阅读说明：本技术 对象身体尺寸测量方法、装置和系统 (Method, device and system for measuring body size of object ) 是由 徐蔚峰 郁彦彬 于 2018-07-17 设计创作，主要内容包括：本发明涉及身体尺寸测量领域,尤其涉及一种基于可穿戴惯性测量单元的对象身体尺寸测量方法、装置和系统。所述方法包括如下步骤：在所述对象执行涉及一个或多个可转动部位的测量动作时,通过与所涉及的一个或多个可转动部位相关联的至少一个惯性测量单元采集运动数据；基于来自所述相关联的至少一个惯性测量单元中的每个惯性测量单元的运动数据来计算该惯性测量单元的旋转半径；并且根据所述相关联的至少一个惯性测量单元的旋转半径以及所述相关联的至少一个惯性测量单元与各自的可转动部位的相应位置关系来计算所述一个或多个可转动部位的尺寸。与传统身体尺寸测量方法相比,本发明的身体尺寸测量方法更加简单、高效。(The invention relates to the field of body size measurement, in particular to a method, a device and a system for measuring the body size of a subject based on a wearable inertial measurement unit. The method comprises the following steps: acquiring motion data by at least one inertial measurement unit associated with the one or more rotatable parts involved while the object performs a measurement action involving the one or more rotatable parts; calculating a radius of rotation of each of the associated at least one inertial measurement unit based on motion data from the inertial measurement unit; and calculating the dimensions of the one or more rotatable portions based on the radius of rotation of the associated at least one inertial measurement unit and the respective positional relationship of the associated at least one inertial measurement unit to the respective rotatable portion. Compared with the traditional body size measuring method, the body size measuring method is simpler and more efficient.)

1. Method (300) for body dimension measurement of a subject, wherein one or more inertial measurement units (220) have been attached to at least one rotatable part of the subject (100), the method comprising the steps of:

acquiring motion data (310) by at least one inertial measurement unit (220) associated with the one or more rotatable parts involved while the subject performs a measurement action involving the one or more rotatable parts;

calculating a radius of rotation (330) of each of the associated at least one inertial measurement unit (220) based on motion data from the inertial measurement unit; and is

Calculating a dimension (340) of the one or more rotatable portions from a radius of rotation of the associated at least one inertial measurement unit (220) and a respective positional relationship of the associated at least one inertial measurement unit (220) to the respective rotatable portion.

2. The method of claim 1, wherein the measuring act comprises at least partial circular movement of the rotatable portion about the respective anatomical point.

3. The method of claim 2, wherein the circular motion is a uniform circular motion.

4. The method of claim 3, wherein the calculating of the radius of rotation further comprises:

determining the time interval [ t ] of each inertial measurement unit for carrying out the uniform circular motion₁，t₂](410)；

According to each inertial measurement unit in the time interval t₁，t₂]Calculating an instantaneous radius of rotation (420) of the inertial measurement unit at each sampling time point from the acquired motion data at that sampling time point; and is

By measuring for each inertial measurement unit during said time interval t₁，t₂]The instantaneous radius of rotation within (430) is averaged to calculate the radius of rotation for each inertial measurement unit.

5. The method of claim 3, wherein the calculating of the radius of rotation further comprises:

determining the start time (t) of each inertial measurement unit when it is stationary₀)(510)；

Determining the time interval [ t ] of each inertial measurement unit for carrying out the uniform circular motion₁，t₂](520)；

Calculating the time interval [ t ] of each inertial measurement unit₁，t₂]Mean velocity in(530)；

Calculating the time interval [ 2 ] of each inertia measurement unit₁，t₂]Mean angular velocity of the inner

Based on the average speed

6. The method of claim 5, wherein the average speed

7. The method according to any one of claims 4-6, wherein, if the change of the consecutive N acquired motion data is smaller than a first threshold, the sampling time point of the last acquired motion data is set as a lower temporal limit of the time interval; and if the change of the M consecutive acquired motion data is larger than the second threshold, the sampling time point of the first acquired motion data is set as the upper time limit of the time interval, wherein N, M are all positive integers larger than 2.

8. The method of any of claims 1-5, wherein the measuring action includes at least one of a back and forth swing, a side to side swing, and an up and down swing.

9. A computer readable medium storing computer program readable code configured such that, on execution by a suitable computer or processor, the computer or processor is caused to perform the method of any of claims 1-8.

10. A computing device (600) comprising:

one or more processors (610); and

a memory (620) storing one or more instructions that, when executed by the one or more processors, cause the one or more processors to perform the method of any one of claims 1-8.

11. A subject body dimension measuring device (210), comprising:

one or more inertial measurement units (220) configured to be attached to at least one rotatable part of the subject, wherein, while the subject performs a measurement action involving the one or more rotatable parts, the at least one inertial measurement unit (220) associated with the one or more rotatable parts involved is further configured to acquire motion data; and

a calculation unit (240) configured to calculate a radius of rotation of each of the associated at least one inertial measurement unit (220) based on motion data from the inertial measurement unit and to calculate dimensions of the one or more rotatable portions from the radius of rotation of the associated at least one inertial measurement unit (220) and the respective positional relationship of the associated at least one inertial measurement unit (220) to the respective rotatable portion.

