A series elastic driven quadruped robot leg structure and torque control method

Abstract

The application belongs to the technical field of robots, and discloses a four-legged robot leg structure and a torque control method of a series elastic drive, which comprises a thigh joint driving unit, a shank joint driving unit and a hip joint driving unit; the hip joint driving unit and the shank joint driving unit are of the same structure and comprise a hollow motor, a speed reducer and a joint output shaft; the thigh joint driving unit comprises a hollow motor, a speed reducer, a thigh joint output shaft and an elastic body; the hollow motor is internally provided with the speed reducer; the speed reducer is connected with the elastic body in output connection; and the elastic body is connected with the thigh joint output shaft in output connection. The hip joint driving unit and the shank joint driving unit adopt a low-speed reducer to reduce the cost. The elastic body is added in the thigh joint driving unit, the torque acting on the thigh joint can be measured, and the torque acting on the shank joint can be analyzed and calculated. The safety of the mechanical leg is improved, the joint speed reducer is protected, the shock absorption and impact resistance of the four-legged robot are improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of robots, and particularly relates to a four-legged robot leg structure with serial elastic driving and a torque control method. BACKGROUND

[0002] With the development of information technology and electronic technology and the application of artificial intelligence, robots are entering many new application fields, such as medical treatment, service and human-machine interaction environment. As a special robot, the four-legged robot has developed rapidly in the past few years and has gradually entered daily production and life from the experimental platform of research institutes. Existing four-legged robot series products have achieved relatively wide application, such as the four-legged robot products of Yushu, Yunshenchu and Boston Dynamics. In order to adapt to more daily application requirements, the leg parts of these four-legged robots basically adopt a three-degree-of-freedom design, that is, a thigh joint, a shank joint and a hip joint, and cost reduction is considered as much as possible. The driving unit as a power source is a core component of the robot, which determines the dynamic performance of the whole robot. The driving and control of the robot must be realized through the control and driving of the driving joint.

[0003] In recent years, the elastic joint represented by the serial elastic driver has attracted the attention of many researchers and has been applied to many experimental robot platforms. Generally, the serial elastic driver is relatively high in price. These to some extent affect the wide application of the serial elastic driver. In addition, a driving system driving structure adopting a low transmission ratio reducer has also attracted attention. Although this low transmission ratio design has a smaller output torque, it has smaller loss, and the output torque can be obtained from the motor model and is called proprioceptive actuator or quasi-straight drive. This makes the price of this driver much lower than that of the serial elastic driver. Today, this driver is widely used in small four-legged robots. However, this proprioceptive actuator cannot completely guarantee contact control. In order to improve the safety of contact and mechanical impact, some designs adopt a clutch design, but the response frequency and speed of the clutch to impact cannot meet the requirement of eliminating dynamic impact. Moreover, the clutch will increase the volume and weight of the driver and bring about the common shortcomings of mechanical clutches such as heating, maintenance, etc. SUMMARY

[0004] The application aims to provide a four-legged robot leg structure with serial elastic driving and a torque control method to solve the above technical problems.

[0005] To solve the above technical problems, the specific technical scheme of the four-legged robot leg structure with serial elastic driving and the torque control method of the application is as follows:

[0006] The application discloses a series elastic driving quadruped robot leg structure, which comprises a thigh joint, a shank joint, a hip joint, a thigh and a shank, wherein the thigh joint, the shank joint and the hip joint are respectively provided with three driving units, namely a thigh joint driving unit, a shank joint driving unit and a hip joint driving unit; the hip joint drives the thigh joint, the thigh joint drives the shank joint, the hip joint driving unit is longitudinally parallel to a robot trunk, the thigh joint driving unit and the shank joint driving unit are parallel to each other and located in a plane perpendicular to the hip joint driving unit, and are orthogonal to the thigh joint and the shank joint; the hip joint driving unit and the shank joint driving unit are the same in structure and comprise a hollow motor, a reducer and a joint output shaft; the hollow motor comprises a motor rotor and a motor stator; the reducer is located in the center of the hollow motor; the reducer comprises a reducer input end and a reducer output end; the reducer input end is fixedly connected with the motor rotor of the hollow motor; and the reducer output end is connected with the joint output shaft.

