CN113607079B - A general-purpose trenching depth detection device - Google Patents

Abstract

The invention discloses a universal ditching depth detection device, which comprises an implement hanging frame, a ground profiling device, a longitudinal displacement measurement device and a transverse displacement balancing device, wherein: the transverse displacement balancing device and the ground profiling device are arranged on the machine tool hanging frame, the ground profiling device is hinged with the machine tool hanging frame, and the transverse displacement balancing device is arranged on the upper part of the profiling device; the upper end of the longitudinal displacement measuring device is connected with the transverse displacement balancing device, and the lower end of the longitudinal displacement measuring device is hinged with the ground profiling device.

Description

A general-purpose trenching depth detection device

technical field

The invention belongs to the field of agricultural machinery, in particular to a general-purpose ditching depth detection device.

Background technique

The consistency of trenching depth is an important indicator of precision seeding, and it is the premise of controlling the consistency and stability of seeding and fertilization depth. During the field work of the opener, due to the spatial variability of the soil and the large amount of surface undulation under the condition of conservation tillage, the depth of the trench is inconsistent, which affects the accuracy of subsequent operations and crop growth. When the machine is moving forward, the real-time detection of the ditch depth can provide data reference for the subsequent control system to adjust the ditch depth.

For the detection of ditching depth in China, most of the methods are to change the shape and structure of the working tools, resulting in poor versatility of the detection device, or to use the distance measuring sensor to detect the distance from a certain plane to the ground surface. Due to the complex surface conditions, especially on no-tillage ground, the measurement error of this detection method is relatively large.

Therefore, the present invention proposes a general-purpose ditching depth detection device, which can be applied to different structures and ditching purposes, and the measurement accuracy is improved by optimizing the detection principle.

Contents of the invention

For realizing the purpose of the present invention, adopt following technical scheme to realize:

A general-purpose ditching depth detection device, comprising a machine tool coupling frame, a ground profiling device, a longitudinal displacement measuring device and a lateral displacement balancing device, wherein: the lateral displacement balancing device and the ground profiling device are installed on the machine tool coupling frame, and the ground profiling device is hingedly connected to the machine tool coupling frame, and the lateral displacement balancing device is arranged on the upper part of the ground profiling device; the upper end of the longitudinal displacement measuring device is connected to the lateral displacement balancing device, and the lower end is hingedly connected to the ground profiling device.

The general-purpose ditching depth detection device, wherein: the ground profiling device includes a connecting rod and a profiling wheel, and the profiling wheel is freely rotatably installed on the lower part of the connecting rod; the upper part of the connecting rod is provided with a connecting shaft of an implement hitch, and the middle part is provided with an intermediate shaft, on which a joint bearing is installed, the lower end of the longitudinal displacement measuring device is connected with the joint bearing, and the connecting shaft of the implement mount is installed on a bearing on the implement mount.

The general-purpose ditching depth detection device, wherein: a step is processed on the intermediate shaft, threads are processed on the shaft end, one end of the inner ring of the joint bearing is against the step of the intermediate shaft, and the other end is pressed by a nut.

The general-purpose ditching depth detection device, wherein: the lateral displacement balance device includes a slide rail fixture, a slider and a slide rail, the slide rail is fixedly connected to the slide rail fixture, and the slide rail fixture is fixedly connected to the implement hitch.

The general-purpose ditching depth detection device, wherein: the slide rail is provided with a chute along the length direction, the slider is slidably installed in the chute, the transverse compression spring is installed in the chute, one end is connected with the chute wall, and the other end is connected with the slide block.

The general-purpose ditching depth detection device, wherein: the front end of the chute runs through the wall of the slide rail, the rear end is a certain distance away from the wall of the slide rail, and the front opening of the chute is closed by a baffle.

The general-purpose trenching depth detection device, wherein: the longitudinal displacement measuring device comprises a slider connector, a longitudinal displacement rod and a longitudinal displacement rod sleeve, the upper part of the longitudinal displacement rod sleeve is fixed on the slider connector, the longitudinal displacement rod can slide up and down and inserted into the sleeve hole of the longitudinal displacement rod sleeve, and the lower end of the longitudinal displacement rod sleeve is exposed outside the sleeve hole of the longitudinal displacement rod sleeve.