12. The apparatus of claim 11, wherein the measuring action comprises at least partial circular movement of the rotatable portion about the respective anatomical point.

13. The apparatus of claim 12, wherein the circular motion is a uniform circular motion.

14. The apparatus of claim 13, wherein the computing unit (240) is further configured to:

determining the time interval [ t ] of each inertial measurement unit for carrying out the uniform circular motion₁，t₂]；

According to each inertial measurement unit in the time interval t₁，t₂]Calculating the instantaneous rotation radius of the inertial measurement unit at each sampling time point by using the acquired motion data at the sampling time point; and is

By measuring for each inertial measurement unit during said time interval t₁，t₂]The instantaneous radius of rotation of each inertial measurement unit is averaged to calculate the radius of rotation of each inertial measurement unit.

15. The apparatus of claim 13, wherein the computing unit (240) is further configured to:

determining the start time (t) of each inertial measurement unit when it is stationary₀)；

Determining the time interval [ t ] of each inertial measurement unit for carrying out the uniform circular motion₁，t₂]；

Calculating the time interval [ t ] of each inertial measurement unit₁，t₂]Mean velocity in

Calculating the time interval [ t ] of each inertial measurement unit₁，t₂]Mean angular velocity of the innerAnd is

Based on the average speed

16. The apparatus of claim 15, wherein the computing unit (240) is further configured to determine the time interval [ t ] by, for each inertial measurement unit₁，t₂]Instantaneous velocity (v) at each sampling time point_i) Averaging to calculate the average speed

17. The apparatus according to any one of claims 14-16, wherein the calculation unit (240) is further configured to set a sampling time point of a last acquired motion data to a lower temporal limit of the time interval when it is determined that a change of N consecutive acquired motion data is smaller than a first threshold; and setting a sampling time point of a first acquired motion data to an upper temporal limit of the time interval when it is determined that a change of M consecutive acquired motion data is greater than a second threshold, wherein N, M are each positive integers greater than 2.

18. The apparatus according to any one of claims 11-16, wherein the calculation unit (240) is integrated in the inertial measurement unit (220).

19. The apparatus according to any one of claims 11-16, wherein the calculation unit (240) is separate from the inertial measurement unit (220), wherein the apparatus further comprises a receiving unit (230) configured to receive the motion data transmitted from the inertial measurement unit (220), and wherein the calculation unit (240) is configured to obtain the motion data from the receiving unit (230) and perform the calculation.

20. A motion capture system (200), comprising:

a subject body dimension measuring device (210) according to any one of claims 11-19; and

a pose analysis unit (250) configured to analyze real-time poses of the one or more rotatable parts by combining the calculated dimensions of the one or more rotatable parts and real-time motion data from the one or more inertial measurement units.

21. The system as recited in claim 20, wherein the subject body dimension measurement device (210) includes at least 17 inertial measurement units (220) for whole body motion capture.

Technical Field

The invention relates to the technical field of measurement, in particular to a method, a device and a system for measuring body dimensions of a subject.

Background

Manufacturing automation is an important component in advanced manufacturing technologies. The connotation is that the core function of a human is played, the human and the machine jointly form a system, and the human and the machine respectively execute the best work, so that the best benefit of the whole system is obtained. Nowadays, man-machine hybrid production lines are introduced in various kinds of factories. When an engineer designs a machine production line, the automated movement of the machine is readily known through the use of industrial design software. However, it is difficult for engineers to know the movement of human interaction with a machine.

With the development of motion capture technology, engineers can directly simulate the designed machine production line interaction with humans, knowing whether the designed machine is suitable for human operation, and whether the machine can work properly with other machines and humans of the same production line. This is commonly referred to as human analysis. Human body size is an important parameter in human-machine analysis when engineers simulate human-machine interaction in a hybrid production line. The measurement deviation of the human body size affects the precision of the captured motion, further affecting the result of the human-machine analysis.

Currently, the body size can only be measured by a conventional length measuring tool or a dedicated body size measuring device. Conventional length measuring tools are for example rulers or tape measures. This method requires the measurement of all joints, and is complicated and time-consuming to operate. Sometimes, even the help of others is needed. The special body size measuring device is, for example, an optical measuring apparatus described in patent CN104434111A or an image measuring apparatus described in patent KR101822571B 1. These methods are fast, accurate and convenient for the user to operate, but are more expensive because of the need to purchase additional special measuring equipment. Moreover, these specialized measurement devices cannot be multiplexed for motion capture.

Although the optical sensor described in patent CN107422857A, for example, can perform both motion capture and obtain high-precision body dimension information. However, this method has higher hardware cost, more complex algorithm, and is greatly influenced by light environment, and the measurement is easily interfered.

Accordingly, there is a need for improved body dimension measuring methods and apparatus that overcome the above-referenced problems and others.

Disclosure of Invention

In view of the above, the present invention provides a simple and efficient method, apparatus and system for measuring the body size of a subject, which allows further obtaining the motion posture of the subject.

