WO2018081986A1 - Wearable device and real-time step length measurement method for device - Google Patents

Abstract

A wearable device and a real-time step length measurement method for the device. A two-dimensional gait of a lower limb when a user walks and step length information of each step can be measured and outputted in real time, and the device and the method can be applied to detection of a gait asymmetry degree of the user. By using angular velocity and acceleration real-time data collected by four inertial sensor units, the lower-limb gesture and the step length of the user are computed and outputted by means of a geometric algorithm. The device is convenient to use, is not limited by sites, has low costs, can highly-accurately output the lower-limb gesture and the step length of the user in real time, and has high reliability and good promotion prospects.

Description

Wearable device and real-time step size measuring method therefor Technical field

The invention belongs to the field of wearable sensors, and in particular relates to a wearable device and a real-time step measurement method for the same.

Background technique

Gait parameters are physical parameters during human walking, which can reflect human exercise ability and have great application value. Therefore, many researchers are currently studying the measurement of gait parameters. Wearable sensors include inertial measurement units, ultrasonic sensors, miniature cameras, etc., compared to large laboratory equipment that measure gait parameters such as optical motion capture systems, force gauges, etc., which are small, inexpensive, and free of time. The advantages of space limitation and easy promotion are widely used in the field of gait parameter measurement. At present, there are many studies using wearable sensors placed on the legs, waist, wrists, chest, etc. to measure gait time parameters, such as gait events, gait cycles, etc.; some also measure gait space parameters, such as walking speed. , step and so on. For example, the invention patent No. CN201510887154.1 discloses an indoor positioning step calculation method, which places the inertial measurement unit at the waist of the person, and the person obtains the inertial sensor data of the person during the indoor walking process, and then calculates the step size. The invention patent of the application No. CN 201310007945.1 discloses a step calculation method and device for acquiring the acceleration values of the respective axes in the three-dimensional coordinate system; calculating the step compensation coefficient according to the acceleration values of the respective axes; The long compensation factor and the preset preset step size determine the final step size of the carrier's movement amplitude. However, in the actual use of the above methods, there are defects such as low gait measurement accuracy and inability to measure single step in real time.

The determination of real-time step size is of great significance. There are many studies that use wearable sensors to measure spatial parameters such as pace and stride, which are more mature, but there are not many studies on measurement steps. Some diseases such as Parkinson's syndrome can reduce the body's ability to exercise, and the pace and stride length are reduced. Therefore, the step and pace can be used to reflect the lower limbs' ability to move. However, the step and pace cannot reflect the difference in the ability of the two sides of the human body caused by hemiplegia, that is, the gait is not correct, and we can quantify the asymmetry of the gait on both sides of the human body according to the ratio of the two-leg steps, and The length can also be used to find parameters such as step size and pace, so the step size has greater clinical application value. In addition, the real-time step size can reflect the user's real-time displacement information, matching the user's real-time lower limbs. The posture information can be used for mechanical devices related to lower limb movement such as a biped robot, a lower limb assisted rehabilitation device, and the like. The use of wearable sensors to calculate step sizes has a wide range of applications. Therefore, it is necessary to propose a step size measurement method that takes into consideration the measurement accuracy and performs the measurement.

Summary of the invention

The object of the present invention is to solve the defects in the prior art that the gait measurement accuracy is low, the single step size cannot be measured in real time, and the wearable device and the real-time step measurement method for the device are provided.

Some of the nouns involved in the present invention have the following meanings:

The step distance refers to the distance between the places where the same foot is adjacent during the walking of the person, and the step size refers to the distance between the adjacent places of the feet during the walking of the person. In general, the step size is equal to the sum of the two leg steps.

Gait events refer to important moments in each gait cycle of a person during walking. There are five gait events in the middle of swing, straight legs, foot landing, middle stance, and foot off the ground. The walking gait cycle of a person is shown in Figure 4. Taking the right leg as an example, the left leg supports the human body, and the right leg takes the forward phase as the swinging phase of the right leg; when the right leg swings to the vicinity of the left leg, it swings. Mid-term; then the right leg kicks forward and straightens; then the right foot falls, the right leg begins to support the human body, the left leg takes the time forward, the right leg stands; the right leg rotates with the right ankle The center moves forward to reach a position close to the ground, at this time in the middle of the stance; then the right foot is off the ground and the right leg is taken forward to complete a gait cycle.

