A vibration sensing manipulator and detection method for fruit quality detection

Abstract

The present invention provides a vibration sensing manipulator for fruit quality detection and a fruit quality detection method, which can sense the vibration generated by the fruit under external excitation, judge the quality of the fruit according to the vibration spectrum, measure accurately, and is suitable for popularization and application. It includes two fingers that can be relatively opened and closed, a vibrator and a vibrometer, and the vibrator and the vibrometer both include a protective shell, a piezoelectric ceramic sheet, a metal sheet, and a silicone gasket that are bonded and fixed in sequence; the silicone gaskets of the vibrator and the vibrometer are respectively bonded to the opposite surfaces of the two fingers; when the two fingers are closed, the fruit is clamped between the vibrator and the vibrometer; the piezoelectric ceramic sheet and the metal sheet of the vibrator are respectively connected to the positive and negative poles of the power supply, and the piezoelectric ceramic sheet of the vibrator vibrates under the change of the amplitude and frequency of the power supply voltage, so that the fruit and the piezoelectric ceramic sheet of the vibrometer vibrate, and the piezoelectric ceramic sheet and the metal sheet of the vibrometer are respectively connected to a detection analyzer for detecting voltage signals and analyzing their vibration spectrum.

Description

Technical Field

[0001] The present invention relates to the field of nondestructive testing of fruit and vegetable quality, and in particular to a vibration sensing manipulator for testing fruit quality and a corresponding testing method. Background Art

[0002] The fruit industry is an important part of my country's agriculture and the third largest industry after grain and vegetables. It plays an important role in social and economic development. At the same time, my country is also one of the largest fruit producers in the world, with rich fruit resources and broad market prospects.

[0003] With the advancement of agricultural modernization and the improvement of consumers' requirements for food safety and quality, the application of manipulators in agricultural production is becoming more and more extensive. Manipulators have shown great potential in fruit picking, sorting, packaging and other links due to their high degree of automation, precision and flexibility.

[0004] Different types of fruits have different quality characteristics. Robots with quality inspection functions can formulate corresponding operation strategies based on individual differences of fruits to avoid damaging the fruits and improve the commodity value of fruits through sorting. However, robots with fruit quality inspection functions are relatively rare in the current fruit picking and processing industry.

[0005] Vibration detection technology directly reflects the internal structure and physical properties of fruits by measuring their vibration response under external excitation, thereby detecting the quality of fruits. Fruits of different varieties, different maturity levels, and those with internal defects will produce different vibration responses when subjected to the same external excitation. Therefore, by collecting and analyzing the vibration signals of fruits, rapid and non-destructive detection of fruit quality can be achieved. However, due to limitations in sensor size, signal acquisition, and data processing, there have been no reports on manipulators with vibration sensing capabilities. Summary of the invention

[0006] The present invention provides a vibration sensing manipulator for fruit quality detection, which can sense the vibration generated by the fruit under external excitation and judge the quality of the fruit according to the vibration spectrum. It has a simple structure and accurate measurement, and can non-destructively detect the quality of various fruits such as pecan, tea fruit, citrus, peach, apple, pear, kiwi and tomato, and is suitable for popularization and application.

[0007] To achieve the above-mentioned purpose, the vibration sensing manipulator for fruit quality detection of the present invention comprises two fingers that can open and close relative to each other, a vibrator and a vibrometer. The structures of the vibrator and the vibrometer are similar, and both comprise a protective shell, a piezoelectric ceramic sheet, a metal sheet, and a silicone gasket that are bonded and fixed in sequence; the silicone gaskets of the vibrator and the vibrometer are respectively bonded to the opposite surfaces of the two fingers; when the two fingers are closed, the fruit is clamped between the vibrator and the vibrometer; the piezoelectric ceramic sheet and the metal sheet of the vibrator are respectively connected to the positive and negative poles of a power supply, the piezoelectric ceramic sheet of the vibrator vibrates under the change of the amplitude and frequency of the power supply voltage, so that the fruit and the piezoelectric ceramic sheet of the vibrometer vibrate, and the piezoelectric ceramic sheet and the metal sheet of the vibrometer are respectively connected to a detection analyzer for detecting a voltage signal and analyzing its vibration spectrum.