In a first aspect, there is provided a method of body dimension measurement of a subject, wherein one or more Inertial Measurement Units (IMUs) have been attached to at least one rotatable part of the subject, the method comprising the steps of:

acquiring motion data by at least one inertial measurement unit associated with the one or more rotatable parts involved while the object performs a measurement action involving the one or more rotatable parts;

calculating a radius of rotation of each of the associated at least one inertial measurement unit based on motion data from the inertial measurement unit; and is

Calculating the size of the one or more rotatable parts according to the rotation radius of the associated at least one inertial measurement unit and the corresponding position relationship of the associated at least one inertial measurement unit and the respective rotatable parts.

An Inertial Measurement Unit (IMU) is a device that measures the three-axis attitude angle (or angular rate) and acceleration of an object. Generally, an IMU includes three single-axis accelerometers and three single-axis gyroscopes, the accelerometers detect acceleration signals of an object in three independent axes of a carrier coordinate system, and the gyroscopes detect angular velocity signals of the carrier relative to a navigation coordinate system, and measure angular velocity and acceleration of the object in three-dimensional space, and then solve the attitude of the object. Conventionally, IMUs are mostly used on devices requiring motion control, such as automobiles and robots; the method is also used in occasions needing to use the attitude for precise displacement calculation, such as inertial navigation equipment of mobile phones, submarines, airplanes, missiles and spacecrafts. The inventors of the present invention first noticed that since the IMU is able to measure the angular velocity ω and the acceleration a of the object in the three-dimensional space, if the formula a of the centripetal acceleration is made ω ═ ω²X r (where a denotes centripetal acceleration, ω denotes angular velocity of the object circular motion, and r denotes radius of the object circular motion) is modified to r ═ a/ω²The radius of motion of the IMU can then be calculated from the motion data such as angular velocity ω and acceleration a obtained from the IMU. In this case, if the IMU is attached to a rotatable part of the human body (for example, an arm), and the person is instructed to make the provision of the rotatable part to which the IMU is attached around the corresponding jointThe size of the rotatable portion can be obtained from the positional relationship of the IMU and the rotatable portion. Considering that the IMU itself is used for motion capture, the present invention actually employs a motion capture device for body dimension measurement. Thus, no additional body size measuring device is added. Therefore, the body size measuring method of the present invention is much cheaper in cost than the optical measuring method. Thus, the present invention provides a simple and effective measurement method for body dimension measurement for human-machine analysis of, for example, Siemens industry design software.

It should be appreciated that although the specific embodiment of the present invention employs an inertial measurement unit to measure the body size and the motion posture of the subject, other measurement devices that can acquire the acceleration and angular velocity of the motion of the object are also applicable to the concept of the present invention.

The term "rotatable portion" refers to a body part of an object, such as a human body, that can rotate about a respective joint or skeleton, including, for example, the head, shoulders, upper arms, lower arms, palms, fingers, waist, thighs, calves, feet, and the like.

The term "measuring action" refers to a rotational or circular motion of the rotatable portion about an anatomical point, such as a corresponding joint or bone. Thus, the present invention can more advantageously use the motion data from the IMU to calculate the dimensions of the corresponding part of the body by means of a formula for centripetal acceleration. It should be appreciated that the measuring motion may be other types of circular motion. In this case, the radius of motion can be measured in conjunction with the IMU, and the size of the corresponding region determined, simply by adding appropriate sensors.

The term "motion data" refers to the angular velocity ω and acceleration a of an object (e.g., a rotatable part) acquired by the IMU in three-dimensional space.

Preferably, the circular motion is uniform circular motion. In this way, the calculation can be performed with only the motion data acquired by the IMU, and the algorithm is simple. Even if the circular motion is a non-uniform circular motion, the calculation may be performed by adding an appropriate sensor.

In one example of the present invention, the calculation of the radius of rotation preferably further comprises: determining the time interval of each inertial measurement unit for performing the uniform circular motion; calculating the instantaneous rotation radius of each inertial measurement unit at each sampling time point in the time interval according to the motion data acquired by the inertial measurement unit at the sampling time point; and calculating the radius of rotation of each inertial measurement unit by averaging the instantaneous radius of rotation of each inertial measurement unit over the time interval. Using the average radius of rotation of each IMU, rather than directly using the instantaneous radius of rotation of each IMU, may reduce measurement errors, thereby improving the accuracy of body part size measurements.

In another example of the present invention, the calculation of the radius of rotation preferably further comprises: determining a start time when each inertial measurement unit is stationary; determining the time interval of each inertial measurement unit for performing the uniform circular motion; calculating the speed of each inertial measurement unit in the time interval; calculating the angular speed of each inertial measurement unit in the time interval; and calculating a radius of rotation of each inertial measurement unit based on the velocity and the angular velocity. Thus, an alternative method is provided for calculating the radius of rotation of each IMU.

In yet another example of the present invention, the velocity is preferably calculated by averaging instantaneous velocities of each inertial measurement unit at sampling time points within the time interval; also, the angular velocity is preferably calculated by averaging instantaneous angular velocities of each inertial measurement unit at respective sampling time points within the time interval. The measurement error can be better filtered by the mode of averaging and calculating.

In still another example of the present invention, if a variation of N consecutive collected motion data is less than a first threshold, a sampling time point of the last collected motion data is set as a lower temporal limit of the time interval; and if the change of the M consecutive acquired motion data is larger than the second threshold, the sampling time point of the first acquired motion data is set as the upper time limit of the time interval, wherein N, M are all positive integers larger than 2. In this way, whether the IMU performs uniform circular motion can be determined more accurately.

