Bionic Foot Research Articles

HTEC foot: A novel foot structure for humanoid robots combining static stability and dynamic adaptability

Passive bionic feet, known for their human-like compliance, have garnered attention for their potential to achieve notable environmental adaptability. In this paper, a method was proposed to unifying passive bionic feet static supporting stability and dynamic terrain adaptability through the utilization of the Rigid-Elastic Hybrid (REH) dynamics model. First, a bionic foot model, named the Hinge Tension Elastic Complex (HTEC) model, was developed by extracting key features from human feet. Furthermore, the kinematics and REH dynamics of the HTEC model were established. Based on the foot dynamics, a nonlinear optimization method for stiffness matching (NOSM) was designed. Finally, the HTEC-based foot was constructed and applied onto BHR-B2 humanoid robot. The foot static stability is achieved. The enhanced adaptability is observed as the robot traverses square steel, lawn, and cobblestone terrains. Through proposed design method and structure, the mobility of the humanoid robot is improved.

Design of Bionic Foot Inspired by the Anti-Slip Cushioning Mechanism of Yak Feet.

In recent years, legged robots have been more and more widely used on non-structured terrain, and their foot structure has an important impact on the robot's motion performance and stability. The structural characteristics of the yak foot sole with a high outer edge and low middle, which has excellent soil fixation ability and is an excellent bionic prototype, can improve the friction between the foot and the ground. At the same time, the foot hooves can effectively alleviate the larger impact load when contacting with the ground, which is an excellent anti-slip buffer mechanism. The bionic foot end design was carried out based on the morphology of the yak sole; the bionic foot design was carried out based on the biological anatomy observation of yak foot skeletal muscles. The virtual models of the bionic foot end and the bionic foot were established and simulated using Solidworks 2022 and Abaqus 2023, and the anti-slip performance on different ground surfaces and the influence of each parameter of the bionic foot on the cushioning effect were investigated. The results show that (1) the curved shape of the yak sole has a good anti-slip performance on both soil ground and rocky ground, and the anti-slip performance is better on soil ground; (2) the curved shape of the yak sole has a larger maximum static friction than the traditional foot, and the anti-slip performance is stronger under the same pressure conditions; (3) the finger pillow-hoof ball structure of the bionic foot has the greatest influence on the buffering effect, and the buffering effect of the bionic foot is best when the tip of the bionic foot touches the ground first.

Modeling and Control of Two Degree of Freedom Bionic Foot

Many people are affected by conditions like stroke, spinal cord diseases, cerebral palsy, and nerve injuries, leading to impaired leg function. Bionic foot assist in maintaining stability and posture, offering vital aid to those with mobility issues for improved quality of life and rehabilitation. Consequently, the use of bionic foot has increased. Bionic foot comprising electrical and mechanical components, provide comfort and support for individuals with mobility problems. An encouraging solution is to introduce bionic foot robots to help patients having mobility problems during their recovery journey. Designed to mimic the human skeletal system, these robots offer valuable assistance in restoring the natural gait cycle of patients having mobility problems. The proposed approach introduces a bionic foot designed to support movement of human ankle joint, marking a significant advancement in rehabilitation technology. Although human ankle joint actually exhibits 3 DOF motion, we consider 2 DOF motion of human ankle joint i.e., plantarflexion and dorsiflexion and, inversion and eversion as they are dominant during normal motion of human body. We designed two systems to control the motion of human ankle joint. Firstly, we have used two actuators, one for each degree of freedom to control the motion of ankle joint. Secondly, we have used an actuator to control the plantarflexion and dorsiflexion motion and Spring-Damper system to control the inversion and eversion motion of the human ankle joint. For both systems, we derive the mathematical model and then we design the PD controller using MATLAB/Simulink. For plantarflexion and dorsiflexion motion, we give standard pattern of human ankle gait as input and for inversion and eversion motion, we provide pulsating signal as our input for both the systems. After implementation, the response of the human ankle motion was precise, accurate and smooth. The torque applied by the actuators was also in the acceptable range.

Foot Bionics Research Based on Reindeer Hoof Attachment Mechanism and Macro/Microstructures.

