This work describes a plantar force measurement system. The MEMS pressure sensor, as the key sensing element, is designed, fabricated and embedded into a flexible silicon oil-filled bladder made of silicon rubber to constitute a single sensing unit. A conditioning circuit is designed for signal processing and data acquisition. The characteristics of the plantar force sensing unit are investigated by both static and dynamic tests. A comparison of characteristics between the proposed plantar force sensing unit and a commercial flexible force sensor is presented. A practical experiment of plantar force measurement has been carried out to validate the system. The results demonstrate that the proposed measurement system has a potential for success in the application of plantar force measurement during normal gait.

A simply constructed but efficacious shock tester is developed for screening or calibration of lightweight devices comprising micro-electro-mechanical systems (MEMS). The proposed shock tester provides a promising solution to the trade-off between cost-effective development and the demands on high-g shock testing devices. By incorporating material of high specific modulus and velocity gain achieved through collisions between vertically stacked masses, the shock tester achieves an acceleration range of about 100 000 g and features relative simplicity, low cost and small size compared with existing drop machines. The experiments were conducted based on a Brüel & Kjær (B&K) high-g accelerometer, the matching charge amplifier and a data acquisition system. The acceleration range, shock duration and reproducibility on given driving force were tested. The results show that the developed high-g shock tester has favorable properties that allow its use in demanding applications.

A simply constructed shock tester, different from existing drop table machines, is developed for high-g level shock environment simulation. The theoretical model, structure design, and working principle of the drop tester are described. A prototype device is set up, where a carbon fiber reinforced polymer with a high specific modulus is used. Using a Brüel & Kjær high-g accelerometer, experiments to verify the validity of the design are carried out and results are given. The maximum acceleration level is in excess of 60,000 g, limited only by the manual driving force.

In this paper, an alternative approach to achieve speed, thrust, and flux regulation is presented for the drive system of permanent magnet synchronous linear motors (PMSLMs). The conventional proportional-integral (PI) speed regulator based direct thrust control (DTC) of PMSLM has problems of degrading the system performances, such as high thrust, flux, and current ripple, high-frequency noise caused by high thrust ripples, and the difficulty to accurately adapting to varying parameters and external loads. We propose an adaptive back-stepping control based DTC for PMSLM servo system. The PI speed regulator and two hysteresis regulators in the classical DTC system are substituted by one adaptive back-stepping controller. The uncertainties in the system are estimated online using adaptive techniques. Moreover, a space vector modulation (SVM) scheme is employed to ensure that the inverter switching frequency remains fixed. The stability of the proposed method is verified by the Lyapunov stable theory, which is difficult to achieve in the classical DTC method. Simulations are conducted to verify the effectiveness of the proposed method.

Pulse shaping techniques are discussed in this paper for the practicability of a developed high-g shock tester. The tester is based on collision principle where there is a one-level velocity amplifier. A theoretical and experimental study of pulse shaping techniques is presented. A model was built and theoretical formulae were deduced for the shock peak acceleration and its duration. Then theoretical analysis and some experiments were conducted. The test results verify the validity of theoretical model and show that the shock tester can generate the expected high-g shock pulses by integrated usage of different impact velocities and pulse shapers made from different materials. This is important in practical applications where the items under test can be shown to excite specific resonances at predetermined acceleration levels using the shock tester.

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