転駆動の合成経路Ｂとして駆動される。
【００７９】
しかしながら、本発明方法に適用される回転方向の切替周波数は、十分に高いために、同図に図示するほどの大きさのギザギザな形状の経路Ｂではなく、点線で示すような円形の頭頂点５ａの回転軌跡Ｃに近いものとなる。
【００８０】
以上、本発明の実施の形態につき、本発明を多自由度超音波モータαに適用した場合を例に挙げて説明したが、本発明は、必ずしも上述した手段にのみ限定されるものではなく、後述する効果を有する範囲内において、適宜、変更実施することが可能なものである。
【００８１】
【発明の効果】
以上、詳細に説明したように、本発明によれば、回転子と固定子間の摩擦力の物理学的特性の複雑さや、多自由度超音波モータの長時間の運転に伴う変化に起因する悪影響や、多自由度超音波モータ間の個体差の影響を受けない、多自由度超音波モータの回転位置制御が可能となる。
【図面の簡単な説明】
【図１】本発明の一実施形態例に係る装置例としての多自由度超音波モータの回転位置制御装置の内部構成図である。
【図２】同上した回転位置制御装置が適用される多自由度超音波モータの外観斜視図である。
【図３】同上した回転位置制御装置が適用された多自由度超音波モータの動作原理を説明する図である。
【図４】本発明の多自由度超音波モータの回転位置制御方法を説明するためのシーケンス図である。
【図５】同上した回転位置制御方法における交流電圧の印加を説明するフロー図である。
【図６】同上した回転位置制御方法が適用される多自由度超音波モータの回転子頭頂点の回転駆動における回転軌跡を示す図である。
【符号の説明】
α…回転位置制御装置
β…多自由度超音波モータ
１…回転角度計測センサ
２…回転位置監視部
３…高周波回転方向切替部
４…固定子
４ａ…ピッチ方向たわみ振動発生用圧電素子
４ｂ…上下方向伸縮振動発生用圧電素子
４ｃ…ロール方向たわみ振動発生用圧電素子
５…回転子
５ａ…頭頂点
Ａ…軸
Ｂ…ロール方向、ピッチ方向、ヨー方向の回転駆動の合成経路
Ｃ…頭頂点の回転軌跡[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method and apparatus for controlling the rotational position of a multi-degree-of-freedom ultrasonic motor, and more particularly, to control the rotational position of a rotor by applying an AC voltage to a piezoelectric element of a stator to generate a desired rotational movement. The present invention relates to a rotation position control method for a multi-degree-of-freedom ultrasonic motor applied to the above-described operation and a rotation position control device directly used for implementing the method.
[0002]
[Prior art]
2. Description of the Related Art In recent years, it has been expected that a multi-degree-of-freedom ultrasonic motor that is space-saving, has a high torque, and has a high level of silence, is used as an actuator applied to a part that requires high torque and high degree of freedom.
[0003]
For example, the conventional one-degree-of-freedom rotary type is used as an indirect mechanism of a humanoid robot, particularly a mechanism that needs to vertically support a heavy object so that the posture can be changed in multiple degrees of freedom, such as a neck part. The application of a multi-degree-of-freedom ultrasonic motor is expected to replace the electromagnetic servo motor.
[0004]
Here, the multi-degree-of-freedom ultrasonic motor includes, for example, a stator having a configuration in which a plurality of piezoelectric elements having different vibration directions are stacked, and a spherical rotor closely attached to the stator. When alternating currents of the same frequency and different phases are applied to the piezoelectric element of the stator of the ultrasonic motor, natural vibrations are excited in the piezoelectric element, and the rotor performs three degrees of freedom rotation by a combination of these natural vibration modes. .
[0005]
As described above, in order to appropriately drive the multi-degree-of-freedom ultrasonic motor that performs three-degree-of-freedom rotation, appropriate control means is required. As such control means, each piezoelectric element constituting the stator is used. There has been proposed a method of controlling a phase difference of an AC voltage applied to an AC power supply. In the above method, the control signal is determined by using a motion model that holds information on an angle value in the rotation direction of the rotor with respect to a vector value formed by a phase difference value of each input signal.
[0006]
The details of the multi-degree-of-freedom ultrasonic motor rotation position control are described in Non-Patent Document 1 below.
[0007]
[Non-patent document 1]
K. Takemura, T .; Maeno, "Control of Multi-DOF Ultrasonic Motor using Neural Network based Inverse Model", Proceedings of 2002, 2002, International Conference of International Conference of International Conferences.
[0008]
[Problems to be solved by the invention]
By the way, the physical characteristics of the frictional force on the surface where the rotor and the stator of the multi-degree-of-freedom ultrasonic motor are in contact are complicated and vary depending on various factors. Therefore, it is very difficult to estimate the motion model required for controlling the rotation direction, and to apply the control using the motion model to a long-time operation, it is necessary to use a multi-degree-of-freedom ultrasonic motor during operation. The exercise model must be updated.
[0009]
However, it is difficult to efficiently update the motion model expressing multi-degree-of-freedom motion in real time, and multi-degree-of-freedom ultrasonic motors have individual differences in the physical characteristics between the rotor and stator. Therefore, there is a problem that a motion model must be prepared for each multi-degree-of-freedom ultrasonic motor.
[0010]
Here, the main objects to be solved by the present invention are as follows.
[0011]
That is, a first object of the present invention is to provide a method and apparatus for controlling the rotational position of a multi-degree-of-freedom ultrasonic motor capable of controlling the rotational positions of three degrees of freedom of a multi-degree-of-freedom ultrasonic motor without using a motion model. It will not be provided.
[0012]
A second object of the present invention is to provide a multi-degree-of-freedom ultrasonic motor capable of operating for a long time and expressing multiple degrees of freedom without being affected by changes in characteristics of a frictional force between a rotor and a stator. And a method and apparatus for controlling the rotational position of a multi-degree-of-freedom ultrasonic motor.
[0013]
A third object of the present invention is to provide a method and apparatus for controlling the rotational position of a multi-degree-of-freedom ultrasonic motor that can be applied regardless of individual differences between the multi-degree-of-freedom ultrasonic motors.
[0014]
Other objects of the present invention will become apparent from the description of the specification, drawings, and particularly from the claims.
