Omnidirectional encoder for robot ball joint and joint attitude calculation method

Abstract

The invention relates to an omni-directional encoder for a robot ball joint and a joint attitude calculation method.The omni-directional encoder comprises a tool body and three encoding assemblies, the tool body is provided with a spherical groove, three openings are formed in the outer wall of the tool body, and each encoding assembly comprises a rolling shaft, magnetic steel and an encoder body; the three rolling shafts are rotatably connected with the tool body, every two of the three rolling shafts are perpendicular to each other, one ends of the three rolling shafts penetrate through the three openings respectively and abut against the spherical joint, the other ends of the three rolling shafts are fixedly connected with the three pieces of magnetic steel respectively, and the three encoder bodies are all fixed to the tool body and right face the corresponding magnetic steel; the spherical joint rotates, the friction force between the spherical joint and the rolling shafts drives the rolling shafts to rotate, the rolling shafts drive the magnetic steel to rotate, the encoder bodies recognize the rotating angles of the magnetic steel, and due to the fact that the three rolling shafts are arranged in a pairwise perpendicular mode, the three encoder bodies can measure the rotating angles of the spherical joint in the three-axis direction, and therefore the omni-directional rotating posture of the spherical joint can be solved.

Description

Technical Field

[0001] The present invention relates to the field of robot technology, and in particular to an omnidirectional encoder for a robot ball joint and a joint posture calculation method. Background Art

[0002] In order to achieve precise control of the robot, encoders are needed to provide accurate angle and angular velocity information for the joints to achieve precise control of the joints.

[0003] The encoder has the following specific functions in the robot: 1. Accurate position control: In the joints of the robot, the encoder is used to measure the angular position of each joint. This information is fed back to the control system to ensure that each joint can move accurately to the target position. 2. Speed ​​control: The encoder can measure the speed of the motor and help the control system adjust the speed of the motor to ensure that the robot runs at the predetermined speed.

[0004] Currently, encoders include magnetic encoders, capacitive encoders, optical encoders and other types, but they are all one-dimensional encoders, which can only measure the movement between joints around one rotation axis.

[0005] However, robot joints have many degrees of freedom. For example, joints such as the hip joint need to rotate in any direction in space, and existing one-dimensional encoders are difficult to measure the full range of rotational motion between joints. Summary of the invention

[0006] In view of this, it is necessary to provide an omnidirectional encoder for robot ball joints and a joint posture calculation method to solve the problem that existing one-dimensional encoders are difficult to measure the omnidirectional rotational motion between joints.

[0007] On the one hand, the present invention provides an omnidirectional encoder for a robot ball joint and a joint posture calculation method, which includes a tooling body and three encoding components, the tooling body has a spherical groove for wrapping the spherical joint and rotatably connected to the spherical joint, three openings connected to the spherical groove are opened on the outer wall of the tooling body, and the three encoding components each include a roller, a magnet and an encoder body, the roller is rotatably connected to the tooling body, the three rollers are vertically arranged in pairs, one end of the three rollers passes through the three openings respectively and abuts against the spherical joint, the other ends of the three rollers are fixedly connected to the three magnets respectively, the three encoder bodies correspond to the three magnets one by one, and the three encoder bodies are all fixed on the tooling body and arranged facing the corresponding magnets.

[0008] Furthermore, the tool body includes two annular connecting plates, which are detachably connected to each other, and grooves are formed on the two annular connecting plates, and the two grooves are connected to form the spherical groove.

[0009] Furthermore, the roller includes a coaxially arranged shaft body and a wheel body, the diameter of the shaft body is smaller than the diameter of the wheel body, the two ends of the shaft body are respectively fixedly connected to the wheel body and the magnetic steel, and the wheel body passes through the opening and abuts against the spherical joint in the spherical groove.

[0010] Furthermore, the three wheel bodies are evenly arranged along the circumference of the spherical groove and are located in the same cross section of the spherical groove.

[0011] Furthermore, the encoding assembly also includes a first fixing frame installed on the side wall of the tooling body, and the roller passes through the first fixing frame and is rotatably connected thereto.

