A closed-loop electromyographic driven neuromuscular electrical stimulation system based on optical link isolation

Abstract

This invention discloses a closed-loop electromyography (EMG) driven neuromuscular electrical stimulation system based on optical link isolation, comprising: a sensing and control module for acquiring surface EMG signals from a first muscle group and generating stimulation command data, wherein the first muscle group is less damaged or located closer to the target muscle group to be stimulated; a stimulation module, physically separated from the sensing and control module, for outputting stimulation pulses to the target muscle group according to the stimulation command data; and an optical communication link, disposed between the two modules, for achieving electrical isolation to eliminate ground loop coupling and conductive interference. This invention achieves system-level electrical isolation and independent power supply between the sensing and control module and the stimulation module through the optical communication link, fundamentally cutting off the ground loop coupling path. Simultaneously, it reliably drives the stimulation of the distal target muscle group using residual proximal EMG signals, solving the control reliability problem in low signal-to-noise ratio clinical scenarios such as motor neuron lesions while maintaining the real-time performance of closed-loop control.

Description

Technical Field

[0001] This invention belongs to the field of medical rehabilitation device technology, specifically relating to a closed-loop control technology that uses surface electromyography signals to drive neuromuscular electrical stimulation. Background Technology

[0002] Closed-loop neuromuscular electrical stimulation (NMES) systems typically rely on electromyography (EMG) measurements to determine stimulation timing, intensity, and control decisions. In traditional wired architectures, the EMG acquisition and sensing subsystems share conductive links (including direct connections and a common ground) and usually operate in the same power domain, easily inducing ground loop coupling and conductive interference pathways. These conductive pathways raise the system's effective noise floor, increase susceptibility to electromagnetic interference, and exacerbate stimulation-induced artifacts, ultimately impairing the control signals based on EMG signals.

[0003] This problem is particularly relevant in motor neuropathy and related peripheral motor dysfunction. In such conditions, electromyographic (EMG) signals from more severely damaged segments of the limb (usually distal muscles) tend to be weak in amplitude, unstable in waveform, or even intermittently absent. For patients with severe motor neuropathy, the amplitude of autonomous surface EMG signals from distal muscles can be as low as tens of microvolts. In traditional wired architectures, the noise floor introduced by ground loop coupling may completely drown out the effective EMG signal. However, in many clinical scenarios, patients retain more reliable autonomous activation in proximal muscle groups (such as the upper part of the same limb / less damaged areas), which can generate EMG signals with relatively high amplitude and good signal-to-noise ratio. Therefore, closed-loop neuromuscular electrical stimulation methods can utilize proximal EMG signals as a control source to generate stimulation commands to assist or reactivate motor function in more severely damaged areas, provided that the sensing and stimulation modules can operate stably and reliably under noise floor constraints.

[0004] For example, US11160971 discloses a wearable EMG-NMES closed-loop system for tremor suppression, which collects electromyographic signals through sensing electrodes and drives the stimulation electrodes to output signals after processing by a control algorithm. However, this system and similar solutions still use traditional electrical connections between the sensing module and the stimulation module, failing to address ground loop coupling and the resulting control reliability issues in low signal-to-noise ratio environments.

[0005] In medical electronic devices, component-level isolation solutions such as optocouplers, isolation amplifiers, or digital isolators are commonly used to achieve electrical isolation and suppress ground loop interference. While these solutions embed isolation devices into the circuit board design and can block conducted interference on the signal link to some extent, they still have the following limitations: First, component-level isolation cannot achieve physical separation and independent power supply between the sensing module and the stimulation module. The two modules typically still share the same power system or ground reference within the same device housing, and the ground loop path is not completely severed. Second, in clinical applications where sensing electrodes need to be deployed on proximal muscle groups and stimulation electrodes on distal muscle groups, component-level isolation solutions cannot support spatial separation between modules, and the sensing module cannot be flexibly and independently positioned at the optimal electromyography (EMG) acquisition location. Optical transmission technologies (such as optical fibers or free-space light) have been used in medical and other fields to achieve signal transmission and electrical isolation. For example, US5411023 discloses the transmission of blood oxygen sensing signals via optical fiber in an MRI environment to isolate the patient from the electronic device. However, such schemes are not designed for EMG-driven NMES closed-loop stimulation command transmission scenarios, nor do they involve specific clinical mapping architectures for proximal muscle groups to control distal target muscle groups.

