Vallery Heike, Duschau-Wicke Alexander, Riener Robert
Sensory-Motor Systems (SMS) Lab, Institute of Robotics and Intelligent Systems (IRIS), ETH Zurich, Switzerland.
Annu Int Conf IEEE Eng Med Biol Soc. 2010;2010:1271-4. doi: 10.1109/IEMBS.2010.5626416.
To enable compliant training modes with a rehabilitation robot, an important prerequisite is that any undesired human-robot interaction forces caused by robot dynamics must be avoided, either by an appropriate mechanical design or by compensating control strategies. Our recently proposed control scheme of "Generalized Elasticities" employs potential fields to compensate for robot dynamics, including inertia, beyond what can be done using closed-loop force control. In this paper, we give a simple mechanical equivalent using the example of the gait rehabilitation robot Lokomat. The robot consists of an exoskeleton that is attached to a frame around the patient's pelvis. This frame is suspended by a springloaded parallelogram structure. The mechanism allows vertical displacement while providing almost constant robot gravity compensation. However, inertia of the device when the patient's pelvis moves up and down remains a source of large interaction forces, which are reflected in increased ground reaction forces. Here, we investigate an alternative suspension: To hide not only gravity, but also robot inertia during vertical pelvis motion, we suspend the robot frame by a stiff linear spring that allows the robot to oscillate vertically at an eigenfrequency close to the natural gait frequency. This mechanism reduces human-robot interaction forces, which is demonstrated in pilot experimental results.
为了实现与康复机器人的合规训练模式，一个重要的前提是，必须通过适当的机械设计或补偿控制策略来避免由机器人动力学引起的任何不期望的人机交互力。我们最近提出的“广义弹性”控制方案利用势场来补偿机器人动力学，包括惯性，这超出了使用闭环力控制所能做到的。在本文中，我们以步态康复机器人Lokomat为例给出一个简单的力学等效模型。该机器人由一个外骨骼组成，该外骨骼附着在患者骨盆周围的框架上。这个框架由一个弹簧加载的平行四边形结构悬挂。该机构允许垂直位移，同时提供几乎恒定的机器人重力补偿。然而，当患者骨盆上下移动时，设备的惯性仍然是产生较大交互力的一个来源，这反映在地面反作用力的增加上。在此，我们研究一种替代的悬挂方式：为了在骨盆垂直运动期间不仅隐藏重力，还隐藏机器人惯性，我们用一个刚性线性弹簧悬挂机器人框架，该弹簧允许机器人以接近自然步态频率的固有频率垂直振荡。这种机制减少了人机交互力，初步实验结果证明了这一点。