The circular motion includes, for example, at least one of back and forth swing, side to side swing, and up and down swing. In this way, corresponding circular motions can be performed according to anatomical features of different rotatable portions, thereby improving measurement efficiency. In addition, it is necessary to determine the time interval during which the IMU makes a circular motion, considering that some rotatable parts may not perform a complete circular motion, e.g. limited by the anatomy, and the head may not perform a complete back and forth or side to side circular motion.

In a second aspect, there is provided a computer readable medium having stored thereon computer program readable code configured to cause, when executed by a suitable computer or processor, the computer or processor to perform the method of any preceding paragraph.

In a third aspect, a computing device is provided that includes one or more processors; and a memory. The memory stores one or more instructions that, when executed by the one or more processors, cause the one or more processors to perform the method of any preceding paragraph.

In a fourth aspect, there is provided a subject body dimension measuring apparatus, the apparatus comprising:

one or more inertial measurement units configured to be attached to at least one rotatable part of the subject, wherein, while the subject performs a measurement action involving the one or more rotatable parts, the at least one inertial measurement unit associated with the one or more rotatable parts involved is further configured to acquire motion data; and

a calculation unit configured to calculate a radius of rotation of each of the associated at least one inertial measurement unit based on motion data from the inertial measurement unit and to calculate dimensions of the one or more rotatable portions from the radius of rotation of the associated at least one inertial measurement unit and the respective positional relationship of the associated inertial measurement unit to the respective rotatable portion.

In one example of the invention, the calculation unit is preferably integrated in the inertial measurement unit. Since the IMU employs a micro-electro-mechanical system (MEMS), it is easy to integrate the computing unit with the IMU. The integrated chip not only can more quickly calculate the size of the rotatable part of the object, but also has very low cost compared with the optical measuring equipment.

In another example of the invention, the calculation unit is preferably separate from the inertial measurement unit. In this case, the apparatus preferably further includes a receiving unit configured to receive the motion data transmitted from the inertial measurement unit. Accordingly, the calculation unit is preferably configured to obtain the motion data from the receiving unit and to perform the calculation. Thus, the present invention can conveniently use an existing IMU to measure the motion data, thereby simplifying the structural design of the subject body dimension measuring apparatus.

In a fifth aspect, there is provided a motion capture system comprising:

a subject body dimension measuring apparatus according to the preceding paragraph; and

a pose analysis unit configured to analyze a real-time pose of the at least one rotatable part by combining the dimensions of the at least one rotatable part and real-time motion data from the one or more inertial measurement units.

By means of the motion capture system, the invention not only can simply and efficiently measure the size of the human body part, but also can simultaneously analyze the motion postures of all parts. Therefore, the invention improves the accuracy of human-computer analysis under the condition of not needing to separately estimate the human body size. In addition, the motion capture system of the present invention is also not susceptible to environmental factors. Furthermore, IMU-based motion capture systems are much cheaper than optical positioning systems.

In one example of the present invention, the subject body dimension measuring apparatus preferably includes at least 17 inertial measurement units for whole body motion capture. In this way, the present invention is also capable of measuring the overall body length of a subject. In view of the low price of the inertial measurement units, the overall cost of even 17 inertial measurement units is much lower than that of a dedicated optical measurement device.

Those skilled in the art will appreciate still other aspects of the present application upon reading and understanding the present specification.

Drawings

The invention will be described and explained in more detail below with reference to embodiments and with reference to the drawings, in which:

fig. 1 is a schematic view of 17 inertial measurement units arranged on a human body.

Fig. 2 is a block diagram of a motion capture system according to an embodiment of the present invention.

Fig. 3 is a flowchart of a method 300 for measuring a body size of a subject according to an embodiment of the present invention.

Fig. 4 is a flowchart of an IMU rotation radius calculation method 400 according to an embodiment of the present invention.

Fig. 5 is a flowchart of an IMU rotation radius calculation method 500 according to another embodiment of the present invention.

Fig. 6 is a block diagram of a computing device for performing body size measurement of a subject according to an embodiment of the present invention.

List of reference numerals：

1-17: IMU worn on each rotatable part of human body

100: human body

200: motion capture system

210: body size measuring device

220: one or more IMUs

230: motion data receiver

240: body size calculation unit

250: attitude analysis unit

300: method for measuring body size of subject

310: collecting movement data during a measurement maneuver

320: transmitting the collected motion data to a motion data receiver

330: calculating the radius of rotation of each IMU from the motion data acquired by that IMU

340: calculating the size of the rotatable part according to the rotation radius and the corresponding position relation

400: IMU (inertial measurement Unit) rotation radius calculation method

410: determining a time interval during which each IMU performs circular motion

420: calculating the instantaneous radius of rotation of each IMU

430: calculating a radius of rotation for each IMU by averaging the instantaneous radius of rotation for each IMU over a time interval

500: another calculation method of IMU rotation radius

510: determining a start time when each IMU is stationary

520: determining a time interval during which each IMU performs circular motion

530: calculating an average velocity of each IMU over a time interval

540: calculating an average angular velocity of each IMU over a time interval

550: calculating a radius of rotation for each IMU based on the average velocity and the average angular velocity

