WO2019202489A1

WO2019202489A1 - Programmable modular system for applications of electrical stimulation of the neuromuscular system, and wearable modules thereof

Info

Publication number: WO2019202489A1
Application number: PCT/IB2019/053111
Authority: WO
Inventors: Marco GAZZONI; Giacinto Luigi CERONE
Original assignee: Politecnico Di Torino
Priority date: 2018-04-16
Filing date: 2019-04-16
Publication date: 2019-10-24
Also published as: IT201800004525A1

Abstract

A programmable and modular system (10) for applications of electrical stimulation of the neuromuscular system is described, which comprises at least one wireless module (20, 30) adapted to be placed on a subject, said wireless module (20, 30) being at least one stimulation module (20) and/or at least one bio-signal acquisition module (30), said module (20, 30) being adapted to receive data from bioelectrical and/or biomechanical sensors and/or to generate a stimulation pattern based on said data, said module (20, 30) being further adapted to be independently programmed through a programming language; two wireless modules (20, 30) are also described.

Description

PROGRAMMABLE MODULAR SYSTEM FOR APPLICATIONS OF ELECTRICAL STIMULATION OF THE NEUROMUSCULAR SYSTEM, AND WEARABLE MODULES THEREOF

DESCRIPTION

The present invention relates to a programmable and modular system for electrical stimulation of an individual’s neuromuscular system, and to wearable modules adapted for use in the system.

In particular, the invention relates to a programmable system for functional electrical stimulation (FES) having a modular wireless architecture.

Functional electrical stimulation involves the application of electrical stimuli to one or more muscles in order to cause them to contract, for the purpose of generating a functional movement as a person performs a given action and/or exercise.

Systems are known which comprise neuromuscular stimulators for use with FES protocols.

However, such systems are not satisfactory, and the neuromuscular stimulators employed suffer from the following problems:

known neuromuscular stimulators are heavy and bulky; this problems translates into difficult exportation of the protocol in daily life contexts;

- difficult programming of the stimulation pattern. In fact, ad-hoc developed software is used which cannot be customized by the user (medical personnel or person involved), resulting in fewer degrees of freedom in the definition of the rehabilitation protocol. In particular, when FES is used for sports applications, this difficulty also translates into less flexibility of the system, which is thus poorly adaptable to different contexts (FES-Cycling, FES-Rowing, etc.) that require the use of different sports equipment;

difficult synchronization with systems for acquisition of (biomechanical and/or bioelectrical) signals that can be used as control variables for the stimulation pattern (e.g. in closed-loop control systems).

The present invention aims at solving the above-mentioned problems of the prior art by providing a programmable modular system for applications of neuromuscular functional electrical stimulation and wearable modules for use in the system which allow generating an appropriate stimulation pattern and/or acquiring signals from external sensors, through the use of a wireless architecture composed of modules that can be programmed by using a high-level programming language; with such an architecture it is possible to simplify the implementation of a stimulation pattern control system for FES applications and increase the flexibility thereof in terms of customization of said protocol.

These and other objects and advantages of the invention, which will become apparent in the light of the following description, are achieved through a programmable modular system for applications of functional electrical stimulation of the neuromuscular system and wearable modules for use in the system as described in the independent claims. Some preferred embodiments and non-obvious variants of the present invention are set out in dependent claims.

It is understood that all the appended claims are an integral part of the present description. It will become immediately apparent that what is described herein may be subject to innumerable variations and modifications (e.g. in shape, dimensions, arrangements and parts having equivalent functionality) without departing from the protection scope of the invention as set out in the appended claims.

The present invention will be described in detail below through a preferred embodiment thereof, which is only provided by way of non-limiting example with reference to the annexed drawings, wherein:

Figure la is a schematic view of a programmable modular system for functional electrical stimulation applications according to the present invention;

- Figure lb shows an example of application of a programmable modular system for functional electrical stimulation applications in FES-Rowing protocols according to the present invention;

Figure 2 is a block diagram of a stimulation module of a programmable modular system for functional electrical stimulation applications according to the present invention;

Figure 3 is a block diagram of an output stage of the stimulation module of a programmable modular system for functional electrical stimulation applications according to the present invention; and

Figure 4 is a block diagram of an acquisition module of a programmable modular system for functional electrical stimulation applications according to the present invention.

