CN111805511B - Lower limb exoskeleton system with actively adjustable leg rod length and control method thereof - Google Patents

Lower limb exoskeleton system with actively adjustable leg rod length and control method thereof Download PDF

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CN111805511B
CN111805511B CN202010445635.8A CN202010445635A CN111805511B CN 111805511 B CN111805511 B CN 111805511B CN 202010445635 A CN202010445635 A CN 202010445635A CN 111805511 B CN111805511 B CN 111805511B
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rod
unit
leg
thigh
phase
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CN111805511A (en
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杨巍
徐铃辉
曹斌
彭桢哲
杨灿军
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Zhejiang University ZJU
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Zhejiang University ZJU
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
    • B25J—MANIPULATORS; CHAMBERS PROVIDED WITH MANIPULATION DEVICES
    • B25J9/00—Programme-controlled manipulators
    • B25J9/0006—Exoskeletons, i.e. resembling a human figure
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61H—PHYSICAL THERAPY APPARATUS, e.g. DEVICES FOR LOCATING OR STIMULATING REFLEX POINTS IN THE BODY; ARTIFICIAL RESPIRATION; MASSAGE; BATHING DEVICES FOR SPECIAL THERAPEUTIC OR HYGIENIC PURPOSES OR SPECIFIC PARTS OF THE BODY
    • A61H1/00—Apparatus for passive exercising; Vibrating apparatus ; Chiropractic devices, e.g. body impacting devices, external devices for briefly extending or aligning unbroken bones
    • A61H1/02—Stretching or bending or torsioning apparatus for exercising
    • A61H1/0237—Stretching or bending or torsioning apparatus for exercising for the lower limbs
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61H—PHYSICAL THERAPY APPARATUS, e.g. DEVICES FOR LOCATING OR STIMULATING REFLEX POINTS IN THE BODY; ARTIFICIAL RESPIRATION; MASSAGE; BATHING DEVICES FOR SPECIAL THERAPEUTIC OR HYGIENIC PURPOSES OR SPECIFIC PARTS OF THE BODY
    • A61H3/00—Appliances for aiding patients or disabled persons to walk about
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
    • B25J—MANIPULATORS; CHAMBERS PROVIDED WITH MANIPULATION DEVICES
    • B25J17/00—Joints
    • B25J17/02—Wrist joints
    • B25J17/0258—Two-dimensional joints
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
    • B25J—MANIPULATORS; CHAMBERS PROVIDED WITH MANIPULATION DEVICES
    • B25J9/00—Programme-controlled manipulators
    • B25J9/16—Programme controls
    • B25J9/1656—Programme controls characterised by programming, planning systems for manipulators
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61H—PHYSICAL THERAPY APPARATUS, e.g. DEVICES FOR LOCATING OR STIMULATING REFLEX POINTS IN THE BODY; ARTIFICIAL RESPIRATION; MASSAGE; BATHING DEVICES FOR SPECIAL THERAPEUTIC OR HYGIENIC PURPOSES OR SPECIFIC PARTS OF THE BODY
    • A61H3/00—Appliances for aiding patients or disabled persons to walk about
    • A61H2003/005—Appliances for aiding patients or disabled persons to walk about with knee, leg or stump rests
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61H—PHYSICAL THERAPY APPARATUS, e.g. DEVICES FOR LOCATING OR STIMULATING REFLEX POINTS IN THE BODY; ARTIFICIAL RESPIRATION; MASSAGE; BATHING DEVICES FOR SPECIAL THERAPEUTIC OR HYGIENIC PURPOSES OR SPECIFIC PARTS OF THE BODY
    • A61H2201/00—Characteristics of apparatus not provided for in the preceding codes
    • A61H2201/01—Constructive details
    • A61H2201/0192—Specific means for adjusting dimensions

Abstract

The invention relates to a lower limb exoskeleton system with actively adjustable leg rod length and a control method thereof, belonging to the technical field of wearable robots. The control method comprises the step of controlling the thigh rod unit and the shank rod unit to adjust the length of a leg rod of the thigh rod unit and the shank rod unit according to parameter detection data which indicate that the lower limb exoskeleton system is in an action state, so as to compensate position deviation between the joint rotation center position of the lower limb exoskeleton system and the lower limb joint rotation center position of a wearer. The control method can effectively improve the wearing comfort and the use safety, and can be widely applied to the rehabilitation training of patients with weakness of lower limbs or hemiplegia or the assistance of walking of old people.

