A robot joint with an output encoder and its control method

Abstract

This invention discloses a robot joint with an output encoder and a control method. The invention integrates a synchronous motor, a planetary gearbox, and an output encoder housed in a casing to form a robot joint. Simultaneously, the motor-end encoder magnet is fixed to the outer rotor cage, allowing the motor controller to measure the angular displacement of the outer rotor cage. The output encoder magnet is fixed to the encoder output gear, allowing the output encoder circuit board to measure the angular displacement of the output flange. When the synchronous motor starts, the relative position of the output flange relative to its zero position is obtained. Even after a power outage and restart, the relative position of the output flange is not lost, thus achieving zero-position maintenance even after power failure. Therefore, there is no need to continuously supply power to the motor controller of the onboard encoder, nor is it necessary to manually return the motor to its zero position after each power outage and restart, greatly reducing the module size and simplifying operation.

Description

Technical Field

[0001] This invention belongs to the field of robot joint design and control, specifically relating to a robot joint with an output encoder and a control method thereof. Background Technology

[0002] With the development of robotics technology in recent years, robots have been widely used in various fields and are gradually becoming smaller and more civilian-oriented. Motors with gearboxes, as actuators that enable robots to perform various functions, are a crucial component of robots and a significant research direction in the field today. For small civilian robots, a semi-direct drive joint design scheme integrating a low-speed, high-torque permanent magnet synchronous motor with a small reduction ratio planetary gearbox has been adopted in various legged robots and some robotic arms due to its numerous advantages, including low cost, light weight, ease of miniaturization, and relatively high output torque.

[0003] Considering the accuracy of angular displacement encoding, for motors with gearboxes, the motor controller typically uses an encoder to measure the angular displacement of the outer rotor cage. This approach offers higher measurement accuracy compared to measuring the angular displacement of the output flange using an encoder; however, it has the drawback of not being able to save the zero point of the output flange. The zero position of the robot joint output axis is crucial for motor control; if the zero position cannot be permanently recorded, the motor may rotate into a dangerous range, potentially causing an accident. To address this issue, traditional solutions include providing an external power supply to the motor controller or manually resetting the motor to near the zero position before each power outage and restart. However, both solutions have significant drawbacks: external power supply increases the size and weight of the robot joint structure, making installation on the robot more difficult; manual resetting complicates the operation before each power outage and restart, severely impacting the efficiency of robot debugging. Summary of the Invention

[0004] The purpose of this invention is to provide a robot joint with an output encoder. By integrating a synchronous motor, a planetary gearbox, and an output encoder housed in a housing to form a robot joint, the overall structure is compact. Simultaneously, the encoder magnet at the motor end is fixed to the outer rotor cage, and the angular displacement of the outer rotor cage can be measured by the motor controller. The output encoder is connected to the planetary gearbox, and the encoder magnet in the output encoder is fixed to the encoder output gear. The angular displacement of the output flange is measured by the output encoder circuit board, thereby achieving zero-position maintenance even when power is off. No external power supply or manual reset is required, resulting in low production costs.

[0005] To achieve the above-mentioned objectives, the technical solution adopted by the present invention is as follows:

[0006] A robot joint with an output encoder, comprising:

[0007] A synchronous motor, comprising a housing, a rotor assembly, a stator, and a motor controller, wherein the stator is fixedly connected to the inner cavity of the housing, the rotor assembly is rotatably connected to the inner cavity of the housing, and the motor controller is fixedly connected to the housing, and the rotor assembly includes a motor-end encoder magnet for providing position feedback of the rotor assembly to the motor controller;

[0008] A planetary gearbox includes an output mechanism and a reduction mechanism. The reduction mechanism includes a fixed component that maintains a fixed relative position with the housing and a rotating component connected to the rotor assembly. The output mechanism is connected to the rotating component, and the rotor assembly drives the rotating component and the output mechanism to rotate.

[0009] An output encoder includes an output encoder circuit board, an output encoder magnet, an encoder output gear, and an encoder input gear. The encoder input gear is connected to the output mechanism, and the output mechanism drives the encoder input gear to rotate. The encoder input gear drives the encoder output gear to rotate. The output encoder magnet is mounted on the encoder output gear, and the output encoder circuit board receives position feedback from the output mechanism provided by the output encoder magnet.

[0010] Preferably, the synchronous motor is an external rotor synchronous motor, and the rotor assembly further includes an external rotor cage and an external rotor steel ring. The external rotor steel ring is fixedly connected to the external rotor cage. The motor end encoder magnet is installed on the end of the external rotor cage facing the motor controller, so that the motor controller can sense the motor end encoder magnet and receive the position feedback of the external rotor cage provided by the motor end encoder magnet. The external rotor cage is rotatably connected to the housing through a rotor bearing.

[0011] Preferably, one end of the housing extends into the inner cavity and is provided with a fixing part. The inner ring of the fixing part is fixed with a rotor bearing. The end of the outer rotor cage facing the motor controller is fixed in the inner ring of the rotor bearing, so that the outer rotor cage can be rotatably connected to the housing. The stator is fixed on the outer ring of the fixing part, so that the stator and the housing maintain a constant relative position and ensure that the stator is stably installed on the housing. The end of the outer rotor cage facing the motor controller is provided with a mounting part. The mounting part is provided with a cavity. The encoder magnet of the motor end is placed in the cavity. At the same time, one end of the rotating component in the reduction mechanism is also inserted into the cavity, so that when the outer rotor cage rotates, it drives the rotating component to rotate.