Gait events can be detected based on the angular velocity characteristics of the ipsilateral calf and thigh, as shown in Figure 5. The angular velocity of the calf usually has two relatively large peaks in one cycle, one high and one short, the higher peak corresponds to the middle of the swing, the shorter one corresponds to the middle of the middle; the middle of the swing has a small number of small negative peaks. In the area, this is the vibration caused by the landing of the foot. The first negative peak is the moment of the foot landing; between the middle of the swing and the moment of the foot landing, there is a thigh, calf angular velocity intersecting, at this moment for the leg straightening moment; After the middle of the next swing, there is a trough, which corresponds to the moment when the foot is off the ground. The standing phase starts from the landing of the leg and ends, and the end of the foot is off the ground. The approximate angle is the area where the angular velocity of the lower leg is negative. The swing phase starts from the leg and ends from the ground to the end of the foot landing. The approximate angular velocity of the lower leg is positive. The area of the value.

The real-time step size measurement refers to the step size of the step when the gait event of the forefoot landing is detected.

The sagittal plane and the plumb line are shown in Figure 1. The sagittal plane is perpendicular to the horizontal plane and divides the human body into two parts. The main movement occurs in the sagittal plane when walking. The plumb line is A line perpendicular to the ground.

In addition, for convenience of description, define the three-dimensional direction of the thigh and the calf, as shown in Figure 2: the X-axis is parallel to the calf or thigh; the Y-axis is in the sagittal plane, perpendicular to the calf or thigh; the Z-axis is perpendicular to the sagittal plane . Place The axis of the sensor on the thigh or calf should be consistent with the thigh or calf, but because the sagittal plane is invisible, the Y-axis and Z-axis shift will occur in the sensor, and the Y measured according to the sensor. The angular velocity of the axis and the Z-axis can roughly calculate the angle of the sagittal plane of the Y-axis of the sensor, and use this angle to calculate the acceleration and angular velocity of the corresponding axis of the thigh or the lower leg.

The thigh length of the human body is the vertical height from the hip joint to the knee joint when the human body stands still; the calf length is the vertical height of the knee joint to the ground at this time.

The present invention solves the technical problem, and the specific technical solutions adopted are as follows:

A real-time step size measurement method for a wearable device, including the following steps:

The Y-axis acceleration and the Z-axis angular velocity during the walking of the thighs and calves on both sides of the user are measured in real time, and the gait events during walking are determined in real time according to the Z-axis angular velocity; the thighs and the calves are determined in real time according to the gait events and the Z-axis angular velocity integrals. The angle between the sagittal plane and the plumb line; the real-time step size is calculated based on the angle and the length of the thigh and the calf. The calculation of the step size can be calculated based on the geometric relationship of the lower limbs during walking.

As a preferred mode, the wearable device includes a sensor for detecting triaxial acceleration and triaxial angular velocity of the left and right thighs and the left and right calves, and the Y-axis acceleration and the Z-axis angular velocity are obtained by a sensor.

In a preferred manner, the gait event includes landing of the foot, middle of standing, and straightening of the leg;

When detecting the middle of the left or right calf, calculate the angle between the lower leg and the vertical line (the following formula for calculating the left or right calf is not calculated at the same time, but is selected according to the current target to be tested. For example, when it is detected that the left lower leg is in the middle of standing, θ _lsms is calculated; when it is detected that the right lower leg is in the middle of standing, θ _rsms is calculated. The subsequent formula also uses the same method):

Where: θ _lsms and θ _rsms are the _angles of the left lower leg and the right lower leg in the middle of the standing with the plumb line, a _lsyms and a _rsyms are the Y-axis accelerations of the left lower leg and the right lower leg respectively; wherein θ _l0 , θ _r0 is the angle between the left calf and the right calf in the sagittal plane and the plumb line in the static standing state of the user (the standing state of the feet naturally standing), and satisfies:

Where: a _lsys and a _rsys are the Y-axis accelerations of the left calf and the right calf when the user is standing statically;

Before the next mid-station event is detected, the angle between the calf of the leg and the plumb line in the sagittal plane is calculated in real time by angular velocity integration:

Where: t is the time of the last standing middle distance from the left or lower calf at the current time, θ _ls (t), θ _rs (t) are the left calf and the right calf in the sagittal plane and plumb at time t The angle of the line, ω _lsz (δ), ω _rsz (δ) are the instantaneous Z-axis angular velocity of the left lower leg and the right lower leg respectively;

Thereby, the angle between the calfs on both sides in the sagittal plane and the plumb line can be obtained in real time.

