A control method for smooth transition of multi-path segments of a six-axis robot arm and the robot arm

Abstract

This invention provides a control method for smooth multi-path transition of a six-axis robotic arm, belonging to the field of robotics. It is characterized by the following steps: obtaining the velocity, position, and preset acceleration upper limit values ​​of the starting and ending points of each axis of the six-axis robotic arm; calculating the shortest total time for smooth motion of each axis; using the maximum value as the synchronous running time of the six axes of the robotic arm, thereby obtaining the acceleration of each axis; and constructing a Single S-curve for each axis to control the motion of each axis of the robotic arm according to the Single S-curve parameters. This invention obtains the maximum smooth transition time in the robotic arm and uses this time as a unified approximation time for the six axes of the robotic arm, thereby determining the jerk and acceleration of each axis at this approximation time, and constructing a Single S-curve for each axis to control the motion of each axis of the robotic arm according to the Single S-curve parameters, thus enabling the six axes of the robotic arm to achieve synchronous motion.

Description

Technical Field

[0001] This invention relates to the field of robotics, and in particular to a control method for smooth transition of multi-path segments in a six-axis robotic arm and the robotic arm itself. Background Technology

[0002] In the field of automotive welding, robots play an unparalleled role. During robot simulation, the end effector path consists of a combination of multiple segments and paths. At the junctions between these segments, without targeted handling, the robot will experience continuous start-stop motion, meaning that the initial and final speeds of each path are both zero, implying constant acceleration and deceleration. This significantly impacts the welding rhythm and hinders the pace of automotive production. Therefore, path planning is necessary at the junctions, or approximation segments.

[0003] In path planning, commonly used methods include cubic polynomial interpolation, quintic polynomial interpolation, seventh polynomial interpolation, parabolic methods, and methods based on dynamic equations. Cubic polynomial interpolation has four constraints and can ensure continuity of velocity and acceleration, but in practical applications, multiple cubic polynomials are needed to meet actual requirements. Quintic polynomial interpolation cannot constrain acceleration and velocity during the process. Seventh polynomial interpolation can guarantee continuous acceleration, but the computational load is too high. The dynamic equation method is prone to entering infinite loops during the optimization process.

[0004] Therefore, a new control method is needed to manipulate the robot. Summary of the Invention

[0005] One objective of this invention is to provide a control method for smooth transition of multi-path segments in a six-axis robotic arm, enabling the six axes of the six-axis robotic arm to move synchronously.

[0006] Specifically, this invention provides a control method for smooth transition of multi-path segments in a six-axis robotic arm, comprising the following steps:

[0007] Obtain the starting speed of each axis of a six-axis robotic arm. Termination speed Starting point position End point location and the preset upper limit of acceleration a m ;

[0008] Let the acceleration 'a' of each axis be equal to the upper limit value 'a' of the acceleration for that axis. m According to the initial speed Termination speed Starting point position End point location and the preset upper limit of acceleration a mCalculate the shortest total time for smooth motion on each axis.

[0009] Will Maximum value T max The synchronous running time of the six axes of the six-axis robotic arm;

[0010] Compare the initial velocities of each axis. Termination speed Size;

[0011] Initial speed of each axis Greater than the termination speed The acceleration of each axis is calculated using the following formula:

[0012]

[0013] Initial speed of each axis Less than the termination speed At that time, the acceleration of each axis is calculated using the following formula:

[0014]

[0015] A Single S-curve is constructed for each axis to control the motion of each axis in the six-axis robotic arm according to the Single S-curve parameters.

[0016] Furthermore, the acceleration 'a' of each axis is equal to the upper limit value 'a' of the acceleration of that axis. m According to the initial speed Termination speed Starting point position End point location and the preset upper limit of acceleration a m Calculate the shortest total time for smooth motion on each axis. In the step, the six-axis robotic arm is made to... It operates in a motion mode.

[0017] Furthermore, each axis of the six-axis robotic arm includes a variable speed section and a constant speed section;

[0018] The acceleration 'a' of each axis is set to be equal to the upper limit value 'a' of the acceleration of that axis. m According to the initial speed Termination speed Starting point position End point location and the preset upper limit of acceleration a m Calculate the shortest total time for smooth motion on each axis. The shortest total time for smooth motion on each axis in the steps. The calculation method includes the following steps:

[0019] The displacement of each segment in the speed change section is calculated using the following formula;

[0020]

[0021] The displacement of the uniform velocity segment is calculated using the following formula;

[0022] q(t i )=v3t u 0 <t u <T u Formula Six

[0023] Where q0 is the initial position of the robotic arm; J is the jerk; q1 is the position of the robotic arm after the first segment of motion; v1 is the velocity of the robotic arm after the first segment of motion; q2 is the position of the robotic arm after the second segment of motion; v2 is the velocity of the robotic arm after the second segment of motion; and v3 is the velocity of the robotic arm after the third segment of motion.