[0007] Further, the thigh joint driving unit, the shank joint driving unit and the hip joint driving unit are respectively provided with a position sensor or an encoder.

[0008] Further, the hollow motor comprises a motor rotor and a motor stator; the reducer is located in the center of the hollow motor; the reducer comprises a reducer input end and a reducer output end; the reducer input end is fixedly connected with the motor rotor of the hollow motor; and the elastic body comprises an elastic body input end and an elastic body output end; the elastic body input end is connected with the reducer output end; and the elastic body output end is fixedly connected with the thigh joint output shaft.

[0009] Further, the hollow motor is externally provided with a shell; the reducer is a first-stage precision planetary gear reducer; and the reducer comprises a reducer pinion, planetary gears, a planetary gear carrier, a gear ring and a reducer output shaft; the reducer pinion is located in the center of the reducer; the reducer pinion is coaxially fixedly connected with a motor shaft; the reducer pinion rotates synchronously with the motor rotor; the three planetary gears are fixed on the planetary gear carrier and simultaneously meshed with the reducer pinion; the planetary gears are externally provided with the gear ring; the gear ring is fixedly connected with the shell of the hollow motor; the three planetary gears are meshed with the gear ring; the planetary gear carrier is fixedly connected with the reducer output shaft; the reducer pinion is the reducer input end; and the planetary gear carrier is the reducer output end.

[0010] Further, the elastic body is a spatial torque spring, the elastic body is a spiral disc structure, the inside of the center of the elastic body is an elastic body input end, and the outer ring is an elastic body output end, the reducer output shaft is fixedly connected with the elastic body input end, the elastic body output end is fixedly connected with the thigh joint output shaft, and the thigh joint output shaft is fixedly connected with the load.

[0011] Further, the motor encoder includes a motor encoder stator and a motor encoder rotor, the motor encoder stator is fixedly connected with the shell, the motor encoder rotor is fixedly connected with the motor rotor, and the motor encoder is used for measuring the position of the motor rotor.

[0012] Further, the joint output encoder includes a joint output encoder stator and a joint output encoder rotor, the joint output encoder stator is fixedly connected with the shell, the joint output encoder rotor is fixedly connected with the elastic body output end and rotates with the elastic body output end and the thigh joint output shaft, and the joint output encoder is used for measuring the position of the thigh joint output shaft.

[0013] Further, the motor encoder resolution is not less than 12 bits.

[0014] Further, the joint output encoder resolution is not less than 16 bits.

[0015] The application further discloses a torque control method of the four-legged robot leg structure driven in series.

[0016] Step 1: calculating the thigh joint torque:

[0017] T j =k e * (θ o - θ i ) (1)

[0018] wherein,

[0019] T 1 represents the torque acting on the output end of the machine leg thigh driving joint;

[0020] k e represents the elastic coefficient of the elastic body;

[0021] θ o represents the angular position of the elastic body output end;

[0022] θ i denotes the angular position of the elastic input end;

[0023] where the elastic coefficient is an elastic design parameter, known, and the angular positions of the elastic input end and output end are both measured values, known;

[0024] Step 2: Calculate the calf driving joint torque according to the dynamics of the two-degree-of-freedom mechanical leg, the specific steps are as follows:

[0025] 1) Double-joint structure mechanical leg

[0026] Single-joint and double-joint torque thigh and calf driving joint torque has the following relationship:

[0027] T 1 = T m + T b , T 2 = T b (2)

[0028] wherein:

[0029] T 2 denotes the calf driving joint torque;

[0030] T m denotes the single-joint driving torque;

[0031] T b denotes the double-joint driving torque;

[0032] If the peak value of the impact is considered to occur in the static state of the mechanical leg:

[0033] T 1 = F c∙ l b∙ sin (θ c - θ m ) (3)

