WO2004084725A1

WO2004084725A1 - Motion analysis system and method

Info

Publication number: WO2004084725A1
Application number: PCT/AU2004/000361
Authority: WO
Inventors: Jan JASIEWCZ; Andrew Barriskill; Michael Duncan; Simon Geoffrey Parker; Branka Curcic
Original assignee: Neopraxis Pty Ltd
Priority date: 2003-03-26
Filing date: 2004-03-23
Publication date: 2004-10-07
Also published as: AU2003901388A0

Abstract

A system (10) to analyse motion of an individual (16) has a sensor array (12) of a plurality of sensors (14). Each sensor is mountable at a predetermined location on the individual and is configured to sense predetermined parameters relating to the motion of the subject. The array of sensors communicates with a control device (18) that includes a data processor to provide analysis of the motion of the subject.

Description

"Motion analysis system and method" Field of the Invention

This invention relates to motion analysis. More particularly, the invention relates to a motion analysis system and to a method of analysing motion.

Background of the Invention

The need to monitor and analyse the motion of various elements of a moving body is important in understanding the relationship each moving element has to the overall desired motion of the body. This is important, whether the body is a piece of machinery with a number of moving components that may interact or whether the body is a human being performing simple motion like walking or complicated motion as may be the case in playing sport.

In all such cases, the ability to monitor and analyse the overall motion by analysing the motion of some moving parts, provides the opportunity to identify aspects of the overall movement that affect the efficiency and functionality of the overall movement. In analysing machinery used in an automated manufacturing plant, this may assist in identifying those parts of the machinery that experience undue force during operation to aid in explaining why such parts fail in the way they do. When applied to human motion, it may be possible to identify limb movements which are deficient or which greatly affect or reduce the efficiency of a simple action such as walking or standing still. This may be particularly important for individuals such as professional athletes who may wish to analyse their motion in great detail to ensure that they are performing to their optimal level or to improve their performance. Equally, individuals suffering from physiological disorders may also wish to analyse their motion in detail to ensure that assistance can be applied to those areas where help is needed.

In terms of human motion, there are very limited facilities to perform such monitoring and analysis. These facilities normally comprise dedicated equipment and laboratories. Typically, monitoring and analysis of human motion only occurs in laboratory settings using laboratory based equipment such as video motion analysis systems and floor mounted force platforms. While these systems are clinically efficient they are expensive to construct and operate. In addition, as there only about 200 suitably equipped laboratories worldwide, access to such facilities is typically restricted. Also, because of the demand placed on these facilities, users are only able to gain access for short periods of time. The laboratory environment is an artificial environment and "real life" analyses cannot be carried out. A need exists for a motion analysis system which is low cost, simple and low cost to operate and which can, if necessary, record "real life" measurements allowing data to be collected under actual community environmental conditions as the subject goes about activities of daily living or the particular activities to be studied. In particular, such a system would make gait analysis far more widely available for those individuals requiring such careful gait monitoring and analysis. Such a system could also be used to analyse real-time motions associated with sporting activities or everyday motions related to various physiological disorders including balance disorders or medication effectiveness associated with diseases such as Parkinson's Disease. The system could also be used to monitor the motion of animals such as horses or machine equipment without removing the subject from its natural setting.

Summary of the Invention According to a first aspect of the invention, there is provided a motion analysis system which comprises a sensor array comprising a plurality of sensors, each sensor being mountable at a predetermined location on an object, the motion of which is to be analysed, and each sensor being configured to sense predetermined parameters relating to the motion of the object; and a control device with which the sensor array communicates, the control device including a data processor for processing data relating to the sensed parameters received from the sensor array to provide an at least partial analysis of the motion of the object. The object being analysed may be an inanimate object such as a piece of machinery or it may be an animate object such as a person or animal.

Each sensor may include a signal processor and a number of parameter measuring devices, the signal processor converting the data relating to the parameters to measurement signals for transmission to the control device. The measuring device may include at least one angular movement measuring device and at least one acceleration measuring device. Typically, each sensor includes an angular movement measuring device in the form of a gyroscope and at least two acceleration measuring devices in the form of accelerometers. Thus, each sensor is able to measure angular velocity in at least one plane and acceleration in three dimensions. Other measuring devices such as magnetometers may also be employed. The system is intended specifically, but not necessarily exclusively, for analysing the movement of a person's body and, particularly, the person's limbs. Thus, by means of the sensor array, measurement of the movement of the person's limbs with reference to the sagittal plane and the coronal plane can be effected to enable such movement to be analysed.