[0006] Furthermore, in existing neuromuscular electrical stimulation technologies, there are implantable systems that detect weak signals in damaged muscles and trigger stimulation via implanted electrodes. However, implantable solutions have inherent problems such as surgical trauma, long-term biocompatibility, and device maintenance. This invention focuses on a non-implantable external module architecture based on surface electrodes.

[0007] Therefore, the reliability of EMG-driven control decreases when conductive coupling and artifacts raise the system noise floor; this problem is particularly pronounced when control signals must be extracted from low-margin EMG signals in functionally impaired individuals. A practical solution is needed that maintains end-to-end latency compatible with closed-loop neuromuscular electrical stimulation systems while providing system-level electrical isolation between the sensing and stimulation modules, thereby enabling stable EMG-driven control even when relying on residual autonomic EMG signals from proximal muscles. Summary of the Invention

[0008] The technical problem this invention aims to solve is to address the issues of weak distal electromyographic signals in patients with motor neuron disease, which are close to the noise floor; the reduced control reliability or even failure of existing wired architectures due to ground loop coupling and conduction interference; and the limitations of existing component-level isolation schemes in achieving physical separation and complete electrical isolation between the sensing module and the stimulation module. This invention provides a closed-loop electromyographic-driven neuromuscular electrical stimulation system that achieves complete electrical isolation between the sensing and control module and the stimulation module while maintaining the end-to-end delay required for closed-loop control, thereby enabling reliable stimulation of distal target muscle groups using residual proximal electromyographic signals.

[0009] The technical solution adopted by this invention to solve the above-mentioned technical problems is a closed-loop electromyography-driven neuromuscular electrical stimulation system based on optical link isolation, comprising: a sensing and control module and a stimulation module.

[0010] The sensing and control module includes surface electromyography electrodes, an electromyography acquisition front end, and a light emitter;

[0011] Surface electromyography electrodes are used to collect surface electromyography signals from a first muscle group that is less damaged or located closer to the end than the target muscle group to be stimulated.

[0012] An electromyography (EMG) acquisition front end is connected to the surface EMG electrodes and is used to condition the surface EMG signals;

[0013] The controller is connected to the electromyography acquisition front end and is used to generate stimulation command data based on the conditioned surface electromyography signal.

[0014] A light emitter, connected to the controller, is used to convert the stimulus command data into light signals;

[0015] The stimulation module is physically separated from the sensing and control module and includes a light receiver, a stimulation controller, an output stage, and an optical communication link.

[0016] An optical receiver, used to receive the optical signal and convert it into an electrical signal;

[0017] A stimulation controller, connected to the light receiver, is used to generate a stimulation control signal based on the converted electrical signal;

[0018] An output stage, connected to the stimulation controller, is used to output stimulation pulses to the target muscle group according to the stimulation control signal;

[0019] An optical communication link is provided between the optical transmitter and the optical receiver to achieve electrical isolation between the sensing and control module and the stimulation module, thereby eliminating ground loop coupling and conductive interference.

[0020] This invention does not simply add isolation devices to the EMG-NMES system, but rather reconstructs the system-level architecture to address the unique clinical predicament of weak distal electromyographic signals in patients with motor neuron disease, which are close to the noise floor.

[0021] Specifically, this invention divides the sensing and control module and the stimulation module into two independent power domains through an optical communication link, achieving physical separation and complete electrical isolation between the modules, fundamentally cutting off the ground loop coupling path; at the same time, it incorporates a mapping strategy that uses the less damaged muscle groups at the proximal end as the control source and the more severely damaged muscle groups at the distal end as the stimulation target, allowing the sensing module to be flexibly deployed at the optimal acquisition position at the proximal end; and through the combined design of data integrity verification and stimulation-side safety limits, it ensures the determinism of command transmission and the safety of stimulation across the isolation barrier.

[0022] System-level optical link isolation, near-end control and far-end mapping, and cross-barrier functional safety mechanisms are coupled and work synergistically: scenario requirements drive architecture design, architecture design enables scenario adaptation, and safety mechanisms ensure reliable architecture operation, together forming a complete solution suitable for clinical conditions with low signal-to-noise ratio.

[0023] The beneficial effects of this invention are:

[0024] 1. System-level electrical isolation to eliminate ground loop interference.

