Electrical generator or motor structure – Non-dynamoelectric – Piezoelectric elements and devices
Patent
1993-03-26
1995-01-17
Dougherty, Thomas M.
Electrical generator or motor structure
Non-dynamoelectric
Piezoelectric elements and devices
310328, H01L 4108
Patent
active
053828658
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a composite multilayer ceramic structure and, in particular, to a controlled force or force limited multilayer ceramic actuator which comprises a combination of an electrostrictive actuator and sensor.
Multilayer ceramic actuators in which a plurality of layers of a dielectric material are separated by a plurality of electrode layers are known in the art. We have now developed a composite multilayer ceramic structure in which a multilayer electrostrictive ceramic actuator is combined with a sensor in a single device.
SUMMARY OF THE INVENTION
Accordingly, the present invention provides a composite multilayer ceramic structure which comprises a plurality of layers of an electrostrictive dielectric material separated by a plurality of electrode layers in which a first portion is adapted to operate as an electrostrictive actuator and a second portion, which is adjacent to the first portion and which is not inherently piezoelectric comprises means to apply a biased voltage thereto whereby the second portion comprises means to apply a bias voltage thereto whereby it is adapted to operate in the same way as a piezoelectric sensor.
The composite multilayer ceramic structure of the present invention is a controlled force or force limited electrostrictive actuator which comprises a stack of a plurality of layers of an electrostrictive dielectric material separated by a plurality of electrode layers, alternate electrodes in a first portion of the stack being connected to positive or negative potential and means to apply a voltage thereto, alternate electrodes in a second portion of the stack being connected to positive or negative potential and means to apply a bias voltage thereto, means to measure the charge produced by the second portion of the stack and means to adjust the voltage applied to the first portion of the stack.
In the composite multilayer structure of the present invention the second portion adapted to operate as a sensor may be sandwiched between first and third portions which are adapted to operate as electrostrictive actuators.
The first portion, and the third portion of the composite composite multilayer ceramic structure when present, are adapted to operate as electrostrictive actuators.
The material which is used as the electrostrictive dielectric material in the different portions of the structure maybe the same or different, although it is preferred to use the same material. For example, the same dielectric material may be used for the different portions of the structure, providing that it is a material in which piezoelectricity can be induced by the application of a bias field.
The present invention also includes within its scope a method of producing a controlled force or force limited multilayer ceramic actuator which comprises forming a stack of a plurality of layers of an electrostrictive dielectric material separated by a plurality of electrode layers, operating a first portion of the stack as an electrostrictive actuator by connecting alternate electrodes in the first portion of the stack to positive or negative potential and applying a voltage thereto, and inducing piezoelectricity in a second portion of the stack by applying a bias field thereto so that it generates a charge which is proportional to the force produced by the actuator.
The charge, Q, generated by the sensor portion of the structure may be measured by conventional techniques. Measurement of the charge enables the force acting on the sensor portion of the structure to be determined and the force applied by the electrostrictive actuator may be controlled or limited by varying the voltage which is applied to the first (and optionally third) portion(s) of the stack.
The controlled force or force limited actuator of the present invention may be used in mechanised devices, such as precision robots.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will be further described with reference to the accompanying drawing in which:
FIG. 1 is a diagram of a mul
REFERENCES:
patent: 3590287 (1971-06-01), Berlincourt et al.
patent: 4325255 (1982-04-01), Howard et al.
patent: 4523121 (1985-06-01), Takahashi et al.
patent: 4564782 (1986-01-01), Ogawa
patent: 4667127 (1987-05-01), Krempl et al.
patent: 4780639 (1988-10-01), Shirasu
patent: 4833358 (1989-05-01), Suzuki et al.
patent: 5118982 (1992-06-01), Inoue et al.
patent: 5237236 (1993-08-01), Culp
patent: 5241236 (1993-08-01), Sasaki et al.
Butcher Steven J.
Hobby James D.
Kings David H. M.
Cookson Group PLC
Dougherty Thomas M.
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