[0012] Furthermore, the encoding assembly also includes a second fixed bracket installed on the side wall of the tooling body, the encoder body and the magnetic steel are respectively arranged on both sides of the second fixed bracket, the encoder body is fixedly connected to the second fixed bracket, and the measuring end of the encoder body is arranged opposite to the through hole opened on the second fixed bracket.

[0013] On the other hand, the present invention provides a joint posture calculation method, which is applied to the omnidirectional encoder for the robot ball joint as described above, comprising the following steps: Obtaining the rotation angle of the magnetic steel recognized by the encoder body; According to the rotation angles of the three magnets identified by the three encoder bodies, the three-axis rotation angles of the spherical joint are analyzed; The omnidirectional rotation posture of the spherical joint is calculated according to the three-axis movement angle of the spherical joint.

[0014] Further, the calculating the omnidirectional rotation posture of the spherical joint according to the three-axis movement angle of the spherical joint includes: Get the radius ratio of the roller and the spherical joint; Obtaining information of the encoder body, wherein the information of the encoder body includes an angle value read by the encoder body at zero position and an angle value read by the encoder body at the current position; The absolute angle of the connection point of the spherical joint is calculated based on the radius ratio of the spherical joint and the roller and the information of the encoder body; According to the absolute angle of the connection point of the spherical joint and the initial position coordinates of the connection point of the spherical joint, the current position coordinates of the connection point of the spherical joint are calculated.

[0015] Further, the calculating the omnidirectional rotation posture of the spherical joint according to the three-axis movement angle of the spherical joint includes: Get the angular velocity of the spherical joint along the rotation direction of the three rolling axes; Calculate the rotation matrix of the connection point of the spherical joint according to the angular velocity; The coordinates of the connection point of the spherical joint at the next moment are calculated according to the rotation matrix of the connection point of the spherical joint, the coordinates of the connection point of the spherical joint at the previous moment, and the rotation time of the spherical joint.

[0016] Furthermore, the angular velocities of the spherical joints measured by the three encoders are , , ,set up , , the angle of rotation around the equivalent rotation axis is , is the angular velocity of the equivalent rotation axis, is the spherical joint rotation time, and the rotation matrix is: .

[0017] Compared with the prior art, when the spherical joint rotates, the friction between it and the roller drives the roller to rotate, the roller drives the magnet to rotate, and the encoder body identifies the rotation angle of the magnet. Since the three rollers are arranged vertically in pairs, the three encoder bodies can measure the rotation angle of the spherical joint along the three-axis direction, thereby solving the omnidirectional rotation posture of the spherical joint. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 A schematic structural diagram of one viewing angle of an omnidirectional encoder for a robot ball joint provided by an embodiment of the present invention; Figure 2 A schematic diagram of the structure of an omnidirectional encoder for a robot ball joint provided by an embodiment of the present invention from another perspective; Figure 3 A schematic diagram of the structure of an encoding component in an omnidirectional encoder for a robot ball joint provided by an embodiment of the present invention; Figure 4 A schematic diagram of a joint posture calculation method provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0019] The preferred embodiments of the present invention are described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not used to limit the scope of the present invention.

[0020] like Figure 1-3As shown, on the one hand, an embodiment of the present invention provides an omnidirectional encoder for a robot ball joint and a joint posture calculation method, which includes a tooling body 100 and three encoding components. The tooling body 100 has a spherical groove 110 for wrapping a spherical joint M and rotatably connected to the spherical joint M. Three openings 120 connected to the spherical groove 110 are opened on the outer wall of the tooling body 100. The three encoding components each include a roller 210, a magnetic steel 220 and an encoder body 230. The roller 210 is rotatably connected to the tooling body 100. The three rollers 210 are vertically arranged in pairs. One ends of the three rollers 210 respectively pass through the three openings 120 and abut against the spherical joint M. The other ends of the three rollers 210 are respectively fixedly connected to the three magnetic steels 220. The three encoder bodies 230 correspond to the three magnetic steels 220 one by one. The three encoder bodies 230 are all fixed on the tooling body 100 and arranged facing the corresponding magnetic steels 220.

