In this paper, a novel robotic assistive system (RAS) for mobility assistance of elderly adults is developed based on admittance control with force exertion ability enhancement (FEAE) of a wheeled mobile manipulator (WMM). The RAS can provide supportive force in the vertical direction and be guided by the user with a limited horizontal plane ability. An admittance controller is adopted to realize compliant behaviour between the end-effector and the user, enabling different admittance performances in different directions without requiring the complex system dynamics. The end-effector force needed by the controller is estimated by employing a nonlinear disturbance observer, avoiding the need for pricey force/torque (F/T) sensor. Meanwhile, with consideration of the limited joint torque output, the FEAE approach is implemented in the null-space of the WMM, which can make the system exert more Cartesian force in a given direction with consideration of Cartesian stiffness requirement using the same joint torque limitation through kinematic reconfiguration. Thus, it improves the capability of the system in realizing the desired admittance requirement. The advantages and effectiveness of the proposed approach are experimentally demonstrated with a 4-wheel omnidirectional mobile manipulator.

在本文中，基于带轮移动机械手（WMM）的力施加能力增强（FEAE）的导纳控制，开发了一种用于老年人行动辅助的新型机器人辅助系统（RAS）。RAS可以在垂直方向上提供支撑力，并由用户以有限的水平面能力进行引导。采用导纳控制器来实现末端执行器和用户之间的顺应性行为，从而在不同方向上实现不同的导纳性能，而无需复杂的系统动力学。控制器所需的末端执行器力是通过使用非线性干扰观测器来估算的，从而无需使用昂贵的力/转矩（F / T）传感器。同时，考虑到有限的关节扭矩输出，FEAE方法是在WMM的零空间中实现的，这可以使系统在给定方向上施加更大的笛卡尔力，同时考虑到笛卡尔刚度要求，并且通过运动学重新配置使用相同的关节扭矩限制。因此，它提高了系统实现所需导纳要求的能力。用四轮全向移动机械手通过实验证明了该方法的优点和有效性。