Multi-stage multi-degree-of-freedom robotic arm and control method

Abstract

The present invention discloses a multi-stage and multi-degree-of-freedom robotic arm, which includes a multi-stage end attitude maintaining swing arm mechanism. Each stage of the end attitude maintaining swing arm mechanism includes a driving shaft, the driving shaft is connected with a power device, the driving shaft is fixedly connected upward with a support arm plate, the top of the support arm plate is rotatably connected with a driven shaft, the driven shaft is fixedly connected with a connecting plate, and the end of the connecting plate is fixedly connected with a carrying platform; the carrying platform of the M-stage end attitude maintaining swing arm mechanism serves as the working platform of the M+1-stage end attitude maintaining swing arm mechanism; each stage of the carrying platform can serve as an operation platform or a transfer platform, and the power devices of each stage of the end attitude maintaining swing arm mechanism are all connected to an electric control device. The present invention also discloses a corresponding control method. In the present invention, the end attitude of each stage of the robotic arm always remains unchanged, thereby greatly simplifying the control algorithm and also reducing the design difficulty of the multi-stage and multi-degree-of-freedom robotic arm. The present invention can meet the requirements of the control accuracy of the multi-stage and multi-degree-of-freedom robotic arm at low cost.

Description

Technical Field

[0001] The present invention relates to the field of mechanical technology, and particularly to a multi-stage robotic arm and an algorithm for the coordinates of the last-stage driven shaft. Background Art

[0002] The working space that a single-stage robotic arm can reach is limited. For example, for a swing-arm single-stage robotic arm, the end manipulator can only work within the arc range passed by the swing, and cannot change the working radius. Within the same working radius, the working range cannot exceed the arc range passed by the swing. To improve the adaptability to the working space, a multi-stage robotic arm is required.

[0003] Although a multi-stage robotic arm can reach a wider working space, it has the following disadvantages:

[0004] The rotation angle of the subsequent stage robotic arm is affected by the rotation angle of the previous stage robotic arm, that is, the algorithms between the stages of the robotic arms are coupled. As a result, the rotation angle of the motor belonging to the current stage robotic arm is not equal to the actual rotation angle of the current stage robotic arm in space. Therefore, when it is required that the end of the robotic arm always maintains a certain fixed posture, or when determining the spatial position of the end robotic arm, the inverse kinematics algorithm of the robotic arm must consider the correction of the end posture in real time, which obviously increases the algorithm complexity and the difficulty of implementation for engineering technicians.

[0005] In industrial applications, the method of teaching is often used to automatically generate robot programs. However, when the accuracy requirement for maintaining the end posture of the robotic arm is high, the method of manual teaching is obviously not sufficient.

[0006] In addition, in some working scenarios, the object to be operated often only has a position change and no posture change. For example, when working on the planar working surface at the end of a bridge, when applying glue to the edge of a planar workpiece, or when transferring the object to be operated from one plane to another parallel plane, the object to be operated only has a position change and no posture change. If the end posture of the robotic arm mechanism can be kept unchanged without an algorithm, it will greatly reduce the design difficulty, significantly simplify the position algorithm, greatly reduce the calculation amount when the electronic control device of the robotic arm mechanism calculates the position of the end of the robotic arm, improve the real-time performance of calculating the end position, and achieve a more accurate and lower-cost control process for the multi-stage robotic arm.

[0007] In summary, for the existing multi-stage multi-degree-of-freedom robotic arm, the algorithm for the end coordinates needs to consider the influence of the rotation of the previous stage robotic arm on the posture of the subsequent stage robotic arm. The algorithms of each stage of the robotic arm need to be coupled, the coupling algorithm is complex, the required computing power is high, and the overall cost is high. Summary of the Invention

[0008] The object of the present invention is to provide a multi-stage and multi-degree-of-freedom robotic arm. During the movement, the attitude of the carrying platform connected to the driven shaft of the last-stage robotic arm remains unchanged, providing a basis for reducing the control cost.

[0009] To achieve the above object, the present invention provides a multi-stage and multi-degree-of-freedom robotic arm, including multi-stage end-attitude-maintaining swing arm mechanisms. Each stage of the end-attitude-maintaining swing arm mechanism includes two bearing seats. A lower bearing is provided in the bearing seat. A driving shaft is rotatably connected between the lower bearings of the two bearing seats. The driving shaft extends out of the bearing seat and is connected with a power device.

[0010] The driving shaft is fixedly connected upward with a support arm plate. The top of the support arm plate is rotatably connected with a driven shaft through an upper bearing. The driven shaft is fixedly connected with a connecting plate. The end of the connecting plate is fixedly connected with a carrying platform.

[0011] The driving shaft and the driven shaft are parallel to each other. A transmission mechanism is connected between the driving shaft and the driven shaft. The transmission mechanism is a chain transmission mechanism, a synchronous belt transmission mechanism or a gear transmission mechanism. The transmission mechanism is rotatably connected with the driving shaft. The part of the transmission mechanism connected to the driving shaft is fixedly connected with the base through a connecting frame. The transmission mechanism is used to keep the attitude of the carrying platform constant during the rotation of the support arm plate.

[0012] The bearing seats of the first-stage end-attitude-maintaining swing arm mechanism are fixed on the ground or the working platform.

[0013] M is a natural number greater than or equal to 1. The carrying platform of the M-stage end-attitude-maintaining swing arm mechanism serves as the working platform of the M + 1-stage end-attitude-maintaining swing arm mechanism and fixes the bearing seats of the M + 1-stage end-attitude-maintaining swing arm mechanism.

[0014] The carrying platform of the last-stage end-attitude-maintaining swing arm mechanism serves as the working platform or the transfer platform. The swinging planes of each stage of the end-attitude-maintaining swing arm mechanism are in the same plane. The driven shaft of the M-stage end-attitude-maintaining swing arm mechanism is directly below the driving shaft of the M + 1-stage end-attitude-maintaining swing arm mechanism.

[0015] The power devices of each stage of the end-attitude-maintaining swing arm mechanism are all connected to an electric control device.

[0016] The transmission mechanism is a chain transmission mechanism. The chain transmission mechanism includes a lower sprocket rotatably connected to the driving shaft, an upper sprocket fixedly installed on the driven shaft, and a chain wound between the upper sprocket and the lower sprocket. The lower sprocket is fixedly connected with the base through a connecting frame. The structures and sizes of the upper sprocket and the lower sprocket are the same.