[0034] T 2 = F c∙ l l∙ sin (θ c - θb ) (4)

[0035] where:

[0036] F c represents the amplitude of the impact force acting on the end segment of the mechanical leg;

[0037] θ c represents the angle of the impact force acting on the end segment of the mechanical leg;

[0038] θ m represents the single-joint driving angle position;

[0039] θ b represents the double-joint driving angle position;

[0040] l l represents the length of the mechanical leg;

[0041] l b represents the length of the double-joint driving;

[0042] The impact force F c in formula (3) is a known quantity or a measured value, and the impact force is solved, and formula (4) is substituted to solve the ankle driving joint torque;

[0043] If the impact occurs during the movement, then:

[0044] T mb = I ∙ ω´+T cd (ω)+T g +T c (5)

[0045] Formula (5) is a matrix form of the mechanical leg mechanical equation, wherein:

[0046] T represents the torque vector,

[0047] The subscripts m and b respectively represent the single joint and the double joint;

[0048] The subscripts c and d respectively represent the torque related to the Coriolis force and the damping, both of which are functions of the speed;

[0049] The subscript g represents the torque related to the gravity;

[0050] The subscript c represents the torque related to the impact force acting on the end of the mechanical leg;

[0051] I represents the moment of inertia matrix;

[0052] ∙ ω and ω´ respectively represent the angular velocity and angular acceleration vectors.

[0053] 2) Series structure mechanical leg

[0054] The dynamics equation of the two-degree-of-freedom mechanical leg is as follows:

[0055] T 12 = I * ω´+T cd (ω)+T g +T c

[0056] T 12 respectively represent the thigh and calf joint torques, T 1 measured directly, T 2 obtained by solving;

[0057] Step 3: According to the measured torque of the thigh joint and the estimated value of the calf driving joint torque, the torque is controlled in real time by using the robot joint control system to realize closed-loop torque control.

[0058] The series elastic driven four-legged robot leg structure and torque control method has the following advantages: the hip joint driving unit and the calf joint driving unit of the application adopt a low reduction ratio reducer to reduce cost. The elastic body is added in the thigh joint driving unit, the torque acting on the thigh joint can be measured, and the torque acting on the calf joint can be calculated. The safety of the mechanical leg is improved, and the joint reducer is protected. The shock absorption and impact resistance of the four-legged robot are improved. Closed-loop torque and position control can be realized. For systems with the same or similar performance, the system cost is reduced. BRIEF DESCRIPTION OF DRAWINGS

[0059] Figure 1 is a schematic diagram of the basic structure of the four-legged robot leg;

[0060] Figure 2 is a top view of the basic structure of the four-legged robot leg;

[0061] Figure 3 ​​Front view of the robot thigh joint driving unit structure section according to the present application;

[0062] Figure 4 Front view of the robot thigh joint driving unit structure section according to the present application; Figure 3 Front view of the robot thigh joint driving unit structure section according to the present application;

[0063] Figure 5 Front view of the robot thigh joint driving unit structure section according to the present application;

[0064] Figure 6 Front view of the robot thigh joint driving unit structure section according to the present application; Figure 5 Front view of the robot thigh joint driving unit structure section according to the present application;

[0065] Figure 7 Front view of the robot thigh joint driving unit structure section according to the present application;

[0066] Figure Marked Description: 1, thigh joint; 2, shank joint; 3, hip joint; 4, thigh; 5, shank; 11, thigh joint driving unit; 21, shank joint driving unit; 31, hip joint driving unit; 10, hollow motor; 110, machine shell; 112, motor shaft; 113, motor rotor; 114, motor stator; 12, speed reducer; 121, speed reducer pinion; 122, planetary gear; 123, planetary gear carrier; 124, ring gear; 125, speed reducer output shaft; 13, elastic body; 131, elastic body input end; 132, elastic body output end; 14, joint output shaft; 15, encoder; 151, motor encoder; 1511, motor encoder stator; 1512, motor encoder rotor; 152, joint output encoder; 1521, joint output encoder stator; 1522, joint output encoder rotor. DETAILED DESCRIPTION

[0067] In order to better understand the purpose, structure and function of the present application, the following will be further described in detail in combination with the drawings.