When it is detected that the left leg or the right leg is straight, calculate the angle between the thigh of the leg and the plumb line in the sagittal plane:

θ _ltls =θ _lsls

θ _rtls = θ _rsls

_Where: θ ltls, θ _rtls respectively, left thigh, right thigh at the time the legs straight in the sagittal plane and the angle between the vertical _line, θ lsls, θ _rsls case were left leg, right leg in the sagittal The angle between the surface and the plumb line;

Before the next leg extension event is detected, the angle between the thigh of the leg and the plumb line in the sagittal plane is calculated in real time by angular velocity integration:

Where: t is the time after the last leg of the left thigh or right thigh is straightened, θ _lt (t), θ _rt (t) are the angles between the left thigh, the right thigh and the plumb line at time t, respectively , ω _ltz (δ), ω _rtz (δ) are the instantaneous Z-axis angular velocities of the left thigh and the right thigh, respectively;

Thereby, the angle between the thighs on both sides and the plumb line in the sagittal plane can be obtained in real time.

When it is detected that the left leg or the right leg is landing, calculate the step size of the leg at this time:

LSL=l ₁ (sinθ _rtic +sin(-θ _ltic ))+l ₂ (sinθ _rsic +sin(-θ _lsic ))

RSL=l ₁ (sin(-θ _rtic )+sinθ _ltic )+ ₂ (sin(-θ _rsic )+sinθ _lsic )

Where: θ _lsic , θ _rsic , θ _ltic , θ _rtic are the _angles of the left leg, the right leg, the left thigh, the right thigh and the plumb line at the time of landing of the leg, respectively, l ₁ and l ₂ are the thigh length, respectively. The calf is long, the LSL is the step length of the leg when the left leg is landing, and the RSL is the step length of the leg when the right leg is landing.

As a further preferred mode, before the step size is measured, the walking process within a certain distance of the target user is monitored in advance, and the angle of the actual direction of the sensor Y-axis from the sagittal plane is determined:

In the formula:

The angle at which the actual direction of the Y-axis of the sensor deviates from the sagittal plane,

The average value of the angular velocity of the Y-axis of the sensor during standing phase during the user's walking,

The average value of the Z-axis angular velocity of the sensor when the user is standing during walking;

During the measurement of the step size, the Y-axis acceleration and Z-axis angular velocity data of each sensor are corrected in advance before being substituted into the above formulas, as the acceleration or angular velocity of the corresponding direction of the lower leg or thigh, the correction formula is:

Where: a _{y is} the Y-axis acceleration measured by the sensor, a _{z is} the Z-axis acceleration measured by the sensor, a _yc is the Y-axis acceleration obtained by correcting the data of the sensor; ω _{y is} the Y-axis angular velocity measured by the sensor , ω _{z is} the Z-axis angular velocity measured by the sensor, and ω _zc is the Z-axis angular velocity obtained by correcting the data of the sensor.

Another object of the present invention is to provide a method for measuring gait asymmetry, which measures the real-time step size according to the above method, and then quantifies the gait asymmetry of the user with unilateral motion disorder, and the calculation formula is as follows:

Where: GA is gait asymmetry,

The average of the left leg step and the right leg step, respectively.

The step size of the leg on one side of the movement disorder.

It is still another object of the present invention to provide a wearable device that implements the real-time step size measuring method, including four inertial sensors and a host computer, each inertial sensor including a three-dimensional accelerometer and a three-dimensional angular velocity meter, an inertial sensor and an upper position The machine is connected for data transmission.

As a preferred mode, the inertial sensor is first connected to a single chip microcomputer, a single chip microcomputer and a bluetooth mode. Blocks are connected, and the upper computer and the Bluetooth module exchange data through Bluetooth.

As a preferred mode, a fixing strap for fixing the inertial sensor is also included.

