Flexible-Drive-Based Bionic Exoskeleton Robot and Its Torque Modeling Method

Abstract

The present invention provides a bionic exoskeleton robot based on flexible drive, which includes a support component, a drive component, a hip joint connection component and a knee joint connection component. A disc motor A and a driver A drive the hip joint to move, and a disc motor B and a driver B drive the knee joint to move. The present invention also provides a torque modeling method for a bionic exoskeleton robot based on flexible drive. The driver of the present invention is a compliant non-linear stiffness driver, which realizes torque output with the characteristics of non-linear stiffness compliance, improving the comfort and safety of the wearer. Aiming at the non-linear hysteresis problem existing in the torque output of the exoskeleton joint, a hysteresis force model based on a power function is designed. By adjusting the parameters of the power function, the non-linear hysteresis force curve under different amplitudes can be accurately fitted, providing a basis for accurate torque control and thus improving the assistance effect of the exoskeleton.

Description

Technical Field

[0001] The present invention relates to the technical field of bionic exoskeleton robot systems, and particularly to a bionic exoskeleton robot based on flexible drive and its torque modeling method. Background Art

[0002] The data of the seventh national census shows that the aging degree of China's population has further deepened. With the growth of age, the body function declines, and senile diseases such as stroke, cardiovascular and cerebrovascular diseases, and arthritis occur frequently. As a wearable device for human-machine coupling, the rehabilitation lower limb exoskeleton integrates cutting-edge technologies in multiple disciplines such as machinery, control, computer, and rehabilitation medicine, and can provide effective motion function assistance for the elderly or patients with motor function disorders, promoting the recovery of motor nerves, and has great development potential and social value.

[0003] The existing exoskeleton robots mainly use motors as the driving source to drive the hip joint and knee joint to rotate, thereby assisting the wearer to move. The motor drive method has an intuitive and effective assistance effect and high control accuracy, but the rigid characteristics of the motor are difficult to ensure the safety and compliance of human-machine interaction. To solve the above problems, a variable stiffness compliant actuator can be designed by imitating the flexible drive characteristics of human joints and muscles (the output stiffness of human muscles increases with the increase of external load), that is, an elastic mechanism is installed between the motor and the exoskeleton, so that the entire exoskeleton system obtains inherent compliance, and the force control problem is transformed into a position control problem, simplifying the control complexity.

[0004] The output torque of the flexible actuator is generally calculated based on Hooke's law or a fitting curve. However, the introduction of elastic elements inevitably leads to hysteretic nonlinearity in the torque curve of the flexible actuator. Due to the hysteresis phenomenon, there is a lag between the input torque and the output displacement of the actuator, which will reduce the control accuracy of the actuator and even lead to control instability. To solve this problem, many effective compensation methods and mathematical models have been proposed by domestic and foreign scholars, such as the classic Preisach model, Maxwell-Slip model, Prandtl–Ishlinskii (PI) model. However, it is difficult to directly obtain the model parameters of these models and a large amount of experimental data is required. Therefore, designing a lower limb exoskeleton robot based on a flexible actuator and establishing a simple and effective hysteresis model for its torque curve is of great significance for further improving the control accuracy and the medical effect of exoskeleton rehabilitation assistance. Summary of the Invention

[0005] To overcome the problems of insufficient compliance and human-machine interaction safety of the existing rigid drive exoskeleton, as well as the hysteretic nonlinearity existing in the compliant actuator, the present invention provides a bionic exoskeleton robot based on flexible drive and its torque modeling method.

[0006] The first aspect of the present invention provides a lower limb exoskeleton robot based on a flexible actuator, comprising a support assembly, a drive assembly, a hip joint connection assembly and a knee joint connection assembly;

[0007] The support assembly includes a back support, a lumbar and back connecting piece, a lumbar support and a leg support rod connected in sequence. The back support is in a plate-like structure, and a back strap is provided on the front surface of the back support; a lumbar and back connecting piece is provided at the lower end of the back support. The lumbar and back connecting piece is a connecting rod, and the lower end of the connecting rod is connected with a lumbar support; the lumbar support is in a plate-like structure, and a lumbar strap is provided on the front surface of the lumbar support; a leg support rod extending horizontally outwards is provided on one side of the lumbar support, and the end of the leg support rod is connected with the hip joint connection assembly;

[0008] The hip joint connection assembly includes an L-shaped connecting piece A, a connecting rod fixing plate A and a thigh connecting rod arranged in sequence; the vertical side of the L-shaped connecting piece A is connected with the end of the leg support rod, the horizontal side of the L-shaped connecting piece A is connected with the connecting rod fixing plate A, and a driver A is provided on the outer side of the upper part of the connecting rod fixing plate A; a motor fixing plate A is provided on the outer side of the driver A, and a disc motor A is provided on the motor fixing plate A; the driver output shaft A of the driver A is installed at the output end of the driver A, the driver output shaft A is connected with the thigh connecting rod, and a bearing A is provided between the thigh connecting rod and the driver output shaft A; a thigh connecting sleeve base is provided on the inner side of the lower part of the connecting rod fixing plate A, and a thigh connecting sleeve is provided on the thigh connecting sleeve base; the lower end of the thigh connecting rod is connected with the knee joint connection assembly;

