CN106595928A - Clamping force detection system and method for seedling clamping manipulator - Google Patents

Abstract

The invention relates to a clamping force detection system of a seedling clamping manipulator and a detection method using the system. The detection method includes the following steps: Step 1, by setting the clamping force inside the clamping section of the rotating seedling clamping needle of the seedling clamping manipulator The pressure sensor is used to detect the pressure F ₂ at the corresponding position of the clamping force section when the rotating clamping needle and the corresponding clamping needle are closed and clamped; step 2, the pressure F ₂ obtained in step 1 is brought into the following calculation The total clamping force F _N of the clamping force section of the rotating clamping needle is calculated from the formula: According to the law that the force of the rotary clamping needle is linearly distributed when clamping pot seedlings, after further analysis, the relationship between the total clamping force of the clamping section of the clamping manipulator and the clamping force at a certain point is obtained , so the pressure sensor is placed close to the inner side of the clamping force section of the rotating clamping needle to make the detected clamping force more accurate and infinitely close to the real value.

Description

Clamping force detection system of seedling manipulator and detection method using the system

technical field

The invention relates to a clamping force detection system of a manipulator for clamping seedlings and a detection method using the system.

Background technique

As early as the 1970s, seedling cultivation and transplanting of vegetables, flowers and other crops had become a specialized greenhouse production mode, and plug seedling technology had appeared and shown extremely strong vitality. Since the beginning of the 21st century, this technology has been widely used in the production of annual and biennial plants and flowers, and has also been widely used in some vegetable crops and some economic crops such as tobacco. At present, my country has preliminarily established an industrialized seedling raising technology system, and the output of commercial seedlings of vegetables alone has reached more than 100 billion plants.

At present, developed countries such as the Netherlands have widely used transplanting machines for seedling transplanting operations, such as the PIC-O-MAT PC-21 automatic transplanting machine for greenhouse seedlings of the Dutch company Fraxel, and the XT616 of the Australian TRANSLATE SYSTEMS company. There is a special transplanting machine for tea tree plug seedlings, but the transplanting operation in China is still labor-intensive work, which is mainly done by hand. However, with the acceleration of urbanization, there is a serious shortage of labor force in rural areas, and domestic growers, especially large-scale farms, are more and more eager for mechanization and automation of seedling transplanting.

The transplanting of plug seedlings in my country is at the level of manual seedling picking and semi-automatic seedling planting, so the research and development of a seedling picking device with simple structure, excellent function and suitable for local seedling production is the key to realize automatic transplanting of plug seedlings. At present, no automatic transplanting machine that can be used in actual production has been designed in China. The main reason is that the interaction between the seedling claws and the pot body is not clear in the mechanism design, the biomechanical characteristics data of the plug seedlings are in short supply, and the mechanism design and seedling raising process are inconsistent. In combination, the clamping force is unstable and inaccurate during the seedling picking process, the seedlings are easy to disperse when the force is too large, and the seedlings cannot leave the seedling tray completely if the force is too small, which seriously restricts the development of automatic transplanting machines.

At present, there is no mature system dedicated to measuring the gripping force of the manipulator on the market, let alone the popularization and application of it in the field of plug seedling transplanting, which is extremely difficult. Some manufacturers obtain a reasonable value by estimating a reasonable value or based on production experience, plus testing and modification. There are also some manufacturers who use inaccurate detection systems, and still need to test and modify, which greatly reduces productivity. Therefore, it is necessary to design a corresponding system and method to detect the clamping force of the manipulator for clamping seedlings, so as to realize automatic, concise and intelligent transplanting of seedlings in plug trays.

Contents of the invention

The purpose of the present invention is to provide a simple structure and low cost detection system for the clamping force of the manipulator for clamping seedlings; meanwhile, the present invention also provides a method for detecting the clamping force of the manipulator for clamping seedlings using the above-mentioned detection system.