Description

Lower limb exoskeleton system with actively adjustable leg rod length and control method thereof
Technical Field
The invention relates to a wearable robot and the field thereof, in particular to a lower limb exoskeleton system with actively adjustable leg and rod length and a control method thereof.
Background
With the aging of the population, the number of stroke patients is increased; in addition, as the spinal cord injuries caused by traffic accidents, sports injuries and other injury factors are in a growing trend, the early rehabilitation training treatment of patients is more and more emphasized, and the main stream is that the plasticity of the central nervous system is utilized, the motor training enables the affected side to generate corresponding reactions, the muscle tension is improved, and a new combination relationship of the nervous system is established. However, the manual rehabilitation training of the patient by means of the experience of the physical therapist is not only inefficient, but also has unsatisfactory effect. The lower limb exoskeleton robot rehabilitation training system can effectively replace heavy manual training work of a physical therapist. Meanwhile, aiming at the paraplegic patient, the lower limb exoskeleton can be used as a compensation tool to assist the patient to stand up again for walking, so that the occurrence of diseases such as osteoporosis, pressure sores and the like can be effectively reduced.
The lower extremity exoskeleton generally includes, in order from top to bottom, a waist wearing unit, a hip joint unit, a thigh rod unit, a knee joint unit, a shank rod unit, an ankle joint unit, and a sole unit, which are connected to each other, as disclosed in patent document No. CN 208989576U. The lower limb exoskeleton with the structure exists in the using process, and generally, the exoskeleton with one specification can only be adapted to the same wearer, so that the using cost is high.
In order to solve the problems, a bionic design lower limb rehabilitation training exoskeleton is disclosed in patent document with publication number CN103932870A, a continuous manual adjusting mechanism of exoskeleton leg rods is invented by combining segmented adjustment and short-distance continuous adjustment, and the specific scheme is that a principle similar to a jack is adopted, the distance between an upper connecting rod and a lower connecting rod can be continuously adjusted when a middle screw is adjusted, and the exoskeleton leg rods can be continuously and manually adjusted in the whole segment by combining with the segmented adjusting mechanism. Since manual adjustment is required, there is a problem that adjustment efficiency is low, and therefore, in some designs, the adjustment mechanism is set as an active adjustment mechanism.
The leg rods and the shank rods are arranged to be of a length-adjustable structure, so that the adaptation range of the lower limb exoskeleton to the height of a wearer can be effectively enlarged, and the cost is effectively reduced; however, the physiological joints of the human body are complex, the designed joints of the exoskeleton are generally similar to hinge joints, and most exoskeleton designs approximate the flexion/extension of hip joints and knee joints to hinge joints with single-degree-of-freedom fixed-axis rotation, so that in the walking process of wearing the exoskeleton on the human body, the relative motion between legs and legs of the exoskeleton is caused by the difference of the motion mechanisms of the joints of the human body and the exoskeleton, and in the walking process, the problem that the central positions of the joints are not matched exists, in the wearing and walking processes, the position deviation between the joints of the skeleton and the joints of the human body can reach the magnitude of 10 mm, because of being relatively small, in the design of the existing exoskeleton, the skin tissue softness of the human body is considered and is ignored, but in the actual use process, because of tight binding between a binding band and the legs, the difference of the small displacement can bring large interference force, the long-term reciprocating can cause injury to soft tissues of joints of lower limbs of a human body, particularly the physical sensation ability of the limbs of a patient with lower limb paralysis is weak, and the negative effects are difficult to feel at ordinary times and have large negative effects.
In addition, in the process of assisting the wearer in moving by the exoskeleton system, the time for driving the thigh rod to swing is judged based on the detection data of the pose detection sensor fixed on the thigh rod, but in the use process, misjudgment is easily caused due to the influence of signal noise of the sensor, so that the walking aid is not coordinated with the movement of the human body.