[0009] The knee joint connection assembly includes an L-shaped connecting piece B, a connecting rod fixing plate B and a calf connecting rod arranged in sequence. The upper end of the vertical side of the L-shaped connecting piece B is connected to the lower end of the thigh connecting rod, and the bottom surface of the horizontal side of the L-shaped connecting piece B is connected with a connecting rod fixing plate B; a driver B is provided on the outer side of the connecting rod fixing plate B, and a motor fixing plate B is provided on the outer side of the driver B; a disc motor B is provided on the outer side of the motor fixing plate B; the driver output shaft B of the driver B is installed at the output end of the driver B, the driver output shaft B is connected with the calf connecting rod, and a bearing B is provided between the calf connecting rod and the driver output shaft B; a calf connecting sleeve base is provided on the inner side of the calf connecting rod, and a calf connecting sleeve is provided on the calf connecting sleeve base;

[0010] The driving assembly includes driver A and driver B, and the structures of driver A and driver B are the same; the driver A includes a circular outer shell plate A and a transmission disc. A vertical guide rail is provided at the center line position on the side of the outer shell plate A, and a slider A and a slider B are slidably mounted on the guide rail; the slider A and the slider B are connected to a spring driving block; on the lower part of the side of the outer shell plate A and on both sides of the guide rail, there are respectively a spring assembly A and a spring assembly B. A pull ring of a spring A is threaded through the cylinder of the spring driving block of the spring assembly A, and the position of the spring A is restricted by a limit bolt A and a limit bolt C; a pull ring of a spring B is threaded through the cylinder of the spring driving block of the spring assembly B, and the position of the spring B is restricted by a limit bolt B and a limit bolt D;

[0011] On the lower end cylindrical structure of the side of the transmission disc, there are a bearing C and a bearing D, and the lower end of the transmission disc passes through the lower semi-circular hole of the spring driving block; a limit bolt E is provided at the lower end of the transmission disc, and a bearing E is installed at the through hole in the center of the transmission disc; a small gear is provided on the transmission disc, and the small gear meshes with a large gear; a bearing F is installed at the through hole of the small gear, and the large gear is fixed at the lower end of the outer shell plate B; on the outer shell plate B, there are a connecting plate A, a connecting plate B and a connecting plate C, and the connecting plate A, the connecting plate B and the connecting plate C connect the outer shell plate A and the outer shell plate B; the motor transmission disc is installed on a disc motor A, and the lower end transmission shaft of the motor transmission disc passes through the U-shaped slot hole of the outer shell plate B, the center through hole of the small gear and the center through hole of the transmission disc;

[0012] The disc motor A drives the motor transmission disc to rotate, the transmission shaft of the motor transmission disc drives the small gear and the large gear to perform a meshing movement, the large gear is fixed on the outer shell plate B, so the small gear drives the transmission disc to perform an arc movement, the lower end shaft of the transmission disc drives the spring driving block to rotate through the bearing, the spring driving block is fixed to the slider A and the slider B, the slider A and the slider B move on the guide rail, and the spring A and the spring B can be stretched synchronously when the spring driving block rotates, and the spring driving block drives the guide rail and the outer shell plate A to rotate axially.

[0013] Further, a semi-circular ring plate A and a semi-circular ring plate B are provided on the connecting plate A and the connecting plate B, and the outer shell plate A, the semi-circular ring plate A, the semi-circular ring plate B and the motor transmission disc form a disc structure.

[0014] Further, the disc motor A and the driver A drive the hip joint to move, and the disc motor B and the driver B drive the knee joint to move.

[0015] The second aspect of the present invention provides a torque control method for a lower limb exoskeleton robot based on a flexible driver, which is used to accurately model the output torque of the driver, and includes the following steps: 1) When a rotation angle θ is input, the spring stretching length △L is:

[0016] △L = 2r(1 - cosθ) (1)

[0017] The corresponding torque can be calculated according to Hooke's law:

[0018] F = KΔL + p (2)

[0019] At this time, the torque generated on the pinion is:

[0020] τ = Frsinθ (3)

[0021] Convert the tooth diameter ratio of the pinion and the gear, and finally the output torque calculation is:

[0022] τ = 4Krsinθ(1 - cosθ) + 2prsinθ (4) 2 sinθ(1 - cosθ) + 2prsinθ (4)

[0023] Perform linearization on the output torque, that is, define the abscissa virtual displacement s as:

[0024] s = 4Krsinθ(1 - cosθ) + 2psinθ (5)

[0025] Then the functional relationship between the output torque of the driver and the input virtual displacement s is:

[0026] τ = Krs (6)