As a preferred mode, the inertial sensor is an inertial sensor based on the MPU6050 chip.

As a preferred mode, the inertial sensor sampling frequency is not less than 100 Hz.

The technical features in each of the above preferred modes can be combined with each other without conflicting each other, and are not limited.

Compared with the prior art, the invention has the following beneficial effects:

1) The use of the present invention to calculate the posture and step size of the lower limbs is inexpensive, convenient, and free from site restrictions, and is easy to promote.

2) Using a method based on lower limb posture to calculate step size and quantify gait asymmetry, can adapt to a variety of pathological gait, has good application value and a wide range of applications.

3) The step size measurement by the wearable device can conveniently and effectively quantify the movement ability of the human body and their differences, and can be conveniently applied to the clinic.

4) The present invention can output the lower limb posture and the step size in real time, and can be used for real-time control of related devices.

DRAWINGS

Figure 1 is a schematic view showing a sagittal plane and a plumb line in the present invention;

2 is a schematic view showing the position of the sensor and the coordinate system of the lower leg and the thigh in the present invention;

Figure 3 is a structural diagram of a wearable real-time step size measuring system in the present invention;

Figure 4 is a schematic view showing the walking cycle of the human body in the present invention;

Figure 5 is a schematic diagram of gait event detection in the present invention;

FIG. 6 is a schematic view showing a two-dimensional geometric model of a double inverted pendulum of a lower limb in the present invention;

Figure 7 is a schematic view showing the mid-angle of the right lower leg swing in the present invention;

In the above figures 1, 2, and 7, P represents a plumb line, and S represents a sagittal plane (Sagittal Plane);

In the above figures 2 and 3, 1 to 4 are inertial sensor units placed on the left thigh, the left lower leg, the right thigh, and the right lower leg, respectively, and 5 is a host computer unit;

In Figures 4 and 5 above, A to E are gait events of the right leg in a gait cycle, where A is the mid-swing gait event, B is the leg extension gait event, and C is the foot landing gait event. D is the mid-term gait event, and E is the foot gait event.

detailed description

The invention will be further described below in conjunction with the drawings, as it is better understood. The technical features of the present invention can be combined with each other without conflicting each other, and are not limited.

The present invention uses a wearable device including four inertial measurement sensors and a geometry-based algorithm to calculate and output the lower limb posture and step size of the user while walking. The real-time step size measurement refers to the step size of the step when the gait event of the forefoot landing is detected. Taking a certain user as an example, the specific implementation process of the present invention is as follows:

(1) Preparation:

In this embodiment, the target user has a thigh length of 42 cm and a calf length of 53 cm, which is input into the upper computer of the wearable device, and then the user wears the wearable device.

The whole device structure is shown in Figure 3. It consists of four inertial sensor units and one upper unit. The specific models of the sensors and other electronic components in the present invention can be selected according to actual needs. Each of the four inertial sensor units includes an inertial measurement sensor module based on the MPU6050 chip. The module includes a three-dimensional accelerometer and a three-dimensional gyroscope for collecting three-dimensional acceleration and three-dimensional angular velocity data during the user's walking. The sampling frequency is 100Hz. The four sensor units are placed on the outside of the user's two thighs and two calves. Define the three-dimensional direction of the thigh and calf, as shown in Figure 2: the X-axis is parallel to the calf or thigh; the Y-axis is in the sagittal plane, perpendicular to the calf or thigh; the Z-axis is perpendicular to the sagittal plane. The axis of the sensor placed on the thigh or calf should be consistent with the thigh or calf to collect data for the corresponding axis. The sensor unit on the lower leg comprises an elastic fixing strap to the MPU6050 sensor module; the sensor unit on the thigh comprises a battery, a fixing strap, a single chip microcomputer, an MPU6050 sensor module and a Bluetooth transmission module. The fixing strap is used for fixing the sensor unit to the user's leg; the single-chip microcomputer in the thigh sensor unit is connected with each module in the unit, and is also connected with the MPU6050 sensor module in the same-side calf sensor unit through the wire for preliminary use. Processing data; the Bluetooth module is used for communication between the inertial sensor unit and the host unit. The upper unit structure includes a Bluetooth module, a single chip microcomputer, a button, a battery, and an OLED display. The single-chip microcomputer is used to process data; the button and the OLED display form an operation interface, which is convenient for the user to use.

