System and method for monitoring the gait of a user with a leg prosthesis

Abstract

Method and system for monitoring the gait of a user with a leg prosthesis (1, 2), comprising: a sensor device (3) configured to be inserted into a lower section of the prosthesis, wherein the sensor device comprises a force sensor (5), an inertial sensor (6) to obtain measurements of angular velocity, linear acceleration and orientation of the prosthesis while walking, and a control module (7) to process the measurements from the sensors and send them to a processor module; and a processor module to receive the measurements processed by the control module, compare them with reference information about the user's gait, determine whether the comparison exceeds a predetermined threshold and, if so, generate a warning signal.

Description

[0001] SYSTEM AND METHOD FOR MONITORING THE GAIT OF A USER WITH A LEG PROSTHESIS

[0002] DESCRIPTION

[0003] OBJECT OF THE INVENTION

[0004] The present invention relates to the technical field of health and biomedical technology and more specifically to intelligent devices for monitoring the gait of users with leg prostheses, one of the objectives being to facilitate their adaptation to it.

[0005] BACKGROUND OF THE INVENTION

[0006] Currently, when a person suffers a leg amputation, whether above or below the knee, health and biomedical technology offers the possibility of regaining mobility, at least partially, using a prosthetic leg. However, adapting to these prostheses is not immediate; it requires a period of adjustment and learning to adapt gait to the patient's new condition.

[0007] As is typical in the prosthesis fitting process, it begins with an initial adjustment phase by the medical team, during which the prosthesis is fitted to the user as closely as possible. The goal is to minimize, as much as possible, damage from weight-bearing, friction sores, and other issues. Subsequently, based on the patient's personal experience, their individual adaptation to the prosthesis, and the healthcare staff's observational skills during the fitting process, the patient receives advice and recommendations to gradually correct their gait through a process of trial and error. This process continues until the patient manages to minimize friction, ulcers, and the risk of falls, for example. Therefore, this process is relatively slow and not very sensitive, as corrections are only made once the issues requiring correction become readily apparent.

[0008] Therefore, there is a lack of a state-of-the-art solution that allows users of prosthetic legs, especially during their adaptation phase, to monitor their movement in a personalized way, so that they can anticipate and avoid potential gait abnormalities through early correction.

[0009] DESCRIPTION OF THE INVENTION

[0010] In order to achieve the objectives and avoid the aforementioned drawbacks, the present invention describes, in a first aspect, a system for monitoring the gait of a user with a prosthetic leg attached to a first leg. The system is characterized in that it comprises:

[0011] - a sensor device configured to be inserted into a lower section of the user's leg prosthesis, wherein the sensor device comprises:

[0012] - a force sensor configured to obtain measurements of the force applied to the prosthesis during walking;

[0013] - an industrial sensor configured to obtain measurements of angular velocity, linear acceleration and orientation of the prosthesis during gait;

[0014] - a control module, configured to process the sensor measurements and send them to a processing module;

[0015] - a processor module configured to receive the measurements processed by the control module, compare them with a reference gait data of the user, determine if the comparison exceeds a predetermined threshold and, if so, generate a warning signal.

[0016] Additionally, one embodiment of the invention comprises a second sensor device configured to be inserted into an upper section of the user's leg prosthesis, where the upper section is defined from an upper end of the prosthesis to an intermediate patella element, where the second sensor device comprises the same elements as the first sensor device.

[0017] In one embodiment of the invention, additional reference sensor devices are also contemplated, configured to be placed on a second leg of the user different from the first leg of the user with a prosthetic leg, wherein the additional sensors comprise: a reference force sensor attachable to a footwear of the user, configured to obtain reference force measurements of the second leg during walking; and at least one reference inertial sensor attachable to the second leg of the user, configured to obtain reference measurements of angular velocity, linear acceleration and orientation of the second leg during walking.The processor module, according to one embodiment of the invention, is configured to determine, based on the measurements received from the sensor devices, a set of variables of interest to monitor the user's gait, comprising one or more of the following: support force pattern of each leg, percentage of load on each leg in static position, percentage of load on each leg in motion, 3D movement of each leg, force-based symmetry index, force-based symmetry index and 3D movement, gait speed, plane of advance, and activity performed.

[0018] According to one embodiment of the invention, the sensor devices comprise a male connector at one end and a female connector at the opposite end, configured to connect the sensor device to the leg prosthesis by means of a tongue-and-groove joint.