[0027] The output torque curve is linearized, where K is the stiffness of the elastic element used in the driver, r is the radius of the pinion, and p is the pre-tightening force of the elastic element in the initial state;

[0028] 2) Model the hysteresis model. In order to achieve decoupling of each stage of the output torque trajectory, the torque curve is divided into a rising stage, a falling stage, and a transition stage:

[0029]

[0030] Among them, τ al , τ dl , τ tl are the functions of the rising curve, the falling curve, and the transition curve respectively, s 01 and s 02 are the turning points of the rising curve and the falling curve respectively;

[0031] For the rising curve and the falling curve, the torque function is as follows:

[0032] τ al (s) = k ij (s - s i ), if s ∈ [s i , s j (8)

[0033] τ dl (s) = k pq (s - sp ), if s ∈ [s p , s q (9)

[0034] Among them,

[0035] 3) Update the turning points s of the rising curve and the transition curve 01 , and the turning points s of the falling curve and the transition curve 02 in real time during the calculation of the torque curve;

[0036] When s 01 satisfies formula (10), it will be updated to the new turning point s 01 , and the value of the turning point is equal to s:

[0037]

[0038] Among them, s pre represents the previous value of s, and s foll represents the next value of s;

[0039] When s 02 satisfies formula (11), it will be updated to the new turning point s 02 , and the value of the turning point is equal to s:

[0040]

[0041] s 01 and s 02 can be solved for each other:

[0042] s 01 = s 02 + △s2(s 02 )

[0043] s 02 = s 01 - △s1(s 01 )

[0044] △s1(s 01 ) = k 11 s 01 + k 01

[0045] △s2(s 02 ) = k 12 s 02 + k 02 (12)

[0046] Among them, k pg , p, g = 0, 1, 2 are constant slopes;

[0047] 4) Build a simulation and fitting for the transition section of the torque curve in formula (4). By updating the parameters of the power function, achieve accurate modeling of the multi-loop non-linear torque curve under different amplitudes;

[0048] The torque function of the transition curve is:

[0049]

[0050]

[0051] Among them, ζ 0i represents the turning point s 01 and s 02 , ζ 0i will be updated according to s 01 and s 02 ;

[0052] Using the curve fitting toolbox in Matlab software, select different values of a and b to fit the transition section torque curves with different amplitudes:

[0053] a(s 0i ) = p 2i s 0i 2 + p1s 0i + p 0i

[0054] b(s 0i ) = g 2i s 0i 2 + g1s 0i + g 0i , i = 1, 2 (15)

[0055] Among them, p ij and g ij are constants;

[0056] 5) Build a hysteresis inverse model and use the drive torque feedforward compensation to eliminate the influence of the hysteresis force; the input value of the inverse hysteresis model is the desired torque, and the output is the virtual displacement s; the modeling methods for the rising section, falling section and transition section are the same as those of the forward model. Obtain the calibration values of the points on the curve from the forward model, and then exchange the abscissa and ordinate to obtain the parameters required for the inverse model.

[0057] Furthermore, in step 4, for different hysteresis loops, the power function parameters of the transition section are updated according to the maximum torque s 01 and s 02 ;

[0058] The beneficial effects of the present invention are:

[0059] 1) The output stiffness of the exoskeleton flexible actuator of the present invention increases with the increase of the external load, has the characteristic of compliant variable stiffness, and is more in line with the variable stiffness characteristics of human joints and muscles.

[0060] 2) The exoskeleton flexible actuator of the present invention adopts a tension spring and installs the tension spring inside the actuator structure. On the basis of ensuring the compactness and safety of the overall exoskeleton structure, the stability of torque output is improved.

[0061] 3) By dividing the exoskeleton joint torque curve into a rising curve, a falling curve, and a transition curve, the present invention realizes the decoupling of the torque curve in different stages.

[0062] 4) Based on the hysteresis model of the power function joint torque curve in the transition stage, the present invention realizes the accurate modeling of the multi-loop non-linear torque curve under different amplitudes by updating the parameters of the power function.

[0063] 5) The joint torque hysteresis model of the present invention is carried out using a low-order function below the second order, which reduces the calculation time of the model.

[0064] 6) The hysteresis model function established by the present invention can directly construct its inverse model, simplifies the inverse hysteresis modeling process, and improves the compensation effect of the hysteresis force. Description of the Drawings

[0065] Figure 1 is the structural diagram of the bionic lower limb exoskeleton with flexible drive of the present invention

[0066] Figure 2 is the structural diagram of the bionic lower limb exoskeleton with flexible drive of the present invention from another perspective

[0067] Figure 3 is the structural diagram of the lumbar and dorsal support part of the present invention

[0068] Figure 4 is the structural diagram of the hip joint connection part of the present invention

[0069] Figure 5 is the structural diagram of the knee joint connection part of the present invention

[0070] Figure 6 is the structural diagram of the actuator part of the present invention

[0071] Figure 7 is the schematic diagram of the actuator of the present invention in the initial state