In order to achieve the above object, the technical solution of the clamping force detection system of the clamping manipulator provided by the present invention is: the clamping force detection system of the clamping manipulator is used to be arranged on the clamping receiving device of the rotating clamping needle of the clamping manipulator. The pressure sensor inside the force section is used to detect the force at the corresponding position of the clamping force section when the seedling clamping needle is rotated and the corresponding seedling clamping needle is closed to clamp the seedlings. The signal output end of the pressure sensor is connected to a corresponding signal processing unit.

The pressure sensor is a PVDF piezoelectric film sensor.

The signal processing unit includes a filter circuit, an amplifier circuit, an A/D conversion circuit and an algorithm processing module arranged in sequence, and the signal processing unit is connected to a mobile display terminal and/or a PC display terminal through a wireless output module.

The technical scheme of the clamping force detection method of the seedling manipulator using the above-mentioned detection system provided by the present invention is: a kind of clamping force detection method of the seedling manipulator, comprising the following steps:

Step 1, through the pressure sensor arranged on the inner side of the clamping force section of the rotating seedling clamping needle of the seedling clamping manipulator, when the rotating seedling clamping needle and the corresponding seedling clamping needle close the clamping seedlings, the corresponding position of the clamping force receiving section is detected Under pressure F ₂ ;

Step 2, put the pressure F ₂ obtained in step 1 into the following calculation formula to calculate the total clamping force F _N of the clamping section of the rotating clamping needle:

The position of the axis of rotation of the rotating clamping needle is defined as the reference point, L3 is the distance between the near end _of the clamping section near the reference point and the reference point, and L4 is the distance away from the reference point of the clamping section _. The distance between the far end and the reference point, ΔL is the width of the pressure sensor in the extension direction of the clamping force section, L is the distance from any hypothetical point on the clamping force section to the reference point, F ₃ is the bearing pressure of the hypothetical point pressure.

The pressure sensor in the first step is a PVDF piezoelectric film sensor.

The beneficial effects of the present invention are:

1. According to the law that the force of the rotating seedling clamping needle is linearly distributed when it cooperates with the corresponding seedling clamping needle to clamp the pot seedlings, after further analysis, it is obtained that the total clamping force of the clamping force section on the clamping manipulator and the force of a certain point The relationship between the clamping force, so the pressure sensor is closely attached to the inner side of the clamping force section of the rotating clamping needle to make the detected clamping force more accurate and infinitely close to the real value.

2. It is convenient for the staff to accurately detect the size of the clamping force, which can facilitate the operator to accurately control the size of the clamping force, realize non-destructive clamping, avoid loss, reduce costs, and have a good prospect in industrial applications.

Description of drawings

Fig. 1 is the structural representation when a kind of seedling clamping manipulator clamps and takes seedling operation in hole tray;

Fig. 2 is the structural representation of an embodiment of the seedling clamping manipulator clamping force detection system provided by the present invention;

Fig. 3 is the force analysis schematic diagram that piezoelectric film sensor is applied on the rotation clamping pin of clamping seedling manipulator shown in Fig. 1 in the detection system shown in Fig. 2;

Fig. 4 is the finite element analysis figure of clamping seedling manipulator shown in Fig. 1;

Fig. 5 is the grid division figure corresponding to Fig. 4 finite element analysis;

Fig. 6 is the maximum stress figure in Fig. 4 finite element analysis;

Fig. 7 is a diagram of the maximum deformation in the finite element analysis of Fig. 4 .

detailed description

Embodiments of the present invention will be further described below in conjunction with the accompanying drawings.

In order to better illustrate the clamping force detection system and detection method of the seedling clamping manipulator provided by the present invention, a seedling clamping manipulator is firstly introduced, which includes a bracket, and the front end of the bracket is provided with two shaft sleeves arranged in parallel. Equipped with supporting rotating shafts, each supporting rotating shaft 1 is respectively fixed with a rotating seedling clamping needle 6, and the rotating seedling clamping needle 6 is fixed to the supporting rotating shaft 1. The bottoms of the two rotating seedling clamping needles 6 respectively have clamping stressed sections, and the clamping stressed sections are located below the supporting rotating shaft 1, and the two rotating clamping seedling needles rotate around the supporting rotating shaft, and the clamping stressed sections of the two rotating clamping seedling needles Closing towards each other and opening towards each other to realize the picking and throwing action of closing the seedlings and opening and throwing.

