CN105414821A - Welding robot welding seam automatic tracking system - Google Patents

Abstract

The invention provides a welding seam automatic tracking system for a welding robot, which includes a welding arm, a rotary box and a position adjustment mechanism are arranged on the welding arm, a laser sensor and a welding torch are arranged on the rotary box, and the position adjustment mechanism includes The first motor and the second motor, the laser sensor is connected to the second motor, the first motor, the second motor and the laser sensor are connected to the DSP control system, the laser sensor is provided with a laser, and the laser is used for welding The surface of the object emits laser light. The DSP control system is connected with two drivers, and the two drivers are respectively connected with the first motor and the second motor. The laser sensor includes a laser, a CCD camera, and Bluetooth. The laser is used to emit laser light to the surface of the welded object. The CCD camera is used to capture images of the surface of the welded object. The Bluetooth transmits the image taken to the DSP control system.

Description

A Welding Robot Seam Automatic Tracking System

technical field

The invention relates to the field of robot welding, in particular to an automatic seam tracking system for a welding robot.

Background technique

Welding robots can improve efficiency, optimize quality, and improve working conditions, so the development and application of welding robots play a huge role in my country's national economy. Most of the current welding robots are programmable teaching and reproduction robots, which can accurately complete the teaching operation in their workspace. During the welding process of the welding robot, if the welding conditions are basically stable, the robot can guarantee the welding quality. However, due to the influence of various factors, the actual welding conditions often change. For example: due to strong arc radiation, high temperature, smoke, spatter, groove conditions, processing errors, fixture clamping accuracy, surface conditions, and thermal deformation of the workpiece, the welding torch will deviate from the weld, resulting in a decline in welding quality or even welding failure .

Contents of the invention

Purpose of the invention: The technical problem to be solved by the present invention is to provide an automatic seam tracking system for a welding robot in view of the deficiencies in the prior art.

In order to solve the above technical problems, the present invention provides a welding robot seam automatic tracking system, including a welding arm, the welding arm is provided with a rotary box and a position adjustment mechanism, the rotary box is provided with a laser sensor and a welding torch, The position adjustment mechanism includes a first motor and a second motor, the laser sensor is connected to the second motor, the first motor, the second motor and the laser sensor are connected to the DSP control system, the laser sensor is provided with a laser, The laser is used to emit laser light to the surface of the object to be welded.

In the present invention, the DSP control system is connected with two drivers, and the two drivers are respectively connected with the first motor and the second motor.

In the present invention, the position adjustment mechanism also includes a transmission belt and a rotary box transmission shaft, the rotary box transmission shaft passes through the rotary box and connects the rotary box to the welding arm, and the transmission belt is connected to the first motor drive shaft and the rotary box transmission shaft , the drive shaft of the first motor drives the transmission shaft of the rotary box through the transmission belt, and the transmission shaft of the rotary box drives the swing of the rotary box, thereby controlling the position of the welding torch.

In the present invention, the box to be installed is provided with a second motor and a sensor drive shaft, the laser sensor is arranged on the sensor drive shaft, the second motor drive shaft drives the sensor drive shaft, and the sensor drive shaft drives the laser sensor on the sensor drive shaft move.

In the present invention, the laser sensor is a CCD camera, and the CCD camera is used to capture images of the surface of the object to be welded.

The present invention also provides an automatic seam tracking method, which includes the following steps:

Step 1: The second motor drives the laser to scan the weld seam, and detects the deviation of the welding torch relative to the welding spot;

Step 2: Bluetooth transmits the deviation signal;

Step 3: The DSP control system accepts the deviation signal;

Step 4: The DSP control system generates a control signal and sends it to the driver;

Step 5: The first motor drives the welding torch to realize real-time tracking of the welding seam.

In the present invention, after receiving the deviation signal, the DSP control system adopts Fuzzy-P dual-mode segmental control to correct the deviation of the weld seam and generates a control signal. When the deviation is greater than 4 mm, the Fuzzy-P dual-mode segmental control adopts proportional control, Fuzzy control is used when the deviation is less than or equal to four millimeters. The Fuzzy-P dual-mode segmentation control formula is:

When |e|≤4mm, U＝[α1E+(1 _- α1)EC]

When |e|＞4mm, U＝[α2E+(1 _- α2)EC]

Among them, e is the deviation, measured by the laser seam sensor, correction factor α1=0.4, α2=0.6, U is the output control quantity; EC is the fuzzy quantity of the deviation change rate, EC is a function of e, controlled by DSP The system automatically generates according to the deviation e, E is the fuzzy amount of the deviation, E is a function of e, and is automatically generated by the DSP control system according to the deviation e.