The general-purpose ditching depth detection device, wherein: the slider connector is fixedly connected to the slider, a columnar part is provided at the lower part of the slider connector, the columnar part is processed with a central hole, the upper part of the longitudinal displacement rod sleeve is socketed and fixedly connected with the columnar part, and the laser ranging sensor is installed in the central hole of the columnar part.

The general-purpose ditching depth detection device, wherein: also includes a longitudinal compression spring, the longitudinal compression spring is installed in the sleeve hole of the longitudinal displacement rod sleeve, and is arranged between the longitudinal displacement rod and the slider connector; the lower end of the longitudinal displacement rod is processed with threads, and the lower end of the longitudinal displacement rod is threadedly connected with the threaded hole of the joint bearing.

The general-purpose ditching depth detection device, wherein: the longitudinal displacement rod and the sleeve hole wall of the displacement rod sleeve are processed with planes that cooperate with each other.

The general-purpose ditching depth detection device, wherein: the ditching depth detection device further includes a control device, and the control device includes a rod-type sensor, a PLC controller, an encoder, a control valve and a speed regulating valve.

The general-purpose ditching depth detection device, wherein: the ditching device includes a complete machine frame and a ditching unit, wherein the complete machine frame is installed on the three-point suspension device of the tractor, a plurality of ditching units are installed on the complete machine frame, each ditching unit is installed on the complete machine frame through a group of hydraulic cylinders, one end of the hydraulic cylinder is fixed on the complete machine frame, and the other end is fixed on a group of ditching units; The telescopic position of the hydraulic cylinder is monitored and fed back to the PLC controller; the encoder housing part is fixed on the swing rod, the rotor part is fixed on the profiling wheel, and the ditch opener is fixedly installed on the ditching unit; the control valve and PLC controller are installed on the machine frame, and the speed regulating valve is installed on the hydraulic cylinder; the implement coupling frame is fixedly installed on the ditching unit.

The general-purpose ditching depth detection device, wherein the ditching depth detection device works as follows: the tractor pulls the whole machine frame 7 to travel in the forward direction, and then drives multiple groups of ditching units to work, and the speed at this time is:

v=ωR (1)

in:

v - travel speed

ω——The angular velocity detected by the encoder

R——radius of profiling wheel

When the laser displacement sensor detects that h changes, that is, it is different from the predetermined h value, the PLC controller calculates the collected data, and after a short delay of t seconds, transmits a signal to the control valve and the speed control valve to control the hydraulic cylinder up and down, so that the h value detected by the laser displacement sensor returns to the predetermined h value, and the speed control valve adjusts the expansion and contraction speed of the hydraulic cylinder to be twice the speed d(Δh)/dt of the laser displacement sensor before the delay of t seconds. The expansion and contraction of the hydraulic cylinder is controlled until the variation is close to or consistent with the ground heaving speed before a short delay of t seconds.

The general-purpose ditching depth detection device, wherein: the delay time t calculation method is:

From (1), (2), (3) the delay time t is:

in:

L——The lateral distance from the hinge center of the connecting rod and the implement hitch to the bottom of the opener

H——The height difference between the connecting rod and the hinge center of the tool hitch from the bottom of the opener

l—the lateral distance from the center of the profiling wheel to the bottom of the opener

l _pendulum - the length of the connecting rod

h - the height difference between the bottom end of the outer circumference of the profiling wheel and the bottom end of the opener.

The general-purpose ditching depth detection device, wherein:

When the front ground is undulating, the profiling wheel in the ditching depth detection device fluctuates up and down, and then the laser displacement sensor detects half of the ground undulation. At this time, the ditching depth detection device detects that the distance h between the profiling wheel and the opener is the sum of the actual ditching depth h' and the variation ∑△h of the profiling wheel in the distance l between the profiling wheel and the opener, so the actual ditching depth is:

h'=h-∑Δh (5)

Among them, ΣΔh is the vector sum of the vertical floating distance of the profiling wheel within t seconds before the moment at a certain moment, and Δh is the difference between the depth value h obtained by the latter detection and the depth value h obtained by the previous detection in two adjacent samples of the laser displacement sensor;

After the actual ditching depth h' has been calculated, in order to keep the ditching depth within the specified ditching depth range, the following control is carried out: after the laser displacement sensor transmits the detection data to the PLC controller, the PLC controller obtains the actual ditching depth through data storage and real-time calculation, compares the actual ditching depth with the predetermined ditching depth in real time, and then controls the speed regulating valve and the control valve and then controls the corresponding upward or downward pressure of the hydraulic cylinder so that the actual ditching depth approaches the specified ditching depth.