[0068] As Figure 1As shown, it is a basic structure of a quadruped robot leg, including thigh joint 1, shank joint 2, hip joint 3, thigh 4 and shank 5. Thigh joint 1, shank joint 2 and hip joint 3 have three driving units respectively, which are thigh joint driving unit 11, shank joint driving unit 21 and hip joint driving unit 31 respectively; the hip joint drives the thigh joint, and the thigh joint drives the shank joint. Hip joint driving unit 31 is longitudinally parallel to the robot trunk, and thigh joint driving unit 11 and shank joint driving unit 21 are parallel to each other and located in a plane perpendicular to hip joint driving unit 31, that is, orthogonal to thigh joint 1 and shank joint 2. Generally, the torque of the hip joint is also relatively small, so the invention does not consider hip joint driving unit 31. Shank joint 2 can adopt a series driving mode with thigh joint 1, that is, thigh joint 1 drives shank joint 2, or a double joint mode to drive shank 5, that is, thigh 4 and shank driving unit 21 drive shank 5 simultaneously. The invention is suitable for mechanical legs with series and double joint structures.

[0069] Among them, the hip joint driving unit 31 and the shank joint driving unit 21 are the same structure, which is a low reduction ratio reducer in the prior art, including a hollow motor, a reducer and a joint output shaft, the hollow motor includes a motor rotor and a motor stator, the reducer is located in the center of the hollow motor, the reducer includes a reducer input end and a reducer output end, the reducer input end is fixedly connected with the motor rotor of the hollow motor, and the reducer output end is connected with the joint output shaft. In addition, all joint driving unit motor sides are provided with position sensors or encoders, which can measure the angular position of the motor and estimate the angular position of the joint.

[0070] The thigh joint driving unit 11 is improved, and an elastic body is added on the basis of the original low reduction ratio reducer. As shown in the figure, the thigh joint driving unit 11 comprises a hollow motor 10, a reducer 12, a thigh joint output shaft 14 and an elastic body 13. The hollow motor 10 has a shell 110 outside, and the shell 110 has a motor shaft 112 and a motor rotor 113 fixedly connected with the motor shaft 112 inside. The inner ring of the motor rotor 113 is a motor stator 114. The reducer 12 is a one-stage precision planetary gear reducer, and the reducer 12 is located at the center of the hollow motor 11 and closely fits the hollow motor 11. The reducer 12 comprises a reducer pinion 121, planetary gears 122, a planetary gear carrier 123, a ring gear 124 and a reducer output shaft 125. The reducer pinion 121 is located at the center of the reducer 2, and the reducer pinion 121 is coaxially fixedly connected with the motor shaft 112. The reducer pinion 121 rotates synchronously with the motor rotor 113. The three planetary gears 122 are fixed on the planetary gear carrier 123 and simultaneously mesh with the reducer pinion 121. The planetary gears 122 have the ring gear 124 outside, and the ring gear 124 is fixedly connected with the shell 110 of the hollow motor 110. The three planetary gears 122 mesh with the ring gear 124. The planetary gear carrier 123 is fixedly connected with the reducer output shaft 125. The reducer pinion 121 is the input end of the reducer, and the planetary gear carrier 123 is the output end of the reducer.

[0071] As shown in the figure, Figure 3 , Figure 4 The elastic body 13 adopts a space torque spring, and the material is preferably spring steel or stainless steel. The elastic body 13 has a spiral disc structure, the inner side of the center is an elastic body input end 131, and the outer ring is an elastic body output end 132. The reducer output shaft 125 is fixedly connected with the elastic body input end 131, and the elastic body output end 132 is fixedly connected with the thigh joint output shaft 14. The thigh joint output shaft 14 meshes with the driving gear 41 in the thigh 4, so as to drive the thigh 4.