[0025] This invention achieves signal transmission between the sensing and control module and the stimulation module via an optical communication link, with both modules operating in independent power domains. Compared to existing component-level isolation schemes, this invention achieves physical separation and complete electrical isolation between modules, fundamentally severing ground loop coupling paths. In scenarios where distal electromyographic signals from patients with motor neuropathy are weak to near the noise floor, this effect allows signals that would otherwise be easily submerged by noise to be reliably used for closed-loop control.

[0026] 2. Proximal electromyography drives distal stimulation, adapting to specific clinical scenarios.

[0027] This invention leverages the modular layout flexibility afforded by optical link isolation, allowing sensing modules to be independently deployed at optimal acquisition locations in less damaged proximal muscle groups. This maps residual high signal-to-noise ratio electromyographic (EMG) signals into stimulation commands, assisting motor function in more severely damaged distal muscle groups. This architecture enables effective closed-loop stimulation assistance as long as reliable EMG signals are present in at least one muscle group.

[0028] 3. Balancing electrical isolation and closed-loop real-time performance

[0029] This invention allocates a clear end-to-end latency budget for the entire process from acquisition, processing, optical link transmission to stimulus generation, while ensuring deterministic command transmission across isolation barriers through data integrity verification and stimulus-side security limits. The system achieves complete electrical isolation while maintaining real-time response capabilities compatible with the closed-loop stimulus update rate, resolving the technical contradiction between isolation and real-time performance. Attached Figure Description

[0030] Figure 1This is a structural block diagram of a light-isolated closed-loop electromyography (EMG) signal-driven neuromuscular electrical stimulation system.

[0031] Figure 2 The operating procedure for a light-isolated closed-loop electromyography (EMG) system driven by neuromuscular electrical stimulation (NMES).

[0032] Figure 3 The signal-to-noise ratio of optical links and wired links is compared under three noise levels.

[0033] Figure 4 A comparison of the coefficients of determination for the three noise levels.

[0034] Figure 5 Comparison of root mean square error under three noise levels.

[0035] Figure 6 A comparison of end-to-end time delays at three noise levels. Detailed Implementation

[0036] 1. System Overall Architecture

[0037] Reference Figure 1 A non-implantable, closed-loop electromyography-driven neuromuscular electrical stimulation system based on body surface electrodes includes two physically separate modules: a sensing and control module operating in a first power domain (power domain A) and a stimulation module operating in a second power domain (power domain B). The two modules are connected by an optical communication link to achieve signal transmission and electrical isolation.

[0038] The sensing and control module is responsible for collecting surface electromyographic signals from the first muscle group (the less damaged proximal muscle group). After signal conditioning, feature extraction, and mapping processing, it generates stimulation command data, which is then converted into optical signals by a light emitter and transmitted. The stimulation module receives the optical signals through a light receiver and converts them into electrical signals. After decoding and integrity verification, the stimulation controller applies safety limits, and finally outputs stimulation pulses to the target muscle group (the more severely damaged distal muscle group) through the output stage.

[0039] The optical communication link serves as the sole signal transmission channel between the two modules. There are no conductive connections along this channel, achieving system-level electrical isolation and independent power supply between the sensing and control module and the stimulation module.

[0040] 2. Sensing and Control Module

[0041] The sensing and control module includes surface electromyography electrodes, an electromyography acquisition front end, a controller, a data packaging and encoding unit, and a light emitter.

[0042] Surface electromyography electrodes: used to collect surface electromyography signals from the first muscle group. The first muscle group is a muscle group that is less damaged or located closer to the end than the target muscle group to be stimulated. For example, in patients with motor neuropathy, the biceps brachii, triceps brachii, and other upper arm muscles can be selected as the control source, while the target muscle group is a more severely damaged distal muscle group such as the forearm flexors, extensors, or intrinsic hand muscles.

[0043] EMG acquisition front end: connected to surface EMG electrodes, including a preamplifier, bandpass filter (e.g., 20-450Hz), power frequency notch filter (e.g., 50Hz), and analog-to-digital converter, used to amplify, filter, and digitize the raw EMG signal.

[0044] Controller: Connected to the EMG acquisition front end, it performs EMG signal feature extraction, feature-to-stimulation parameter mapping calculation, and safety limit presets. Feature extraction can use a sliding window to calculate the root mean square value of the EMG signal or other time-domain / frequency-domain features. Mapping calculation can use a linear mapping function or a calibrated mapping relationship to convert feature values ​​into stimulation command parameters (such as stimulation current amplitude, pulse width, pulse frequency, stimulation timing, etc.). Safety limit presets include maximum current limit, single-phase charge limit, and duty cycle limit.

