Online Self-body Image Acquisition Considering Changes in Muscle Routes Caused by Softness of Body Tissue for Tendon-driven Musculoskeletal Humanoids

Dynamic Cloth Manipulation Considering Variable Stiffness and Material Change Using Deep Predictive Model With Parametric Bias

“…Regarding the musculoskeletal humanoid with variable stiffness mechanism used in this study, we will describe the details of θ ref and k ref . In this study, we use the following relationship of joint angle θ , muscle tension f , and muscle length l (Kawaharazuka et al, 2018 ).…”

“…When using this trained network for control, the target joint angle θ ref and the target muscle tension f ref are determined and the corresponding target muscle length is calculated. However, since this value is the muscle length to be measured, not the target muscle length, l send , which takes into account the muscle elongation in muscle stiffness control (Shirai et al, 2011 ), is sent to the actual robot (Kawaharazuka et al, 2018 ) in practice.…”

“…Normally, f ref should be the value required to realize θ ref . On the other hand, in Kawaharazuka et al ( 2018 ), a constant value f const is first given to f ref for all muscles to achieve θ ref to a certain degree, and then the current muscle tension f is given as f ref to achieve θ ref more accurately. The body stiffness can be changed to some extent depending on the value of f const sent at the beginning.…”

Online Learning Feedback Control Considering Hysteresis for Musculoskeletal Structures

“…Ookubo, et al have expressed JMM by polynomials, and used it for the state estimation and control [8]. Kawaharazuka, et al have developed a learning method of JMM by a neural network using vision [9] and its extended method considering the effect of muscle tensions [10]. However, because these methods use a one-to-one relationship between joint angles and muscle lengths, they cannot consider hysteresis of joint angle tracking, which makes realizing target joint angles accurately difficult.…”

“…To avoid these problems, it is required to complete the feedback trial quickly or estimate its muscle Jacobian accurately. Although there are several methods estimating muscle Jacobian for musculoskeletal humanoids [10], [12], [13], there will always be some errors. Also, although there are methods to realize target posture using reinforcement learning [14], they are mostly performed in simulation only and are difficult to handle actual musculoskeletal humanoids with multiple degrees of freedom.…”