[0019] The sensor device, according to one embodiment of the invention, also comprises a barometer sensor, configured to obtain height measurements of the leg prosthesis during walking.

[0020] The sensor device, according to one embodiment of the invention, further comprises an obstacle detection sensor, selectable between an infrared sensor and an ultrasonic sensor, configured to detect an object in proximity to the user while walking.

[0021] The sensor device, according to one embodiment of the invention, further comprises audio playback means configured to emit a sound if the processor module determines that one of the variables has exceeded the preset threshold and generates a warning signal to correct the driving.

[0022] The force sensor, according to one embodiment of the invention, is a piezoelectric sensor that has a toroidal washer configured to establish a preload level in the sensor.

[0023] The control module, according to one embodiment of the invention, comprises a low-power wireless communications module. The processor module, according to one embodiment of the invention, is integrated into a mobile device, selectable from a computer, a mobile phone, or a digital tablet.

[0024] A second aspect of the invention relates to a method for monitoring the gait of a user with a prosthetic leg on one leg. The method comprises the following steps:

[0025] - inserting, in a lower section of the user's leg prosthesis, a sensor device according to any of the above embodiments;

[0026] - to obtain, by means of a force sensor of the sensor device, measurements of the force applied to the prosthesis during walking;

[0027] - to obtain, by means of an industrial sensor of the sensor device, measurements of angular velocity, linear acceleration and orientation of the prosthesis during walking;

[0028] - to process, by a control module, the measurements from the sensors;

[0029] - send the processed measurements to a processing module;

[0030] - compare, by the processing module, the processed measurements with a reference information of the user's gait;

[0031] - determine, by the processor module, whether the comparison exceeds a predetermined threshold;

[0032] - if so, generate a warning signal, which advantageously provides biofeedback to the user.

[0033] Additionally, one embodiment of the invention includes: inserting a second sensor device, according to any of the preceding embodiments, into an upper section of the user's leg prosthesis, where the upper section is defined from an upper end of the prosthesis to an intermediate patellar element; obtaining, by means of a second force sensor of the second sensor device, second measurements of force applied to a patellar element of the prosthesis during gait; obtaining, by means of a second inertial sensor of the second sensor device, second measurements of angular velocity, linear acceleration, and orientation of the prosthesis during gait; processing, by means of a second control module, the second measurements from the second sensors; sending the processed second measurements to the processing module; and comparing, by means of the processing module, the processed second measurements with a second reference gait data of the user.determine, by the processor module, whether the comparison exceeds a predetermined threshold; and if so, generate a warning signal that provides biofeedback for the user.

[0034] According to one embodiment of the invention, obtaining the user's gait reference information comprises: having additional reference sensors on a second leg of the user, different from the first leg of the user with a prosthetic leg; obtaining, by means of a reference force sensor, reference force measurements of the second leg during gait; and obtaining, by means of at least one reference industrial sensor, reference measurements of angular velocity, linear acceleration and orientation of the second leg during gait.

[0035] In a specific embodiment, it is also contemplated to determine, by the processor module, a set of variables of interest to monitor the user's gait, based on the measurements received from the sensor devices comprising one or more of the following: support force pattern of each leg, percentage of load on each leg in static, percentage of load on each leg in motion, 3D movement of each leg, force-based symmetry index, force-based symmetry index and 3D movement, gait speed, plane of advance and activity performed.

[0036] BRIEF DESCRIPTION OF THE FIGURES

[0037] To complete the description of the invention and to aid in a better understanding of its characteristics, according to a preferred embodiment thereof, a set of drawings is included in which, for illustrative and non-limiting purposes, the following figures have been represented:

[0038] - Figures 1A and 1B represent two of the possible prostheses that a patient can use, depending on how the amputation was performed: below the knee (represented in figure 1A) or above the knee (represented in figure 1B).

[0039] - Figure 2 shows in detail the internal components of the sensor devices.

[0040] Figure 3 shows a detail of the obstacle sensor that can be placed on the front surface of a first sensor device in a transtibial position. Figure 4 shows a detail of the tongue-and-groove mechanical connections of the first sensor device, in a transtibial position, and of the second sensor device, in a transfemoral position, with the rest of the leg prosthesis.

[0041] - Figure 5 represents an embodiment of a sensor device, valid for placement above the patella (transfemoral) as well as below the patella (transtibial), which incorporates a piezoelectric force sensor.