[0008] The above-mentioned vibration sensing manipulator for fruit quality detection, the exciter also includes a thin film pressure sensor for reflecting the clamping force of two fingers clamping the fruit; the protective shell, piezoelectric ceramic sheet, metal sheet, thin film pressure sensor and silicone gasket are bonded in sequence.

[0009] The above-mentioned vibration sensing manipulator for fruit quality inspection has two fingers connected to the main frame through a symmetrical transmission mechanism; the fingers are fixed at the head end of the joint, the middle part of the joint is hinged to one end of the rocker, the other end of the rocker is hinged to the main frame, the end of the joint is hinged to one end of the connecting rod, the other end of the connecting rod is fixedly connected to the worm gear, and the worm gear is rotatably set on the main frame; the worm gear cooperating with the two worm gears is located between the two worm gears; the worm gear is fixedly connected to the main shaft rotatably set on the main frame; the main shaft is used to be connected to a driving device that drives it to rotate.

[0010] In the above-mentioned vibration sensing manipulator for fruit quality detection, the center of the worm is provided with a cross-shaped groove that matches the main shaft, and the worm is fixed to the main shaft through a pin shaft.

[0011] The above-mentioned vibration sensing manipulator for fruit quality detection has a cross-shaped connection structure at the end of the main shaft for connecting to a mechanical arm that drives it to rotate.

[0012] The above-mentioned vibration sensing robot for fruit quality detection has a piezoelectric ceramic sheet made of lead barium zirconate titanate ceramic with a diameter of 10 mm and a thickness of 1 mm; the metal sheet is a metal sheet made of brass with a diameter of 15 mm and a thickness of 1 mm, and the piezoelectric ceramic sheet and the metal sheet are bonded with epoxy resin.

[0013] The above-mentioned vibration sensing manipulator for fruit quality detection uses a sinusoidal sweep signal with an amplitude of 5V and a frequency of 0-1500Hz as the power supply voltage, and the sweep speed is 2000Hz / s.

[0014] The present invention also provides a fruit quality detection method, which is fast, non-destructive and accurate, and can detect the quality of various fruits such as pecan, tea fruit, citrus, peach, apple, pear, kiwi and tomato. The method can formulate the best grasping and operation strategy for different fruits.

[0015] The fruit quality detection method adopts the above-mentioned vibration sensing manipulator and the same vibration excitation fruit to judge the fruit quality according to the obtained vibration response.

[0016] In the above-mentioned fruit quality detection method, the fruit is peach. The closer the resonance peak in the frequency domain vibration response curve of peach is to the high frequency, the higher the hardness of the peach is, and the softer the peach is, the higher the amplitude of the resonance peak is.

[0017] In the above-mentioned fruit quality detection method, the fruit is a pear. The more serious the brownness of the inner core of the pear is, the closer the resonance peak in the frequency domain vibration response curve of the pear is to the low frequency.

[0018] The method of using a vibration sensing manipulator to grab fruits and perform quality inspection is as follows:

[0019] The main shaft of the manipulator is connected to the manipulator arm, so that the vibrator and the vibration detector are fixed on the manipulator arm along with the manipulator. The motor in the manipulator arm drives the main shaft to rotate, and then the left and right fingers are gradually closed through the transmission of each component. When the left and right fingers touch the fruit, the left and right film pressure sensors begin to detect the finger pressure. At this time, the fingers are continued to be driven to close so that the pressure detected by the left and right film pressure sensors reaches a given threshold value to grasp the fruit. The threshold value can be adjusted according to the softness and hardness of the fruit. After grasping the fruit, the vibrator generates vibration on the left side to excite the fruit. The present invention preferentially uses a sinusoidal sweep frequency signal with an amplitude of 5V and a frequency of 0-1500Hz to excite the fruit. The sweep frequency speed is 2000Hz / s. The amplitude, frequency range and sweep frequency speed of the excitation can also be adjusted according to the test requirements. The vibration of the fruit is measured on the right side using a vibration detector.

[0020] To further explain the effect of fruit quality on its vibration response, the fruit is simplified into a spring-mass-damper system. When the system vibrates under the action of a sinusoidal force f(t), its vibration equation can be calculated as follows:

[0021]

[0022] Where m is the mass, x is the displacement, c is the damping constant, and k is the elastic coefficient.

