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High-precision and fault-tolerant six-dimensional force/torque sensor is one of the core components of intelligent robots for force feedback perception. This paper is aiming at the fault-tolerant measurement mechanism research on piezoelectric six-dimensional force/torque sensors with four-point support structure. Based on principle of leverage and deformation consistent, the fault-tolerant measurement mechanism of the pre-tightened four-point supported piezoelectric six-dimensional force/torque sensor is revealed. The mapping mathematical models of spatial six-dimensional force and four-fulcrum quartz crystal group detection signal for the sensor without signal fault and with signal fault are constructed respectively. The static calibration system of the sensor is built to realize the fault-tolerant static calibration experiment of the four-point supported piezoelectric six-dimensional force/torque sensor prototype under unidirectional loading without signal fault and with signal fault. In order to improve the measurement precision of six-dimensional force/torque sensor for robot, a decoupling method based on Genetic Algorithm to optimize Back Propagation algorithm (GABP) for piezoelectric six-dimensional force/torque sensor is adopted to solve the nonlinear cross coupling problem of multiple-input and multiple-output. Through Maltlab software, the test data are analyzed and calculated, and the percentage coupling error matrix of the sensor is calculated. The percentage coupling error is different when the sensor is fault-free and the fault-free measurement model is different. When the sensor is fault-free, the linearity of the sensor is the best and the maximum coupling error is less than 1.5%. When the sensor has any branch fault, the overall performance of the sensor is relatively weakened and the maximum coupling error increases. When the sensor has two branch faults, the linearity of the sensor is the worst. It cannot satisfy the requirement of accurate measurement. The research content is of great significance to the development and practicality of fault-tolerant multi-point supported piezoelectric six-dimensional force/torque sensor.

Using near-field scanning optical microscopy (NSOM), we explore the chromatic dispersion and absorption characteristics of fractal clusters in Eu doped polymer fiber. We present the near-field transmitted light intensity of fiber slice. The near-field light intensity of dots with clusters and without clusters is analyzed and compared and the agreement is obtained between experiment and theory which is based on the effective-medium approximation (EMA) and the differential effective-medium approximation (DEMA) of fractal clusters, respectively.

Birefringent gratings induced by 532 nm polarized laser in an azobenzene-doped polymethyl methacrylate (PMMA) fibers and blocks were investigated. Significant photo-induced birefringence with about 3.0×10−5 has been observed from the fiber. It was found that there is an intensity threshold, which is 0.29 mW/cm 2 at 532 nm. The birefringence decayed gradually when the writing laser turned off. So the dynamic process of the birefringence was studied. Both the rise and the decay processes of the birefringence include an initial “fast” response mode and a subsequent “slow” response mode. Both the fast response and the slow response become faster with increasing irradiating laser intensity. The birefringence was induced by the combination of the nonlinear absorption, linear absorption and thermal effect.

Raman spectra from polymethyl methacrylate (PMMA) core polymer optical fibres (POFs) in the 200–6800 cm−1 range were investigated using an Ar+ ion laser. Raman peak shifting and Raman spectra broadening were observed and analysed in the POFs. Polarized laser-induced birefringence in an azobenzene-doped PMMA fibre material was investigated. We found both a fast response mode and a slow response mode in the rise and decay process of the laser-induced birefringence. It is demonstrated that the characteristics of polarized laser-induced birefringence were strongly dependent on the pump laser power.

Discussed in this paper are the challenges facing the boosting systems of Low Temperature Combustion (LTC) system. A new term named “Gas to Fuel Ratio (GFR) in cylinder” is introduced to deal with the combined dilution effect of fresh air and cooled external EGR. Formulas are derived to illuminate the fundamental relationship between engine BMEP and GFR targets, with the required mass flowrate and pressure ratio for the boosting system. The theoretic models are correlated with experimental data and applied to optimize for the boosting system of a two stroke two cylinder diesel engine with up to 50% of external EGR.