[0012] Preferably, the motor controller is fixed to the end of the housing away from the output encoder, and the motor controller is fixed to one end of the housing by circuit board screws. Since the motor-end encoder magnet is fixed to the outer rotor cage, the angular displacement of the outer rotor cage can be measured by the motor controller. The output encoder magnet is fixed to the encoder output gear, and the angular displacement of the output flange can be measured by the output encoder circuit board.

[0013] Preferably, the synchronous motor further includes a rear cover, which is installed at one end of the housing by rear cover screws, and places the motor controller inside the rear cover, thereby ensuring that the motor controller is enclosed in the inner cavity of the housing, thus protecting the motor controller.

[0014] Preferably, the output mechanism includes an end cover, an output flange, and an output planetary carrier arranged in sequence. The end cover is fixedly connected to the end of the housing away from the motor controller. The output flange is rotatably connected to the end cover. The output planetary carrier is fixedly connected to the output flange, so that the output planetary carrier and the output flange rotate together relative to the end cover.

[0015] Preferably, an end cover bearing is installed on the end cover, and the end cover bearing is located in the middle of the end cover. The outer ring of the output flange is fitted in the end cover bearing so that the output flange and the end cover are rotatably connected. The output planetary carrier is installed on the output flange by screws, and the outer ring of the output planetary carrier can also be fitted and fixed in the inner ring of the end cover bearing. This can ensure the stability of the output planetary carrier during rotation.

[0016] Preferably, the output encoder circuit board is mounted on the end cover with screws.

[0017] Preferably, the fixing component of the reduction mechanism includes a fixed ring gear, which is fixedly connected to the end cover. An end cover bearing washer is also provided between the end face of the fixed ring gear and the end cover, pressing the end cover bearing with the end cover bearing. The rotating component of the reduction mechanism includes a planetary gear set, which is installed in the inner cavity of the fixed ring gear. The planetary gear set is connected to the output planetary carrier and the outer rotor cage respectively, so that when the outer rotor cage rotates, it drives the planetary gear set and the output planetary carrier to rotate. The planetary gear set is used to control the speed ratio of the outer rotor cage and the output planetary carrier, thereby controlling the reduction ratio of the entire planetary gearbox.

[0018] Preferably, the planetary gear set includes a central gear and a plurality of planetary gears located on the outer periphery of the central gear. The central gear is disposed at the center of the inner cavity of the fixed ring gear. The inner ring of the fixed ring gear is provided with an internal gear ring. The planetary gears are placed between the internal gear ring and the central gear. The planetary gears mesh with both the outer ring of the central gear and the internal gear ring. The central gear is connected to the outer rotor cage so that the outer rotor cage drives the central gear to rotate.

[0019] Preferably, the output planetary carrier is provided with a plurality of gear mounting slots, and the planetary gears are placed in the gear mounting slots so that when the central gear drives the planetary gears to rotate, the planetary gears drive the output planetary carrier to rotate.

[0020] Preferably, a gear mounting post is provided in the gear mounting slot, and the planetary gear is rotatably mounted on the gear mounting post through a bearing. Each gear mounting slot corresponds to one planetary gear. By adjusting the number of planetary gears and / or the diameter ratio of the planetary gears to the central gear, the transmission ratio of the central gear and the planetary gears is changed, thereby adjusting the speed ratio of the output planetary carrier, the output flange and the outer rotor cage, and thus changing the reduction ratio of the entire planetary gearbox.

[0021] Preferably, a multi-stage planetary gear set is provided, each stage of which includes a central gear and planetary gears. Adjacent planetary gear sets are connected by a supporting planetary carrier. Each stage of the planetary gear set corresponds to a supporting planetary carrier, which is also provided with several gear mounting slots for mounting planetary gears. The central gear in the planetary gear set near the outer rotor cage mounting part is inserted into the cavity of the mounting part. The supporting planetary carriers of the planetary gear sets near the output planetary carrier are arranged opposite to each other, and the gear mounting slots on them are also correspondingly arranged. The supporting planetary carrier near the output planetary carrier has a semi-open structure. The gear mounting slots on the output planetary carrier and the corresponding gear mounting slots on the supporting planetary carrier together form a mounting area for mounting planetary gears, so that the planetary gears near the output planetary carrier can be mounted in this mounting area through the mounting shaft, ensuring that the planetary gears drive the supporting planetary carriers and the output planetary carriers to rotate simultaneously when they rotate. The connection between any two adjacent planetary gear sets is as follows: the central gear of one planetary gear set is connected to the mounting cavity on the supporting planetary carrier of the other planetary gear set. This allows one planetary gear set to drive the supporting planetary carrier to rotate, which in turn drives the central gear of the other planetary gear set to rotate. This central gear then drives its corresponding planetary gears and the supporting planetary carrier to rotate, ultimately transmitting the rotation of the outer rotor cage to the output planetary carrier and output flange via a multi-stage planetary gear set. This configuration allows for power transmission with multiple stages of planetary gear sets when the synchronous motor's height is too large, preventing the problem of excessively large central and planetary gears and limited service life caused by using only one planetary gear set.

