Direct Comparisons of Upper-Limb Motor Learning Performance Among Three Types of Haptic Guidance With Non-Assisted Condition in Spiral Drawing Task.

In robot-assisted rehabilitation, it is unclear which type of haptic guidance is effective for regaining motor function because of the lack of direct comparisons among multiple types of haptic guidance. The objective of this study was to investigate the effects of different types of haptic guidance on upper limb motor learning in a spiral drawing task. Healthy young participants performed two experiments in which they practiced the drawing movement using a robotic manipulandum with a virtual wall (Path guidance), running direction pushing and virtual wall (Path & Push guidance), restriction to the target movement (Target guidance), or without haptic guidance (Free guidance). Experiment 1 compared the learning effects of the four types of guidance. Experiment 2 investigated the effects of pre-learning with Path, Path & Push, or Target guidance on post-learning with Free guidance. In Experiment 1, Free guidance demonstrated the greatest learning effect, followed by Path guidance, which showed a significantly greater improvement in task performance than the other two types of guidance. In Experiment 2, the type of pre-learning did not influence post-learning with Free guidance. The results suggested that learning with Path guidance showed a slightly slower but comparable effect to Free guidance and was the most effective among the three types of haptic guidance. The superiority of Path guidance over other haptic guidance was interpreted within the framework of error-based learning, in which the intensity of sensory feedback and voluntary motor control play important roles.

A highly sensitive friction-imaging device based on cascading stimuli responsiveness.

Imaging and measurement of friction forces are required in a variety of fields. If the friction forces originating from the motions of professionals are quantitatively analyzed, the data can be applied to a motion-copying system by a robot. However, weak friction forces have not been visualized and quantified using conventional sensing materials and devices because of their low sensitivity. Here we present a highly sensitive friction-imaging device based on the cascading responses of stimuli-responsive materials, namely polydiacetylene (PDA) and dry liquid (DL). Weak friction forces disrupt the DL, which is composed of liquid droplets surrounded by solid particles. The outflowing liquid under chemical stress changes the color of PDA. The cascading responses enable colorimetric imaging and measurement of weak friction forces in the range of 0.006-0.080 N. Furthermore, the device visualizes the force distribution of handwriting in calligraphy depending on the individual characteristics of an expert, a practician, and a beginner. A high-sensitivity friction-imaging device can be used to understand various motions.