In the present invention, in the step 2, the image taken by the laser sensor is transmitted to the DSP control system through bluetooth. Beneficial effects: 1. The present invention drives the sensor to scan horizontally above the weld seam through the motor and the laser, detects the horizontal distance and the longitudinal distance between the sensor and the weld seam, and drives the welding torch horizontal stepping motor and longitudinal stepping motor through the three-dimensional adjustment device Action, realize the real-time automatic tracking of the welding seam by the welding torch of the welding robot, adjust the position of the welding torch in real time according to the change of welding conditions, and reduce the number of adjustment operations by workers.

2. The present invention adopts the Fuzzy-P dual-mode subsection control method, and the adjusted error range is large, and the sub-deviation adjustment method ensures the accuracy of welding and the adjustment method is flexible.

3. The present invention provides a welding robot system calibration method guided by a line structured light vision sensor, which is flexible, high in precision, fast in speed, good in stability, strong in real time, simple in method, small in calculation amount, and strong in versatility.

Description of drawings

The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, and the advantages of the above and other aspects of the present invention will become clearer.

Figure 1 is a structural diagram of the welding arm;

Fig. 2 is a structural schematic diagram of a welding arm;

Fig. 3 is a block diagram of a welding robot seam automatic tracking system; Fig. 4 is a DSP-based weld seam tracking stepper motor control system;

Figure 5 is a flow chart of the system software.

detailed description

The present invention will be described in detail below in conjunction with the accompanying drawings.

Example:

As shown in Figures 1 and 2, this embodiment includes a welding arm 1, a rotating box 2, a position adjustment mechanism 3, a laser 4, a laser sensor 5, a welding torch 6, a first motor 7, a second motor 8, and a first motor drive shaft 9 , rotary box transmission shaft 10, second motor drive shaft 11 and sensor drive shaft 12, the first motor is provided in the described welding arm 1, the first motor drives the conveyor belt on the position adjustment mechanism 3 through the first motor drive shaft 9, The conveyor belt drives the transmission shaft 10 of the rotary box, and drives the rotary box 2 to rotate, thereby controlling the welding torch and the laser device arranged on the rotary box, the second motor is arranged on the rotary box, and the second motor drives the shaft 11 and the sensor drive shaft 12 through the second motor Control the lateral movement of the laser on the rotating box.

As shown in Figure 3, this embodiment includes a non-contact laser seam sensor, a swing device, a three-dimensional welding torch adjustment device, and a DSP (digital signal processing) control system. This system uses a scanning laser sensor seam tracking method, that is, the laser seam The sensor is installed on the front of the welding torch to observe the weld, and the second motor drives the laser weld sensor to scan horizontally above the weld to detect the horizontal and vertical distances between the sensor and the weld, which is the deviation of the welding torch to the weld. The DSP control system receives the deviation signal of the welding torch to the welding seam, and adopts the Fuzzy-P dual-mode segmental control to correct the deviation of the welding seam and generate a control signal. The control signal is sent to the three-dimensional adjustment device of the welding torch installed at the connection between the welding torch and the rotary box, which drives the horizontal stepping motor and the vertical stepping motor of the welding torch to move, realizing the real-time automatic tracking of the welding seam by the welding torch of the welding robot.

The non-contact laser seam sensor includes a CCD camera and one or two semiconductor lasers. The semiconductor laser is used as a structured light source to project laser stripes onto the workpiece surface below the sensor at a predetermined angle. The camera looks directly at the stripes on the lower part of the sensor. On the front of the camera is an optical filter that allows the laser light to pass through but blocks all other light, such as welding arcs. The sensor can thus be very close to the welding arc. The sensor is mounted at a pre-set distance to the front of the torch (look-ahead distance), so it can see the weld. When the torch is properly positioned over the weld, the weld should be close to the center of the laser stripe so that the camera can see the laser stripe and weld.

Since the laser stripes are projected at a certain angle, if the workpiece is close to the sensor, the laser stripes on the surface of the workpiece will be relatively front. Conversely, if the workpiece is farther away from the sensor, the laser stripes on the surface of the workpiece will be relatively behind. Thus, by viewing the position of the laser stripes with a camera, the sensor is able to measure the vertical distance from the workpiece. From the shape of the laser stripe on the workpiece, the sensor is also able to measure the contour of the surface and the position of the weld within the stripe, thus measuring the lateral distance between the sensor and the weld. The image observed from the camera is processed by electronic components in the signal processing link. The image is first acquired and digitized to form a laser stripe image, and then the control software uses specific settings to segment the stripe into multiple line segments. Using these line segments, the position of the weld can be measured and converted into a distance in mm. This system is designed for pipeline welding robots, and is mainly used for welding V-groove circumferential welds. According to the actual parameters, the MLP2/60 laser seam sensor is selected. The horizontal field of view of this type of sensor is 60mm at the standard installation height, and the effective depth of field is -35 to +55mm.