[0072] Figure 8 is the schematic diagram of the actuator of the present invention in the working state

[0073] Figure 9 is the curve diagram of the output torque of the actuator of the present invention relative to the rotation angle

[0074] Figure 10 It is a curve graph of the output torque of the driver of the present invention with respect to the virtual displacement

[0075] Figure 11 It is a schematic diagram of the hysteresis force model of the driver of the present invention

[0076] Figure 12 It is a schematic diagram of the power function of the transition section of the hysteresis model of the present invention

[0077] Figure 13 It is a schematic diagram of the inverse hysteresis model of the output torque of the driver of the present invention

[0078] Description of reference numerals:

[0079] 1 Back support 19 Lower leg connection sleeve base 37 Limit bolt D 2 Back connecting piece 20 Lower leg connecting rod 38 Tension spring A 3 Waist support 21 Back strap 39 Tension spring B 4 Leg support rod 22 Waist strap 40 Limit bolt E 5 L-shaped connecting piece A 23 Bearing A 41 Bearing C 6 Motor fixing plate A 24 Driver output shaft A 42 Bearing D 7 Disc motor A 25 Bearing B 43 Bearing E 8 Link fixing plate A 26 Driver output shaft B 44 Drive disc 9 Driver A 27 Outer shell plate A 45 Bearing F 10 Thigh connection sleeve 28 Limit bolt A 46 Pinion 11 Thigh connection sleeve base 29 Limit bolt B 47 Gear 12 Thigh connecting rod 30 Tension spring assembly A 48 Connection plate A 13 L-shaped connecting piece B 31 Tension spring assembly B 49 Connection plate B 14 Motor fixing plate B 32 Guide rail 50 Connection plate C 15 Disc motor B 33 Slider A 51 Semicircular ring plate A 16 Link fixing plate B 34 Slider B 52 Semicircular ring plate B 17 Driver B 35 Tension spring drive block 53 Outer shell plate B 18 Lower leg connection sleeve 36 Limit bolt C 54 Motor drive disc Specific embodiments

[0080] Next, the technical solutions of the present invention will be clearly and completely described in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of them. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0081] In the description of the present invention, it should be noted that, as terms such as "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. appear, the orientation or positional relationship indicated is based on the orientation or positional relationship shown in the accompanying drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present invention. In addition, as terms such as "first", "second", "third" appear, they are only for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0082] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, as terms such as "installation", "connection", "connection" are used, they should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0083] Embodiment 1

[0084] The lower limb exoskeleton robot based on a flexible driver is characterized in that it includes a support assembly, a drive assembly, a hip joint connection assembly, and a knee joint connection assembly;

[0085] SeeFigure 3 As shown, the support assembly mainly consists of a back support member 1, a back strap 21, a lumbar and back connecting member 2, a lumbar support member 3, a lumbar strap 22, and a leg support rod 4;

[0086] The support assembly includes a back support member 1, a lumbar and back connecting member 2, a lumbar support member 3, and a leg support rod 4 connected in sequence. The back support member 1 is in a plate-like structure, and the front of the back support member is provided with a back strap 21; a lumbar and back connecting member 2 is provided at the lower end of the back support member 1. The lumbar and back connecting member 2 is a connecting rod, and the lower end of the connecting rod is connected to a lumbar support member 3; the lumbar support member 3 is in a plate-like structure, and the front of the lumbar support member 3 is provided with a lumbar strap 22; a leg support rod 4 extending horizontally outward is provided on one side of the lumbar support member 3, and the end of the leg support rod 4 is connected to a hip joint connection assembly;

[0087] See Figure 4 As shown, the hip joint connection assembly mainly consists of a thigh connecting rod 12, an L-shaped connecting piece A 5, a motor fixing plate A 6, a connecting rod fixing plate A 8, a thigh connecting sleeve 10, a thigh connecting sleeve base 11, a driver output shaft A 24, a bearing A 23, and a driver A 9;

[0088] The hip joint connection assembly includes an L-shaped connecting piece A 5, a connecting rod fixing plate A 8, and a thigh connecting rod 12 arranged in sequence; the vertical side of the L-shaped connecting piece A 5 is connected to the end of the leg support rod 4, the horizontal side of the L-shaped connecting piece A 5 is connected to the connecting rod fixing plate A 8, and a driver A 9 is provided on the outer side of the upper part of the connecting rod fixing plate A 8; a motor fixing plate A 6 is provided on the outer side of the driver A 9, and a disc motor A 7 is provided on the motor fixing plate A 6; the driver output shaft A 24 of the driver A 9 is installed at the output end of the driver A 9, the driver output shaft A 24 is connected to the thigh connecting rod 12, and a bearing A 23 is provided between the thigh connecting rod 12 and the driver output shaft A 24; a thigh connecting sleeve base 11 is provided on the inner side of the lower part of the connecting rod fixing plate A 8, and a thigh connecting sleeve 10 is provided on the thigh connecting sleeve base 11; the lower end of the thigh connecting rod 12 is connected to a knee joint connection assembly;