The attachment performances of mechanical feet are significant in improving the trafficability and mobility of robots on the extreme ground. In the future, frozen-ground robots can be used to replace human soldiers in scouting and deep space exploration. In this study, the influence factors on the attachment function of the bionic feet were analyzed. Soft frozen soil and tight frozen soil close to natural frozen soil were prepared, and the friction between ungula and frozen soil ground was simulated together with the plantar pressures of reindeer under trotting. The major attachment parts were the ungula cusp, outer edges, and ungula capsules, and the stress on the ungula was mainly 4.56-24.72 MPa. According to the microstructures of plantar fur and ungula, the corresponding ratio of the rib width and length was 0.65:1, and the corresponding ratio of the rib width and distance was 3:1. In addition, the scales of the plantar fur were very tightly arranged and had large ripples. Based on typical curves, an ungula capsule-curved surface, and a nonsmooth plantar fur surface, four types of bionic feet and the corresponding ordinary multidamboard foot were designed. On the frozen soil, the bionic foot with ribs and an ungula capsule showed the best attachment performance. Compared with the multidamboard foot, the dynamic coefficient of friction of the bionic foot with ribs and ungula capsules increased by 11.43-31.75%. The attachment mechanism of the bionic feet is as follows: under the action of pressure, the fine patterns of the bionic convex-crown generate friction with the nonsmooth structure of the frozen soil surface, which improves the attachment performance.

From the Analysis of Anatomy and Locomotor Function of Biological Foot Systems to the Design of Bionic Foot: An Example of the Webbed Foot of the Mallard.

This study utilized the mallard's foot as the subject, examining the bone distribution via computed tomography (CT) and analyzing pertinent parameters of the tarsometatarsal bones. Additionally, gross anatomy methods were employed to elucidate the characteristics of the toes and webbing bio-structures and their material composition. Biologically, the mallard's foot comprises tarsometatarsal bones and 10 phalanges, enveloped by fascia, tendons, and skin. Vernier calipers were used to measure the bones, followed by statistical analysis to acquire structural data. Tendons, originating in proximal muscles and terminating in distal bones beneath the fascia, facilitate force transmission and systematic movement of each segment's bones. Regarding material composition, the skin layer serves both encapsulation and wrapping functions. Fat pads, located on the metatarsal side of metatarsophalangeal joints and each phalanx, function as cushioning shock absorbers. The correlation between the force applied to the tarsometatarsal bones and the webbing opening angle was explored using a texture analyzer. A simplified model describing the driving force behind the webbing opening angle was introduced. Furthermore, we designed a bionic foot, contributing a foundational reference for anti-sinking bionic foot development.

An investigation into the effect of cross-ply on energy storage and vibration characteristics of carbon fiber lattice sandwich structure bionic prosthetic foot

Abstract Made a pioneering attempt to use the lattice sandwich structure in prosthetic foot design and pioneered the study for the lay-up design of the prosthetic foot. An innovative carbon fiber bionic prosthetic foot was designed using a sandwich structure. The effect of cross-ply on the prosthetic foot’s energy storage properties and vibration characteristics was investigated using the lattice sandwich structure prosthetic foot. The bionic prosthetic foot’s finite element model was constructed under normal working conditions according to international standards. The results indicate that the storage of strain energy increases with an increase in cross-ply under heel-strict working conditions. Under the toe-off condition, the strain energy distribution increases with the increase in cross-ply. The cross-ply number influences the mode of displacement of the bionic foot. The natural frequencies of the bionic foot increase with the increase in the cross-ply.