600: computing device

610: one or more processors

620: memory device

Detailed Description

As mentioned above, in the case of the step-by-step man-machine hybrid production method, the human body size is an important parameter for man-machine analysis. Currently, measurements of body dimensions are made either with length measuring tools such as rulers or tape measures or with optical or image measuring devices. However, the former is complex and time-consuming, and the latter is fast, accurate and expensive, and requires additional special measuring equipment and complex analysis software. To this end, the present invention pioneers the use of an Inertial Measurement Unit (IMU) to measure the body dimensions of a subject, such as a human body. The IMU-based body size measurement of the object is simple and efficient, and the simulation and verification of human-computer analysis are accelerated, so that the design cycle of a human-computer hybrid production line is accelerated. Furthermore, in connection with optical measurements, IMU-based body size measurements of a subject are not susceptible to environmental factors.

The method and apparatus provided by the embodiments of the present invention are described in detail below with reference to the accompanying drawings.

Fig. 1 is a schematic view of 17 inertial measurement units arranged on a human body.

Using an Inertial Measurement Unit (IMU) for body dimension measurement requires that the IMU used be first worn at the appropriate location on the body 100 to be measured. Preferably, as shown in fig. 1, to measure the size of the various parts of the entire body, at least 17 IMUs are arranged at different rotatable parts of the back of the human body 100. For example, IMU1 is disposed at the medial lumbar spine of human body 100, IMU2 is disposed directly below the intersection of the clavicle and the spine of human body 100, IMU 3 is disposed at the medial center of the head of human body 100, IMU 4 is disposed at the left side of the clavicle center of human body 100, IMU 5 is disposed at the left upper arm center of human body 100, IMU 6 is disposed at the left lower arm center of human body 100, IMU 7 is disposed at the left palm center of human body 100, IMU 8 is disposed at the right side of the clavicle center of human body 100, IMU 9 is disposed at the right upper arm center of human body 100, IMU 10 is disposed at the right lower arm center of human body 100, IMU 11 is disposed at the right palm center of human body 100, IMU12 is disposed at the left thigh center of human body 100, IMU13 is disposed at the left lower leg center of human body 100, IMU 14 is disposed at the left heel of human body 100, IMU 15 is disposed at the right thigh center of human body 100, The IMU 16 is disposed in the center of the right lower leg of the human body 100 and the IMU 17 is disposed in the right heel of the human body 100. In fig. 1, the solid dots represent the joints or bones (e.g., lumbar vertebrae) around which the respective parts rotate. It should be understood that an appropriate number of IMUs may be selected for the location of the measurement and arranged at corresponding locations. In addition, a greater number of IMUs is allowed for more accurate measurements. In one example, the IMUs may be pre-arranged in specialized housings to facilitate the ability of a person under test to put each IMU in place by donning the housing.

Fig. 2 is a block diagram of a motion capture system 200 according to an embodiment of the present invention.

The motion capture system 200 includes one or more Inertial Measurement Units (IMUs) 220, a motion data receiver 230, a body dimension calculation unit 240, and a pose analysis unit 250. The IMU220 may be placed in position at a rotatable location in the person to be measured before taking measurements as described above. During the measurement, the person to be measured performs corresponding measurement actions on the rotatable portion of the measured dimension as required, and the IMU220 collects the motion data in real time. Preferably, the motion data acquired by the IMU includes angular velocity ω and acceleration a of the measurement site in three-dimensional space. The sampling rate of the IMU220 is preferably greater than 200 Hz. It should be appreciated that motion data acquired at other sampling rates can be used to calculate body dimensions without performing a pose analysis. In one example, the motion capture system 200 may instruct the person under test to perform the corresponding measurement action according to the measurement action requirement pre-stored in the database by means of voice or image. In another example, the operator may verbally direct the person to be tested according to the respective measurement action requirements.

In one example, the body size calculation unit 240 may be integrated into the IMU 220. The body size calculation unit 240 may then be configured to calculate the size of the respective turnable part from the motion data acquired by the IMU. The specific calculation method will be described in detail below. In this case, the IMU220 and the body size calculation unit 240 may collectively constitute the subject body size measurement device 210. In this way, the calculated body dimensions of the subject can be used for various purposes.

In another example, the IMU220 sends the measured motion data to a separate motion data receiver 230. Then, the body size calculation unit 240 receives the motion data from the motion data receiver 230 and calculates the size of the corresponding rotatable part therefrom. In this case, the body size calculation unit 240 is also separate from the IMU220, and the IMU220, the motion data receiver 230, and the body size calculation unit 240 may collectively constitute the subject body size measurement device 210 (not shown). Such a subject body size measuring apparatus can directly employ respective IMUs commercially available, thereby simplifying the structural design.

Regardless of the manner in which the dimensions of the turnable parts are calculated, the posture analyzing unit 250 analyzes the posture of one or more turnable parts by combining the body dimension results from the body dimension calculating unit 240 and the motion data measured in real time by the IMU220 from the motion data receiver 230. Advantageously, by employing an Inertial Measurement Unit (IMU), the present invention can perform body part size measurement and motion pose analysis simultaneously.