[0072] As shown in the figure, Figure 4 , Figure 5As shown, the thigh joint driving unit 11 of the application further comprises an encoder 15, which is a high-precision absolute encoder with a resolution of no less than 16 bits, and preferably 18 bits. The encoder 15 comprises a motor encoder 151 and a joint output encoder 152. The motor encoder 151 comprises a motor encoder stator 1511 and a motor encoder rotor 1512. The motor encoder stator 1511 is fixedly connected to the housing 110, and the motor encoder rotor 1512 is fixedly connected to the motor rotor 113. The motor encoder 151 is used to measure the position of the motor rotor 113. The joint output encoder 152 comprises a joint output encoder stator 1521 and a joint output encoder rotor 1522. The joint output encoder stator 1521 is fixedly connected to the housing 110, and the joint output encoder rotor 1522 is fixedly connected to the elastomer output end 132 and rotates with the elastomer output end 132 and the thigh joint output shaft 14. The joint output encoder 152 is used to measure the position of the thigh joint output shaft 14.

[0073] During operation, the motor shaft 112 rotates to drive the speed reducer pinion 121 of the speed reducer 12 to rotate, the speed reducer pinion 121 drives the planetary gear carrier 123 to rotate, thereby driving the speed reducer output shaft 125 to rotate, the speed reducer output shaft 125 drives the thigh joint output shaft 14 through the elastic member 13, and the angular positions of the motor rotor 113 and the elastomer output end 132 are still measured by the encoder 5. When the mechanical arm encounters an obstacle, the robot is reversely driven, the input-output relationship described above is reversed, the thigh joint output shaft 14 drives the elastomer 13 to rotate, thereby driving the speed reducer output shaft 125, then driving the planetary gear carrier 123 and the planetary gear 122, and finally driving the motor rotor 113 through the speed reducer pinion 121. At this time, the hollow motor 10 works in the generator mode, and energy regeneration can be achieved. The angular positions of the motor rotor 113 and the elastomer output end 132 in this process are still measured by the encoder 15. The torque acting on the thigh joint output shaft 14 is also derived from the angle difference between the elastomer input end 131 and the elastomer output end 132, but the torque direction is opposite to that in the forward driving.

[0074] Because the transmission ratio of the speed reducer is known, the position of the speed reducer output end, i.e., the elastomer input end 131, can be calculated from the position of the motor rotor 113, and thus the angle difference between the elastomer input end 131 and the elastomer output end 132 can be derived. The torque of the thigh joint output end can be derived with reference to the elastic coefficient of the elastomer 13.

[0075] The application provides a four-legged robot leg structure torque control method of a series elastic robot joint, which comprises the following steps:

[0076] Step 1: The thigh joint has accurate real-time measurement values of position and torque, and the torque is obtained by measuring the deformation of the elastomer:

[0077] T j =k e * (θ o - θ i ) (1)

[0078] Equation (1) is the calculation formula of the thigh joint contact force. Wherein,

[0079] T 1 represents the torque acting on the output end of the machine leg thigh driving joint;

[0080] k e represents the elastic coefficient of the elastic body;

[0081] θ o represents the angular position of the elastic body output end;

[0082] θ i represents the angular position of the elastic body input end;

[0083] Wherein the elastic coefficient is the elastic body design parameter, known, the elastic body input end and output end angular position are both measured values, known. Thus, the torque acting on the output end of the robot thigh joint, that is, the output end of the elastic body, can be directly calculated.

[0084] Step 2: According to the dynamics of the two-degree-of-freedom mechanical leg, the ankle driving joint torque is calculated, and the specific steps are as follows:

[0085] 1) Double joint structure mechanical leg

[0086] Single joint and double joint torque thigh and ankle driving joint torque has the following relationship:

[0087] T 1 = T m + T b , T 2 = T b (2)

[0088] Wherein:

[0089] T 2 represents the ankle driving joint torque;

[0090] Tm single joint drive torque;

[0091] T b double joint drive torque;

[0092] If the peak of the impact is considered to occur when the mechanical leg is at rest:

