A Multimodal Sensory Apparatus for Robotic Prosthetic Feet Combining Optoelectronic Pressure Transducers and IMU

Abstract

Timely and reliable identification of control phases is functional to the control of a powered robotic lower-limb prosthesis. This study presents a commercial energy-store-and-release foot prosthesis instrumented with a multimodal sensory system comprising optoelectronic pressure sensors (PS) and IMU. The performance was verified with eight healthy participants, comparing signals processed by two different algorithms, based on PS and IMU, respectively, for real-time detection of heel strike (HS) and toe-off (TO) events and an estimate of relevant biomechanical variables such as vertical ground reaction force (vGRF) and center of pressure along the sagittal axis (CoPy). The performance of both algorithms was benchmarked against a force platform and a marker-based stereophotogrammetric motion capture system. HS and TO were estimated with a time error lower than 0.100 s for both the algorithms, sufficient for the control of a lower-limb robotic prosthesis. Finally, the CoPy computed from the PS showed a Pearson correlation coefficient of 0.97 (0.02) with the same variable computed through the force platform.

A low-power ankle-foot prosthesis for push-off enhancement

“…Moreover, it is responsible for detecting gait events -Foot Contact (FC) and Foot Off (FO). The FC and FO events can be detected using either a threshold on the vGRF estimated from the sensorized foot or a rule-based algorithm on signals from the foot IMU (Fiumalbi et al, 2022). 1. from FC to FO, the motor is controlled in zero current, thus the actuator does not provide additional deformation of the foot; 2. at FO, the LLC mode is set to velocity control and the LLC ref is instantaneously set to À2000 rpm to unload the residual elastic energy in swing; 3. the motor control mode is set to zero current whenever the foot is in a neutral, unloaded, position, which is detected when the camshaft angle is lower than a manually tuned threshold angle θ unload , close to the lower instability point I1 of the 4-bar linkage:…”

“…One IMU is embedded in the main electronic board, monitoring the orientation of the shank (iNemo, LSM9DS1, STMicroelectronics), and the other two are wired and placed on the rear of the foot and the thigh of the user (MPU9250, TDK/InvenSense Inc.). The bottom plate of the foot is equipped with 16 wired pressure-sensitive elements based on optoelectronic technology (Fiumalbi et al, 2022 ), embedded in scalable sets of PCB matrices. The placement of the sensors follows the most stressed plantar areas, namely the heel and forefoot regions, to improve the detection of gait events such as foot contact and foot off.…”

“…Threshold-based algorithms use the information from the pressure-sensitive elements to provide online estimates of the center of pressure ( ) progression and the vertical ground reaction force ( ). Detailed information can be found in Fiumalbi et al ( 2022 ). Signals from pressure-sensitive elements are collected by the sensorized foot control board that interfaces with the main electronic board.…”

“…Moreover, it is responsible for detecting gait events – Foot Contact (FC) and Foot Off (FO). The FC and FO events can be detected using either a threshold on the estimated from the sensorized foot or a rule-based algorithm on signals from the foot IMU (Fiumalbi et al, 2022 ). Middle-level control layer: The middle-level controller uses the information measured by the onboard sensors and provided from the high-level control layer to (i) compute a continuous estimate of the gait phase, and (ii) send the reference motor commands to the low-level controller ( Figure 5(b) ).…”

A review on the recent developments in design and integration of electromyography textile electrodes for biosignal monitoring

“…It is also used in guided effective therapeutics (iSMD), robotic interfacing and improving prosthetics. [60][61][62] Textile EMG integrated systems are tested practically by contracting and relaxing the muscle. An example given by D.Farinal et al, proposes the use of smart fabric and interactive textile for EMG measurements based prostheses control.…”