Power plants – Motor operated by expansion and/or contraction of a unit of... – Mass is a solid
Reexamination Certificate
2001-03-22
2002-08-20
Nguyen, Hoang (Department: 3748)
Power plants
Motor operated by expansion and/or contraction of a unit of...
Mass is a solid
C060S528000
Reexamination Certificate
active
06434932
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a control mechanism having an actuator which employs a shape memory alloy, and relates to a method for adjusting its servo control of the control mechanism.
2. Description of the Related Arts
In recent years, there has been a growing demand and necessity of a miniature mechanism for controlling a position of a driven member to be moved, which can be employed for a compensation mechanism to correct any blurred image caused by a camera shake of a lens shutter camera, for example. In order to satisfy such a demand and necessity, there is proposed an actuator which makes use of a shape memory alloy (or SMA) and a spring. As a method for controlling the actuator which makes use of the shape memory alloy, there has been proposed an on/off controlling method only, in which it is employed as a switch. On the other hand, a “System and Control, Vol. 29, No. 5: Kuribayashi, 1985” discloses mathematical models of control elements employing the shape memory alloy, and it discloses a PID control. However, it does not disclose any concrete technique thereof.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a control mechanism for controlling position of a driven member by employing an actuator which makes use of the shape memory alloy.
It is another object of the present invention to provide the control mechanism having the actuator which is simple in construction and compact in size.
It is still another object of the present invention to provide a method for adjusting servo control of the control mechanism, in which a driving condition of the control mechanism is stabilized, and in which error in the servo control is small (i.e. accuracy in the servo control is high).
In accomplishing these and other objects of the present invention, according to one aspect thereof, there is provided a control mechanism comprising: a shape memory alloy which memorizes a predetermined dimension thereof; a biasing device for exerting a biasing force on the shape memory alloy and for changing dimension of the shape memory alloy, wherein the shape memory alloy and the biasing device constitute an actuator for moving a driven member which is driven by the actuator, and wherein the driven member is controlled to move in a first direction in which the shape memory alloy returns to the predetermined dimension and in a second direction in which the biasing means changes the dimension of the shape memory alloy, so as to control a position of the driven member, by the actuator; an operation means for performing an operation repeatedly on a basis of information upon a target position and an actual position (or then position or existing position) of the driven member, and for calculating a voltage to be supplied to the shape memory alloy; and a voltage supplier having a limiting circuit for supplying the voltage, calculated by the operation means, to the shape memory alloy, only when the driven member is moved in the first direction, on a basis of a result of the operation performed by the operation means.
In the mechanism, preferably, the biasing device is a spring such as a bias spring.
In the mechanism, the first direction and the second direction may be opposite to each other.
According to the mechanism, the limiting circuit of the voltage supplier limits, or stops, the supply of the voltage, gained by the operation (or calculation) of the operation means, to the shape memory alloy, when the driven member should be moved in the second direction, on a basis of a result of the operation performed by the operation means. By the way, the operation performed by the operation means includes not only the operation (or calculation) of the voltage to be supplied to the shape memory alloy, but also the operation (or calculation) of the voltage corresponding to an electric current to be supplied to the shape memory alloy.
In the mechanism, only when the driven member should be moved in the first direction, the voltage is supplied to the shape memory alloy. As a result, the driven member is moved toward the target position. On the other hand, when the driven member should be moved in the second direction, if the result of the operation performed by the operation means becomes negative, the supply of the voltage to the shape memory alloy is prevented by the limiting circuit of the voltage supplier and thus the driven member is not further driven, nor moved. Namely, with this function, a wrong control is surely prevented, and the driven member is moved towards the target position by the biasing force exerted by the biasing device.
Therefore, according to the arrangement, the control mechanism for controlling the position of the driven member by employing the actuator which makes use of the shape memory alloy is provided
Also, according to the arrangement, because the actuator is constituted by the shape memory alloy and the biasing means such as the spring, the actuator itself becomes simple in construction and compact in size. Therefore, the control mechanism having the actuator also becomes simple in construction and compact in size.
In the mechanism, it is preferable that the limiting circuit of the voltage supplier puts a limit with respect to a final output of the operation means.
According to another aspect of the present invention, there is provided a control mechanism comprising: a shape memory alloy which memorizes a predetermined dimension thereof; a biasing device for exerting a biasing force on the shape memory alloy and for changing dimension of the shape memory alloy, wherein the shape memory alloy and the biasing device constitute an actuator for moving a driven member which is driven by the actuator, and wherein the driven member is controlled to move in a first direction in which the shape memory alloy returns to the predetermined dimension and in a second direction in which the biasing means changes the dimension of the shape memory alloy, so as to control a position of the driven member, by the actuator; an operation means for performing an operation repeatedly on a basis of information upon a target position and an actual position of the driven member, and for calculating a voltage to be supplied to the shape memory alloy; and a voltage supplier having a limiting circuit for limiting a supply of the voltage, calculated by the operation means, to the shape memory alloy, when the driven member is moved in the second direction, on a basis of a result of the operation performed by the operation means.
According to still another aspect of the present invention, there is provided a control mechanism for controlling a position of a driven member in a first direction and in a second direction by an actuator, the control mechanism comprising: a target position determination means for determining a target position to which the driven member is to be moved; an actual position detection means for detecting an actual position of the driven member; and a control output operation means for calculating a control output with a phase being led (or with a phase being forwarded or with a phase being fast) by executing an operation which includes a differential calculus executed twice relative to a difference between the target position and the actual position.
By executing the operation including the differential calculus executed twice, or more than twice, relative to the difference between the target position and the actual position, it is possible to compensate a phase by 180° or more. As a result, a control with higher response is realized.
In the above mechanism, the actuator can be constituted by: a shape memory alloy which memorizes a predetermined dimension thereof; and a biasing device for exerting a biasing force on the shape memory alloy and for changing dimension of the shape memory alloy.
In the mechanism, preferably, the biasing device is a spring.
Alternatively, the actuator can be constituted by a pair of shape memory alloys one ends of which are connected to each other.
By the way, an o
Hara Yoshihiro
Kosaka Akira
Tanii Junichi
Wada Shigeru
Burns Doane , Swecker, Mathis LLP
Minolta Co. , Ltd.
Nguyen Hoang
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