[0093] T 1 = F c∙ l b∙ sin (θ c - θ m ) (3)

[0094] T 2 = F c∙ l l∙ sin (θ c - θ b ) (4)

[0095] wherein:

[0096] F c represents the amplitude of the impact force acting on the end segment of the mechanical leg;

[0097] θ c represents the angle of the impact force acting on the end segment of the mechanical leg;

[0098] θ m represents the single joint drive angle position;

[0099] θ b represents the double joint drive angle position;

[0100] l l represents the length of the mechanical leg;

[0101] l b represents the double joint drive length;

[0102] The impact force F c in equation (3) are known quantities or measured values, from which the impact force can be solved, and the shank drive joint torque can be solved by substituting equation (4).

[0103] If the impact occurs during the motion, the resolution process follows the dynamic equation.

[0104] T mb = I ∙ ω´+T cd (ω)+T g +T c (5)

[0105] Equation (5) is the mechanical equation of the mechanical leg in matrix form, where:

[0106] T is the torque vector,

[0107] The subscripts m and b represent single-joint and double-joint, respectively;

[0108] The subscripts c and d represent the torques related to the Coriolis force and damping, respectively, both of which are functions of velocity;

[0109] The subscript g represents the torque related to gravity;

[0110] The subscript c represents the torque related to the impact force acting on the end of the mechanical leg;

[0111] I is the moment of inertia matrix;

[0112] ∙ ω and ω´ represent the angular velocity and angular acceleration vectors, respectively.

[0113] The torque of the calf driving joint can be estimated through resolution. This estimated value will contain a large amount of noise and uncertainty. To improve the accuracy of torque estimation, the estimated value is combined with the torque estimation value based on the motor current through an observer.

[0114] 2) Series structure mechanical leg

[0115] The dynamic equation of the two-degree-of-freedom mechanical leg is as follows:

[0116] T 12 = I * ω´+T cd (ω)+T g +T c (6)

[0117] T 12respectively represent the thigh and shank joint torque, T 1 can be directly measured, T 2 can be obtained by solving.

[0118] Step 3: According to the measured torque of the thigh joint and the estimated value of the shank driving joint torque, the load of the mechanical leg and joint can be monitored in real time. The torque is controlled in real time by using the robot joint control system to realize closed-loop torque control. If the impact torque is close to or exceeds the system allowable value, the corresponding control strategy can protect the joint and the mechanical leg from damaging the mechanical structure, especially the reducer gear.

[0119] The hip joint driving unit 31 and the shank joint driving unit 21 of the present application adopt a low reduction ratio reducer to reduce the cost. The elastic body 13 is added in the thigh joint driving unit 11, the torque acting on the thigh joint can be measured, and the torque acting on the shank joint can be analyzed and calculated. Therefore, appropriate control strategies and algorithms can be used to reduce the impact of mechanical impact on the joints of the mechanical leg, especially the reducer and transmission gear, and to improve the control accuracy.

[0120] It can be understood that the present application is described by some embodiments, and those skilled in the art know that various changes or equivalent replacements can be made to these features and embodiments without departing from the spirit and scope of the present application. In addition, under the guidance of the present application, these features and embodiments can be modified to adapt to specific conditions and materials without departing from the spirit and scope of the present application. Therefore, the present application is not limited by the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of the present application are within the scope of the present application.