Further, the signal processor of each sensor may include signal modifying capabilities for modifying a signal resulting from an out-of-range measurement to cater for extremes in the parameters being measured. This aspect is particularly useful due to high peak values arising in certain circumstances such as, for example, impact of a person's foot with the ground when walking or running. The peak value of such impact may be out of range of the sensor's measuring devices. By appropriate software manipulation of the measured signal, an approximation of the peak value may be able to be obtained for analysis purposes.

Still further, each sensor may include a data storage device in which data are stored to be transferred to the control device when that sensor is next interrogated or sampled by the control device.

Each sensor may include an input for receiving a signal from a secondary sensing device for onward transmission to the control device. The input may be an analog input and at least certain of the sensors of the sensor array may be used to transfer data from the secondary sensing devices to the control device. Thus, the system may include at least one secondary sensing device, the secondary sensing device being selected from the group comprising a pressure sensing device and a strain sensing device.

The control device may be a portable device. More particularly, the control device may be a pocket computer or PDA. If desired, the control device could be a personal computer (PC).

To facilitate operation of the control device, the control device may have a touch screen implemented user interface. This enables a user to enter data by means of a stylus of the control device in an efficient and user-friendly manner. The screen may be a liquid crystal display (LCD) and may be used for display of the analysed data.

The system may include a host computer to which the control device is connectable for uploading data from the control device to the host computer.

Typically, the control device may be connected to the host computer by a USB connection or an RS-232 connection. It will, however, be appreciated that the control device could communicate with the host computer wirelessly. The system may include a database for storing records relating to motion analysis of a group of objects, the database being accessible by at least one of the control device and the host computer.

The sensor array may communicate with the control device via a dedicated communications interface unit. The control device may include a flash memory card slot. The communications interface unit may include a flash memory card which interfaces to the control device via a compact flash bus. The sensor array may connect to the interface unit via one or more serial peripheral interface (SPI) buses or via wireless link. According to a second aspect of the invention, there is provided a method of analysing motion of an object, the method comprising mounting a sensor of a sensor array at each of predetermined locations on the object, the motion of which is to be analysed; sensing predetermined parameters relating to the motion of the object; and processing data relating to the sensed parameters received from the sensor array in a control device with which the sensor array is in communication to provide an at least partial analysis of the motion of the object.

The method may include, in each sensor, converting the data relating to the parameters to measurement signals for transmission to the control device. In particular, the method may include measuring at least one of angular movement and acceleration at each location.

In addition, the method may include modifying a signal resulting from an out- of-range measurement to cater for extremes in the parameters being measured.

Further, the method may include storing data in each sensor and transferring the data from that sensor to the control device when that sensor is next interrogated by the control device.

The method may include measuring at least one of pressure and strain at at least certain of the locations and forwarding data of such measurement via at least one of the sensors to the control device. Also, the method may include connecting the control device to a host computer and uploading data from the control device to the host computer.

The method may include storing records relating to motion analysis of a group of objects in a database accessible by at least one of the control device and the host computer.

Brief Description of the Drawings An embodiment of the invention is now described by way of example with reference to the accompanying drawings in which

Figure 1 shows a schematic diagram of a motion analysis system, in accordance with an embodiment of the invention; Figure 2 shows a block diagram of a sensor of the system;

Figure 3 shows a three dimensional view of a control device of the system;

Figure 4 shows a screen display of data to be entered prior to use of the system;

Figure 5 shows a schematic representation of where measurements are to be taken to enter into the screen display of Figure 4; Figure 6 shows a schematic representation of mounting of the sensors of the system on a person's body;

Figure 7 shows a schematic representation of initialising the system prior to commencing analysis;

Figure 8 shows a screen display of the control device after initialisation; and Figure 9 shows a screen display of a host computer of the system.

Detailed Description of Exemplary Embodiment

In Figure 1 of the drawings, reference numeral 10 generally designates a motion analysis system, in accordance with an embodiment of the invention, for measuring the motion of an object. The system 10 includes a sensor array 12 comprising a plurality of sensors 14.

The system 10 is intended particularly for use in the analysis of the gait of a subject or person 16 and will be described with reference to that application hereafter.

Those skilled in the art will, however, readily appreciate that the system 10 could be used in other applications without significant modification. In particular, the system 10 could be used for analysing the motion of animals and/or parts of machinery.