[0021] During implementation, when the spherical joint M rotates, the friction between it and the roller 210 drives the roller 210 to rotate, and the roller 210 drives the magnet 220 to rotate. The encoder body 230 identifies the rotation angle of the magnet 220. Since the three rollers 210 are arranged vertically in pairs, the three encoder bodies 230 can measure the rotation angle of the spherical joint M along the three-axis directions, thereby solving the omnidirectional rotation posture of the spherical joint M.

[0022] The tool body 100 in this embodiment is installed on a robot, and the spherical joint M rotates relative to the tool body 100 .

[0023] In one embodiment, the tool body 100 includes two annular connecting plates, which are detachably connected to each other. Grooves are formed on both annular connecting plates, and the two grooves are connected to form a spherical groove 110 .

[0024] In the present embodiment, three encoding components are provided, including a first encoding module 200, a second encoding module 300 and a third encoding module 400 respectively. The first encoding module 200, the second encoding module 300 and the third encoding module 400 have the same structure. The three encoding components each include a roller 210, a magnet 220 and an encoder body 230. The roller 210 is rotatably connected to the tooling body 100. The three rollers 210 are vertically arranged in pairs. One ends of the three rollers 210 pass through the three openings 120 respectively and abut against the spherical joint M. The other ends of the three rollers 210 are fixedly connected to the three magnets 220 respectively. The three encoder bodies 230 correspond to the three magnets 220 one by one. The three encoder bodies 230 are all fixed on the tooling body 100 and arranged facing the corresponding magnets 220.

[0025] like Figure 1-2As shown in , the roller 210 of the first encoding module 200 and the roller 210 of the second encoding module 300 are located in the same cross-section of the spherical joint M, and the two are perpendicular to each other. The roller of the third encoding module 400 is arranged perpendicular to the cross-section. Correspondingly, the encoder body 230 in the first encoding module 200 is used to measure the rotation angle of the spherical joint M around the X-axis direction, the encoder body 230 in the second encoding module 300 is used to measure the rotation angle of the spherical joint M around the Y-axis direction, and the encoder body 230 in the third encoding module 400 is used to measure the rotation angle of the spherical joint M around the Z-axis direction.

[0026] In one embodiment, the roller 210 includes a coaxially arranged shaft body and a wheel body, the diameter of the shaft body is smaller than the diameter of the wheel body, the two ends of the shaft body are fixedly connected to the wheel body and the magnet 220 respectively, and the wheel body passes through the opening 120 and abuts against the spherical joint M in the spherical groove 110.

[0027] In one embodiment, the three wheel bodies are evenly arranged along the circumference of the spherical groove 110 and are located in the same cross section of the spherical groove 110 .

[0028] In one embodiment, the encoding assembly further includes a first fixing frame 211 mounted on a side wall of the tooling body 100 , and the roller 210 passes through the first fixing frame 211 and is rotatably connected thereto.

[0029] In one embodiment, the encoding component also includes a second fixed bracket installed on the side wall of the tooling body 100, the encoder body 230 and the magnet 220 are respectively arranged on both sides of the second fixed bracket, the encoder body 230 is fixedly connected to the second fixed bracket, and the measuring end of the encoder body 230 is arranged facing the through hole opened on the second fixed bracket.

[0030] The coding component further includes a spring 212 connecting the first fixing frame 211 and the second fixing frame 231. The first fixing frame 211 is cylindrical, and the second fixing frame 231 is "7" shaped. The spring 212 can improve the connection strength between the first fixing frame 211 and the second fixing frame 231.

[0031] The encoder body 230 in this embodiment is a low-cost, high-precision 14-bit absolute magnetic encoder.

[0032] It should be noted that the radius of the roller 210 is much smaller than the radius of the spherical joint M. On the one hand, the installation space can be reduced, and on the other hand, the angle change of the spherical joint M will be magnified by the roller 210. Specifically, when the spherical joint M rotates one circle, the roller 210 will rotate R / r circles.