[0023] The system will undergo forced simple harmonic vibration, and its amplitude X can be calculated as follows:

[0024]

[0025] Where F0 and ω are the amplitude and angular frequency of f(t), respectively.

[0026] In summary, the vibration response of the fruit is related to the excitation signal and its own physical properties. When the same signal is used to excite the fruit, the vibration response of the fruit is only related to its own physical properties, while quality indicators such as maturity, weight, hardness, and internal defects will affect the physical properties of the fruit. Therefore, by obtaining the vibration response of the fruit and establishing different detection models, specific quality parameters of the object under test can be non-destructively evaluated.

[0027] Compared with the prior art, the present invention has the following advantages:

[0028] The present invention provides a vibration sensing manipulator for fruit quality detection and a fruit quality detection method, which can perform personalized operations in the picking, sorting, packaging and other links according to the quality characteristics of the fruit to avoid damaging the fruit, and improve the commercial value of the fruit through sorting, thereby providing technical support for improving the quality and efficiency of the fruit industry. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a schematic diagram of the overall structure of the vibration sensing manipulator;

[0030] Figure 2 A three-dimensional graph of the main axis;

[0031] Figure 3 It is the structural diagram of the exciter;

[0032] Figure 4 is a structural schematic diagram of a vibrometer;

[0033] Figure 5 This is a schematic diagram of the working state changes of the vibration sensing manipulator during measurement;

[0034] Figure 6 Vibration response signals obtained for grasping peaches of different hardness;

[0035] Figure 7 Vibration response signals obtained for grasping pears with different degrees of internal brownness;

[0036] Figure 8 A three-dimensional image of the vibration-sensing manipulator.

[0037] In the figure, 1-vibrator, 2-vibrometer, 3-left finger, 4-left joint, 5-left rocker, 6-left connecting rod, 7-left worm gear, 8-worm, 9-main frame, 10-spindle, 11-right worm gear, 12-right connecting rod, 13-right joint, 14-right rocker, 15-right finger, 101-left protective shell, 102-left piezoelectric ceramic sheet, 103-left metal sheet, 104-left thin film pressure sensor, 105-left silicone gasket, 201-right protective shell, 202-right piezoelectric ceramic sheet, 203-right metal sheet, 204-right thin film pressure sensor, 205-right silicone gasket. DETAILED DESCRIPTION

[0038] The present invention will be further described below in conjunction with the accompanying drawings, but the present invention is not limited to the following embodiments.

[0039] See also Figure 1 , 8 The vibration sensing manipulator of the present invention includes a vibration exciter for stimulating the fruit, the vibration exciter is integrated on the left finger of the manipulator, and a vibration detector for measuring the vibration response of the fruit, the vibration detector is integrated on the right finger of the fruit, the fingertips of the left and right fingers are provided with grooves, and the vibration exciter and the vibration detector are respectively fixed in the grooves of the left and right fingers with adhesive. The left and right fingers are fixedly connected to the left and right joints, the middle parts of the left and right joints are hinged to the left and right rockers, the left and right rockers are hinged to the main frame, the ends of the left and right joints are hinged to the left and right connecting rods, the ends of the left and right connecting rods are fixedly connected to the left and right worm gears, and the left and right worm gears are rotatably arranged on the main frame (or, the ends of the left and right connecting rods are hinged to the main frame, the left and right worm gears are fixed on the left and right connecting rods, but the center lines of the left and right worm gears coincide with the axis lines of the left and right connecting rod ends hinged to the main frame). See. Figure 1 / 2, there is a worm in the middle of the main frame, which forms a transmission pair with the left and right worm wheels. A cross-shaped groove is provided inside the worm, which is fixed to the main shaft by a pin. The main shaft is rotatably set on the main frame, and a cross-shaped connecting structure is provided at the end of the main shaft for easy connection with the robotic arm.

[0040] During operation, the motor of the robotic arm drives the main shaft of the robot arm of the present invention to rotate, the main shaft drives the worm to rotate, the worm drives the left worm gear and the right worm gear to rotate, the left and right connecting rods rotate around the connection point of the main frame, and then drive the left and right joints and the left and right fingers to open and close, and the left and right rockers play the role of supporting the joints.