[0015]
[Means for Solving the Problems]
First, in the method of the present invention, first, the current rotational position of the rotor associated with the rotational motion is measured, and then the stator is moved from the measured value so that the rotor reaches a preset target rotational position. Calculate the amplitude value of the AC voltage to be applied to the piezo element to be configured, and then give the piezo element the same amplitude value as the amplitude value and the phase difference necessary to rotate the rotor. A characteristic configuration technique of controlling the rotation direction of the rotor by applying a plurality of phases of AC voltages.
[0016]
On the other hand, in the device of the present invention, the rotation angle measurement sensor that measures the current rotation position of the rotor accompanying the rotation motion, and the rotor is set in advance from the measurement value of the current rotation position measured by the rotation angle measurement sensor. A rotation position monitoring unit that calculates the amplitude value of the AC voltage applied to the piezoelectric element and outputs the amplitude value as an amplitude command value so as to reach the target rotation position, and the amplitude input from the rotation position monitoring unit. A high frequency rotation direction switching unit that outputs to the piezoelectric element a plurality of AC voltages having the same amplitude value as the command value and having a phase difference necessary for rotating the rotor. Take configuration steps.
[0017]
More specifically, in solving the problem, the present invention has been made to achieve the above object by adopting new characteristic constitution means ranging from a superordinate concept to a subordinate concept listed below. You.
[0018]
That is, a first feature of the method of the present invention is that a stator constituted by a plurality of stacked piezoelectric elements that excite a plurality of natural vibrations having the same natural frequency when an AC voltage having a different phase is applied, And a rotor that is driven to rotate in an arbitrary direction by the natural vibration of the stator.In a multi-degree-of-freedom ultrasonic motor, a piezoelectric element of the stator is used to generate a desired rotational motion. A method of controlling the rotational position of the rotor by applying the AC voltage to the rotor, first measuring the current rotational position of the rotor associated with the rotational movement, then, from the measured value, the rotation In order to make the stator reach a preset target rotation position, the amplitude value of the AC voltage to be applied to the piezoelectric element constituting the stator is calculated, and then, for the piezoelectric element, the amplitude value is calculated. Same as A multi-degree-of-freedom ultrasonic motor having a width value and controlling the rotation direction of the rotor by applying a plurality of phases of AC voltages having a phase difference necessary for rotating the rotor. The present invention resides in adopting a configuration of a rotation position control method.
[0019]
According to a second aspect of the method of the present invention, the application of the AC voltages of the plurality of phases in the first aspect of the present invention excites the natural vibrations in three directions of virtual three-dimensional coordinates which are orthogonal to each other. The output of the AC voltage to the piezoelectric element is switched at a high frequency having a cycle shorter than the rotation acceleration required time of the rotor, and the natural vibration of the virtual three-dimensional coordinate three-axis direction is applied to each of the plurality of piezoelectric elements. The present invention resides in adopting a configuration of a rotation position control method for a multi-degree-of-freedom ultrasonic motor, which is obtained by applying the AC voltage for exciting either one.
[0020]
According to a third aspect of the method of the present invention, the application of the multi-phase AC voltage in the first or second aspect of the above-described method of the present invention is performed by applying a z-axis to a position vertically above a contact end face of the stator with the rotor. A roll-direction flexural vibration generating piezoelectric element that rotates about the x-axis, and that excites the natural vibrations in the three-dimensional virtual three-dimensional coordinate system, which comprises x, y, and z axes that are orthogonal to each other. The piezoelectric element for generating a vertical expansion / contraction vibration that expands / contracts in the z-axis direction and the piezoelectric element for generating a flexural vibration in a pitch direction that rotates about the y-axis are repeated until the target rotation position is reached. The present invention is to adopt a configuration of a rotation position control method for a multi-degree-of-freedom ultrasonic motor, which controls the rotation direction by applying the AC voltage and synthesizing the natural vibration to be excited.
[0021]
A fourth feature of the method of the present invention is that the calculation of the amplitude value in the third feature of the method of the present invention is performed by using the rotation required to reach the target rotation position from the current rotation position on the virtual three-dimensional coordinates. The angle is decomposed into components in a pitch direction, a roll direction, and a yaw direction in which the x, y, and z axes excited by the piezoelectric element are respectively rotated, and the amplitude value of the AC voltage is divided into three components. The present invention resides in adopting a configuration of a rotational position control method of a multi-degree-of-freedom ultrasonic motor, which is calculated for each component in the rotational direction.
[0022]
A fifth feature of the method of the present invention is that, in the third or fourth feature of the above-described method of the present invention, the application of the AC voltages of the plurality of phases corresponds to the virtual three-dimensional coordinate three-dimensional natural vibrations which are orthogonal to each other. When excited, the roll-direction bending vibration generating piezoelectric element that bends in the direction of rotating the x-axis, the vertical stretching vibration-generating piezoelectric element that expands and contracts in the z-axis direction, and rotates the y-axis. The AC voltage is applied to each of the two types of piezoelectric elements by giving a phase difference of 90 degrees to the two types of piezoelectric elements among the pitch direction bending vibration generating piezoelectric elements that bend in the direction. A multi-degree-of-freedom ultrasonic motor, wherein the two types of piezoelectric elements to be applied and the phase and amplitude of the AC voltage applied to the piezoelectric elements are switched to cause the rotor to reach the target rotational position. of Rolling in the configuration adopted position control method.
[0023]
A sixth feature of the method of the present invention is that the calculation of the amplitude value in the first, second, third, fourth or fifth feature of the method of the present invention is performed in advance with respect to the rotational driving of the rotor. When the target rotational angular velocity is set, by continuously measuring the rotational position, the rotational angular velocity of the rotor is monitored in association with the AC voltage applied to the piezoelectric element. By comparing the rotational angular velocity and the AC voltage, the amplitude value of the AC voltage to be applied next is calculated so as to reach the target rotational speed. In configuration adoption.
[0024]
A seventh feature of the method of the present invention is that the control of the rotation direction of the rotor according to the first, second, third, fourth, fifth or sixth feature of the method of the present invention is performed by changing the rotation direction of the current rotational position. In order to reach the target angle of the target rotation position from the rotation angle, for a rotation direction that requires more rotation control, by performing preferential control over other rotation directions, a multi-degree-of-freedom ultrasonic motor The present invention resides in adopting a configuration of a rotation position control method.