[0042] Figures 6A and 6B illustrate different embodiments of the force sensor of the sensing device, both with a compressible fluid, where Figure 6A comprises a piezoelectric force sensor, while Figure 6B comprises a strain sensor.

[0043] - Figure 7 illustrates the patient's forward movement plane, defined by the x' axis, the direction of the person's forward movement, and the z' axis perpendicular to the ground, rotated a certain angle with respect to a fixed reference system.

[0044] - Figures 8A and 8B represent the arrangement of sensors on the patient's healthy leg, according to the respective prosthetic leg configurations of Figures 1A and 1B.

[0045] - Figure 9 illustrates a block diagram with all the elements of an embodiment of the invention with a first sensor device, in a transtibial position, and a second sensor device, in a transfemoral position.

[0046] - Figure 10 represents a hardware architecture of the sensors attachable to the patient's healthy leg equivalent to that of Figure 9 for the prosthetic leg.

[0047] - Figure 11 graphically represents an example of a support pattern as a variable of interest.

[0048] - Figure 12 represents a flowchart of the procedure of the present invention during the user's adaptation to the prosthesis, according to one of the embodiments. - Figure 13 represents an example on-screen HMI interface.

[0049] - Figure 14 represents a flowchart of the anomaly detection procedure of the present invention, according to one of the embodiments

[0050] DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION

[0051] With the support of the figures accompanying this description, the present invention discloses a method and a sensor-based system that allows for the non-invasive characterization of the gait of individuals requiring the use of a leg prosthesis. It is particularly useful in the patient's adaptation process to a leg prosthesis following an amputation, in which the affected person must first learn to walk with the prosthesis and modify their gait until achieving optimal balance between both limbs. During the initial adaptation phase, the monitoring method and system of the present invention provides biofeedback data associated with certain parameters of the user's gait, allowing them to become aware when the prosthesis is not being used correctly and to correct their gait accordingly.As a result, the user's adaptation period to the prosthesis is reduced, as well as the possibility of suffering falls during learning or the appearance of ulcers in the contact areas.

[0052] Figure 1 illustrates two of the possible prostheses that a patient can use, depending on how the amputation was performed: below the knee (represented in Figure 1A) or above the knee (represented in Figure 1B).

[0053] Thus, Figure 1B illustrates a prosthesis 2 adapted for cases of above-knee amputation. In this case, the monitoring system of the present invention comprises two main sensor devices: a first sensor device 3 located in the transtibial (lower) portion and a second sensor device 4 located in the transfemoral (upper) portion. Therefore, throughout the text, the first sensor device may be referred to interchangeably as the transtibial device or transtibial sensor device, and the second sensor device as the transfemoral device or transfemoral sensor device.

[0054] The transfemoral sensor device 4 (at the top of the prosthesis) comprises at least one force sensor 5 and one inertial sensor 6 for capturing three-dimensional movements. Both sensors 5 and 6 are arranged on the central axis of the prosthesis 2 above the prosthetic knee 26. The information obtained from the force sensor 5, in isolation, is a direct measurement of the force applied along the axial axis of the prosthesis (up to the knee). However, in combination with the transtibial sensor device 3 and the 3D motion inertial sensors 6 of the transtibial sensor 3 and transfemoral sensor 4, it allows the determination of the force vectors on the prosthesis (the support on the amputated limb).On the other hand, the information obtained from the inertial sensor 6, in isolation, provides a measurement of the angular velocity of movement in the prosthesis's reference frame, linear acceleration in the prosthesis's reference frame, and the 3D orientation of the prosthesis with respect to the fixed reference frame associated with the ground. However, when combined with the transtibial sensor device 3, it allows for the determination of the prosthesis's "knee" or joint angle, in order to characterize the complete movement of the lower limb. Additionally, in some embodiments, a barometer 8 is also incorporated into the transfemoral sensor device 4 to obtain a height measurement of the transfemoral sensor device 4.