[0089] See Figure 5 As shown, the knee joint connection assembly mainly consists of a calf connecting rod 20, an L-shaped connecting piece B 13, a motor fixing plate B 14, a connecting rod fixing plate B 16, a calf connecting sleeve 18, a calf connecting sleeve base 19, a driver output shaft B 26, a bearing B 25, and a driver B 17;

[0090] The knee joint connection assembly includes an L-shaped connecting piece B13, a connecting rod fixing plate B16, and a calf connecting rod 20 arranged in sequence. The upper end of the vertical side of the L-shaped connecting piece B13 is connected to the lower end of the thigh connecting rod 12, and the bottom surface of the horizontal side of the L-shaped connecting piece B13 is connected with a connecting rod fixing plate B16; a driver B17 is arranged on the outer side of the connecting rod fixing plate B16, and a motor fixing plate B14 is arranged on the outer side of the driver B17; a disc motor B15 is arranged on the outer side of the motor fixing plate B14; the driver output shaft B26 of the driver B17 is installed at the output end of the driver B17, the driver output shaft B26 is connected to the calf connecting rod 20, and a bearing B25 is arranged between the calf connecting rod 20 and the driver output shaft B26; a calf connecting sleeve base 19 is arranged on the inner side of the calf connecting rod 20, and a calf connecting sleeve 18 is arranged on the calf connecting sleeve base 19;

[0091] See Figure 6 As shown, the drive assembly includes a driver A9 and a driver B17, and the structures of the driver A9 and the driver B17 are the same; the driver A9 mainly consists of a housing plate A27, a limit bolt A28, a limit bolt B29, a tension spring assembly A30, a tension spring assembly B31, a guide rail 32, a slider A33, a slider B34, a tension spring drive block 35, a limit bolt C36, a limit bolt D37, a tension spring A38, a tension spring B39, a limit bolt E40, a bearing C41, a bearing D42, a bearing E43, a transmission disc 44, a bearing F45, a pinion 46, a large gear 47, a connecting plate A48, a connecting plate B49, a connecting plate C50, a semi-circular ring plate A51, a semi-circular ring plate B52, a housing plate B53, a motor transmission disc 54, and a disc motor A7; among them, the structures of the tension spring assembly A30 and the tension spring assembly B31 are the same; the semi-circular ring plate A51 and the semi-circular ring plate B52 have the same structure, and the connecting plates A48, B49, and C50 have the same structure; the sliders A33 and B34 have the same structure; the tension springs A38 and B39 have the same structure;

[0092] The drive assembly includes a driver A9 and a driver B17, and the structures of the driver A9 and the driver B17 are the same; the driver A9 includes a circular housing plate A27 and a transmission disc 44. A vertical guide rail 32 is arranged at the center line position on the side of the housing plate A27, and a slider A33 and a slider B34 are slidably installed on the guide rail 32; the slider A33 and the slider B34 are connected to the tension spring drive block 35; tension spring assemblies A30 and B31 are respectively arranged on both sides of the guide rail 32 at the lower part of the side of the housing plate A27. A pull ring of the tension spring A38 is threaded through the column of the tension spring drive block 35 of the tension spring assembly A30, and the position of the tension spring A38 is restricted by the limit bolt A28 and the limit bolt C36; a pull ring of the tension spring B39 is threaded through the column of the tension spring drive block 35 of the tension spring assembly B31, and the position of the tension spring B39 is restricted by the limit bolt B29 and the limit bolt D37;

[0093] On the lower cylindrical structure on the side of the transmission disk 44, there are bearing C41 and bearing D42. The lower end of the transmission disk 44 passes through the lower semi-circular hole of the tension spring driving block 35. A limit bolt E40 is provided at the lower end of the transmission disk 44, and a bearing E43 is installed at the through hole in the center of the transmission disk 44. A small gear 46 is provided on the transmission disk 44, and the small gear 46 meshes with the large gear 47. A bearing F45 is installed at the through hole of the small gear 46, and the large gear 47 is fixed to the lower end of the outer shell plate B53. Connecting plates A48, B49, and C50 are provided on the outer shell plate B53, and the connecting plates A48, B49, and C50 connect the outer shell plate A27 and the outer shell plate B53. The motor transmission disk 54 is installed on the disk motor A7, and the lower transmission shaft of the motor transmission disk 54 passes through the U-shaped slot hole of the outer shell plate B53, the central through hole of the small gear, and the central through hole of the transmission disk 44.

[0094] The motor drives the motor transmission disk 54 to rotate. The transmission shaft of the motor transmission disk 54 drives the small gear 46 and the large gear 47 to engage. The large gear 47 is fixed to the outer shell plate B53. Therefore, the small gear 46 drives the transmission disk 44 to perform an arc motion. The lower shaft of the transmission disk 44 drives the tension spring driving block 35 to rotate through the bearing. The tension spring driving block 35 is fixed to the slider A33 and the slider B34. The slider A33 and the slider B34 move on the guide rail 32. The tension spring A38 and the tension spring B39 can be stretched synchronously when the tension spring driving block 35 rotates. The tension spring driving block 35 drives the guide rail 32 and the outer shell plate A27 to rotate axially.

