Combination piezoelectric actuator and sensor

Inventors

Saari, Byron John • Johnson, Scott Gale

Assignees

MTS Systems Corp

Abstract

A test system includes a frame. A hydraulic actuator is mounted to the frame and is configured to support a test specimen. A piezoelectric actuator is configured to apply a force to the test specimen. A controller is configured to excite the piezoelectric actuator and provide an indication of force generated by the piezoelectric actuator by measurement of current or charge provided to the piezoelectric actuator.

Core Innovation

The disclosure describes a servo-hydraulic test system that combines a hydraulic actuator and a piezoelectric actuator to apply forces to a test specimen. A frame supports the hydraulic actuator configured to provide a force to the test specimen and a piezoelectric actuator configured to apply a second force to the test specimen. A controller excites the piezoelectric actuator and provides an indication of the second force generated by the piezoelectric actuator by measurement of current or charge provided to the piezoelectric actuator.

The controller-based force indication for the piezoelectric actuator is used to enable dynamic stiffness testing at high excitation frequencies. Embodiments describe a frequency bandwidth from about 0.01 Hz to greater than about 1,000 Hz, with bandwidth embodiments also described at greater than about 2,000 Hz and greater than about 3,000 Hz. The described arrangement includes exciting the piezoelectric actuator and estimating or providing force information from electrical measurement of current or charge delivered to the piezo driver amplifier.

Mechanical integration arrangements are described in which the hydraulic actuator is mounted to a crosshead, and an inertial mass is coupled to a hydraulic actuator piston rod. The piezoelectric actuator is mounted on a side opposite the piston or movable element such that the piezoelectric actuator applies the second force to the test specimen. Additional force-sensing and displacement-estimation elements are described, including a strain-gage load cell for lower frequencies when the piezo transducer is insufficient and, in some embodiments, an accelerometer for displacement estimation or related measurement.

Claims Coverage

The independent claims define a test system with a frame, a hydraulic actuator, and a piezoelectric actuator in cooperation with a controller that excites the piezoelectric actuator and indicates the second force by measuring current or charge. The independent claims add distinct structural couplings: one focuses on a general combination of hydraulic and piezoelectric actuators with controller-based force indication, while the other specifies a hydraulic actuator with a piston mounted in a crosshead, an inertial mass coupled to the piston, and a piezoelectric actuator mounted to the inertial mass on a side opposite the piston.

Across the independent claims, the central coverage is the combination of a hydraulic actuator and a piezoelectric actuator on a frame with a controller that excites the piezoelectric actuator and provides an indication of the piezo-generated second force by measuring current or charge. Claim 14 further narrows the structural configuration to a crosshead-mounted piston with an inertial mass coupled thereto, and a piezoelectric actuator mounted to the inertial mass on the side opposite the piston.

Stated Advantages

Documented Applications