A control method of a passive-active hybrid drive intelligent prosthetic knee joint

Abstract

The application discloses a control method of an active and passive hybrid driving intelligent artificial knee joint, and relates to the field of rehabilitation robots.The method comprises a mode recognition module and a control module.The mode recognition module is used for recognizing the gait phase of a wearer and the terrain information in front of the wearer, and provides decision data for the control module, and is characterized in that the mode recognition module comprises gait detection and terrain detection.The control module selects a corresponding control mode according to the decision data of the mode recognition module and feeds back the current sensing state, and the control mode comprises a passive mode and an active mode.The gait detection and terrain detection algorithms are used to recognize the gait phase of the wearer and the terrain in front of the wearer, different terrains are distinguished, and the active and passive modes are accurately switched, so that the control efficiency of the artificial knee joint is improved, and the energy consumption is reduced.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of human rehabilitation auxiliary tool control, and relates to a prosthetic knee joint, in particular to a passive and active hybrid driving intelligent prosthetic knee joint with energy recovery function. BACKGROUND

[0002] With the increasing number of lower limb amputees and the continuous development of microelectronics and control technologies, intelligent lower limb prostheses have gradually become a research hotspot in the field of rehabilitation robots. As the core component of the lower limb prosthesis system, the design of high-performance knee joint prosthesis is still one of the technical difficulties in current prosthesis design. The existing intelligent prosthetic knee joints can be divided into passive and active types according to the joint driving mode. The passive type of prosthetic knee joint can realize the self-adaptation of walking speed by adjusting the knee joint damping torque in real time according to the walking speed of the wearer through microprocessor technology, but it does not provide active torque, so it cannot naturally complete activities such as climbing stairs. The active type of prosthetic knee joint can provide positive work for the prosthetic knee joint through a large-torque motor, making the wearer better complete walking patterns such as climbing stairs that require active torque, but it has the disadvantages of high energy consumption, large battery size and weight, and short battery life. The above two types of prostheses have their own advantages and disadvantages, but neither can simulate the mechanism of passive and active hybrid driving of the leg muscles in the walking process of healthy people, causing unnecessary energy metabolism consumption for the wearer of the prosthesis.

[0003] Therefore, the technical personnel in the field are committed to developing a passive and active hybrid driving intelligent prosthetic knee joint with energy recovery function to improve the control efficiency of the prosthesis and reduce energy consumption. SUMMARY

[0004] In view of the above problems, the purpose of the present application is to provide a control method for a passive and active hybrid driving intelligent prosthetic knee joint. The method first identifies the gait phase of the wearer and the terrain in front through gait detection and terrain detection algorithms. The terrain is divided into high terrain, low terrain and flat terrain. In the case of high terrain, i.e. climbing stairs, uphill and other situations that require active torque of the knee joint, the prosthesis switches to active mode, the trajectory of the knee joint flexion angle is planned according to the height of the terrain in front, and then the trajectory following of the prosthesis knee joint is realized through the motor and transmission mechanism, achieving active torque control. In the case of low terrain, i.e. going down stairs, downhill and other situations that require passive torque of the knee joint to consume energy, the prosthesis switches to passive mode, a certain damping torque and flexibility are provided through the control of the hydraulic cylinder valve size to ensure the bionics of the prosthesis movement. In the case of flat terrain, the prosthesis switches to passive mode, the gait phase of the wearer is detected, and the appropriate damping mode is selected according to the current gait phase to realize adaptive damping control. At the same time, the energy recovery module is turned on, the joint kinetic energy drives the motor to generate electricity through the transmission module, and finally the electricity is converted into electrical energy for storage, improving the battery life. In order to achieve the above purpose, the present application adopts the following technical solutions:

[0005] A control method of a passive-active hybrid driven intelligent prosthetic knee joint, characterized in that the control method comprises a mode recognition module and a control module.

[0006] The mode recognition module is used for recognizing the gait phase of the wearer and the front terrain information, and providing decision data for the control module, and the mode recognition module comprises a gait detection module and a terrain detection module.

[0007] The control module selects a corresponding control mode according to the decision data of the mode recognition module and feeds back the current sensing state, and the control mode comprises a passive mode and an active mode.