[0022] More preferably, a two-stage planetary gear set is provided, comprising a lower-stage planetary gear set and an upper-stage planetary gear set. The lower-stage planetary gear set is mounted on the lower support planetary carrier, and the upper-stage planetary gear set is mounted on the upper support planetary carrier. The lower-stage planetary gear set is located near the mounting portion of the outer rotor cage, and the upper-stage planetary gear set is located near the output planetary carrier. The center gear in the lower-stage planetary gear set is inserted into the cavity of the mounting portion of the outer rotor cage. The upper support planetary carrier and the output planetary carrier are arranged opposite to each other, and their gear mounting slots are also correspondingly provided. The upper support planetary carrier has a semi-open structure, and the gear mounting slots on the output planetary carrier and the gear mounting slots on the upper support planetary carrier together form a mounting area for mounting the planetary gears of the upper-stage planetary gear set. The outer rotor cage is connected to the mounting cavity on the lower support planetary carrier via the central gear in the upper planetary gear set. This allows the outer rotor cage to rotate when it drives the central gear in the lower planetary gear set to rotate. The central gear then drives the meshing planetary gears to rotate, which in turn drives the lower support planetary carrier to rotate. The rotation of the lower support planetary carrier, in turn, drives the central gear in the upper planetary gear set to rotate. This, in turn, drives the corresponding planetary gears, the lower support planetary carrier, and the output planetary carrier to rotate. Ultimately, the rotation of the outer rotor cage is transmitted to the output planetary carrier and the output flange through the lower and upper planetary gear sets.

[0023] Preferably, the output encoder further includes an encoder output gear bearing and an encoder output gear retainer. The encoder output gear retainer is provided with a bearing cavity for mounting the encoder output gear bearing. The encoder output gear is provided with a connecting shaft that is assembled with the encoder output gear bearing, so that the encoder output gear is rotatably mounted on the encoder output gear retainer. The encoder output gear retainer is fixed to the end cover. Preferably, the encoder output gear retainer is fixed to the inner side of the end cover by screws.

[0024] Preferably, the output encoder further includes an encoder drive gear. The encoder input gear is mounted on the outer ring of the output planetary carrier or output flange so that the encoder input gear rotates together with the output planetary carrier or output flange. The encoder drive gear is disposed between the encoder input gear and the encoder output gear. Both sides of the encoder drive gear mesh with the encoder input gear and the encoder output gear respectively, and the power of the encoder input gear is transmitted to the encoder output gear through the encoder drive gear.

[0025] With this configuration, when the output flange or output planetary carrier rotates, the output flange, output planetary carrier, and encoder input gear rotate synchronously as a whole. The encoder input gear drives the encoder transmission gear to rotate, and the encoder transmission gear drives the encoder output gear to rotate. The output encoder circuit board can then receive one-to-one output flange position feedback provided by the output encoder magnet.

[0026] Preferably, the output encoder further includes an encoder output gear shaft retainer and an encoder wire slot. The encoder output gear shaft retainer is installed in a groove on the connecting shaft of the encoder output gear, and the encoder output gear shaft retainer can prevent the encoder output gear from axially moving. The wires of the output encoder circuit board are installed on the encoder wire slot; the encoder wire slot is fixed inside the housing to protect the wires of the output encoder circuit board. These wires can connect the output encoder circuit board and the motor controller, thereby realizing the transmission of electrical signals from the output encoder circuit board to the onboard encoder motor controller.

[0027] Preferably, the motor controller is a motor controller with an onboard encoder, which integrates a motor-end encoder for measuring the angular displacement of the outer rotor cage, and the output encoder circuit board integrates an encoder for measuring the angular displacement of the output flange.

[0028] The second objective of this invention is to provide a control method for a robot joint with an output encoder, comprising the following steps:

[0029] S1. Use the motor controller to record the electrical signal of the zero position of the outer rotor cage in the rotor assembly and the electrical signal of the zero position of the output flange in the output mechanism;

[0030] S2. When the motor controller is powered on, the motor end encoder on the motor controller converts the absolute position of the outer rotor cage into an electrical signal and sends it to the motor controller. The motor controller records the number of revolutions of the outer rotor cage based on the single-turn absolute code electrical signal output by the motor end encoder on its motor controller, and converts the single-turn absolute code electrical signal into a multi-turn absolute code.

[0031] S3. Determine if the motor controller has been powered off and restarted. If yes, the motor-end encoder on the motor controller converts the position of the outer rotor cage into an electrical signal, and the output-end encoder converts the position of the output flange into an electrical signal. Both signals are sent to the motor controller so that the motor controller can obtain the current readings of the motor-end encoder and the output-end encoder. If no, continue to step S2.

[0032] S4. The motor controller calculates the number of revolutions the outer rotor cage has made based on the reduction ratio of the planetary gearbox and the readings of the encoders at both the motor and output ends. This calculation then determines the absolute position of the output flange relative to its zero point. This step allows the calculation and acquisition of the actual position of the planetary gearbox output shaft, i.e., the actual position of the output flange.

[0033] Beneficial effects:

[0034] This invention integrates a synchronous motor, a planetary gearbox, and an output encoder housed in a housing to form a robot joint, achieving a compact overall structure. The synchronous motor, in conjunction with the planetary gearbox, transmits power to the output flange and achieves a deceleration effect. Simultaneously, the output encoder can acquire the position of the output flange in real time and convert it into an electrical signal, which is then sent to the motor controller. The motor controller calculates the number of revolutions of the outer rotor cage based on the reduction ratio of the planetary gearbox and the readings of the output encoder and the encoder on the motor controller, thereby calculating the absolute position of the output flange relative to its zero point.

[0035] In this invention, the encoder magnet at the motor end of the robot joint is fixedly connected to the outer rotor cage. The angular displacement of the outer rotor cage can be measured by the motor controller. The output encoder is connected to the planetary gearbox, and the encoder magnet at the output end is fixedly connected to the encoder output gear. The angular displacement of the output flange is measured by the encoder circuit board. Therefore, the robot joint of this invention can obtain the relative position of the output flange with respect to its zero position when the synchronous motor starts. Even after a power outage and restart, the relative position of the output flange will not be lost, thus achieving zero position retention after power outage. Therefore, there is no need to continuously supply power to the motor controller of the onboard encoder, nor is it necessary to manually place the motor back to the zero position after each power outage and restart, which greatly reduces the module size and reduces the difficulty of operation. Attached Figure Description

[0036] Figure 1 The diagram shown is an overall structural diagram of the robot joint of this invention;

[0037] Figure 2 The figure shown is an exploded view of the structure of the robot joint of the present invention;

[0038] Figure 3 The figure shown is a cross-sectional view of the robot joint of the present invention;

[0039] Figure 4 The diagram shown is an internal structural diagram of the robot joint of this invention;

[0040] Figure 5 The diagram shown is a structural diagram of the planetary gearbox and synchronous motor assembly in the robot joint of this invention.