With reference to the drawings, the programmable modular system 10 for neuromuscular functional electrical stimulation (FES) applications according to the invention is preferably a multi-channel system and comprises at least one wireless module 20, 30 adapted to be positioned on a person; preferably, the system 10 comprises a plurality of wireless modules 20, 30 adapted to make up a network of wearable modules (body network - BN) connected to one another in wireless mode. The system 10 is a multi- channel one (i.e. it may comprise multiple stimulation and/or bio-signal acquisition channels), since it is possible to use as many modules as the number of necessary channels and/or signals.

In the example of Figure lb, two stimulation modules 20 and five signal acquisition modules 30 are used. The signal acquisition modules 30 serve to acquire the position of the person’s arm and forearm (by means of inertial sensors) and the positions of the seat, handle and carriage of the rowing ergometer. The system 10 of the invention comprises two different types of wireless modules 20, 30: 1) stimulation module 20 (Stimulation Unit - SU), shown in Fig. 2; 2) bio-signal acquisition module 30 (Bio-signal acquisition Unit - BU), shown in Fig. 4.

Said module 20, 30 is adapted to receive data from bioelectrical and/or biomechanical sensors and/or to generate a stimulation pattern based on said data and on an algorithm defined beforehand by the user during the programming stage, according to the acquired signals, the type of stimulation protocol to be implemented (FES-Rowing, FES-Cycling, etc.) and the type of muscles to be stimulated; said module 20, 30 is also adapted to be programmed independently by using a high-level programming language, e.g. Python, for which a set of libraries are provided in order to simplify the programming task (e.g. Master/Slave mode management, data acquisition or reception, etc.), and can operate in Master or Slave mode.

A stimulation module 20 or a bio-signal acquisition module 30, if configured in Master mode, receives data from sensors, processes them, and drives other sensors configured in Slave mode; conversely, when configured in Slave mode, the module 20, 30 only behaves as a stimulator (module 20, SU) or as a data acquisition unit (module 30, BU), receiving commands from the Master module 20, 30 and generating the required outputs.

The functions of the Master module may also be carried out by any mobile device 1, e.g. a smartphone or a tablet, or by a PC connected to the wireless module 20, 30, should high performance be required for processing the acquired data and applying the (user-defined) algorithm for generating the stimulation pattern.

Figure la schematically shows an example of a programmable modular system 10 according to the invention, consisting of a network of four modules 30 of the BU type, two modules 20 of the SU type, and one PC 1. Figure lb shows an example of application of the system 10 of the invention within a FES-Rowing context, consisting of combining the voluntary exercise of the upper part of the body with electrical stimulation of the lower part of the body, e.g. of a paraplegic person. In this example, the system 10 comprises a sensorized rowing ergometer 11 with three bio-signal acquisition modules 30 (BU) that acquire the positions of a carriage 14 and a handle 15, as well as the force exerted on the latter.

Two more BU modules 30 are arranged on the user’s upper limbs and are used in order to acquire kinematic variables (displacement, speed, acceleration) relating to the movements of the upper limbs while rowing.

A mobile device 1 placed on the rowing ergometer 11 processes the data received from the bio-signal acquisition modules 30 (BU) and appropriately controls the stimulation modules 20 (SU) that stimulate the muscles of a person’s lower limbs.

In brief, the stimulation module SU 20 performs the following functions:

- Electrical stimulation of a muscle with constant current (preferably programmable and comprised between 0,1 mA and 100 mA);

- Generation of stimulation patterns according to a predefined program that can be customized by the user;

- Reception of the stimulation start/stop command, if configured in Slave mode;

- Reception of signals from BU modules 30, if configured in Master mode.

In brief, the bio-signal acquisition module 30 performs the following functions:

- Acquisition of bioelectrical signals (e.g. EMG) and/or biomechanical signals (force, displacement, etc.);

- Transmission of the signals acquired by the module configured in Master mode;

- Transmission of the stimulation start/stop command to other SU modules 20, if configured in Master mode;

- Reception of signals from other BU modules 30, if configured in Master mode.

Preferably, the stimulation module (SU) 20, shown in Fig. 2, comprises the following units: a power unit 22, comprising electric energy supplying means adapted to supply power to the stimulation module 20, e.g. a single-cell lithium-polymer (LiPo) battery, e.g. with a no-load voltage of 3,7 V; a power management unit 21 and a control unit 23 connected thereto; a stimulation unit 27 comprising an output stage connected to stimulation electrodes 28, a synchronization unit 24, and a storage unit 25, e.g. an SD Card, said stimulation unit 27, synchronization unit 24 and storage unit 25 being connected to the control unit 23.