Compared with prior art, the beneficial effect of the present invention is:

(1) The trenching depth detection device is designed as an independent structure, which can be bolted to any machine trenching device. The depth detection range is 0-20cm, which can meet the detection needs of most trenching operations.

(2) The planar movement of the profiling wheel is converted into the displacement of the slider in the x and y directions and the displacement of the longitudinal displacement rod. The actual depth of the ditch is twice the displacement of the longitudinal displacement rod, which simplifies the measurement principle and facilitates data post-processing.

(3) The displacement of the longitudinal displacement rod is detected by the laser displacement sensor inside the longitudinal displacement measurement device. Compared with the ground as the measurement object, this measurement method can improve the accuracy of the measurement results.

(4) The profiling wheel adopts oblique traction floating design to optimize the force of the longitudinal displacement measuring device during the profiling process.

(5) The hinged parts of the trenching depth detection device are connected by bearings, which improves the detection accuracy in terms of mechanical structure.

(6) The ditching depth detection device is placed on the front side of the ditch opener. By using a separate control system, the error of the ditching depth detection is smaller and the plowing depth adjustment is more stable.

Description of drawings

Fig. 1 is the overall structural diagram of the universal ditching depth detection device of the present invention;

Fig. 2 is a structural diagram of the ground profiling device of the present invention;

Fig. 3 is a structural diagram of the lateral displacement balance device of the present invention;

Fig. 4 is a structural diagram of the longitudinal displacement measuring device of the present invention;

Fig. 5 is a schematic diagram of the lowest swinging position of the profiling wheel of the present invention;

Fig. 6 is a schematic diagram of the highest swinging position of the profiling wheel of the present invention

Fig. 7 is the schematic diagram of ditching device structure;

Fig. 8 is a schematic diagram of the control system of the present invention.

Detailed ways

The specific implementation manner of the present invention will be described in detail below in conjunction with accompanying drawings 1-8.

As shown in FIG. 1 , the general-purpose ditching depth detection device includes an implement hitch 1 , a ground profiling device 2 , a longitudinal displacement measuring device 4 and a lateral displacement balancing device 5 . Wherein the lateral displacement balance device 5 and the ground profiling device 2 are installed on the implement hitch 1, and the lateral displacement balance device 5 is arranged on the upper part of the ground profiling device 2, the upper end of the longitudinal displacement measuring device 4 is connected with the lateral displacement balance device 5, and the lower end is connected with the ground profiling device 2. The implement hitch 1 is laterally connected with the ditching device through bolts.

As shown in Figure 2, ground profiling device 2 comprises connecting rod 202 and profiling wheel 203, and profiling wheel 203 is freely rotatably installed on the bottom of connecting rod 202, and preferably connecting rod 202 bottom is welded and connected with a rotating shaft, and this rotating shaft is installed on the bearing at the center of profiling wheel 203; 4. Preferably, they are all fixedly connected to the connecting rod 202 by welding. The direction of the connecting shaft 201 of the implement coupling frame and the intermediate shaft 204 are opposite. Preferably, the intermediate shaft 204 is arranged at 1/2 of the distance between the connecting shaft 201 of the implement coupling frame on the connecting rod 202 and the installation position of the profiling wheel 203 (that is, the position of the rotating shaft), so as to increase the measuring depth range of the profiling wheel; A step is processed on 4, and the shaft end is processed with threads. The spherical plain bearing 3 is installed on the intermediate shaft 204, and one end of the inner ring of the spherical plain bearing 3 is against the step of the intermediate shaft, and the other end is compressed by a nut installed on the intermediate shaft. The main body of the profiling wheel 203 is disc-shaped, and its outer peripheral surface is densely covered with a plurality of protrusions to prevent the profiling wheel from slipping and ensure that the profiling wheel is pure rolling.