[0017] Two support arm plates are arranged in parallel at intervals. The transmission mechanism is arranged in space between the two support arm plates. The carrying platform straddles above the support arm plates.

[0018] It further includes a rotating table, which serves as the working platform of the first-stage end attitude-holding swing arm mechanism, and the bearing seat of the first-stage end attitude-holding swing arm mechanism is installed on the rotating table.

[0019] The present invention also provides a control method for the above multi-stage and multi-degree-of-freedom robotic arm, including a table building method and a table-based control method;

[0020] The table building method is as follows:

[0021] Taking the midpoint of the axis of the driving shaft of the first-stage end attitude-holding swing arm mechanism as the origin, an xy coordinate system is established in the swinging plane. The multi-stage and multi-degree-of-freedom robotic arm includes N-stage end attitude-holding swing arm mechanisms, where N is a natural number greater than or equal to 2, and the last stage is the Nth stage;

[0022] The angle between the support arm plate in the end attitude-holding swing arm mechanism and the x-axis of the xy coordinate system is called θ. The value range of θ in the end attitude-holding swing arm mechanism is MIN - MAX, where both MIN and MAX are real numbers and the unit is degree; θ1 is the θ value of the first-stage end attitude-holding swing arm mechanism; θ2 is the θ value of the second-stage end attitude-holding swing arm mechanism; θ M is the θ value of the Mth-stage end attitude-holding swing arm mechanism;

[0023] The first step of the table building method is to determine the working space;

[0024] The first sub-step is to adjust the θ of each stage of the end attitude-holding swing arm mechanism to MIN through the electric control device, and then synchronously adjust the θ value of each stage of the end attitude-holding swing arm mechanism to gradually rise from MIN to MAX synchronously. During this process, the path passed by the midpoint of the axis of the driven shaft of the last-stage end attitude-holding swing arm mechanism in the xy coordinate system is the upper contour curve of the working space; the coordinates of the left and right endpoints of the upper contour curve are (D1, D2) and (D3, D4), and D1 to D4 are all real numbers;

[0025] The second sub-step is to manually determine the coordinates (0, D5) of the lowest position of the midpoint of the axis of the driven shaft of the last-stage end attitude-holding swing arm mechanism in the Y-axis direction, where D5 is a real number;

[0026] The third sub-step is to use the connection line between (0, D5) and (D1, D2) as the lower left contour curve, and the connection line between (0, D5) and (D3, D4) as the lower right contour curve. The area enclosed by the lower left contour curve, the lower right contour curve and the upper contour curve is used as the working space;

[0027] The second step of the table building method is to divide the area;

[0028] Before leaving the factory, the motion accuracy of the multi-stage and multi-degree-of-freedom robotic arm is determined to be L centimeters according to the application target of the robotic arm; according to the value of L, the working space is divided into multiple working areas, and the distance between any two points on the contour line of each working area is less than 0.5L centimeters;

[0029] The second step of the table building method is to specify a set of values of θ1 to θ for each working area; M of the values;

[0030] In the second step, according to Formula 1, a mapping table is established in which each working area corresponds one-to-one with a set of values of θ1 to θ M of the values;

[0031] The first sub-step is to establish an N-level correspondence table;

[0032] Taking (D1, D2) as the starting point (at this time, the θ values of the end attitude maintaining swing arm mechanisms at all levels are MAX), first keep the end attitude maintaining swing arm mechanisms at the first to the N-1th levels stationary, where ⊿H1 is greater than or equal to 0.1 degree and less than or equal to 0.3 degrees. Taking ⊿H1 as the first step size, make the θ value of the end attitude maintaining swing arm mechanism at the Nth level gradually decrease from MAX to MIN. In each step, calculate the coordinate points of the midpoint of the driven shaft axis of the end attitude maintaining swing arm mechanism at the last level using Formula 1, and establish the correspondence between these coordinate points and the working areas in the working space; if a certain working area corresponds to more than two coordinate points, manually delete the redundant coordinate points, and retain one coordinate point and the corresponding set of values of θ1 to θ M of the values for each working area; for the missing working areas, leave them for the fourth sub-step to handle;

[0033] The second sub-step is table building for the N-1th level;

[0034] Taking ⊿H2 as the second step size, where ⊿H2 is greater than or equal to 0.1 degree and less than or equal to 0.3 degrees; make the θ value of the end attitude maintaining swing arm mechanism at the N-1th level gradually decrease from MAX to MIN;

[0035] For each further step of the second step size, make the θ value of the end attitude maintaining swing arm mechanism at the Nth level gradually decrease from MAX to MIN with ⊿H1 as the first step size;

[0036] In the second step, in each step, calculate the coordinate points of the midpoint of the driven shaft axis of the end attitude maintaining swing arm mechanism at the last level using Formula 1, and establish the correspondence between these coordinate points and the working areas in the working space. If a certain working area corresponds to more than two coordinate points, manually delete the redundant coordinate points, and retain one coordinate point and the corresponding set of values of θ1 to θ M of the values for each working area; for the missing working areas, leave them for the fourth sub-step to handle;

[0037] The third sub-step is to build a table at the N-2 level in the way of the second sub-step, gradually decreasing until the table building at the first level is completed; during the table building process at each level, if there are more than two coordinate points corresponding to a certain work area, redundant coordinate points are manually deleted, and one coordinate point and the corresponding set of θ1 to θ M values are reserved for each work area; for the missing work areas, they are left for the fourth sub-step to handle;

[0038] The fourth sub-step is a manual leak filling step;

[0039] After the third sub-step, manually check the work areas without corresponding coordinate points, and call any work area without corresponding coordinate points a pending area;

[0040] For each pending area, find the adjacent work area with corresponding coordinate points, and look up the table to obtain a set of θ1 to θ M values that can reach the adjacent work area; with this set of θ1 to θ M values as the center, manually fine-tune this set of θ1 to θ M values, calculate the coordinates of the midpoint of the axis of the driven shaft of the last-stage multi-degree-of-freedom robotic arm according to Formula 1, and continue to fine-tune θ1 to θ M values according to the distance between the obtained coordinates and the pending area until the coordinates calculated according to Formula 1 are within the pending area, and establish a mapping relationship between the last set of θ1 to θ M values and this pending area and store them in the table;

