JPS61180581A - Controlling method for piezoelectric effect element - Google Patents

Abstract

PURPOSE:To enable to finely displace accurately at a high speed by adequately determining a voltage waveform to be applied to a piezoelectric effect element. CONSTITUTION:A voltage is applied from a controller 1 through an amplifier 2 to a piezoelectric effect element 3 displacing in response to an applied voltage. In this case, a voltage higher than the voltage to be applied to the element 3 is applied for the prescribed ultrashort time, the applied voltage is set to zero for the prescribed ultrashort time, a voltage slightly higher than the voltage corresponding to a desired displacement is then applied, the voltage corresponding to the desired displacement is applied to displace the element.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for controlling a piezoelectric effect element, and more particularly to a method for controlling a piezoelectric effect element that can displace the piezoelectric effect element with high precision and at high speed.

Conventionally, piezoelectric effect elements such as piezo elements have been frequently used as drive elements for obtaining minute displacements. - This piezoelectric effect element generally has a hysteresis voltage-displacement characteristic t-4 as shown in Figure 1, and even after voltage is applied, the amount of displacement gradually increases over time as shown in Figure 2. It has the so-called creep phenomenon that it takes time to stabilize, and even when the applied voltage is returned to zero, it takes a long time until the amount of displacement returns to the original KJR, and that time varies depending on the applied voltage. I'm staying there. For this reason, for example, if a given voltage is repeatedly applied to a piezoelectric effect element at regular intervals using a drive device as shown in Fig. 3, the amount of displacement of the piezoelectric effect element will gradually increase even after the voltage is applied, as shown in Fig. 4. Even if the same voltage is applied, if the previous applied voltage is different, there will be a difference in the amount of displacement of the piezoelectric effect element. .

For the above reasons, when a piezoelectric effect element is used as a drive element for ultra-fine positioning, it is customary to equip the displacement part with some kind of position detector and perform nine-closed-loop control with feedback control. to control,
The open-loop control method, which is a simple and inexpensive method, is the preferred method to control ultra-small displacements.

An object of the present invention is to provide a method for controlling a piezoelectric effect element, which alleviates hysteresis voltage-displacement characteristics and creep phenomena, and enables ultra-minute displacement with high accuracy and high speed, despite the open-loop control method.

The main feature of the method for controlling a piezoelectric effect element to achieve the object of the present invention is that when applying a voltage to a piezoelectric effect element that is displaced in accordance with the applied voltage, first, the control method for the piezoelectric effect element is controlled for a certain minute period of time. Apply a voltage higher than the applied voltage, then reduce the applied voltage to zero for a certain minute period of time, then apply a voltage somewhat higher than the voltage corresponding to the desired amount of displacement, and after that, the desired amount of displacement is reached. The piezoelectric effect element was displaced by applying a corresponding voltage.

The present invention uses the method described above to apply a voltage to a piezoelectric effect element to create a hysteresis characteristic, so that when an arbitrary voltage is applied, even if the applied voltage is the same, if the previous applied voltage is different, displacement will occur. This alleviates the hysteresis phenomenon in which the amount of displacement is not necessarily the same, and the creep phenomenon in which the amount of displacement gradually increases after voltage application and takes time to stabilize. This makes it possible to perform positioning control with high accuracy and high speed without using feedback from a position detector or the like when performing ultra-precise positioning, for example.

Next, FIG. 5 shows a schematic diagram of an embodiment of the piezoelectric effect element control method of the present invention. The figure (,) shows the control voltage waveform to the piezoelectric effect element, the figure (b) shows the voltage waveform applied to the piezoelectric effect element amplified by the amplifier, and the figure (c) shows the displacement amount of the piezoelectric effect element. It is something.

First, in the configuration shown in FIG. 3, the control device 1 is shown in FIG. 5(a).
As shown in K, a voltage higher than the planned applied voltage is generated for a certain minute time t□. This voltage is amplified by the amplifier 2 in FIG. 3 and becomes an erroneous waveform shown in section t in FIG. 5(b) and is applied to the piezoelectric effect element. The displacement during this period is as shown in the section tiK in FIG. 5(C).

Furthermore, during the next minute time t2, the voltage generated by the control device is made zero. The applied voltage and displacement to the piezoelectric effect element at this time are shown in FIG. 5(b), respectively, as described above.

The interval tz of (,) is as shown in K.

The above control method alleviates the phenomenon that occurs due to the hysteresis voltage-displacement characteristic of piezoelectric effect elements, where even if the same voltage is applied, the same amount of displacement cannot be obtained if the previous applied voltage is different. It becomes possible to do so.

Furthermore, for the next minute time t3, the control device 1 generates a voltage somewhat higher than the voltage corresponding to the desired amount of displacement, and thereafter controls to maintain the voltage corresponding to the desired amount of displacement.

This control makes it possible to almost eliminate the rough leap phenomenon, which occurs when a voltage is simply applied to the piezoelectric effect element and the amount of displacement that occurs in an emergency gradually increases over time and takes time to stabilize. Furthermore, by appropriately providing the time t3, it is possible to prevent overshedding during final positioning.

In this embodiment, a voltage higher than the planned applied voltage means a voltage that is sufficient to achieve the purpose of the present invention. Also, the time td shown in FIG.

Similarly, 12 and 13 also mean a period that can achieve the object of the present invention, and are appropriately set depending on the piezoelectric effect element.

As explained above, according to this embodiment, when the control device generates a waveform as shown in FIG. 5(a) and applies it to the piezoelectric effect element through the amplifier, the repeatability of positioning is greatly improved. Furthermore, the stability of displacement after voltage application can be significantly improved.

As a result of 7, conventionally, when using a piezoelectric effect element for ultra-fine positioning, only closed-loop control was required using a position detector to feedback the entire displacement amount, but according to this embodiment, it is possible to simply control the amount of displacement in advance. It becomes possible to use simple and inexpensive open-loop control that generates a voltage corresponding to the amount of displacement.

As described above, according to the present invention, the piezoelectric effect element can be displaced with high precision and at high speed.

As a result, ultra-precise positioning can be easily achieved using, for example, piezoelectric effect elements! l! If used in a precision positioning device controlled by the fK1 microcomputer, the effect will be extremely large.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram showing the hysteresis voltage-displacement characteristics of a general piezoelectric effect element, Fig. 2 is an explanatory diagram showing the state of displacement when voltage is applied to the piezoelectric effect element, and Fig. 3 is an explanatory diagram showing the state of displacement when a voltage is applied to the piezoelectric effect element. FIG. 4 is an explanatory diagram showing the conventional control voltage waveform to the piezoelectric effect element, and an explanatory diagram showing the applied voltage and displacement amount to the piezoelectric effect element amplified by the amplifier at that time. The figure is an explanatory diagram showing a control voltage waveform of a piezoelectric effect element, a voltage waveform applied to the piezoelectric element at that time, and a displacement amount of the piezoelectric effect element according to the present invention. In the figure, 1 is a control device, 2 is an amplifier, 3 is a piezoelectric effect element, 4
．． 5 are lead wires.

Claims (1)

[Claims] When applying a voltage to a piezoelectric effect element that is displaced in response to an applied voltage, first a voltage higher than the intended voltage to be applied to the piezoelectric effect element is applied for a certain minute time, and then the applied voltage is applied for a certain minute time. A piezoelectric effect characterized in that the piezoelectric effect element is displaced by applying a voltage slightly higher than a voltage corresponding to a desired amount of displacement, and then applying a voltage corresponding to a desired amount of displacement. How to control the element.