An extension spring 4 is arranged between the two clip seedling needle mounting frames, and the extension spring 4 applies to the two rotating clip seedling needles 6 to force the two rotating clip seedling needles to rotate so that the two clamping stressed sections open oppositely.

Between the two rotating seedling clamping needles, there is a rotating push plate 2, the axis of rotation of the pushing plate 2 extends in the left and right direction in Fig. The seedling needle pushes and fits and gradually rises toward the pushing transition surface toward the pushing direction, and the displacement force exerted by the pushing transition surface on the clamping needle is opposite to the direction of the elastic force exerted by the extension spring.

The rotating seedling clamping needle is provided with a compression screw 5 for pressing on the push plate. During the rotation of the push plate, when the pressure screw 5 moves to the transition surface of the push, the pressure screw will wrap around the corresponding support. The rotating shaft rotates toward the direction away from the push plate. At this time, under the situation of overcoming the active force of the tension spring 4, the two clamping force sections will be forced to close to realize clamping.

When the clamping manipulator used, it stretched into the hole plate 7 to clamp the inner pot seedlings.

The embodiment of the clamping force detection system of the clamping manipulator provided by the present invention is shown in Figure 2. The sensor, the pressure sensor is a PVDF piezoelectric film sensor to detect the force at the corresponding position of the clamping force section when the rotating clamping needle and the corresponding clamping needle are closed and clamped, and the signal output end of the pressure sensor is connected to the corresponding signal processing The signal processing unit here includes a filter circuit, an amplification circuit, an A/D conversion circuit and an algorithm processing module arranged in sequence, and the signal processing unit is connected to a mobile display terminal or a PC display terminal through a wireless output module.

For the PVDF piezoelectric film sensor, the surface of the piezoelectric material generates a charge after being stressed, and the charge is amplified by the charge amplifier and the measurement circuit and transformed into an electrical output proportional to the external force. Piezoelectric sensors are used to measure force and non-electrical quantities that can be transformed into force. Its advantages are wide frequency band, high sensitivity, high signal-to-noise ratio, simple structure, reliable operation and light weight.

The analysis shows that the seedling manipulator will slide and tremble during the seedling clipping process, which will affect the piezoelectric film sensor. Therefore, attention should be paid to removing clutter signals during analysis, and a filter circuit should be designed for interference signal processing. Design the corresponding filter circuit after the piezoelectric film sensor to filter out the clutter, and the corresponding amplifier circuit to amplify the signal, and then transmit the signal to the computer through the wireless transmission module. When designing the detection circuit, fully consider its accuracy, standard value degree of linear correlation, etc.

After analysis of the filter circuit, it is known that when the manipulator rotates the clamping needle from contacting the seedlings in the hole to clamping, there will be slight sliding and shaking. At this time, it will affect the piezoelectric film sensor. Real-time detection brings the impact of errors, so attention should be paid to removing clutter signals during analysis, and a filter circuit should be designed for interference signal processing. The role of the filter circuit is to reduce the AC component in the pulsating DC voltage as much as possible, retain its DC component, reduce the ripple coefficient of the output voltage, and make the waveform smoother.

The amplifying circuit adopts a high-precision millivolt and microvolt small signal differential/single-ended voltage AD620 amplifier. High precision, low offset, high linearity. The differential voltage amplifier can output positive and negative voltages, and can also amplify single-ended signals. The default amplification is 23-1000 times adjustable. The working power range is wide, and when the power supply is 4-30V, the maximum output range is constant. The maximum output amplitude can be set, the default is -10.5V-+10.5V, no amplitude potentiometer. The magnification and zero output voltage can be adjusted.

