A Case Study on Influence of Utilizing Hill-Type Muscles on Mechanical Efficiency of Biped Running Gait
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International Applied Mechanics, Vol. 56, No. 4, July, 2020
A CASE STUDY ON INFLUENCE OF UTILIZING HILL-TYPE MUSCLES ON MECHANICAL EFFICIENCY OF BIPED RUNNING GAIT B. Dadashzadeh1*, A. Allahverdizadeh1, M. Esmaeili1, H. Fekrmandi2
The presence of compliant elements in biped running mechanisms generates a smoother motion and decreases the impact forces. Biological creatures that have a complicated actuation system with parallel and series elastic elements in their muscles demonstrate very efficient and robust bipedal gaits. The main difficulty of implementing these systems is duplicating their complicated dynamics and control. This paper studies the effects of an actuation system, including Hill-type muscles on the running efficiency of a kneed biped robot model with point feet. In this research, we implement arbitrary trajectories compatible with the initial condition of the robot, and we calculate the necessary muscle forces using an analytical inverse dynamics model. To verify the results, we execute the direct dynamics of the robot with the calculated control inputs to generate the robot’s trajectory. Finally, we calculate the contractile element force of the muscles and its cost of transport, and we investigate the effects of the muscles’ elements on reducing or increasing the cost of transport of the gait and maximum actuating forces. Keywords: biped running, gait planning, hill-type muscle, cost of transport 1. Introduction. Despite numerous research on planning and controlling bipedal running, there is still no biped robot capable of running as efficiently as animals. In this area, the main difference between robots and animals is that, in robots, muscles are replaced with electric or pneumatic motors. Developing actuators that operate with a dependency on muscle structure can be a solution for future robotic efficiency. In this research, we consider Hill-type muscles instead of rotational motors as actuators of a biped robot model. Additionally, we plan periodic running gaits including a stance phase, take-off event, flight phase, and touch-down event. By investigating muscle structure, Hill [1] described its mechanical model elements as follows: one contractile element; a series elastic element; and a parallel elastic element. This model has been used by biomechanics researchers as a base model for muscles. Lichtwark et al. [2] used ultrasonic sensors to detect length variations of muscle elements during walking and running. Iida et al. [3] proposed bi-articular springs on the thigh and shin, instead of muscles for a robot with minimal hip actuation, which could generate walking and a special running gait in experiments. Pneumatic artificial muscles have been developed as a mechanical realization of muscles. However, they have some drawbacks; pneumatic muscles have small movement strides, and it is difficult to supply compressed air for a biped robot. Hosoda et al. [4] used antagonistic pneumatic actuators to generate biped walking and running gaits and showed that pneumatic actuators have good character
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