Human-In-The-Loop Optimization of A Wearable Robot Using Foot Pressure Sensors

Background: Individuals with below-knee amputation (BKA) experience increased physical effort when walking, and the use of a robotic ankle-foot prosthesis (AFP) can reduce such effort. Our prior study on a robotic AFP showed that walking effort could be reduced if the robot is personalized to the wearer. The personalization is accomplished using human-in-the-loop (HIL) optimization, in which the cost function is based on a real-time physiological signal indicating physical effort. The conventional physiological measurement, however, requires a long estimation time, hampering real-time optimization due to the limited experimental time budget. In addition, the physiological sensor, based on respiration uses a mask with rigid elements that may be difficult for the wearer to use. Prior studies suggest that a symmetry measure using a less intrusive sensor, namely foot pressure, could serve as a metric of gait performance. This study hypothesized that a function of foot pressure, the symmetric foot force-time integral, could be used as a cost function to rapidly estimate the physical effort of walking; therefore, it can be used to personalize assistance provided by a robotic ankle in a HIL optimization scheme. Methods: We developed a new cost function derived from a well-known clinical measure, the symmetry index, by hypothesizing that foot force-time integral (FFTI) symmetry would be highly correlated with metabolic cost. We conducted experiments on human participants (N = 8) with simulated amputation to test the new cost function. The study consisted of a discrete trial day, an HIL optimization training day, and an HIL optimization data collection day. We used the discrete trial day to evaluate the correlation between metabolic cost and a cost function using symmetric FFTI percentage. During walking, we varied the prosthetic ankle stiffness while measuring foot pressure and metabolic rate. On the second and third days, HIL optimization was used to find the optimal stiffness parameter with the new cost function using symmetric FFTI percentage. Once the optimal stiffness parameter was found, we validated the performance with comparison to a weight-based stiffness and control-off conditions. We measured symmetric FFTI percentage during the stance phase, prosthesis push-off work, metabolic cost, and user comfort in each condition. We expected the optimized prosthetic ankle stiffness based on the newly developed cost function could reduce the energy expenditure during walking for the individuals with simulated amputation. Results: We found that the cost function using symmetric foot force-time integral percentage presents a reasonable correlation with measured metabolic cost (Pearson’s R > 0.62). When we employed the new cost function in HIL ankle-foot prosthesis parameter optimization, 8 individuals with simulated amputation reduced their cost of walking by 15.9% (p = 0.01) and 16.1% (p = 0.02) compared to the weight-based and control-off conditions, respectively. The symmetric FFTI percentage for the optimal condition tended to be closer to the ideal symmetry value (50%) compared to weight-based (p = 0.23) and control-off conditions (p = 0.04). Conclusion: This study suggests that foot force-time integral symmetry using foot pressure sensors can be used as a cost function when optimizing a wearable robot parameter.

Tails stabilize landing of gliding geckos crashing head-first into tree trunks

Animals use diverse solutions to land on vertical surfaces. Here we show the unique landing of the gliding gecko, Hemidactylus platyurus. Our high-speed video footage in the Southeast Asian rainforest capturing the first recorded, subcritical, short-range glides revealed that geckos did not markedly decrease velocity prior to impact. Unlike specialized gliders, geckos crashed head-first with the tree trunk at 6.0 ± 0.9 m/s (~140 body lengths per second) followed by an enormous pitchback of their head and torso 103 ± 34° away from the tree trunk anchored by only their hind limbs and tail. A dynamic mathematical model pointed to the utility of tails for the fall arresting response (FAR) upon landing. We tested predictions by measuring foot forces during landing of a soft, robotic physical model with an active tail reflex triggered by forefoot contact. As in wild animals, greater landing success was found for tailed robots. Experiments showed that longer tails with an active tail reflex resulted in the lower adhesive foot forces necessary for stabilizing successful landings, with a tail shortened to 25% requiring over twice the adhesive foot force.

Rotorcraft Dynamic Platform Landings Using Robotic Landing Gear

Articulating landing gear that use closed-loop feedback control are proven to expand the landing capabilities of rotorcraft on sloped and rough terrain. These systems are commonly referred to as robotic landing gear (RLG). Modern robotic landing gear systems have limitations for landing on dynamic platforms because their controllers do not incorporate fuselage roll and roll rate feedback. This work presents a proven crashworthy cable-driven RLG system for the commercial S-100 Camcopter that expands static landing zone limits by a factor of three and enables dynamic platform landings in rough Sea State conditions. A new roll and foot-force feedback fused control algorithm is developed to enable ship deck landings of an RLG equipped S-100 without the need for deck lock or advanced vision based landing systems. Multibody dynamic simulations of the aircraft, landing gear, and new control system show the benefits of this combined roll and force feedback approach. Results include experimental dynamic landings on platforms rolling under sinusoidal motion and simulated Sea State conditions. The experiments demonstrate, in a limited fashion, the usability of the RLG through ground experimentation, and the results are compared to simulations. Additional simulations of landings of the S-100 with rigid and active landing gear with more challenging landing conditions than experimentally tested are presented. Such results aid in understanding how RLG with this new roll and contact force fused controller prevent dynamic roll-over.