Aiming at the problem of uncoordinated motion, the current solution is to predict a quasi-periodic gait track by collecting human muscle electric signals and combining an adaptive oscillator algorithm to realize accurate assistance of a robot to hip joints of a human body; although the method can eliminate the assistance delay through prediction, certain requirements are imposed on the walking periodicity, and when a wearer frequently changes the walking rhythm, the coordination is influenced by the disorder of the assistance time due to the inaccurate prediction. Or the corresponding gait phase of the human body in each walking cycle is accurately identified through the phase angle oscillator, so that the accurate power-assisted control of the corresponding gait phase is realized, but the power-assisted value in the current state can be obtained through calculation after the joint angle is detected through the attitude sensor, the prediction function is not provided, and the power-assisted value is still influenced by time delay and has hysteresis.
Disclosure of Invention
The invention mainly aims to provide a control method of a lower limb exoskeleton system with actively adjustable leg rod length, which can effectively improve the wearing comfort and the use safety;
another object of the present invention is to provide a lower extremity exoskeleton system with actively adjustable leg bar length, which can effectively improve the wearing comfort and the use safety;
the invention further aims to provide a control method of the lower limb exoskeleton system with the actively adjustable leg rod length, so that the wearing comfort can be improved while the output assistance can be controlled according to the walking rhythm change condition of a wearer.
In order to achieve the main purpose, the invention provides a control method of a lower limb exoskeleton system with actively adjustable leg length, wherein the lower limb exoskeleton system sequentially comprises a waist wearing unit, a hip joint unit, a thigh rod unit, a knee joint unit, a shank rod unit, an ankle joint unit and a foot bottom unit which are connected with each other from top to bottom, and the rod lengths of the thigh rod unit and the shank rod unit are both actively adjustable; the control method comprises the following steps:
and adjusting and compensating, namely controlling the thigh rod unit and the shank rod unit to adjust the length of the shank rod of the thigh rod unit and the shank rod unit according to the parameter detection data which indicate that the lower limb exoskeleton system is in the action state, so as to compensate the position deviation between the joint rotation center position of the lower limb exoskeleton system and the lower limb joint rotation center position of a wearer.
In the technical scheme, the length of the thigh rod and the length of the shank rod are controlled to be matched and adjusted through representing parameter detection data of the exoskeleton system in an action state, so that the deviation of the position of the joint rotation center is compensated, the position of the joint rotation center of the lower limb exoskeleton system and the position of the joint rotation of a wearer are reduced to be below a preset threshold value in the processes of sitting down, standing up and walking, and the wearing comfort is improved, and the use safety is improved.
The specific scheme is that the step of adjusting and compensating comprises the following steps:
an acquisition step, wherein detection data used for representing the position deviation between the joint position of the lower limb exoskeleton system and the lower limb joint of a wearer are acquired;
an adjusting step, when the detected data represents that the position deviation exceeds a first deviation threshold value, controlling the thigh rod unit and the shank rod unit to adjust the length of the shank rod of the thigh rod unit and the shank rod unit until the position deviation is smaller than a second deviation threshold value; the second deviation threshold is less than or equal to the first deviation threshold.
More specifically, the detection data is the tension detection data of a tension sensor at a bandage fixedly arranged on the leg rod, and the step of adjusting the length of the leg rod comprises the following steps:
when the tension detection value is larger than a first tension threshold value, the length of a leg rod for fixing the binding band is shortened until the tension detection value is smaller than a second tension threshold value; the second tension threshold value is less than or equal to the first tension threshold value;
when the tension detection value is smaller than a third tension threshold value, the length of a leg rod for fixing the binding band is extended until the tension detection value is larger than a fourth tension threshold value; the fourth pulling force threshold value is greater than or equal to the third pulling force threshold value, and the third pulling force threshold value is less than or equal to the first pulling force threshold value.
This technical scheme uses the bandage pulling force as the judgement benchmark, and not only the judgement process is simple, and more can press close to its safety in utilization benchmark.
The further scheme is that the second pulling force threshold value is smaller than the first pulling force threshold value, the fourth pulling force threshold value is larger than the third pulling force threshold value, and the third pulling force threshold value is smaller than the first pulling force threshold value.
Preferably, the second deviation threshold is smaller than the first deviation threshold.