[0033] like Figure 4As shown, on the other hand, an embodiment of the present invention provides a joint posture calculation method, which is applied to the omnidirectional encoder for the robot ball joint as described above, and includes the following steps: Step S100, obtaining the rotation angle of the magnetic steel recognized by the encoder body; Step S200, analyzing the three-axis rotation angle of the spherical joint according to the rotation angles of the three magnetic steels identified by the three encoder bodies; Step S300: Calculate the omnidirectional rotation posture of the spherical joint according to the three-axis movement angle of the spherical joint.

[0034] In step S300, calculating the omnidirectional rotation posture of the spherical joint M according to the three-axis movement angle of the spherical joint includes: Step S310, obtaining the radius ratio of the roller and the spherical joint; Step S320, obtaining information of the encoder body, wherein the information of the encoder body includes an angle value read by the encoder body at zero position and an angle value read by the encoder body at the current position; Step S330, calculating the absolute angle of the connection point of the spherical joint according to the radius ratio of the spherical joint and the roller and the information of the encoder body; Step S340: Calculate the current position coordinates of the connection point of the spherical joint according to the absolute angle of the connection point of the spherical joint and the initial position coordinates of the connection point of the spherical joint.

[0035] Specifically: the encoder body 230 is a single-turn encoder. When the zero position is set, the zero position is saved in the EEPROM of the microcontroller. Then the current angle of the ball joint is: ; in, is the absolute angle of the spherical joint M (i.e. the angle at the current position), is the angle value read by the encoder body 230, The angle value read by the encoder body 230 at the zero position (i.e. the initial position) is is the number of times the encoder body 230 passes through 360° in the positive direction (from 360° to 0°, n+1; from 0° to 360°, n-1), r is the radius of the roller 210, R is the radius of the spherical joint M, is the power-off memory, Also stored in EEPROM.

[0036] In order to obtain the position of the end of the connecting rod connected to the joint, the above formula can be used to obtain the angles of rotation of the ball joint around the X, Y, and Z axes respectively.

[0037] Assuming that the coordinates of the end of the connecting rod of the ball joint are (1,0,0), the three angles obtained above are the angles of rotation around the fixed axes (i.e., the X-axis, Y-axis, and Z-axis). If the joint rotation sequence is specified as XYZ, the coordinates of the end of the connecting rod are: ; in, , , are the rotation angles around the XYZ axes respectively.

[0038] In addition to the above calculation method, if the encoder body 230 rotates at a uniform speed, the following method can also be used for calculation.

[0039] When the encoder body 230 rotates at a uniform speed, the omnidirectional rotation posture of the spherical joint M is calculated according to the three-axis movement angle of the spherical joint, including: The method of calculating the omnidirectional rotation posture of the spherical joint according to the three-axis movement angle of the spherical joint includes: Get the angular velocity of the spherical joint along the rotation direction of the three rolling axes; Calculate the rotation matrix of the connection point of the spherical joint according to the angular velocity; The coordinates of the connection point of the spherical joint at the next moment are calculated according to the rotation matrix of the connection point of the spherical joint, the coordinates of the connection point of the spherical joint at the previous moment, and the rotation time of the spherical joint.

[0040] Among them, the angular velocities of the spherical joint M measured by the three encoders are , , ,set up , , the angle of rotation around the equivalent rotation axis is , is the angular velocity of the equivalent rotation axis, is the rotation time of the spherical joint M, and the rotation matrix is: .

[0041] The coordinates of each moment are: ; in, is the coordinate of the previous moment, is the current coordinate, and a rotation transformation is performed at each step to obtain the current coordinate of the joint end at all times.

[0042] It can be understood that the connection point of the above-mentioned spherical joint refers to the position where the spherical joint is connected to the connecting rod.

[0043] Compared with existing technologies: 1) The orthogonal distribution of encoders enables omnidirectional rotation measurement. The encoders are placed on the outer surface of the spherical joint M, making use of the internal space of the joint for line layout; 2) Low-cost, high-precision encoder, based on the transmission principle, further improves accuracy through the small radius roller 210 structure, and provides a multi-turn measurement method for single-turn encoders; 3) Based on the omnidirectional encoder, a method for calculating joint posture using the angles obtained by the three-axis encoder is provided.

