TITLE: Nonlinear Muscle-Like-Compliant Controller for Active Control with Remote Force Sensing.

Inventors: Dr. Chi-haur Wu and Dr. D.T. Lee
Dept. of Electrical and Computer Engineering,
Northwestern University

The Invention pertains to a muscle-like-compliant controller that can be applied to any actuator driven dynamic system such that the system becomes totally compliant and adaptable to a wide range of loads without using a force sensor. This Invention can be used for active suspension control, vibration control, impact force absorption, rehabilitation robot control, and tele-manipulation with remote force sensing and control.

The nonlinear muscle-like-compliant controller is modeled from a primate limb that possesses muscle-stiffness mechanisms for position (stiffness) control and nonlinear muscle-reflex mechanisms for force control. The controller therefore provides not only compliance or an adjustable damping effect for any actuator-driven dynamic system without using a force sensor, but also the ability to adapt to a wide range of loads without adjusting its gains while maintaining stability of the dynamic system. This adaptability to various loads gives the controller a unique plug-and-play feature.

The controller's force-following capability eliminates the need for using traditional teach pendants for trajectory planning in robotics and facilitates the teaching process for task planning. The muscle-like compliant property gives the linkages of the controlled system a totally compliant capability in relation to its environment, thus providing a safety feature for the system and its environment. The nonlinear damping capability, however, provides the system with an ability to absorb impacting forces and to dampen vibration levels. Due to the force-absorbing capability provided to the controlled robot or system and adaptability in responding to commands and varying loads, this invention is very well suited for manipulating remote robots and exoskeleton suits, as well as a man-machine interface in rehabilitation robots. Because of its compliant capability, the controller is also perfect for controlling a pair of master-slave manipulators, either locally or via tele-manipulation. Aided by smart-material sensor/actuator mechanisms, the slave manipulator, controlled by the Invention, can provide the human operator with remote force feedback and enable the operator to actively control the force applied to the master manipulator without the need of additional force sensors. The ability to perform tele-manipulation using remote force sensing and control is particularly useful for performing material handling and other operations in hazardous environments.

FIELD OF APPLICATION: Robotic compliance control, damping control, vibration control, active suspension control, impact force absorbing, rehabilitation robot control, tele-manipulation with remote force sensing, and control of any actuator-driven system.

ADVANTAGES: This controller can provide compliance capability without using force sensors. It also possesses non-linear damping property and adapts to a wide range of loads without having to adjust the gain. Furthermore, the stiffness and damping characteristics of the controller are programmable.

STAGE OF DEVELOPMENT: The controller has been implemented to control a demonstration robot. The force-following and absorbing, as well as tele-manipulation capabilities can be demonstrated. A prototype of a quarter-car model has been built to demonstrate active suspension control capability. A GUI has been implemented allowing commands to the demonstration robot to be sent via the Internet.