Effect of Adapted Ergometer Setup and Rowing Speed on Lower Extremity Loading in People with and without Spinal Cord Injury

IntroductionFunctional electrical stimulation assisted rowing (FES-rowing) on an adapted ergometer is used in spinal cord injury (SCI) rehabilitation. A primary goal is to mechanically load the lower extremity to prevent disuse osteoporosis. Recent studies reported the small foot reaction force in FES-rowing was not sufficient to prevent bone loss.ObjectiveThis study aims to investigate the effect of ergometer setup and rowing speed on lower extremity loading in able-bodied and SCI individuals.DesignTwenty able-bodied novice rowers and one experienced SCI rower rowed on an adapted ergometer with different speeds and setups. Motion capture system and force sensors were used to calculate forces and moments at the knee.Main Outcome MeasuresFoot reaction force and knee moment for all participants, and tibiofemoral force of the SCI rower.ResultsPeak foot reaction forces of able-bodied rowers ranged from 0.28 – 0.45 body weights (BW), which was less than half the force in normal rowing. A fast rowing speed, forward seat position, and large knee RoM were associated with higher foot force and knee moment during able-bodied rowing. The SCI subject had the greatest foot reaction force (0.40 BW) when rowing with small knee RoM at a rear seat position and the highest tibiofemoral force (2.23 BW) with large knee RoM at a rear seat position.ConclusionErgometer setup and speed can double the force generation at the foot during both able-bodied rowing and FES-rowing. Rowing forms (range of motion and speed) that resulted in the greatest foot reaction force were different for able-bodied rowers and SCI rowers, indicating a trade-off between motion and force generation in FES-rowing that warrants further investigation with more SCI rowers. Clinicians and physical therapist should be aware that ergometer setups can be easily adjusted to modify rowing forms and loading patterns of users with SCI.

Modeling and Effective Foot Force Distribution for the Legs of a Quadruped Robot

SUMMARY This paper presents the detailed dynamic modeling of a quadruped robot. The forward and inverse kinematic analysis of each leg of the proposed model is deduced using Denavit-Hartenberg (D-H) parameters. It desires to calculate the optimal feet forces of the quadruped robot’s joint torque, which is essential for its online control. To find out the optimal feet force distribution, two approaches are implemented to fulfill the locomotion objective. The four-legged quadruped robot and torso body’s detailed dynamics are modeled to generate an equation of motion for the robot control system. The Euler–Langrage theory has been used to find out the joint motion. The computer simulation results are presented to verify the effectiveness of the dynamic model.

Research on the Posture Control Method of Hexapod Robot for Rugged Terrain

This paper proposes a hexapod robot posture control method for rugged terrain to solve the problem of difficulty in realizing the posture control of a foot robot in rough terrain. The walking gait and original position of a six-legged robot is planned, and the Layer Identification of Tracking (LIT) strategy is developed to enable the robot to distinguish mild rugged terrain and severe rugged terrains automatically. The virtual suspension dynamic model is established. In mild rugged terrain, the posture maintenance strategy is adopted to keep the stability of the torso. In severe rugged terrain, the posture adjustment strategy is adopted to ensure the leg workspace and make it more widely adapt to the changing terrain, and a gravity center position adjustment method based on foot force distribution is designed to use foot force as feedback to control the position and attitude. The experiment of posture control in rough terrain and climbing experiment in the ladder terrain shows that the hexapod robot has good posture maintenance and posture adjustment effects when traversing complex terrain through the posture maintenance strategy and the posture adjustment strategy. Combined with the terrain identification method based on LIT, the hexapod robot can successfully climb the ladder terrain through the identification of the changing ladder terrain, and the movement of the posture adjustment process is stable.