Preferably, the power management unit 21 comprises means 26 for connection to an electric power supply, and is adapted to recharge the power unit 22; for example, the battery is recharged by means of an element 26 for wireless inductive charging.

Preferably, the control unit 23 comprises a microcontroller of a known type comprising wireless connectivity means (e.g. Texas Instruments CC3200 or CC3220), said microcontroller incorporating firmware programmed by using a programming language comprising a high-level language interpreter, e.g. the Python language, for programming the main functions of the system (signal acquisition, stimulation pattern generation, etc.), which allows the user to configure the behaviour of each stimulation module 20. In particular, said control unit 23 is adapted to interpret the program set by the user, manage the Master/Slave modes, transmit/receive data and commands, generate the stimulation pattern, and control the output stage of the stimulation unit 27.

Preferably, the synchronization unit 24 is of a known type and is adapted to manage the synchronization of multiple modules 20, 30 making up a system 10. For example, the modules may be synchronized by means of a digital trigger signal simultaneously sent from the outside to all the modules 20, 30 in use. Such signal prompts the modules to start the operations for which they have been programmed (signal sampling, stimulation pattern generation, etc.). The trigger signal can be obtained by connecting a push-button or a device (e.g. an infrared one) for command transmission/reception. In particular, in the case of a stimulation module 20 in Master mode, said synchronization unit 24 is adapted to send a digital signal (trigger signal) simultaneously to the control units 23 of each module in Slave mode, which signal may be sent, for example, by pressing a key or via an infrared optical command of a remote control, and indicates the beginning/end of a work session. Preferably, the storage unit 25 comprises memory means, e.g. an SD Card unit, and is adapted to store the user-defined program files.

The stimulation unit 27 is connected to the control unit 23 and comprises the output stage, which includes a switched capacity circuit 40 providing control over the current being applied to the load. The block diagram of the output stage of the stimulator is shown in Figure 3.

The switched capacity circuit 40 comprises a first switch SW1, e.g. a transistor -based electronic switch, preferably of the MOSFET type, interposed between a high-voltage generator (200 V- 350 V) VCHG, consisting of the power unit 22, e.g. a Boost-type DC/DC converter like those used for recharging camera flashes (LT3468 chip - Linear Technology), and a capacitor C adapted to store the energy required for applying electrical stimuli through the stimulation electrodes 28 that deliver the current that causes muscle contraction.

The switched capacity circuit 40 comprises a second switch SW2, e.g. a transistor-based electronic switch, preferably of the MOSFET type, connected in series to the first switch SW1, downstream of the capacitor C, and a closed-loop current control system 45 comprising current intensity control means 46, e.g. consisting of a conditioning circuit for acquisition of the current applied to the load ZL (46, e.g. based on the LT6100 chip - Linear Technology) and a circuit for comparing said current with the predefined threshold via the STIM AMP command (I-Lim, e.g. obtained through a classical Schmitt trigger hysteresis comparator), connected to the second switch SW2 and adapted to detect the current intensity I_I in the circuit 40 and to control the activation (if IL<=STIM_AMP) or deactivation (if IL>STIM_AMP) of the second switch SW2 depending on the detected current intensity I_I.

During the operation of the switched capacity circuit 40, the first switch SW 1 switches in the period during which no stimulation command is applied (STIM CMD = Off), while the second switch SW2, on the contrary, is disabled. During such period, the capacitor C is charged to the voltage VCHG, e.g. 150V. When the stimulation command is activated (STIM CMD = On), the first switch SW1 is disabled and the second switch SW2 switches. During this phase, the energy stored in the capacitor C is discharged through the load ZL, which represents the electrode-skin impedance across the stimulation electrodes 28. At the same time, based on the STIM AMP command, which is proportional to the current amplitude to be injected into the load during the stimulation, the current I_I injected into the load ZL is monitored. Control of the current intensity is effected by the control means 46 by disabling the second switch SW2 whenever the limit of the injected current monitored by a closed-loop current control system 45 comprising current intensity control means 46, set through the STIM AMP command, is exceeded.

Preferably, the bio-signal acquisition module (BU) 30, shown in Fig. 4, comprises the following units, which are similar to those of the stimulation module (SU) 20 already described: the power unit 22, adapted to supply power to the bio-signal acquisition module 30, e.g. a rechargeable single-cell lithium-polymer (LiPo) battery, e.g. with a no-load voltage of 3 ,7 V; the power management unit 21 and the control unit 23 connected thereto; the synchronization unit 24 and the storage unit 25, e.g. an SD Card, connected to the control unit 23.