The sensors 14 of the sensor array 12 are mounted in predetermined locations on the body of the person 16, as will be described in greater detail below. Each sensor 14 is configured to sense predetermined parameters relating to the motion of the person's body to enable the gait of the person 16 to be analysed.

The sensor array 12 communicates with a control device 18. The control device 18 includes a data processor for processing data relating to the sensed parameters received from the sensor array 12 to provide an at least partial analysis of the gait of the person 16. Still further, the system 10 includes a host computer 20 with which the control device 18 communicates via an appropriate bus 22 such as a USB port or an RS-232 connection.

In addition, the system 10 includes a plurality of secondary sensing devices in the form of pressure sensors 24 and/or strain gauges 26. The secondary sensing devices 24, 26 communicate with the control device 18 through one or more of the sensors 14 of the sensor array 12.

Referring now to Figure 2 of the drawings, a block diagram of one of the sensors 14 is shown and is described in greater detail. Each sensor 14 includes a signal processor or microprocessor 28 which controls operation of the sensor 14. The microprocessor 28 includes a data storage device, or memory, (not shown) for storing data relating to measured parameters.

Each sensor 14 is intended to provide sagittal and coronal angle information, three dimensional linear acceleration and angular velocity in at least one dimension to the control device 18. These data are then used by the control device 18 to calculate the real time position and velocity of lower extremities 30 of the person 16. In so doing, analysis of the gait patterns of the person 16 can be effected.

Thus, each sensor 14 includes an angular movement measuring device in the form of a gyroscope 32. In addition, each sensor 14 includes two acceleration measuring devices in the form of accelerometers 34. The gyroscope 32 and the accelerometers 34 communicate with the microprocessor 28 via signal conditioning circuitry 36.

As described above, the pressure sensors 24 and strain gauges 26 communicate with the control device 18 via at least one of the sensors 14. For this purpose, each sensor 14 includes general purpose analog inputs 38. Each analog input 38 communicates with the microprocessor 28 via signal conditioning circuitry 40.

Each sensor 14 communicates with the control device 18 via a communications bus 42. The communications bus 42 is a serial peripheral interface (SPI) bus.

The sensor 14 also receives power from the control device via the SPI bus as indicated at 44. The power 44 is fed to the microprocessor 28 of the sensor 14 via a regulator circuit 46 and a brownout/reset circuit 48.

In addition, each sensor 14 includes an electronic serial number 50 for enabling that sensor 14 to be identified by the control device 18 for identification, addressing and re-configuration purposes. By means of the gyroscope 32 and the accelerometers 34, each sensor 14 is able to measure the sagittal angle, coronal angle, angular velocity in the sagittal plane, acceleration in three dimensions and, via the pressure sensors 24 and strain gauges 26, external voltage inputs. As a result, each sensor 14 is able to calculate the dynamic orientation of that sensor in one plane of motion, the sagittal plane. It is also able to calculate the static orientation of the sensor in the coronal plane. Still further, the sensor 14 measures angular velocity in the sagittal plane and measures acceleration components in three dimensions. The measurements are forwarded to the control device 18 to enable the control device 18 to analyse the gait of the person 16.

In measuring certain parameters, very high peak values result. For example, when the person's foot makes contact with a substrate, a very high, instantaneous peak value of angular velocity results. This peak value is out of range of the measuring capabilities of the sensor 14. To compensate for this, the microprocessor 28 of the sensor 14 includes signal modifying capabilities, implemented in software, for enabling signal modification to occur to enable an approximation of the peak value to be obtained for onward transmission to the control device 18 for analysis purposes. Thus, the microprocessor 28 effects error correction of such peak value signals prior to forwarding the signals to the control device 18.

As indicated above, the microprocessor 28 of each sensor 14 includes a data storage device. Data stored in the data storage device include data relating to peak acceleration values. These peak acceleration values are needed to detect acceleration spikes that are too brief to be detected when the control device 18 samples the sensor 14 at its normal sampling rate. The sampling rate is significantly slower than the internal analysis rate of the sensor 14. These peak acceleration values are the highest magnitude accelerations and these are stored between interrogation intervals. When such a peak acceleration value is detected by the sensor 14, that value is stored in the data storage device. When the control device 18 next interrogates the sensor 14, the stored peak acceleration value is made available to the control device 18.