[0008] The passive mode is used for damping control of the prosthetic knee joint, and the passive mode comprises a high-damping mode, an adaptive damping mode and an energy recovery mode; when the wearer is in a static standing, heel striking, stair descending, downhill walking or the like state, the prosthesis is in a high-damping state to provide good standing stability for the prosthesis; the initial state of the prosthesis is the high-damping state; when the wearer is in a flat ground walking state, the adaptive damping mode adjusts the damping of the prosthesis in real time according to the gait phase, and the energy recovery mode is started to convert mechanical energy into electrical energy for storage.

[0009] The active mode is used for controlling the active flexion and extension of the prosthetic knee joint, and the active mode comprises knee joint flexion trajectory planning and control of the prosthetic knee joint for trajectory following; when the wearer is in an activity state such as stair climbing or uphill walking, the prosthetic knee joint switches to the active mode, the knee joint flexion trajectory is planned according to the front terrain height, and the prosthetic knee joint is controlled for trajectory following to realize the active flexion and extension of the prosthetic knee joint.

[0010] The gait detection module realizes gait phase recognition by acquiring a combination of pressure signals, knee joint angle signals and thigh angle signals, and divides a complete gait cycle T into a support period and a swing period, i.e. a support phase and a swing phase.

[0011] The support period starts with heel striking and ends with toe-off, and the swing period starts with toe-off and ends with heel striking; the support period and the swing period are subdivided into state stages to finally determine that a gait cycle is divided into five phases of heel striking, standing extension, toe-off, swing flexion and swing extension; if the wearer is in the standing extension period for more than a threshold time t, the wearer is in a static standing state, and the static standing state is the initial state of the prosthetic knee joint, at which time the terrain detection is started.

[0012] The terrain detection module comprises sensor detection and height detection.

[0013] The sensor detects the front of the residual limb of the wearer and forms a 25° angle with the vertical plane of the ground, and the data collected by the laser sensor is the distance from the residual limb of the wearer to the terrain in front; according to the different distance characteristics of the wearer's residual limb to the terrain in front, the terrain type is divided into three types: flat terrain, high terrain and low terrain.

[0014] The terrain type is respectively: when the wearer is in a static state, if the distance is greater than the threshold h1, the terrain in front is low terrain; if the distance is less than the threshold h2, the terrain in front is high terrain; if the distance is between the interval [h2, h1], the terrain in front is flat low terrain; wherein the high terrain represents that the front will occur uphill, upstairs or obstacle climbing and other movements that require joint active torque; the low terrain represents that the front will occur downhill, downstairs and other movements that require joint energy absorption; the flat terrain represents that the front will occur walking, standing and other movements.

[0015] 7. The control method of claim 4, wherein the height detection is used to calculate the terrain height when the terrain in front of the wearer is high, and wherein the calculation formula of the terrain height is:

[0016] h = l - d*cos(25°)

[0017] Wherein h is the height of the high terrain in front, l is the vertical distance from the installation position of the laser ranging sensor to the ground, and d is the output of the laser ranging sensor, i.e. the distance from the residual limb to the ground in front.

[0018] The knee flexion angle trajectory planning is to select a suitable knee flexion angle trajectory by inputting the terrain height, which is used as the ideal reference trajectory of the motor closed-loop control, and the knee flexion angle trajectory motion function is:

[0019] x(t) = a0 + a1t + a2t 2 +a3t 3 +a4t 4 +a5t 5

[0020]

[0021]

[0022] Wherein a0...a5 are motion parameters, t is the motion time length of the gait, x(t) is the position motion function, is the velocity motion function, is the acceleration motion function. The motion parameters are determined by the terrain height; when the gait phase of the wearer is switched from the toe-off phase to the swing-flexion phase, the motor starts to follow the knee flexion angle trajectory.

[0023] The adaptive damping control includes that when the wearer is in a flat terrain, the prosthetic knee joint automatically adjusts the damping of joint flexion according to the result of gait detection; in the heel-strike gait phase, the flexion damping of the joint is high damping; in the stance-extension gait phase, the flexion damping of the joint is medium damping; in the toe-off gait phase, the flexion damping of the joint is low damping; in the swing-flexion gait phase, the flexion damping of the joint is low damping; in the swing-extension gait phase, the flexion damping of the joint is medium damping; in the static standing state, the flexion damping of the joint is high damping, at this time, the terrain detection is started; if the wearer stays in a certain gait phase, the damping state of the joint remains unchanged until the gait change is detected.

