Design of robotic systems that safely and efficiently operate in uncertain operational conditions, such as rehabilitation and physical assistance robots, remains an important challenge in the field. Current methods for the design of energy efficient series elastic actuators use an optimization formulation that typically assumes known operational conditions. This approach could lead to actuators that cannot perform in uncertain environments because elongation, speed, or torque requirements may be beyond actuator specifications when the operation deviates from its nominal conditions. Addressing this gap, we propose a convex optimization formulation to design the stiffness of series elastic actuators to minimize energy consumption and satisfy actuator constraints despite uncertainty due to manufacturing of the spring, unmodeled dynamics, efficiency of the transmission, and the kinematics and kinetics of the load. In our formulation, we express energy consumption as a scalar convex-quadratic function of compliance. In the unconstrained case, this quadratic equation provides an analytical solution to the optimal value of stiffness that minimizes energy consumption for arbitrary periodic reference trajectories. As actuator constraints, we consider peak motor torque, peak motor velocity, limitations due to the speed-torque relationship of DC motors, and peak elongation of the spring. As a simulation case study, we apply our formulation to the robust design of a series elastic actuator for a powered prosthetic ankle. Our simulation results indicate that a small trade-off between energy efficiency and robustness is justified to design actuators that can operate with uncertainty.
End-to-End Control of a Powered Knee-Ankle Prosthesis Towards Unified, Tuning-Free Assistance
Georgia Institute of Technology（佐治亚理工学院）；Woodruff School of Mechanical Engineering（伍德拉夫机械工程学院）；Institute for Robotics and Intelligent Machines（机器人与智能机器研究所）
A compliant ankle-actuated compass walker with triggering timing control
School of Physics, Georgia Institute of Technology, Atlanta, USA（物理学院，佐治亚理工学院，美国亚特兰大）；Electrical and Electronics Engineering, Hacettepe University, Ankara, Türkiye（电子与电气工程，哈科特佩大学，土耳其安卡拉）
A Framework for Optimal Ankle Design of Humanoid Robots
Artificial and Mechanical Intelligence Laboratory, Istituto Italiano di Tecnologia (IIT)（人工与机械智能实验室，意大利技术研究院）；School of Computer Science, University of Manchester（计算机科学学院，曼彻斯特大学）；iCub Tech Facility, Istituto Italiano di Tecnologia (IIT)（iCub技术设施，意大利技术研究院）