Each sensor 14 also includes an enunciator (not shown), in the form of a light emitting diode (LED). The manner in which the LED is energised, or the cadence at which the LED flashes, is indicative of the status of the sensor 14. For example, if the LED flashes at a rapid cadence, this is an indication that a built in test of the LED has failed. Conversely, if the LED gives a short flash every few seconds, this indicates that the sensor 14 is operating normally. An inversion of this flashing sequence is an indication that the control device is currently addressing that sensor 14 for setup purposes. The control device 18 is in the form of a PDA 52. The PDA 52 has a touch screen 54 which is the form of a liquid crystal display. The sensor array 12 communicates with the control device 18 via an interface unit 56. The interface unit 56 has sockets 58 into which the SPI buses 42 from the sensors 14 are inserted.

The control device 18 has a flash memory card socket (not shown). The interface unit 56 has a flash connector which plugs into the memory card socket so that the interface unit 56 communicates with the control device 18 via a compact flash bus.

In measuring the gait of the person 16, seven sensors are used. As indicated in Figure 6 of the drawings, a first sensor 14.1 is mounted posteriorly on a torso 60 of the person 16. A sensor 14.2 is mounted anteriorly on each thigh of the person 16. A sensor

14.3 is mounted anteriorly on each shank of the person 16.

Finally, a sensor 14.4 is mounted on each foot of the person 16. The sensors 14.1-14.4 are interconnected via PDI cables 62 and a Y adaptor 64 to the interface unit 56 mounted on the control device 18. In use, the system 10 is provided together with a set of callipers for taking anthropometric measurements of the body of the person 16.

Thus, when a new subject is presented, before the person's gait can be analysed, the predetermined measurements must be taken. In particular, the following measurements are taken: - 1. trunk - as measured from glenohumeral joint 66 (Figure 5) to corresponding greater trochanter 68;

2. left thigh - as measured from left greater trochanter (not shown) to left tibial epicondyle (not shown);

3. right thigh - as measured from right greater trochanter 68 to right tibial epicondyle 70;

4. left shank - as measured from left tibial epicondyle to left lateral malleolus (not shown);

5. right shank - as measured from right epicondyle 70 to right lateral malleolus 72;

6. left foot - as measured from left lateral malleolus to left second metatarsal; 7. right foot - as measured from right lateral malleolus 72 to right second metatarsal;

8. left malleolus height - height of left lateral malleolus to ground;

9. right malleolus height - height of right lateral malleolus 72 to ground; and

10. distance from left greater trochanter to right greater trochanter 68. Each of these measurements is entered into the control device 18 via the touch screen 54 of the control device 18. A screen display of the control device 18 for enabling these measurements to be entered is shown at 74 in Figure 4 of the drawings. Once the person's measurements have been completed and their identification particulars entered into the control device 18, the sensors 14 of the sensor array 12 are attached to the body of the person 16 as shown in Figure 6 of the drawings. Each sensor 14 is labelled according to where it must be placed on the body of the person 16. Each sensor 14 is of a biocompatible material and is attached via suitable attachments such as a belt with a pocket for the sensor or via appropriate biocompatible adhesive tape. To facilitate correct orientation of each sensor 14, a housing of the sensor contains an appropriate marking such as an arrow.

Once the sensors 14 have been attached to the body of the person 16, the sensors 14 are connected together via the cables 62. The sensor array 12 is then connected via the interface unit 56 to the control device 18. After the sensor array 12 has been attached to the person 16, the person 16 is instructed to stand erect, as shown in Figure 7 of the drawings and the control device 18 is initialised. Initialisation of the control device is effected by touching a "Zero" icon 76 as shown in a screen display 78 in Figure 8 of the drawings. When this occurs a straight vertical line 80 appears on the screen display 78 indicating that the control device 18 has been initialised.

Gait analysis involves the consideration of various measurements. In particular, gait analysis involves determination of the gait velocity in metres per second, step length of both left and right limbs in metres and duration of double support (ie, standing on both feet) measured as a percentage of the gait cycle. The gait cycle comprises a two metre initial walk to get started followed by a ten metre walk while the gait of the person 16 is measured and recorded followed by a final two metres to finish the cycle. The test is conducted over the ten metre section of the cycle and a "Start" icon 82, which had previously been greyed out on the screen display 78 prior to initialisation of the control device 18, is touched to commence recording. As the person 16 walks along, the relative positions of the parts of the body of the person 16 carrying the sensors 14 are measured by means of the sensors 14 together with the acceleration components associated with movement of those parts. From the measured parameters, the required gait velocity, step length and duration of double support can be determined. Once the test has been completed, the information recorded can be reviewed by touching a "Review" icon (not shown) on the screen display of the control device 18. A seven segment stick figure moves on the screen showing how the subject walked in the test. The recorded information relating to gait velocity, step length and double support is also displayed on the screen.