Since the position where the sensor is placed usually does not reach the standard ideal state (the X axis is parallel to the calf or thigh; the Y axis is in the sagittal plane, perpendicular to the calf or thigh; the Z axis is perpendicular to the sagittal plane), the sensor detects Data needs to be dynamically corrected and statically calibrated before use. In order to reduce the sensor during walking For the error caused by the vibration, the modified Y-axis acceleration needs to be filtered by a low-pass filter with a cutoff frequency of 3.2 Hz for later use. Subsequent steps require stepwise calculation using the filtered Y-axis acceleration data of the sensor unit and the corrected Z-axis angular velocity data.

Dynamic correction is a constant correction of the Y- and Z-axis data of the sensors on the thigh or calf. When the user places the sensor, the X axis of the sensor can be roughly parallel to the thigh or the lower leg, but the sagittal plane is invisible, the sensor placement position is prone to deviation, and the Y and Z axes of the sensor are more likely to be in the plane they form. Offset, so you need to determine the angle at which the Y axis deviates from the sagittal plane

The dynamic correction is as follows:

By pre-monitoring the walking process within a certain distance of the user, the Y-axis and Z-axis angular velocity detected by the sensor are used to determine the angle of the actual Y-axis of the sensor from the sagittal plane:

In the formula:

The angle at which the actual direction of the Y-axis of the sensor deviates from the sagittal plane,

The average value of the angular velocity of the Y-axis of the sensor during standing phase during the user's walking,

The average value of the Z-axis angular velocity of the sensor during standing phase during the user's walking.

After that, the Y-axis acceleration and Z-axis angular velocity data of each sensor are corrected in advance before use as the acceleration or angular velocity of the calf or thigh in the corresponding direction:

Where: a _{y is} the Y-axis acceleration measured by the sensor, a _{z is} the Z-axis acceleration measured by the sensor, a _yc is the Y-axis acceleration obtained by correcting the data of the sensor; ω _{y is} the Y-axis angular velocity measured by the sensor , ω _{z is} the Z-axis angular velocity measured by the sensor, and ω _zc is the Z-axis angular velocity obtained by correcting the data of the sensor.

The static calibration is to calibrate the zero point of the angle between the calf and the plumb line. Because the subsequent calculation requires the angle between the calf and the plumb line, after the user adjusts the sensor position, the X axis can be kept parallel with the calf, but it is difficult to achieve a precise parallel state. At this time, the X axis is regarded as the direction of the calf, which will cause There is a certain amount of error, so it is necessary to recalibrate the calf direction. The static calibration is as follows:

Before measuring the step size, it is also necessary to monitor the static standing state of the user in advance, and define that the thigh and the calf are perpendicular to the ground when the human body stands still, that is, the angle with the plumb line is 0, and the gravity acceleration is used to determine the state. The angle between the X-axis of the left lower leg and the right lower leg in the sagittal plane and the plumb line:

Where: θ _l0 , θ _r0 are the angle between the left calf and the right calf X axis of the user in the static standing state and the plumb line in the sagittal plane, respectively, a _lsys and a _rsys are the left calf of the user when standing statically, Y-axis acceleration of the right lower leg.

(2) gait event detection:

After the above preparations are completed, you can start measuring the user's step size. The user walks on a flat ground, and four inertial sensors collect acceleration and angular velocity data in real time. The MCU uses the corresponding algorithm to detect gait events. The walking gait cycle of a person is shown in Fig. 4. In one cycle, there are mainly five gait events of mid-swing A, leg straight B, foot landing C, standing mid-D, and foot off-E, which need to be detected in this method. The gait event is the landing of the foot, the middle of the stance, and the straightening of the legs. The Z-axis angular velocity of the calf and thigh on the same side can detect the gait event in each gait cycle of the user's side leg in real time, as shown in FIG. The foot landing event is the moment of landing before the forefoot during the walking process, occurring at the first negative trough in the angular velocity vibration region after the highest peak of the calf angular velocity in each gait cycle, that is, the first after the highest peak Negative turning point, and can be detected immediately after it occurs; the middle of the standing is the leg as the supporting leg, moving to the position close to the vertical and the ground, at the small short peak of the angular velocity of the lower leg, and the peak value is negative Between the middle of the swing and the landing event, there is a moment when the angular velocity of the thigh is equal to the angular velocity of the lower leg, that is, the moment when the leg straightening event occurs, at which time the user's leg swings and straightens in the forward direction.