[0055] The transtibial sensor device 3 (located on the underside of the prosthesis) comprises at least one force sensor 5 and one inertial sensor 6 for capturing three-dimensional movements. Both sensors 5 and 6 are positioned on the central axis of the prosthesis 2 at the ankle. The force sensor 5 of the transtibial sensor device 3 measures the force applied along the axial axis of the prosthesis, thus determining the force exerted on the prosthesis and, consequently, the weight applied to it.On the other hand, the information obtained from the inertial sensor 6 of the transtibial device 3 is a measurement of the angular velocity of movement in the prosthesis's reference frame, linear acceleration in the prosthesis's reference frame, and the three-dimensional orientation of the prosthesis with respect to the fixed reference frame associated with the ground. This information is used to determine the prosthesis's movement velocities, as well as to calculate its orientation and displacement. Optionally, some embodiments also incorporate a barometer 8 into the transtibial sensor device 3 to obtain a height measurement of the device.Optionally, some embodiments, such as the one shown in Figures 2 and 3, also include an obstacle sensor 10, which can be implemented using ultrasound or infrared technology. This sensor is located on the front surface of the sensor device so that it detects any obstacle 11 that may be in the patient's path. The information obtained is a measurement of the distance of an obstacle from the prosthetic leg, with the aim of preventing the user from falling by alerting them before exceeding a predetermined minimum distance.

[0056] Figure 1A illustrates a prosthesis 1 adapted for below-knee amputations. In this case, the monitoring system of the present invention consists of a single sensor device 3, located on the transtibial (lower) portion. In this case, information regarding knee joint movement is not available (it does not exist in this type of prosthesis), but it allows the determination of the weight or load-bearing capacity of the amputated limb.

[0057] Figure 4 illustrates a connection of the transtibial 3 and transfemoral 4 sensor devices with the rest of the leg prosthesis 1, 2. Since the mechanical connections of the different elements of a prosthesis (shaft, prosthetic foot, joints, etc.) are standardized by each manufacturer, to minimize the impact of incorporating the present invention into said prostheses, standardized male 13 and female 12 connections are provided on the sensor devices 1, 2 to facilitate their incorporation into the prosthesis by means of tongue and groove joints.

[0058] The force sensor 5 described in sensor devices 3 and 4 can be implemented in various ways. A piezoelectric force sensor is preferred, but other alternatives are not excluded. For more accurate force measurement, a preload is provided to ensure operation within the sensor's linear range, thus avoiding dead zones in the measurement or undesirable effects such as friction in the elements that transmit and subsequently measure the forces.

[0059] Figure 5 illustrates an embodiment of a sensor device, suitable for both transfemoral and transtibial placement, which incorporates a piezoelectric force sensor 14 to receive the force transmitted by the prosthesis shaft. The prosthesis shaft allows for micrometric movement of a stem 27 that contacts the piezoelectric sensor 14, compressing it according to the applied force. To ensure accurate measurement, a toroidal washer 15 is incorporated between the pressure point of the piezoelectric force sensor 14 and the force transmission means. This ensures that the sensor is always compressed to a pre-calculated force consistent with the sensor's measurement curve. Thus, when an additional force is applied via the stem 27, this force is added to that of the toroidal washer 15. The measurement offset generated by the washer is subsequently compensated for during data processing.Furthermore, since pre-charging ensures that, in the absence of a real load, the sensor always measures a known and bounded minimum value, the safety and reliability of the system are improved, because if the microcontroller measures a null value, it means that the sensor or the connections are damaged.

[0060] Figures 6A and 6B illustrate an embodiment of the sensor device, valid for both transfemoral and transtibial placement, where the sensor encapsulation incorporates, in addition to a hollow area 29 common to all embodiments in which to house the necessary electronic components, a cavity 28 that is filled with a compressible fluid 30. This fluid 30 is actuated by a plunger 31 attached to the prosthesis coupling, so that the axial force exerted on the prosthesis displaces the plunger 31 and compresses the fluid 30. In order to guarantee a constant and known pressure in the absence of load, the fluid is introduced at a certain pressure into the cavity 28, or a spring mechanism or other compressible material is incorporated that exerts a force on the plunger, guaranteeing an offset pressure when there is no applied axial load.

[0061] The measurement of the applied force can be performed using two possible alternatives. Figure 6A is a similar embodiment to that of Figure 5, in that there is a pressure sensor located in cavity 28 (piezoelectric, diaphragm-based, or similar sensor). In contrast, in Figure 6B, cavity 28 is designed to be slightly deformable by incorporating a deformable material 32 into its side walls, so that resistive strain sensors 33 or similar can be used to characterize the applied force as a function of the measured deformation.