Data from the control device 18 are uploaded to the computer 20 via the link 22. Figure 9 shows a screen display 84 of the computer 20. When the recorded information is being analysed or studied, a stick figure 86, similar to that which had been displayed on the screen 54 of the control device, is displayed on a part 88 of the screen display

84.

The screen display 84 comprises additional parts 90, 92 and 94 containing information relevant to the test.

The computer 20 contains, or is connected to, a database in which information regarding each person 16 is recorded for subsequent analysis and other record keeping purposes.

It will be appreciated that the system 10 can also be used in a more natural, day- to-day environment where movement of the person 16 is recorded for a longer period of time.

It is an advantage of the invention that a system 10 is provided which enables data to be recorded without the need for dedicated laboratories, force platforms, video cameras, or the like. Hence, the system 10 results in considerable cost savings while providing an easy to use, user-friendly interface for an operator. Very little expert training is required to implement the system 10.

The system 10 is particularly useful in situations where it is desirable to ascertain the effectiveness of medication associated with certain motor disorders such as Parkinson's Disease. It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the invention as shown in the specific embodiments without departing from the spirit or scope of the invention as broadly described. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.

Claims

CLAIMS:

1. A motion analysis system which comprises a sensor array comprising a plurality of sensors, each sensor being mountable at a predetermined location on an object, the motion of which is to be analysed, and each sensor being configured to sense predetermined parameters relating to the motion of the object; and a control device with which the sensor array communicates, the control device including a data processor for processing data relating to the sensed parameters received from the sensor array to provide an at least partial analysis of the motion of the object.

2. The system of claim 1 in which each sensor includes a signal processor and a number of parameter measuring devices, the signal processor converting the data relating to the parameters to measurement signals for transmission to the control device.

3. The system of claim 2 in which the measuring devices include at least one angular movement measuring device and at least one acceleration measuring device.

4. The system of claim 2 or claim 3 in which the signal processor includes signal modifying capabilities for modifying a signal resulting from an out-of-range measurement to cater for extremes in the parameters being measured.

5. The system of any one of claims 2 to 4 in which each sensor includes a data storage device in which data are stored to be transferred to the control device when that sensor is next interrogated by the control device.

6. The system of any one of the preceding claims in which each sensor includes an input for receiving a signal from a secondary sensing device for onward transmission to the control device.

7. The system of claim 6 which includes at least one secondary sensing device, the secondary sensing device being selected from the group comprising a pressure sensing device and a strain sensing device.

8. The system of any one of the preceding claims which includes a host computer to which the control device is connectable for uploading data from the control device to the host computer.

9. The system of claim 8 which includes a database for storing records relating to motion analysis of a group of objects, the database being accessible by at least one of the control device and the host computer.

10. The system of any one of the preceding claims in which the sensor array communicates with the control device via a dedicated communications interface unit.

11. A method of analysing motion of an object, the method comprising mounting a sensor of a sensor array at each of predetermined locations on the object, the motion of which is to be analysed; sensing predetermined parameters relating to the motion of the object; and processing data relating to the sensed parameters received from the sensor array in a control device with which the sensor array is in communication to provide an at least partial analysis of the motion of the object.

12. The method of claim 11 which includes, in each sensor, converting the data relating to the parameters to measurement signals for transmission to the control device.

13. The method of claim 11 or claim 12 which includes measuring at least one of angular movement and acceleration at each location.

14. The method of any one of claims 11 to 13 which includes modifying a signal resulting from an out-of-range measurement to cater for extremes in the parameters being measured.

15. The method of any one of claims 11 to 14 which includes storing data in each sensor and transferring the data from that sensor to the control device when that sensor is next interrogated by the control device.

16. The method of any one of claims 11 to 15 which includes measuring at least one of pressure and strain at at least certain of the locations and forwarding data of such measurement via at least one of the sensors to the control device.

17. The method of any one of claims 11 to 16 which includes connecting the control device to a host computer and uploading data from the control device to the host computer.

18. The method of any one of claims 11 to 17 which includes storing records relating to motion analysis of a group of objects in a database accessible by at least one of the control device and the host computer.