Fig. 3 is a flowchart of a method 300 for measuring a body size of a subject according to an embodiment of the present invention. The method may preferably be performed by a motion capture system 200 or a subject body dimension measurement device 210 as shown in fig. 2. It should be understood that the method 300 may be performed by other means, such as other computing units or computer processors.

After a subject, such as a person under test, has worn an appropriate number of IMUs, subject body size measurement may begin.

At step 310, the test person performs a measurement action involving one or more rotatable parts as required for the rotatable parts to be measured and having the IMU already disposed. Simultaneously, at least one IMU associated with the one or more rotatable portions involved acquires motion data. Preferably, the motion data comprises an angular velocity ω and an acceleration a of the rotatable part in three-dimensional space.

Optionally, at step 320, the associated IMUs transmit the respective acquired motion data to the motion data receiver 230 separately, e.g., via a wired or wireless connection. In the case where the body size calculation unit 240 is integrated into the IMU220, the associated IMU may also output the acquired motion data directly to the body size calculation unit 240. In this case, step 320 may be omitted.

At step 330, for example, the body size calculation unit 240, calculates a radius of rotation r _ i _ j of each of the associated at least one IMU from the acquired motion data for that IMU, where i represents the group number of the measurement action and j represents the number of the IMU. The specific calculation method of the radius of rotation will be described in detail with reference to fig. 4 to 5.

In one example, the measurement actions include (but are not limited to) the following actions, and the respective radii of rotation to be calculated are:

1. stoop and keep the head and back in line while obtaining radii of rotation for IMU2, IMU 3, IMU 4, and IMU 8: r _1_2, r _1_3, r _1_4, and r _1_ 8.

2. T-position, turning body and arms in line with shoulders, while obtaining radius of rotation of IMU 4 and IMU 8: r _2_4 and r _2_ 8.

3. Raising and lowering the head and keeping the head and neck in line while obtaining the radius of rotation of the IMU 3: r _3_ 3.

4. Swing the entire arm and keep the upper arm, lower arm and palm in line while obtaining the radius of rotation of the IMU 5, IMU 6, IMU 7, IMU 9, IMU 10 and IMU 11: r _4_5, r _4_6, r _4_7, r _4_9, r _4_10, and r _4_ 11.

5. Swing the forearm and keep the forearm in line with the palm while obtaining the radius of rotation of the IMU 6, IMU 7, IMU 10 and IMU 11: r _5_6, r _5_7, r _5_10, and r _5_ 11.

6. The palm was swung, while obtaining the radius of rotation of the IMU 7 and IMU 11: r _6_7 and r _6_ 11.

7. Swing the entire leg and keep the thigh in line with the calf, keeping the foot perpendicular to the calf, while obtaining radii of rotation for IMU12, IMU13, IMU 14, IMU 15, IMU 16 and IMU 17: r _7_12, r _7_13, r _7_14, r _7_15, r _7_16, and r _7_ 17.

8. Swing the lower leg and keep the foot perpendicular to the lower leg while obtaining the radius of rotation of the IMU13, IMU 14, IMU 16 and IMU 17: r _8_13, r _8_14, r _8_16 and r _8_ 17.

9. Swing the foot while obtaining the radius of rotation of the IMU 14 and IMU 17: r _9_14 and r _9_ 17.

It will be appreciated that it is preferably at least 1 second stationary before each measuring action is performed. Preferably, the measuring motions are steady, smooth, at least partial circular motions of the one or more rotatable portions involved about the respective joints or bones (e.g., lumbar vertebrae), including at least one of back and forth, side to side, and up and down. More preferably, the measuring motion is a uniform circular motion. Other measurement actions are also conceivable by the person skilled in the art, depending on the measurement requirements. For better measurement results, each measurement action is performed more than once.

It should be appreciated that some of the measurement actions may be omitted as required by the motion capture. For example, the above-described measuring actions 7, 8, 9 for the lower body may be omitted if only motion capture of the upper body of the human body is required. If only motion capture of the arm is required, only the above-mentioned measuring actions 4, 5, 6 involving the arm need to be performed.

Advantageously, the body size measurement can also be extended to the length measurement of a finger. The principle of finger length measurement is the same as that of arm/leg length measurement.

At step 340, for example, the body size calculation unit 240, calculates the size of the one or more rotatable portions according to the radius of rotation of the associated at least one inertial measurement unit and the corresponding positional relationship of the associated at least one inertial measurement unit to the respective rotatable portions.

In one example, the distance d of each rotatable portion to its respective joint or bone of rotation may be calculated from the IMU involved in that rotatable portion and the respective positional relationship of the IMU to the respective rotatable portion. For example, the calculation equation for the relative distance of each rotatable portion is as follows:

d _ body ═ r _1_4+ r _1_8+ (r _1_3-r _1_ 2))/3;

d _ header r _3_ 3;

d _ shoulder width ═ r _4_5-r _2_4) + (r _4_9-r _2_ 8);

d _ left big arm — r _4_6-r _5_ 6;

d _ right big arm — r _4_10-r _5_ 10;

d _ left forearm r _5_7-r _6_ 7;

d _ right forearm r _5_11-r _6_ 11;

d _ left half palm — r _6_ 7;

d _ right half palm — r _6_ 11;

d _ left thigh — r _7_13-r _8_ 13;

d _ right thigh — r _7_16-r _8_ 16;

d _ left shank ═ r _8_14²-r_9_14²)^1/2；

d _ right calf ═ r _8_17²-r_9_17²)^1/2。

Those skilled in the art will be able to arrive at other locations on how to calculate after reading and understanding the present invention. Alternatively, other similar methods may be used to calculate the size of the rotatable portion.