This embodiment adopts the TMS320LF2812 microprocessor of American TI Company. The architecture of the TMS320 series DSP of American TI Company is designed for real-time signal processing. This series of DSP controllers integrates real-time processing capabilities and controller peripheral functions, and provides an ideal solution for control system applications. After the laser seam sensor detects the deviation of the welding torch to the weld, the DSP control system receives the deviation signal of the welding torch to the weld, and uses Fuzzy-P dual-mode segmental control to correct the deviation of the weld and generate a control signal. The control signal is sent to the three-dimensional adjustment device of the welding torch, which drives the welding seam tracking stepping motor (horizontal stepping motor and vertical stepping motor of the welding torch) to move, and realizes real-time automatic tracking of the welding seam by the welding torch of the welding robot. Simply put, the purpose of the control system is to realize the control of the horizontal stepping motor and the vertical stepping motor of the welding torch of the welding robot according to the input control signal and sensor sampling signal. The core of the problem is to control the start, stop, speed and direction of the motor. control. According to the working principle of the stepper motor, the speed control method of frequency conversion is adopted, and the internal phase sequence circuit of the driver is controlled by the level signal to change the pulse sequence phase sequence method to realize the motor commutation, and the control pulse is provided by the internal PWM output of the DSP. After the power is amplified, it enters the windings of each phase of the welding torch to track the stepper motor. The control scheme of the stepper motor for welding seam tracking based on DSP is shown in Figure 4. This program adopts the Japanese SANYO103H7123 stepping motor, and uses the OEM750 of the American Parker company as the driver. The driver completes the digital subdivision task of the stepping motor. The last stepper motor is used as the adjustment control motor for the welding torch to track the weld seam. Because the 2812 chip has a PWM output function, it is very convenient to obtain the control pulse required by the stepper motor driver. In addition, in order to compile the application program in the most concise way, the pulses sent by the DSP control circuit are continuous pulses, that is, as long as the user program is running, the pulses are continuously sent to the outside. If the pulses are directly transmitted to the stepping motor, the stepping motor will will run continuously without interruption. Therefore, an enable signal is set in the system, so that the level of the enable signal controls whether the stepper motor can obtain pulses.

Due to the uncertainty and time-varying nature of the welding process, the seam tracking process cannot be described by an accurate mathematical model. Therefore, it is difficult to obtain satisfactory results by applying traditional control theory including modern control theory. With the development of fuzzy control theory, the seam tracking control is developing towards intelligence. This embodiment adopts Fuzzy-P dual-mode segmental control. The control process of the controller is: when there is a large deviation, proportional control is used to improve the response speed of the system and reduce the adjustment time; when the deviation is small, fuzzy control is used to reduce the overshoot of the system and improve the stability of the system response and control accuracy . The switching between the two control modes is realized according to a predetermined deviation threshold. According to the experiment, the segmentation threshold selected by this system is ep=4mm, that is, when the deviation is greater than 4mm, proportional control is adopted; when the deviation is less than or equal to 4mm, fuzzy control is adopted. In fuzzy control, the key is the establishment of fuzzy control rules. In formula fuzzy control, the commonly used fuzzy control mathematical model is:

U=[αE+(1-α)EC]α∈(0,1)(1)

Among them, U is the output control quantity; E(e) is the fuzzy quantity of the deviation; EC(ec) is the fuzzy quantity of the deviation change rate. α is a correction factor, and α takes a value between 0 and 1, which reflects the different weights of the deviation e and the deviation change rate ec. Generally, when e is large, the main contradiction of the control system is to eliminate e, so the value of α should be increased at this time, so that e takes a larger weight in the control rules to improve the dynamic characteristics of the system; when e is small, the control system The main contradiction is to suppress the system overshoot and make the system reach a steady state as soon as possible, so the value of α should be reduced at this time, and the value of 1-α should be increased accordingly, so that ec takes a larger weight in the control rules. It can be seen that by adjusting the value of α, the fuzzy control rules can be modified. Once α is determined, the fuzzy control rules are also determined. In actual welding, due to the influence of various processing conditions, the deviation of the weld seam and the working state of the system are very complicated, and the fuzzy control with a fixed α factor cannot meet the needs of actual weld seam tracking. Therefore, this system adopts two-factor self-adjusting fuzzy control method, and its mathematical model is as follows:

When |e|≤4mm, U=[α1E+(1-α1)EC]

When |e|>4mm, U=[α2E+(1-α2)EC]

α1, α2∈(0,1), α1≤α2

Through experiments, the correction factors α1=0.4 and α2=0.6 of the system are determined. According to the determined fuzzy control rules, a table of fuzzy control rules is made. In the actual seam tracking, according to the size of the deviation, different α factors can be selected, that is, different fuzzy control rules are selected, and the required control amount can be obtained through the corresponding fuzzy control rule table.