[0041] After performing the above operations on all pending areas, obtain a complete mapping table of the values of θ1 to θ M and the work areas;

[0042] The coordinates of the midpoint of the axis of the driven shaft of the last-stage multi-degree-of-freedom robotic arm are calculated according to Formula 1, and Formula 1 is:

[0043] ;

[0044] In Formula 1, x is the abscissa of the xy coordinate system, and y is the ordinate of the xy coordinate system;

[0045] The distance between the driving shaft and the driven shaft in the same-level end attitude maintaining swing arm mechanism is called the wheelbase L,

[0046] L1 is the wheelbase of the first-level end attitude maintaining swing arm mechanism;

[0047] L2 is the wheelbase of the second-level end attitude maintaining swing arm mechanism;

[0048] L M is the wheelbase of the M-level end attitude maintaining swing arm mechanism;

[0049] The distance between the driven shaft of the M-level end attitude-holding swing arm mechanism and the driving shaft of the (M + 1)-level end attitude-holding swing arm mechanism is defined as the stage spacing h;

[0050] h1 is the distance between the driven shaft of the first-level end attitude-holding swing arm mechanism and the driving shaft of the second-level end attitude-holding swing arm mechanism;

[0051] h N－1 is the distance between the driven shaft of the (N - 1)-level end attitude-holding swing arm mechanism and the driving shaft of the N-level end attitude-holding swing arm mechanism.

[0052] The table control method is as follows: When the multi-level and multi-degree-of-freedom robotic arm is working, through the coordinates in the xy coordinate system of the predetermined working position, a corresponding working area is obtained; the electronic control device retrieves the mapping table of the values of θ1 to θ M and the working area, and obtains a set of values of θ1 to θ M According to the set of values of θ1 to θ M control the rotation angles of the end attitude-holding swing arm mechanisms at all levels, so that the midpoint of the axis of the driven shaft of the last-level end attitude-holding swing arm mechanism reaches the predetermined working position.

[0053] The present invention has the following advantages:

[0054] In the present invention, during the operation of the end attitude-holding swing arm mechanisms at all levels, the attitude of the carrying platform always remains unchanged. The lower-level end attitude-holding swing arm mechanism is installed on the carrying platform of the upper-level end attitude-holding swing arm mechanism. Therefore, the attitude of the carrying platform of the last-level end attitude-holding swing arm mechanism also always remains unchanged. It not only expands the working space of the robotic arm through the multi-level setting, but also always keeps the end attitude unchanged, thus greatly simplifying the control algorithm and reducing the design difficulty of the multi-level and multi-degree-of-freedom robotic arm.

[0055] In the end attitude-holding swing arm mechanism of the present invention, when the carrying platform revolves around the driving shaft, the transmission mechanism can make the driven shaft generate self-rotation to offset the angular change brought by the revolution, so that the carrying platform always keeps its initial inclination angle (the inclination angle relative to the working platform of this level of end attitude-holding swing arm mechanism) unchanged. The present invention is applied to the occasions where only the position of the working object needs to be changed without changing the attitude of the working object. It has a simple structure, reliable operation, low cost, and the algorithm has a very small amount of operation, so the delay caused when calculating the end position can be ignored, and the angle of the carrying platform is stable without fluctuation.

[0056] The structure of the present invention is compact and highly scalable. It can be installed in different ways and adapted to a variety of different end devices. It is simple and convenient to construct a multi-degree-of-freedom robotic arm by connecting the end attitude-maintaining swing arm mechanisms end to end. It is easy to design and manufacture (the end attitude-maintaining swing arm mechanisms at all levels can be the same or only different in size, and assemble as many levels as required), meeting more application scenarios.

[0057] Through its own rotation, the rotating table extends the working positions that the midpoint coordinate of the driven shaft axis of the last-stage end attitude-maintaining swing arm mechanism can reach from the working surface to the rotating space formed by rotating the working surface around the y-axis, covering a wider space and making it more flexible and convenient to use, improving the versatility (for occasions with unchanged working positions, it can adapt to more working situations) and flexibility (for occasions where the working positions are not unique or will change, the present invention can flexibly adapt to different working positions in a relatively larger space) of the present invention.

[0058] By adopting the control method of the present invention, only a planar coordinate system is required. The algorithm is simple, with very low requirements for computing power, fast table building speed, and convenient and fast control process. The specific values of θ1 to θ are obtained through the retrieval-based calculation method in the actual work of the multi-stage multi-degree-of-freedom robotic arm. M The running speed is extremely fast. An ordinary single-chip microcomputer can achieve a time delay at the microsecond level, meeting the control accuracy requirements of the multi-stage multi-degree-of-freedom robotic arm at a very low cost, which is conducive to the popularization and application of the multi-stage multi-degree-of-freedom robotic arm. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] Figure 1 is a schematic structural view of the end attitude-maintaining swing arm mechanism in the present invention;

[0060] Figure 2 is Figure 1 the left view of;

[0061] Figure 3 is the left view of at another rotation angle Figure 1 ;

[0062] Figure 4 is a schematic perspective view of the end attitude-maintaining swing arm mechanism;

[0063] Figure 5 is a schematic structural view of the multi-stage multi-degree-of-freedom robotic arm in the xy coordinate system, which visually shows the meanings of the parameters L, h, and θ in Formula (1). To reduce the figure for overall expression, Figure 5 the ratio of the outer contour curve to the size of the end attitude-maintaining swing arm mechanism in is smaller than the actual ratio, that is, the outer contour curve is expressed in a smaller scale. DETAILED DESCRIPTION OF THE INVENTION

[0064] Such as Figures 1 to 5As shown in the figure, the multi-stage and multi-degree-of-freedom robotic arm of the present invention includes a multi-stage end attitude-holding swing arm mechanism. Each stage of the end attitude-holding swing arm mechanism includes two bearing seats 2. A lower bearing 3 is provided inside the bearing seat 2. A driving shaft 4 is rotatably connected between the lower bearings 3 of the two bearing seats 2. The driving shaft 4 extends out of the bearing seat 2 and is connected to a power device, which is used to drive the driving shaft 4 to rotate. The power device can be a motor or a motor equipped with a reducer, which is a conventional technology and not shown in the figure.

[0065] The driving shaft 4 is fixedly connected upward with a support arm plate 5. The top of the support arm plate 5 is rotatably connected with a driven shaft 7 through an upper bearing 6. The driven shaft 7 is fixedly connected with a connecting plate 8. The end of the connecting plate 8 is fixedly connected with a bearing platform 9.