[0045] Data Packaging and Encoding Unit: Connected to the controller, it encapsulates stimulus command parameters into a data packet format, optionally adding a frame header, address field, control field, and cyclic redundancy check (CRC).

[0046] Optical transmitter: Connected to the data packetization and encoding unit, it is used to convert encoded electrical signal data into optical signals. The optical transmitter can be a light-emitting diode or a laser diode, and the operating wavelength can be selected from the visible light, infrared, or near-infrared bands.

[0047] 3. Stimulation Module

[0048] The stimulation module operates in a second power domain, electrically isolated from the first power domain, and includes a light receiver, a decoding and integrity verification unit, a stimulation controller, and an output stage.

[0049] Optical receiver: Used to receive optical signals transmitted through an optical communication link and convert them into electrical signals. An optical receiver can employ a photodiode in conjunction with a transimpedance amplifier and a limiting amplifier.

[0050] Decoding and Integrity Verification Unit: Connected to the optical receiver, this unit decodes received data packets, extracts stimulus command parameters, and verifies data integrity through methods such as cyclic redundancy check. If verification fails, it can trigger a safety fallback behavior (e.g., discarding the current command, retaining the previous valid parameter, or entering a safe state).

[0051] Stimulation controller: Connected to the decoding unit, it is used to parse stimulation command parameters and enforce safety limits. Safety limits include maximum stimulation current amplitude, upper limit of single-phase charge, upper limit of duty cycle, etc. Even if the received command parameters exceed the limits, the stimulation controller will limit the output within the safe range.

[0052] Output stage: Connected to the stimulation controller, it uses a current-driven circuit to generate stimulation pulses, which are then output to the surface neuromuscular electrical stimulation electrodes acting on the target muscle group. The stimulation pulse waveform can be symmetrical or asymmetrical biphasic pulses, with a current amplitude range of, for example, 0-90mA, a pulse width range of, for example, 50-500μs, and a pulse frequency range of, for example, 20-50Hz.

[0053] 4. Optical communication link

[0054] An optical communication link is set between the optical transmitter and the optical receiver to achieve electrical isolation between the sensing and control module and the stimulation module.

[0055] In a preferred embodiment, the optical communication link uses optical fiber as the transmission medium, including plastic optical fiber or silica optical fiber. The two ends of the optical fiber are connected to an optical transmitter and an optical receiver, respectively, providing complete electrical isolation along the transmission path. Fiber optic links also offer advantages such as resistance to electromagnetic interference, flexibility, and ease of wearable deployment.

[0056] In an alternative embodiment, the optical communication link can employ free-space optical communication, such as through an infrared transceiver pair or a visible light communication module to achieve contactless optical signal transmission. This method further enhances the flexibility of module layout, eliminating the need for physical cable connections.

[0057] The optical communication link serves as the sole signal channel between the two modules in the system, ensuring that there are no conductive paths between them, thereby achieving complete electrical isolation and independent power domain division.

[0058] 5. Signal transmission and modulation methods

[0059] This invention supports multiple signal transmission variants, and the content transmitted via optical communication links may include: digitally encoded stimulation instructions, digital electromyographic characteristics, or other control-related state parameters.

[0060] In a preferred embodiment, stimulation commands are transmitted using digital data packet encapsulation. The sensing and control module encodes the stimulation command parameters into digital data packets, adds a frame header and integrity verification field, and then converts them into optical signals for transmission via an optical transmitter. Upon receiving the data packets, the stimulation module parses them, verifies their integrity, and extracts the command parameters.

[0061] In an alternative embodiment, digital electromyographic features (such as RMS values) can be directly transmitted to the stimulation module via an optical link, and the controller on the stimulation module side can generate stimulation commands based on the feature values. In addition, status information such as device status, battery level, and fault codes can also be transmitted.

[0062] The modulation method of the optical link can be digital baseband modulation (such as non-return-to-zero code NRZ), pulse width modulation, or other modulation formats suitable for optical communication.

[0063] 6. Operating Procedures

[0064] Reference Figure 2 The operation procedure of the closed-loop electromyography-driven neuromuscular electrical stimulation system of the present invention includes the following steps:

[0065] S1 Electromyography (EMG) signal acquisition: Surface EMG signals were acquired from the first muscle group (muscle group with less proximal damage).

[0066] S2 Preprocessing: Bandpass filtering (20-450Hz) and power frequency notch filtering (50Hz) are applied to the acquired electromyography signals to suppress motion artifacts and electromagnetic interference.