FIG. 4 is a flow diagram of a method 400 for calculating IMU radius of rotation r _ i _ j according to one example of the invention. The method may preferably be performed by the body size calculation unit 240 shown in fig. 2. It should be understood that the method 400 may also be performed by other means, such as other computing units or computer processors. Each IMU is assumed to make a uniform circular motion around an anatomical point such as a joint or bone. Then, from the formula of the centripetal acceleration, the distance r of the IMU to this point is a/ω²Where a is the centripetal acceleration and ω is the angular velocity of the IMU circular motion. The a and ω are also the IMU outputs. The calculated distance is the radius of rotation of the IMU.

At step 410, a time interval [ t ] for each IMU to perform a circular motion, preferably a uniform circular motion, is determined, e.g., by the body size calculation unit 240 or computer processor₁，t₂]。

Ideally, when the IMU performs a uniform circular motion, its tangential acceleration is zero, with only a fixed centripetal acceleration perpendicular to the direction of travel. Thus, when N motion data are continuously acquired by the IMU and the variation of the N motion data is smaller than a predefined first threshold, for example, when the variation of N continuously acquired accelerations a is smaller than a threshold thre _ a _ t1 and the variation of N continuously acquired angular velocities ω is smaller than a threshold thre _ ω _ t1, the time of the last acquired motion data of these motion data is determined as the lower limit t of the time interval₁. When M pieces of motion data are continuously acquired again by the IMU and the variation of the M pieces of motion data is larger than a predefined second threshold, for example, when the variation of the M pieces of continuously acquired acceleration a is larger than a threshold thre _ a _ t2 and the variation of the M pieces of continuously acquired angular velocity ω is larger than a threshold thre _ ω _ t2, the time of the first acquired piece of motion data among the pieces of motion data is determined as the upper limit t2 of the time interval. Here, N, M are all positive integers greater than 2.

At step 420, for example, the body size calculation unit 240 or computer processor, calculates a time interval [ t ] according to each IMU₁，t₂]The motion data acquired at each sampling time point is used to calculate the instantaneous radius of rotation of the IMU at that sampling time point.

According to the equation r _ i _ j _ k ═ a_k/ω_k ²The instantaneous radius of rotation is calculated. In the equation, a_kIs said time interval t₁，t₂]During the kth sampled value of acceleration, and_kis said time interval t₁，t₂]During the period, the kth sampled value of acceleration, where k is 1, …, M (M is a positive integer greater than 1). In this way, a set containing M instantaneous turning radii is obtained.

At step 430, for example, the body size calculation unit 240 or computer processor, the time interval [ t ] is determined for each IMU₁，t₂]The instantaneous radius of rotation r _ i _ j _ k within to calculate the radius of rotation r _ i _ j for each IMU. Any averaging method may be used, such as arithmetic mean, squared evaluation, harmonic mean, and the like.

FIG. 5 is a flow diagram of a method 500 for calculating IMU radius of rotation r _ i _ j according to another example of the present invention. The method may preferably be performed by the body size calculation unit 240 shown in fig. 2. It should be understood that the method 500 may also be performed by other means, such as other computing units or computer processors. Each IMU is assumed to make a uniform circular motion around an anatomical point such as a joint or bone. Then, from the formula of centripetal acceleration, the distance of the IMU to this point can also be r ═ v/ω, where v denotes the linear velocity (tangential velocity) and ω is the angular velocity of the IMU circular motion. The ω is also the output of the IMU, and v can be calculated from the IMU output. The calculated distance is the radius of rotation of the IMU.

At step 510, a start time t at which each IMU is stationary is determined, e.g., by the body size calculation unit 240 or a computer processor₀。

Ideally, when the IMU is stationary, both its angular velocity ω and its acceleration a approach zero. Therefore, when N pieces of motion data are continuously acquired by the IMU and the variation of the N pieces of motion data is smaller than the predetermined threshold thre _ zero, for example, when the variation of the N pieces of continuously acquired acceleration a is smaller than the threshold thre _ a _ zero and the variation of the N pieces of continuously acquired angular velocity ω is smaller than the threshold thre _ ω _ zero, the time of the last acquired piece of motion data among the pieces of motion data is determined as the start time t₀。

At step 520, a time interval [ t ] for each IMU to perform a circular motion, preferably a uniform circular motion, is determined, e.g., by the body size calculation unit 240 or computer processor₁，t₂]。

Ideally, when the IMU performs a uniform circular motion, its tangential acceleration is zero, with only a fixed centripetal acceleration perpendicular to the direction of travel. Therefore, when N motion data are continuously acquired by the IMU and the variation of the N motion data is smaller than a predefined first threshold, for example, when the variation of the N continuously acquired acceleration a is smaller than the threshold thre _ a _ t1 and the variation of the N continuously acquired angular velocity ω is smaller than the threshold thre _ ω _ t1, the time of the last acquired motion data in the motion data is determined as the lower limit t of the time interval₁. When the IMU acquires M pieces of motion data again continuously and the change of the M pieces of motion data is larger than a predefined second threshold, for example, when the change of the M pieces of continuously acquired acceleration a is larger than a threshold thre _ a _ t2 and the change of the M pieces of continuously acquired angular velocity ω is larger than a threshold thre _ ω _ t2, the change of the motion data acquired first among the pieces of motion data is larger than a threshold thre _ ω _ t2The time is determined as the upper limit t2 of the time interval. Here, N, M are all positive integers greater than 2.