[0025]
An eighth feature of the method of the present invention is that the application of the multi-phase AC voltage according to the first, second, third, fourth, fifth, sixth or seventh feature of the method of the present invention is performed by the piezoelectric device. The present invention resides in the configuration of a method of controlling the rotational position of a multi-degree-of-freedom ultrasonic motor, in which the AC voltage is applied to the piezoelectric element with the same value as the natural frequency of the element as the frequency.
[0026]
On the other hand, the first feature of the device of the present invention is that a stator constituted by a plurality of stacked piezoelectric elements that excite a plurality of natural vibrations having the same natural frequency when an AC voltage having a different phase is applied, And a rotor that is rotatably driven in an arbitrary direction by the natural vibration of the stator, and a multi-degree-of-freedom ultrasonic motor configured to generate a desired rotational motion in the multi-degree-of-freedom ultrasonic motor. A rotation position control device for a degree ultrasonic motor, comprising: a rotation angle measurement sensor for measuring a current rotation position of the rotor associated with the rotation motion; and a measurement of the current rotation position measured by the rotation angle measurement sensor. In order to cause the rotor to reach a preset target rotation position from the value, a rotation position at which the amplitude value of the AC voltage applied to the piezoelectric element is calculated and the amplitude value is output as an amplitude command value The viewing unit and the plurality of AC voltages having the same amplitude value as the amplitude command value input from the rotation position monitoring unit and having a phase difference necessary for rotating the rotor, And a high-frequency rotation direction switching unit for outputting the rotation position of the multi-degree-of-freedom ultrasonic motor.
[0027]
A second feature of the present invention device is that the high-frequency rotation direction switching unit in the first feature of the present invention device outputs the AC voltage at a high frequency having a cycle shorter than the required rotation acceleration time of the rotor. Another object of the present invention is to adopt a configuration of a rotational position control device for a multi-degree-of-freedom ultrasonic motor, which is configured to be capable of switching output.
[0028]
A third feature of the device of the present invention is that the high-frequency rotation direction switching unit in the first or second feature of the device of the present invention is arranged such that a z-axis is a position vertically above a contact end face of the stator with the rotor. A piezoelectric element for generating a flexural vibration in a roll direction that excites the natural vibrations in three directions of virtual three-dimensional coordinates composed of x, y, and z axes that are orthogonal to each other and bends in a direction in which the x axis is axially rotated; The AC voltage is applied to each of the piezoelectric element for generating a vertical expansion / contraction vibration that expands and contracts in the z-axis direction and the piezoelectric element for generating a bending vibration in a pitch direction that bends in the direction of rotating the y-axis. The present invention resides in adopting a configuration of a rotational position control device of a multi-degree-of-freedom ultrasonic motor, which is connected as possible.
[0029]
A fourth feature of the present invention device is the rotation feature monitor according to the third feature of the present invention device, wherein the rotation position monitoring unit performs rotation necessary to reach the target rotation position from the current rotation position on the virtual three-dimensional coordinates. The angle is decomposed into components in rotation directions of a roll direction, a pitch direction, and a yaw direction that respectively rotate the x, y, and z axes excited by the piezoelectric element, and the amplitude value of the AC voltage is divided into three components. A rotational position control device for a multi-degree-of-freedom ultrasonic motor, which is configured so as to be capable of calculating for each component in the rotational direction and outputting the calculated amplitude values as the three amplitude command values to the high-frequency rotational direction switching unit. Configuration.
[0030]
A fifth feature of the device of the present invention is that the rotation position monitoring unit according to the fourth feature of the device of the present invention is configured such that the rotor rotates the target rotation in each of the roll direction, the pitch direction, and the yaw direction. When the position reaches the position, a voltage value of 0 V is output as the amplitude command value in the rotation direction, and when a further rotation angle is required to the target rotation position, the voltage is set in advance to the piezoelectric element. Another aspect of the present invention resides in the adoption of a configuration of a rotational position control device for a multi-degree-of-freedom ultrasonic motor, which is configured to output the output voltage value as the amplitude command value.
[0031]
A sixth feature of the device of the present invention is that the high-frequency rotation direction switching unit according to the third, fourth, or fifth feature of the device of the present invention is configured such that the high-frequency rotation direction switching unit includes A functional configuration for inducing a rotational drive for rotating the rotor in the roll direction on the stator by applying the AC voltage having a phase difference of 90 degrees to the generating piezoelectric element, respectively. Another object of the present invention is to adopt a configuration of a rotational position control device for a multi-degree-of-freedom ultrasonic motor.
[0032]
A seventh feature of the device of the present invention is that the high-frequency rotation direction switching unit according to the third, fourth, fifth, or sixth feature of the device of the present invention is arranged such that the high-frequency rotation direction switching unit includes By applying each of the AC voltages having a phase difference of 90 degrees to the piezoelectric element for generating directional expansion and contraction vibration, a rotational drive for rotating the rotor in the pitch direction is induced on the stator. The present invention resides in adopting a configuration of a rotational position control device for a multi-degree-of-freedom ultrasonic motor having such a functional configuration.
[0033]
An eighth feature of the device of the present invention resides in that the high-frequency rotation direction switching unit in the third, fourth, fifth, sixth or seventh feature of the above-described device of the present invention is configured such that A rotational drive for rotating the rotor in the yaw direction on the stator by applying the AC voltage having a phase difference of 90 degrees to the roll direction flexural vibration generating piezoelectric element. And a rotation position control device for a multi-degree-of-freedom ultrasonic motor, which is configured so as to induce the vibration.
[0034]
A ninth feature of the device of the present invention is that the high-frequency rotation direction switching unit in the sixth, seventh, or eighth feature of the device of the present invention inverts a 90-degree phase difference between the two AC voltages. Another aspect of the present invention resides in the adoption of a rotation position control device for a multi-degree-of-freedom ultrasonic motor, which is functionally configured to apply the AC voltage that induces a negative rotation drive to the rotor.
[0035]
A tenth feature of the device of the present invention is that the rotation position monitoring unit in the first, second, third, fourth, fifth, sixth, seventh, eighth or ninth feature of the above-described device of the present invention When a target rotational angular velocity is set in advance for the rotational driving of the rotor, the measured value output from the rotational angle measurement sensor corresponds to the AC voltage output from the high frequency rotation direction switching unit. The rotational position control of the multi-degree-of-freedom ultrasonic motor, which is configured so as to be continuously held and configured so that the amplitude value of the AC voltage applied to the piezoelectric element can be adjusted to reach the target rotational speed. The configuration of the device is adopted.
