A Hybrid Impedance Controller for Series Elastic Actuators to Render a Wide Range of Stable Stiffness in Uncertain Environments
Journal
IEEE Robotics and Automation Letters
Journal Volume
6
Journal Issue
2
Start Page
739
End Page
746
ISSN
23773766
Date Issued
2021
Author(s)
Abstract
Accurate and wide-range stiffness control is important for safe human-robot interaction. Accurate stiffness control can be better achieved using series elastic actuators (SEAs) than conventional rigid actuators. However, the stable range of virtual stiffness rendered by SEAs is limited by the stiffness of the actual spring, which cannot be too high in order to ensure good force control accuracy. Adding a virtual damper or derivative gain can increase the stable range of virtual stiffness, but the stable range would highly depend on the environmental stiffness. To relax the stiffness limitation in uncertain environments and explore more merits of SEAs, this letter proposes a hybrid impedance controller. This new controller linearly combines the spring force feedback and inertia force feedback. The stable range of virtual stiffness can be easily increased to ten times the actual spring stiffness with minimum effect on the force control accuracy. Unlike typical impedance controllers, the environmental stiffness can be used to raise the stable range of stiffness and hence the robustness of the controller can be ensured. Experiments will be provided to verify the hybrid impedance controller. We expect that the hybrid impedance controller can be used for SEAs in unstructured environments to provide a wide range of virtual stiffness.
Subjects
Environmental Stiffness
High-stiffness Control
Impedance Controller
Series Elastic Actuator
Virtual Damping
Virtual Stiffness
Actuators
Agricultural Robots
Biofeedback
Controllers
Force Control
Human Robot Interaction
Springs (components)
Stiffness
Control Accuracy
Impedance Controllers
Safe Human-robot Interaction
Series Elastic Actuators
Stiffness Control
Uncertain Environments
Unstructured Environments
Virtual Stiffness
Feedback
Publisher
Institute of Electrical and Electronics Engineers Inc.
Type
journal article