Bionic Design of Multi-Toe Quadruped Robot for Planetary Surface Exploration

To increase the knowledge and exploit new resources beyond the Earth, planetary surface exploration on the Moon or Mars attracts significant attention around the globe. Due to the fact that these planetary surfaces are widely covered by soil-like materials, various structures of planetary rovers have been proposed to adapt to the terrains. Nonetheless, the traditional rover structures, such as wheeled and leg-wheeled, have shown limitations in moving on granular soils. To improve the mobility, this paper proposes a multi-toe quadruped robot inspired by the desert chameleon animal. The key features are that each bionic foot possesses four toes to stabilize them on granular materials. Moreover, a bionic flexible spine is designed to coordinate with walking and turning gaits and to make the robot approach an animal-like mobility. To assess the robot performances, kinematics analysis and analytical modeling of foot, leg, and spine movements are carried out. The results demonstrate that this robot can effectively walk and turn in accordance with the adopted gaits. Finally, field tests of moving over sands have been conducted. It shows that the robot can stably walk and turn on sands, which indicates that it is adaptable to planetary granular terrains.

An innovative forestry chassis with legs installed bionic walking foot

An innovative forestry chassis with legs installed bionic walking foot

Research in mechanical model of bionic foot intruding into sands with different physical characteristics

In this study, a bionic foot with sand fixation and fluidization limitation functions was designed. Also a rectangular foot with the same sizes, named the common foot, was designed for comparison. Three kinds of quartz sands were selected to study how particle size, shape and compactness affected the intrusion performances of mechanical feet. The intrusion resistive forces and pressures of the bionic foot on these three kinds of quartz sands were all smaller compared with the common foot. Discrete element simulations showed particle disturbance areas were smaller and particle motion trends were more consistent under the bionic foot versus the common foot. The intrusion resistive forces of these two kinds of mechanical feet firstly increased and then decreased with the increasing particle sizes of quartz sands. Moreover, the intrusion resistive force on spherical particles was less than that of irregular particles for both the bionic foot and the common foot. The corresponding resistive forces of mechanical feet were characterized based on quartz sand compactness. The classic pressure-sinkage model was modified based on the intrusion tests, and the relationships between intrusion resistive force and mechanical foot depth were obtained.

Design of Bionic Buffering and Vibration Reduction Foot for Legged Robots.

When legged robots walk on rugged roads, they would suffer from strong impact from the ground. The impact would cause the legged robots to vibrate, which would affect their normal operation. Therefore, it is necessary to take measures to absorb impact energy and reduce vibration. As an important part of a goat's foot, the hoof capsule can effectively buffer the impact from the ground in the goat's running and jumping. The structure of the hoof capsules and its principle of buffering and vibration reduction were studied. Inspired by the unique shape and internal structure of the hoof capsules, a bionic foot was designed. Experimental results displayed that the bionic foot could effectively use friction to consume impact energy and ensured the stability of legged robot walking. In addition, the bionic foot had a lower natural vibration frequency, which was beneficial to a wide range of vibration reduction. This work brings a new solution to the legged robot to deal with the ground impact, which helps it adapt to a variety of complex terrain.

Research on Bionic Foot Design and Climbing Strategy of Quadruped Robot

Aiming at the problem that it is difficult for a quadruped robot to climb a large Angle slope, the bionics principle of goat climbing was analyzed. A bionic goat hoofs structure and a foot-to-ground coupling climbing model were designed. A climbing strategy of lateral sloping on a large slope was proposed, and foot trajectory planning under this model was studied. This design can assist the quadruped robot to climb the specific rugged surface with large slope, By building a single leg control model, combining with the Simulink and Simpack co-simulation technology, the single leg bench 60° slope simulation test, simulation results show that this design can effectively improve the quadruped bionic robot for rugged terrain with large slope stability of slope surface support.

Immediate sensorimotor grounding of novel concepts learned from language alone

Theories of grounded cognition postulate that concepts are grounded in sensorimotor experience. But how can that be for concepts like Atlantis for which we do not have that experience? We claim that such concepts obtain their sensorimotor grounding indirectly, via already-known concepts used to describe them. Participants learned novel words referring to up or down concepts (mende = enhanced head or mende = bionic foot). In a first experiment, participants then judged the sensibility of sentences implying up or down actions (e.g., “You scratch your bionic foot”) by performing up or down hand movements. Reactions were faster when the hand movement matched the direction of the implied movement. In the second experiment, we observed the same congruency effect for sentences like, “You scratch your mende”, whose implied direction depended entirely on the learning phase. This offers a perspective on how concepts learned without direct experience can nonetheless be grounded in sensorimotor experience.