Claims

1. A series elastic driven quadruped robot leg structure, comprising a thigh joint (1), a shank joint (2), a hip joint (3), a thigh (4) and a shank (5), the thigh joint (1), the shank joint (2) and the hip joint (3) are respectively provided with three driving units, which are respectively a thigh joint driving unit (11), a shank joint driving unit (21) and a hip joint driving unit (31); the hip joint (3) drives the thigh joint (1), the thigh joint (1) drives the shank joint (2), the hip joint driving unit (31) is longitudinally parallel to the robot trunk, the thigh joint driving unit (11) and the shank joint driving unit (21) are parallel to each other and located in a plane perpendicular to the hip joint driving unit (31), and are orthogonal to the thigh joint (1) and the shank joint (2), characterized in that, The hip joint driving unit (31) and the lower leg joint driving unit (21) are structurally identical, comprising a hollow motor, a reducer and a joint output shaft, the hollow motor comprising a motor rotor and a motor stator, the reducer being located in the center of the hollow motor, the reducer comprising a reducer input end and a reducer output end, the reducer input end being fixedly connected with the motor rotor of the hollow motor, and the reducer output end being connected with the joint output shaft; the thigh joint driving unit (11) comprises a hollow motor (10), a reducer (12), a thigh joint output shaft (14) and an elastic body (13), the hollow motor (10) having the reducer (12) therein, the reducer (12) being connected with the elastic body (13) in output, and the elastic body (13) being connected with the thigh joint output shaft (14) in output; the motor side of the thigh joint driving unit (11), the lower leg joint driving unit (21) and the hip joint driving unit (31) are all provided with an encoder, the encoder comprising a motor encoder (151) and a joint output encoder (152); the hollow motor (10) comprises a motor rotor (113) and a motor stator (114), the reducer (12) being located in the center of the hollow motor (10), the reducer (12) comprising a reducer input end and a reducer output end, the reducer input end being fixedly connected with the motor rotor (113) of the hollow motor (10), the elastic body (13) comprising an elastic body input end (131) and an elastic body output end (132), the elastic body input end (131) being connected with the reducer output end, and the elastic body output end (132) being fixedly connected with the thigh joint output shaft (14); the elastic body (13) is a spatial torque spring, the elastic body (13) being in a spiral disc structure, the center inner side of the elastic body (13) being the elastic body input end (131), and the outer ring being the elastic body output end (132), the reducer output shaft (125) being fixedly connected with the elastic body input end (131), the elastic body output end (132) being fixedly connected with the thigh joint output shaft (14), and the thigh joint output shaft (14) being fixedly connected with a load; the motor encoder (151) comprises a motor encoder stator (1511) and a motor encoder rotor (1512), the motor encoder stator (1511) being fixedly connected with a machine shell (110), and the motor encoder rotor (1512) being fixedly connected with the motor rotor (113), the motor encoder (151) being used for measuring the position of the motor rotor (113); the joint output encoder (152) comprises a joint output encoder stator (1521) and a joint output encoder rotor (1522), the joint output encoder stator (1521) being fixedly connected with the machine shell (110), the joint output encoder rotor (1522) being fixedly connected with the elastic body output end (132) and rotating with the elastic body output end (132) and the thigh joint output shaft (14), and the joint output encoder (152) being used for measuring the position of the thigh joint output shaft (14).

2. The series elastic driven quadruped robot leg structure of claim 1, wherein, The hollow motor (10) is externally provided with a casing (110), the speed reducer (12) is a one-stage precision planetary gear reducer, the speed reducer (12) comprises a speed reducer pinion (121), a planetary gear (122), a planetary gear carrier (123), a ring gear (124) and a speed reducer output shaft (125); the speed reducer pinion (121) is located at the center of the speed reducer (12), the speed reducer pinion (121) is coaxially fixedly connected with the motor shaft (112), the speed reducer pinion (121) rotates synchronously with the motor rotor (113), three planetary gears (122) are fixed on the planetary gear carrier (123) and simultaneously mesh with the speed reducer pinion (121), the planetary gear (122) is externally provided with the ring gear (124), the ring gear (124) is fixedly connected with the casing (110) of the hollow motor (10), three planetary gears (122) mesh with the ring gear (124), the planetary gear carrier (123) is fixedly connected with the speed reducer output shaft (125), the speed reducer pinion (121) is an input end of the speed reducer, and the planetary gear carrier (123) is an output end of the speed reducer.

3. The series elastic driven quadruped robot leg structure of claim 1, wherein, The motor encoder (151) has a resolution of not less than 12 bits.

4. The series elastic driven quadruped robot leg structure of claim 1, wherein, The joint output encoder (152) has a resolution of not less than 16 bits.

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