Double Position Servo Synchronous Drive System Based on Cross-Coupling Integrated Feedforward Control for Broacher

Synchronization errors directly deteriorate the machining accuracy of metal parts and the existed method cannot keep high synchronization precision because of external disturbances. A new double position servo synchronous driving scheme based on semi-closed-loop cross- coupling integrated feedforward control is proposed. The scheme comprises a position error cross-coupling feedfor-ward control and a load torque identification with feed- forward control. A digital integrated simulation system for the dual servo synchronous drive system is established. Using a 20 t servo broacher, performance analysis of the scheme is conducted based on this simulation system and the simulation results show that systems with traditional parallel or single control have problems when the work- table works with an unbalanced load. However, the system with proposed scheme shows good synchronous perfor- mance and positional accuracy. Broaching tests are performed and the experimental results show that the maximum dual axis synchronization error of the system is only 8μm during acceleration and deceleration processes and the error between the actual running position and the given position is almost zero. A double position servo synchronous driving scheme is presented based on crosscoupled integrated feedforward compensation control, which can improve the synchronization precision.

Dual-wavelength ultraviolet photodetector based on vertical(Al,Ga)N nanowires and graphene

Due to the wide application of UV-A(320 nm–400 nm)and UV-C(200 nm–280 nm)photodetectors,dual-wavelength(UV-A/UV-C)photodetectors are promising for future markets.A dual-wavelength UV photodetector based on vertical(Al,Ga)N nanowires and graphene has been demonstrated successfully,in which graphene is used as a transparent electrode.Both UV-A and UV-C responses can be clearly detected by the device,and the rejection ratio(R254 nm/R450 nm)exceeds35 times at an applied bias of-2 V.The short response time of the device is less than 20 ms.Furthermore,the underlying mechanism of double ultraviolet responses has also been analyzed systematically.The dual-wavelength detections could mainly result from the appropriate ratio of the thicknesses and the enough energy band difference of(Al,Ga)N and Ga N sections.

Realize ultralow-energy-consumption photo-synaptic device based on a single(Al,Ga)N nanowire for neuromorphic computing

The rapid development of artificial intelligence poses an urgent need for low-energy-consumption and small-sized artificial photonic synapses.Here,it is pretty novel to demonstrate a light-stimulated synaptic device based on a single(Al,Ga)N nanowire successfully.Thanks to the presence of vacancy defects in the single nanowire,the artificial synaptic device can simulate multiple functions of biological synapses under stimulation of both 310 and 365 nm light photons,including paired-pulse facilitation,spike timing dependent plasticity,and memory learning capabilities.The energy consumption of artificial synaptic device can be reduced as little as 5.58×10^(-13) J,which is close to that of the biological synapse in human brain.Furthermore,the synaptic device is demonstrated to have the high stability for both long-time stimulation and long-time storage.Based on the experimental conductance of long-term potentiation and long-term depression,the simulated three-layer neural network can achieve a high recognition rate of 92%after only 10 training epochs.With a brain-like behavior,the single-nanowire-based synaptic devices can promote the development of visual neuromorphic computing technology and artificial intelligence systems requiring ultralow energy consumption.

Flexible bidirectional self-powered photodetector with significantly reduced volume and accelerated response speed based on hydrogel and lift-off GaN-based nanowires

Due to the wide range of potential applications for next-generation multi-functional devices,the flexible selfpowered photodetector(PD)with polarity-switchable behavior is essential but very challenging to be realized.Herein,a wearable bidirectional self-powered PD based on detached(Al,Ga)N and(In,Ga)N nanowires has been proposed and demonstrated successfully.Arising from the photovoltage-competing dynamics across(Al,Ga)N and(In,Ga)N nanowire photoelectrodes,such PD can generate the positive(33.3 mA W−1)and negative(-0.019 mA W−1)photo-responsivity under ultraviolet(UV)and visible illumination,respectively,leading to the bidirectional photocurrent behavior.Thanks to the introduction of quasi solid-state hydrogel,the PD can work without the liquid-electrolyte,thus remarkably reducing the volume from about 482 cm3 to only 0.18 cm3.Furthermore,the use of hydrogel is found to enhance response speed in the UV range by reducing the response time for more than 95%,which is mainly attributed to the increased open circuit potential and reduced ion transport distance.As the GaN connecting segment is pretty thin,the piezoelectric charges generated by stress are proposed to have only a limited effect on the photocurrent density.Therefore,both the stable on-off switching characteristics and photocurrent densities can still be achieved after being bent 400 times.With an excellent flexibility,this work creates opportunities for technological applications of bidirectional photocurrent PDs in flexible optoelectronic devices,e.g.,wearable intelligent sensors.

Light-stimulated low-power artificial synapse based on a single GaN nanowire for neuromorphic computing

The fast development of the brain-inspired neuromorphic computing system has ignited an urgent demand for artificial synapses with low power consumption. In this work, it is the first time a light-stimulated low-power synaptic device based on a single GaN nanowire has been demonstrated successfully. In such an artificial synaptic device, the incident light, the electrodes, and the light-generated carriers play the roles of action potential,presynaptic/postsynaptic membrane, and neurotransmitter in a biological synapse, respectively. Compared to those of other synaptic devices based on GaN materials, the energy consumption of the single-GaN-nanowire synaptic device can be reduced by more than 92%, reaching only 2.72 × 10^(-12)J. It is proposed that the oxygen element can contribute to the synaptic characteristics by taking the place of the nitrogen site. Moreover, it is found that the dynamic “learning-forgetting” performance of the artificial synapse can resemble the behavior of the human brain, where less time is required to relearn the missing information previously memorized and the memories can be strengthened after relearning. Based on the experimental conductance for long-term potentiation(LTP) and long-term depression(LTD), the simulated network can achieve a high recognition rate up to 90%after only three training epochs. Such few training times can reduce the energy consumption in the supervised learning processes substantially. Therefore, this work paves an effective way for developing single-nanowire-based synapses in the fields of artificial intelligence systems and neuromorphic computing technology requiring lowpower consumption.