[0062] The 3D inertial motion sensor 6 is used to determine the orientation of the prosthetic leg. These inertial sensors 6, or IMUs, which are incorporated into both the transfemoral 4 and transtibial 3 sensor devices—equivalent to the inertial sensors 17 attached to the patient's non-prosthetic leg as described later—generally provide three types of measurements: acceleration, velocity, and magnetic field, all along three axes. Techniques for determining the absolute orientation of these devices (in their local reference frame) with respect to a "world" (global) (xyz) reference frame, in which the z-axis is perpendicular to the ground and the xy-plane is parallel to it, are widely known in the literature. Different techniques exist to achieve this functionality, such as extracting the fundamental acceleration components to determine the gravity vector, which will always be located along the -z-axis.The use of a magnetometer also allows these motion sensor measurements, regardless of the technique used, to provide their orientations relative to a reference system where the x-axis is oriented towards magnetic north. However, for the 3D motion monitoring required by these devices, it is necessary to consider a reference system that is not global (located anywhere in the world and oriented towards the north), but rather relative to the user's body (x'y'z'). Therefore, the concept of the forward plane is defined as the plane formed by the z' axis (perpendicular to the ground) and the user's forward direction vector (x'y'). This plane, perpendicular to the ground and linked to the user's body, allows for the definition of a common reference for calculating the angles associated with the user's gait.

[0063] To calculate the forward motion, the kinetic sensor 17 located in the tibial region is used along with a force template 16 (when collecting measurements of a leg without a prosthesis), or the transtibial sensor device 3 with the kinetic sensor 6 and the force sensor 5 (when collecting measurements of the leg with a prosthesis). These devices are in contact with the ground, making it possible to calculate the forward motion based on the pivoting on the ground, as detailed below.

[0064] 1- In each cycle (or step), the phase in which the foot or prosthesis is in contact with the ground (stance phase) is determined. In this phase, the prosthesis or leg pivots on the ground, and forward movement occurs within a certain time frame. Therefore, with respect to the force sensor output signal, the stance phase coincides with the period in which the output signal is not zero.

[0065] 2- During the stance phase, the absolute orientation of the 3D position sensor is calculated with respect to the global reference frame. This allows the definition of a vector that represents the tibia of the non-prosthetic leg (or the prosthetic shaft) in 3D within this reference frame.

[0066] 3- During the stance phase, this vector is represented in the global reference system, defining a point cloud associated with the movement of the tibia / shaft of the prosthesis. The point cloud is calculated in the global reference system with the XY planes parallel to the ground and the z-axis perpendicular.

[0067] 4- A linear regression of the points is performed to establish the main direction of movement, and this is projected onto the XY plane. From this line, it is possible to determine the angle 0 that must be rotated around the z-axis so that the x-axis aligns with the direction of the patient's movement.

[0068] 5- Finally, the rotation is carried out by an angle 0, defining the forward plane 34 by the x' axis, the direction of the person's forward movement and the z' axis, perpendicular to the ground, as can be seen in figure 7.

[0069] Figures 8A and 8B illustrate the devices corresponding to the patient's leg without a prosthesis. Since the objective is to obtain reference values ​​for monitoring the prosthetic leg, the number and arrangement of sensors on the sound leg depends on the type of prosthesis used on the other leg, aiming for the most symmetrical arrangement possible. Therefore, corresponding to a prosthesis 1 adapted for below-knee amputations, two sensor devices are incorporated into the sound leg: a 3D inertial motion sensor 17 (IMU) in the transtibial area and a force insole 16 attachable to the patient's footwear, as shown in Figure 8A.In contrast, in correspondence with a prosthesis 2 adapted for cases with above-the-knee amputation, three sensor devices are incorporated in the healthy leg: two inertial motion sensors 17, one of them in the transtibial area and the other in the transfemoral area, and a force insole 16 as represented in figure 8B.

[0070] The 17 3D inertial motion sensors provide information on angular velocity along the sensor's local axes, linear acceleration along the sensor's local axes, and 3D orientation in the Global Reference System. This is traditionally achieved by detecting the gravity vector (aligned with the -z axis, perpendicular to the ground) and detecting magnetic north with the magnetometer, aligning this north with the global x-axis. Once this Global Reference System is established, the relative angles between the sensor and the Global Reference System are determined.

[0071] The reference force measurement sensor, which in this case is implemented in a force template 16 attachable to the patient's footwear, provides a measurement of the force applied to the healthy leg, in order to measure the difference in force applied with respect to the prosthetic leg.

[0072] Figure 9 shows a block diagram with all the elements in an embodiment of the invention comprising a transtibial sensor device 3 and a transfemoral sensor device 4. The signals generated by the transfemoral and transtibial sensor devices 4 must be correctly processed and digitized. For this purpose, a hardware architecture is provided in which the sensors (barometer 8, force sensor 5, inertial sensor 6, and obstacle sensor 10) are connected to a data acquisition board consisting of the following blocks.