[0024] Based on the time T1, T2, T3 and T within each displacement segment u T1, T2, T3 and T u The starting point q is obtained by summing the results. s to the endpoint q e Total time T all ,

[0025] Furthermore, the calculation obtains the shortest total time for smooth motion on each axis. The process also includes the following steps:

[0026] Initial speed of each axis Less than the termination speed The acceleration J and the shortest total time T are calculated using the following formula. all Relationship:

[0027]

[0028] Initial speed of each axis Greater than the termination speed The acceleration J and the shortest total time T are calculated using the following formula. all Relationship:

[0029]

[0030] Furthermore, the acceleration a of each axis is calculated based on the jerk J of each axis.

[0031] Furthermore, the initial speed of each axis of the six-axis robotic arm is obtained. Termination speed Starting point position End point location and the preset upper limit of acceleration a m The process also includes the following steps:

[0032] By acquiring the position and approximation percentage of each stage after the robotic arm's movement, the starting point position of each axis in the six-axis robotic arm can be calculated. and termination point position

[0033] Furthermore, the step of constructing Single S-curves for each axis to perform motion control on each axis of the six-axis robotic arm according to the Single S-curves also includes the following steps:

[0034] The Single S-curve parameters for each axis are calculated by using the acceleration 'a' for each axis.

[0035] Furthermore, it also includes: transmitting the Single S-curve parameters via RSI to transmit the parameters of each axis to each axis of the six-axis robotic arm.

[0036] The present invention also discloses a six-axis robotic arm, including the control method described above.

[0037] This invention obtains the maximum smooth transition time in a six-axis robotic arm and uses this time as the unified approximation time for the six axes of the robotic arm. Then, it determines the jerk J and acceleration a of each axis at this approximation time, and constructs a single S-curve for each axis. The six axes of the six-axis robotic arm are then motion-controlled according to the parameters of the single S-curve, thereby enabling the six axes of the six-axis robotic arm to move synchronously.

[0038] The above and other objects, advantages and features of the present invention will become more apparent to those skilled in the art from the following detailed description of specific embodiments of the invention in conjunction with the accompanying drawings. Attached Figure Description

[0039] The following sections will describe some specific embodiments of the invention in a detailed manner by way of example and not limitation, with reference to the accompanying drawings. The same reference numerals in the drawings denote the same or similar parts or portions. Those skilled in the art should understand that these drawings are not necessarily drawn to scale. In the drawings:

[0040] Figure 1 This is a flowchart illustrating an embodiment of the present invention;

[0041] Figure 2 This is a diagram showing the relationship between the approximation segment and the non-approximation segment according to an embodiment of the present invention;

[0042] Figure 3 This is a graph showing the relationship between normal speed and time according to an embodiment of the present invention;

[0043] Figure 4 This is a diagram illustrating the effect of single-axis approximation according to an embodiment of the present invention. Detailed Implementation

[0044] Figure 1 This is a flowchart illustrating an embodiment of the present invention. In one embodiment, as shown... Figure 1 As shown, a control method for smooth transition of multi-path segments in a six-axis robotic arm mainly includes the following steps:

[0045] Obtain the starting speed of each axis of a six-axis robotic arm. Termination speed Starting point position End point location and the preset upper limit of acceleration a m ;

[0046] Let the acceleration 'a' of each axis be equal to the upper limit value of the acceleration 'a' of that axis. m According to the initial speed Termination speed Starting point position End point location and the preset upper limit of acceleration a m Calculate the shortest total time for smooth motion on each axis.

[0047] Will maximum value The synchronized operation time of the six axes of a six-axis robotic arm;

[0048] Compare the initial velocities of each axis. Termination speed Size;

[0049] Initial speed of each axis Greater than the termination speed The acceleration of each axis is calculated using the following formula:

[0050]

[0051] Initial speed of each axis Less than the termination speed At that time, the acceleration of each axis is calculated using the following formula:

[0052]

[0053] A Single S-curve is constructed for each axis to enable motion control of each axis in the six-axis robotic arm according to the Single S-curve parameters.