[0041] See also Figure 3The exciter consists of a left protective shell, a left piezoelectric ceramic sheet, a left metal sheet, a left thin film pressure sensor and a left silicone gasket. The left piezoelectric ceramic sheet and the left metal sheet are respectively connected to the positive and negative electrodes of the power supply. Under the action of the external voltage, the piezoelectric ceramic sheet will produce a piezoelectric effect, and mechanical deformation and vibration will occur with the change of the amplitude and frequency of the voltage. The size of the piezoelectric ceramic sheet and the metal sheet can be customized according to the size of the manipulator, and bonded with adhesive grease. The present invention uses lead zirconate barium titanate ceramic to make a left piezoelectric ceramic sheet with a diameter of 10mm and a thickness of 1mm, and uses brass to make a left metal sheet with a diameter of 15mm and a thickness of 1mm, and bonded with epoxy resin. The left thin film pressure sensor is used to detect the contact force between the left finger and the grasped target to ensure the reliability of the excitation. The present invention uses a Force Sensing Resistor left thin film pressure sensor with a diameter of 14mm and a thickness of 0.3mm. The left silicone gasket is used as the base of the exciter and is fixed to the bottom of the left finger groove by an adhesive.

[0042] See also Figure 4 The vibrometer is composed of a right protective shell, a right piezoelectric ceramic sheet, a right metal sheet, a right thin film pressure sensor and a right silicone gasket. When the right piezoelectric ceramic sheet is subjected to mechanical vibration, the charge distribution inside it will change, thereby generating a voltage signal. The magnitude of the voltage signal is related to the amplitude and frequency of the vibration, so the vibration can be detected by measuring the voltage signal. The size of the piezoelectric ceramic sheet and the metal sheet can be customized according to the size of the manipulator, and bonded with adhesive. The present invention uses lead barium zirconate titanate ceramic to make a right piezoelectric ceramic sheet with a diameter of 10mm and a thickness of 1mm, and uses brass to make a right metal sheet with a diameter of 15mm and a thickness of 1mm, and bonded with epoxy resin. The right thin film pressure sensor is used to detect the contact force between the right finger and the grasped target to ensure the accuracy of the vibration measurement result. The present invention uses a ForceSensing Resistor right thin film pressure sensor with a diameter of 14mm and a thickness of 0.3mm. The right silicone gasket serves as the base of the vibrometer and is fixed to the bottom of the right finger groove by an adhesive.

[0043] like Figure 5 As shown, when grasping the fruit, the mechanical arm equipped with the manipulator of the present invention is moved to the top of the fruit, and the motor in the mechanical arm drives the manipulator to gradually close. When the left finger and the right finger touch the fruit, the left film pressure sensor and the right film pressure sensor begin to detect the finger pressure, and continue to drive the fingers to close so that the pressure detected by the left and right film pressure sensors reaches a given threshold value, at which time it is considered that the fruit has been grasped. After grasping the fruit, the exciter generates vibration on the left side to excite the fruit, and the vibration of the fruit is measured on the right side using a vibrometer. When the same vibration is used to excite the fruit, fruits of different qualities will produce different vibration responses, so the quality of the fruit can be judged by the obtained vibration response.

[0044] like Figure 6 As shown, the present invention grabs peaches of three different hardnesses: soft, medium, and hard, and measures the vibration responses of the three peaches. The frequency domain vibration response curves of peaches of different hardnesses are significantly different. As the hardness increases, the resonance peak of the peach gradually moves toward the high frequency direction, and the softer the peach, the higher the amplitude of the resonance peak. In addition, soft peaches have higher energy in the low frequency band. Figure 7 As shown, the present invention grabs pears with three different degrees of internal brown core, namely healthy, sub-healthy and brown core, and measures the vibration responses of the three pears. The frequency domain vibration response curves of pears with different degrees of internal brown core are obviously different. The main resonance frequency of healthy pears is 670Hz, the main resonance frequency of slightly brown core sub-healthy pears is 520Hz, and the main resonance frequency of severely brown core pears is 430Hz. As the degree of brown core of pears increases, its resonance peak gradually moves toward the low frequency direction, and the amplitude of the resonance peak decreases slightly.