Design and Development of Insole Monitoring System for Runner

Nowadays, running is said to be one of the common activities that be practiced by various people especially athletes. Back then, there were some researchers report that most of the injuries among athletes involves lower hip bodies. It is due to some factors such as body and foot posture during running activity, selection shoe and style of running. Hence, this research is about to design and develop an insole monitoring system using ESP 32 development board and FSR sensor for the purpose of force distribution detection on runner’s foot. The development of smart insole is to countermeasure the risk of injury to the athletes. This system includes (ESP 32) development board which act as a microcontroller that interfaced with a Wi-Fi module and force sensing resistance (FSR) sensor to detect the force distribution of runner’s foot in (kg) unit. The system able to detect the foot force distribution acts by the runner and transmits the output data of the FSR sensor through the application which called Blynk. The experiments had done through two methods which are jogging and running. The force monitoring data was obtained through the Blynk Application via Wi-Fi. The design and development of insole monitoring system has successfully done and implemented on the runner.

Differences in ground reaction waveforms between elite senior and junior academy sprinters during the block phase and first two steps

The block start and initial steps following block exit are fundamental aspects of sprinting and their development is key to junior athletes’ progression. This study assessed the difference in force production between elite senior (including two sub-10 s 100-m sprinters) and junior academy sprinters during the block phase and the first two steps of a sprint. Thirty-seven male sprinters (17 senior, 20 junior) performed a series of maximal effort 20–40 m acceleration from blocks on an indoor track, with the ground reaction forces produced during the block phase and first two steps measured using force platforms. Senior athletes produced better block-phase performances (average horizontal external power; 15.52 ± 1.48 W/kg, M ± SD) compared with the juniors (12.37 ± 2.21 W/kg; effect size ± 90% confidence interval = 1.28 ± 0.38). However, force production during the initial two steps was comparable across groups. Specifically, senior athletes exhibited higher relative force production and ratio of forces during the early (∼15–35%) block phase and higher anteroposterior forces during the transition from bilateral to unilateral pushing (58–62% of the block phase). Front foot force production was also found to differentiate senior and junior groups at rear block exit (∼55% of the block phase). This may be a required response to the greater centre of mass displacement in order to prevent over-rotation in the senior athletes during the front block pushing phase. Collectively, these results indicate that the progression of junior athletes is non-uniform across the block phase and subsequent two contacts, which should be considered when attempting to progress junior athletes towards senior ranks.

Preventative Taping in Futsal: An Exploratory Analysis of Low-Dye Taping on Planter Force Distribution and Pain Sensitivity

The purpose of the present study was to investigate the changes in plantar foot force distribution (i.e., the percentage of force and force distribution under the rearfoot and forefoot) and plantar pressure pain sensitivity maps in professional futsal players after long-term low-dye taping (LDT). The subjects (n = 25) were male futsal players (age 23.03 ± 1.15 years). During the experiment, a nonelastic tape was applied on the plantar foot surface according to the standards of LDP. The experimental protocol consisted of a 3-day cycle during which the plantar foot force distribution (FFD) and plantar pressure pain threshold (PPT) were measured: (1) before the tape was applied, (2) 24 h after application, and (3) 72 h after application. The results revealed a significant decrease in the force distribution under the rearfoot (p ≤ 0.001) and forefoot (p ≤ 0.001) on the right and left sides. Moreover, the results showed an increase in the plantar pressure pain threshold in all regions of the foot (p ≤ 0.001). The results of this study suggest that plantar fascial taping can be an effective method for normalizing the force distribution on the foot and reducing the plantar pain threshold. The findings provide useful information regarding the prevention of and physical therapy of lower extremity injuries in soccer and futsal.

Distribution of feet pressure on ground and maintaining body balance among 8–10-year-old children with and without external load application

Purpose: The aim of this study was to analyse the impact of applying an external load on the distribution of pressure on the plantar side of the foot and maintaining body balance, using the podobarographic platform. Methods: The study was conducted on 130 school children aged 8–10: girls (n = 68, body mass = 22.8 ± 6.0 kg, body height = 129.3 ± 7.5 cm) and boys (n = 62, body mass = 31.1 ± 6.5 kg, body height 134.4 ± 7.3 cm). The study involved 2 trials. At first, children stood on the platform assuming a natural position. Then, they put on a 5-kg backpack and stood on the platform once more. Results: The results indicate that after backpack loading, for the total research group of girls and boys, statistically significant differences were found in the distribution of foot force on the ground in the left forefoot (p = 0.008), metatarsus (p = 0.000) and heel areas (p = 0.002). While in the right foot, these differences were noted for the forefoot (p = 0.024) and metatarsus (p = 0.000). The results of balance testing were also statistically significant. They concerned measurements of the body barycentre area (cop-bars p = 0.003), the barycentre area of the left foot (l-bars p = 0.034) and the parameter comparing distance to surface ratio (cop-lsf p = 0.000). Conclusions: It may be concluded that prolonged overloading with backpacks affects movement patterns, which may further lead to the acquisition and consolidation of postural defects.