[0054] In this embodiment, the maximum smooth transition time in the six-axis robotic arm is obtained and used as the unified approximation time of the six axes of the robotic arm. Then, the acceleration 'a' of each axis at the approximation time is determined by reverse calculation. Then, a single S-curve is constructed for each axis to control the motion of each axis in the six-axis robotic arm according to the Single S-curve parameters, so that the six axes of the six-axis robotic arm can achieve synchronous motion.

[0055] Furthermore, such as Figure 2 As shown, to construct a Single S-curve, the starting point position of each axis must first be determined. and termination point position The positions of the starting and ending points are calculated by obtaining the positions and approximation percentages of the robotic arm at each stage of its movement.

[0056] Starting point q s = (q3-q2)*(1-0.5*approximation percentage);

[0057] Termination point q e = (q3-q2)*(0.5*approximation percentage)+q2;

[0058] Starting velocity v s Let a be the velocity of the current uniform segment of the non-approximation path. s Zero;

[0059] End point velocity v e Let a be the velocity and acceleration a of the uniform segment of the next non-approximation path. e Zero;

[0060] Furthermore, such as Figure 3 and Figure 4 As shown, to facilitate the explanation of the principles and content of this invention, the following example uses a single axis of a six-axis robotic arm. To obtain the shortest total time T for the smooth motion of each axis... all Then it is necessary to obtain the effect of different average velocities on time, by Figure 2 It can be concluded that, in the planning process, in order to reach the destination in less time, one should try to travel at a higher speed for a while, and then change speed accordingly. Therefore, with... The total time T of the movement all The shortest path is the trajectory planning, which is then divided into two segments: a constant speed segment and a variable speed segment.

[0061] The speed change segment is implemented using a three-stage cubic polynomial. The expressions for each stage are analyzed below. Let t... i (i = 1, 2, 3) represents the three local time segments of the variable speed, T i (i = 1, 2, 3) represent the three running times. The local time of the uniform speed segment is t. u T u Let be the time of uniform motion. Assuming the acceleration (J) is constant for each segment, integrating it yields the acceleration:

[0062]

[0063] Uniform speed segment:

[0064] a(t i ) = 0 0 <t u <T u

[0065] Integrating the acceleration for each segment yields the velocity:

[0066]

[0067] Uniform speed segment:

[0068] v(t i =v30 <t u <T u

[0069] The displacement is obtained by integrating the velocity segments:

[0070]

[0071] Uniform speed segment:

[0072] q(t i )=v3t u 0 <t u <T u Formula Six

[0073] Where: q0 is the initial position of the robotic arm; J is the jerk; q1 is the position of the robotic arm after the first segment of motion; v1 is the velocity of the robotic arm after the first segment of motion; q2 is the position of the robotic arm after the second segment of motion; v2 is the velocity of the robotic arm after the second segment of motion; and v3 is the velocity of the robotic arm after the third segment of motion.

[0074] The existing known conditions are: initial velocity v s Termination speed v e Initial position q s Termination position q e and the upper limit of acceleration a mThen, the unknown parameters J, T1, T2, T3, and T are solved. u

[0075] Solving for unknown parameters based on the type of velocity change:

[0076] a) When the initial velocity v s Less than the velocity v at the termination point e hour:

[0077] To maximize average speed, the motion should first accelerate, then return to a constant speed. That is, as described above. v3 = v e ,t4=t u J>0, a m >0

[0078] Find:

[0079]

[0080] Let T all =T1+T2+T3+T u Then calculate T. all Relationship with J

[0081]

[0082] T u =T all -(T1+T2+T3)Formula 12

[0083] b) When the initial velocity v s greater than the velocity v at the termination point e Similarly, we can conclude that:

[0084] To maximize the average velocity, solve for the shortest smooth transition time T. u It should first move at a constant speed, and then decelerate. That is, in the above, v3 = v s ,t0=t u ,J<0,a m <0,

[0085] Find:

[0086]

[0087] T u =T all -(T1+T2+T3)Formula 17

[0088] The approximation time is related to the set upper limit of acceleration. A larger upper limit results in a shorter approximation time, and vice versa. Furthermore, the upper limit of acceleration can be deduced from the time value, allowing calculation of the total approximation time T for each axis.all Determine the maximum time T max By making the total approximation time the same for each axis, we can then deduce the 'a' value of the single S-curve for each axis.

[0089] The derivation is based on the characteristics of the single S-curve, and the results are as follows:

[0090] Starting velocity v s greater than the velocity v at the termination point e At that time, seek

[0091]

[0092] Starting velocity v s Less than the velocity v at the termination point e At that time, seek

[0093]

[0094] Then, a single S-curve is constructed for each axis. In addition, the constructed data is transmitted via RSI to transmit the parameters of each axis to each axis of the six-axis robotic arm, so as to realize the control of the six-axis robotic arm.

