The virtual sensing technique allows the active noise control (ANC) system to work with error microphones that are placed far from the desired zone of quietness (ZoQ). Conventionally, a training stage is required to obtain the auxiliary filters with the temporary error microphones placed in the ZoQ. When the characteristics of the primary noise changes, the auxiliary filters have to be retrained. As a result, the conventional virtual sensing technique can only be used when the frequency band of the primary noise remains unchanged. In order to solve this limitation, this paper proposes a selective virtual sensing technique for the multi-channel feedforward ANC system. The selective virtual sensing technique obtains a bank of auxiliary filters in the subband structure. Based on the frequency-band-matching mechanism, a linear combination of the auxiliary filters is calculated and used in the realtime control stage. Experimental results show that the selective virtual sensing technique achieves better noise reduction performance than the conventional virtual sensing technique when the frequency band of the primary noise fluctuates.

Silks play an important role in the life of various arthropods. A highly neglected prerequisite to make versatile use of silks is sufficient attachment to substrates. Although there have been some studies on the structure and mechanics of silk anchorages of spiders, for insects only anecdotal reports on attachment-associated spinning behaviour exist. Here, we experimentally studied the silk attachment of the pupae and last instar caterpillars of the tea bagworm (Butler 1881) (Lepidoptera, Psychidae) to the leaves of its host plant We found that the bagworms spin attachment discs, which share some structural features with those of spiders, like a plaque consisting of numerous overlaid, looped glue-coated silk fibres and the medially attaching suspension thread. Although the glue, which coats the fibres, cannot spread and adhere very well to the leaf surface, high pull-off forces were measured, yielding a mean safety factor (force divided by the animal weight) of 385.6. Presumably, the bagworms achieve this by removal of the leaf epidermis prior to silk attachment, which exposes the underlying tissue that represents a much better bonding site. This ensures a reliable attachment during the immobile, vulnerable pupal stage. This is the first study on the biomechanics and structure of silk attachments to substrates in insects.

Climbing robots that use bionic claws can climb vertical or even inverted rough surfaces. However, wall-climbing robots with unidirectional spiny feet cannot crawl horizontally or downward on vertical rough surfaces. In this paper, a pair of gripping spiny feet is used to give a robot the capacity to crawl in any direction on a rough wall. On the basis of observations of the gecko’s method for grasping onto a vertical rough surface, a multilevel interlocking structure is proposed. A spherical contact model of the claw tip on a vertical rough surface is established, and the influences of the contact angle, friction coefficient, and other factors on the grappling claw action are analyzed. Moreover, the optimal structure of the grappling claws is proposed. The force during the grasping and detachment of the mechanism and the influence of the number of feet on grasping performance are determined through experiments. Furthermore, a six-legged wall-climbing robot is designed and evaluated in terms of crawling on a vertical rough surface at various angles. The feasibility of using an opposed gripping mechanism to allow a robot to crawl in any direction on a vertical rough surface is also verified.

An enhanced Doppler resolution and sidelobe suppression have long been practical issues for moving target detection using Golay complementary waveforms. In this paper, Golay complementary waveform radar returns are combined with a proposed processor, the pointwise thresholding processor (PTP). Compared to the pointwise minimization processor (PMP) illustrated in a previous work, which could only achieve a Doppler resolution comparable to existing methods, this approach essentially increases the Doppler resolution to a very high level in theory. This study also introduced a further filtering process for the delay-Doppler map of the PTP, and simulations verified that the method results in a delay-Doppler map virtually free of range sidelobes.

This study describes the design of a new force measuring array with a quasi-cylindrical surface for measuring the 3D ground reaction forces of animals climbing on a surface with high curvature. This force-measuring array was assembled from 24 individual 3D force sensors, each with a resolution at the millinewton (mN) level, which were installed from top to bottom in four columns and six rows, with sensors in neighbouring columns staggered in height. Three cameras were used to simultaneously record the climbing behaviours of animals (in these experiments tree frogs) on the cylinder-like force measuring array. We were thus able to simultaneously record the ground reaction forces of each of the four limbs of tree frogs (here six individuals of the Chinese gliding or flying frog, Rhacophorus dennysi, with forelimb spans in the range 163-201 mm) climbing or descending both smooth and rough surfaces on a quasi-cylindrical structure with an overall diameter of 79 mm. We describe the design and calibration of the individual force sensors, their installation and arrangement on the quasi-cylindrical climbing tower, the recording of ground reaction forces and climbing behaviour, data transformations necessitated by the angular relationship of neighbouring sensors, and data processing using MATLAB scripts. Additionally, we present preliminary data on the use of a clamping grip by climbing frogs and the existence of small pull-off forces that aid toe-pad detachment at the end of each locomotor stance phase.