As shown in Figure 5, the system software and hardware cooperate to realize the scanning of the laser seam sensor, the collection and calculation of signals, and the adjustment of the position of the welding torch. The specific program flow is that when the welding robot is working, first set the allowable deviation |e| of DSP to 4mm in the control program, and then detect the deviation Δe of the welding torch to the weld seam measured by the laser sensor, and judge whether the deviation is greater than the minute Segment threshold, that is, judging |e|≥Δe, if the judging result is true, the proportional control is used, otherwise, the fuzzy control is used to generate a control signal and send it to the motor driver to correct the position of the welding torch until the end of welding is detected.

The present invention provides a welding robot seam automatic tracking system. There are many methods and approaches to realize this technical solution. The above description is only a preferred embodiment of the present invention. , under the premise of not departing from the principle of the present invention, some improvements and modifications can also be made, and these improvements and modifications should also be regarded as the protection scope of the present invention. All components that are not specified in this embodiment can be realized by existing technologies.

Claims (8)

1. a welding robot weld seam automatic tracking system, it is characterized in that, comprise welding arm, described welding arm is provided with rotary box and position adjusting mechanism, described rotary box is provided with laser sensor and welding gun, described position adjusting mechanism comprises the first motor and the second motor, described laser sensor connects the second motor, described first motor, the second motor and laser sensor are communicated to DSP control system, described laser sensor is provided with laser instrument, and laser instrument is used for soldered body surface Emission Lasers.

2. a kind of welding robot weld seam automatic tracking system according to claim 1, it is characterized in that, described DSP control system connects two drivers, and two drivers are connected respectively the first motor and the second motor.

3. a kind of welding robot weld seam automatic tracking system according to claim 1, it is characterized in that, described position adjusting mechanism also comprises driving-belt and rotary box power transmission shaft, rotary box power transmission shaft passes rotary box and is connected to by rotary box on welding arm, driving-belt is connected on the first motor driving shaft and rotary box power transmission shaft, first motor driving shaft is by driving-belt driven rotary case power transmission shaft, and rotary box power transmission shaft driven rotary case swings, thus controls welding torch position.

4. a kind of welding robot weld seam automatic tracking system according to claim 1, it is characterized in that, described rotary box is provided with the second motor and sensor driving shaft, laser sensor is arranged on sensor driving shaft, second motor driving shaft band dynamic sensor driving shaft, sensor driving shaft drives laser sensor to move on sensor driving shaft.

5. a kind of welding robot weld seam automatic tracking system according to claim 1, it is characterized in that, described laser sensor is CCD camera, and CCD camera is for taking the image of soldered body surface.

6. a welding robot weld seam automatic tracking system, is characterized in that, comprises weld seam method for automatic tracking, and described weld seam method for automatic tracking comprises the following steps:

Step 1: the second motor drive laser scanning weld seam, detects the deviation of welding gun relative to solder joint;

Step 2: laser sensor transmission deviation signal;

Step 3:DSP control system accepts deviation signal;

Step 4:DSP control system produces control signal and sends to driver;

Step 5: the first motor drives welding gun, realizes the real-time tracking of butt welded seam.

7. a kind of welding robot weld seam of one according to claim 6 automatic tracking system, it is characterized in that, described DSP control system adopts Fuzzy-P bimodulus Discrete control to carry out the correction of weld seam after accepting deviation signal, produce control signal, Fuzzy-P bimodulus Discrete control adoption rate when deviation is greater than four millimeters controls, deviation adopts fuzzy control when being less than or equal to four millimeters, and described Fuzzy-P bimodulus Discrete control formula is:

When | during e|≤4mm, U=[α 1E+ (1-α 1) EC],

When | during e| > 4mm, U=[α 2E+ (1-α 2) EC],

Wherein, e is deviation, is recorded by laser seam sensor, and modifying factor α 1=0.4, α 2=0.6, U are the controlled quentity controlled variable exported; EC is the fuzzy quantity of deviation variation rate, and EC is the function about e, is automatically produced according to departure e by DSP control system, and E is the fuzzy quantity of deviation, and E is the function about e, is automatically produced according to departure e by DSP control system.

8. a kind of welding robot weld seam automatic tracking system according to claim 7, is characterized in that, by bluetooth, the image that laser sensor is taken is passed to DSP control system in described step 2.