(3) Calculation of the real-time angle of the thigh and calf:

Next, using the detected gait events and angular velocity integrals, the angle between the thigh and the calf in the sagittal plane and the plumb line during walking is calculated in real time. The lower limbs of the human body are simplified into a two-dimensional geometric model of the double pendulum, and the user's motion is simplified into a plane motion in the sagittal plane. As shown in Fig. 6, the lower leg and the thigh are simplified into a rod, and the hip joint and the two knee joints are simplified as Hinge. According to the static calibration in step (1), the simplified rod model of the thigh and the calf is perpendicular to the ground when the human body stands still, that is, the angle with the plumb line is 0, thereby obtaining the left and right calf simplified rod model and the The angle of the X-axis of the calf is θ _l0 and θ _r0 . The real-time angle between the thigh and the calf during the walking process and the plumb line is mainly obtained by real-time integration of the Z-axis angular velocity, but as the integration time goes on, the integral error will become larger and larger, so it needs to be in each cycle. They are recalibrated once. For the calibration of the calf angle, it is carried out in the middle of the standing, as shown in Figure 7. At this time, the foot is in contact with the ground, the angular velocity of the lower leg reaches a maximum value, the angular acceleration is approximately 0, and the calf reaches a state of stable motion, so it can be utilized. The Y-axis acceleration at this time calculates the angle between the lower leg and the vertical line according to gravity:

Where: θ _lsms and θ _rsms are the _angles between the left lower leg and the right lower leg in the middle of the standing and the vertical line, a _lsyms and a _rsyms are respectively corrected by a low-pass filter with a cutoff frequency of 3.2 Hz. Y-axis acceleration of the left calf and right calf.

Before the next mid-station event is detected, the angle between the real left left leg, the right calf and the plumb line above the angle of the standing mid-point calibration is taken as the starting point, calculated by the angular velocity integral:

Where: t is the time from the middle of the left or lower calf, θ _ls (t), θ _rs (t) are the angles between the left calf, the right calf and the plumb line at time t, ω _Lsz (δ), ω _rsz (δ) is the instantaneous Z-axis angular velocity of the left lower leg and the right lower leg.

Then there is the calibration of the thigh angle. When it is detected that the left leg or the right leg is straight, the thigh calf is approximately in a straight line, thereby calculating the angle between the thigh and the plumb line of the leg.

θ _ltls =θ _lsls

θ _rtls = θ _rsls

_Where: θ ltls, θ _rtls respectively, left thigh, right thigh of the leg straight line time and the vertical _angle, θ lsls, θ _rsls respectively, left thigh angle At this time, the vertical lines of the right thigh.

The angle between the real left thigh, the right thigh and the plumb line is calculated by the angular velocity integral before the next leg extension event is detected:

Where: t is the time after the last leg of the left thigh or right thigh is straightened, θ _lt (t), θ _rt (t) are the angles between the left thigh, the right thigh and the plumb line at time t, respectively , ω _ltz (δ), ω _rtz (δ) are the instantaneous Z-axis angular velocities of the left thigh and the right thigh.

(4) Calculation of the step size:

The calculation in the above steps is mainly completed in the single-chip microcomputer in the thigh inertial sensor unit, and then the result of the real-time detection of the gait event and the real-time angle of the thigh and the calf are transmitted to the upper computer unit through Bluetooth.

When the foot landing event of the left leg or the right leg is detected, the host computer calculates the step size of the user's leg by real-time calculation of the geometric model as shown in FIG. 6:

LSL=l ₁ (sinθ _rtic +sin(-θ _ltic ))+l ₂ (sinθ _rsic +sin(-θ _lsic ))

RSL=l ₁ (sin(-θ _rtic )+sinθ _ltic )+ ₂ (sin(-θ _rsic )+sinθ _lsic )

Where: θ _lsic , θ _rsic , θ _ltic , θ _rtic are the _angles of the left calf, the right calf, the left thigh, the right thigh and the plumb line at the time of landing of the leg of the leg calculated in step (3), respectively. ₁ and l ₂ are the length of the thigh and the length of the calf, respectively. The LSL is the step length of the leg when the left leg is landing, and the RSL is the step length of the leg when the right leg is landing.