Bionic design and anti-slip characteristics study of quadruped robot foot

Quadruped robot has been widely used in the field of national defense because of its high adaptability. The stability and balance capacity is the important performances needed during the quadruped robot moving under uneven terrains, and the slip resistance of the foot affects the balance performance of robot. As the goat hoof with irregular surface morphology adapts to rugged terrain, its plantar geometric shape was reconstructed using reverse engineering technology based on the point clouds which were obtained by using a 3D hand laser scanner. The bionic foot was designed based on goat hoof plantar surface, and the anti-slip characteristics were analyzed by finite element method, and then compared with the spherical foot and cylindrical foot. The frictions between these feet and soils or rocks at different pressures were investigated, and the result shows that the maximum static frictions between bionic and soil and rock are greater than that of the two others, which means bionic foot has better anti-slip performance.

Prosthetic gait of unilateral lower-limb amputees with current and novel prostheses: A pilot study

BackgroundNovel lower-limb prostheses aim to improve the quality of locomotion of individuals with an amputation. This study evaluates the biomechanics of a novel bionic foot during walking. MethodsAble-bodied individuals (n = 7) and individuals with a transfemoral (n = 6) or transtibial amputation (n = 6) were included. Able-bodied individuals conducted one experimental trial, whereas individuals with transtibial and transfemoral amputations conducted a familiarization (with current prosthesis) and two experimental trials using a passive and bionic prosthesis. Each trial consisted of 3 bouts of 2 min of treadmill walking at different speeds. Biomechanical data were gathered using a force platform and motion capture system and analysed using Statistical Parametric Mapping and (non)-parametric tests. FindingsConventional prosthetic feet alter gait patterns and induce locomotion difficulties. While walking at a normal speed with the passive prosthesis, transtibial amputees display reduced maximum heel forces, increased ankle and trunk angular velocities at midstance, and increased knee angle during stance and swing phases on their effected side (P ≤ 0.026). Improved lower-limb kinematics was demonstrated during slow and normal speed walking with the bionic prosthesis; however, dynamic trunk stability was negatively impacted during this condition. The bionic prosthesis did not benefit transfemoral amputees at any walking speed. InterpretationTranstibial amputees can better approximate typical movement patterns at slow and normal walking speeds using the novel bionic prosthesis; however the same benefit was not observed in transfemoral amputees.

Research on Low Energy Consumption Static Postures of Bionic Feet

By studying the relation of the robot’s postures and its energy consumption, a static analysis-based method to obtain the low-energy postures of the robot is proposed. This method decreases the energy consumption and increases the battery life by adjusting the postures in the horizontal environment. The method takes the low-speed hexapod bionic robot as the research object. First, we obtain the output torque of each joint of the leg through static analysis and establish the energy consumption model of the robot. Considering the flexibility of the robot, we then introduce the performance index of the maximum step length and establish an equilibrium solution based on energy consumption and maximum step size. Finally, we derive the low-energy postures of the robot using MATLAB (MATLAB 2014a, The MathWorks, Natick, Massachusetts State, USA, 2014) simulations. An energy consumption experiment is carried out with a physical prototype to verify the validity of the method.

Cognitive performance and brain dynamics during walking with a novel bionic foot: A pilot study