[0041] Figure 6 The diagram shown is a structural diagram of the planetary gearbox in the robot joint of this invention;

[0042] Figure 7 The diagram shown is an internal structural diagram of the planetary gearbox in the robot joint of this invention.

[0043] Figure 8 The diagram shown is a partial schematic of the deceleration mechanism of the planetary gearbox in the robot joint of the present invention.

[0044] Figure 9 The diagram shown is a control flowchart of the robot joint with an output encoder according to the present invention.

[0045] Figure Labels

[0046] 1. Synchronous motor; 101. Outer rotor cage; 1011. Mounting part; 102. Outer rotor steel ring; 103. Stator; 104. Motor end encoder magnet; 105. Rotor bearing; 106. Housing screws; 107. Housing; 108. Circuit board screws; 109. Motor controller; 110. Rear cover screws; 111. Rear cover;

[0047] 2. Planetary gearbox; 201. Output flange; 202. End cover; 203. Output planetary carrier; 204. End cover bearing; 205. End cover bearing washer; 206. Reduction mechanism; 2061. Fixed ring gear; 2062. Center gear; 2063. Planetary gear; 2064. Lower support planetary carrier; 2065. Upper support planetary carrier;

[0048] 3. Output encoder; 301. Output encoder circuit board; 302. Output encoder magnet; 303. Encoder output gear; 304. Encoder output gear bearing; 305. Encoder output gear shaft snap ring; 306. Encoder output gear cage; 307. Encoder drive gear; 308. Encoder input gear; 309. Encoder wire groove; Detailed Implementation

[0049] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the specific implementation methods of the present invention will be described below with reference to the accompanying drawings. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings and other implementation methods can be obtained based on these drawings without any creative effort.

[0050] The technical solution of the present invention will be described in detail below with specific embodiments.

[0051] Example 1

[0052] like Figure 1-3 As shown, a robot joint with an output encoder 3 includes: a synchronous motor 1, a planetary gearbox 2, and an output encoder 3;

[0053] The synchronous motor 1 includes a housing 107, a rotor assembly, a stator 103, and a motor controller 109. The stator 103 is fixedly connected to the inner cavity of the housing 107, the rotor assembly is rotatably connected to the inner cavity of the housing 107, and the motor controller 109 is fixedly connected to the housing 107. The rotor assembly includes a motor-end encoder magnet 104, which is used to provide position feedback of the rotor assembly to the motor controller 109.

[0054] The planetary gearbox 2 includes an output mechanism and a reduction mechanism 206. The reduction mechanism 206 includes a fixed component that maintains a fixed relative position with the housing 107 and a rotating component connected to the rotor assembly. The output mechanism is connected to the rotating component, and the rotor assembly drives the rotating component and the output mechanism to rotate.

[0055] The output encoder 3 is disposed in the housing 107 and is connected to the output mechanism. The output encoder 3 includes an output encoder circuit board 301, an output encoder magnet 302, an encoder output gear 303, and an encoder input gear 308. The encoder input gear 308 is connected to the output mechanism, and the output mechanism drives the encoder input gear 308 to rotate. The encoder input gear 308 is used to drive the encoder output gear 303 to rotate. The output encoder magnet 302 is mounted on the encoder output gear 303. The output encoder circuit board 301 is used to receive the position feedback of the output mechanism provided by the output encoder magnet 302.

[0056] The motor controller 109 is a motor controller 109 with an onboard encoder. The motor controller 109 with the onboard encoder integrates a motor end encoder for measuring the angular displacement of the outer rotor cage 101. The output end encoder circuit board 301 integrates an encoder for measuring the angular displacement of the output flange 201.

[0057] The synchronous motor is an external rotor synchronous motor, and more specifically, it is an external rotor permanent magnet synchronous motor. The rotor assembly also includes an external rotor cage 101 and an external rotor steel ring 102. The external rotor steel ring 102 is fixedly connected to the external rotor cage 101. Specifically, the external rotor steel ring 102 is fixedly connected to the outer ring of the external rotor cage 101. The motor-end encoder magnet 104 is installed at the end of the external rotor cage 101 facing the motor controller 109, so that the motor controller 109 can sense the motor-end encoder magnet 104 and receive the position feedback of the external rotor cage 101 provided by the motor-end encoder magnet 104. The external rotor cage 101 is rotatably connected to the housing 107 through a rotor bearing 105.

[0058] like Figure 3 As shown, a fixing part extends into the inner cavity from one end of the housing 107. A rotor bearing 105 is fixed to the inner ring of the fixing part. The end of the outer rotor cage 101 facing the motor controller 109 is fixed in the inner ring of the rotor bearing 105, so that the outer rotor cage 101 can be rotatably connected to the housing 107. The stator 103 is fixed on the outer ring of the fixing part, so that the stator 103 and the housing 107 maintain a constant relative position, ensuring that the stator 103 is stably installed on the housing 107. A mounting part 1011 is provided at the end of the outer rotor cage 101 facing the motor controller 109. The mounting part 1011 is provided with a cavity. The motor end encoder magnet 104 is placed in the cavity. At the same time, one end of the rotating component in the reduction mechanism 206 is also inserted into the cavity, so that the outer rotor cage 101 rotates and drives the rotating component to rotate.