[0036]
An eleventh feature of the device of the present invention is the high-frequency rotation according to the first, second, third, fourth, fifth, sixth, seventh, eighth, ninth, or tenth feature of the device of the present invention. The direction switching unit has a higher priority than the other rotation directions for the rotation direction that requires more rotation control to reach the target angle of the target rotation position from the rotation angle of the current rotation position. The present invention resides in adopting a configuration of a rotational position control device for a multi-degree-of-freedom ultrasonic motor, which is functionally configured to apply the AC voltage.
[0037]
The twelfth feature of the device of the present invention is the same as the first, second, third, fourth, fifth, sixth, seventh, eighth, ninth, tenth, or eleventh feature of the device of the present invention. The high-frequency rotation direction switching unit is configured to apply a frequency of the AC voltage having the same value as the natural frequency of the piezoelectric element to the piezoelectric element. In configuration adoption.
[0038]
BEST MODE FOR CARRYING OUT THE INVENTION
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings, in which an example of an apparatus and an example of a method are applied to a multi-degree-of-freedom ultrasonic motor having a spherical rotor. I do.
[0039]
(Example of device)
First, FIG. 1 is an internal configuration diagram of a rotation position control device of a multi-degree-of-freedom ultrasonic motor as an example of a device according to an embodiment of the present invention, and FIG. FIG. 3 is an external perspective view of the multi-degree-of-freedom ultrasonic motor, in which coordinate axes shown in FIG. 2 are orthogonally different x and x, respectively, where the z-axis is a vertical direction above a contact end face of the stator 4 with the rotor 5. A virtual three-dimensional coordinate system including the y and z axes is provided.
[0040]
The rotational position control device α according to the present example is applied to, for example, a multi-degree-of-freedom ultrasonic motor β as shown in FIG. 2, and the multi-degree-of-freedom ultrasonic motor β is unique when an AC voltage having a different phase is applied. A stator 4 composed of a plurality of stacked piezoelectric elements for exciting a plurality of natural vibrations having the same frequency, and holding a load (not shown) and rotating in an arbitrary direction by the natural vibration of the stator 4 And a driven rotor 5.
[0041]
As shown in the figure, the stator 4 firstly includes a pitch-direction bending vibration generating piezoelectric element 4a that bends in a pitch direction in a direction of axial rotation around the y-axis when an AC voltage is applied, It comprises a piezoelectric element 4b for generating vertical stretching vibration that expands and contracts in the positive and negative directions of the z-axis, and a piezoelectric element 4c for generating bending vibration in the roll direction that bends in the roll direction in which the axis rotates about the x-axis.
[0042]
On the other hand, the rotor 5 is, for example, spherical, and is mounted on the upper end surface of the stator 4, and the multi-degree-of-freedom ultrasonic motor β A multi-degree-of-freedom ultrasonic motor that is capable of generating a high torque capable of maintaining the rotational position at that time without applying a voltage to each of the piezoelectric elements 4a, 4b, and 4c, and performing a rotational motion. Even if the voltage applied to the piezoelectric elements 4a, 4b, 4c of β is suddenly dropped to 0 V, for example, the rotor 5 has a characteristic that the rotation of the rotor 5 is stopped within ten and several milliseconds.
[0043]
On the other hand, as shown in FIG. 2, the rotation position control device α of the present invention includes a rotation angle measurement sensor 1 for measuring a current rotation position of the rotor 5 associated with the rotation motion, and a current rotation measured by the rotation angle measurement sensor 1. The amplitude value of the AC voltage applied to the piezoelectric elements 4a, 4b, 4c is calculated from the measured position value so that the rotor 5 reaches the preset target rotation position, and this amplitude value is output as an amplitude command value. A rotational position monitor 2 and a plurality of AC voltages having the same amplitude value as the amplitude command value input from the rotational position monitor 2 and having a phase difference necessary for rotating the rotor 5 are applied to the piezoelectric element. 4a, 4b, and 4c.
[0044]
Here, the rotation angle measurement sensor 1, for example, can measure the rotation position of the rotor 5 at any time, and uses the measured rotation position, which is a measurement value indicating the measured current rotation position of the rotor 5, as the rotation position. The monitoring unit 2 and the high frequency rotation direction switching unit 3 can be output at any time.
[0045]
On the other hand, the rotation position monitoring unit 2 calculates the rotation angles required to reach the preset target rotation position from the current rotation position input from the rotation angle measurement sensor 1 as x, y, z shown in FIG. Each coordinate axis of the coordinates is decomposed into rotational components of a roll direction, a pitch direction, and a yaw direction for rotating the axes, and the amplitude values of the AC voltage applied to the piezoelectric elements 4a, 4b, and 4c are divided into three rotational directions. Each of the components is calculated, and the calculated amplitude values are output to the high frequency rotation direction switching unit 3 as three amplitude command values.
[0046]
When the rotor 5 reaches the target rotation position in each of the roll direction, the pitch direction, and the yaw direction, the rotation position monitoring unit 2 outputs a voltage as an amplitude command value for the rotation direction. When a value of 0 V is output and the target rotational position is not reached, a constant voltage value of a magnitude that can be applied to the piezoelectric elements 4a, 4b, and 4c is output as an amplitude command value.
[0047]
Further, when a target rotation speed in each direction of the multi-degree-of-freedom ultrasonic motor β is given, the rotation position monitoring unit 2 outputs an amplitude value of the applied AC voltage corresponding to the target rotation speed as an amplitude command value. By doing so, the rotation speed of the rotor 5 can be controlled.
[0048]
At this time, if an appropriate value of the applied AC voltage with respect to the target rotational speed is unknown, the rotational angular speed of the rotor 5 is continuously monitored based on the measured value of the current rotational position input from the rotational angle measurement sensor 1. The value of the applied AC voltage is adjusted by feedback control using the measured value of the rotation speed of the rotor 5 to control the rotation angular speed.
