Conveyor Belt With Robotic

- Dec 26, 2018-

The invention relates to the technical field of industrial robots, in particular to an industrial robot conveyor belt dynamic tracking method.


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Background technique:


Industrial robots are widely used in automated production lines. Many automated production lines are in the form of a pipeline, which is connected to a station by a conveyor belt. The workpiece to be machined follows the conveyor belt, from one station to another, and the robot on the station grabs or places the workpiece from the conveyor belt.


The simplest way to work with the robot and the conveyor belt is to stop the movement of the workpiece on the conveyor belt when it reaches the specified position. The robot grabs the stationary workpiece and the conveyor continues to move. The disadvantages of this method are also very obvious. On the one hand, frequent acceleration and deceleration of the conveyor belt will reduce the average running speed of the conveyor belt, increase the loss, and the robot will often be in a waiting state; on the other hand, if multiple robots serve the same conveyor belt, and each robot has The conveyor is required to be stationary before the workpiece can be operated. The working beat of each robot will be interfered by other robots. In addition, some special application scenarios require the conveyor to continue running and cannot be stopped.


echnical realization elements:


It is an object of the invention to at least address one of the technical drawbacks.


To this end, an object of the present invention is to provide a method for dynamically tracking an industrial robot conveyor belt.


In order to achieve the above object, an embodiment of the present invention provides a method for dynamically tracking an industrial robot conveyor belt, including the following steps:


Step S1, according to the relative position between the industrial robot and the conveyor belt, the conveyor belt tracking is sequentially divided into the following stages: a start segment, a tracking segment and a disengagement segment, and an encoder is arranged on the conveyor belt to measure the conveyor belt position and speed;


Step S2, when the synchronous switch located on the conveyor belt detects that a new workpiece arrives, issues a notification instruction to the industrial robot, and when the workpiece enters the start window and the industrial robot is in a waiting state, the industrial robot starts tracking the workpiece. And adjusting the running speed such that the industrial robot's end tool speed coincides with the speed of the conveyor belt before entering the tracking area;


The industrial robot performs a corresponding acceleration and deceleration strategy according to different positions of the workpiece in the starting segment:


When the workpiece is located in a starting area of the start window, the industrial robot first moves backwards, and then accelerates the tracking of the workpiece in a forward direction;


When the workpiece is located in an intermediate area of the start window, the industrial robot first accelerates and then decelerates, and the speed of the industrial robot is greater than 0 and does not exceed the conveyor speed during the whole process;


The workpiece is located at an end region of the start window, and the industrial robot first accelerates and then decelerates, and the maximum speed exceeds the conveyor speed during the whole process;


Step S3, after the workpiece enters the tracking segment, the industrial robot synthesizes the end speed of the industrial robot according to the preset teaching speed and the conveyor speed measured by the encoder, and integrates the end speed of the industrial robot. Obtaining a travel path of the industrial robot, in the tracking segment, the industrial robot operates the workpiece according to a preset action, and after the operation is completed, the robot stops tracking the workpiece into the disengaged segment;


In step S4, after the tracking segment completes the task relative to the workpiece, the robot enters the disengagement segment, and the actual speed of the industrial robot is reduced from the conveyor speed to zero.


Further, the industrial robot starts at a speed of 0, the position at the end of the start segment is the starting point of the tracking area, the speed is the conveyor speed, and the starting robot running time = conveyor displacement / conveyor speed.


Further, in the step S3, a correction term V-correction=f (position error) is introduced, and f is a correction function whose input is the current position error of the industrial robot, and the actual speed of the industrial robot=V- Teach +V-conveyor +V-correction.


The industrial robot conveyor belt dynamic tracking method decouples the robot motion from the conveyor belt motion according to the embodiment of the invention: the robot can compensate the conveyor belt movement regardless of the movement of the conveyor belt, ensuring that the path and speed of the tool relative to the workpiece on the conveyor belt are consistent with the preset . Regardless of whether the conveyor belt is moving or not, the robot can ensure that the movement of the workpiece relative to the workpiece is consistent with the pre-teaching, and the production efficiency is improved without increasing the difficulty of use. The invention supports the robot to open and track the workpieces at different positions in the starting window, can adapt to the complex production environment, and start different speed strategies corresponding to different positions in the beginning; use the encoder to collect the conveyor belt speed in real time, and use the speed vector synthesis to obtain the robot speed, and introduce at the same time The speed correction amount can cope with the scene of the belt speed fluctuation and has excellent tracking performance.


The additional aspects and advantages of the invention will be set forth in part in the description which follows.



Detailed ways


The embodiments of the present invention are described in detail below, and the examples of the embodiments are illustrated in the accompanying drawings, in which the same or similar reference numerals indicate the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the drawings are intended to be illustrative of the invention and are not to be construed as limiting.



In step S1, since the working range of the industrial robot is limited, according to the relative position between the industrial robot and the conveyor belt, the conveyor belt tracking is sequentially divided into the following stages: a start section, a tracking section and a disengagement section, and an encoder and a synchronous switch are arranged on the conveyor belt. The encoder is used to measure the position and speed of the conveyor belt, and the synchronous switch is used to detect the arrival of new workpieces.


Step S2, when the synchronous switch located on the conveyor belt detects that a new workpiece arrives, sends a notification instruction to the industrial robot. When the workpiece enters the start window and the industrial robot is in the waiting state, the industrial robot starts tracking the workpiece and adjusts the operation. The speed is such that the industrial robot's end tool speed is consistent with the speed of the conveyor belt before the industrial robot enters the tracking area.