The calculated step size results can be displayed directly on the OLED display in real time or sent to other devices via the serial port.

During the measurement process, the step size of each step of the user is measured by the above method. After the user finishes walking, if the user has dyskinesia on one side of the lower limb, the gait asymmetry of the user can also be quantified:

Where: GA is gait asymmetry,

The average of the left leg step and the right leg step, respectively.

The average step size of the leg on one side of the dyskinesia.

(5) Step measurement effect:

In this example, the user has no lower extremity dyskinesia. In the step measurement process, a total of 22 steps are taken. Each step can be detected in real time and the step size is calculated in real time. By comparing the actual value of the step size of each step, the root mean square error of all steps measured by the process is 3.9 cm, which is 6.2% of the user's actual average step size (63.1 cm); it is assumed that the user's left leg is motion On one side of the obstacle, the actual gait asymmetry is 0.503, and the measured value of the process is 0.508 with an error of 0.005. It can be seen that the device and method of the present invention can not only realize real-time measurement of step size and gait asymmetry, but also actual precision thereof. The degree has also been greatly improved.

The embodiments described above are only some of the preferred embodiments of the present invention, but are not intended to limit the present invention. Various changes and modifications can be made by those skilled in the art without departing from the spirit and scope of the invention. For example, the above embodiment may also use other algorithms or use other sensors to calculate the angle of the thigh and the calf in real time, such as using an accelerometer, a gyroscope, and a magnetic field sensor fusion to calculate the angles of the left and right thighs and the calves by using a Kalman filter algorithm. The step size calculation is further performed using the geometric model of FIG. 6. The above-mentioned wearable device may also adopt other structures in the prior art or modify the device shown in the drawing. For example, the wired connection in the original device is removed, and all the four inertial sensors are wirelessly communicated for more convenient use. The single chip microcomputer can also be integrated in the upper computer unit. The host computer unit can also be in the form of a remote PC or the like. In addition, in the method of the present invention, in the case where the sensor mounting angle and position are accurate, the step of correcting the data collected by the sensor placed on the leg may be omitted, and the sensor data is directly used for the step length measurement process. .

It can be seen that the technical solutions obtained by adopting the equivalent replacement or equivalent transformation are all within the protection scope of the present invention.

Claims (10)

1. A real-time step size measuring method for a wearable device, comprising the steps of: measuring a Y-axis acceleration and a Z-axis angular velocity during walking of a thigh and a calf on both sides of a user in real time, and determining in real time according to the Z-axis angular velocity Gait events during walking; the angle between the thigh and the calf in the sagittal plane and the plumb line is determined in real time according to the gait event and the Z-axis angular velocity integral; and the real time is calculated according to the angle and the length of the thigh and the calf. Step size.
2. The real-time step size measuring method for a wearable device according to claim 1, wherein the wearable device includes a sensor for detecting three-axis acceleration and three-axis angular velocity of the left and right thighs and the left and right lower legs. The Y-axis acceleration and the Z-axis angular velocity are obtained by a sensor.
3. The method for measuring a real-time step size for a wearable device according to claim 1, wherein the gait event comprises a foot landing, a middle standing, and a leg straightening;

   When the middle of the left or right calf is detected, the angle between the lower leg and the plumb line is calculated:

   

   

   Where: θ _lsms and θ _rsms are the _angles of the left lower leg and the right lower leg in the middle of the standing with the plumb line, a _lsyms and a _rsyms are the Y-axis accelerations of the left lower leg and the right lower leg respectively; wherein θ _l0 , θ _r0 is the angle between the left lower leg and the right lower leg in the sagittal plane and the plumb line in the static standing state of the user, and satisfies:

   

   

   Where: a _lsys and a _rsys are the Y-axis accelerations of the left calf and the right calf when the user is standing statically;

   Before the next mid-station event is detected, the angle between the calf of the leg and the plumb line in the sagittal plane is calculated in real time by angular velocity integration:

   

   