[0045] The above results show that the vibration sensing manipulator of the present invention can obtain the vibration response of the grasped fruit and can judge the quality of the fruit based on the vibration response.

[0046] The vibration sensing manipulator and detection method for fruit quality detection proposed in the present invention are intended to achieve rapid, non-destructive and accurate detection of fruit quality, formulate optimal grasping and operation strategies based on individual differences of fruits, and provide strong support for the intelligent and automated development of the fruit industry.

Claims

1. A method for detecting fruit quality, characterized in that: A vibration sensing manipulator is used, and the vibration sensing manipulator includes two fingers that can open and close relative to each other, a vibrator and a vibrometer. The structures of the vibrator and the vibrometer are similar, and both include a protective shell, a piezoelectric ceramic sheet, a metal sheet, a thin film pressure sensor, and a silicone gasket that are bonded and fixed in sequence; the silicone gaskets of the vibrator and the vibrometer are respectively bonded to the opposite surfaces of the two fingers; when the two fingers are closed, the fruit is clamped between the vibrator and the vibrometer; the thin film pressure sensor is used to reflect the clamping force of the two fingers clamping the fruit; the piezoelectric ceramic sheet and the metal sheet of the vibrator are respectively connected to the positive and negative poles of the power supply, and the piezoelectric ceramic sheet of the vibrator vibrates under the change of the amplitude and frequency of the power supply voltage, so that the fruit and the piezoelectric ceramic sheet of the vibrometer vibrate, and the piezoelectric ceramic sheet and the metal sheet of the vibrometer are respectively connected to a detection analyzer for detecting voltage signals and analyzing their vibration spectrum; When the vibration sensing manipulator grasps the fruit, when the left and right fingers touch the fruit, the left and right film pressure sensors begin to detect the finger pressure, and the fingers continue to close so that the pressure detected by the left and right film pressure sensors reaches a given threshold, at which time it is considered that the fruit has been grasped; after grasping the fruit, the exciter generates vibration on the left side to stimulate the fruit, and the vibration meter is used to measure the vibration of the fruit on the right side; the same vibration is used to excite the fruit, and the fruit quality is judged based on the obtained vibration response; the power supply voltage uses a sinusoidal sweep signal with an amplitude of 5 V and a frequency of 0-1500 Hz, and the sweep speed is 2000 Hz / s.

2. The fruit quality detection method according to claim 1, characterized in that: The two fingers are connected to the main frame through a symmetrical transmission mechanism; the fingers are fixed at the head end of the joint, the middle part of the joint is hinged to one end of the rocker, the other end of the rocker is hinged to the main frame, the end of the joint is hinged to one end of the connecting rod, the other end of the connecting rod is fixedly connected to the worm gear, and the worm gear is rotatably set on the main frame; the worm gear cooperating with the two worm gears is located between the two worm gears; the worm gear is fixedly connected to the main shaft rotatably set on the main frame; the main shaft is used to be connected to a driving device that drives it to rotate.

3. The fruit quality detection method according to claim 2, characterized in that: The center of the worm is provided with a cross-shaped groove matched with the main shaft, and the worm is fixed to the main shaft through a pin shaft.

4. The fruit quality detection method according to claim 2, characterized in that: A cross-shaped connecting structure is provided at the end of the main shaft for connecting with a mechanical arm that drives it to rotate.

5. The fruit quality detection method according to claim 1, characterized in that: The piezoelectric ceramic sheet is a piezoelectric ceramic sheet made of lead barium zirconate titanate ceramic with a diameter of 10 mm and a thickness of 1 mm; the metal sheet is a metal sheet made of brass with a diameter of 15 mm and a thickness of 1 mm, and the piezoelectric ceramic sheet and the metal sheet are bonded with epoxy resin.

6. The fruit quality detection method according to claim 1, characterized in that: The fruit is a peach. In the frequency domain vibration response curve of the peach, the closer the resonance peak is to the high frequency, the higher the hardness of the peach is, and the softer the peach is, the higher the amplitude of the resonance peak is.

7. The fruit quality detection method according to claim 1, characterized in that: The fruit is a pear. The more severely brown the inner core of the pear is, the closer the resonance peak in the frequency domain vibration response curve of the pear is to the low frequency.

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