Another specific solution is that the step of adjusting the compensation comprises the following steps:
an acquisition step, namely acquiring joint angle data of a lower limb skeleton system;
calculating target leg rod lengths of the thigh rod unit and the shank rod unit based on joint angle data according to a preset calculation model;
and an adjusting step of adjusting the leg rod length of the thigh rod unit and the leg rod unit based on the calculated target leg rod length.
The technical scheme has the advantages of simple condition detection mode, convenient calculation and high effectiveness.
The specific scheme is that the calculation model is a cubic spline fitting calculation model represented by the following formula:
Figure GDA0003090269370000051
Figure GDA0003090269370000052
wherein Hhip(. alpha.) and Hknee(β) The target leg rod lengths of the exoskeleton thigh rod and the exoskeleton shank rod are respectively, alpha and beta are angles of hip joints and knee joints of lower limbs respectively, and a and b are length calculation coefficients of the thigh rod and the shank rod respectively.
The preferred solution is that in the thigh bar unit and the shank bar unit: the leg rod units respectively comprise a leg rod inner rod and a leg rod outer rod which can relatively slide along the rod length direction, and a linear displacement output device for adjusting the axial position between the inner rod and the outer rod; the linear displacement output device comprises a screw rod fixedly connected with one of the leg rod inner rod and the leg rod outer rod, a screw rod nut screwed with the screw rod to form a ball screw rod nut mechanism, a rotary driving motor driving the screw rod nut to rotate through a synchronous belt speed reducing mechanism, and an encoder for detecting the rotation angle of the rotary driving motor; the screw rod nut is rotationally fixedly connected with the other one of the leg rod inner rod and the leg rod outer rod. In the using process of the technical scheme, the speed can be reduced based on the two stages formed by the ball screw nut mechanism and the synchronous belt, so that the length of each leg rod can be continuously and electrically adjusted, and self-locking can be formed, so that overlarge reverse load can not be brought to a driving motor when normal stress is ensured.
In order to achieve the other purpose, the lower limb exoskeleton system with actively adjustable leg length provided by the invention comprises a control unit, and a waist wearing unit, a hip joint unit, a thigh rod unit, a knee joint unit, a shank rod unit, an ankle joint unit and a sole unit which are sequentially connected, wherein the rod lengths of the thigh rod unit and the shank rod unit are actively adjustable; the control unit comprises a processor and a memory, and the memory stores a computer program; the computer program, when executed by a processor, is capable of implementing the steps of the control method described in any of the above-mentioned embodiments.
In order to achieve the above another object, the present invention provides a control method comprising the steps of:
a stage identification step, namely predicting the current walking phase by utilizing an adaptive oscillator algorithm based on pose detection information output by a pose detection sensor; if the difference between the predicted phase and the phase represented by the detection information is smaller than a preset threshold value, the phase is a stable phase, otherwise, the phase is a variable phase;
a change phase control step, when the walking rhythm is in a change phase, identifying a gait phase based on the phase angle oscillator, and calculating power-assisted data corresponding to the gait phase and output by the hip joint flexion/extension driving unit;
and a stationary phase control step, namely predicting a periodic gait track based on an adaptive oscillator algorithm when the walking rhythm is in a stationary phase, and calculating assistance data output by the hip joint flexion/extension driving unit by combining joint angle data output by a pose sensor distributed on a thigh rod.
According to the technical scheme, in the assisting control process of an exoskeleton, the characteristics of strong adaptability of a phase angle oscillator to gait change and accurate gait prediction of a self-adaptive oscillator are combined, a delaying effect is allowed when a walking rhythm frequently changes by adopting an assisting control method based on the phase angle oscillator, and a non-delaying assisting effect is realized by accurately predicting the gait when the walking rhythm is stable by adopting an assisting control method based on the self-adaptive oscillator, so that the output assisting effect can be better controlled according to the walking rhythm change condition of a wearer.
Drawings
Fig. 1 is a front view of a lower extremity exoskeleton system in accordance with embodiment 1 of the present invention;
FIG. 2 is a schematic structural view of a leg bar length adjusting unit in embodiment 1 of the present invention;
FIG. 3 is a front view of the lower extremity exoskeleton system of embodiment 1 of the present invention in a sitting position;
FIG. 4 is a schematic diagram of the process of the lower extremity exoskeleton system of embodiment 1 of the present invention from a sitting position to a standing position;
fig. 5 is a flowchart illustrating a method for controlling the lower extremity exoskeleton system according to embodiment 3 of the present invention.