[0049]
On the other hand, the high-frequency rotation direction switching unit 3 switches and outputs the output of the AC voltage applied to the piezoelectric elements 4a, 4b, and 4c at a high frequency having a cycle shorter than the rotation acceleration required time of the rotor 5, and outputs the AC voltage. Is configured to be capable of outputting independently to each of the piezoelectric elements 4a, 4b, 4c, for example.
[0050]
FIG. 3 is a diagram for explaining the operation principle of the multi-degree-of-freedom ultrasonic motor to which the rotational position control device of the present invention is applied. In FIG. 3, a forward rotation in the pitch direction is shown as an example.
[0051]
As shown in the drawing, the rotation of the rotor 5 in the pitch direction includes an alternating current controlled by the high frequency rotation direction switching unit 3 with the pitch direction bending vibration generating piezoelectric element 4a and the vertical direction expansion / contraction vibration generating piezoelectric element 4b. A voltage is applied, and the phase difference of the applied AC voltage at this time is, for example, 90 degrees, and the induced piezoelectric vibration element 4a for generating the bending vibration in the pitch direction and the piezoelectric element 4b for generating the expansion / contraction vibration in the vertical direction are induced by this. Mechanical vibration also has a similar phase difference.
[0052]
Therefore, the flexural vibration in the pitch direction and the expansion and contraction movement in the vertical direction are combined with a phase difference of 90 degrees, and the upper end surface of the stator 4 is exposed to the rotation in the pitch direction. This rotational drive is transmitted to the rotor 5 by the frictional force between the stator 4 and the rotor 5, and rotation in the pitch direction is induced in the rotor 5.
[0053]
Here, for example, first, FIG. 3A shows that the rotor 5 is driven to rotate in the positive direction of the pitch direction by bending in the direction shown by the one-dot chain arrow in the pitch direction bending vibration generating piezoelectric element 4a. FIG. 3B shows the initial state, and FIG. 3B shows the friction for transmitting the rotational drive from the stator 4 to the rotor 5 when the vertical expansion / contraction vibration generating piezoelectric element 4b is extended in the vertical direction. 3 (3) shows that the rotor 5 is moved from the position shown in FIG. 3 (1) by bending in the direction indicated by a dashed line in the pitch direction bending vibration generating piezoelectric element 4a. FIG. 3D shows a state in which the piezoelectric element 4 b for generating the vertical stretching vibration is contracted and the rotational driving force is transmitted from the stator 4 to the rotor 5. Indicating the state in which is suppressed A.
[0054]
3 (1), (2), (3) and (4), for example, as shown in FIG. 3, the applied piezoelectric elements 4a, 4b are, for example, shorter than the time required for the rotational acceleration of the rotor 5. The piezoelectric element 4b for generating vertical stretching vibration is rotated from the stator 4 when it is vertically extended as shown in FIG. 3 (2). The rotational drive is transmitted to the stator 5, while the rotational drive from the stator 4 to the rotor 5 is not transmitted during the contraction shown in FIG. The order of the phase difference of the AC voltage applied to the piezoelectric elements 4a, 4b, 4c to be excited can be appropriately combined in accordance with a preset target rotation position.
[0055]
Similarly, in order to rotate the rotor 5 in the roll direction, the high-frequency rotation direction switching unit 3 sets the piezoelectric element 4b for generating expansion / contraction vibration in the up-down direction and the piezoelectric element 4c for generating flexural vibration in the roll direction into 90. By applying an AC voltage having a phase difference of each degree, a rotational drive for rotating the rotor 5 in the roll direction is induced in the stator 4, and in the yaw direction, a piezoelectric element for generating flexural vibration in the pitch direction is generated. It is configured to apply to the element 4a and the roll-direction bending vibration generating piezoelectric element 4c, and to apply to the two piezoelectric elements 4a and 4b, 4b and 4c or 4c and 4a in any direction of rotation. I do.
[0056]
Further, in order to reverse the direction of rotation, the sign of the value of the phase difference between the two applied AC voltages may be inverted, and the rotation speed can be controlled by the amplitude value of the applied AC voltage. is there.
[0057]
Here, Table 1 shows the phase difference of the voltage applied to each piezoelectric element 4a, 4b, 4c in each rotation direction.
[0058]
[Table 1]

[0059]
Furthermore, the high-frequency rotation direction switching unit 3 needs more rotation control to reach a preset target rotation position target angle from the current rotation position rotation angle input from the rotation angle measurement sensor 1. The rotation direction may be configured such that an AC voltage is applied with a higher priority than the other rotation directions, and a limited number of piezoelectric elements 4a, 4b, 4c are driven in a direction requiring a rotation speed. It can be used effectively for rotation.
[0060]
In addition, the rotational drive of the rotor 5 of the multi-degree-of-freedom ultrasonic motor β is induced by mechanical vibration generated when an AC voltage is applied from the high frequency rotation direction switching unit 3 to the piezoelectric elements 4a, 4b, 4c. For example, the natural frequency of each of the piezoelectric elements 4a, 4b, 4c exceeds 20 kHz, and the high-frequency rotation direction switching unit 3 sends the piezoelectric elements 4a, 4a, 4c to vibrate the piezoelectric elements 4a, 4b, 4c. By configuring so as to apply a frequency of an AC voltage having the same value as the natural frequency of 4b, 4c, energy efficiency is increased.
[0061]
(Example of method)
Subsequently, the rotation of the multi-degree-of-freedom ultrasonic motor adapted to control the rotational position of the rotor 5 of the multi-degree-of-freedom ultrasonic motor β by using the rotational position control device α configured as described above. A specific example of the position control method will be described.
[0062]
FIG. 4 is a sequence diagram for explaining the rotational position control method of the multi-degree-of-freedom ultrasonic motor of the present invention.
[0063]
As shown in the figure, in the present embodiment, first, the rotation angle measurement sensor 1 measures the current rotational position of the rotor 5 associated with the rotational movement of the multi-degree-of-freedom ultrasonic motor β (ST1), and then measures the current rotational position. In the rotation position monitoring unit 2 to which the measured value of the rotation position has been output, the rotor 5 should be applied to the piezoelectric elements 4a, 4b, 4c constituting the stator 4 in order to reach the preset target rotation position. The amplitude value of the AC voltage is calculated (ST2).