[0024] The energy recovery module includes a transmission system, a motor and a rectification and voltage boosting circuit; when the prosthetic knee joint is in the active mode, the energy recovery mode is closed, at this time, the motor transmits the torque to the joint through the transmission system to provide the active torque for the prosthetic knee joint in the high terrain environment in front, so as to realize the active flexion and extension of the knee joint; when in the passive mode, the energy recovery mode is started, the knee joint drives the motor to generate electricity when flexing and extending through the transmission system, and then the electricity is stored through rectification and voltage boosting.

[0025] In the preferred embodiment of the present application, the gait detection module is realized by using three sensors, i.e., an IMU on the prosthesis, a pressure sensor in the leg tube and an IMU in the rotation shaft of the knee joint, the gait cycle is divided into five gait phases, i.e., heel-strike, stance-extension, toe-off, swing-flexion and swing-extension according to the collected knee joint angle, vertical pressure and thigh angle; the static standing state is that the wearer stays in the stance-extension stage for a long time, at this time, the terrain detection is started; when the terrain detection result is low terrain, i.e., the activities such as going downstairs and downhill that need the joint to absorb negative work may occur in front, at this time, the damping modes of the five gait phases in the passive control mode are all high damping, so as to ensure the standing stability of the user; when the terrain detection result is high terrain, i.e., the activities such as going upstairs and uphill that need the joint to do positive work may occur in front, at this time, the damping modes of the five gait phases in the active control mode are low damping, so as to ensure the flexibility of the joint driven by the motor to flex and extend actively; when the terrain detection result is flat terrain, the damping of the prosthesis is adjusted according to the current gait phase to realize the adaptive damping control in the flat walking, so as to adapt to different walking speeds of the wearer.

[0026] The present application has the following beneficial effects due to the above technical solutions:

[0027] 1.A control method of a passive-active hybrid drive intelligent prosthetic knee joint, which can improve the control efficiency of the prosthetic knee joint and reduce energy consumption. The method provides active torque to the patient in the case of uphill or stair climbing, etc. requiring the knee joint to provide active torque; provides high damping to the patient in the case of downhill and stair descending, etc. requiring the knee joint to absorb energy; adjusts the joint damping in real time according to the gait phase of the wearer in the case of flat ground walking, to provide a more comfortable walking experience for the wearer, and converts passive torque into motor driving torque through an energy recovery module to generate electricity, converts kinetic energy into electrical energy for storage, and increases the working endurance of the prosthetic knee joint.

[0028] 2.The gait phase and the terrain in front of the wearer are accurately predicted through a laser ranging sensor, an IMU and a pressure sensor, which can ensure that the prosthetic knee joint accurately switches between active and passive control modes, and the height of the stairs or slope in front can be calculated according to the ranging result, to provide decision data for the flexion angle trajectory of the active control knee joint, to help the wearer efficiently complete activities such as stair climbing, uphill walking or obstacle crossing that require active torque of the joint. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 is a whole schematic diagram of a control method of a passive-active hybrid drive intelligent prosthetic knee joint according to the present application.

[0030] Figure 2 is a flowchart of gait detection of a control method of a passive-active hybrid drive intelligent prosthetic knee joint according to the present application.

[0031] Figure 3 is a flowchart of terrain detection and passive-active control of a control method of a passive-active hybrid drive intelligent prosthetic knee joint according to the present application.

[0032] Figure 4 is a flowchart of passive-active control of a control method of a passive-active hybrid drive intelligent prosthetic knee joint according to the present application.

[0033] Figure 5 is a flowchart of adaptive damping control of a control method of a passive-active hybrid drive intelligent prosthetic knee joint according to the present application. DETAILED DESCRIPTION

[0034] The following reference to the drawings of the specification introduces several preferred embodiments of the present application, so that the technical content thereof is more clear and convenient to understand. The present application can be embodied in many different forms of embodiments, and the protection scope of the present application is not limited to the embodiments mentioned herein.