[0067] S3 Feature Extraction: Calculate electromyographic signal feature values, such as root mean square values, using a sliding window (e.g., 100ms).

[0068] S4 Mapping and Limiting: Transforms eigenvalues ​​into stimulus instruction parameters through linear or calibration mapping and applies safety limits.

[0069] S5 Light Emission Conversion: Converts stimulus command data into light signals.

[0070] S6 Isolated Transmission: Transmits optical signals across electrical isolation barriers via optical communication links.

[0071] S7 Optical Reception Conversion: Converts optical signals back into electrical signal command data on the stimulation module side.

[0072] S8 Stimulation Pulse Generation: Generates stimulation pulses based on the decoded instruction parameters and outputs them to the NMES electrodes of the target muscle group.

[0073] The system repeatedly executes S1 to S8 at a set update rate to form a closed-loop control.

[0074] In a typical clinical application, the user is a patient with motor neuron disease. The amplitude of the autonomic surface electromyography (EMG) signal of the patient's distal muscle groups (such as intrinsic muscles of the hand) is as low as tens of microvolts, making it difficult to reliably use for closed-loop control; while the proximal muscle groups (such as the biceps brachii of the upper arm) still retain usable autonomic activation ability and can generate EMG signals with higher amplitude and better signal-to-noise ratio.

[0075] When using the system of this invention, the surface electromyography (EMG) electrodes of the sensing and control module are deployed on the proximal muscle groups of the patient, and the NMES electrodes of the stimulation module are deployed on the distal target muscle groups. The system uses the residual proximal EMG signals as a control source, extracts features and maps them to generate stimulation commands, and transmits them to the stimulation module via an optical link to assist the distal muscle groups in completing functional movements. This system is suitable for neuromuscular or peripheral nerve injuries in which at least one muscle group can still generate residual voluntary EMG signals, and these signals can be mapped into stimulation assistance commands.

[0076] Alternative embodiments of the present invention include, but are not limited to: using free-space optical communication instead of optical fiber for the optical communication link; using digital electromyographic features or state information instead of stimulation commands for the transmitted content; using analog modulation instead of digital modulation for the optical link; the system supports bidirectional optical links to increase the feedback channel from the stimulation module to the sensing and control module; and using adaptive mapping, threshold-based control, or other alternative algorithms for the control strategy.

[0077] Simulation Experiment

[0078] A simulation-based proof of concept was conducted to verify the feasibility of the proposed optically isolated closed-loop electromyography-driven neuromuscular electrical stimulation architecture under representative noise floor conditions. The evaluation reports objective performance metrics including signal-to-noise ratio (SNR), coefficient of determination (R²), root mean square error (RMSE), and end-to-end delay.

[0079] To facilitate explanation and fair comparison, we define a baseline internal reference, representing idealized conditions with no transmission channel effects and no additional injected channel noise (i.e., no optical link and no wired link). This baseline serves as a general internal benchmark for comparison with optical and wired link configurations.

[0080] In addition, three noise levels were used to stress-test the transmission configurations (fiber and wired) under progressively increasing noise floor constraints: Clean, Noisy, and Very Noisy. The parameter values ​​used to define the noise levels and related channel settings (including latency and jitter, if applicable) are summarized in Table 1.

[0081] Table 1

[0082] Scene No noise Noise High noise RMS (mA) of optical link noise 0.5 1.0 2.0 Optical link delay (ms) 1.0 1.5 2.5 Optical link jitter (ms) 0.05 0.10 0.20 Wired link noise RMS (mA) 1.0 2.0 3.5 Wired link latency (ms) 0.4 0.8 1.2 Wired link jitter (ms) 0.02 0.05 0.10 Event threshold (proportion) 0.25 0.30 0.40 Minimum event interval (ms) 350 400 450

[0083] The comparison results with the benchmark reference are summarized in the following sections: Figures 3 to 6 It covers signal-to-noise ratio, coefficient of determination, root mean square error, and end-to-end delay:

[0084] from Figure 3It can be seen that the signal-to-noise ratio (SNR) of the optical link is significantly higher than that of the wired link at all three noise levels (no noise / noisy / high noise). The SNR advantage of the optical link further increases with the noise level. The electrical isolation of the optical link effectively suppresses ground loop coupling and conducted interference, resulting in higher fidelity for controlling electromyographic signals in low SNR scenarios.