As shown in Figure 3, the lateral displacement balance device 5 includes a slide rail fixture 6, a slide block 503 and a slide rail 501, the slide rail 501 and the slide rail fixture 6 are fixedly connected by means of welding or threaded connection, the slide rail fixture 6 is provided with a plurality of bolt holes, and the slide rail fixture 6 is bolted to the implement mounting bracket 1. The slide rail 501 is provided with a slide groove 505 along the length direction, and the slide block 503 is slidably installed in the slide groove 505. The front end of the slide groove 505 runs through the slide rail wall, and the rear end is a distance away from the slide rail wall. The plate 502 is fixedly installed on the slide rail 501 by bolts. The lateral displacement balance device 5 is installed on the implement hitch 1, and the direction of the chute 505 is arranged downward.

As shown in Figure 4, the longitudinal displacement measuring device 4 comprises a slider connector 404, a longitudinal displacement rod 401 and a longitudinal displacement rod sleeve 405, the upper part of the longitudinal displacement rod sleeve 405 is fixed on the slider connector 404, and the longitudinal displacement rod 401 can slide up and down and is inserted in the sleeve hole of the longitudinal displacement rod sleeve 405.

Specifically, the slider connecting piece 404 is provided with a plurality of bolt holes, the slider connecting piece 404 is bolted to the slider 503, and the lower part of the slider connecting piece 404 is provided with a columnar piece. Between the longitudinal displacement rod 401 and the slider connector 404, the upper end of the longitudinal compression spring 402 is fixed on the sleeve hole wall, and the lower end is connected with the upper part of the longitudinal displacement rod 401; The lower end of the longitudinal displacement rod 401 is exposed outside the sleeve hole of the longitudinal displacement rod sleeve 405, and the lower end of the longitudinal displacement rod 401 is processed with threads, and the lower end of the longitudinal displacement rod 401 is threadedly connected with the threaded hole of the joint bearing 3; in order to prevent the longitudinal displacement rod 401 from rotating during the movement process, a plane that cooperates with each other is processed on the longitudinal displacement rod 401 and the sleeve hole wall of the displacement rod sleeve 405; , used to measure the moving distance of the longitudinal displacement rod 401 .

As shown in Figure 5, the lowest position of the profiling wheel is the state where the opener is not in the soil. At this time, the bottom end of the outer circumference of the profiling wheel body is flush with the bottom end of the opener. This state is the minimum detectable range of the ditching depth. As shown in FIG.

The trenching depth detection device also includes a control device, which includes a rod sensor 8 , a PLC controller 15 , an encoder 10 , a control valve 14 and a speed regulating valve 13 .

As shown in Figure 7, the ditching device includes a complete machine frame 7 and a ditching unit 9, wherein the complete machine frame 7 is installed on the three-point suspension of the tractor, and is powered by the tractor. A plurality of ditching units 9 are installed on the complete machine frame 7, and each ditching unit 9 is installed on the complete machine frame 7 through a group (at least 2) of hydraulic cylinders 12. The rod-type displacement sensor 8 is installed between the machine frame 7 and the ditching unit 9, and is parallel to the hydraulic cylinder 12. It is used to detect the expansion and contraction position of the hydraulic cylinder in real time, and feeds back to the PLC controller 15, and then controls the hydraulic cylinder 12 in real time to achieve the desired expansion and contraction. The housing part of the encoder 10 is fixed on the connecting rod 202, and the rotor part is fixed on the profiling wheel 203. During operation, the encoder can detect the rotational speed of the profiling wheel 203. The ditch opener 11 is fixedly installed on the ditching unit 9 , and the implement coupling frame 1 is fixedly installed on the ditching unit 9 . The control valve 14 and the PLC controller 15 are installed on the complete machine frame 7, and can control the work of multiple groups of hydraulic oil cylinders. The speed regulating valve 13 is installed on the hydraulic oil cylinder 12 .

The working process of the universal ditching depth detection device of the present invention is as follows:

First of all, when the opener is not in the soil, the bottom end of the outer edge of the profiling wheel is flush with the bottom end of the opener. At this time, it is the lowest swing position of the profiling wheel. The longitudinal displacement rod in the longitudinal displacement measuring device and the slider in the lateral displacement balance device are in the initial state. The laser ranging sensor measures the current position of the longitudinal displacement rod (the current position is the initial position of the profiling wheel), and sends an electrical signal to the PLC controller.