[0064]
The amplitude value calculated by the rotation position monitoring unit 2 is output to the high frequency rotation direction switching unit 3 as an amplitude command value (ST3), and subsequently, the high frequency rotation direction switching unit 3 has the same amplitude as the amplitude command value. By applying a plurality of AC voltages having a phase difference necessary for rotating the rotor 5 to the piezoelectric elements 4a, 4b, 4c (ST4), the rotation direction of the rotor 5 is controlled. Do
[0065]
Here, the measurement of the current rotation position by the rotation angle measurement sensor 1 (ST1) is performed, for example, by measuring the current rotation position of the rotor 5 at a preset cycle (ST1 '), and determining the measured current rotation position. It is checked whether or not the target rotational position has been reached. If the target rotational position has been reached, the processing is terminated. If not, processing such as outputting the measured current rotational position again to the rotational position monitoring unit 2 is performed. The process may be repeated (ST5).
[0066]
The calculation of the amplitude value (ST2) is performed by calculating the rotation angle required to reach from a current rotation position input from the rotation angle measurement sensor 1 to a preset target rotation position, for example, the piezoelectric elements 4a, 4b, 4c. Each of the coordinate axes shown in FIG. 2 to be excited is decomposed into components in the rotation directions of the pitch direction, the roll direction, and the yaw direction, and the calculation is performed for each of these rotation direction components.
[0067]
In addition, in the calculation of the amplitude value (ST2), the current rotation position is continuously measured when the target rotation angular velocity is set in advance for the rotation driving of the rotor 5 (ST1, ST1 ',...). ..) The output from the rotation angle measurement sensor is continuously monitored, the rotation angular velocity obtained from the measured value of the current rotation position is compared with the calculated amplitude value, and the amplitude value of the AC voltage to be applied next is calculated. May be calculated so as to reach the target rotation speed.
[0068]
Next, FIG. 5 is a flowchart illustrating application of an AC voltage in the present embodiment. This figure is for describing in detail the application of the AC voltage (ST4) shown in FIG.
[0069]
As shown in the figure, the application of the AC voltage (ST4) performed by the high frequency rotation direction switching unit 3 is performed by first outputting the amplitude command value from the rotation position monitoring unit 2 (ST3) shown in FIG. , The amplitude command value in each component direction of the roll direction and the yaw direction is received.
[0070]
Subsequent to the reception of the amplitude command value (ST3), in the present embodiment, for example, pitch direction rotation control (ST4a) may be used as control in the virtual three-dimensional coordinate three-axis directions different from each other and corresponding to the received amplitude command value. ), Roll direction rotation control (ST4b), and yaw direction rotation control (ST4c), and the order of execution may be set as appropriate. , ST4c) are switched at a high frequency with a cycle shorter than the required rotation acceleration time of the rotor 5.
[0071]
In the pitch direction rotation control (ST4a), an AC voltage is applied to the pitch direction bending vibration generating piezoelectric element 4a and the vertical direction expansion / contraction vibration generating piezoelectric element 4b. Similarly, the roll direction rotation control (ST4a) is performed. ST4b) controls the piezoelectric element 4b for generating vertical expansion / contraction vibration and the piezoelectric element 4c for generating bending vibration in the roll direction. An AC voltage is applied to each of the piezoelectric elements 4a.
[0072]
At this time, the AC voltage applied to each of the two piezoelectric elements (4a and 4b, 4b and 4c, 4c and 4a) has a phase difference of 90 degrees, and the two applied piezoelectric elements (4a and 4a) 4b, 4b and 4c, and 4c and 4a), the phase and amplitude command values are switched at high speed until the rotor 5 reaches the target rotational position.
[0073]
In the figure, the pitch direction rotation control (ST4a), the roll direction rotation control (ST4b), and subsequently the yaw direction rotation control (ST4c) are sequentially performed. When the AC voltage is applied to the piezoelectric elements 4a, 4b, and 4c (ST4) by ST3, the measurement value obtained in the current rotation position measurement (ST1 ') is output to the high-frequency rotation direction switching unit 3. In the AC voltage application (ST5), the rotation direction requiring more rotation control in order to reach the target angle of the target rotation position from the measured rotation angle of the current rotation position is higher than the other rotation directions. Can also perform preferential control.
[0074]
That is, the order of the pitch direction rotation control (ST4a), the roll direction rotation control (ST4b), and the yaw direction rotation control (ST4c) may be in the order of priority, or may be in a preset order. On the other hand, when the rotation control in all the directions is completed, the process of ST4 is terminated, and the process again has the reception of the amplitude command value (ST3).
[0075]
In the rotation control (ST4a, ST4b, ST4c) of the present embodiment, the switching is performed at regular time intervals, and the switching time in the rotation control (ST4a, ST4b, ST4c) direction exceeds the applicable multi-degree of freedom. It is determined in consideration of the acceleration characteristics of the sound wave motor β.
[0076]
For example, the time from the start of applying an AC voltage having a constant amplitude to each of the piezoelectric elements 4a, 4b, and 4c of the multi-degree-of-freedom ultrasonic motor β until the rotation speed of the rotor 5 stabilizes to a constant speed is about ten millimeters. In the case of seconds, the switching time of the rotation direction in the high-frequency rotation direction switching unit 3 is preferably a value smaller than 5 milliseconds.
[0077]
Next, FIG. 6 is a diagram illustrating a rotation trajectory in the rotation driving of the top of the rotor to which the present embodiment is applied.
[0078]
As shown in the figure, for example, when a rotational drive with the rotation axis as the axis A is induced, the top apex 5a of the spherical rotor 5 is controlled in the roll direction and the pitch direction by the above-described rotation control. On the upper end surface of the stator 4 induced to rotate in the yaw direction, the three-dimensional virtual three-dimensional coordinates in the roll direction, the pitch direction, and the yaw direction are respectively indicated by the dashed-dotted arrows in FIG. It is driven as a synthesis path B of a minute rotation drive.
[0079]
However, since the switching frequency in the rotation direction applied to the method of the present invention is sufficiently high, it is not a jagged path B as large as shown in FIG. The rotation locus C of FIG.
[0080]
As described above, the embodiment of the present invention has been described by exemplifying a case where the present invention is applied to a multi-degree-of-freedom ultrasonic motor α, but the present invention is not necessarily limited to only the above-described means, Changes can be made as appropriate within a range having the effects described below.
