Abstract
In the present study, we investigate a control mechanism that dampens hand vibrations. Here, we propose a control method with two components to suppress hand vibrations. The first is a passive suppression method that lowers the joint stiffness to passively dampen the hand vibrations. The second is an active suppression method that adjusts an equilibrium point based on skyhook control to actively dampen the hand vibrations. In a simulation experiment, we applied these two methods to dampen hand vibrations during the shoulder’s horizontal oscillation. We also conducted a measurement experiment wherein a subject’s shoulder was sinusoidally oscillated by a platform that generated horizontal oscillations. The results of the measurement experiments showed that the jerk of each part of the arm in a task using a cup filled with water was smaller than the shoulder jerk and that in a task with a cup filled with stones was larger than the shoulder jerk. Moreover, the amplitude of the hand trajectory in both horizontal and vertical directions was smaller in a task using a cup filled with water than in a task using a cup filled with stones. The results of the measurement experiments were accurately reproduced by the active suppression method based on skyhook control. These results suggest that humans dampen hand vibrations by controlling the equilibrium point through the information of the external workspace and the internal body state rather than by lowering joint stiffness only by using internal information.
Highlights
The human body has many degrees of freedom (DOFs) and can perform daily movements by dexterously coordinating redundant body parts without requiring special attention
When the joint stiffness values (Table 3) were based on the WS task, the hand, wrist, and elbow jerks were larger than the shoulder jerk (Fig 3a), and the hand trajectory amplitudes in the horizontal direction were larger than the oscillation amplitude of the platform (0.03 m, Fig 3b)
We investigated the control mechanism for dampening hand vibrations
Summary
The human body has many degrees of freedom (DOFs) and can perform daily movements by dexterously coordinating redundant body parts without requiring special attention. Investigating a control mechanism of dexterous human movement supports the understanding of the role played by the human central nervous system (CNS) in motor control. We investigated human daily and dexterous movements that we previously described as “carrying a cup filled with water without spilling it” [1]. Control Model for Dampening Hand Vibrations maintained a constant cup angle by coordinating their multi-joints to carry a cup filled with water. This study investigates the human control mechanism that dampens hand vibrations. The control mechanism of dampening hand vibrations approached in this study supports the understanding of the role of the human CNS and is applicable to the control of a robot in a real-world environment and the development of a human support robot
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