Detailed Description
The invention is further illustrated by the following examples and figures.
Example 1
Referring to fig. 1 to 4, the lower extremity exoskeleton system of the present invention comprises a control unit, a detection unit and an exoskeleton 1. The control unit comprises a processor and a memory, and the detection unit outputs detection signals to the control unit; the control unit outputs control signals to the driving mechanisms of the exoskeleton to drive the exoskeleton to walk according to the preset track.
The exoskeleton 1 comprises a waist wearing unit 11, a hip joint unit 12, thigh rods 13, thigh straps 14, a knee joint unit 15, calf straps 16, calf rods 17, an ankle joint unit 18 and a flexible sole unit 19. The waist wearing unit 11 is used for fixing the exoskeleton system with the waist of the human body; the thigh rod 13 is used for driving the thigh of the human body to move, and forms a thigh rod unit with actively adjustable leg rod length in the embodiment together with the thigh bandage 14 and the leg rod length adjusting mechanism 10; the shank 17 is used for driving the shank of the human body to move, and forms a shank unit with actively adjustable shank length in the embodiment together with the shank binding band 16 and the shank length adjusting mechanism 10. The binding bands are used for connecting the leg rods and the legs of the person, so that the leg rods can drive the legs of the person to move according to a preset track; the flexible sole unit is engaged with the foot of the person so that movement of the ankle unit 18 relative to the shank 17 drives the sole of the foot to move relative to the calf. Among them, the hip joint unit 12 includes a link arm 123, a hip-joint adduction/abduction joint mechanism 121 for connecting an inner end of the link arm 123 to the back frame 110 of the lumbar wearing unit 11, and a hip-joint flexion/extension driving unit 122 for connecting the thigh link 13 to an outer end of the link arm 123.
As shown in fig. 2, in order to adjust the length of the leg rod, the thigh rod and the shank rod are both provided to include an inner leg rod 21 and an outer leg rod 22 which can relatively slide along the rod length direction, the leg rod length adjusting mechanism is a linear displacement output device for adjusting the axial position between the inner rod and the outer rod, and specifically includes a lead screw 31 fixedly connected with the outer leg rod 22, a lead screw nut 32 screwed with the lead screw 31 to form a ball lead screw nut mechanism, a rotary driving motor 34 for driving the lead screw nut 32 to rotate through a synchronous belt speed reducing mechanism 33, and an encoder for detecting the rotation angle of the rotary driving motor 34; the feed screw nut 32 is rotatably fixed to the leg inside lever 21.
In use, the method for controlling the lower extremity exoskeleton system comprises the steps of obtaining S11 and adjusting S12, wherein when the computer program stored in the memory is executed by the processor, the two steps can be implemented as follows:
an acquisition step S11 acquires detection data indicative of positional deviations between joint positions of the lower extremity exoskeleton system and lower extremity joints of the wearer.
In the step, the position deviation between the rotation center positions of the two joints is judged by judging whether the tension of the binding band is outside a preset interval, so that the actual situation can be better approached, and the adaptability is wide; detecting the change of the pulling pressure along the length direction of the leg rod by adopting a force sensor arranged at the position of the binding band, and correspondingly adjusting the length of the corresponding leg rod when a threshold value is exceeded so as to reduce the pulling pressure value; the method avoids the establishment of a fitting calculation model in the early stage, and has better adaptability to different habits of human body differentiation such as walking, sitting and standing.
An adjusting step S12, when the detected data indicate that the position deviation of the two joint rotation centers exceeds a first deviation threshold value, controlling the thigh rod unit and the shank rod unit to adjust the leg rod length until the position deviation is less than a second deviation threshold value; wherein the second deviation threshold is less than or equal to the first deviation threshold.