[0095] like Figure 4 As shown in the figure, the robot arm has a comparison between the approximation motion effect and the non-approximation motion effect of a single axis. When the robot arm performs approximation motion, the acceleration continuity of the six axes is guaranteed and the speed and acceleration are limited during the process. There will be no excessive speed or acceleration, which effectively improves the service life of the motor.

[0096] The present invention also discloses a six-axis robotic arm, including the control method described above.

[0097] Therefore, those skilled in the art should recognize that although numerous exemplary embodiments of the present invention have been shown and described in detail herein, many other variations or modifications conforming to the principles of the present invention can be directly determined or derived from the disclosure of the present invention without departing from the spirit and scope of the invention. Thus, the scope of the present invention should be understood and construed as covering all such other variations or modifications.

Claims

1. A control method for smooth transition of multi-path segments in a six-axis robotic arm, characterized in that, Includes the following steps: Obtain the starting speed of each axis of a six-axis robotic arm. Termination speed Starting point position End point location and the preset acceleration upper limit value ; Let the acceleration 'a' of each axis be equal to the upper limit value of the acceleration for that axis. According to the initial speed Termination speed Starting point position End point location and the preset acceleration upper limit value Calculate the shortest total time for smooth motion on each axis. ; Will maximum value The synchronous running time of the six axes of the six-axis robotic arm; Compare the initial velocities of each axis. Termination speed Size; Initial speed of each axis Greater than the termination speed The acceleration of each axis is calculated using the following formula: Formula 1 Initial speed of each axis Less than the termination speed At that time, the acceleration of each axis is calculated using the following formula: Formula 2 A Single S-curve is constructed for each axis to control the motion of each axis in the six-axis robotic arm according to the Single S-curve parameters.

2. The control method according to claim 1, characterized in that, The acceleration 'a' of each axis is set to be equal to the upper limit value of the acceleration of that axis. According to the initial speed Termination speed Starting point position End point location and the preset acceleration upper limit value , Shortest total time for smooth axis motion In the step, the six-axis robotic arm is made to... It operates in a motion mode.

3. The control method according to claim 2, characterized in that, Each axis of the six-axis robotic arm includes a variable speed section and a constant speed section; The acceleration 'a' of each axis is set to be equal to the upper limit value of the acceleration of that axis. According to the initial speed Termination speed Starting point position End point location and the preset acceleration upper limit value , Shortest total time for smooth axis motion The shortest total time for smooth motion on each axis in the steps. The calculation method includes the following steps: The displacement of each segment in the speed change section is calculated using the following formula; Formula 5 The displacement of the uniform velocity segment is calculated using the following formula; Formula Six in, J represents the initial position of the robotic arm; J is the jerk. This is the position of the robotic arm after the first segment of motion; The speed of the robotic arm after the first segment of motion; This is the position of the robotic arm after the second phase of motion. The speed of the robotic arm after the second phase of motion. The speed of the robotic arm after the third segment of motion; Based on the time within each displacement segment , , and ,Will , , and The starting point is obtained by addition. To the end point Total time .

4. The control method according to claim 3, characterized in that, The calculation obtains the shortest total time for smooth motion on each axis. The process also includes the following steps: Initial speed of each axis Less than the termination speed The following formula is used to calculate the jerk J and the shortest total time. Relationship: Formula 8 Initial speed of each axis Greater than the termination speed The following formula is used to calculate the jerk J and the shortest total time. Relationship: Formula Thirteen.

5. The control method according to any one of claims 1-4, characterized in that, The starting speed of each axis of the six-axis robotic arm is obtained. Termination speed Starting point position End point location and the preset acceleration upper limit value The process also includes the following steps: By acquiring the position and approximation percentage of each stage after the robotic arm's movement, the starting point position of each axis in the six-axis robotic arm can be calculated. and termination point position .

6. The control method according to claim 5, characterized in that, The step of constructing a Single S-curve for each axis to control the motion of each axis of the six-axis robotic arm according to the Single S-curve further includes the following steps: The Single S-curve parameters for each axis are calculated by using the acceleration 'a' for each axis.

7. The control method according to claim 6, characterized in that, Also includes: The Single S-curve parameters are transmitted via RSI, transferring the parameters of each axis to each axis of the six-axis robotic arm.

8. A six-axis robotic arm, characterized in that, Includes the control method as described in any one of claims 1-7 above.

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