[0066] The driving shaft 4 and the driven shaft 7 are parallel to each other. A transmission mechanism is connected between the driving shaft 4 and the driven shaft 7. The transmission mechanism is a chain transmission mechanism, a synchronous belt transmission mechanism or a gear transmission mechanism. The transmission mechanism is rotatably connected with the driving shaft 4, and the part of the transmission mechanism connected to the driving shaft 4 is fixedly connected with the base 1 through a connecting frame 10. The transmission mechanism is used to keep the attitude of the bearing platform 9 constant during the rotation of the support arm plate 5.

[0067] The bearing seats 2 of the first-stage end attitude-holding swing arm mechanism are fixed on the ground or the working platform 1.

[0068] M is a natural number greater than or equal to 1. The bearing platform 9 of the M-stage end attitude-holding swing arm mechanism serves as the working platform 1 of the M + 1-stage end attitude-holding swing arm mechanism and fixes the bearing seats 2 of the M + 1-stage end attitude-holding swing arm mechanism.

[0069] The bearing platform 9 of the last-stage end attitude-holding swing arm mechanism serves as an operation platform or a transfer platform. The swinging planes of each stage of the end attitude-holding swing arm mechanism are in the same plane. The driven shaft 7 of the M-stage end attitude-holding swing arm mechanism is directly below the driving shaft 4 of the M + 1-stage end attitude-holding swing arm mechanism.

[0070] The power devices of each stage of the end attitude-holding swing arm mechanism are all connected to an electronic control device. The electronic control device uses a single-chip microcomputer, which is a conventional device and not shown in the figure.

[0071] In the present invention, during the operation of each stage of the end attitude-holding swing arm mechanism, the attitude of the bearing platform 9 always remains unchanged. The lower-stage end attitude-holding swing arm mechanism is installed on the bearing platform 9 of the upper-stage end attitude-holding swing arm mechanism. Therefore, the attitude of the bearing platform 9 of the last-stage end attitude-holding swing arm mechanism also always remains unchanged. This not only expands the working space of the robotic arm through the multi-stage setting but also always keeps the end attitude unchanged.

[0072] Next, taking the transmission mechanism as a chain transmission mechanism as an example, the transmission mechanism will be specifically described.

[0073] The transmission mechanism is a chain transmission mechanism, which includes a lower sprocket 11 rotatably connected to the driving shaft 4, an upper sprocket 12 fixedly mounted on the driven shaft 7, and a chain 13 wound between the upper sprocket 12 and the lower sprocket 11; the lower sprocket 11 is fixedly connected to the base 1 through a connecting frame 10; the upper sprocket 12 and the lower sprocket 11 have the same structure and size. A tensioning device is installed on the support arm plate 5 to keep the chain 13 in a tensioned state. The tensioning device of the chain 13 is a conventional device, which is not described in detail and is not shown in the figure.

[0074] The present invention can make the rotation of the driven shaft 7 offset the angle change caused by the revolution through the transmission mechanism when the carrying platform 9 revolves around the driving shaft 4, so that the carrying platform 9 always maintains its initial inclination angle (relative to the inclination angle of the working platform 1 of the end posture holding type swing arm mechanism of this level). The present invention is applied to occasions where only the position of the working object needs to be changed but not the posture of the working object. It has a simple structure, reliable operation, and low cost. The algorithm has a very small amount of calculation, and the delay caused by calculating the end position can be ignored. The angle of the carrying platform 9 is stable without fluctuation.

[0075] The present invention has a compact structure and strong scalability. It can be installed in different ways and can be adapted to a variety of different terminal devices. It is simple and convenient to construct a multi-degree-of-freedom robotic arm by connecting multiple terminal posture-maintaining swing arm mechanisms end to end. It is easy to design and manufacture (the terminal posture-maintaining swing arm mechanisms at each level can be the same or only different in size, and as many levels as needed can be assembled), meeting more application scenarios.

[0076] The support arm plates 5 are provided with two parallel and spaced apart; the transmission mechanism is spatially arranged between the two support arm plates 5 , so that the overall structural strength is higher. The bearing platform 9 is arranged across the support arm plates 5 .

[0077] It also includes a rotating table 24 , which serves as a working platform 1 of the first-stage end posture retaining type swing arm mechanism, and a bearing seat 2 of the first-stage end posture retaining type swing arm mechanism is installed on the rotating table 24 .

[0078] The rotating table 24 is a conventional device and will not be described in detail. The rotating table 24, through its own rotation, expands the working position that can be reached by the coordinate of the midpoint of the axis of the driven shaft 7 of the final-stage terminal posture-maintaining swing arm mechanism from the working surface to the rotation space formed by the rotation of the working surface around the y-axis, covering a wider space and being more flexible and convenient to use, thereby improving the versatility of the present invention (for occasions where the working position remains unchanged, it can adapt to more working occasions) and flexibility (for occasions where the working position is not unique or will change, the present invention can flexibly adapt to different working positions in a relatively wider space).

[0079] The present invention also discloses a control method for the above multi-stage and multi-degree-of-freedom robotic arm, including a table building method and a table-based control method;

[0080] The table building method is as follows:

[0081] Taking the midpoint of the axis of the driving shaft 4 of the first-stage end attitude-maintaining swing arm mechanism as the origin, an xy coordinate system is established in the swing plane. The multi-stage and multi-degree-of-freedom robotic arm includes N-stage end attitude-maintaining swing arm mechanisms, where N is a natural number greater than or equal to 2, and the last stage is the Nth stage;

[0082] The angle between the support arm plate 5 in the end attitude-maintaining swing arm mechanism and the x-axis of the xy coordinate system is called θ (unit: degree). The value range of θ in the end attitude-maintaining swing arm mechanism is MIN - MAX (for example, MIN = 0 degree, MAX = 180 degrees), and both MIN and MAX are real numbers and the unit is degree; θ1 is the θ value of the first-stage end attitude-maintaining swing arm mechanism; θ2 is the θ value of the second-stage end attitude-maintaining swing arm mechanism; θ M is the θ value of the Mth-stage end attitude-maintaining swing arm mechanism;

[0083] The first step of the table building method is to determine the working space;