In the step, the deviation threshold value is a tension threshold value of a tension sensor on the binding band, and the specific judgment process is that when the tension detection value is greater than a first tension threshold value, the length of a leg rod for fixing the binding band is shortened until the tension detection value is smaller than a second tension threshold value; when the tension detection value is smaller than a third tension threshold value, the length of the leg rod for fixing the binding band is extended until the tension detection value is larger than a fourth tension threshold value; the fourth pulling force threshold value is greater than or equal to the third pulling force threshold value, and the third pulling force threshold value is less than or equal to the first pulling force threshold value. The specific setting of the tension threshold is set according to the actual use object and the lower limb exoskeleton structure, and usually the second tension threshold is required to be smaller than the first tension threshold, the fourth tension threshold is larger than the third tension threshold, the third tension threshold is smaller than the first tension threshold, and the second deviation threshold is smaller than the first deviation threshold.
In this embodiment, the tension threshold settings of a plurality of users are stored, and when the identity information of the corresponding user is detected, the adjustment step is controlled by using the threshold settings adapted to the user, for example, identification based on identification technologies such as card swiping identification and fingerprint identification.
In the control process, the compensation adjustment of the joint rotation center position in the two action stages of the process of switching from the position between the standing position and the sitting position and the process of walking is mainly included.
The position switching process between the standing pose and the sitting posture is generally a process of wearing the exoskeleton by a human body, the exoskeleton is worn by the human body under the sitting posture in the walking process of wearing the exoskeleton by the human body, and in the standing process after binding the binding bands, the binding bands of all parts can deviate from the limbs of the human body to cause discomfort to the human body; for example, in the process from a sitting posture to a standing posture, the thigh of a human body can move downwards relative to the thigh binding belt, the length of the thigh rod needs to be controlled to be adjusted at the moment, the length of the thigh rod is ensured to be lengthened, the binding belt moves downwards to compensate the downward movement distance of the thigh of the human body, and the binding belt is still fixedly connected with the limb at the same binding position after the human body is in the sitting posture to the standing posture.
In the walking process of a wearer, the physiological joint rotation center can move regularly along with the change of the angle of each joint, and the length of the leg rods at different joint angles can be adjusted by controlling the positions of the driving motors of the leg rod length adjusting modules; for example, in the process of knee joint flexion, as the flexion angle increases, the knee joint rotation center shifts, so that the distance between the exoskeleton lower leg strap and the exoskeleton knee joint rotating shaft needs to be lengthened, and at the moment, the length of the lower leg rod can be electrically adjusted to realize the dynamic joint rotating shaft matching at the position.
In the process of adjusting the length of each leg rod, the motor of the belt encoder is adopted for driving, and the continuous electric adjustment of the length of each leg rod is realized by matching with the two-stage speed reduction consisting of the synchronous belt and the ball screw. The secondary speed reducing mechanism has a self-locking function so as to ensure that overlarge reverse load is not brought to the driving motor when the driving motor is normally stressed. The quantitative relational expression of the motor corner and the leg rod length can be obtained through the reduction ratio calculation of the secondary speed reducer, therefore, in the actual control process, the expected value of the leg rod length is obtained through calculation, then the motor control position value is obtained through reverse calculation, the position of the motor is controlled, and the actual operation position of the motor is detected through an encoder.
Example 2
As an explanation of embodiment 2 of the present invention, only differences from embodiment 1 will be explained below.
In this embodiment, the control method includes an obtaining step S21, a calculating step S22, and an adjusting step S23, and the specific process is as follows:
in the acquisition step S21, joint angle data of the lower limb skeletal system is acquired.
In the calculation step S22, the target leg rod lengths of the thigh rod unit and the shank rod unit are calculated based on the joint angle data based on the preset calculation model.
In this step, the calculation model is a cubic spline fitting calculation model represented by the following formula based on the relationship between the existing leg length and the joint angle:
Figure GDA0003090269370000121
Figure GDA0003090269370000122
wherein Hhip(. alpha.) and Hknee(beta) is the target leg rod length of the exoskeleton thigh rod and the exoskeleton shank rod respectively, alpha and beta are the angles of the hip joint and the knee joint of the lower limb respectively, and a and b are the length calculation coefficients of the thigh rod and the shank rod respectively.
In the adjustment step S23, the thigh lever unit and the shank lever unit are controlled to adjust the leg lever lengths thereof based on the calculated target leg lever length.
Example 3
As an explanation of embodiment 3 of the present invention, only differences from embodiment 1 will be explained below.