At step 530, for example, the body size calculation unit 240 or computer processor, calculates each IMU over the time interval t₁，t₂]Mean velocity in

In said time interval t₁，t₂]At any sampling time point in the IMU, the instantaneous velocity of the IMU is

In the equation, a_tIs the time interval t₁，t₂]Internal sampling time t_iAcceleration of t_sIs the sampling interval. Then, in the time interval t₁，t₂]The average speed of the inner uniform circular motion isWhere n is the time interval t₁，t₂]The number of inter-sampled data.

At step 540, for example, the body size calculation unit 240 or computer processor, calculates each IMU over the time interval t₁，t₂]Mean angular velocity of the inner

In the time interval t₁，t₂]The average angular velocity of the inner uniform circular motion is

Where n is the time interval t₁，t₂]The number of internally sampled data, and ω_iIs the time interval t₁，t₂]Internal sampling time t_iThe instantaneous angular velocity of (a).

At step 550, for example, the body size calculation unit 240 or computer processorBased on said average speed

And the average angular velocity

To calculate the radius of rotation of each IMU

It should be appreciated that other methods for calculating the radius of rotation of each IMU may be used by those skilled in the art, while remaining within the spirit of the present invention.

Fig. 6 is a block diagram of a computing device 600 for performing body size measurements of a subject according to an embodiment of the invention. According to one embodiment, computing device 600 may include one or more processors 610. The processor 610 executes one or more computer-readable instructions stored or encoded in a computer-readable storage medium (i.e., memory 620).

In one embodiment, computer-executable instructions are stored in the memory 620 that, when executed, cause the one or more processors 610 to perform any of the methods previously described.

Embodiments of the invention provide a machine-readable medium having stored thereon machine-readable instructions, which, when executed by a processor, cause the processor to perform any of the methods described above. In particular, a system or apparatus may be provided which is provided with a machine-readable medium on which software program code implementing the functionality of any of the embodiments described above is stored and which causes a computer or processor of the system or apparatus to read and execute machine-readable instructions stored in the machine-readable medium.

In this case, the program code itself read from the machine-readable medium can realize the functions of any of the above-described embodiments, and thus the machine-readable code and the machine-readable medium storing the machine-readable code form part of the present invention.

Examples of the machine-readable medium include floppy disks, hard disks, magneto-optical disks, optical disks (e.g., CD-ROMs, CD-R, CD-RWs, DVD-ROMs, DVD-RAMs, DVD-RWs, DVD + RWs), magnetic tapes, nonvolatile memory cards, and ROMs. Alternatively, the program code may be downloaded from a server computer or from the cloud via a communications network.

It should be noted that not all steps and modules in the above flows and system structure diagrams are necessary, and some steps or modules may be omitted according to actual needs. The execution order of the steps is not fixed and can be adjusted as required. The system structure described in the above embodiments may be a physical structure or a logical structure, that is, some modules may be implemented by the same physical entity, or some modules may be implemented by a plurality of physical entities, or some components in a plurality of independent devices may be implemented together.

In the above embodiments, the hardware unit may be implemented mechanically or electrically. For example, a hardware element may comprise permanently dedicated circuitry or logic (such as a dedicated processor, FPGA or ASIC) to perform the corresponding operations. The hardware elements may also comprise programmable logic or circuitry, such as a general purpose processor or other programmable processor, that may be temporarily configured by software to perform the corresponding operations. The specific implementation (mechanical, or dedicated permanent, or temporarily set) may be determined based on cost and time considerations.

While the invention has been shown and described in detail in the drawings and in the preferred embodiments, it is not intended to limit the invention to the embodiments disclosed, and it will be apparent to those skilled in the art that various combinations of the code auditing means in the various embodiments described above may be used to obtain further embodiments of the invention, which are also within the scope of the invention.

In summary, the embodiment of the invention provides a method, a device and a system for measuring the body size of a subject based on a wearable inertial measurement unit. After attaching one or more inertial measurement units to at least one rotatable part of the object, the method comprises the steps of: acquiring motion data by at least one inertial measurement unit associated with the one or more rotatable parts involved while the object performs a measurement action involving the one or more rotatable parts; calculating a radius of rotation of each of the associated at least one inertial measurement unit based on motion data from the inertial measurement unit; and calculating the dimensions of the one or more rotatable portions based on the radius of rotation of the associated at least one inertial measurement unit and the respective positional relationship of the associated at least one inertial measurement unit to the respective rotatable portion. Compared with the traditional body size measuring method, the body size measuring method is simpler and more efficient. In addition, the invention can further analyze the motion gesture, thereby accelerating the simulation and verification of human-computer analysis and further accelerating the design cycle of a human-computer hybrid production line.