[0035] In the drawings, the same components have the same reference numerals, and components similar in structure or function bear like reference numerals. The size and thickness of each component shown in the drawings are arbitrarily shown, and the size and thickness of each component are not limited in the present application. In order to make the drawing clearer, the thickness of some components is appropriately exaggerated in some places in the drawing.

[0036] Figures 1-5 respectively are a whole schematic diagram of a control method of a passive-active hybrid driven intelligent prosthetic knee joint, a gait detection flow chart, a terrain detection flow chart, a passive-active control flow chart, and an adaptive damping control flow chart.

[0037] As shown in Figure 1 A whole schematic diagram of a control method of a passive-active hybrid driven intelligent prosthetic knee joint, characterized in that the control method comprises a mode recognition module and a control module. The mode recognition module predicts the gait data and the front terrain data of the wearer to provide decision data for the control module; the control module selects the current prosthetic control mode according to the data provided by the mode recognition module, and simultaneously feeds back the motion state of the prosthetic knee joint.

[0038] As shown in Figure 2 A gait detection flow chart of a control method of a passive-active hybrid driven intelligent prosthetic knee joint, characterized in that the gait detection is realized by using three sensors, i.e. an IMU on the prosthesis, a pressure sensor in the leg tube, and an IMU in the joint rotation shaft, the gait cycle is divided into five gait phases, i.e. heel landing, standing extension, toe lifting, swing flexion, and swing extension, according to the collected knee joint angle, vertical pressure, and thigh angle; the gait detection algorithm first uses the pressure signal to determine whether the current gait phase is the standing phase or the swing phase, when the pressure signal in the lower leg tube is greater than a threshold value a, the wearer is in the standing phase, at this time, when the thigh angle is greater than 0, the gait phase is heel landing; when the thigh angle is less than 0 and the knee joint angle is less than a threshold value b, the gait phase is standing extension; otherwise, it is the toe lifting phase. When the pressure signal in the lower leg tube is less than the threshold value a, the wearer is in the swing phase, when the thigh angle is less than 0, the gait phase is swing flexion, otherwise, it is swing extension. If the wearer stays in the standing extension stage for more than a time threshold value t, it is determined that the wearer is in a static standing state, at this time, the terrain detection is started.

[0039] As shown in Figure 3As shown, the terrain detection determines whether to make terrain decisions for the terrain in front of the wearer by the gait detection. When the wearer is in a static standing state, a laser sensor installed in front of the wearer's receiving cavity measures the distance to the front ground to obtain the distance d from the wearer's residual limb to the front ground. According to the distance d characteristics corresponding to different terrains, the terrain in front is divided into high terrain, low terrain and flat terrain. When d is between the threshold interval [h1, h2], it is determined that the front is a flat terrain. When d is less than the threshold h1, it is determined that the front terrain is a high terrain, that is, the distance from the wearer's residual limb to the ground is shortened due to the increased height of the terrain in front. When d is greater than the threshold h2, it is determined that the front terrain is a low terrain, that is, the distance from the wearer's residual limb to the ground is lengthened due to the decreased height of the terrain in front. The flat terrain, high terrain and low terrain are used to switch the active and passive control modes of the prosthetic knee joint, characterized in that the flat terrain includes activities such as flat ground walking and standing; the low terrain includes activities such as downhill, stair descent and standing; the high terrain includes activities such as stair ascent, uphill and obstacle crossing; the activities included in the flat terrain and the low terrain do not require the knee joint to provide active torque, while the activities included in the high terrain require the knee joint to provide active torque, so if the detection result is high terrain, the active mode is switched, otherwise the passive mode is defaulted.

[0040] As shown in Figure 4 , the active and passive control includes passive mode and active mode. The active mode includes terrain height detection, knee flexion angle trajectory planning and control of knee flexion trajectory following.

[0041] The terrain height detection provides decision data for the knee flexion angle trajectory planning, characterized in that when a high terrain is detected, the prosthesis is in an active control mode. In the high terrain, i.e. the active control mode, the height of the terrain in front is calculated according to the result of the laser ranging sensor, and the calculation formula of the terrain height is:

[0042] h = l - d * cos(25°)

[0043] where h is the height of the high terrain in front, l is the vertical distance from the installation position of the laser ranging sensor to the ground, and d is the output of the laser ranging sensor, i.e. the distance from the residual limb to the front ground.