After the opener enters the soil, the profiling wheel continues to walk close to the ground. When the depth of the opener increases, the profiling wheel is lifted by the ground, and then drives the middle shaft of the connecting rod to swing upwards. Further, the joint bearing installed on the middle shaft translates to the upper right relative to the implement coupling frame. Further, the translation of the joint bearing is decomposed into movement in the directions of x and y axes. In the direction of the x axis, the joint bearing drives the overall longitudinal displacement measuring device to move horizontally to the right, and then drives the slider to move to the right along the slide rail, and the transverse compression spring is compressed. In the y-axis direction, the joint bearing drives the longitudinal displacement rod to move upward in the longitudinal displacement rod sleeve. At this time, the longitudinal compression spring is compressed. The laser displacement sensor detects the current position of the longitudinal displacement rod and sends an electrical signal to the PLC controller. The distance difference between the current position and the initial position is the displacement of the longitudinal movement rod, which is 1/2 of the ditching depth h. The distance between the bottom end of the outer circumference of the profiling wheel and the bottom end of the opener is the ditching depth. Since the longitudinal displacement rod is hinged in the middle of the connecting rod, the longitudinal displacement of the longitudinal displacement rod is half of h. The highest detection ditching depth in the present invention is 200mm, which can meet the ditching requirements of most crops. When the soil depth of the opener decreases, the transverse compression spring stretches, pushing the slider to the left, and then pushing the longitudinal displacement device to move to the left. At the same time, the longitudinal compression spring stretches, pushing the longitudinal displacement rod to move down, further driving the connecting rod to swing down, so that the profiling wheel fits the ground under the action of its own gravity and the thrust of the connecting rod. At this time, the laser displacement sensor detects the current position of the longitudinal displacement rod.

The control process of the present invention is shown in FIG. 8 .

During work, the tractor pulls the complete machine frame 7 to travel in the forward direction, and then drives a plurality of ditching units to work. The travel speed at this time is:

v=ωR (6)

in:

v - travel speed

ω——The angular velocity detected by the encoder

R——radius of profiling wheel

If the ground is flat, the ditch opener enters the predetermined depth in the soil, and at this moment, the bottom end of the outer circumference of the profiling wheel and the bottom end of the ditch opener form a predetermined height difference h, which is the predetermined ditching depth (at this time, the working state is shown in Figure 7). However, there are always undulations on the ground. Since the trench depth detection device is installed in front of the opener, the distance from the opener is 1 (that is, the lateral distance between the center of the profiling wheel and the bottom of the opener is 1), therefore, the terrain fluctuation detected by the trench depth detection device is always earlier than that at the position of the opener.

In the present invention, when the laser displacement sensor detects that h changes, that is, when it is different from the predetermined h value, the PLC controller calculates the collected data, and after a short delay, transmits a signal to the control valve and the speed control valve to control the lifting of the hydraulic oil cylinder, and the speed control valve adjusts the expansion and contraction speed of the hydraulic oil cylinder. The difference between the displacement of the rod and the displacement of the longitudinal displacement rod obtained in the previous detection), so that the penetration depth of the opener is equal to the predetermined h value (predetermined depth). At this time, the rod-type displacement sensor detects the expansion and contraction of the hydraulic cylinder in real time, and feeds back to the PLC controller in real time to control the expansion and contraction of the hydraulic cylinder again until the expansion and contraction speed of the hydraulic cylinder is similar to or consistent with the ground undulation speed before a short delay of t seconds, that is, the ditching depth at this time is within the specified ditching depth range.

The calculation method of the delay time t is:

From (1), (2), (3) the delay time t is:

in:

L——The lateral distance from the hinge center of the connecting rod and the implement hitch to the bottom of the opener

H——The height difference between the connecting rod and the hinge center of the tool hitch from the bottom of the opener

l—the lateral distance from the center of the profiling wheel to the bottom of the opener

l _pendulum - the length of the connecting rod

h——Height difference between the bottom end of the outer circumference of the profiling wheel and the bottom end of the opener

The present invention also proposes another ditching depth control method, as follows:

When working, when the ground in front is undulating, the profiling wheel in the ditching depth detection device undulates up and down, and then the laser displacement sensor detects half of the undulation of the ground. At this time, the distance h between the profiling wheel and the opener detected by the ditching depth detection device is the sum of the actual ditching depth h′ and the variation ∑△h of the profiling wheel in the distance l between the profiling wheel and the opener, so the actual ditching depth is:

h'=h-∑Δh (10)

Among them, ∑△h is the vector sum of the up and down floating distance of the profiling wheel within t seconds before this moment at a certain moment (note that floating up is positive, and floating down is negative); △h is the difference between the depth value h obtained by the latter detection and the depth value h obtained by the previous detection in two adjacent samples of the laser displacement sensor.

