Patent Application
20230363692
The present invention relates to an integrated system for detecting electromyographic signals, processing such signals and controlling devices such as prostheses, orthoses or exoskeletons.
The mechanical portion (including suitable moving means) of anyone of these kinds of devices is referred to as “actuator”. So, in the present invention the word actuator indicates a wearable device able to carry out a movement in substitution of the movement carried out by the user, in addition to such movement or for correcting it.
At the state of the art, there are known many embodiments of prostheses provided with moving means controlled by the analysis of electromyographic signals. Some examples are described in documents EP1857081, EP2525746, EP2688523, EP3150120B1.
In these ones and in other documents known at the state of the art, electromyography sensors are described, which are integrated in various manners inside the prostheses or “socks” worn by the user.
At the state of the art, there are also known systems made up of a variable number of surface electromyography electrodes, positioned in contact to the user skin, that detect the electromyographic signals generated by the muscle contraction and send such signals to the electronic device carrying out the function of prosthesis control.
An example is reported in document US2019343661, where it is described a system for the configuration of a myoelectric-controlled prosthetic device made up of a storage and a variable number of surface electrodes made up of metal contacts in contact to the user skin, positioned along the stump circumference and arranged for detecting the electromyographic signal. Such system has many drawbacks, the first one of which being linked to the fact that being the electrodes remote/passive the AD conversion does not occur at the metal contacts and so at the muscle tissue of the subject, but in a controller positioned downstream of the system. So, the distance covered by the electromyographic signal is such that the probability of coupling with other outer analog signals increases and that SNR increases. Another limit of such system is represented by the fact that the electrodes are necessarily positioned around the stump at the same distance to each other, according to a predefined position which does not allow the customization and the individuation of the most suitable muscle sites so that the intramuscular crosstalk is reduced and the spatial configuration of the system is optimized with respect to the user anatomy.
The last limit relates also to another system known at the state of the art, described in document U.S. Pat. No. 9,299,248, in which an armband is described which is positioned on the forearm and provided with a variable number of surface electrodes for detecting the electromyographic signal of the user. Since it is an armband, the electrodes are necessarily arranged radially at predefined distance to each other and so it is not possible to optimize their positioning. Moreover, the system described in such document comprises a module apt to provide haptic feedback to the user; such module can be represented by a little motor generating a vibration. Anyway, the feedback provided consists exclusively in the confirmation of the recognition of gestures carried out by the user and does not give other information allowing to facilitate the device usage.
Document U.S. 10,152,082 B2 describes a wearable electronic device, with variable circumference, that is provided with a series of housings to house many kinds of sensors, among which electromyography sensors, in number between two and eight, with necessarily radial arrangement of the electrodes and with predefined distance to each other.
Anyway, at the best of the present inventors' knowledge, no one of the devices known at the state of the art allows to solve a series of technical problems at the same time:
In fact, all the kinds of electromyography sensors integrated in the sock of the device or in the armband are in fixed position, and their arrangement is not customizable for the single user. Moreover, the physical distance between their position and the digitalizing device makes it impossible to limit disturbances in the transmission of the analog signal.
On the other hand, sensors not integrated in the sock (which are generally enclosed in independent and repositionable envelopes) known at the state of the art have the same defects in terms of disturbances and interferences in the transmission of the analog signals.
Aim of the present invention is to provide an integrated system for detecting and processing electromyographic signals and for controlling an actuator, which overcomes the limits linked to embodiments known at the state of the art. More in particular, the present invention provides an integrated system for detecting and processing electromyographic signals and for controlling an actuator comprising at least an electrode which is easily repositionable, so that it is adapted to the anatomy of any user, which is configured to acquire electromyographic signals and to carry out their digital conversion while reducing disturbances and interference at minimum.
According to another aim, the present invention provides an integrated system for detecting and processing electromyographic signals, and for controlling an actuator which is easily reconfigurable with regard to number and position of the used electrodes.
The present invention realizes the prefixed aims since it is an integrated system for detecting and processing electromyographic signals and for controlling an actuator (40) comprising at least a mechanical moving means and configured to carry out at least a kind of movements as a function of at least an input signal, said system comprising:
As it is shown in the appended figures, the system comprises:
Preferably, the system comprises a plurality of electrodes (20).