[0044] The knee flexion angle trajectory planning generates a smooth prosthesis knee flexion motion trajectory, which provides an ideal following curve for the closed-loop control of the prosthesis knee joint, characterized in that the motion function of the knee flexion angle trajectory is:

[0045] x(t) = a0 + a1t + a2t 2 + a3t 3 + a4t 4 + a5t 5

[0046]

[0047]

[0048] wherein a0...a5 are motion parameters, t is the motion time length of the gait, x(t) is the position motion function, is the velocity motion function, is the acceleration motion function. The motion parameters are determined by the terrain height, and different heights of stairs or slopes correspond to different motion parameters, that is, different knee flexion angle trajectories, helping the wearer to efficiently complete activities such as going upstairs and uphill. After the prosthesis selects the appropriate knee flexion angle trajectory, if the wearer is in the swing flexion gait phase, the prosthesis knee joint damping mode switches to the low damping mode, and the motor is controlled to drive the prosthesis to follow the trajectory, otherwise it is determined to be in the standing phase, and the prosthesis is in the high damping mode, and the motor is servo-driven.

[0049] The passive mode includes a high damping mode, an adaptive damping control mode, and an energy recovery mode.

[0050] The high damping mode is used to provide the prosthesis knee flexion locking function to ensure the gait stability of the wearer in the low terrain environment, characterized in that when the terrain detection result is low terrain, the damping mode in all gait phases is high damping.

[0051] As shown in the flowchart of the adaptive damping control mode, Figure 5 the adaptive damping control mode is used to provide the function of real-time adjustment of the prosthesis knee flexion damping according to the gait phase when the wearer walks on flat ground, to ensure the walking comfort of the wearer at different walking speeds, characterized in that the heel strike phase corresponds to the high damping mode, the standing extension phase switches to the medium damping mode, the toe-off and swing flexion phases switch to the low damping mode, and the swing extension phase switches to the medium damping mode. The low damping mode, the medium damping mode and the high damping mode correspond to three states of full opening, half opening and full closing of the oil way valve of the prosthesis hydraulic cylinder respectively.

[0052] The energy recovery mode is used to recover the kinetic energy generated in the passive mode, characterized in that when the prosthesis knee joint is in the passive mode, the motor does not provide active torque, and when the wearer drives the prosthesis knee joint to flex and extend through the inertia of the residual limb, the transmission system drives the motor to rotate to generate electricity, the rectifier circuit rectifies the forward and reverse rotation current formed by the knee flexion and extension, and the boost module inputs the generated electric energy to the battery for charging, thereby improving the endurance time of the battery.

[0053] The preferred embodiments of the present application have been described above in detail. It should be understood that modifications and variations to the preferred embodiments could be made by those skilled in the art without departing from the spirit and scope of the application. Accordingly, it is intended that there be included within the scope of the application, all such modifications and variations as would be apparent to those skilled in the art upon reading this disclosure. It is intended to obtain for the inventors such patent rights as are available for any patent granted on the present application.