In particular, the power management unit 21 is adapted to recharge the battery 22, as already described with reference to the stimulation module 20, and the battery 22 is adapted to supply power to the bio-signal acquisition module 30, as already described with reference to the stimulation module 20.

The control unit 23 is also similar to the one already described with reference to the stimulation module 20, and allows the user to configure the behaviour of each bio-signal acquisition module 30. In particular, said control unit 23 is adapted to interpret the program set by the user, manage the Master/Slave modes, and transmit/receive data and commands.

The bio-signal acquisition module 30 further comprises a bio-signal acquisition unit 31 connected to the control unit 23 and adapted to acquire data relating to biomechanical parameters from sensors connected thereto, preferably via a connector 32, e.g. inertial sensors, optical encoders, generic analogue signals (0 V - 3,3 V dynamics) or digital signals (e.g. from external triggers).

Preferably, the synchronization unit 24 is similar to the one already described with reference to the stimulation module 20 and is adapted to manage the synchronization of multiple modules 20, 30 making up a system 10, and the storage unit 25 is similar to the one already described with reference to the stimulation module 20 and is adapted to store the user-defined program files.

The programmable modular system 10 for functional electrical stimulation applications of the invention offers the following advantages:

due to its modular architecture, the system allows acquiring and processing data while at the same time generating appropriate stimulation patterns according to a predefined program;

it allows choosing the number of stimulation channels and the number and type of signals to be acquired depending on the specific application, the type of stimulation protocol to be implemented (FES-Rowing, FES-Cycling, etc.) and the type of muscles to be stimulated;

- the system can be controlled by a mobile device, such as a smartphone or a tablet, provided with wireless connectivity (e.g. Wi-Fi or Bluetooth), or it may operate independently in stand-alone mode once a stimulation pattern has been set;

it avoids the need for specific software for generating the stimulation pattern, and any processing of the control signals can be carried out directly on board and in real time; dimensions are reduced and power comes from a battery;

it allows for wireless synchronization with existing systems for bioelectrical and/or biomechanical signal acquisition.

The preferred embodiment of the invention described herein is of course susceptible of further modifications and variations without departing from the inventive idea. In particular, numerous functionally equivalent variations and modifications will be immediately apparent to those skilled in the art, which will still fall within the protection scope of the invention as set out in the appended claims, wherein any reference signs between brackets should not be considered to limit the scope of the claims. Furthermore, the word“comprising” does not exclude the presence of elements and/or steps other than those listed in the claims. The article“a”,“an” or“one” before an element does not exclude the presence of a plurality of such elements. The simple fact that some features are mentioned in different dependent claims does not suggest that a combination of such features cannot be used to advantage.

Claims

1. Programmable and modular system (10) for applications of electrical stimulation of the neuromuscular system comprising at least one wireless module (20, 30) adapted to be placed on a subject, said wireless module (20, 30) being at least one stimulation module (20) and/or at least one bio-signal acquisition module (30), said module (20, 30) being adapted to receive data from bioelectrical and/or biomechanical sensors and/or to generate a stimulation pattern based on said data, said module (20, 30) being further adapted to be independently programmed through a programming language.

2. Programmable and modular system (10) for applications of electrical stimulation of the neuromuscular system according to claim 1, characterized in that it comprises a plurality of wireless modules (20, 30) adapted to compose a network of wearable modules mutually connected in wireless mode.

3. Programmable and modular system (10) for applications of electrical stimulation of the neuromuscular system according to claim 1 or 2, characterized in that said module (20, 30) is adapted to operate in Master or Slave mode, said stimulation module (20) or bio- signal acquisition module (30) being adapted to, if configured in Master mode, receive data from sensors, process them, and drive other sensors configured in Slave mode; if configured in Slave mode, instead, said module (20, 30) is adapted to behave only as a stimulator (20) or as a data acquisition unit (30), receiving commands from the Master module (20, 30) and generating the required outputs.

4. Programmable and modular system (10) for applications of electrical stimulation of the neuromuscular system according to any one of the preceding claims, characterized in that it comprises a mobile device (1), or a computer, connected to said at least one wireless module (20, 30) and adapted to perform the functions of a Master module.