It is to be specified that in the present invention, for “module” it is intended a device connectable to other devices by means of digital connections with bus logic, configured to carry out some specific functions and to share the electric supply with the other modules.
As yet said, the modules usable in the system according to the invention are of three kinds: supplying module (30), electrode module (20), control module (10).
Moreover, in the present invention for “actuator” (40) it is intended a prosthetic device, an orthosis or exoskeleton, configured to be able to carry out at least a kind of movements as a function of at least an input signal.
As it is known, a prosthesis can also comprise more than one moving means, and can be configured to carry out a plurality of different movements as a function of one or more input signals. For example, in case of hand-wrist prosthesis, and as a function of how the mechanism of the prosthesis is realized, movements of finger flexion and extension, wrist flexion and extension and pronosupination of the same are possible.
The controller (10), the electrodes (20) and the supplying module (30) are connected to each other in parallel on the same bus.
The connection of each module to the modules connected thereto occurs by means of at least 3 terminals, at least one of which being used for the transmission of the digital signal and two of which being used for the transmission of the positive pole and negative pole of the electric supply.
Moreover, the supplying module (30) comprises preferably, in addition to the connection (31) supplying all the modules connected as a chain and communicating with them, also another electric connection (32) configured to supply said actuator (40) directly or by means of said control module (10).
To such aim, preferably but not limitingly, said control module (10) comprises, in addition to the connection (11) by means of which it communicates with and shares an electric supply with the remaining modules, also another electric connection (12) configured to be supplied directly from said supplying module.
The separation of the modules supplying—which is functional exclusively for the management of the functioning of the electronics thereof—from the supplying of the actuator—which instead requires to transport the power needed for the actuation of the various movements—allows to reduce the noise associated to less filtered power supplies, to increase the robustness of the system while keeping the control functions supplied by the low power section in case of first failure of the higher power portion, to reduce through the physical separation of wires disturbances induced in the lower power wires.
After showing the connection modes of the various modules inside the system, it is now possible to show the functioning of each module.
The electrode module (20) according to the invention comprises at least a sensor (21) configured to detect a signal on the skin surface deriving from the muscle contraction. In a first embodiment said sensor is an electromyography sensor (23), comprising at least two electrodes configured to detect a difference of potential between two distinct skin regions; in a second embodiment said sensor is a force myography sensor (25) comprising a capacitive pressure sensor configured to measure the pressure exerted on the electrode by the muscle under the skin region where the electrode module is installed.
In a third embodiment, the module comprises both the just described sensors.
Preferably, the electrode module (20) comprises further a magnetic insulating module of the supply (29) which has the function to decouple electrically the user from the supplying module (30) and to reduce the noise associated to the supply and a monitoring system (28) of the supply apt to decouple the board from the skin in case of overcurrents and/or over/undervoltages.
The electrode module (20) comprises also amplification means (2) of the signal detected by said at least one sensor (21), and analog/digital conversion means, configured to convert the analog signal in digital signal, amplified by said amplification means (22).
The electrode module (20) is characterized in that the position of the analog/digital conversion means is at the acquisition position, between the electrodes (or the pressure sensor) acquiring the signal and the analog/digital converter filtration steps or other processing steps not being interposed, except for an amplification step of the signal (optional step in case of pressure sensor). In this way, electromagnetic interferences in the detected signal are reduced.
In case the sensor provided is an EMG sensor (23), such sensor has at least two conductive, preferably metallic surfaces, positioned on the outer side of the envelope of the electrode module (20), in contact with the skin.
Such conductive surfaces are preferably three in number, as it is shown in the appended
In this case, the A/D conversion means are installed on a printed circuit board, contained inside the same envelope of the electrode module (20) and in electric contact with the inner portion of said conductive surfaces.
So, the conductive portion of the EMG sensor has a portion facing outwards of the envelope of the electrode module and a second portion facing inwards.
In case the sensor provided is a capacitive force sensor (25), the reading circuits of the capacity are installed on the same printed circuit board of the analog/digital conversion means, such board being enclosed inside the same envelope of the electrode module (20).
The electrode module (20) comprises further electronic means (24) on which computer programs are loaded (in the following also indicated as electrode firmware), configured to process the signal acquired by said at least one sensor (21) configured to detect a signal on the skin surface deriving from muscle contraction.