[0044] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. An omnidirectional encoder for a robot ball joint, characterized in that: include: A tool body, which has a spherical groove for wrapping the spherical joint and rotatably connected to the spherical joint, and three openings connected to the spherical groove are opened on the outer wall of the tool body; The three encoding components each include a roller, a magnet and an encoder body. The roller is rotatably connected to the tooling body. The three rollers are vertically arranged in pairs. One end of the three rollers passes through the three openings respectively and abuts against the spherical joints. The other ends of the three rollers are fixedly connected to the three magnets respectively. The three encoder bodies correspond to the three magnets one by one. The three encoder bodies are all fixed on the tooling body and arranged facing the corresponding magnets.

2. The omnidirectional encoder for a robot ball joint according to claim 1, characterized in that: The tool body comprises two annular connecting plates, which are detachably connected to each other, and grooves are formed on the two annular connecting plates, and the two grooves are connected to form the spherical groove.

3. The omnidirectional encoder for a robot ball joint according to claim 1, characterized in that: The roller includes a coaxially arranged shaft body and a wheel body, the diameter of the shaft body is smaller than the diameter of the wheel body, two ends of the shaft body are fixedly connected to the wheel body and the magnetic steel respectively, and the wheel body passes through the opening and abuts against the spherical joint in the spherical groove.

4. The omnidirectional encoder for a robot ball joint according to claim 3, characterized in that: The three wheel bodies are evenly arranged along the circumference of the spherical groove and are located in the same cross section of the spherical groove.

5. The omnidirectional encoder for a robot ball joint according to claim 1, characterized in that: The encoding assembly also includes a first fixing frame installed on the side wall of the tooling body, and the roller passes through the first fixing frame and is rotatably connected thereto.

6. The omnidirectional encoder for a robot ball joint according to claim 5, characterized in that: The encoding assembly also includes a second fixed bracket installed on the side wall of the tooling body, the encoder body and the magnetic steel are respectively arranged on both sides of the second fixed bracket, the encoder body is fixedly connected to the second fixed bracket, and the measuring end of the encoder body is arranged opposite to the through hole opened on the second fixed bracket.

7. A method for calculating joint posture, characterized in that: The omnidirectional encoder for a robot ball joint as claimed in any one of claims 1 to 6 comprises the following steps: Obtaining the rotation angle of the magnetic steel recognized by the encoder body; According to the rotation angles of the three magnets identified by the three encoder bodies, the three-axis rotation angles of the spherical joint are analyzed; The omnidirectional rotation posture of the spherical joint is calculated according to the three-axis movement angle of the spherical joint.

8. The joint posture calculation method according to claim 7, characterized in that: The method of calculating the omnidirectional rotation posture of the spherical joint according to the three-axis movement angle of the spherical joint includes: Get the radius ratio of the roller and the spherical joint; Obtaining information of the encoder body, wherein the information of the encoder body includes an angle value read by the encoder body at zero position and an angle value read by the encoder body at the current position; According to the radius ratio of the spherical joint and the roller and the information of the encoder body, the absolute angle of the connection point of the spherical joint is calculated; According to the absolute angle of the connection point of the spherical joint and the initial position coordinates of the connection point of the spherical joint, the current position coordinates of the connection point of the spherical joint are calculated.

9. The joint posture calculation method according to claim 7, characterized in that: The method of calculating the omnidirectional rotation posture of the spherical joint according to the three-axis movement angle of the spherical joint includes: Get the angular velocity of the spherical joint along the rotation direction of the three rolling axes; Calculate the rotation matrix of the connection point of the spherical joint according to the angular velocity; The coordinates of the connection point of the spherical joint at the next moment are calculated according to the rotation matrix of the connection point of the spherical joint, the coordinates of the connection point of the spherical joint at the previous moment, and the rotation time of the spherical joint.

10. The omnidirectional encoder for robot ball joint and the joint posture calculation method according to claim 9, characterized in that: The angular velocities of the spherical joints measured by the three encoders are , , ,set up , , the angle of rotation around the equivalent rotation axis is , is the angular velocity of the equivalent rotation axis, is the spherical joint rotation time, and the rotation matrix is: 。

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