[0081]
【The invention's effect】
As described above in detail, according to the present invention, the physical characteristics of the frictional force between the rotor and the stator are complicated, and the multi-degree-of-freedom ultrasonic motor is changed due to long-term operation. The rotational position of the multi-degree-of-freedom ultrasonic motor can be controlled without being affected by an adverse effect or individual differences between the multi-degree-of-freedom ultrasonic motors.
[Brief description of the drawings]
FIG. 1 is an internal configuration diagram of a rotation position control device of a multi-degree-of-freedom ultrasonic motor as an example of an apparatus according to an embodiment of the present invention.
FIG. 2 is an external perspective view of a multi-degree-of-freedom ultrasonic motor to which the above rotational position control device is applied.
FIG. 3 is a diagram illustrating the operating principle of a multi-degree-of-freedom ultrasonic motor to which the above-described rotational position control device is applied.
FIG. 4 is a sequence diagram for explaining a rotational position control method of the multi-degree-of-freedom ultrasonic motor of the present invention.
FIG. 5 is a flowchart illustrating application of an AC voltage in the above-described rotational position control method.
FIG. 6 is a diagram showing a rotational trajectory of the multi-degree-of-freedom ultrasonic motor to which the above-described rotational position control method is applied in a rotational drive of a rotor head apex.
[Explanation of symbols]
α ... Rotation position control device
β ... Multi-degree-of-freedom ultrasonic motor
1. Rotation angle measurement sensor
2 ... Rotation position monitor
3. High frequency rotation direction switching unit
4 ... Stator
4a: Pitch direction piezoelectric element for generating flexural vibration
4b: Piezoelectric element for generating vertical stretching vibration
4c: Piezoelectric element for generating flexural vibration in the roll direction
5 ... rotor
5a ... top of the head
A: axis
B: Synthetic path of rotational drive in the roll direction, pitch direction, and yaw direction
C: The rotation locus of the top of the head

Claims (20)

A stator constituted by a plurality of stacked piezoelectric elements that excite a plurality of natural vibrations having the same natural frequency when an AC voltage having a different phase is applied thereto, and a stator holding a load heavy object and being arbitrary by the natural vibration of the stator In the multi-degree-of-freedom ultrasonic motor configured to rotate in the direction of, the AC voltage is applied to the piezoelectric element of the stator to generate a desired rotational motion, A method of controlling a rotational position,
First, measuring the current rotational position of the rotor with the rotational movement,
Then, in order to reach the rotor to a preset target rotation position from the measured value, to calculate the amplitude value of the AC voltage to be applied to the piezoelectric element constituting the stator,
Subsequently, a multiple-phase AC voltage having the same amplitude value as the amplitude value and having a phase difference necessary for rotating the rotor is applied to the piezoelectric element to rotate the rotor. Control the direction,
A method for controlling the rotational position of a multi-degree-of-freedom ultrasonic motor, characterized in that: The application of the AC voltage of the plurality of phases includes:
Switching the output of the AC voltage to the piezoelectric element, which respectively excites the natural vibrations in the virtual three-dimensional coordinate three-axis directions different from each other orthogonally, at a high frequency having a cycle shorter than the rotation acceleration required time of the rotor,
Applying the AC voltage that excites any of the natural vibrations in the virtual three-dimensional coordinate three-axis direction to each of the plurality of piezoelectric elements;
2. The method for controlling the rotational position of a multi-degree-of-freedom ultrasonic motor according to claim 1, wherein: The application of the AC voltage of the plurality of phases includes:
Exciting the natural vibrations in the three-dimensional virtual three-dimensional coordinate system comprising x, y, and z axes that are orthogonal to each other and have x, y, and z axes perpendicular to each other with the z-axis being vertically above a contact end surface of the stator with the rotor. a roll-direction bending vibration generating piezoelectric element that rotates about the x-axis, a vertical stretching vibration generating piezoelectric element that expands and contracts in the z-axis direction, and a pitch-direction bending vibration generating piezoelectric rotation that rotates about the y-axis. Applying the AC voltage repeatedly until each of the piezoelectric elements of the element reaches the target rotational position,
Controlling the rotation direction by synthesizing the natural vibration to be excited;
3. The method for controlling the rotational position of a multi-degree-of-freedom ultrasonic motor according to claim 1, wherein: The calculation of the amplitude value,
The rotation angle required to reach the target rotation position from the current rotation position on the virtual three-dimensional coordinates is determined by a pitch direction and a roll direction in which the x, y, and z axes excited by the piezoelectric element are respectively rotated. And the component in the rotational direction of the yaw direction,
Calculating the amplitude value of the AC voltage for each of the three components in the rotation direction;
4. The method according to claim 3, wherein the rotational position of the multi-degree-of-freedom ultrasonic motor is controlled. The application of the AC voltage of the plurality of phases includes:
The virtual three-dimensional coordinate three-axis direction natural vibrations, which are orthogonal to each other, are excited, and the roll-direction bending vibration generating piezoelectric element that bends in the direction in which the x-axis is axially rotated, and the piezoelectric element that expands and contracts in the z-axis direction. A phase difference of 90 degrees is given to two kinds of the piezoelectric element for generating a vertical expansion / contraction vibration and the piezoelectric element for generating a bending vibration in the pitch direction which bends in the direction of rotating the y axis. Applying the AC voltage to each of the two types of piezoelectric elements,
By switching the two types of piezoelectric elements to be applied and the phase and amplitude values of the AC voltage applied to the piezoelectric elements, the rotor reaches the target rotation position,
5. The method for controlling the rotational position of a multi-degree-of-freedom ultrasonic motor according to claim 3 or 4, wherein: The calculation of the amplitude value,
When the target rotational angular velocity is set in advance for the rotational driving of the rotor,
By continuously measuring the rotational position, the rotational angular velocity of the rotor is monitored in correspondence with the AC voltage applied to the piezoelectric element,
By comparing the rotation angular velocity and the AC voltage, the amplitude value of the AC voltage to be applied next is calculated so as to reach the target rotation speed,
5. The method for controlling the rotational position of a multi-degree-of-freedom ultrasonic motor according to claim 1, wherein: The control of the rotation direction of the rotor,
In order to reach the target angle of the target rotation position from the rotation angle of the current rotation position, for rotation directions that require more rotation control, perform priority control over other rotation directions,
7. The method of controlling the rotational position of a multi-degree-of-freedom ultrasonic motor according to claim 1, wherein: The application of the AC voltage of the plurality of phases includes:
With the same value as the natural frequency of the piezoelectric element as the frequency, applying the AC voltage to the piezoelectric element,
8. The method of controlling the rotational position of a multi-degree-of-freedom ultrasonic motor according to claim 1, 2, 3, 4, 5, 6, or 7. A stator constituted by a plurality of stacked piezoelectric elements that excite a plurality of natural vibrations having the same natural frequency when an AC voltage having a different phase is applied thereto, and a stator holding a load heavy object and being arbitrary by the natural vibration of the stator In a multi-degree-of-freedom ultrasonic motor composed of a rotor driven to rotate in the direction of, a multi-degree-of-freedom ultrasonic motor rotation position control device applied to generate a desired rotational motion,
A rotation angle measurement sensor that measures a current rotation position of the rotor with the rotation motion,
From the measurement value of the current rotation position measured by the rotation angle measurement sensor, to reach the rotor to a preset target rotation position, to calculate the amplitude value of the AC voltage applied to the piezoelectric element, A rotation position monitoring unit that outputs an amplitude value as an amplitude command value,
A high frequency having the same amplitude value as the amplitude command value input from the rotation position monitoring unit and outputting a plurality of phases of AC voltages having a phase difference necessary for rotating the rotor to the piezoelectric element. A rotation direction switching unit;
A rotational position control device for a multi-degree-of-freedom ultrasonic motor, comprising: The high frequency rotation direction switching unit,
The output of the AC voltage is configured to be capable of being switched and output at a high frequency having a cycle shorter than the rotation acceleration required time of the rotor.