[0084] The first sub-step is to adjust the θ of each stage of the end attitude-maintaining swing arm mechanism to MIN through the electric control device, and then synchronously adjust the θ value of each stage of the end attitude-maintaining swing arm mechanism to gradually rise from MIN to MAX synchronously. During this process, the path passed by the midpoint coordinate of the axis of the driven shaft 7 of the last-stage end attitude-maintaining swing arm mechanism in the xy coordinate system is the upper contour curve 21 of the working space; the coordinates of the left and right endpoints of the upper contour curve 21 are (D1, D2) and (D3, D4), and D1 to D4 are all real numbers;

[0085] The second sub-step is to manually determine the coordinate (0, D5) of the lowest position of the midpoint of the axis of the driven shaft 7 of the last-stage end attitude-maintaining swing arm mechanism in the Y-axis direction, where D5 is a real number;

[0086] The third sub-step is to use the connection line between (0, D5) and (D1, D2) as the lower left contour curve 22, and the connection line between (0, D5) and (D3, D4) as the lower right contour curve 23. The area enclosed by the lower left contour curve 22, the lower right contour curve 23 and the upper contour curve 21 is used as the working space; among them, the adjacent points below the lower left contour curve 22 and the lower right contour curve 23 are also the reachable range of the last-stage load-bearing platform 9 of the multi-stage and multi-degree-of-freedom robotic arm. However, since it is too close to the X-axis (usually the ground), it is not worth using the multi-stage and multi-degree-of-freedom robotic arm for operation, so it is excluded from the working space.

[0087] The second step of the table building method is to divide the area;

[0088] Before leaving the factory, the motion accuracy of the robotic arm is determined to be L centimeters according to the application target of the multi-stage and multi-degree-of-freedom robotic arm; according to the value of L, the working space is divided into multiple working areas 25, and the distance between any two points on the contour line of each working area 25 is less than 0.5L centimeters (this ensures that operating according to the θ value parameters corresponding to this working area 25 after table building can meet the accuracy requirements);

[0089] The second step of the table building method is to specify a set of values of θ1 to θ for each working area 25; M of the value;

[0090] In the second step, according to Formula 1, a mapping table is established in which each working area 25 corresponds one-to-one with a set of values of θ1 to θ; M of the value;

[0091] The first sub-step is to establish an N-level correspondence table;

[0092] Taking (D1, D2) as the starting point (at this time, the θ values of the end posture maintaining swing arm mechanisms at all levels are all MAX), first keep the end posture maintaining swing arm mechanisms at the first to the N-1th levels stationary, ⊿H1 is greater than or equal to 0.1 degree and less than or equal to 0.3 degree, taking ⊿H1 as the first step length, make the θ value of the end posture maintaining swing arm mechanism at the Nth level gradually decrease from MAX to MIN, and in each step, calculate the coordinate points of the midpoint of the axis 7 of the driven shaft of the end posture maintaining swing arm mechanism at the last level according to Formula 1, and establish the correspondence between these coordinate points and the working areas 25 in the working space; if a certain working area 25 corresponds to more than two coordinate points, manually delete the redundant coordinate points, and retain one coordinate point and the corresponding set of values of θ1 to θ for each working area 25; for the missing working areas 25, leave them for the fourth sub-step to handle; M of the value;

[0093] The second sub-step is table building for the N-1th level;

[0094] Taking ⊿H2 as the second step length, ⊿H2 is greater than or equal to 0.1 degree and less than or equal to 0.3 degree; make the θ value of the end posture maintaining swing arm mechanism at the N-1th level gradually decrease from MAX to MIN;

[0095] With each further step of the second step length, make the θ value of the end posture maintaining swing arm mechanism at the Nth level gradually decrease from MAX to MIN with ⊿H1 as the first step length;

[0096] In the second step, in each step, the coordinate points of the midpoint of the axis of the driven shaft 7 of the end-stage attitude-maintaining swing arm mechanism are calculated according to Formula 1, and the corresponding relationship between these coordinate points and the working area 25 in the working space is established. If there are more than two coordinate points corresponding to a certain working area 25, redundant coordinate points are manually deleted, and one coordinate point and the corresponding set of θ1 to θ M values are reserved for each working area 25; for the missing working areas 25, they are left for processing in the fourth sub-step;

[0097] In the third sub-step, the table building for the N-2 level is carried out in the same way as in the second sub-step, gradually decreasing until the first-level table building is completed; during the table building process at each level, if there are more than two coordinate points corresponding to a certain working area 25, redundant coordinate points are manually deleted, and one coordinate point and the corresponding set of θ1 to θ M values are reserved for each working area 25; for the missing working areas 25, they are left for processing in the fourth sub-step;

[0098] The fourth sub-step is a manual leak-filling step;

[0099] After the third sub-step, manually check the working areas 25 that do not have corresponding coordinate points, and any working area 25 without corresponding coordinate points is called a pending area;

[0100] For each pending area, find the adjacent working area 25 with corresponding coordinate points, and look up the table to obtain a set of θ1 to θ M values that can reach the adjacent working area 25; with this set of θ1 to θ M values as the center, manually fine-tune this set of θ1 to θ M values, calculate the coordinates of the midpoint of the axis of the driven shaft 7 of the end-stage multi-degree-of-freedom robotic arm according to Formula 1, and continue to fine-tune θ1 to θ M values according to the distance between the obtained coordinates and the pending area until the coordinates calculated according to Formula 1 are within the pending area, and establish a mapping relationship between the last set of θ1 to θ M values and this pending area and store them in the table;

[0101] After performing the above operations on all pending areas, a complete mapping table of the values of θ1 to θ M and the working area 25 is obtained;

[0102] The coordinates of the midpoint of the axis of the driven shaft 7 of the end-stage multi-degree-of-freedom robotic arm are calculated according to Formula 1, and Formula 1 is:

[0103] ;

[0104] In Formula 1, x is the abscissa of the xy coordinate system, and x is the ordinate of the xy coordinate system;

[0105] The distance between the driving shaft 4 and the driven shaft 7 in the swing arm mechanism with the same-level end attitude retention is defined as the wheelbase L (unit: meter).

