Passive Toe Joint Research Articles

The experimental investigation of foot slip-turning motion of the musculoskeletal robot on toe joints.

Owing to their complex structural design and control system, musculoskeletal robots struggle to execute complicated tasks such as turning with their limited range of motion. This study investigates the utilization of passive toe joints in the foot slip-turning motion of a musculoskeletal robot to turn on its toes with minimum movements to reach the desired angle while increasing the turning angle and its range of mobility. The different conditions of plantar intrinsic muscles (PIM) were also studied in the experiment to investigate the effect of actively controlling the stiffness of toe joints. The results show that the usage of toe joints reduced frictional torque and improved rotational angle. Meanwhile, the results of the toe-lifting angle show that the usage of PIM could contribute to preventing over-dorsiflexion of toes and possibly improving postural stability. Lastly, the results of ground reaction force show that the foot with different stiffness can affect the curve pattern. These findings contribute to the implementations of biological features and utilize them in bipedal robots to simplify their motions, and improve adaptability, regardless of their complex structure.

Study of bipedal locomotion considering property of toe mechanism

Walking behaviour of the humanoid robot depends on many parameters of body structure, in which, the foot structure is one of the most important factors since it directly interacts with the environment in the locomotion. In this paper, joint characteristics of the robot’s foot have been investigated for our further understanding of biped motion. These properties are stiffness and damping factor of spring of passive toe joints. The subject of this paper is a small humanoid robot named Kondo KHR-3HV belonging to the Kondo Kagaku company. The foot structure of the robot consists of a big toe and a tiptoe with passive joints using torsion spring. The effect of the structure property is collected and evaluated through dynamic simulation on Adams and analysis of variance (ANOVA).

Optimizing Vertical Jumping Height of Single-Legged Robots with Passive TOE Joints Using the Genetic Algorithm

Legged robots have been interesting for researchers because they can move on uneven terrain and operate in dangerous areas for humans. Among these robots, the single-legged robot is an excellent choice to study because they are simpler than another legged robot. In this paper, we have designed a single-legged robot similar to the anatomy of the human leg. It consists of four active joints and one passive joint. The hip, knee, and ankle joint are considered active joints, and the toe joint is a passive joint. To make the simulation more accurate, we should define the physical property of the environment in detail. So, ground contact and friction model should be specified. After defining the robot model, we designed joint motion. Path planning aims to make the robot jump in the vertical direction. Besides, the robot must start jumping on the toe joint. The toe joint stiffness and damping play the leading role in jumping height. So, there should be optimum values for these parameters. The genetic algorithm is then used to optimize jumping height.

Design and control of an assistive exoskeleton with passive toe joint

Several exoskeletons with various configurations and degrees-of-freedoms (DOFs) have been introduced in the literature, but not many have addressed the optimal selection of the mechanism's DOFs. In the proposed system a semi-passive toe joint is introduced to achieve several advantages. The performance of the proposed novel passive toe joint is evaluated experimentally. In addition, the semi-passive abduction/adduction DOFs in the hip joint and eversion/inversion DOFs in ankle joint is proposed to facilitate turning while providing more comfort during normal walking. The effect of passive DoFs existence on the user comfortability is studied with the aid of three kinematic indices. In the proposed mechanism, a set of compact, low-backlash rotary series elastic actuators are designed and incorporated to actuate the joints. A novel torque control is also introduced and evaluated experimentally. Results show good performance of the robot in zero-force control and impedance control during swing phase of motion.

Design and control of an assistive exoskeleton with passive toe joint

Design and control of an assistive exoskeleton with passive toe joint

Design of Biomechanical Legs with a Passive Toe Joint for Enhanced Human-like Walking

This paper presents the design procedure of a biomechanical leg, with a passive toe joint, which is capable of mimicking the human walking. This leg has to provide the major features of human gait in the motion trajectories of the hip, knee, ankle, and toe joints. Focus was given to the approach of designing the passive toe joint of the biomechanical leg in its role and effectiveness in performing human like motion. This study was inspired by experimental and theoretical studies in the fields of biomechanics and robotics. Very light materials were mainly used in the design process. Aluminum and carbon fiber parts were selected to design the proposed structure of this biomechanical leg, which is to be manufactured in the Mechanical Lab of the Sultan Qaboos University (SQU). The capabilities of the designed leg to perform the normal human walking are presented. This study provides a noteworthy and unique design for the passive toe joint, represented by a mass-spring damper system, using torsion springs in the foot segment. The working principle and characteristics of the passive toe joint are discussed. Four-designed cases, with different design parameters, for the passives toe joint system are presented to address the significant role that the passive toe joint plays in human-like motion. The dynamic motion that is used to conduct this comparison was the first stage of the stance motion. The advantages of the presence of the passive toe joint in gait, and its effect on reducing the energy consumption by the other actuated joints are presented and a comparison between the four-designed cases is discussed.

Adding low-cost passive toe joints to the feet structure of SURENA III humanoid robot

SUMMARYAdding active toe joints to a humanoid robot structure has lots of difficulties such as mounting a small motor and an encoder on the robot feet. Conversely, adding passive toe joints is simple, since it only consists of a spring and a damper. Due to lots of benefits of implementing passive toe joints, mentioned in the literature, the goal of this study is to add passive toe joints to the SURENA III humanoid robot which was designed and fabricated at the Center of Advanced Systems and Technologies (CAST), University of Tehran. To this end, a simple passive toe joint is designed and fabricated, at first. Then, stiffness and damping coefficients are calculated using a vision-based measurement. Afterwards, a gait planning routine for humanoid robots equipped with passive toe joints is implemented. The tip-over stability of the gait is studied, considering the vibration of the passive toe joints in swing phases. The multi-body dynamics of the robot equipped with passive toe joints are presented using the Lagrange approach. Furthermore, system identification routine is adopted to model the dynamic behaviors of the power transmission system. By adding the calculated actuating torques for these two models, the whole dynamic model of the robot is computed. Finally, the performance of the proposed approach is evaluated by several simulations and experimental results. Results show that using passive toe joints reduces energy consumption of ankle and knee joints by 15.3% and 9.0%, respectively. Moreover, with relatively large values of stiffness coefficients, the required torque and power of the knee and hip joints during heel-off motion reduces as the ankle joint torque and power increases.

