Abstract
This study proposes two novel methods for determining the muscular internal force (MIF) based on joint stiffness, using an MIF feedforward controller for the musculoskeletal system. The controller was developed in a previous study, where we found that it could be applied to achieve any desired end-point position without the use of sensors, by providing the MIF as a feedforward input to individual muscles. However, achieving motion with good response and low stiffness using the system, posed a challenge. Furthermore, the controller was subject to an ill-posed problem, where the input could not be uniquely determined. We propose two methods to improve the control performance of this controller. The first method involves determining a MIF that can independently control the response and stiffness at a desired position, and the second method involves the definition of an arbitrary vector that describes the stiffnesses at the initial and desired positions to uniquely determine the MIF balance at each position. The numerical simulation results reported in this study demonstrate the effectiveness of both proposed methods.
Highlights
Humans are able to achieve specific complex movements by manipulating the structure of the human body
We proposed a muscular internal force (MIF) feedforward controller for a musculoskeletal system (Kino et al, 2009, 2013)
The primary objective of this study is, to resolve the issues in the MIF feedforward controller proposed in previous studies
Summary
Humans are able to achieve specific complex movements by manipulating the structure of the human body. The human body structure can be described in terms of a musculoskeletal structure in which muscles, corresponding to actuators, cover bones and joints. Verrelst et al (Verrelst et al, 2005) developed a biped robot actuated with antagonistic pneumatic artificial muscles. This robot can control joint stiffness and achieve stable walking. Niiyama et al (Niiyama et al, 2012) developed a double legged robot with a musculoskeletal structure that emulates an athlete’s physique and style of running. Their robot had the capability of running stably for 4 m. Niiyama et al (Niiyama et al, 2007) developed a jumping robot with a musculoskeletal structure that
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