[0073] • Control Module 7: Implemented by a controller configured to capture and process data. It manages the entire device, including communication and charging of the associated battery, performs status diagnostics, and allows synchronization with other devices (in the case of combined transtibial, transfemoral, and unaffected leg devices).

[0074] • Signal processing circuits 18: adapt the sensor signals to be processed by the control module 7. These can be analog signals or digital communications such as SPI or I2C. They include the circuitry necessary to ensure proper signal processing, and may include filters or amplifiers.

[0075] • Power and supply circuit 9: allows the transfer of energy from the battery and its conversion to the appropriate voltage levels for each sensor. It also allows the incorporation of elements that help manage the battery's charging via an external charger.

[0076] • Communications module 19: incorporates low-power wireless communication electronics such as Bluetooth or WiFi. Data captured by the sensor devices, through their respective sensors, is sent, once processed by control module 7, to a mobile device 21 from communications module 19 of the transtibial sensor device 3. The processor module integrated into the mobile device 21, through a specific software application, allows monitoring and configuration of the sensor devices.

[0077] Additionally, the transtibial sensor device 3 can incorporate notification elements 20 to provide biofeedback to the user. For example, a speaker to generate beeps or alarms if risky situations are detected, such as a fall, or an LED to indicate risky situations or low battery by flashing.

[0078] Figure 10 represents a hardware architecture for the sensors attachable to the patient's healthy leg, equivalent to that shown in Figure 9 for the prosthetic leg. Thus, the 3D motion inertial sensors 17 and the force insoles 16 are connected to a data acquisition board identical to that shown in Figure 9, i.e., composed of a control module 22, a signal processing circuit 24, a power and supply circuit 23, and a communications module 25, all of which are identical or equivalent components to those described above.

[0079] The set of sensor devices described, according to the configurations described, results in a sensorized prosthetic device that allows the user, or a third party, to monitor the use they are making of the prosthesis and accelerate their adaptation thanks to the correction signals generated by the system by comparing it with the reference measurements obtained from the healthy leg.

[0080] The available variables are defined below, which are extracted from the information provided by the sensors and from the interrelation between them:

[0081] Figure 11 graphically represents one of these variables, specifically the support pattern, where the force sensor generates a peak-and-valley signal in response to the force exerted during each support phase of the monitored leg. The graph reveals that the sections with no signal (36) correspond to the moments when the leg is not in support, and conversely, the sections with a signal (37) correspond to the moments when the leg is in support. Additionally, a preload value (38) is also observed in the graph. For comparing values ​​between both legs and monitoring gait within pre-established ranges referenced to the unaffected leg, the following variables are of particular interest.

[0082] As illustrated in the flowchart in Figure 12, once the sensors are arranged according to one of the configurations described above, the test (39) begins for a specific patient, thus initiating the monitoring (40) of the patient's gait. The objective is to obtain the variables of interest detailed in the table above from the data provided by the sensors defined in the different implementations. These variables of interest are extracted according to each detected gait cycle (41), which is defined as each step taken by the user with each leg.Thus, after two consecutive steps (one with each leg), the data associated with each leg can be extracted independently. On one hand, the signals from the sensorized prosthesis are captured and processed (42), and on the other hand, the signals from the healthy leg are captured and processed (43). This allows for a comparison of the movement patterns of each leg and the extraction of variables of interest to characterize gait (44). This also helps determine, for example, the degree of symmetry / similarity of these estimated variables of interest for each leg. At this point, it is checked whether the gait monitoring remains within the established thresholds (45) for the variables of interest. If any of the established thresholds are exceeded, a warning signal (46) is generated (also known as 'biofeedback'), allowing the user to correct (47) the prosthesis's gait pattern / use.However, if the established threshold is significantly exceeded or not corrected within a certain time (e.g., twice the reference value, or during half of the test), a specific warning signal (48) is generated to review the prosthesis settings, since in this case the variation in the pattern may be due to an incorrect fit of the prosthesis to the stump.