ObjectivesThe objectives are to determine neural dynamics during gait using electro-encephalography and source localization, and to investigate the attentional demand during walking in able-bodied individuals, and individuals with an amputation.Materials & methodsSix able-bodied individuals conducted one experimental trial, and 6 unilateral transtibial and 6 unilateral transfemoral amputees performed 2 experimental trials; the first with the prosthesis currently used by the subjects and the second with a novel powered transtibial prosthesis, i.e. the Ankle Mimicking Prosthetic foot 4.0. Each experimental trial comprised 2 walking tasks; 6 and 2 minutes treadmill walking at normal speed interspersed by 5 minutes of rest. During 6 minutes walking the Sustained Attention to Response (go-no go) Task, which measures reaction time and accuracy, was performed. Electro-encephalographic data were gathered when subjects walked 2 minutes. Motor-related cortical potentials and brain source activity during gait were examined. Normality and (non-) parametric tests were conducted (p<0.05).Results and discussionIn contrast to transtibial amputees, transfemoral amputees required more attentional demands during walking with Ankle Mimicking Prosthetic foot 4.0 compared to the current passive prosthetic device and able-bodied individuals (reaction time and accuracy: p≤0.028). Since risk of falling is associated with altered attentional demands, propulsive forces of the novel device need to be better controlled for transfemoral amputees. No motor-related cortical potentials at Cz were observed in transfemoral amputees walking with the novel prosthesis, whereas motor-related cortical potentials between transtibial amputees and able-bodied individuals during walking at normal speed did not differ. The first positive electro-physiological peak deflection appeared during toe-off phase and showed higher activity within the underlying brain sources in transtibial amputees walking with Ankle Mimicking Prosthetic foot 4.0 compared to able-bodied individuals. The required higher neural input to accomplish the same physical activity compared to able-bodied individuals is possibly due to the limited acclimation period to the novel device and consequently increased afferent sensory feedback for postural control.

Modeling, Design and Test-Bench Validation of a Semi-Active Propulsive Ankle Prosthesis With a Clutched Series Elastic Actuator

Driven by the desire of amputees to reduce their physical shortcomings, prosthetic feet evolved from passive to propulsive bionic feet, actuated by different types of compliant actuators to provide the push-off power and with the advantage of reducing the motor power requirements. The two-latest in-house developed Ankle Mimicking Prosthetic Foot prototypes used explosive elastic actuation. They were proven to be energy efficient, but are bulky and heavy, which increases gait asymmetries and metabolic cost. In this letter, we present the modeling, design, and test-bench validation of a novel semi-active ankle prosthesis using a resettable overrunning clutch with a series elastic actuator. Unlike many designs found in literature, which are only optimized and evaluated in the mechanical domain, we modeled the drive-train dynamics to have a better understanding of the electrical energy consumption. During the performance evaluation, it is shown that the nonpathological gait cycles at different walking speeds are well replicated in both simulations and test-bench experiments. The results reveal that this clutch is a suitable device to add to a series elastic driven ankle since it offers, for an 8% relative weight increase of the prosthesis, besides the assets of natural adaptability to different gaits and terrains, also an electrical energy reduction of up to 22% for the slow walking speed.