Mechanical design of powered prosthetic leg and walking pattern generation based on motion capture data

In this paper, we describe the design procedure of an above-knee powered prosthetic leg and an algorithm to generate appropriate gait patterns that are synchronized with the movement of the user. The developed prosthetic leg has powered knee and ankle joints for transfemoral amputees, and its weight and dimensions were determined on the basis of human body data. In particular, two degrees of freedom (roll and pitch axes) were adopted in the ankle joint to achieve dynamic balance control on uneven ground, and passive toe joints using a crank-rocker mechanism and torsional springs were attached at the foot to increase the walking stability. In addition, we developed a walking pattern simulator that is able to test the walking patterns of the powered prosthetic leg in the air. By attaching two inertial sensors on both thighs of the user and measuring both thigh motions, the per cent of gait cycle is suitably calculated from the proposed algorithm, and smooth gait motions are generated according to the gait cycle percent. Finally, walking patterns of the powered prosthetic leg were successfully generated by synchronizing to the human gait, and the generated gaits were analyzed by comparing them to the human gait.

Effects of toe stiffness on ankle kinetics in a robotic transtibial prosthesis during level-ground walking

Robotic transtibial prostheses are gaining popularity, as they significantly improve amputees’ locomotion. Existing studies mainly concentrate on the importance of ankle joints in these prostheses. However, there are few studies that focus on the effects of prosthetic toe joints. Different from human feet, most prosthetic feet are single-segment structures without toe joints. In order to develop more human-like prostheses with ankle and toe joints, it is of great importance to investigate the effects of toe stiffness on ankle kinetics, as it contributes to the design and control optimizations. In this paper, we analyze the effects of toe stiffness on ankle kinetics in a robotic transtibial prosthesis we have built recently. Dynamic models of the prosthesis’ ankle and toe joints are built. The imposed plantar pressures and objective joint angles of these models are obtained from locomotion experiments on able-bodied subjects. Simulation results indicate when the toe joint is fixed, the ankle energy consumption in one gait cycle is almost 1.2 times of that when the toe joint is driven to track the able-bodied toe motion. Experiments of the prosthesis prototype are carried out on an amputee subject with a transtibial amputation. The results show that compared with the fixed toe joint either the active toe joint or the passive toe joint can reduce the ankle output moment and power consumption. This means adding a toe joint to the foot can reduce the designing requirements of the ankle joint. In addition, the active toe joint can help the prosthesis perform more human-like behaviors compared with the passive toe joint. On the other hand, the passive toe joint can simplify the prosthesis structures and reduce the total weight compared with the active toe joint.

AAU-BOT1: A Platform for Studying Dynamic, Life-Like Walking

This paper describes the development of the humanoid robot AAU-BOT1. The purpose of the robot is to investigate human-like walking and in this connection, test prosthetic limbs. AAU-BOT1 has been designed with modularity in mind making it possible to replace, e.g. the lower leg to test transfemoral or transtibial prosthesis or orthosis. Recorded motion data from a male test person, along with approximated inertial and mass properties, were used to determine necessary joint torques in human walking which was used as design parameters for the robot. The robot has 19 degrees of freedom (DoF), 17 actuated and 2 unactuated acting as passive toe joints. The project was granted 60,000 Euro, and to keep development costs below this, the development and instrumentation was carried out by three groups of master students from the Department of Mechanical Engineering (ME) and the Department of Electronic Systems at Aalborg University and supported by the Department of Health Sciences and Technology (HST). To further reduce the cost, the robot uses off-the-shelf hardware which also reduced the time from idea to practical implementation. The result is a low-cost humanoid robot fully assembled and equipped with sensors ready to take its first steps.

Emulation of Human Walking by Biped Humanoid Robot with Heel-Contact and Toe-Off Motion

The foot mechanism and pattern generation we propose for a biped humanoid robot achieves human-like heel-contact toe-off walking. Placing its heel and toes simultaneously on the ground while walking makes it difficult for a robot to take long strides and mimic human gaits. To solve this problem, we developed a biped foot with one passive toe joint based on human gaits analyzed by motion capture and propose pattern generation for human-like walking based on the zero moment point (ZMP) criterion. Using a genetic algorithm, we optimize walking parameters to generate continuous, smooth foot trajectories. Results of experiments in heel-contact toe-off walking in ground reaction force (GRF) using the biped humanoid robot WABIAN-2 demonstrated the similarity between proposed and human walking.

Modular Architecture for Humanoid Walking Pattern Prototyping and Experiments

In this paper we describe the use of design patterns as a basis for creating humanoid walking pattern generator software having a modular architecture. This architecture enabled the rapid porting of several novel walking algorithms on a full-size humanoid robot, HRP-2. The body of work currently available allows extracting a general software architecture usable with inter-exchange between simulations and real experiments. The proposed architecture with the associated design patterns is described together with several applications: a pattern generator for a HRP-2 with passive toe joints, a pattern for dynamically stepping over large obstacles and a new quadratic problem (QP) formulation for the generation of the reference zero-momentum point. Thanks to the versatility and the modularity of the proposed framework, the QP method has been implemented and experienced within 4 days only.