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

Abstract

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.

Humanoids’ Feet: State-of-the-Art & Future Directions

“…Structure refers to the physical structure of the foot. Most humanoids adopt flat feet consisting of a unique rigid segment or of two rigid segments joined by a revolute joint [31][32][33][34][35][36][37][38][39][40][42][43][44][45][46][47][48][49][50][51]. One humanoid robot adopts a different solution with a unique rigid segment with a wheel on the foot [41].…”

“…With this joint, H6 [42,43] can move forward with its knees in contact with the ground. Eldirdiry et al provide a robotic foot with a passive joint and try to avoid foot drop [36][37][38][39][40]. Takahashi et al proposed an active joint in the foot for the first time and implemented it in the robot Ken [31].…”

Development of a Passive Ankle Foot Prosthesis with Manually Adjustable Ankle Stiffness

“…The full structure of the ankle-foot prosthesis is made up of the forefoot section, the adjustment mechanism and a cam and leaf spring transmission for the ankle such that they closely resemble the dimensions of a natural ankle-foot complex of a 1.73 m tall human subject [13]. The dimensions of the natural limb and those of the designed prosthesis are presented in Table 1.…”

“…The designed prosthesis was also evaluated for other properties, using the work Open Journal of Therapy and Rehabilitation by Zaier and Al-Yahmedi [13] as a standard for the natural human foot properties. The designed prosthesis closely resembles the dimensions of the natural ankle-foot complex.…”

“…The achieved weight, with all appropriate materials applied in the 3D model, was found to be just above 1.1 kg. For the natural foot, the weight is taken to be 1.37% of the body weight [13], and thus applying the 75 kg as before, the comparable weight of an intact ankle-foot complex would be about 1 kg. Thus, the prosthesis also closely mimics the weight of the natural limb.…”