A/D conversion circuit, the process of A/D conversion is to convert the received analog signal into a digital format through several processes of sampling, holding, quantization, and encoding in sequence, sampling and holding to sample the analog signal at uniform intervals, and every After a sampling operation, keep the sampling value constant for a sufficient time to ensure that the output value can be accurately converted by the A/D converter. The rounding method is used during quantization, and finally the quantized result is expressed in binary code, which is called coding. ADS1256, 24-bit data conversion, and 8-channel AD module are used for A/D conversion to realize this function.

The algorithm processing module is the STM32 register, and the collected signal is stored in the STM32 register through related processing.

The wireless transmission module is specifically a Bluetooth module, which transmits the data information stored in the memory after processing to the PC display terminal and/or the visual interface of the mobile display terminal in the form of wireless transmission through the Bluetooth module, and the mobile display terminal can specifically be a mobile phone.

In this embodiment, the detection system pastes a pressure sensor on the inner side of one of the clamping force-bearing sections of the rotating seedling clamping needle, and the force on the corresponding rotating seedling clamping needle is shown in FIG. 3 .

When using the above detection system to detect the clamping force of the seedling manipulator, the following steps can be taken:

Step 1, through the pressure sensor arranged on the inner side of the clamping force section of the rotating seedling clamping needle of the seedling clamping manipulator, when the rotating seedling clamping needle and the corresponding seedling clamping needle close the clamping seedlings, the corresponding position of the clamping force receiving section is detected Under pressure F ₂ ;

Step 2. Put the pressure F ₂ obtained in step 1 into the following calculation formula to calculate the total clamping force F _N of the clamping section of the rotating clamping needle:

The position of the axis of rotation of the rotating clamping needle is defined as the reference point, L3 is the distance between the near end _of the clamping section near the reference point and the reference point, and L4 is the distance away from the reference point of the clamping section _. The distance between the far end and the reference point, ΔL is the width of the piezoelectric sensor in the extension direction of the clamping force section, L is the distance from any hypothetical point on the clamping force section to the reference point, F ₃ is the distance between the hypothetical point under pressure.

What needs to be explained here is that, according to the force of rotating the seedling clamping needle as shown in Figure 3, combined with the finite element analysis of the seedling clamping manipulator, referring to Figures 4 to 7, it can be known that the rotating seedling clamping needle of the manipulator is in the position of clamping seedlings. The stress size during the time changes linearly, so, accordingly, the stress analysis of the single rotating seedling clamping needle 10 as shown in Figure 3 can be provided, and according to the lever principle, the following two formulas can be drawn:

F ₂ L ₂ =F ₁ L ₁ =F ₃ L (2)

As shown in Figure 3, point O represents the position of the axis of rotation of the rotating shaft that rotates the clamping needle 10, and it is defined as a reference point. In the above formulas (2) and (3), F1 is the pressure _of the rotating clamping needle 10 _The pushing force between the clamping screw and the pushing plate, L1 is the distance between the clamping screw and the reference point, F2 is the pressure measured by the PVDF piezoelectric film sensor ₂₀₀ pasted on the clamping force section 100, L ₂ is the distance between the PVDF piezoelectric film sensor 200 and the reference point O, L is the distance from any hypothetical point on the clamping section to the reference point, and F ₃ is the pressure borne by the hypothetical point.

The formula is integrated to obtain the total clamping force F _N of the clamping section, which is the formula (1). The upper and lower limits of the integral are L ₄ and L ₃ , L ₃ is the distance between the near end of the clamping force section close to the reference point and the reference point, and L ₄ is the distance between the far end of the clamping force section away from the reference point and the reference point The selection of the upper and lower limits is determined according to the position where the rotating clamping needle contacts the soil. After the integral calculation of the upper and lower limits, the clamping force at the position where the rotating clamping needle contacts the soil is just obtained. In the formula (1), the overall clamping force can be obtained by integrating the force at any point measured by the pressure sensor on the distance between the rotating clamping needle and the soil, because the contact between the sensor and the clamping needle cannot be equal. The effect is a point, so ΔL appears in the denominator of the formula for correction. After force analysis, the linear distribution relationship of clamping force and a specific method for calculating clamping force are obtained.