[0095] Embodiment 2

[0096] A torque control method for a lower limb exoskeleton robot based on a flexible actuator, which is used to accurately model the output torque of the actuator, includes the following steps:

[0097] 1) The working principle of the actuator of the present invention is as Figure 7 、 8 shown. When a rotation angle θ is input, the tension spring stretching length △L is:

[0098] △L = 2r(1 - cosθ) (1)

[0099] According to Hooke's law, the corresponding torque can be calculated:

[0100] F = K△L + p (2)

[0101] At this time, the torque generated on the small gear is:

[0102] τ = Frsinθ (3)

[0103] Convert the tooth diameter ratio of the small gear and the large gear, and finally the output torque calculation is:

[0104] τ = 4Kr2 sinθ(1 - cosθ) + 2prsinθ (4)

[0105] See Figure 9 is the actual output torque curve of the driver. It can be seen that the output torque trajectory curve is non - linear and the shapes of the transition sections are different at different amplitudes. For the convenience of modeling and calculation of the model, a linearization process is performed on the output torque, that is, the abscissa virtual displacement s is defined as:

[0106] s = 4Krsinθ(1 - cosθ) + 2psinθ (5)

[0107] Then the functional relationship between the output torque of the driver and the input virtual displacement s is:

[0108] τ = Krs (6)

[0109] See Figure 10 is the relationship diagram between the output torque and the virtual displacement s. It can be seen that the output torque curve is linearized. Among them, K is the stiffness of the elastic element used in the driver, r is the radius of the pinion, and p is the pre - tightening force of the elastic element in the initial state;

[0110] 2) See Figure 11 As shown, a model is built for the hysteresis model. In order to decouple each stage of the output torque trajectory, the torque curve is divided into a rising stage, a falling stage, and a transition stage:

[0111]

[0112] Among them, τ al , τ dl , τ tl are the functions of the rising curve, the falling curve, and the transition curve respectively, and s 01 and s 02 are the turning points of the rising curve and the falling curve respectively;

[0113] For the rising curve and the falling curve, the torque functions are as follows:

[0114] τ al (s) = k ij (s - s i ), if s ∈ [s i , s j (8)

[0115] τ dl (s) = k pq (s - s p ), if s ∈ [s p , s q (9)

[0116] Among them,

[0117] 3) Update the turning points s of the rising curve and the transition curve 01 , and the turning points s of the falling curve and the transition curve 02 in real-time during the calculation of the torque curve;

[0118] When s 01 satisfies formula (6), it will be updated to the new turning point s 01 , and the value of the turning point is equal to s:

[0119]

[0120] where s pre represents the previous value of s, and s foll represents the next value of s;

[0121] When s 02 satisfies formula (7), it will be updated to the new turning point s 02 , and the value of the turning point is equal to s:

[0122]

[0123] s 01 and s 02 can be solved for each other:

[0124]

[0125] where k pg , p, g = 0, 1, 2 are constant slopes;

[0126] 4) Build a simulation and fitting for the transition section of the torque curve in formula (4). By updating the parameters of the power function, achieve an accurate modeling of the multi-loop nonlinear torque curve under different amplitudes. The principle of this model is shown in Figure 12 ;

[0127] The torque function of the transition curve is:

[0128]

[0129] where ζ 0i represents the turning points s 01 and s 02 , and ζ 0i will be updated according to s 01 and s 02 ;

[0130] When the values of a and b change, the curve of the transition section will also change accordingly. Therefore, for different hysteresis loops that appear in the modeling, using the curve fitting toolbox in Matlab software, different values of a and b are selected to fit the torque curves of the transition section with different amplitudes:

[0131] a(s 0i ) = p 2i s 0i 2 + p1s 0i + p 0i

[0132] b(s 0i ) = g 2i s 0i 2 + g1s 0i + g 0i , i = 1, 2 (15)

[0133] where p ij and g ij are constants; in step 4, for different hysteresis loops, the power function parameters of the transition section are updated according to the maximum torque s 01 and s 02 .

[0134] 5) Build a hysteresis inverse model and use the drive torque feedforward compensation to eliminate the influence of the hysteresis force; Figure 13 As shown in the hysteresis inverse model, compared with the Figure 11 hysteresis model shown, the difference is that the input value of the inverse hysteresis model is the desired torque and the output is the virtual displacement s; the modeling methods of the rising section, falling section and transition section are the same as those of the forward model. Obtain the calibration values of the points on the curve from the forward model, and then exchange the abscissa and ordinate to obtain the parameters required for the inverse model.