[0059] The motor controller 109 is fixed to the end of the housing 107 away from the output encoder 3, and is secured to the housing 107 by circuit board screws 108. Since the motor-end encoder magnet 104 is fixed to the outer rotor cage 101, the angular displacement of the outer rotor cage 101 can be measured by the motor controller 109. The output encoder magnet 302 is fixed to the encoder output gear 303, and the angular displacement of the output flange 201 can be measured by the output encoder circuit board 301.

[0060] The output mechanism of the planetary gearbox 2 includes an end cover 202, an output flange 201, and an output planetary carrier 203 arranged sequentially. The end cover 202 is fixedly connected to the end of the housing 107 away from the motor controller 109 by housing screws 106. The output flange 201 is rotatably connected to the end cover 202, and the output planetary carrier 203 is fixedly connected to the output flange 201, so that the output planetary carrier 203 and the output flange 201 rotate together relative to the end cover 202. The output encoder circuit board 301 is mounted on the end cover 202 by screws.

[0061] An end cover bearing 204 is installed on the end cover 202, and the end cover bearing 204 is located in the middle of the end cover 202. The outer ring of the output flange 201 is fitted in the end cover bearing 204 so that the output flange 201 and the end cover 202 are rotatably connected. The output planetary carrier 203 is installed on the output flange 201 by screws, and the outer ring of the output planetary carrier 203 can also be fitted and fixed in the inner ring of the end cover bearing 204. This can ensure the stability of the output planetary carrier 203 during rotation.

[0062] like Figure 3 and 6 As shown, the fixing component of the reduction mechanism 206 includes a fixed ring gear 2061, which is fixedly connected to the end cover 202. An end cover bearing washer 205 is also provided between the end face of the fixed ring gear 2061 and the end cover 202, pressing the end cover bearing 204 by the end cover bearing washer 205. The rotating component of the reduction mechanism 206 includes a planetary gear set 2063, which is installed in the inner cavity of the fixed ring gear 2061. The planetary gear set 2063 is connected to the output planetary carrier 203 and the outer rotor cage 101 respectively, so that when the outer rotor cage 101 rotates, it drives the planetary gear set 2063 and the output planetary carrier 203 to rotate. The planetary gear set 2063 is used to control the speed ratio of the outer rotor cage 101 and the output planetary carrier 203, thereby controlling the reduction ratio of the entire planetary gearbox 2.

[0063] like Figure 3As shown, the planetary gear 2063 group includes a central gear 2062 and a plurality of planetary gears 2063 located on the outer periphery of the central gear 2062. The central gear 2062 is disposed at the center of the inner cavity of the fixed ring gear 2061. The inner ring of the fixed ring gear 2061 is provided with an internal gear ring. The planetary gears 2063 are placed between the internal gear ring and the central gear 2062. The planetary gears 2063 mesh with both the outer ring of the central gear 2062 and the internal gear ring. The central gear 2062 is connected to the outer rotor cage 101 so that the outer rotor cage 101 drives the central gear 2062 to rotate.

[0064] The output planetary carrier 203 is provided with a plurality of gear mounting slots, and the planetary gear 2063 is placed in the gear mounting slots so that when the central gear 2062 drives the planetary gear 2063 to rotate, the planetary gear 2063 drives the output planetary carrier 203 to rotate.

[0065] A gear mounting post is provided in the gear mounting slot. The planetary gear 2063 is rotatably mounted on the gear mounting post through bearings. Each gear mounting slot corresponds to one planetary gear 2063. By adjusting the number of planetary gears 2063 and / or the diameter ratio of the planetary gear 2063 to the central gear 2062, the transmission ratio of the central gear 2062 and the planetary gear 2063 is changed, thereby adjusting the speed ratio of the output planetary carrier 203, the output flange 201 and the outer rotor cage 101, and thus changing the reduction ratio of the entire planetary gearbox 2.

[0066] This embodiment can be configured with multiple sets of planetary gears 2063. Each set of planetary gears 2063 includes a center gear 2062 and planetary gears 2063. Adjacent sets of planetary gears 2063 are connected by a supporting planetary carrier. Each set of planetary gears 2063 corresponds to one supporting planetary carrier. The supporting planetary carrier is also provided with several gear mounting slots for mounting planetary gears 2063. Among them, the center gear 2062 of the planetary gear 2063 set near the mounting part 1011 of the outer rotor cage 101 is inserted into the cavity of the mounting part 1011, and the center gear 2062 near the output planetary gear 2063 is inserted into the cavity of the mounting part 1011. The planetary gear 2063 set of the planetary gear set of the planetary gear set is mounted on the supporting planetary carriers opposite each other, and the gear mounting slots on the two are also correspondingly arranged. The supporting planetary carrier closer to the output planetary carrier 203 is a semi-open structure. The gear mounting slot of the output planetary carrier 203 and the gear mounting slot on the corresponding supporting planetary carrier together form a mounting area for mounting the planetary gear 2063, so that the planetary gear 2063 closer to the output planetary carrier 203 can be mounted in this mounting area through the mounting shaft, ensuring that the planetary gear 2063 drives the supporting planetary carrier and the output planetary carrier 203 to rotate simultaneously when rotating. The connection between any two adjacent planetary gear sets 2063 is as follows: the central gear 2062 of one planetary gear set 2063 is connected to the mounting cavity on the supporting planetary carrier of the other planetary gear set 2063. This allows one planetary gear set 2063 to drive the supporting planetary carrier to rotate, which in turn drives the central gear 2062 of the other planetary gear set to rotate. The central gear 2062 then drives its corresponding planetary gear 2063 and the supporting planetary carrier to rotate, ultimately transmitting the rotation of the outer rotor cage 101 to the output planetary carrier 203 and output flange 201 via a multi-stage planetary gear set 2063. This configuration allows for power transmission from multiple stages of planetary gear sets 2063 when the synchronous motor's height is too large, preventing the problem of excessively large central gear 2062 and planetary gear 2063, which would limit their service life, caused by using only one set of planetary gear sets.