The rotational position control device for a multi-degree-of-freedom ultrasonic motor according to claim 9, wherein: The high frequency rotation direction switching unit,
Exciting the natural vibrations in three directions of virtual three-dimensional coordinates composed of x, y, and z axes that are orthogonal to each other and that are perpendicular to the end surface of the stator that makes contact with the rotor and that are the z axis, A roll-direction bending vibration generating piezoelectric element that bends in the direction of rotating the x-axis, a vertically expanding and contracting vibration generating piezoelectric element that expands and contracts in the z-axis direction, and a pitch-direction bending that bends in the direction of rotating the y-axis. For each piezoelectric element of the vibration generating piezoelectric element, each is connected so that the AC voltage can be applied,
The rotational position control device for a multi-degree-of-freedom ultrasonic motor according to claim 9 or 10, wherein: The rotation position monitoring unit,
The rotation angle required to reach the target rotation position from the current rotation position on the virtual three-dimensional coordinates is determined by the roll direction and the pitch direction in which the x, y, and z axes excited by the piezoelectric element are respectively rotated. And the amplitude value of the AC voltage is calculated for each of the three components in the rotation direction, and the calculated amplitude values are used as the three amplitude command values, respectively, in the high frequency rotation direction. It is configured to be able to output to the switching unit,
The rotational position control device for a multi-degree-of-freedom ultrasonic motor according to claim 11, wherein: The rotation position monitoring unit,
In each of the roll direction, the pitch direction, and the yaw direction, when the rotor reaches the target rotational position, the rotor outputs a voltage value of 0 V as the amplitude command value in the rotational direction. If a further rotation angle is required up to the target rotation position, a function is configured to output a voltage value preset to the piezoelectric element as the amplitude command value,
The rotational position control device for a multi-degree-of-freedom ultrasonic motor according to claim 12, wherein: The high frequency rotation direction switching unit,
By applying the AC voltage having a phase difference of 90 degrees to each of the piezoelectric element for generating vertical stretching vibration and the piezoelectric element for generating flexural vibration in the roll direction, the stator is rotated. Functionally configured to induce a rotational drive to rotate the child in the roll direction,
14. The rotational position control device for a multi-degree-of-freedom ultrasonic motor according to claim 11, 12, or 13. The high frequency rotation direction switching unit,
By applying the AC voltage having a phase difference of 90 degrees to the pitch direction flexural vibration generating piezoelectric element and the vertical stretching vibration generating piezoelectric element, respectively, Functionally configured to induce rotational drive to rotate the child in the pitch direction,
The rotational position control device for a multi-degree-of-freedom ultrasonic motor according to claim 11, 12, 13, or 14, wherein: The high frequency rotation direction switching unit,
By applying the AC voltage having a phase difference of 90 degrees to each of the pitch-direction flexural vibration generating piezoelectric element and the roll-direction flexural vibration generating piezoelectric element, Functionally configured to induce a rotational drive to rotate the child in the yaw direction,
The rotational position control device for a multi-free ultrasonic motor according to claim 11, 12, 13, 14, or 15, wherein: The high frequency rotation direction switching unit,
Inverting the 90-degree phase difference between the two AC voltages to apply the AC voltage that induces the rotor to rotate in the negative direction,
17. The rotation position control device for a multi-degree-of-freedom ultrasonic motor according to claim 14, 15, or 16. The rotation position monitoring unit,
When the target rotational angular velocity is set in advance for the rotational driving of the rotor,
The measured value output from the rotation angle measurement sensor is continuously held in association with the AC voltage output from the high-frequency rotation direction switching unit, and the amplitude of the AC voltage applied to the piezoelectric element is held. Value is configured to be adjustable to reach the target rotational speed,
The rotational position control device for a multi-degree-of-freedom ultrasonic motor according to any one of claims 9, 10, 11, 12, 13, 14, 15, 16, and 17. The high frequency rotation direction switching unit,
In order to reach the target angle of the target rotation position from the rotation angle of the current rotation position, to the rotation direction that requires more rotation control, the application of the AC voltage has higher priority than other rotation directions. Is configured to perform
The rotational position control device for a multi-free ultrasonic motor according to claim 9, 10, 11, 11, 12, 13, 14, 15, 16, 17, or 18. The high frequency rotation direction switching unit,
The frequency of the AC voltage having the same value as the natural frequency of the piezoelectric element is configured to be applied to the piezoelectric element,
20. The rotational position control device for a multi-degree-of-freedom ultrasonic motor according to claim 9, 10, 11, 11, 12, 13, 14, 15, 16, 17, 18 or 19.

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