[0106] L1 is the wheelbase of the first-level end attitude retention swing arm mechanism;

[0107] L2 is the wheelbase of the second-level end attitude retention swing arm mechanism;

[0108] L M is the wheelbase of the M-level end attitude retention swing arm mechanism;

[0109] The meanings of θ1, θ2 and θ M have been defined above;

[0110] The distance between the driven shaft 7 of the M-level end attitude retention swing arm mechanism and the driving shaft 4 of the (M + 1)-level end attitude retention swing arm mechanism is defined as the stage spacing h (unit: meter);

[0111] h1 is the distance between the driven shaft 7 of the first-level end attitude retention swing arm mechanism and the driving shaft 4 of the second-level end attitude retention swing arm mechanism;

[0112] h N－1 is the distance between the driven shaft 7 of the (N - 1)-level end attitude retention swing arm mechanism and the driving shaft 4 of the N-level end attitude retention swing arm mechanism.

[0113] For existing multi-stage and multi-degree-of-freedom robotic arms, when calculating the end position, it is necessary to consider the influence of the rotation of the previous-stage robotic arm on the attitude of the next-stage robotic arm. The algorithms of each stage of the robotic arm need to be coupled, the coupling algorithm is complex, and the required computing power is very high. Using an ordinary single-chip microcomputer cannot produce practical value - it takes more than two hours to calculate the coordinates once (two hours is a conservative estimate, and it may take a whole day to run). Such a time delay is unacceptable in any industrial scenario. Therefore, existing multi-stage and multi-degree-of-freedom robotic arms need to be equipped with computing devices with stronger computing power, which not only have high equipment costs but also are troublesome in software design.

[0114] Formula 1 does not consider the correction of the end attitude, the algorithm is simple, the required computing power in actual work is very low, and low-cost real-time calculation can be achieved. Even an ordinary single-chip microcomputer can achieve real-time operation (the operation delay of the single-chip microcomputer is also as low as the microsecond level, which does not affect the continuous operation of the multi-stage and multi-degree-of-freedom robotic arm), enabling the multi-stage and multi-degree-of-freedom robotic arm to be more widely used.

[0115] Formula 1, in cooperation with the rotary table 24, rotates the rotary table 24 to such an extent that the swinging plane covers the predetermined working position, so that Formula 1 does not need to introduce three-dimensional space coordinates and only needs to calculate the plane coordinates to calculate the effective coordinates, providing effective coordinate support for the electric control device to control the midpoint of the axis of the driven shaft 7 of the end-stage end attitude-holding swing arm mechanism to reach the predetermined working position, and correspondingly greatly simplifies the coordinate algorithm.

[0116] The table control method is as follows: when the multi-stage and multi-degree-of-freedom robotic arm is working, through the coordinates in the xy coordinate system of the predetermined working position (i.e., the working position where the midpoint of the axis of the driven shaft 7 of the end-stage end attitude-holding swing arm mechanism needs to be), a corresponding working area 25 is obtained; the electric control device retrieves the mapping table of the values of θ1 to θ M and the working area 25, and obtains a set of values of θ1 to θ M According to the set of values of θ1 to θ M controls the rotation angles of the end-stage end attitude-holding swing arm mechanisms at all levels, so that the midpoint of the axis of the driven shaft 7 of the end-stage end attitude-holding swing arm mechanism reaches the predetermined working position.

[0117] During operation, when the external power device drives the rotation of the driving shaft 4, the lower sprocket 11 will not rotate because it is fixed. The driving shaft 4 drives the support arm plate 5 and the driven shaft 7 to rotate around the driving shaft 4, thereby driving the carrying platform 9 to rotate and move between the predetermined conversion positions.

[0118] The rotation of the driven shaft 7 around the driving shaft 4 with the support arm plate 5 is called revolution, and the rotation of the driven shaft 7 around its own axis is called rotation.

[0119] When the driven shaft 7 makes a revolution along with the supporting arm plate 5, the lower sprocket 11 remains stationary. In this way, the chain 13 starts to wind in the same direction on the lower sprocket 11. Under the cooperation of the transmission relationship between the chain 13 and the sprockets, the upper sprocket 12 is forced to rotate in the reverse direction, thereby driving the driven shaft 7 to rotate in the reverse direction. During this process, since the upper sprocket 12 and the lower sprocket 11 have the same structure and size (identical specifications), and the chain 13 is in a tensioned state, the angle by which the driving shaft 4 rotates relative to the lower sprocket 11 is the same as the angle by which the chain 13 winds on the lower sprocket 11. At the same time, the chain 13 also forces the upper sprocket 12 to rotate in the reverse direction by the same angle. The angle by which the upper sprocket 12 rotates in the reverse direction is also the angle of self-rotation of the driven shaft 7. The angle of self-rotation of the driven shaft 7 exactly cancels out the angle of rotation of the driven shaft 7 due to revolution, so that the angle of rotation of the driven shaft 7 due to revolution and the angle of rotation due to self-rotation are equal in magnitude and opposite in direction, making the driven shaft 7 not rotate relative to the base 1. That is to say, when the driving shaft 4 rotates, the spatial position of the driven shaft 7 relative to the base 1 changes, but the attitude (rotation angle) of the driven shaft 7 relative to the base 1 does not change. From the perspective of the coordinate system, if the coordinate system is established on the base 1, the position coordinates of the driven shaft 7 change, but the attitude angles of the driven shaft 7 and the carrying platform 9 thereon remain unchanged.

[0120] Adopting the control method of the present invention only requires a planar coordinate system, with a simple algorithm, very low requirements for computing power, fast table building speed, convenient and fast control process. In actual work of a multi-stage and multi-degree-of-freedom robotic arm, the specific values of θ1 to θ M are obtained through a retrieval-based calculation method, with extremely fast operating speed. An ordinary single-chip microcomputer can achieve a time delay at the microsecond level, meeting the control accuracy requirements of a multi-stage and multi-degree-of-freedom robotic arm at extremely low cost, which is conducive to the popularization and application of a multi-stage and multi-degree-of-freedom robotic arm.

[0121] Of course, in addition to using Formula 1 to calculate and build the table, the present invention also provides a time-consuming and laborious but feasible table building method, that is, manually controlling the θ values of each level of the multi-stage and multi-degree-of-freedom robotic arm to make the midpoint of the axis of the driven shaft 7 of the end-effector attitude-maintaining swing arm mechanism sweep back and forth in the working space. During this process, a set of corresponding values of θ1 to θ M are recorded for each working area 25 swept through, until a set of corresponding values of θ1 to θ M are recorded for each working area 25, and the table building work is completed.