[0067] like Figure 7 and 8As shown, this embodiment specifically sets up a two-stage planetary gear set 2063. The planetary gear set 2063 includes a lower-stage planetary gear set 2063 and an upper-stage planetary gear set 2063. The lower-stage planetary gear set 2063 is mounted on the lower support planetary carrier 2064, and the upper-stage planetary gear set 2063 is mounted on the upper support planetary carrier 2065. The lower-stage planetary gear set 2063 is located near the mounting portion 1011 of the outer rotor cage 101, and the upper-stage planetary gear set 2063 is located near the output planetary carrier 203. The center gear 2062 of the lower planetary gear 2063 set is inserted into the cavity of the mounting part 1011 of the outer rotor cage 101. The upper support planetary carrier 2065 and the output planetary carrier 203 are arranged opposite to each other, and the gear mounting slots on them are also correspondingly arranged. The upper support planetary carrier 2065 has a semi-open structure. The gear mounting slots on the output planetary carrier 203 and the gear mounting slots on the upper support planetary carrier 2065 together form the mounting area for mounting the planetary gears 2063 of the upper planetary gear 2063 set. The outer rotor cage 101 is connected to the mounting cavity on the lower support planetary carrier 2064 via the central gear 2062 in the upper planetary gear 2063 group. When the outer rotor cage 101 drives the central gear 2062 in the lower planetary gear 2063 group to rotate, the central gear 2062 drives the meshing planetary gear 2063 to rotate. When the planetary gear 2063 rotates, it drives the lower support planetary carrier 2064 to rotate. When the lower support planetary carrier 2064 rotates, it drives the central gear 2062 in the upper planetary gear 2063 group to rotate. In turn, the central gear 2062 in the upper planetary gear 2063 group drives its corresponding planetary gear 2063, the lower support planetary carrier 2064, and the output planetary carrier 203 to rotate. Finally, the rotation of the outer rotor cage 101 is transmitted to the output planetary carrier 203 and the output flange 201 through the lower planetary gear 2063 group and the upper planetary gear 2063 group.

[0068] like Figure 4 and 5 As shown, the output encoder 3 further includes an encoder output gear bearing 304 and an encoder output gear retainer 306. The encoder output gear retainer 306 is provided with a bearing cavity for mounting the encoder output gear bearing 304. The encoder output gear 303 is provided with a connecting shaft that is assembled with the encoder output gear bearing 304, so that the encoder output gear 303 is rotatably mounted on the encoder output gear retainer 306. The encoder output gear retainer 306 is fixed to the end cover 202. Preferably, the encoder output gear retainer 306 is fixed to the inner side of the end cover 202 by screws.

[0069] The output encoder 3 also includes an encoder drive gear 307. The encoder input gear 308 is mounted on the outer ring of the output planetary carrier 203 or the output flange 201 so that the encoder input gear 308 rotates together with the output planetary carrier 203 or the output flange 201. The encoder drive gear 307 is disposed between the encoder input gear 308 and the encoder output gear 303. The encoder drive gear 307 is rotatably mounted on one end of the fixed ring gear 2061 near the end cover 202. The two sides of the encoder drive gear 307 mesh with the encoder input gear 308 and the encoder output gear 303 respectively, and the encoder drive gear 307 transmits the power of the encoder input gear 308 to the encoder output gear 303.

[0070] When the output flange 201 or the output planetary carrier 203 rotates, the output flange 201, the output planetary carrier 203, and the encoder input gear 308 rotate synchronously as a whole. The encoder input gear 308 drives the encoder transmission gear 307 to rotate, and the encoder transmission gear 307 drives the encoder output gear 303 to rotate. The output encoder circuit board 301 can then receive a one-to-one position feedback of the output flange 201 provided by the output encoder magnet 302. When using the robot joint, the zero position of the output flange 201 is recorded by the output encoder circuit board 301, and the zero position of the outer rotor assembly is recorded by the motor controller 109. Specifically, the zero position of the outer rotor cage 101 is recorded by the motor controller 109. After power failure and restart, the absolute position of the output flange 201 in one revolution is calculated based on the encoder readings of the output encoder circuit board 301 and the motor controller 109. The robot joint is the robot joint described in the above embodiment.

[0071] Example 2

[0072] This embodiment only describes the differences from the above embodiments, while other technical features are the same. In this embodiment, the synchronous motor also includes a rear cover 111. The rear cover 111 is installed on one end of the housing 107 by rear cover screws 110, and the motor controller 109 is placed inside the rear cover 111, thereby ensuring that the motor controller 109 is enclosed in the inner cavity of the housing 107, thus protecting the motor controller 109.

[0073] Example 3

[0074] This embodiment only describes the differences from the above embodiments; other technical features are the same. In this embodiment, the output encoder 3 further includes an encoder output gear shaft retainer 305 and an encoder wire groove 309. The encoder output gear shaft retainer 305 is installed in a groove on the connecting shaft of the encoder output gear 303, and can prevent the encoder output gear 303 from axially moving. The wires of the output encoder circuit board 301 are installed on the encoder wire groove 309; the encoder wire groove 309 is fixed inside the housing 107 to protect the wires of the output encoder circuit board 301. These wires can connect the output encoder circuit board 301 and the motor controller 109, thereby enabling the transmission of electrical signals from the output encoder circuit board 301 to the onboard encoder motor controller 109.