Bionic foot design: an inside view

Researchers in India have designed a physiologically controlled ankle prosthesis that is capable of mimicking the natural movements and flexibility of a human foot. To find out more about this promising device we spoke to Oishee Mazumder and her colleagues at Indian Institute of Engineering Science and Technology to find out more. The important considerations to take into account when designing ankle-foot prostheses are low cost, inclusion of a power saving mode and ensuring the foot is mechanically resilient in power-off mode. Commercially available ankle foot prostheses are completely passive, and consequently, their mechanical properties remain fixed with walking speed and terrain. However, human ankle stiffness actually varies within each gait cycle (stride) and also with walking speed, which must be taken into account in prosthetic design. Below-knee amputees who use passive ankle foot prostheses also exhibit non-symmetric gait patterns and high metabolic ambulatory rates. The primary challenges in this field are associated with size, weight, controlling parameters, sensor fusion, realisation in embedded platform and the final cost of the product. Our group aims to make user friendly prototypes with physiological control by using multimodal sensory input signals. Limitations of current prosthetic technology includes: inability to provide net power at the joints (passive prostheses), high cost and the absence of feedback systems. Also, loss of net power generation at the lower limb impairs the ability of the prosthetics to biomechanically restore normal locomotive functions during many locomotive activities, such as walking, running and jumping. The elevated metabolic demand and slower preferred speeds of transtibial amputees are likely to be the cause of conventional passive prosthetics being unable to produce power at the ankle. In our published Letter we report the design and development of a wearable, low-cost, low-power prosthetic active ankle foot. The foot is controlled by myoelectric, inertial and pressure sensors that are actuated by custom designed servo motors, thus ensuring natural ankle spring-like behaviour is created. Our reported system is adaptable to variation of cadence and different terrain. Most modern ankle-foot prostheses employ a single spring in their design, such as a carbon fibre leaf spring. The gait of an amputee who uses these passive compliant prostheses mimics the unaffected ankle during normal walking, but deviates from normal as walking speed increases. Common ankle design is mostly related with DC motor and proper spring actions. In the present development, spring stiffness is adjusted to control the motor action in each gait phase. Our design is a cost-effective solution for transtibial amputees, which will help them regain their lost mobility in a relatively small time span. The design concept that we have followed can also be utilised in gait analysis, orthotic design in spinal cord injury (lower body exoskeleton) and in rehabilitation devices. As an extension of the concept of myoelectric controlled active ankle foot prosthesis, we have already started on the development of a lower limb active exoskeleton and its control strategy for regenerating and enhancing mobility. Immediately, the device can be improved in several ways, such as by the introduction of a low-weight, high-strength carbon nanotube-based fibre structure, long-life packing sensors and the incorporation of compact light-weight actuators. In the long run, the knowledge that we have developed will be used to design lower body exoskeleton devices with intelligent ankle feet. Prosthetic ankle prototype with custom designed servo motor to enable amputees to have physiological control of the artificial limb. Labelled design of the fabricated ankle foot prosthetic prototype. The device is currently under clinical testing with testing already carried out on three subjects under the supervision of a qualified prosthesist. The remaining challenges that we have yet to address are the need to reduce the limbs, weight, incorporate an efficient actuator and improve the battery power. A completely new prototype is under development, which will take care of the described deficiencies of the existing system. Amputation in general often leads to loss of work and mental disturbance. Every amputee needs training and counselling to be habituated and comfortable with the prosthetic device. This requires frequent follow up in rehabilitation centres. In many cases, such extensive follow-ups are not possible and desired results are not achieved. To address this we would like to develop an electromyogram (EMG) based rehabilitation, which will serve dual-purpose of regenerating and strengthening EMG signals and provide interactive training for prosthetic use.

The Ankle Mimicking Prosthetic Foot 3—Locking mechanisms, actuator design, control and experiments with an amputee

The Ankle Mimicking Prosthetic Foot 3 is an energy efficient bionic foot using the principle of optimal power distribution. The main challenge behind this research is focused on retrieving as much energy as possible from the gait and to incorporate an electric actuator with minimized power consumption. The Ankle Mimicking Prosthetic (AMP-) Foot 2, as a proof-of-concept, showed the advantage of using the Explosive Elastic Actuator capable of delivering the full ankle torques (±120N m) and power (±250W) with only a 60W motor. The novelty of this work is focussed on the addition of an extra locking mechanism to the AMP-Foot 3 which bring additional assets such as natural adaptability to different walking speeds and slopes and an improved energy storage during early stance implying a greater reduction of the power requirements of the motor to only 50W while still being able to produce the peak output torque and power necessary for walking.In this article, the authors present the AMP-Foot 3 focussing on its critical mechanical parts, its actuation design and its control. Experiments with an amputee are also presented to show its effectiveness.

The AMP-Foot 3, new generation propulsive prosthetic feet with explosive motion characteristics: design and validation.

The last decades, rehabilitation has become a challenging context for mechatronical engineering. From the state-of-the-art it is seen that the field of prosthetics offers very promising perspectives to roboticist. Today’s prosthetic feet tend to improve amputee walking experience by delivering the necessary push-off forces while walking. Therefore, several new types of (compliant) actuators are developed in order to fulfill the torque and power requirements of a sound ankle-foot complex with minimized power consumption. At the Vrije Universiteit Brussel, the Robotics and Multibody Mechanics research group puts a lot of effort in the design and development of new bionic feet. In 2013, the Ankle Mimicking Prosthetic (AMP-) Foot 2, as a proof-of-concept, showed the advantage of using the explosive elastic actuator capable of delivering the full ankle torques (pm 120 Nm) and power (pm 250 W) with only a 60 W motor. In this article, the authors present the AMP-Foot 3, using an improved actuation method and using two locking mechanisms for improved energy storage during walking. The article focusses on the mechanical design of the device and validation of its working principle.