In the control methods of the two embodiments, the thigh rod unit and the shank rod unit are controlled to adjust the leg rod length thereof according to parameter detection data, such as bandage tension detection data and joint angle data, which are used for representing the action state of the lower limb exoskeleton system, so as to compensate the position deviation between the joint rotation center position of the lower limb exoskeleton system and the lower limb joint rotation center position of a wearer; in the embodiment, during the use of the lower limb exoskeleton system, the length of the leg rod is not only properly adjusted, but also the leg rod swing state of the hip joint unit controller is controlled based on the deformation condition of the walking rhythm during the exercise.
As shown in fig. 5, the control method includes the steps of:
a stage identification step S31 of predicting the current walking phase by using an adaptive oscillator algorithm based on the pose detection information output by the pose detection sensor; if the difference between the predicted phase and the phase represented by the detection information is smaller than a preset threshold value, the phase is a stable phase, otherwise, the phase is a variable phase.
The change phase in which the walking tempo changes frequently is generally the walking speed switching transition phase, and in the present embodiment, it is judged that the posture detection data is acquired based on the posture sensor fixed to the thigh lever.
In the change phase control step S32, when the walking rhythm is in the change phase, the gait phase is identified based on the phase angle oscillator, and the assist data corresponding to the gait phase output by the hip flexion/extension drive unit is calculated.
In the variation phase, the power assistance data is calculated by adopting a phase angle power assistance method, the power assistance data is the moment tau, and the calculation is specifically carried out according to the following formula.
τ＝c sinφ+d cosφ
Where φ is the predicted phase angle.
And a stationary phase control step S33, when the walking rhythm is in a stationary phase, predicting a periodic gait trajectory based on an adaptive oscillator algorithm, and calculating assistance data output by the hip joint flexion/extension driving unit by combining joint angle data output by a pose sensor arranged on a thigh rod.
In the stationary stage, the error angle boosting method is adopted to calculate the boosting data, namely the moment tau, and specifically, the calculation is carried out according to the following formula.
τ＝k·θerror
Wherein, thetaerrorIs the angle error between the predicted angle and the actual measured angle, and k is the calculated ratio.
Other calculation methods in the prior art can be adopted for the specific calculation method of the stationary phase and the changing phase, and are not limited to the two methods.
The power-assisted control based on the Phase Oscillator (PO) has strong adaptability to the changing gait, but has delay lag, the method is used for the power-assisted control of the walking aid in the walking rhythm changing stage, the power-assisted opportunity is ensured not to be disordered under the condition of sacrificing the delay, and certain coordination is ensured; the power-assisted control based on the Adaptive Oscillators (AOs) is accurate when the walking rhythm changes little and the periodicity is strong, and the method can eliminate the lag feeling caused by time delay, ensure the accurate walking power-assisted time and enhance the coordination.
The calculation formula of the phase angle is
Figure GDA0003090269370000141
The phase angle phi of the walking-aid robot worn by the human body oscillates periodically in the walking process; the variation trend is that even if the walking rhythm is changed, the phase angle is still kept unchanged; therefore, the gait cycle at the current moment can be accurately acquired based on the phase angle oscillator PO, and the power-assisted driving torque is correspondingly given. However, because the gait track, namely the flexion/extension angle value of the hip joint of the human body, cannot be predicted, the assistance delay exists, namely, the assistance is delayed for a certain time from the gesture signal acquisition moment when the assistance is realized at the joint end.
And gait prediction can be achieved by means of the adaptive oscillator AOs. The bending/stretching angle data of the hip joint of the human body walking is used as input, the variation rule of the input angle can be learned through an AOs dynamic system, and an angle learning predicted value is obtained. When the similar period is stable to walk, the AOs dynamic system is accurate to the angle predicted value, and can use the predicted value to judge the corresponding gait period, thereby controlling the walking aid to provide corresponding assistance value. The method is characterized in that the angle value is predicted by fixing the delay time in advance, the power value sent to the motor controller is the value after the fixed delay, and the power value realized at the joint end is just the power value really needed after the fixed delay, so that the lag feeling generated by the delay is avoided.
In the use process, when a human body walks, the posture sensor arranged at the thigh rod detects the bending/extending angle and the angular speed data of the hip joint, so that the motor torque control information is sent to the motor controller through the power assisting control algorithm based on the mixture of PO and AOs, the swing of the hip joint is controlled, and the power assisting is transmitted to the thigh of the human body through the thigh strap of the walking aid to assist the walking of the human body.