[0075] Example 4

[0076] This embodiment provides a control method for a robot joint with an output encoder. The robot joint is the robot joint described in embodiments 1-3 above. The motor controller of the onboard encoder in the robot joint is equipped with a motor-end encoder, which is used to convert the angular displacement of the outer rotor cage into an electrical signal. It is a single-turn absolute encoder, and the direction of the increase in the number of encoder output pulses when the measuring structure rotates is set to positive. The output encoder is used to convert the angular displacement of the output flange into an electrical signal. It is a single-turn absolute encoder, and the direction of the increase in the number of encoder output pulses when the measuring structure rotates is set to positive.

[0077] like Figure 9 As shown, the control method for a robot joint with an output encoder in this embodiment includes the following steps:

[0078] S1. Use the motor controller to record the electrical signal of the zero position of the outer rotor cage in the rotor assembly and the electrical signal of the zero position of the output flange in the output mechanism;

[0079] S2. When the motor controller is powered on, the motor end encoder on the motor controller converts the absolute position of the outer rotor cage into an electrical signal and sends it to the motor controller. The motor controller records the number of revolutions of the outer rotor cage based on the single-turn absolute code electrical signal output by the motor end encoder on its motor controller, and converts the single-turn absolute code electrical signal into a multi-turn absolute code.

[0080] S3. Determine if the motor controller has been powered off and restarted. If yes, the motor-end encoder on the motor controller converts the position of the outer rotor cage into an electrical signal, and the output-end encoder converts the position of the output flange into an electrical signal. Both signals are sent to the motor controller so that the motor controller can obtain the current readings of the motor-end encoder and the output-end encoder. If no, continue to step S2.

[0081] S4. The motor controller calculates the number of revolutions the outer rotor cage has made based on the reduction ratio of the planetary gearbox and the readings of the encoders at both the motor and output ends. This calculation then determines the absolute position of the output flange relative to its zero point. This step allows the calculation and acquisition of the actual position of the planetary gearbox output shaft, i.e., the actual position of the output flange.

[0082] Furthermore, step S5 is also included. Based on the angular displacement of the output flange relative to its zero position when the motor controller is powered off, and the number of pulses output by the encoder at the output end at this time, combined with the reduction ratio of the planetary gearbox, the angular displacement of the outer rotor cage relative to its zero point is calculated, and then the number of rotations of the outer rotor cage can be calculated in reverse.

[0083] In step S2, when the motor controller is powered on, it is also necessary to determine whether the motor controller needs to record the zero position. If yes, then step S3 is executed; if no, it is necessary to determine whether the output flange (reducer output shaft) is placed at the desired zero position. If no, then the reducer output shaft is manually placed to the desired zero position. If yes, then the motor controller records the readings of the motor end encoder and the output end encoder, thereby completing the zero position signal input.

[0084] More specifically, in one embodiment of the present invention, the planetary gearbox 2 has a reduction ratio of 1:9, and the motor-end encoder and output-end encoder 3 on the motor controller 109 have 14 bits of encoding. When the outer rotor cage 101 rotates one revolution, the motor-end encoder outputs 16384 pulses. When the output flange 201 rotates one revolution, the output-end encoder 3 outputs 16384 pulses. Simultaneously, when the outer rotor cage 101 rotates nine revolutions, the motor-end encoder outputs 147456 pulses. Therefore, assuming that the output flange 201 rotates 60° positively relative to its zero position when the power is off, the output-end encoder 3 outputs 2731 pulses. According to the reduction ratio, the outer rotor cage 101 rotates 540° positively relative to its zero point. However, since the encoder used is a single-turn absolute value encoder, the number of output pulses from the output-end encoder at this time is the same as when the outer rotor cage 101 rotates 180° positively relative to its zero point, which is 8192. Therefore, it can be deduced that the outer rotor cage 101 rotated one revolution.

[0085] Thus, the robot joint example with output encoder 3 used in this invention can obtain the relative position of the output flange relative to its zero position when the motor starts. Even if it is restarted after a power outage, the relative position of the output flange 201 will not be lost. Therefore, there is no need to continuously supply power to the motor controller 109 with the onboard encoder, and there is no need to manually place the motor back to the zero position after each power outage and restart, which greatly reduces the module size and reduces the difficulty of operation.

[0086] The embodiments provided by the present invention have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of the present invention, and the descriptions of the embodiments above are only for the purpose of helping to understand the core ideas of the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A robot joint with an output encoder, characterized in that, include: A synchronous motor (1) includes a housing (107), a rotor assembly, a stator (103), and a motor controller (109). The stator (103) is fixedly connected to the inner cavity of the housing (107). The rotor assembly is rotatably connected to the inner cavity of the housing (107). The motor controller (109) is fixedly connected to the housing (107). The rotor assembly includes a motor-end encoder magnet (104), which is used to provide position feedback of the rotor assembly to the motor controller (109). Planetary gearbox (2), the planetary gearbox (2) includes an output mechanism and a reduction mechanism (206), the reduction mechanism (206) includes a fixed component that maintains a fixed relative position with the housing (107) and a rotating component connected to the rotor assembly, the output mechanism is connected to the rotating component, and the rotor assembly drives the rotating component and the output mechanism to rotate; The output encoder (3) includes an output encoder circuit board (301), an output encoder magnet (302), an encoder output gear (303), and an encoder input gear (308). The encoder input gear (308) is connected to the output mechanism, and the output mechanism drives the encoder input gear (308) to rotate. The encoder input gear (308) is used to drive the encoder output gear (303) to rotate. The output encoder magnet (302) is mounted on the encoder output gear (303). The output encoder circuit board (301) is used to receive the position feedback of the output mechanism provided by the output encoder magnet (302).