In this example, according to the force model of the pot seedlings clamped by the rotating clamping needle in the seedling clamping manipulator and combined with the finite element analysis, an effective and feasible detection method for the clamping force of the manipulator is obtained: The entire process of clamping and picking seedlings from the outside of the plug into the plug, the PVDF piezoelectric film sensor will synchronously transmit the detected changes in the dynamic clamping force to the signal processing unit, and synchronize the data to the mobile phone or PC through the Bluetooth module At the terminal, the force at the position where the PVDF piezoelectric film sensor is pasted on the clamping force section can be obtained. Carry out such tests many times to obtain multiple sets of force data, respectively take the maximum value on the force measurement curve of the PVDF piezoelectric film sensor in one cycle as the clamping force, calculate the average value through multiple actual measurements, and finally determine a Instructive blessing.

In fact, when testing, a plurality of PVDF piezoelectric film sensors can also be pasted on the clamping section of the rotating clamping needle to be tested, so as to improve the measurement accuracy. For a plurality of rotating clamping needles used in conjunction, the measurement can be performed only on a single rotating clamping needle, and pressure sensors can also be pasted on all the rotating clamping needles used in conjunction. Of course, the rotating clamping needle can also be used in conjunction with the fixed clamping needle.

The present invention also provides a method for detecting the clamping force of the manipulator for clamping seedlings. The content of the detection method is the same as that of the detection system for the detection system for the clamping force of the manipulator for clamping seedlings, and will not be repeated here.

Claims (5)

1. seedling clipping machine tool handss clamp force detection system, it is characterised in that：For being arranged on the rotating clip that seedling clipping machine tool handss have Pressure transducer on the inside of the clamping stress section of Seedling pin, with the detection clamping when rotating clip Seedling pin is with corresponding folder Seedling pin closure folder Seedling Stress section corresponding position stress, the signal output part of pressure transducer are connected with corresponding signal processing unit.

2. seedling clipping machine tool handss according to claim 1 clamp force detection system, it is characterised in that：The pressure transducer is PVDF piezoelectric film sensors.

3. seedling clipping machine tool handss according to claim 1 and 2 clamp force detection system, it is characterised in that：The signal processing Unit includes filter circuit, amplifying circuit, A/D change-over circuits and the algorithm processing module being sequentially arranged, and signal processing unit leads to Cross wireless output module to be connected with mobile display terminal and/or PC display terminal signals.

4. a kind of seedling clipping machine tool handss chucking power detection method, it is characterised in that：Comprise the steps：

Step one, by the pressure sensing being arranged on the inside of the clamping stress section of the rotating clip Seedling pin that seedling clipping machine tool handss have Device, the pressure F that detection clamping stress section corresponding position is born when rotating clip Seedling pin is with corresponding folder Seedling pin closure folder Seedling₂；

Step 2, by the pressure F obtained in step one₂, bring into and the clamping of rotating clip Seedling pin is calculated during formula is calculated as below receives Total chucking power F of power section_N：

$F_N={\mathrm{\ΣF}}_3={\∫}_{L_3}^{L_4}\frac{F_2{L}_3}{\mathrm{\Δ}L\·L}dL$

The position that the pivot center of rotating clip Seedling pin is located is set to into reference point, L₃To clamp the near of the close reference point of stress section End and the distance of reference point, L₄To clamp the distal end away from reference point of stress section and the distance of reference point, Δ L is pressure sensing Width of the device on clamping stress section bearing of trend, L is the distance for clamping any one postulated point distance reference point in stress section, F₃The pressure born by the postulated point.

5. seedling clipping machine tool handss chucking power detection method according to claim 4, it is characterised in that：Pressure in the step one Force transducer is PVDF piezoelectric film sensors.