   Where: t is the time of the last standing middle distance from the left or lower calf at the current time, θ _ls (t), θ _rs (t) are the left calf and the right calf in the sagittal plane and plumb at time t The angle of the line, ω _lsz (δ), ω _rsz (δ) are the instantaneous Z-axis angular velocity of the left lower leg and the right lower leg respectively;

   When it is detected that the left leg or the right leg is straight, calculate the angle between the thigh of the leg and the plumb line in the sagittal plane:

   θ _ltls =θ _lsls

   θ _rtls = θ _rsls

   _Where: θ ltls, θ _rtls respectively, left thigh, right thigh at the time the legs straight in the sagittal plane and the angle between the vertical _line, θ lsls, θ _rsls case were left leg, right leg in the sagittal The angle between the surface and the plumb line;

   Before the next leg extension event is detected, the angle between the thigh of the leg and the plumb line in the sagittal plane is calculated in real time by angular velocity integration:

   

   

   Where: t is the time after the last leg of the left thigh or right thigh is straightened, θ _lt (t), θ _rt (t) are the angles between the left thigh, the right thigh and the plumb line at time t, respectively , ω _ltz (δ), ω _rtz (δ) are the instantaneous Z-axis angular velocities of the left thigh and the right thigh, respectively;

   When it is detected that the left leg or the right leg is landing, calculate the step size of the leg at this time:

   LSL=l ₁ (sinθ _rtic +sin(-θ _ltic ))+l ₂ (sinθ _rsic +sin(-θ _lsic ))

   RSL=l ₁ (sin(-θ _rtic )+sinθ _ltic )+l ₂ (sin(-θ _rsic )+sinθ _lsic )

   Where: θ _lsic , θ _rsic , θ _ltic , θ _rtic are the _angles of the left leg, the right leg, the left thigh, the right thigh and the plumb line at the time of landing of the leg, respectively, l ₁ and l ₂ are the thigh length, respectively. The calf is long, the LSL is the step length of the leg when the left leg is landing, and the RSL is the step length of the leg when the right leg is landing.
4. The real-time step size measuring method for a wearable device according to claim 2, wherein before the step size is measured, the walking process within a certain distance of the target user is monitored in advance, and the actual direction of the sensor Y-axis is determined to be sagittal. Face angle:

   

   In the formula:

   

   The angle at which the actual direction of the Y-axis of the sensor deviates from the sagittal plane,

   

   The average value of the angular velocity of the Y-axis of the sensor during standing phase during the user's walking,

   

   The average value of the Z-axis angular velocity of the sensor when the user is standing during walking;

   During the measurement of the step size, the Y-axis acceleration and Z-axis angular velocity data of each sensor are corrected in advance before use as the acceleration or angular velocity of the corresponding direction of the lower leg or thigh. The correction formula is:

   

   Where: a _{y is} the Y-axis acceleration measured by the sensor, a _{z is} the Z-axis acceleration measured by the sensor, a _yc is the Y-axis acceleration obtained by correcting the data of the sensor; ω _{y is} the Y-axis angular velocity measured by the sensor , ω _{z is} the Z-axis angular velocity measured by the sensor, and ω _zc is the Z-axis angular velocity obtained by correcting the data of the sensor.
5. A method for measuring gait asymmetry, characterized in that the method according to claim 1 measures the real-time step size and then quantifies the gait asymmetry of the user with unilateral dyskinesia:

   

   Where: GA is gait asymmetry,

   

   The average of the left leg step and the right leg step, respectively.

   

   The step size of the leg on one side of the movement disorder.
6. A wearable device for realizing the real-time step measurement method according to claim 1, comprising four inertial sensors and a host computer, each inertial sensor comprising a three-dimensional accelerometer and a three-dimensional angular velocity meter, an inertial sensor and a host computer Connected for data transmission.
7. The wearable device according to claim 6, wherein the inertial sensor is first connected to the single chip microcomputer, and the single chip microcomputer is connected to the bluetooth module, and the upper computer and the bluetooth module exchange data through Bluetooth.
8. The wearable device of claim 6 further comprising a securing strap for securing the inertial sensor.
9. The wearable device according to claim 6, wherein said inertial sensor is an inertial sensor based on an MPU6050 chip.
10. The wearable device according to claim 6, wherein said inertial sensor sampling frequency is not less than 100 Hz.

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