[0135] The content described in the embodiments of this specification is only an enumeration of the implementation forms of the inventive concept. The protection scope of the present invention should not be regarded as limited to the specific forms stated in the embodiments. The protection scope of the present invention also extends to equivalent technical means that can be conceived by those skilled in the art based on the inventive concept.

Claims

1. Lower limb exoskeleton robot based on a flexible actuator, characterized in that: It includes a support component, a drive component, a hip joint connection component, and a knee joint connection component; The support component includes a back support (1), a lumbar and back connecting piece (2), a lumbar support (3), and a leg support rod (4) connected in sequence. The back support (1) is in a plate-like structure, and a back strap (21) is provided on the front of the back support. The lower end of the back support (1) is provided with a lumbar and back connecting piece (2), and the lumbar and back connecting piece (2) is a connecting rod, and the lower end of the connecting rod is connected with a lumbar support (3). The lumbar support (3) is in a plate-like structure, and a lumbar strap (22) is provided on the front of the lumbar support (3). A leg support rod (4) extending horizontally outward is provided on one side of the lumbar support (3), and the end of the leg support rod (4) is connected to the hip joint connection component; The hip joint connection component includes an L-shaped connecting piece A (5), a connecting rod fixing disk A (8), and a thigh connecting rod (12) arranged in sequence. The vertical side of the L-shaped connecting piece A (5) is connected to the end of the leg support rod (4), the horizontal side of the L-shaped connecting piece A (5) is connected to the connecting rod fixing disk A (8), and a driver A (9) is provided on the outer side of the upper part of the connecting rod fixing disk A (8). A motor fixing disk A (6) is provided on the outer side of the driver A (9), and a disk motor A (7) is provided on the motor fixing disk A (6). The driver output shaft A (24) of the driver A (9) is installed at the output end of the driver A (9), and the driver output shaft A (24) is connected to the thigh connecting rod (12). A bearing A (23) is provided between the thigh connecting rod (12) and the driver output shaft A (24). A thigh connecting sleeve base (11) is provided on the inner side of the lower part of the connecting rod fixing disk A (8), and a thigh connecting sleeve (10) is provided on the thigh connecting sleeve base (11). The lower end of the thigh connecting rod (12) is connected to the knee joint connection component; The knee joint connection component includes an L-shaped connecting piece B (13), a connecting rod fixing disk B (16), and a calf connecting rod (20) arranged in sequence. The upper end of the vertical side of the L-shaped connecting piece B (13) is connected to the lower end of the thigh connecting rod (12), and the bottom surface of the horizontal side of the L-shaped connecting piece B (13) is connected to a connecting rod fixing disk B (16). A driver B (17) is provided on the outer side of the connecting rod fixing disk B (16), and a motor fixing disk B (14) is provided on the outer side of the driver B (17). A disk motor B (15) is provided on the outer side of the motor fixing disk B (14). The driver output shaft B (26) of the driver B (17) is installed at the output end of the driver B (17), and the driver output shaft B (26) is connected to the calf connecting rod (20). A bearing B (25) is provided between the calf connecting rod (20) and the driver output shaft B (26). A calf connecting sleeve base (19) is provided on the inner side of the calf connecting rod (20), and a calf connecting sleeve (18) is provided on the calf connecting sleeve base (19); The driving assembly includes a driver A (9) and a driver B (17), and the structures of the driver A (9) and the driver B (17) are the same; the driver A (9) includes a circular outer shell plate A (27) and a transmission disk (44). A vertical guide rail (32) is provided at the center line position on the side of the outer shell plate A (27). A slider A (33) and a slider B (34) are slidably mounted on the guide rail (32); the slider A (33) and the slider B (34) are connected to a spring driving block (35); on the lower part of the side of the outer shell plate A (27) and on both sides of the guide rail (32), a spring assembly A (30) and a spring assembly B (31) are respectively provided. A pull ring of a spring A (38) is passed through a column of the spring driving block (35) of the spring assembly A (30). The position of the spring A (38) is restricted by a limit bolt A (28) and a limit bolt C (36); a pull ring of a spring B (39) is passed through a column of the spring driving block (35) of the spring assembly B (31), and the position of the spring B (39) is restricted by a limit bolt B (29) and a limit bolt D (37). Bearings C (41) and D (42) are provided on the lower end cylindrical structure on the side of the transmission disk (44). The lower end of the transmission disk (44) passes through the lower semi-circular hole of the spring driving block (35); a limit bolt E (40) is provided at the lower end of the transmission disk (44), and a bearing E (43) is installed at the through hole in the center of the transmission disk (44); a small gear (46) is provided on the transmission disk (44), and the small gear (46) meshes with a large gear (47); a bearing F (45) is installed at the through hole of the small gear (46), and the large gear (47) is fixed to the lower end of the outer shell plate B (53); connecting plates A (48), B (49) and C (50) are provided on the outer shell plate B (53), and the connecting plates A (48), B (49) and C (50) connect the outer shell plate A (27) and the outer shell plate B (53); a motor transmission disk (54) is installed on a disk motor A (7). The lower end transmission shaft of the motor transmission disk (54) passes through the U-shaped slot hole of the outer shell plate B (53), the central through hole of the small gear and the central through hole of the transmission disk (44). The disk motor A (7) drives the motor transmission disk (54) to rotate. The transmission shaft of the motor transmission disk (54) drives the small gear (46) and the large gear (47) to perform a meshing motion. The large gear (47) is fixed to the outer shell plate B (53). Therefore, the small gear (46) drives the transmission disk (44) to perform an arc motion. The lower end shaft of the transmission disk (44) drives the spring driving block (35) to rotate through a bearing. The spring driving block (35) is fixed to the slider A (33) and the slider B (34). The slider A (33) and the slider B (34) move on the guide rail (32). The spring A (38) and the spring B (39) are stretched synchronously when the spring driving block (35) rotates. The spring driving block (35) drives the guide rail (32) and the outer shell plate A (27) to rotate axially.