[0083] The feedback provided by the method and system of the present invention, enabling the user to receive real-time correction instructions, can be implemented in various embodiments, including, individually or in combination, visual and auditory systems. One embodiment comprises a series of multicolored LEDs that activate in different colors according to the detection of abnormal gait patterns. When the LEDs are integrated into the sensor devices, a therapist is required to supervise the test, although it is also possible to display the LEDs in an external module visible to the patient. The sensor devices are equipped with a speaker configured to emit sounds of varying frequencies depending on the degree of deviation detected, remaining silent when the device detects correct gait.Another visual mechanism considered in one of the implementations is a wirelessly connected HMI (human-machine interface) screen. Placed, for example, at the end of a patient's trial run, it displays information on relevant variables within the patient's field of vision. Figure 13 shows an example interface, where the HMI screen 49 includes a first information panel 50, displayed as a bar graph, showing the patient's trunk tilt; a second information panel 51, showing certain relevant variables for the prosthetic leg; and a third information panel 52, showing the same relevant variables for the sound leg. This allows for the addition of gamification elements to the learning and fitting process of the prosthesis.

[0084] Another application of the monitoring system of the present invention is the detection of gait abnormalities once the user has adapted to the prosthesis and is using it daily. Since the sensors are not removed from the sensorized prosthesis, they can be used to continue monitoring the user's gait and physical activity on a daily basis, thus allowing for the prevention and detection of complications. For this monitoring, it is not necessary to attach the sensors to the healthy leg. The monitoring and abnormality detection process consists of three phases, represented in the flowchart in Figure 14. In the first phase, gait monitoring (53) is performed, for which the methodology is similar to that defined in Figure 12. First, gait cycle detection (54) is performed, considering one gait cycle (one step of the prosthesis) as a reference. Therefore, it is necessary to identify this cycle.To achieve this, the captured data is stored in a buffer, and when a complete cycle is detected, the process jumps to the next phase. Next, signals from the prosthesis are captured and processed (55), where, once a step is detected, the signals associated with that time frame are processed independently. Finally, variables are extracted (56) for gait characterization, selecting from: percentage of load on each leg, 3D movement of each leg; symmetry index, gait cadence / speed; plane of stride, activity performed, and risk of falling.

[0085] In a second phase, the data obtained for each step is stored in a buffer or memory (57), where the history of the variables associated with the last few steps is recorded. This memory is periodically analyzed by a physical activity detector module. The most recent steps (for example, those corresponding to the last 5 minutes) are processed by this detector, which determines the physical activity being performed for each step and, in particular, whether the user is walking (58). If walking is detected during the last few minutes, the direction is analyzed using the forward movement plane. If the user has been walking in a straight line for the last few meters, the process moves to the next phase, as this scenario allows for the evaluation of the user's condition.

[0086] In the third phase, if the standardized test conditions (walking in a straight line) are detected, the data associated with the variables of interest for that activity are retrieved from the "steps" memory (i.e., the last 10 meters are extracted from memory), and the variables of interest (59) are processed to determine if their value corresponds to the previously established ranges. Specifically, the percentage of load on each leg, the force-based symmetry index, the plane of stride, and the risk of falling are considered. If an anomaly (60) is detected—that is, if any of the indicated variables falls outside the range configured during the prosthesis adaptation phase—the device generates a warning signal (61) so that the user is aware of the detected anomaly and can take the necessary preventative measures.

[0087] The present invention is not limited to the embodiment described herein. Other configurations may be realized by those skilled in the art in light of this description. Accordingly, the scope of the invention is defined by the following claims.

Claims

CLAIMS 1. A system for monitoring the gait of a user with a prosthetic leg (1, 2) on a first leg, wherein the system is characterized in that it comprises: - a sensor device (3) configured to be inserted into a lower section of the user's leg prosthesis, wherein the sensor device (3) comprises: - a force sensor (5) configured to obtain measurements of force applied to the prosthesis during walking; - an inertial sensor (6) configured to obtain measurements of angular velocity, linear acceleration and orientation of the prosthesis during walking; - a control module (7), configured to process the sensor measurements and send them to a processing module; - a processor module configured to receive the measurements processed by the control module, compare them with a reference gait data of the user, determine if the comparison exceeds a predetermined threshold and, if so, generate a warning signal.

2. The system of claim 1 further comprising a second sensor device (4) configured to be inserted into an upper section of the user's leg prosthesis, wherein the upper section is defined from an upper end of the prosthesis to an intermediate patella element, wherein the second sensor device (4) comprises the same elements as the sensor device (3).