After the actual ditching depth h' has been calculated, in order to keep the ditching depth within the specified ditching depth range, the following control process can be used: After the laser displacement sensor transmits the detection data to the PLC controller, the PLC controller obtains the actual ditching depth through data storage and real-time calculation, compares the actual ditching depth with the predetermined ditching depth in real time, then controls the speed regulating valve and the control valve, and then controls the corresponding upward or downward pressure of the hydraulic cylinder to make the actual ditching depth approach the specified ditching depth. The whole process is carried out multiple times in a very short time to make the actual ditching If there is a slight deviation between the depth and the predetermined ditching depth, it will be corrected in real time, so that the actual ditching depth is within the appropriate ditching range.

Through the present invention, accurate detection of ditching depth can be realized, the depth adjustment is more precise and stable, and the farming efficiency and quality are improved.

Claims (1)

1. The utility model provides a general ditching degree of depth detection device, includes that the machines articulates frame, ground copying device, vertical displacement measuring device and horizontal displacement balancing unit, its characterized in that:

the transverse displacement balancing device and the ground profiling device are arranged on the machine tool hanging frame, the ground profiling device is hinged with the machine tool hanging frame, and the transverse displacement balancing device is arranged on the upper part of the ground profiling device; the upper end of the longitudinal displacement measuring device is connected with the transverse displacement balancing device, and the lower end of the longitudinal displacement measuring device is hinged with the ground profiling device; the ground profiling device comprises a connecting rod and a profiling wheel, and the profiling wheel is arranged at the lower part of the connecting rod in a free rotation way;

the upper part of the connecting rod is provided with an implement hanging frame connecting shaft, the middle part of the connecting rod is provided with an intermediate shaft, the intermediate shaft is provided with a joint bearing, the lower end of the longitudinal displacement measuring device is connected with the joint bearing, and the implement hanging frame connecting shaft is arranged on the bearing on the implement hanging frame; the intermediate shaft is provided with a step, the shaft end is provided with threads, one end of the inner ring of the knuckle bearing is abutted against the intermediate shaft step, and the other end of the knuckle bearing is pressed by a nut; the transverse displacement balancing device comprises a sliding rail fixing piece, a sliding block and a sliding rail, wherein the sliding rail is fixedly connected with the sliding rail fixing piece, and the sliding rail fixing piece is fixedly connected with the machine tool hanging frame;

a sliding groove is formed in the sliding rail along the length direction, the sliding block is slidably arranged in the sliding groove, the transverse compression spring is arranged in the sliding groove, one end of the transverse compression spring is connected with the sliding groove wall, and the other end of the transverse compression spring is connected with the sliding block; the front end of the sliding chute penetrates through the sliding rail wall, the rear end of the sliding chute is away from the sliding rail wall by a distance, and the opening at the front part of the sliding chute is closed by a baffle; the longitudinal displacement measuring device comprises a sliding block connecting piece, a longitudinal displacement rod and a longitudinal displacement rod sleeve, wherein the upper part of the longitudinal displacement rod sleeve is fixed on the sliding block connecting piece, the longitudinal displacement rod can be inserted into a sleeve hole of the longitudinal displacement rod sleeve in a vertical sliding way, and the lower end of the longitudinal displacement rod is exposed out of the sleeve hole of the longitudinal displacement rod sleeve; the sliding block connecting piece is fixedly connected with the sliding block, a columnar piece is arranged at the lower part of the sliding block connecting piece, a central hole is formed in the columnar piece in a processing mode, the upper part of the longitudinal displacement rod sleeve is fixedly connected with the columnar piece in a sleeving mode, and the laser ranging sensor is arranged in the central hole of the columnar piece; the universal ditching depth detection device also comprises a longitudinal compression spring, wherein the longitudinal compression spring is arranged in a trepanning of the longitudinal displacement rod sleeve and is arranged between the longitudinal displacement rod and the sliding block connecting piece; the lower end of the longitudinal displacement rod is provided with threads, and the lower end of the longitudinal displacement rod is in threaded connection with a threaded hole of the knuckle bearing; the longitudinal displacement rod and the trepanning wall of the displacement rod sleeve are provided with mutually matched planes;

