Figure 3.(a) Actual profile of the sheet; (b) Processed profile obtained from the image.This signal contains the information on the deformation of the sheet. Therefore, there is a correspondence between the significant points of this signal (Figure 3b) and the significant points of the sheet deformation (Figure 3a). These points are:Point 0: start point of the imperfection. At this point there is a change of curvature in the sheet (Figure 3a), changing the slope sign. In the processed profile (Figure 3b) it results in an inflection point.Point 2: point of maximum height of the defect (Figure 3a). In the processed profile (Figure 3b) it is equivalent to an inflection point at which the gradient is maximum. The information from this gradient is related to the height or severity of the imperfection.

Point 4: end point of the imperfection. At this point there is a change of curvature in the sheet (Figure 3a), changing the slope sign. In the processed profile (Figure 3b) it results in a new inflection point.4.2. Profile ObtainingTherefore, an algorithm has been implemented that takes into account the specific characteristics of the profiles obtained from the image. This algorithm processes the profile signal, detecting the maximum, the minimum, and the inflection points and it stores the information. The steps followed by the algorithm are:Image filter: for the direction in which the profile is going to be analyzed, a box is set in the image and a media filtering is performed around this direction with a width between 5 and 10 pixels. This way the effects of the illumination system are reduced.

Signal filter: to eliminate the noise in the signal obtained from the profile, a filter based on wavelets is applied. It is a smooth filter based on a heuristic variant of the Stein risk principle with a rescaled threshold depending on the noise level of the signal. The problem with this filter is that the filtered signal is affected Carfilzomib by the length of the signal, especially if a big length is taken in which the initial and final ends do not contain information of the imperfection and generate a high component of noise. To avoid this problem, the signal filter divides into two stages:(a)In a first stage the signal is filtered by the wavelet filter and the start and end points limiting the useful information of the profile are
Generally, the quality of oil palm fruits is categorized based on the texture, shape and color of the fruit [1].

Currently in Malaysia, the human expert grading approach is used to inspect the maturity of oil palm FFB and classify them for harvesting. Typically, the color of the surface of the fruit and the number of loose fruit drops from bunches are the two main factors that guide the judgement of human experts [1,2]. In practice, this type of grading method often leads to mistakes where there is high potential to grade the fruit wrongly.

In these review we investigate the functional materials and the tactile sensor devices, presented in literature, exploiting flexible composites with piezoresistive properties. These materials are one of the best candidates to fabricate a sensing ��skin��, able to reproduce the tactile sense and to fit the shape of the robot structure. Beyond the high conformability required to mimic the human skin, these composite sensing materials can be employed to generate devices with a wide range of sensitivity, a low power consumption and an elevate mechanical resistance guaranteeing protection from external physical agents that could damage the sensor. The major drawbacks of these types of devices are represented by the temperature sensitivity and hysteresis phenomena of the sensing response, which could influence the repeatability of the measurements [2,3].

We perform a classification on the basis of the piezoresistive conduction mechanism dividing the tactile sensors into piezoresistors, strain gauges, percolative and quantum tunnelling devices. For each flexible tactile device family we analyze the physics behind the conduction mechanism and we describe the state-of-the-art from the point of view of the material employed and the adopted architecture. The design and the performance are also reviewed, with a perspective outlook on the main promising applications. To introduce the following detailed analysis a general qualitative comparison of the four different tactile sensor types is presented in Table 2.

Furthermore a table (Tables 3, ,4,4, ,55 and and6)6) with a quantitative comparison of each analyzed device is reported at the end of each section.Table 2.Comparison of the different flexible composite tactile sensors.Table 3.Comparison of tactile sensor solutions based on flexible piezoresistor.Table 4.Comparison of tactile sensor solutions based on flexible strain gauges.Table 5.Comparison of tactile sensor solutions based on percolation mechanism.Table 6.Comparison of tactile sensor solutions based on quantum tunnelling mechanism.2.?PiezoresistorsThe work principle in piezoresistors consists in a variation of the resistivity of the material itself due to an applied stress. In general piezoresistors are made of silicon or other semiconductors, like germanium.

Here the stress modifies the width of the band-g
The bell-shaped vibratory angular rate gyro (BVG) is a kind of solid wave gyro that detects the input angular rate using the standing wave’s precession on a bell-shaped resonator. Its core component is a bell-shaped resonator-like millimeter-scale Chinese traditional bell. The resonator uses the exciting AV-951 and detecting electrodes on its wall to control the resonator’s mode to generate a special standing wave and extracts the precession to detect the angular rate.