Claims

1. A control method of a passive-active hybrid drive intelligent prosthetic knee joint, characterized in that, The control method comprises a pattern recognition module and a control module; The pattern recognition module is used for recognizing gait phase and terrain information in front of a wearer and providing decision data for the control module, and the pattern recognition module comprises a gait detection module and a terrain detection module; The control module selects a corresponding control mode according to the decision data of the pattern recognition module and feeds back a current sensing state, and the control mode comprises a passive mode and an active mode; The passive mode is used for damping control of a prosthetic knee joint, and the passive mode comprises a high-damping mode, an adaptive damping mode and an energy recovery mode; When the wearer is in a static standing, heel-striking, stair-descending or downhill state, the prosthetic knee joint is in a high-damping state, thereby providing good standing stability for the prosthetic knee joint; The initial state of the prosthetic knee joint is the high-damping state; when the wearer is in a flat-ground walking state, the adaptive damping mode adjusts the damping of the prosthetic knee joint in real time according to the gait phase, and the energy recovery mode is started, and the energy recovery module converts mechanical energy into electrical energy for storage; The active mode is used for controlling active flexion and extension of the prosthetic knee joint, and the active mode comprises knee joint flexion angle trajectory planning and control of the prosthetic knee joint for trajectory following; When the wearer is in a stair-climbing or uphill state, the prosthetic knee joint is switched to the active mode, the knee joint flexion angle trajectory is planned according to the height of the terrain in front, and the prosthetic knee joint is controlled for trajectory following, thereby realizing active flexion and extension of the prosthetic knee joint; The terrain detection module comprises sensor detection and height detection; the sensor detection uses a laser sensor installed in front of a residual limb socket of the wearer and forms a 25° angle with a vertical plane of the ground, and the data collected by the laser sensor is the distance from the residual limb of the wearer to the terrain in front; the height detection is used for calculating the terrain height when the terrain in front of the wearer is a high terrain, and the calculation formula of the terrain height is: = ； wherein, is the height of the front terrain, is the vertical distance from the laser ranging sensor mounting position to the ground, is the output of the laser ranging sensor, i.e. the distance from the residual limb to the front ground; The knee joint flexion angle trajectory planning is to select a suitable knee joint flexion angle trajectory by inputting the terrain height, as an ideal reference trajectory for closed-loop control of the motor, and the motion function of the knee joint flexion angle trajectory is: wherein, is a motion parameter, is a motion duration of a gait, is a position motion function, is a velocity motion function, is an acceleration motion function; the motion parameter is determined by a terrain height; when a gait phase of the wearer switches from a toe-off phase to a swing-flexion phase, the motor starts to perform following the knee flexion angle trajectory.

2. The control method according to claim 1, characterized by, The gait detection module realizes gait phase recognition by acquiring a combination of pressure signals, knee joint angle signals and thigh angle signals, and divides a complete gait cycle T into a support period and a swing period, i.e. a support phase and a swing phase.

3. The control method according to claim 2, characterized by, The support period starts with heel-striking and ends with toe-off, and the swing period starts with toe-off and ends with heel-striking; the support period and the swing period are subdivided into state stages, and a gait cycle is finally determined to have five phases, i.e. heel-striking, standing extension, toe-off, swing flexion and swing extension; if the wearer is in the standing extension phase for more than a threshold time, the wearer is in a static standing state, and the static standing state is the initial state of the prosthetic knee joint, at which time the terrain detection is started.

4. The control method according to claim 3, characterized by, According to different distance characteristics of the terrain in front of the wearer, the terrain type is divided into three types, i.e. flat terrain, high terrain and low terrain.

5. The control method according to claim 4, characterized by The terrain types are respectively: when the wearer is in a static standing state, if the distance is greater than a threshold , then the front terrain is low terrain; if the distance is less than a threshold , then the front terrain is high terrain; if the distance is between intervals , , then the front terrain is low flat terrain; The high terrain represents that the terrain in front will have uphill, stair-climbing or obstacle-clearing motion requiring joint active torque; The low terrain represents that the terrain in front will have downhill or stair-descending motion requiring energy absorption of the joint; Flat terrain represents the front will be walking, standing movement.

6. The control method according to claim 1, characterized by The adaptive damping mode includes that when the wearer is in the flat terrain, the prosthetic knee joint automatically adjusts the damping of joint flexion according to the result of gait detection; In the heel-strike gait phase, the flexion damping of the joint is high damping; In the stance extension gait phase, the flexion damping of the joint is medium damping; in the toe-off gait phase, the flexion damping of the joint is low damping; in the swing flexion gait phase, the flexion damping of the joint is low damping; In the swing extension gait phase, the flexion damping of the joint is medium damping; in the static standing state, the flexion damping of the joint is high damping, at this time, the terrain detection is started; if the wearer stays in a certain gait phase, the damping state of the joint remains unchanged until the gait change is detected.

7. The control method according to claim 1, characterized by The energy recovery module includes a transmission system, a motor and a rectification and voltage boosting circuit; when the prosthetic knee joint is in the active mode, the energy recovery mode is closed, at this time, the motor transmits the torque to the joint through the transmission system, provides the active torque for the prosthetic knee joint in the high terrain environment in the front, realizes the active flexion and extension of the knee joint; When in the passive mode, the energy recovery mode is started, the knee joint drives the motor to generate electricity when flexing and extending through the transmission system, and then stores the electric energy through rectification and voltage boosting.

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