5. Programmable and modular system (10) for applications of electrical stimulation of the neuromuscular system according to any one of the preceding claims, characterized in that the stimulation module (20) comprises the following units: a power unit (22) comprising electric energy supplying means adapted to supply power to the stimulation module (20); a power management unit (21), adapted to recharge the power unit (22), and a control unit (23) connected thereto and comprising a microcontroller comprising wireless connectivity means and adapted to configure the stimulation module (20); a stimulation unit (27) comprising an output stage connected to stimulation electrodes (28); a synchronization unit (24) adapted to control the synchronization of multiple modules (20, 30) of the system (10); a storage unit (25) adapted to store user-defined program files; wherein said stimulation unit (27), synchronization unit (24) and storage unit (25) are connected to the control unit (23).

6. Programmable and modular system (10) for applications of electrical stimulation of the neuromuscular system according to claim 5, characterized in that the output stage of the stimulation unit (27) is implemented with a switched capacity circuit (40) comprising: a first switch (SW 1) interposed between the power unit (22) and a capacitor (C) adapted to store the energy required for applying, through the stimulation electrodes (28), electrical stimuli that cause muscle contraction; a second switch (SW2) connected in series to the first switch (SW1), downstream of the capacitor (C), and a closed-loop current control system (45) comprising current intensity control means (46) connected to the second switch (SW2) and adapted to detect the current intensity (I_I) in the circuit (40) and to control the activation/deactivation of the second switch (SW2) depending on the detected current intensity (I_I).

7. Programmable and modular system (10) for applications of electrical stimulation of the neuromuscular system according to any one of the preceding claims, characterized in that the bio-signal acquisition module (30) comprises the following units: a power unit (22) adapted to supply power to the bio-signal acquisition module (30); a power management unit (21), adapted to recharge the power unit (22), and a control unit (23) connected thereto, comprising a microcontroller for configuring the bio-signal acquisition module (30); a bio-signal acquisition unit (31) connected to the control unit (23) and adapted to acquire data relating to biomechanical parameters from sensors connected thereto; a synchronization unit (24) adapted to control the synchronization of multiple modules (20, 30) of the system (10); a storage unit (25) adapted to store user-defined program files; wherein said bio-signal acquisition unit (31), synchronization unit (24) and storage unit (25) are connected to the control unit (23).

8. Programmable and modular system (10) for applications of electrical stimulation of the neuromuscular system according to any one of the preceding claims, characterized in that it is a multi-channel system.

9. Stimulation module (20) for a programmable and modular system (10) for applications of electrical stimulation of the neuromuscular system according to any one of the preceding claims, characterized in that it comprises the following units: a power unit (22) adapted to supply power to the stimulation module (20); a power management unit (21), adapted to recharge the power unit (22), and a control unit (23) connected thereto, comprising a microcontroller for configuring the stimulation module (20); a stimulation unit (27) comprising an output stage connected to stimulation electrodes (28); a synchronization unit (24) adapted to control the synchronization of multiple modules (20, 30) of the system (10); a storage unit (25) adapted to store user-defined program files; wherein said stimulation unit (27), synchronization unit (24) and storage unit (25) are connected to the control unit (23).

10. Stimulation module (20) for a programmable and modular system (10) for applications of electrical stimulation of the neuromuscular system according to claim 9, characterized in that the output stage of the stimulation unit (27) is implemented with a switched capacity circuit (40) comprising: a first switch (SW1) interposed between the power unit (22) and a capacitor (C) adapted to store the energy required for applying, through the stimulation electrodes (28), electrical stimuli that cause muscle contraction; a second switch (SW2) connected in series to the first switch (SW1), downstream of the capacitor (C), and a closed-loop current control system (45) comprising current intensity control means (46) connected to the second switch (SW2) and adapted to detect the current intensity (I_I) in the circuit (40) and to control the activation/deactivation of the second switch (SW2) depending on the detected current intensity (I_I).

11. Bio-signal acquisition module (30) for a programmable and modular system (10) for applications of electrical stimulation of the neuromuscular system according to any one of claims 1 to 8, characterized in that it comprises the following units: a power unit (22) adapted to supply power to the bio-signal acquisition module (30); a power management unit (21), adapted to recharge the power unit (22), and a control unit (23) connected thereto, comprising a microcontroller for configuring the bio-signal acquisition module (30); a bio-signal acquisition unit (31) connected to the control unit (23) and adapted to acquire data relating to biomechanical parameters from sensors connected thereto; a synchronization unit (24) adapted to control the synchronization of multiple modules (20, 30) of the system (10); a storage unit (25) adapted to store user-defined program files; wherein said bio-signal acquisition unit (31), synchronization unit (24) and storage unit (25) are connected to the control unit (23).