[0122] The multi-stage and multi-degree-of-freedom robotic arm can also adopt different solutions. For example, by making the swing plane of the swing arm mechanism for maintaining the end attitude of one stage different from the swing planes of the swing arm mechanisms for maintaining the end attitudes of other stages (preferably, the swing and translation of the last stage change), the task of sending the carrier platform 9 of the swing arm mechanism for maintaining the end attitude of the last stage to a predetermined coordinate in the three-dimensional space can be achieved. Of course, doing so will make the working space unable to be solved by the plane coordinate system, and will significantly increase the difficulty of the control method.

[0123] Compared with the swing planes of the swing arm mechanisms for maintaining the end attitudes of all stages being in the same plane, as long as the swing plane of any one of the swing arm mechanisms for maintaining the end attitude is not in the same plane (such as perpendicular) as those of the other stages, the swing arm mechanism for maintaining the end attitude above this stage and the weight it bears will generate a deflection force on the carrier platform 9 of the swing arm mechanism for maintaining the end attitude of this stage, which is not perpendicular to the driving shaft 4 and the driven shaft 7, deteriorating the stress condition of the structure. The swing arm mechanism for maintaining the end attitude of this stage will also generate a deflection force on the carrier platform 9 of the swing arm mechanism for maintaining the end attitude of the lower stage that bears it, which is not perpendicular to the driving shaft 4 and the driven shaft 7.

[0124] In short, in terms of the stress of the structure, if the swing plane of a certain (some) stage of the swing arm mechanism for maintaining the end attitude is not in the same plane as those of the other swing arm mechanisms for maintaining the end attitudes (such as the swing plane of the swing arm mechanism for maintaining the end attitude of the last stage is perpendicular to the swing planes of the swing arm mechanisms for maintaining the end attitudes of other stages), it will cause the swing arm mechanism for maintaining the end attitude below it to be subjected to a deflection force that is not perpendicular to the driving shaft 4 and the driven shaft 7, requiring higher mechanical performance for the overall structure and making the structure relatively vulnerable to stress damage.

[0125] In terms of the working space, the rotating table 24 can enable the working positions that the carrier platform 9 of the swing arm mechanism for maintaining the end attitude of the last stage can reach to cover a larger space, which is a solution with a wider coverage space.

[0126] The above embodiments are only used to illustrate rather than limit the technical solutions of the present invention. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: the present invention can still be modified or equivalently replaced, and any modification or partial replacement without departing from the spirit and scope of the present invention should be covered by the scope of the claims of the present invention.