the ditching depth detection device also comprises a control device, wherein the control device comprises a pull rod type sensor, a PLC (programmable logic controller), an encoder, a control valve and a speed regulating valve; the ditching device comprises a complete machine frame and ditching units, wherein the complete machine frame is arranged on a three-point suspension device of a tractor, a plurality of ditching units are arranged on the complete machine frame, each ditching unit is arranged on the complete machine frame through a group of hydraulic cylinders, one end of each hydraulic cylinder is fixed on the complete machine frame, and one end of each hydraulic cylinder is fixed on one group of ditching units; the pull rod type displacement sensor is arranged between the whole machine frame and the ditching unit, is parallel to the hydraulic oil cylinder, is used for monitoring the telescopic position of the hydraulic oil cylinder in real time and is fed back to the PLC; the encoder shell part is fixed on the connecting rod, the rotor part is fixed on the profiling wheel, and the furrow opener is fixedly arranged on the furrow opening unit; the control valve and the PLC are arranged on the whole machine frame, and the speed regulating valve is arranged on the hydraulic cylinder; the machine tool hanging frame is fixedly arranged on the ditching unit;

the ditching depth detection device works in the following manner: the tractor pulls the whole machine frame to travel in the forward direction, and then drives a plurality of groups of ditching units to work, and the travelling speed at the moment is as follows:

v＝ωR (1)

wherein:

v-speed of travel

Angular velocity detected by w-encoder

R-profile wheel radius

When the laser displacement sensor detects that h changes, namely the h is different from a preset h value, the PLC calculates collected data, after a short delay time of t seconds, signals are transmitted to the control valve and the speed regulating valve, the hydraulic cylinder is controlled to lift, so that the h value detected by the laser displacement sensor is restored to the preset h value, the speed regulating valve regulates the expansion speed of the hydraulic cylinder to be 2 times of the speed d (delta h)/dt of the laser displacement sensor before the delay time of t seconds, at the moment, the pull rod type displacement sensor detects the expansion amount of the hydraulic cylinder in real time and feeds back the expansion amount to the PLC in real time, and the hydraulic cylinder is controlled to expand again until the change amount is similar to or consistent with the ground fluctuation speed before the short delay time of t seconds;

the delay time t is calculated by the following steps:

the delay time t obtained by (1), (2) and (3) is as follows:

wherein:

l-distance between the articulated center of the connecting rod and the machine hanging frame and the bottom end of the furrow opener

H-height difference between hinged center of connecting rod and machine hanging frame and bottom end of furrow opener

l-lateral distance of the centre of the copying wheel from the bottom end of the furrow opener

l _Pendulum Length of connecting rod

h, the height difference between the bottom end of the peripheral circle of the profiling wheel and the bottom end of the furrow opener;

when the front ground fluctuates, the profiling wheel in the ditching depth detection device fluctuates up and down, so that the laser displacement sensor detects half of the fluctuation of the ground, at the moment, the distance h between the profiling wheel and the ditcher detected by the ditching depth detection device is the sum of the actual ditching depth h' and the variable quantity Sigma delta h of the profiling wheel in the distance l between the profiling wheel and the ditcher, and therefore, the actual ditching depth is as follows:

h′ ＝h-ΣΔh (5)

wherein ΣΔh is the vector sum of the up-and-down floating distances of the profiling wheel within t seconds before a certain moment, and Δh is the difference value between the depth value h obtained by the latter detection and the depth value h obtained by the former detection in two adjacent samples of the laser displacement sensor;

after the actual trench depth h' has been calculated, the following control is performed to bring the trench depth within the prescribed trench depth range: after the laser displacement sensor transmits detection data to the PLC controller, the PLC controller obtains the actual ditching depth through data storage and real-time calculation, compares the actual ditching depth with the preset ditching depth in real time, and then controls the speed regulating valve and the control valve to further control the corresponding ascending or descending of the hydraulic cylinder so that the actual ditching depth approaches to the preset ditching depth.