[0085] from Figure 4 It can be seen that the determination coefficient of the optical link is higher than that of the wired link at all noise levels, indicating a stronger linear correlation between the stimulus command transmitted by the optical link and the ideal control signal. The higher the noise level, the greater the decrease in the determination coefficient of the wired link compared to the optical link. Optical link isolation reduces the contamination of the control signal by stimulus artifacts and electromagnetic interference, making the mapping relationship between the electromyographic signal-derived control variables and the stimulus output more stable and reliable.

[0086] from Figure 5 It can be seen that the root mean square error (RMSE) of the optical link is lower than that of the wired link at all noise levels. Under high noise conditions, the RMS error of the wired link increases significantly, while the error increase of the optical link is relatively gradual. The optical link can maintain a lower control deviation under noise constraints, and the system output is closer to the expected stimulus parameters, which is beneficial to the accuracy and safety of closed-loop control.

[0087] from Figure 6 It can be seen that although the preset transmission delay of the optical link is higher than that of the wired link, the total end-to-end delay of the system is still within the range required by the closed-loop NMES update rate at all noise levels. This indicates that the optical link isolation scheme has not had a substantial impact on the closed-loop real-time performance, and has achieved a significant improvement in signal-to-noise ratio and control accuracy at an acceptable delay cost.

[0088] The results show that, at all noise levels, the optical link outperforms the wired link in both signal-to-noise ratio and coefficient of determination, while exhibiting a lower root mean square error. Although the end-to-end delay is slightly higher than that of the wired link, it remains within the range required for the closed-loop NMES update rate. The performance advantages of the optical link are particularly pronounced under high noise conditions, demonstrating the unexpected technical effectiveness of this invention in low signal-to-noise ratio clinical scenarios such as motor neuron lesions.

Claims

1. A closed-loop electromyographic drive neuromuscular electrical stimulation system based on optical link isolation, characterized by, Includes a sensing and control module and a stimulation module: The sensing and control module includes surface electromyography electrodes, an electromyography acquisition front end, and a light emitter; Surface electromyography electrodes are used to collect surface electromyography signals from a first muscle group that is less damaged or located closer to the end than the target muscle group to be stimulated. An electromyography (EMG) acquisition front end is connected to the surface EMG electrodes and is used to condition the surface EMG signals; The controller is connected to the electromyography acquisition front end and is used to generate stimulation command data based on the conditioned surface electromyography signal. A light emitter, connected to the controller, is used to convert the stimulus command data into light signals; The stimulation module is physically separated from the sensing and control module and includes a light receiver, a stimulation controller, an output stage, and an optical communication link. An optical receiver, used to receive the optical signal and convert it into an electrical signal; A stimulation controller, connected to the light receiver, is used to generate a stimulation control signal based on the converted electrical signal; An output stage, connected to the stimulation controller, is used to output stimulation pulses to the target muscle group according to the stimulation control signal; An optical communication link is provided between the optical transmitter and the optical receiver to achieve electrical isolation between the sensing and control module and the stimulation module, thereby eliminating ground loop coupling and conductive interference.

2. The system of claim 1, wherein, The optical communication link is either an optical fiber link or a free-space optical link.

3. The system of claim 1, wherein, The sensing and control module also includes a data packaging and encoding unit connected between the controller and the light emitter, used to encapsulate the stimulation command data into a data packet and add an integrity verification field.

4. The system of claim 3, wherein, The integrity verification field includes a cyclic redundancy check code.

5. The system as described in claim 3, characterized in that, The stimulation module also includes a decoding and integrity verification unit connected between the optical receiver and the stimulation controller, used to decode and verify the integrity of the received data packets.

6. The system as described in claim 1, characterized in that, The controller is also configured to apply predefined safety limits when generating the stimulus instruction data, the safety limits including maximum current limit, single-phase charge limit and duty cycle limit.

7. The system as described in claim 1, characterized in that, The stimulation controller is also used to enforce safety limits when generating the stimulation control signal, the safety limits including the maximum stimulation current amplitude, the upper limit of single-phase charge, and the upper limit of duty cycle.

8. The system as described in claim 1, characterized in that, The sensing and control module operates in the first power domain, and the stimulation module operates in the second power domain, which is electrically isolated from the first power domain.

9. The system as described in claim 1, characterized in that, The system is a non-implantable system, the surface electromyography electrode is a body surface electrode, and the output stage is connected to the body surface neuromuscular electrical stimulation electrode.

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