Stiffness Control of Variable Stiffness Link Using a Conductive Fabric Based Proximity Sensor
Stiffness Control of Variable Stiffness Link Using a Conductive Fabric Based Proximity Sensor
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DOI：
10.1109/ieeeconf49454.2021.9382706
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发表时间：
2021-01
期刊：
影响因子：
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通讯作者：
Mana Ishihara;Takahiro Matsuno;K. Althoefer;S. Hirai
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作者：
Mana Ishihara;Takahiro Matsuno;K. Althoefer;S. Hirai
随着人们对创建允许人类和机器人之间安全物理交互的解决方案的持续兴趣，出现了设计机器人手臂的新方法。一个例子是最近开发的可变刚度链接（VSL）-一种新型的充气软机器人链接，由柔性但不可伸展的织物套筒制成，并能够改变其刚度。在高刚度下，VSL可以与标准机器人臂内的刚性连杆（例如，在工厂环境中执行拣选和放置任务。然而，通过降低这些连杆中的空气压力，它们的刚度也会降低，并且机器人臂的顺应性会增加。因此，当人错误地侵入机器人工作区域时，可以通过简单地减小机器人的连杆中的压力来确保安全性。在这种情况下，一个主要的挑战是确定人类是否在机器人的范围内。在这项研究中，我们建议集成一个接近，基于电容的传感器与VSL的导电织物制成。由于所提出的接近传感器由织物制成，因此非常适合与VSL集成：传感器材料是柔性的，同时不可延伸，因此可以用作VSL的外层，而不会影响其刚度可控性。开发了一种适当的控制策略，能够根据VSL和附近的人或物体之间的距离使用新的传感器来改变VSL的刚度。所提出的传感器/控制系统通过评估由集成接近传感器测量的电容来确定到VSL附近的人或物体的距离，并相应地调整链路的刚度以确保安全。实验证明，我们的新方法能够降低VSL的刚度时，一个人正在接近，甚至在接触发生。
With an ongoing interest to create solutions allowing for safe physical interaction between humans and robots, new approaches to the design of robot arms are appearing. One example is the recently developed Variable Stiffness Link (VSL) -a new type of inflatable soft robot link made of flexible, yet inextensible fabric sleeves and capable of changing its stiffness. At high stiffness, the VSL can perform comparable to a rigid link within a standard robot arm, e.g., carry out picking and placing tasks in a factory environment. However, by decreasing the air pressure in such links their stiffness also decreases, and the robot arm’s compliance increases. Hence, when a human erroneously intrudes into the robot working area, safety can be ensured by simply reducing the pressure in the robot’s links. In this context, a major challenge is to determine whether a human is within the robot’s range. In this study, we propose to integrate a proximity, capacitance-based sensor made of conductive fabric with a VSL. Since the proposed proximity sensor is made of fabric, it is ideally suited for integration with the VSL: the sensor material is flexible and at the same time inextensible and as such can be used as the outer layer of a VSL without affecting its stiffness controllability. An appropriate control strategy was developed capable of changing the stiffness of the VSL depending on the distance between the VSL and a human or object nearby using the new sensor. The proposed sensor/control system determines the distance to a human or object in the vicinity of the VSL by evaluating the capacitance as measured by the integrated proximity sensor and adjusts the link’s stiffness accordingly to ensure safety. It was experimentally validated that, our new approach was capable of reducing the VSL’s stiffness when a human was approaching, even before contact occurred.