In one embodiment of the invention, a buffer zone is provided between the synchronizing switch and the start segment, in which the industrial robot does not track the workpiece. As shown in Figure 3, when the workpiece passes the synchronous switch, the workpiece is not tracked by the industrial robot before entering the start window; when the workpiece is within the start window, the industrial robot will start tracking and keeping up with the workpiece. When the workpiece is in the start window and the robot is in the waiting state, the industrial robot can start tracking the workpiece, which is the beginning segment before the workpiece leaves the start window.


In one embodiment of the invention, the industrial robot performs a corresponding acceleration and deceleration strategy based on the different positions of the workpiece in the starting segment:


When the workpiece is in the starting area of the start window, the industrial robot first moves backwards and then accelerates the tracking of the workpiece in the forward direction;


When the workpiece is located in the middle of the start window, the industrial robot first accelerates and then decelerates. The speed of the industrial robot is greater than 0 and does not exceed the conveyor speed during the whole process;


The workpiece is located at the end of the start window. The industrial robot first accelerates and then decelerates. The maximum speed during the whole process will exceed the conveyor speed.


The above acceleration/deceleration strategy will be described below by taking FIG. 4 as an example.


As shown in FIG. 4, B is located in the middle of the start area, and A and C are located before and after B, respectively. According to the different acceleration and deceleration strategies of the position of the workpiece when the robot starts to track, the final effect is to ensure that the position and speed of the end point of the industrial robot are consistent with the workpiece when the workpiece enters the tracking area. If it is located at position B, the industrial robot first accelerates and then decelerates. The robot speed is greater than 0 and does not exceed the conveyor speed during the whole process. If it is located at position A, the robot will move backwards first, then accelerate the tracking workpiece in the forward direction; if it is in position C The robot accelerates and then decelerates, and the maximum speed will exceed the conveyor speed during the whole process.


Figure 5 is a schematic illustration of a starting segment speed mode in accordance with an embodiment of the present invention. The above three acceleration and deceleration curves are constrained by the endpoint conditions. The starting position is the robot position and the speed is 0; the end position is the starting point of the tracking area, the speed is the conveyor speed; the starting stage robot running time = conveyor displacement / conveyor speed. The general robot allows speed and acceleration to be much higher than the conveyor belt, so the beginning robot can keep up with the workpiece.


Step S3, after the workpiece enters the tracking segment, the industrial robot synthesizes the end speed of the industrial robot according to the preset teaching speed and the conveyor belt speed measured by the encoder, and integrates the end speed of the industrial robot to obtain the traveling path of the industrial robot. In the tracking segment, the industrial robot operates the workpiece according to a preset action. After the operation is completed, the robot stops tracking the workpiece and enters the disengagement segment.


Specifically, when the workpiece enters the tracking segment, the robot end speed has been consistent with the conveyor belt. At this time, the robot starts the movement relative to the workpiece according to the program taught by the user, and the speed is V-teaching; the conveyor speed is V-belt; the two speed vector synthesis V-synthesis is the ideal robot end speed. During the entire tracking process, the encoder measures the conveyor speed in real time, ensuring the accuracy of the robot's end speed even if the conveyor speed fluctuates. Therefore, the tracking segment synthesizes the robot speed based on the teaching speed and the conveyor speed, and the speed integral determines the path the robot walks. FIG. 6 is a schematic diagram of tracking segment velocity synthesis according to an embodiment of the invention.


In step S3, a correction term V-correction=f (position error) is introduced, and f is a correction function whose input is the current position error of the industrial robot, and the actual speed of the industrial robot=V-teaching+V-belt+V- Corrected.


Since there is inevitably a delay in the system and measurement, the simple velocity synthesis is prone to cumulative error after long-distance tracking. Therefore, the correction term V-correction=f (position error) is introduced, f is the correction function, and the input is the current position error of the robot. The actual speed of the robot = V - teach + V - conveyor + V - correction.


In an embodiment of the present invention, after the workpiece enters the tracking area, the robot operates the workpiece according to a preset action, such as grabbing, gluing, etc.; after the operation is completed, the robot stops tracking the workpiece, and returns Go to the waiting location or perform other non-tracking operations.


In step S4, after the tracking segment completes the task relative to the workpiece, the robot enters the disengagement segment, and the actual speed of the industrial robot is reduced from the conveyor speed to zero.


After the tracking segment completes the task relative to the workpiece, the robot enters the disengagement segment. Since the speed of the workpiece is reduced to zero at this time, the robot end speed is equal to the conveyor speed. There is no special requirement for the deceleration section. The actual speed of the robot can be reduced from the conveyor speed to zero.


The industrial robot conveyor belt dynamic tracking method decouples the robot motion from the conveyor belt motion according to the embodiment of the invention: the robot can compensate the conveyor belt movement regardless of the movement of the conveyor belt, ensuring that the path and speed of the tool relative to the workpiece on the conveyor belt are consistent with the preset . Regardless of whether the conveyor belt is moving or not, the robot can ensure that the movement of the workpiece relative to the workpiece is consistent with the pre-teaching, and the production efficiency is improved without increasing the difficulty of use. The invention supports the robot to open and track the workpieces at different positions in the starting window, can adapt to the complex production environment, and start different speed strategies corresponding to different positions in the beginning; use the encoder to collect the conveyor belt speed in real time, and use the speed vector synthesis to obtain the robot speed, and introduce at the same time The speed correction amount can cope with the scene of the belt speed fluctuation and has excellent tracking performance.


In the description of the present specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" and the like means a specific feature described in connection with the embodiment or example. A structure, material or feature is included in at least one embodiment or example of the invention. In the present specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in a suitable manner in any one or more embodiments or examples.


Although the embodiments of the present invention have been shown and described, it is understood that the foregoing embodiments are illustrative and not restrictive Variations, modifications, alterations and variations of the above-described embodiments are possible within the scope of the invention. The scope of the invention is defined by the appended claims and their equivalents.

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