Preferably, but not limitingly, said electrode module comprises also temperature sensors (26) and/or humidity sensors (27), configured to detect temperature and humidity relating to the skin region where the electrode is positioned. In this case, said electronic means (24) are also configured to acquire and process the signals detected by said temperature sensors (26) and/or humidity sensors (27).
Preferably, but not limitingly, the previously described system comprises also at least a module for generating a vibro-tactile feedback (50), connected in parallel with said digital communication bus.
In a first embodiment, said module for generating a vibro-tactile feedback comprises a generator of mechanical vibrations, in a second embodiment said module for generating a vibro-tactile feedback (50) comprises a device for transcutaneous electric stimulation.
The electrode firmware is configured to carry out the following operations:
It is to be specified that the notch filtering execution on the digital signal allows to vary at one's pleasure the notch frequency to be used, by simple software configuration,
Moreover, the electrode firmware is also preferably configured to modify the gain and offset of the analog/digital conversion step as a function of the control set by the user.
This allows to obtain a correct conversion of the signal in case of using by users with a compromised muscle tone, thus enlarging the range of users who can use the control device.
The electrode firmware is also configured to receive in input by said control module (10) and by means of said communication means, information about the gain and offset to be used in the analog/digital conversion step, the notch frequency to be used in the signal processing and the passband of the frequency filter to be applied.
The electrode firmware is also configured to receive in input by said control module (10) and by means of said communication means, information about the sampling frequency of the signal by said at least one sensor (21) and the sending frequency of the signal processed to said control module (10).
Moreover, said electrode firmware is preferably configured to compare the shape of the frequency spectrum of the signal detected by said at least one sensor (21) configured to detect a signal on the skin surface with the shape of at least a reference spectrum, to individuate the presence of anomalous peaks of the signal, indicating the presence of interferences (electromagnetic coupling with outer sources). In such case, the firmware sends a warning signal to said control module, so that the user can evaluate if to modify the cutting frequencies of said bandpass filter.
Said firmware is also configured to detect the presence of peaks under 10 Hz of frequency indicating the presence of electrode-skin movements. In such case the firmware sends a warning signal to said control module so that the user can check the correct positioning and clamping of the device.
Moreover, said firmware is configured also to detect periodically a central frequency of the PSD spectrum of said signal, and to send a warning signal to said control module in case said frequency shifts over the time at ever lower frequencies. Such shifting indicates muscle fatigue of the user.
As yet said, the device comprises preferably a plurality of electrode modules (20), which can be arranged in different positions to each other, with no mutual positioning constraints.
In particular, in order to be connected to the system each electrode module needs only an at least 3 contacts wiring to the module preceding it and to the module following it (regardless of the kind of module connected), so that both electric supplying contacts and digital communication contacts can be connected.
Wiring, having to transport unimportant intensity electric currents, being functional only for supplying little electronic devices, can be obtained with wires with extremely little section, with lengths needed to position the electrodes in the sites more significant for the anatomy of the subject wearing the device.
It is to be specified that this possibility of customization is possible only by means of the features of the just described electrode module, which integrates the functions of signal acquisition, amplification, conversion and filtration.
Moreover, preferably, the lines of the digital bus and low-power supply are insulated by magnetic coupling, so that the user is isolated from electrostatic discharges, leakage currents or direct coupling with the electric network in case of battery recharge while the user wears the device, since the electrodes are in direct contact with the skin of the user. This allows to obtain an insulation which guarantees more safety when the user connects the supplying module to an outer supply source (for example: coupling to the electric network by means of the battery charger).
All the just described components for the electrode module (20) are preferably enclosed inside an envelope with waterproof and powder resistance features and apt to guarantee its functioning without damage even in presence of natural humidity, splashes or sweating. Said envelope has preferably waterproof and power resistance features at least equal to IP67 standard, and to such aim any type of electric connection among the known ones at the state of the art can be used for wiring. The observance of the waterproof and powder resistance features of the envelope is applied also to other kinds of modules usable with the device.
The supplying module (30) comprises at least a rechargeable electric battery, provided with a suitable connector for the recharge by means of connection to the electric network, preferably by means of a common outer voltage transformer with respect to the supplying module.
The controller (10) comprises control electronic means on which computer programs are loaded (in the following also indicated as controller firmware), digital communication means (11) configured to communicate with other electrodes, and at least an output (13) for the control of an actuator.
Said at least one output for the control of an actuator can comprise an output of analog kind, or an output of digital kind.