3. The system of any of the preceding claims further comprising additional reference sensor devices configured to be placed on a second leg of the user, different from the first leg of the user with a prosthetic leg, wherein the additional sensors comprise: - a reference force sensor (16) attachable to a user's footwear, configured to obtain reference force measurements of the second leg during walking; - at least one reference industrial sensor (17) attachable to the user's second leg, configured to obtain reference measurements of angular velocity, linear acceleration and orientation of the second leg during walking.

4. The system of claim 3 wherein the processor module is configured to To determine, based on the measurements received from the sensor devices, a set of variables of interest to monitor the user's gait comprising one or more of the following: support force pattern of each leg, percentage of load on each leg in static position, percentage of load on each leg in motion, 3D movement of each leg, force-based symmetry index, force-based symmetry index and 3D movement, gait speed, plane of advance, and activity performed.

5. The system of any of the preceding claims, wherein the sensor devices comprise a male-type connector (12) at one end and a female-type connector (13) at the opposite end, configured to connect the sensor device to the leg prosthesis by means of a tongue-and-groove joint.

6. The system of any of the preceding claims wherein the sensor device further comprises a barometer sensor (8), configured to obtain height measurements of the leg prosthesis during walking.

7. The system of any of the preceding claims wherein the sensor device (3) further comprises an obstacle detection sensor (10), selectable from an infrared sensor and an ultrasonic sensor, configured to detect an object in proximity to the user while walking.

8. The system of any of the preceding claims wherein the sensor device further comprises audio playback means configured to emit a sound if the processor module determines that one of the variables has exceeded the preset threshold and generates a warning signal to correct the driving.

9. The system of any of the preceding claims wherein the force sensor is a piezoelectric sensor (14) having a toroidal washer (15) configured to establish a preload level on the sensor.

10. The system of any of the preceding claims wherein the control module (7) comprises a low-power wireless communications module.

11. The system of any of the preceding claims, wherein the processor module is integrated into a mobile device (21) to be selected from a computer, a mobile phone and a digital tablet.

12. A method for monitoring the gait of a user with a prosthetic leg on a first leg, wherein the method is characterized in that it comprises the following steps: - inserting, in a lower section of the user's leg prosthesis, a sensor device according to any of claims 1-11; - to obtain, by means of a force sensor of the sensor device, measurements of the force applied to the prosthesis during walking; - to obtain, by means of an industrial sensor of the sensor device, measurements of angular velocity, linear acceleration and orientation of the prosthesis during walking; - to process, by a control module, the measurements from the sensors; - send the processed measurements to a processing module; - compare, by the processing module, the processed measurements with a reference information of the user's gait; - determine, by the processor module, whether the comparison exceeds a predetermined threshold; and - If so, generate a warning signal.

13. Method according to claim 12 further comprising: - inserting a second sensor device according to any of claims 2-11, in an upper section of the user's leg prosthesis, wherein the upper section is defined from an upper end of the prosthesis to an intermediate patella element; - to obtain, by a second force sensor of the second sensor device, a second measurement of force applied to a patella element of the prosthesis during walking; - to obtain, by a second industrial sensor of the second sensor device, second measurements of angular velocity, linear acceleration and orientation of the prosthesis during walking; - to process, by a second control module, the second measurements from the second sensors; - send the second processed measurements to the processing module; - compare, by the processing module, the second processed measurements with a second reference information of the user's gait; - determine, by the processor module, whether the comparison exceeds a predetermined threshold; and - If so, generate a warning signal.

14. A method according to any of claims 12-13, further comprising obtaining the user's gait reference information by the following steps: - place additional reference sensors on a second leg of the user, different from the first leg of the user with a prosthetic leg; - obtain, by means of a reference force sensor, reference force measurements of the second leg during walking; - obtain, by at least one reference industrial sensor, reference measurements of angular velocity, linear acceleration and orientation of the second leg during walking.

15. Method according to claim 14 further comprising: - determine, by the processor module, a set of variables of interest to monitor the user's gait, based on the measurements received from the sensor devices comprising one or more of the following: support force pattern of each leg, percentage of load on each leg in static, percentage of load on each leg in motion, 3D movement of each leg, force-based symmetry index, force-based symmetry index and 3D movement, gait speed, plane of advance and activity performed.

16. Method according to any of claims 12-13 wherein generating a warning signal comprises: - store the sensor measurements in memory; - detect a user's gait cycle; - determine if the user is walking based on the analysis of the sensor measurements associated with the detected gait cycle; - detect an anomaly in the user's gait if the sensor measurements in the gait cycle exceed a predetermined threshold.

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