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An inertial actuator that improves load capacity within a miniaturized structure has drawn wide attention. This work proposes an inertial piezoelectric linear actuator and investigates a method that improves its load capacity. The structure and operational principle of the actuator are introduced. A dynamic model of the system is established that simulates the stepping characteristics. The dominant parameters affecting load capacity are discussed in detail. A prototype was manufactured and its main performance features tested. The experimental results confirm that the proposed actuator achieves a load capacity of 3.65 N, a resolution of 0.47 μm, and a speed of 6.15 mm s −1 , despite its compact size of Φ 9 mm×27 mm. The actuator has an improved load capacity given its smaller configuration than those reported in the literature. The model established provides a theoretical guide to the design of similar inertial actuators and may be used to predict and evaluate their load capacity.

A microelectromechanical system (MEMS) torsional resonant magnetometer based on Lorentz force was investigated, consisting of torsional structures, torsional beams, metal plates, a coil, and a glass substrate. The Lorentz force, introduced by the interaction between the current in the MEMS coil and an external horizontal magnetic field, leads to displacement of the torsional structure. The strength of the magnetic field is proportional to this displacement, and can be detected with two sensing capacitors fabricated on the torsion structure and the substrate. To improve sensor sensitivity, a folded torsional beam and a double-layer excitation coil were introduced. The fabrication processes included lift-off, anodic bonding, chemical mechanical planarization, silicon nitride (SiNx) deposition, plasma-enhanced chemical vapor deposition, and inductively coupled plasma release. The prototype of the magnetometer was finished and packaged. The sensor performance, including its sensitivity and repeatability, was tested in a low-pressure environment. Additionally, the influences of structural parameters were analyzed, including the resistance of the excitation coil, the initial value of the capacitors, the elastic coefficient of the torsional beam, and the number of layers in the excitation coil. The test results demonstrated that this sensor could meet the requirements for attitude determination systems in low earth orbit satellites.

SUMMARYNew 8-node solid elements with two parallel faces and one traction-free cylindrical surface are derived using the assumed stress hybrid model. Six new expressions of stress components are developed by using four stress functions and cylindrical co-ordinates, so that the normal stress 0, on the plane perpendicular to the two parallel faces varies as a parabola, and the assumed stress field satisfies the equilibrium equations as well as the traction-free conditions over the cylindrical boundary. The assumed stress field also satisfies the compatibility conditions when the new element is degenerated into the 2-dimensional case. Examples have clearly demonstrated that these present special elements are far superior in predicting the stress concentration factors, the distributions of circumferential stresses and the normal stress 6 , .