The control module (10) comprises also outwards communication means, configured to communicate with outer processing means where respective computer programs are loaded configured to allow the user to communicate with said control means by means of a suitable user interface.
As yet said, the control module (10) can be configured in two modes.
In a first embodiment the control module (10) controls directly at least an actuator (40), providing the same with both the control signal and the power needed for supplying motors included in the actuator.
To such aim, the control module (10) comprises hardware means for electronic control of at least a power actuator and respective computer programs (firmware) for closed/open loop control of at least an actuator (40).
In a second embodiment, the control module (10), unlike the first configuration, does not control the actuator/actuators directly, but it does it by means of an outer controller, configured to implement the power control of at least an actuator (40).
Such outer controller is configured to receive in input different kinds of analog and/or digital signals, and to provide the actuator with control signals and the power needed for moving the motors included in the actuator.
In this embodiment the control module (10) acts as real interface between the system according to the invention and actuators of third preexisting parts, thus guaranteeing a functioning compatibility with them. The control module (10) is also configured to carry out the supervision function of the system, by monitoring continuously the presence of error messages, warning coming from all the nodes connected to the bus together with the control of the interactions with the outer environment.
It is also able to individuate automatically the modules connected to the chain when these are connected, and to manage their mutual interaction as a consequence.
In particular, the bus allows one or more electrode modules (20) to be hot connected, while the system is functioning. This is possible thanks to initialization packets which each module is able to exchange with the controller at the moment it is connected to the system.
After a predetermined configuration time, the module will acquire an address, which will remain fixed, also after the system restart. The address will be useful to communicate with the controller and with all the modules yet present on the bus. At the same way, a module can be hot removed from the system.
Through acknowledgment techniques, implemented at low level, the controller is able to detect the presence of a module and to ask the re-transmission of the information, if corrupted. This occurs continuously during the normal functioning of the system and it is useful to adapt the system behaviour according to the modules provided.
Another advantage of the system according to the invention is that the system is self-calibrating, since each electronic module (20), thanks to a calibration procedure, is able to detect the signals associated to the basic state (i.e. the rest state) and to use them to eliminate the portion of signal not giving any useful information for movement recognition.
In particular, the self-calibration procedure is made up of two steps.
In a first step the controller records the basal signals acquired by the electrode modules (20) during a muscle rest condition of the user and adapts the acquisition parameters (gain, offset, etc.) of the A/D converter provided on each electrode module (20) and the digital filtering parameters, so that the SNR is improved for each electrode module (20).
During such step the controller is configured to signal the user to remain at rest. This occurs by means of a signaling device (buzzer, display, LED, haptic feedback etc.) or by means of a digital communication protocol with an outer HMI (human machine interface).
In the second step, the controller controls the ranges of the acquisition parameters of the ND converter and digital filtering, so that the calibration is adapted automatically as a function of the observed time window.
To such aim, the control module is configured to detect periodically the range of acquisition parameters of the ND converter and digital filtering, so that the calibration is adapted automatically as a function of the observed time window. In particular, a procedure of self-calibration is carried out, subdivided in two steps:
It is to be specified that rest condition means a condition in which the subject is asked to remain still, with relaxed muscles, in an inactivity state, thus avoiding contracting muscles, avoiding exerting pressure on the portions of the prosthesis and avoiding activating possible sensors provided.
In such condition, the controller on board of the electrode keeps the preset gain and notch values while recalculating, to optimize SNR of the signal, the offset parameters, passband and resolution of the ND quantization. For each of said three parameters, starting from a predetermined maximum range a dichotomic research of the optimal values is carried out evaluating SNR after each variation of each parameter, up to maximum 5 iterations;
During the functioning, the electrode module analyzes the EMG and/or FMG signals according to preset time windows.
Each window is analyzed and clustered by the control module which communicate the intention of the user.
In case the precision, the recall and F1 score do not satisfy the safety requirements in the prediction of the user intention as a function of the stored calibration, the control module communicates this event through a warning and the electrode module/modules carries/carry out a rapid research of the optimal offset parameters, passband and resolution of the ND quantization to reach the safety thresholds needed for the actuator moving.
| Number | Date | Country | Kind |
|---|---|---|---|
| 102020000022933 | Sep 2020 | IT | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/IB2021/058209 | 9/9/2021 | WO |