Claims

1. Control method for a multi-stage and multi-degree-of-freedom robotic arm, characterized in that: The multi-stage multi-degree-of-freedom robotic arm includes multi-stage end attitude-holding swing arm mechanisms. Each stage of the end attitude-holding swing arm mechanism includes two bearing seats. A lower bearing is provided inside the bearing seats. A driving shaft is rotatably connected between the lower bearings of the two bearing seats. The driving shaft extends out of the bearing seats and is connected with a power device. The driving shaft is fixedly connected upward with a support arm plate. The top of the support arm plate is rotatably connected with a driven shaft through an upper bearing. The driven shaft is fixedly connected with a connecting plate. The end of the connecting plate is fixedly connected with a carrying platform. The driving shaft and the driven shaft are parallel to each other. A transmission mechanism is connected between the driving shaft and the driven shaft. The transmission mechanism is a chain transmission mechanism, a synchronous belt transmission mechanism or a gear transmission mechanism. The transmission mechanism is rotatably connected with the driving shaft. The part of the transmission mechanism connected with the driving shaft is fixedly connected with the base through a connecting frame. The transmission mechanism is used to keep the attitude of the carrying platform constant during the rotation of the support arm plate. The bearing seats of the first-stage end attitude-holding swing arm mechanism are fixed on the ground or the working platform. M is a natural number greater than or equal to 1. The carrying platform of the M-stage end attitude-holding swing arm mechanism serves as the working platform of the (M + 1)-stage end attitude-holding swing arm mechanism and fixes the bearing seats of the (M + 1)-stage end attitude-holding swing arm mechanism. The carrying platform of the last-stage end attitude-holding swing arm mechanism serves as the working platform or the transfer platform. The swinging planes of each stage of the end attitude-holding swing arm mechanism are in the same plane. The driven shaft of the M-stage end attitude-holding swing arm mechanism is directly below the driving shaft of the (M + 1)-stage end attitude-holding swing arm mechanism. The power devices of each stage of the end attitude-holding swing arm mechanism are all connected to an electronic control device. The transmission mechanism is a chain transmission mechanism. The chain transmission mechanism includes a lower sprocket rotatably connected to the driving shaft, an upper sprocket fixedly installed on the driven shaft, and a chain wound between the upper sprocket and the lower sprocket. The lower sprocket is fixedly connected with the base through a connecting frame. The structures and sizes of the upper sprocket and the lower sprocket are the same. Two support arm plates are arranged in parallel at intervals. The transmission mechanism is arranged in space between the two support arm plates. The carrying platform straddles above the support arm plates. It further includes a rotating table. The rotating table serves as the working platform of the first-stage end attitude-holding swing arm mechanism. The bearing seats of the first-stage end attitude-holding swing arm mechanism are installed on the rotating table. The control method of the multi-stage multi-degree-of-freedom robotic arm includes a table building method and a table-based control method. The table building method is: Taking the midpoint of the axis of the driving shaft of the first-stage end attitude-holding swing arm mechanism as the origin, an xy coordinate system is established in the swinging plane. The multi-stage multi-degree-of-freedom robotic arm includes N stages of end attitude-holding swing arm mechanisms. N is a natural number greater than or equal to 2. The last stage is the Nth stage. The angle between the support arm plate and the x-axis of the xy coordinate system in the end attitude maintaining swing arm mechanism is defined as θ. The value range of θ for the end attitude maintaining swing arm mechanism is MIN - MAX, where both MIN and MAX are real numbers and the unit is degree; θ1 is the value of θ for the first-level end attitude maintaining swing arm mechanism; θ2 is the value of θ for the second-level end attitude maintaining swing arm mechanism; θM is the value of θ for the M-level end attitude maintaining swing arm mechanism; The first step of the table building method is to determine the working space; The first sub-step is to adjust θ of each level of the end attitude maintaining swing arm mechanism to MIN through the electric control device, and then synchronously adjust the θ values of each level of the end attitude maintaining swing arm mechanism to gradually rise from MIN to MAX synchronously. During this process, the path passed by the midpoint of the axis of the driven shaft of the last-level end attitude maintaining swing arm mechanism in the xy coordinate system is the upper contour curve of the working space; the coordinates of the left and right endpoints of the upper contour curve are (D1, D2) and (D3, D4), and D1 to D4 are all real numbers; The second sub-step is to manually determine the coordinates (0, D5) of the lowest position of the midpoint of the axis of the driven shaft of the last-level end attitude maintaining swing arm mechanism in the Y-axis direction, where D5 is a real number; The third sub-step is to use the connection line between (0, D5) and (D1, D2) as the lower left contour curve, and the connection line between (0, D5) and (D3, D4) as the lower right contour curve, and take the area enclosed by the lower left contour curve, the lower right contour curve and the upper contour curve as the working space; The second step of the table building method is to divide the area; Before leaving the factory, determine the motion accuracy of the robotic arm as L cm according to the application target of the multi-level and multi-degree-of-freedom robotic arm; divide the working space into multiple working areas according to the L value, and the distance between any two points on the contour line of each working area is less than 0.5L cm; The second step of the table building method is to assign a set of values of θ1 to θM to each working area; In the second step, according to Formula 1, establish a mapping table in which each working area corresponds one-to-one with a set of values of θ1 to θM; The first sub-step is to establish an N-level correspondence table; Taking (D1, D2) as the starting point, at this time, the θ value of each level of the end attitude maintaining swing arm mechanism is MAX. First, keep the end attitude maintaining swing arm mechanisms from the first level to the (N - 1)th level stationary. ⊿H1 is greater than or equal to 0.1 degree and less than or equal to 0.3 degrees. Taking ⊿H1 as the first step length, make the θ value of the end attitude maintaining swing arm mechanism of the Nth level gradually decrease from MAX to MIN. In each step, calculate the coordinate point of the midpoint of the driven shaft axis of the end attitude maintaining swing arm mechanism of the last level according to Formula 1, and establish the corresponding relationship between these coordinate points and the working areas in the working space. If there are more than two coordinate points corresponding to a certain working area, manually delete the redundant coordinate points, and retain one coordinate point and the corresponding set of values of θ1 to θM for each working area. For the missing working areas, leave them for the fourth sub-step to handle; The second sub-step is to build a table for the (N - 1)th level; Taking ⊿H2 as the second step length, ⊿H2 is greater than or equal to 0.1 degree and less than or equal to 0.3 degrees; make the θ value of the end attitude maintaining swing arm mechanism of the (N - 1)th level gradually decrease from MAX to MIN; For each further step of the second step length, make the θ value of the end attitude maintaining swing arm mechanism of the Nth level gradually decrease from MAX to MIN with ⊿H1 as the first step length; In the second step, in each step, calculate the coordinate point of the midpoint of the driven shaft axis of the end attitude maintaining swing arm mechanism of the last level according to Formula 1; establish the corresponding relationship between these coordinate points and the working areas in the working space. If there are more than two coordinate points corresponding to a certain working area, manually delete the redundant coordinate points, and retain one coordinate point and the corresponding set of values of θ1 to θM for each working area. For the missing working areas, leave them for the fourth sub-step to handle; The third sub-step is to build a table for the (N - 2)th level in the same way as the second sub-step, and gradually decrease level by level until the first level table is completed; during the table building process of each level, if there are more than two coordinate points corresponding to a certain working area, manually delete the redundant coordinate points, and retain one coordinate point and the corresponding set of values of θ1 to θM for each working area. For the missing working areas, leave them for the fourth sub-step to handle; The fourth sub-step is the manual filling of missing areas step; After the third sub-step, manually check the working areas without corresponding coordinate points, and call any working area without a corresponding coordinate point a pending area; For each undetermined area, find the adjacent working area with corresponding coordinate points, and look up the table to obtain a set of values of θ1 to θM that can reach the adjacent working area; taking this set of values of θ1 to θM as the center, manually fine-tune this set of values of θ1 to θM, calculate the coordinates of the midpoint of the axis of the driven shaft of the last-stage multi-degree-of-freedom robotic arm according to Formula 1, and according to the distance between the obtained coordinates and the undetermined area, continue to fine-tune the values of θ1 to θM until the coordinates calculated according to Formula 1 are within the undetermined area, and establish a mapping relationship between the last set of values of θ1 to θM and this undetermined area and store it in the table; After performing the above operations on all undetermined areas, obtain a complete mapping table of the values of θ1 to θM and the working areas; The coordinates of the midpoint of the axis of the driven shaft of the last-stage multi-degree-of-freedom robotic arm are calculated according to Formula 1, and Formula 1 is: ； In Formula 1, x is the abscissa of the xy coordinate system, and y is the ordinate of the xy coordinate system; The distance between the driving shaft and the driven shaft in the same-stage end-attitude-maintaining swing arm mechanism is called the wheelbase L, and L1 is the wheelbase of the first-stage end-attitude-maintaining swing arm mechanism; L2 is the wheelbase of the second-stage end-attitude-maintaining swing arm mechanism; LM is the wheelbase of the Mth-stage end-attitude-maintaining swing arm mechanism; The distance between the driven shaft of the Mth-stage end-attitude-maintaining swing arm mechanism and the driving shaft of the (M + 1)th-stage end-attitude-maintaining swing arm mechanism is called the stage spacing h; h1 is the distance between the driven shaft of the first-stage end-attitude-maintaining swing arm mechanism and the driving shaft of the second-stage end-attitude-maintaining swing arm mechanism; hN−1 is the distance between the driven shaft of the (N - 1)th-stage end-attitude-maintaining swing arm mechanism and the driving shaft of the Nth-stage end-attitude-maintaining swing arm mechanism; The table control method is: when the multi-stage multi-degree-of-freedom robotic arm works, obtain a corresponding working area through the coordinates in the xy coordinate system of the predetermined working position; The electronic control device retrieves the mapping table of the values of θ1 to θM and the working areas, obtains a set of values of θ1 to θM, and controls the rotation angles of the end-attitude-maintaining swing arm mechanisms at all levels according to this set of values of θ1 to θM, so that the midpoint of the axis of the driven shaft of the last-stage end-attitude-maintaining swing arm mechanism reaches the predetermined working position.

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