In the using process of the control method, the length adjustment of each leg rod of the exoskeleton is controlled on line, so that the rotation center of the exoskeleton can be well matched with the corresponding joint of a human body in each stage, and the auxiliary force is transmitted between the exoskeleton binding band and the limb of the human body at a normal and reasonable fixed matching position.

Claims (4)

1. A control method of a lower limb exoskeleton system with actively adjustable leg and rod length is characterized in that the control method comprises the following steps that from top to bottom, the lower limb exoskeleton system sequentially comprises a waist wearing unit, a hip joint unit, a thigh rod unit, a knee joint unit, a shank rod unit, an ankle joint unit and a sole unit which are connected with one another, and the rod lengths of the thigh rod unit and the shank rod unit are actively adjustable:
adjusting and compensating, namely controlling the thigh rod unit and the shank rod unit to adjust the length of a leg rod of the thigh rod unit and the shank rod unit according to parameter detection data for representing that the lower limb exoskeleton system is in an action state, so as to compensate position deviation between the joint rotation center position of the lower limb exoskeleton system and the lower limb joint rotation center position of a wearer;
the adjusting and compensating step comprises the following steps:
an acquisition step, wherein joint angle data of the lower limb exoskeleton system are acquired;
a calculation step of calculating target leg rod lengths of the thigh rod unit and the shank rod unit based on the joint angle data according to a preset calculation model;
an adjustment step of controlling the thigh bar unit and the shank bar unit to adjust the leg bar lengths thereof based on the calculated target leg bar length;
the calculation model is a cubic spline fitting calculation model represented by the following formula:
Figure FDA0003090269360000011
Figure FDA0003090269360000021
wherein Hhip(. alpha.) and Hknee(beta) is the target leg rod length of the exoskeleton thigh rod and the exoskeleton shank rod respectively, alpha and beta are the angles of the hip joint and the knee joint of the lower limb respectively, and a and b are the length calculation coefficients of the thigh rod and the shank rod respectively.
2. The control method according to claim 1, wherein, in the thigh bar unit and the shank bar unit:
the leg rod units respectively comprise a leg rod inner rod and a leg rod outer rod which can relatively slide along the rod length direction, and a linear displacement output device for adjusting the axial position between the inner rod and the outer rod;
the linear displacement output device comprises a screw rod fixedly connected with one of the leg rod inner rod and the leg rod outer rod, a screw nut screwed with the screw rod to form a ball screw nut mechanism, a rotary driving motor driving the screw nut to rotate through a synchronous belt speed reducing mechanism, and an encoder for detecting the rotation angle of the rotary driving motor; the screw rod nut is rotationally fixedly connected with the other one of the leg rod inner rod and the leg rod outer rod.
3. Control method according to claim 1 or 2, characterized in that it comprises, during walking, the steps of:
a stage identification step, namely predicting the current walking phase by utilizing an adaptive oscillator algorithm based on pose detection information output by a pose detection sensor; if the difference between the predicted phase and the phase represented by the detection information is smaller than a preset threshold value, the phase is a stable phase, otherwise, the phase is a variable phase;
a change phase control step, when the walking rhythm is in a change phase, identifying a gait phase based on the phase angle oscillator, and calculating power-assisted data corresponding to the gait phase and output by the hip joint flexion/extension driving unit;
and a stationary phase control step, namely predicting a periodic gait track based on an adaptive oscillator algorithm when the walking rhythm is in a stationary phase, and calculating assistance data output by the hip joint flexion/extension driving unit by combining joint angle data output by a pose sensor distributed on a thigh rod.
4. A lower limb exoskeleton system with actively adjustable leg and rod length comprises a control unit, and a waist wearing unit, a hip joint unit, a thigh rod unit, a knee joint unit, a shank rod unit, an ankle joint unit and a foot bottom unit which are sequentially connected, wherein the rod length of the thigh rod unit and the shank rod unit is actively adjustable; the control unit comprises a processor and a memory, the memory stores a computer program, and the control unit is characterized in that:
the computer program, when being executed by the processor, is adapted to carry out the steps of the control method of any one of claims 1 to 3.
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