2. The lower limb exoskeleton robot based on a flexible actuator according to claim 1, wherein: The connecting plate A (48) and the connecting plate B (49) are provided with a semi-circular ring plate A (51) and a semi-circular ring plate B (52), and the outer shell plate A (27), the semi-circular ring plate A (51), the semi-circular ring plate B (52) and the motor drive disc (54) form a disc structure.

3. The lower limb exoskeleton robot based on a flexible actuator according to claim 1, wherein: The disc motor A (7) and the driver A (9) drive the hip joint to move, and the disc motor B (15) and the driver B (17) drive the knee joint to move.

4. The torque control method of the lower limb exoskeleton robot based on a flexible actuator according to any one of claims 1-3, which is used to accurately model the output torque of the actuator, is characterized in that: It includes the following steps: 1) When a rotation angle θ is input, the stretching length △L of the tension spring is: △L = 2r(1 - cosθ) (1) According to Hooke's law, the corresponding torque can be calculated: F = K△L + p (2) At this time, the torque generated on the pinion is: τ = Frsinθ (3) Convert the tooth diameter ratio of the pinion and the big gear, and finally the output torque is calculated as: τ = 4Kr 2 sinθ(1 - cosθ) + 2prsinθ (4) Perform linearization processing on the output torque, that is, define the abscissa virtual displacement s as: s = 4Krsinθ(1 - cosθ) + 2psinθ (5) Then the functional relationship between the output torque of the driver and the input virtual displacement s is: τ = Krs (6) The output torque curve is linearized, where K is the stiffness of the elastic element used in the driver, r is the radius of the pinion, and p is the pre-tightening force of the elastic element in the initial state; 2) Model the hysteresis model. In order to decouple each stage of the output torque trajectory, the torque curve is divided into an ascending stage, a descending stage and a transition stage: Among them, τ al , τ dl , τ tl are the functions of the rising curve, the falling curve and the transition curve respectively, s 01 and s 02 are the turning points of the rising curve and the falling curve respectively; For the ascending curve and the descending curve, the torque function is as follows: τ al (s) = k ij (s - s i ), if s ∈ [s i , s j (8) τ dl (s) = k pq (s - s p ), if s ∈ [s p , s q (9) Among them, 3) Update the turning points s of the rising curve and the transition curve 01 and the turning points s of the falling curve and the transition curve 02 in real time during the calculation of the torque curve; When s 01 satisfies formula (10), it will be updated to a new turning point s 01 , and the value of the turning point is equal to s: where s pre represents the previous value of s, and s foll represents the next value of s; When s 02 satisfies formula (11), it will be updated to a new turning point s 02 , and the value of the turning point is equal to s: s 01 and s 02 can be solved for each other: where k pp , p, g = 0, 1, 2 are constant slopes; 4) Model and fit the transition section of the torque curve in formula (4). By updating the parameters of the power function, accurate modeling of the multi-loop non-linear torque curve under different amplitudes is achieved; The torque function of the transition curve is: Among them, ζ 0i represents the turning point s 01 and s 02 , ζ 0i will be updated according to s 01 and s 02 for update; Using the curve fitting toolbox in Matlab software, select different a and b values to fit the torque curves of the transition sections with different amplitudes: a(s 0i ) = p 2i s 0i 2 + p1s 0i + p 0i b(s 0i ) = g 2i s 0i 2 + g1s 0i + g 0i , i = 1, 2 (15) where p ij and g ij are constants; 5) Build a hysteresis inverse model and use the torque feedforward compensation of the driver to eliminate the influence of the hysteresis force; the input value of the inverse hysteresis model is the desired torque, and the output is the virtual displacement s; the modeling methods of the ascending section, the descending section and the transition section are the same as those of the forward model. Obtain the calibration values of the points on the curve from the forward model, and then exchange the abscissa and the ordinate to obtain the parameters required for the inverse model.

5. The torque control method according to claim 4, characterized in that: In step 4, for different hysteresis loops, the power function parameters of the transition section are updated according to the turning points s 01 and s 02 are updated.

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