Parallel robots provide the potential to be leveraged for human-robot collaboration (HRC) due to low collision energies even at high speeds resulting from their reduced moving masses. However, the risk of unintended contact with the leg chains increases compared to the structure of serial robots. As a first step towards HRC, contact cases on the whole parallel robot structure are investigated and a disturbance observer based on generalized momenta and measurements of motor current is applied. In addition, a Kalman filter and a second-order sliding-mode observer based on generalized momenta are compared in terms of error and detection time. Gearless direct drives with low friction improve external force estimation and enable low impedance. The experimental validation is performed with two force-torque sensors and a kinetostatic model. This allows a new identification method of the motor torque constant of an assembled parallel robot to estimate external forces from the motor current and via a dynamics model. A Cartesian impedance control scheme for compliant robot-environmental dynamics with stiffness from 0.1-2N/mm and the force observation for low forces over the entire structure are validated. The observers are used for collisions and clamping at velocities of 0.4-0.9m/s for detection within 9-58ms and a reaction in the form of a zero-g mode.

翻译：并联机器人因运动部件质量轻而具有高速运动下碰撞能量低的特性，这为其在人机协作（HRC）领域提供了应用潜力。然而，相较于串联机器人结构，其支链结构增大了意外接触的风险。作为迈向人机协作的第一步，本文研究了并联机器人整体结构上的接触案例，并应用了基于广义动量与电机电流测量的扰动观测器。此外，对基于广义动量的卡尔曼滤波器与二阶滑模观测器在误差与检测时间方面进行了比较。采用低摩擦无齿轮直驱电机可改善外力估计精度并实现低阻抗。实验验证通过两个力-扭矩传感器与动力学静力学模型完成。由此提出一种针对装配完成的并联机器人电机扭矩常数的新型辨识方法，能够通过电机电流与动力学模型估算外力。本文验证了用于机器人-环境柔顺动力学的笛卡尔阻抗控制方案（刚度范围0.1-2N/mm），以及针对整个结构低作用力的力观测方法。所提出的观测器可检测速度0.4-0.9m/s下的碰撞与夹持工况，在9-58ms内完成检测并触发零重力模式反应。