2. The robot joint with an output encoder according to claim 1, characterized in that, The synchronous motor is an external rotor synchronous motor. The rotor assembly also includes an external rotor cage (101) and an external rotor steel ring (102). The external rotor steel ring (102) is fixedly connected to the external rotor cage (101). The motor end encoder magnet (104) is installed at one end of the external rotor cage (101) facing the motor controller (109). The external rotor cage (101) and the housing (107) are rotatably connected through a rotor bearing (105).

3. The robot joint with an output encoder according to claim 1 or 2, characterized in that, The output mechanism includes an end cover (202), an output flange (201), and an output planetary carrier (203) arranged sequentially. The end cover (202) is fixedly connected to the end of the housing (107) away from the motor controller (109). The output flange (201) is rotatably connected to the end cover (202). The output planetary carrier (203) is fixedly connected to the output flange (201) so that the output planetary carrier (203) and the output flange (201) rotate together relative to the end cover (202).

4. The robot joint with an output encoder according to claim 3, characterized in that, The fixed component of the reduction mechanism (206) includes a fixed ring gear (2061), which is fixedly connected to the end cover (202); the rotating component of the reduction mechanism (206) includes a planetary gear (2063) set, which is installed in the inner cavity of the fixed ring gear (2061) and is connected to the output planetary carrier (203) and the outer rotor cage (101) respectively, so that when the outer rotor cage (101) rotates, it drives the planetary gear (2063) set and the output planetary carrier (203) to rotate. The planetary gear (2063) set is used to control the speed ratio of the outer rotor cage (101) and the output planetary carrier (203).

5. The robot joint with an output encoder according to claim 4, characterized in that, The planetary gear (2063) assembly includes a central gear (2062) and a plurality of planetary gears (2063) located on the outer periphery of the central gear (2062). The central gear (2062) is disposed at the center of the inner cavity of the fixed ring gear (2061). The inner ring of the fixed ring gear (2061) is provided with an internal gear ring. The planetary gears (2063) are placed between the internal gear ring and the central gear (2062). The planetary gears (2063) mesh with both the outer ring of the central gear (2062) and the internal gear ring. The central gear (2062) is connected to the outer rotor cage (101) so that the outer rotor cage (101) drives the central gear (2062) to rotate.

6. The robot joint with an output encoder according to claim 5, characterized in that, The output planetary carrier (203) is provided with a plurality of gear mounting slots, and the planetary gear (2063) is placed in the gear mounting slots so that when the central gear (2062) drives the planetary gear (2063) to rotate, the planetary gear (2063) drives the output planetary carrier (203) to rotate.

7. A robot joint with an output encoder according to claim 3, characterized in that, The output encoder (3) further includes an encoder output gear (303) bearing and an encoder output gear retainer (306). The encoder output gear retainer (306) is provided with a bearing cavity for mounting the encoder output gear (303) bearing. The encoder output gear (303) is provided with a connecting shaft that is assembled with the encoder output gear (303) bearing, so that the encoder output gear (303) is rotatably mounted on the encoder output gear retainer (306). The encoder output gear retainer (306) is fixedly connected to the end cover (202).

8. A robot joint with an output encoder according to claim 3, characterized in that, The output encoder (3) also includes an encoder drive gear (307). The encoder input gear (308) is mounted on the outer ring of the output planetary carrier (203) or the output flange (201) so that the encoder input gear (308) rotates together with the output planetary carrier (203) or the output flange (201). The encoder drive gear (307) is disposed between the encoder input gear (308) and the encoder output gear (303). Both sides of the encoder drive gear (307) mesh with the encoder input gear (308) and the encoder output gear (303) respectively. The encoder drive gear (307) transmits the power of the encoder input gear (308) to the encoder output gear (303).

9. A robot joint with an output encoder according to claim 1, characterized in that, The motor controller (109) is a motor controller (109) with an onboard encoder. The motor controller (109) with the onboard encoder integrates a motor end encoder for measuring the angular displacement of the outer rotor cage (101). The output end encoder circuit board (301) integrates an encoder for measuring the angular displacement of the output flange (201).

10. A control method for a robot joint with an output encoder, characterized in that, Includes the following steps: S1. Use the motor controller to record the electrical signal of the zero position of the outer rotor cage in the rotor assembly and the electrical signal of the zero position of the output flange in the output mechanism; S2. When the motor controller is powered on, the motor end encoder on the motor controller converts the absolute position of the outer rotor cage into an electrical signal and sends it to the motor controller. The motor controller records the number of revolutions of the outer rotor cage based on the single-turn absolute code electrical signal output by the motor end encoder on its motor controller, and converts the single-turn absolute code electrical signal into a multi-turn absolute code. S3. Determine if the motor controller has been powered off and restarted. If yes, the motor-end encoder on the motor controller converts the position of the outer rotor cage into an electrical signal, and the output-end encoder converts the position of the output flange into an electrical signal. Both signals are sent to the motor controller so that the motor controller can obtain the current readings of the motor-end encoder and the output-end encoder. If no, continue to step S2. S4. The motor controller calculates the number of revolutions the outer rotor cage has made based on the reduction ratio of the planetary gearbox and the readings of the encoders at the motor end and the output end, and then calculates the absolute position of the output flange relative to its zero point. The robot joint is the robot joint described in any one of claims 1-9.

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